Abstract:

Transition metal carbides have similar electron structure and hydrogenation performance with noble metal.NiW/γ-Al₂O₃ catalysts with different Ni/W ratio were prepared by equi-volumetic impregnation method,and then the samples were converted to carbides by temperature programed carburization and used for hydroprocessing of aromatic model compounds and aromatic fraction separated from low temperature coal tar.Results of N₂ adsorption,XRD,H₂-TPR and SEM showed that Ni addition promoted the dispersion and reduction of WO₃ species on the support surface,inhibited the aggregation of WO₃ crystals to form large particles.The hydrogenation results of naphthalene showed that the activity of catalyst with Ni/W atomic ratio of 0.6 was the best,while the naphthalene conversion and decalin yield reduced obviously after phenol and pyridine were added in the model oil,which resulted the catalysts with Ni/W atomic ratio of 0.47 and 0.6 showed similar performance.The one with Ni/W atomic ratio of 0.47 showed the better performance for hydroprocessing of the aromatic fraction separated from coal tar.The results showed that Ni and W were both active for hydrogenation,however,Ni was less resistant to heteroa-toms,thus the hydrogenation performance for NiW catalyst was the best with the optimal Ni/W ratio.With the present of heteroatomic compounds,such as coal-derived aromatic fraction,NiW carbide catalyst with Ni/W atomic ratio of 0.47 showed the best performance.

Key words: Ni/W ratio, carbide, hydrogenation, aromatic, coal tar