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非均相多钼氧簇/活性炭催化碘离子氧化性能研究
Studies on Iodide Oxidation Catalyzed by Heterogeneous Molybdenum Oxide Clusters/Activated Carbon
【摘要】 采用浸渍法制备了多钼氧簇/活性碳(PMoO/AC)非均相催化剂。通过傅里叶红外光谱仪(FT-IR)、X射线粉末衍射(XRD)、比表面积孔径测试仪(BET)、扫描电子显微镜(SEM)等方法对其进行表征。研究了其在过氧化氢氧化低浓度碘离子反应中的催化及重复使用性能;利用分子力学和量子化学方法对PMoO与AC之间的吸附进行模拟计算,研究其吸附机理。结果表明:在多钼氧簇的质量分数为40%、pH为1.8、过氧化氢的用量为3.6 mmol/L,催化剂的用量为1.0 g,反应温度为25℃条件下,反应速率为2.7×10-5 mol·L-1·s-1,较之未添加催化剂体系,反应速率提高了2.7×103倍,且具有较好的重复使用性;PMoO可以以物理吸附的方式吸附在活性炭表面,但其表面不同修饰基团对PMoO的吸附能甚至催化性能造成不同影响:OH和NH2修饰活性炭有利于增加PMoO的物理吸附稳定性,COOH修饰活性炭降低了其物理吸附能;改性基团均可以与PMoO键合发生化学吸附,提高体系稳定性,同时改变了PMoO的电子性质,使其最高占据轨道能级(HOMO)降低,使与反应物过氧化氢之间能隙减小,有利于催化反应的进行,其中,COOH修饰造成能级降低幅度最大。
【Abstract】 Polymolybdenum oxygen cluster/activated carbon(PMoO/AC) heterogeneous catalyst was prepared by impregnation method. The catalyst was characterized by Fourier infrared spectroscopy(FTIR), X-ray powder diffraction(XRD), specific surface area apeture tester(BET) and scanning electron microscope(SEM). Its catalysis and reuse performance in low concentration iodide ion oxidation by hydrogen peroxide were studied. The adsorption mechanism between PMoO and AC was studied by molecular mechanics and quantum chemistry. The results showed that the reaction rate reached 2.7×10-5 mol·L-1·s-1 under the condition that the mass fraction of polymolybdate oxygen cluster was 40%, the pH was 1.8, the concentration of hydrogen peroxide was 3.6 mmol/L, and the amount of catalyst was 1.0 g, Within 10 min, the conversion rate of iodide ion reached 99.7%, Compared to the system without catalyst, the reaction rate increased by 2.7×103 times and the conversion rate increased by 7.7%, and the catalyst has good reusability; PMoO can be adsorbed on the surface of activated carbon by physical adsorption, but different modified groups on the surface have different effects on the adsorption energy and even catalytic performance of PMoO: OH and NH2 can improve the physical adsorption stability of PMoO, while COOH can reduce the physical adsorption energy of activated carbon. All modified groups can be bonded with PMoO to form chemical adsorption, which could improve the stability of system. At the same time, the electronic properties of PMoO changed so as to lower the highest occupied orbital level(HOMO) and reduce the energy gap between them and the reactant hydrogen peroxide, which is conducive to the catalytic reaction.
【Key words】 polymolybdenum oxygen cluster; activated carbon; iodine ion; heterogeneous catalysis;
- 【文献出处】 化学世界 ,Chemical World , 编辑部邮箱 ,2020年10期
- 【分类号】O643.36;O613.44
- 【下载频次】307