Catalytic partial oxidation of cyclohexane in a single-gauze reactor

Cyclohexane oxidation in a single-gauze reactor can produce similar to 85% selectivity to olefins and oxygenates at 25% cyclohexane conversion and 100 % oxygen conversion, with cyclohexene and 5-hexenal as the dominant product s. Experiments are performed with a 90% platinum-10% rhodium single gauze ( similar to 90-mu m wire diameter) at cyclohexane/oxygen (C6H12/O-2) molar r atios of 0.4 to 5.0, flow rates of 1 to 3 standard liters per minute, prehe at temperatures of 100 to 300 degrees C, N-2 dilution from 5% to the air co mposition, and pressures of 1.2 to 2 atm. The cyclohexane/oxygen ratio is t he most important variable for operation of the single-gauze reactor becaus e temperatures, reactant conversions, and product selectivities all change significantly as C6H12/O-2 is varied. Low dilution favors olefin production while high dilution suppresses the homogeneous reactions necessary for oxy genate formation. Oxygenates are also favored by high flow rates and low in let temperatures. Higher reactor pressures (up to 2 atm) increase the yield of cyclohexene and 5-hexenal and allow complete oxygen conversion. Cyclohe xanone can be produced with 5% selectivity at C6H12/O-2 approximate to 4. R eaction pathways for cyclohexane partial oxidation are hypothesized, and th e products are consistent with the proposed surface-assisted gas-phase sequ ences. (C) 2000 Academic Press.