| The pyrolysis oil of lignin is composed of various phenolic compounds,which can only be fully hydrogenated and deoxygenated under high temperature.However,the high temperature will lead to the problems of carbon deposition,catalyst sintering and large energy consumption,which restrict the development of the conversion of lignin to liquid hydrocarbon fuel.Therefore,it is of great significance for efficient energy utilization of lignin to improve the heat and mass transfer characteristics of lignin pyrolysis oil at low temperature by modifying the catalyst.The synergistic effect between the bimetals can effectively enhance the activity of the catalyst,showing better catalytic performance than that of single metal.In this paper,a series of RuNi/SiO2-ZrO2 bimetallic catalyst was prepared by impregnation method.In the HDO reaction of guaiacol,the catalytic performance of RuNi bimetallic catalysts were obviously better than that of Ru and Ni catalysts,and the yield of cyclohexane was close to 100%.The effect of metal loading on the performance of the catalyst was studied.It was found that the best hydrogenation and deoxidation performance of the catalyst was obtained when the metal loading of Ru and Ni were both 5wt.%.In the HDO process of guaiacol,the saturation of aromatic ring was the first to occur,followed by the removal of methoxy group to form cyclohexanol,and finally the removal of hydroxyl group to form cyclohexane.RuNi bimetal catalyst also had good HDO performances on other phenolic model compounds.All phenolic compounds could be completely converted at 260℃,and the alkane selectivity was above 89%.In the hydrogenation and deoxygenation of real lignin pyrolysis oil,RuNi bimetal catalyst also increased the hydrocarbon composition from 9.2%to 22.6%.Then,the RuCo bimetallic catalyst was investigated,and found that this catalyst has a higher catalytic activity compared with RuNi bimetallic catalyst.In the HDO of guaiacol and other phenolic compounds,the high yield of hydrocarbon products can be obtained at 260℃.The results of catalyst characterization showed that the bimetallic catalyst had better reductivity than the mono-metal catalyst,which was conducive to the formation of metal active sites.The existence of electron transfer between Ru and Co metals were verified the synergistic effect between the bimetals.In addition,the bimetallic catalyst also had better adsorption capacity of hydrogen and substrate,and stronger activation of substrate.The synergistic effect of bimetallic in the catalyst on the adsorption and activation of guaiacol was verified by DFT simulation calculation,and explained the hydrogenation and deoxidation reaction process.Besides,we also studied the Ni Co/SiO2-ZrO2 bimetallic catalyst,The application of two transition metals can effectively reduce the cost and improve the application value of the catalyst,which had a good application potential.The results of catalyst characterization showed that Ni Co catalyst had better reduction performance than single metal under the synergistic action of bimetallic.At the same time,electron transfer existed between Ni and Co metals,which enhanced the activity of metal site,and also improved the adsorption performance of catalyst for H2.Kinetic studies show that the activation energy of guaiacol over NiCo/SiO2-ZrO2 bimetallic catalyst was55.87kJ/mol,which was lower than the results reported in relevant literature,indicating that the catalyst had a good catalytic performance for the guaiacol HDO reaction.In addition,when NiCo/SiO2-ZrO2 bimetallic catalyst was used for the hydrodeoxygenation of lignin depolymerization products,the proportion of hydrocarbons can be increased from 4.2%to 60.6%,which greatly improves the calorific value of lignin depolymerization products,and was expected to be used as a biological alternative fuel directly. |
