Reaction Engineering Calculation And Multi-scale Simulation For Ethylene Catalytic Oxidation Over Irregular-shaped Catalysts

For ethylene epoxidation reaction system, a three-dimensional reaction-mass transfer-heat transfer model is developed to calculate internal and external effectiveness factor of the irregular-shaped catalyst pellet. Effective diffusivities, effective thermal conductivity and enthalpy are the function of temperature and(or) concentration distribution in catalyst pellet. The finite element software COMSOL Multiphysics is employed to solve the set of highly nonlinear partial differential equations, and the values obtained by COMSOL agree well with the values given by literatures.Based on reaction-mass transfer-heat transfer model for a single pellet, EO oxidation process belongs to internal diffusion control and the length of the diffusion resistance is 0.2 mm for the internal reaction rate with a 90% reduction. Internal effectiveness factor and maximum temperature rise for 7-hole catalyst is 0.2155 and 1.24 K, respectively. The internal effectiveness factor almost increases linearly with the increasing of geometrical specific surface area. The EO average selectivity of 7-hole catalyst is 85%, higher than hollow cylindrical catalyst. Irregular-shaped catalysts have higher selectivity, smaller temperature rise and higher internal effectiveness factors than traditional catalysts. Different active ingredient loading conditions are calculated, the order of promoting the reaction is as follow: shell distribution, uniform distribution, parabolic distribution, yolk distribution.The quantitative calculation for reaction-transport phenomena in a single catalyst pellet could be a guide for catalyst design and a basis for multi-scale simulation of coupling hydromechanics and catalytic reaction-transport phenomena. The Re of reactor inlet is 7256. 7-hole catalyst of different inclination with mainstream are established. When the inclination is 30°, the catalyst external effectiveness factor and overall effectiveness factor are the biggest. Catalyst particle group model is established, the maximum temperature rise for 7-hole catalyst particles is 25.53 K anf EO average selectivity is 84.30%. The pellet of 30° inclination with main stream (catalyst No.1)internal effectiveness factor is 0.2155, external effectiveness factor is 0.6837, the overall effectiveness factor is 0.3340.