CONVERSION OF LACTIC-ACID TO ACRYLIC-ACID IN NEAR-CRITICAL WATER

The dehydration of lactic acid is studied in a Hastelloy C-276 annular reactor in near-critical water. Experiments are performed at a pressu re of 310 bar, at temperatures of 320-400-degrees-C, at residence time s of 25-110 s, and with various catalysts, including disodium hydrogen phosphate, phosphoric acid, and sodium hydroxide. Three main reaction pathways are investigated and evaluated. A temperature of 360-degrees -C optimizes the formation of acrylic acid with molar yields as high a s 58%, based on conversion. The presence of phosphate salts and/or bas e increases the yields of acrylic acid by suppressing the competing pa thways. The aging of the Hastelloy reactor for 60-70 h decreases the d egradation reactions resulting in higher yields of acrylic acid.