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BACKGROUND: Benzene (C6H6) is a typical kind of volatile organic compound (VOC) which can exert great harm to both human health and the environment, and, thus, which needs to be eliminated before its emission. In this work, porous manganese–nickel (Mn‐Ni) composite oxide catalysts were synthesized through the oxalate route and applied to thermal catalytic oxidation of C6H6. By means of activity tests and relative physico‐chemical characterizations, the factors affecting the activity of those Mn‐Ni composite oxides were explored. RESULTS: Nitrogen (N2)‐adsorption/desorption and X‐ray photoelectron spectroscopy (XPS) measurements indicated that the Brunauer–Elmett–Teller (BET) surface area and the content of surface‐adsorbed oxygen species were increased due to the addition of Ni into Mn oxide (MnOx). Meanwhile, the oxygen mobility and reducibility also were improved in the Mn‐Ni composite oxides. Accordingly, compared with MnOx, the Mn‐Ni catalysts showed higher activity for thermal catalytic oxidation of C6H6. Moreover, porous Mn‐Ni composite oxides with a Mn:Ni molar ratio of 4:1 (Mn4Ni1) displayed the best catalytic activity. Further investigation indicated that the excellent catalytic performance of Mn4Ni1 composite oxides could be ascribed mainly to the larger BET surface area and the richer content of surface‐adsorbed oxygen species, as well as stronger oxygen mobility and better reducibility compared with other Mn‐Ni catalysts. CONCLUSIONS: The Mn4Ni1 composite oxides showed a lowest T90 value of 172 °C (C6H6 concentration 200 ppm, WHSV 60 000 mL g−1 h−1) among all of the obtained Mn‐Ni composite oxides. Moreover, it also exhibited favourable catalytic stability at 210 °C in the presence or absence of moisture. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Series of MnOx catalysts were synthesized through oxalate route and calcined at facile temperatures. Characterizations through XRD, N2-adsorption/desorption, HRTEM, C6H6-TPD, O2-TPD, XPS, and H2-TPR revealed that MnOx calcined at 250 °C (N250) with a main crystal phase of Mn2O3 showed micro-mesopores and largest specific surface area, and therefore had a high adsorption capacity of C6H6. N250 also presented better oxygen mobility, rich surface adsorbed oxygen species (Oads), and proper ratio of surface Mn4+/Mn3+. The starting temperature of H2-TPR of N250 was the lowest among the obtained MnOx samples. As a result, N250 exhibited the lowest T90 value of 191 °C in C6H6 thermal catalytic oxidation (WHSV 60,000 mL gcat.−1 h−1, initial C6H6 concentration 190 ppm) among all the catalysts, and this T90 value is lower than those reported in many research. At last, a potential reaction pathway was proposed according to the results of in-situ FTIR measurement. [ABSTRACT FROM AUTHOR]

Various manganese oxides (MnO x) 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 MnO x , 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 Mn 2 O 3 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 CO 2 and H 2 O. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In this study, rod-like Co 3 O 4 (Co 3 O 4 -rod) nanocatalyst was prepared by a modified precipitation method, which showed an excellent performance for formaldehyde oxidation to carbon dioxide and water. The light-off temperature (10% conversion) and the temperature for complete conversion of formaldehyde was at 60 °C and 120 °C, respectively. XPS and CO 2 -TPD analyses indicated that Co 3 O 4 -rod had abundant Co 3 + and OH (hydroxyl) species on the surface compared with other morphologies of Co 3 O 4 investigated (e.g. Co 3 O 4 -sheet and Co 3 O 4 -cube). It was proposed that Co 3 + ions should be considered as active sites of good oxidation ability for formaldehyde catalytic oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hollow spherical-shell NiO was prepared by a ligand modulation MOFs-derived method. • Hollow NiO improved benzene conversion and CO 2 selectivity, reducing energy consumption significantly. • Abundant surface O species of NiO are activated by plasma and thus induce superior catalytic ability. • Synergistic effect was clarified as NiO enhancing plasma field while plasma inspiring NiO oxidation ability. While catalyst morphology plays an essential role in traditional thermal catalysis, the specific effects in plasma catalysis deserve further in-depth study. In the present study, hollow NiO nanospheres with a rambutan-like structure were successfully prepared by MOFs-derived method involving morphology modulation, and employed for the in-plasma catalytic oxidation of benzene. The results show an enhancement of 60 % for benzene removal, while CO 2 selectivity was increased by 20 %. The energy consumption for 95 % benzene removal efficiency (RE 95%) was also reduced from 3600 J/L to 1100 J/L. Specifically, the hollow spherical shell structure is more abundant in surface oxygen species, including chemisorbed oxygen and surface lattice oxygen, which can be activated by plasma; the hollow structure also modulates the plasma discharge by shielding effect. The plasma field in turn also excites the oxidation activity of NiO, thus achieving the synergistic effect. In addition, a more comprehensive benzene decomposition pathway is proposed by analysis of the gaseous and non-gaseous intermediates (tar), where the plasma non-selectively breaks the chemical bonds of reactants and the catalyst selectively oxidizes the organic intermediates to CO 2 , and they promote each other to achieve synergistic effects. [ABSTRACT FROM AUTHOR]