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On the location, strength and accessibility of Brønsted acid sites in hierarchical ZSM-5 particles

Paper ID Volume ID Publish Year Pages File Format Full-Text
55181 47043 2012 9 PDF Available
Title
On the location, strength and accessibility of Brønsted acid sites in hierarchical ZSM-5 particles
Abstract

Microporous and mesoporous (hierarchical) ZSM-5 samples, prepared by desilication, dealumination and templating with carbon nanoparticles have been characterized by adsorbing benzene, cyclohexane and 1,3,5-trimethylbenzene (mesitylene) to probe the location, the strength and the accessibility of Brønsted acid sites. The mesoporosity introduced by the methods explored resulted in a statistical accommodation of benzene at the channel intersections. Cyclohexane showed the highest strength of physisorption in micro- and mesopores and, thus, probes the largest fractions of acid sites. Mesitylene adsorption showed that mesopores of hierarchical zeolites do not contain Brønsted acid sites. All results indicated that the mesoporosity influences only the accessibility of the acid sites in the ZSM-5 crystals mostly via shortening diffusion pathways, but not the strength of the interaction with the cyclic hydrocarbons. The enhanced transport rates observed for benzene are associated to the decreased pore length inside the mesoporous particles, rather than to changes of the pore structure or the generation of additional sites.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (105 K)Download as PowerPoint slideHighlights► Decrease in the size of microporous domains responsible for enhanced adsorption rates. ► Unchanged adsorption properties upon introduction of mesoporosity in ZSM5 zeolites. ► Mesopores are free of Brønsted acid sites.

Keywords
HZSM-5; Mesoporosity; Adsorption; Infrared spectroscopy; Brønsted acid sites
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On the location, strength and accessibility of Brønsted acid sites in hierarchical ZSM-5 particles
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 198, Issue 1, 30 December 2012, Pages 3–11
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