The Study On Liquid-phase Catalytic Hydrogenation Of Guaiacol To Cyclohexanol

Lignin is one of the three major components in lignocellulose,its content is second only to cellulose and its energy is relatively high.At present,lignin is converted into bio-oil liquid fuel mainly by rapid pyrolysis.Bio-oil contains many high-oxygen phenol derivatives,and the development and utilization of lignin phenol derivatives to produce high-value chemicals has great economic and social benefits.As one of the most typical lignin phenolic derivatives,it is not only of great economic value to produce cyclohexanol from guaiacol by hydrodeoxygenation,but also has a certain guiding significance for the study of lignin hydrodepolymerization process.In this paper,Ru-Co/TiO₂-Al₂O₃ bimetallic catalyst was prepared and applied in the hydrodeoxygenation of guaiacol.Firstly,a series of TiO2-Al2O3 composite supports with different Ti/Al molar ratios were prepared by sol-gel method.And then a series of Ru-Co/TiO₂-Al₂O₃ bimetallic catalysts with different Ru and Co loading were prepared by impregnation-thermal decomposition method.It was found that the addition of metal promoter Co and the application of composite supporter can effectively improve the selectivity to the main product of cyclohexanol when the conversion of guaiacol is higher than 99%.In this work,5Ru-5Co/TiO₂-Al₂O₃?Ti/Al=1/1.6?presents the best catalytic performance of 99.69%conversion of guaiacol and 81.73%selectivity to main product of cyclohexanol under 200°C reaction temperature,2MPa H2 pressure and 210 min reaction time.Moreover,the catalyst still has high catalytic activity after five recycle.The"structure-effect"relationship between catalyst structure and catalytic performance was investigated by XRD,BET,XPS,H2-TPR,FT-IR,TEM and other characterization.In order to further reduce the economic cost of the catalyst,a series of Ni-Fe/Mg/Al catalysts with different Ni and Fe ratios were prepared by urea coprecipitation method and applied in the hydro-deoxygenation of guaiacol.It was found that the ratio of metal Ni and Fe and the selection of solvent have a great influence on the catalytic performance of guaiacol and the selectivity to the main product of cyclohexanol,and the proper addition of transition metal Fe can effectively improve the selectivity to the cyclohexanol.The best catalyst was 8Ni-4Fe/Mg/Al,and it presents the best catalytic performance of 99.49%conversion of guaiacol and82.7%selectivity to main product of cyclohexanol under 200°C reaction temperature,2MPa H2 pressure and 480 min reaction time.The results of the reusability of8Ni-4Fe/Mg/Al showed that the catalyst did not undergo significant phase change and the content of Ni and Fe was not lost before and after the reaction of guaiacol hydrodeoxygenation,so the catalyst possess good stability.The characterization of XPS,H2-TPR and TEM showed that the strong interaction between metal Ni and Fe and the good dispersibility of the active components are one of the main reasons for the selectivity to cyclohexanol.