MODELING OF A TRICKLE-BED REACTOR FOR A CATALYTIC-HYDROGENATION IN SUPERCRITICAL CO2

The hydrogenation of organic substrates in a fixed-bed catalytic react or is considered, using supercritical CO2 as a solvent to increase the solubility of hydrogen in the liquid reactants. Reaction rates can be adjusted by changing operating conditions, allowing the reaction volu me to be much smaller than in conventional processes. Although it is p ossible to perform the reaction in a homogeneous phase, to avoid inter phase mass-transfer limitations, extremely high temperature and pressu re may be needed to reach such a condition; therefore, the reaction is carried out at conditions where both a gas and a liquid phase are pre sent. Taking into account the solid catalyst, a three-phase reaction s ystem has to be dealt with. A trickle-bed high-pressure reactor was si mulated using a pseudo-homogeneous two-dimensional model, where both m ass and energy balance are considered, The PDE system was solved using an orthogonal collocation method. The model does not include any adju stable parameters, and was developed as an user-written subroutine to be linked with a widely used process simulator (Aspen Plus), thus allo wing accurate and flexible thermophysical and VLE calculations. Experi ments were carried out in a pilot-scale unit running at Hoffmann-La Ro che facilities, so that simulated and experimental values could be com pared to state the accuracy of the model. (C) 1997 Elsevier Science Lt d.