Deactivation by coke deposition on the HZSM-5 catalysts in the methanol-to-hydrocarbon conversion

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HZSM-5 used to be the main catalyst component for the MTG process of Exxonmobil Co. Catalyst deactivation by coke in methanol-to-hydrocarbon (MTH) over HZSM-5 was studied in a fixed-bed reactor by observing the activity and selectivity with time-on-stream at 500 degrees C and WHSV=4.25 h(-1). The HZSM-5 with SiO2/Al2O3 ratios of 40 and 280 were synthesized and characterized with XRD. N-2 adsorption/desorption and NH3-TPD. The used catalysts were investigated by N-2 adsorption/desorption, XRD, elemental analysis (EA) and UV-vis spectroscopy to identify the nature of coke. If the acidity of HZSM-5 is low (SiO2/Al2O3=280), the coke deposited is mainly mono- or bi-aromatic which did not affect the catalyst activity significantly. On the other hand when the acidity is high (SiO2/Al2O3=40), the coke deposited is polycyclic aromatics with 3 or 4 fused rings which leads to significant deactivation after 24 h. It is presumed that the coke on the HZSM-5 with low acidity must be located inside the pores and/or in the framework, since the coke particles without polycyclic aromatics should be small. The deactivation of HZSM-5 with high acidity is mainly caused by the bulky coke molecules, most probably inducing the topological blocking of the zeolite pores and channels. (C) 2012 Elsevier Ltd. All rights reserved.
Publisher
PERGAMON-ELSEVIER SCIENCE LTD
Issue Date
2012-12
Language
English
Article Type
Article; Proceedings Paper
Keywords

ZEOLITE ZSM-5; MESOPOROSITY; SELECTIVITY; PROPYLENE; STABILITY; H-ZSM-5; ACIDITY; SHAPE

Citation

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, v.73, no.12, pp.1542 - 1545

ISSN
0022-3697
DOI
10.1016/j.jpcs.2012.09.005
URI
http://hdl.handle.net/10203/102812
Appears in Collection
CBE-Journal Papers(저널논문)
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