Preparation Of Solid Acid-base Catalyst And Study On Its Catalytic Synthesis Of Fuel Precursor From Benzaldehyde

The use of renewable biomass as raw material to produce hydrocarbon fuels and reduce the dependence on fossil energy has received extensive attention from researchers.The aldol condensation reaction is a key step in the generation of biomass-based aviation fuel.Traditional homogeneous acid-base catalysts are widely used in aldol condensation.Although these homogeneous catalysts exhibit high catalytic activity,they are prone to corrosion of equipment,difficult to recover,and easy to affect the environment,which is not conducive to industrial application.Heterogeneous solid acid-base catalysts have the advantages of high efficiency and recyclability,which can effectively avoid these problems.Three kinds of heterogeneous solid acid-base catalysts with excellent performance were constructed,and then useing the aldol condensation of benzaldehyde and acetone as a model reaction,and their catalytic performance in the aldol condensation of benzaldehyde and acetone was systematically studied.The main research contents are as follows:（1）The Nb₂O₅-ZrO₂ catalysts were prepared by doping different Nb contents into ZrO₂ catalysts using hydrothermal method.The relationship between the prepared catalysts and the catalytic performance was constructed by characterization techniques such as XRD,XPS,SEM,TEM,NH₃-TPD,and N₂ adsorption-desorption.The appropriate amount of Nb doping will not only significantly increase the specific surface area of the Nb₂O₅-ZrO₂ catalyst,but also significantly increase the acid-base sites of the catalyst.While the conditions of 1:9 molar ratio of benzaldehyde to acetone,the reaction temperature 130℃ and the reaction time 4h,the yield of monomer could reach 85.32%and the yield of dimer was 9.76%.（2）The prepared catalyst TiO₂is doped with La species with different contents,and La₂O₃-Ti O₂ catalyst can be obtained by calcination.Combined with XRD,XPS,SEM,TEM,NH₃-TPD,N₂ adsorption and desorption,etc.,the relationship between the structure morphology and catalytic performance of the catalyst was explored.The study found that the doping of an appropriate amount of La species is beneficial to the increase of the specific surface area,thereby promoting the increase of acid-base sites;and also conducive to the generation of oxygen vacancies,and promotes the adsorption of carbonyl groups and promotes the aldol condensation.When the reaction temperature 110℃ and the reaction time 4h,the yield of the monomer can reach 88.41%,and the yield of the dimer can reach 8.87%.A possible kinetic model was proposed based on the reaction mechanism and the required activation energy was calculated to be 13.54 kcal/mol.（3）The Nb₂O₅/Al₂O₃ catalysts with different Nb loadings were prepared by precipitation method.The morphology and structure of the catalyst were analyzed by means of XRD,XPS,SEM,TEM,NH₃-TPD,N₂ adsorption and desorption,and the catalytic performance of the catalyst in the aldol condensation reaction was investigated.The Nb₂O₅ with Lewis acid has a unique activation effect on carbonyl,and at the same time,Nb⁴⁺and Nb⁵⁺ions with oxophilic sites are beneficial to the adsorption of carbonyl,thereby promoting the aldol condensation reaction.Under the conditions of a reaction temperature 130℃,a reaction time 4h,and a molar ratio of benzaldehyde to acetone of 1:9,the yield of the monomer can reach 81.84%,and the yield of the dimer can reach 13.42%.