双金属离子水热催化转化葡萄糖制备乳酸

选择不同的双金属阳离子作为催化剂, 在碱性条件下用于水热转化葡萄糖制备乳酸, 发现Sn$^{2+}$和Cu$^{2+}$具有一定的协同作用. 研究了反应温度、时间、碱加入量和金属离子比例对乳酸产率的影响, 获得最优工艺条件如下: 0.025 g葡萄糖, 2 mmolNaOH, $n$(Sn$^{2+})$:$n$(Cu$^{2+})$=0.25:0.75(共1 mmol), 20 mL水, 200 ${^\circ}$C反应温度, 3 h反应时间. 在最优条件下, 乳酸产率为64.1%, 甲酸产率为20.3%, 乙酸产率为11%. 选用几种模型化合物作为反应的中间产物进行水热转化实验, 并根据实验结果对水热转化葡萄糖的转化机理进行了探究. 结果发现, 转化过程中重要的中间产物为果糖、1,3-二羟基丙酮和丙酮醛. 两种金属离子存在协同作用, Cu$^{2+}$抑制了乳酸的分解, Sn$^{2+}$提高了丙酮醛转化为乳酸的转化效率, 最终提高了乳酸产率.

Preparation of lactic acid by catalytic conversion of glucose by dual-metal ions

Different dual-metal ions were selected as catalysts to prepare lactic acid (LA) by hydrothermal conversion of glucose under alkaline conditions, and Sn$^{2+}$ and Cu$^{2+}$ were found to have a certain synergistic effect. The effects of reaction temperature, time, alkali addition amount, and metal ion ratio on lactic acid yield were studied to optimise the experimental conditions. The optimum process conditions were as follows: 0.025 g glucose, 2 mmol sodium hydroxide, $n$(Sn$^{2+})$:$n$(Cu$^{2+})$=0.25:0.75 (1 mmol total), 20 mL water, reaction temperature 200 ${^\circ}$C, and reaction time 3 h. Under optimal conditions, the yields of lactic acid, formic acid (FA), and acetic acid (AA) were 64.1%, 20.3% and 11%, respectively. Several model compounds were selected as intermediate products for the hydrothermal transformation experiments. According to the experimental results, the conversion mechanism of the hydrothermal conversion of glucose was investigated. Important intermediates detected in the conversion process were fructose, 1,3-dihydroxyacetone and pyruvaldehyde. There was a synergistic effect between the two metal ions, as Cu$^{2+}$ inhibited the decomposition of lactic acid, and Sn$^{2+}$ increased the conversion efficiency of pyruvaldehyde to lactic acid, finally increasing the yield of lactic acid.