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SAPO-34 and ZSM-5 nanocrystals’ size effects on their catalysis of methanol-to-olefin reactions

Paper ID Volume ID Publish Year Pages File Format Full-Text
40854 45868 2012 11 PDF Available
Title
SAPO-34 and ZSM-5 nanocrystals’ size effects on their catalysis of methanol-to-olefin reactions
Abstract

The catalysis of methanol-to-olefin (MTO) reactions over SAPO-34 and ZSM-5 was strongly shown to depend on the crystallites sizes. Four samples (average size of 50–5000 nm) of each catalyst were characterized for shape, size, acidity and diffusion properties. Materials adsorbed and occluded on them during the reaction were directly monitored in situ by IR spectroscopy and analyzed ex situ by GC–MS after extraction. Crystallites of 200–500 nm showed the best conversions and lifetimes because of their large external surfaces and short diffusion lengths. SAPO-34 with the smallest crystallites (<150 nm) deactivated rapidly due to pore blocking by heavy coke deposits; similarly sized ZSM-5 exhibited low conversion due to the low number of strong Brönsted acid sites in its micropores. The adverse effects of the nanocrystallity of zeolite catalysts are discussed in terms of their framework topology, acidity, and diffusivity.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (143 K)Download as PowerPoint slideHighlights► Four catalysts each of 20–5000 nm SAPO-34 and ZSM-5 were prepared. ► The smallest (<150 nm) catalysts exhibited poor activity in the MTO reaction. ► The largest (>5000 nm) catalysts also exhibited poor catalytic activity. ► The catalyst with moderate crystallites (200–500 nm) show high catalytic activity. ► Extremely small nanocrystallites (<150 nm) significantly hindered catalysis.

Keywords
MTO reaction; SAPO-34; ZSM-5; Crystallite size; Deactivation
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SAPO-34 and ZSM-5 nanocrystals’ size effects on their catalysis of methanol-to-olefin reactions
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volumes 437–438, 26 September 2012, Pages 120–130
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us