Selective hydrogenation of acetylene through a short contact time reactor

A novel approach to the selective hydrogenation of acetylene involves a short contact time reactor. A thin Pd/γ‐Al 2 O 3 catalytic membrane (about 5 μm thick) was observed to be void of minor defects. Forcing a dilute C 2 H 2 /H 2 /Ar mixture through the layer produced high conversions coupled with high selectivity at high temperatures. The selectivity was observed to increase with temperature. A gas‐dispersion model with derived kinetics was employed to explain the results. A solution to the corresponding coupled nonlinear differential equations resulted in a Peclet number of 64.5 and a contact time of 9.5 × 10 −3 s through the reactor at 100°C. A critical thickness is predicted to exist for a maximum in ethylene concentration. A value of 2.5 μm at 200°C is representative. Lastly, permeability experiments agree with modeling results to show that Knudsen diffusion is absent despite a narrow pore‐size distribution.