Sulphur-Containing Oils

Corrosion by sulphur additives Sulphur compounds occur naturally in most lubricants and many oil additives contain sulphur. In a properly formulated lubricant these sulphur compounds should be inactive at ambient temperature. At elevated temperatures they may decompose to give more active materials which can stain and corrode metals, particularly silver and copper. However, these same sulphur compounds have many beneficial qualities this is why they are not removed com.pletely in refining and why they are used as additives. 

Sulphur dioxide Combustion of coal, oil and other sulphur-containing fuels Petroleum refining, metal smelting, paper-making Vegetation damage Sensory and respiratory irritation Corrosion Discoloration of buildings... 

Shennan, I. L., Microbial Attack on Sulphur-Containing Hydrocarbons Implications for the Biodesulfurization of Oils and Coals../. Chem.Tech. Biotechnol., 1996. 67 p. 109. 

The mine has an annual capacity to move 83.7 million tonnes of oil sand containing 8.6 million tonnes of bitumen with approximately 0.4 million tonnes of contained sulphur. 

These formulas, which have been deduced for individual aromatic compounds, are also suitable for the characterization of aromatic mineral oil fractions,aromatic concentrates, etc., provided that only small amounts of tri-aromatics and higher aromatic compounds are present. For sulphur-containing oils the value of Rn should be corrected ... 

In the case of statistical methods of analysis of sulphur-containing crude oil fractions one generally confines oneself to small corrections on the applied graphs or equations. These corrections, which have been estimated empirically, are valid only for small percentages of sulphur and do not take into account the nature of the sulphur compounds present in the fractions. 

Garra and Muth [24] characterised cmde, semi-refined and refined oils by gas chromatography. Separation followed by dual-response detection (flame ionisation for hydrocarbons and flame photometric detection for sulphur-containing compounds) was used as a basis for identifying oil samples. By examination of chromatograms, it was shown that refinery oils can be artificially weathered so that the source of oil spills can be determined. 

Sulphate is the form in which S is normally absorbed by plant roots and the reduction of sulphate for the synthesis of sulphur-containing compounds is universal for plants. Sulphur occurs in some amino acids, proteins and also in the oils of some plants such as cabbages and turnips. The S—H group is very important for the action of some enzymes and coenzymes. S is also a constituent of ferredoxins. A deficiency leads to stunting and yellowing but can be cured. A classical case of S deficiency known as tea yellows was identified in 1933 by Storey and Leach (reported in Hewitt and Smith, 1975). Sulphur deficiency leads to accumulation of amine and ammonia nitrogen, with little change in the total. 

Sulphur has to be removed for many petrochemical operations. All crude oils contain sulphur. The sulphur is distributed throughout the boiling range. The amount and type of sulphur present depends on the source crude oil. This is illustrated in Figure 4.3 for Saudi Arabian light and heavy crude oils which contain 1.77 and 2.8 wt. % sulphur respectively. 

Werkhoff, P., Briining, J., Emberger, R., Matthias, G., Kopsel, M., Kuhn, W. (1989). Studies on volatile sulphur-containing flavour components in yeast extrat. In 11 th International Congress of Essential Oils, Fragances and Flavours. New Dehli. Proceedings, 4, 215-243. 

Wood derived fast pyrolysis oil and slaked lime produce a Calcium-Enriched Bio-oil (CEB) capable to remove SO2 while combusting sulphur-containing fuels. The bio-oil required is produced in a 200 kg/hr fast pyrolysis plant, while CEB is made in batch-wise operation by slowly mixing slaked lime with bio-oil at controlled conditions. 

There are some different approaches to extend gas oil hydrotreating technology so as to increase sulphur compounds conversion to reach the new specification of 500 ppm. At this lower level the most difficult sulphur-containing molecules in gas oil have to be removed. 

For further information on the essential oil see [28, 29[. The sulphur-containing trace constituent 4-methoxy-2-methyl-2-butanthiol has been identified as an important flavour carrier [30[. 

The essential oil has a strong smell and the sulphur-containing constituents give the characteristic smell and taste. Depending on the method of production the amount of active compounds in the oil is highly variable, which has an influence on the pharmacological effects. 

Hydrocarbon compounds are composed of hydrogen and carbon, which are therefore the main elements in oils. Oils also contain varying amounts of sulphur, nitrogen, oxygen, and sometimes mineral salts, as well as trace metals such as nickel, vanadium, and chromium. 

Both chain-terminating oxidation inhibitors, e.g. hindered phenols and amines, and peroxide-destroying inhibitors, e.g. dithiophosphate and dithiocarbamates, can be included in marine formulations. Mixtures of phenols and amines are often used for synergy but they must have good high-temperature performance. The sulphur-containing oxidation inhibitors also have extremely useful anti-wear properties. Oxidation inhibitors can be used advantageously in some base oils refined from low sulphur crudes and in synthetic basestocks. They compensate for the lack of natural antioxidant species. 

Sulphur dioxide is formed when sulphur-containing fuels such as oil and coal are burned. In contact with humid air, it transforms to sulphuric acid, which contributes to the acidification of soil and water. 

Fig. 4.23 Major hydrocarbons and simple heteroatomic compounds in crude oils (a) acyclic alkanes (paraffins) (b) cycloalkanes (naphthenes) (c) aromatic hydrocarbons (d) sulphur-containing aromatics. (R. = alkyl group.)...

Sulphur-containing petroleum components such as benzothiophene, DBT, and naphthobenzothiophene were obtained from seawater extracts (Warner, 1975) and were related to an oil spill. The detection of diphenyl sulphone and bis-(p-chlorphenyl) sulphone in ng amounts in the Mediterranean, as well as in oxic and anoxic Baltic waters, suggests anthropogenic input (Bouchertall, 1979) — the former compound is used as wood preserving agent and ovicide. 

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