On the catalytic vapor-phase dehydration of lactic acid to acrylic acid: a systematic review

Acrylic acid is one of the fastest growing monomers. Acrylic acid and its derivatives are very versatile monomers for many industrial and commodity chemicals such as absorbents, detergents, dispersants, and flocculants. The catalytic dehydration of lactic acid is a promising approach for the renewable, efficient, economic, and green production of acrylic acid. The understanding and control of lactic acid reaction pathways and catalytic selectivity are of critical importance for the rational design of new generations of catalyst systems. This review summarizes the developments of heterogeneous catalyst systems applied in the vapor-phase dehydration of lactic acid to acrylic acid to date with our constructive comments and appropriate discussion. We systematically and comparatively present the catalytic performance of various types of heterogeneous catalyst systems including sulfate salts, phosphate salts, nitrate salts, hydroxyapatites, and modified zeolites. We also deal with crucial factors controlling the catalytic selectivity, possible catalytic active species involved, and reaction mechanisms proposed by different groups.