Catalytic dehydration of lactic acid to acrylic acid over modified ZSM-5 catalysts

The modification of H-ZSM-5 catalysts with NaOH and Na2HPO4 was carried out and the resulted catalysts were used in the catalytic dehydration of lactic acid to acrylic acid. The modification included first NaOH treatment to transform the strong acid into acid with medium strength and generate mesopores and macropores, and then Na2HPO4 loading to regulate the matching of acid and base for the alkalimodified catalyst. A lactic acid conversion of 96.8% with high selectivity of 77.9% for acrylic acid was achieved over the modified ZSM-5 catalyst. The catalyst stability with time on stream was investigated within 52 h and reaction conditions were also optimized. The results show that the modified ZSM-5 catalyst demonstrates a good catalytic stability. The characterization of XRD, NH3-TPD and CO2-TPD indicates that the modified ZSM-5 catalyst produces some extra mesopores, and thus possesses abundant medium acidic sites and some medium basic sites, which may be responsible for high acrylic acid selectivity and good catalytic stability. (C) 2015 Elsevier B.V. All rights reserved.