Influence of the incorporation of palladium on Ru/MCM hydrotreating catalysts

Zirconium-doped mesoporous silica with a Si/Zr molar ratio of 5 has been used as a support for bimetallic Ru-Pd catalysts. The effect of palladium as a promoter in a catalyst containing ruthenium as active phase, and the influence of the Ru/Pd atomic ratio were studied in the hydrogenation and ring-opening reaction of tetralin. The results indicate the promotional effect of Pd on hydrotreating activity of catalyst since an increase is observed in the formation of hydrogenation products, especially trans-decalin at low temperatures for 5-RuPd(8/1) and 5-RuPd(4/1), while at higher temperatures, there is an enhacement in the production of hydrogenolysis/hydrocracking products. In contrast 5-RuPd(15/1) catalyst shows at low temperatures lower yields of hydrogenation products and higher yields of high molecular weight products (HMW) than 5-Ru catalyst while at higher temperatures than 315 °C only produces HMW products. The best catalytic performance is displayed by the 5-RuPd(8/1) catalyst, giving a conversion of tetralin of 98.5% as well as high yields of hydrogenation (20.8%) and ring-opening (70.1%) products under the following experimental conditions: temperature of reaction 350 °C; H2/tetralin molar ratio of 10; contact time 2.8 s and total pressure of 6 MPa (P(H2) = 4.5 MPa and P(N2) = 1.5 MPa). Moreover, this catalyst exhibits good thiotolerance in the presence of 600 ppm of dibenzothiophene in the feed, and an excellent tolerance to nitrogen compounds even with 2000 ppm of acridine.