Synergistic effects and kinetic evidence of a transition metal-tin modified Beta zeolite on conversion of Miscanthus to lactic acid

Abstract

The direct catalytic transformation of raw lignocellulosic biomass into valuable chemicals is of great significance for sustainable production. This work reports the combination of a transition metal chromium with tin in Beta zeolites to efficiently catalyse the conversion of Miscanthus into lactic acid with a yield of 33.4% and a selectivity of 53.2%. On the basis of experiment and kinetic studies, chromium and tin were beneficial for the retro-aldol condensation and isomerization of carbohydrates, respectively. The acidity of the catalyst was investigated based on important insight into the synergetic catalytic mechanism. The strong Lewis acidity possessed by the transition metals was remarkably advantageous for catalysing the retro-aldol fragmentation reaction, while the relatively weak Lewis acidity of the tin species was considered a dominant factor in the isomerization reaction. The coupling of multifunctional active sites provided a new director for the transformation towards lactic acid formation.