β-Mo2C和Ni3Mo3N/β-Mo2C的制备及其甲烷化反应性能研究

Preparation of β-Mo2C, Ni3Mo3N/β-Mo2C and its catalytic performance for methanation

  • 摘要: 通过焙烧钼酸铵和六次甲基四胺(HMT)生成的络合物,制备β-Mo2C。在此基础上加入Ni助剂制备了Ni3Mo3N/β-Mo2C双金属碳化物催化剂。采用XRD、SEM、HRTEM、低温氮吸附、元素分析等方法对催化剂进行了表征,考察了其合成气甲烷化反应性能。结果表明,β-Mo2C有较高的CO转化率,但CO转化率和CH4选择性分别从第10 h的75.93%和36.79%降低到了第100 h的67.41%和33.54%。因此,β-Mo2C活性不够稳定且CH4选择性较低。而Ni助剂的加入显著提高了催化剂的甲烷化活性及稳定性,使CO转化率和CH4选择性分别从第10 h的83.15%和46.64%升高到了第100 h的92.51%和57.23%。这是因为Ni助剂的加入有助于生成Ni3Mo3N,新生成的Ni3Mo3N有利于甲烷化反应。

     

    Abstract: A complexes was produced using hexamethylenetetramine(HMT) as the complexing agent of ammonium molybdate, and β-Mo2C was prepared by a simple thermal decomposition of this complexes. And then Ni was introduced and the bimetallic carbide Ni3Mo3N/β-Mo2C was prepared. The as-prepared products were characterized by XRD, low-temperature nitrogen adsorption, SEM, HRTEM, element analysis (EA), and the performances of the prepared catalysts for methanation were investigated. The results showed that the bulk molybdenum carbide exhibited high conversion of CO (xCO), but xCO and selectivity of CH4 (sCH4) on β-Mo2C decreased from 75.93% and 36.79% to 67.41% and 33.54% within 100 h. Thus the catalytic activity was not stable and sCH4 was low. The addition of Ni markedly promoted the catalyst activity and stability, xCO and sCH4 on Ni3Mo3N/β-Mo2C increased from 83.15% and 46.64% to 92.51% and 57.23% within 100h, which should be attributed to the newly produced Ni3Mo3N after Ni addition.

     

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