A series of cobalt-based catalysts with different supports have been prepared using impregnation method, and characterized by X-ray diffraction (XRD), laser Raman (LR), and infrared spectroscopy (IR). The catalytic activities for methane combustion were assessed in a micro-reactor. The ZrO2 and Al2O3 supports are themselves active in methane combustion, and ZrO2 supported cobalt catalyst was found to have the highest activity amongst the TiO2, Al2O3, MgO supported catalysts and bulk Co3O4. The Co content has a marked effect on the activity of the ZrO2 supported catalyst with 1.0 and 15 wt.% of Co having the lowest light-off temperature in methane combustion. In the MgO supported catalyst, Co oxide was highly dispersed over the MgOsupport surface or enters the lattice ofMgOto form a solid solution, whose activity for methane combustion is reasonable. The zirconia supported cobalt catalysts are very active and stable when calcination or reaction temperature is no more than 900◦C. Calcining the catalysts at temperatures above 900℃ for more than 1h decreases the catalyst activity. The deactivation of the catalyst probably results from the decrease of the surface area.

Investigation on molybdenum carbide catalyst, its oxide precursor and its modifiers was performed using temperature programmed surface reaction (TPSR) technique, BET surface specific area and X-ray diffraction (XRD) measurement. The carbide catalyst and its modifiers were evaluated using microreactor apparatus. The evaluation result showed that the addition of nickel promoted the POM to syngas, the addition of copper exhibited weaker promotion at the initial stage, but it turned unfavorable to the POM to syngas hereafter. As for potassium doped catalyst, it was unfavorable to the POM. According to the characterizations, the effect of added metals on the carburization, especially under the condition of POM, was elucidated.

Alumina-supported molybdenum carbide and its modifier with small amounts of nickel were evaluated and characterized. The evaluation results showed that a nickel-doped carbide catalyst exhibited a much higher conversion of methane and selectivity to CO and H2for the partial oxidation of methane (POM) to syngas. Also, the addition of a small amount of nickel resulted in significant improvement of catalysis stability. Characterization by temperature programmed surface reaction (TPSR) indicated that the addition of nickel promoted the carburization of molybdenum oxide. Especially under the conditions of the POM to syngas, this promotion resulted in more active phases being held. The nickel doped catalyst had small particles, larger specific area and greater ability to resist sintering. All these improved the catalytic stability. The other characterizations by XRD, XPS, SEM as well as BET surface area measurement also confirmed these promotions of nickel. In addition, the doped nickel made possible the increase of the intrinsic activity of catalytic centers over molybdenum carbide catalyst.

The performance of supported and unsupported molybdenum carbide for the partial oxida-tion of methane (POM) to syngas was investigated. An evaluation of the catalysts indicates that bulk molybdenum carbide has a higher methane conversion during the initial stage but a lower selectivity to CO and H2/CO ratio in the products. The rapid deactivation of the catalyst is also a signi cant problem. However, the supported molybdenum carbide catalyst shows a much higher methane conversion, increased selectivity and signi cantly improved catalytic stability. The characterization by XRD and BET specic area measurements depict an improved dispersion of molybdenum carbide when using alumina as a carrier. The bulk or the supported molybdenum carbide exists in the -Mo2C phase, while it is transformed intomolybdenum dioxide postcatalysis which is an important cause of molybdenum carbide deactivation.

考察了反应温度、气体空速和进料中CH4∶O2比值对Mo2C/Al2O3催化的POM反应制合成气的影响。结果发现较高的温度具有较高的甲烷转化率、CO和H2的选择性；而在较低的温度下，对CO的选择性比对H2的影响更大。反应气体的空速较小时对于甲烷的转化率、CO和H2的选择性是有利的；而在较高的气体空速下，氢气的选择性则更低。进料中CH4∶O2 比值稍高于2∶1时有利于获得高的甲烷转化率、CO和H2的选择性，并且还可以增加催化剂的稳定性。当CH4∶O 2比值低于2∶1时，甲烷转化率、CO和H2选择性随反应的进行急剧下降，而当此比值调整到高于2∶1时，转化率和选择性都可以得到恢复。