碳化终温对β-Mo2C催化喹啉加氢脱氮性能影响

以MoO_3为前驱物,CH_4/H_2为碳源,采用程序升温直接还原碳化法制备不同碳化终温(640、660、680、700和720℃)的碳化钼催化剂,通过XRD、N_2吸附-脱附、SEM、TEM、XPS和Raman表征研究碳化钼的物理性质和结构性质,并研究不同碳化终温碳化钼对喹啉加氢脱氮的催化性能。结果表明,不同碳化终温的碳化钼催化剂均为β-Mo_2C,碳化终温可显著改变碳化钼表面物种含量、平均孔径和介孔分布。碳化终温为680℃时,催化剂碳化程度较高,表面氧物种含量最低,表面C/Mo物质的量比最高,对应的催化活性也最佳,在340℃、4 MPa条件下,喹啉的转化率和脱氮率均高达99%以上,芳香族类化合物的选择性可达37.8%,显示出较低的芳环破坏性。表面组成尤其是表面氧对于β-Mo_2C上喹啉加氢脱氮反应途径的调控至关重要。

Effect of final carbonization temperature on catalytic performance of β-Mo2C in quinoline hydrodenitrogenation

MoO₃ was used as precursor, CH₄/H₂ as carbon source, and a direct reduction carbonization method with programmed temperature rise was used to prepare molybdenum carbide catalysts at different final carbonization temperatures (640, 660, 680, 700, and 720℃). The physical properties and structural properties of molybdenum carbide were characterized by XRD, N₂ adsorption, SEM, TEM, XPS and Raman. The effect of final carbonization temperature on the catalytic performance of molybdenum carbide in quinoline hydrodenitrogenation was studied. The results showed that the molybdenum carbide catalysts with different final carbonization temperatures were all existed in the phase of β-Mo₂C. The final carbonization temperature could significantly change content of species on the surface, average pore size, and mesopore distribution of molybdenum carbide. When the final carbonization temperature was 680℃, a higher carbonization degree, the lowest content of oxygen species on the surface and the highest surface C/Mo molar ratio of catalyst were obtained; accordingly, the best catalytic activity of catalysts was achieved. At 340℃ and 4 MPa, the conversion and denitrification rate of quinoline were up to 99%, while the selectivity of aromatic compounds was up to 37.8%, showing a lower aromatic ring destruction. Surface composition, especially surface oxygen, was essential for the regulation of the quinoline hydrodenitrogenation reaction pathway on β-Mo₂C.