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Temperature effects in benzene alkylation with ethane into ethylbenzene over a PtH-MFI bifunctional catalyst

Paper ID Volume ID Publish Year Pages File Format Full-Text
40478 45855 2013 8 PDF Available
Title
Temperature effects in benzene alkylation with ethane into ethylbenzene over a PtH-MFI bifunctional catalyst
Abstract

Benzene alkylation with ethane into ethylbenzene (EB) over a PtH-MFI bifunctional catalyst was thoroughly studied at six different temperatures between 290 and 490 °C. Our work demonstrates that temperature affects in a different way the thermodynamic equilibrium of two major reaction steps: (i) ethane dehydrogenation into ethene over Pt sites and (ii) benzene alkylation with ethene over acid sites. This, in turn, leads to significant differences in the product distribution and catalyst performance at different temperatures. It is shown that with increasing temperature ethane dehydrogenation is highly accelerated, while the EB formation rate increases in much lesser extent. As a consequence, high concentration of ethene is observed at high temperatures (450–490 °C), while the maximum concentrations of EB are very similar at all temperatures. Ethene, which is formed in excess at high temperatures, is converted via oligomerization and cracking steps into higher alkenes that alkylate benzene (or aromatic products). These alkylation reactions are followed by cyclization and dehydrogenation steps leading to formation of polyaromatics (coke precursors) and subsequent catalyst deactivation. On the other hand, at lower temperatures (290–410 °C) ethene reacts preferably with benzene forming EB. Hence, side reactions are suppressed and high EB selectivity and catalyst stability are observed at these temperatures. Based on the analysis of the catalyst activity, selectivity and stability, it is concluded that 370–410 °C can be considered as the optimum temperature range for the direct benzene alkylation with ethane into EB. Further improvement of the process may be achieved by selective removal of hydrogen from the reactor and by optimization of the ethane/benzene ratio in the feed.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (242 K)Download as PowerPoint slideHighlights► Coupling of ethane dehydrogenation (1) and benzene alkylation with ethene (2). ► At temperatures below ∼370 °C formation of ethylbenzene is limited by step (1). ► At temperatures above ∼410 °C formation of ethylbenzene is limited by step (2). ► Excessive formation of ethene above 410 °C leads to side products and deactivation. ► Optimum reaction temperature range: 370–410 °C.

Keywords
Alkylation; Dehydrogenation; Bifunctional catalysis; Zeolite
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Temperature effects in benzene alkylation with ethane into ethylbenzene over a PtH-MFI bifunctional catalyst
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 454, 15 March 2013, Pages 137–144
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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