Kinetics and Mechanisms of n-Propylbenzene Hydrodealkylation Reactions over Pt(Sn)/SiO2 and (Cl–)Al2O3 Catalysts in Reforming Conditions

Kinetics of n-propylbenzene hydrodealkylation (HDA) was investigated over model catalysts under reforming operating conditions (773 K, 5 bars, and H2/HC=5). Silica-supported platinum catalysts (Pt/SiO2 and PtSn/SiO2) and alumina materials (Al2O3 and 1 wt% Cl–Al2O3) were chosen to evaluate the influence of the metallic and acidic phases on the HDA reactions, respectively. The kinetic study showed (i) that the HDA processes occurred to a significant extent over both catalytic phases under identical operating conditions and (ii) that hydrodealkylated products (benzene, toluene, and ethylbenzene) were formed through concurrent pathways whatever the nature of the catalytic phase. In addition, product intermediates were identified and mechanisms were suggested to explain the HDA reactions over either different patches of metallic sites or different acid sites (Brønsted and Lewis). Finally, as compared to toluene and ethylbenzene, the formation rate of benzene was the highest over the acidic function and the lowest over Pt/SiO2.