Insights into reaction-diffusion behaviors of acetylene selective hydrogenation on pellet catalysts

In this work, a particle-resolved computational fluid dynamics model of the acetylene hydrogenation process is developed to investigate the effects of catalyst particle structures on the reaction-diffusion behaviors aiming to improve selectivity toward target ethylene. The effects of packing structures on mass and heat transfer are explored by employing particles with varying shapes, wall thicknesses, and external diameters. The simulation results reveal that decreasing diffusion paths and elevating reactor bed temperature will enhance ethylene selectivity, and cylinder and Raschig ring packing structures exhibit the lowest and highest ethylene selectivity of 35.6% and 48.9% at 70% of acetylene conversion, respectively. Reducing wall thicknesses of Raschig ring particles facilitates the diffusion of generated ethylene from the interior zone of catalysts but concurrently inhibits the conversion of acetylene to ethylene. The Raschig ring catalyst particle with 1.9 mm of wall thickness and 3.5 mm of external diameter is finally revealed to exhibit the highest ethylene selectivity.