Investigation of chlorine-poisoning mechanism of MnOx/TiO2 and MnOx-CeO2/TiO2 catalysts during o-DCBz catalytic decomposition: Experiment and first-principles calculation

New mechanistic insight into catalytic decomposition of dioxins over MnOx-CeO2/TiO2 catalysts: A combined experimental and density functional theory study

Elucidation of the catalytic decomposition mechanism of dioxins is pivotal in developing highly efficient dioxin degradation catalysts. In order to accurately simulate the whole molecular structure of dioxins, two model compounds, o-dichlorobenzene (o-DCB) and furan, were employed to represent the chlorinated benzene ring and oxygenated central ring within a dioxin molecule, respectively. Experiments and Density Functional Theory (DFT) calculations were combined to investigate the adsorption as well as oxidation of o-DCB and furan over MnOx-CeO2/TiO2 catalyst (denoted as MnCe/Ti). The results indicate that competitive adsorption exists between furan and o-DCB. The former exhibits superior adsorption capacity on MnCe/Ti catalyst at 100 °C - 150 °C, for it can adsorb on both surface metal atom and surface oxygen vacancies (Ov) via its O-terminal; while the latter adsorbs primarily by anchoring its Cl atom to surface Ov. Regarding oxidation, furan can be completely oxidized at 150 °C - 300 °C with a high CO2 selectivity (above 80 %). However, o-DCB cannot be totally oxidized and the resulting intermediates cause the deactivation of catalyst. Interestingly, the pre-adsorption of furan on catalyst surface can facilitate the catalytic oxidation of o-DCB below 200 °C, possibly because the dissociated adsorption of furan may form additional reactive oxygen species on catalyst surface. Therefore, this work provides new insights into the catalytic decomposition mechanism of dioxins as well as the optimization strategies for developing dioxin-degradation catalysts with high efficiency at low temperature.

Ash problems and prevention measures in power plants burning high alkali fuel: Brief review and future perspectives

Large-scale utilization of high-alkali fuels is considered an effective solution for alleviating energy shortages and reducing CO2 emissions. However, combustion of high-alkali fuels in boilers releases alkali metals into the flue gas, which leads to severe ash deposition and corrosion on the heating surface. Consequently, research into the efficient use of highly alkaline fuels has been conducted in recent years. In this review, ash issues and measures for their prevention during high-alkali fuel combustion are summarized. First, the characteristics of fly ash produced from high-alkali fuel combustion are reviewed, and the form, migration, and deposition characteristics of alkali metals are summarized. Subsequently, research progress of high alkali fuel ash is introduced in detail. Mechanisms of slagging, fouling, corrosion on the heating surface and the selective catalytic reduction (SCR) unit deactivation are summarized. Prevention and control methods for the high-alkali fuel ash problem are then introduced. Finally, based on current research, existing problems and future development directions for high-alkali fuel research are proposed. Through this review, we hope to provide insights into the effective utilization of high-alkali fuels.

Low-energy production of a monolithic catalyst with MnCu-synergetic enhancement for catalytic oxidation of volatile organic compounds

Producing a low-cost catalyst by a low-cost method is one of the hottest topics in the field of catalytic oxidization of volatile organic compounds (VOCs). In this work, a catalyst formula with a low-energy requirement was optimized in the powdered state, and verified in the monolithic state. An effective MnCu catalyst was synthesized at a temperature as low as 200 °C. Removals were all bigger than 88% for toluene, ethyl acetate, hexane, formaldehyde, and cyclohexanone at a low temperature of 240 °C. The MnCu catalyst was then loaded on a honeycomb cordierite, which was also effective for toluene removal at 240 °C. After characterizations, active phases were Mn₃O₄/CuMn₂O₄ in both the powdered and monolithic catalysts. The enhanced activity was attributed to balanced distributions of low-valence Mn and Cu, as well as abundant surface oxygen vacancies. The obtained catalyst is produced by low energy and effective at low temperature, which suggests a perspective application.

The research on CO oxidation over Ce-Mn oxides: The preparation method effects and oxidation mechanism

A series of CeO₂-MnO_x for highly efficient catalytical oxidation of carbon monoxide were prepared by citrate sol-gel (C), hydrothermal (H) and hydrothermal-citrate complexation (CH) methods. The outcome indicates that the catalyst generated using the CH technique (CH-1:8) demonstrated the greatest catalytic performance for CO oxidation with a T₅₀ of 98 °C, and also good stability in 1400 min. Compared to the catalysts prepared by C and H method, CH-1:8 has the highest specific surface of 156.1 m² g^-1, and the better reducibility of CH-1:8 was also observed in CO-TPR. It is also observed the high ratio of adsorbed oxygen/lattice oxygen (1.5) in the XPS result. Moreover, characterizations by the TOF-SIMS method indicated that obtained catalyst CH-Ce/Mn = 1:8 had stronger interactions between Ce and Mn oxides, and the redox cycle of Mn³⁺+Ce⁴⁺ ↔ Mn⁴⁺+Ce³⁺ was a key process for CO adsorption and oxidation process. According to in-situ FTIR, the possible reaction pathway for CO was deduced in three ways. CO directly oxidize with O₂ to CO₂, CO adsorbed on Mn⁴⁺ and Ce³⁺ reacts with O to form intermediates (COO^-) (T > 50 °C) and carbonates (T > 90 °C), which are further oxidized into CO₂.

Promoting effect of Ru-doped Mn/TiO2 catalysts for catalytic oxidation of chlorobenzene

Mn/TiO2 catalysts were synthesized using deposition-precipitation method. Ru-doped Mn/TiO2 catalysts were prepared by incipient-wetness impregnation method. To investigate the effect of Ru and Mn species, the catalytic performances of Mn/TiO2...