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Our group has designed a process to manufacture 101,520,000 lb/yr of acetaldehyde by hydrogenation of acetic acid over a 20% wt. palladium on iron oxide catalyst. The reaction conditions used are the optimum according to a patent filed by Eastman Chemical (Tustin, et.al., U.S. Patent No. 6,121,498): temperature is range is from 557-599 °F at a pressure of 254 psi. The conversion of acetic acid in the reactor is 46 %, with selectivity of 86% to acetaldehyde. Major by-products are ethanol, acetone, carbon dioxide, and the light hydrocarbons methane, ethane, and ethylene. Acetaldehyde is purified in a series of steps: it is first absorbed with an acetic-acid rich solvent, then distilled to separate acetaldehyde from heavier components. A refrigerated condenser is then used to recover additional acetaldehyde from the vapor distillate of the main separation. Acetic acid is purified and recycled to the reactor to limit the amount of feedstock required. Ethyl acetate is produced as a by-product in the acetaldehyde distillation column and is purified and sold.
The economics of the process is strongly dependent on the price of acetic acid, and we examined scenarios under which acetic acid was available at either $0.16/lb or $0.12/lb. The total capital investment in either situation is approximately $47,000,000. If acetic acid is available at $0. 16/1b, we estimate an IRR of 11.3 %, but if acetic acid can be purchased for $0.12/Ib the IRR is 18.5% after 20 years. It is our recommendation to pursue more research into projecting both the cost of acetic acid and the market for acetaldehyde. If acetic acid will be available at the lower price, the company should pursue production of acetaldehyde.
Date Posted: 26 October 2012