Intensified microwave-assisted heterogeneous catalytic reactors for sustainable chemical manufacturing

Abstract

Microwave-assisted catalysis is an emerging route for reactor modularization and decarbonization of chemical manufacturing with energy-intensive reactions. While laboratory-scale microwave-assisted heterogeneous catalytic reactors are being developed, hot spots and reactor stability under increased catalyst inventory remain impediments for high throughput processing. Here, we engineer the electromagnetic field-material interactions by introducing a packed monolith configuration, consisting of a microwave absorbing monolith filled with catalytic pellets. Electromagnetic simulations reveal the crucial role of monolith electrical conductivity in diminishing the local power dissipation between the pellets' contact points by absorbing the heat directly. Compared to traditional fixed beds, where hot spots form within minutes of operation, and catalyst-coated monoliths, whose active catalyst loading is limited, the proposed system is stable at all tested temperatures up to 900 °C and has a catalyst packing density near that of fixed beds. We demonstrate its versatility first on the ethane dehydrogenation to produce ethylene over a Ga2O3/Al2O3 catalyst. Repeatable performance over multiple cycles of reaction and regeneration highlights long-term operation. Second, the dry reforming of methane (CH4) is carried out over a commercial Rh/Al2O3 catalyst, achieving a high (~86%) CH4 conversion with an order of magnitude higher H2 throughput (~85 m3/kg/hr) than previous laboratory-scale reactors. By enhancing the catalyst inventory, packed monoliths create a potential avenue for broader adoption of microwave-assisted heterogeneous catalytic reactors.