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。

对不同碳化终温和经过H2、CO2预处理的Mo2C/Al2O3催化剂进行了POM催化活性评价与结构表征。结果表明，高碳化终温的Mo2C/Al2O3催化剂对于POM反应制合成气有高的甲烷转化率，CO和H2选择性，在580℃时H2预处理比CO2预处理的催化剂具有好的甲烷转化率和好的CO、H2选择性，但H2预处理时间过长会使CO和H2的选择性有所降低，CO2预处理会导致低的甲烷转化率和极低的CO和H2的选择性，XRD结果表明，在700～850℃之间碳化的样品均为β-Mo2C, BET比表面的测定结果表明随碳化终温的增加，Mo2C/Al2O3催化剂的比表面有所增加。

制备了一系列不同Mo2C担载量的Mo2C/Al2O3催化剂，利用微型固定床反应器对其POM反应进行了活性评价,并采用XRD、SEM和BET等方法进行了结构表征。实验结果表明，纯Mo2c催化剂在反应初期有较高的CH4转化率，但CO和H2的选择性很低，随着反应时间的增加，CH4转化率急剧下降，Mo2C担载量小于24.8%的摧化剂，随担载量增加，CH4转化率明显升高。同时，随着反应时间的增加，CH4转化率有所下降，CO和H2的选择性则明显升高。Mo2C担二项式国量在35.4～42.5%的摧剂，具有好的CH4转化率和CO、H2选择性，但担载量过高时，CH4转化率会随反应时间的增加而下降。结构表征表明，未担载的和担载的碳化物催化剂均为β-Mo2C，担载量小于10.6%，Mo2C高度分散于Al2O3表面，担载量较高时，Mo2c颗粒变大，比表面减少。