Modeling of hydrogenation of maleic acid in a bubble-column slurry reactor

Abstract

A bubble-column slurry-reactor model has been developed for the hydrogenation of aqueous maleic acid (MAC) to tetrahydrofuran (THF). This particular reaction system has recent commercial relevance and represents a case where complex multistep catalytic hydrogenation reactions are conducted at high pressure (>15 MPa) and high temperature (>240°C). It also has additional complexities associated with the reaction chemistry, since the THF reaction product is volatile and the reaction is highly exothermic. The proposed model is derived using the mixing cell approach and incorporates the contributions of gas-liquid and liquid-solid mass transfer, intraparticle diffusion effects, product volatility, heat effects, and complex multistep reaction kinetics. The effect of gas and liquid velocities, catalyst loading, inlet maleic acid concentration, and temperature on the conversion, selectivity, temperature rise, and productivity of the desired products (THF and γ-butyrolactone (GBL)) is also discussed. Since the reaction step involving the hydrogenation of GBL to THF is relatively slow, severe operating conditions are necessary to achieve high THF selectivity. The distribution pattern of THF in the gas and liquid phases is also discussed. The model proposed could be useful for simulation of existing pilot- or industrial-scale reactors, as well as the design and scale-up of new reactors for this particular reaction or one that has similar characteristics.