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Applying a NOx trap catalyst to effectively remove NOx contaminants from the oxygen–rich exhaust is still very challenging, due to the lack of use guidance based on deactivation mechanisms. The temperature–dependent Pt sintering rate constant was described using Pt dispersion determined by pulse CO chemisorption. It was found that 700–850 °C was the determining temperature regions for the significant Pt sintering, according to the sintering kinetics and the evolution of active Ptδ+ sites. The weak basicity plays a critical role in trapping NOx at low–temperature (≤300 °C), and the NOx trap efficiency decreases because of the loss of catalytic activity and medium basicity caused by forming BaAl2O4 phase. The reduction of NOx towards N2 on the Pt crystallites smaller than 18 nm is structure sensitive and decreases with losing the reducibility of catalysts. The security for long–time use of a NOx trap catalyst should be exposed to the exhaust gas within 750 °C, and effectively removing NOx contaminants requires it to be worked in the 350–500 °C regions. These findings can guide engineers and applied chemists how to efficiently use a NOx trap catalyst in the automotive exhaust purification system. [ABSTRACT FROM AUTHOR]

Passive NOx adsorber (PNA) is one of the important means to effectively reduce NOx emission control in the cold start of a diesel engine. A series of Pd/SSZ-13 catalysts with different SiO2/Al2O3 ratios (11, 17, and 25) were prepared using the impregnation method. Furthermore, the effect of the SiO2/Al2O3 ratio on the adsorption performance of Pd/SSZ-13 at low-temperature NOx under realistic exhaust conditions was studied. The results show that the Pd/SSZ-13 catalyst with a low SiO2/Al2O3 ratio after loading Pd has a higher specific surface area and palladium ion content. There is a negative correlation between NOx adsorption performance and the SiO2/Al2O3 ratio. After high-temperature heat treatment, the acid sites closely related to palladium species increase and palladium species will redisperse, producing more palladium ions. The palladium ions coexist in Pd/SSZ-13 in the form of Pd2+ and Pd+, among which Pd2+ is divided into two types: Z−Pd2+Z− and Z−[Pd(II)OH]+. The NOx adsorption performance of the Pd/SSZ-13 catalyst was significantly improved, and the higher the SiO2/Al2O3 ratio, the more obviously the advantage of NOx adsorption performance increased after heat treatment. The NOx adsorption kinetic model of the Pd/SSZ-13 catalyst under realistic exhaust conditions was most suitably described by the pseudo-first-order model. [ABSTRACT FROM AUTHOR]

This study investigates the specific circulation anomalies that have sustained the low Antarctic sea ice state since 2016. Firstly, we find a significant strengthening and southward shift in the Ferrel Cell (FC) during 2016–2022, resulting in a marked increase in southward transport of heat and moisture. Secondly, this enhanced FC is closely associated with a stronger mid‐latitude wave pattern. This pattern is zonally asymmetric and greatly amplifies the poleward advections of heat and moisture, leading to the increased downward longwave radiation, more liquid precipitation and sea ice retreat in specific regions, including the western Pacific and Indian Ocean sectors, Ross and northern Weddell Seas. The mechanism deduced from the short‐term period is further supported by the results of 40 ensemble members of simulations. The southward expansion of the FC and sea ice decline are closely linked to La Niña‐like conditions but may also be driven by anthropogenic global warming. Plain Language Summary: Following the sudden decline in 2016, the Antarctic sea ice extent has persisted at historically low levels. In 2023, it reached unprecedented record lows. However, the specific atmospheric circulation anomalies that have sustained the Antarctic sea ice at low levels are still unknown. It is well‐established that the Ferrel Cell, a mid‐latitude atmospheric meridional circulation, plays a pivotal role in the energy exchange between the high‐ and mid‐latitudes. Our findings indicate that the enhanced Ferrel Cell zonally intensified southward transport of heat and moisture over the sea ice regions, which sustains the overall low Antarctic sea ice state. Additionally, in the horizontal plane, the enhanced mid‐latitude wave pattern is responsible for the regional sea ice retreat over the western Pacific sector, Ross Sea, Indian Ocean sector, and northern Weddell Sea, and is also closely associated with the enhanced Ferrel Cell. The effects of the enhanced Ferrel Cell on Antarctic sea ice decline are further supported by the results of large ensemble simulations. Therefore, this study suggests that concurrent with the southward shifting of the Ferrel Cell, the stronger warm and moist air intrusions, and the increased liquid precipitation, restrict the Antarctic sea ice expansion following its sudden decline. Key Points: Since 2016, the low Antarctic sea ice extent has persisted, consistent with heat and moisture accumulation over the sea ice edgesThe Ferrel Cell was enhanced and shifted southward, leading to the increased southward heat/moisture advection, and liquid precipitationThe effects of the enhanced Ferrel Cell on Antarctic sea ice decline are further supported by the results of large ensemble simulations [ABSTRACT FROM AUTHOR]

In order to obtain a lightweight, high-strength, and customizable cellular structure to meet the needs of modern production and life, the mechanical properties of four thickness gradient honeycomb structures were studied. In this paper, four types of honeycomb structure specimens with the same porosity and different Poisson's ratios were designed and manufactured by using SLA 3D-printing technology, including the honeycomb, square honeycomb, quasi-square honeycomb, and re-entrant honeycomb structures. Based on the plane compression mechanical properties and failure mode analysis of these specimens, the thickness gradient is applied to the honeycomb structure, and four structural forms of the thickness gradient honeycomb structure are formed. The experimental results show that the thickness gradient honeycomb structure exhibits better mechanical properties than the honeycomb structure with a uniform cellular wall thickness. In the studied thickness gradient honeycomb structure, the mechanical properties of the whole structure can be significantly improved by increasing the thickness of cell walls at the upper and lower ends of the structure. The wall thickness, arrangement order, shape, and Poisson's ratio of the cell all have a significant impact on the mechanical properties of the specimens. These results provide an effective basis for the design and application of cellular structures in the future. [ABSTRACT FROM AUTHOR]

Methane is the second largest greenhouse gas, with an annual warming potential 26~28 times that of CO2. The main components of exhaust emissions from natural gas vehicles are incompletely burned methane waste gas and high concentrations of water (up to 20%). Numerous studies have indicated that water can significantly affect the catalytic stability of the Pd active component and the alumina support. Therefore, the treatment of methane in high-humidity exhaust gas has been a hot research topic in the post-treatment catalysts for natural gas vehicles. How to treat these low-concentration methane waste gases in a high-humidity atmosphere has always been a hot topic in academic research. In this study, modified supports (AlLa5, AlLa10, and AlLa15) were prepared using the incipient wetness impregnation method, and 0.5% Pd was loaded onto the modified supports and unmodified support (γ-Al2O3) using the excess impregnation method. The effect of the introduction of La on the water-thermal stability of the catalyst for methane oxidation was investigated. The prepared catalysts were characterized by N2 physical adsorption-desorption, CO-TPR, XPS, and XRD. The results showed that the addition of La significantly improved the water-thermal stability of the catalyst in methane oxidation, with Pd/AlLa5 exhibiting the best hydrothermal-resistant performance. [ABSTRACT FROM AUTHOR]