The transformations of toluene on alumina and bifunctional catalysts

The activity of Pt, Rh, and Ni catalysts deposited on Al₂O₃ and tungsten-containing catalysts 20% H₄SiW₁₂O₄₀/ZrO₂ and 15% WO_x/ZrO₂ in the hydrogenation of toluene and toluene ring opening and isomerization in the presence of hydrogen was studied. Under experimental conditions (160–360°C, 2.2 MPa), the main reactions on Rh/Al₂O₃ were the hydrogenation of toluene into methylcyclohexane, hydrogenolysis into isoheptanes, and hydrocracking into alkanes C₁–C₆. On Pt, Rh, and Ni catalysts on carriers with strong acid properties, the isomerization of the six-membered into five-membered ring followed by hydrogenolysis (hydrocracking) of alkylcyclopentanes occurred. The yield of heptane isomers, however, did not exceed 13%. The activity of Pt and Rh catalysts on a high-acidity carrier (WO_x/ZrO₂) in hydrocracking was much higher than that of catalysts based on deposited heteropoly acid. The yields of hydrogenolysis (hydrocracking) products on Ni/WO_x/ZrO₂ were much lower than on Pt(Rh)/WO_x/ZrO₂. The highest yield of ring opening products (isoheptanes and n-heptane) was obtained with layered loading of two catalysts; it reached 58 wt % at 300°C and a 2.2 MPa pressure, which was 4.5 and 2 times higher than the yield obtained on Ni-Pt/WO_x/ZrO₂ and 2% Rh/Al₂O₃ catalysts. Hydrodemethylation was not the main direction of toluene transformations on any of the catalysts studied.