Hydrodeoxygenation Of Biomass-based Aldehydes And Ketones Over Supported Copper-based Catalysts

Modern industries have rapidly developed with the help of fossil energy sources.On the other hand,hidden dangers such as energy crises and ecological pollution caused by over-reliance on these non-renewable resources have gradually emerged.Thence,for the sustainable development of society,the exploration of renewable energy to replace depleted fossil fuels has received intimate attention.Biomass resources with rapid regeneration possess the advantages of being cheap,environmentally friendly,and widely available,which are also widely recognized as the only renewable green carbon resources that are capable of replacing ore energy on a large scale.Therefore,the exploitation and research on the transformation of biomass resources are of great significance for promoting the revolution of new-energy production.Cellulose and hemicellulose are the main components of biomass and are polymers composed of carbohydrates.Compared with fossil fuels,these components have higher oxygen content,lower energy density,and more complex degradation products.Then,the highly selective conversion of lignocellulosic biomass to fuel molecules is equivalent to the conversion of carbohydrates to hydrocarbons.Therefore,one of the research cores of biomass conversion is to achieve highly selective conversion of multiple oxygen-containing functional groups in different chemical environments,which requires the development of efficient hydrodeoxygenation catalytic systems.According to reports,inexpensive supported copper-based catalysts perform high activity on the hydrodeoxygenation of biomass-derived aldehydes and ketones.However,there are also disadvantages on copper-based catalysts,such as easy loss of Cu1+ species,harsh reaction conditions,narrow substrate application range,poor carbonyl-hydrogenation selectivity,and agglomeration inactivation caused by high loading of copper.In this thesis,the copper-based catalyst was modified by means of adding different auxiliaries to improve the above defects and increase the yield of the target product.In addition,various characterization techniques were used to explore the properties of materials and the doping effect of additives.Meanwhile,the optimal reaction system was also screened out.In the first work,a series of Cu-Fe bimetallic catalysts to hydrogenate biomass-based ethyl levulinate(EL)to 1,4-pentanediol(1,4-PDO)were prepared by modifiing low-loading Cu-based catalysts with variable inorganic metal Fe.Among them,2.8Cu-3.5Fe/SBA-15(Cu/Fe molar ratio of 1:1.5)show the best performance,on which 97%yield of y-valerolactone(GVL)intermediate can be obtained at 140℃.In this system,GVL can also be continuously hydrogenated to 1,4-PDO with a selectivity of 92.6%;or EL can be directly converted to 1,4-PDO by a one-pot strategy.The high activity of copper-based catalysts at such a lower loading of 2.8 wt%is due to highly dispersed active species and the doping effect of the auxiliary iron.Various characterization techniques have shown that Fe is both a structural modifier and an electronic modifier for copper species.At the same time,the introduction of Fe provided abundant Lewis acid sites and accelerated the reaction process.In addition,combined with characterization and reaction kinetics,the bimetal oxide phase(CuFeO2)has been confirmed to form on the catalyst surface,and plays an important role in improving catalyic performance.In the second work,organic-SO3H groups were selected to modify copper-based catalysts.The synthesized bifunctional Cu/SBA-15-SO3H catalyst can convert xylose to furfuryl alcohol with a yield of 62.6%in one-pot,at the condition of 140℃ and 4 MPa.On the basis of characterization analysis,it can be concluded that the auxiliary-SO3H groups play the role of structure and electronic modifier as well,which improves the physical and chemical properties of copper species.Furthermore,-SO3H group also shows the dual function effect,coexisted with Cu sites and collaboratively catalyzes the cascade conversion.Besides,various factors in reaction system were also studied:higher reaction temperature and hydrogen pressure will promote the side hydrogenation of products and substrates,respectively;a biphasic solvent composed of water and n-butanol can satisfy the solvation of xylose and the extraction of furfuryl products;excessive acidic sites and large pore sizes can promote xylose conversion,but result in low yields of furfuryl alcohol.