Simulating cyclohexane millisecond oxidation: Coupled chemistry and fluid dynamics

Cyclohexane partial oxidation over a 40‐mesh Pt–10% Rh single‐gauze catalyst can produce ∼85% selectivity to oxygenates and olefins at 25% cyclohexane conversion and 100% oxygen conversion, with cyclohexene and 5‐hexenal as the dominant products. A detailed 2‐D model of the reactor is solved using density‐functional theory (with 35 reactions among 25 species) and computational fluid dynamics. Rapid quenching in the wake of the wires allows highly nonequilibrium species to be preserved. The simulations show that the competition between cyclohexyl and cyclohexylperoxy radicals is crucial in determining product selectivities. At high temperatures and low pressures, the cyclohexyl radical is favored, leading to high selectivities to cyclohexene. At lower temperatures or high pressures, cyclohexylperoxy radicals are favored, allowing the formation of parent oxygenates to dominate. Numerical simulations suggest ways to tune reactor operation for desired product distributions and allow the investigation of dangerous or costly operating conditions, such as high pressure.