Effects of different methods of introducing Mo on denitration performance and anti-SO2 poisoning performance of CeO2

Catalytic removal of gaseous pollutant NO using CO: Catalyst structure and reaction mechanism

Carbon monoxide (CO) has recently been considered an ideal reducing agent to replace NH3 in selective catalytic reduction of NOx (NH3-SCR). This shift is particularly relevant in diesel engines, coal-fired industry, the iron and steel industry, of which generate substantial amounts of CO due to incomplete combustion. Developing high-performance catalysts remain a critical challenge for commercializing this technology. The active sites on catalyst surface play a crucial role in the various microscopic reaction steps of this reaction. This work provides a comprehensive overview and insights into the reaction mechanism of active sites on transition metal- and noble metal-based catalysts, including the types of intermediates and active sites, as well as the conversion mechanism of active molecules or atoms. In addition, the effects of factors such as O2, SO2, and alkali metals, on NO reduction by CO were discussed, and the prospects for catalyst design are proposed. It is hoped to provide theoretical guidance for the rational design of efficient CO selective catalytic denitration materials based on the structure-activity relations.

Enhanced degradation of polyethylene terephthalate plastics by CdS/CeO2 heterojunction photocatalyst activated peroxymonosulfate

Waste plastics have posed enormous to the environment, but their recycling, especially polyethylene terephthalate plastics, was still a huge challenge. Here, CdS/CeO₂ was used as the photocatalyst to promote the degradation of PET-12 plastics by activating peroxymonosulfate (PMS) synergistic photocatalytic system. The results showed that 10 % CdS/CeO₂ had the best performance under the illumination condition, and the weight loss rate of PET-12 could reach 93.92 % after adding 3 mM PMS. The effects of important parameters (PMS dose and co-existing anions) on PET-12 degradation were systematically studied, and the excellent performance of the photocatalytic-activated PMS system was verified by comparison experiments. SO₄^•- contributed the most to the degradation performance of PET-12 plastics, which was demonstrated by electron paramagnetic resonance (EPR) and free radical quenching experiments. Furthermore, the results of GC showed that the gas products including CO, and CH₄. This indicated that the mineralized products could be further reduced to hydrocarbon fuel under the action of the photocatalyst. This job supplied a new idea for the photocatalytic treatment of waste microplastics in the water, which will help recycle waste plastics and recycle carbon resources.

Promotional effects of Nb5+ and Fe3+ co-doping on catalytic performance and SO2 resistance of MnOx-CeO2 low-temperature denitration catalyst

As we know, SO₂ can cause MnO_x-CeO₂ (MnCeO_x) catalyst poisoning, which seriously shortens the service life of the catalyst. Therefore, to enhance the catalytic activity and SO₂ tolerance of MnCeO_x catalyst, we modified it by Nb⁵⁺ and Fe³⁺ co-doping. And the physical and chemical properties were characterized. These results illustrate that the Nb⁵⁺ and Fe³⁺ co-doping can optimally improve the denitration activity and N₂ selectivity of MnCeO_x catalyst at low temperature by improving its surface acidity, surface adsorbed oxygen as well as electronic interaction. What's more, NbO_x-FeO_x-MnO_x-CeO₂ (NbFeMnCeO_x) catalyst possesses an excellent SO₂ resistance due to less SO₂ being adsorbed and the ammonium bisulfate (ABS) formed on its surface tends to decompose, as well as fewer sulfate species formed on its surface. Finally, the possible mechanism that Nb⁵⁺ and Fe³⁺ co-doping enhances the SO₂ poisoning resistance of MnCeO_x catalyst is proposed.

Understanding structure-performance relationships of CoOx/CeO2 catalysts for NO catalytic oxidation: Facet tailoring and bimetallic interface designing

Crystalline structure and bimetallic interaction of metal oxides are essential factors to determine the catalytic activity. Herein, three different CoO_x/CeO₂ catalysts, employing CeO₂ nanorods (predominately exposed {110 facet), CeO₂ nanopolyhedra ({111} facet) and CeO₂ nanocubes ({100} facet) as the supports, are successfully prepared for investigating the effect of exposed crystal facets and bimetallic interface interaction on NO oxidation. In comparison with the {111} and {100} facets, the exposed crystal facet {110} exists the best superiority to anchor and stabilize Co species. Moreover, ultra-small CoO_x clusters composed of strong Co-O coordination shells with minor Co-O-Ce interaction are formed and uniformly dispersed on the CeO₂ nanorods. Structural characterizations reveal that the active exposed crystal facet {110} and the strong bimetallic interface interaction in CoO_x/CeO₂-nanorods (R-CC) result in more structural defect, endowing it with abundant oxygen vacancies, excellent reducibility and strong adsorption capacity. The DRIFTs spectra further indicate that the exposed crystal facet {110} has a significant promoting effect on the strength of nitrates compared with {111} and {100} facets. The bimetallic interface interaction not only significantly facilitates the formation of nitrate species at lower temperature, but also effectively suppresses the generation of sulfate and lower the sulphation rate. Therefore, R-CC catalyst exhibits the maximum NO oxidation activity with the conversion of 86.4 % at 300 °C and still sustains its high activity under cyclic condition or 50 ppm SO₂. The provided crystalline structure and interaction-enhanced strategy sheds light on the design of high-activity NO oxidation catalysts.

Insight into the potential application of CuOx/CeO2 catalysts for NO removal by CO: a perspective from the morphology and crystal-plane of CeO2

A series of CuOx/CeO2-X were fabricated and employed as the NO + CO reaction catalysts.