球磨法合成钒基催化剂及其催化生物质制备甲酸

分别采用无溶剂机械球磨法和浸渍法合成了V/ZSM-5固体催化剂,通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱分析(XPS)、N2物理吸附和电感耦合等离子体质谱(ICP-MS)等手段表征了催化剂的物相、表面形貌、V的价态、比表面积以及V的含量。结果表明,两种方法合成的催化剂中V元素的负载量接近(约为1.7%)。相比于传统浸渍法,本研究提出的球磨法无需任何溶剂,时间短(1 h),其合成的催化剂颗粒较小,比表面积更大(367.0 m^2·g^-1 vs 223.9 m^2·g^-1),且球磨法得到的催化剂V的价态较高,相同催化条件下球磨法合成的催化剂性能优于浸渍法合成的催化剂(45%vs 35%)。系统研究了不同实验因素对催化反应的影响规律,在温度180℃、水为溶剂、催化剂与底物质量比为1∶2、氧气3 MPa、反应时间30 min时,葡萄糖转化产甲酸的产率最高,达到45%。此外,在该球磨法合成的催化剂作用下,多种生物质基碳水化合物均能用来制备甲酸。本研究为金属负载型催化剂的设计合成提供了另一种途径,简单、高效、易操作且环境友好,对于木质纤维素类农林废弃物向高附加值化学品的转化具有重要意义。

Synthesis of V/ZSM-5 by ball milling for catalytic conversion of biomass to formic acid

V/ZSM-5 solid catalyst was prepared using the solvent-free mechanical ball milling method and the conventional impregnation method.X-ray powder diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),N2 physical adsorption,and inductively coupled plasma mass spectrometry(ICP-MS)were used to characterize the catalyst.The results showed that the catalysts prepared using the two methods had similar V content(~1.7%).Compared to the traditional impregnation method,the ball milling process was solvent-free and needs less time(1 h).In addition,the particle size was smaller and had a larger specific area(367 m^2·g^-1 vs 223.90 m^2·g^-1),and the ball milling treatment results in a higher valence state of V leading to the better yield of the ball milled catalyst(45%vs 35%).The effect of different experimental factors on the catalytic reaction in water was studied systematically.Under the optimal conditions(180℃;catalyst∶substrate=1∶2;3 MPa oxygen;30 min),the yield of formic acid from glucose was up to 45%.In addition,various carbohydrates could be converted to formic acid with the prepared catalyst.This study provides an additional method for the synthesis of metal-supported catalysts which is simple,efficient,easy to operate,and environmentally friendly.It is of great significance for the conversion of lignocellulosic biomass to high value-added chemicals.