Influence of the metallic precursor in the hydrogenation of tetralin over Pd–Pt supported zirconium doped mesoporous silica

Abstract

Palladium–platinum supported on zirconium doped mesoporous silica catalysts have been prepared by incipient wetness impregnation with two different precursors: (i) a dinuclear precursor [PdPtCl₂(μ-dppm)₂] where dppm = Ph₂PCH₂PPh₂; and (ii) PdCl₂ and H₂PtCl₆·6H₂O. The catalysts obtained with the bimetallic precursor show a much smaller metallic particle size than those prepared using monometallic precursors. The influence of the precursor in the hydrogenation of tetralin at high hydrogen pressure was studied. Both types of catalysts exhibit a good hydrogenation activity with a poor hydrogenolysis/ring opening activity. The type of precursor has a marked influence in the observed trans- to cis-decalin ratio being higher for catalysts prepared with monometallic precursors. Both types of catalysts show a good thiotolerance against dibenzothiophene, but the observed poisoning is more reversible in the case of catalysts prepared using monometallic precursors. A positive effect of the hydrogen pressure over the catalyst thiotolerance was observed, and using a P(H₂) of 6 MPa, the catalyst with a 2 wt% PdPt prepared from monometallic salts was found to be very resistant to sulfur poisoning, with a tetralin conversion higher than 95% in the presence of 1375 ppm of DBT in the feed, at 588 K.