Sulfur-containing odorants

Present formula gasolines contain approximately 300 ppm. No. 2 fuel oil contains 2,200 to 2,600 ppm by weight of sulfur. Even pipeline gas contains sulfur-containing odorants (mercaptans, disulfides, or commercial odorants) for leak detection. Metal catalysts in the fuel reformer can be susceptible to sulfur poisoning and it is very important that sulfur in the fuel reformate be removed. Some researchers have advised limiting the sulfur content of the fuel in a stream reformer to less than 0.1 ppm, but noted the limit may be higher in an autothermal... 

N2. Sulfur containing odorants (mercaptans, disulfides, or commercial odorants) are added for leak detection. Because neither fuel cells nor commercial reformer catalysts are sulfur tolerant, the sulfur must be removed. This is usually accomplished with a zinc oxide sulfur polisher and the possible use of a hydrodesulfurizer, if required. The zinc oxide polisher is able to remove the mercaptans and disulfides. However, some commercial odorants, such as Pennwalf s Pennodorant 1013 or 1063, contain THT (tetrahydrothiophene), more commonly known as thiophane, and require the addition of a hydrodesulfurizer before the zinc oxide catalyst bed. 

Sen, A. and Grosch, W. 1991. Synthesis of six deu-terated sulfur containing odorants to be used as internal standards in quantification assays. Z Lebensm.-Unters. -Forsch.A 192 541-547. 

Synthesis and Sensorial Description of New Sulfur-Containing Odorants... 

This article deals with the combinatorial synthesis of various sulfur-containing odorants. We used this approach for the identification of natural aroma components in different ingredients such as fiied onion or bell peppers. 

In a study of 63 industrial effluents collected from a wide range of chemical manufacturers from across the United States, carbon disulfide was found in six of the effluents at concentrations less than 10 pg/L and in two of the effluents at 10-100 pg/L (EPA 1979). Analysis of influent and effluent samples from a waste water treatment plant in Tokyo showed carbon disulfide to be the least prevalent among five sulfur-containing odorous compounds for which testing was done (Hwang et al. 1995). 

Natural Gas Processing The major constituents of pipeline gas are methane, ethane, propane, CO2, and, in some cases, N2. Sulfur-containing odorants (mercaptans, disulfides, or commercial odorants) are added for leak detection. Because neither fuel cells nor commercial reformer... 

Natural gas, liquefied petroleum gas (LPG), and carbon materials serving as the raw materials for cheap technical hydrogen usually contain marked amounts of sulfur compounds. In addition, sulfur-containing odorants (tetrahydrothiophene or ethylmercaptan) often are purposely added to the gas distribution network so that gas leaks may be detected in a timely manner, because natural gas is usually odorless. 

The physical properties of the principal constituents of natural gas are Hsted in Table 5. These gases are odorless, but for safety reasons, natural gas is odorized before distribution to provide a distinct odor to warn users of possible gas leaks in equipment. Sulfur-containing compounds such as organic mercaptans, aUphatic sulfides, and cycHc sulfur compounds are effective odorants at low concentrations and are added to natural gas at levels ranging from 4 to 24mg/m. ... 

Sulfoxides occur widely in small concentrations in plant and animal tissues, eg, aHyl vinyl sulfoxide [81898-53-5] in garlic oil and 2,2 -sulfinylbisethanol [3085-45-8] as fatty esters in the adrenal cortex (1,2). Homologous methyl sulfinyl alkyl isothiocyanates, which are represented by the formula CH3SO(CH2) NCS, where n = 3 [37791-20-1], 4 [4478-93-7], 5 [646-23-1], 8 [75272-81-0], 9 [39036-83-4], or 10 [39036-84-5], have been isolated from a number of mustard oils in which they occur as glucosides (3). Two methylsulfinyl amino acids have also been reported methionine sulfoxide [454-41-1] from cockroaches and the sulfoxide of i -methylcysteine, 3-(methylsulfinyl)alaiiine [4740-94-7]. The latter is the dominant sulfur-containing amino acid in turnips and may account in part for their characteristic odor (4). 

Another area in which sulfur compounds have long found use is in the area of agricultural chemicals. Many of these materials had been produced by the manufacturer of the agricultural chemicals, but difficulties in containing odor and the use of hydrogen sulfide in heavily populated areas again pushed toward specialization by several companies. A Hst of agricultural chemicals, and the thiol that is used or has been used in production, follows ... 

Foul-smelling gases Sulfur-containing gases such as hydrogen sulfide that have an odor even at low concentrations. 

Hydrogen is odorless, colorless, and tasteless and therefore undetectable by human senses. Adding odorants to hydrogen is one of the options for leak detection because people can smell it. The most common odorants for natural gas that is also odorless, colorless, and tasteless are sulfur containing. These odorants, however, are not appropriate for hydrogen... 

Odorization. Natural gas is odorized so that leaks can be detected, whereas gasoline is normally smelly. Odorization of natural gas is a prudent although not entirely effective safety measure. Hydrogen as an industrial gas or fuel cell vehicle fuel is not odorized because sulfur-containing substances (mercaptans) contaminate the catalysts of a fuel cell. 

Enantiomers of a chiral compound show many different physiological responses, including those of odor and taste2 and it has long been known that enantiomers of some sulfur-containing compounds may have different odors. The examples discussed here are for sulfur-containing compounds where the chirality is based on carbon. While certain compounds can show sulfur-based chirality, there are apparently no known cases where enantiomers dependent on sulfur chirality exhibit different odors. 

As would be expected, the chemistry is complex. Unpleasant, off flavor odors usually derive from sulfur compounds, such as MT, DMS, DMDS, and DMTS, formed either enzymatically or non-enzymatically from sulfur-containing amino acids.35 Enzymatic routes to MT are essentially those previously considered (Section 11.1.2.4.5). Some DMS may derive by methylation of MT (Equation 8) with the donor, 5-adenosylmethionine, AdoMet ... 

TABLE 4.3. Sulfur and Nitrogen-Containing Odorous Compounds in the Influent Wastewater at a Treatment Plant (Hwang et al., 1995). 

Hwang, Y., T. Matsuo, K. Hanaki, and N. Suzuki (1995), Identification and quantification of sulfur and nitrogen containing odorous compounds in wastewater, Water Res., 29(2), 711-718. Jensen, N.Aa. (1994), Air-water oxygen transfer in gravity sewers, Ph.D. dissertation, Environmental Engineering Laboratory, Aalborg University, Denmark. 

Organic solvents such as methanol, ethanol, and other alcohols are used for pulping. This process is economical for small- to medium-scale mills with significant recovery of chemicals for reuse. However, pulping must be conducted in enclosed containers to prevent the loss of volatile solvents and for workers safety. Additionally, some of these processes are more energy intensive than traditional methods. Major benefits include the elimination of odorous sulfur-containing compounds in the effluents and air. 

Sulfur dioxide is a colorless gas with a sharp, pungent odor, like that of a burning match. Most people are able to detect this highly characteristic odor at concentrations of about 0.5 ppm or greater. Its chemical formula is SO2. Sulfur dioxide is readily soluble in water, forming the weak acid sulfurous acid (H2SO3). Sulfur dioxide is formed when sulfur or a sulfur-containing compound is burned ... 

The impact of oxygen on wine aroma is likely to involve several oxidation mechanisms. One pathway involves pol) henol quinones, particularly in the case of the removal of unwanted sulfur-containing off-odors (RSH Mestres et ah, 2000), as illustrated in Fig. 4.4A. 

The sulfur-containing combustion gases sulfur dioxide and sulfur trioxide both have unpleasant odors. These gases form during the burning of fuel sulfur. Although... 

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