Comparison between Zeolite β and γ-Al2O3 Supported Pt for Reforming Reactions

Abstract

The performance of zeolite β supported platinum as a bifunctional catalyst for the reforming of n-hexane, methylcyclopentane, and cyclohexane, typical representatives of reforming feeds, has been examined under low severity conditions. A comparison under the same conditions with γ-Al2O3 supported Pt was carried Out. Both catalysts were impregnated with 0.5 wt% Pt. It is found that β-zeolite exhibits skeletal isomerization reactions to a higher extent than alumina, producing molecules with much higher octane number than the feed molecules. Bimolecular alkylation reactions that take place in the zeolite pores have as a result the formation of products with a carbon number larger than that of the feed molecule. The enlargement of the cyclic ring of methylcyclopentane leads at suitable temperatures to aromatics, a reaction of great importance for reforming. This behavior is a result of the relatively large acidity of the zeolite and of its pore structure that favors the proximity among different molecules increasing the probability for reaction. In contrast, Pt/Al2O3 stimulates dehydrogenation-hydrogenation and to a smaller extent skeletal isomerization. The β-zeolite is deactivated more easily than alumina due to the coke build up on the acidic sites. The characterization of the catalysts has been carried out using XRD, NH3-TPD, SEM, FTIR, BET, TEM, and H2-Chemisorption.