碳化钼催化剂加氢脱氮性能研究

An investigation on the hydrodenitrogenation performance of molybdenum carbide catalyst

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。

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 10.7 m^2/g, which is 2.7 times higher than that of MoO3. Over MOEC, pyridine HDN conversion reaches 86.30% under 340 ℃, 3.0 MPa, and a space velocity 8 h^-1, which is about 8 percentages higher than that over MoS2. The optimal carburizing conditions for preparing MOEC are around 675 ℃ with a CH4/H2 gas velocity of about 1.8 × 10^4 h^-1. Further increase of carburizing temperature may result in a decrease of the BET surface area of MOEC and an increase of free carbon content deposited on the catalyst surface, which can then decrease the HDN activity of MOEC.