壳聚糖基固体酸催化果糖合成5-羟甲基糠醛

Chitosan-derived Solid Acid as a Catalyst for Fructose Dehydration into 5-Hydroxymethylfurural

摘要:

以壳聚糖为原料，一步水热碳化和磺化法合成壳聚糖基固体酸（CASA）材料，并将其用于催化无溶剂条件下果糖脱水合成5-羟甲基糠醛（5-HMF）的反应中，考察了催化剂用量、反应温度、反应时间及催化剂循环利用次数对该脱水反应的影响，并与甲壳素基固体酸（CISA）材料进行了催化性能比较。采用X射线衍射、扫描电镜、吡啶吸附红外光谱等手段对CASA材料进行了结构和酸性质表征，建立了催化剂结构与性能的关系。结果表明，CASA材料含有大量的表面强Brӧnsted酸性位点，因而其催化性能较CISA突出；当m(果糖):m(CASA)=6:1、120 ℃反应5 h时，5-HMF的收率高达63.2%，且CASA可重复利用4次而无明显失活。

Abstract:

A kind of chitosan-derived solid acid (CASA) material with chitosan as a precursor was successfully synthesized via in situ partially hydrothermal carbonization and sulfonation method. Thereafter, the CASA material was used for catalytic fructose dehydration to 5-hydroxymethylfurural (5-HMF) under solvent-free conditions. The effects of catalyst amount, reaction temperature, reaction time and catalyst recyclability on the dehydration were studied in detail. Meanwhile, comparison of catalytic activities with the chitin-derived solid acid (CISA) material was further investigated. Besides, the obtained CASA material was characterized by various techniques, such as X-ray diffraction, scanning electron microsco-py and infrared spectra of pyridine adsorption etc. The structure-performance relationship was built by elucidating the structural and acidic properties of the material. According to the results, it was suggested that adequate strong Brӧnsted surface acid sites were grafted onto the CASA material, indicating the su-perior catalytic performance for 5-HMF production to the CISA material. The 5-HMF yield was obtained up to 63.2% at 120 ℃ within 5 h when the mass ratio of fructose to CASA material was 6:1. It was no-ticeable that the CASA catalyst could be recycled up to 4 times without any obvious deactivation.