Ammonia promoted barium sulfate catalyst for dehydration of lactic acid to acrylic acid

Abstract

The dehydration of lactic acid (LA) to acrylic acid over ammonia promoted barium sulfate was studied under various conditions. Interplanar spacing (d) calculated from the enlarged (121) diffraction peak of XRD patterns with the Bragg equation is influenced by preparation conditions, which determines the acid–base properties of the prepared barium sulfate. The present work focused on the preparation conditions such as alkaline agents, pH values and calcination temperatures, which affected the d value. It was found that aqueous ammonia was used as an alkaline agent at pH = 5 to synthesize barium sulfate with an appropriate d value, which displayed an excellent catalytic performance for LA dehydration to acrylic acid. In the presence of the prepared barium sulfate with an appropriate d value, the dehydration reaction of lactic acid proceeded efficiently, with 100% lactic acid conversion and ∼82% acrylic acid selectivity. The unprecedented catalytic performance is due to a balance between acidic sites and basic sites existing on the surface of the prepared catalyst. The catalyst is very stable for at least 24 h. The deactivation catalyst can be easily regenerated as it is calcined at 500 °C for 10 h under the air atmosphere.