Construction Of Non-Noble Metal Catalysts And Its Catalytic Performance In Selective Hydrogenation Of α,β-Unsaturated Aldehydes

α,β-unsaturated alcohols prepared by selective hydrogenation ofα,β-unsaturated aldehydes have extensive application and research value as an important chemical raw material and pharmaceutical intermediate.The selective hydrogenation ofα,β-unsaturated aldehydes has always been a research hotspot because of its internal conjugated double bonds C=O and C=C.At present,there are homogeneous catalysis and heterogeneous catalysis in the study ofα,β-unsaturated aldehydes.Although homogeneous catalysis has good selectivity for unsaturated alcohols,the separation between catalyst and solution is very difficult,there are many wastes,and the process conditions are harsh,which does not accord with the concept of modern green catalysis.Solid catalysts are mostly used in heterogeneous catalysis,which can reduce the discharge of organic waste and effectively realize the separation between catalysts and organic products,thus reducing the loss of catalysts and pollution to organic products.and the catalyst can be reused in industry,which improves the comprehensive utilization of the catalyst,which is also in line with the basic requirements of modern green chemistry in China.In recent years,a large number of scientific researchers have devoted themselves to the development and utilization of heterogeneous catalysts and achieved some satisfactory results.However,at present,there are still many problems to be solved in the development of catalysts with high activity and high selectivity.The development of non-precious metal catalysts with low cost,high efficiency and simple preparation is still the focus of the current research.Firstly,the hydrogenation of cinnamaldehyde catalyzed by ZIFs catalyst prepared by microwave-assisted method was studied.Compared with conventional solvothermal method and room temperature stirring method,ZIFs prepared by microwave-assisted method showed excellent catalytic performance.The results of analysis and characterization show that the defective ZIFs contains both independent Lewis acid（metal center）and Lewis base（N）site in 2-methylimidazole.The ZIFs synthesized by microwave-assisted synthesis has more abundant acidic and basic sites,which can form heterogeneous FLP-like catalysts.At the same time,the experimental results show that the coexistence of acidic and basic sites of ZIFs is necessary to activate the H bond and obtain high activity.The theoretical results show that the FLPs site in the defect ZIFs can easily dissociate the H-H bond and the activation energy is only 8.7Kcal/mol.The hydrophobically modified core-shell structure ZIF-67@Si O₂-DMDES can effectively transform the hydrophilic surface into a hydrophobic surface,thus improving the adsorption performance of the reactants on the catalyst.At the same time,the target product cinnamyl alcohol can be desorbed from the catalyst in time to avoid further hydrogenation.The properties of defect ZIFs and ZIF-67@Si O₂-DMDES can also be extended to other selective hydrogenation ofα,β-unsaturated aldehydes.Under the reaction temperature of 180°C and 1MP hydrogen pressure,the ZIF-67-MW@Si O₂-DMDES catalyst obtained more than 99%conversion of cinnamaldehyde and 95.3%selectivity of cinnamyl alcohol.In the investigation of the cycle availability of ZIFs and ZIF-67-MW@Si O₂-DMDES catalysts,it was found that the catalytic performance of ZIFs catalysts decreased significantly in the fifth round.However,the efficiency loss of hydrophobically modified ZIF-67-MW@Si O₂-DMDES catalyst in the fifth operation is small.The hydrophobically modified core-shell catalyst not only improves the activity of the catalyst,but also improves the reuse performance of the catalyst.In this work,ZIF-67 and ZIF-67@Si O₂-CPTEOS were successfully prepared and applied to the transfer hydrogenation of cinnamaldehyde.This was proved to be a homogeneous reaction in heterogeneous system.However,the transfer hydrogenation of cinnamaldehyde on ZIF-67 has serious recovery problems.Therefore,the hydrophobic modified ZIF-67@Si O₂-CPTEOS core-shell nano-reactor was successfully prepared,which effectively limited the active center of metal-N in the core-shell structure,and greatly improved the activity of the catalyst through hydrophobic modification.Therefore,ZIF-67@Si O₂-CPTEOS has good catalytic performance and stability.under the N₂pressure of 453K and 1MPa,cinnamaldehyde can be completely converted and the selectivity of cinnamyl alcohol can reach 93.2%.The experimental results show that ZIFs catalyst has better catalytic performance than nitrate catalyst,which is mainly due to the introduction of n and the formation of Co-N bond in ZIFs,which can greatly improve the catalytic activity of the catalyst.The results of density functional calculation show that the activation energy barrier of Co-N in ZIF-67 is lower than that of metal Co dissociated by Co（NO₃）₃·6H₂O,which further proves that the generated Co-N has higher catalytic activity than metal co,so it is easier to obtain the target product.Finally,the possible reaction mechanism of transfer hydrogenation of cinnamaldehyde on ZIF-67 was proposedIn this work,the application of different metal salts in the transfer hydrogenation of cinnamaldehyde was investigated.The self-selective catalyst prepared by the introduction of substrate cinnamaldehyde can efficiently realize the transfer hydrogenation of cinnamaldehyde to cinnamyl alcohol.The experimental and characterization results show that the transfer hydrogenation of cinnamaldehyde catalyzed by metal salts is essentially a heterogeneous catalytic reaction,and its active center is amorphous zirconia formed in situ.The NH₃-TPD characterization shows that the precipitates of,Zr（SO₄）₂·4H₂O and Zr Cl₄have stronger acidic sites and more acidic sites.This is the main reason for the high ether yield of Zr Cl₄ catalyst.The characterization of XRD,SEM,TEM,HRTEM and HAADF-STEM shows that Sel-α-Zr O₂ has smaller nanoparticles and more uniform distribution.At the same time,XPS,FT-IR and in situ infrared characterization show that Sel-α-Zr O₂ has more surface hydroxyl groups.Under the reaction temperature of 180°C and the reaction nitrogen pressure of 1MPa,the conversion of>99%and the selectivity of cinnamyl alcohol of 94.6%were obtained.Characterization and theoretical analysis show that the synergistic catalysis of zirconium active sites and surface hydroxyl groups can effectively activate the C=O bond in cinnamaldehyde and reduce the energy barrier,thus significantly improving the transfer hydrogenation activity.In addition,self-selective Zr O2 showed excellent catalytic performance for a series of unsaturated aldehydes.Finally,the recycling performance of Sel-α-Zr O₂ catalyst was investigated,and it was found that the catalytic activity changed little after being reused for 10 times.The results show that Sel-α-Zr O₂ catalyst has good stability.The preparation of N-modified MOF derivative catalyst and its catalytic performance for selective hydrogenation ofα,β-unsaturated aldehydes were investigated.Porous nano-carbon materials were prepared by two-stage calcination using MOFs as precursor.The characterization of N₂ physical adsorption and desorption shows that the Co₃O₄@NC material shows a typical IV curve,indicating that it has obvious mesoporous structure,which is also proved by the corresponding pore size distribution.The formation of mesopores can be attributed to the two-step calcination process,in which the organic ligands in Co-MOF@N are converted into N-doped carbon,while Co²⁺is transformed into uniformly distributed Co₃O₄ nanoparticles,which are embedded in the N-doped carbon skeleton in situ.The formation of mesoporous structure is stronger than mass transfer,thus improving the catalytic performance.According to the XPS characterization,the N species of the Co₃O₄@NC materials synthesized with nitrogen-doped MOFs as precursors partially replaced the lattice O in the oxides,which increased the intensity of oxygen vacancies and formed rich oxygen vacancy defects,which was beneficial to the adsorption of substrates.The experimental results also confirmed that the introduction of nitrogen effectively improved the catalytic performance.At the same time,it was also found that the doping of nitrogen sites in Co₃O₄ also effectively improved the catalytic efficiency of the catalyst.The characterization of SEM and TEM showed that the nano-porous materials prepared from MOFs precursors after two-part calcination retained the morphological characteristics of MOFs precursors,and the derived catalysts were rougher than the parent MOFs,with a large number of nanoparticles embedded in the skeleton surface and a large number of pore structures.Compared with the morphology of Co₃O₄@C,Co₃O₄@NC,the morphology is more conducive to the exposure of active species,and its porous structure is conducive to the diffusion of reactants and products.Compared with other Co₃O₄catalysts,Co₃O₄@NC showed the best catalytic activity,with 99%conversion of cinnamaldehyde and 93.4%selectivity of cinnamyl alcohol at 180°C and 1MPa nitrogen.The cycle performance of Co₃O₄@NC catalyst was studied.The results showed that the catalyst could keep high catalytic performance after being recycled for ten times.