Preparation Of Solid Catalyst And Study On Cataliytic Synthesis Of Ionones From Citral

Ionone is an important spice, which is used in cosmetics, food and beverages. In addition, it is an important intermediate of chemical and medicine, which is further used for synthesis of other spices and products, such as vitamin A, vitamin E, β-carotene.Liquid catalysts are conventionally used for producing the ionone. But liquid catalyst usually leads to a large number of problems such as, corrosion and needs disposal of wastes, etc. Therefore, it is necessary to develop some better catalysts for the synthesis of ionone. Because the solid acid catalyst has the advantages of the being recoverable and reusable, little corrosion, being processed much conviently, and hence, environmental friendly. In this paper, citral was used as raw material, the pseudoionone preparation from the condensation of citral with acetone catalyzed by solid base KNO3/Al2O3 was carried out, then the ionone was prepared from the cyclization of pseudoionone catalyzed by solid acid SO42-/TiO2. The results are as follows:1. The preparation of solid base catalyst (KNO3/Al2O3)The solid base catalyst KNO3/Al2O3 was prepared by impregnation method. The catalysts were characterized by Hammett indicator method, FTIR and XRD. The pseudoionone was prepared from the condensation of citral with acetone catalyzed by solid base KNO3/Al2O3, the influence effects such as load capacity, impregnated time and the calcination temperature on the catalytic properties were investigated. The optimum conditions of preparation were obtained:the solid base catalyst loaded with 25% KNO3, impregnation time 6 h and calcination temperature 600 ℃.Under these conditions, the yield of pseudoionone was 87.5%.2. The synthesis of pseudoiononeThe process conditions of pseudoionone preparation from the condensation of citral with acetone catalyzed by solid base KNO3/Al2O3 was researched and the influence effects such as reaction time, reaction temperature, the amount of acetone, the amount of catalyst were investigated. Orthogonal experiments were used to optimize the conditions of synthesis:the amount of citral 5 g, reaction temperature 50 ℃, the amount of catalyst 6 g, the amount of acetone 10 g, reaction time 5 h.,the yield of pseudoionone is 90.37%.3. The preparation of solid acid catalyst (SO42-/TiO2)The precursor of TiO2 was prepared by sol-gel method, and the solid superacid SO42-/TiO2 was prepared using H2SO4 impregnation through drying and calcination. The catalysts were characterized by Hammett indicator method, FTIR and XRD. The ionone preparation was carried out from the cyclization of pseudoionone catalyzed by solid acid SO42-/TiO2, the influence effects such as H2SO4 impregnation concentration, H2SO4 impregnation time and the calcination temperature on the catalytic properties were investigated. The optimum conditions of preparation were obtained:H2SO4 impregnation concentration 1.25 mol·L-1, H2SO4 impregnation time 4 h, the calcination temperature 500 ℃. Under these conditions, the yield of ionone was 54.32%.4. The synthesis of ionone Toluene was used as solvent, solid superacid SO42-/TiO2 as catalyst,the process conditions of ionone preparation from the cyclization of pseudoionone was optimized, the influence effects such as reaction time, the amount of solvent and the amount of catalyst were investigated. The optimum synthesis conditions were:the amount of pseudoionone 3 mL reaction time 70 min, the amount of solvent 15 mL, the amount of catalyst 1.4 g. Under these conditions, the yield of ionone was 68.45%.