External mass transfer in a laser sintered structured reactor for continuous hydrogenation of alkynes

This work presents a study on the continuous operation of a structured reactor for alkyne hydrogenation in the field of Process Intensification. The reactor consists of a laser sintered metal structure characterized by a regular geometry, coated with a layer of ZnO/Al2O3 and impregnated with palladium nanoparticles. The partial hydrogenation of 2-methyl-3-butyn-2-ol with co-current gas-liquid upward flow was used as the test reaction system. A plug flow reactor model was applied to study the mass transfer phenomena under the reacting conditions. The reaction kinetics with the Pd/ZnO-based catalyst were simplified using a power rate law expression. The results in terms of the overall mass transfer coefficient Km, were modelled with a predictive Sherwood number correlation whose parameters were estimated by means of an optimization procedure. The structured reactor shows an overall mass transfer coefficient ranging between 0.2 and 1.2 s(-1) depending on the operating conditions. The model is able to predict the impact of temperature (333-363 K), pressure (3.0-7.0 bar), gas velocity (0.005-0.024 ms(-1)) and liquid velocity (0.025-0.085 ms(-1)) on the overall mass transfer coefficient with a maximum deviation of 15%.