Various manganese oxides (MnOx) 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 MnOx,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 T90 (the temperature when 90％ of benzene was catalytically oxidized) of 212℃.Further investigation showed that C2M1 was Mn2O3 with abundant nano-pores,the largest surface area and the proper ratio of surface Mn4+/Mn3+,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 CO2 and H2O.