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Hierarchical ZSM-5 zeolites synthesized by silanization of protozeolitic units: Mediating the mesoporosity contribution by changing the organosilane type

Paper ID Volume ID Publish Year Pages File Format Full-Text
54153 46999 2014 11 PDF Available
Title
Hierarchical ZSM-5 zeolites synthesized by silanization of protozeolitic units: Mediating the mesoporosity contribution by changing the organosilane type
Abstract

•The usage of silylated polymers allows obtaining larger mesopores than with PHAPTMS.•Hierarchical ZSM-5 obtained with the silylated polymer showed lower acidity and less acid strength.•Both hierarchical ZSM-5 showed similar activity in LDPE cracking.

Hierarchical ZSM-5 zeolites were prepared by crystallization of silanized protozeolitic units employing silylated polypropylene oxide diamine polymers as organosilanes. The influence of the (Sipol/Sigel) molar ratio was investigated within 0–0.15 range. High synthesis yields (∼90%) of well-crystallized hierarchical zeolites exhibiting a high proportion of secondary porosity (additional to the zeolitic micropores) was reached for (Sipol/Sigel) molar ratios lower than 0.08. The usage of the silylated polymer resulted in hierarchical ZSM-5 with larger mesopores (4–20 nm) in higher share than the hierarchical ZSM-5 prepared with a smaller organosilane (phenyl-aminopropyl-trimethoxysilane, PHAPTMS). However, it also contained meaningfully lower amount of acid sites and with less acid strength. The best catalytic performance in the cracking of low density polyethylene (LDPE) was showed by the material prepared from a (Sipol/Sigel) ratio of 0.03. Noteworthy, in addition to the gasoline range fraction (C6–C12), light C1–C5 olefins are the main reaction products, which are interesting feedstock for the petrochemical industry. Its catalytic performance is similar to the hierarchical ZSM-5 prepared using the smaller organosilane (PHAPTMS), which is indicative that the enhanced accessibility to the acid sites due to the presence of larger mesopores (4–20 nm) makes up for the lower amount and strength of its acid sites. Thereby, it is possible to enhance the mesoporosity by using bulkier organosilane (silylated polymers) but at the expense of losing acid properties.

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Keywords
Hierarchical porosity; ZSM-5; Silanization; Silylated polymer; PHAPTMS
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Hierarchical ZSM-5 zeolites synthesized by silanization of protozeolitic units: Mediating the mesoporosity contribution by changing the organosilane type
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 227, 15 May 2014, Pages 15–25
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