Generation of active protonic acid site from cyclohexane over Pt/SO42--Al2O3 catalyst

Abstract

Generation of active protonic acid sites for isomerisation of cyclohexane over Pt/SO4 2--Al2O3 catalyst was studied. Pt/SO4 2--Al2O3 was synthesized and calcined at 823K. Characterization was carried out with XRD, BET ammonia-TPD, pyridine-preadsorbed IR spectroscopy, and FTIR. The XRD result showed that the addition of Pt and SO4 2- did not change the phase of ?-Al2O3. The specific surface area of Pt/SO4 2--Al2O3 was 163 m2/g. Pyridine-preadsorption study showed that Pt/SO4 2--Al2O3 consists of protonic acid and Lewis acid sites which appear at wavenumber of 1455 cm-1 and 1545 cm-1. The ratio of extinction coefficient,e1455/e1545 was 2.0. In the absence of hydrogen, isomerization of cyclohexane resulted 3% and 85% of conversion of cyclohexane and selectivity of methyl-cyclopentane, respectively. These results indicated that the isomerisation occurs although in the absence of hydrogen. Generation of protonic acid sites from cyclohexane was observed by pyridinepreadsorbed FTIR, where protonic acid sites were formed and Lewis acid sites were decreased in the heating of Pt/SO4 2--Al2O3 in cyclohexane. This phenomenon indicated that the formation of protonic acid sites induced by cyclohexane is a reversible process. Generation of active site from cyclohexane is widely applicable concept for active sites over Pt/SO4 2--Al2O3.