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 Al(2)O(3) content of MSA from 52 to 9 wt.%. This treatment mainly removed the non-acidic extra-framework Al(oct) species, exposed the Bronsted 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(NH(3))(4)(OH)(2) and Pd(OAc)(2) + H(2)PtCl(6). The bimetallic catalyst prepared from Pt(NH(3))(4)(OH)(2) showed significant promotional effect and exhibited the highest activity in HDS of thiophene and benzothiophen

\u201cMesoporous silica-allumina modified by acid leaching as support of Pt catalysts in HDS of model compounds\u201d

The potential of mesoporous silica\u2013alumina (MSA) modified by acid leaching as alternative support for Pt catalysts was studied in hydrodesulfurization (HDS) of thiophene and benzothiophene. The supports were characterized by N2 adsorption, XRD, 27AL MAS NMR, electron microscopy (SEM, HRTEM) and by activities in cyclohexene isomerization and cumene cracking. The composition of the catalysts and Pt dispersion were determined by ICP andH2 or CO sorption, respectively. Progressive leaching of the parent MSA from 50% Al2O3 to 11% Al2O3 content led to increase of the BET surface area and exposition of strong acidity. This positively affected the activities of the reduced Pt catalysts in thiophene HDS. Deposition of 1.5 wt.% Pt on MSA (11% Al2O3) by using Pt(NH3)4(OH)2 as precursor gave the best catalyst, several times more active in thiophene HDS than the weight equivalents of sulfided CoMo/Al2O3 or reduced Pt/HY zeolite. In benzothiophene reaction, its activity was slightly above that of CoMo/Al2O3 and about twofold compared to Pt/HY