Dehydroisomerization of butane into isobutene on Pt-Sn intermetallic compounds supported on H-SAPO-11

The dehydroisomerization of butane to form isobutene was carried out on Pt-based bimetallic catalysts supported on zeolite. Among various zeolites, Si-rich H-SAPO-11 was most appropriate for obtaining high selectivity to isobutene at higher butane conversions. The acid sites of Si-rich H-SAPO-11 were characterized by ammonia adsorption, Si-29 MAS NMR, and the cracking of cumene. The addition of second elements, such as Sn, Pb, Zn and In, onto Pt/H-SAPO-11 retarded the hydrogenolysis activity of Pt, resulting in decreased methane selectivity. Among the second elements, tin was the most effective additive for obtaining higher isobutene selectivity. The formation of Pt-Sn intermetallic compounds, Pt3Sn, PtSn, and PtSn2, was revealed by XRD. The surface of Pt-Sn bimetallic particles was characterized through the dispersion of Pt and IR spectra of adsorbed CO. The formation of surface intermetallic compounds is proposed to retard hydrogenolysis by the ensemble effect. (c) 2006 Elsevier Inc. All rights reserved.