chemical reaction  low-temperture plasma SO2 NO2 resolving
208018700
Unraveling a New Chemical Mechanism of Missing Sulfate Formation in Aerosol Haze Gaseous NO2 with aqueous HSO3 /SO32.
A missing source of sulfate production associated with high level fine particle pollution in megacities of Asia is believed to stem from oxidation of a notable fraction of sulfur dioxide (SO2) by nitrogen dioxide (NO2) in aqueous aerosol environment, suggesting an unknown reaction pathway for the aqueous sulfur oxidation. The estimated pH values of haze aerosols range from about 4 to 7 from previous studies. At the low end pH value (for weakly acidic aerosols) the dissolved SO2 mainly exists in the form of HSO3 whereas at the high end pH value (for neutral aerosols) SO32 becomes the main form. Herein, by using both ab initio molecular metadynamics simulation and high level quantum mechanical calculations, we show a hith erto unreported chemical mechanism for the formation of sulfate through the reaction between HSO3 /SO32 anions, at the surface/interior of water droplet, and the gas phase NO2 molecules. For weakly acidic aerosol, contrary to the conventional high barrier electron transfer pathway in the gas phase, HSO3 at the surface of water droplet can transfer electron to NO2 with a low energy barrier of 4.7 kcal/mol through a water bridge triggered by the NO2 molecule. The electron transfer can simultaneously promote the O H bond dissociation in HSO3 to form SO3 For neutral aerosol, the electron transfer pathway between SO32 in the interior of water droplet and NO2 molecule only needs to overcome a lower energy barrier of 3.6 kcal/mol to form SO3 with the assistance of the hydrogen bonding network of water molecules. In either acidic or neutral aerosol, the SO3 can react with another NO2 molecule to form the NO2SO3 specie, followed by forming bisulfate HSO4 and HONO (HNO2) with another water molecule. The free energy barrier of 5.8 kcal/mol is much lower than that associated with the gas phase reaction. This new reaction pathway to the sulfate formation from HSO3 /SO32 in water nanodroplet and the gaseous NO2 provide a new perspective on the growth of haze particles from preexisting aqueous aerosols, thereby benefiting new pollution control strategies to resolve the haze problem.
Journal of the American Chemical Society
Jinrong Yang Li Li Shixiang Wang Haiying Li Joseph S Francisco Xiao Cheng Zeng Yi Gao
100344982
Removal of NO in Mist by the Combination of Plasma Oxidation and Chemical Absorption
A coaxial nonthermal plasma (NTP) reactor was used for oxidizing and removing NO in mist. The effects of gas/mist components on O3 formation, NO oxidation, and NOx removal by NTP in simulated flue gas after wet desulfurization were investigated. The presence of mist results in the significant decrease of O3 concentration. Formation of active species, such as OH and HO2, would promote the reactions between NO and OH/HO2. Thus, the NO oxidation, NOx removal, and energy efficiency are significantly improved in the presence of mist. The promotion effects of mist component on the NO oxidation and NOx removal follow the order: Na2SO3 mist FeSO4 mist Na2SO4 mist. Increase of the mist pH can enhance the absorption of nitrogen oxides with the mist. Adding SO2 to the gas mixtures or raising the NO2/NOx ratio of simulated gas increases the NOx removal efficiency. This process demonstrates that NO oxidation by NTP and subsequently absorption by mist are feasible and have great value to practical application.
Deyuan Xie Ye Sun Tianle Zhu Li Ding
173174390
Pilot Scale NOx and SOx Aftertreatment Using a Two Phase Ozone and Chemical Injection in Glass Melting Furnace Exhaust Gas
As NO<sub>x</sub> and SO<sub>x</sub> have significant environmental impacts, advanced treatments are required to remove them from the exhaust gas of a glass melting furnace. Here, we investigate a plasma chemical hybrid process (PCHP) for this purpose. A pilot scale experiment of the simultaneous removal of NO<sub>x</sub> and SO<sub>x</sub> using a PCHP combined with the existing semi dry type desulfurization reactor is conducted on actual high temperature exhaust gas from a glass melting furnace. NO (the majority of NO<sub>x</sub> exist as NO) in the exhaust gas is oxidized to NO<sub>2</sub> using active oxygen (ozone: O<sub>3</sub> generated by a plasma ozonizer. The exhaust gas must be cooled to less than 150 degC in order to suppress the thermal decomposition of O<sub>3</sub> while the gas temperature at the outlet of the semi dry reactor must be kept at 200 ;250 degC to protect the dry type electrostatic precipitator. Therefore, it is important to form a local cooling area for NO oxidation in the reactor. In this article, we use the three fluid nozzles of O<sub>3</sub> water, and air to form the local cooling area and effectively oxidize NO to NO<sub>2</sub> In addition, we spray NaOH aqueous solution for SO<sub>2</sub> absorption downstream of the NO oxidation area to allow sufficient time for NO oxidation. The SO<sub>2</sub> reacts with NaOH to produce Na<sub>2</sub>SO<sub>3</sub> a powerful reducing agent. Subsequently, NO<sub>2</sub> reacts with Na<sub>2</sub>SO<sub>3</sub> and is reduced to N<sub>2</sub> and the Na<sub>2</sub>SO<sub>4</sub> generated in this reaction is reused as a clarifier of the raw materials for glass manufacturing. As a result, the ratio of the amount of removed NO and NO<sub>x</sub> to the amount of injected O<sub>3</sub> (de NO/O<sub>3</sub> and de NO<sub>x</sub>/O<sub>3</sub> is 64% and 78% respectively; therefore, high efficiency is obtained. This article includes actual examples of the treatment of exhaust gas in a glass melting furnace, using PCHP de SO<sub>x</sub> and de NO<sub>x</sub> technologies along with results from pilot scale experiments.
IEEE Transactions on Industry Applications
Hashira Yamamoto Tomoyuki Kuroki Hidekatsu Fujishima Masaaki Okubo
205952383
Kinetics of the unimolecular reaction of CH2OO and the bimolecular reactions with the water monomer, acetaldehyde and acetone under atmospheric conditions.
Stabilized Criegee Intermediates (sCIs) have been identified as oxidants of atmospheric trace gases such as SO2, NO2, carboxylic acids or carbonyls. The atmospheric sCI concentrations, and accordingly their importance for trace gas oxidation, are controlled by the rate of the most important loss processes, very likely the unimolecular reactions and the reaction with water vapour (monomer and dimer) ubiquitously present at high concentrations in the troposphere. In this study, the rate coefficients of the unimolecular reaction of the simplest sCI, formaldehyde oxide, CH2OO, and its bimolecular reaction with the water monomer have been experimentally determined at T (297 1) K and at atmospheric pressure by using a free jet flow system. CH2OO was produced by the reaction of ozone with C2H4, and CH2OO concentrations were probed indirectly by detecting H2SO4 after titration with SO2. Time resolved experiments yield a rate coefficient of the unimolecular reaction of k(uni) (0.19 0.07) s( 1) a value that is supported by quantum chemical and statistical rate theory calculations as well as by additional measurements performed under CH2OO steady state conditions. A rate coefficient of k(CH2OO+H2O) (3.2 1.2) x 10( 16) cm(3) molecule( 1) s( 1) has been determined for sufficiently low H2O concentrations <10(15) molecule cm( 3) that allow separation from the CH2OO reaction with the water dimer. In order to evaluate the accuracy of the experimental approach, the rate coefficients of the reactions with acetaldehyde and acetone were reinvestigated. The obtained rate coefficients k(CH2OO+acetald) (1.7 0.5) x 10( 12) and k(CH2OO+acetone) (3.4 0.9) x 10( 13) cm(3) molecule( 1) s( 1) are in good agreement with literature data.
Physical chemistry chemical physics PCCP
Torsten Berndt Ralf Kaethner Jens Voigtlander Frank Stratmann Mark Pfeifle Patrick Reichle Mikko Sipila Markku Kulmala Matthias Olzmann
94685378
The chemical reduction of small inorganic gases in an electrothermal plasma reactor
Abstract Chemical reduction of small inorganic gases is accomplished using an electro thermal plasma reactor. This benchscale reactor maintains a highly reactive plasma zone in a fluidized bed of carbon particles through which an electrical current is discharged. The carbon particles function as current controlling media, heat sinks and reaction sites. Chemicals introduced into this medium are subjected to a variety of energy sources and chemically reactive species, which result in chemical reduction. It is shown that the inorganic gases, H2O, CO2, NO, NO2 and SO2, are chemically reduced in the plasma zone of the reactor. The end products consist of hydrogen, carbon monoxide and nitrogen gases. Additionally, elemental sulfur is deposited onto the carbon particles.
Paul B Steinbach Stanley E Manahan David W Larsen
53629829
Development of a new corona discharge based ion source for high resolution time of flight chemical ionization mass spectrometer to measure gaseous H2SO4 and aerosol sulfate
Abstract A new corona discharge (CD) based ion source was developed for a commercial high resolution time of flight chemical ionization mass spectrometer (HRToF CIMS) (Aerodyne Research Inc. to measure both gaseous sulfuric acid (H2SO4) and aerosol sulfate after thermal desorption. Nitrate core ions (NO3 were used as reagent ions and were generated by a negative discharge in zero air followed by addition of excess nitrogen dioxide (NO2) to convert primary ions and hydroxyl radicals (OH) into NO3 ions and nitric acid (HNO3) The CD HRToF CIMS showed no detectable interference from hundreds parts per billion by volume (ppbv) of sulfur dioxide (SO2) Unlike the atmospheric pressure ionization (API) ToF CIMS, the CD ion source was integrated onto the ion molecule reaction (IMR) chamber and which made it possible to measure aerosol sulfate by coupling to a filter inlet for gases and aerosols (FIGAERO) Moreover, compared with a quadrupole based mass spectrometer, the desired HSO4 signal was detected by its exact mass of m/z 96.960, which was well resolved from the potential interferences of HCO3 (H2O)2 (m/z 97.014) and O H2OHNO3 (m/z 97.002) In this work, using laboratory generated standards the CD HRToF CIMS was demonstrated to be able to detect as low as 3.1 x 105 molecules cm 3 gaseous H2SO4 and 0.5 mg m 3 ammonium sulfate based on 10 s integration time and two times of the baseline noise. The CD ion source had the advantages of low cost and a simple but robust structure. Since the system was non radioactive and did not require corrosive HNO3 gas, it can be readily field deployed. The CD HRToF CIMS can be a powerful tool for both field and laboratory studies of aerosol formation mechanism and the chemical processes that were critical to understand the evolution of aerosols in the atmosphere.
Jun Zheng Dongsen Yang Yan Ma Mindong Chen Jin Cheng S Li Ming Wang
14891935
Removal Dynamics of Nitric Oxide (NO) Pollutant Gas by Pulse Discharged Plasma Technique
Nonthermal plasma technique has drawn extensive attentions for removal of air pollutants such as NOx and SO2. The NO removal mechanism in pulse discharged plasma is discussed in this paper. Emission spectra diagnosis indicates that the higher the discharge voltage is, the more the NO are removed and transformed into O, N, N2, NO2, and so forth. Plasma electron temperature T e is ranged from 6400 K at 2.4 kV discharge voltage to 9500 K at 4.8 kV. After establishing a zero dimensional chemical reaction kinetic model, the major reaction paths are clarified as the electron collision dissociation of NO into N and O during discharge and followed by single substitution of N on NO to form N2 during and after discharge, compared with the small fraction of NO2 formed by oxidizing NO. The reaction directions can be adjusted by N2 additive, and the optimal N2/NO mixing ratio is 2 1. Such a ratio not only compensates the disadvantage of electron competitive consumption by the mixed N2, but also heightens the total NO removal extent through accelerating the NO oxidization process.
TheScientificWorldJournal
Lianshui Zhang Xiaojun Wang Weidong Lai Xuelian Cheng Kuifang Zhao
30524203
Spontaneous growth of superstructure alpha Fe2O3 nanowire and nanobelt arrays in reactive oxygen plasma.
One dimensional a Fe2O3 is a promising nanomaterial for advanced applications in catalysis and water splitting, environmental protection, sensors, dye solar cells, magnetic storage media, bioprocessing, and controlled drug delivery and detection, especially as carriers of antigens for prion detection and PCR manipulation. a Fe2O3 nanowires have been successfully synthesized by various methods based on templates, hydrothermal conditions, sol gel mediated reactions, solvothermal conditions, gas decomposition, direct thermal oxidation (in a gas atmosphere of CO2, SO2, O2, and NO2) [7] chemical vapor deposition (CVD) and plasmaenhanced chemical vapor deposition (PECVD) The methods based on direct thermal oxidation, gas decomposition, and CVD reported to date require long synthesis times and high temperatures and therefore limit the efficiency of oxide nanowire synthesis. The application and commercialization of nanowires or nanobelts requires simple synthetic methods that can be scaled for both large areas and large quantities. Recently, we discovered a new universal method for the synthesis of transition metal oxide nanowires and nanobelts by direct plasma oxidation of bulk materials. It has been successfully applied for the rapid synthesis of high density niobium oxide nanowires. In this process, there is no
Small
Uros Cvelbar Zhiqiang Chen Mahendra Sunkara Miran Mozetic
97103642
Dust and Gas Emissions from Small Scale Peat Combustion
While peatland has long been exploited for agricultural activities, these make it vulnerable to fires, which emit pollutants into the atmosphere and adversely affect air quality. The aim of this study was thus to determine the main composition of air pollutants from peat soil combustion. The main parameters of the related gas pollutants, e.g. SO2, NO2, CO, O3 and PM10, and their components, such as anions, cations, heavy metals and levoglucosan, have been determined. The gas concentration was determined using the colorimetric method after the air had been assimilated into absorbing solutions. The PM10 concentration was established using a low volume air sampler equipped with weighted filter paper. The anion concentration of PM10 was analyzed using ion chromatography, while the cation and heavy metal concentrations were ascertained using inductively couple plasma mass spectroscopy (ICP MS) Moreover, the concentration of levoglucosan was determined using the Anthrone Sulfuric Colorimetric method. The results show that the dominant gas from the emission of burning peat soil was CO (13850 20610 mg/m 3 followed by NO2 (608 831 mg/m 3 SO2 (113 367 mg/m 3 and O3 (76 156 mg/m 3 A high PM10 concentration was released from 1 h peat soil combustion with a range of 778 3444 mg/m 3 The composition of heavy metals in PM10 shows the sequence of Zn Al Fe Cr Pb Cu Ni Cd. The sequence of anion and cation concentrations in PM10 was NO3 SO4 2 Na Cl Ca 2+ K >F Mg 2+ Levoglucosan was found to be a good indicator for peat combustion at a range of 1.44 3.90 mmol/m 3 This research shows that the emission of peat soil fires produces various amounts of air pollutants that affect the environment and chemical reactions in the atmosphere.
Murnira Othman Mohd Talib Latif
93328406
Chemical kinetics of NO removal by pulsed corona discharges
Nitric oxides (NO and NO2) and SO2 emissions are a major environmental problem because of their negative influence on human health and vegetation. The federal regulations on limiting the pollution emitted by the engines of motor vehicles have triggered intense research on new techniques for the removal of these pollutants. New methods for exhaust gas cleaning are needed and among the several approaches to reduce the pollutant emissions, the non thermal plasma technique shows promise (Luo J, Suib S L, Marques M, Hayashi Y and Matsumoto H 1998 J. Phys. Chem. A 102 7954) In this work, a volume averaged model is presented that can describe the removal of NOx by the multi pulse treatment of the exhaust gases at low temperatures and at atmospheric pressure in corona reactors. The model takes into account the production of active radicals after every discharge and the removal of NO by these radicals. Furthermore, the effect of ethene, one of the most important unburnt hydrocarbons in the exhaust gas, on the removal of NO is also investigated in this study. The effect of ethene has been investigated experimentally by several authors (Mizuno A, Chakrabati A and Okazaki K 1993 Non Thermal Plasma Techniques for Pollution Control ed B M Penetrante and S E Schultheis (Berlin: Springer) p 165, Prather M J and Logan J A 1994 Proc. Combustion Institute 25 1513) but there are almost no studies which try to explain, in detail, the chemical processes in such a system. The detailed reaction mechanism used in this study consists of 443 elementary reactions and 50 chemical species. The results of our numerical simulations show good agreement with the experimental results published in the literature. Reaction flow analysis and sensitivity analysis are performed in order to identify the specific reaction paths and the rate limiting reactions for typical operating conditions of pulsed corona reactors.
Igor Orlandini Uwe Riedel