Cumene cracking functionalities on sulfided Co(Ni)Mo/TiO₂-SiO₂ catalysts

Abstract

Cumene cracking reaction was carried out on pure support as well as sulfided Mo, CoMo, and NiMo catalysts in a plug flow micro-reactor at 400°C and atmospheric pressure. Catalytic activity was studied as a function of Mo content, promoter content (Co, Ni), and support composition [Ti/(Ti+Si)=0.0, 0.15, 0.30, 0.45, 0.70, 1.0]. Surface acid–base properties of pure supports were measured with 2-propanol decomposition, showed that the supports were acidic in nature, the acidic character increases with increasing TiO₂ content in SiO₂. Techniques used for characterization were BET specific surface area (SSA), pore volume, X-ray diffraction, CO₂ chemisorption, and low temperature oxygen chemisorption (LTOC). CO₂ chemisorption on sulfided catalysts showed a strong decrease in the amount of CO₂ adsorption as a function of metal loading. The sulfided-supported catalysts exhibited better cracking activity in presence of hydrogen, which suggests that sulfided molybdenum phases were responsible for cumene cracking activity. The LTOC and catalytic activity results showed similar trends with variation of molybdenum content which indicated that the cracking activity of Mo and CoMo catalysts has significant contribution from the supported phases. The cumene cracking activity over supported catalysts is attributed to the Brønsted (S-H) sites like sulfhydryl groups. Variation of support composition strongly affects the catalytic cracking activity which decreases with increasing TiO₂ content in SiO₂.