碳化钼催化剂加氢脱氮性能研究

MoO3在CH4/H2气氛中程序升温还原碳化反应制备了Mo2C催化剂，用XRD、BET、SEM、XPS进行了表征。以吡啶/环己烷溶液为模型化合物，在高压微反装置上评价了碳化钼催化剂的吡啶加氢脱氮性能。结果表明，MoO3在CH4/H2气氛中程序升温至675℃可制得高纯度的β-Mo2C，SEM表征其形貌为板块状颗粒，平均粒径约3.9μm，比表面积达到了10.7m2/g，高于其前驱体MoO3 的2.7倍。在反应压力3.0MPa，空速为8h－1，H2/原料液体积比为500∶1，体积分数为5%的吡啶/环己烷溶液中，碳化钼催化剂在340℃下的吡啶加氢脱氮转化率达到了86.30%，高于相应MoS2约8%。随还原碳化温度的升高，碳化钼催化剂的比表面积降低，表面积炭增多，导致其吡啶加氢脱氮活性下降。确定的碳化钼催化剂的合成条件以还原碳化温度675℃、还原碳化气体空速1.8×104h－1左右较为适宜。

An investigation on the hydrodenitrogenation performance of molybdenum carbide catalyst

Molybdenum carbide catalysts were prepared through temperature programmed carburization of molybdenum trioxide with CH4/H2 gas mixture and characterized by XRD, BET, SEM, and XPS. The hydrodenitrogenation (HDN) performance of the molybdenum carbide catalyst was evaluated by using 5% pyridine/cyclohexane as a model reactant. The β-Mo2C prepared (carburized at 675℃) is in high purity with an average dimension of about 3.9 μm; its BET surface area is 10.7m2/g, which is 2.7 times higher than that of MoO3. Over Mo2C, pyridine HDN conversion reaches 86.30% under 340℃, 3.0MPa, and a space velocity 8h－1, which is about 8 percentages higher than that over MoS2. The optimal carburizing conditions for preparing Mo2C are around 675℃ with a CH4/H2 gas velocity of about 1.8×104h－1. Further increase of carburizing temperature may result in a decrease of the BET surface area of Mo2C and an increase of free carbon content deposited on the catalyst surface, which can then decrease the HDN activity of Mo2C.