Origin of cracking functionality of sulfided (Ni) CoMo/SiO2-ZrO2 catalysts

A systematic investigation of the hydrocracking activity of Mo, CoMo, and N iMo catalysts as a function of support composition, Mo content, and Co or N i content on supported ZrO2-SiO2 catalysts of varying composition (Zr/Zr Si = 0.0, 0.15, 0.30, 0.45, 0.70, 1.0) carried out in a microcatalytic reac tor at 400 degrees C and atmospheric pressure is presented. Varying the com position of the support, the Mo content, and the Co or Ni content was studi ed. Cumene cracking in the presence of hydrogen on the sulfided catalysts i ndicated that the supported molybdenum phase and the promoted counterparts contribute significantly to the cracking functionality of the catalysts. Fr om the studies based on SiO2 and carbon supported catalysts it appears that it is unlikely that the observed high activities of supported MoS2 and its promoted analogues are due to increased activity as a result of reduction in coke formation on the support surface. The creation of sulfhydryl groups and their role in generating the acid function are discussed. (C) 2000 Aca demic Press.