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n-Heptane transformation over a HMCM-22 zeolite: Catalytic role of the pore systems

Paper ID Volume ID Publish Year Pages File Format Full-Text
43237 45959 2008 10 PDF Available
Title
n-Heptane transformation over a HMCM-22 zeolite: Catalytic role of the pore systems
Abstract

n-Heptane transformation was carried out at 350 °C over a HMCM-22 zeolite (Si/Al = 14.5) previously characterized by various techniques: X-ray diffraction, nitrogen adsorption, scanning electron microscopy, pyridine and 2,4-dimethylquinoline (2,4-DMQ) adsorption followed by FTIR. A pronounced deactivation was shown to occur in the first 10 min reaction, due to a very fast initial coke formation, followed by a quasi-plateau in activity. Cracking was the main reaction. The role played by each of the three pore systems was established by selectively deactivating the supercage sites by coking then by selectively poisoning the protonic sites of the external cups with a bulky base molecule (2,4-DMQ). The supercage sites (∼70% of the inner ones) were found to be responsible for 97% of n-heptane transformation, those of the sinusoidal channels (∼20%) for only 3%, which means that these latter sites were ∼16 times less active probably because of pronounced steric constraints. Unexpectedly, the protonic sites of the external cups, which were demonstrated as able to catalyse efficiently various reactions including methylcyclohexane cracking, were found to be completely inactive.

Graphical abstractn-Heptane transformation was carried out at 350 °C over a HMCM-22 zeolite (Si/Al = 14.5). The role played by each of the three pore systems was established by selectively deactivating the supercage sites by coking then by selectively poisoning the protonic sites of the external cups with a bulky base molecule (2,4-DMQ). The supercage sites were found to be responsible for 97% of n-heptane transformation, those of the sinusoidal channels for only 3%. The protonic sites of the external cups, which were demonstrated as able to catalyse efficiently various reactions including methylcyclohexane cracking, were found to be completely inactive. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
HMCM-22; n-Heptane cracking; Deactivation by coking; Location of reactions
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 351, Issue 2, 30 December 2008, Pages 174–183
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
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