Selective transformation of typical sugars to lactic acid catalyzed by dealuminated ZSM-5 supported erbium

The tremendous demand of lactic acid (LaA) in widespread applications has impelled the development of chemical strategies for LaA production. We developed dealuminzated ZSM-5 loaded erbium catalyst, which exhibited outstanding activity. As high as >96% of LaA yield was obtained using triose as raw material over 15-Er/deAl-ZSM-5 (2) catalyst. When xylose-glucose mixture (C-molar ratio, 1:1) was employed, the simultaneous conversion of xylose and glucose selectively to LaA with ∼69.1 C-mol% yield could be achieved. The characterization of catalyst revealed that the pretreatment by HNO3 successfully removed partial Al in the extra-framework of ZSM-5, leading to enlarged surface areas and promoted dispersion of Er species, as well as strengthened weak interaction between Er species and support. Er loading might replace the H of OH group in bridging (Si–O(H)–Al) and Si–OH/Al–OH, which significantly strengthened the Lewis acidity of catalyst but decreased the Brønsted acidity. Consequently, LaA formation was remarkably promoted, while levulinic acid generation was inhibited. The catalyst also showed good catalytic activity for the conversion of other water-soluble polysaccharides. This work might provide a potential approach for the simultaneous conversion of cellulose and hemicellulose in actual biomass to produce LaA in an effective, low-cost and environment-friendly chemical way.