Carbonyl sulfide sources

Other components in the feed gas may react with and degrade the amine solution. Many of these latter reactions can be reversed by appHcation of heat, as in a reclaimer. Some reaction products cannot be reclaimed, however. Thus to keep the concentration of these materials at an acceptable level, the solution must be purged and fresh amine added periodically. The principal sources of degradation products are the reactions with carbon dioxide, carbonyl sulfide, and carbon disulfide. In refineries, sour gas streams from vacuum distillation or from fluidized catalytic cracking (FCC) units can contain oxygen or sulfur dioxide which form heat-stable salts with the amine solution (see Fluidization Petroleum). 

Charcoal—sulfur processes need low ash hardwood charcoal, prepared at 400—500°C under controlled conditions. At the carbon disulfide plant site, the charcoal is calcined before use to expel water and residual hydrogen and oxygen compounds. This precalcination step minimises the undesirable formation of hydrogen sulfide and carbonyl sulfide. Although wood charcoal is preferred, other sources of carbon can be used including coal (30,31), lignite chars (32,33), and coke (34). Sulfur specifications are also important low ash content is necessary to minimise fouling of the process equipment. 

Khalil, M.A.K. and Rasmussen, R.A. Global sources, lifetimes and mass balances of carbonyl sulfide (OCS) and carbon disulfide (CS2) in the earth s atmosphere, Atmos. Environ., 18(9) 1805-1813, 1984. 

Barnes, I., K. H. Becker, and I. Patroescu, The Tropospheric Oxidation of Dimethyl Sulfide A New Source of Carbonyl Sulfide, Geophys. Res. Lett., 21, 2389-2392 (1994b). 

In this review we have attempted to cover the very recent literature relevant to the coordination chemistry of carbon dioxide and its use as a source of chemical carbon. We have omitted similar investigations involving the more reactive substrates, carbon disulfide and carbonyl sulfide. The reader is referred to a recent review by Ibers (722) which has contrasted the behavior of these sulfides to carbon dioxide. Likewise we have, as stated at the onset, elected to neglect heterogeneous processes involving the reduction... 

A U. S. national biogenic sulfur emissions inventory with county spatial and monthly temporal scales has been developed using temperature dependent emission algorithms and available biomass, land use and climatic data. Emissions of dimethyl sulfide (DMS), carbonyl sulfide (COS), hydrogen sulfide (H2S), carbon disulfide (CS2), and dimethyl disulfide (DMDS) were estimated for natural sources which include water and soil surfaces, deciduous and coniferous leaf biomass, and agricultural crops. The best estimate of 16100 MT of sulfur per year was predicted with emission algorithms developed from emission rate data reported by Lamb et al. (1) and is a factor of 22 lower than an upper bound estimate based on data reported by Adams et al. 

The hydrogen sulfides (H2S, SH-, S2 and their metal complexes) are well known in restricted reducing regions of the world ocean such as anoxic basins (1), but they have traditionally been dismissed as unimportant for, or even nonexistent in, most oxic seawaters 12-41. Several lines of reasoning are now beginning to suggest that sulfides actually do exist in the surface ocean, and enter into a rich metal chemistiy there. Extensive measurements of carbonyl sulfide (OCS) in seawater (5.61 permit the quantification of a mixed layer source, the hydrolysis reactions f7-111... 

Biogenic Sulfur Emissions from the Ocean. The ocean is a source of many reduced sulfur compounds to the atmosphere. These include dimethylsulfide (DMS) (2.4.51. carbon disulfide (CS2) (28). hydrogen sulfide (H2S) (291. carbonyl sulfide (OCS) (30.311. and methyl mercaptan (CH3SH) ( ). The oxidation of DMS leads to sulfate formation. CS2 and OCS are relatively unreactive in the troposphere and are transported to the stratosphere where they undergo photochemical oxidation (22). Marine H2S and CH3SH probably contribute to sulfate formation over the remote oceans, yet the sea-air transfer of these compounds is only a few percent that of DMS (2). 

Although there have been only a few studies to date, it has been suggested that coastal plumes and estuaries may be important atmospheric sources of DMS. Other sulfur compounds such as carbonyl sulfide (OCS) and carbon disulfide (CS2) have also been shown to possible sources of S in estuaries. 

F.Y.T. Leung, et ah. Isotopic fractionation of carbonyl sulfide in the atmosphere Implications for the source of background stratospheric sulfate aerosol, Geophys. Res. Lett. 29 (10) (2002), doi 10.1029/2001GL013955. 

In the last 150 years the anthropogenic emission of sulfur has increased dramatically, primarily due to combustion processes [1]. In the 1950s anthropogenic emission surpassed natural emission and the atmospheric sulfur cycle is one of the most perturbed biogeochemical cycles [1,2]. The oceans are the largest natural source of atmospheric sulfur emissions, where sulfur is emitted in a reduced form, predominantly as dimethyl sulfide (DMS) and to a much lesser extent carbonyl sulfide (OCS) and carbon disulfide (CS2) [3]. Ocean emitted DMS and CS2 are initially oxidised to OCS, which diffuses through the troposphere into the stratosphere where further oxidation to sulfur dioxide (SO2), sulfur trioxide (SO3) and finally sulfuric acid (H2SO4) occurs [1-4]. 

In almost all of the gas-phase kinetic-mechanistic studies on sulfur atom reactions made to date, the source has been the in situ photolysis of carbonyl sulfide (COS). The reasons for this choice are not far to seek. Carbonyl sulfide is a stable, readily available gas. Its absorption spectrum is located in a convenient spectral region and the carbon monoxide formed in the photodissociation provides an excellent internal monitor for sulfur atom production. 

Carbonyl sulfide is also the most abundant reduced sulfur gas in Earth s troposphere, but for completely different reasons. Volcanic sources of OCS are negligible by comparison with biogenic emissions, which are important sources of several reduced sulfur gases (e.g., OCS, H2S, (CH3)2S, (CH3)2S2, and CH3SH) in the terrestrial troposphere. Many of these gases are ultimately converted into sulfate aerosols in the troposphere, but OCS is mainly lost by transport into the stratosphere, where it is photochemically oxidized to SO2 and then to sulfuric acid aerosols, which form the Junge layer at —20 km in Earth s stratosphere. 

The Oceans as a Source of Gases to the Atmosphere 2.1 Dimethyl sulfide Methyl mercaptan Carbonyl sulfide Carbon disulfide Hydrogen sulfide Methyl iodide Methyl chloride Chloroform Nitrous oxide Methane... 

Elhott S., Lu E., and Rowland F. S. (1987) Carbonyl sulfide hydrolysis as a source of hydrogen-sulfide in open ocean seawater. Geophys. Res. Lett. 14(2), 131 — 134. 

Carbonyl sulfide is an important gas kinetic source of ground state and electronically excited sulfur atoms, and its photodissociation has been employed by several groups to study the rates and products of reactions of S(3 P2), S(3- Sq), and 3(3 02). It is, in addition, one of the Interstellar molecules, has been proposed as a minor constituent of the Venus atmosphere, and leads to laser emission in CO following photodissociation. 

Carbonyl sulfide is a flammable gas, and may be explosive or spontaneously flammable in air under the right conditions. Vapors may ignite at distant ignition sources and flash back. When exposed to fire, humidity, or strong alkalis, carbonyl sulfide may form the toxic decomposition products carbon monoxide and hydrogen sulfide gas. In the presence of strong oxidizers, carbonyl sulfide presents a fire or explosion hazard. Carbonyl sulfide has a vapor density of 2.1 and is therefore heavier than air. Cylinders or tank cars containing carbonyl sulfide may rupture violently or rocket under fire conditions. 

The Clean Air Act (CAA) Amendments of 1990 list carbonyl sulfide as a hazardous air pollutant (HAP) generally known or suspected to cause serious health effects. Section 112(b) (1) of the CAA lists pollutants that are judged to be hazardous if emitted into the air. Carbonyl sulfide is included on this list. The statute calls for the identification of source categories that emit these HAPs, and the subsequent promotion of technology-based emission standards requiring compliance with maximum achievable control technology. 

A further potential concern in gas processing is the presence of carbon disulfide (CS2) or carbonyl sulfide (COS) in the natural gas. These may be from natural sources or are occasionally contributed from the use of carbon disulfide to remove sulfur blockages from sour gas wells or components of the Girbotol plant. These sulfur compounds react with monoethanolamine to yield complex thiazolidine and oxazolidine heterocycles and polymerization products of these which are not dissociated in the regeneration step of the gas cleaning plant [28] (Eq. 9.15). 

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