Expediting Toluene Combustion by Harmonizing the Ce–O Strength over Co-Doped CeZr Oxide Catalysts

Environmental Science & Technology, Journal Year: 2023, Volume and Issue: 57(4), P. 1797 - 1806

Published: Jan. 13, 2023

Low-temperature catalytic degradation of volatile organic compounds (VOCs) by enhancing the activity non-precious metal catalysts has always been focus attention. The mineralization aromatic VOCs requires participation a large number oxygen atoms, so activation species is crucial in reaction. Herein, we originally adjust Ce-O bond strength CeZr oxide cobalt doping to promote species, thus improving toluene performance while maintaining high stability. Subsequent characterizations and theoretical calculations demonstrate that weakening increases vacancy content, promotes enhances redox ability catalysts. This strategy also accelerates depletion intermediate species. study will contribute enhance non-noble catalysts, thereby VOCs.

Language: Английский

---

Boosting toluene deep oxidation by tuning metal-support interaction in MOF-derived Pd@ZrO2 catalysts: The role of interfacial interaction between Pd and ZrO2

Fuel, Journal Year: 2023, Volume and Issue: 357, P. 129833 - 129833

Published: Sept. 20, 2023

Language: Английский

---

Modulating the Electronic Metal‐Support Interactions in Single‐Atom Pt₁−CuO Catalyst for Boosting Acetone Oxidation

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(28)

Published: March 29, 2022

The development of highly active single-atom catalysts (SACs) and identifying their intrinsic sites in oxidizing industrial hazardous hydrocarbons are challenging prospects. Tuning the electronic metal-support interactions (EMSIs) is valid for modulating catalytic performance SACs. We propose that modulation EMSIs a Pt1 -CuO SAC significantly promotes activity catalyst acetone oxidation. promote charge redistribution through unified Pt-O-Cu moieties, which modulates d-band structure atomic Pt sites, strengthens adsorption activation reactants. positively charged atoms superior activating at low temperatures, stretched Cu-O bonds facilitate lattice oxygen to participate subsequent believe this work will guide researchers engineer efficient SACs application hydrocarbon oxidation reactions.

Language: Английский

---

Molecular Analysis of Secondary Brown Carbon Produced from the Photooxidation of Naphthalene

Environmental Science & Technology, Journal Year: 2022, Volume and Issue: 56(6), P. 3340 - 3353

Published: March 1, 2022

We investigate the chemical composition of organic light-absorbing components, also known as brown carbon (BrC) chromophores, formed in a proxy anthropogenic secondary aerosol generated from photooxidation naphthalene (naph-SOA) absence and presence NOx. High-performance liquid chromatography equipped with photodiode array detector electrospray ionization high-resolution mass spectrometer is employed to characterize naph-SOA its BrC components. provide molecular-level insights into optical properties individual components their relevance. This work reveals formation strongly absorbing nitro-aromatic chromophores under high-NOx conditions describes degradation during atmospheric aging. NOx addition enhanced light absorption while reducing wavelength-dependence, seen by coefficient (MAC) Ångström exponent (AAE). Optical parameters low- showed range values MACOM 405nm ∼ 0.12 m2 g–1 AAE300–450nm 8.87 (low-NOx) 0.19 7.59 (high-NOx), consistent "very weak" "weak" classes, respectively. The weak-BrC class commonly attributed biomass smoldering emissions, which appear have comparable naph-SOA. Molecular contributing were identified substantial nitro-aromatics, indicating that these species may be used source-specific markers related emissions.

Language: Английский

---

Low-Temperature Combustion of Toluene over Cu-Doped SmMn₂O₅ Mullite Catalysts via Creating Highly Active Cu²⁺–O–Mn⁴⁺ Sites

Environmental Science & Technology, Journal Year: 2022, Volume and Issue: 56(14), P. 10433 - 10441

Published: June 25, 2022

Catalytic combustion of volatile organic compounds (VOCs) at low temperatures is still an urgent issue to be solved. Herein, low-temperature toluene over Cu-doped SmMn2O5 mullite catalysts via creating highly active Cu2+-O-Mn4+ sites has been originally demonstrated. exhibited 90% conversion 206 °C and displayed robust stability even in the presence water. It demonstrated that Cu doping created composite were more exposed after removing surface Sm species acid-etching. Benefiting from this, redox oxygen activation ability was significantly enhanced. The consumption benzaldehyde benzoic acid as intermediate CO2 generation apparently promoted, which direct reasons for enhanced toluene. This work provides novel ideas development high-performance VOC combustion, great industrial application prospects.

Language: Английский

---

Nitrogen-Containing Compounds Enhance Light Absorption of Aromatic-Derived Brown Carbon

Environmental Science & Technology, Journal Year: 2022, Volume and Issue: 56(7), P. 4005 - 4016

Published: Feb. 22, 2022

The formation of secondary brown carbon (BrC) is chemically complex, leading to an unclear relationship between its molecular composition and optical properties. Here, we present in-depth investigation molecular-specific properties aging BrC produced from the photooxidation ethylbenzene at varied NOx levels for first time. Due pronounced unsaturated products, mass absorption coefficient (MAC) organic aerosols (ESOA) 365 nm was higher than that biogenic SOA by a factor 10. A high level ([ethylbenzene]0/[NOx]0 < 10 ppbC ppb–1) found significantly increase average MAC300–700nm ESOA 0.29 m2 g–1. data two complementary high-resolution spectrometers quantum chemical calculations suggested nitrogen-containing compounds were largely responsible enhanced light high-NOx ESOA, multifunctional nitroaromatic (such as C8H9NO3 C8H9NO4) identified important chromophores. High-NOx underwent photobleaching upon direct exposure ultraviolet light. Photolysis did not lead significant decomposition C8H9NO4, indicating may serve relatively stable nitrogen reservoirs would effectively absorb solar radiation during daytime.

Language: Английский

---

Molecular insights into the composition, sources, and aging of atmospheric brown carbon

Chemical Society Reviews, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

The light-absorbing chemical components of atmospheric organic aerosols are commonly referred to as Brown Carbon (BrC), reflecting the characteristic yellowish brown appearance aerosol.

Language: Английский

---

Optical Properties of Secondary Organic Aerosol Produced by Photooxidation of Naphthalene under NOx Condition

Environmental Science & Technology, Journal Year: 2022, Volume and Issue: 56(8), P. 4816 - 4827

Published: April 6, 2022

Secondary organic aerosols (SOAs) affect incoming solar radiation by interacting with light at ultraviolet and visible wavelength ranges. However, the relationship between chemical composition optical properties of SOA is still not well understood. In this study, complex refractive index (RI) produced from OH oxidation naphthalene in presence nitrogen oxides (NOx) was retrieved online range 315–650 nm bulk characterized an high-resolution time-of-flight mass spectrometer. addition, molecular-level brown carbon chromophores determined using high-performance liquid chromatography coupled to a photodiode array detector The real part RI increases both NOx/naphthalene ratio aging time, likely due increased mean polarizability decreased molecular weight fragmentation. Highly absorbing nitroaromatics (e.g., C6H5NO4, C7H7NO4, C7H5NO5, C8H5NO5) under higher NOx conditions contribute significantly absorption SOA. imaginary linearly NOx/VOCs formation nitroaromatic compounds. As function aging, O/C (slope = 0.024), mainly attributed achieved ratio, which favors light-absorbing nitroaromatics. enhancement as significant extensive it lower time opening aromatic rings reactions.

Language: Английский

---

Measurement report: Optical properties and sources of water-soluble brown carbon in Tianjin, North China – insights from organic molecular compositions

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(10), P. 6449 - 6470

Published: May 19, 2022

Abstract. Brown carbon (BrC) aerosols exert vital impacts on climate change and atmospheric photochemistry due to their light absorption in the wavelength range from near-ultraviolet (UV) visible light. However, optical properties formation mechanisms of ambient BrC remain poorly understood, limiting estimation radiative forcing. In present study, fine particles (PM2.5) were collected during 2016–2017 a day/night basis over urban Tianjin, megacity northern China. Light fluorescence water extracts PM2.5 investigated obtain seasonal diurnal patterns water-soluble BrC. There obvious seasonal, but no evident diurnal, variations winter, showed much stronger light-absorbing ability, with mass efficiency at 365 nm (MAE365) winter (1.54±0.33 m2 gC−1) that was 1.8 times larger than MAE365 summer (0.84±0.22 gC−1). Direct effects by relative black UV 54.3±16.9 % 44.6±13.9 summer, respectively. addition, five fluorescent components BrC, including three humic-like fluorophores two protein-like identified excitation–emission matrix spectrometry parallel factor (PARAFAC) analysis. The less oxygenated contributed more nighttime samples, while increased daytime samples. higher humification index (HIX), together lower biological (BIX) (FI), suggests chemical compositions associated high aromaticity degree photobleaching. Fluorescent indicate wintertime predominantly affected primary emissions fresh secondary organic aerosol (SOA), ones influenced aging processes. Results source apportionments using molecular same set reveal fossil fuel combustion processes, bioaerosol emission, biomass burning, biogenic anthropogenic SOA main sources Biomass burning nighttime, daytime. particular, our study highlights emission is an important Tianjin summer.

Language: Английский

---

Characteristics and evolution of brown carbon in western United States wildfires

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(12), P. 8009 - 8036

Published: June 21, 2022

Abstract. Brown carbon (BrC) associated with aerosol particles in western United States wildfires was measured between July and August 2019 aboard the NASA DC-8 research aircraft during Fire Influence on Regional to Global Environments Air Quality (FIREX-AQ) study. Two BrC measurement methods are investigated, highly spectrally resolved light absorption solvent (water methanol) extracts of collected filters situ bulk particle at three wavelengths (405, 532 664 nm) a photoacoustic spectrometer (PAS). A light-absorption closure analysis for 300 700 nm performed. The combined pure black material, including enhancements due internally mixed materials, plus soluble Mie-predicted factor conversion BrC, compared spectra from power law fit PAS wavelengths. For various parameters used, wavelength roughly 400 they agreed, lower individual component-predicted significantly exceeded higher consistently but more variable. Limitations extrapolation data below 405 missing species low solubility that strongly absorb may account differences. Based measurements closest fires, emission ratio PAS-measured relative monoxide (CO) average 0.13 Mm−1 ppbv−1; ratios also provided. As smoke moved away burning regions, evolution over time observed be complex; enhancement, depletion or constant levels age were all first 8 h after different plumes. Within following emissions, 4-nitrocatechol, well-characterized chromophore commonly found particles, largely depleted BrC. In descending plume where temperature increased by 15 K, 4-nitrocatechol dropped, possibly temperature-driven evaporation, remained unchanged. Evidence reactions ozone, related species, as pathway secondary formation under both high oxides nitrogen (NOx) conditions, while bleached regions ozone NOx, consistent complex behaviors laboratory studies. Although hours is variable, limited number aged (15 30 h) indicate net loss It yet determined how near-field affects characteristics longer timescales spatial scales, its environmental impacts likely greater.

Language: Английский

---