Preparation And Application Of Sulfonic Silica-based Solid Acid

In the field of chemical production,liquid acid is generally used as catalysts.Howerver,liquid acid has some disadvantages such as corrosion equipment,environmental pollution,and cumbersome industrial treatment.In order to resolve these problems,solid acid with high activity,good stability and easy separation has been made to replace traditional liquid acid.With high porosity and strong stability,SiO₂ is often used as carriers for solid acid,and the prepared solid acid has good catalytic activity.In this work,SiO₂ microspheres and magnetic SiO₂ synthesized by sol-gel method were used as carriers to prepare a series of silica-based solid acid by impregnation and grafting.The influences of preparation conditions on the catalytic performance of solid acid were studied,and the application of solid acid in the synthesis of adipate plasticizer was discussed.The main results are as follows:1.The SiO₂ microspheres were prepared by sol-gel method using tetraethyl orthosilicate as the silicon source.The effects of reaction temperature and concentration of ammonia,water,TEOS,ethanol on the morphology and structure of SiO₂microspheres were discussed.The results showed that:With the increase of ammonia concentration,the particle size of SiO₂ microspheres gradually increased,the sphericity became better,and the dispersion was better;With the increase of TEOS concentration,the SiO₂ microspheres also became larger.The agglomeration of SiO₂ microspheres was aggravated and the average particle size was decreased when the TEOS concentration was too high;With the increase of ethanol concentration,the particle size of SiO₂microspheres decreased;With the increase of reaction temperature,the particle size of SiO₂ microspheres increased significantly,and the sphericity and dispersibility were better.2.The sulfonic silica-based solid acid was prepared by immersion method using SiO₂ microspheres as carriers.The effects of sulfonation conditions on the activity of solid acid were discussed.And the catalytic efficiency of silica-based solid acid was investigated by catalyzing the esterification of adipic acid and n-butanol.It's found that the structure of SiO₂ microspheres had an important influence on the catalytic performance of solid acid.The prepared SiO₂ microspheres with 180 nm diameter were used as carriers.The acidity of solid acid obtained at the sulfonation temperature of220°C and sulfonation time of 4 h was the best.In the process of synthesis of dibutyl adipate,the esterification rate could obtain 99.64%.3.The sulfonic silica-based solid acid was prepared by grafting method using SiO₂microspheres as carriers.The effects of grafting conditions on the activity of silica-based solid acid were discussed.And the catalytic efficiency of silica-based solid acid was investigated by catalyzing the esterification of adipic acid and n-butanol.It was found that when the grafting temperature was 140°C,the grafting time was 12 h,and the oxidation time was 6 h,the acidity and esterification rate of the solid acid were the best.In the process of synthesis of dibutyl adipate,the esterification rate could run up to 94.44%.4.The magnetic SiO₂ was prepared by sol-gel method using Fe₃O₄ microspheres prepared by hydrothermal method as magnetic cores.The sulfonic magnetic solid acid was prepared by the impregnation method and the grafting method using magnetic SiO₂as carriers.The effects of reactant concentration on the magnetic properties of the magnetic SiO₂ and the acidity of the corresponding magnetic solid acid were discussed.And the catalytic efficiency of silica-based solid acid was investigated by catalyzing the esterification of adipic acid and n-butanol.It was found that the change of reactant concentration had an important influence on the silicon shell encapsulation of magnetic SiO₂,which affected the magnetic properties of magnetic particles and the acidity of magnetic solid acid.In the process of synthesis of dibutyl adipate,the esterification rate of the impregnated magnetic solid acid could be as high as 99%,and the esterification rate of the grafted magnetic solid acid was only 86.92%.The catalytic effect of the impregnated solid acid was better than that of the grafted solid acid,and the magnetic solid acid was better than that of the silica-based solid acid.