Thuriot-Roukos Joëlle, Khadraoui Romaissa, Paul Sébastien, Wojcieszak Robert
Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000 Lille, France.
ACS Omega. 2020 Jun 9;5(24):14283-14290. doi: 10.1021/acsomega.0c00091. eCollection 2020 Jun 23.
In this paper, Raman spectroscopy is used as a tool to study the mechanism of furfural oxidation using HO as a reagent on gold nanoparticles (NPs) supported on hydrotalcites (HTs). This reaction was repeated, under the same conditions, but with different reaction times in a parallel multireactor system. The reaction media were analyzed using a macro device associated with a multipass cell permitting us to enhance the Raman signal by reflecting the laser beam 3 times. The Raman spectra showed the conversion of furfural to furoic acid without any chemical intermediates, thus privileging a direct pathway. Combining the results of the catalytic tests with those of the Raman study, the mechanism of furfural oxidation to furoic acid using gold NPs supported on HTs is proposed. The key points of this mechanism were found to be as follows: (i) the formation of a base, originating from the Mg leaching from the HT support, initiates the oxidation of furfural by deprotonation; (ii) HO used as a reagent in the solution increases the catalytic activity by its dissociation to form hydroxide ions; and (iii) the oxidation of furfural occurs on the surface of gold NPs and leads to higher furoic acid yield.
在本文中，拉曼光谱被用作一种工具，以研究糠醛在水滑石（HTs）负载的金纳米颗粒（NPs）上，以羟基自由基（HO）为试剂进行氧化的机理。在平行多反应器系统中，在相同条件下重复该反应，但反应时间不同。使用与多程池相关联的宏观装置对反应介质进行分析，该装置通过使激光束反射3次来增强拉曼信号。拉曼光谱表明糠醛直接转化为糠酸，没有任何化学中间体，因此优先选择直接途径。结合催化测试结果和拉曼研究结果，提出了水滑石负载的金纳米颗粒催化糠醛氧化为糠酸的机理。该机理的关键点如下：（i）碱的形成源于水滑石载体中镁的浸出，通过去质子化引发糠醛的氧化；（ii）溶液中用作试剂的羟基自由基通过离解形成氢氧根离子来提高催化活性；（iii）糠醛的氧化发生在金纳米颗粒表面，导致糠酸产率更高。
