Acrylic acid is an unsaturated carboxylic acid with a
vinyl group connected to the carboxyl group. It is a colorless liquid with unpleasant
odor. Acrylic acid readily undergoes addition polymerization reactions with a
wide variety of organic and inorganic compounds. About half of the crude
acrylic acid is processed to high purity (glacial) acrylic acid. The other is
transformed into various acrylate esters.
Earlier Acrylic acid was manufactured by the reaction between
acetylene with water and carbon monoxide, or an alcohol and carbon monoxide.
Nowadays, it is prepared industrially by the catalytic oxidation of vapor phase
propylene. A two-step oxidation process is involved, in which propylene is
converted to acrolein first and then to acrylic acid. Metallic oxides are used
as catalysts, such as Mn2O3, V2O5,
and MoO3 which are ground together and then calcined at high
temperatures. Single or two stage reactors are used to carry out the oxidation
process, wherein the obtained acrylic acid is purified by azeotropic
distillation to form glacial acrylic acid.