Preparation Of Cu-based Catalyst And Study On Hydrogenation Technology Of Oils

With the rapid development of the world economy,the consumption of oil resources increases,sharply,and human beings are facing serious resource shortage and environmental pollution problems.There are abundant sources of raw materials to produce biofuel from waste food oil.It can not only avoid the return of waste food oil to the dining table,but also realize the circular utilization of waste food oil,which plays a supplementary role in the situation of fuel shortage.Catalytic hydrogenation technology has the advantages of simple technological process,low investment,and good product quality,which is the most convenient technology to be put into industrial production.The preparation of biodiesel by hydrogenation from oil mainly involves two reaction pathways:hydrodecarbonylation or hydrodecarboxylation（HDC）;hydrodeoxygenation（HDO）.From the points of atomic economy and efficient utilization of carbon resources,HDO reaction is more ideal and more consistent with the core content of green chemistry than HDC reaction.Catalyst is the core of oil catalytic hydrogenation technology,which has aroused great interest of researches.The physicochemical properties of precursors and catalysts are studied by H₂-TPR,XRD,BET,in-situ XPS and H₂-TPD characterizations.The catalytic hydrogenation performance of Cu/γ-Al₂O₃ catalyst is studied by using methyl laurate as a model compound.The main conclusions are as follows:1.The active Cu⁰ species on the surface of the prepared Cu/γ-Al₂O₃ catalyst is the main catalytic hydrogenation site,and the HDO of methyl laurate mainly forms C₁₂alkane.The hydrogenation performance of methyl laurate over Cu/γ-Al₂O₃ catalyst is closely related to the metal Cu loading.When the loading is small,the number of active Cu⁰centers on the surface of the support is small.However,excessive loading makes metal Cu aggregate on the surface of the support,the dispersibility of active component decreases,and the grain size of metal Cu increases.These reasons can lead to poor hydrogenation performances of the corresponding catalysts for methyl laurate.When Cu loading is 10 wt.%,the correspomding Cu/γ-Al₂O₃ catalyst has large specific surface area,high Cu⁰ content,and suitable Cu⁰grain size,which promotes the adsorption and activation ability of reactant molecules,thus showing the best HDO performances for methyl laurate.When the reaction temperature is 400°Сand pressure is 2 MPa,the methyl laurate conversion and the selectivity of C₁₂ alkane are 89.2%and75.1%,respectively.The prepared Cu/γ-Al₂O₃ catalyst has good stability of cyclic hydrogenation and reproducibility.2.The reduction temperature has significant effects on the Cu⁰ species content,Cu⁰ grain size,and pore structure of the catalysts.With the increase of reduction temperature,the grain size of metal Cu increases,and the specific surface area of catalyst decreases.Under low temperature conditions,Cu²⁺can not be effectively reduced to form Cu⁰species,and high reduction temperature is easy to lead to the formation of Cu Al₂O₄spinel.These reasons can make poor hydrogenation performances of the corresponding catalysts for methyl laurate.Cu/γ-Al₂O₃catalyst can be effectively prepared after the reduction of Cu O/g-Al₂O₃precursor in H₂ at350°C for 2.0 h（RT350）.RT350 catalyst has large specific surface area,high Cu⁰species content,and suitable metal Cu grain size,which makes it has excellent hydrogenation performance for methyl laurate.When the reaction temperature is400°C and pressure is 2 MPa,the methyl laurate conversion and C₁₂ alkane selectivity are 89.2%and 75.1%,respectively.Besides,appropriate H₂/Oil and reaction pressure are favorable for the hydrogenation of methyl laurate to C₁₂ alkane.3.The polarity and viscosity of impregnation solvent have significant effects.on the distribution of active component,metal Cu species content,and Cu⁰ grain size of the prepared Cu/γ-Al₂O₃catalyst.With the decrease of solvent polarity,the impregnation depth of metal Cu species decreases,and the content of Cu⁰ on the surface of the corresponding catalyst increases.The Cu-CPA catalyst prepared by using acetone as solvent contains a large number of metal Cu species,and the Cu⁰ species mainly distributes in the outer region of the support in a highly dispersed state.This phenomenon enables Cu-CPA catalyst to have superior ability to adsorb and activate reactant molecules,which is conducive to the hydrogenation of methyl laurate.When the reaction temperature is 400°C and pressure is 2 MPa,the methyl laurate conversion and C₁₂ alkane selectivity are 87.2%and 80.1%,respectively.The Cu-CPA catalyst with Cu loading of 3 wt.%and Cu-DIA with Cu loading of 10 wt.%catalysts are prepared by using acetone and water as impregnation solvents,respectively,and they have similar hydrogenation activities for methyl laurate.The acetone can improve the utilization rate of active components,which laies a good foundation for the preparation of economical and efficient catalysts.The prepared catalysts all have good cyclic hydrogenation performances for methyl laurate.