Mechanistic studies of the hydroxyl-initiated oxidation of carbon disulfide in the presence of oxygen

Abstract

We have investigated production of carbon-and sulfur-containing end products of the OH-initiated oxidation of CS2 in the presence of 02, an important atmospheric chemical reaction which is known to proceed via the following three elementary steps: O H + CS2 + M CSzOH + M; CS20H + 0 2 -products. Two different experimental approaches were employed. In one set of experiments (CP-FTIR studies) continuous photolysis of CH30NO/NO/CS2/Air mixtures at 298 K and 700-Torr total pressure was combined with product detection by Fourier transform infrared spectroscopy; these studies measured moles of products formed per mole of CS2 consumed. In a second set of experiments (LFP-TDLAS studies) 248-nm laser flash photolysis of H202/ CS2/N20/He/02 mixtures at 298 K and 25-100-Torr total pressure was combined with product detection by time-resolved tunable diode laser absorption spectroscopy; in this case, the quantity measured was moles of product formed per mole of O H consumed. In both studies OCS and CO are observed as carbon-containing products with yields of 0.83 f 0.08 and 0.16 f 0.03, respectively; uncertainties represent estimates of absolute accuracy at the 95% confidence level. The LFP-TDLAS experiments demonstrate that the above yields represent "prompt" product formation; i.e., OCS and CO are formed either as primary products of the CSzOH + 0 2 reaction or as products of a fast (k > cm3 molecule-' s-') secondary reaction of a primary product with 0 2 . The CP-FTIR experiments show that, under atmospheric conditions, SO2 is produced with a yield of 1.1 5 f 0.10; in this case, the LFP-TDLAS results strongly suggest that only about three-fourths of the SO2 is formed as a prompt product, with the remainder generated via slow reaction of SO (generated as a prompt product of the CS2OH + 0 2 reaction) with 0 2 . The implications of our results for understanding the detailed mechanism of the very complex CS2OH + 0 2 reaction are discussed, as are their implications for understanding the atmospheric cycles of CS2 and OCS.

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume I - gas phase reactions of O<sub>x</sub>, HO<sub>x</sub>, NO<sub>x</sub> and SO<sub>x</sub> species

“…The overall yield of SO 2 (1.15 ± 0.10) was made up of two components, a 'prompt' value of 0.84 ± 0.20 resulting from SO 2 produced in a primary channel of the reaction and a longer time component assumed due to production of SO 2 from reaction of O 2 with S or SO produced in another primary channel. The data of Stickel et al (1993) thus suggest two primary channels, the major one leading to OCS and SO 2 and a minor channel leading to CO and SO. There are a number of possible reaction channels leading directly to these species or to their precursors, which subsequently produce them on a very short time scale.…”

“…followed by reactions of HCO and S to form HO 2 + CO and SO 2 accounts for ∼15% of the overall reaction , with the remainder (∼85%) proceeding by (Zhang and Qin, 2000) suggests that HOSO and OCS are the main dissociation products, which would then be followed by the reaction HOSO + O 2 → HO 2 + SO 2 . ] (c) HO generated from the H + NO 2 reaction.…”

Reviews and Syntheses: Carbonyl Sulfide as a Multi-scale Tracer for Carbon and Water Cycles

“…Significantly larger concentrations have been found in coastal waters (Uher, 2006, and references therein). A molar yield of CS 2 to OCS of 0.81-0.93 was established by Stickel et al (1993) and Chin and Davis (1993), resulting in OCS emissions from CS 2 with an uncertainty of 20-80 Gg S yr -1 . This uncertainty arises from the uncertainty in the emissions, not the molar yield, for which a globally constant factor is used.…”

Anthropogenic contributions to global carbonyl sulfide, carbon disulfide and organosulfides fluxes

“…Most of this secondary OCS derives from the oxidation of atmospheric CS 2 which yields 0.83 parts OCS and 1.17 SO 2 (Stickel et al, 1993). The oxidation is relatively slow which leads to a CS 2 residence time of about six days, so in the case of marine CS 2 , 90% of the marine (i.e.…”

“…In the present work we take CS 2 oxidation to convert 0.415 of the sulfur to OCS (Stickel et al, 1993). This suggests that 58 Gg S a -1 of OCS arises from the oxidation of marine CS 2 and some 36 Gg S a -1 from oxidation of naturally produced CS 2 over land, which includes 18 Gg S a -1 derived from marshes and 14.5 Gg S a -1 from vegetation.…”