Zhang, L. L.; Theng, D. S.; Du, Y. H.; Xi, S. B.; Huang, L.; Gao, F.; Wang, C.; Chen, L. W.; Borgna, A., Selective conversion of lactic acid to acrylic acid over alkali and alkaline-earth metal co-modified NaY zeolites. Catalysis Science & Technology 2017, 7 (24), 6101-6111.
Alkali and alkaline-earth metal cation co-modified NaY zeolites were systematically synthesized and comprehensively investigated as catalysts for gas-phase dehydration of lactic acid (LA) to acrylic acid (AA). The long-term (time-on-stream >55 h) catalytic performance in four repeated reaction–regeneration cycles was studied. The best performing catalyst shows a consistently high AA selectivity of ∼84% at different weight hourly space velocity (WHSV) values ranging from 0.48 to 4.8 h−1. Most importantly, the catalyst can still deliver a high AA selectivity of ∼82% after four long-term reaction–regeneration cycles. The investigation shows that mild etching increases the defect density of the zeolite and thus leads to poor hydrothermal stability in the long-term reaction–regeneration cycles. The strong acidic adsorbate/catalyst surface interaction (base property) and the acidity of the catalyst are responsible for the catalyst deactivation. The role of the alkali and alkaline-earth metal cations and the transformation of these cations during the reaction and regeneration process are presented.
This work was funded by the Cell Factory: Biomass to Chemicals program (project numbers: 1124004026 & 1326004119) of the Science & Engineering Research Council (SERC), Agency for Science, Technology and Research (A*STAR).