制备Mo2C催化剂的最佳工艺条件及其反应机理

摘要

Molybdenum trioxide as precursor was prepared by roasting ammonium molybdate. Then using molybdenum trioxide and the gas mixture of H2 and CH4 as raw materials .molybdenum carbide was prepared by the temperature-programmed reaction method.The best temperature of preparing molybdenum trioxide from ammonium molybdate was investigated as well as the best ratio of H2 to CH4 and terminal temperature in the temperature-programmed reaction; the final product was characterized by X-ray diffraction.The results show that the optimum process conditions for the reaction: roasting temperature is at 450 °C, V(H2)V(CH4) is in the range of 2 : 1 ~ 4 : 1, the final temperature of carbonization is at 700 °C; the reaction mechanism: firstly, MoO3 is reduced to MoO2, then MoO2 must be reduced to transition state Mo, finally Mo2C is gained.%钼酸铵焙烧制备碳化钼前驱体MoO3，以MoO3为钼源、V(H2)／V(CH4)混合气体为碳化介质采用程序升温反应法制备Mo2C催化剂;考察钼酸铵制备.MoO3适宜的温度，以及程序升温反应法制备Mo2C的最适V(H2)／V(CH4)比和碳化终温，用XRD表征分析产物。得出制备Mo2C催化剂的最佳工艺条件是：钼酸铵焙烧温度为450℃、V(H/V(CH4)为2：1～4：1、碳化终温为700℃;其反应机理是：MoO3先被还原为MoO2，MoO2需经历过渡态的单质Mo才能碳化生成Mo2C。