Propionic Acid Production Process
propionic acid and propanoic acid Propionaldehyde Oxidation Method
Propionaldehyde oxidation is an important route for producing propionic acid, accounting for over 90% of propionic acid production in the United States. The process involves two steps: propionaldehyde production and propionaldehyde oxidation. Propionaldehyde is typically produced via ethylene hydroformylation. Current methods for propionaldehyde synthesis include high-pressure carbonylation with cobalt catalysts and low-pressure carbonylation with rhodium catalysts. The high-pressure carbonylation method operates at 140–180°C and 20–25 MPa. In this process, partial hydrogenation of propionaldehyde to propanol reduces the yield of propionaldehyde. After cobalt removal, azeotropic distillation separates the aldehyde from a mixture containing about 10% aldehyde. The low-pressure carbonylation method operates at 1.0–1.5 MPa and 100–120°C, allowing aldehydes to be directly distilled from the reaction mixture with a yield of up to 95%. Propionaldehyde oxidizes at 40–50°C and 0.3 MPa under mild conditions to produce propionic acid with high selectivity. This method produces few by-products, allows easy product separation, and is economically highly attractive, making it the primary method for propionic acid and propanoic acid production today.