At present, the production methods of epoxidized soybean oil mainly include solvent method and solvent-free method. The specific production methods mainly include peroxyformic acid oxidation method, ion exchange resin catalysis method, aluminum sulfate catalysis method, peroxycarboxylic acid oxidation method and Phase transfer catalytic oxidation, etc.
Peroxyformic acid oxidation
The process uses benzene as a solvent, sulfuric acid as a catalyst, formic acid and hydrogen peroxide in the presence of sulfuric acid to generate peroxyformic acid, which is then epoxidized with soybean oil to generate epoxidized soybean oil. Put soybean oil, formic acid, sulfuric acid and benzene into the reaction kettle according to a certain dosage ratio, stir and mix evenly. Slowly add 40% (mass fraction) hydrogen peroxide solution with stirring. During the dropwise addition, the reaction temperature was adjusted by passing cooling water and adjusting the dropping speed, so that it was controlled at around room temperature. After the hydrogen peroxide is added, stir for a period of time. When the temperature of the material does not rise even when the cooling water is blocked, the stirring can be stopped. Then stand for stratification, the upper layer is the oil layer, containing the product and benzene, and the lower layer is the waste acid water.
After the waste acid water is separated, the oil layer is first neutralized and washed with 2% to 5% dilute soda ash, and then washed with soft water until neutral. After water separation, the oil layer is distilled, the mixture of distilled benzene and water is separated by condensation, and 80% of the benzene can be recovered and returned to the application. The kettle liquid is distilled under reduced pressure, and then filtered to obtain the finished product. The process has fast reaction speed and low temperature, but the process flow is long and complicated, the product quality is unstable, the epoxy value is about 5%, the production cost is high, the equipment is many, the “three wastes” are large, and the solvent benzene is toxic. methods are gradually being replaced by solvent-free methods.
peroxycarboxylic acid oxidation
Formic acid or acetic acid and hydrogen peroxide react under the action of catalyst sulfuric acid to form an epoxidant, and the epoxidant is added dropwise to soybean oil within a certain temperature range. After the reaction is completed, the product is obtained by alkali washing, water washing and vacuum distillation. The production process of the method is short, the reaction temperature is low, the reaction time is short, the by-products are few, and the product quality is high, and the production process using benzene as a solvent has been basically replaced at present. Because the molecule of formic acid is smaller than that of acetic acid, and the oxidation rate of peroxyformic acid is higher than that of peroxyacetic acid, the quality of the product obtained by using formic acid to produce is slightly better, and the reaction process is shorter.
At present, most production enterprises use formic acid as the active oxygen carrier for epoxidation, and attention should be paid to the toxicity of carbon monoxide generated by the decomposition of formic acid and part of formic acid. Dalian Institute of Light Chemical Industry carried out research on the synthesis of epoxidized soybean oil from peroxyformic acid under solvent-free conditions, and discussed the influence of the main reaction conditions on the epoxidation reaction. The technical route, process flow, process conditions and product quality of soybean oil were compared, and it was found that the solvent-free method compared with the solvent method has a simple production process, no solvent recovery problems, low consumption of raw materials, short production cycle, and product quality reaches the current domestic similar products. The advanced level has solved the problem of benzene solvent pollution in the production process and improved the production environment of workers. At the same time, with the cooperation of Zhangzhou Chemical Plant, Fujian Institute of Chemical Industry adopted a solvent-free one-step in-situ epoxidation process, that is, hydrogen peroxide and glacial acetic acid reacted in the presence of a catalyst to generate peracetic acid, and peracetic acid and refined Soybean oil is reacted to obtain epoxidized soybean oil. It overcomes the disadvantages of using benzene as a solvent and sulfuric acid as a catalyst process, such as many synthesis steps, high product cost, large “three wastes” processing capacity and low yield.
The thermal stability of epoxy soybean oil plasticizer produced by solvent-free process is significantly improved, and the thermal stability of epoxy group (retention rate of epoxy value) is increased from 60%-80% of solvent process to more than 95%. At the same time, the problems of “three wastes” pollution and equipment pipeline corrosion have
been overcome. In addition, the researchers found that refining crude soybean oil with dilute ammonia water-hydrogen peroxide can reduce the loss of oil and make the color of the refined oil better than that of edible first-class oil; the epoxidation reaction does not require a catalyst, and uses urea as the main component to stabilize the oil. The epoxidation reaction time can be shortened, and the color of the crude product is light; the organic acid in the crude epoxidized product is washed three times to remove the organic acid, etc., instead of the alkali washing-water washing process, which can greatly reduce the emulsification and loss of the crude product, and is beneficial to oil and water Two-phase stratification. At present, this technology has obtained industrial application.
Ion exchange resin catalytic method
Although the solvent-free method overcomes many shortcomings of the solvent method, it also has disadvantages such as poor reaction stability, low epoxy value of the finished product, dark product color, equipment corrosion and serious environmental pollution. Peroxyformic acid or acetic acid is used as oxidant, and the process of synthesizing epoxidized soybean oil by reaction under solvent-free conditions can overcome these shortcomings. Add soybean oil, ion exchange resin and acetic acid to the reaction kettle, heat and raise the temperature to 70～80℃, under stirring, add hydrogen peroxide into the reaction kettle evenly within 40min, pass cold water to cool when the temperature rises, and keep the reaction temperature for 12～80 minutes. 18h. After the reaction is completed, filter, filter out the ion exchange resin, stand for stratification, neutralize the oil phase to slightly alkaline (pH value reaches 8.5 to 9.0) with a saturated aqueous sodium chloride solution containing 2% to 3% sodium hydroxide, and then Wash with pure water until neutral and free of chloride ions. After standing for 30 min, the lower aqueous layer was separated. The crude product after washing is put into a still, and the epoxidized soybean oil product can be obtained by decompression distillation and dehydration.
The disadvantage is that the cyclization time is relatively long. The study found that the cationic resin used can be reused. When the catalyst activity is significantly reduced, the resin is recovered by reflux washing with 95% ethanol for 2 hours, washing with water, drying, and then pretreatment of the resin. The catalytic activity of the resin is restored. .
Wang Longjiang of Shandong University of Technology and others used soybean oil as raw material, adopted a solvent-free production process, macroporous strong acid cation resin as catalyst, and peroxyformic acid as epoxidant to prepare PVC environment-friendly plasticizer epoxidized soybean oil. The obtained product has the characteristics of high epoxy value, low acid value and iodine value, and less waste water discharge in the production process, which is beneficial to environmental protection. The step-by-step synthesis process of first peroxidation and then epoxidation can greatly shorten the epoxidation time, reduce the degree of side reactions, and improve the production efficiency and product quality.
Aluminum sulfate catalytic method
Formic acid and hydrogen peroxide react under the action of catalyst aluminum sulfate to generate epoxidant, and then add epoxidant to soybean oil within a certain temperature range, and after the reaction is completed, epoxidized soybean oil is obtained by alkali washing, water washing and vacuum distillation. The process has high reaction activity, easy post-treatment, and the yield can be as high as 96%. Compared with the cation exchange resin catalysis method, the catalyst cost is low. The disadvantage is that the catalyst used needs to strictly control the content of Fe2+. In the presence of hydrogen peroxide, it is easy to play a catalytic role, accelerate the decomposition of hydrogen peroxide, and is not conducive to the epoxidation reaction. At the same time, Fe2+ will also cause the material temperature to rise sharply, making it difficult to control the epoxidation reaction temperature.
Phase Transfer Catalytic Oxidation
Deng Fang et al. from the School of Chemistry and Materials Science, Shaanxi Normal University, under the condition of no carboxylic acid, using ethyl acetate as solvent and methyl trioctyl ammonium hydrogen sulfate as phase transfer catalyst, with 30% (mass fraction) peroxide Hydrogen solution directly epoxidized soybean oil to synthesize epoxidized soybean oil. The experimental results show that under the condition of no carboxylic acid, the epoxidation of soybean oil can be successfully achieved by using hydrogen peroxide as the oxidant. It is 6.27%, and the iodine value is 5.80g/10
0g. This method avoids the formation of peracid in the reaction, reduces the amount of by-products generated, and improves product quality.
Sstudied the epoxidation of soybean oil in the presence of hydrogen peroxide using tungsten peroxide complexes as phase transfer catalysts. The results showed that the reaction temperature was 60 °C. ℃, the petroleum enigma is the solvent, and 1,2-phosphotungstic acid pyridinium salt (CWP) is used as the catalyst, the epoxy value of the reaction product reaches 6.4%, and the iodine value is 4.4g/100g. The reaction does not use dangerous peroxyacid and strong corrosive sulfuric acid, and the obtained product has light color, high epoxy value and good quality, but the recovery and reuse of peroxygen complex needs to be further studied.
PO4(WO3)4) as catalyst, 1,2-dichloroethane as solvent, H2O2 (30%, mass fraction) as oxygen source, epoxidized soybean oil was directly synthesized in acid-free environment. The research results show that when nH2O2 : n (soybean oil double bond)=1.25:1, m (dichloroethane): m (soybean oil)=3.5:1, the reaction temperature is 70℃, the reaction time is 4h, the epoxy value of the product epoxidized soybean oil is greater than 6.2%, the iodine value is less than 2.60Gi/100g, which meets the requirements of first-class products. The catalytic activity remains unchanged after the catalyst is recycled for the second time. The epoxidation reaction of soybean oil under neutral conditions was also studied by using phosphotungstic heteropoly acid salt as the reaction-controlled phase transfer catalyst, 1,2-dichloroethane as the solvent, and 30% H2O2 as the oxygen source. The effect of each reaction condition on the epoxidation reaction.
The results show that when the catalyst mass fraction is 3%, n(H2O2):n(double bond)=1.2:1, m(solvent)/m(soybean oil)=3.2, the reaction temperature is 70℃, and the reaction time is 4h, the formation of The iodine value in the epoxidized soybean oil is less than 0.04g(I)/g, the epoxy value is greater than 6%, and the catalytic activity does not decrease after the catalyst is recycled for 5 times. Anhui University of Science and Technology Li Deji et al. used phase transfer catalyst to improve the synthesis of epoxidized soybean oil catalyzed by aluminum sulfate. The experimental results show that the epoxy value of the improved product has been greatly improved, and the reaction time has been greatly shortened. The optimal feeding ratio determined by the experiment is: m (soybean oil): m (27% hydrogen peroxide): m (formic acid): m (aluminum sulfate): m (phase transfer catalyst) = 1: (0.8～1.0): (0.13 ~0.15): (0.075 ~ 0.085): (0.0001 ~ 0.001). The epoxy value of epoxidized soybean oil product is about 8.0%, the acid value is 0.40～0.50mgKOH/g, and the color is lighter.