Mechanism of COS Hydrolysis on Alumina

Atmospheric Environment

Geng

et al. 2007

Carbonyl sulfide (COS) exchange fluxes between a lawn soil and the atmosphere as well as influencing factors (temperature and water content of soil) were investigated using a static cuvette. The optimal soil temperature and water content for COS consumption were about 298 K and 12.5%, respectively. The converting products of the consumed COS in the lawn soil were researched using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The peaks of gas-phase products of CO 2 and surface HCO À 3 , HS À , SO 2À 3 , HSO À 3 , and SO 2À 4 species were observed. The possible mechanism of COS conversion in the lawn soil was discussed. The conversion rates of consumed COS into water-soluble sulfate in the lawn soil were studied by ion chromatography (IC). The experimental results show that about 50% sulfur from the soil consumed COS was eventually converted into water-soluble sulfate. r

Section: The Conversion Of Cos In the Lawn Soilsupporting

confidence: 41%

Uptake and conversion of carbonyl sulfide in a lawn soil

Atmospheric Environment

Geng

et al. 2007

“…Therefore, the effect of water on the heterogeneous reaction or adsorption of OCS on the surface of MgO appears to utilize different reaction mechanisms under conditions of low water vapor pressures versus high humidity conditions. In previous work, hydrogen thiocarbonate (HSCO − 2 ) was determined to be the crucial intermediate for the heterogeneous oxidation and hydrolysis of OCS on mineral oxides; HSCO − 2 is formed via the reaction of OCS with surface −OH on mineral oxides (He et al, 2005;Hoggan et al, 1994;Liu et al, 2006Liu et al, , 2007a. Additionally, we found that surface −OH contributes to not only the formation of HSCO − 2 but also to the decomposition of HSCO − 2 (Liu et al, 2007a).…”

Section: Mechanism For the Effect Of Water On The Heterogeneous Reactmentioning

confidence: 42%

Comparative study of the effect of water on the heterogeneous reactions of carbonyl sulfide on the surface of α-Al<sub>2</sub>O<sub>3</sub> and MgO

2009

Atmos. Chem. Phys.

Abstract.Here we compared the heterogeneous reactions of carbonyl sulfide (OCS) on the surface of α-Al 2 O 3 and MgO and the effect of water on the reactions at 300 K using Knudsen cell -mass spectrometry, diffuse reflectance infrared Fourier transform spectroscopy, and temperature programmed reactions. H 2 S and CO 2 were found to be hydrolysis products of OCS on both α-Al 2 O 3 and MgO at ambient temperature. At low water vapor pressure (<6.8×10 −6 Torr), when water vapor pressure in the Knudsen cell reactor increased from 2.3×10 −6 to 6.8×10 −6 Torr, the initial true uptake coefficient of OCS on α-Al 2 O 3 decreased from 4.70±0.45×10 −7 to 3.59±0.34×10 −7 ; while it increased from 5.19±0.49×10 −7 to 6.48±0.62×10 −7 on MgO under the same conditions. At high relative humidity (0.07-0.67), the observed uptake coefficients of OCS on α-Al 2 O 3 and MgO, which were measured using an in situ DRIFTS, decreased from 4.63±0.22×10 −6 to 1.00±0.47×10 −6 and from 9.72±0.46×10 −5 to 7.68±0.36×10 −5 , respectively, when RH increased from 0.07 to 0.67 corresponding to 1.7-15.9 Torr of water vapor pressure. In the RH region of 0.17-0.67, the average observed uptake coefficient of OCS on α-Al 2 O 3 and MgO was equal to 8.34±2.19×10 −7 and 8.19±0.48×10 −5 , respectively. The restrictive effect of water on the heterogeneous reaction of OCS on the surface of α-Al 2 O 3 and MgO was found to be related to competitive adsorption between water and OCS molecules; while the promotive effect of water on the heterogeneous reaction of OCS on the surface of MgO at low coverage was ascribed to the formation of surface hydroxyl groups. When the environmental RH was greater than the RH of the monolayer, Correspondence to: H. He (honghe@rcees.ac.cn) which occurred readily at the atmospherically relevant humidity in the troposphere, thick water layer formed on the mineral dusts, especially, the basic thick water layer formed on the basic component of mineral dusts may be the primary contributor to the heterogeneous hydrolysis of OCS in the troposphere.

“…- (13,27), was observed. It is apparent that the Al2O3 pretreated by H2 slows down COS oxidation and enables the observation of a reaction intermediate.…”

Section: Dynamic State In Situ Drifts Study Of Ocs + 95% O2 On the Prmentioning

confidence: 45%

Heterogeneous Oxidation of Carbonyl Sulfide on Atmospheric Particles and Alumina

et al. 2005

Environ. Sci. Technol.

Heterogeneous oxidation of carbonyl sulfide (OCS) on atmospheric particles and alumina (Al 2 O 3 ) was investigated in a closed system and a flowed system using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). At room temperature, OCS could be catalytically oxidized on the surface of atmospheric particles and Al 2 O 3 to form gas-phase CO 2 and surface sulfate (SO 4 2-), sulfite (HSO 3 -), and hydrogen carbonate (HCO 3 -) species. The real atmospheric particles were characterized using X-ray fluorescence (XRF) and the Brunauer-Emmett-Teller (BET) method. As a simplified model, Al 2 O 3 was used to study the reaction mechanism of heterogeneous oxidation of OCS. The hydrogen thiocarbonate surface (HSCO 2 -) species, an intermediate formed in the reaction of OCS with surface hydroxyl (OH), could only be observed on the prereduced Al 2 O 3 sample. The experimental results also indicate that surface oxygen containing species on the atmospheric particle sample and the Al 2 O 3 sample might be the key reactant for OCS oxidation. A reaction mechanism of heterogeneous oxidation of OCS on Al 2 O 3 surface is discussed.