Abstract
In this paper we report on the hydrogenation of 1,5,9-cyclododecatriene in three phase catalytic reactors with emphasis on selectivity of intermediates. Batch hydrogenations have been performed in a stirred autoclave using shell catalyst pellets and powdered pellets of 0.5% Pd on porous gamma-Al2O3. Analysis of experimental data shows the presence of strong pore diffusion for pellets. Selectivity is found to increase slightly with temperature and with decreasing pressure. At identical operating conditions, selectivity is higher for pellets than for powder. Intrinsic kinetics are derived from complete reaction data with the powder catalyst. The model accounts for hydrocarbon adsorption as well as for pressure and temperature effects on selectivity. In the continuous packed bed reactor, gas-liquid mass transfer is strongly limiting but improves with the hydrogen flow rate. Efficiency and overall volumetric gas-liquid-solid mass transfer coefficients of the continuous reactor are calculated on the basis of experimental reaction rates of the two reactors. On the other hand, selectivity is found to be nearly unchanged due to the opposed effects of liquid back-mixing and decrease of hydrogen concentration by mass transfer limitations.