Construction And Performance Regulation Of Hydrogenation Catalysts For The Catalytic Conversion Of Biomass Derivatives

Biomass is the only renewable carbon resource that is expected to replace fossil energy in the new energy field.It has the advantages of large reserves and facile access,but the calorific value of biomass is low,and the thermal stability is poor.Direct use of biomass as primary energy material has low efficiency,serious pollution and other shortcomings.In recent years,it is a hot research topic to convert the biomass into liquid fuel or high-value chemicals.Catalytic conversion is an effective way to realize high value utilization of biomass resources,and the construction of efficient catalyst is the key to the catalytic conversion of biomass resources.Hydrodeoxygenation is an important step in the conversion of biomass and its derivatives into liquid fuel or high-value chemicals.For converting the different types of carbon-oxygen structures in biomass,three hydrogenation catalysts were constructed by changing the types of active metals and regulating the properties of the supports.The prepared catalysts were applied to the hydrodeoxygenation processes of carbonyls,aromatic ethers,phenols and esters as well as real bio-oil.The reaction performance of the catalysts were evaluated in an intermittent reactor,and the structure of the catalyst was analyzed by various characterization techniques.The structure-activity relationship of catalysts was studied systematically.Specific research contents and conclusions are as follows:?1?A series of unsupported micro/nano cobalt were prepared by one-step liquid phase reduction.Using H₂ as the hydrogen source,the catalytic performance of the prepared catalyst in the preparation of?-valerolactone from biomass platform molecule ethyl levulinate was investigated.The influence of solvent on the structure and hydrogenation performance of catalyst was studied.The cobalt catalyst obtained from ethanol has the best catalytic hydrogenation performance,and the yield of?-valerolactone was as high as 91.4%under relatively mild reaction conditions?150°C,4 h?.The catalysts had magnetic correspondence and could be easily recovered under the action of external magnetic field.The catalytic activity of the catalyst did not decrease significantly after cycle use for 6 times,indicating that the catalyst had good stability.?2?In order to further improve the utilization efficiency of cobalt and make the reaction conditions more mild,five kinds of cobalt-carbon catalysts supported by different carbon materials were prepared,and liquid hydrogen source isopropanol was used to replace gaseous hydrogen source H₂.The performance of the cobalt-carbon catalysts in the hydrogenation of biomass derived carbonyl compounds,ethers and phenols was evaluated.The results showed that the catalyst Co-CNT?COOH?supported by carboxylate carbon nanotubes had higher catalytic activity and better stability for the preparation of?-valerolactone by transfer hydrogenation of ethyl levulinate.At 150°C for 5 h,the yield of?-valerolactone can reach 85.7%.The Co-CNT?COOH?catalyst contains the most oxygen-containing structure among the five cobalt-carbon catalysts,and the acidity was the strongest.The oxygen-containing structure in the supports and the active component cobalt had a synergistic catalytic effect on transfer hydrogenation,thus the Co-CNT?COOH?catalyst had good transfer hydrogenation performance on carbonyl substrates.The results of hydrogenation performance evaluation of Co-CNT?COOH?on anisole and p-cresol showed that Co-CNT?COOH?can deoxidize partially on anisole,but can only produce hydrogenation products but no deoxidization products on phenolic substances.The supported Co-CNT?COOH?catalyst has higher cobalt catalytic efficiency and more moderate reaction conditions.?3?In order to further improve the hydrodeoxygenation performance of the catalyst on the oxygen-containing compounds derived from biomasses,the active component and support of the catalyst were improved and optimized.The Ru-Nb OPO₄ catalyst was prepared to study the hydrodeoxygenation of ethoxy bond,phenolic hydroxyl group and ester bond in the derivatives.The influence of catalyst composition and reaction conditions on catalytic performance of Ru-Nb OPO₄ was studied.The relationship between the structure of catalyst and its hydrodeoxygenation properties was analyzed.The characterization results showed that the support Nb OPO₄ had strong acidity of Lewis acid.The Lewis acid site was derived from Nb-O bond structure.The Ru-Nb OPO₄ catalyst has both strong acidity of Nb-O structure and excellent hydrogenation activity of metallic Ru,showing excellent catalytic activity to hydrodeoxygenation of aromatic ethers,phenols and esters of different structures.In the process of recycling,carbon deposition and the increase of Ru nanoparticles lead to the slight deactivation of Ru-Nb OPO₄ catalyst,which can be recovered by simple calcination and hydrogen reduction.?4?The hydrodeoxygenation of real corn straw bio-oil by catalyst Ru-Nb OPO₄was investigated.The results showed that the yield of hydrocarbon could reach 88.2%and the oxygen content could be reduced to 6.9%from 91.8%at 170°C.The hydrodeoxidizing capacity of Ru-Nb OPO₄ catalyst on the real bio-oil system is very significant.A mixture of hydrocarbon products was obtained by hydrodeoxidizing a variety of oxygen-containing compounds in bio-oil at 300°C.The hydrocarbon yield was 89.4%and the oxygen content decreased to 8.7%from 80.5%.In this paper,three kinds of hydrogenation catalysts were constructed by regulating the types of active metals and the properties of supports.The hydrogenation ability of three hydrogenation catalysts were enhanced in turn,and they showed excellent performance in the conversion of biomass derivatives platform molecules and bio-oils.The catalyst reference and basic data were provided for the conversion of biomass to liquid fuels and high-value chemicals.