Lecture 8

Sulfur compounds of oil. Varieties of sulfur compounds in crude oil, their physical and chemical properties. Qualitative and quantitative determination of total sulfur content. The content of sulfur compounds in various types of oil. Influence of the presence of sulfur compounds on the properties of oil.

Plan of the lecture

1. Types of sulfur compounds of oil

2. The content of sulfur compounds in petroleum and petroleum products

3. Effect of sulfur compounds on the properties of petroleum

1.Most of the world's oil reserves is currently sulfur or sour. Most of the oil CIS refers to sulfur and sour. Deposits of the Volga-Ural depression, Western Siberia, Kazakhstan, part of the oil and southern Uzbekistan contain sulfur from 1 to 2% (wt). Moreover, in the territory of the old oil fields with sweet crude open up new fields of sulfurous and even high-sulfur oil (Yuzhnoembinsky district). All this requires a thorough study of the composition and properties of oil sulfur compounds, methods of their removal and use.

Sulfur in the crudes may occur in small quantities, and may sometimes exceed 3%. Currently, most of the world's oil reserves is sour or sour.

Sulfur compounds oils differ significantly in their chemical composition. Oils can contain sulfur compounds in a dissolved or colloidal. Sulfur compounds are presented in the form of elemental sulfur and hydrogen sulfide dissolved mercaptans (thioalcohols, thiols), sulfides (thioethers) and polysulfides, cyclic sulfides (such as tetrahydrothiophene) and thiophene derivatives. Furthermore there mixed sulfur- and oxygen-containing compounds - sulfones, sulfoxides, and sulfonic acid. In the resinous-asphaltene oil portion observed more complex compound containing sulfur, nitrogen and oxygen.

2. The distribution of sulfur in fractions of oil varies, generally sulfur content increases from the lower to the higher fractions. In heavy petroleum residues usually contain from 70 to 90% (wt.) of sulfur compounds, especially in asphalt-resinous portion.

In general it can be said that the oil residue boiling above 350⁰C is more than 75% of the total sulfur present in the oil. It should be borne in mind that the primary part of the sulfur compounds is decomposed during the distillation.

Free sulfur has been repeatedly found in crude oils by the formation of a black cinnabar modification by shaking with mercury. Some oils contain a large enough amount of hydrogen sulfide, which upon reaction with oxygen in the air is converted to elemental sulfur, which may be the cause of sulfur deposits.

The presence of sulfur in petroleum distillates that may be explained by the reaction, since the superheated steam is always contains free oxygen (from the air dissolved in water is converted into steam). Free sulfur during prolonged interaction with hydrocarbons when heated forms hydrogen sulfide. Its concentration may range from 0.0001 to 0.1% (wt.), and generally in proportion to the sulfur content of oil.

Oils hydrogen sulfide occurs quite often. Hydrogen sulfide can be in a secondary oil origin, apparently from mercaptans, some of which have broken during the distillation. According to some observations, sulphurous oil, freed from hydrogen sulfide by blowing air or by treatment with alkaline solutions, even when heated at relatively low temperatures, forms hydrogen sulfide again.

Found that the most stable (at 200-300°C) sulfur-containing compounds in the oil sand deposits; whereas oils limestone decomposition begins at 40 -80 ° C. Age of oil and the content of sulfur compounds does not affect their stability.

3. The sulfur compound - oil undesirable components, as due to its ability to degrade to release the hydrogen sulfide and elemental sulfur, which contribute to corrosion and failure of equipment and thereby make it difficult treatment processes. Undesirable presence of sulfur compounds in finished petroleum products. However, in this case one has to take into account mainly the active sulfur compounds which include mercaptans, hydrogen sulfide and elemental sulfur. These substances have a negative effect during the processing of crude oil and petroleum fractions, due to its high corrosive capacity, even at low temperatures.

Increasing the sulfur content in motor fuels increases the fuel consumption, reduces the wear and increases the power of the engine. Increasing fuel sulfur content leads to deterioration of ecological environment.

Sulfur compounds must be removed from the processed oil fractions most appropriate way - removing or destruction to simple compounds to facilitate their removal. Methods of refining fuel by hydrogenating (hydrofinishing), which removes sulfur, oxygen and nitrogen in the form of volatile compounds.

The control questions

1. Sulphur compounds oil

2. Distribution of sulfur petroleum fractions

3. The main representatives of sulfur compounds of oil

4. Classification of oil sulfur content.