Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 47
Filter
Add more filters










Publication year range
1.
J Environ Sci (China) ; 141: 261-276, 2024 Jul.
Article in English | MEDLINE | ID: mdl-38408827

ABSTRACT

Metal-organic frameworks (MOFs) have favorable characteristics such as large specific surface area, high porosity, structural diversity, and pore surface modification, giving them great potential for development and attractive prospects in the research area of modern materials electrocatalysis. However, unsatisfactory catalytic activity and poor electronic conductivity are the main challenges facing MOFs. This review focuses on MOF-based materials used in electrocatalysis, based on the types of catalytic reactions that have used MOF-based materials in recent years along with their applications, and also looks at some new electrocatalytic materials and their future development prospects.


Subject(s)
Metal-Organic Frameworks , Catalysis , Electric Conductivity , Porosity
2.
Sci Total Environ ; 920: 170748, 2024 Apr 10.
Article in English | MEDLINE | ID: mdl-38340848

ABSTRACT

Catalytic oxidation, an end-of-pipe treatment technology for effectively purifying volatile organic compounds (VOCs), has received widespread attention. The crux of catalytic oxidation lies in the development of efficient catalysts, with their optimization necessitating a comprehensive analysis of the catalytic reaction mechanism. Two-dimensional (2D) ultra-thin nanomaterials offer significant advantages in exploring the catalytic oxidation mechanism of VOCs due to their unique structure and properties. This review classifies strategies for regulating catalytic properties and typical applications of 2D materials in VOCs catalytic oxidation, in addition to their characteristics and typical characterization techniques. Furthermore, the possible reaction mechanism of 2D Co-based and Mn-based oxides in the catalytic oxidation of VOCs is analyzed, with a special focus on the synergistic effect between oxygen and metal vacancies. The objective of this review is to provide valuable references for scholars in the field.

3.
ACS Appl Mater Interfaces ; 16(3): 3593-3604, 2024 Jan 24.
Article in English | MEDLINE | ID: mdl-38215440

ABSTRACT

Mining the scientific literature, combined with data-driven methods, may assist in the identification of optimized catalysts. In this paper, we employed interpretable machine learning to discover ternary metal oxides capable of selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR). Specifically, we devised a machine learning framework utilizing extreme gradient boosting (XGB), identified for its optimal performance, and SHapley Additive exPlanations (SHAP) to evaluate a curated database of 5654 distinct metal oxide composite catalytic systems containing cerium (Ce) element, with records of catalyst composition and preparation and reaction conditions. By virtual screening, this framework precisely pinpointed a CeO2-MoO3-Fe2O3 catalyst with superior NOx conversion, N2 selectivity, and resistance to H2O and SO2, as confirmed by empirical evaluations. Subsequent characterization affirmed its favorable structural, chemical bulk properties and reaction mechanism. Demonstrating the efficacy of combining knowledge-driven techniques with experimental validation and analysis, our strategy charts a course for analogous catalyst discoveries.

4.
J Environ Sci (China) ; 138: 482-495, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38135414

ABSTRACT

In this work, the phosphomolybdate (HPMo) modification strategy was applied to improve the N2 selectivity of MnCo-BTC@SiO2 catalyst for the selective catalytic reduction of NOx, and further, the mechanism of HPMo modification on enhanced catalytic performance was explored. Among MnCo-BTC@SiO2-x catalysts with different HPMo concentrations, MnCo-BTC@SiO2-0.75 catalyst exhibited not only the highest NH3-SCR performance (∼95% at 200-300°C) but also the best N2 selectivity (exceed 80% at 100-300°C) due to the appropriate redox capacity, greater surface acidity. X-ray photoelectron spectrometer (XPS) and temperature programmed reduction of H2 (H2-TPR) results showed that the modification with HPMo reduced the oxidation-reduction performance of the catalyst due to electron transfer from Mo5+ to Mn4+/Mn3+ and prevent the excessive oxidation of ammonia adsorption species. NH3 temperature-programmed desorption of (NH3-TPD) results showed that the modification with HPMo could significantly improve the surface acidity and NH3 adsorption, which enhance the catalytic activity and N2 selectivity. In-situ diffused reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) revealed that modification with HPMo increased significantly the amount of adsorbed NH3 species on the Bronsted acid site and CB/CL, it suppressed the production of N2O by inhibiting the production of NH species, the deep dehydrogenation of ammonia adsorption species. This study provided a simple design strategy for the catalyst to improve the low-temperature catalytic performance and N2 selectivity.


Subject(s)
Ammonia , Silicon Dioxide , Ammonia/chemistry , Oxidation-Reduction , Temperature , Cold Temperature , Catalysis
5.
Nanoscale ; 15(29): 12157-12174, 2023 Jul 27.
Article in English | MEDLINE | ID: mdl-37431630

ABSTRACT

Chlorinated benzene-containing compounds (CBCs) refer to volatile organic compounds which simultaneously contain benzene rings and Cl atoms. It has been widely believed to cause serious harm to human health and the natural environment due to high toxicity, high persistence, and refractory degradation, thus, it is urgent to develop CBC abatement technology. In this review, several CBCs control techniques are compared, and the catalytic oxidation technology stands out for its good low-temperature activity and chlorine resistance of metal oxide catalysts. Then, the common and individual reaction pathways and water impact mechanisms of CBC catalytic oxidation on transition metal catalysts are concluded. Subsequently, three typical metal oxides (namely, VOx, MnOx, and CeO2-based catalysts) are introduced in the catalytic degradation of CBCs, whose catalytic activity influence factors are also proposed on active components, support properties, surface acidity, and nanostructure (crystal, morphology, etc.). Furthermore, the effective strategies to enhance the REDOX cycle and surface acidic sites are summarized by the doping of metals, the modification of support or/and acidic groups, and the construction of nanostructures. Finally, the key points for efficient catalyst design are speculated. This review may provide ideas for the breakthroughs of activity-enhanced strategies, the design of efficient catalysts, and research on reaction-promoted mechanisms.

6.
Sci Total Environ ; 891: 164580, 2023 Sep 15.
Article in English | MEDLINE | ID: mdl-37286009

ABSTRACT

The cement industry is one of the most energy- and carbon-intensive industries in China, and it is difficult to attain deep decarbonization toward carbon neutrality. This paper provides a comprehensive review of the historical emission trend and future decarbonization pathway of China's cement industry, in which the opportunities and challenges of key technologies, carbon mitigation potential and co-benefits are examined. The results showed that from 1990 to 2020, the carbon dioxide (CO2) emissions of China's cement industry experienced a growing trend, while air pollutant emissions were largely decoupled from cement production growth. Between 2020 and 2050, China's cement production may decrease by over 40 %, and CO2 emissions will decline from 1331 Tg to 387 Tg under the Low scenario given a combination of certain mitigation measures, including energy efficiency improvement, alternative energy sources, alternative materials, carbon capture, utilization, and storage (CCUS) technology, and new cement. Before 2030, carbon reduction under the low scenario is determined by factors including energy efficiency improvement, alternative energy sources, and alternative materials. Afterward, CCUS technology will become increasingly imperative and conducive to deep decarbonization of the cement industry. After implementation of all the above measures, 387 Tg of CO2 will still be emitted by the cement industry in 2050. As such, improving the quality and service life of buildings and infrastructure as well as the carbonation of cement materials has a positive effect on carbon reduction. Finally, carbon mitigation measures in the cement industry can provide air quality improvement co-benefits.

8.
J Environ Sci (China) ; 126: 308-320, 2023 Apr.
Article in English | MEDLINE | ID: mdl-36503759

ABSTRACT

Energy-saving and efficient monolithic catalysts are hotspots of catalytic purification of industrial gaseous pollutants. Here, we have developed an electrothermal catalytic mode, in which the ignition temperature required for the reaction is provided by Joule heat generated when the current flows through the catalyst. In this paper, Mn/NiAl/NF, Mn/NiFe/NF and Mn/NF metal-based monolithic catalysts were prepared using nickel foam (NF) as the carrier for thermal and electrothermal catalysis of n-heptane. The results indicated that Mn-based monolithic catalysts exhibit high activity in thermal and electrothermal catalysis. Mn/NiFe/NF achieve conversion of n-heptane more than 99% in electrothermal catalysis under a direct-current (DC) power of 6 W, and energy-saving is 54% compared with thermal catalysis. In addition, the results indicated that the introduction of NiAl (or NiFe) greatly enhanced the catalytic activity of Mn/NF, which attributed to the higher specific surface area, Mn3+/Mn4+, Ni3+/Ni2+, adsorbed oxygen species (Oads)/lattice oxygen species (Olatt), redox performance of the catalyst. Electrothermal catalytic activity was significantly higher than thermal catalytic activity before complete conversion, which may be related to electronic effects. Besides, Mn/NiFe/NF has good cyclic and long-term stability in electrothermal catalysis. This paper provided a theoretical basis for applying electrothermal catalysis in the field of VOCs elimination.


Subject(s)
Nickel , Oxides , Manganese Compounds , Oxygen
9.
J Environ Sci (China) ; 125: 112-134, 2023 Mar.
Article in English | MEDLINE | ID: mdl-36375898

ABSTRACT

As the main contributor of the formation of particulate matter as well as ozone, volatile organic compounds (VOCs) greatly affect human health and the environmental quality. Catalytic combustion/oxidation has been viewed as an efficient, economically feasible and environmentally friendly way for the elimination of VOCs. Supported metal catalyst is the preferred type of catalysts applied for VOCs catalytic combustion because of the synergy between active components and support as well as its flexibility in the composition. The presence of support not only plays the role of keeping the catalyst with good stability and mechanical strength, but also provides a large specific surface for the good dispersion of active components, which could effectively improve the performance of catalyst as well as decrease the usage of active components, especially the noble metal amount. Mesoporous molecular sieves, owing to their large surface area, unique porous structures, large pore size as well as uniform pore-size distribution, were viewed as superior support for dispersing active components. This review focuses on the recent development of mesoporous molecular sieve supported metal catalysts and their application in catalytic oxidation of VOCs. The effect of active component types, support structure, preparation method, precursors, etc. on the valence state, dispersion as well as the loading of active species were also discussed and summarized. Moreover, the corresponding conversion route of VOCs was also addressed. This review aims to provide some enlightment for designing the supported metal catalysts with superior activity and stability for VOCs removal.


Subject(s)
Ozone , Volatile Organic Compounds , Humans , Volatile Organic Compounds/chemistry , Catalysis , Oxidation-Reduction , Particulate Matter , Metals
10.
J Environ Sci (China) ; 124: 491-504, 2023 Feb.
Article in English | MEDLINE | ID: mdl-36182157

ABSTRACT

Ce1-xZrxO2 composite oxides (molar, x = 0-1.0, interval of 0.2) were prepared by a cetyltrimethylammonium bromide-assisted precipitation method. The enhancement of silver-species modification and catalytic mechanism of adsorption-transformation-desorption process were investigated over the Ag-impregnated catalysts for low-temperature selective catalytic oxidation of ammonia (NH3-SCO). The optimal 5 wt.% Ag/Ce0.6Zr0.4O2 catalyst presented good NH3-SCO performance with >90% NH3 conversion at temperature (T) ≥ 250°C and 89% N2 selectivity. Despite the irregular block shape and underdeveloped specific surface area (∼60 m2/g), the naked and Ag-modified Ce0.6Zr0.4O2 solid solution still obtained highly dispersed distribution of surface elements analyzed by scanning electron microscope-energy dispersive spectrometer (SEM-EDS) (mapping), N2 adsorption-desorption test and X-ray diffraction (XRD). H2 temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) results indicated that Ag-modification enhanced the mobility and activation of oxygen-species leading to a promotion on CeO2 reducibility and synergistic Ag0/Ag+ and Ce4+/Ce3+ redox cycles. Besides, Ag+/Ag2O clusters could facilitate the formation of surface oxygen vacancies that was beneficial to the adsorption and activation of ammonia. NH3-temperature programmed desorption (NH3-TPD) showed more adsorption-desorption capacity to ammonia were provided by physical, weak- and medium-strong acid sites. Diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments revealed the activation of ammonia might be the control step of NH3-SCO procedure, during which NH3 dehydrogenation derived from NHx-species and also internal selective catalytic reduction (i-SCR) reactions were proposed.


Subject(s)
Ammonia , Silver , Ammonia/chemistry , Catalysis , Cetrimonium , Oxidation-Reduction , Oxides , Oxygen
11.
Ceram Int ; 48(23): 34148-34168, 2022 Dec 01.
Article in English | MEDLINE | ID: mdl-36059853

ABSTRACT

Food packages have been detected carrying novel coronavirus in multi-locations since the outbreak of COVID-19, causing major concern in the field of food safety. Metal-based supported materials are widely used for sterilization due to their excellent antibacterial properties as well as low biological resistance. As the principal part of antibacterial materials, the active component, commonly referred to Ag, Cu, Zn, etc., plays the main role in inhibiting and killing pathogenic microorganisms by destroying the structure of cells. As another composition of metal-based antibacterial materials, the carrier could support and disperse the active component, which on one hand, could effectively decrease the usage amount of active component, on the other hand, could be processed into various forms to broaden the application range of antibacterial materials. Different from other metal-based antibacterial reviews, in order to highlight the detailed function of various carriers, we divided the carriers into biocompatible and adsorptable types and discussed their different antibacterial effects. Moreover, a novel substitution antibacterial mechanism was proposed. The coating and shaping techniques of metal-based antibacterial materials as well as their applications in food storage at ambient and low temperatures are also comprehensively summarized. This review aims to provide a theoretical basis and reference for researchers in this field to develop new metal-based antibacterial materials.

12.
Environ Sci Pollut Res Int ; 29(37): 55367-55399, 2022 Aug.
Article in English | MEDLINE | ID: mdl-35672638

ABSTRACT

With the awakening of environmental awareness, the importance of air quality to human health and the proper functioning of social mechanisms is becoming increasingly prominent. The low cost and high efficiency of catalytic technique makes it a natural choice for achieving deep air purification. Stainless steel alloys have demonstrated their full potential for application in a variety of catalytic fields. The diversity of 3D networks or fibrous structures increases the turbulence within the heterogeneous catalysis, balance the temperature distribution in the reaction bed and, in combination with a highly thermally conductive skeleton, avoid agglomeration and deactivation of the active components; corrosion resistance and thermal stability are adapted to highly endothermic/exothermic or corrosive reaction environments; oxide layers formed by bulk transition metals activated by thermal treatment or etching can significantly alter the physico-chemical properties between the substrate and active species, further improving the stability of stainless steel catalysts; suitable electronic conductivity can be applied to the electrothermal catalysis, which is expected to provide guidance for the reduction of intermittent emission exhausts and the storage of renewable energy. The current applications of stainless steel as catalyst or support in the air purification have covered soot particle capture and combustion, catalytic oxidation of VOCs, SCR, and air sterilization. This paper summarizes several preparation methods and presents the relationships between the preparation process and the activity, and reviews its application and the current status of research in atmospheric environmental management, proposing the advantages and challenges of the stainless steel-based catalysts.


Subject(s)
Air Pollution , Stainless Steel , Air Pollution/prevention & control , Catalysis , Corrosion , Humans , Soot/chemistry , Stainless Steel/chemistry
13.
Environ Pollut ; 307: 119512, 2022 Aug 15.
Article in English | MEDLINE | ID: mdl-35605835

ABSTRACT

The iron and steel industry (ISI) is one of the most energy-intensive industries in China, which makes a substantial contribution to the emissions of air pollutants. Among the various manufacturing processes, sintering is the major emitting process, which shares over half of the emissions of sulfur dioxide (SO2), nitrogen oxide (NOx) and particulate matter (PM) for the entire industry. In this study we made a comprehensive evaluation of the air pollutant emissions from the sintering process of China's ISI in 2017 based on the Continuous Emission Monitoring System (CEMS) database and estimated the future reduction potentials. We found that there was a general decreasing trend of emission concentrations in the sintering flue gas in response to the strengthened emission control policies, but the mild increase of the oxygen content in the second half of the year flattened the decreasing trend, indicating the necessity for simultaneous control of the oxygen content in the flue gas. Despite the relative high standard-reaching rates of 90% to the emission concentration limits in GB 28662-2012, the standard-reaching rates to the ultra-low emission standards were only 12%, 40% and 27% for NOx, SO2 and PM respectively, with the lowest value mostly occurred in the western provinces. In 2017, the NOx, SO2 and PM emissions from the sintering process were 378.6 kt, 169.0 kt and 51.9 kt, respectively. If the ultra-low emission standards were met, the corresponding NOx, SO2 and PM emissions would decrease by 69.9%, 52.9%, and 56.4% respectively, illustrating large emission reducing potentials by achieving the ultra-low emission standards.


Subject(s)
Air Pollutants , Air Pollution , Air Pollutants/analysis , Air Pollution/analysis , Air Pollution/prevention & control , China , Environmental Monitoring , Iron , Oxygen , Particulate Matter/analysis , Steel
14.
Environ Sci Pollut Res Int ; 29(22): 33595-33608, 2022 May.
Article in English | MEDLINE | ID: mdl-35029827

ABSTRACT

MCM-48 molecular sieve with a large specific area (1470.87 m2/g) was hydrothermally synthesized for VOCs elimination by the adsorption method. The dynamic adsorption behaviors of toluene on this material were evaluated via breakthrough curves under both dry and wet conditions. A high toluene adsorption capacity of 171.13 mg/g was observed under dry conditions; however, in the presence of water vapor (20% RH), the adsorption capacity greatly decreased to 58.88 mg/g due to the competitive occupation of adsorption sites between water molecules and toluene molecules. To improve the affinity to toluene, functionalized MCM-48 materials were obtained by the co-condensation method and grafting method, respectively. It was found that co-M48(1:5)-100/48 sample by co-condensation method presents the highest dynamic adsorption capacity at both dry condition (194.62 mg/g) and 20% RH (122.42 mg/g), which has a significant advantage in the same type of adsorbent. This could be ascribed to the conjugated π-electrons effect between aromatic rings of phenyl groups uniformly distributed in MCM-48 skeleton and toluene molecules, which was qualitatively confirmed by FTIR. Moreover, cycle tests confirmed that this adsorbent possesses superior stability. The Yoon-Nelson model was successfully employed to describe the dynamic adsorption behavior of toluene over the organofunctionalized MCM-48 adsorbents, and the adsorption force of toluene was explained. Finally, a diagram describing the effect of different functionalization methods on the hydrophobicity and organophilicity of MCM-48 was given for a better understanding.


Subject(s)
Toluene , Adsorption , Hydrophobic and Hydrophilic Interactions , Toluene/chemistry
15.
J Environ Sci (China) ; 113: 204-218, 2022 Mar.
Article in English | MEDLINE | ID: mdl-34963529

ABSTRACT

NH3-SCR performances were explored to the relationship between structure morphology and physio-chemical properties over low-dimensional ternary Mn-based catalysts prepared by one-step synthesis method. Due to its strong oxidation performance, Sn-MnOx was prone to side reactions between NO, NH3 and O2, resulting in the generation of more NO2 and N2O, here most of N2O was driven from the non-selective oxidation of NH3, while a small part generated from the side reaction between NH3 and NO2. Co or Ni doping into Sn-MnOx as solid solution components obviously stronged the electronic interaction for actively mobilization and weakened the oxidation performance for signally reducing the selective tendency of side reactions to N2O. The optimal modification resulted in improving the surface area and enhancing the strong interaction between polyvalent cations in Co/Ni-Mn-SnO2 to provide more surface adsorbed oxygen, active sites of Mn3+ and Mn4+, high-content Sn4+ and plentiful Lewis-acidity for more active intermediates, which significantly broadened the activity window of Sn-MnOx, improved the N2 selectivity by inhibiting N2O formation, and also contributed to an acceptable resistances to water and sulfur. At low reaction temperatures, the SCR reactions over three catalysts mainly obeyed the typical Elye-rideal (E-R) routs via the reactions of adsorbed l-NHx (x = 3, 2, 1) and B-NH4+ with the gaseous NO to generate N2 but also N2O by-products. Except for the above basic E-R reactions, as increasing the reaction temperature, the main adsorbed NOx-species were bidentate nitrates that were also active in the Langmuir-Hinshelwood reactions with adsorbed l-NHx species over Co/Ni modified Mn-SnO2 catalyst.


Subject(s)
Ammonia , Oxides , Catalysis , Nitrogen Oxides , Oxidation-Reduction
16.
Environ Sci Pollut Res Int ; 29(14): 21210-21220, 2022 Mar.
Article in English | MEDLINE | ID: mdl-34755296

ABSTRACT

In this research, one-step synthesis of redox co-precipitation method (using sodium lauryl sulfate, KMnO4, and metal precursor) was well applicable in universally preparing low-dimensional Me-MnOx nanosheet catalysts with different metal doping (Me=Co, Ni, or Sn). NH3-SCR activity was explored to the relationship with structure morphology and physio-chemical properties via the characterization techniques of SEM, XRD, XPS, H2-TPR, and NH3-TPD. It was found that Ni-MnOx has a relatively poor activity at low-down temperature but was improved as the reaction temperature rising. Co-MnOx presented a relatively stable catalytic activity of which the NOx conversion rate can be maintained 80~90% in a wide temperature window of 100-250 °C with relatively better N2 selectivity. Compared with Co- or Ni-modified MnOx, Sn-MnOx catalyst has an excellent low-temperature catalytic activity (93% NOx conversion at 100 °C) that was maintained > 80% before 200 °C but with poor selectivity to N2. Due to its nanosheet-structured solid solution structure, Sn-MnOx promoted the interaction between MnOx and SnO2 with the increased contents of adsorbed oxygen and also the numbers of surface Lewis acid sites, which integrally promoted the NH3-SCR reaction at low temperature and also contributed to an acceptable resistances to water and sulfur. High content of adsorbed oxygen was beneficial to improve the catalytic activity at lower temperatures, while the electron cycle interaction of different metal valence ions will play a more important role with the increase of reaction temperature.


Subject(s)
Ammonia , Oxides , Ammonia/chemistry , Catalysis , Oxidation-Reduction , Oxides/chemistry , Temperature
17.
Chemosphere ; 291(Pt 2): 132917, 2022 Mar.
Article in English | MEDLINE | ID: mdl-34793850

ABSTRACT

China is the largest iron and steel producer and consumer in the world. The iron and steel manufacture, especially the sintering process, is energy-intensive, and contributes substantially to air pollutant emissions in China. Compared with other regions, the Fenwei Plain, a coal base, has a heavy industry concentration, and high pollutant emission total amount. In addition, urban air pollution has rebounded, and the pollutants concentrations in many cities have increased rather than decreased. In this study, we investigated the inter-annual trends of particulate matter (PM), sulfur dioxide (SO2) and nitrogen oxide (NOx) from the sintering process of iron and steel industry (ISI) in the Fenwei Plain and the surrounding regions in China from 2014 to 2017 based on the Continuous Emission Monitoring System (CEMS). We found that the oxygen content of the flue gas is the key to judge whether the sintering flue gas air pollutant emission concentration can meet the standard. Therefore, we adopted the converted concentration by the reference oxygen content in the final analysis. Overall, the SO2 and PM emission concentrations exhibit a downward trend from 2014 to 2017, in response to the strengthening of the emission control policies and standards in the ISI, whereas the NOx emission concentration did not change significantly during the same period The emission factors (EFs) of PM, NOx and SO2 obtained in this study are lower than previous estimates. In 2017, the SO2 and PM emissions were 27% and 32% lower than the levels in 2014.While NOx was 22% higher than the level in 2014. Our study confirmed the effectiveness of current emission control policies and standards in the iron and steel sector. However, the levels of NOx emissions were still high until 2017, illustrating the urgent need for more advanced emission control technologies to further reduce NOx emissions from the sintering flue gas in China.


Subject(s)
Air Pollutants , Air Pollution , Air Pollutants/analysis , Air Pollution/analysis , China , Environmental Monitoring , Iron , Metallurgy , Particulate Matter/analysis , Steel
18.
J Colloid Interface Sci ; 603: 291-306, 2021 Dec.
Article in English | MEDLINE | ID: mdl-34214720

ABSTRACT

Improving the SO2 resistance of catalysts is crucial to driving commercial applications of Mn-based catalysts. In this work, the phosphotungstic acid (HPW) modification strategy was applied to improve the N2 selectivity, SO2 and H2O resistance of the Mn-Ce-Co catalyst, and further, the mechanism of HWP modification on enhanced catalytic performance was explored. The results showed that HPW-Mn-Ce-Co catalyst exhibits higher NOx conversion (~100% at 100-250 °C) and N2 selectivity (exceed 80% at 50-350 °C) due to more oxygen vacancies, greater surface acidity, and lower redox capacity. In situ diffused reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) reveal that HPW changed the reaction path of Mn-Ce-Co catalysts, promoted the adsorption and activation of NH3, and reduced the effect of SO2 on the active bidentate nitrate species, and thereby exhibiting good SO2 resistance. X-ray photoelectron spectrometer (XPS) and NH3 temperature-programmed desorption of (NH3-TPD) results show that HPW can inhibit the formation of metal sulfate, and SO2 can be combined with Ce species more easily. The generated Ce2(SO3)3 can not only protect Mn species but also increase the acid sites and weaken the poisoning effect of metal sulfate. This study provides a simple design strategy for the catalyst to improve the low-temperature catalytic performance and toxicity resistance.


Subject(s)
Cerium , Sulfur Dioxide , Ammonia , Catalysis , Cobalt , Manganese , Oxidation-Reduction , Phosphotungstic Acid
19.
J Hazard Mater ; 413: 125361, 2021 Jul 05.
Article in English | MEDLINE | ID: mdl-33930946

ABSTRACT

The unexpected phenomenon in which different transition metals (Co, Ni and Cu) presented significant variation of participation levels as the auxiliaries in Mn-based bimetallic oxide catalysts were reported here. It is found that the Co element more easily to form Mn enriched surface bimetallic oxides with Mn than Ni and Cu, resulting in Co-MnOx exhibited the best deNOx activity and SO2 tolerance, followed by Ni-MnOx and Cu-MnOx. The role of different transition metal and structure-activity relationships were systematically investigated by advanced techniques including Synchrotron XAFS and in situ DRIFTs analysis. The excellent activity of Co-MnOx was related to its unique Mn-enriched surface (Co2+)tet(Mn3+ Co3+)octO4 structure with Mn cations occupying the octahedral sites, which is superior to the Ni-MnOx and Cu-MnOx with Mn-lean surface. In addition, the reaction energy barrier of Co-MnOx is weakened due to the lower electron cloud density around the Mn atom as compared to Ni-MnOx and Cu-MnOx. Moreover, Co-MnOx benefiting from the rapid electron migration between Mn and Co, more active bidentate/bridged nitrates could react with adsorbed NH3 in faster reaction rates following the L-H mechanism.

20.
Environ Pollut ; 277: 116770, 2021 May 15.
Article in English | MEDLINE | ID: mdl-33640815

ABSTRACT

Ambient air pollution is one of the leading environmental risk factors to human health, largely offsetting economic growth. This study evaluated health burden and cost associated with the short-term and long-term exposure of major air pollutants (fine particulate matter [PM2.5] and ozone [O3]) during 2013-2018. We developed a database of gridded daily and annual PM2.5 and O3 exposure in China at 15 km × 15 km resolution. Then, we estimated the age- and cause-specific premature deaths and quantified related health damage with an age-adjusted value of statistical life (VSL) measure. The health cost estimated in this study captured direct cost, indirect cost and intangible cost of the premature death attributable to ambient PM2.5 and O3. We found that the national premature deaths attributable to long-term and short-term exposure to PM2.5 decreased by 15% and 59%, whereas the national premature deaths attributable to long-term and short-term exposure to O3 increased by 36% and 94%. Despite a 15% reduction of attributable deaths, the health cost attributable to long-term exposure to PM2.5 did not change significantly as a result of GDP growth and population aging. On the other hand, the long-term O3 related health cost in 2018 doubled that in 2013. Our study suggests that while premature deaths fell as a result of China's clean air actions, the health costs of air pollution remained high. The growing trends of O3 highlighted the needs for strategies to reduce both PM2.5 and O3 emissions, for the sake of public health and social well-being in China.


Subject(s)
Air Pollutants , Air Pollution , Air Pollutants/analysis , Air Pollution/analysis , China/epidemiology , Cost of Illness , Environmental Exposure , Health Care Costs , Humans , Particulate Matter/analysis
SELECTION OF CITATIONS
SEARCH DETAIL
...