heavy crude oil in order to reduce the concentration of the metal ions before it gets through to the downstream processing units. This would decrease cost, ...
VOL. 4, NO. 3, March 2014
ISSN 2225-7217
ARPN Journal of Science and Technology ©2011-2014. All rights reserved. http://www.ejournalofscience.org
Performance of Natural Zeolites in the Removal of Metal Ions from Crude Oil 1
Rose E. Ikyereve1, Abubakar Mohammed2, Chindo Nwankwo3
School of Applied Sciences, University of Wolverhampton, Wolverhampton, United Kingdom 2 Department of Mechanical Engineering, Federal University of Technology Minna, Nigeria 3 Department of Environmental Engineering, University of Port Harcourt, Port Harcourt, Nigeria
ABSTRACT The removal efficiencies of different natural zeolite materials for the selective removal of metal ions from crude oil were investigated. Three natural zeolite materials were used for the study; clinoptilolite, aluminum phillipsite and chabazite. The study was particularly focused on the metals that cause problems during processing of crude oil (nickel, vanadium and sulphur). The result shows that, clinoptilolite is efficient for the removal of nickel and sulfur at concentrations of 0.023ppm and 36.582ppm respectively. Aluminum phillipsite showed removal of vanadium and sulfur at concentrations of 0.2279ppm and 58.068ppm respectively, while chabazite was unable to remove any of the metal ions. The study thus showed the selectivity of the natural zeolites for the different metal ions, while one zeolite is good for the removal of a particular metal ion from the crude oil; the other is not, except for sulfur. Keywords: natural zeolite, clinoptilolite, philipsite, chabasite, nickel, vanadium, sulfur, crude oil
1. INTRODUCTION Despite the contribution from other fossil fuels such as coal and natural gas, the demand for petroleum continues to be higher as transportation fuel [1]. This has resulted in depletion of light oil reserves, scarcity and increase in oil price [2]. There is therefore a decrease in the light oil while the heavier oils increase with an increase in impurities such as metals, sulphur, asphaltenes, nitrogen etc. These impurities make the processing of the oils costly thus making the oil less desirable. New technologies to improve the quality and quantity of transportation fuel from natural sources other than the conventional crude have recently been explored [1]. Other fields like biofuels production, gas to liquid production or unconventional oil refining processes are currently been investigated [1, 3]. A number of technologies have been investigated to increase production of transportation fuel from heavy oil [4]. Of these technologies, hydrocracking is the most efficient yielding high selectivity to middle distillate and low selectivity to coke. Hydrocracking in most cases is said to be combined with other pre-treatment processes like solvent deasphalting and mild hydro treating [1]. The crude stock for hydro cracking most times contains high concentration of Ni and V metals (heavy oil) that conventional acid catalyst is easily poisoned/deactivated [5-7]. These among other metals have prompted the need for search of materials that can effectively remove them from crude oil during hydroprocessing. A solution to this problem would be to find a method of pretreating the heavy crude oil in order to reduce the concentration of the metal ions before it gets through to the downstream processing units. This would decrease cost, as catalysts would be less quickly poisoned and thus increasing lifetime and also throughput rate. Zeolites, both natural and synthetic, with porous open framework, large surface area, catalytic and ionic exchange properties, known for industrial applications such as heterogeneous catalysis, separation, water
softening, environmental remediation, etc. [8] could serve as good materials for the removal of these metal ions. Zeolites are inorganic aluminosilicates that are derived from silica (SiO2) by the isomophous substitution of SiO44- tetrahedra by AlO45- tetrahedra. The composition of a zeolite is represented thus: Comp. of a Zeolite = m/xx+[(SiO2)n(AlO2)m] ·yH2O
(1)
The term in square brackets represents the framework structure of the zeolite. The isomorphous substitution of Si by Al generates an excess negative charge on the oxygen framework. This negative charge is compensated by the cations (M of valence x) present during synthesis and held in the interstices of the structure on crystallization [9]. Water is also present in the structure of the zeolite though not part of the zeolite framework. The properties of the zeolites such as the ion exchange, adsorption, catalytic etc. are largely dependent on the nature of the charge balancing cations and the exchange capacity is governed by the Si/Al ratio [10-12]. Zeolites have already been successfully applied in the removal of heavy metals such as Cr3+, Fe3+, Co2+, and Zn2+ among others from aqueous solutions [13-16] and for the catalytic cracking of heavy crude oils and bitumen [17-19]. However, to the best of our knowledge, no work has been done on the selective contributions of these three natural zeolites at removing catalysts poisons from crude oil. This paper presents the performance of natural zeolites in the removal of metal ions from crude oil.
2. MATERIALS AND METHOD 2.1 Materials Clinoptilolite (K, Na, Ca) 2-3 [Al6Si30O72].24H2O), high-alumina phillipsite (Na6.3 K4.2 [Al10.5Si21.5O64]. 23 H2O) and chabasite (Ca, Na2, K2, Mg) Al2Si4O12·6H2O) and the crude oil samples were obtained from the UK. Ethylenediaminetetraacetic acid (EDTA) was purchased from sigma Aldrich, UK.
141
VOL. 4, NO. 3, March M 2014
ISSN 2225-7217
ARPN N Journal of Science S and Technology T ©2011-2014. All rights reserved d. http://www.eejournalofscience.orgg
2..2 Experimen ntal Method The meetal ions extraaction/removal was done as shhown by the seetup in Fig.1. 1g of clinoptiilolite powder w suspended in 50mL of th was he crude oil inn a separating flaask containingg 25mL of EDTA. E This mixture was prroperly mixed using the flaskk shaker for an hour at room teemperature (188°C) to properlly homogenizee the mixture. Thhe mixture wass then left to sttand for a day so as to attain eq quilibrium andd enable the separation off the distinct laayers. The aquueous layer waas then carefuully separated from the organicc (oil) layer. This T procedure was repeated fo or each of the three zeolites used and the aqueous a layer ussed for metal aanalysis. A sim milar experimennt was carried ouut but without introducing anny zeolite. This was labeled ass a ‘control’ since it waas used to compare the efffectiveness off the heavy metal m immobiliisation of the diifferent zeolite materials used d. 2..3 Characteriization The aqqueous sampless containing thhe metal ions w were analyzed using the in nductively couupled plasma attomic emissionn spectroscopyy (ICP-AES), a spectrociros IC CP-AES spectrrometer.
forms. T These metal ions i are believved to be asssociated with aspphaltenes, mosst likely in the porphyrinic foorm. To get thesse metal ions removed from m crude oil rrequires breakingg down the higgher molecular weight fractioons such as the asphaltenes a thaat forms aggreg gates with Porrphyrins by nonn-covalent intteractions. Zeeolites due too their catalyticc property aree able to breeakdown thesee large molecullar fractions. The conversion of the higher molecullar weight to loower moleculaar weight oil frractions exposess a significannt amount of the metal ioons for removall from crude oil. Thus, the metal m ions whicch were not avaailable for exxtraction in the control bbecame availablle in the presennce of zeolite catalysts. It is observed from the Figures 2 to 4 tthat the efficienccies of metalss removal by the different zzeolites differedd significantly,, while one zeeolite is goodd at the removall of a particulaar metal ion frrom the crude oil, the other is not. This coulld be due to th he nature of accid sites for the different zeollites. From thee study, clinopptilolite was fouund to be efficcient in the reemoval of nickkel at a concentrration of 0.0233ppm and sulfu fur at concentraation of 36.582pppm. Aluminnum phillipsiite was fouund to effectiveely remove vanadium and sulfur at a concentrration of 0.2377ppm and 58.068ppm respeectively. The conncentrations off sulfur from the experimennt were found to increase froom concentratiion of 31.557pppm to m phillipsite sample s was shhown to 58.068pppm. Aluminum remove the highest aamount of sullfur comparedd to the other zeeolite materialls used. Chabaazite from this study was onlly able to remoove sulfur and d not any of thhe other problem m causing metals from the cru ude oil.
Fig 1: Experim mental setup
3.. RESULT TS AND DIS SCUSSION The reesult from thee ICP analysiis in Figure2 cllearly shows thhe effect of thhe different zeeolites on the reemoval of metaal ions from cru ude oil. This iss evident from thhe appearance of o metal ions such as nickel and a vanadium thhat were initiallly absent from m the ‘control’. This can be ex xplained basedd on the fact th hat, heavy crudde oil is made upp of three groups g of com mpounds; oil, resins and assphaltenes. Thhe resins and asphaltenes are a the large m molecules contaaining metal impurities. i Thee metal ions, paarticularly vannadium and nickel in crrude oil are deescribed in twoo forms, porph hyrinic and nonn-porphyrinic
Figg 2: .Nickel conncentrations in different zeoliites
VOL. 4, NO. 3, March M 2014
ISSN 2225-7217
ARPN N Journal of Science S and Technology T ©2011-2014. All rights reserved d. http://www.eejournalofscience.orgg
REFE ERENCES [1]
Shimada, H., Saato, K., Honnaa, K., Enomoto, T. and S O Ohshio, N. (20009). Design an nd developmennt of Tim modified zeolitte-based catalyyst for hydroccracking h heavy petroleum m. Catalysis Today, T 141(1--2): 435 51.
[2]
Dalai, A. K. annd Chung, K. H. D H (2001). Heaavy Oil U Upgrading, Reenewable En nergy and Catalysis S Symposium, 499th Canadian Chemical C Engiineering C Conference. Fuuel, 80(8): 10411-1042.
[3]
Agarwa, A.K. (2007). Bioofuels (alcohools and A b biodiesel) appplications as fuels for iinternal combustion enngines. Progrress in energgy and combustion Sciience 33(3): 233-27. 2
[4]
Rana, M. S., Sáámano, V., Anccheyta, J. and D R Diaz, J. A I. (2007). A review of recent advannces on A. p process technollogies for upggrading of heaavy oils a residua. Fuel, 86(9): 12166-1231. and
[5]
Paweewan, B., Barrie, P. J. and Gladdenn, L. F. P (1999). Cokingg and deactivaation during n--hexane cracking in ultrrastable zeolitee Y. Applied C Catalysis A General, 1855(2): 259-268. A:
[6]
Gawel, I., Bociiaska, D., and Biskupski, P. (2005). G E Effects of asphaltens on hydrroprocessing of heavy o and residuaa. Applied catalysis 295: 89-994. oils
[7]
Furimsky, E., M F Massoth, F.E. (1999).Catal. Today 5 381. 52:
[8]
Auerbach, S.M. Carrado, K.A A A. Dutta, P.K. (2003). H Handbook of Zeolite Sciennce and Technnology, M Marcel Dekker,, New York.
Naturall zeolites such as clinoptiloliite, aluminum phhillipsite and chabasite havve been show wn to play a poositive role in the t removal off poisonous meetal ions from crrude oil. The different zeolites were observed to be seelective at rem moving the mettals. It is thereefore possible thhat these zeollites have thee potential to be used as caatalysts in the processing of crude oil, mayybe not as the co onversional crracking catalyysts but catallysts for the prretreatment off heavy crudee oil. This will w hopefully reeduce the overaall cost to crude oil processinng.
[9]
Dyer, A. (19988). An intrroduction to zeolite D m molecular sievees, Bath, Bath Press P Ltd.
[10]
Barrer, R.M. (1989). Zeolites and Clay Minnerals as B S Sorbents and M Molecular Siev ves, Academicc Press, F London. FRS
[11]
R. Szostak. (19989). Molecular sieves, Principles of R S Synthesis andd Identification, Van N Nostrand R Reinold, New York. Y
A ACKNOWL LEDGEMEN NTS
[12]
The Authors A would like to exprress profound grratitude to Proff. Craig D. Wiilliams for his guidance and suupport during tthe course of this t research. The T technical staff of Enviroonmental Scieence at the University U of W Wolverhampton n is also being appreciated for the ICP an nalysis. The finnancial supportt received from m Benue State U University Makuurdi, Nigeria iss also appreciated.
D. W. Breck. (1974). Zeolite Molecular Sieves, D S Structure Chem mistry and Usee, Wiley, New w York, N NY.
[13]
M.A.S.D. Barroos, E.A. Silva,, P.A. Arroyo, C.R.G. M T Tavares, R.M. Schneider, M.. Suszek, E.F. SousaA Aguiar. (2004). Removal of Cr(III) C in the fixxed bed column and bbatch reactors using as addsorbent z zeolite NaX, Chhem. Eng. Sci. 59: 5959–5966.
Fig 3: Vanaddium concentraations in differeent zeolites
Fig 4: Sulfu fur concentratioons in differentt zeolites
4.. CONCLU USION
VOL. 4, NO. 3, March 2014
ISSN 2225-7217
ARPN Journal of Science and Technology ©2011-2014. All rights reserved. http://www.ejournalofscience.org
[14]
M.A.S.D. Barros, P.A. Arroyo, E. Sousa-Aguiar, C.R.G. Tavares. (2004). Thermodynamics of the exchange processes between K+, Ca2+ and Cr3+ in zeolite A, Adsorption 10: 227–235.
[15]
J.S. Kim, M.A. Keane. (2002). The removal of iron and cobalt from aqueous solutions by ion exchange with Na-Y zeolite: batch, semi-batch and continuous operation, J. Chem. Technol. Biotechnol. 77: 633–640.
[16]
I.C. Ostroski, C.E. Borba, E.A. Silva, P.A. Arroyo, R. Guirardello, M.A.S.D. Barros. (2011). Mass transfer mechanism of ion exchange in fixed bed columns, J. Chem. Eng. Data 56:375–382.
[17]
G.O Chivadze, TsINaskidashvili, E.K. Kvantaliani. (1990). Catalytic cracking of heavy petroleum fractions over modified natural zeolites. Izvestiya Akademii Nauk Gruzinskoi SSR Seriya Khimicheskaya, 16:186–189. Russian
[18]
W. Wang. (2010). Catalytic cracking of Athabasca oilsands using clinoptilolite. MSc dissertation, Edmonton (AB): University of Alberta.
[19]
A.S.M Junaid, M. Rahman, H. Yin, W.C. McCaffrey, S.M Kuznicki. (2011). Natural zeolites for oilsands bitumen cracking: Structure and acidity. Micropor, Mesopor Material, 144:148–57.
144
