Monte Carlo Simulations Of The Catalytic Reaction Of Propylene Ammoxidation

Acrylonitrile is a versatile petrochemical intermediate used in extensively in the production of acrylic fibers, resins, dicyanide and acrylamide. It is currently produced by catalytic ammoxidation of propylene in fluidised beds. Several disadvantages still remain in the process: high ammonia concentration in the raw gas; high CO2 yielding and considerable ammonia concentration in output gas. The key subjects in the research domain are effective catalyst design and environment-friendly process development.Gas atmosphere, transport properties and surface state of catalyst act each other in the ammoxidation process, which forms a nonlinear system. Monte Carlo method is a powerful approach to such complex network problems. An industrial ammoxidation catalyst was characterized by XRD and BET. The role of bismuth, NHX species and possible reaction mechanism were discriminated. γ-Bi2MoO6 was chosen as physical model. Flowchart of the code together with the main technical details and the involved calculation method were given in the paper. The simulation results are in good consistency with the previous relevant experimental results.Four parameters were chosen to investigate the dynamic responses to catalysts of different performance: probability of adsorption of ammonia, combustion percent of ammonia, probability of over oxidation of adsorbed acrolein and the rate of re-oxidation of lattice oxygen. Increasing the probability of adsorption of ammonia, acrylonitrile selectivity becomes higher while combustion percent of ammonia decreases. High NH4+ ion concentration on the catalyst surface is preferable to prompt acrylonitrile selectivity. If the combustion percent of ammonia is decreased, acrolein selectivity will be cut down meanwhile acrylonitrile selectivity increase sharply.When ammonia/propylene ratio is lower than 1.0, acrylonitrile selectivity decreasesgradually. If the rate of over oxidation of adsorbed acrolein is decreased, theselectivity to acrylonitrile and acrolein increase. If the rate of re-oxidation of latticeoxygen is increased, acrylonitrile selectivity decreases while acrolein selectivity increases. This is due to the rate of ammonia combustion is higher than that of propylene ammoxidation. Ammonia/propylene ratio is required to rise to maintain and/or increase acrylonitrile selectivity. With the participation of ammonia, Ammoxidation of olefins differs from selective oxidation of olefins by lattice oxygen. Ammoxidation catalyst design and process intensification scheme were proposed.