In the industry propionic acid is received ethylene hydroxycarboxylation. Also it is formed as a result of propionate fermentation. Propionic acid is a by-product of many processes that allows to use them for its allocation.
Propionic acid can be received in two ways: propionate fermentation and hydrocarboxylation of ethylene. The second way at the moment is considered the most widespread in the industry. There are also other less known ways of receiving propionic acid, for example, allocation from oil, catalytic oxidation of propionic aldehyde, allocation as a by-product at vapor-phase oxidation of hydrocarbons with amount of carbon atoms 4-10.
Hydroksikarboksilirovaniye of ethylene
For the first time receiving propionic acid was realized this way by BASF. It was characterized by a high exit of the final product (about 95%), but had a number of shortcomings:
1) Process demanded severe conditions: pressure reached 25-30 MPas, temperature – about 300 wasps.2) as Catalysts served cancerogenic and silnokorrozionny substances – a carbonyl of nickel and iodohydrogen, respectively. Later on the basis of VNIINeftehimiya this way of receiving was finished. As a result of replacement of aggressive catalysts by cobalt - a pyridinic complex [Co(Py)6] [Co(CO)4]2 became softer synthesis course conditions which were carried out in one stage now. Temperature was reduced to 150-170 wasps, and pressure – to 5-15 MPas. Shortcomings of this way became: 1) Small decrease in an exit of the final product to 92%. 2) Formation of a by-product of diethylketone (5-7%). However it has independent application. The equation of synthesis of propionic acid in one stage: CH2=CH2 + WITH + H2O SN3SN2SOON
Propionate fermentation is carried out by propionate anaerobic bacteria of the sort Propionibacterium. Acid is formed as the final product of their activity as a result of absorption of carbohydrates. In the presence of oxygen the sbrazhivaniye does not occur as oxidizing process is carried out. At first bacteria process carbohydrates into a number of products among which there is propionic acid. Here it yet not the final product. The formed carbon dioxide is fixed and, connecting to pyroracemic acid, turns into shchavelevouksusny which turns then into amber. Amber acid is decarboxylized with formation of propionic acid – the final product of fermentation. For short the scheme of fermentation can be written so: 3C6H12O6 → 4CH3CH2COOH + 2CH3COOH + 2CO2 ↑ + 2H2O + E.