The condensation/polymerisation of dimethyl siloxane fluids in a three-phase trickle flow monolith reactor

For the prodn. of siloxane fluids, the viability of using a multi-channel monolith as a catalyst support system in a three-phase reactor has been studied. The catalyst was tripotassium phosphate (K3PO4). Expts. were performed in a single-channel flow reactor (15 mm i.d. and 500 mm catalyst coated length). The rate of reaction was followed by monitoring the disappearance of the hydroxyl group (-OH). Reaction expts. were performed at a hydroxyl group concn. range from 150 to 170 mol m-3, T=373-413 K and P=7.9 kPa with a nitrogen purge. The max. temp. of operation was restricted to 413 K to avoid the formation of undesirable byproducts. In the regime controlled by chem. kinetics, reaction was of an apparent first order with respect to -OH concn., and in the apparent rate const., the pre-exponential factor was 4.19*10-4 m s-1, and the apparent activation energy was 16.1 kJ mol-1. These are only valid for the operating pressure and purge gas flowrate used, as both of these are shown to affect water removal from the liq. phase and, hence, reaction rates. Mass transfer coeffs. from the liq. to the catalyst surface were estd. and these increased rapidly with flowrate and were higher than expected for a falling liq. film.