Abstract
The methanol-to-olefin (MTO) process has attracted much attention and many problems including lifetime and selectivity of light olefins have all been connected to the diffusion problems in zeolite crystals. However, a quantitative study of diffusion problems in SAPO-34 zeolites is lacking. In this paper, we performed a high-precision diffusion measurement of the diffusion behavior of ethane and propane, which represent ethylene and propylene respectively, over SAPO-34. The diffusions of ethane and propane over fresh and coked SAPO-34 zeolites with different crystal sizes were carefully studied. Ethane and propane show different diffusion behavior in SAPO-34. The diffusion of ethane is almost not influenced by the crystal size and coke percentage, whereas that of propane is strongly affected. A slower diffusion velocity was observed in bigger crystals, and the diffusion velocity decline significantly with the coke percentage increasing. The diffusion coefficient was calculated with both the internal and surface diffusion models, and the results show that the surface diffusion plays a key role in the diffusion process of both ethane and propane. We believe that this work would be helpful for understanding the diffusion of different molecules in SAPO-34 zeolites, and may lay the foundation of MTO research.
Similar content being viewed by others
References
Su D S, Wen G, Wu S, Peng F, Schlögl R. Carbocatalysis in liquidphase reactions. Angewandte Chemie International Edition, 2017, 56(4): 936–964
Losch P, Pinar A B, Willinger M G, Soukup K, Chavan S, Vincent B, Pale P, Louis B. H-ZSM-5 zeolite model crystals: Structurediffusion-activity relationship in methanol-to-olefins catalysis. Journal of Catalysis, 2017, 345: 11–23
Liang T, Chen J, Qin Z, Li J, Wang P, Wang S, Wang G, Dong M, Fan W, Wang J. Conversion of methanol to olefins over H-ZSM-5 zeolite: Reaction pathway is related to the framework aluminum siting. ACS Catalysis, 2016, 6(11): 7311–7325
Fickel D W, Sabnis K D, Li L, Kulkarni N, Winter L R, Yan B, Chen J G. Chloromethane to olefins over H-SAPO-34: Probing the hydrocarbon pool mechanism. Applied Catalysis A, General, 2016, 527: 146–151
Li Y, Zhang M, Wang D, Wei F, Wang Y. Differences in the methanol-to-olefins reaction catalyzed by SAPO-34 with dimethyl ether as reactant. Journal of Catalysis, 2014, 311: 281–287
Li J, Wei Y, Liu G, Qi Y, Tian P, Li B, He Y, Liu Z. Comparative study of MTO conversion over SAPO-34, H-ZSM-5 and H-ZSM-22: Correlating catalytic performance and reaction mechanism to zeolite topology. Catalysis Today, 2011, 171(1): 221–228
Sun X, Mueller S, Shi H, Haller G L, Sanchez-Sanchez M, van Veen A C, Lercher J A. On the impact of co-feeding aromatics and olefins for the methanol-to-olefins reaction on HZSM-5. Journal of Catalysis, 2014, 314: 21–31
Sun X, Mueller S, Liu Y, Shi H, Haller G L, Sanchez-Sanchez M, van Veen A C, Lercher J A. On reaction pathways in the conversion of methanol to hydrocarbons on HZSM-5. Journal of Catalysis, 2014, 317: 185–197
Ilias S, Bhan A. Mechanism of the catalytic conversion of methanol to hydrocarbons. ACS Catalysis, 2013, 3(1): 18–31
Zhou H, Wang Y, Wei F, Wang D, Wang Z. Kinetics of the reactions of the light alkenes over SAPO-34. Applied Catalysis A, General, 2008, 348(1): 135–141
Li M, Wang Y, Bai L, Chang N, Nan G, Hu D, Zhang Y, Wei W. Solvent-free synthesis of SAPO-34 nanocrystals with reduced template consumption for methanol-to-olefins process. Applied Catalysis A, General, 2017, 531: 203–211
Wu X C, Abraha M G, Anthony R G. Methanol conversion on SAPO-34: Reaction condition for fixed-bed reactor. Applied Catalysis A, General, 2004, 260(1): 63–69
Wei Y, Li J, Yuan C, Xu S, Zhou Y, Chen J, Wang Q, Zhang Q, Liu Z. Generation of diamondoid hydrocarbons as confined compounds in SAPO-34 catalyst in the conversion of methanol. Chemical Communications, 2012, 48(25): 3082
Li Y, Huang Y, Guo J, Zhang M, Wang D, Wei F, Wang Y. Hierarchical SAPO-34/18 zeolite with low acid site density for converting methanol to olefins. Catalysis Today, 2014, 233: 2–7
Wei Z, Chen Y, Li J, Wang P, Jing B, He Y, Dong M, Jiao H, Qin Z, Wang J, et al. Methane formation mechanism in the initial methanolto-olefins process catalyzed by SAPO-34. Catalysis Science & Technology, 2016, 6(14): 5526–5533
Xu S, Zheng A, Wei Y, Chen J, Li J, Chu Y, Zhang M, Wang Q, Zhou Y, Wang J, et al. Direct observation of cyclic carbenium ions and their role in the catalytic cycle of the methanol-to-olefin reaction over chabazite zeolites. Angewandte Chemie International Edition, 2013, 52(44): 11564–11568
Qi L, Li J, Wei Y, Xu L, Liu Z. Role of naphthalene during the induction period of methanol conversion on HZSM-5 zeolite. Catalysis Science & Technology, 2016, 6(11): 3737–3744
Wei Y, Yuan C, Li J, Xu S, Zhou Y, Chen J, Wang Q, Xu L, Qi Y, Zhang Q, Liu Z. Coke formation and carbon atom economy of methanol-to-olefins reaction. ChemSusChem, 2012, 5(5): 906–912
Tian P, Wei Y, Ye M, Liu Z. Methanol to olefins (MTO): From fundamentals to commercialization. ACS Catalysis, 2015, 5(3): 1922–1938
Chen D, Rebo H P, Moljord K, Holmen A. Methanol conversion to light olefins over SAPO-34. Sorption, diffusion, and catalytic reactions. Industrial & Engineering Chemistry Research, 1999, 38 (11): 4241–4249
Aguayo A T, Del Campo A, Gayubo A G, Tarrio A, Bilbao J. Deactivation by coke of a catalyst based on a SAPO-34 in the transformation of methanol into olefins. Journal of Chemical Technology and Biotechnology (Oxford, Oxfordshire), 1999, 74 (4): 315–321
Hwang A, Prieto-Centurion D, Bhan A. Isotopic tracer studies of methanol-to-olefins conversion over HSAPO-34: The role of the olefins-based catalytic cycle. Journal of Catalysis, 2016, 337: 52–56
Yang G, Wei Y, Xu S, Chen J, Li J, Liu Z, Yu J, Xu R. Nanosizeenhanced lifetime of SAPO-34 catalysts in methanol-to-olefin reactions. Journal of Physical Chemistry C, 2013, 117(16): 8214–8222
Zhu W, Kapteijn F, Moulijn J A, den Exter M C, Jansen J C. Shape selectivity in adsorption on the all-silica DD3R. Langmuir, 2000, 16 (7): 3322–3329
Olson D H, Camblor M A, Villaescusa L A, Kuehl G H. Light hydrocarbon sorption properties of pure silica Si-CHA and ITQ-3 and high silica ZSM-58. Microporous and Mesoporous Materials, 2004, 67(1): 27–33
Cui Y, Zhang Q, He J, Wang Y, Wei F. Pore-structure-mediated hierarchical SAPO-34: Facile synthesis, tunable nanostructure, and catalysis applications for the conversion of dimethyl ether into olefins. Particuology, 2013, 11(4): 468–474
Bhatia S K, Perlmutter D D. A random pore model for fluid-solid reactions: II. Diffusion and transport effects. AIChE Journal. American Institute of Chemical Engineers, 1981, 27(2): 247–254
Thiele E W. Relation between catalytic activity and size of particle. Industrial & Engineering Chemistry, 1939, 31(7): 916–920
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Cai, D., Cui, Y., Jia, Z. et al. High-precision diffusion measurement of ethane and propane over SAPO-34 zeolites for methanol-to-olefin process. Front. Chem. Sci. Eng. 12, 77–82 (2018). https://doi.org/10.1007/s11705-017-1684-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11705-017-1684-5