Hydrothermally synthesized Sn-Beta is an excellent catalyst for the conversion of sugars to alkyl lactates. However, its catalytic performance is highly dependent on the synthesis parameters. In this work, the effects of the synthesis parameters such as the water amount of the synthesis gel and the crystallization time on the synthesis and properties and catalytic performance of Sn-Beta in the conversion of glucose to methyl lactate (MLA) were investigated. The crystallization rate was accelerated remarkably by reducing the water amount of the synthesis gel. With the aid of the Si-Beta seed, Sn-Beta was almost fully-crystallized after one day with n_H2O/n_SiO2 of 4.5, but seven days were needed with n_H2O/n_SiO2 of 7.5. However, Sn-Beta synthesized with n_H2O/n_SiO2 of 4.5 has more extraframework SnO₂ due to the fast formation of the *BEA structure and the slow incorporation of Sn⁴⁺ into the framework sites, which resulted in the lower activity of MLA formation. More Sn⁴⁺ species were incorporated into the framework sites and thus more Lewis acid sites were generated with increasing crystallization time. At the same time, the ratio of open to closed Sn sites (R_O/C) increased, which led to the decrease in the activity of MLA formation and due to that, the open Sn site with a proximal silanol is unfavorable for the conversion of glucose to MLA. During recycling study, it is surprisingly found that the yield of MLA increased gradually over the fully-crystallized Sn-Beta catalyst. Characterization results of the recovered catalyst from the eighth run indicate that the structure was preserved well, but the value of R_O/C reduced due to the change of the state and microenvironment of Sn species.

中文翻译：

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种子辅助水热合成Sn-β-葡萄糖将葡萄糖转化为乳酸甲酯：凝胶中H2O量和结晶时间的影响

水热合成的Sn-β是将糖转化为乳酸烷基酯的极佳催化剂。但是，其催化性能高度依赖于合成参数。在这项工作中，研究了诸如合成凝胶的水量和结晶时间等合成参数对Sn-β-葡萄糖在葡萄糖转化为乳酸甲酯（MLA）的合成，性能和催化性能的影响。通过减少合成凝胶的水量，结晶速度显着提高。与Si-β晶种的帮助下，锡-β几乎有一天之后完全结晶ñ _{^ h 2 Ø} / ñ_{的SiO 2}的4.5，但需要与7天ñ_{H 2 O} / n _{SiO 2}为7.5。然而，由于* BEA结构的快速形成以及Sn ⁴⁺缓慢引入骨架部位，以4.5的n _{H 2 O} / n _{SiO 2}合成的Sn-Beta具有更多的骨架外SnO _2。 MLA形成的活性。更多的Sn ⁴⁺物种被纳入框架的网站，因此增加结晶时间生成更多的路易斯酸网站。同时，开放和封闭锡站点的比例（ R _{O / C}）增加，这导致MLA形成活性的降低，因此，具有近端硅烷醇的开放Sn位点不利于葡萄糖向MLA的转化。在再循环研究中，令人惊讶地发现，MLA的产率比完全结晶的Sn-Beta催化剂逐渐增加。从第八轮回收的催化剂的表征结果表明，该结构保存得很好，但是由于Sn物种的状态和微环境的变化，R _{O / C}值降低。