| Recently,biomass becomes the main source for renewable fuels and chemicals,due to its advantages of abundant,geographically ubiquitous,low price and so on.?-Valerolactone?GVL?is an important biomass-based platform compound,which can be obtained from hydrogenation of levulinic acid?LA?.In generally,Ru catalysts have good activity in hydrogenation of levulinic acid to?-valerolactone.Particularly,the activity of Ru supported on carbon materials?active carbon,mesoporous carbon?were better than those supported on oxide supports?SiO2,Al2O3,TiO2?in hydrogenation levulinic acid to?-valerolactone.This may be closely related to the nature of carriers.Although,Ru catalysts prepared by impregnation method have high activity,the stability was not so good.In order to improve the activity and stability of Ru supported on carbon materials,we explored the influence of different carbon supports and catalysts preparation methods in hydrogenation of levulinic acid to?-valerolactone.In order to study the effect of different carbon supports for Ru catalysts in hydrogenation levulinic acid to?-valerolactone,three carbon materials including activated carbon,mesoporous and nitrogen doped mesoporous carbon?AC,OMC and NOMC?were used as the carriers to support Ru nano particles.The Ru/NOMC and Ru/OMC catalysts were prepared by impregnation method,and the commercial Ru/AC catalyst was used for comparison.The catalysts were characterized by XRD,TEM,H2-TPR,N2 adsorption and desorption and XPS techniques.And the performance and the stability of the three catalysts were investigated for hydrogenation levulinic acid to?-valerolactone under the same conditions.The results showed that Ru supported on N-doped mesoporous carbon catalyst had the highest activity.N-doped mesoporous carbon can reduce the diameter sizes of Ru nano particles,improve the dispersion of metal and enhance the interaction between the metal and supports.Although the Ru/NOMC catalyst had high activity,its stability was not so good.After being reused five times,the conversion of levulinic acid decreased from 100%to 78.9%.On the basis of above research,in order to improve the stability of the Ru-NOMC catalyst,the catalyst was prepared by the embedding method and was used for hydrogenation levulinic acid to?-valerolactone.Additionally,a series of characterization including XRD,TEM,N2adsorption and desorption and XPS were carried out.The reaction conditions including the dosage of catalyst,reaction time,reaction temperature and reaction pressure in the hydrogenation of levulinic acid were optimized.And the stability of the catalyst was studied.The results indicated that under the optimized conditions?methanol as solvent,5wt%of catalyst dosage,4 h,120oC and 1.3 MPa H2?,the conversion of levulinic acid and the selectivity to?-valerolactone can reach 100%and100%,respectively.The embedding Ru-NOMC catalyst still kept good activity and stability for the hydrogenation of levulinic acid after being reused five times,with 100%of conversion of levulinic acid and 97%of selectivity to?-valerolactone,respectively. |
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