Bismuth Molybdate Catalysts. Kinetics and Mechanism of Propylene Oxidation

Abstract

Oxidation of propylene to acrolein over bismuth molybdate catalysts was studied in a flow reactor at atmospheric pressure and at temperatures between 400°and 460°C. The kinetics were determined as first order in propylene and zero order in oxygen. Over this temperature range, the activation energy was 29 kcal per mole. The side products.• acetaldehyde, formaldehyde, ethylene, carbon monoxide, and carbon dioxide, were formed almost exclusively in a consecutive pathway via acrolein or its surface species precursor when excess oxygen was present, A parallel pathway from propylene for the formation of carbon dioxide became important when there was an oxygen deficiency. A gas-phase, homogeneous oxidation of acrolein also became important when the postcatalytic volume of the reactor was increased.

The kinetics of the oxidation of propylene over a bismuth molybdate catalyst

“…In addition, at oxygen concentrations lower than 1 .O mmol/L and propylene concentrations higher than 8.0 mmol/L, the rate of propylene oxidation decreased rapidly with time. This was attributed to the loss of catalyst activity due to the depletion of catalyst surface oxygen (Gel'bshtein et al, 1965;Keulks et al, 1971). This oxygen deficiency constraint marked the l i m i t s of lower oxygen concentration and upper propylene concentration.…”

Mesostructural Bi-Mo-O catalyst: correct structure leading to high performance

“…By measuring the catalytic kinetics over the two catalysts at 623 K using the steady state reaction method similar to that reported in Ref. 13,27 and described in Supplementary and Additional Information, the activation energy (Ea) for propene conversion, in the temperature range of 583~623 K, over MoBi-m (157 kJ/mol) is found to be lower than that over MoBi-c catalyst (199 kJ/mol). The difference in the activation energy offers about three thousand times of reaction rate over the MoBi-m higher than that over MoBi-c catalyst at the reaction temperature used.…”

“…The kinetics of propene oxidation over the two catalysts at 623 K was measured using the steady state reaction method similar to that reported in Ref. 13,27. For the measurement of kinetic parameters, 0.35 g catalyst was put in a U-type quartz tube in a furnace and the reaction flow was composed of propene, air and balance He, controlled by mass flow controller.…”

Sol–Gel Synthesis of Bismuth Molybdate Catalysts for the Selective Oxidation of Propylene to Acrolein: Influence of pH Value and Theoretical Molar Atomic Ratio

“…Later, they were found to be capable of catalyzing the ammoxidation of propylene to acrylonitrile and the oxidation of propylene to acrolein . Their potential for further catalytic processes was extensively studied thereafter . Nowadays, they have became popular catalysts for the oxidation of light hydrocarbons .…”