Comparative Study of Vanadium Supported on MCM-36 and MCM-22 and Their Catalytic Perfomance in C3-ODH

Total Oxidation of Toluene and Propane over Supported Co3O4 Catalysts: Effect of Structure/Acidity of MWW Zeolite and Cobalt Loading

A set of supported Co₃O₄ catalysts have been designed and prepared to study the effect of textural characteristics and Brønsted acid sites concentration of MWW zeolite support, as well as cobalt loading on catalyst activity. Detailed characterization of the catalysts with a thorough study on their performance in the total oxidation of toluene and propane revealed that MCM-22 is the optimal support and that increasing Si/Al and decreasing external surface of MCM-22 positively affect the activity of supported Co₃O₄ catalysts, which is determined by their low-temperature reducibility. The activity of the Co/MCM-22 catalysts increased with cobalt content (5-20 wt %), consistent with enhancing the amount of low-temperature reducible Co₃O₄. The optimized catalyst containing 20% Co supported on dealuminated MCM-22 presented high turnover frequency (TOF) values in both toluene (2.6 × 10^-5 s^-1 at 270 °C) and propane (3.9 × 10^-5 s^-1 at 215 °C) oxidation and was characterized by outstanding cycling stability, long-term durability, water tolerance, and sintering resistance.

Catalytic Applications of Vanadium: A Mechanistic Perspective

The chemistry of vanadium has seen remarkable activity in the past 50 years. In the present review, reactions catalyzed by homogeneous and supported vanadium complexes from 2008 to 2018 are summarized and discussed. Particular attention is given to mechanistic and kinetics studies of vanadium-catalyzed reactions including oxidations of alkanes, alkenes, arenes, alcohols, aldehydes, ketones, and sulfur species, as well as oxidative C-C and C-O bond cleavage, carbon-carbon bond formation, deoxydehydration, haloperoxidase, cyanation, hydrogenation, dehydrogenation, ring-opening metathesis polymerization, and oxo/imido heterometathesis. Additionally, insights into heterogeneous vanadium catalysis are provided when parallels can be drawn from the homogeneous literature.

Effect of the grafting agent on the structure and catalytic performance of Ti-MCM-22

Ti-MCM-22 prepared by grafting with Ti(OEt)₄ has more Ti(iv) at Td sites than those prepared with Ti(OPr)₄ and Ti(OBu)₄, and gives higher catalytic activities in cyclohexene and cyclooctene epoxidation using t-butylhydrogen peroxide as the oxidant.