Preparation And Catalytic Performance Of Carbon-base Solid Acid Catalyst

Two new type and efficient solid acid catalysts were researched in this study. Sulfonated carbon was prepared by charring-sulfonated method with Chinese fir chips as raw material. The optimum preparation condition was determined by the single factor experiments, and the results were as follows:sulfonated time8h, carbonization temperature400℃, carbonization time3h and sulfonated temperature170℃, surface acidity of sulfonated carbon was up to1.616mmol/g. The catalysts were characterized by Fourier transform infrared spectroscopy (FT-IR), Elemental Analysis (EA), thermogravimetric analysis(TG),the results of which showed that, sulfonic acid groups were well loaded on carbon materials, and sulfonated carbon had a strong thermal stability. N-Butyl acetate was catalytic synthesis with sulfonated carbon, the refractive index of product was determined and the structure of product was identified by GC-MS, which proved that the main product was n-butyl acetate and the only byproduct was n-butyl ether. The best condition for catalytic synthesis determined by single factor experiments and response surface methodology, the results were as follows:the reaction temperature130℃, molar ratio of butanol to acetic acid1.51:1,reaction time3.45h,mass of catalyst0.7g, and the esterification yield up to99.20%.Carbon base phosphotungstic acid was in-situ synthesized by using saw dust of Chinese Fir. By this method, wood materials are charred and activated to form prototype active carbon under the effect of phosphate, meanwhile the process of catalyst loading to carrier completed.This method has a lot of advantages such as low-carbon and environmental protection, energy efficiency, low costs and high economic efficiency,etc.The optimum condition for preparation was determined by the single factor experiments, the results of which were as follows:calcination temperature380℃,holding time1.5h,mass concentration of phosphotungstic acid150g/L. The load of phosphotungstic acid was0.3895g/g and its esterification yield was up to88.72%under the condition of reaction temperature130℃, molar ratio of butanol to acetic acid1.2:1,reaction time2.5h,mass of catalyst0.8g.The catalysts were characterized by FT-IR,XRD and TG, the results showed that phosphotungstic acid was well supported on carbon materials, keggin structural characteristic absorption peak of carbon-based phosphotungstic acid had not obviously changed, and the structure of phosphotungstic acid began decomposition at387℃. N-Butyl acetate was catalytic synthesis by carbon-based phosphotungstic acid. The refractive index of product was determined and the structure of product was identified by GC-MS, which proved that the main product was n-butyl acetate and the only byproduct was n-butyl ether. The best condition for catalytic synthesis was determined by single factor experiments and response surface methodology, and the results were as follows:the reaction temperature130℃, molar ratio of butanol to acetic acid1.72:1, reaction time3.19h,mass of catalyst0.79g. Under this condition, the esterification yield amounted to99.12%.Synthesis reaction kinetics of n-butyl acetate were further studied, which confirmed that the reaction could be described by secondary irreversible reaction kinetics model through the analysis of experimental data. The reaction rate constant, the activation energy, the reaction kinetics equation were calculated by secondary irreversible reaction kinetics model. The results show that, with using sulfonated carbon as catalyst, its reaction activation energy is70.1kj/mol and its reaction kinetic equationwas was r=8.37×106xexp(-7.01×105/RT)×CACB;with carbon based phosphor tungstic acid as catalyst, its reaction activation energy was73.0kj/mol and its reaction kinetic equation was r=1.47×107×exp(-7.30×105/RT)×CACB.Based on the study, it can be concluded that the capacity of catalyzed esterification of sulfonated carbon was better than that of carbon-based phosphotungstic acid.