Direct synthesis of ethyl acetate from ethanol carried out under pressure

Direct synthesis of ethyl acetate from ethanol over a Cu-Zn-Zr-Al-O catalyst was investigated under pressured conditions between 473 and 533 K. Both the selectivity to ethyl acetate and the space-time yield of ethyl acetate increase with increasing reaction pressure, whereas ethanol conversion decreases. The highest space-time yield of ethyl acetate is attained at a reaction pressure of about 0.8 MPa with maximum selectivity of 93 wt%. During the process, ethanol is first dehydrogenated to acetaldehyde and is then coupled with another ethanol molecule to form hemiacetal, which is further dehydrogenated to ethyl acetate. The concentration of by-products such as 1-butanol and butanone, which form after the aldol addition of acetaldehyde, decreases with increasing reaction pressure. Since the equilibrium of the dehydrogenation of ethanol to acetaldehyde shifts to an ethanol-rich composition at high pressure, the decrease in the partial pressure of acetaldehyde explains the suppression of the by-products formed through acetaldol. (C) 2002 Elsevier Science (USA).