COS Concentration Research Articles

Spectroscopic study on sorption of hydrogen sulfide by means of red soil

This paper reports the results of the characterization of red soils in relation to the sorption of H 2S from coal gas at 500 °C by spectroscopic techniques in order to provide more information on red soils’ structural change both before and after reaction. In addition, by-products analysis has also been studied using Fourier transform infrared (FTIR) spectroscopy. Before and after the experiments the red soils were characterized with X-ray powder diffraction (XRPD), energy dispersion spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and FTIR spectroscopy. XRPD results indicate that iron oxide species disappear from the original to reacted red soil. EDS analysis shows that a significant amount of sulfur is present in the reacted red soil, which is in agreement with the results of the elemental analysis and the calculated value based on breakthrough curve. XPS regression fitting results further indicate that sulfur retention may be associated with the iron oxides. S 2p XPS fittings point out that the major sulfur species present in the reacted red soil are composed of S −2, elemental sulfur, polysulfide, sulfite and sulfate. Additionally, the binding energy of iron shifts to a lower position for the reacted red soil, which indicates that iron oxides in the original red soil have been converted into iron sulfide. Appreciable amounts of the by-products CO 2, SO 2 and COS are detected by on-line FTIR spectroscopy during the initial and later stages of the sorption process. The formation of CO 2 is related to the water-shift reaction, and SO 2 is probably attributable to the reaction of organic matters and H 2S. The concentration of COS is quantified by GC/FPD and found it to be about 350 ppm, which is close to the equilibrium concentration of the reaction of inlet CO and H 2S at a temperature of 500 °C.

Selective catalytic oxidation: a new catalytic approach to the desulfurization of natural gas and liquid petroleum gas for fuel cell reformer applications

In both natural gas and liquid petroleum gas (LPG), sulfur degrades the performance of the catalysts used in fuel reformers and fuel cells. In order to improve system performance, the sulfur must be removed to concentrations of less than 200 ppbv (in many applications to less than 20 ppbv) before the fuel reforming operation. Engelhard Corporation presents a unique approach to the desulfurization of natural gas and LPG. This new method catalytically converts the organic and inorganic sulfur species to sulfur oxides. The sulfur oxides are then adsorbed on a high capacity adsorbent. The sulfur compounds in the fuel are converted to sulfur oxides by combining the fuel with a small amount of air. The mixture is then heated from 250 to 270 °C, and contacted with a monolith supported sulfur tolerant catalyst at atmospheric pressure. When Engelhard Corporation demonstrated this catalytic approach in the laboratory, the result showed sulfur breakthrough to be less than 10 ppbv in the case of natural gas, and less than 150 ppbv for LPG. We used a simulated natural gas and LPG mixture, doped with a 50–170 ppmv sulfur compound containing equal concentrations of COS, ethylmercaptan, dimethylsulfide, methylethylsulfide and tetrahydrothiophene. There is no need for recycled H2 as in the case for hydrodesulfurization.

Kinetics of removal of carbonyl sulfide by aqueous monoethanolamine.

The kinetics of the reaction between carbonyl sulfide and aqueous monoethanolamine (MEA) were studied over a range in temperature (298-348 K) and amine concentrations (5-20 wt%) using a wetted-sphere absorber. The experimental data were interpreted using a zwitterion mechanism. The key physicochemical properties needed to interpret the data are the solubility and diffusivity of COS in the aqueous amine solution. These properties were estimated using the N2O analogy method. Experimental values of N2O solubility were correlated using an extended scaled-particle model, and the measured N2O diffusion coefficients were correlated using a modified Stokes-Einstein equation. Solution densities and viscosities were also measured and correlated in this work. On the basis of the zwitterion mechanism whose rate-limiting step was the deprotonation of a zwitterion, the Arrhenius relationship between the third-order rate constant and the temperature was well correlated with an absolute mean deviation of 0.3%. It could be thus concluded that the overall reaction rate was first-order in the COS concentration and second-order in the MEA concentration.

Deactivation model of Fischer-Tropsch synthesis over an Fe [sbnd]Cu [sbnd]K commercial catalyst

The effects of COS in synthesis gas on the Fischer-Tropsch (F-T) synthesis over a commercial Fe Cu K catalyst in a fixed-bed reactor under 2.31 MPa and at 524 K were investigated. Activity of catalyst decreased rapidly within the first few hours, and then slowly when COS in the syngas was in the range of 51.4–245.6 ppm, while the activity changed little during 72 h when the COS concentration was 4.8 ppm. Prepoisoning of the catalyst was more serious than poisoning in situ. The sulfur resistance of larger catalyst particles was stronger than that of smaller particles and the water-gas shift (WGS) reaction was faster on smaller pellets. A deactivation model in a fixed-bed reactor for F-T synthesis was developed in this paper. Deactivation rate constants obtained from nonlinear regression with the model decrease with the increase of COS concentration, suggesting that the deactivation of catalyst is faster at lower COS concentrations than at higher COS concentrations. The calculated results from the model fitted well with the experimental data. The selectivities of methane and gaseous C 2–C 4 hydrocarbons increased when the catalyst was poisoned by COS. The C 5 + content in product decreased significantly with increase of sulfur fed to the catalyst. The alkene to alkane ratio in gaseous hydrocarbons decreased over the poisoned catalyst, but C 2 =–C 4 = in total C 2–C 4 hydrocarbons changed only slightly. XPS, XRD and TEM studies studies showed that sulfide compounds were formed on the poisoned catalysts, but the structures were different with variation of COS concentrations, due to the formation of monolayer or mutilayer sulfides on catalysts.

MOSSBAUER STUDY OF Fe-Cu-K CATALYST FOR FISCHER-TROPSCH SYNTHESIS

ABSTRACT Mosshauer spectroscopy (MES) has been used to study the characteristics of iron catalysLs preireated in different ways for Fischer-Tropsch (F-T) synthesis. The Mosshauer spectrum results showed that the fine particle of α-Fe2o3is the main phase of oxide catalyst. Catalysts preireated in H2:CO ratio of 2.1 syngas at 250°C and under 0.5 MPa with the gas hourly space velocity of 1500 h−for 32 h in a fixed-bed reactor resulted in the reduction of 91% of iron to Fe3o4, FeO and X-FC5C2- The κ-Fe5s2content of reacted catalyst increased greatly as compared with reduced catalyst, while FeO and Fe3o4contents decreased. The Fe3O4 content of catalyst poisoned by oxygen increased as compared with reduced catalyst. FeS2 is the main phase of catalyst poisoned at high COS concentration, while FeS is the main phase of catalyst poisoned by COS al low concentration. The Fe3o4content decreased with the increase of sulfur fed to catalyst. The deactivation rate is related to the composition of the catalyst treated in ...

Carbonyl sulfide emissions from biomass burning in the tropics

Carbonyl sulfide emissions from biomass burning have been studied during field experiments conducted both in an African savanna area (Ivory Coast) and rice fields, central highland pine forest and savanna areas in Viet-Nam. During these experiments CO2, CO and C2H2 or CH4 have also been also monitored. COS values range from 0.6 ppbv outside the fires to 73 ppbv in the plumes. Significant correlations have been observed between concentrations of COS and CO (R2=0.92,n=25) and COS and C2H2 (R2=0.79,n=26) indicating a COS production during the smoldering combustion. COS/CO2 emission factors (ΔCOS/ΔCO2) during field experiments ranged from 1.2 to 61×10−6 (11.4×10−6 mean value). COS emission by biomass burning was estimated to be up to 0.05 Tg S/yr in tropics and up to 0.07 Tg S/yr on a global basis, contributing thus about 10% to the global COS flux. Based on the S/C ratio measured in the dry plant biomass and the ΔCOS/ΔCO2 emission factor, COS can account for only about 7% of the sulfur emitted in the atmosphere by biomass burning.

Measurements of Reduced Sulphur Compounds in an Industrialized Tropical Region—Cubatão (BRAZIL)

Abstract Ambient concentrations of SO2, H2S, COS and CS2 have been determined at various sites in the highly industrialized area of Cubatao (Brazil) and in adjacent ecosystems during the years 1990 to 1993. Sulphate has been analyzed in rain samples collected at three sites in the Serra do Mar. The sites are called Vale do Mogi (heavily polluted), Paranapiacaba (moderately polluted), and Vale do Pil[otilde]es (less polluted). Gas exchange of reduced sulphur compounds between biosphere and atmosphere has been examined with the aid of ambient air enclosures. The investigated sulphur sources (and sinks) were the estuaries south of Cubatao, a reservoir north of Cubatao, and vegetated soils at Vale do Mogi, Paranapiacaba, and Vale do Pil[otilde]es. The content of reduced sulphur compounds was determined in surface water samples from lakes, rivers, and estuaries in the area under investigation. Wet sulphate deposition and ambient SO2 concentrations revealed a similar hierarchy of Vale do Mogi, Paranapiacaba, an...

Measurements of atmospheric carbonyl sulfide during the NASA Chemical Instrumentation Test and Evaluation project: Implications for the global COS budget

Atmospheric COS concentrations were measured by three analytical systems during the Chemical Instrumentation Test and Evaluation (CITE 3) project. The three systems all used cryogenic sample preconcentration and gas chromatographic (GC) separation but differed in the method of detection. The FPD system used a flame photometric detector, the MS system used a mass selective detector, and the ECD‐S system used a fluorinating catalyst followed by an electron capture detector. With the FPD system, we found a mean COS concentration of 510 ppt over the North Atlantic and 442 ppt over the Tropical Atlantic. With the ECD‐S system, we found a mean COS concentration of 489 ppt over the North Atlantic and 419 ppt over the Tropical Atlantic. All three systems registered a latitudinal gradient in atmospheric COS of between 1.6 and 2.0 ppt per degree of latitude, with increasing COS concentrations northward which was similar to the gradient measured by Bingemer et al. (1990). It is difficult to reconcile the measured latitudinal concentration gradient with present theories of the global COS budget since the largest sink of COS is thought to be a flux to land plants, most of which are in the northern hemisphere.

ARAS Measurements on the S(1D) Formation in Shock Heated COS/Ar mixtures

AbstractThe formation of electronically excited S(1D) atoms was studied during the thermal decomposition of carbonyl sulfide behind reflected shock waves by using atomic resonance absorption spectroscopy (ARAS). The experiments were performed in highly diluted mixtures of Ar with relative concentrations of COS between 8 to 100 ppm in the temperature range 2130 K≤T≤3020 K at pressures of about 1.2 bar. The measured rate of the linear S(1D) increases divided by the initial reactants was found to obey the Arrhenius law: magnified image.Assuming a fast thermalisation between the (3P) and (1D) states of S atoms this result is in agreement with previous measurements of the S(3P) formation during the thermal decomposition of COS reported recently [1].

Shock Tube Measurements on the Thermal Decomposition of COS

AbstractThe thermal decomposition of carbonyl sulfide was studied behind reflected shock waves by direct measurements of the time‐dependent S(3P) atom concentration using atomic resonance absorption spectroscopy (ARAS). The experiments were performed in highly diluted mixtures of Ar with relative concentrations of COS between 4 to 100 ppm in the temperature range 1750 K ≤ T ≤ 2990 K at pressures between 0.5 bar and 1.5 bar. In reaction systems with very low concentrations (4 – 30 ppm COS in Ar) the initial reaction magnified image was found to dominante the initial slope of the measured S(3P) atom concentration profiles. The rate coefficient obtained results in: magnified image In reaction systems with higher initial concentrations of 100 ppm COS the measured S(3P) atom concentration profiles were additionally affected by secondary reactions consuming sulfur atoms. The most probable reaction is magnified image which has an influence on S(3P) at later reaction times. A rate coefficient for reaction (R2) of magnified image was determined from the present experiments by fitting calculated S(3P) atom profiles to measured ones. The given mean value is to be valid for temperatures near 2000 K.

Vertical distributions of COS, CS 2, DMS and other sulfur compounds in a loblolly pine forest

Measurements of atmospheric COS, CS 2, DMS, SO 2 and aerosol sulfate and methanesulfonate (MSA) concentrations were conducted in a loblolly pine forest in central Georgia between July and September 1990. The daytime profiles obtained for the reduced sulfur gases (COS, CS 2, DMS) often showed significantly higher concentrations at the canopy level than above the forest canopy, indicating a net emission of these gases from the tree tops. No evidence was found for a net uptake of COS by the canopy during daytime. With one exception, all COS concentrations measured during the day were significantly higher than corresponding nighttime values. These results appear to be in conflict with recent studies suggesting a net uptake of atmospheric COS by plants during photosynthetic activity. Possible explanations for these different findings are discussed. Nighttime profiles indicated no major biosphere-atmosphere exchange of COS, CS 2 or DMS. Nighttime DMS concentrations were significantly higher than corresponding daytime values. A clear inverse relationship between the diel variations of DMS and MSA was observed, consistent with rapid photochemical oxidation of DMS under the given conditions.

Kinetics of COS with primary and secondary amines in aqueous solutions

AbstractThe reaction between COS and aqueous solutions of primary and secondary amines has been studied by means of the stirred cell technique. Kinetic experiments at temperatures 283 to 333 K were carried out with MEA, DGA, DEA, DIPA, MMEA, AMP, and MOR. All kinetic experiments could be described by a zwitterion reaction mechanism similar to the mechanism proposed by Caplow (1968) for the reaction between CO2 and secondary amines: Analysis of concentrated amine solutions at high COS concentrations by various analytical techniques confirmed the conclusions from the kinetic experiments. For all amines except for MEA, the overall reaction rate was found to be determined entirely by the zwitterion deprotonation rate.

Atmospheric trace compounds at a European coastal site—application to CO2, CH4 and COS flux determinations

Abstract The variations of CO2, CH4, COS, and NMHC concentrations, and of 222Rn activity were studied simultaneously in the boundary layer in a littoral site in Brittany, France. Various meteorological conditions occurred during the experiment allowing determination of trace gas concentrations characteristic of air masses having either dominant continental or oceanic influence. The relative NMHC concentration of the air reflects the origin of the air masses. Oceanic air is characterized by high proportions of alkenes, whereas the alkanes concentration is higher in continental air masses. In 1986 alternate sea- and land-breeze conditions allowed measurement of the evolution of the composition of an oceanic air mass under continental influence. By using the variabilities of 222Rn activities measured during the experiment, as well as the estimation of its mean flux over continents, we deduced the mean regional fluxes of CO2, CH4 and COS to be 5.8, 0.07 and −36 × 10−6 m mol m−2 h−1, respectively.

Dispersion of soil gas around micron gold deposits

Kesler, S.E., Gerdenich, M,J., Steininger, R.C. and Smith, C., 1990. Dispersion of soil gas around micron gold deposits. In: S.E. Kesler (Editor), Soil and Rock Gas Geochemistry. J. Geochem. Explot., 38:117-132. Experimental weathering of sediment-hosted micron gold (SHMG) ore from the Alligator Ridge deposit indicates that ore and adjacent Pilot Shale wallrock release gas with larger concentrations of COS, CS2 and CH4, and lower CH4/(CH4 + C2H4 ) and CH4 / (CH4 + C2H 6 ) ratios than does barren Pilot Shale. The COS and CS2 are derived from decomposition of disseminated pyrite, which is probably more abundant in mineralized zones, and variations in the CH-gas ratios are thought to reflect increased thermal maturity of organic material in the mineralized zones. Surveys designed to determine whether these gases are present in detectable haloes around SHMG mineralization were carried out over the Yankee prospect, a relatively similar deposit several km south of Alligator Ridge. The surveys included analysis of interstitial soil gas, gases desorbed from soils, and gases desorbed from two sets of Carbotrap collectors, one left on the bedrock interface (at depths of about 30-70 cm below the surface) and another placed in holes drilled about 3 m into bedrock. All of the gases observed in the experiments were detected, as well as organo-sulfur and higher alkane and alkene gases. The surveys indicated systematic variations in gas dispersal related to faults and/or mineralization, with the most consistent patterns being elevated COS values and depressed CH4/(CH4 + C2H4) ratios over mineralization. Similar highs in COS, as well as other gases including SO2 and ethyl mercaptan, were associated with faults, and it was not possible to distinguish these two sources of anomalous gas patterns in all cases. In general, best results were obtained with gases desorbed from bulk soil, and no significant advantage was observed with the use of collectors placed in deep holes. Although all of the survey methods yielded anomalous patterns, none of these patterns are sufficiently strong to merit the use of gas geochemistry as a primary guide in exploration for SHMG deposits.

Sulfur gas tolerance and toxicity of co-utilizing and methanogenic bacteria

Anaerobic bacteria have been shown to be capable of converting CO, H2, and CO2 in synthesis gas to valuable products, such as acetate, methane, and ethanol. However, synthesis gas also contains small quantities of sulfur gases such as H2S and COS, that may inhibit the performance of these organisms. This paper compares the performance of several CO-utilizing and methanogenic bacteria in converting CO, CO2, and H2 to products in the presence of various concentrations of H2S and COS. The sulfur gas toxicity levels, growth, substrate uptake, and product formation for each organism are compared.

Fate of coal-sulphur in a laboratory-scale coal gasifier

This work summarizes several observations concerning the effects of pressure and oxygen-to-coal mass ratio on the fate of coal-sulphur during entrained gasification. A high-volatile bituminous coal was pulverized to a mass mean of near 50μm. The coal was gasified with oxygen in a laboratory-scale entrained-flow gasifier. No steam was used. Test pressures were 1, 5 and 10atm (10, 500, 100 kPa). Oxygen-to-coal mass ratios between 0.60 (SR = 0.30) and 1.10 (SR = 0.56) were investigated. Gas-particulate samples were collected with a water-quenched probe from the gasifier chamber effluent stream. Measurements were made of the sulphur in the char particles and of the levels of H 2S, SO 2, COS, and CS 2 in the product gas. Increasing pressure yielded a significant decrease (about 25%) in net conversion of coal sulphur. This decrease was shown by an increase in the sulphur content of the char samples, and by a decrease in total sulphur concentration in the gas phase. Gas species measurements showed that increased pressure yielded lower SO 2 and CS 2 concentration, but did not significantly affect H 2S and COS concentrations. It was concluded that increased pressure shifted the distribution of sulphur among the gas phase species, yielding higher H 2S and lower SO 2 and CS 2 concentrations. The increase in H 2S was not seen in the measurements, because increased pressure also tended to increase the capture of H 2S by char. Increasing oxygen-to-coal mass ratio increased sulphur conversion and SO 2 and COS levels, while it decreased H 2S and CS 2 levels.

Uptake of COS by growing vegetation: A major tropospheric sink

Laboratory measurements of the uptake of COS by soybeans, corn, wheat, and alfalfa under conditions of controlled illumination, temperature, and CO2 concentration, and at COS concentrations spanning those typically found in the troposphere (∼500 parts per trillion by volume), indicate that the major uptake pathway is through open stomata. Similarities between the uptake resistances observed for COS and CO2 provide a means of estimating global COS uptake from estimates of global terrestrial primary plant productivity. With an estimated annual plant uptake of 0.2–0.6 Tg COS (Tg = 1012 g), this appears to be the largest global sink for this major tropospheric sulfur reservoir species. With this vegetative sink included, estimated known sources and sinks appear to be in approximate balance.

Carbonyl Sulfide: An Inhibitor of Inorganic Carbon Transport in Cyanobacteria

Cells of a high CO(2)-requiring mutant (E(1)) and wild type of Synechococcus PCC7942 were incubated with COS in the light, then suspended in COS-free medium and their CO(2) exchange was measured using an open gas-analysis system under the conditions where photosynthetic CO(2) fixation is inhibited. When the suspension of cells untreated with COS was illuminated, the rate of CO(2) uptake was high and addition of carbonic anhydrase during illumination released a large amount of CO(2) from the medium into the gas phase. The COS treatment in the light markedly reduced the rate of CO(2) uptake by the cells and the amount of CO(2) released by carbonic anhydrase. Incubation of cells with COS in the dark had no effect on the CO(2)-exchange profile. The COS concentration required for 50% inhibition of CO(2) uptake was about 25 micromolar when the concentration of inorganic carbon (C(i)) in the medium was 60 micromolar; higher C(i) concentrations reduced the inhibitory effect of COS. Measurement of C(i) uptake in E(1) cells by a silicone oil centrifugation method also indicated marked reduction of the activities of (14)CO(2) and H(14)CO(3) (-) uptake in the cells treated with COS in the light. The results demonstrated that COS is a potent inhibitor of C(i) transport.

Responses of C4 Grasses to Atmospheric CO2 Enrichment. II. Effect of Water Stress1

Changes in leaf water potential, photosynthesis, and stomatal conductance in response to atmospheric COs enrichment at two watering regimes were studied in :Four species of C4 grasses: Echinochloa crusgalli, Digitaria sanguinalis, Eleusine indica, and Setaria faberi. Plants were grown in controlled environment chambers at 350 and 675 μmol mol‐1 CO2 with 1000 μmol m‐2 s‐1 photosynthetic photon tux density (PPFD). One group plants of each of the COs concentrations was subjected to water stress by withholding irrigation for 10 days starting 21 days after planting. Water potentials of the leaves of plants grown at 350 #tool mol‐1 CO2 declined more rapidly and reached lower values at the end of the stress period than the water potential of those grown at 675 μmol mol‐1 CO2. High COs‐grown plants maintained higher turgor pressures than low CO2‐grown plants. All plants had lower rates of photosynthesis during water stress compared to non‐stressed conditions. However, the net photosynthetic rates of the plants grown at high CO2 concentration did not decline as rapidly as the rates of plants grown at low CO2 when subjected to water stress. The maintenance of turgor along with CO2 enrichment during water stress development in plant leaves may be responsible for the higher rates of net photosynthesis observed in high CO2‐grown plants compared to those in low CO2‐grown plants.

Preparation of high purity carbonyl[35S]sulphide

AbstractThe title compound was synthesised by the reaction between elementary[35s]sulphur and carbon monoxide at 300°C, and purified by passage over Porapak QS. The only detectable S‐impurity in the purified product was CS2 at <0.05% (v/v) of the COS concentration.