Optimization of the continuous coprecipitation in a microfluidic reactor: Cu-based catalysts for CO2 hydrogenation into methanol

Abstract

CuO-ZnO-ZrO2 catalysts were synthetized by controlled continuous coprecipitation in a microfluidic reactor. CuO, ZnO and ZrO2 contents in catalysts were kept constant at 37.5 wt% of CuO (corresponding to 30% Cu0), 41.0 wt% of ZnO and 21.5 wt% of ZrO2. Numerous parameters of the continuous microfluidic coprecipitation, such as the nature of the carrier fluid, the residence time in the microfluidic synthesis reactor, the reagents flow rates during the synthesis and the pH, were studied in order to obtain perfectly homogeneous catalytic materials. All catalysts were characterized and then tested in methanol synthesis via CO2 hydrogenation on the REALCAT platform using high-throughput experiments. The optimum catalytic results were obtained for the catalyst synthesized by the continuous coprecipitation in a microfluidic reactor at following controlled parameters: water as carrier fluid, 30 s of residence time, low total reagent flowrate of 35 µL min−1 and pH equal to 8. This catalyst presented a good CO2 conversion of 21.4 % along with a methanol selectivity of 33 %, leading to a record methanol productivity of 1135 gMeOH kgcat-1 h−1 at 280 °C, 50 bar and a GHSV of 25,000 h−1 (STP).