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1
Fiorenza, Roberto. "Bimetallic Catalysts for Volatile Organic Compound Oxidation." Catalysts 10, no. 6 (June 12, 2020): 661. http://dx.doi.org/10.3390/catal10060661.
Повний текст джерелаАнотація:
In recent years, the impending necessity to improve the quality of outdoor and indoor air has produced a constant increase of investigations in the methodologies to remove and/or to decrease the emission of volatile organic compounds (VOCs). Among the various strategies for VOC elimination, catalytic oxidation and recently photocatalytic oxidation are regarded as some of the most promising technologies for VOC total oxidation from urban and industrial waste streams. This work is focused on bimetallic supported catalysts, investigating systematically the progress and developments in the design of these materials. In particular, we highlight their advantages compared to those of their monometallic counterparts in terms of catalytic performance and physicochemical properties (catalytic stability and reusability). The formation of a synergistic effect between the two metals is the key feature of these particular catalysts. This review examines the state-of-the-art of a peculiar sector (the bimetallic systems) belonging to a wide area (i.e., the several catalysts used for VOC removal) with the aim to contribute to further increase the knowledge of the catalytic materials for VOC removal, stressing the promising potential applications of the bimetallic catalysts in the air purification.
2
Benard, S., M. Ousmane, L. Retailleau, A. Boreave, P. Vernoux, and A. Giroir-Fendler. "Catalytic removal of propene and toluene in air over noble metal catalystThis article is one of a selection of papers published in this Special Issue on Biological Air Treatment." Canadian Journal of Civil Engineering 36, no. 12 (December 2009): 1935–45. http://dx.doi.org/10.1139/l09-135.
Повний текст джерелаАнотація:
In this paper we present the study of catalytic oxidation of volatile organic compound (VOC) traces in air over Pt/γ-Al2O3 catalysts. The study was carried out using a laboratory fixed-bed catalytic reactor (FBCR) with catalytic oxidation of propene and toluene as model reactions. For better understanding of catalytic activity in a FBCR, the influence of operating parameters such as of platinum (Pt) loading, total gas flow rate, VOC concentration, and oxygen content were studied. The results showed that catalytic activity increases with increase in VOC concentration and a decrease in total gas flow rate. This displayed behaviour is instrumental to working at a low temperature region for complete oxidation of volatile organic compounds.
3
Lebedeva, O. E., and A. G. Sarmurzina. "Industrial wastes as catalyst precursors: VOC oxidation." Applied Catalysis B: Environmental 26, no. 1 (April 2000): L1—L3. http://dx.doi.org/10.1016/s0926-3373(99)00146-0.
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4
Fletcher, David B. "Successful UV/oxidation of VOC-contaminated groundwater." Remediation Journal 1, no. 3 (June 1991): 353–57. http://dx.doi.org/10.1002/rem.3440010310.
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Urbutis, Aurimas, and Saulius Kitrys. "Dual function adsorbent-catalyst CuO-CeO2/NaX for temperature swing oxidation of benzene, toluene and xylene." Open Chemistry 12, no. 4 (April 1, 2014): 492–501. http://dx.doi.org/10.2478/s11532-013-0398-x.
Повний текст джерелаАнотація:
AbstractA less common cyclic process of decontamination of benzene, toluene and o-xylene (BTX) using a dual function adsorbent-catalyst, referred to as the temperature swing oxidation, is introduced and discussed in this research. Preparation technique and characterization of the dual function adsorbent-catalyst CuO-CeO2/NaX are presented. The temperature swing oxidation of BTX consists of two stages: adsorption of the VOC from the stream saturating the adsorbent-catalyst at different levels and catalytic oxidation of concentrated VOC induced by raising bed temperature at different flow rates of regenerative air. The results indicate that at lower saturation levels and lower flow rates of regenerative air a complete oxidation performance is better. The highest obtained values of the overall conversion of toluene, o-xylene and benzene into CO2 and H2O were 99.3, 99.8 and 77.5%, respectively, proving that the temperature swing oxidation using a dual function adsorbent-catalyst is a promising VOC decontamination technique under properly selected operating conditions.
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Padilla, Ornel, Jessica Munera, Jaime Gallego, and Alexander Santamaria. "Approach to the Characterization of Monolithic Catalysts Based on La Perovskite-like Oxides and Their Application for VOC Oxidation under Simulated Indoor Environment Conditions." Catalysts 12, no. 2 (January 28, 2022): 168. http://dx.doi.org/10.3390/catal12020168.
Повний текст джерелаАнотація:
Catalysts are very important in controlling the pollutant emissions and are used for hundreds of chemical processes. Currently, noble metal-based catalysts are being replaced for other kinds of materials. In this study, three lanthanum-based perovskite-like oxides were synthesized (LaCo, LaCoMn, and LaMn) by the glycine-combustion method. The powder catalysts obtained were supported onto cordierite ceramic monoliths using an optimized washcoating methodology to obtain the subsequent monolithic catalysts (LaCo-S, LaCoMn-S, and LaMn-S). Sample characterization confirmed the formation of the perovskite-like phase in the powder materials as well as the presence of the perovskite phase after supporting it onto the monolithic structure. The XPS analysis showed a general decrease in lattice oxygen species for monolithic catalysts, mainly caused by the colloidal silica used as a binder agent during the washcoating process. Additionally, some variations in the oxidation state distribution for elements in Co-containing systems suggest a stronger interaction between cordierite and such catalysts. The catalytic activity results indicated that powder and monolithic catalysts were active for single-component VOC oxidation in the following order: 2-propanol > n-hexane ≅ mixture > toluene, and there was no evidence of loss of catalytic activity after supporting the catalysts. However, LaMn-S had a better catalytic performance for all VOC tested under dry conditions, achieving oxidation temperatures between 230–420 °C. The oxidation efficiency for the VOC mixture was strongly affected by the presence of moisture linking the oxidation efficiency at wet conditions to the VOC chemical nature. Additionally, for higher VOC concentrations, the catalyst efficiency decreased due to the limited number of active sites.
7
Clarke, Holly J., William P. McCarthy, Maurice G. O’Sullivan, Joseph P. Kerry, and Kieran N. Kilcawley. "Oxidative Quality of Dairy Powders: Influencing Factors and Analysis." Foods 10, no. 10 (September 29, 2021): 2315. http://dx.doi.org/10.3390/foods10102315.
Повний текст джерелаАнотація:
Lipid oxidation (LO) is a primary cause of quality deterioration in fat-containing dairy powders and is often used as an estimation of a products shelf-life and consumer acceptability. The LO process produces numerous volatile organic compounds (VOC) including aldehydes, ketones and alcohols, which are known to contribute to the development of off-flavours in dairy powders. The main factors influencing the oxidative state of dairy powders and the various analytical techniques used to detect VOC as indicators of LO in dairy powders are outlined. As the ability to identify and quantify specific VOC associated with LO improves this review highlights how these techniques can be used in conjunction with olfactory and sensory analysis to better understand product specific LO processes with the aim of maximizing shelf-life without compromising quality.
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Kiralan, M., G. Çalik, S. Kiralan, A. Özaydin, G. Özkan, and M. F. Ramadan. "Stability and volatile oxidation compounds of grape seed, flax seed and black cumin seed cold-pressed oils as affected by thermal oxidation." Grasas y Aceites 70, no. 1 (January 28, 2019): 295. http://dx.doi.org/10.3989/gya.0570181.
Повний текст джерелаАнотація:
The old-pressed oils (CPO) from grape seeds (GSO), flax seeds (FSO) and black cumin seeds (BSO) were analyzed for their fatty acid profiles, tocopherols, total phenolics, bioactives and phenolic compositions. The stability of CPO under thermal oxidation conditions was evaluated. The main fatty acid in FSO was linolenic acid (56.5% of total fatty acids); while GSO and BSO were rich in linoleic acid, which accounted for 66.8 and 56.8%, respectively. GSO was rich in ?-tocopherol (123.0 mg/kg), while ?-tocopherol was a prevalent isomer in FSO and BSO (137.9 and 128.9 mg/kg, respectively). The total phenolic contents in the oils ranged from 554 mg GAE/kg oil (FSO) to 1140 mg GAE/kg oil (BSO). Luteolin, dihydroquercetin and benzoic acids were the dominant bioactives and phenolics in FSO, GSO and BSO, respectively. Based on the oxidative stability index (OSI) value, BSO showed the highest value (6.14 h) among the other oils. The oxidative stability of FSO and BSO were higher than GSO according to peroxide value (PV) and conjugated diene (CD) values of the oils during storage at 60 °C. Hexanal, 2,4-heptadienal and (E,E)-2,4-heptadienal were the major volatile oxidation compounds (VOC) in FSO. Hexanal and (E)-2-heptanal were the main identified VOC in the GSO and BSO under the same oxidation conditions.
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Esparza-Isunza, Tristán, and Felipe López-Isunza. "Modeling the Transient VOC (toluene) Oxidation in a Packed-Bed Catalytic Reactor." International Journal of Chemical Reactor Engineering 14, no. 6 (December 1, 2016): 1177–85. http://dx.doi.org/10.1515/ijcre-2016-0026.
Повний текст джерелаАнотація:
Abstract A model is developed to study the transient behavior of a non-isothermal, non-adiabatic packed-bed reactor during VOC (toluene) oxidation with air on a mixed-oxide catalyst via Mars-van Krevelen kinetic scheme. The aim is to find a safe reactor design and operating conditions for VOC elimination, which has been collected in a battery of adsorption units from dilute VOC streams. Once each adsorption column is saturated, a non-isothermal desorption takes place, and the gas stream exiting the sequence of VOC desorption columns feeds continuously the catalytic reactor for VOC elimination. The reactor model describes a 2D two-phase system interacting through the gas-solid interphase, including convection and axial and radial dispersions of mass and heat. The simulations show that the gas flow velocity, and reactor and particle diameters, are key parameters to achieve a safe design, and that traveling reaction fronts in the packed-bed exist when a series of reversible stepwise changes are performed in the concentration and temperature at the feed, as a result of the transient balance between heat generation and heat elimination along the packed-bed. When comparing the perturbation in VOC concentration at the feed versus those in temperature, a large parametric sensitivity is observed for the latter case without the presence of multiple steady states. Due to the uncertainty in the values of the effective heat transport parameters, transient responses of different magnitude are observed for the same operating conditions when using heat transport parameter of different magnitude.
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OJALA, S., U. LASSI, M. HARKONEN, T. MAUNULA, R. SILVONEN, and R. KEISKI. "Durability of VOC catalysts in solvent emission oxidation." Chemical Engineering Journal 120, no. 1-2 (July 1, 2006): 11–16. http://dx.doi.org/10.1016/j.cej.2006.03.023.
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Agarwal, Sanjay K., and James J. Spivey. "Economic effects of catalyst deactivation during VOC oxidation." Environmental Progress 12, no. 3 (August 1993): 182–85. http://dx.doi.org/10.1002/ep.670120306.
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Karl, T., A. Guenther, A. Turnipseed, P. Artaxo, and S. Martin. "Rapid formation of isoprene photo-oxidation products observed in Amazonia." Atmospheric Chemistry and Physics Discussions 9, no. 3 (June 22, 2009): 13629–53. http://dx.doi.org/10.5194/acpd-9-13629-2009.
Повний текст джерелаАнотація:
Abstract. Isoprene represents the single most important reactive hydrocarbon for atmospheric chemistry in the tropical atmosphere. It plays a central role in global and regional atmospheric chemistry and possible climate feedbacks. Photo-oxidation of primary hydrocarbons (e.g. isoprene) leads to the formation of oxygenated VOCs (OVOCs). The evolution of these intermediates affects the oxidative capacity of the atmosphere (by reacting with OH) and can contribute to secondary aerosol formation, a poorly understood process. An accurate and quantitative understanding of VOC oxidation processes is needed for model simulations of regional air quality and global climate. Based on field measurements conducted during the Amazonian aerosol characterization experiment (AMAZE-08) we show that the production of certain OVOCs (e.g. hydroxyacetone) from isoprene photo-oxidation in the lower atmosphere is significantly underpredicted by standard chemistry schemes. A recently suggested novel pathway for isoprene peroxy radicals could explain the observed discrepancy and reconcile the rapid formation of these VOCs. Furthermore, if generalized our observations suggest that prompt photochemical formation of OVOCs and other uncertainties in VOC oxidation schemes could result in substantial underestimates of modelled OH reactivity that could explain a major fraction of the missing OH sink over forests which has previously been attributed to a missing source of primary biogenic VOCs.
13
Camredon, M., B. Aumont, J. Lee-Taylor, and S. Madronich. "The SOA/VOC/NOx system: an explicit model of secondary organic aerosol formation." Atmospheric Chemistry and Physics Discussions 7, no. 4 (August 2, 2007): 11223–56. http://dx.doi.org/10.5194/acpd-7-11223-2007.
Повний текст джерелаАнотація:
Abstract. Our current understanding of secondary organic aerosol (SOA) formation is limited by our knowledge of gaseous secondary organics involved in gas/particle partitioning. The objective of this study is to explore (i) the potential for products of multiple oxidation steps contributing to SOA, and (ii) the evolution of the SOA/VOC/NOx system. We developed an explicit model based on the coupling of detailed gas-phase oxidation schemes with a thermodynamic condensation module. Such a model allows prediction of SOA mass and speciation on the basis of first principles. The SOA/VOC/NOx system is studied for the oxidation of 1-octene under atmospherically relevant concentrations. In this study, gaseous oxidation of octene is simulated to lead to SOA formation. Contributors to SOA formation are shown to be formed via multiple oxidation steps of the parent hydrocarbon. The behaviour of the SOA/VOC/NOx system simulated using the explicit model agrees with general tendencies observed during laboratory chamber experiments. This explicit modelling of SOA formation appears as a useful exploratory tool to (i) support interpretations of SOA formation observed in laboratory chamber experiments, (ii) give some insights on SOA formation under atmospherically relevant conditions and (iii) investigate implications for the regional/global lifetimes of the SOA.
14
Camredon, M., B. Aumont, J. Lee-Taylor, and S. Madronich. "The SOA/VOC/NO<sub>x</sub> system: an explicit model of secondary organic aerosol formation." Atmospheric Chemistry and Physics 7, no. 21 (November 13, 2007): 5599–610. http://dx.doi.org/10.5194/acp-7-5599-2007.
Повний текст джерелаАнотація:
Abstract. Our current understanding of secondary organic aerosol (SOA) formation is limited by our knowledge of gaseous secondary organics involved in gas/particle partitioning. The objective of this study is to explore (i) the potential for products of multiple oxidation steps contributing to SOA, and (ii) the evolution of the SOA/VOC/NOx system. We developed an explicit model based on the coupling of detailed gas-phase oxidation schemes with a thermodynamic condensation module. Such a model allows prediction of SOA mass and speciation on the basis of first principles. The SOA/VOC/NOx system is studied for the oxidation of 1-octene under atmospherically relevant concentrations. In this study, gaseous oxidation of octene is simulated to lead to SOA formation. Contributors to SOA formation are shown to be formed via multiple oxidation steps of the parent hydrocarbon. The behaviour of the SOA/VOC/NOx system simulated using the explicit model agrees with general tendencies observed during laboratory chamber experiments. This explicit modelling of SOA formation appears as a useful exploratory tool to (i) support interpretations of SOA formation observed in laboratory chamber experiments, (ii) give some insights on SOA formation under atmospherically relevant conditions and (iii) investigate implications for the regional/global lifetimes of the SOA.
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Chiemchaisri, Wilai, Chettiyappan Visvanathan, and Shing Wu Jy. "Effects of trace volatile organic compounds on methane oxidation." Brazilian Archives of Biology and Technology 44, no. 2 (June 2001): 135–40. http://dx.doi.org/10.1590/s1516-89132001000200005.
Повний текст джерелаАнотація:
The effects of volatile organic compounds (VOCs) on methane oxidation in landfill cover soils were examined. The batch experiments were conducted using single and mixed VOCs, such as, dichloromethane (DCM), trichloroethylene (TCE), tetrachloroethylene (PCE), and benzene. The results from all combinations showed a decrease in methane oxidation rate with increase in VOC concentrations. Moreover, inhibition effects of TCE and DCM were found higher than benzene and PCE. The reduction of methane oxidation by benzene and PCE could be attributed to the toxicity effect, whereas TCE and DCM were found to exhibit the competitive-inhibition effect. When the soil was mixed with DCM, no methane oxidation was found. Damage to the cell’s internal membrane was found in a methanotrophic culture exposed to VOC gases which is the attachment site of a key enzyme needed for methane oxidation
16
Topudurti, Kirankumar, Mary Wojciechowski, Sandy Anagnostopoulos, and Richard Eilers. "Field evaluation of a photocatalytic oxidation technology." Water Science and Technology 38, no. 7 (October 1, 1998): 117–25. http://dx.doi.org/10.2166/wst.1998.0284.
Повний текст джерелаАнотація:
A commercial-scale photocatalytic oxidation system developed by Matrix Photocatalytic Inc. (Matrix) was evaluated to generate performance and cost data for the treatment of groundwater contaminated with volatile organic compounds (VOCs). High percent removals (up to 99.9%) were observed for aromatic and unsaturated VOCs. However, saturated VOC removals were insignificant. Oxidant addition to the contaminated groundwater significantly improved the treatment system performance. The Matrix system performance was reproducible under identical operating conditions. Treatment by the Matrix system did not reduce the groundwater toxicity for water fleas and fathead minnows at the 95% confidence level. Toxicity reduction achieved through VOC removal appears to have been negated by the formation of toxic byproducts including aldehydes and haloacetic acids. Estimated treatment costs are about $7.60 per 1,000 litres of groundwater.
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Kelly, Jamie M., Ruth M. Doherty, Fiona M. O'Connor, Graham W. Mann, Hugh Coe, and Dantong Liu. "The roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production: a global perspective using the UKCA chemistry–climate model (vn8.4)." Geoscientific Model Development 12, no. 6 (June 28, 2019): 2539–69. http://dx.doi.org/10.5194/gmd-12-2539-2019.
Повний текст джерелаАнотація:
Abstract. The representation of volatile organic compound (VOC) deposition and oxidation mechanisms in the context of secondary organic aerosol (SOA) formation are developed in the United Kingdom Chemistry and Aerosol (UKCA) chemistry–climate model. Impacts of these developments on both the global SOA budget and model agreement with observations are quantified. Firstly, global model simulations were performed with varying VOC dry deposition and wet deposition fluxes. Including VOC dry deposition reduces the global annual-total SOA production rate by 2 %–32 %, with the range reflecting uncertainties in surface resistances. Including VOC wet deposition reduces the global annual-total SOA production rate by 15 % and is relatively insensitive to changes in effective Henry's law coefficients. Without precursor deposition, simulated SOA concentrations are lower than observed with a normalised mean bias (NMB) of −51 %. Hence, including SOA precursor deposition worsens model agreement with observations even further (NMB =-66 %). Secondly, for the anthropogenic and biomass burning VOC precursors of SOA (VOCANT∕BB), model simulations were performed by (a) varying the parent hydrocarbon reactivity, (b) varying the number of reaction intermediates, and (c) accounting for differences in volatility between oxidation products from various pathways. These changes were compared to a scheme where VOCANT∕BB adopts the reactivity of a monoterpene (α-pinene), and is oxidised in a single-step mechanism with a fixed SOA yield. By using the chemical reactivity of either benzene, toluene, or naphthalene for VOCANT∕BB, the global annual-total VOCANT∕BB oxidation rate changes by −3 %, −31 %, or −66 %, respectively, compared to when using α-pinene. Increasing the number of reaction intermediates, by introducing a peroxy radical (RO2), slightly slows the rate of SOA formation, but has no impact on the global annual-total SOA production rate. However, RO2 undergoes competitive oxidation reactions, forming products with substantially different volatilities. Accounting for the differences in product volatility between RO2 oxidation pathways increases the global SOA production rate by 153 % compared to using a single SOA yield. Overall, for relatively reactive compounds such as toluene and naphthalene, the reduction in reactivity for VOCANT∕BB oxidation is outweighed by accounting for the difference in volatility of RO2 products, leading to a net increase in the global annual-total SOA production rate of 85 % and 145 %, respectively, and improvements in model agreement (NMB of −46 % and 56 %, respectively). However, for benzene, the reduction in VOCANT∕BB oxidation is not outweighed by accounting for the difference in SOA yield pathways, leading to a small change in the global annual-total SOA production rate of −3 %, and a slight worsening of model agreement with observations (NMB =-77 %). These results highlight that variations in both VOC deposition and oxidation mechanisms contribute to substantial uncertainties in the global SOA budget and model agreement with observations.
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Deng, Shuang Mei, and Min Wang. "Applications of Titanium Dioxide Photocatalytic Technology in Degrading VOC in Cars." Applied Mechanics and Materials 217-219 (November 2012): 1204–8. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.1204.
Повний текст джерелаАнотація:
The current situation of research on titanium dioxide photocatalytic oxidation technology is introduced. Based on the general characteristics of VOC in cars, the application and the research of the titanium dioxide photocatalytic technology in degrading VOC in cars are described and then analyze the problems of the technology in industrial application and its prospects in the future.
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Kim, Hyo-Sik, Hyun-Ji Kim, Ji-Hyeon Kim, Jin-Ho Kim, Suk-Hwan Kang, Jae-Hong Ryu, No-Kuk Park, Dae-Sik Yun, and Jong-Wook Bae. "Noble-Metal-Based Catalytic Oxidation Technology Trends for Volatile Organic Compound (VOC) Removal." Catalysts 12, no. 1 (January 7, 2022): 63. http://dx.doi.org/10.3390/catal12010063.
Повний текст джерелаАнотація:
Volatile organic compounds (VOCs) are toxic and are considered the most important sources for the formation of photochemical smog, secondary organic aerosols (SOAs), and ozone. These can also greatly affect the environment and human health. For this reason, VOCs are removed by applying various technologies or reused after recovery. Catalytic oxidation for VOCs removal is widely applied in the industry and is regarded as an efficient and economical method compared to other VOCs removal technologies. Currently, a large amount of VOCs are generated in industries with solvent-based processes, and the ratio of aromatic compounds is high. This paper covers recent catalytic developments in VOC combustion over noble-metal-based catalysts. In addition, this report introduces recent trends in the development of the catalytic mechanisms of VOC combustion and the deactivation of catalysts, such as coke formation, poisoning, sintering, and catalyst regeneration. Since VOC oxidation by noble metal catalysts depends on the support of and mixing catalysts, an appropriate catalyst should be used according to reaction characteristics. Moreover, noble metal catalysts are used together with non-noble metals and play a role in the activity of other catalysts. Therefore, further elucidation of their function and catalytic mechanism in VOC removal is required.
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Kaiser, J., G. M. Wolfe, B. Bohn, S. Broch, H. Fuchs, L. N. Ganzeveld, S. Gomm, et al. "Evidence for an unidentified ground-level source of formaldehyde in the Po Valley with potential implications for ozone production." Atmospheric Chemistry and Physics Discussions 14, no. 18 (October 1, 2014): 25139–65. http://dx.doi.org/10.5194/acpd-14-25139-2014.
Повний текст джерелаАнотація:
Abstract. Ozone concentrations in the Po Valley of Northern Italy often exceed international regulations. As both a source of radicals and an intermediate in the oxidation of most volatile organic compounds (VOCs), formaldehyde (HCHO) is a useful tracer for the oxidative processing of hydrocarbons that leads to ozone production. We investigate the sources of HCHO in the Po Valley using vertical profile measurements acquired from the airship Zeppelin NT over an agricultural region during the PEGASOS 2012 campaign. Using a 1-D model, the total VOC oxidation rate is examined and discussed in the context of formaldehyde and ozone production in the early morning. While model and measurement discrepancies in OH reactivity are small (on average 3.4±11%), HCHO concentrations are underestimated by as much as 1.5 ppb (45%) in the convective mixed layer. A similar underestimate in HCHO was seen in the 2002–2003 FORMAT Po-Valley measurements, though the additional source of HCHO was not identified. Oxidation of unmeasured VOC precursors cannot explain the missing HCHO source, as measured OH reactivity is explained by measured VOCs and their calculated oxidation products. We conclude that local direct emissions from agricultural land are the most likely source of missing HCHO. Model calculations demonstrate that radicals from degradation of this non-photochemical HCHO source increase model ozone production rates by as much as 0.7 ppb h−1 (10%) before noon.
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Kaiser, J., G. M. Wolfe, B. Bohn, S. Broch, H. Fuchs, L. N. Ganzeveld, S. Gomm, et al. "Evidence for an unidentified non-photochemical ground-level source of formaldehyde in the Po Valley with potential implications for ozone production." Atmospheric Chemistry and Physics 15, no. 3 (February 6, 2015): 1289–98. http://dx.doi.org/10.5194/acp-15-1289-2015.
Повний текст джерелаАнотація:
Abstract. Ozone concentrations in the Po Valley of northern Italy often exceed international regulations. As both a source of radicals and an intermediate in the oxidation of most volatile organic compounds (VOCs), formaldehyde (HCHO) is a useful tracer for the oxidative processing of hydrocarbons that leads to ozone production. We investigate the sources of HCHO in the Po Valley using vertical profile measurements acquired from the airship Zeppelin NT over an agricultural region during the PEGASOS 2012 campaign. Using a 1-D model, the total VOC oxidation rate is examined and discussed in the context of formaldehyde and ozone production in the early morning. While model and measurement discrepancies in OH reactivity are small (on average 3.4 ± 13%), HCHO concentrations are underestimated by as much as 1.5 ppb (45%) in the convective mixed layer. A similar underestimate in HCHO was seen in the 2002–2003 FORMAT Po Valley measurements, though the additional source of HCHO was not identified. Oxidation of unmeasured VOC precursors cannot explain the missing HCHO source, as measured OH reactivity is explained by measured VOCs and their calculated oxidation products. We conclude that local direct emissions from agricultural land are the most likely source of missing HCHO. Model calculations demonstrate that radicals from degradation of this non-photochemical HCHO source increase model ozone production rates by as much as 0.6 ppb h−1 (12%) before noon.
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Chi-Sheng Wu, Jeffrey, and Tai-Yuan Chang. "VOC deep oxidation over Pt catalysts using hydrophobic supports." Catalysis Today 44, no. 1-4 (September 1998): 111–18. http://dx.doi.org/10.1016/s0920-5861(98)00179-5.
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Raciulete, Monica, and Pavel Afanasiev. "Manganese-containing VOC oxidation catalysts prepared in molten salts." Applied Catalysis A: General 368, no. 1-2 (October 2009): 79–86. http://dx.doi.org/10.1016/j.apcata.2009.08.012.
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Saarikoski, Sanna, Heidi Hellén, Arnaud P. Praplan, Simon Schallhart, Petri Clusius, Jarkko V. Niemi, Anu Kousa, et al. "Characterization of volatile organic compounds and submicron organic aerosol in a traffic environment." Atmospheric Chemistry and Physics 23, no. 5 (March 6, 2023): 2963–82. http://dx.doi.org/10.5194/acp-23-2963-2023.
Повний текст джерелаАнотація:
Abstract. Urban air consists of a complex mixture of gaseous and particulate species from anthropogenic and biogenic sources that are further processed in the atmosphere. This study investigated the characteristics and sources of volatile organic compounds (VOCs) and submicron organic aerosol (OA) in a traffic environment in Helsinki, Finland, in late summer. The anthropogenic VOCs (aVOCs; aromatic hydrocarbons) and biogenic VOCs (bVOCs; terpenoids) relevant for secondary-organic-aerosol formation were analyzed with an online gas chromatograph mass spectrometer, whereas the composition and size distribution of submicron particles was measured with a soot particle aerosol mass spectrometer. This study showed that aVOC concentrations were significantly higher than bVOC concentrations in the traffic environment. The largest aVOC concentrations were measured for toluene (campaign average of 1630 ng m−3) and p/m xylene (campaign average of 1070 ng m−3), while the dominating bVOC was α-pinene (campaign average of 200 ng m−3). For particle-phase organics, the campaign-average OA concentration was 2.4 µg m−3. The source apportionment analysis extracted six factors for OA. Three OA factors were related to primary OA sources – traffic (24 % of OA, two OA types) and a coffee roastery (7 % of OA) – whereas the largest fraction of OA (69 %) consisted of oxygenated OA (OOA). OOA was divided into less oxidized semi-volatile OA (SV-OOA; 40 % of OA) and two types of low-volatility OA (LV-OOA; 30 %). The focus of this research was also on the oxidation potential of the measured VOCs and the association between VOCs and OA in ambient air. Production rates of the oxidized compounds (OxPR) from the VOC reactions revealed that the main local sources of the oxidation products were O3 oxidation of bVOCs (66 % of total OxPR) and OH radical oxidation of aVOCs and bVOCs (25 % of total OxPR). Overall, aVOCs produced a much smaller portion of the oxidation products (18 %) than bVOCs (82 %). In terms of OA factors, SV-OOA was likely to originate from biogenic sources since it correlated with an oxidation product of monoterpene, nopinone. LV-OOA consisted of highly oxygenated long-range or regionally transported OA that had no correlation with local oxidant concentrations as it had already spent several days in the atmosphere before reaching the measurement site. In general, the main sources were different for VOCs and OA in the traffic environment. Vehicle emissions impacted both VOC and OA concentrations. Due to the specific VOCs attributed to biogenic emissions, the influence of biogenic emissions was more clearly detected in the VOC concentrations than in OA. In contrast, the emissions from the local coffee roastery had a distinctive mass spectrum for OA, but they could not be seen in the VOC measurements due to the measurement limitations for the large VOC compounds. Long-range transport increased the OA concentration and oxidation state considerably, while its effect was observed less clearly in the VOC measurements due to the oxidation of most VOC in the atmosphere during the transport. Overall, this study revealed that in order to properly characterize the impact of different emission sources on air quality, health, and climate, it is of importance to describe both gaseous and particulate emissions and understand how they interact as well as their phase transfers in the atmosphere during the aging process.
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Karl, T., A. Guenther, A. Turnipseed, G. Tyndall, P. Artaxo, and S. Martin. "Rapid formation of isoprene photo-oxidation products observed in Amazonia." Atmospheric Chemistry and Physics 9, no. 20 (October 19, 2009): 7753–67. http://dx.doi.org/10.5194/acp-9-7753-2009.
Повний текст джерелаАнотація:
Abstract. Isoprene represents the single most important reactive hydrocarbon for atmospheric chemistry in the tropical atmosphere. It plays a central role in global and regional atmospheric chemistry and possible climate feedbacks. Photo-oxidation of primary hydrocarbons (e.g. isoprene) leads to the formation of oxygenated VOCs (OVOCs). The evolution of these intermediates affects the oxidative capacity of the atmosphere (by reacting with OH) and can contribute to secondary aerosol formation, a poorly understood process. An accurate and quantitative understanding of VOC oxidation processes is needed for model simulations of regional air quality and global climate. Based on field measurements conducted during the Amazonian Aerosol Characterization Experiment (AMAZE-08) we show that the production of certain OVOCs (e.g. hydroxyacetone) from isoprene photo-oxidation in the lower atmosphere is significantly underpredicted by standard chemistry schemes. Recently reported fast secondary production could explain 50% of the observed discrepancy with the remaining part possibly produced via a novel primary production channel, which has been proposed theoretically. The observations of OVOCs are also used to test a recently proposed HOx recycling mechanism via degradation of isoprene peroxy radicals. If generalized our observations suggest that prompt photochemical formation of OVOCs and other uncertainties in VOC oxidation schemes could result in uncertainties of modelled OH reactivity, potentially explaining a fraction of the missing OH sink over forests which has previously been largely attributed to a missing source of primary biogenic VOCs.
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Torrente-Murciano, Laura, Benjamín Solsona, Saïd Agouram, Rut Sanchis, José Manuel López, Tomás García, and Rodolfo Zanella. "Low temperature total oxidation of toluene by bimetallic Au–Ir catalysts." Catalysis Science & Technology 7, no. 13 (2017): 2886–96. http://dx.doi.org/10.1039/c7cy00635g.
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Tsigaridis, K., J. Lathière, M. Kanakidou, and D. A. Hauglustaine. "Naturally driven variability in the global secondary organic aerosol over a decade." Atmospheric Chemistry and Physics Discussions 5, no. 2 (March 9, 2005): 1255–83. http://dx.doi.org/10.5194/acpd-5-1255-2005.
Повний текст джерелаАнотація:
Abstract. In order to investigate the variability of the secondary organic aerosol (SOA) distributions and budget and provide a measure for the robustness of the conclusions on human induced changes of SOA, a global 3-dimensional chemistry transport model describing both the gas and the particulate phase chemistry of the troposphere has been applied. The response of the global budget of SOA to temperature and moisture changes as well as to biogenic emission changes over a decade (1984–1993) has been evaluated. The considered emissions of biogenic non-methane volatile organic compounds (VOC) are driven by temperature, light and vegetation. They vary between 756 and 810 TgC y-1 and are therefore about 5.5 times higher than the anthropogenic VOC emissions. All secondary aerosols (sulphuric, nitrates and organics) are computed on-line together with the aerosol associated water. Over the studied decade, the computed natural variations (8%) in the chemical SOA production from biogenic VOC oxidation equal the chemical SOA production from anthropogenic VOC oxidation. This computed variability results from a 7% increase in biogenic VOC emissions combined with 8.5% and 6% increases in the wet and dry deposition of SOA and leads to about 11.5% increase in the SOA burden of biogenic origin. The present study also demonstrates the importance of the hydrological cycle in determining the built up and fate of SOA in the atmosphere. It also reveals the existence of significant positive and negative feedback mechanisms in the atmosphere responsible for the non linear relationship between emissions of biogenic VOC and SOA burden.
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Sydorenko, Jekaterina, Arvo Mere, Malle Krunks, Marina Krichevskaya, and Ilona Oja Acik. "Transparent TiO2 thin films with high photocatalytic activity for indoor air purification." RSC Advances 12, no. 55 (2022): 35531–42. http://dx.doi.org/10.1039/d2ra06488j.
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Vimont, Isaac J., Jocelyn C. Turnbull, Vasilii V. Petrenko, Philip F. Place, Colm Sweeney, Natasha Miles, Scott Richardson, Bruce H. Vaughn та James W. C. White. "An improved estimate for the <i>δ</i><sup>13</sup>C and <i>δ</i><sup>18</sup>O signatures of carbon monoxide produced from atmospheric oxidation of volatile organic compounds". Atmospheric Chemistry and Physics 19, № 13 (5 липня 2019): 8547–62. http://dx.doi.org/10.5194/acp-19-8547-2019.
Повний текст джерелаАнотація:
Abstract. Atmospheric carbon monoxide (CO) is a key player in global atmospheric chemistry and a regulated pollutant in urban areas. Oxidation of volatile organic compounds (VOCs) is an important component of the global CO budget and has also been hypothesized to contribute substantially to the summertime urban CO budget. In principle, stable isotopic analysis of CO could constrain the magnitude of this source. However, the isotopic signature of VOC-produced CO has not been well quantified, especially for the oxygen isotopes. We performed measurements of CO stable isotopes on air samples from two sites around Indianapolis, US, over three summers to investigate the isotopic signature of VOC-produced CO. One of the sites is located upwind of the city, allowing us to quantitatively remove the background air signal and isolate the urban CO enhancements. as well as the isotopic signature of these enhancements. In addition, we use measurements of Δ14CO2 in combination with the CO:CO2 emission ratio from fossil fuels to constrain the fossil-fuel-derived CO and thereby isolate the VOC-derived component of the CO enhancement. Combining these measurements and analyses, we are able to determine the carbon and oxygen isotopic signatures of CO derived from VOC oxidation as -32.8‰±0.5‰ and 3.6 ‰±1.2 ‰, respectively. Additionally, we analyzed CO stable isotopes for 1 year at Beech Island, South Carolina, US, a site thought to have large VOC-derived contributions to the summertime CO budget. The Beech Island results are consistent with isotopic signatures of VOC-derived CO determined from the Indianapolis data. This study represents the first direct determination of the isotopic signatures of VOC-derived CO and will allow for improved use of isotopes in constraining the global and regional CO budgets.
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Tsigaridis, K., J. Lathière, M. Kanakidou, and D. A. Hauglustaine. "Naturally driven variability in the global secondary organic aerosol over a decade." Atmospheric Chemistry and Physics 5, no. 7 (July 26, 2005): 1891–904. http://dx.doi.org/10.5194/acp-5-1891-2005.
Повний текст джерелаАнотація:
Abstract. In order to investigate the variability of the secondary organic aerosol (SOA) distributions and budget and provide a measure for the robustness of the conclusions on human induced changes of SOA, a global 3-dimensional chemistry transport model describing both the gas and the particulate phase chemistry of the troposphere has been applied. The response of the global budget of SOA to temperature and moisture changes as well as to biogenic emission changes over a decade (1984-1993) has been evaluated. The considered emissions of biogenic non-methane volatile organic compounds (VOC) are driven by temperature, light and vegetation. They vary between 756 and 810 Tg Cy-1 and are therefore about 5.5 times higher than the anthropogenic VOC emissions. All secondary aerosols (sulphuric, nitrates and organics) are computed on-line together with the aerosol associated water. Over the studied decade, the computed natural variations (8%) in the chemical SOA production from biogenic VOC oxidation equal the chemical SOA production from anthropogenic VOC oxidation. Maximum values are calculated for 1990 (warmer and drier) and minimum values for 1986 (colder and wetter). The SOA computed variability results from a 7% increase in biogenic VOC emissions from 1986 to 1990 combined with 8.5% and 6% increases in the wet and dry deposition of SOA and leads to about 11.5% increase in the SOA burden of biogenic origin. The present study also demonstrates the importance of the hydrological cycle in determining the built up and fate of SOA in the atmosphere. It also reveals the existence of significant positive and negative feedback mechanisms in the atmosphere responsible for the non linear relationship between emissions of biogenic VOC and SOA burden.
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Steiner, A. L., R. C. Cohen, R. A. Harley, S. Tonse, A. H. Goldstein, D. B. Millet, and G. W. Schade. "VOC reactivity in central California: comparing an air quality model to ground-based measurements." Atmospheric Chemistry and Physics Discussions 7, no. 5 (September 7, 2007): 13077–119. http://dx.doi.org/10.5194/acpd-7-13077-2007.
Повний текст джерелаАнотація:
Abstract. Volatile organic compound (VOC) reactivity in central California is examined using a photochemical air quality model (the Community Multiscale Air Quality model; CMAQ) and ground-based measurements to evaluate the contribution of VOC to photochemical activity. We classify VOC into four categories: anthropogenic, biogenic, aldehyde, and other oxygenated VOC. Anthropogenic and biogenic VOC consist of primary emissions, while aldehydes and other oxygenated VOC include both primary anthropogenic emissions and secondary products from primary VOC oxidation. To evaluate the model treatment of VOC chemistry, we compare measured and modeled OH and VOC reactivities using the following metrics: 1) cumulative distribution functions of NOx concentration and VOC reactivity (ROH,VOC), 2) the relationship between ROH,VOC and NOx, 3) total OH reactivity (ROH,total) and speciated contributions, and 4) the relationship between speciated ROH,VOC and NOx. We find that the model predicts ROH,total to within 25–40% at three sites representing urban (Sacramento), suburban (Granite Bay) and rural (Blodgett Forest) chemistry. However in the urban area of Fresno, the model under predicts NOx and VOC emissions by a factor of 2–3. At all locations the model is consistent with observations of the relative contributions of total VOC. In urban areas, anthropogenic and biogenic ROH,VOC are predicted fairly well over a range of NOx conditions. In suburban and rural locations, anthropogenic and other oxygenated ROH,VOC relationships are reproduced, but measured biogenic and aldehyde ROH,VOC are often poorly characterized by measurements, making evaluation of the model with available data unreliable. In central California, 30–50% of the modeled urban VOC reactivity is due to aldehydes and other oxygenated species, and the total oxygenated ROH,VOC is nearly equivalent to anthropogenic VOC reactivity. In rural vegetated regions, biogenic and aldehyde reactivity dominates. This indicates that more attention needs to be paid to the accuracy of models and measurements of both primary emissions of oxygenated VOC and secondary production of oxygenates, especially formaldehyde and other aldehydes, and that a more comprehensive set of oxygenated VOC measurements is required to include all of the important contributions to atmospheric reactivity.
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Steiner, A. L., R. C. Cohen, R. A. Harley, S. Tonse, D. B. Millet, G. W. Schade, and A. H. Goldstein. "VOC reactivity in central California: comparing an air quality model to ground-based measurements." Atmospheric Chemistry and Physics 8, no. 2 (January 29, 2008): 351–68. http://dx.doi.org/10.5194/acp-8-351-2008.
Повний текст джерелаАнотація:
Abstract. Volatile organic compound (VOC) reactivity in central California is examined using a photochemical air quality model (the Community Multiscale Air Quality model; CMAQ) and ground-based measurements to evaluate the contribution of VOC to photochemical activity. We classify VOC into four categories: anthropogenic, biogenic, aldehyde, and other oxygenated VOC. Anthropogenic and biogenic VOC consist of primary emissions, while aldehydes and other oxygenated VOC include both primary anthropogenic emissions and secondary products from primary VOC oxidation. To evaluate the model treatment of VOC chemistry, we compare calculated and modeled OH and VOC reactivities using the following metrics: 1) cumulative distribution functions of NOx concentration and VOC reactivity (ROH,VOC), 2) the relationship between ROH,VOC and NOx, 3) total OH reactivity (ROH,total) and speciated contributions, and 4) the relationship between speciated ROH,VOC and NOx. We find that the model predicts ROH,total to within 25–40% at three sites representing urban (Sacramento), suburban (Granite Bay) and rural (Blodgett Forest) chemistry. However in the urban area of Fresno, the model under predicts NOx and VOC emissions by a factor of 2–3. At all locations the model is consistent with observations of the relative contributions of total VOC. In urban areas, anthropogenic and biogenic ROH,VOC are predicted fairly well over a range of NOx conditions. In suburban and rural locations, anthropogenic and other oxygenated ROH,VOC relationships are reproduced, but calculated biogenic and aldehyde ROH,VOC are often poorly characterized by measurements, making evaluation of the model with available data unreliable. In central California, 30–50% of the modeled urban VOC reactivity is due to aldehydes and other oxygenated species, and the total oxygenated ROH,VOC is nearly equivalent to anthropogenic VOC reactivity. In rural vegetated regions, biogenic and aldehyde reactivity dominates. This indicates that more attention needs to be paid to the accuracy of models and measurements of both primary emissions of oxygenated VOC and secondary production of oxygenates, especially formaldehyde and other aldehydes, and that a more comprehensive set of oxygenated VOC measurements is required to include all of the important contributions to atmospheric reactivity.
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Chen, Xin, Dylan B. Millet, Hanwant B. Singh, Armin Wisthaler, Eric C. Apel, Elliot L. Atlas, Donald R. Blake, et al. "On the sources and sinks of atmospheric VOCs: an integrated analysis of recent aircraft campaigns over North America." Atmospheric Chemistry and Physics 19, no. 14 (July 17, 2019): 9097–123. http://dx.doi.org/10.5194/acp-19-9097-2019.
Повний текст джерелаАнотація:
Abstract. We apply a high-resolution chemical transport model (GEOS-Chem CTM) with updated treatment of volatile organic compounds (VOCs) and a comprehensive suite of airborne datasets over North America to (i) characterize the VOC budget and (ii) test the ability of current models to capture the distribution and reactivity of atmospheric VOCs over this region. Biogenic emissions dominate the North American VOC budget in the model, accounting for 70 % and 95 % of annually emitted VOC carbon and reactivity, respectively. Based on current inventories anthropogenic emissions have declined to the point where biogenic emissions are the dominant summertime source of VOC reactivity even in most major North American cities. Methane oxidation is a 2× larger source of nonmethane VOCs (via production of formaldehyde and methyl hydroperoxide) over North America in the model than are anthropogenic emissions. However, anthropogenic VOCs account for over half of the ambient VOC loading over the majority of the region owing to their longer aggregate lifetime. Fires can be a significant VOC source episodically but are small on average. In the planetary boundary layer (PBL), the model exhibits skill in capturing observed variability in total VOC abundance (R2=0.36) and reactivity (R2=0.54). The same is not true in the free troposphere (FT), where skill is low and there is a persistent low model bias (∼ 60 %), with most (27 of 34) model VOCs underestimated by more than a factor of 2. A comparison of PBL : FT concentration ratios over the southeastern US points to a misrepresentation of PBL ventilation as a contributor to these model FT biases. We also find that a relatively small number of VOCs (acetone, methanol, ethane, acetaldehyde, formaldehyde, isoprene + oxidation products, methyl hydroperoxide) drive a large fraction of total ambient VOC reactivity and associated model biases; research to improve understanding of their budgets is thus warranted. A source tracer analysis suggests a current overestimate of biogenic sources for hydroxyacetone, methyl ethyl ketone and glyoxal, an underestimate of biogenic formic acid sources, and an underestimate of peroxyacetic acid production across biogenic and anthropogenic precursors. Future work to improve model representations of vertical transport and to address the VOC biases discussed are needed to advance predictions of ozone and SOA formation.
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Young, C. J., R. A. Washenfelder, P. M. Edwards, D. D. Parrish, J. B. Gilman, W. C. Kuster, L. H. Mielke, et al. "Chlorine as a primary radical: evaluation of methods to understand its role in initiation of oxidative cycles." Atmospheric Chemistry and Physics 14, no. 7 (April 7, 2014): 3427–40. http://dx.doi.org/10.5194/acp-14-3427-2014.
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Abstract. The role of chlorine atoms (Cl) in atmospheric oxidation has been traditionally thought to be limited to the marine boundary layer, where they are produced through heterogeneous reactions involving sea salt. However, recent observation of photolytic Cl precursors (ClNO2 and Cl2) formed from anthropogenic pollution has expanded the potential importance of Cl to include coastal and continental urban areas. Measurements of ClNO2 in Los Angeles during CalNex (California Nexus – Research at the Nexus of Air Quality and Climate Change) showed it to be an important primary (first generation) radical source. Evolution of ratios of volatile organic compounds (VOCs) has been proposed as a method to quantify Cl oxidation, but we find no evidence from this approach for a significant role of Cl oxidation in Los Angeles. We use a box model with the Master Chemical Mechanism (MCM v3.2) chemistry scheme, constrained by observations in Los Angeles, to examine the Cl sensitivity of commonly used VOC ratios as a function of NOx and secondary radical production. Model results indicate VOC tracer ratios could not detect the influence of Cl unless the ratio of [OH] to [Cl] was less than 200 for at least a day. However, the model results also show that secondary (second generation) OH production resulting from Cl oxidation of VOCs is strongly influenced by NOx, and that this effect obscures the importance of Cl as a primary oxidant. Calculated concentrations of Cl showed a maximum in mid-morning due to a photolytic source from ClNO2 and loss primarily to reactions with VOCs. The [OH] to [Cl] ratio was below 200 for approximately 3 h in the morning, but Cl oxidation was not evident from the measured ratios of VOCs. Instead, model simulations show that secondary OH production causes VOC ratio evolution to follow that expected for OH oxidation, despite the significant input of primary Cl from ClNO2 photolysis in the morning. Even though OH is by far the dominant oxidant in Los Angeles, Cl atoms do play an important role in photochemistry there, constituting 9% of the primary radical source. Furthermore, Cl–VOC reactivity differs from that of OH, being more than an order of magnitude larger and dominated by VOCs, such as alkanes, that are less reactive toward OH. Primary Cl is also slightly more effective as a radical source than primary OH due to its greater propensity to initiate radical propagation chains via VOC reactions relative to chain termination via reaction with nitrogen oxides.
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Kaiser, J., G. M. Wolfe, K. E. Min, S. S. Brown, C. C. Miller, D. J. Jacob, J. A. deGouw, et al. "Reassessing the ratio of glyoxal to formaldehyde as an indicator of hydrocarbon precursor speciation." Atmospheric Chemistry and Physics Discussions 15, no. 5 (March 4, 2015): 6237–75. http://dx.doi.org/10.5194/acpd-15-6237-2015.
Повний текст джерелаАнотація:
Abstract. The yield of formaldehyde (HCHO) and glyoxal (CHOCHO) from oxidation of volatile organic compounds (VOCs) depends on precursor VOC structure and the concentration of NOx (NOx = NO +NO2). Previous work has proposed that the ratio of CHOCHO to HCHO (RGF) can be used as an indicator of precursor VOC speciation, and absolute concentrations of the oxidation products as indicators of NOx. Because this metric is measurable by satellite, it is potentially useful on a global scale; however, absolute values and trends in RGF have differed between satellite and ground-based observations. To investigate potential causes of previous discrepancies and the usefulness of this ratio, we present measurements of CHOCHO and HCHO over the Southeast United States (SE US) from the 2013 SENEX flight campaign and compare these measurements with OMI satellite retrievals. High time-resolution flight measurements show that high RGF is associated with monoterpene emissions, low RGF is associated with isoprene oxidation, and emissions associated with oil and gas production can lead to small-scale variation in regional RGF. During the summertime in the SE US, RGF is not a reliable diagnostic of anthropogenic VOC emissions, as HCHO and CHOCHO production are dominated by isoprene oxidation. Our results show that the new glyoxal retrieval algorithm reduces the previous disagreement between satellite and in situ RGF observations. We conclude that satellite-based observations of RGF can be used alongside other measurements as a global diagnostic of the chemical conditions leading to secondary pollutant formation.
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Laaksonen, A., M. Kulmala, C. D. O'Dowd, J. Joutsensaari, P. Vaattovaara, S. Mikkonen, K. E. J. Lehtinen, et al. "The role of VOC oxidation products in continental new particle formation." Atmospheric Chemistry and Physics Discussions 7, no. 3 (June 4, 2007): 7819–41. http://dx.doi.org/10.5194/acpd-7-7819-2007.
Повний текст джерелаАнотація:
Abstract. Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March–April, 2003, in Hyytiälä, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono- and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were measured using the Aerodyne Aerosol Mass Spectrometer, and chemical compositions of aerosol samples collected with low-pressure impactors and a high volume sampler were analysed using a number of techniques. The results indicate that during and after new particle formation, all particles larger than 50 nm in diameter contained similar organic substances that are likely to be mono- and sesquiterpene oxidation products. The oxidation products identified in the high volume samples were shown to be mostly aldehydes. In order to study the composition of particles in the 10–50 nm range, we made use of Tandem Differential Mobility Analyzer results. We found that during nucleation events, both 10 and 50 nm particle growth factors due to uptake of ethanol vapour correlate strongly with gas-phase monoterpene oxidation product (MTOP) concentrations, indicating that the organic constituents of particles smaller than 50 nm in diameter are at least partly similar to those of larger particles. We furthermore showed that particle growth rates during the nucleation events are correlated with the gas-phase MTOP concentrations. This indicates that VOC oxidation products may have a key role in determining the spatial and temporal features of the nucleation events. This conclusion was supported by our aircraft measurements of new 3–10 nm particle concentrations, which showed that the nucleation event on 28 March 2003, started at the ground layer, i.e. near the VOC source, and evolved together with the mixed layer. Furthermore, no new particle formation was detected upwind away from the forest, above the frozen Gulf of Bothnia.
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Laaksonen, A., M. Kulmala, C. D. O'Dowd, J. Joutsensaari, P. Vaattovaara, S. Mikkonen, K. E. J. Lehtinen, et al. "The role of VOC oxidation products in continental new particle formation." Atmospheric Chemistry and Physics 8, no. 10 (May 20, 2008): 2657–65. http://dx.doi.org/10.5194/acp-8-2657-2008.
Повний текст джерелаАнотація:
Abstract. Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March–April 2003, in Hyytiälä, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono- and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were measured using the Aerodyne Aerosol Mass Spectrometer, and chemical compositions of aerosol samples collected with low-pressure impactors and a high volume sampler were analysed using a number of techniques. The results indicate that during and after new particle formation, all particles larger than 50 nm in diameter contained similar organic substances that are likely to be mono- and sesquiterpene oxidation products. The oxidation products identified in the high volume samples were shown to be mostly aldehydes. In order to study the composition of particles in the 10–50 nm range, we made use of Tandem Differential Mobility Analyzer results. We found that during nucleation events, both 10 and 50 nm particle growth factors due to uptake of ethanol vapour correlate strongly with gas-phase monoterpene oxidation product (MTOP) concentrations, indicating that the organic constituents of particles smaller than 50 nm in diameter are at least partly similar to those of larger particles. We furthermore showed that particle growth rates during the nucleation events are correlated with the gas-phase MTOP concentrations. This indicates that VOC oxidation products may have a key role in determining the spatial and temporal features of the nucleation events. This conclusion was supported by our aircraft measurements of new 3–10 nm particle concentrations, which showed that the nucleation event on 28 March 2003, started at the ground layer, i.e. near the VOC source, and evolved together with the mixed layer. Furthermore, no new particle formation was detected upwind away from the forest, above the frozen Gulf of Bothnia.
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Kim, Min-Ryeong, and Suhan Kim. "Enhanced Catalytic Oxidation of Toluene over Hierarchical Pt/Y Zeolite." Catalysts 12, no. 6 (June 6, 2022): 622. http://dx.doi.org/10.3390/catal12060622.
Повний текст джерелаАнотація:
The development of efficient Pt-supported zeolite catalysts with tunable micro/mesopore structures for the removal of volatile organic compounds (VOCs) presents a major challenge. Herein, hierarchical Pt/Y zeolites with tunable mesopores are fabricated by varying the etching time before the surfactant-templated crystal rearrangement method and used as catalyst supports for VOC oxidation. The hierarchical Pt/Y zeolites provided an excellent environment for Pt nanoparticle loading with abundant accessible acidic sites. The catalytic performance of the obtained hierarchical Pt/Y zeolites is analyzed using toluene oxidation, with the modified zeolites exhibiting improved catalytic activities. The hierarchical Pt/Y zeolites exhibited higher catalytic toluene oxidation activities than non-hierarchical Pt/Y zeolites. Pt/Y-6h demonstrated the highest catalytic toluene oxidation activity of the prepared catalysts, with a T90 of 149 °C, reaction rate of 1.15 × 10−7 mol gcat−1 s−1, turnover frequency of 1.20 × 10−2 s−1, and an apparent activation energy of 66.5 kJ mol−1 at 60,000 mL g−1 h−1 at a toluene concentration of 1000 ppm. This study will facilitate the fine-tuning of hierarchically porous materials to improve material properties and achieve higher catalytic performance toward VOC oxidation.
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Rosanka, Simon, Bruno Franco, Lieven Clarisse, Pierre-François Coheur, Andrea Pozzer, Andreas Wahner, and Domenico Taraborrelli. "The impact of organic pollutants from Indonesian peatland fires on the tropospheric and lower stratospheric composition." Atmospheric Chemistry and Physics 21, no. 14 (July 27, 2021): 11257–88. http://dx.doi.org/10.5194/acp-21-11257-2021.
Повний текст джерелаАнотація:
Abstract. The particularly strong dry season in Indonesia in 2015, caused by an exceptionally strong El Niño, led to severe peatland fires resulting in high volatile organic compound (VOC) biomass burning emissions. At the same time, the developing Asian monsoon anticyclone (ASMA) and the general upward transport in the Intertropical Convergence Zone (ITCZ) efficiently transported the resulting primary and secondary pollutants to the upper troposphere and lower stratosphere (UTLS). In this study, we assess the importance of these VOC emissions for the composition of the lower troposphere and the UTLS and investigate the effect of in-cloud oxygenated VOC (OVOC) oxidation during such a strong pollution event. This is achieved by performing multiple chemistry simulations using the global atmospheric model ECHAM/MESSy (EMAC). By comparing modelled columns of the biomass burning marker hydrogen cyanide (HCN) and carbon monoxide (CO) to spaceborne measurements from the Infrared Atmospheric Sounding Interferometer (IASI), we find that EMAC properly captures the exceptional strength of the Indonesian fires. In the lower troposphere, the increase in VOC levels is higher in Indonesia compared to other biomass burning regions. This has a direct impact on the oxidation capacity, resulting in the largest regional reduction in the hydroxyl radical (OH) and nitrogen oxides (NOx). While an increase in ozone (O3) is predicted close to the peatland fires, simulated O3 decreases in eastern Indonesia due to particularly high phenol concentrations. In the ASMA and the ITCZ, the upward transport leads to elevated VOC concentrations in the lower stratosphere, which results in the reduction of OH and NOx and the increase in the hydroperoxyl radical (HO2). In addition, the degradation of VOC emissions from the Indonesian fires becomes a major source of lower stratospheric nitrate radicals (NO3), which increase by up to 20 %. Enhanced phenol levels in the upper troposphere result in a 20 % increase in the contribution of phenoxy radicals to the chemical destruction of O3, which is predicted to be as large as 40 % of the total chemical O3 loss in the UTLS. In the months following the fires, this loss propagates into the lower stratosphere and potentially contributes to the variability of lower stratospheric O3 observed by satellite retrievals. The Indonesian peatland fires regularly occur during El Niño years, and the largest perturbations of radical concentrations in the lower stratosphere are predicted for particularly strong El Niño years. By activating the detailed in-cloud OVOC oxidation scheme Jülich Aqueous-phase Mechanism of Organic Chemistry (JAMOC), we find that the predicted changes are dampened. Global models that neglect in-cloud OVOC oxidation tend to overestimate the impact of such extreme pollution events on the atmospheric composition.
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Jolly, J., B. Pavageau, and J. M. Tatibouët. "High Throughput Approach Applied to VOC Oxidation at Low Temperature." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 68, no. 3 (March 28, 2013): 505–17. http://dx.doi.org/10.2516/ogst/2012053.
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Papaefthimiou, Panayiotis, Theophilos Ioannides, and Xenophon E. Verykios. "VOC removal: investigation of ethylacetate oxidation over supported Pt catalysts." Catalysis Today 54, no. 1 (November 1999): 81–92. http://dx.doi.org/10.1016/s0920-5861(99)00170-4.
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Mo, J., Y. Zhang, and R. Yang. "Novel insight into VOC removal performance of photocatalytic oxidation reactors." Indoor Air 15, no. 4 (August 2005): 291–300. http://dx.doi.org/10.1111/j.1600-0668.2005.00374.x.
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Dissanayake, Shanka, Niluka Wasalathanthri, Alireza Shirazi Amin, Junkai He, Shannon Poges, Dinithi Rathnayake, and Steven L. Suib. "Mesoporous Co3O4 catalysts for VOC elimination: Oxidation of 2-propanol." Applied Catalysis A: General 590 (January 2020): 117366. http://dx.doi.org/10.1016/j.apcata.2019.117366.
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Gnesdilov, N. N., K. V. Dobrego, and I. M. Kozlov. "Parametric study of recuperative VOC oxidation reactor with porous media." International Journal of Heat and Mass Transfer 50, no. 13-14 (July 2007): 2787–94. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2006.11.004.
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Kornilova, A., S. Moukhtar, M. Saccon, L. Huang, W. Zhang, and J. Rudolph. "A method for stable carbon isotope ratio and concentration measurements of ambient aromatic hydrocarbons." Atmospheric Measurement Techniques Discussions 8, no. 1 (January 30, 2015): 1365–400. http://dx.doi.org/10.5194/amtd-8-1365-2015.
Повний текст джерелаАнотація:
Abstract. A technique for compound specific analysis of stable carbon isotope ratios and concentration of ambient volatile organic compounds (VOC) is presented. It is based on selective VOC sampling onto adsorbent filled cartridges by passing large volumes of air (up to 80 L) through the cartridge. The hydrocarbons are recovered by thermal desorption followed by two step cryogenic trapping and then are separated by gas chromatography in the laboratory. Once separated, individual VOC are subjected to online oxidation in a combustion interface and isotope ratio analysis by isotope ratio mass spectrometry. The method allows measurements of stable carbon isotope ratios of ambient aromatic VOC present in low pptV to ppbV levels with an accuracy of typically better than 0.5‰. The precision of concentration measurements is better than 10%. Examples of measurements conducted as part of a joint Environment Canada-York University (EC-YU) measurement campaign at a semi-rural location demonstrate that the ability to make accurate measurements in air with low VOC mixing ratios is important to avoid bias from an over-representation of samples that are strongly impacted by recent emissions.
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Einaga, Hisahiro, Takashi Ibusuki, and Shigeru Futamura. "Photocatalytic Oxidation of Benzene in Air." Journal of Solar Energy Engineering 126, no. 2 (May 1, 2004): 789–93. http://dx.doi.org/10.1115/1.1687402.
Повний текст джерелаАнотація:
Photocatalytic oxidation of benzene in air at room temperature was studied in order to obtain the information on its reactivity on the photoirradiated TiO2 catalyst. The objective of this paper is to describe in detail the dependence of the rate for benzene photooxidation on humidity, initial benzene concentration, and incident light intensity, since they are important factors for construction of VOC control system utilizing solar energy. The reaction mechanism is also discussed to understand the decomposition behavior of benzene.
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Wang, Xiuyun, Weitao Zhao, Tianhua Zhang, Yongfan Zhang, Lilong Jiang та Shuangfen Yin. "Facile fabrication of shape-controlled CoxMnyOβ nanocatalysts for benzene oxidation at low temperatures". Chemical Communications 54, № 17 (2018): 2154–57. http://dx.doi.org/10.1039/c8cc00023a.
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Gaálová, Jana, and Pavel Topka. "Gold and Ceria as Catalysts for VOC Abatement: A Review." Catalysts 11, no. 7 (June 29, 2021): 789. http://dx.doi.org/10.3390/catal11070789.
Повний текст джерелаАнотація:
Due to its excellent oxygen storage capacity, ceria is a well-known oxidation catalyst. However, its performance in the oxidation of volatile organic compounds can be improved by the introduction of gold. Depending on the type of VOC to be oxidized, the surface of gold nanoparticles and the gold/ceria interface may contribute to enhanced activity and/or selectivity. Choosing a proper preparation method is crucial to obtain optimal gold particle size. Deposition–precipitation was found to be more suitable than coprecipitation or impregnation. For industrial applications, monolithic catalysts are needed to minimize the pressure drop in the reactor and reduce mass and heat transfer limitations. In addition to the approach used with powder catalysts, the method employed to introduce gold in/on the washcoat has to be considered.
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Trendafilova, Ivalina, Manuel Ojeda, John M. Andresen, Alenka Ristić, Momtchil Dimitrov, Nataša Novak Tušar, Genoveva Atanasova, and Margarita Popova. "Low-Temperature Toluene Oxidation on Fe-Containing Modified SBA-15 Materials." Molecules 28, no. 1 (December 26, 2022): 204. http://dx.doi.org/10.3390/molecules28010204.
Повний текст джерелаАнотація:
Transition metals as catalysts for total VOC oxidation at low temperatures (150–280 °C) are a big challenge nowadays. Therefore, iron-modified SBA-15, AlSBA-15, and ZrSBA-15 materials with 0.5 to 5.0 wt.% Fe loading were prepared and tested for toluene oxidation. It was found that increasing Fe loading significantly improved the rate of oxidation and lowered the temperature of achieving 100% removal of toluene from above 500 °C for the supports (AlSBA-15 and ZrSBA-15) to below 400 °C for 5FeZrSBA-15. The formation of finely dispersed iron oxide active sites with a particle size less than 5 nm was observed on all the SBA-15, AlSBA-15, and ZrSBA-15 supports. It was found that the surface properties of the mesoporous support due to the addition of Al or Zr predetermined the type of formed iron oxide species and their localization on the support surface. Fe-containing SBA-15 and AlSBA-15 showed activity in total toluene oxidation at higher temperatures (280–450 °C). However, 5 wt. % Fe-containing ZrSBA-15 showed excellent activity in the total oxidation of toluene as a model VOC at lower temperatures (150–380 °C) due to the synergistic effect of Fe-Zr and the presence of accessible and stable Fe2+/Fe3+ active sites.
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Le, Toan Minh, Ha Than Quoc An, and Thien Pham Huu. "SYNTHESIS OF COPPER-BASED NANOPARTICLE CATALYSTS BY DIFFERENT METHODS FOR TOTAL OXIDATION OF VOC." Vietnam Journal of Science and Technology 56, no. 3B (September 13, 2018): 228. http://dx.doi.org/10.15625/2525-2518/56/3b/12776.
Повний текст джерелаАнотація:
In this paper, the process of preparing 10 wt.% Cu/g-Al2O3 catalysts was studied by different methods. The changes in structure and texture of the catalysts were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FT-IR). The activities of catalyst were investigated completely oxidized VOC (toluene and n-butanol) on gas-phase reactions over the Cu/g-Al2O3 catalyst. The results were found that influence of the size of copper nanoparticles enhancing copper dispersion and selectivity of the catalyst prepared by non-thermal plasma (NTP) was superior to those obtained from the impregnation (WI) and deposition-precipitation (DP). The total oxidation of VOC to CO2 and H2O was achieved above 275oC. Compared to the WI and DP, the NTP method increased the oxidation efficiency by 15-30%.