Hydrogenation Of Ethyl Levulinate To γ-Valerolactone Catalyzed By Hydrotalcite Based Sulfide Catalysts

Cellulose is a natural and sustainable resource with abundant content and wide range of sources.And it is rich in natural polymer compounds,in which glucose can be directly alcoholized to get ethyl levulinate,and ethyl levulinate can further synthesizeγ-valerolactone.γ-Valerolactone is a kind of biomass platform compounds,which can be used as solvent,food additive,liquid fuel additive and so on.In this paper,we used hydrotalcite precursor to prepare a series of hydrotalcite based sulfide catalysts,and their performance in the hydrogenation of ethyl levulinate toγ-valerolactone was studied.Firstly,we used MgFe hydrotalcite precursor to prepare a series of MgFe hydrotalcite based sulfide catalysts,and studied the active components of the catalysts.The results show that MoS₂ dispersed in the layered structure of the catalysts was the main factor leading to the high activity of the catalysts.Through the selection of different Mg/Fe ratios,we found that Mg₁Fe₁Mo-S catalyst had the best catalytic effect.We also found that Mg₁Fe₁Mo-S catalyst showed the best catalytic activity under the conditions of reaction temperature of 220℃,initial hydrogen pressure of 1.5 MPa and reaction time of 2 h.The conversion of ethyl levulinate reached 99.0%,and the yield ofγ-valerolactone reached 97.9%.In addition,we had studied the recyclability of Mg₁Fe₁Mo-S catalyst,but the result was not good.The effect of different solvents on the hydrogenation of ethyl levulinate toγ-valerolactone was also studied.It was found that the effect of hydrogen donors was related to the reduction potential of alcohol solvents,the higher the reduction potential was,the worse the effect of hydrogen supply was.The hydrogenation route of ethyl levulinate over hydrotalcite based sulfide catalyst system was also deduced.Secondly,CoFe and NiFe hydrotalcite based sulfide catalysts were prepared by the same method.The characterization results showed that the two precursors had the unique layered structure of hydrotalcite precursor,and no characteristic peak of MoS₂was observed,which showed that hydrotalcite based sulfide catalyst was very conducive to the high dispersion of MoS₂.It was found that the Co₁Fe₁Mo-S catalyst showed the best catalytic activity at 240℃and 1.5 MPa initial hydrogen pressure,the conversion of ethyl levulinate was 93.2%,and the yield ofγ-valerolactone was 91.0%.And Ni₁Fe₁Mo-S catalyst showed the best catalytic activity at 230℃and 0.5 MPa initial hydrogen pressure,the conversion of ethyl levulinate was 90.8%,and the yield ofγ-valerolactone was 79.8%.