物理化学学报2020，Vol.36Issue(1)：113-119,7.DOI:10.3866/PKU.WHXB201904066
碱催化剂g-C3N4在液相反应中溶胀特性的研究
Swelling Characteristics of g-C3N4 as Base Catalyst in Liquid-Phase Reaction
摘要
Abstract
Graphitic carbon nitrides (g-C3N4) with different surface areas were prepared by pyrolysis using different precursors including melamine, dicyandiamide, thiourea and urea, and subsequently characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and N2 adsorption. Their basicities were measured by temperature-programmed desorption of CO2 (CO2-TPD) and acid-base titration. The catalytic properties for the Knoevenagel condensation of benzaldehyde andmalononitrile were investigated in various solvents. In non-polar toluene solution, the benzaldehyde conversions of the g-C3N4 catalysts were low and changed according to their respective surface areas and basicities. However, in polar ethanol solution, the benzaldehyde conversions of all catalysts were similar, and much higher than those in toluene. This could not be explained by the results obtained from either of the two conventional basicity measurements. Further experimental results proved that g-C3N4 catalysts swelled in polar solutions, and more basic sites were exposed on the surface of the swollen catalysts, leading to the imminent increase in catalytic activity. This was proved by the catalyst poisoning data, which showed that the g-C3N4 catalyst lost its activity completely in toluene by adding 40.9 mmol·g?1 benzoic acid, while the same catalyst was still active in ethanol until the added amount exceeded 143.3 m·g?1. Additionally, the reaction tests in various solutions showed that the swelling effect was enhanced according to the polarity of the solvent used. A similar conclusion could be reached for the Knoevenagel condensation of furfural and malononitrile in various solvents. The reusability of g-C3N4 catalyst in Knoevenagel condensation was also studied, which showed that g-C3N4 was stable in liquid-phase reactions, whose activity dropped from 74.2％ to 63.8％ after three regeneration processes.关键词
g-C3N4/碱催化/Knoevenagel缩合/溶胀效应Key words
g-C3N4/Base catalysis/Knoevenagel condensation/Swelling effect分类
化学化工引用本文复制引用
吴结群,华伟明,乐英红,高滋..碱催化剂g-C3N4在液相反应中溶胀特性的研究[J].物理化学学报,2020,36(1):113-119,7.基金项目
The project was supported by the National Natural Science Foundation of China (91645201,21273043),the National Key R&D Program of China (2017YFB0602204),and the Science & Technology Commission of Shanghai Municipality,China (13DZ2275200).国家自然科学基金(91645201,21273043),国家重点研发计划(2017YFB0602204),上海市科委(13DZ2275200)资助项目 （91645201,21273043）
