聚合离子液体在催化转化果糖制备乳酸中的应用

Application of Polymeric Ionic Liquids in the Catalytic Conversion of Fructose to Lactic Acid

化学法分解糖类制备乳酸大都需要苛刻的反应条件,如高浓度强碱、较高的反应温度等.介绍了一种以聚合离子液体([IMEP]Cl)为催化剂,采用水热法直接催化转化果糖制备乳酸的方法,并对聚合离子液体类型、碱类型、反应温度、[IMEP]Cl与Na OH相对量以及底物浓度等实验条件进行了优化.结果表明,在100℃条件下,底物浓度为25mmol/L时,反应30 min乳酸达到最高收率65%,[IMEP]Cl与Na OH浓度分别为100和50 mmol/L.该方法有效降低了水热法合成乳酸的反应温度和碱浓度,并且[IMEP]Cl经过5次循环利用仍有较好的催化效果,乳酸收率仍保持在55%以上.对该体系催化转化果糖制备乳酸的反应机理进行了初步的推测.表明以聚合离子液体为催化剂催化转化碳水化合物制备乳酸有着较好的前景.

Preparation of lactic acid via chemical transformation of carbohydrates requires rigorous reaction conditions, such as high concentrations of alkali, high temperature, etc. This paper reports the use of polymeric ionic liquids（[IMEP]Cl） as catalyst for the hydrothermal conversion of fructose to lactic acid; the main variables of the reaction, temperature, substrate concentration, as well as the relative amount of [IMEP]Cl and Na OH were optimized. Results showed that, at 100 ℃, substrate concentration of 25 mmol/L, reaction time of 30 min, the highest yield of lactic acid was 65% with [IMEP]Cl and Na OH concentrations of 100 and 50 mmol/L respectively. This method reduces the reaction temperature and alkali concentration compared to traditional hydrothermal method, additionally it was found that [IMEP]Cl can be used during 5 catalytic cycles without losing its catalytic effect with a lactic acid yield of 55% in the 5th reuse cycle. This demonstrates that the use of polymer ionic liquids as catalysts has a better prospect for future developments. A possible reaction mechanism has been proposed, but further investigation is required.