Preparation And Catalytic Performance Study Of Mesoporous Zirconia Supported Trifluoromethylsulfonic Acid

Trifluoromethylsulfonic acid is one of the strongest organic acids.It and its conjugated base have extremely high thermal stability and antioxidant reduction properties,which is widely used in many organic reactions as a highly efficient homogeneous catalyst.However,it is easy to cause equipment corrosion,environmental pollution,and complex aftertreatment processes.Therefore,loading trifluoromethylsulfonic acid on a solid carrier instead of a homogeneous catalyst attracts widespread attention.However,such solid acids also have problems like small loading capacity,low specific surface area,and need to be improved in stability.Therefore,in this thesis,pure mesoporous zirconia,zirconia coated mesoporous silica composite material are used as carriers to immobilize trifluoromethanesulfonic acid.The performance of the catalyst was evaluated by the Beckmann rearrangement reaction,the esterification reaction and alkylation reaction.The effects of carrier heat treatment temperature,zirconia coating amount,trifluoromethanesulfonic acid loading amount,and other preparation conditions were investigated.The main conclusions are as follows:Firstly,pure mesoporous zirconia was prepared by different models.Load TFMSA by solvent impregnation.The better carrier is mesoporous zirconia prepared by sol-gel method.XRD,N2 adsorption-desorption,FT-IR,NH3-TPD,elemental analysis and other characterization methods were used to analyze the properties.Then study the influence of different loading amounts of trifluoromethylsulfonic acid.Under better reaction conditions:cyclohexanone oxime 0.1 g,reaction time 4 h,reaction temperature 140℃,catalyst dosage 0.3 g,solvent benzonitrile dosage 30 mL,the conversion of CHO was 95%,the selectivity of CPL was 65%.No obvious deactivation of the catalyst after repeated use for three times.Secondly,in order to improve the specific surface area and TFMSA loading amount of the catalyst,using SBA-15 as the primary carrier,zirconia was coated on the inner surface of the pore channel to obtain a mesoporous carrier with good dispersion of zirconia ZrT-w@SBA-15.Then impregnate with TFMSA.The effects of zirconia loading,heat treatment temperature,and TFMSA loading were still investigated by Beckmann rearrangement with multiple characterization methods to analyze the results.The experimental results showed that the increase in heat treatment temperature leads to a decrease in textural parameters of the catalysts,and the optimal temperature is 100℃.If the amount of zirconia coating is too small,the acidity will be lower,while if the amount of zirconia coating is too large,the textural parameters will decrease.The preferred coating amount is 40 wt%.Increasing the TFMSA load will optimize textural parameters,with a better TFMSA load of 25 wt%.Under optimized Beckmann rearrangement reaction conditions,the conversion of CHO achieved 100%,while the selectivity of CPL achieved 66%.The activity of the catalyst did not significantly decrease after three times of recycle.Finally,TFMSA25ZrT-w@SBA-15 was applied to the esterification of cyclohexanol and acetic acid,the alkylation reaction of phenol and tert butanol to investigate the expanding performance of the catalysts.Under the optimal reaction conditions,the yield of cyclohexyl acetate can reach 96%in esterification,while the conversion of phenol was 57%and the selectivity of 2-tert butylphenol can reach 55%in alkylation reaction.To sum up,the immobilized trifluoromethylsulfonic acid prepared in this paper has strong acidity,large specific surface area,stable properties,and good catalytic performance in acid catalytic reactions,providing a new idea for the development of immobilized trifluoromethylsulfonic acid.