R & D in Oxidative Desulfurization of Fuels ...

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Recent Patents on Chemical Engineering, 2012, 5, 174-196

R & D in Oxidative Desulfurization of Fuels Technologies: From Chemistry to Patents José Luis García-Gutiérrez1*, Irene Patricia Lozano2, Fidencio Hernández-Pérez1, Georgina C. Laredo1 and Federico Jimenez-Cruz1* 1

Programa de Investigación en Procesos de Transformación, Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, San Bartolo Atepehuacan, México 07730 D.F. Mexico; 2Programa de Administración del Conocimiento y Patrimonio intelectual. Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, San Bartolo Atepehuacan, México 07730 D.F. Mexico Received: October 03, 2012

Revised: November 28, 2012

Accepted: December 04, 2012

Abstract: At present, a large number of research centers and private companies worldwide have been interested in the development of Oxidative Desulfurization (OD) processes to reduce the sulfur levels in transportation fuels. The application of this OD expertise has given rise to innovative technologies, which could be integrated with existing HydroDeSulfurization (HDS) units in a revamp situation for the efficient production of cheap and environmentally friendly fuels. The literature in this area is extensive due to the amount of research performed in the last 10 years. However, there are few reviews addressing different issues of OD. To our knowledge, only a review specific for OD processes has been published previously. In this review, we present and discuss the results obtained in the development of new catalytic systems for OD process, with the aim of understanding the State of the Art based on information published in scientific, technological and patent information sources through bibliometric and content analysis tools, and also integrating the status of the commercial development of the technology. It should be noticed that chemistry process in this technology involves the oxidant system, the catalyst, the reaction conditions, the reactor engineering and the extraction process. After the exhaustive revision of the literature, we found that those technologies have a very good present in research and technology developments and a promising future in terms of the potential of commercial applicability.

Keywords: Desulfurization, oxidation, extraction, oxidative desulfurization, oxidesulfurization, hydrodesulfurization, dibenzothiophenes, refractory compounds, sulfones, gasoline, diesel, fuels, catalysis. 1. INTRODUCTION The production of free polluting compounds in fuels is required worldwide. It is well known that the sulfur and nitrogen impurities present in the fuels are an important source of air pollution because acid rain and the negative effect of pollution in control devices. In order to decrease pollution, new specifications for sulfur in fuels have been established in many countries, e.g., in the United States sulfur concentration less than 15 ppmw have been established [1, 2]. In this feature, HydroDeSulfurization (HDS) is the conventional process for removing organosulfur compounds present in crude oils during production of gasoline, diesel and other intermediate distillates. This process is highly efficient in removing thiols, sulfides, disulfides, and some thiophene derivatives, but is less effective in the case of highly substituted thiophenic compounds and dibenzothiophene derivatives with steric hindrance on the sulfur atom (refractory organosulfur compounds), such as 4,6dimethyldibenzothiophene (4,6-DMDBT), which are present *Address correspondence to these authors at the Programa de Investigación en Procesos de Transformación. Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, San Bartolo Atepehuacan, México 07730 D.F. Mexico; Tel: +52 5591756607; Fax: +52 5591758429; E-mails: [email protected], [email protected] 1874-4788/12 $100.00+.00

in diesel fuel with sulfur concentrations of the order of 400 ppmw [3, 4], see (Fig. 1). It is possible to increase the effectiveness of HDS against refractory compounds by using higher temperatures and pressures, more active catalysts or longer residence times [5]. However, these alternatives are costly to refineries and may have an impact upon the global selectivity of the process. This fact has stimulated research in deep HDS, as well as the development of alternative or complementary desulfurization technologies for the production of clean fuels [6]. An interesting alternative technology to meet the low sulfur specifications in fuels is the Oxidative Desulfurization (OD) process, also called Conversion/Extraction Desulfurization (CED) or OxiDeSulfurization (ODS). In this, the organosulfur compounds, particularly the refractory compounds, are oxidized to their corresponding sulfones, and these products are removed by extraction, adsorption, distillation or decomposition [7-12]. The chemistry can be represented by the (Fig. 2). In the OD process the reactivity of organosulfur compounds is increased with the increase of electron density on the sulfur atom. The reactivities of DBT derivatives are influenced by the electron donation of substituted alkyl groups. Thus, the reactivity decrease in the order of 4,6-DMDBT > 4-MDBT > DBT, reversing the order of reactivities for HDS [13], see (Fig. 1). © 2012 Bentham Science Publishers

Recent Patents on Chemical Engineering, 2012, Vol. 5, No. 3

Dialkyl disulfide R-S-S-R Alkyl thiophenes (T)

175

-

+

R & D in Oxidative Desulfurization of Fuels Technologies: From Chemistry

R

Relative reactivity in HDS

S

Relative reactivity in OD

Benzothiophene (BT) S

Dibenzothiophenes (DBT) S

4-Methyl dibenzothiophene (4-MDBT) S

4,6-Dimethyl dibenzothiophene (4,6-DMDBT) S

+

-

2-Ethyl-4,6-dimethyldibenzothiophene ((2-E-4,6-DMDBT) S

1000-500

500-300

300-50

99% for DBT in heptane (490 ppmw S) at 333 K. Subsequently, the same authors reported the oxidative desulfurization of diesel fuel with 320 ppmw S using H2O2 at 30 and a 15 wt.% W/ZrO2 catalyst at 333 K and atmospheric pressure [105]. The extraction was carried out with four polar solvents: -butyrolactone, N,Ndimethylformamide, 2-ethoxyethanol and acetonitrile. The authors showed a comparison between the results of sulfur removal of the feedstock by OD process after 60 min. of reaction and with only the extraction process. Thus, the removal percentage of sulfur with OD and extraction process using -butyrolactone, N,N-dimethylformamide, 2ethoxyethanol and acetonitrile were 72 and 45, 61 and 53, 59 and 40, and 56 and 27, respectively. A detailed study of the solvent effect in OD of DBT/n-hexadecane model mixture using H2O2, W/ZrO2, and methanol, ethanol, acetonitrile, or -butyrolactone as oxidizing reagent, catalyst and extraction solvents, respectively, were carried out by the same authors [104]. -Butyrolactone was the solvent that could remove the highest quantity of DBT. Also, DBT oxidation reactivity is highest in -butyrolactone, either with or without catalyst. This result agrees with other studies [107]. Finally, the authors propose an oxidation mechanism involving the formation of surface peroxo-metal intermediates as was supported by Raman spectroscopy (Fig. 8). [100, 104, 105] Likewise, 5, 10, 15, and 20 wt.% W/TiO2 catalysts were prepared by impregnating aqueous (NH4)2WO4 on hydrous titania nanotubes, which were calcined in air at 773 K [101]. It was observed that after calcination the structure of catalyst transformed to 1 nm tetrahedral Nax(WO4) nanoparticles on the surface of anatase TiO2 nanoparticles. The materials were highly active at 333 K for the DBT/-butyrolactone oxidation by H2O2 in a batch reactor in the absence of external mass transfer limitations. The DBT oxidation yields quantitatively the corresponding sulfone with 100 % selectivity, showing a linear dependence on the W surface density at concentrations below 6.9 W/nm2 (maximum activity). The apparent kinetic constants were calculated assuming a pseudo-first order reaction. The turnover rates during the oxidation of DBT suggest that isolated W atoms in tetrahe-


dral coordination are at least twice as active as octahedral ones. W=O

+ H 2O 2 _ _ HO W OOH

W(O 2) W(O 2)

+ +

_ _ HO W OOH W(O 2)

+

(1) H 2O (2)

DBT

W=O

+

DBT

DBTO

W=O

+

DBTO

(3) 2

(4)

Fig. (8). A proposed mechanism to DBT oxidation using H2O2 through the formation of surface peroxo-tungsten intermediates W(O2).

This way a series of mesoporous phosphotungstic acid/TiO2 (HPW/TiO2) nanocomposites with HPW content of 9.5-28.1 wt.% have been synthesized by evaporationinduced self-assembly method. These nanocomposites were used as catalysts for OD of model fuel, which was composed of DBT and hydrocarbon, and used H2O2 as oxidant. Catalytic oxidation results show that the catalysts are very active in refractory bulky molecule organosulfur compounds in fuel oil. The oxidative removal of DBT increases as the HPW content increases. The mesoporous HPW/TiO2 also shows high selectivity for DBT oxidation in the DBT–petroleum ether–benzene system In addition, the mesoporous HPW/TiO2 catalyst shows excellent reusing ability [108]. In order to achieve the advantages of both the mesoporous silica support and monovacant lacunary Keggintype POMs associated to quaternary ammonium salt, a novel mesoporous material (C19H42N)4H3(PW11O39)/SiO2 with different (C19H42N)4H3(PW11O39) loadings (6.3-19.4 wt.%) was prepared by direct sol-gel method. This material showed high oxidation activity for OD of DBT using H2O2 as oxidizing reagent, and reduced its sulfur contents from 500 to 0.2 ppmw corresponding to 99.96 % sulfur removal in 90 min. [109]. Yan et al. [99] reported the use of HPW/SiO2, with Keggin-type heteropolyacids encapsulated in a SiO2 framework as the catalyst for OD of diesel fuel. The desulfurization of diesel was carried out with H2O2 as the oxidant and acetonitrile as the extraction agent in the temperature range 323-353 K. The sulfur content in diesel was reduced to as low as 4886 g/g from an initial level of 438 g/g. Oxidation of model compounds showed that both electron density and the steric hindrance affected the reactivity of the organosulfur compounds. Thus, the reactivities of the organosulfur compounds studied followed the order: DBT > 4,6-DMDBT > BT. The loss in catalytic activity was negligible even after five cycles of use, and there was enhanced reduction of the sulfur content as the immobilized phosphotungstic acid concentration increased. Layered double hydroxides (LDHs) with Mg2+ and Al3+ cations in the brucite-like layer and W-containing anions in the interlayer have been prepared by direct ion exchange of an MgAl-NO3 LDH precursor with tungstate anions [65,97]. The material characterization indicated the presence of both WO42 and W7O246 anions in the interlayer gallery. The catalytic oxidation of thiophenes and thioethers was investigated using H2O2 (30 wt.% in H2O) as oxidizing agent in the


181

presence of W-containing LDH as catalyst. They used various organic solvents miscible in water. W-containing LDHs are active catalysts and promote the fast oxidation of organosulfur compounds under mild reaction conditions. However, the catalytic activity depends on the nature of the Wcontaining anions. On the other hand, the kinetic modeling of OD using H2O2 over tungsten-containing layered double hydroxide using the experimental data provided by Hulea et al. [97] was carried out [110]. Several alternate micro-kinetic models based on elementary kinetic mechanisms were evaluated and discriminated. Further, an economic index is presented regarding the economic aspects of the novel catalytic technology with the parameters obtained during regression analysis. Drago et al. [102] reported that tungstate-doped porous carbons are very effective catalysts for the oxidation of sulfides with 30 % aqueous H2O2. The novel feature of these catalysts is that they are active under basic conditions. Similarly, it was reported that an immobilized 12tungstophosphoric acid on an anion exchange resin (PWA/AER) catalyzes the oxidation of DBT and 4,6DMDBT with H2O2 in an octane/acetonitrile biphasic system. Sulfones were the major product [98]. The oxidation rates increased with increasing amounts of H2O2 and PWA/AER. The oxidative desulfurization of diesel oil containing 330 ppmw S was performed using PWA/AER as catalyst. The sulfur content in diesel oil was reduced to below 50 ppmw. PWA/AER is reusable since the catalytic activity did not decrease even after five re-uses. Mesoporous TiO2 materials were prepared with tetrabutyl titanate as the precursor, PWA as the catalyst and quaternary ammonium bromide as the structure-directing agent by a modified sol-gel process [111]. Octadecyltrimethylammonium bromide (STAB) was the best structure-directing agent. The TiO2 materials prepared by STAB exhibited a well disordered wormhole-like mesostructure without discernible long-range order due to agglomeration of TiO2 nanoparticles. W-TiO2 prepared with STAB showed specific contents of Ti, W, and P of 39.7, 9.9 and 0.09 %, respectively. No PWA was found in TiO2 materials. The evaluation of the catalytic oxidative desulfurization activity of these mesoporous TiO2 materials was carried out using DBT in n-octane (3000 or 300 ppmw) and H2O2 in a batch system at 343 K. In the case of the DBT solution with an initial concentration of 3000 ppmw, TiO2 prepared by STAB was the best catalyst. About 45 % DBT conversion was achieved within 10 min. TiO2 prepared by DTAB showed the least catalytic reactivity towards DBT, 20 % DBT conversion after 10 min. A rise in the reaction temperature from 333 to 353 K led to a remarkable increase in the reaction rate. DBT conversion substantially increased with temperature, from 29 % at 333 K to 60 % at 353 K for a 10 min. reaction time. The reaction rate with low DBT initial concentrations was much higher than that of a higher concentration mixture. DBT removal from a 300 ppmw DBT-octane mixture was as high as 98 % after 2 min. of reaction. The H2O2 concentration had a strong influence on the reaction rate. The reaction rate decreased when the H2O2 concentration decreased. No DBT removal was detected in the absence of H2O2, suggesting that TiO2 adsorptive removal of the sulfur species over the mesoporous

182 Recent Patents on Chemical Engineering, 2012, Vol. 5, No. 3

TiO2 material does not happen, in spite of its large surface area and pore volume. Therefore, DBT removal in the experiment was due to the catalytic oxidation with H2O2 as the oxidant. DBT oxidation was catalyzed less effectively by TiO2 materials prepared without STAB, and only 80 % conversion of DBT was achieved within 10 min. The difference in the catalytic reactivity of these TiO2 materials suggests that the mesoporous structure has an important effect on DBT desulfurization. Larger pore volume and pore size will facilitate DBT mass transfer and therefore the rate of DBT oxidation. Experiments showed that no DBT conversion was detected when PWA was used as catalyst under the same conditions. It is estimated that TiO2 catalysts show good catalytic activity because PWA is introduced into the TiO2 structures rather than existing as a free solid acid. Thus, it is estimated that W in TiO2 is the active site for DBT oxidation. It was proposed that W6+ peroxide is formed in the presence of H2O2 and it further reacts with the sulfur compound by inserting oxygen into the S-atom of the DBT molecule. Kinetics of DBT oxidation with TiO2 prepared via the STAB-assisted route was investigated. Several authors have carried out the OD of organosulfur model compounds and fuels using supported molybdenum oxides [102, 107, 112-117]. Mo/Al2O3 catalysts were prepared and evaluated for OD of T, 2,5-DMT, BT, DBT and 4,6-DMDBT in heptane or diesel fuel with H2O2 in a batch reactor by Garcia-Gutierrez et al. [107, 117]. The catalyst was prepared by equilibrium adsorption using several molybdenum precursors and aluminas with different acidity values. Characterization by various techniques suggests the presence of hydrated hepta- and octamolybdates as well as phosphate ions on the surface of alumina (Fig. 9). There was an effect of the molybdenum precursor of the synthesized catalysts on the sulfur elimination of model solutions as well as of diesel fuel, the activity decreased in the order: phosphomolybdic acid > ammonium phosphomolybdate > molybdenum trioxide > ammonium dimolybdate > ammonium heptamolybdate > ammonium molybdate > sodium molybdate. An increase in support

García-Gutiérrez et al.

acidity, the presence of phosphate on the catalyst support and the use of a polar aprotic solvent as -butyrolactone markedly increased the oxidation activity. Likewise, the oxidation reactivity of the organosulfur compounds in the phosphomolybdic acid-based Mo/Al2O3–H2O2 system decreased in the order: 4,6-DMDBT > DBT > BT > 2,5-DMT > T. The activity was linearly correlated with the calculated electronic density in the sulfur atom of these compounds [117]. In this way, it was possible to reduce the sulfur level in diesel from about 320 to less than 10 ppmw at 333 K after 75 min. of oxidation reaction followed by solvent extraction in situ. It should be noticed that the catalyst was reused several times in the OD of diesel fuel without loss in activity and without leaching. The effect of the reaction time, reaction temperature, concentration of solvent and hydrogen peroxide and content of molybdenum in the catalyst were investigated. Additionally, on the basis of the results obtained a mechanistic proposal for this reaction was set forth. It appears that the oxidation mechanism involves a nucleophilic attack of the sulfur atom on peroxo species of hepta- and octamolybdates (Fig. 10), whereas a mechanism involving the presence of singlet oxygen was discarded [107]. Typical HDS catalysts have also been evaluated for the OD process. As an example, we have the oxidation of a mixture of T (3000 ppmw), BT (3000 ppmw) and DBT (2000 ppmw) in hexadecane using a commercial CoMo/Al2O3 catalysts and a batch reactor operated at 333K [113]. Hydrogen peroxide 30 wt.% in H2O was the reducing agent and the extraction of the oxidation products was done with acetonitrile. The results indicated that after 20 min. of reaction the conversion of T, BT and DBT were 67, 59 and 54 %, respectively. The authors infer from the results that the catalyzed decomposition of the H2O2 competes with the OD. Drago et al. [102] reported that molybdate doped porous carbons are very effective catalysts for the oxidation of sulfides with 30% aqueous H2O2. The novel feature of these catalysts is that they carry out oxidations under basic conditions.

Acetonitrile phase

R1

2H2O2 2H2O

[MonO2n+10](20-2n)Hepta- and octamolybdate supported on alumina

R2

S O O DBT sulfone alkylated

R1

[MonO2n+8(O2)2(H2O)2n-14](20-2n)Diperoxo species supported on alumina

R2

S

R3

DBT alkylated

320 ppmw S Diesel phase

R1, R2, R3 = H, Me, Et

n=7,8

Fig. (9). Catalytic desulfurization of diesel by OD process using the Mo/-Al2O3-H2O2 system.

10 ppmw S >

R3



183

Fig. (10). Proposed mechanism for the oxidation of organosulfur compounds by the Mo/-Al2O3 – H2O2 system.

A 7 wt.% Cr2O3/ZnAl2O4 catalyst was prepared by impregnation of zinc aluminate [17, 118] with an alcoholic solution of chromium nitrate. This catalyst was evaluated in the OD of a mixture of T (3000 ppmw), BT (3000 ppmw) and DBT (2000 ppmw) in hexadecane. H2O2 30 wt.% in water was the reducing agent and the solvent was acetonitrile. The experiments, performed at 333 K reveal that after 20 min. the conversion of T, BT and DBT was roughly 68, 58 and 50 %, respectively. A 0.05 wt.% Cr/Ti-MCM-22 material were used to catalyze the oxidation of DBT/iso-octane (1000 m/mL S) with H2O2 in acetonitrile as solvent at mild reaction conditions [119]. The oxidation activity of Cr modified Ti-MCM-22 increased slightly compared with Ti-MCM-22. Thus, the conversion of DBT was 65, 83 and 95 % at 303, 313 and 323 K, respectively. Several researchers have reported that vanadosilicate molecular sieves catalyze the oxidation of aromatics, alkanes, olefins, and alkyl sulfides. Thus, in recent OD studies, V-based catalysts with different supports have been evaluated [120-124], showing high S-removal of a commercial diesel fuel and a model diesel with organonitrogen compounds using H2O2. 3.3.2. The Group 5: Vanadium In this context, Shiraishi et al. [121] investigated an OD process for commercial LGO using a vanadosilicate molecular sieve as the catalyst and H2O2 as the oxidizing agent in a batch system. Three types of vanadosilicates having different structures, such as VS-1 (MFI structure), VS-2 (MEL structure), and V-HMS (hexagonal mesoporous silica), were hydrothermally synthesized. The catalytic activities of the

vanadosilicates were studied using an acetonitrile solution containing a pure organosulfur compound (DBT and BT) and organonitrogen compounds (aniline, indole, and carbazole) with a concentration of 11 mM, where the mesoporous vanadosilicate showed high activity. In the case of LGO, it was mixed with acetonitrile containing the required amount of H2O2. DBT and BT, dissolved in acetonitrile, were converted quantitatively into the corresponding sulfoxides and sulfones on the vanadosilicates at 333 K in 1 h. The catalytic activity lies in the order: V-HMS > VS-2 > VS-1. Although V-HMS appears to be the most effective catalyst for the oxidation of DBT and BT, with this catalyst a larger amount of H2O2 is consumed during the reaction. The order agrees reasonably well with the sequence of average pore diameters for the catalysts. This suggests that it is difficult for the bulky DBT and BT molecules to penetrate the small micropores of VS-1 and VS-2, but they can easily penetrate the large mesopores of V-HMS. V-HMS also accelerated the desulfurization of the LGO. The sulfur content of the LGO decreased from 425 to less than 50 ppmw. The lower conversion of DBT obtained using V-HMS at 363 K is caused by the complete decomposition of H2O2 via the radical species, which are thermally decomposed. During the process, organonitrogen compounds were also removed successfully from the LGO. Thus, the applicability of V-HMS for the denitrogenation was examined. The results indicated that V-HMS is also effective for the denitrogenation of LGO. The reactivity of the compounds on V-HMS lies in the order of DBT > aniline > indole > BT > carbazole, suggesting that the carbazole is the most difficult compound to oxidize among the organonitrogen compounds. The product of carbazole and indole was a polymeric structure. Nitrobenzene was the sole


oxidation product of aniline with H2O2 in the presence of VHMS. The effects of aromatic hydrocarbons on the oxidation of organosulfur compounds and the oxidation selectivity were also studied. V-HMS oxidizes the organosulfur compounds very effectively even in the presence of aromatic hydrocarbons (tetralin and naphthalene). Finally, the VHMS, recovered following the reaction, could not be reused for further treatment of LGO. OD of diesel and real diesel fuel was conducted in presence of various vanadium-based catalysts in a batch reactor at 333 K [78, 125-127]. Vanadia on alumina, titania, ceria, niobia, silica (SBA-15 mesoporous silica material) and mixed oxides as alumina–titania and silica-alumina were prepared by thermal spreading (TS), incipient wetness impregnation (IWI), and/or and sol-gel (SG) synthesis. Each catalyst was prepared with a V2O5 loading equivalent to a monolayer coverage, which corresponds to 0.1 wt.% of V2O5/m2 of support. Additionally, several catalysts with various V2O5 loading were prepared in order to compare the preparation method effect and on OD reactivity of benzothiophenic compounds.: V2O5/Ti (5, 10, 12 and 15 wt.%, by TS and IWI), V2O5/Nb2O5 (2, 4, 6, 10 and 20 wt.%, by TS), V2O5/Al2O3 (17 wt.%), V2O5/Al2O3–TiO2 (7.5, 15.0 and 22.5 wt.%, by TS), and V2O5/SBA-15 (5 and 10 wt.%, by IWI). The synthetic diesel was prepared with 936 ppmw S: 308 of BT, 224 of DBT, 209 of 4-MDBT and 195 of 4,6DMDBT in hexadecane. Commercial diesel fuel with 350 ppmw S, and with additional amounts of DBTs (800 and 1005 ppmw S) was used. Results showed that S-removal and yield to DBT sulfone were close to 99 % using vanadia on titania as catalyst and H2O2 in about 30 min. and this decreased in the order: alumina > titania > niobia > Al-Ti mixed oxide > SBA-15. While the oxidation activity of DBTs for vanadia catalyst supported on niobia or alumina presented higher catalytic activity than all the other catalysts (niobia > alumina > SBA-15 > titania > ceria > alumina– titania). The oxidation activities increased with increasing V loading up to the equivalent of a monolayer: 12 wt.% V2O5/Ti, 15 wt.% V2O5/Al2O3–TiO2 and 6 wt.% V2O5/Nb2O5. Under the experimental conditions above described, the oxidation reaction of benzothiophene compounds led directly to the corresponding sulfone. Sulfoxides were not detected in the products. In general, TS method presents slight advantages over the IWI method, because it is very simple to achieve and can increase OD activities. For all catalysts, OD of BT, DBT, 4-MDBT and 4,6-DMDBT decreased in the following order: DBT > 4-MDBT > 4,6DMDBT > BT. The efficiencies of OD of diesel fuel (with 350, 800 and 1005 ppmw S, using the V2O5/Al2O3 , V2O5/TiO2 and V2O5/Al2O3-TiO2, were up to 99 % and the sulfur level was below 10 ppmw. During OD there were no significant changes in either distribution or concentration of paraffinic hydrocarbon (C9-C2). However, the concentration of aromatic compounds decreased slightly due to extraction into the solvent. To V2O5/Al2O3 catalysts, [127] results evidenced the presence of different superficial V species, which depend on both vanadium loading and preparation method, while significant differences in OD activity were observed due to the catalysts preparation method. Thus, catalysts prepared by IWI resulted in better dispersed V species than TS. SG catalysts have a strong interaction with alumina, and OD


activity decrease with increasing V loading while their reducibility exhibits a reverse trend. IWI method produced a higher amount of vanadium Lewis acidic sites compared with TS and SG methods according to adsorption results. Apparently the V Lewis acidic sites could be related to OD activity. [127] In general, It was reported [120] that organonitrogen compounds present the OD activity when the vanadium oxide catalysts-H2O2 is used. The OD activities decrease in this order: quinoline > indole > carbazole. The poisoning by indole during OD of DBTs using the vanadium-based catalysts was very strong with V2O5/Al2O3 and V2O5/Nb2O5, and slightly less so with V2O5/TiO2 and V2O5/CeO2 [125]. 3.3.3. The Group 4: Titanium Titanium is considered highly active for oxidation reactions. There have been numerous reports for preparation and application of titaniosilicate (TS-1) for oxidation of various small organosulfur compounds such as sulfides, mercaptans, thioether, and thiophene using aqueous H2O2 as oxidizing agent [64, 128-134]. However, TS-1 suffers from intracrystalline diffusion limitations owing to the small size of the zeolite micropores. This limitation is very pronounced for oxidation of bulky organosulfur compounds such as DBT and prohibits their wide use in the OD process. Ti-HMS is a Ti-containing mesoporous molecular sieve, which possesses large pores (2-3 nm), and exhibits good properties for the oxidation of bulky reactants and products, and hoped to be used to overcome the diffusion limitation [135-139]. Thus, Ti-HMS exhibited excellent activity in the removal of organosulfur compounds such as BT, DBT and 4,6DMDBT for model oil using H2O2 as oxidant [140-141]. BT and its derivatives are oxidized into their corresponding sulfoxides or sulfones which are then removed by simple liquid-liquid extraction. However, continuous decomposition of H2O2 was observed during the reaction at 333 K. In the other hand, in order to avoid H2O2 decomposition, It is generated H2O2 in situ from H2 and O2 by Au/Ti-HMS [142], the bulky organosulfur compounds are expected to be eliminated by an oxidation process. Similarly, a novel Ti-containing SBA-16-type mesoporous material (with various Ti loadings of 5, 10, and 15 wt.%) showed high activity in the OD of DBT by H2O2 and its activity was not reduced even after three times recycling; further reuse resulted in a gradual decrease in its activity [143]. The oxidative removal of organsulfur compounds from model fuel with H2O2 over Ti-containing molecular sieves in the presence of organonitrogen compounds had been studied. It has been shown that pyridine and pyrrole have adverse impact on the oxidation of thiophene and lead to the decrease of corresponding removal rate. The pyridine has stronger influence than pyrrole. Quinoline and indole have no impact on the final removal rate of thiophene. However, the two kinds of nitrides, as well as carbazole, have obvious impact on the oxidation removal of DBT and 4,6-DMDBT. The effect of nitrides on OD can be attributed to the strong adsorption of nitrides and their oxidized products on the active sites of catalysts. For pyridine and quinoline, which are basic


nitrides, their adsorptions on catalysts are even stronger than that of sulfides [144]. 3.3.4. The Group 7: Rhenium Oxidation of sulfides [145], disulfides [146], and sulfoxides [147] to corresponding sulfones has been studied, using methyltrioxorhenium (CH3ReO3) and H2O2 or urea-H2O2 adduct (UHP) under homogeneous conditions [148]. Recently, Crucianelli et al. [149] studied the oxidation of BTs and DBTs derivatives, of model fuel and authentic diesel fuel with homogeneous and heterogeneous rhenium catalysts based on CH3 ReO3 and H2O2. Excellent results in terms of both conversion of substrates and yields of sulfones were also obtained. Heterogeneous rhenium catalysts were stable systems to be used for several runs without any appreciable reduction of reactivity and selectivity. 3.3.5. The Group 10: Palladium Oxidation of a mixture of organosulfur compounds with H2O2 using supported Pd as catalysts has been studied by Zapata et al. [118]. The palladium catalysts (1 wt.%) were prepared by impregnating the Al2O3, MgO-Al2O3, and ZrO2 with an aqueous solution of PdCl2.2H2O. The organosulfur compounds-hexadecane solution was prepared with T (3000 ppmw), BT (3000 ppmw) and DBT (2000 ppmw). The catalysts were evaluated at 333 K in the OD reaction using a batch glass reactor. H2O2 30 wt.% in H2O was the reducing agent and the solvent was acetonitrile. The reaction time was 50 min. The Pd/MgO-Al2O3 catalyst showed a conversion of 85, 81 and 78 % for T, BT and DBT, respectively. Use of Pd/Al2O3 and Pd/ZrO2 resulted in a similar conversion for the three organosulfur compounds. Oxidation of DBT/iso-octane solution with H2O2 over 0.05 wt.% Pd/Ti-MCM-22 in acetonitrile after 3 h showed much higher conversion than that of Ti-MCM-22 [119]. Thus, the conversion of DBT at different reaction temperature was 79, 93 and 100 % to 303, 313 and 323 K, respectively. In the case of Ti-MCM-22 the conversion of DBT was 60, 72 and 85% at 303, 313 and 323 K, respectively. Further studies found that MCM-22 and Pd/MCM-22 had no activity for DBT oxidation at same reaction conditions. It appears that Ti atoms play a decisive role in the oxidation of organosulfur compounds. 3.3.6. The Group 11: Silver and Gold Wang et al. [150] reported an effective Ag/TS-1 (0.06 wt.%) catalyst for OD of organosulfur compounds in gasoline. This catalyst was prepared by impregnation. The oxidation of organosulfur compounds was performed in a batch reactor using 10 mL of thiophene solutions with a sulfur content of 1000 μg/g or FCC gasoline, 0.05 g of the catalyst and 10 mL of water containing H2O2. The resulting mixture was stirred for 4-24 h at 333 K. In general, the catalytic performance of TS-1 for selective oxidation of thiophene improved in the presence of Ag. There were differences in selective oxidation of thiophene solutions between Ag/TS-1 and TS-1 (blank test). Thiophene can be oxidized by H2O2 in water in the presence of alkane and aromatics over TS-1, but in the presence of alkenes such as n-octene, TS-1 shows no activity toward thiophene oxidation. The activity for thiophene oxidation is also poor in n-octane-1,5-hexadiene.


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When using Ag/TS-1, the activity for thiophene oxidation in n-octane-n-octene increased significantly. Ag/TS-1 exhibits better performance in model gasoline composed of thiophene/n-octane-1,5-hexadiene. Ag/TS-1 also shows higher activity than TS-1 during oxidation of thiophene in n-octane. The thiophene conversion was only 42.2 % over TS-1 in 30 min., while it was 78.4 % in 30 min. with Ag/TS-1. The catalytic performance does not differ much for the model gasoline consisting of the alkane-aromatics between the two catalysts. For selective oxidation of thiophene in n-octane the activity of the catalyst with Ag loadings of 0.6 and 0.01 wt.% does not change much compared with that of TS-1. In model gasoline composed of thiophene in a mixture of noctane and n-octene, the catalytic activity decreased with the amount of Ag loaded onto the catalyst. The results suggest that the Ti species of TS-1 probably are covered by the Ag species. On the other hand, the results showed that the sulfur content in FCC gasoline was lowered from 136.5 to 18.8 μg/g after 4 h using Ag/TS-1 (0.06 wt.%) catalyst, while TS1 does not show any selective sulfur removal. The authors proposed that the existence of Ag active species was responsible for the selective adsorption of the organic sulfur, and then the sulfur was oxidized at the Ti sites. Thus, a large amount of Ag loading will adversely influence the performance of TS-1 because it will sterically hinder the oxidation of organic sulfur. Recently, 0.01, 0.05 and 0.10 wt.% Au/Ti-MCM-22 catalysts, prepared by impregnation of Ti-MCM-22 with HAuCl4, were evaluated in the oxidation reactions of T, BT, DBT and 4,6-DMDBT with H2O2 [119]. The OD experiments were carried out in a batch reactor. In a typical oxidation reaction, the 100 mg of solid catalyst was stirred with 10 mL of model organosulfur compounds in iso-octane 1000 ppmw, 10 mL acetonitrile and H2O2 in aqueous solution 30 wt.% (O/S molar ratio of 2:1 to 4:1) for 3 h at 313 K. Among these catalysts, Au/Ti-MCM-22 with 0.05 wt.% Au gave the highest activity. In comparison, the oxidation activity of TiMCM-22, 0.05 % Au/Ti-MCM-22 was higher activity for T, BT, DBT and 4,6-DMDBT than Ti-MCM-22. The conversion percentage of T, BT, DBT and 4,6-DMDBT increased from 55 to 71, 68 to 90, 60 to 84, and 50 to 68, respectively. The improvement was probably due to the adsorption of organosulfur compounds on the metal. The main oxidative product was the corresponding sulfone (90 %). Other products identified were sulfuric acid (about 5 %), sulfoxide and biphenyl. The conversion of DBT increased with the reaction temperature or O/S ratio. 3.3.7. The Group 2: Magnesium The oxidation of thioethers to sulfones using calcined hydrotalcite has been reported by Cheng et al. [151]. In this context, the oxidation of DBT by H2O2 was performed using hydrotalcite in the range 1.82 < Mg/Al < 5.79 as catalysts and nitriles (acetonitrile, benzonitrile, acrylonitrile, 3methoxypropionitrile) or methanol as solvents in a batch reactor. The oxidation reaction was investigated under the following conditions: 0.05 M substrate, 10 g/L catalyst, and O/S mol/mol 10, at 333 K. High activity is found only after calcination followed by rehydration of hydrotalcite. The reaction is initially first-order, and the rate goes through a maximum as a function of the concentration of DBT, sug-


gesting competitive adsorption between DBT and H2O2 . Likewise, the initial rate reaches a maximum at about 333 K. The best solvent was acetonitrile, while much lower reaction rates were observed in methanol. Decomposition of H2O2 does not occur in the absence of nitrile. The hydrotalcites selectivity for the decomposition of H2O2 to oxygen increased with the reaction temperature and is the major reaction above 353 K. These results are in agreement with the decomposition of an iminoperacid intermediate oxidant formed by the base-catalyzed addition of H2O2 to the nitrile via perhydroxyl anion specie [8]. The activity increases with increasing Mg/Al ratio due to a lower rate of H2O2 decomposition attributed to a lower basicity of the solid. The activity reached by this process is comparable to that obtained with Ti-BEA as catalyst under similar reaction conditions [7]. Since conversion reached 34 % in 120 min., the rate was 5.6105 mol/ming for Ti-BEA, while for hydrotalcite, the rate was 1.2105 mol/ming. The specific activity per square meter would favor hydrotalcite (surface area 20 m2/g) compared to Ti-BEA (470 m2/g). 4. OXIDATIVE DESULFURIZATION USING ALKYL PEROXIDES Soluble alkyl peroxides, such as tert-butyl hydroperoxide (TBHP) [120, 152-159] and cyclohexanone peroxide (CYHPO) [160, 161], provide an efficient and simple OD process by homogeneous oxidation; nevertheless, their cost is still greatly concerned for developing an industrial feasible process. TBHP has shown interesting OD results when it was employed with catalysts and it has been suggested for continuous processes [154, 162, 163]. The oxidation of DBT in kerosene was conducted with TBHP in the presence of 11 wt.% CrO3/Al2O3 catalyst [112]. This catalyst was prepared by the same impregnation method with Al2O3 using chromium nitrate. The oxidation experiments were carried out with a fixed-bed flow reactor packed with 1 g of catalyst particles. Typical oxidative reaction conditions were as follows: atmospheric pressure, WHSV=60 h-1, O/S molar ratio = 1.5, 383 K. The W/ZrO2 catalyst was also used for OD of DBT, but now using TBHP in decane. This OD system showed good yield and selectivity for oxidation of DBT [96]. Recently, Yang et al. [103] reported the use of PWA/SBA-15 as a catalyst and sorbent, a material combining the mesoporous structure of SBA-15 and the Keggin structure of phosphotungstic acid, H3PW12O40 (PWA), for the oxidation-adsorption desulfurization of solutions of DBT in isooctane using TBHP as oxidant. In this case, DBT formed a polar DBT sulfone that readily adsorbed on PWASBA-15. It was possible to remove 90 % of the DBT in the solution in one-step. The oxidation of DBTs with TBHP in kerosene was catalyzed by 35 % WO3/Al2O3 in a fixed-bed flow reactor [112]. Conversion of DBT was 78.76 % at 383 K. The oxidative reaction conditions were the same as those used in the case of 11 % CrO3/Al2O3 mentioned before. Ishihara et al. [164] reported the oxidation of DBT in kerosene with TBHP using a fixed-bed flow reactor for a series of Mo catalysts supported on Al2O3 with various Mo


contents. The results indicated that the oxidation activity of DBT increased with increasing Mo content up to about 16 wt.% and decreased when Mo content was beyond this value. Thus, in order to know the oxidation reactivities of organosulfur compounds in the OD process the oxidation of BT, DBT, 4-MDBT, and 4,6-DMDBT dissolved in decalin was also carried out on 16 wt.% Mo/Al2O3 catalyst with TBHP. The results show that the oxidation reactivities of these sulfur compounds decreased in the order: DBT > 4-MDBT > 4,6-DMDBT >> BT. Analyses of the oxidative reactions of the organosulfur compounds suggested that the oxidative reaction of organosulfur compound can be treated as a firstorder reaction. The authors propose a peroxidic oxidation mechanism of DBT on MoO3 catalyst with TBHP, the peroxide reacts with DBT to produce DBT sulfoxide, and further oxidation produces the corresponding sulfone. The oxidation of the sulfoxide to the sulfone occurred by the same mechanism [112]. Likewise, under similar conditions the oxidation of organosulfur compounds present in a desulfurized light gas oil (LGO) with a content of 39 ppmw S was performed with TBHP and 16 wt.% MoO3/Al2O3 catalyst. The oxidation activity of the organosulfur compounds in the LGO increased when the oxidant/sulfur (O/S) molar ratio increased up to 15; the activity slightly decreased for higher ratios. This optimal ratio was significantly higher than the stoichiometric one (equal to 2) because of parallel oxidation reactions of olefins, etc., present in the LGO. Then, according to the proposed global process, the previously oxidized molecules in the treated LGO were further removed by adsorption over a silica gel at ambient temperature. As a result, the sulfur content could be decreased after oxidation/adsorption below 5 ppmw. Likewise, the effect of organonitrogen compounds such as indole, quinoline, acridine, carbazole for OD of light gas oil with MoO3/Al2O3-TBHP was studied by same authors [155]. Jeong et al. [115] report the OD of 4,6-DMDBT to the corresponding sulfone using TBHP as an oxidant over 15 wt.% MoO3 catalysts supported on alumina and Siral 1 at 353 K in a batch reactor with a feed comprising 4,6-DMDBT (1000 ppmw S) dissolved in 80:20 mixture of toluene and hexane. 3 wt.% bismuth oxide promoted Mo/Siral 1 catalyst was also prepared and its activity compared with that of the unpromoted catalysts. The conversions of 4,6-DMDBT after 2 h were 84, 95 and 100 % for the catalyst based on alumina, Siral 1 and Bi-Siral 1, respectively. The Bi-Mo/Siral 1 catalyst also showed high conversion with appreciable stability up to 300 h on stream during OD of light cycle oil (LCO, 8000 ppmw S) in batch and fixed bed reactor conditions. The performance of the catalysts was correlated well with the molybdenum oxide dispersion and acidic properties of the support [115]. The effect of the support acidity agrees with that reported by Garcia-Gutierrez et al. [107, 117]. Corma et al. [158] also studied the OD of model solutions of T, 2-MT, BT, 2-MBT, DBT, 4-MDBT, and 4,6DMDBT, as well as simulated and industrial diesel in a continuous fixed-bed reactor using TBHP and MoOx/Al2O3 catalysts. The catalysts were active, but rapid deactivation occurred due to metal leaching (about 20 % of Mo after 8 h of reaction) and sulfone adsorption. This last observation is


contrary to results reported by Garcia-Gutierrez et al. [117] and Jeong et al. [115]. Similarly, the oxidation of DBT (400 ppmw) dissolved in sulfur-free liquid paraffin oil was carried out using TBHP as an oxidant in the presence of two commercially available NiMo/Al2O3 catalysts (catalyst A: 16.3 wt.% Mo, 3.3 wt.% Ni; catalyst B: 22.0 wt.% Mo, 2.9 wt.% Ni) using a fixed-bed continuous-flow reactor and reaction temperatures ranging from 353 to 413 K [116]. The oxidized liquid products were collected after reaching steady state for 2 h for each of the reaction conditions studied. The oxidized diesel sample was passed through an adsorption column packed with alumina. The concentration of the DBT model organosulfur compound was reduced to 36 and 9 ppmw using catalysts A and B, respectively, from the feed level of 400 ppmw. The results of the study on model solution were compared by carrying out similar experiments on diesel fuel. The sulfur in the diesel fuel was 387 ppmw with the speciation: C1-DBT (5.6 ppmw), 4,6-DMDBT (125 ppmw), Other C2-DBTs (17.1 ppmw), C3-DBTs (156.1 ppmw) and C3+-DBTs (83.2 ppmw). The studies were carried out by changing reaction conditions such as O/S molar ratio, WHSV, temperature, etc., to achieve product diesel with sulfur content below 20 ppmw. The sulfur content in product diesel at similar operating conditions of 413 K, 22 O/S ratio, and 9 h-1 WHSV, using Ni-Mo catalysts A and B were found to be 38 and 14 ppmw, respectively. The kinetics of desulfurization was studied [116]. The oxidation of organosulfur compounds in kerosene was conducted with TBHP in the presence of 10 wt.% V2O5/Al2O3 in a fixed-bed reactor [112]. The reaction conditions were similar to the case of 11 wt.% CrO3/Al2O3 already mentioned. The conversion of DBT was 53 % at 383 K. Similarly, OD of synthetic diesel was carried out with V2O5/Al2O3-TBHP, the sulfur removal achieved was lower than that with V2O5/Al2O3-H2O2 [164]. 5. OXIDATIVE DESULFURIZATION USING MOLECULAR OXYGEN Molecular oxygen is an environment-friendly and abundantly available cheap oxidant and its use is attractive in fuel desulfurization if it could oxidize organosulfur compounds under acceptable conditions. However, only a few studies dealt with this oxidant [50, 165-167]. Manganese and cobalt oxide catalysts supported on Al2O3 (2-13 wt.%) were found to be effective in catalyzing air oxidation of the organosulfur compounds in model and real diesel fuel to corresponding sulfones [168, 169]. Model diesel was prepared by adding equimolar amounts of DBT, 4-MDBT, 4,6-DMDBT and 4,6-DEDBT to n-tetradecane to make up a solution with a sulfur content of 400 ppmw. The oxidation experiments in this study were carried out with 20 mL of model diesel, 20-30 mg of catalyst in a batch system at a temperature range of 363-453 K, during which air was introduced via a gas disperser at a constant flow rate of 100 mL/min. while the reaction mixture was stirred throughout the experiment. The oxidized products in the model diesel were extracted after the completion of the reaction. On the other hand, 150 mL real diesel underwent OD reaction in the presence of about 100 mg of catalyst at temperature range of


187

403-473 K. The sulfones were removed by extraction with polar solvent (acetonitrile, dimethylformamide, 1-methyl-2pyrrolidinone and methanol). Among the polar solvents tested, 1-methyl-2-pyrrolidinone was the most efficient in extracting organosulfur compounds from both diesel and oxidized diesel. The effects of metal loading and reaction temperature were investigated. Thus, catalysts with higher metal loading led to higher conversions in the temperature range 403-473 K. The best results were obtained with catalysts containing the highest MnO2 loadings (11 and 13 wt.%) at 453 K. Similar results were observed for the oxidation of real diesel. The thiophenes conversion increased with time and it reached its maximum conversion of about 80-90 % at 8 h. The oxidative reactivity of the model thiophene compounds follows the order of 4,6-DEDBT > 4,6-DMDBT > 4MDBT > DBT. Oxidation of model compounds showed that the most refractory organosulfur compounds in HDS of diesel were more reactive in OD process. Similar results were obtained with real diesel containing approximately 450 ppmw S. The conversion of the substituted thiophenes to corresponding sulfones was in the range of 57-90 % depending on the catalyst, solvent and temperature. The selectivity was about 90-100 %, because some of the organosulfur compounds were over oxidized and converted into SO2. The oxidized diesel was analyzed for diesel specification parameters, such as density, cetane index, pour point, kinematic viscosity, etc. The studies show that the olefin content of the diesel was increased and aromatic content of the diesel decreased substantially. Cetane index increased approximately 20 %. Density and other parameters were within the required limits. Lubricity of the treated diesel increased a substantial amount. This OD process shows advantages, for example, the reaction can be carried out using inexpensive oxygen from air, compared to costly oxidants, such as H2O2 or ozone. In addition, the use of air as oxidant also eliminates the need to carry out any oxidant recovery process that is usually required if liquid oxidants (TBHP or H2O2) are used. Likewise, Ma et al. [170] explored a novel OD method of liquid hydrocarbon fuels, which combines a catalytic oxidation step of the sulfur compounds directly in the presence of molecular oxygen and an adsorption step of the oxidationtreated fuel over the activated carbon. Deep OD of DBT using molecular oxygen was performed in the presence of iron tetranitrophthalocyanine (FePc(NO2)4) catalyst in non-polar hydrocarbon solvent under water-free condition [171]. Conversion of DBT in decalin reached 98.7 wt.% at 373 K and 0.3 MPa of initial pressure with 1 wt.% of FePc(NO2)4 over a whole solution after 2 h. Activity of iron phthalocyanines with different substituents decreases in the order of FePc(NO2)4 > NFePc(NO2)3 > NH2NFePc(NH2)4, reversing the order of electron density of Pc resonance ring. Conversion of DBT using FePc(NO2)3NH2 supported on polyacrylic cationic exchange resin reached nearly the level of FePc(NO2)4. The activity of FePc(NO2)4 was kept unchanged after 5 cycles, whereas activity of FePc(NO2)3NH2 and FePc(NH2)4 decreased. OD of the model fuel, 500 μg/g solution of DBT in decalin, was performed based on the catalytic oxidation using molecular oxygen. The lowest sulfur content in the model fuel could be decreased to less than 4 μg/g after the treatment of this oxidation and a combined adsorption.


Lu et al. demonstrated a new aerobic OD process of gasoline-range organosulfur compounds using ceria supported Pt and Cu catalysts, [50] or Hydrotalcite-like compounds derived CuZnAl oxide catalysts [172]. By mixing the fuel with a small amount of air at near 573 K and atmospheric pressure within a continuous fixed bed reactor, the organosulfur compounds in the fuels can be catalytically converted to SO2. Such mild experimental conditions, combined with the fact that the SO2 product can be scrubbed by passing an on-line adsorber, make aerobic OD of gasoline an attractive process for applications in a compact and efficient on-board gasoline fuel processor. In concept, this reaction can be performed in the fuel evaporator unit of a gasoline fuel processor and only a SO2 adsorber needs to be added before the reformer. Choudary et al. [173] reported the first example of direct oxidation of sulfide to sulfone with excellent yields by an osmate molecular system. Thus, osmate-exchange Mg-Al layered double hydroxides catalyzed the delivery of two oxygen atoms simultaneously via a 3 + 1 cycloaddition to sulfide to form sulfone directly. The catalyst is easily recoverable and reusable. Various studies on the OD process have reported the use of O2/aldehyde [16, 168]. Rao et al. [174, 184] reported oxidation of acyclic sulfides. Kaneda et al. [175] reported oxidation of DBT at elevated temperature. Nobile et al. [176178], Song et al. [179], and Rao et al. [180] studied acyclic sulfides oxidation in the presence of metal catalysts. Murata et al. [60] studied oxidation of DBT and alkyl DBTs in the presence of various metal salts as catalysts and extended these studies for oxidative OD of diesel. Higher DBT conversion rates were observed at lower temperature for Co(II) and Mn(II) acetates (90 %, in 15 min.). The cost of co-oxidants and the loss of fuel during the separation of organic acids are the major disadvantages for this technology. Zub et al. [181] took use of metal phthalocyanines as catalysts for direct oxidation of mercaptanes by O2, and similarly Sun et al. [182] investigated the oxidation of sulfides using O2 in the presence of immobilized aluminum tetrasulfophthalocyanine in methanol–water solution. The oxidation of DBT by an oxygen/aldehyde system using catalysts based on Mn, Co and Ni, was examined. In all instances, Co- and Mn-based systems were the most active catalysts. In contrast, a markedly lower activity was measured for Ni(II) acetate whereas NiO and the aluminasupported NiO were inactive [183]. Nobile et al. [176-178] show that a mixture of sacrificial iso-valeraldehyde, oxygen or air, and a Co(II) supported resin in 1,2-dichloroethane can oxidize alkyl- and arylsulfides to the corresponding sulfoxides or sulfones at room temperature and atmospheric pressure. The heterogeneous catalytic copolymers were obtained by reaction of Co(2(acetoacetoxy)-ethyl-metacrylate)2 with acrylamides. The supported complexes were recyclable with negligible loss of efficiency and did not suffer from metal leaching. In this way, under suitable conditions excellent conversions and very good selectivities can be achieved to oxidation of dimethylsulfide, di-n-butylsulfide, diphenylsulfide, di-tertbutylsulfide, dibenzylsulfide and p-tolylmethylsulfide. Ac-


cording to results, it was suggested that the oxidation proceeds first via high yields of sulfoxides and then through almost complete transformation into sulfones. Cobalt oxide catalysts supported on alumina (2 and 5 wt.% Co3O4/Al2O3) have been found to be effective in catalyzing air oxidation of the sulfur compounds in real diesel to corresponding sulfones [16, 168]. The sulfones were removed by extraction with polar solvent. The catalysts were prepared by impregnation of Al2O3 pellet with cobalt nitrate aqueous solution using an incipient wetness method. The oxidation experiments were carried out with 15 mL of diesel fuel (450 ppmw S) in a batch system in the presence of about 20-30 mg of catalyst and bubbled with air (100 mL/min.). Among the polar solvents tested, 1-methyl-2-pyrrolidone was found to be the most efficient in extracting organosulfur compounds from both diesel and oxidized diesel. The conversion of the sulfur compounds to corresponding sulfones was in the range of 47-71 % depending on the type of catalysts and solvent. For example, when oxidation was carried out with 2 wt.% Co3O4/Al2O3 at 403 K treated diesel showed a sulfur content of 237 and 129 ppmw after extraction with 10 mL of acetonitrile and 1-methyl-2-pyrrolidone, respectively. The effects of metal loading and reaction temperature were investigated. Below 383 K, the oxidation reaction was not observed. There was no significant difference in conversions for the oxidation of model diesel catalyzed by either 2 or 5 wt.% Co3O4/Al2O3 at 403 or 423 K. In this context, recently, It was reported [25] for the first time results on oxidation of DBT, 4-MDBT, 4,6-DMDBT, and organosulfur compounds present in HDS diesel using the aldehyde/molecular oxygen system in the absence of metal catalyst and removal of oxidized organosulfur compounds from HDS diesel by solvent extraction/adsorption. According to literature, heterogeneous oxidation of organosulfur compounds using O2 involved aldehydes as cooxidants, which transfer O2 from gas-phase to liquid-phase by itself oxidation to peroxyacids, which has been used for OD process [25, 67]. In general, aldehydes are known to undergo autoxidation by a free radical chain mechanism that involves the oxidation of the aldehyde to the corresponding acyl radical [185]. The acyl radical then reacts with O2 to form the corresponding peracid, which is capable of oxidizing an additional aldehyde molecule to the corresponding acid. Although the autoxidation of aldehydes occurs at ambient conditions, the reaction rate can be increased by the use of metal catalysts [186]. Other species present in the reaction solution can also be oxidized by the generated peracid, resulting in the oxidation of sulfides to sulfoxides and sulfones [187-189]. 6. OTHER SYSTEMS (MISCELLANEOUS) Ultrasound-assisted OD has been proposed using H2O2, phosphotungstic acid and a phase transfer agent, such as tetraoctylammonium bromide and/or fluoride [74, 190, 191], a biphasic diesel–acetonitrile system with H2O2 and sodium carbonate [192] and Fenton’s reagent [49], complexes [193], and CF3COOH/titanosilicates [194]. Aquasonolysis of thioethers [195] and thiophenes and its derivates has been also reported [196]. Regarding desulfurization, ultrasoundassisted OD process can play an important role in future


technology to produce low and/or ultra-low sulfur fuels, offering a non-hydrogen consuming with lower cost when compared to conventional HDS technology. Although this technology can be considered as an attractive strategy to desulfurize fuels few studies related to the application of ultrasound have been reported in the petroleum field [49, 74, 190, 192,]. The application of this photochemical oxidation to desulfurization has been reported in some literatures [52, 197203], using oil–water and oil–polar solvent two-phase systems. The desulfurization of light oil to a sulfur content of less than 0.05 wt.% has been achieved successfully. However, ultraviolet irradiation was found to be essential to oxidize DBTs, and the desulfurization hardly progressed at wavelength of 400 nm. Considering there are some interesting recent examples of using ionic IL as medium for photochemical reaction or photocatalyst at room temperature, so a novel coupling technique of desulfurization by combination of photochemical oxidation and ionic liquid extraction without any catalyst was explored at room temperature [203]. That is, the IL [bmim]PF6 was used to be the extractant and photochemical reaction medium in the oxidation of organosulfur compounds in the presence of H2O2 and UV irradiation. 7. STATE OF THE ART IN OXIDATIVE DESULFURIZATION PATENTS The development of the OD process for fuels using air, oxygen, nitrogen oxides, nitric acid or ozone as oxidant has been ongoing for over 70 years [204-208]. Guth and Diaz [209] proposed an oxidative process for treating diesel by using nitrogen oxides as the oxidant. The results show an increase of sulfur elimination with respect to the percentage of sulfur elimination in previous patent [206]. However, in the presence of oxygen, nitrogen oxides do not yield the appropriately oxidized organosulfur compounds in distillate hydrocarbons without creating many undesirable byproducts e.g., nitro-aromatic compounds, oxiranes and arylalkanes. The authors also propose the use of methanol, ethanol, a combination of the two, and mixtures of these and water as an extraction solvent for polar molecules. Guth et al. [210] patented the desulfurization of petroleum oils using nitrogen oxides and oxygen to convert organic sulfur into sulfur trioxide, which absorbed in sulfuric acid. Other oxidative processes using nitric acid or nitrogen oxides have been patented by Schulz et al. [211], and Tam et al. [212, 213]; in these processes the oxidized products were removed by solvent extraction. Darian and Sayed-Hamit [214] also proposed the use of nitrogen oxides to oxidize sulfur- and nitrogen-containing compounds followed by extraction using two solvents. The decrease in sulfur and nitrogen compounds reported in this patent are consistent with those expected from their incomplete oxidation followed by extraction. Paris-Marcano reported in two patents the oxidative desulfurization of petroleum using nitric acid with H2O2 [215, 216]. More recently, Murata et al. [217] patented the oxidation of organosulfur compounds in diesel fuel with molecular oxygen in the presence of cobalt catalysts and aldehydes via


189

peracid. They claimed a reduction of sulfur content from 193 to < 5 ppmw in diesel feedstocks. Likewise, Thirugnanasampanthar et al. [218] reported the use of cobalt and manganese based catalysts for air oxidation of DBTs compounds. While Gues et al. [219] reported the use of silica supported iron catalyst for thiophene oxidation with oxygen. Lyapin et al. [220] claim a method and apparatus for oxidizing an organic liquid. The invention further relates to a method and apparatus for producing an oxidizing gas which comprises substantial amounts of ozone. Likewise, Sherman [221] claimed the oxidation of diesel with ozone. Nevertheless, disclosures in this patent indicate an increased interest in the alternate oxidative routes for sulfur removal. Thus, the OD of aromatic sulfur species by H2O2 and peracids have been reported in several patents from different oil companies, dating from 1950’s; for example, Anglo Iranian oil [222], Shell [223], BP [224, 225] and Texaco [226]. In this context [227], organosulfur compounds contained in petroleum fractions are oxidized by contact with a mixture of H2O2 and a carboxylic acid to produce sulfones, which are degraded by thermal treatment to volatile sulfur compounds. Some patents claimed the oxidation and thermal treatment steps are combined with HDS to greatly reduce the hydrocarbon sulfur content. [224, 225] That is, organosulfur compounds were oxidized with peroxide using Ni-V catalyst followed of thermal decomposition by ferric oxide and hydrogenation by Co-Mo catalyst. Likewise, sulfur contaminants in a hydrocarbon fraction are oxidized using H2O2 or other suitable oxidizing reagent to convert bivalent (or divalent) sulfur to sulfones [228]. The hydrocarbon, after having been subjected to oxidation conditions, is then contacted in this case with molten sodium hydroxide to produce a treated product of reduced sulfur content. Several patents claimed the oxidation of thiophene derivatives with H2O2 catalyzed by formic, chloroacetic and fluoroacetic acids [229-232]. The sulfone products can be removed according to a number of possible separations known in the art, such as distillation, extraction or adsorption. Corma et al. [233] claimed an invention related to a material comprised of silicotitanates having a crystalline structure similar to MCM-41 zeolites, said material being characterized in that it contains atoms of titanium in its lattice and channels in its porous structure, making possible its utilization in catalytic reactions wherein are involved large organic molecules, such as the oxidation of thio-ethers to sulfoxides and sulfones using H2O2. Ho et al. claimed a process for removing hard sulfurs from hydrocarbon streams by selectively oxidizing hard sulfurs in a hydrotreated stream under the presence of H2O2 and a peroxometal complex as catalyst into the corresponding sulfoxides and sulfones [234]. Gore et al. of Petro Star Inc. claimed a method for the removal of sulfur- and nitrogen-containing compounds from petroleum distillates by using a selective oxidant to produce compounds that can be preferentially extracted from a petroleum distillate due to their increased relative polarity. Oxidation is accomplished by contacting an oxidant with a distillate under optimum conditions for that distillate and continuing the reaction until oxidized sulfur- and nitrogen-containing


compounds are confirmed. The oxidant is peroxoacetic acid, which is formed by mixing H2O2 and acetic acid. Extraction is accomplished by contacting oxidized distillate with a nonmiscible solvent that is selective for the relatively polar oxidized sulfur- and nitrogen-containing compounds. The oxidized compounds and solvent are separated from the distillated by gravity separation or centrifugation. The distillate is water washed and polished using clay filtration. The extraction solvent is separated from the solvent/oxidized compound mixture by a simple distillation for recycling [235237]. Cabrera et al. from UOP claimed a process for the desulfurization of hydrocarbonaceous oil, in which is contacted with a HDS catalyst in a HDS reaction zone to reduce the sulfur level to a relatively low level and further contacting the resulting hydrocarbonaceous stream from the HDS zone with an oxidizing reagent to convert the residual. The resulting stream containing the sulfur-oxidated compounds is separated after decomposing any residual oxidizing reagent to produce a stream containing the sulfur-oxidated compounds and a hydrocarbonaceous oil stream having a reduced concentration of sulfur-oxidated compounds. The process uses oxidizing reagents such as H2O2 and carboxylic acids, and a solid catalyst based on transition metals [238]. Aida claimed many oxidants as being essentially equal in their ability to oxidize sulfur- and nitrogen-containing compounds using H2O2 [239]. However, many of these oxidants are not selective and others are non-effective and producing numerous side reactions and various undesirable byproducts. Fajula et al. [240, 241] proposed a method for selectively desulfurizing thiophene compounds contained in hydrocarbons derived from crude oil distillation. It involves oxidizing the thiophene sulfur atoms into sulfone in the presence of H2O2 followed by separation of said sulfonated compounds from said hydrocarbons. The thiophene compounds are oxidized in a two-phase turbulent medium comprising a hydrocarbon phase and an aqueous phase, in the presence of at least an oxidizing reagent soluble in at least one of the two phases and of at least a metal catalyst in soluble or dispersed form in a liquid or in solid form, separation and oxidation occurring simultaneously. Stowe disclosed a process to oxidatively desulfurize hydrocarbon oil with ultrasonic assistance [242]. Cullen from Petrosonics patented an oxidative, reactive, ultrasonic desulfurization technology [243]. In this way, the oxidation of crude oil was carried out by H2O2 in the presence of a catalyst, surface-active agent and radiation with sonic energy. Ohsohl of Unipure has registered two patents for desulfurization of crude oil [244, 245]. Likewise, Unipure registered four patents for OD using performic acid [246-249]. In these patents, the authors claimed an alternative for ultra-low desulfurization process, which is based on a two liquid phase reactive extraction using a hydrogen peroxide-organic acid mixture. The organic acid is unspecified, although formic and acetic acids are typical. In this way, the organosulfur species are oxidized to sulfones at near atmospheric pressure and mild temperature. The reaction consumes a relatively insignificant amount of oxidant. Conversion to sulfones is complete with reactor residence times of less than five minutes. After separation from the oil, the aqueous phase, con-


taining spent catalyst and some of the sulfones, is sent to a recovery section for removal of sulfones and regeneration of the catalyst. The resulting sulfones are extracted by methanol and separated by flash distillation of the methanol-sulfone mixture. The treated diesel stream is neutralized and any remaining sulfones are adsorbed on an alumina bed, which is regenerated by washing with methanol. The methanol is then also regenerated. The product diesel oil then contains 5 ppmw S or less. Levy et al. claimed that the dibenzothiophene sulfone generated in the oxidation process is converted into biphenyl and hydrogen sulfide by hydrogenation under mild conditions [248]. Figueras et al. claim another chemical oxidation process to remove sulfur from fuels by the use of H2O2 [250]. This process is based on the use of a calcined tungsten supported on titania or zirconia catalyst. Mei et al. proposed an effective OD of diesel by phosphotungstic acid, tetraoctyl ammonium bromide, H2O2 and ultrasound using acetonitrile as an extraction solvent for oxidized products [251]. Yoo et al. proposed an oxidative/adsorptive process, having as a first step the oxidation of organosulfur compounds in hydrocarbons using any conventional oxidant to form an oxidized organosulfur compound. The oxidant is selected from the group consisting of organic peroxides, organic hydroperoxides, organic peracids and mixtures thereof [252]. In a second step, the oxidized sulfurcontaining hydrocarbon is contacted with a metal to form a metal-sulfur-containing compound. This process is distinguished from conventional HDS because the sulfur is immobilized in the form of a metallic sulfur compound rather than converted to hydrogen sulfide. In this features, a hydrogen atmosphere is apparently needed in order to effect the reduction of oxidized sulfur to the metal sulfur compound. Recently, a novel process effective for the removal of organosulfur compounds from liquid hydrocarbons was claimed. [253, 254] The process more specifically addressed to the removal of thiophene and derivatives thereof from a number of petroleum fractions, including gasoline, diesel fuel, and kerosene. In the first step of the process, the liquid hydrocarbon is subjected to oxidation conditions in order to oxidize at least some of the thiophene compounds to sulfones with alkyl hydroperoxide, peroxides, percarboxylic acids or oxygen. The oxidation step is carried out in the presence of an oxidation catalyst comprising a solid carrier, such as molecular sieve or an inorganic metal oxide, having a metal deposited thereon. Then, these sulfones can be catalytically decomposed to hydrocarbons (e.g., hydroxybiphenyl) and volatile sulfur compounds, such as sulfur dioxide, by a solid decomposition catalyst selected from the group consisting of layered double hydroxides, molecular sieves, inorganic metal oxides, and mixtures thereof. The hydrocarbon decomposition products remain in the treated liquid, while the volatile sulfur compounds are easily separable from the treated liquid using well-known techniques such as flash vaporization or distillation. On the other hand, a crude oil is dissolved in petroleumether and treated with tert-butyl hydroperoxide, t-BuOOH (TBHP), in the presence of a molybdenum catalyst, the re-


moval of oxidized organosulfur compounds was carried out using a hydrocarbon with 3-6 carbon atoms [255]. A similar oxidative desulfurization process for crude oil was claimed [256], which is based on TBHP oxidation assisted by vanadium catalysis. Lyondell oxidative desulfurization technology has been described [257]. In this case, the fuel and TBHP are co-fed over a fixed bed catalyst, at mild temperatures and pressures, in order to keep the TBHP/fuel mixture in a liquid state and to maintain the hydraulic pressure required to move the fuel stream over the fixed bed catalyst.


the cost of OD. Thus, the organic stream can be blended into the CED raffinate or sold separately as a solvent or petrochemical feed. In the case of biological treatment, microbes can strip the sulfur from the compounds creating a stream of raffinate that could be blended back into the CED raffinate. This way, experiments have shown sulfur removal to levels as low as 10 ppmw beginning with a 4200 ppmw-sulfur diesel fuel while not adversely affecting other fuel properties. The CED process can function as a stand-alone process or be installed after an existing HDS unit to reach the ultralow sulfur. Early in 2000, Petro Star announced a pilot scale study of the CED process operable by late that year, and to build the first CED unit at a Petro Star refinery to process 5,000 bbl/day of straight run diesel fuel by after three years [258].

8. PROCESS DESIGN AND COMMERCIAL DEVELOPMENT Petro Star Inc. has been developing a technology called Conversion/Extraction Desulfurization (CED) process to remove sulfur from diesel fuel [258-263]. The CED process is based on the oxidation of the organosulfur compounds present in fuels to their corresponding sulfones using a stoichiometric amount of peroxyacetic acid, which is formed by mixing H2O2 and acetic acid. This is followed by liquid/liquid extraction by a polar non-miscible solvent, or solvent cocktails, to yield a fuel low in sulfur and an extract high in sulfur [259]. The extraction solvent is then removed from the extract for re-use and the concentrated extract is made available for further processing to remove sulfur and return some of the hydrocarbon yield, see (Fig. 11). However, it was observed that a small amount of organosulfur compounds, oxidized organosulfur compounds and other polar compounds may remain in the raffinate after liquid/liquid extraction so that an additional polishing to remove effectively may be required. In this context, the use of some sulfones adsorbent materials, e.g., clay, silica gel, and alumina have been tested with great success. These materials are being considered based on their cost, efficiency, and ease of recycling.

Nowadays, the cost for HDS of $3.50-$5.50 per bbl of converted feed for a 5000 bbl a day unit makes this process difficult for the small refiner to justify. High capital costs and the lack of economics of scale, combined with hydrogen production facilities, Claus units, tail gas scrubbers, etc. combine to make the process uneconomic for the small refiner [258]. Thus, the CED process is feasible because variable operating costs are relatively low; the oxidation reaction is carried out at relatively low temperatures, 348 to 369 K, and ambient pressure with a residence time of less than 30 min. It is this step where most of the costs occur. H2O2 , used to make the peroxyacetic acid, is most expensive single operating cost with nearly half of the operating costs, see Table 1. In the case of liquid/liquid extraction, low extraction temperatures tend to improve the solvent selectivity for the sulfones and eliminate the need for costly heat [259]. Recycled extraction solvent will reduce the need for a fresh supply. So, this step will contribute little to the operating cost. With regard to raffinate polishing, a small stream of high sulfur extract will be created during the adsorbent recycle and will be mixed into the concentrated extract stream that goes to extract treatment. The extract/solvent produced in the liquid/liquid extraction will go to a solvent recovery stage. This is accomplished using a small distillation unit. The solvent vapors will be recovered and available for re-use as extraction solvent.

On the other hand, it is proposed that the high sulfur extract stream (about 15 % of the fuel feed). can be sent to a coker, blended into asphalt, burned as refinery fuel with stack scrubbing, or available for either biological or further chemical treatment. Chemical treatment of the extract can be used to oxidize the sulfur to a free sulfate, sulfite, or sulfonate with a conversion up to 95 %. In the case of sulfone can be converted to a surfactant which could be sold to the soap industry, the sales of the surfactant could offset much of

Extraction solvent Oxidant

Oxidation

Diesel fuel

Sulfone extraction

Extraction Solvent Recovery

Solid phase adsorption

Extract treatment

Low sulfur diesel fuel

Desulfurized hydrocarbon extract Sulfate, sulfite, etc. salts

Fig. (11). Diagram of the CED process [258].

191


Table 1.


Petro Star Inc.: CED Process Economic Viability Assessment [258].

Assumptions: Plant capacity

10,000 BPSD, 95 % annual operating rate [345 d/y]

Total installed

$12 million, year 2000, Gulf Coast location

Capital cost

$1,200/BPSD=$3.47/BPSY

Feedstock

AGO or VGO with 0.30 wt.% S and 25 wt.% aromatics

Product raffinate

30 ppmw max. S and 17 wt.% max. aromatics

Example of economic feasibility assessment Operating Costa

Unit Consumption/bbl

Cost ¢/Unit

Cost, ¢/bbla

Oxidant

3.25 lb

35(70%soln.)

114

Solvent loss

0.1 lb

30

3

Catalyst

0.1 lb

1

1

Process heat (steam)

80 Ib

0.4

32

Electricity

2 kwh

7

14

Operator and supervision

-

-

15

Maintenance expenses

-

-

8

General and administrative

-

-

8

Capital related charges (11 years, 8 % interest, capital recovery factor 0.140)

-

-

49

Total a

244

Estimated order-of-magnitude based on multiple feasible design options.

Petro Star carried out a comparison of untreated LAGO and treated LAGO by CED process [259]. Sulfur levels are markedly lower after processing (from 4,720 to 70 ppmw), and two other important properties improve, API Gravity and Cetane number. The treated LAGO showed an increases in API Gravity, from 33.3 to 35.4 °API, and Calculated Cetane Index, from 49 to 53, which is result from removal of aromatic compounds in the diesel fuel. Additional tests for smoke point and gum formation do not show a significant divergence from the norm. Tests for nitrogen show an expected decrease indicating this process may be useful for nitrogen removal as well. Similarly, a sample of jet fuel containing 1400 ppmw S was desulfurized by CED process. The treated sample was below detection limits of 10 ppmw S. The tests showed a 25 % decrease in the amount of sediment formed from the untreated sample. This improvement indicates the removal of organosulfur compounds from a fuel favorably affects the long-term storage stability of that fuel.

commercial-scale. The company has demonstrated this process in a small continuous pilot unit for diesel. Thus, the fuel and TBHP are co-feed over a fixed bed catalyst with a temperature less than 366 K and less than 7 atm. The oxidation takes place in less than 10 min. with near quantitative conversion of the thiophenes to sulfones. Subsequently, the unreacted TBHP is decomposed or removed from the fuel, because hydroperoxides decreased the store stability of fuels, similarly, the t-Butyl alcohol by-product is removed from the fuel during post processing. The removal of the sulfones from the fuel is affected, for example, by low cost solvent extraction process. The extraction solvent is recovered by distillation and reused. The solvent is taken overhead and the sulfones are concentrated as a heavy stream. Several options exist for disposition of sulfone stream, including processing in the coker or sending for bioprocessing. The t-butyl alcohol that is produced as a co-product of the oxidation along with that which serves as a diluent for the TBHP is recovered.

Similar to CED process by Petro Star, the Lyondell OD process converts the sulfur compounds to sulfones, which are subsequently removed from the fuel either by solvent extract or by adsorption [264-273]. Unlike to other OD Processes based on H2O2 and require the recycle of an organic acid cooxidant, the Lyondell OD process uses TBHP, this oxidant is completely fuel soluble, making it well suited for oxidative process. Lyondell’s proprietary catalyst, while not currently used in any commercial process, has been produced on a

Lyondell Chemical Company has demonstrated that OD offers a lower capital alternative to HDS [264-267]. The nature of process makes it well suited to be used as a finishing process to reach ultra-low sulfur fuels and has advanced to the state where it is nearing commercialization. This way, Lyondell has been developing oxidation desulfurization for both gasoline and diesel, however, this has been focus on converting diesel fuel with 350-500 ppm of sulfur to ultralow sulfur fuel with less than 10 ppmw S [264]. Lyondell has


achieved over 3000 h of continuous operation in a laboratory-scale continuous pilot unit, with near quantitative oxidation of the sulfur to sulfones. Either solvent extraction or adsorption of the oxidized fuel stream produces a fuel with less than 10 ppmw S. Over this period a limited amount of deactivation of the catalyst has been observed. Based on the results obtained thus far in this work and on prior experience with the catalyst, the catalyst life is estimated to be in excess of one year. The oxidation process results in a darkening of the fuel. While the fuel directly exiting the oxidation reactor has darkened, the final product is nearly colorless after removal of the sulfones and other polar species. The one to two number increase in cetane number has been confirmed over multiple samples and fuels, which is a valuable secondary benefit. t-Butyl hydroperoxide is not as corrosive as peroxyacetic acid. Thus, the Lyondell process has the clear advantages of does not require the use of special materials of construction [264]. With the exception of equipment used in the solvent extraction to remove the sulfones from the fuel, the major pieces of equipment can be constructed from carbon steel. It the extraction should be used to remove the sulfones, it is anticipated that stainless steel may be required for that section of the unit. As a result of the mild process conditions, the capital cost required to install the process in reduced. It was estimated that the capital expenditure required for this implement this process is $600 - $750 per BPD of capacity. This estimate assumes that the unit is constructed on a cleared site and includes all ISBL and project specific OSBL, such as TBHP feed tanks. Based on current estimates [264], it is expected that the cash operating cost for a unit desulfurize low sulfur diesel fuel to ultra-low sulfur diesel with less than 10 ppmw S to be less than 2.5¢ per gallon. Included in this estimate is the cost of the TBHP, all utilities, labor, and taxes and insurance. In this estimate the byproduct t-butyl alcohol is valued at its BTU value, assuming that it is used as fuel within the refinery. The t-butyl alcohol by product can be converted to MTBE or isooctane or used as fuel in the refinery. The choice of either solvent extraction or adsorption will affect the final cost. 9. CURRENT AND FUTURE DEVELOPMENTS In this review, we presented and discussed the results obtained in the development of new catalytic systems for OD process, with the aim of understanding the State of the Art based on information published in scientific, technological and patent information sources through bibliometric and content analysis tools, and also integrating the status of the commercial development of the technology. It should be noticed that chemistry process in this technology involves the oxidant system, the catalyst, the reaction conditions, the reactor engineering and the extraction process. It has been done a bibliometric analysis of 1519 records from the database of Chemical Abstracts and the results give a general landscape of the evolution of the R&D activities at international level. The bibliometric analysis of the information collected leads to the organizations that support the R&D reported in the literature analyzed, are the oriental entities which have the major number of publications, par-


193

ticularly the ones from China and Japan. The other organizations with high frequency of publication are from United States and Mexico. This technology could be integrated with existing HDS units in a revamp situation. At present, some companies worldwide have been involved in the development of OD processes to reduce sulfur level in transportation fuels. After the exhaustive revision of the literature, we found that those technologies have a very good present in research and technology developments and a promising future in terms of the potential of commercial applicability. CONFLICT OF INTEREST The authors confirm that this article content has no conflicts of interest. ACKNOWLEDGEMENTS Declared none. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]

[18]

[19] [20]

[21] [22] [23] [24]

S. F. Venner, Hydrocarbon Process., Int. Ed., 51, 2000, 5. S. Mayo, N. J. Gudde, E. Brevoord, F. Plantenga, G. Hoekstra, Paper AM-02-38, National Petroleum and Refiners Association Annual Meeting, San Antonio, TX, 17–19 March 2002. H. Schulz, W. Böhringer, F. Ousmanov, P. Waller, Fuel Process. Technol., 61, 1999, 5. H. Schulz, W. Böhringer, P. Waller, F. Ousmanov, Catal. Today, 49, 1999 87. I.V. Babich, J. A. Moulija, Fuel, 82, 2003, 607. C. Song, X. Ma, Appl. Catal. B, 41, 2003, 207. V. Hulea, F. Fajula, J. Bousquet, J. Catal., 198, 2001, 179. A.V. Anisimov, E. V. Fedorova, A. Z. Lesnugin, V. M. Senyavin, L. A. Aslanov, V. B. Rybakov, A. V. Tarakanova, Catal. Today, 78, 2003, 319. J. Palomeque, J. M. Clacens, F. Figueras, J. Catal. 211, 2002, 103. L. Wang, C. Li, H. Yingfei, Adv. Mater. Res., 79-82, 2009, 1683. S. Djangkung, S. Murti, H. Yang, K. Choi, Y. Kora, I. Mochida, Appl. Catal. A, 252, 2003, 331. Y. Shiraishi, Y. Taki, T. Hirai, I. Komasawa, Chem. Commun. 1998, 2601. T. Aida, Catalysts & Catalysis, 37(3), 1995, 243. C. Song, Catal. Today, 86, 2003, 211. E. W. Qian, J. Jpn. Pet. Inst., 51(1), 2008, 14. A. Avidan, B. Klein, R. Ragsdale, Hydrocarbon Process., Int. Ed., 80(2), 2001, 1. EPA-Gasoline RIA, Regulatory Impact Analysis—Control of Air Pollution from New Motor Vehicles: Tier 2 Motor Vehicle Emissions Standards and Gasoline Sulfur Control Requirements, US Environmental Protection Agency, Air and Radiation, EPA420-R99-023, December 1999. EPA-RFG-II, Phase II RFG Report on Performance Testing, US Environmental Protection Agency, Air and Radiation, EPA420-R99-025, April 1999. EPA, Control of Air Pollution from New Motor Vehicles Amendment to the Tier-2/Gasoline Sulfur Regulations, US Environmental Protection Agency, April 13, 2001. EPA-Diesel RIA, Regulatory Impact Analysis: Heavy-duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements, US Environmental Protection Agency, Air and Radiation, EPA420-R-00-026, December 2000. EPA, EPA Gives the Green Light on Diesel Sulfur Rule, Press Release, US Environmental Protection Agency, February 28, 2001. EPA, Reducing Non-road Diesel Emissions, US Environmental Protection Agency, April 2003. Directive of the European Parliament and of the Council. Brussels COM(2001) 11.05.2001 241final. J.F. Larive, Hydrocarbon Eng., 4, 2000, 15.

194 Recent Patents on Chemical Engineering, 2012, Vol. 5, No. 3 [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70]

T.V. Rao, B. Sain, S. Kafola, B. R. Nautiyal, Y. K. Sharma, S. M. Nanoti, M. O. Garg, Energy & Fuels, 21, 2007, 3420. G. Yu, S. Lu, H. Chen, Z. Zhu, Energy & Fuels, 19, 2005, 447. C. Komintarachat, W. Trakarnpruk, Ind. Eng. Chem. Res., 45, 2006, 1853. H. Gilman, D. Esmay, J. Am. Chem. Soc., 74, 1952, 2021. B.N. Heimlich, T. Wallace, Tetrahedron, 22, 1966, 3571. A.S. Rappas, US Patent 6,402,940, 2002. T. Aida, US Patent 0,565,324, 1993. T. Aida, D. Yamamoto, Prepr. Pap. Am. Chem. Soc. Div. Fuel Chem., 39, 1994, 623. S. Otsuki, T. Nonaka, N. Takashima, W. Qian, A. Ishihara, T. Imai, T. Kabe, Energy & Fuels, 14, 2000, 1232. G. Yu, S. Lu, H. Chen, Z. Zhu, Carbon, 43, 2005, 2285. T. Aida, D. Yamamoto, M. Iwata, K. Sakata, Rev. Heteroatom. Chem., 22, 2000, 241. P. D. Filippis, M. Scarsella, Energy & Fuels, 17, 2003, 1452. L.F. Ramírez-Verduzco, F. Murrieta-Guevara, J. L. GarciaGutierrez, R. S. Martin-Castanon, M. C. Martinez-Guerrero, M. C. Montiel-Pacheco, R. Manta-Diaz, Pet. Sci. Technol., 22, 2004, 129. P.S. Tam, J. R. Kittrell, J. W. Eldridge, Ind. Eng. Chem. Res., 29, 1990, 321. G.X. Yu, S. X. Lu, H. Chen, Z. N. Zhu, Energy & Fuels, 19, 2005, 447. A.M. Dehkordi, Z. Kiaei, M. A. Sobati, Fuel Processing Technology, 90, 2009, 435. P. Moreau, V. Hulea, S. Gomez, D. Brunel, F. Di Renzo, Appl. Catal. A Gen. 155, 1997, 253. S.E. Abonde, W. Gore, G. E. Dolbear, E. R. Skov, Prepr. Pap. Am. Chem. Soc., Div. Pet. Chem. 45, 2000, 364. S.E. Bonde, D. Chapados, W. L. Gore, G. E. Dolbear, E. Skov, National Petrochemical and Refiners Association (NPRA), Annual Meeting, A M-00-25, San Antonio, TX, March 26–28, 2000. F. Zannikos, E. Lois, S. Stournas, Fuel Process. Technol, 42, 1995, 35. W.-H. Lo, H.-Y. Yang, G.-T. Wei, Green Chem., 5, 2003, 639. K. Yazu, M. Makino, K. Ukegawa, Chem. Lett., 33, 2004, 1306. J. Nehlseh, J. Benziger, I. Kerrekidis, Ind. Eng. Chem. Res., 45(2), 2006, 518. M. Te, C. Fairbridge, Z. Ring, Appl. Catal. A, 219, 2001, 267. K. Yazu, Y. Yamamoto, K. Miki, K. Ukegawa, J. Oleo. Sci. 50(6), 2001, 521. Y. Lu, Y. Wang, L. Gao, J. Chen, J. Mao, Q. Xue, Y. Liu, H. Wu, G. Gao, M.-Y. He, ChemSusChem., 1, 2008, 302. W. H. Lo, H. Y. Yang, G. T. Wei, Green Chem., 5, 2003, 639. L. Lu, S. Cheng, J. Gao, G. Gao, M.-Y. He, Energy & Fuels, 21, 2007, 383. W. S. Zhu, H. M. Li, X. Jiang, Y. S. Yan, J. D. Lu, J. X. Xia, Energy & Fuels, 21, 2007, 2514. D. S. Zhao, J. L. Wang, E. P. Zhou, Green Chem., 9, 2007, 1219. P, Wasserscheid, A. Jess, Green Chem., 6, 2004, 316. Y. Nie, C. X. Li, Z. H. Wang, Ind. Eng. Chem. Res., 46, 2007, 5108. J. Planeta, P. Karasek, M. Roth, Green Chem., 8, 2006, 70. Y. Nie, C. X. Li, A. J. Sun, H. Meng, Z. H. Wang, Energy & Fuels, 20, 2006, 2083. X. C. Jiang, Y. Nie, C. X. Li, Z. H. Wang, Fuel, 87, 2008, 79. S. Murata, K. Murata, K. Kidena, M. Nomura, Energy & Fuels, 18, 2004, 116. C. P. Huang, B. H. Chen, J. Zhang, Z. C. Liu, Y. X. Li, Energy & Fuels, 18, 2004, 1862. A.Bösmann, L. Datsevich, A. Jess, A. Lauter, C. Schmitz, P. Wasserscheid, Chem. Commun., 2001, 2494. L. N. He, H. M. Li, W. S. Zhu, J. X. Guo, X. Jiang, J. D. Lu, Y. S. Yan, Ind. Eng. Chem. Res. 47, 2008, 6890. G. Gao, S. Cheng, Y. An, X. Si, X. Fu, Y. Liu, H. Zhang, P. Wu, M.Y. He, ChemCatChem, 2(4), 2010, 459. A.L. Maciuca, C.E. Ciocan, E. D. Dumitriu, F. Fajula, V. Hulea, Catal. Today, 138(1-2), 2008, 33. F.-T. Li, R.-H. Liu, J.-H. Wen, D.-S. Zhao, Z.-M. Sun, Y. Liu, Green Chem., 11, 2009, 883. K. Yazu, Y. Yamamoto, T. Furuya, K. Miki, K. Ukegawa, Energy & Fuels, 15, 2001, 1535. K. Yazu, T. Furuya, K. Miki, K. Ukegawa, Chem. Lett., 32, 2003, 920. F. M. Collins, A. R. Lucy, C. Sharp, J. Mol. Catal. A: Chem., 117, 1997, 397. H. Li, W. Zhu, J. Lu, X. Jiang, L. Gong, G. Zhu, Y. Yan, React. Kinet. Catal. Lett., 96(1), 2009, 165.

García-Gutiérrez et al. [71] [72] [73]

[74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100]

[101] [102] [103] [104] [105] [106] [107] [108] [109] [110]

J. Gao, S. Wang, Z. Jiang, H. Lu, Y. Yang, F. Jing, J. Mol. Catal. A: Chem., 258, 2006, 261. D. Huang, Z. Zhai, Y. C. Lu, L. M. Yang, G. S. Luo, Ind. Eng. Chem. Res., 46, 2007, 1447. F. Al-Shahrani, T. C. Xiao, S. A. Llewellyn, S. Barri, Z. Jiang, H. H. Shi, G. Martinie, M. L. Green, Appl. Catal. B: Environ. 73, 2007, 311. H. Mei, B. M. Mei, T. F. Yen, Fuel, 82, 2003, 405. P. De Filippis, M. Scarsella, Ind. Eng. Chem. Res., 47, 2008, 973. F. Bigi, A. Corradini, C. Quarantelli, G. Sartori, J. Catal., 250, 2007, 222. F. Villaseñor, O. Loera, A. Campero, G. Viniegra-González, Fuel Process. Technol., 86, 2004, 49. L. C. Caero, E. Hernández, F. Pedraza, F. Murrieta, Catal. Today, 107-108, 2005, 564. D. Huang, Y. J. Wang, L. M. Yang, G. S. Luo, Ind. Eng. Chem. Res., 45, 2006, 1880. X. Jiang, H. M. Li, W. S. Zhu, L. N. He, H. M. Shu, J. D. Lu, Fuel, 88, 2009, 431. X. Jiang, H. Li, W. Zhu, L. He, H. Shu, J. Lu, Fuel, 88, 2009, 431. W. S. Nathan, US Patent 3,284,342, 1966. W. B. Friedrich, US Patent 2,697,682, 1954. C. Li, Z. Jiang, J. Gao, Y. Yang, S. Wang, F. Tian, Chem. Eur. J., 10, 2004, 2277. H. Lü, J. Gao, Z. Jiang, F. Jing, Y. Yang, G. Wang, J. Catal., 239, 2006, 369. S. Vincent, C. Lion, M. Hedayatullah, A. Challier, Phosphorus, Sulfur, and Silicon, 92, 1994, 189. W. Trakarnpruk, K. Rujiraworawut, Fuel Processing Technology, 90, 2009, 411. D. Huang, Y. J. Wang, L. M. Yang, G. S. Luo, Ind. Eng. Chem. Res., 45, 2006, 1880. L. Lu, S. Cheng, J. Gao, G. Gao, M. Y. He, Energy & Fuels, 21, 2007, 383. W. H. Lo, H. Y. Yang, G. T. Wei, Green Chem., 5, 2003, 639. L. N. He, H. M. Li, W. S. Zhu, J. Guo, X. Jiang, J. D. Lu, Y. S. Yan, AIChE Spring National Meeting, New Orleans, L.A. 6 April 2008, code 74098. W. S. Zhu, H. M. Li, X. Jiang, Y. S. Yan, J. D. Lu, L. N. He, Green Chem., 10, 2008, 641. H. Li, L. He, J. Lu, W. Zhu, X. Jiang, Y. Wang, Y. Yan, Energy & Fuels, 23, 2009, 1354. S. Zhang, Z. C. Zhang, Green Chem., 4, 2002, 376. H. Li, W. Zhu, Y. Wang, J. Zhang, J. Lu, Y. Yan, Green Chem., 11, 2009, 810. F. Figueras, J. Palomeque, S. Loridant, C. Fèche, N. Essayem, G. Gelbard, J. Catal., 226, 2004, 25. V. Hulea, A.-L. Maciuca, F. Fajula, E. Dumitriu, Appl. Catal. A: General, 313, 2006, 200. K. Yazu, T. Furuya, K. Miki, J. Jpn Pet. Inst., 46(6), 2003, 379. C. Li, J. Gao, Z. Jiang, S. Wang, H. Lu, Y. Yang, F. Jing, Top. Catal., 35, 2005, 169. E. Torres-García, G. Canizal, S. Velumani, L. F. RamírezVerduzco, F. Murrieta-Guevara, J. A. Ascencio, Appl. Phys. A, 79, 2004, 2037. M.A. Cortes-Jácome, M. Morales, C. Angeles-Chavez, L.F. Ramírez-Verduzco, E. López-Salinas, J.A. Toledo-Antonio, Chem. Mater., 19(26), 2007, 6605. R. S. Drago and D. S. Burns, J. Catal., 166, 1997, 377. L. Yang, J. Li, X. Yuan, J. Shen, Y. Qi, J. Mol. Catal. A: Chemical, 262, 2007, 114. L. F. Ramírez-Verduzco, J. A. De los Reyes, and E. Torres-García, Ind. Eng. Chem. Res., 47(15), 2008, 5353. L. F. Ramírez-Verduzco, E. Torres-García, R. Gómez-Quintana, V. González-Peña, and F. Murrieta-Guevara, Catal. Today, 98, 2004, 289. S. Dhir, R. Uppaluri, M.K. Purkait, J. Hazardous Mater., 161, 2009, 1360. J. L. García-Gutiérrez, G. A. Fuentes, M. E. Hernández-Terán, P. García, F. Murrieta-Guevara, F. Jiménez-Cruz, Appl. Catal. A: General, 334, 2008, 366. X.-M. Yan, P. Mei, J. Lei, Y. Mi, L. Xiong, L. Guo, J. Mol. Catal. A: Chem., 304, 2009, 52. Z. E. Ali Abdalla, B. Li, A. Tufail, Colloids and Surfaces A: Physicochem. Eng. Aspects, 341, 2009, 86. Hulea, A.-L. Maciuca, F. Fajula, E. Dumitriu, Appl. Catal. A, 313, 2006, 200.

R & D in Oxidative Desulfurization of Fuels Technologies: From Chemistry [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138]

[139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158]

D. Huang, Y.J. Wang, Y.C. Cui, G.S. Luo, Microporous and Mesoporous Materials, 116, 2008, 378. D. Wang, E. W. Qian, H. Amano, K. Okata, A. Ishihara, T. Kabe, Appl. Catal. A: General, 253, 2003, 91. B.Zapata, F. Pedraza, M. A. Valenzuela, Catal. Today. 106, 2005, 219. W. Zhu, H. Li, X. Jiang, Y. Yan, J. Lu, J. Xia, Energy & Fuels, 21(5), 2007, 2514. V. V. D. N. Prasad, K.-E. Jeong, H.-J. Chae, C.-U. Kim, S.-Y. Jeong, Catal. Comm. 9, 2008, 1966. V. Selvavathi, A. Meenakshisundaram, B. Sairam, and B. Sivasankar, Pet. Sci. Tech., 26, 2008, 208. J. L. Garcia-Gutierrez, G. A. Fuentes, M. E. Hernandez-Teran, F. Murrieta, J. Navarrete, F. Jimenez-Cruz, Appl. Catal. A, 305, 2006, 15. B. Zapata, F. Pedraza, M. A. Valenzuela, Catal. Today, 106, 2005, 219. X. Si, S. Cheng, Y. Lu, G. Gao, M.-Y. He, Catal. Lett., 122, 2008, 321. L. Cedeño-Caero, J. F. Navarro, Catal. Today, 116, 2006, 562. Y. Shiraishi, T. Naito, T. Hirai, Ind. Eng. Chem. Res., 42(24), 2003, 6034. L. Cedeño, H. Gómez, A. Fraustro, H. Guerra, R. Cuevas, Catal. Today, 133, 2008, 244. H. Gomez, L. Cedeño, Int. J. Chem. Reactor Eng. 3, 2005, A28. L. Cedeño-Caero, J. F. Navarro, A. Gutiérrez-Alejandre, Catal. Today. 116, 2006, 562. L. Cedeño-Caero, H. Gomez-Bernal, A. Fraustro-Cuevas, H. D. Guerra-Gomez, R. Cuevas-Garcia, Catal. Today, 133–135, 2008, 244. L. Cedeño-Caero, E. Hernández, F. Pedraza, F. Murrieta, Catal. Today, 107–108, 2005, 564. H. Gomez-Bernal, L. Cedeño-Caero, A. Gutierrez-Alejandre, Catal. Today, 142, 2009, 227. L.Y. Kong, G. Li, X.S. Wang, Catal. Lett. 92, 2004, 163. L.Y. Kong, G. Li, X.S. Wang, Catal. Today, 93–95, 2004, 341. L. Kong, G. Li, X. Wang, B. Wu, Energy & Fuel, 20, 2006, 896. L. Kong, G. Li, X. Wang, Y. Wang, Chin. J. Catal, 25(2), 2004, 89. Y. Shiraishi, T. Hirai, I. Komasawa, J. Chem. Eng. Jpn., 35, 2002, 1305. V. Hulea, F. Fajula, J. Bousquet, J. Catal., 198, 2001, 179. S. Cheng, Y. Liu, J. Gao, L. Wang, X. Liu, G. Gao, P. Wu, M.-Y. He, Chin. J. Catal., 27, 2006, 547. C. Jin, G. Li, X. Wang, Y. Wang, L. Zhao, D. Sun, Microporous Mesoporous Mater., 111, 2008, 236. Y. Fang, H. Hu, Catal. Commun. 8, 2007, 817. A.Taguchi, F. Schuth, Microporous Mesoporous Mater., 77, 2005, 1. N. N. Trukhan, V. N. Romannikov, A. N. Shmakov, M. P. Vanina, E. A. Paukshtis, V. . Bukhtiyarov, V. V. Kriventsov, I. Y. Danilov, O. A. Kholdeeva, Microporous Mesoporous Mater., 59, 2003, 73. O. A. Kholdeeva, M. S. Melgunov, A. N. Shmakov, N. N. Trukhan, V.V. Kriventsov, V.I. Zaikovskii, M. E.Malyshev, V. N. Romannikov, Catal.Today, 91–92, 2004, 205. C.Z. Jin, G. Li, X. S. Wang, L. X. Zhao, L. P. Liu, H. O. Liu, Y. Liu, W. P. Zhang, X. W. Han, X. H. Bao, Chem. Mater., 19, 2007, 1664. Y. Wang, G. Li, X. S. Wang, C. Z. Jin, Chin. J. Catal. 26, 2005, 567. H. Y. Song, G. Li, X. S. Wang, S. Q. Ma, C. Z. Jin, D. W. Sun, Prepr. Pap. Am. Chem. Soc., Div. Petr. Chem., 52, 2007, 297. A.T. Shah, B. Li, Z. E. A. Abdalla, Journal of Colloid and Interface Science, 336, 2009, 707. Y. Jia, G. Li, G. Ning, C. Jin, Catal. Today, 140, 2009, 192. S. Yamazaki, Bull. Chem. Soc. Jpn., 69, 1996, 2955. Y. Wang, J. H. Espenson, J. Org. Chem. 65, 2000, 104. D. W. Lahti, J. H. Espenson, Inorg. Chem., 39, 2000, 2164. H. Q. N. Gunaratne, M. A. McKervey, S. Feutren, J. Finlay, J. Boyd, Tetra. Lett. 39, 1998, 5655. A.Di Giuseppe, M. Crucianelli, F. De Angelis, C. Crestini, R. Saladino, Appl. Catal. B: Environmental, 89, 2009, 239. Y. Wang, G. Li, X. S. Wang, C. Z. Jin, Energy & Fuels, 21, 2007, 1415. S. S. Cheng, T. F. Yen, Energy & Fuels, 22, 2008, 1400. T. A. Koch, K. R. Krause, L. E. Manzer, M. Mehdizadeh, J. M. Odom, S. K. Senupta, New J. Chem. 20, 1996, 163. J. K. Stanger, J. R. Angelici, Energy & Fuels, 20, 2006, 1757. D. Wang, E. W. Qian, H. Amano, K. Okata, A. Ishihara, T. Kabe, Appl. Catal., A, 253, 2003, 91. A.Ishihara, D. Wang, F. Dumeignil, H. Amano, E. W. Qian, T. Kabe, Appl. Catal. A: Gen., 279, 2005, 279. E.L. Sughrue et al., US Patent 20,040,007,501, 2004. A.Chica, G. Gatti, B. Moden, L. Marchese, E. Iglesia, Chem. Eur. J., 12, 2006, 1960. A.Chica, A. Corma, M. E. Dómine, J. Catal., 242, 2006, 299.

Recent Patents on Chemical Engineering, 2012, Vol. 5, No. 3 [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208]

195

Y. Wang, G. Lente, J. H. Espenson, Inorg. Chem., 41, 2002, 1272. X. Zhou, C. Zhao, J. Yang, S. Zhang, Energy & Fuels, 21, 2007, 7. J. Li, X. Zhou, D. Zhao, J. Fuel Chem. Technol., 34(2), 2006, 249. E.W. Qian, J. Jpn. Pet. Inst., 51, 2008, 14. D. Wang, E. W. Qian, H. Amano, K. Okata, A. Ishihara, T. Kabe, Appl. Catal. A: Gen. 253, 2003, 61. E.W. Qian, F. Dumeignil, H. Amano, A. Ishihara, Prepr. Am. Chem. Soc., Div. Pet. Chem., 50, 2005, 430. W. Y. Liu, Zh. L. Lei, J. K. Wang, Energy & Fuels, 15, 2001, 38. H. Lu, J. Gao, Z. Jiang, Y. Yang, B. Song, C. Li, Chem. Commun., 2007, 150. S. R. Livingston, C. C. Landry, J. Am. Chem. Soc., 130, 2008, 13214. J. T. Sampanthar, H. Xiao, J. Dou, T. Y. Nah, X. Rong, W. P. Kwan, Appl. Catal. B: Environmental, 63, 2006, 85. V. R. Landaeta, L. Gonsalvi, M. Peruzzini, J. Mol. Catal. A, 257, 2006, 112. X. Ma, A, Zhou, C. Song, Catal. Today, 123, 2007, 276. X. Zhou, J. Li, X. Wang, K. Jin, W. Ma Fuel Processing Technology, 90, 2009, 317. L. Gao, Y. Tang, Q. Xue, Y. Liu, Y. Lu, Energy & Fuels, 23, 2009, 624. B.M. Choundary, C. R. V. Reddy, B. V. Prakash, M. L. Kantan, B. Sreedhar, Chem. Comm., 2003, 754. V.T. Rao, B. Sain, K. Kumar, P. S. Murthy, T. S. R. P. Rao, G. C. Joshi, Synth. Commun., 28, 1998, 319. T. Kaneda, H. Daimon, Jpn. Kokai. Tokkyo Koho, 540, 1979. P. Mastrorilli, C. F. Nobile, Tetrahedron Lett., 35, 1994, 4193. M. M. Dell’Anna, P. Mastrorilli, C. F. Nobile, J. Mol. Catal. A: Chem., 108, 1996, 57. M. M. Dell´Anna, P. Mastrorilli, C. F. Nobile, J. Mol. Catal. A: Chemical, IQ8, 1996, 57. G. Song, F. Wang, H. Zhang, X. Lu, C. Wang, Synth. Commun., 28, 1998, 2783. S. Cheng, Y. Liu, J. Gao, L. Wang, X. Liu, G. Rao, P. Wu,M.-Y. He, Chin. J. Catal., 27, 2006, 547. Y. L. Zub, A. B. Pecheny, A. A. Chuiko, T. L. Stuchinskaya, N. N. Kundo, Catal. Today, 17, 1993 31. A.H. Sun, G. C. Zhang, Y. M. Xu, Materials Letters, 59, 2005, 4016. V. Dumont, L. Oliviero, F. Maugé, M. Houalla, Catal. Today, 130, 2008, 195. V.T. Rao, B. Sain, P. S. N. Murthy, G.C. Joshi, G.C. Prasada, T. S. R. P. Rao, Sut. Sur. Sci. Catal., 113, 1998, 920. J.R. McNesby, C. A. Heller, Chem. Rev., 54, 1954, 325. W.Y. Suprun, D. Kiebling, T. Machold, H. Papp, Chem. Eng. Technol., 29, 2006, 1376. P.S. Tam, J. R. Kittrell, J. W. Eldridge, Ind. Eng. Chem. Res., 29, 1990, 324. K. Imagawa, T. Nagata, T. Yamada, T. Mukaiyama, Chem. Lett. 1995, 335. I.V. Khavrutskii, G. M. Maksimov, O. A. Kholdeeva, React. Kinet. Catal. Lett., 66, 1999, 325. M. Wan, T. Yen, Appl. Catal. A, 319, 2007, 237. T.F. Yen, H. Mei, S. H.-M. Lu, US Patent 6,402,939, 2002. A.Deshpande, A. Bassi, A. Prakash, Energy & Fuels, 19, 2005, 28. Y. Hangun, L. Alexandrova, S. Khetan, C. Horwitz, A. Cugint, D. D. Link, B. Howard, T. Collins, J. Prepr. Am. Chem. Soc., Div. Pet. Chem., 47, 2002, 42. A.Treiber, P. M. Dansette, H. El Amri, J. P. Girault, D. Ginderow, J. P. Mornon, J. Am. Chem. Soc., 119, 1997, 1565. Z. Wu, B. Ondruschka, Ultrason. Sonochem., 13, 2006, 371. Z. Wu, B. Ondruschka, Ultrason. Sonochem., 13, 2006, 86. T. Hirai, K. Ogawa, I. Komasawa, Ind Eng Chem Res, 35, 1996, 586. S. Matsuzawa, J. Tanak, S. Sato, I. Takashi, J. Photoch, Photobiol. A, 149, 2002, 183. Y. Shiraishi, T. Hirai, I. Komasawa, J Chem Eng Jpn, 32, 1999, 158. A.Marcinek, Z. Jacek, J. Geübicki, J. Phys. Chem. A, 105, 2001, 9305. C.Lee, T. Winston, A. Unni, R. M. Pagni, G. Mamantov, J. Am. Chem. Soc.118(21), 1996, 4919. M. G. Charles, J. M. Andrew, Chem. Commun. 2000, 1395. D. S. Zhao, R. Liu, J. L. Wang, B. Y. Liu, Energy & Fuels, 22, 2008, 1100. R. Brown, US Patent 2,671,049, 1954. C.Shiah, US Patent 2,834,717, 1958. W.L. Fierce, R. L. Weichman, US Patent 3,135,680, 1964. R.D. Smetana, S. Herbstman, T. C. Mead, US Patent 3,595,778, 1971. S.Herbstman, US Patent 3,719,589, 1973.

196 Recent Patents on Chemical Engineering, 2012, Vol. 5, No. 3 [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247]

E.D. Guth, A. F. Diaz, US Patent 3,847,800, 1974. E.D. Guth, N. L. Helgeson,K. W. Arledge, A. R. Brienza, US Patent 3,919,402, 1975. J.G. Schulz, J. J. Stanulonis, W. R. Wajert, US Patent 4,280,818, 1981. P.S. Tam, J. R. Kittrell, US Patent 4,485,007, 1984. J.R. Kittrell, S. T. Darian, P. S. Tam, European Patent 236 021, 1987. D. Sayed-Hamit, US Patent 4,746,420, 1988. L. Paris-Marcano, US Patent 5,017,280, 1991. L. Paris-Marcano, US Patent 5,087,350, 1992. M. Nomura, S. Murata, Japant Patent 168 663, 2004. J. Thirugnanasampanthar, R. Xu, F. M. Dautzenberg, Worldwide Patent 116169, 2005. J. W. Gues, C. M. A. M. Mesters, R. J. Schoonebeek, Worldwide Patent 030638 A1, 2005. Lyapin et al., US Patent 5,824,207, 1998. J. H. Sherman, US Patent 2001/0015339 A1, 2001. D. Alexander, J. Nobel, British Patent 713 740, 1954. A.B. Webster, R. Righy, US Patent 3,163,593, 1964. J.F. Ford, T. A. Rayne, D. G. Adlington, US Patent 3,341,448, 1967. J.F. Ford, T. A. Rayne, D. G. Adlington, GB Patent 972 803, 1964. E.L. Cole, R. F.Wilson, F. Herbstman, S. Herbstman, US Patent 3,551,328, 1970. A.B. Webster, R. Righy, US Patent 3,163,593, 1964. L. Wallace, US Patent 3,505,210, 1970. T. Aida, F. Izumi, European Patent 565 324 A1, 1993. F. M. Collins, A. R. Lucy,D. J. H. Smith, European Patent 482 841, 1991. T. Aida, F. Izumi, Japanese Patent. 04 072 384, 1998. T. Aida, F. Izumi, US Patent 5,753,102, 1998. A. Corma, T. Navarro, Perez-Pariente J., US Patent 5,783,167. T. C. Ho, C. S. Hsu, G. D. Dupre, R. Liotta, V. Buchholz, US Patent 5, 958,224, 1999. W. Gore et al. U.S. Patent. 6,274,785, 2000. W. Gore et al. U.S. Patent 6,160,193, 1998. W. Gore, S. Bonde, G. E. Dolbare, E. R. Skov, US Patent 6,596,914 B2, 2003. C.A. Cabrera et al., US Patent 6,171,478, 2001. T. Aida, European Patent 93 302 642.9, 1999. F. Fajula, A. Rabion, J. R. Bernard, V. Hulea, Worldwide Patent 01/48119 A1, 2001. F. Fajula, A. Rabion, J. R. Bernard, V. Hulea, French Patent 99 16559, 1999. L. R. Stowe, US Patent 5,547,563, 1995 M. Cullen, US Patent 2004/0074812 A1, 2004. E.O. Ohsol, T. E. Gillespie, J. W. Pinkerton, US Patent 5,985,137, l999. E.O. Ohsol, US Patent 5,948,242, 1997. A.S. Rappas, US Patent. 6,402,940, 2002. A.S. Rappas, US Pantent 6,406,616, 2001.

García-Gutiérrez et al. [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258]

[259] [260] [261] [262] [263] [264]

[265] [266]

[267]

[268] [269] [270] [271] [272] [273]

R.E. Levy, A. Stavros, C. Sudhakar, V. P. Nero, S. J. De Canio, US Patent 2003/009440 A1, 2003. R.E. Levy, A. S. Rappas, C. Sudhakar, V. P. Nero, S. J. De Canio, Worldwide Patent 2003014266, 2003. F. Figueras et al., BFF 02/0235/JLP/20020628, 2002. T.F. Yen, H. Mei, S. H. M. Lu, US Patent 6,412,939 B1. 2002. J.S. Yoo, A. P. Voss, US Patent 3,945,914, 1976. Kocal, US Patent 6,368,495, 2002. Kocal, Brandvold, US Patent 6,277,271, 2001. E.L. Cole, R. F. Wilson, S. Herbstman, US Patent 3,551,328, 1970. S. Herbstman, F. E. Guptill, 3,565,793, 1971. H.A. Sorgenti, US Patent 3,816,301, 1974. S.E. Bonde, D. Chapados, W. L. Gore, G. Dolbear, E. Skov. Desulfurization by selective oxidation and extraction of sulfur-containing in diesel fuel. AM-00-25. NPRA. 2000 Annual Meeting. San Antonio, Texas. March 26-28, 2000. S.E. Bonde, W. Gore, G. E. Dolbear, Prepritns. Am.Chem. Soc. Div. Pet. Chem., 44(2), 1999, 199. G.E. Dolbear, E. R. Skov, Prepr. Am.Chem. Soc. Div. Pet. Chem., 45(2), 2000, 375. W. Gore, S. Bonde, G. E. Dolbare, E. R. Skov, US Patent 6,596,914 B2, 2003. W. Gore, US Patent 6,274,785, 2001. W. Gore, US Patent 6,160,193, 2000. F.J. Liotta, Y. Z. Han. Production of Ultra-Low Sulfur Fuels by Selective Hydroperoxide Oxidation. NPRA. AM-03-23. Annual Meeting. San Antonio, TX. March 23-25, 2003. Cullen, M.; Avidan, A.; “SulphCo – Desulfurization via Selective Oxidation”, AM- 01-55, NPRA 2001 Annual Meeting. R.E Levy, A. S. Pappas, V. P. Nero, S. J. De Canio, Unipure’s ASR-2 Diesel Desulfurization Process: A Novel, Cost-Effective Process for Ultra-low Sulfur Diesel Fuel. AM-01-10, NPRA 2001. Annual Meeting. Chapados, D.; Bonde, S. E.; Gore, W. L.; Dolbear, G.; Skov, E. Desulfurization by Selective Oxidation and Extract of SulfurContaining Compounds to Economically Achiebe Ultra-low Proposed Diesel Fuel Sulfur Requirements. AM-00-25, NPRA, 2000. Annual Meeting. H.A. Sorgenti, US Patent 3,674,885, 1972. J. Novel, et al. British Patent 713,740, 1954. A.B. Webster, R. Righy, US Patent 3,163,593, 1964. J.F. Ford, T. A. Rayne, D. G. Adlington, US Patent 3,341,448, 1967. Cole, E., L., Wilson, R. F., Herbstman, S., US Patent 3,551,328, 1970. T.C. Ho, C. S. Hsu, G. D. Dupre, R. Liotta, V. B. Buckholz, US Patent 5,958,224, 1998.