Highly selective and stable alkylation of benzene with ethane into ethylbenzene over bifunctional PtH-MFI catalysts

Benzene alkylation with ethane into ethylbenzene (EB) was studied at 370 degrees C over two Pt-containing NFI catalysts with the Si/Al ratios of 36 and 140, and the reaction temperature and catalysts were selected based on the analysis of the thermodynamic and kinetic limitations associated with this reaction. The experimental results suggest that EB formation proceeds via ethane dehydrogenation into ethene over Pt sites and subsequent benzene alkylation with ethene over acid sites. Under selected reaction conditions the whole process of EB formation is driven by the alkylation reaction and many side reactions (including coke formation) are suppressed due to the inherently low ethene concentration at 370 degrees C. Also, the low and moderate acidity of the catalysts allows decoupting of EB fort-nation steps and the steps of its subsequent transformation into side products. As a consequence, both catalysts demonstrate a remarkably stable performance (during 45-49 h on stream) with EB selectivity in the aromatic products in the range between 92.6 and 95.3 mol%, with the highest (benzene-based) EB yield of 10.7%. These observed EB selectivities and yield are essentially higher than those reported previously both for the zeolite and superacidic catalytic systems. (c) 2007 Elsevier B.V. All rights reserved.