Patent ID: 6229053
Filing Date: 2001-05-08
Classification: C07C,C07D,C08G

Abstract:
(Amended) A process for purifying formaldehyde in which formaldehyde is reacted with alcohol to form the hemiformal and the hemiformal thus formed is freed from unwanted feedstocks and synthesis by-products and/or impurities and the hemiformal thus purified is pyrolyzed to form formaldehyde, which comprises scrubbing the formaldehyde in an absorption unit with an alcohol having a boiling point markedly above the boiling point of water and markedly below the pyrolysis temperature of the hemiformal and [in this case]reacting [this virtually] the alcohol and formaldehyde completely to give the hemiformal and, simultaneously, separating it off, in a first separation step, from gaseous impurities not absorbed in the scrubbing solution, converting residual impurities into a gaseous state in a desorption unit, the desorption temperatures and desorption pressures employed being above the evaporation conditions of water and below the pyrolysis conditions of the hemiformal, and separating [them] off the residual impurities from the liquid hemiformal, cleaving the hemiformal thus purified to the alcohol and formaldehyde in a pyrolysis unit and recovering the alcohol and the formaldehyde, and wherein a temperature in the range from 15 to 40.degree.C is maintained in the absorption column, and wherein desorption is carried out at temperatures in the range of 20 to 1.degree.C and pyrolysis is carried out at temperatures in the range of 100 to 200.degree.C.