1,2-propanediol is an important raw material of epoxy resin, unsaturated polyester, and polyurethane, accounting for about 45% of the total consumption. 1,2-propanediol viscosity and moisture absorption, and non-toxic, so in food, medicine and cosmetics industry widely used as a hygroscopic agent, antifreeze, lubricant, solvent and food emulsifier; In the pharmaceutical industry and cosmetics industry, it is often used as a solvent, softener, and excipient in the manufacture of various ointments and ointments. 1, 2-propylene glycol is also used as a tobacco humidifier and mildew proofing agent. The aqueous solution is an effective antifreeze.
Propylene glycol is produced by direct water method, indirect water method, and propylene direct catalytic oxidation method. According to reports, glycerol can be converted into 1, 2-propanediol by using Raney-nickel catalyst at 190℃ and 10Bar of hydrogen pressure, and a small number of by-products are only ethanol and carbon dioxide. Suppes and his colleagues suggest that copper-chromium catalytic hydrolysis of glycerol is the most effective, with a 73 percent conversion rate at 200℃ and 14Bar hydrogen pressure.
Global demand for propylene glycol has reached 2 million tons per year, and the industry is expected to grow at a rate of 3% to 7%. Major chemical suppliers such as Dow, Cargill, and ADM have announced investment plans to produce high-quality propanediol from glycerol.
1, 3-propanediol (PDO) is a colorless and viscous liquid, which is often used as a solvent in drugs, coatings, lubricants, inks, printing and dyeing, antifreeze, as well as in the preparation of new polyurethane resins, emulsifiers, and pharmaceuticals. Its main use is as a polymer monomer synthesis of propanediol terephthalate (PTT).PTT is a new type of polyester material which can form fibers in industrial-scale after polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). The development of PTT fiber indicates that the demand for 1, 3- propanediol will increase. It is estimated that the potential market capacity of 1, 3-propanediol could reach 2.27 million tons by 2020.
So far, only Shell (Shell), Degussa (Degussa) and DuPont (DuPont) respectively by ethylene oxide catalytic hydrogenation acylation method (Shell) and acrolein hydration method (Degussa – DuPont technology) chemical synthesis routes for 1, 3 – propanediol large-scale production, but the production cost is high, the product price is expensive, by-products and environmental pollution.
The production of 1, 3 – propanediol by glycerol can be divided into chemical synthesis and biological fermentation. The preparation of 1, 3-propanediol by glycerol chemical synthesis can be divided into three methods: dehydroxylation, hydro dehydration and dehydrating into acrolein. The biological fermentation method mainly studies the production of 1, 3-propanediol by fermentation with pure glycerol as the substrate. Microorganisms synthesizing 1, 3-propanediol with glycerol as the substrate in nature are mainly anaerobes or facultative anaerobes, among which klebsiella pneumonia-ae, Citrobacterfreundii, and Clostridiumbutyricum are three bacteria with the high conversion rate. According to literature, under strict anaerobic conditions, the fermentation level can reach 70 ~ 80g/L. Biological fermentation is mainly carried out in two steps. First, glycerol is catalyzed by active dehydrase to generate 3-hydroxy propionic aldehyde (3-hPa) and water, while 3-hpa is further generated by REDOX enzyme.
Epichlorohydrin (ECH) is a volatile and unstable colorless oily liquid. The various types of epoxy resin produced with it as raw material are resistant to chemical corrosion, high adhesion, good stability and small shrinkage, which are widely used in coating, adhesive, reinforcing material, casting material and other industries. In addition, epichlorohydrin can also be used in glass fiber reinforced plastics, coatings, surfactants, medicine, pesticides, chlorohydrin rubber and other products, but also can be used as cellulose ester, resin solvents. In 2005, the production capacity of epichlorohydrin reached 150,000 tons/year, the actual output was 120,000 to 130,000 tons, and the demand was 220,000 tons, about 50% of which were imported. In recent years, the demand of our country still grows at a speed of 9% above.
Industrial production methods of epichlorohydrin include propylene high-temperature chloride method based on petroleum raw materials and propylene acetate method. The production of epichlorohydrin by glycerol method can be divided into continuous method and batch method. The continuous method means to prepare epichlorohydrin by cyclization reaction without any treatment after chlorination of glycerol. The intermittent method means to neutralize excessive hydrogen chloride with alkali solution after chlorination of glycerol, and then distill chlorohydrin by vacuum distillation, and then cyclization reaction. The continuous process is simple and easy to operate. However, excessive lye is needed in cyclization. The intermittent method is complex in operation and can make up for the deficiency of the continuous method.