Shen Zheng, Kong Ling, Zhang Wei, Gu Minyan, Xia Meng, Zhou Xuefei, Zhang Yalei
National Engineering Research Center of Protected Agriculture, Tongji University Shanghai 200092 China
State Key Laboratory of Pollution Control and Resource Reuse, Tongji University Shanghai 200092 China.
RSC Adv. 2019 Jun 17;9(33):18989-18995. doi: 10.1039/c9ra01264h. eCollection 2019 Jun 14.
The catalytic conversion of glucose into lactic acid (LA) provides an alternative approach for LA production to bio-fermentation. Nevertheless, during the process, the dehydration of glucose and fructose into 5-hydroxymethylfurfural catalyzed by Brønsted acid exists as the main side reaction that leads to the decrease in LA yield. In order to promote the yield and selectivity of LA, a series of acid-base bifunctional Sn-Beta-NH catalysts were prepared by post-grafting aminopropyl groups with the surface silanol groups of Sn-Beta zeolite. The catalysts were systematically characterized by X-ray diffraction, N adsorption-desorption, elemental analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectra analysis following pyridine adsorption, and CO temperature-programmed desorption. The as-prepared Sn-Beta-NH catalysts exhibiting both Lewis acid and moderate base sites facilitated the conversion of glucose to LA in competition with undesirable side reactions. In addition, effects of reaction parameters including reaction temperature and time, catalyst dosage, and glucose concentration were investigated. A high LA yield up to 56% was achieved under optimized hydrothermal conditions (190 °C, 2 h), along with a complete conversion of glucose and a 5-hydroxymethylfurfural yield of 7%. The result indicated an alternative modification method of Sn-Beta zeolite for a more favorable LA yield.
将葡萄糖催化转化为乳酸（LA）为LA生产提供了一种替代生物发酵的方法。然而，在此过程中，由布朗斯特酸催化的葡萄糖和果糖脱水生成5-羟甲基糠醛是主要的副反应，导致LA产率降低。为了提高LA的产率和选择性，通过将氨丙基与Sn-Beta沸石的表面硅醇基团进行后接枝，制备了一系列酸碱双功能的Sn-Beta-NH催化剂。通过X射线衍射、N吸附-脱附、元素分析、X射线光电子能谱、吡啶吸附后的傅里叶变换红外光谱分析以及CO程序升温脱附对催化剂进行了系统表征。所制备的具有路易斯酸和适度碱位的Sn-Beta-NH催化剂促进了葡萄糖向LA的转化，同时抑制了不良副反应。此外，还研究了反应温度和时间、催化剂用量以及葡萄糖浓度等反应参数的影响。在优化的水热条件（190℃，2小时）下，LA产率高达56%，同时葡萄糖完全转化，5-羟甲基糠醛产率为7%。结果表明，Sn-Beta沸石的一种替代改性方法可实现更有利的LA产率。
