Research Center for Combustion and Environmental Technology, Shanghai Jiao Tong University, Shanghai 200240, China.
Department of Energy and Material Sciences, Faculty of Engineering Sciences, Kyushu University, Fukuoka 816-8580, Japan.
J Environ Sci (China). 2020 Dec;98:196-204. doi: 10.1016/j.jes.2020.06.008. Epub 2020 Jun 21.
Various manganese oxides (MnO) prepared via citric acid solution combustion synthesis were applied for catalytic oxidation of benzene. The results showed the ratios of citric acid/manganese nitrate in synthesizing process positively affected the physicochemical properties of MnO, e.g., BET (Brunauer-Emmett-Teller) surface area, porous structure, reducibility and so on, which were in close relationship with their catalytic performance. Of all the catalysts, the sample prepared at a citric acid/manganese nitrate ratio of 2:1 (C2M1) displayed the best catalytic activity with T (the temperature when 90% of benzene was catalytically oxidized) of 212℃. Further investigation showed that C2M1 was MnO with abundant nano-pores, the largest surface area and the proper ratio of surface Mn/Mn, resulting in preferable low-temperature reducibility and abundant surface active adsorbed oxygen species. The analysis results of the in-situ Fourier transform infrared spectroscopy (in-situ FTIR) revealed that the benzene was successively oxidized to phenolate, o-benzoquinone, small molecules (such as maleates, acetates, and vinyl), and finally transformed to CO and HO.
采用柠檬酸溶液燃烧合成法制备了各种锰氧化物（MnO），并将其应用于苯的催化氧化反应中。结果表明，柠檬酸/硝酸锰在合成过程中的比例对 MnO 的物理化学性质有积极的影响，例如 BET（Brunauer-Emmett-Teller）表面积、多孔结构、还原性能等，这些性质与它们的催化性能密切相关。在所有催化剂中，柠檬酸/硝酸锰比例为 2:1（C2M1）的样品表现出最佳的催化活性，其 T（苯催化氧化 90%时的温度）为 212℃。进一步的研究表明，C2M1 是具有丰富纳米孔、最大表面积和适当表面 Mn/Mn 比例的 MnO，这导致其具有较好的低温还原性能和丰富的表面活性吸附氧物种。原位傅里叶变换红外光谱（in-situ FTIR）的分析结果表明，苯依次被氧化为酚盐、邻苯醌、小分子（如马来酸酯、醋酸盐和乙烯基），最后转化为 CO 和 HO。
