Browsing by Subject "NO2"

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Afşin-Elbistan Termik Santralinin insan sağlığına ve doğaya olan etkileri
(Bilkent University, 2020) Baltacı, Berk; Er, Erhan; Eraslan, Nur; Gezay, Mina; Turunç, Furkan
Afşin-Elbistan A Termik Santrali 1984 yılında Çoğulhan mahallesinde kurulmuştur. 2006 yılında ise termik santralin B ünitesinin yapım aşaması tamamlanmıştır. Bugün her iki ünite de çalışmaya devam etmektedir. Araştırmada A santralinin çevre ve insan sağlığı üzerindeki etkileri incelenmiştir. Santral bacalarından NO2 ve SO2 gazlarının salınımının çevreye ve insan sağlığına etkileri mevcuttur. Kurulduğu günden bu yana termik santral Çoğulhan bölgesinde yaşayan insanlarda görülen çeşitli sağlık sorunlarıyla ilişkilendirilmiştir. Araştırmada ise bu sağlık sorunları istatistiklere dayanarak ortaya konulmuştur ve alınan önlemler ele alınmıştır.
Open Access
BaOx
(2011) Emmez, Emre
In this work, formation anddecomposition pathways of of Ba(NO3)2 on BaOBaO2 /Pt(111) surfaces were investigated at the molecular levelfordifferent BaOBaO2coverages starting from small 2D islands of 0.5 MLE (MLE: monolayer equivalent) to thick multilayers of 10 MLE via temperature-programmed desorption (TPD), and X-ray Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED). BaOxoverlayerswith a surface coverage of ~ 1 MLEreveallong range ordering with (2×2) and/or (1×2) structures while BaOx films with a surface coverage of1.5 MLEyields aBaO(110) termination and thicker films ( ≥ 5 MLE) were observed to be amorphous. Saturation of thick (10 MLE) BaOxoverlayers with NO2 leads to the formation of nitrates. Nitrate thermal decomposition was demonstrated to proceed through nitrite intermediates. In TPD experimentstwo major pathwaysfornitrate decomposition were observed: 1) nitrate decomposition yielding only NO evolutionat ~650 K, and 2) nitrate decomposition withNO + O2evolutionat ~700 K. This multi-step decomposition behavior was explained by BaO2 formation during the first stage. The influence of the BaOxdeposition method on the morphology of the BaOxoverlayers were established: when a thick BaOx layer is prepared using NO2 for Ba oxidation, BaOx overlayer efficiently wets the Pt(111) substrate forming a well-dispersed film. On the other hand, ifa thick BaOx layer is heated in O2 (to 873 K), BaOx overlayer agglomerates into 3D clusters, resulting in the formation of exposed (uncovered) Pt sites. BaOxoverlayers with uncoveredPt sitescan be “cured” by nitration – thermal decomposition procedures. When the BaOx layer coverage is below 2.5 MLE, nitrate decomposition temperature is observed at significantly lower temperatures, demonstrating the catalytic influence of the Pt sites facilitating the nitrate decomposition. It is proposed that initially, Ba(NO3)2 decomposesatthe boundary/peripheralsites of the Pt/BaOx interface, followed by the nitrate decomposition originating from 2D BaOx islands, and eventually from the 3D BaOx agglomerates. Catalytic deactivation of TiO2-promoted NOx-storage reduction (NSR) catalysts due to thermal aging effects was investigated using a BaO/TiO2/Pt(111) model catalyst system. At room temperature, metallic Ba overlayers on TiO2/Pt(111) was found to be very reactive towards oxide ions on TiO2/Pt(111) resulting in the formation of BaOx and partial reduction of TiO2. Ba films adsorbed on TiO2/Pt(111) that are further oxidized in O2 at 523 K lead to BaO and BaO2 surface domains which can efficiently adsorb both NO2 and CO2. Thermal treatment of BaOBaO2/TiO2/Pt(111) surface at T ≥ 300 K leads to a monotonic decrease in the surface Ba/Ti atomic ratio indicating the diffusion of BaO-BaO2 domains into the underlying TiO2 framework. Solid state reactions between BaOx and TiO2 particularly within 473-873K facilitate the formation of BaTiO3/Ba2TiO4/BaxTiyOz overlayers. After oxidation at higher temperatures (T > 873 K), surface becomes Badeficient and the enrichment of the surface with the Ti4+ sites results in a TiO2- terminated surface. Diffusion of BaOx into the TiO2 matrix and the enrichment of the surface with Ti sites drastically suppress the NO2 and CO2 adsorption/storage capacity of the model NOx storage system. These results reveal a direct evidence for the structural changes associated with the thermal deactivation of TiO2-promoted NSR catalysts.
Open Access
BaOx/ Pt(111) AND BaOx/ TiO2/ Pt(111) MODEL CATALYSTS FOR UNDERSTANDING NOx STORAGE-REDUCTION (NSR) CATALYSIS AT THE MOLECULAR LEVEL
(2011) Emmez, Emre
In this work, formation anddecomposition pathways of of Ba(NO3)2 on BaOBaO2 /Pt(111) surfaces were investigated at the molecular levelfordifferent BaOBaO2coverages starting from small 2D islands of 0.5 MLE (MLE: monolayer equivalent) to thick multilayers of 10 MLE via temperature-programmed desorption (TPD), and X-ray Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED). BaOxoverlayerswith a surface coverage of ~ 1 MLEreveallong range ordering with (2×2) and/or (1×2) structures while BaOx films with a surface coverage of1.5 MLEyields aBaO(110) termination and thicker films ( ≥ 5 MLE) were observed to be amorphous. Saturation of thick (10 MLE) BaOxoverlayers with NO2 leads to the formation of nitrates. Nitrate thermal decomposition was demonstrated to proceed through nitrite intermediates. In TPD experimentstwo major pathwaysfornitrate decomposition were observed: 1) nitrate decomposition yielding only NO evolutionat ~650 K, and 2) nitrate decomposition withNO + O2evolutionat ~700 K. This multi-step decomposition behavior was explained by BaO2 formation during the first stage. The influence of the BaOxdeposition method on the morphology of the BaOxoverlayers were established: when a thick BaOx layer is prepared using NO2 for Ba oxidation, BaOx overlayer efficiently wets the Pt(111) substrate forming a well-dispersed film. On the other hand, ifa thick BaOx layer is heated in O2 (to 873 K), BaOx overlayer agglomerates into 3D clusters, resulting in the formation of exposed (uncovered) Pt sites. BaOxoverlayers with uncoveredPt sitescan be “cured” by nitration – thermal decomposition procedures. When the BaOx layer coverage is below 2.5 MLE, nitrate decomposition temperature is observed at significantly lower temperatures, demonstrating the catalytic influence of the Pt sites facilitating the nitrate decomposition. It is proposed that initially, Ba(NO3)2 decomposesatthe boundary/peripheralsites of the Pt/BaOx interface, followed by the nitrate decomposition originating from 2D BaOx islands, and eventually from the 3D BaOx agglomerates. Catalytic deactivation of TiO2-promoted NOx-storage reduction (NSR) catalysts due to thermal aging effects was investigated using a BaO/TiO2/Pt(111) model catalyst system. At room temperature, metallic Ba overlayers on TiO2/Pt(111) was found to be very reactive towards oxide ions on TiO2/Pt(111) resulting in the formation of BaOx and partial reduction of TiO2. Ba films adsorbed on TiO2/Pt(111) that are further oxidized in O2 at 523 K lead to BaO and BaO2 surface domains which can efficiently adsorb both NO2 and CO2. Thermal treatment of BaOBaO2/TiO2/Pt(111) surface at T ≥ 300 K leads to a monotonic decrease in the surface Ba/Ti atomic ratio indicating the diffusion of BaO-BaO2 domains into the underlying TiO2 framework. Solid state reactions between BaOx and TiO2 particularly within 473-873K facilitate the formation of BaTiO3/Ba2TiO4/BaxTiyOz overlayers. After oxidation at higher temperatures (T > 873 K), surface becomes Badeficient and the enrichment of the surface with the Ti4+ sites results in a TiO2- terminated surface. Diffusion of BaOx into the TiO2 matrix and the enrichment of the surface with Ti sites drastically suppress the NO2 and CO2 adsorption/storage capacity of the model NOx storage system. These results reveal a direct evidence for the structural changes associated with the thermal deactivation of TiO2-promoted NSR catalysts.
Open Access
Evaluation of NO2 column variations over the atmosphere of Kazakhstan using satellite data
(SPIE, 2018) Darynova, Z.; Maksot, A.; Kulmukanova, L.; Malekipirbazari, M.; Sharifi, H.; Torkmahalleh, M. A.; Holloway, T.
Tropospheric NO2 concentrations obtained from the measurements of the Ozone Monitoring Instrument on board the NASA Aura satellite from 2005 to 2016 were studied to identify major NO2 emission hot spots, trends, and seasonal variations over Kazakhstan. Emission hot spots are observed over the locations of thermal power plants (Ekibastuz) and major urban and industrial regions (Almaty and Shymkent), as well as the capital city (Astana). Some decreasing trends have been observed for NO2 over Ekibastuz, whereas the regions of Almaty and Shymkent showed increasing trends due to industrial growth. The seasonal pattern of the NO2 concentration shows a difference between three industrial cities of Almaty, Shymkent, and Ekibastuz versus the rest of Kazakhstan. In these three cities, a NO2 maximum is found during wintertime, which we attribute to seasonality of emissions associated with electricity production and the longer chemical lifetime of NO2 in winter. In contrast, in Astana and the rest of Kazakhstan, the NO2 concentration reaches a maximum in the summer.
Open Access
Finding an optimum surface chemistry for [Formula] systems as NOx storage materials
(2010) Şentürk, Göksu Seda
Titania promoted NOx storage materials in the form of BaO/TiO2/Al2O3 were synthesized via two different sol-gel preparation techniques, with varying surface compositions and morphologies [1, 2]. The influence of the TiO2 units on the NOx storage component (8 - 20 wt. % BaO), the nature of the crystallographic phases, thermal stabilities and the dispersion of the surface oxide/nitrate domains were investigated. The structural characterization of the synthesized NOx storage materials were analyzed by means of BET surface area analysis, X-ray diffraction (XRD), ex-situ Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X- ray (EDX) and transmission electron microscopy (TEM). Comparative analysis of the results showed that the TiO2/Al2O3 support material derived by the co-precipitation of the corresponding hydroxides via the sol-gel technique, exhibited distinctively more homogenous distribution of TiO2 domains. The functionality/performance of these materials upon NOx and SOx adsorptions were monitored by temperature programmed desorption (TPD) and insitu Fourier transform infrared (FTIR) spectroscopy. An improved Ba surface dispersion was observed for the BaO/TiO2/Al2O3 materials synthesized via the coprecipitation of alkoxide precursors which was found to originate mostly from the increased fraction of accessible TiO2/TiOx sites on the surface. These TiO2/TiOx sites functioned as strong anchoring sites for surface BaO domains and were tailored to enhance surface dispersion of BaO. The relative stability of the NOx species adsorbed on the BaO/TiO2/Al2O3 system was found to increase in the following order: NO+ /N2O3 on alumina << nitrates on alumina < surface nitrates on BaO < bridged/bidentate nitrates on large/isolated TiO2 clusters < bulk nitrates on BaO on alumina surface and bridged/bidentate nitrates on TiO2 crystallites homogenously distributed on the surface < bulk nitrates on the BaO sites located on the TiO2 domains. The detailed study of the interaction of SOx with BaO/TiO2/Al2O3 ternary oxide materials showed that titania (TiO2) was a promising candidate for improving the sulfur tolerance on these type of surfaces. Adsorption of SOx on both pure Al2O3 and TiO2 showed that Al2O3 formed strongly bound SOx species, that were thermally stable up to T > 1073 K. SOx adsorption directly altered stability of the nitrate species on the Ti/Al (Protocol 1, Protocol 2) samples. SOx uptake properties of the BaO/TiO2/Al2O3 materials were found to be strongly influenced by the morphology of the TiO2/TiOx domains and the BaO loadings (8/20 wt% BaO). Consequently, the presence of titania domains was seen to decrease the SOx desorption temperatures and enhance the sulfur-tolerance of these materials by destabilizing the accumulated sulfate species. SOx exposure on the synthesized materials led to a significant decrease in the NOx adsorption capacities. The results obtained from FT-IR spectra showed that the sulfur deposition on the NOx storage materials promoted by Ti
Open Access
Global air quality and COVID-19 pandemic: do we breathe cleaner air?
(Taiwan Association for Aerosol Research,Taiwan Qijiao Yanjiu Xuehui, 2021-02-08) Torkmahalleh, M. A.; Akhmetvaliyeva, Z.; Omran, A. D.; Omran, F. D.; Kazemitabar, M.; Naseri, M.; Motahareh, N.; Hamed, S.; Malekipirbazari, Milad; Adotey, E. K.; Soudabeh, G.; Neda, E.; Sabanov, S.; Alastuey, A.; Andrade, M. F.; Buonanno, G.; Carbone, S.; Cárdenas-Fuentes, D. E.; Cassee, F. R; Dai, Q.; Henríquez, A.; Hopke, P. K.; Keronen, P.; Khwaja, H. A.; Kim, J.; Kulmala, M.; Kumar, P.; Kushta, J.; Kuula, J.; Massagué, J.; Mitchell, T.; Mooibroek, D.; Morawska, L.; Niemi, J. V.; Ngagine, S. H.; Norman, M.; Oyama, B.; Oyola, P.; Öztürk, F.; Petäjä, T.; Querol, X.; Rashidi, Y.; Reyes, F.; Ross-Jones, M.; Salthammer, T.; Savvides, C.; Stabile, L.; Sjöberg, K.; Söderlund, K.; Raman, R. S.; Timonen, H.; Umezawa, M.; Viana, M.; Xie, S.
The global spread of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has challenged most countries worldwide. It was quickly recognized that reduced activities (lockdowns) during the Coronavirus Disease of 2019 (COVID-19) pandemic produced major changes in air quality. Our objective was to assess the impacts of COVID-19 lockdowns on groundlevel PM2.5, NO2, and O3 concentrations on a global scale. We obtained data from 34 countries, 141 cities, and 458 air monitoring stations on 5 continents (few data from Africa). On a global average basis, a 34.0% reduction in NO2 concentration and a 15.0% reduction in PM2.5 were estimated during the strict lockdown period (until April 30, 2020). Global average O3 concentration increased by 86.0% during this same period. Individual country and continent-wise comparisons have been made between lockdown and business-as-usual periods. Universally, NO2 was the pollutant most affected by the COVID-19 pandemic. These effects were likely because its emissions were from sources that were typically restricted (i.e., surface traffic and non-essential industries) by the lockdowns and its short lifetime in the atmosphere. Our results indicate that lockdown measures and resulting reduced emissions reduced exposure to most harmful pollutants and could provide global-scale health benefits. However, the increased O3 may have substantially reduced those benefits and more detailed health assessments are required to accurately quantify the health gains. At the same, these restrictions were obtained at substantial economic costs and with other health issues (depression, suicide, spousal abuse, drug overdoses, etc.). Thus, any similar reductions in air pollution would need to be obtained without these extensive economic and other consequences produced by the imposed activity reductions.
Open Access
NOx reduction on a transition metal-free γ-Al2O3 catalyst using dimethylether (DME)
(2008) Ozensoy, E.; Herling, D.; Szanyi, J.
NO2 and dimethylether (DME) adsorption as well as DME and NO2 co-adsorption on a transition metal-free γ-alumina catalyst were investigated via in-situ transmission Fourier transform infrared spectroscopy (in-situ FTIR), residual gas analysis (RGA) and temperature programmed desorption (TPD) techniques. NO2 adsorption at room temperature leads to the formation of surface nitrates and nitrites. DME adsorption on the alumina surface at 300 K leads to molecularly adsorbed DME, molecularly adsorbed methanol and surface methoxides. Upon heating the DME-exposed alumina to 500-600 K the surface is dominated by methoxide groups. At higher temperatures methoxide groups are converted into formates. At T > 510 K, formate decomposition takes place to form H2O(g) and CO(g). DME and NO2 co-adsorption at 423 K does not indicate a significant reaction between DME and NO2. However, in similar experiments at 573 K, fast reaction occurs and the methoxides present at 573 K before the NO2 adsorption are converted into formates, simultaneously with the formation of isocyanates. Under these conditions, NCO can further be hydrolyzed into isocyanic acid or ammonia with the help of water which is generated during the formate formation, decomposition and/or NCO formation steps. © 2008 Elsevier B.V. All rights reserved.