What Are The Production Processes Of Epoxy Soybean Oil
In the early 50, foreign countries began to produce epoxy soybean oil, the main production state-owned United States, Britain, Germany, Japan and the former Soviet Union. From the 70 's, the production process of epoxy soybean oil was changed from organic solvent to solvent free method, from intermittent production to continuous production, from single catalyst to compound type. In the early 60 's, the production of epoxy soybean oil was mainly prepared by solvent method and solvent-free method. Prior to the use of solvent production, due to the existence of solvent recovery difficulties, long production cycle, poor product quality, high cost, environmental pollution and other shortcomings, slow development. Since the 80 's beginning to study the process of solvent-free synthesis, the 90 has achieved a greater development, has gradually replaced the solvent method of production technology. The solvent-free process is based on soybean oil, and different synthetic processes choose different organic carboxylic acids (mainly formic acid or acetic acid), oxidant, catalyst, stabilizer, etc. The crude oil can be used as essential oil and crude oil, and the essential oil is directly oxidized to the ring, and the coarse oils need to be refined beforehand. Wen Jinping  and other alkaline medium of crude oil refining process research, achieved good results. According to the use of organic carboxylic acid, the synthetic process of epoxy soybean oil can be divided into peracetic acid oxidation method, no carboxylic acid catalytic oxidation method (belongs to solvent method), and the catalysts used in the peroxide carboxylic acid oxidation are concentrated, ion exchange resins, aluminum, phase transfer catalyst, heteropoly acid (salt), etc.
Peracetic acid Oxidation method
This process is the organic carboxylic acid and hydrogen peroxide under the action of the catalyst, the reaction to produce epoxy acid ring oxidant, and soybean oil oxidation reaction to produce epoxy soybean oil. In the process of epoxidation, there are two ways to prepare the ring oxidant:
First, the preparation of Peracetic acid method: The organic carboxylic acid and hydrogen peroxide to create peroxide acid, and then add the peroxide acid drop to soybean oil in the epoxidation reaction;
The second is the preparation of Peracetic acid method: First, soybean oil and organic carboxylic acid into the reactor, and then drip and hydrogen peroxide for the epoxidation reaction. After the reaction of the material at a certain temperature is finished, the coarse products are neutralized by dilute alkali, and then the products are obtained by soft water washing, vacuum distillation and pressure filtration. The production process is simple, the reaction temperature is low, the production cycle is short, the by-product is few, the post treatment process is simple, the product quality is good, meets the GB requirement.
Because the effect of formic acid is better than that of acetic acid, most manufacturers use formic acid as active oxygen carrier of epoxidation. Basically replaces the production process with benzene as solvent, improves the production environment of workers, solves the pollution problem of solvent benzene toxicity to products, and overcomes the many production equipment, high cost and "waste" of solvent method. Large amount of processing, such as shortcomings , so that the quality of products significantly improved, such as the stability of the 60%-80% by the solvent method rose to more than 95%. Solvent-free method has made great progress in comparison with solvent method, and various catalyst methods have different advantages and disadvantages.
Concentrated Catalytic method
The catalytic method has a long history mature technology, the most widely used inindustry, its shortcomings are mainly reflected in: ① over oxygen acid easy to decompose, the reaction process a large number of exothermic, temperature change amplitude, resulting in poor epoxidation stability, promote epoxy ring, by-products increased, the product epoxy value reduced; ② ring oxidation reaction in acid system, resulting in a deeper product color, the later treatment process is more complex, the reactor and pipeline is heavily corrosive, not adapt to the process requirements, temperature control difficult, easy to "punch" or even explosion, safety is not high, single kettle production capacity is small. In order to overcome the disadvantage of this process, because of the existence of carboxylic acid in the reaction system, it is necessary to add the stabilizer with urea as the main ingredient to produce the peracetic acid, which can obtain better high quality and low consumption products.
Catalytic method of ion exchange resins
Strong acidic cation exchange resins are also commonly used catalysts. The production of epoxy soybean oil by cationic resin catalytic countercurrent method is a good solution to the shortcomings of the catalysis method, the deficiency of which is that the resin must be strictly pretreated, the operation is complex, the epoxidation time is longer and the cost is higher. Cationic resin can be reused, when the resin activity significantly decreased, with 95% ethanol reflux washing 2h, washing, drying, and then the resin pretreatment, so that the catalytic activity of the resin recovery, recycling and reuse.
Aluminum Catalysis method
The use of aluminum as a catalyst, can be satisfied with the product, epoxy value of 6.2%, the acid number is lower than 0.5mgkoh/g. The process has high reactive activity, easy processing, yield up to 96%, catalyst cost is lower than ion exchange resin. The deficiency is the high content of Fe2 in the catalyst, the catalysis of the decomposition of hydrogen peroxide, causes the material temperature to rise rapidly, it is difficult to control temperature, it is unfavorable to the epoxidation reaction.
Phase Transfer Catalysis method
A composite phase transfer catalyst (also called an Oxygen transfer agent) which is equivalent to 1% of the oil weight is added to the reaction system, the active oxygen in the aqueous phase can be transferred to the unsaturated bond of organic phase, so that the rate of epoxidation is increased by more than one time, and the value of epoxy is significantly higher, both the iodine value and the acid number are obviously decreased.
Heteropoly acid (salt) Catalysis method
By using heteropoly acid (salt) as catalyst, peracetic acid produced by formic acid and hydrogen peroxide was used as epoxy soybean oil by ring oxidizer. The method has the advantages of simple process, short reaction time, high epoxy value, shallow color and low acid number. The experiment shows that the best reaction time of soybean oil is 3.5h, the best reaction temperature is 45 ℃, epoxy oil is 6.6%, iodine is 4.4gl/100g, acid value is less than 0.2mg/g, color is less than No. 250, and the retention rate of epoxy is 99%. Heteropoly acid Catalyst CPW is insoluble in water and can be reused after filtration.
Non-carboxylic acid catalytic oxidation method
Under the condition of no carboxylic acid, acetic acid ethyl ester was used as solvent, phosphor-tungsten compound, methyl tri-octyl hydrogen ammonia as phase transfer catalyst, soybean oil was synthesized by epoxidation by hydrogen peroxide as oxidant. The results showed that the epoxy value, the iodine value and the acid number were 6.28%, 5.80gl/100g, 0.3mgkoh/g and Color (PT-CO) by using the phosphor-tungsten compound (WPC) as the catalyst and ethyl acetate as solvent, and the reaction was 7h under the condition of the system solution ph 2,60℃. As the 250￣300 number, all reached the national standard quality standards, reducing the production of by-products. The process avoids the use of organic carboxylic acid and effectively solves the harm caused by the intervention of peracetic acid. However, the use of solvents with flammable and explosive characteristics, the production process has hidden danger, the production process is not mature.