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.