Abstract
The influence of degree of H + exchange and calcination temperature of H · Na-ZSM-8 on its acidity distribution (measured by the chemisorption and stepwise thermal desorption of pyridine at 373–773 K) and catalytic properties for hydrocarbon conversion (viz., isomerization of o- and m-xylene and disproportionation of toluene) and methanol-to-aromatics conversion reactions have been investigated. Both the acidity and catalytic activity in these reactions increase with the decrease in Na + content and calcination temperature of the zeolite. The effect of poisoning of stronger acid sites with pyridine on the catalytic properties of the zeolite has also been studied. The catalytic activity and selectivity of the zeolite are strongly affected by this poisoning. The hydrocarbon conversion and aromatization reactions occur on strong protonic acid sites of the zeolite. Good correlations between catalytic activity and acidity (measured in terms of the chemisorption of pyridine at 673 K) have been obtained for these reactions. The increase in Na + content and calcination temperature and the poisoning have resulted in the increase in the shape selectivity of the zeolite in the formation of xylene isomers (i.e., the formation of p-xylene is increasingly favored) because of diffusion-reaction interactions. The physical, acidic, and catalytic properties, shape-selectivity behavior, and catalyst deactivation characteristics of ZSM-8 and ZSM-5 zeolites are compared.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.