High pressure microreactor for minute amounts of catalyst on planar supports: a case study of CO2 hydrogenation over Pd0.25Zn0.75Ox nanoclusters

High-pressure studies of catalyst quantities down to a few hundred nanograms, particularly well-defined catalysts prepared using physical methods in ultra-high vacuum on planar supports can potentially bridge the surface science and applied catalysis approaches to catalyst development. However, the chemical reactors required for such investigations are lacking. We present the novel design and evaluation of a 50 µL rectangular microchannel reactor capable of testing small quantities of catalyst at pressures up to 40 bar and temperatures up to 250°C. To evaluate the microreactor's performance, Pd0.25Zn0.75Ox nanoclusters soft-landed on SiO2-coated mica sheets using the cluster beam deposition technique, were tested for the reverse water-gas shift reaction through a series of kinetic experiments. Experimental results, combined with computational fluid dynamics and mass transport analysis, demonstrate that the proposed microreactor setup allows for testing minute quantities of catalysts with high sensitivity at industrially relevant temperatures and pressures. Although not restricted to a particular catalyst preparation method, the setup is an excellent platform for conducting catalytic tests on composition-controlled, mass-selected, gas-phase nanoparticles deposited on planar substrates, facilitating the development of reliable structure-activity relationships and enabling a more rational design of catalysts.