Ethylbenzene disproportionation and p-xylene selectivity enhancement in xylene isomerization using high crystallinity desilicated H-ZSM-5

doi:10.1016/j.cjche.2017.03.023

摘要/Abstract

摘要： Desilication accompanied with minimum loss of crystallinity effect of a high alumina ZSM-5 zeolite on the isomerization reaction of ethylbenzene/xylene mixtures has been considered. Desilication was assessed through XRF, XRD, FTIR, TEM, nitrogen adsorption/desorption, NH₃-TPD, ²⁹Si and ²⁷Al MAS NMR analytical techniques. Desilication was accompanied with the creation of super acid sites. There exists a limit (Si/Al molar ratio of 9.67) for keeping high crystallinity and obtaining improved catalytic performance. Desilication promotes ethylbenzene conversion by disproportionation and trans-alkylation reactions while the same reactions are limited for the xylene isomers. The p-xylene approach to equilibrium improves by more than 7% at 400℃ and a WHSV of 2 h^-1 for the optimum sample with respect to the parent zeolite. At the same conditions, the optimum sample exhibits the maximum ethylbenzene conversion of 89%, i.e. more than 40% w.r.t. of the parent zeolite. However, the xylene yield decreases only 3%.

关键词: Zeolite, Catalyst, Kinetics, Xylene isomerization, ZSM-5 zeolite, Desilication

Abstract: Desilication accompanied with minimum loss of crystallinity effect of a high alumina ZSM-5 zeolite on the isomerization reaction of ethylbenzene/xylene mixtures has been considered. Desilication was assessed through XRF, XRD, FTIR, TEM, nitrogen adsorption/desorption, NH₃-TPD, ²⁹Si and ²⁷Al MAS NMR analytical techniques. Desilication was accompanied with the creation of super acid sites. There exists a limit (Si/Al molar ratio of 9.67) for keeping high crystallinity and obtaining improved catalytic performance. Desilication promotes ethylbenzene conversion by disproportionation and trans-alkylation reactions while the same reactions are limited for the xylene isomers. The p-xylene approach to equilibrium improves by more than 7% at 400℃ and a WHSV of 2 h^-1 for the optimum sample with respect to the parent zeolite. At the same conditions, the optimum sample exhibits the maximum ethylbenzene conversion of 89%, i.e. more than 40% w.r.t. of the parent zeolite. However, the xylene yield decreases only 3%.

Key words: Zeolite, Catalyst, Kinetics, Xylene isomerization, ZSM-5 zeolite, Desilication

Marjan Farshadi, Cavus Falamaki. Ethylbenzene disproportionation and p-xylene selectivity enhancement in xylene isomerization using high crystallinity desilicated H-ZSM-5[J]. Chinese Journal of Chemical Engineering, 2018, 26(1): 116-126.

参考文献

[1] T.C.Tsai,I.Wang,C.K.Huang,S.D.Liu,Studyontheethylbenzeneandxyleneconversion over modified ZSM-5, Appl. Catal. A Gen. 321(2007) 125-134.

[2] J. Zhou, Z. Liu, L. Li, Y. Wang, H. Gao, W. Yang, Z. Xie, Y. Tang, Hierarchical mesoporous ZSM-5 zeolite with increased external surface acid sites and high catalytic performance in o-xylene isomerization, Chin. J. Catal. 34(2013) 1429-1433.

[3] S. Gui, Y. Hao, L. Zhou, Z. Jing, Y. Qiao, H. Gu, Y. Li, B. Cheng, J. Wang, Catalyst supported with noble metals for the isomerization of alkylaromatics, United State Patent, 5, 1998759950.

[4] N.M. Tukur, S. Al-Khattaf, Comparison studies of xylene isomerization and disproportionation reactions between SSZ-33, TNU-9, mordenite and ZSM-5 zeolite catalysts, Chem. Eng. J. 166(2011) 348-357.

[5] X. Li, P. Ren, Y. Zhang, X. Liu, X. Sun, M. Gao, M. Jia, Z. Lü, T. Dou, Synthesis, characteristics of hierarchical EU-1 zeolite for xylene isomerization probe reaction, Chin. J. Chem. Eng. 24(2016) 1577-1583.

[6] E. Guillon, S. Lacombe, T. Sozinho, P. Magnoux, S. Gnep, P. Moreau, M. Guisnet, How to improve the selectivity of zeolite catalysts in C8 aromatic cut isomerization, Oil Gas Sci. Technol. Rev. IFP 64(2009) 731-744.

[7] F.J. Llopis, G. Sastre, A. Corma, Xylene isomerization and aromatic alkylation in zeolites NU-87, SSZ-33, β, and ZSM-5:Molecular dynamics and catalytic studies, J. Catal. 227(2004) 227-241.

[8] J.M. Silva, M.F. Ribeiro, F. Ramoa Ribeiro, E. Benazzi, Influence of platinum on the transformation of an ethylbenzene-o-xylene mixture on HZSM-5, Appl. Catal. A Gen. 125(1995) 1-14.

[9] A.A. Susu, C.T. Ako, Ethylbenzene isomerization on bifunctional platinum/alumina product yields and pseudo mass action kinetics, Appl. Catal. 16(1985) 179-192.

[10] K. Toch, J.W. Thybaut, B.D. Vandegehuchte, C.S.L. Narasimhan, L. Domokos, G.B. Marin, A single-event microkinetic model for ethylbenzene dealkylation/xylene isomerization on Pt/H-ZSM-5 zeolite catalyst, Appl. Catal. A Gen. 425-426(2012) 130-144.

[11] F. Moreau, P. Moreau, N.S. Gnep, P. Magnoux, S. Lacombe, M. Guisnet, Ethylbenzene isomerization over bifunctional platinum alumina-EUO catalysts:Location of active sites, Microporous Mesoporous Mater. 90(2006) 327-338.

[12] P. Moreau, Isomerization of ethylbenzene on Pt/zeolite bifuctional catalysts with intermediate-size pores, University of Poitiers (LACCO), 2005.

[13] D. Verboekend, J. Perez-Ramirez, Towards a sustainable manufacture of hierarchical zeolites, ChemSusChem 7(2014) 753-764.

[14] R. Mahmoudi, C. Falamaki, Ni²⁺-ion-exchanged dealuminated clinoptilolite:A superior adsorbent for deep desulfurization, Fuel 173(2016) 277-284.

[15] R. Mahmoudi, C. Falamaki, Systematic study on the effect of desilication of clinoptilolite zeolite on its deep-desulfurization characteristics, Nanochem. Res. 1(2016) 64-72.

[16] S. Fathi, M. Sohrabi, C. Falamaki, Improvement of HZSM-5 performance by alkaline treatments:Comparative catalytic study in the MTG reactions, Fuel 116(2014) 529-537.

[17] N. Ghasemian, C. Falamaki, M. Kalbasi, M. Khosravi, Enhancement of the catalytic performance of H-clinoptilolite in propane-SCR-NOx process through controlled dealumination, Chem. Eng. J. 252(2014) 112-119.

[18] S. Abello, A. Bonilla, J. Perez-Ramirez, Mesoporous ZSM-5 zeolite catalysts prepared by desilication with organic hydroxides and comparison with NaOH leaching, Appl. Catal. A Gen. 364(2009) 191-198.

[19] J. Ding, H. Liu, P. Yuan, G. Shi, X. Bao, Catalytic properties of a hierarchical zeolite synthesized from a natural aluminosilicate mineral without the use of a secondary mesoscale template, ChemCatChem 5(2013) 2258-2269.

[20] M. Milina, S. Mitchell, N.L. Michels, J. Kenvin, J. Perez-Ramirez, Interdependency between porosity, acidity, and catalytic performance in hierarchical ZSM-5 zeolites prepared by post-synthesis modification, J. Catal. 308(2013) 398-407.

[21] B. Puertolas, L. Garcia-Andujar, T. Garcia, M.V. Navarro, S. Mitchell, J. Perez-Ramirez, Bifunctional Cu/H-ZSM-5 zeolite with hierarchical porosity for hydrocarbon abatement under cold-start conditions, Appl. Catal. B Environ. 154-155(2014) 161-170.

[22] C. Fernandez, I. Stan, J.P. Gilson, K. Thomas, A. Vicente, A. Bonilla, J. Perez-Ramirez, Hierarchical ZSM-5 zeolites in shape-selective xylene isomerization:Role of mesoporosity and acid site speciation, Chem. Eur. J. 16(2010) 6224-6233.

[23] L. Shirazi, E. Jamshidi, M.R. Ghasemi, The effect of Si/Al ratio of ZSM-5 zeolite on its morphology, acidity and crystal size, Cryst. Res. Technol. 43(2008) 1300-1306.

[24] B. Gil, L. Mokrycki, B. Sulikowski, Z. Olejniczak, S. Walas, Desilication of ZSM-5 and ZSM-12 zeolites:Impact on textural, acidic and catalytic properties, Catal. Today 152(2010) 24-32.

[25] M. Osman, L. Atanda, M.M. Hossain, S. Al-Khattaf, Kinetics modeling of disproportionation and ethylation of ethylbenzene over HZSM-5:Effects of SiO₂/Al₂O₃ ratio, Chem. Eng. J. 222(2013) 498-511.

[26] K. Sadowska, A. Wach, Z. Olejniczak, P. Kustrowski, G. Datka, Hierarchical zeolites:Zeolite ZSM-5 desilicated with NaOH and NaOH/tetrabutylamine hydroxide, Microporous Mesoporous Mater. 167(2013) 82-88.

[27] D. Verboekend, J. Perez-Ramirez, Desilication mechanism revisited:Highly mesoporous all-silica zeolites enabled through pore-directing agents, Chem. Eur. J. 17(2011) 1137-1147.

[28] R.D. Chirico, W.V. Steele, Thermodynamic equilibria in xylene isomerization. 5. Xylene isomerization equilibria from thermodynamic studies and reconciliation of calculated and experimental product distributions, J. Chem. Eng. Data 42(1997) 784-790.

[29] M. Guisnet, N.S. Gnep, S. Morin, Mechanism of xylene isomerization over acidic solid catalyst, Microporous Mesoporous Mater. 35-36(2000) 47-59.

[30] K.H. Roebschleager, E.G. Christoffel, Reaction mechanism of ethylbenzene isomerization, Ind. Eng. Chem. Prod. Res. Dev. 18(1979) 347-352.

[31] H. Vinek, J.A. Lercher, Production and reaction of xylenes over H-ZSM-5, J. Mol. Catal. 64(1991) 23-29.

[32] D.H. Olson, W.O. Hang, Structure-selective relationship in xylene isomerization and selective toluene disproportionation, ACS Symp. Ser. 248(1984) 275-307.

[33] C.H. Christensen, K. Johannsen, I. Schmidt, C.H. Chritensenm, Catalytic benzene alkylation over mesoporous zeolite single crystals:Improving activity and selectivity with a new family of porous materials, J. Am. Chem. Soc. 125(2003) 13370-13371.

[34] J. Shi, Y. Wang, W. Yang, Y. Tang, Z. Xie, Recent advances of pore system construction in zeolite-catalyzed chemical industry processes, Chem. Soc. Rev. 44(2015) 8877-8903.

[35] H.K. Min, S.B. Hong, Mechanistic investigations of ethylbenzene disproportionation over medium-pore zeolites with different framework topologies, J. Phys. Chem. C 115(2011) 16124-16133.