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Product selectivity and catalytic deactivation of MOR zeolites with different acid site densities in methanol-to-olefin (MTO) reactions

Paper ID Volume ID Publish Year Pages File Format Full-Text
42807 45942 2008 10 PDF Available
Title
Product selectivity and catalytic deactivation of MOR zeolites with different acid site densities in methanol-to-olefin (MTO) reactions
Abstract

The effects of the acid site densities of MOR zeolites on their product selectivity and deactivation were investigated in the methanol-to-olefin (MTO) reactions. The MOR zeolites showed a high conversion and high yield of the lower olefins at the initial time of the MTO reaction, regardless of their acid site density. However, the conversion and the yield of the lower olefins over them rapidly decreased in the order of MOR(103) < MOR(55) < MOR(12) < MOR(5), where the numbers in parenthesis represent their Si/Al ratios. The materials occluded on the MOR zeolites during the MTO reaction were investigated by the IR, 13C NMR and UV–vis spectroscopic methods. A large amount of polycyclic aromatic hydrocarbons (PAHs) with 3–4 fused aromatic rings was occluded on the MOR(5) zeolite with the highest acid site density. However, alkylbenzenes and alkylnaphthalenes were the major components of the materials occluded on the MOR(103) zeolite with the lowest acid site density. The IR spectra recorded in situ during the MTO reaction over the MOR zeolites clearly exhibited the differences in the accumulation rates of PAH on their pores according to the acid site density. The rapid accumulation of PAH on the MOR zeolites with high acid site densities leads to the loss of the active alkylbenzene intermediates as well as to the blockage of the pores, resulting in their rapid deactivation. The sparse distribution of acid sites in the pores of the MOR zeolites suppresses the condensation of alkylbenzenes in their pores and lengthens their catalyst lifetime.

Graphical abstractThe IR spectra recorded in situ during the MTO reaction over four kinds of MOR zeolites with different Si/Al ratios clearly exhibited some differences in the formation of active intermediates (1465 cm−1) and in the accumulation rate of polycyclic aromatic hydrocarbons (1570 cm−1) in pores according to their acid site density. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Methanol to olefin (MTO); MOR zeolite; Acid site density; Deactivation
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Product selectivity and catalytic deactivation of MOR zeolites with different acid site densities in methanol-to-olefin (MTO) reactions
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 349, Issues 1–2, 31 October 2008, Pages 76–85
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
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Any Questions? feel free to contact us