Structure Regulation And Surface Modification Of TS-1 Catalyst And Its Catalytic Epoxidation Of Methyl Oleate

Compared with the traditional phthalate plasticizers,epoxidized fatty acid ester with green,non-toxic,odorless polymer plasticizer,which can significantly improve plastic durability and anti-aging properties.In recent years,the global plastic production has exceeded 40,000 tons,and the amount used for food packaging accounts for one-tenth of the total output.Food plastic packaging has become the most active field in the field of packaging materials.With the application of plasticizers The market prospect is also very broad.Among them,epoxidized methyl oleate（EMO）has become a typical epoxidized fatty acid ester plasticizer due to its good lubricity,compatibility and dispersibility.EMO was prepared by catalytic epoxidation of methyl oleate（MO）with an H₂O₂ oxidant.In this study,based on the good catalytic epoxidation performance of titanium silicalite（TS-1）,hydrogen peroxide was used as a clean oxidant to efficiently and greenly catalyze the epoxidation of methyl oleate.Firstly,TS-1 based catalyst with high catalytic activity was synthesized by zeolite structure regulation and surface metal modification.Secondly,the microstructure of the synthesized TS-1-based catalysts,including crystal morphology,structure,valence state,composition,acidity and surface properties,were tested and analyzed in detail by using various characterization techniques.Thirdly,the catalytic performance,stability performance and regeneration performance of the catalyst in the epoxidation reaction of methyl oleate were investigated.The efficient catalytic effect of the catalyst in the epoxidation reaction was studied combined with the structural characterization information of the catalyst,and further reveal the promoting mechanism of its catalytic epoxidation of methyl oleate.Finally,the reaction conditions of methyl oleate epoxidation were optimized by single factor experiment,and the optimal process conditions for preparing epoxidized methyl oleate were obtained.The specific research contents are as follows:（1）On the basis of the previous research on the traditional hydrothermal synthesis of TS-1zeolite,the small-sized TS-1（TS-1-s）was prepared by steam-assisted crystallization method.And its catalytic activity was investigated in the epoxidation of methyl oleate,and then the results showed better catalytic performance.TS-1-s catalysts were characterized by XRD,N₂-adsorption,UV-vis,SEM,TEM,and so on.The results showed that the morphology and framework structure of the TS-1-s zeolite did not change significantly compared with the traditional TS-1 zeolite,which has smaller particle size,larger surface area and good four-coordinated framework titanium species.Moreover,the solid-liquid ratio and crystallization time have no obvious effect on the grain size during the synthesis process.In order to obtain a higher performance TS-1-s catalyst,the synthesis conditions were optimized,and the optimal process was as follows:the crystallization solvent is distilled water,the crystallization time is 18 h,the sol drying temperature is 70°C,and the crystallization temperature is 170°C.The mass ratio of powder to distilled water is 1:10,the conversion rate of methyl oleate is 53.58%,and the selectivity of epoxidized methyl oleate is 85.48%.（2）A series of large-sized TS-1#xACh zeolite catalysts were successfully prepared by introducing an appropriate amount of acetylcholine into the synthesis process of TS-1zeolite,and its catalytic activity was investigated in the epoxidation of methyl oleate.The catalyst was characterized by XRD,FT-IR,N₂-adsorption,XPS,SEM and TEM.The results show that the crystal structure of TS-1#xACh zeolite does not change significantly when the addition amount of acetylcholine is low.And the introduced acetylcholine can promote the rapidly growth of crystals and improve the crystallinity of zeolite and the particle size of TS-1#0.1ACh zeolite is reach to 3μm.However,excessive acetylcholine will prevent the growth of zeolite crystals and TS-1 zeolite cannot be synthesized.In addition,the influence of reaction parameters on the epoxidation of methyl oleate was investigated,and the optimal reaction conditions were obtained:the addition amount of acetylcholine was 0.1（TS-1#0.1ACh catalyst）,the reaction time was 9 h,and the reaction temperature was 80°C,the amount of catalyst is 0.1 g,and the molar ratio of H₂O₂ to methyl oleate is 1:4.（3）A series of xMo/TS-1-bs catalysts with Mo only supported on the outer surface of uncalcined TS-1-s（TS-1-bs）were synthesized by the equivalent-volumetic impregnation method.Its catalytic performance was tested in the epoxidation of methyl oleate.Combined with the characterization information of the catalyst,such as XRD,FT-IR,N₂-adsorption,ICP,UV-vis,NH₃-TPD,pyridine infrared,XPS,SEM,TEM,etc.The results show that the highly dispersed Mo species are introduced on the TS-1-bs support without affecting the coordination environment of Ti⁴⁺and Mo⁶⁺oxidation state is formed on the catalyst surface.Based on the activity test data of xMo/TS-1-bs catalyst in the epoxidation reaction of methyl oleate,its influence on the catalytic performance and stability of the epoxidation reaction was studied.And further reveal the promoting mechanism of Mo species to this reaction.Finally,the optimal reaction conditions were obtained through single-factor experiments:the metal Mo loading was 2%（2Mo/TS-1-bs catalyst）,the reaction solvent was acetonitrile,the reaction temperature was 80°C,the reaction time was 12 h,the amount of catalyst is 0.1 g and the molar ratio of H₂O₂ to methyl oleate is 1:3.