| The energy crisis caused by the excessive consumption of fossil energy and the increasing environmental problems have made the importance of seeking new,green and renewable energy.Biomass resources can be used as a substitute for fossil resources for the preparation of fine chemicals and energy because of its wide distribution and abundant reserves.Therefore,the conversion and utilization of biomass resources have attracted much attention.Glycerol can be converted into a series of high-value chemicals through processes such as oxidation,hydrogenation,and carbonylation.Glycerol can convert to lactic acid and 1,2-propanediol through dehydrogenation and hydrogenolysis,and lactic acid can be used in the preparation of foods,the pharmaceutical industry,degradable plastics,solvents,and so on.At present,the catalytic materials used in the processing and high-value utilization of glycerin are mainly concentrated on noble metal catalysts(Au,Pt,Ru,et al)and non-precious metal catalysts(Cu,Ni,et al).Precious metals have severely limited their large-scale applications due to their high price and scarcity of resources.Although non-precious metals have good catalytic performance,they are generally harsh in reaction conditions(high temperature,high pressure),poor catalyst stability,and cannot be reused.Therefore,how to create a new high-efficiency catalyst by creating and developing new preparation methods and ideas,control the composition,structure,active center type and dispersion,catalyst table/interface properties,etc.,and explore the intrinsic relationship between catalyst composition and structure.Strengthening the catalytic performance of the catalyst has important theoretical and practical significance for the high-value conversion and utilization of biomass resources,especially glycerol resources.On the surface of the research results,the type of active center and the choice of carrier have an important influence on the performance of heterogeneous catalytic materials for glycerol conversion.Currently,Cu-based catalysts have relatively high activity and selectivity in the selection of active centers.In the catalytic conversion of glycerol has a wide range of applications;in the choice of carrier,ZrO2 has both acidic and basic amphoteric traits,often used as a functional carrier material in the catalytic conversion and utilization of glycerol.However,in the preparation of Cu-based catalysts,the conventional methods often have the disadvantages of poor dispersion of active centers,easy agglomeration,inert surface of the carrier,low catalyst activity,poor selectivity,and short life.Therefore,how to design and develop a new type of high-efficiency supported Cu-based catalytic materials to achieve high-value and high-efficiency conversion of glycerol is a hotspot and a difficult point in this field,and it is also the main content of this thesis.In this thesis,a highly dispersed CuMgAlZr quaternary composite metal oxide(CuO-MgO-Al2O3-ZrO2)was constructed by hydrotalcite precursor method,nucleation/crystallization separation method and dynamic hydrothermal crystallization method.Catalytic material is applied to the reaction of glycerol dehydrogenation to prepare lactic acid to prepare highly dispersed Al-modified Cu/ZrO2 catalyst.It is applied to the hydrogenolysis of glycerol to prepare 1,2 propanediol,and constructs abundant defect sites and acid-base on the surface of the carrier.The new high-efficiency Cu-based catalytic materials were constructed by strengthening the interaction between the carrier and the active center and increasing the dispersion of the active center.The performance of the catalyst in the catalytic conversion of glycerol was investigated.The specific research contents are as follows:(?)Using the unique lattice positioning effect and the minimum lattice energy effect of hydrotalcite,four elements of Cu,Mg,Al and Zr are introduced into the hydrotalcite laminate to achieve uniform distribution of each element and control a certain temperature.The following baking treatment is performed to construct a quaternary composite metal oxide.The results show that the unique preparation method and the introduction of Zr can effectively organize the agglomeration of Cu element in the roasting process,and achieve the uniform distribution of each component.At the same time,the introduction of Zr can also modulate the overall acidity and alkalinity of the catalyst.The high degree of dispersion,the synergistie effect between the components,and the suitable surface acid-base microenvironment make the conversion rate and selectivity of the obtained catalytic material in glycerol selective dehydrogenation conversion to lactic acid up to 93.1%and 93.2%,The catalyst embodies high recyclability.After repeated use for 5 times,the catalytic performance remains basically unchanged,which shows a high application prospect.(?)The Cu-ZrO2-Al2O3 catalyst was prepared by the combination of nueleation/erystallization separation method and dynamic hydrothermal crystallization method,and the doping and modification of Al were realized.The results show that the strong interaction between the active center Cu and the high specific surface area porous ZrO2 carrier material acts to block and anchor the Cu active center,achieving a highly uniform dispersion of the Cu active components,and the introduction of Al can build more The defect position can also modulate the acidity and alkalinity of the catalyst surface and increase the proportion of medium and strong acid.The high dispersion of the active center,the synergy between the metal active center and the acid-base active center,the catalytic performance of the hydrogenolysis of glycerol to 1,2-propanediol was significantly improved,and the calculation results showed that The Cu-ZrO2-10%Al2O3 catalyst has the lowest reaction activation energy,and the conversion and selectivity in the reaction of hydrogenolysis to 1,2-propanediol are as high as possible,and the catalyst has good reusability,and the performance is basically unchanged after 5 consecutive uses. |
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