Chen Gongzhe, Sun Qianhui, Xu Jia, Zheng Lufan, Rong Junfeng, Zong Baoning
State Key Laboratory of Catalytic Materials and Reaction Engineering, Research Institute of Petroleum Processing, SINOPEC, Beijing 100083, China.
ACS Omega. 2021 Mar 5;6(10):6798-6809. doi: 10.1021/acsomega.0c05857. eCollection 2021 Mar 16.
Biphasic systems have received increasing attention for acid-catalyzed dehydration of hexoses to 5-hydroxymethylfurfural (HMF) because of their high efficiency in in situ extraction and stabilization of HMF. Different organic solvents and acid catalysts were applied in these systems, but their effects on the dehydration activity and HMF yield, and the recycling of homogeneous acid catalysts remain largely unexplored. Here, we tested different solvent systems containing a wide range of organic solvents with low boiling points to study the effects of their chemical structures on fructose dehydration and provided stable HO-dioxane and HO-acetonitrile biphasic systems with high HMF yields of 76-79% using water-soluble sulfonic derivatives as homogeneous acid catalysts under mild conditions (383 K). By analyzing the partition coefficients of HMF and sulfonic derivatives, 94.3% of HMF and 87.1% of NHSOH were, respectively, restrained in the dioxane phase and aqueous phase in the HO-dioxane biphasic system and easily divided by phase separation. The effects of the adjacent group in sulfonic derivatives and reaction temperature on fructose conversions and HMF yields suggest that in a specific biphasic system, the catalysts' acidity and reaction conditions significantly affect the fructose dehydration activity but hardly influence the optimal yield of HMF, and an almost constant amount of carbon loss was observed mainly due to the poor hydrothermal stability of fructose. Such developments offer a promising strategy to address the challenge in the separation and recycling of homogeneous acid catalysts in the practical HMF production.
双相体系因其在原位萃取和稳定5-羟甲基糠醛（HMF）方面的高效率，在己糖酸催化脱水制备HMF过程中受到越来越多的关注。在这些体系中应用了不同的有机溶剂和酸催化剂，但它们对脱水活性和HMF产率的影响，以及均相酸催化剂的循环利用在很大程度上仍未得到充分研究。在此，我们测试了含有多种低沸点有机溶剂的不同溶剂体系，以研究其化学结构对果糖脱水的影响，并在温和条件（383K）下，使用水溶性磺酸衍生物作为均相酸催化剂，提供了稳定的HO-二氧六环和HO-乙腈双相体系，HMF产率高达76 - 79%。通过分析HMF和磺酸衍生物的分配系数，在HO-二氧六环双相体系中，94.3%的HMF和87.1%的NHSOH分别被限制在二氧六环相和水相中，并且通过相分离很容易分开。磺酸衍生物中相邻基团和反应温度对果糖转化率和HMF产率的影响表明，在特定的双相体系中，催化剂的酸度和反应条件显著影响果糖脱水活性，但对HMF的最佳产率影响不大，并且观察到几乎恒定的碳损失量，这主要归因于果糖较差的水热稳定性。这些进展为解决实际HMF生产中均相酸催化剂的分离和循环利用挑战提供了一个有前景的策略。
