Search

Oxygen vacancy regulation in metal catalysts has emerged as a crucial strategy for efficiently degrading volatile organic compounds (VOCs), while the acquisition of kinetic and mechanistic insights into the oxygen vacancy roles remains highly desirable yet challenging. Herein, we conduct a combined kinetics and mechanistic investigation into the oxygen vacancy effects of Cu catalysts on toluene oxidation. Cu catalysts with varying oxygen vacancy contents are prepared using three representative metal oxide supports, including reducible ZrO2 with strong oxygen storage capacity, reducible ZnO, and unreducible Al2O3. Toluene oxidation and CO oxidation are tested for these catalysts, revealing the superior catalytic activity of the Cu/ZrO2 catalyst. Multiple characterization studies demonstrate that the strong reducibility and abundance of oxygen vacancies within the Cu/ZrO2 catalyst are the key factors for these reactions. A redox-based kinetics strategy is further applied to decouple the reduction and oxidation steps, thus affording a rate diagram to elucidate the promotional effects of oxygen vacancies on toluene decomposition. Additionally, in situ DRIFTS study unveils the reaction pathway, showing the transformation from toluene into benzyl alcohol, benzaldehyde, benzoate, phenol, anhydride, carbonate, and ultimately CO2. As a result, the oxygen vacancy-tuned rate-relevant step is disclosed, shifting from C–H bond cleavage for the Cu/Al2O3 catalyst with limited oxygen vacancies to the C＝O and C＝C bond cleavage for the Cu/ZnO and Cu/ZrO2 catalysts with more oxygen vacancies. The kinetic and mechanistic insights gained here would help guide the design of highly efficient oxidative catalysts by tuning the oxygen vacancies of the support. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET) hydrogenolysis can produce benzene, toluene, and xylene (BTX), where the selectivity control is challenging. We report a reaction pathway dictated by the Ru coordination environment by examining the binding geometries of adsorbates on differently coordinated Ru centers and their evolution during PET hydrogenolysis. A BTX yield of 77 % was obtained using a Ru/TiO2 with a Ru coordination number of ca. 5.0 where edge/corner sites are dominant, while more gas and saturated products were formed for Ru/TiO2 containing primarily terrace sites. Density functional theory and isotopic labelling revealed that under‐coordinated Ru edge sites favor "upright" adsorption of aromatic adsorbates while well‐coordinated Ru sites favor "flat‐lying" adsorption, where the former mitigates ring hydrogenation and opening. This study demonstrates that reaction pathways can be directed through controlled reactant/intermediate binding via tuning of the Ru coordination environment for efficient conversion of PET to BTX. [ABSTRACT FROM AUTHOR]

Methyl methacrylate (MMA) is an important monomer for the production of acrylic plastics and polymer dispersions. In this study, we demonstrate a strategy to synergize the electronic and geometric effects of the Au/CeO2 catalyst, achieving three orders of magnitude improvement in reaction rate for the oxidative esterification of methacrolein to MMA. The electronic properties of Au in terms of the valence electron population of 5d states are decoupled from the redox ability and acid–base properties of catalyst support as the main cause for the significant increase in the specific activity of the active site. Moreover, the Au edge site is identified as the main active site for this reaction, whose number reaches the maximum for the 1.6 nm‐sized Au particles. Hence, the synergism between the electronic (lower valence electron population of 5d states) and geometric (more edge active sites) promotions of the Au‐10/CeO2 catalyst contributes to the highest catalytic activity. [ABSTRACT FROM AUTHOR]

China is in a critical air quality management stage. Rapid industrial development and urbanization has resulted in non‐ignorable air pollution, which seriously endangers human health. Assessment of the health impacts and economic losses of air pollution is essential for the prevention and control policy formulation. Based on ozone (O3) and fine particulate matter concentration (PM2.5) monitoring data in 331 Chinese cities from 2015 to 2020, this study evaluated the health effects and the corresponding economic losses of O3 and PM2.5 pollution on three health endpoints. The ratio of population exposed to O3 levels that exceeded the Chinese Ambient Air Quality Standards (CAAQS) increased from 13.35% in 2015 to 14.15% in 2020, which resulted in 133,415 (2015) ‐ 156,173 (2020) all‐cause deaths, 88,941 (2015) ‐ 104,051 (2020) cardiovascular deaths, and 28,614 (2015) ‐ 33,456 (2020) respiratory deaths. The ratio of population exposed to PM2.5 levels that exceeded the CAAQS decreased, but in many regions, especially in North China and the Yangtze River Delta, the PM2.5 concentration remained high. By 2020, nearly half of the population in China was still exposed to PM2.5 levels that exceeded the CAAQS, and the corresponding economic losses reached CNY 3.46 and 3.05 billion, respectively. These results improved the understanding of the spatial‐temporal variation trends of major air pollutants at city scale in China, and emphasize the continued coordination urgently needed for controlling O3 and PM2.5 following the implementation of the 2013 policy to mitigate air pollution to protect human health. Plain Language Summary: Based on ozone (O3) and fine particulate matter concentration monitoring data in 331 Chinese cities from 2015 to 2020, this study adopted the health impact assessment model to evaluate the health effects of O3 and PM2.5 pollution on three health endpoints: premature, cardiovascular and respiratory mortality. Key Points: PM2.5 showed a significant decrease but still severe impacts on human healthOzone (O3) is posing an increasingly serious threat to human health and economic loss in ChinaCoordinated control of PM2.5 and O3 is essential [ABSTRACT FROM AUTHOR]