Efficient Conversion of Glucose to Methyl Lactate with Sn-USY: Retro-aldol Activity Promotion by Controlled Ion Exchange

Abstract

Sn-USY materials have been prepared through an optimized post-synthetic catalytic metalation procedure. These zeolites displayed, upon ion exchange with alkaline metals, an outstanding activity in the direct transformation of glucose into methyl lactate, yielding more than 70% of the starting glucose as the target product, and an overall combined retro-aldol condensation product yield above 95% in a short reaction time (<4 h). This outstanding catalytic performance is ascribed to the neutralization of Brønsted acid sites, the consequent depression of side reactions, and a higher population of tin open sites in the ion-exchanged Sn-USY zeolites. Reusability tests evidenced some loss of catalytic activity, partially caused by the closing of tin sites, although the use of small amounts of water in the reaction media demonstrated that this deactivation mechanism can be, at least, partially alleviated.

Conversion of biomass-derived sugars to 1,1,2-trialkoxyethane via a [2 + 4] retro-aldol reaction over alkaline and alkaline earth metal salts of phosphotungstic acid

“…The poor yield and selectivity in converting fructose is reasonable because fructose could undergo [3 + 3] retro-aldol condensation, rather than [2 + 4] retro-aldol condensation. 37 Actually, we observed the formation of glyceraldehyde and 1,3-dihydroxyacetone as the products of [3 + 3] retro-aldol condensation and their etherification products during the conversion of fructose. The formation of a small amount of TriEE and GDEA might result from two plausible reaction pathways: one is that fructose first isomerizes to glucose and then takes part in the [2 + 4] retro-aldol condensation; the other pathway is the direct cleavage of C2–C3 bonds of fructose, namely the [2 + 4] retro-aldol condensation of fructose.…”

“…These findings suggest that the stronger the alkalinity of the metal, the more active the metal salt of HPW. 31,37 Among the catalysts tested, Cs 2 HPW demonstrated the highest catalytic activity and selectivity towards TriEE. Fig.…”

Temperature-responsive Zn-based catalysts for efficient catalytic conversion of biomass-derived carbohydrates to ethyl lactate

“…The peak at 1450 cm −1 resulted from pyridine adsorption over the Lewis acid sites, while the peak at 1540 cm −1 resulted from pyridine adsorption on the Brønsted acid sites. The band centered at 1489 cm −1 was ascribed to the adsorption of pyridine on both weak Lewis and Brønsted acid sites, 35 while the peak at 1609 cm −1 resulted from the hydrogen bond interaction between pyridine and the catalyst surface. 22 The calculated Lewis acid contents were 0.17 mmol g −1 for ZnSi-1, 0.28 mmol g −1 for ZnSi-2, 0.31 mmol g −1 for ZnSi-3, and 0.26 mmol g −1 for ZnSi-4, while the Brønsted acid contents were 0.021 mmol g −1 , 0.024 mmol g −1 , 0.029 mmol g −1 and 0.032 mmol g −1 (Table 2).…”

“…Using metal oxides and metal-beta zeolites as the catalyst for converting glucose either into ML or EL, the low yield of lactate falls in the range of 29.7-52.1%. [17][18][19]21,[24][25][26]48 Under the bimetallic catalysts (Fe-Sn/Beta, 28 Ga-Zn/H-nanozeolite Y, 49 K-Sn-USY zeolite, 35 and Sn-In-MCM-41 50 ), the yields of lactates were slightly higher, 64.0-70.0%. In contrast, under our ZnSi-2 catalyst, a yield of the EL as high as 74.5% could be achieved only after reacting for 45 min.…”

Recent advances of single-atom catalysts in CO2 conversion

“…The typical strategy of H, Na, and K ion-exchange process was used for the modulation of the zeolite microenvironment. [123][124][125] The advantage of spatial confinement is an efficient approach for improving the synthesis of zeolite-supported SACs. A variety of organometallic complexes are encapsulated into the zeolite cavity that can be transformed into single atoms or subnanoclusters with superior catalytic performance in catalytic reactions, inhibiting the migration and aggregation of mononuclear metal centers.…”