To investigate the effects of the acid characteristic of Sn-MFI zeolite on catalytic performance in the transformation of dihydroxyacetone to methyl lactate, multiple characterization and experimental methods were employed. Firstly, the transformation between Lewis and Brönsted acid sites was initially confirmed by ³¹P-TMP NMR method, owing to the introduction of CH₃OH by framework Sn species to donate protons. It is found that Lewis acid sites are cooperative with Brönsted acid sites to boost the primary reactions of dihydroxyacetone (DHA) to methyl lactate (ML). Yet, too high ratio of Brönsted acid sites to Lewis acid sites favors the generation of side product pyruvic aldehyde dimethyl acetal (PADA). That is because Brönsted acid sites majorly catalyze the dehydration of DHA, the addition of pyruvaldehyde (PA) with methanol and the addition of hemiacetal (HA) with methanol to PADA, whereas Lewis acidic framework Sn sites are responsible for the isomerization of HA to ML, which can be further verified by the isotopic labeling experiments. Therefore, this study provides a definite and systematical insight on the impacts of acid property on product selectivity.

为了研究Sn-MFI分子筛的酸性特征对二羟基丙酮转化为乳酸甲酯的催化性能的影响，采用了多种表征方法和实验方法。首先，由于引入了CH ₃，最初通过³¹ P-TMP NMR法确认了路易斯酸和布朗斯台德酸位之间的转化OH通过构架锡物种来捐赠质子。发现路易斯酸位点与布朗斯台德酸位点协作以促进二羟基丙酮（DHA）与乳酸甲酯（ML）的主要反应。然而，布朗斯台德酸位点与路易斯酸位点的比例太高则有利于生成副产物丙酮醛二甲基乙缩醛（PADA）。这是因为布朗斯台德酸位点主要催化DHA的脱水，向甲醇中添加丙酮醛（PA）和向甲醇中添加半缩醛（HA）至PADA，而路易斯酸性骨架Sn位点则负责将HA异构化为ML ，可以通过同位素标记实验进一步验证。因此，本研究对酸性质对产物选择性的影响提供了确定而系统的见解。