Catalytic degradation of benzene over non-thermal plasma coupled Co-Ni binary metal oxide nanosheet catalysts

Non-thermal plasma(NTP)has been demonstrated as one of the promising technologies that can degrade volatile organic compounds(VOCs)under ambient condition.However,one of the key challenges of VOCs degradation in NTP is its relatively low mineralization rate,which needs to be addressed by introducing catalysts.Therefore,the design and optimization of catalysts have become the focus of NTP coupling catalysis research.In thiswork,a series of two-dimensional nanosheet Co-Ni metal oxides were synthesized by microwave method and investigated for the catalytic oxidation of benzene in an NTP-catalysis coupling system.Among them,Co_(2)Ni_(1)O_(x)achieves 60%carbon dioxide(CO_(2))selectivity(SCO_(2))when the benzene removal efficiency(REbenzene)reaches more than 99%,which is a significant enhancement compared with the CO_(2)selectivity obtained without any catalysts(38%)under the same input power.More intriguingly,this SCO_(2)is also significantly higher than that of single metal oxides,NiO or Co_(3)O_(4),which is only around 40%.Such improved performance of this binary metal oxide catalyst is uniquely attributed to the synergistic effects of Co and Ni in Co_(2)Ni_(1)O_(x)catalyst.The introduction of Co_(2)Ni_(1)O_(x)was found to promote the generation of acrolein significantly,one of the key intermediates found in NTP alone system reported previously,suggest the benzene ring open reaction is promoted.Compared with monometallic oxides NiO and Co_(3)O_(4),Co_(2)Ni_(1)O_(x)also shows higher active oxygen proportion,better oxygenmobility,and stronger low-temperature redox capability.The above factors result in the improved catalytic performance of Co_(2)Ni_(1)O_(x)in the NTP coupling removal of benzene.

Catalytic activity of porous manganese oxides for benzene oxidation improved via citric acid solution combustion synthesis

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 T(90)(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 Mn^4+/Mn^3+, 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.