So <sub> 4 </ Sub> <sup> 2 - </ Sup> / Zro <sub> 2 </ Sub> Nanometer Solid Superacid Preparation And Catalytic Esterification Of Study

With increasing environmental awareness and demands on the process of economic development, a kind of catalyst, which protects environment and improves economic efficiency, needs to be applied in the practically chemical industry. Solid acid being a hotspot in industrial catalyst field because its advantages such as high catalytic activity, good selectivity, non-polluting, non-corroding, and easy to be separated from reaction mixture. SO₄^2-/M_xO_y solid superacid is one of the most representative and industrial valuable.This paper based on t analyzing the preparation of SO₄^2-/M_xO_y solid superacid and the problems of application, investigated the preparation method of SO₄^2-/ZrO₂ and SO₄^2-/ZrO₂-SiO₂Solid superacid, and then studied the application on catalyzing amyl butyrate and amyl propionate, preliminary studied the reaction mechanism on esterification, has a great significance for further development and application of this solid superacid catalysts. The major aspects of the present study are as follows:1. Preparation and analysis of nano-ZrO₂ and ZrO2-SiO₂Using ZrOCl₂ and urea as the starting materials, water and ethylene glycol as solvent, prepared ZrO₂ according to hydrothermal and microwave method under different conditions. ZrO₂ was characterized by FT-IR,BET,XRD,TEM,HRTEM. The results show nano-ZrO₂ prepared by direct hydrothermal and microwave method were monoclinic phase, the average size was big, particles with different degrees of reunion, however, ZrO₂ prepared by indirect hydrothermal method was tetragonal phase and little monoclinic phase, the average size was small, particles uniformity and high surface area. A certain amount SiO₂ doped by indirect hydrothermal method to prepared ZrO₂-SiO₂, the ZrO₂-SiO₂ was tetragonal phase, the average size was small, particles uniformity and surface area is bigger than ZrO₂.2. Preparation and analysis of SO₄^2-/ZrO₂ and SO₄^2-/ZrO₂-SiO₂ solid superacidSolid superacid was prepared by immersing ZrO₂ and ZrO₂-SiO₂ in a 0.5 M H₂SO₄ solution. After characterized by FT-IR,BET and acid strength, The results show all the catalysts were superacid, Ho<-14.52, SO₄^2-/ZrO₂ has the strongest acid strength after calcined at 500℃; 5%SiO₂ doped to SO₄^2-/ZrO₂ can improve its surface area, but its acid strength was reduced. There are two kinds of structures in SO₄^2-/ZrO₂ solid superacid: the bridge type double coordinating structure and the chelate type double coordinating structure.3. Study esterification used solid superacid catalystUsing SO₄^2-/ZrO₂ as catalyst, investigated its influence on catalyzing synthesize amyl butyrate and amyl propionate. The optimum conditions to synthesize amyl butyrate were the followings: basing on 0.1 mol n-butyric acid, molar ratio of n-amyl alcohol to n-butyric acid was 1.3:1, mass of catalyst was 0.5g (2.3% of reactant), reaction time was 1h, calcined at 500℃, and the yield reached 94.75 %.The optimum conditions to synthesize amyl propionate were the foliowings: basing on 0.1mol n-propionic acid, molar ratio of n-amyl alcohol to n- propionic acid was 1.3:1, mass of catalyst was 0.4g (2% of reactant), reaction time was lh, calcined at 500℃, and the yield reached 96.77 %.Nano-solid superacid SO₄^2-/ZrO₂ in this paper shows good catalytic activity to esterification of amyl butyrate and amyl propionate, and also has high catalytic activity to other butyric acid esters and acid propionic esters. The catalytic activity is different by different methods: hydrothermal method is better than the microwave method; indirect hydrothermal method is superior to direct hydrothermal method. 5%SiO₂ doped to SO₄^2-/ZrO₂ can improve its catalytic activity. SO₄^2-/ZrO₂ have a good reusability after re-activated.