Aerogel Re/Pd-TiO2/SiO2 and Co/Mo-Al2O3/SiO2 catalysts for hydrodesulphurisation of dibenzothiophene and 4,6-dimethyldibenzothiophene

Abstract

Re/Pd-TiO2/SiO2 and Co/Mo-Al2O3/SiO2 aerogel catalysts were synthesized using sol-gel method and super-critical drying in excess solvent, and investigated in the hydrodesulphurisation (HDS) of dibenzothiophene (DBT) and 4,6-dimethyl dibenzothiophene (4,6-DMDBT). The influence of supercritical drying on the final catalytic properties of the materials was determined by parallel synthesis of aerogels and xerogels for Re/Pd-TiO2/SiO2 catalysts. The sol-gel method and supercritical drying were found to result in amorphous aerogels with relatively high degree of uniformity, of both supports and active phases. Corresponding xerogels were found to be similar to aerogels in terms of composition and structure, but characterized by lower specific surface areas. Catalytic activity of Co/Mo-Al2O3/SiO2 aerogel catalysts in HDS of DBT and 4,6-DMDBT has shown no major improvement in comparison to conventional Co/Mo catalyst. On the other hand, Re/Pd-TiO2/SiO2 aerogels, obtained with the addition of mesitylene or without it, achieved 70 % and 64 % higher conversion of 4,6-DMDBT than conventional Co/Mo catalyst, respectively. Increased catalytic activity can be attributed to well dispersed Re and Pd active phases across the catalyst structure, good incorporation of Ti within silica matrix, increased mesopore volumes and high specific surface areas.