The conversion of levulinic acid into γ-valerolactone using Cu–ZrO2 catalysts†
A series of Cu–ZrO2 catalysts prepared by a co-precipitation method were studied for the hydrogenation of levulinic acid to give γ-valerolactone (GVL). The effects of a range of catalyst preparation parameters, namely molar Cu/Zr ratio, calcination temperature and the ageing time of the precipitates, were systematically investigated. The molar Cu/Zr ratio was found to have a strong influence on the BET surface area of the material leading to a high activity for catalysts prepared with a Cu/Zr molar ratio of unity. Using this molar ratio the calcination temperature was varied from 300 °C to 800 °C, the material calcined at 400 °C showed the highest activity. Increasing the ageing time used in the catalyst preparation identified 6 h as the optimum to achieve the highest activity for LA conversion. Based on characterisation of all materials we conclude that the active Cu species is present in only low concentration suggesting that it should be possible to produce a catalyst of high activity with much lower Cu content.