In this study, α-Fe 2 O 3 spherical particles with an average diameter of approximately 200 nm were synthesized by a solvothermal method for use as both a catalyst and medium for a Pd catalyst. The kinetics of CO oxidation over powders of α-Fe 2 O 3 spherical particles and 14 wt % Pd/α-Fe 2 O 3 spherical particles were measured in a static reactor by using a CO 2 laser-based photoacoustic technique. The total pressure was fixed at 40 Torr for the CO/O 2 /N 2 mixture for temperatures in the range of 225-350 • C. The variation in the CO 2 photoacoustic signal with the CO 2 concentration during CO oxidation was recorded as a function of time, and the CO 2 photoacoustic data at the early reaction stage was used to estimate the rates of CO 2 formation. Based on plots of ln(rate) vs. 1/T, apparent activation energies were calculated as 13.4 kcal/mol for the α-Fe 2 O 3 submicron powder and 13.2 kcal/mol for the 14 wt % Pd/α-Fe 2 O 3 submicron powder. Reaction orders with respect to CO and O 2 were determined from the rates measured at various partial pressures of CO and O 2 at 350 • C. The zero-order of the reaction with respect to Po 2 was observed for CO oxidation over α-Fe 2 O 3 submicron powder, while 0.48 order to Po 2 was observed for CO oxidation over Pd/α-Fe 2 O 3 submicron powder. The partial orders with respect to P CO were determined as 0.58 and 0.54 for the α-Fe 2 O 3 , and the Pd/α-Fe 2 O 3 submicron powders, respectively. The kinetic results obtained from both catalysts were compared with those for the α-Fe 2 O 3 fine powder catalysts and were used to understand the reaction mechanism.

Ni/CeO2 catalysts with different Ni loadings (5, 7, 10, 12, and 14 wt% Ni) were prepared by an impregnation method and examined for the CO2 reforming of methane using flow and static reactors. Their catalytic activities and selectivities were measured under CO2/CH4/Ar (=5/5/40 cm3/min) flow at 450–800°C using a flow reactor system with an on‐line gas chromatography. At fixed temperature, the CO2 and CH4 conversions varied only slightly with the Ni wt%, whereas the H2/CO ratio increased with increasing Ni wt%. The conversions increased with temperature, reaching 98% at 800°C. The H2/CO ratio varied with temperature in the range of 450–800°C, from less than 1 below 550°C to close to 1 at 550–600°C and then back to less than 1 above 600°C. The apparent activation energies were determined to be 43.1 kJ/mol for the CO2 consumption and 50.2 kJ/mol for the CH4 consumption based on the rates measured for the reforming reaction over 5 wt% Ni/CeO2 catalyst at 550–750°C. Additionally, the catalytic reforming reaction at low pressure (40 Torr) was investigated by a static reactor system by using a differential photoacoustic cell, in which the rates were measured from the CO2 photoacoustic signal data at early reaction times over the temperature range of 460–610°C. Apparent activation energies of 25.5–30.1 kJ/mol were calculated from the CO2 disappearance rates. The CO2 adsorption on the Ni/CeO2 catalyst was investigated by the CO2 photoacoustic spectroscopy and Fourier transform infrared spectroscopy. Feasible side reactions during the catalytic CO2/CH4 reaction were suggested on the basis of the kinetic and spectroscopic results.