Preparation of Acrylic Acid

Abstract

A modified Reppe process for manufacturing acrylic acid (AA) under normal pressure and another method by hydrolysis of acrylonitrile (AN) are reported. I. Modified Reppe process using normal pressure under continous operation.Thier reaction is affected by various factors such as molar ratio, acetylene feeding velocity, reaction temperature, circulation velocity, viz, agitating velocity and so on.The best reaction conditions were as follows : Acetylene feeding velocity : 200 l/hr.Reaction temperature : 40°CCirculation velocity for the reaction mixture : 1, 800 l/hr.Reaction composition : AA/Solvent=1/1 (wt.) Solvents : MEK, MIBKThe yield was about 80%.II. AN hydrolysisThe follwing reactions for conversion of AN into AA were studied.CH2=CHCN+H2SO4+H2O→CH2=CHCONH2·H2SO4CH2=CHCONH2·H2SO4 +H2O→CH2=CHCOOH + NH4HSO41. The first step reaction (formation of acrylamide).AN/sulfuric acid/water=1/1.5/4 (molar ratio) was employed at 12°C for 5 hrs with strring.The yield was about 95%.2. The second step reaction (formation of AA) The hydrolysis of acrylamide was effected by using 6 mol suplementary water per mol of acrylamide at 100°C for 2 hrs with stirring.Over-all yield of AA was about 850.3. KineticsThe apparent activation energy for the hydrolysis of AN was about 11.3 kcal/mol and the reaction was found to be second order in the concentrations of AN and water.