Toluene hydrogenation over Ni₂P/TiO₂ catalysts

A series of Ni₂P/TiO₂ catalysts with loading of 10% to 15%(wt) Ni₂P were prepared by temperature-programmed reduction (TPR) of phosphate precursors and were characterized by X-ray powder diffraction (XRD). The catalytic activities of these Ni₂P/TiO₂ catalysts for toluene hydrogenation were measured at atmospheric pressure and different temperatures in a packed-bed reactor. The XRD patterns of Ni₂P/TiO₂ catalysts with varying Ni/P ratios indicate that the main obtained phase is Ni₂P mainly, but Ni₁₂P₅ phase appears when P content is low. Activity measurements of these catalysts indicate that Ni₂P/TiO₂ catalysts have high activity with 100% methylcyclohexane selectivity and excellent stability in toluene hydrogenation reaction, and it also show that the reaction temperature and hydrogen flow rate have great effect on the activity for the toluene hydrogenation. The toluene conversion rate decreases with the increase of H₂ flow rate and increases at first with the increase of the reaction temperature and then decreases when the temperature is too high, it reaches a maximum at 250°C. The activity of Ni₂P/TiO₂ varies with Ni loading and P content. With the increase of Ni loading or P content, the steady activity of the catalyst increases at first and then decreases. The catalyst with lower P content will be partial deactivated in toluene hydrogenation reaction.