The effect of copper on benzene hydrogenation to cyclohexane over Ni/Al2O3 catalyst

• Copper as an efficient modifier of Ni/Al2O3 catalyst for benzene to cyclohexane hydrogenation.
• Considerably better selectivity of Ni–Cu catalyst compared to the reference one due to enrichment of the catalyst surface with copper.
• Improvement of the catalytic activity upon addition of up to 20 wt% CuO and decrease of the activity above that content.

The effect of a copper modifier on physicochemical properties of coprecipitated precursors and final Ni–Cu/Al2O3 catalysts for benzene to cyclohexane hydrogenation was investigated. Based on the studies of physicochemical properties, the influence of copper on the catalytic activity and selectivity of Ni–Cu/Al2O3 systems was discussed. The addition of copper resulted in a decrease of the specific and nickel surface area, improvement of the selectivity and a slight decrease of the benzene hydrogenation activity compared to the reference catalyst. A decrease of methylcyclopentane and methylcyclohexane by-products formation on the surface of Ni–Cu/Al2O3 catalyst containing 10–17 wt% CuO by, respectively, 70% and 10% was observed. The results reveal a distinct, beneficial effect of the Ni/Al2O3 modification by copper on the catalyst selectivity. However, this effect depends on temperature and is limited to ca. 20 wt% CuO, above this content the activity was found to decrease considerably.

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