ABSTRACT
Acetaldehyde was made by the silver gauze catalytic oxidation or dehydrogenation of ethyl alcohol using copper activated with chromium oxide. Acetaldehyde can be produced from lower hydrocarbons or synthesis gas but neither route has been developed industrially because of low yields. Acetaldehyde is also obtained as a by-product in a number of processes. Crude acetaldehyde is double distilled to give a pure product, first extractively with water to remove lower boiling point products, and second by fractionation to remove higher boiling fractions. The gaseous reaction mixture containing acetaldehyde passes to a flash tower where an acetaldehyde-water mixture passes overhead. The acetaldehyde-water vapour is concentrated and double distilled to remove light and heavy by-products as in the one stage process. Acetaldehyde forms two polymers–paraldehyde which is a cyclic trimer, and metaldehyde, a cyclic tetramer. Containers should be constructed of stainless steel or aluminium and pressure tested because of vapour build-up caused by the low boiling point of acetaldehyde.
