Manganese oxide supported Pt single atoms (Pt1/MnOx) are prepared by the molten salt method. Catalytic oxidation of toluene and iso-hexane, typical emissions from furniture paints industry, is ...tested. Pt1/MnOx shows poor and high catalytic stability for toluene and iso-hexane oxidation, respectively. Enhancement in the catalytic stability for toluene oxidation is observed after the hydrogen reduction treatment of Pt1/MnOx at 200 °C. The hydrogen treated catalyst possesses the weaker Mn–O bonds and lower coordination number of PtO, with superior mobility of lattice oxygen and appropriate toluene adsorption. Balancing lattice oxygen mobility and volatile organic compounds adsorption is important for the catalytic stability of Pt1/MnOx. For the oxidation of toluene and iso-hexane mixture, owing to the competitive adsorption, iso-hexane oxidation is greatly inhibited, while toluene oxidation is not influenced. The present Pt1/MnOx catalyst holds promising prospect in furniture paints industry applications because of high catalytic stability and water resistance ability.
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•Single-atom Pt catalyst is synthesized via a novel one-pot molten salt strategy.•Simple H2 reduction treatment enhances the catalytic stability of single-atom Pt catalyst.•Balancing oxygen mobility and VOCs adsorption is the key for catalytic stability.•Single-atom Pt catalyst exhibits high performance for VOCs mixture removal in the presence of water.
In this study, Ce-modified SCR catalysts under different Ce loading amounts and different calcination temperatures were prepared by sol-gel method, aiming for simultaneous removal of nitrogen oxide ...(NOX) and typical volatile organic compounds (VOCS) (i.e. benzene and toluene) during coal-fired power generation process. Characterization techniques including Nitrogen adsorption and desorption, SEM-EDS, XRD, XPS and NH3-TPD were applied to reveal the influences of Ce loading amounts and calcination temperatures on surface properties, adsorption abilities, physical structures, valence state and acid sites of catalysts, which interpreted the result of removal efficiency a step further. Among catalysts of Ceα-V-W/Ti-β (α = 0, 0.025, 0.05 and 0.1 in molar ratio; β = calcination temperature of 400, 500 and 600 °C), Ce0.05-V-W/Ti-500 presented optimal physicochemical properties which had more pore structure, larger specific surface area, higher components dispersion and better redox ability. Ce0.05-V-W/Ti-500 could reach 92.5% NO removal efficiency, 97.3% benzene and 99.4% toluene removal efficiency when at 380 °C reaction temperature.
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•SCR catalysts of different Ce dosages and calcination temperatures were prepared.•Ce-modified V-W/Ti type SCR catalyst could remove over 90% benzene and toluene.•NO removal efficiency kept higher than 75% in SCR temperature window.•Catalyst after Ce modification improved the porosity.•Ce modified catalyst owned better oxygen mobility and acid site distribution.
•A broad overview of recent progress in combination of membrane processes and ionic liquids for VOCs or CO2 separation.•Comprehensive summary of ionic liquids membranes advantages and ...disadvantages.•Membrane contactor with ILs as adsorbents are perspective for VOCs and CO2 separation.•Separation performances and regeneration results were discussed in context of challenges and future research.•Introduction of a new ILs membrane will broaden new fields of their applications.
Combination of membrane processes and ionic liquids have received more and more attention in pollutants removal because it enhances separation efficiency but also broaden their research and application areas. This review provides a first and systematical summary on ionic liquids incorporate in membrane processes for VOCs or CO2 separation, including supported ionic liquid membranes (SILMs), ILs composite polymer membranes (ILPMs), ionic liquids composite mixed matrix membranes (ILMMMs), poly(ionic liquid)s membranes (PILMs), ionic liquid gel membranes (ILGMs), and ionic liquid membrane contactors (ILMCs). Moreover, a new concept, combination of the membrane separation processes and absorption processes of ionic liquids, is introduced. Those separation processes are described detailly and compared with other conventional processes. With their separation performances and the processes of regeneration, membrane contactor shows stronger competitive advantages and it has the potential to be a major process in VOCs and CO2 separation. The advantages and disadvantages posed by all present ionic liquid membrane processes are summarized. Finally, challenges and opportunities in ionic liquid membrane separation processes are identified and discussed.
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Since the environmental hazards of volatile organic compounds (VOCs) are well known, heterogeneous catalysis has become one of the most popular methods to treat VOCs due to its ...environmental friendliness and simplicity of operation. Although a large number of reports have reviewed the application of catalytic oxidation for the degradation of VOCs, relatively few reports are based on this direction of metal organic frameworks (MOFs) and MOF derivatives. Herein, this paper reviews the recent applications of heterogeneous catalytic technologies in the degradation of VOCs, including photocatalysis, thermal catalysis and other catalytic approaches. The applications of MOFs and their derivatives in VOCs degradation, such as the progress of MOF-derived metal oxides in the treatment of toluene, were highlighted. The mechanisms of VOCs degradation by different catalytic approaches were systematically presented. Finally, we presented the views and directions of VOCs treatment technology development. We hope that this reaction type-oriented review will provide important insights into MOFs and MOF-derived materials for VOCs pollution control.
Ozone (O3) has become the most critical air pollutant in the Yangtze River Delta (YRD) region of China. Research on the O3 formation mechanism and its precursor sources (including nitrogen oxides ...(NOX) and volatile organic compounds (VOCs)) could provide a theoretical basis for mitigating O3 pollution in this region. In this study, simultaneous field experiments were conducted for air pollutants in a typical urban area (Suzhou) in the YRD region in 2022. The capacity of in-situ O3 formation, O3-NOX-VOCs sensitivities and sources of O3 precursors were analyzed. The results showed that in-situ formation contributed 20.8 % of the O3 concentration in the warm season (April to October) of the Suzhou urban area. Compared with the warm season average, the concentrations of various O3 precursors increased on pollution days. The O3-NOX-VOCs sensitivity was the VOCs-limited regime based on the average concentrations during the warm season. O3 formation was most sensitive to anthropogenic VOCs, of which oxygenated VOCs, alkenes and aromatics were the key species. There was a VOCs-limited regime in spring and autumn, while a transitional regime in summer due to the changes in NOX concentrations. This study considered NOX emission from VOCs sources and calculated the contribution of various sources to O3 formation. The results of VOCs source apportionment showed that diesel engine exhaust and fossil fuel combustion had a dominant proportion, but O3 formation presented significant negative sensitivities to the above two sources because of their high NOX emissions. There were significant sensitivities of O3 formation to gasoline vehicle exhaust and VOCs evaporative emissions (gasoline evaporation and solvent usage). The contribution of VOCs evaporative emissions during the O3 pollution episode was significantly higher than the average; therefore, controlling VOCs evaporative emissions during the O3 pollution episode is critical. These results provide feasible strategies to mitigate O3 pollution.
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•The concentrations of VOCs and NOX were increased during O3 pollution episodes.•The O3-NOX-VOCs sensitivity was the VOCs-limited regime in Suzhou urban area.•VOCs and NOX emissions of various sources on O3 formation were comprehensively considered.•Reducing high-NOX emission sources was not conducive for mitigating O3 pollution.•The key emission sources were VOCs evaporation and gasoline vehicle exhaust.
Spatiotemporal change patterns of China's industrial VOCs emissions were explored in response to integrated air quality control policies during 2013–2019, and future emissions predicted under the two ...different scenarios targeting 2030. China's industrial VOCs emissions were decreased to 15.72 Tg in 2019, of which chemical industry, industrial painting, petroleum industry, coal-coking industry, and other industries respectively accounted for 31.0%, 23.9%, 15.6%, and 13.0%, 16.3%, after peaking at 16.40 Tg in 2016. VOC emissions from the petroleum industry and industrial painting showed a continuous increase, with emissions increasing by 0.46 Tg and 0.71 Tg. VOC emissions from the chemical industries increased by 0.91 Tg during 2013–2016 and decreased by 0.72 Tg during 2016–2019. Industrial VOCs emissions in the Beijing-Tianjin-Hebei, Shandong Peninsula, and Central Plain in 2019 respectively reduced by 12.0%, 3.2%, and 8.7% compared to 2013 due to stringent control measures and closure/relocation of highly polluting enterprises. By contrast, industrial VOCs emissions in the West Coast of the Strait and the Central Guizhou increased by 38.1% and 31.8% during 2013–2019. In summary, China's industrial high VOCs emission areas were shifting from key areas to its surrounding areas, resulting in little change in total VOCs emissions. The coal-coking industry, architectural painting, petroleum refining, and pharmaceutical industry will have the most considerable reduction responsibility to reduce VOCs emissions in the future. Guangdong, Jiangsu, Shandong, and Zhejiang will share the highest reduction responsibility, accounting for approximately 40% of national emission reduction.
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•Spatiotemporal trends of China's industrial VOCs were analyzed during 2013–2019•China's industrial VOCs showed decreasing after peaking at 2016 with 16 Tg emissions•High industrial VOCs emission area were shifting from key areas to surrounding areas•Coking and oil refining will have the largest reduction responsibility in the future
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•The VOCs adsorption performance of different adsorbents were summarized.•The controlling factors of VOCs adsorption on adsorbent materials were explored.•Methods for increasing the ...adsorption capacity were demonstrated.•ACs and MOFs are good adsorption materials for the reduction of VOCs emission.
Volatile organic compounds are harmful to the environment and human health. Adsorption technology has been used to VOCs abatement for over 30 years and has proven to be an effective technology. This work provides a critical review of the recent research developments of VOCs adsorption materials and the key factors controlling the VOCs adsorption process. The average specific surface area, pore volume and VOCs adsorption capacity of different adsorption materials are metal organic frameworks (MOFs) > activated carbons (ACs) > hypercrosslinked polymeric resin (HPR) > zeolites. The mechanism of VOCs adsorption in adsorbent mainly includes electrostatic attraction, interaction between polar VOCs and hydrophilic sites, interaction between non-polar VOCs and hydrophobic sites, and partition in non-carbonized portion. With the specific surface area, pore volume, and surface chemical functional groups increase and the pore size decreases, the adsorption capacity increases. The volume of narrow micropores (size < 0.7 nm) controls the adsorption of VOCs. In addition, methods of activation and surface modification for improving the adsorption capacity of VOCs are discussed. The development of targeted modified adsorption materials and new adsorption materials and reduction of production costs of adsorption materials are especially important in future research.
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•Efficient and stable photocatalytic VOCs decomposition was achieved on SrTiO3.•The perovskites with special electronic structures dictate photocatalysis efficiency.•The electronic ...structure of SrTiO3 could promote the activation of O2 and H2O.•The DFT and In situ DRIFTS are combined to reveal the ring-opening mechanism.•The reaction mechanisms of photocatalytic decomposition of VOCs was proposed.
Considering that the structural differences could dictate the photocatalytic efficiency, the cubic SrTiO3 (STO) and tetragonal CaTiO3 (CTO) were developed to illustrate the structure–activity relationship. The STO with cubic structure demonstrates much higher photocatalytic toluene removal efficiency (ca. 80.0%) than that of CTO (ca. 20.0%), which can be ascribed to boosted formation of reactive oxygen species (ROS), increased selectivity of intermediates, and promoted ring-opening and mineralization rate. Combining theoretical simulation and experimental characterization, the results reveal that the O2 and H2O molecules tend to be adsorbed on the cubic STO, which boosts the formation of ROS. Also, highly selective formation of intermediate (benzoic acid) has been realized to accelerate ring-open and mineralization process as evidenced by the smooth conversion of STO as indicated by Gibbs free energy. This work provides new perspectives on the understanding of relationship between intrinsic structure and photocatalytic performance.
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