The catalytic transformation of cellulose into valuable chemicals such as lactic acid under mild conditions represents a promising route for the efficient utilization of renewable biomass. Here, we report that the combination of Al(III) and Sn(II) cations can efficiently catalyse the conversion of cellulose and related carbohydrates into lactic acid in water. Al(III)–Sn(II) is the most efficient combination for lactic acid formation among the many dual cations investigated. Al(III) and Sn(II) with a molar ratio of 1/1 work cooperatively, providing lactic acid with yields of 90%, 81% and 65% in the conversions of fructose, glucose and cellulose, respectively. The formation of lactic acid involves a series of tandem steps including the hydrolysis of cellulose to glucose, the isomerisation of glucose to fructose, the retro-aldol fragmentation of fructose to C₃ intermediates and the subsequent conversion of the C₃ intermediates to lactic acid. Our experimental and computational studies suggest that Al(III) mainly catalyses the isomerisation of glucose or the C₃ intermediates, whereas Sn(II) is primarily responsible for the retro-aldol fragmentation. The combination of the two cations enables the reaction to proceed smoothly with few side reactions, providing outstanding catalytic performances for lactic acid production from cellulose or the related carbohydrates.

中文翻译：

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双功能Al（III）-Sn（II）催化剂将纤维素和相关碳水化合物转化为乳酸

在温和的条件下，纤维素催化转化为有价值的化学物质，例如乳酸，是有效利用可再生生物质的有前途的途径。在这里，我们报告Al（III）和Sn（II）阳离子的组合可以有效催化水中的纤维素和相关碳水化合物向乳酸的转化。Al（III）–Sn（II）是研究的许多双阳离子中乳酸形成的最有效组合。Al（III）和Sn（II）摩尔比为1/1的）协同作用，以果糖，葡萄糖和纤维素的转化率分别提供90％，81％和65％的乳酸收率。乳酸的形成涉及一系列串联步骤，包括纤维素水解为葡萄糖，葡萄糖异构化为果糖，果糖的逆醛醇裂解成C ₃中间体以及随后的C ₃中间体转化为乳酸。我们的实验和计算研究表明，Al（III）主要催化葡萄糖或C ₃中间体的异构化，而Sn（II）主要负责后羟醛的断裂。两种阳离子的结合使反应平稳进行，几乎没有副反应，从而为从纤维素或相关碳水化合物生产乳酸提供了出色的催化性能。