COMPARISON OF MONOLITH-SUPPORTED METALS FOR THE DIRECT OXIDATION OF METHANE TO SYNGAS

The partial oxidation of CH4 in O2 near atmospheric pressure to produce syngas was investigated on monolith-supported Rh, Ni, Pt, Ir, Pd, Pd-La2O3, Fe, Co, Re, and Ru catalysts in an autothermal flow reactor at residence times of approximately 10 msec (GHSV approximately 100,000 hr-1). Optimal CH4 conversion and CO and H-2 selectivities of 0.89, 0.95, and 0.90, respectively, were achieved on Rh at 1000-degrees-C with no loss in activity over many hours. Ni showed similar conversion and selectivities but deactivated. Experiments with up to 25 vol% H2O added to the feed showed little evidence of the occurrence of steam reforming and water-gas shift reactions. Pt and Ir sustained stable reactions but at lower selectivities and conversion than Rh or Ni. Pd, Pd-La2O3, and Co deactivated rapidly, while Re, Ru, and Fe would not sustain autothermal reaction. Ni and Re deactivated by volatilization and metal loss, while Pd-La2O3 deactivated by carbon formation, and Pd deactivated by a combination of metal loss and carbon formation. Pd produced up to 14% selectivity to C2H4 and C2H6, Pd-La2O3 UP to 5%, Pt approximately 1%, and other metals less than 0.2%. (C) 1994 Academic Press, Inc.