Patent ID: 8884079

Claim:
A process for producing ethanol comprising: feeding acetic acid to a reactor vessel comprising the first reaction zone and second reaction zone; hydrogenating the acetic acid in the first reaction zone operated at a first temperature to form a first reaction mixture comprising ethanol and one or more impurities selected from the group consisting of ethyl acetate, acetaldehyde, acetals, and mixtures thereof; feeding the first reaction mixture directly to the second reaction zone, without separation; hydrogenating at least a portion of the one or more impurities in the second reaction zone operated at a second temperature from 50° C. to 225° C., wherein the second temperature is less than the first temperature, to form a second reaction mixture; and recovering ethanol from the second reaction mixture, wherein the second reaction mixture comprises at least 50% less acetals than the first reaction mixture, at least 50% less acetaldehyde than the first reaction mixture, or at least 5% less ethyl acetate than the first reaction mixture.