The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
Robert M. Moore - One of the best experts on this subject based on the ideXlab platform.
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Seasonal and spatial variations in Methyl Chloride in NW Atlantic waters
Journal of Geophysical Research, 2007Co-Authors: S. Macdonald, Robert M. MooreAbstract:[1] Methyl Chloride concentrations were measured in the upper 200 m of the water column of the NW Atlantic during three cruises along the same track in spring, summer and fall of 2003. Distinct seasonality was apparent, with the surface waters being either undersaturated or close to equilibrium with the atmosphere in spring, but with supersaturation of the warmer waters in summer and fall. Cooler waters at the more northerly stations were always undersaturated, thus representing a continual sink for atmospheric Methyl Chloride. Even on an annual basis, the concentration anomaly (the difference between measured concentration and equilibrium with the atmosphere) was strongly dependent on sea surface temperature (SST). This empirical relationship can be used to extrapolate fluxes globally or to estimate the influence of global warming on ocean-to-atmosphere fluxes of Methyl Chloride. The global flux of Methyl Chloride to the atmosphere estimate based on the full-year relationship between concentration anomaly and SST is 17 Gmol/y, and is reduced to 6 Gmol/y if separate seasonal relationships are used. It appears that the ocean component of the flux is highly sensitive to temperature, but the actual source of the Methyl Chloride in ocean waters remains largely unknown.
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Ocean‐atmosphere exchange of Methyl Chloride: Results from NW Atlantic and Pacific Ocean studies
Journal of Geophysical Research: Oceans, 1996Co-Authors: Robert M. Moore, Wayne Groszko, Stewart J. NivenAbstract:Measurements of Methyl Chloride concentrations and saturations in the NW Atlantic and Pacific Ocean from 40°N to 40°S are presented. Labrador Sea waters, analyzed in July, were at or below saturation, while warmer waters south of the Gulf Stream and all Pacific samples were consistently supersaturated. We find no correlation between Methyl Chloride concentrations and chlorophyll a, but much of the variation in Methyl Chloride partial pressure appears to be accounted for by variations in sea surface temperature. We estimate ocean-atmosphere fluxes of Methyl Chloride, using exchange velocities for spot wind speeds and climatological wind speeds. These indicate that none of the waters we sampled support the magnitude of fluxes which have hitherto been considered to be emitted by the ocean. A simple extrapolation yields a global efflux of 0.8 to 1.1 × 1010 mol yr−1 (0.4 to 0.6 Tg yr−1) supplied by warm waters and a high-latitude influx of 0.2 to 0.5 × 1010 mol yr−1 (0.1 to 0.3 Tg yr−1). The net global ocean source to the atmosphere is 0.3 to 0.9 × 1010 mol yr−1 (0.2–0.4 Tg yr−1), which accounts for 5 to 12% of the total required to balance loss by reaction with hydroxyl radicals. Unless its atmospheric reactivity has been overestimated, we conclude that other sources of Methyl Chloride make major contributions to its atmospheric budget.
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Measurements of Methyl Chloride in the northwest Atlantic
Journal of Geophysical Research, 1994Co-Authors: V. K. Tait, Robert M. Moore, Ryszard TokarczykAbstract:Methyl Chloride was measured directly in seawater using a purge and trap system and gas chromatography with electron capture detection. The results indicate that surface waters of the northwest Atlantic are a source of Methyl Chloride to the atmosphere during late spring/early summer. The average surface concentration was 271 pM (σ = 68 pM), supersaturated with respect to an assumed tropospheric boundary layer mixing ratio of 0.7 ppbv. Elevated concentrations were observed throughout the region in waters above the seasonal thermocline. Near-surface maxima of differing thickness and intensity were also seen within this upper layer. Broad maxima within the 200–800m depth range were associated with water masses more recently subducted from the surface than the surrounding main thermocline waters. Coastal inputs of Methyl Chloride appear not to be an important source in the area of study. Although there is some indication of elevated concentrations associated with higher phytoplankton activity in shelf edge regions, the picture concerning phytoplankton production of Methyl Chloride is still unclear. Further work is required to look at direct and indirect mechanisms by which phytoplankton may influence the distribution of Methyl Chloride in the oceans. The global ocean-to-atmosphere flux estimated from this data set, 3.3 - 4.8 × 1010 mol CH3Cl yr−1 (1.7 - 2.4 × 1012 g CH3Cl yr−1) suggests that the oceans may contribute a smaller flux of Methyl Chloride to the atmosphere than previously thought.
Vicki H. Grassian - One of the best experts on this subject based on the ideXlab platform.
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Infrared study of the adsorption and reaction of Methyl Chloride and Methyl iodide on silica-supported Pt catalysts
Journal of Catalysis, 1996Co-Authors: K. C. Mcgee, M. D. Driessen, Vicki H. GrassianAbstract:The low-temperature adsorption of Methyl Chloride andMethyl iodide on silica-supported Pt catalysts has beeninvestigated by transmission Fourier transform infraredspectroscopy. The IR data show that Methyl Chloride and Methyliodide dissociate at low temperatures (near 200 K) to form anadsorbed hydrocarbon fragment on the surface, identified asMethyl groups. Methyl groups are characterized by a singleinfrared absorption band near 2965 cm−1. Methyl groups reactwith hydrogen to form gas-phase methane as the sample is warmedbetween 200 and 473 K. Reaction of approximately 10 Torr ofMethyl Chloride at 473 K over a Pt/SiO2catalyst shows that only20% of the Methyl Chloride decomposes to form gas-phase methaneand hydrogen Chloride in the absence of hydrogen. However, inthe presence of an equal amount of hydrogen, all of the MethylChloride is converted to methane and hydrogen Chloride. Incontrast to the quantitative conversion of Methyl Chloride, lessthan 10% of the initial 10 Torr of Methyl iodide forms methaneat 473 K and no hydrogen iodide forms in the presence or absenceof hydrogen gas. Although the activation barrier for C–Cl bonddissociation in adsorbed Methyl Chloride is higher than thebarrier for C–I bond dissociation in adsorbed Methyl iodide, thelower energy barrier for removal of adsorbed chlorine comparedto adsorbed iodine is the cause of the higher catalytic activityof Pt/SiO2toward Methyl Chloride decomposition. In addition tothe thermal decomposition of CH3Cl, we have investigated thepossibility of using solar radiation for the decomposition ofCH3Cl on Pt/SiO2. The results for the photo-assisteddecomposition of CH3Cl adsorbed on Pt/SiO2are presented and discussed.
O. Bozdag - One of the best experts on this subject based on the ideXlab platform.
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Pressure−Volume−Temperature Properties of Methyl Chloride at High Pressures and Temperatures
Journal of Chemical & Engineering Data, 2006Co-Authors: O. BozdagAbstract:PVT data of Methyl Chloride were measured up to 400 MPa at eight isotherms ranging from (298.15 to 573.15) K. Experiments were performed with a thin-walled sample holder under equal pressure, both inside and outside. The volume change of the sample was determined with a separation system at 298.15 K by making use of a magnetic float on mercury and a linear variable differential transformer. The specific volume of Methyl Chloride varies in this region from (0.8366 to 7.8806) cm3·g-1. The uncertainty of data for specific volumes was estimated to be ± 0.34 % or less. The specific volume data was fitted to the Tait equation of state.
Ishwar K. Puri - One of the best experts on this subject based on the ideXlab platform.
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The structure of nonpremixed Methyl Chloride and Methyl Chloride/methane air flames near extinction
Combustion and Flame, 1994Co-Authors: J.y. Huh, Kyeong-ook Lee, Ishwar K. PuriAbstract:Abstract Experimental measurements are conducted to determine the structure of counterflow halogenated flames near extinction. The flames are simulated using a detailed chemical kinetic mechanism. Two flames are studied, one burning Methyl Chloride, and the other an equimolar mixture of methane and Methyl Chloride as fuel. The measured velocity, temperature, and species composition profiles are compared with the calculations. Whereas there is overall good agreement between the measurements and predictions, it appears that Methyl Chloride consumption occurs at a rate slower than predicted, and some areas of further refinement in the kinetic mechanism are identified.
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The extinction of methane/Methyl Chloride nonpremixed flames
Hazardous Waste and Hazardous Materials, 1993Co-Authors: C.a. Philbrick, Suresh K. Aggarwal, Ishwar K. PuriAbstract:ABSTRACT The extinction of nonpremixed flames burning mixtures of methane and Methyl Chloride, air, and nitrogen is studied in a counterflowing flame. The flowrates entering the counterflow are varied so as to measure the critical strain rate at extinction. Increasing amounts of Methyl Chloride, as expected, are determined to lower the value of the critical strain rate at extinction. The experiments are conducted at conditions corresponding to several fixed values of the stoichiometric mixture fractions and compared with a previously developed analysis in order to determine forced global kinetic parameters characterizing these cases. The kinetic parameters are found to be useful engineering quantities that enumerate an incinerability ranking. It is determined from the experimental results that small amounts of added Methyl Chloride have a significant inhibitory effect on methane-air flames, but that larger addition of Methyl Chloride does not yield a proportional inhibitory effect.
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Experimental investigation of stretched premixed flames burning mixtures of methane and Methyl Chloride in air and comparison with numerical simulations
Combustion and Flame, 1993Co-Authors: M H. Yang, Ishwar K. PuriAbstract:Abstract Experimental measurements of the laminar burning velocities of flames burning methane/Methyl Chloride mixtures, and Methyl Chloride in air, are made in a counterflow burner. The flame speeds are observed to decrease with increasing chlorine loading, from 40 cm s−1 for a stoichiometric methane-air flame to 4.9 cm s−1 for a stoichiometric Methyl Chloride-air flame. Good agreement is found between flame speeds deduced from experiments and those predicted by numerical simulations at the periphery of the domain, i.e., for methane-air and Methyl Chloride-air flames. The agreement between experiments and calculations at intermediate regions, that is, for varying methaneMethyl Chloride-air mixtures is at best reasonable. Sources for the discrepancies in the kinetic mechanism are identified. The critical extinction stretch rate for flames burning Methyl Chloride in air is measured, as is the stretched flame speed close to extinction.
K. C. Mcgee - One of the best experts on this subject based on the ideXlab platform.
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Infrared study of the adsorption and reaction of Methyl Chloride and Methyl iodide on silica-supported Pt catalysts
Journal of Catalysis, 1996Co-Authors: K. C. Mcgee, M. D. Driessen, Vicki H. GrassianAbstract:The low-temperature adsorption of Methyl Chloride andMethyl iodide on silica-supported Pt catalysts has beeninvestigated by transmission Fourier transform infraredspectroscopy. The IR data show that Methyl Chloride and Methyliodide dissociate at low temperatures (near 200 K) to form anadsorbed hydrocarbon fragment on the surface, identified asMethyl groups. Methyl groups are characterized by a singleinfrared absorption band near 2965 cm−1. Methyl groups reactwith hydrogen to form gas-phase methane as the sample is warmedbetween 200 and 473 K. Reaction of approximately 10 Torr ofMethyl Chloride at 473 K over a Pt/SiO2catalyst shows that only20% of the Methyl Chloride decomposes to form gas-phase methaneand hydrogen Chloride in the absence of hydrogen. However, inthe presence of an equal amount of hydrogen, all of the MethylChloride is converted to methane and hydrogen Chloride. Incontrast to the quantitative conversion of Methyl Chloride, lessthan 10% of the initial 10 Torr of Methyl iodide forms methaneat 473 K and no hydrogen iodide forms in the presence or absenceof hydrogen gas. Although the activation barrier for C–Cl bonddissociation in adsorbed Methyl Chloride is higher than thebarrier for C–I bond dissociation in adsorbed Methyl iodide, thelower energy barrier for removal of adsorbed chlorine comparedto adsorbed iodine is the cause of the higher catalytic activityof Pt/SiO2toward Methyl Chloride decomposition. In addition tothe thermal decomposition of CH3Cl, we have investigated thepossibility of using solar radiation for the decomposition ofCH3Cl on Pt/SiO2. The results for the photo-assisteddecomposition of CH3Cl adsorbed on Pt/SiO2are presented and discussed.