Abstract

Two different series of alumina supported platinum catalysts have been prepared and tested in the methylcyclohexane dehydrogenation. In each series the same metallic content, 1 and 2 wt.%, and different types of metal precursors, H2PtCl6 and Pt(acac)2, have been used to deposit platinum on the support. The catalysts were characterized by means of H2 chemisorption, O2-H2 titrations, XPS and surface acidity by TPD of t-butylamine. In order to evaluate the effect on the metallic function, this reaction was also performed in the presence of 10 ppm of thiophene in feed stream. The obtained results indicate that the catalysts prepared by the organometallic route present higher metal dispersions and lower surface acidity compared with those prepared from H2PtCl6. Additionally, XPS results showed that the state of platinum is essentially Pt° in the catalysts obtained from Pt(acac)2 while in the other series there exists an important contribution of Pt?+ species which plays a positive role in dehydrogenation of methylcyclohexane. The presence of tiophene in the feed produces an increase in the turnover number which may be attributed to an electronic effect induced by the sulphur in the metallic crystal.