Effect of phosphorus modification on the catalytic properties of NiW/γ-Al₂O₃ in the hydrogenation of aromatics from coal tar

Modified with different contents of phosphorus, the NiW/γ-Al₂O₃ catalysts prepared using the impregnation method were used to catalyze the hydrogenation reaction of naphthalene and the aromatics compounds separated from low temperature coal tar in a fixed-bed reactor. The properties of the catalysts were characterized by N₂ adsorption, XRD, H₂-TPR, XPS and NH₃-TPD. The products were analyzed by GC-MS and GC×GC-TOFMS. Results showed that the addition of P can enhance the distribution of Ni and W compounds on the surface of supports and expand the pore diameter. Adding 1%~1.5%P could generate more Ni-W-O phase and increase the proportion of the weak acid. The results of naphthalene hydrogenation indicated that the highest conversion rate of nearly 80% and the decalin yield of over 50% were achieved when using the NiW+1%P catalyst. For the tests using the catalyst with 1.0%P to catalyze the hydrogenation of enriched aromatics compounds from coal tar, the results indicated that the effect of transforming aromatics into cycloalkanes and the removal of heteroatoms were remarkable in the presence of the catalyst.