Process Intensification of Catalysed Henry Reaction using Copper-Wool Catalyst in a Spinning Mesh Disc Reactor

The spinning mesh disc reactor (SMDR) is a novel process intensification technology which uses centrifugal force to drive reaction fluid over a mesh supported catalyst on a rotating disc. The potential of the SMDR for organic synthesis has been demonstrated for the first time for Henry reaction using copper immobilised on woollen cloth mesh. A new protocol for copper immobilisation on wool has been developed producing a superior catalyst to the homogeneous copper triflate system: copper heterogenised on wool afforded a higher batch conversion (85%) (cf. 57% for the homogeneous case) in the same timeframe. In the SMDR, the reaction was more efficient than either homogeneous or heterogeneous batch reaction: with further optimisation the conversion increased from 77% to 93% as the spinning speed of the disc increased from 250 to 450 RPM at a flowrate of 3 ml s-1. There was only a 3% reduction in conversion on re-use of copper wool over 3 cycles under similar experimental conditions indicating that this catalyst is robust. Pure wool was also found to have some catalytic activity for the Henry reaction, giving a maximum conversion of 85% at 450 RPM in the SMDR. However, it deactivated significantly with reuse and therefore cannot be considered a stable, robust catalyst. Overall, the results show that the copper immobilised wool in the SMDR can be used to improve the conversions for the Henry reaction and that there is therefore promise for the SMDR to be extended to other traditional solvent based reactions.