GENESIS OF ACID-BASE SUPPORT PROPERTIES WITH VARIATIONS OF PREPARATION CONDITIONS: CUMENE CRACKING AND ITS KINETICS

Mixed oxides (Al-Si, Zr-Si, Mg-Si) were synthesized by the sol-gel method at different gelation times. The synthesized supports were impregnated by the incipient wetness method to obtain Ni-Mo, Co-Mo, and Ni-W supported catalysts. Both the supports and catalysts were characterized by N2 physisorption for determining textural properties, and their catalytic activities were tested with isopropyl alcohol (2-propanol) and cumene decomposition in order to evaluate their acid-base properties. According to the obtained products, it was possible to assess qualitatively that Al-Si and Zr-Si supports and their respective catalysts were mainly acidic. In the case of NiMo/AlSi catalyst, high conversion during cumene cracking particularly at higher temperatures was observed. Cracking activity results indicated that surface acidity predominated due to Brønsted acid sites, which are mainly dependent on the support composition as well as their preparation methods. Conversion of isopropyl alcohol leads to the dehydration products, typically propylene with a very low amount of di-isopropyl ether or acetone. NiMo/AlSi catalyst was evaluated for cumene cracking and its kinetic parameters were obtained by applying the Langmuir-Hinshelwood model. The activation energy was found to be 27.75 kcal mol-1 while the heat of adsorption calculated with the Van’t Hoff equation was-14.15 kcal mol-1 taking into account a single-site surface reaction