SO4^2--TiO2／MOR新型固体酸催化果糖制备5-羟甲基糠醛

SO_4^(2-)-TiO_2/MOR as novel solid acid catalyst for dehydration of fructose to 5-hydroxymethylfurfural

采用溶胶-凝胶-水热工艺制备了一系列SO42--TiO2/MOR(STM)固体酸催化剂。相对SO42--TiO2催化剂,制备的STM催化剂有高的硫负载量、大的比表面积和好的分散性。吡啶分子探针-傅里叶变换红外光谱、X射线光电子能谱及Ti2p、S2p和O1s分峰拟合图谱分析表明,硫负载量和结合态、活性组分和丝光沸石载体的相互作用影响到催化剂的B酸中心和L酸中心分布进而影响催化活性。STM0.2催化剂促进果糖转化反应,5-羟甲基糠醛的产率和果糖的转化率分别达到71.6%和91.9%。催化剂回收实验结果预示二氧化钛的L酸中心有助于稳定果糖的转化率,丝光沸石载体能够提高催化剂的耐热性和目标产物的选择性。

SO4^2--TiO2 catalysts are active for the hydrolysis of fructose, but they are deactivated in hot water in the next run. SO4^2--TiO2/MOR （STM） solid acid catalysts were successfully prepared to promote or stabilize SO4^2--TiO2 by using the sol-gel-hydrothermal new process. The activated natural mordenite （MOR） supports had low costs, abundant microporous structure with high BET surface area, excellent thermal stability and easy recycling. As nanosized TiO2 could interact with the structural hydroxide of MORs, a binary STM catalyst was expected to be more acidic than either material alone. The binary mesoporous catalysts with high sulfate loading, high BET surface area and good dispersion showed better catalytic activities. The analysis results of pyridine molecular probe-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Ti2p, S2p and Ols peak fitting curves showed that loading and binding state of sulfur, interaction between active components and mordenite carriers made connection to distribution of Bronsted acid sites and Lewis acid sites. The 5-hydroxymethylfurfural （HMF） yield and fructose conversion for STM0.2 catalyst reached 71.6% and 91.9% respectively. Recycling experiments showed that activities of STM0.2 catalysts decreased with increasing recycling times, the HMF yield declined to 44.5 % in the third cycle. The Lewis acid sites of titanium dioxide helped to promote the conversion of fructose. Mordenite supports could improve the heat resistance of catalyst and the selectivity of target product.