Synthesis of mixed oxides AMn2O4 (Co, Cu and Ni) prepared by auto combustion to control emissions of volatile organic compounds

ABSTRACT Volatile organic compounds (VOCs) have a high vapor pressure and low water solubility and are recognized either as major contributors of air pollution either, through their toxic nature, or as precursors of ozone and photochemical smog. The objectives of this work were to synthesize several manganite oxides under the same preparation conditions and the study of their properties and activities to develop as friendly environmental catalysts in oxidation of toluene, the VOC more abundant in the Earth's atmosphere. AMn2O4 (A=Co, Ni, Cu) manganite spinels were prepared by using by using auto combustion method under the same synthesis conditions and their physico-chemical properties were studied by XRD, BET, FTIR and MEV. The relationship between the properties and activity of spinels in oxidation of toluene was investigated. Among all, Cu and Co catalysts exhibited the most promising activity, converting 92 and 99%, respectively. The higher activity was explained in terms of the possible synergetic effect between Mn3+ and Co2+, Cu2+ phases in that manganite oxides. No direct relationship was resulted between activity with either specific surface area.

摘要 挥发性有机化合物（Volatile Organic Compounds，VOCs）具有高蒸气压与低水溶性的特性，其既会因毒性特征成为大气污染的主要贡献源，也可作为臭氧与光化学烟雾的前体物。本研究旨在在统一制备条件下合成多种锰尖晶石氧化物，并探究其理化性能与催化活性，以开发适用于甲苯氧化反应的环境友好型催化剂——甲苯是地球大气中含量最为丰富的挥发性有机化合物。本研究采用自燃烧法，在相同合成条件下制备了AMn₂O₄（A=Co、Ni、Cu）型锰尖晶石，并通过X射线衍射（X-ray Diffraction，XRD）、布鲁诺尔-埃米特-特勒比表面分析法（Brunauer-Emmett-Teller，BET）、傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy，FTIR）以及MEV对其理化性质进行了表征，同时探究了该类锰尖晶石在甲苯氧化反应中的性能与催化活性之间的关联。结果表明，在所有受试催化剂中，铜基与钴基催化剂表现出最优异的催化活性，甲苯转化率分别可达92%与99%。该优异催化活性可归因于该锰氧化物中Mn³+与Co²+、Cu²+物相之间可能存在的协同效应；研究未发现催化活性与比表面积之间存在直接关联。