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Series of α, β, γ, δ type MnO2 supported on LaMnO3 perovskite was developed by a one-pot synthesis route. Compared with α-MnO2, β-MnO2, γ-MnO2, δ-MnO2 and LaMnO3 oxides, all MnO2/LaMnO3 showed promotional catalytic performance for toluene degradation. Among them, α-MnO2/LaMnO3 holds the best active and mineralization efficiency. By the analysis of N2 adsorption-desorption, XPS and H2-TPR, it can be inferred that the improved activity should be ascribed to the higher proportion of lattice oxygen, better low-temperature reducibility and larger specific surface area. Besides, the byproducts from the low-temperature reaction of toluene oxidation were detected by a TD/GC-MS, confirming the presence of the intermediates. Combined with the in-situ DRIFTS, the catalytic degradation path of toluene oxidation has also been discussed in depth. [ABSTRACT FROM AUTHOR]

[Display omitted] A series of Sm-Mn perovskite@mullite composites with different amounts of acid sites were successfully synthesized by regulating the level of in situ etched-surface modification. X-ray diffraction (XRD) test showed that the crystal structure of catalyst gradually changed from perovskite to perovskite@mullite composites and mullite. The characterization of temperature programmed desorption with ammonia (NH 3 -TPD) confirmed the acid sites on the surface of catalyst can be deployed by the in-situ modification. The temperature-programmed reduction with hydrogen (H 2 -TPR), and N 2 adsorption–desorption showed that the surface modification also increased the reducibility, surface area, and mesoporosity of catalyst. The catalytic activities were compared by a long-term catalytic oxidation of chlorobenzene evaluation for 20 h of uninterrupted reaction at a relatively low temperature of 300 °C, and the Sm-Mn perovskite@mullite composite (SMPM-1.2) possessed the best catalytic stability. The X-ray photoelectron spectroscopy (XPS) measurement determined that the high ratios of lattice oxygen and tetravalent manganese did not improve the stability of catalyst in the catalytic oxidation of chlorobenzene, but the activities trends of samples were consistent with the change of surface (Mn4++Mn3+)/Mn2+ ratios. Meanwhile, the catalytic experiments for benzene, toluene, o-xylene and acetone showed that the as-prepared catalyst was also suitable for the efficient removal of the different types of VOCs. This work supplied a method for the further development of high activity catalysts for the removal of VOCs. [ABSTRACT FROM AUTHOR]

The selectivity of a facile reductive and extractive desulfurization process was studied. In this desulfurization method, polyethylene glycol was used as the extractant, and sodium borohydride was used as the reductant. Several different simulated fuels were prepared by dissolving thiophenic sulfides, methylbenzene and hexylene in octane. The results showed that methylbenzene and olefins had different effects on different sulfur compounds during this desulfurization process. The extraction and reduction mechanisms were also explained. Four factors could affect the desulfurization performance: (1) intermolecular hydrogen bonding: (a) active O bonding with aromatic H or (b) S bonding with H atoms in hydroxide radicals, (2) "like-dissolves-like" interactions between polyethylene glycol and thiophenic sulfides, (3) the methyl steric hindrance effect and the electron density of sulfur atoms, and (4) the combination of S atoms with produced nickel boride to form active desulfurization centres. The desulfurization reaction path was also deduced according to the GC/MS results. [ABSTRACT FROM AUTHOR]

• Cobalt, copper, cobalt and nickel were recovered from spent mobile phone batteries. • Cobalt-based composite oxides (Co 3 O 4 -M-500), as high-efficiency catalyst for toluene oxidation, was prepared from spent mobile phone batteries. • The presence of lithium can severely inhibit the catalytic activity of toluene oxidation over the Co 3 O 4 -M(Li)-500 catalyst. • The existence of synergistic effect among nickel, copper, manganese and cobalt plays a significant role in promoting the catalytic activity of Co 3 O 4 -M-500 catalyst. In order to recycle and reuse metal resources from spent ternary lithium batteries, manganese-based composite perovskite is synthesized from waste by citrate sol–gel method and is used as catalyst for VOC removal. The characterization results indicate that manganese-based composite perovskite catalyst has a crystal phase of LaMnO 3 , and owns higher specific surface area, better reductivity at low temperature, more abundant Mn4+ ions and lattice oxygen species than pure manganese perovskite catalyst. The results of catalytic evaluation show that manganese-based composite perovskite catalyst prepared from waste performs better catalytic performance of toluene oxidation in comparison with pure manganese perovskite. The effects of other cations existing in spent ternary lithium batteries are further investigated. The results imply that the catalytic performance can be significantly inhibited with the introduction of lithium ions, while appropriate amounts of copper, nickel and cobalt ions can improve the catalytic performance over pure manganese perovskite catalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • γ-MnO 2 /SmMnO 3 catalyst was prepared by an in situ etching method. • The catalyst showed superior activity for BETX removal at high WHSV and moisture. • The inner principle of VOCs oxidation was revealed by a dynamics investigation. • The strategy is low cost, scalable and efficient. Abstract γ-MnO 2 , SmMnO 3 , and γ-MnO 2 /SmMnO 3 catalysts were prepared by facile methods, wherein the SmMnO 3 (SMO) perovskite was synthesized through one-step calcination and the γ-MnO 2 /SmMnO 3 was formed by an in situ growth of γ-MnO 2 on the surface of SMO. These materials ware characterized by XRD, SEM-mapping, N 2 -adsorption, XPS and H 2 -TPR to investigate their textural properties. Compared with that of SMO and γ-MnO 2 , the γ-MnO 2 /SMO shows better performance for catalytic oxidation of aromatic VOCs in wet air (10 vol. %), which may be attributed to its higher surface molar ratio of lattice oxygen to adsorbed oxygen (O latt /O ads) and better low-temperature reducibility. Besides, for γ-MnO 2 /SMO catalyst, a successive oxidation route and the inner principle of BETX (benzene, ethylbenzene, toluene, and o-xylene) oxidation were also revealed via various tests and a comprehension of dynamics investigation. Meanwhile, the experiments under simulated realistic exhaust conditions displayed that the γ-MnO 2 /SmMnO 3 is also a good catalyst with high stability for aromatic VOCs oxidation, and fulfilled endurability to high humidity (20 vol.%). [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe4+, Co3+, Ni3+ and Cu3+ are introduced into MnO 2 by ozone driving redox. • The first functional group adsorbed on the surface of catalyst is confirmed. • The internal relationship of structure and catalytic behavior is revealed. • The byproducts and degradation path for low-temperature oxidation are explored. A series of heteroatom-doped MnO 2 have been successfully synthesized by the ozone driving redox reaction, wherein the Fe, Co, Ni and Cu were directly introduced into MnO 2. It was inferred that the doped heteroatoms existed in the form of Fe2+, Fe3+, Fe4+, Co3+, Ni3+, Cu2+ and Cu3+ in MnO 2 by the characterization of XRD, XPS, Raman and HRTEM. Their catalytic activities of toluene oxidation were positively correlated with the molar ratios of (Mn2++Mn3+)/Mn4+, the proportion of adsorbed oxygen species and the low-temperature reducibility. The larger radius of high-valence Fe ions led to obvious structural distortion of MnO 2 , which brought about more active oxygen species on the surface of the most active Fe-MnO 2. According to BET and SEM characterization, the high specific surface area and nanostructure should contribute to the high activity of Fe-MnO 2. In addition, the in-situ DRIFTS confirmed that the first functional group adsorbed on the surface of Fe-MnO 2 was the methyl group, and thus toluene was oxidized to some carbonyl-containing species. TD/GC–MS detection showed that the organic compounds existed in the exhaust gas. Ultimately, the catalytic mechanism and the degradation of toluene oxidation were also discussed. [ABSTRACT FROM AUTHOR]

A series of highly active manganese oxide with different oxygen species were synthesized by one pot method, wherein the active species were induced by in-situ combination of crystal phase. The scanning electron microscope (SEM) showed the successful combination of rodlike MnO 2 and flowerlike MnO 2. The x-ray diffraction (XRD) indicated an increase in the oxygen defects due to the in-situ assembly. Compared with that of pure α-MnO 2 and β-MnO 2 , the combined-phase x α/y β -MnO 2 ((x , y represents the molar ratio of α and δ) presented the higher activities for the catalytic oxidation of toluene. Through the analysis of X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction with hydrogen (H 2 -TPR) technologies, the order of catalytic activity was completely consistent with the change trend of the hydrogen consumption and the molar ratio of adsorbed oxygen/lattice oxygen (O ads /O latt), showing that the high catalytic activities of catalysts were main attributed to their more low-valent manganese and high content of adsorbed oxygen. Moreover, the intermediates of toloune oxidation over α/ β -MnO 2 with the best catalytic activity were detected by in-situ diffuse reflectance FTIR spectroscopy (DRIFTS), and the by-products in the exhaust gases were detected by a thermal desorption/gas chromatograph mass spectrometer (TD/GC–MS), which confirmed the presence of the intermediates. Furthermore, the catalytic mechanism and degradation path of toluene oxidation have been studied in depth. Finally, the effect of moisture on catalytic activity of α/δ-MnO 2 for toluene oxidation were also discussed. [Display omitted] • Active species on MnO 2 are adjusted by constructing dual-phase structure. • The deployment of crystal phase is realized by self-assembling the precursors. • The internal relationship of structure and catalytic behavior is also revealed. • The catalytic mechanism, intermediates and degradation path are explored. [ABSTRACT FROM AUTHOR]