The use of lignin to prepare fine chemicals is a hot research topic. Here, we propose a strategy for esterification of the syringyl group, which is abundant in lignin, to produce 3,4-dimethoxyphenyl acetic acid ester. Lignin reacts with alcohols over acidic pure silica catalyst, L-MCM-41, to generate 3,4-dimethoxyphenyl acetic acid esters. The esterification yield from alkali lignin (Indulin AT) reached more than 60%. Furthermore, L-MCM-41 was easily and quickly prepared using hydroxyl free radicals. The obtained L-MCM-41 exhibited enhanced Lewis acidity and stability compared to silica MCM-41 derived from a traditional hydrothermal system. The enhanced Lewis acidity of the surface silicon atoms of L-MCM-41 can be attributed to the electron-withdrawing effect of abundant geminal hydroxyl groups that they bear. Based on spectroscopic data and the concentration of hydroxyl free radicals, the mechanism underpinning the enhanced acidity and stability of the mesoporous silica molecular sieves is proposed. This work enables production of fine chemicals using lignin as feedstock and provides a reliable and simple method for the synthesis of strongly acidic mesoporous silica molecular sieves.

使用木质素制备精细化学品是一个热门的研究主题。在这里，我们提出了一种对木质素中丰富的丁香基酯化的策略，以生产3,4-二甲氧基苯基乙酸酯。木质素在酸性纯二氧化硅催化剂L-MCM-41上与醇反应，生成3,4-二甲氧基苯基乙酸酯。碱木质素（Indulin AT）的酯化收率达到60％以上。此外，使用羟基自由基可以轻松快速地制备L-MCM-41。与衍生自传统水热体系的二氧化硅MCM-41相比，所获得的L-MCM-41表现出增强的路易斯酸度和稳定性。L-MCM-41的表面硅原子的Lewis酸度提高，可以归因于它们所带有的丰富双键羟基的吸电子作用。基于光谱数据和羟基自由基的浓度，提出了中孔二氧化硅分子筛增强酸性和稳定性的机理。这项工作能够使用木质素作为原料生产精细化学品，并为合成强酸性介孔二氧化硅分子筛提供了可靠而简单的方法。