Catalytic activity of Mo oxide before and after alkali metal addition for methylcyclohexane and methylcyclopentane compounds

• A bifunctional (metal-acid) Mo catalyst is presented.
• In-situ characterization by XPS–UPS surface techniques were performed.
• Ring contraction and isomerization of methylcyclohexane were performed.
• Comparable RC isomerization activity of MoTi to Pt–HY for MCH reactant.
• Dehydrogenation of MCH to toluene occur at temperatures between 623 and 673 K.

Different catalytic reactions of methylcyclohexane MCH are performed depending on the nature of the catalytic active site (s) and experimental conditions. Ring contraction RC catalytic processes, producing dimethylcyclopenanes DMCP’s of high octane numbers as compared to MCH are catalysed by acidic function of zeolites systems such as HY. Better activity, selectivity and stability concerning these RC reactions were obtained using Pt/HY catalyst. At higher reaction temperature, dehydrogenation of MCH to toluene and hydrocracking reactions are catalyzed by Pt. Comparable catalytic behavior is obtained using a bifunctional (metal–acid) MoO2-x(OH)y/TiO2 (MoTi) system. Different metallic character strength is observed following the suppression of the Brønsted acid MoOH function(s) to MoO2-x(OA)y/TiO2 (A = Na, K, Rb) by the addition of small amount of alkali metal A. Rubidium addition seems to be the most performant in the dehydrogenation of MCH to toluene. The metallic functions in MoTi and modified AMoTi are not efficient for RO in MCP. In-situ characterization of the different oxidation states of Mo at different experimental conditions were conducted using in-situ XPS–UPS techniques.

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