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The effect of gas phase O2and reversibly adsorbed oxygen on the decomposition of CH4and the surface state of a Ni/Al2O3catalyst during partial oxidation of CH4were studied using the transient response technique at atmospheric pressure and 700°C. The results show that, when the catalyst surface is completely oxidized under experimental conditions, only a small amount of CO and H2can be produced from non‐selective oxidation of CH4by reversibly adsorbed oxygen which is more active in oxidizing CH4completely than NiO via the Rideal–Eley mechanism and both the conversions of CH4and O2and the selectivities to CO and H2are very low. Therefore, keeping the catalyst surface in the reduced state is the precondition of high conversion of CH4and high selectivities to CO and H2. The surface state of the catalyst decides the reaction mechanism and plays a very important role in the conversions and selectivities of partial oxidation of CH4. During partial oxidation of CH4, no oxygen species but a small amount of carbon exists on the catalyst surface, which is favorable for maintaining the catalyst in the reduced state and the selectivity of CO. The results also indicate that direct oxidation is the main route for partial oxidation of CH4, and the indirect oxidation mechanism is not able to gain dominance in the reaction under the experimental conditions.

The adsorption, desorption and decom position of NO on Ni(100 ) was studied with XPS, UPS, XAES, ΔΦ, temperature programmed thermal desorption (TPD) and LEED in the temperature range 80 to 1300 K. NO adsorbs molecularly on Ni(100 ) at low temperatures; dissociation occurs above 200 K. Up to ≈ 1/4 saturation coverage, only N2desorbs in a second order peak around 1100 K. At saturation three NO desorption states at 350, 420 and 1200 K and two N2peaks at 660 and 1020 K are observed for a heating rate β of 5 K/s. Activation energies for desorption are obtained by TPD with variable β. Coadsorption experiments show that the NO -TPD peak at 1200 K is due to recombination of N and O on the surface. The relative areas of some TPD maxima depend strongly on coadsorbed O-, C- and N-impurities. At 100 K, ΔΦ increases up to a maximum of 1.1 eV at 3 /4 saturation coverage and drops to 1.0 eV at saturation. Complex LEED patterns are observed for saturated layers adsorbed below 200 K which change during heating. The nature o f the observed binding and desorption states is discussed.

The supported Ni catalysts with CaAl2O4spinel compound layer existed between Ni and Al2O3have been prepared, and the effect of the CaAl2O4spinel layer on the stability of the catalysts for the partial oxidation of methane to syngas (CO+H2) has been investigated at high space velocity (250 L·g−1·h−1). Also, the catalysts have been characterized by XRD, TG/DTA. The Ni catalysts with CaAl2O4spinel layer existed between Ni and Al2O3show good stability for this process with the CH4conversion of ∼83%, syngas selectivity of >90% and the coke deposit of <1 wt% during a long-time running at 873 K. The CaAl2O4spinel layer can effectively suppress the phase transformation to form NiAl2O4spinel phases and stabilize the Ni tiny crystallite, to which the good stability of the catalyst contributes.

The effect of pressure on oxidative coupling of methane (OCM) over MgO/BaCO3catalyst was studied at the range of 0.1∼1.1 MPa at 1053 K. Deactivation of the MgO/BaCO3catalyst at elevated pressure was attributed to the migration of BaCO3from bulk to the surface of the catalyst.

XPS/AES and pulse reaction characterizations were combined to study the reaction mechanism of CH4/CO2reforming to syngas over Co/γ-Al2O3. Surface carbide carbons formed from CH4dissociation were active C species for CO generation. Metallic Co species played an important role in dissociating CH4to form carbide carbon and H2, abstracting an O atom from CO2molecule, and transferring O atom to carbide to form CO.