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首页> 外文期刊>Catalysis science & technology >Catalytic activity and stability of hydrophobic Mg-Al hydrotalcites in the continuous aqueous-phase isomerization of glucose into fructose
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Catalytic activity and stability of hydrophobic Mg-Al hydrotalcites in the continuous aqueous-phase isomerization of glucose into fructose

机译：葡萄糖连续水相异构化中疏水Mg-Al水力钙化的催化活性和稳定性

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摘要

The aqueous-phase isomerization of glucose into fructose, catalyzed by Mg-Al hydrotalcites, has been investigated under batch and continuous conditions. A commercial hydrotalcite with a hydrophobic surface modification and two hydrophilic hydrotalcites in carbonate form, or with OH- anions in the interlayer space, served as catalysts. With the hydrophobic hydrotalcite a lower conversion but superior selectivity to fructose could be demonstrated, reaching above 92% selectivity at 30% conversion. The observed by-products confirm retroaldolization of glucose and fructose as the main side reactions causing catalyst deactivation via adsorption. Additionally, acidic degradation products such as lactic acid cause neutralization of the hydrotalcites facilitating leaching of the Mg2+ ions. Fructose contributes a greater extent to by-product formation. Applying continuous operation conditions, fructose is removed from the reaction mixture. Therefore, by-product formation is notably suppressed and catalyst stability increases. During 70 to 100 h time-on-stream a slow deactivation of the hydrophobic hydrotalcite occurs. Regeneration can be achieved via calcination and treatment in an aqueous sodium n-dodecyl sulfate solution to introduce dodecyl sulfate anions to the interlayer space of the hydrotalcite, restoring the hydrophobic material properties.
机译：在批处理和连续条件下，已经研究了葡萄糖的水相异构化，该葡萄糖被MG-Al Hydrotalcites催化的果糖。具有疏水表面修饰的商业水力充血和两种以碳酸盐形式的亲水性水直体形式，或在层间空间中的Oh-阴离子作为催化剂。使用疏水性水力钙岩的转化率较低，但可以证明对果糖的选择性较高，以30％的转化率达到92％的选择性。观察到的副产品证实了葡萄糖和果糖的逆转录化为主要侧反应，导致通过吸附导致催化剂失活。此外，酸性降解产物（例如乳酸产物）导致水力钙化物促进MG2+离子的浸出。果糖对副产品形成的贡献更大。应用连续的操作条件，从反应混合物中除去果糖。因此，副产物的形成显着抑制，催化剂稳定性增加。在70至100 h的过程中，会发生疏水性水力钙岩的缓慢失活。可以通过在N-二烷基硫酸钠水溶液中钙化和处理来实现再生，以将硫酸十二烷基硫酸盐阴离子引入水力钙岩的层间空间，从而恢复疏水性材料的性质。

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