LIQUID-PHASE HYDROGENATION OF ACETYLENE IN A MONOLITHIC CATALYST REACTOR

The selective, liquid-phase hydrogenation of acetylene in the presence of excess ethylene has been studied. A new process using a monolith reactor is presented. The liquid, heptane, was used to continuously remove the green oil formed by polymerization. The Liquid also absorbs most of the heat formed in the exothermic hydrogenation reactions. The total pressure was 1.3-2.0 MPa and the temperature was 303-313 K. Several Pd catalysts supported on alumina have been tested. The best selectivity was obtained using an a-alumina support with an average pore diameter of 0.08 mu m. This reaction is known to be structure-sensitive in the gas phase and the same was found for the liquid phase. The best catalyst was tested for a total of 113 h. The activity in the acetylene hydrogenation reaction and the selectivity toward ethylene dropped during the first 60 h of reaction (turnover number from 3 to 1 s(-1) and selectivity from 80 to 55%). After that period, both remained approximately constant.