Saulnier-Bellemare Thomas, Patience Gregory S
Chemical Engineering, Polytechnique Montréal, Montréal H3T 1J4, Canada.
ACS Omega. 2024 May 20;9(22):23121-23137. doi: 10.1021/acsomega.3c10015. eCollection 2024 Jun 4.
The current societal demand to replace polymers derived from petroleum with sustainable bioplastics such as polylactic acid (PLA) has motivated industry to commercialize ever-larger facilities for biobased monomers like lactic acid. Even though most of the lactic acid is produced by fermentation, long reaction times and high capital costs compromise the economics and thus limit the appeal of biotechnological processes. Catalytic conversion of hexose from biomass is a burgeoning alternative to fermentation. Here we identify catalysts to convert glucose to lactic acid, along with their proposed mechanisms. High Lewis acidity makes erbium salts among the most active homogeneous catalysts, while solvent coordination with the metal species polarize the substrate, increasing the catalytic activity. For heterogeneous catalysts, Sn-containing bimetallic systems combine the high Lewis acidity of Sn while moderating it with another metal, thus decreasing byproducts. Hierarchical bimetallic Sn-Beta zeolites combine a high number of open sites catalyzing glucose isomerization in the mesoporous regions and the confinement effect assisting fructose retro-aldol in microporous regions, yielding up to 67% lactic acid from glucose. Loss of activity is still an issue for heterogeneous catalysts, mostly due to solvent adsorption on the active sites, coke formation, and metal leaching, which impedes its large scale adoption.
当前社会要求用聚乳酸（PLA）等可持续生物塑料取代石油衍生聚合物，这促使工业界将越来越大的基于生物的单体（如乳酸）生产设施商业化。尽管大多数乳酸是通过发酵生产的，但反应时间长和资本成本高影响了经济效益，从而限制了生物技术工艺的吸引力。生物质中己糖的催化转化是一种新兴的发酵替代方法。在此，我们确定了将葡萄糖转化为乳酸的催化剂及其提出的作用机制。高路易斯酸度使铒盐成为最具活性的均相催化剂之一，而溶剂与金属物种的配位使底物极化，提高了催化活性。对于多相催化剂，含锡双金属体系结合了锡的高路易斯酸度，同时用另一种金属对其进行调节，从而减少了副产物。分级双金属Sn-β沸石结合了大量在介孔区域催化葡萄糖异构化的开放位点以及在微孔区域协助果糖逆羟醛反应的限制效应，葡萄糖制乳酸产率高达67%。活性损失仍然是多相催化剂面临的一个问题，主要是由于溶剂吸附在活性位点上、积炭形成以及金属浸出，这阻碍了其大规模应用。
