The presence of naphthenic acids (NAs) in crude oil is the major cause of corrosion in the refineries and its processing equipment. The goal of this study is to reduce the total acid number (TAN) of NAs by treating them with subcritical methanol in the presence of acidic ionic liquid (AIL) catalysts. Experiments were carried out in an autoclave batch reactor and the effect of different reaction parameters was investigated. It was observed that TAN reduction was positively dependent on the temperature and concentration of the AIL whereas excess of methanol has a negative effect. Approximately 90% TAN reduction was achieved under the optimized reaction conditions using [BMIM]HSO4 as catalyst. It was also perceived from the experimental results that the AILs with longer alkyl chain exhibited higher catalytic activity. The activity and stability of AIL showed that they can be promising catalyst to esterify NAs under subcritical methanol.
1. Clemente, J.S. & Fedorak, P.M. (2005). A review of the occurrence, analyses, toxicity, and biodegradation of naphthenic acids. Chemosphere 60(5), 585–600. DOI: 10.1016/j.chemosphere.2005.02.065.
2. Headley, J.V., Peru, K.M. & Barrow, M.P. (2016). Advances in mass spectrometric characterization of naphthenic acids fraction compounds in oil sands environmental samples and crude oil—a review. Mass Spectr. Rev. 35(2), 311–328. DOI: 10.1002/mas.21472.
3. Mandal, P.C. & Nagarajan, T. (2016) Kinetics and reaction pathways of total acid number reduction of cyclopentane carboxylic acid using subcritical methanol. Pol. J. Chem. Technol. 18(3) 44–49. DOI: 10.1515/pjct-2016-0047.
4. Shi, L.J., Shen, B.X. & Wang, G.Q. (2008). Removal of naphthenic acids from Beijiang crude oil by forming ionic liquids. Energy Fuels 22(6), 4177–4181. DOI: 10.1021/ef800497p.
5. Lirong, D. (2005). Formation mechanism and model of oil and gas accumulations in the Melut Basin, Sudan. Bulletin of Mineralogy Petrol. Geochem. 24(1), 50–57.
6. Shukri, N.M., Bakar, W.A.W.A., Jaafar, J. & Majid, Z.A. (2015). Removal of naphthenic acids from high acidity Korean crude oil utilizing catalytic deacidification method. J. Ind. Eng. Chem. 28, 110–116. DOI: 10.1016/j.jiec.2015.02.005.
8. Nasir Shah, S., Mutalib, M.I.A., Pilus, R.B.M. & Lethesh, K.C. (2014). Extraction of Naphthenic Acid from Highly Acidic Oil Using Hydroxide-Based Ionic Liquids. Energy Fuels 29(1), 106–111. DOI: 10.1021/ef502169q.
9. Shah, S.N., Chellappan, L.K., Gonfa, G., Mutalib, M.I.A., Pilus, R.B.M. & Bustam, M.A. (2016). Extraction of naphthenic acid from highly acidic oil using phenolate based ionic liquids. Chem. Eng. J. 284, 487–493. DOI: 10.1016/j.cej.2015.09.017.
10. Shohaimi, N.A.M., Bakar, W.A.W.A. & Jaafar, J. (2014). Catalytic neutralization of acidic crude oil utilizing ammonia in ethylene glycol basic solution. J. Ind. Eng. Chem. 20(4), 2086–2094. DOI: 10.1016/j.jiec.2013.09.037.
11. Wang, Y.Z., Sun, X.Y., Liu, Y.P. & Liu, C.G. (2007). Removal of naphthenic acids from a diesel fuel by esterification. Energy Fuels 21(2), 941–943. DOI: 10.1021/ef060501r.
12. Zifeng, L., Songbai, T. & Zijun, W. (2009). Study on esterification for reducing total acid number of high acid crude oil by Mg/Al oxides [J]. Pet. Process. Petrochem. 8, 024.
13. Wang, Y.Z., Duan, H.I., Song, C.M., Han, X.T. & Ma, X.R. (2014). Removal of naphthenic acids from crude oils by catalytic decomposition using Mg–Al hydrotalcite/γ-Al2O3 as a catalyst. Fuel 134, 499–504. DOI: 10.1016/j.fuel.2014.06.026.
14. Wang, H., Duan, W., Lei, Y., Wu, Y., Guo, K. & Wang, X. (2015). An intracrystalline catalytic esterification reaction between ethylene glycol intercalated layered double hydroxide and cyclohexanecarboxylic acid. Catal Cammun. 62, 44–47. DOI: 10.1016/j.catcom.2015.01.004.
15. Lee, Y.H., Park, J.Y., Park, S.Y., Kim, C.H., Nam, J., Kim, Y.J. & Bae, J.W. (2016). Removal of benzoic acid in heavy oils by esterification using modified Ferrierite: Roles of Bronsted and Lewis acid sites. Energy Fuels, 30(7), 5391–5397. DOI: 10.1021/acs.energyfuels.6b00448.
16. Dastjerdi, Z. (2010). The Esterification of Naphthenic Acids for Methyl Ester Production. Environ. Prog. Sustain. Energ. 32(2), 406–410. DOI: 10.1002/ep.11606.
18. Li, X., Zhu, J., Liu, Q. & Wu, B. (2013). The removal of naphthenic acids from dewaxed VGO via esterification catalyzed by Mg–Al hydrotalcite. Fuel Process. Technol. 111, 68–77. DOI: 10.1016/j.fuproc.2013.01.016.
19. Mandal, P.C., Sasaki, M. & Goto, M. (2013). Non-catalytic reduction of total acid number (TAN) of naphthenic acids (NAs) using supercritical methanol. Fuel Process. Technol. 106, 641–644. DOI: 10.1016/j.fuproc.2012.09.058.
20. Khan, M.K., Insyani, R., Lee, J., Yi, M., Lee, J.W. & Kim, J. (2016). A non-catalytic, supercritical methanol route for effective deacidification of naphthenic acids. Fuel 182, 650–659. DOI: 10.1016/j.fuel.2016.06.023.
21. Sitthithanaboon, W., Reddy, H.K., Muppaneni, T., Ponnusamy, S., Punsuvon, V., Holguim, F., Dungan, B. & Deng, S. (2015). Single-step conversion of wet Nannochloropsis gaditana to biodiesel under subcritical methanol conditions. Fuel 147, 253–259. DOI: 10.1016/j.fuel.2015.01.051.
22. Wan, L., Liu, H. & Skala, D. (2014). Biodiesel production from soybean oil in subcritical methanol using MnCO3/ZnO as catalyst. Appl. Catal. B. 152, 352–359. DOI: 10.1016/j.apcatb.2014.01.033.
23. Caldas, B.S., Nunes, C.S., Souza, P.R., Rosa, F.A., Visentainer, J.V., Oscar de Olivera, S. & Muniz, E.C. (2016). Supercritical ethanolysis for biodiesel production from edible oil waste using ionic liquid [HMIM][HSO4] as catalyst. Appl. Catal. B. 181, 289–297. DOI: 10.1016/j.apcatb.2015.07.047.
24. Ullah, Z., Bustam, M.A. & Man, Z. (2015). Biodiesel production from waste cooking oil by acidic ionic liquid as a catalyst. Renew. Energ. 77, 521–526. DOI: 10.1016/j.renene.2014.12.040.
25. Andreani, L. & Rocha, J. (2012). Use of ionic liquids in biodiesel production: a review. Braz. J. Chem. Eng. 29(1), 1–13. DOI: 10.1590/S0104-66322012000100001.
26. Seddon, K.R. (1997). Ionic liquids for clean technology. J. Chem. Tech. Biotech. 68(4), 351–356. DOI: 10.1002/(SICI)1097-4660(199704)68:4<351::AID-JCTB613>3.0.CO;2-4
27. Olkiewicz, M., Plechkova, N.V., Earle, M.J., Fabregat, A., Stüber, F., Fortuny, A., Font, J. & Bengoa, C. (2016). Biodiesel production from sewage sludge lipids catalysed by Brønsted acidic ionic liquids. Appl. Catal. B 181, 738–746. DOI: 10.1016/j.apcatb.2015.08.039.
28. Kumar, M., Sharma, K. & Arya, A.K. (2012). Use of SO3H-functionalized halogenfree ionic liquid ([MIM(CH2)4SO3H] [HSO4]) as efficient promoter for the synthesis of structurally diverse spiroheterocycles. Tetra. Lett. 53(34), 4604–4608. DOI: 10.1016/j.tetlet.2012.06.085.
29. Ullah, Z., Bustam, M.A., Muhammad, N., Man, Z. & Khan, A.S. (2015). Synthesis and thermophysical properties of hydrogensulfate based acidic ionic liquids. J. Sol. Chem. 44(3-4), 875–889. DOI: 10.1007/s10953-015-0329-x.
30. Aghabarari, B., Ghiaci, M., Amini, S.G., Rahimi, E. & Martinez-Huerta, M. (2014). Esterification of fatty acids by new ionic liquids as acid catalysts. J. Taiwan Inst. Chem. Eng. 45(2), 431–435. DOI: 10.1016/j.jtice.2013.08.003.
31. Mahajan, S. & Konar, S.K. (2006). Determining the acid number of biodiesel. J. Am. Oil Chem. Soc. 83(6), 567–570. DOI: 10.1016/j.fuel.2016.06.023.
32. Li, Y., Hu, S., Cheng, J. & Lou, W. (2014). Acidic ionic liquid-catalyzed esterification of oleic acid for biodiesel synthesis. Chin. J. Catal. 35(3), 396–406. DOI: 10.1016/S1872-2067(14)60005-X.
33. Dharaskar, S.A., Wasewar, K.L., Varma, M.N., Shende, D.Z. & Yoo, C. (2016). Synthesis, characterization and application of 1-butyl-3-methylimidazolium tetrafluoroborate for extractive desulfurization of liquid fuel. Arab. J. Chem. 9(4), 578–587. DOI: 10.1016/j.arabjc.2013.09.034.
34. Chuah, L.F., Bokhari, A., Yusup, S., Klemeš, J.J., Abdullah, B. & Akbar, M.M. (2015). Optimisation and kinetic studies of acid esterification of high free fatty acid rubber seed oil. Arab. J. Sci. Eng. 1–12. DOI: 10.1007/s13369-015-2014-1.