Sn@SBA-15 with temperature responsive acid-base dual functional sites for catalyzing biomass-derived sugars to ethyl lactate

Herein, a series of Sn-based catalysts supported on SBA-15 with temperature responsive ability to in situ construct acidic and basic sites are reported for efficient conversion of biomass-derived sugars into ethyl lactate (EL). Based on the investigation on the effects of the molar ratio of Cl/OH in Sn(OH)_xCl_2-x and the support types, it is found that Sn(OH)_0.5Cl_1.5@SBA-15 is an excellent catalyst in catalytic conversion of various sugars to EL, achieving a maximum EL yield of 68.1 % from sucrose. The in situ generated basic SnO sites play important roles in accelerating the retro-aldol condensation reaction, while the concomitantly released acidic sites (Sn^2 +, SnCl⁺ and H⁺) could catalyze the reactions of hydrolysis, isomerization, intermolecular rearrangement and esterification to EL. Benefiting from the temperature responsive effect, not only can the reaction pathways be regulated toward high EL selectivity, but also the catalyst can be recycled easily. This research paves an avenue for exploring efficient catalysts for biomass valorization.