Applied Mechanics and Materials Vol. 625 (2014) pp 205-208 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.625.205
Extractive desulphurization of model oil using sulphonium based ionic liquids Kallidanthiyil Chellappan Lethesh 1, a,*, Nurul Hidayah Binti Hasnan 2, b and M. I. Abdul Mutalib 1, c 1
PETRONAS Ionic Liquids Centre, Universiti Teknologi PETRONAS, Malaysia
2
Department of Chemical Engineering, Universiti Teknologi PETRONAS, Malaysia a
[email protected]
Key Words: Desulphurization, Model Oil, Sulphonium cation, liquid-liquid extraction
Abstract. Synthesis of a novel class of cyclic sulphonium based ionic liquids was performed. The ionic liquids were characterized using 1H NMR spectroscopy, FTIR spectroscopy and CHNS elemental analysis. The physicochemical properties of the ionic liquids such as density viscosity and thermal decomposition temperature of the synthesized ionic liquids were determined. The potential of these ionic liquids for the extractive desulphurization of model oil was investigated. Introduction Crude oil is the largest and most widely used source of energy in the world. Major portions of the crude oils used as transportation fuels such as gasoline, kerosene, diesel etc. The crude oil contains sulphur in the form of organic and inorganic sulphur compounds. Sulphur is the third most abundant element in the fossil fuels apart from carbon and nitrogen. It is an undesirable compound because it forms SO2 during the fuel oil combustion and is responsible for many environmental and health problems[1].Sulphur compounds are responsible for corrosion problems in pipeline, pumping, and refining equipment. They are also responsible for the failure of combustion engines and poisoning of the catalytic converters that are used in automotive engines. Therefore, desulphurization of crude oil is extremely important in the petroleum-refining. Conventional hydro desulphurization (HDS) is currently being used in the petroleum industry[2]. In the HDS process, sulphur compounds are converted to hydrogen sulfide by catalytic hydrogenation of crude oil by treating it with hydrogen at elevated temperature (>350 ºC) and pressure (30-100 bar). The hydrogen sulfide was then converted to elemental sulphur by catalytic air oxidation. This process is very efficient in the case of thiols, sulfides and disulfides. However, it is not effective in removing sterrically hindered sulphur compounds such as (DBT). Harsh conditions are necessary to remove such compounds, which require large amount of hydrogen and will make the process expensive. Therefore, there is a need to explore new media for desulphurization which are cost effective, more efficient and can meet the environmental regulations and refining requirements. A new media for the removal of sulphur from crude oil is the so-called ionic liquids (ILs). Ionic liquids (ILs) have been described as molten salts that are entirely ionic in nature, comprising both cationic and anionic species and having a melting point below 100 ° C[3,4]. Recently ionic liquids were extensively used for the desulphurization process [5-7]. In this manuscript, the performance of a new class of low viscous cyclic sulphonium based ionic liquids in the extractive desulphurization of model oil is evaluated. Experimental Extractive desulphurization 1-Butyltetrahydrothiophenium thiocyanate (1.5 g) ionic liquid is added into sample bottle containing model oil (1.5 g with 500 ppm of DBT).The mixture stirred (500 rpm) at 30 ºC for 30 minutes. The mixture was allowed to settle for 10 minutes and the model oil layer and ionic liquid layer were separated using a micro pippete. In order to ensure the accurate result, extraction step
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 203.135.191.3-10/09/14,03:15:00)
206
Process and Advanced Materials Engineering
was performed in triplicate.The model oil layer is analyzed using gas chromatogram to determine the sulphur content after the extraction. Results and Discussion Synthesis of the sulphonium based ionic liquids was performed according to the literature procedure[4]. All the ionic liquids prepared were obtained as solids except 1Butyltetrahydrothiophenium thiocyanate. The density and viscosity of the salts which are liquids at room temperature is given in Figure 1 and 2 as a function of temperature. The extraction of the sulphur was performed by mixing an equal amount of ionic liquids and the model oil in a vial at room temperature for 30 minutes at a stirring speed of 500 rpm. The sulphur content in the model oil before and after the extraction was determined using gas chromatogram (GC).The results of the liquid-liquid extraction with the ionic liquid is given in Figure 4. The initial concentration of DBT in the model oil was 500 ppm. The extraction process repeated three times for the accuracy of the results. After the extraction the sulphur content reduced to about 50%. It was reported that the extraction temperature, stirring speed and the water content in the ionic liquids has strong influence in the extraction of performance.
1000
Viscosity (mPa.s)
800
600
400
200
0
20
40
60
80
100
0
Temperature ( C)
Fig. 1. Viscosity of 1-Butyltetrahydrothiophenium thiocyanate as function of temperature. The extraction DBT from the model oil by sulphonium based ionic liquid is below 50 %. From this result, it is clear that the sulphonium ionic liquid has the potential to extract DBT from model oil. Higher water content in ionic liquid is responsible its low performance in extractive desulphurization[8]. In the future, the performance of the ionic liquids in sulphur extraction will enhance by changing the temperature and reducing the water content in the ionic liquids.
Applied Mechanics and Materials Vol. 625
207
1.13
Density(g/cm3)
1.12
1.11
1.10
1.09
1.08 20
40
60
80
100
0
Temperature( C)
Fig. 2. Density of 1-Butyl tetrahydrothiophenium thiocyanate as function of temperature.
Before Extraction After Extraction 500
Sulphur Content
400
300
200
100
0 42
43
44
45
46
Extraction Performance
Fig. 3. Extraction of DBT using 1-Butyltetrahydrothiophenium thiocyanate Conclusions The synthesis and characterization of sulphonium based ionic liquids with different alkyl chain length was performed. The physicochemical properties of the ionic liquids were determined. The density and viscosity of the ionic liquids decreased as the temperature increases. The extraction of sulphur from the model oil using the synthesized ionic liquids was successfully carried out. The cyclic sulphonium based ionic liquids could able to reduce the sulphur content in model by 50% at ambient conditions. References [1] [2] [3]
A. Nozik, J. Miller, Introduction to solar photon conversion. Chem.Rrev. 110(2010) 64436445. R.E, Kirk, D.F, Othmer. Encyclopedia of Chemical Technology, Vol. 6. Interscience, New York 1951. T. Welton. Room-temperature ionic liquids. Solvents for synthesis and catalysis. Chem.Rev. 99(1999) 2071-2084.
208
Process and Advanced Materials Engineering
[4]
P.Wasserscheid, W. Keim. Ionic liquids-new" solutions" for transition metal catalysis. Angew. Chemie. 39(2000) 3772-3789. A.R, Hansmeier, G.W, Meindersma, A.B, de Haan. Desulfurization and denitrogenation of gasoline and diesel fuels by means of ionic liquids. Green Chem. 13 (2011) 1907-1913. F. Li, R. Liu, J. Wen, D. Zhao, Z. Sun, Y. Liu. Desulfurization of dibenzothiophene by chemical oxidation and solvent extraction with Me3NCH2C6H5Cl· 2ZnCl2 ionic liquid. Green Chem. 11(2009) 883-888. J.D, Holbrey, I. López-Martin, G. Rothenberg, K. R. Seddon, G. Silvero, X. Zheng, Desulfurisation of oils using ionic liquids: selection of cationic and anionic components to enhance extraction efficiency. Green Chemistry 2008, 10, 87-92. H. Gao, M. Luo, J. Xing, Y. Wu, Y. Li, W. Li, Q. Liu, H. Liu, H.: Desulfurization of fuel by extraction with pyridinium-based ionic liquids. Ind.Eng. Chem. Res. 47(2008), 83848388.
[5] [6]
[7]
[8]
