Effect of preparation of Pd and Pd–Pt catalysts from acid leached silica–alumina on their activity in HDS of thiophene and benzothiophene

Mesoporous silica–alumina (MSA) modified by post-synthesis acid leaching was studied as a support for Pd and Pd–Pt catalysts. Activity of catalysts was evaluated in hydrodesulfurization (HDS) of model compounds (thiophene and benzothiophene). The leaching decreased the Al2O3 content of MSA from 52 to 9 wt.%. This treatment mainly removed the non-acidic extra-framework Aloct species, exposed the Brønsted acidic sites and increased the BET surface area by 50%. The higher acidity and surface area improved the activities of Pd catalysts in HDS of thiophene and benzothiophene. Pd(OAc)2 deposited on the leached MSA gave the best monometallic Pd catalyst. Two bimetallic Pd–Pt catalysts were prepared by co-impregnation of the leached MSA with Pd(OAc)2 + Pt(NH3)4(OH)2 and Pd(OAc)2 + H2PtCl6. The bimetallic catalyst prepared from Pt(NH3)4(OH)2 showed significant promotional effect and exhibited the highest activity in HDS of thiophene and benzothiophene.

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► Extraction of part of alumina from mesoporous silica–alumina (MSA) by HNO3 increased the Brønsted acidity and surface area of MSA support.
► Both properties improved the HDS activities of Pd/MSA catalysts.
► Promotional effects over bimetallic Pd–Pt/MSA catalyst were observed in HDS of thiophene and benzothiophene.