Why we make the process of removal of sulfur from crude oil?

Sulfur in crude oil is mainly present in the form of organ sulfur compounds. Hydrogen sulfur is the only important inorganic sulfur compound find in crude oil.

Its presence however, is harmful because of its corrosive nature organ sulfur compounds may generally be classified as acidic and non acidic. Acidic sulfur compounds are the thiols (mercaptans).

Thiophene, sulfides and disulfides are examples of non-acidic sulfur compounds found in crude oil fractions.

Extensive research has been carried out to identify some sulfur compounds in a narrow light petroleum fraction.

Most Common Methods Of Removal Of Sulphur:

I.Catalytic Desulfurization.

II.Chemical Desulphurization.

III.Physical Adsorption Of Sulphur Oxide.

IIII.Wet Sulfuric acid process.

IV. Spray dry scrubbing using similar sorbent slurries.

I. By Catalytic Desulfurization:Hydrodesulfurization (HDS), the industry standard method of

removing sulfur in petroleum refining operations, uses types of catalysts to add hydrogen in order to reduce unwanted sulfur compounds. Unfortunately, the HDS process typically requires expensive, high-pressure (up to 1,000 psig), high-temperature (400 –550°C) equipment to help produce environmentally friendly fuels.

Hydrodesulfurization (HDS) is the standard catalytic process for the removal of sulfur from petroleum products. In this process, the sulfurous fractions of the crude oil are mixed with hydrogen and a catalyst to react to hydrogen sulfide. Typically, the catalyst consists of an alumina base impregnated with cobalt and molybdenum. As the oilsupplies get more sour, higher pressures and alternative catalysts are required for the desulfurization. Recalcitrant aromatic sulfur compounds (e.g. 4,6-dimethyldibenzothiophene) cannot be removed using hydrodesulfurization, due to their low reactivity

II.By Chemical Desulphurization:a) Acid chromous chloride treatment.

b) Peroxyacetic acid treatment.

II.b)Peroxyacetic acid treatment:

Chemical desulphurisation was carried out according to the method described by Palmer et al. 13 with some modifications. About 2 g of coal (< 250 µm) in 70 mL of glacial acetic acid and 30 mL of 6% hydrogen peroxide concentration were reacted at room temperature for a specific reaction time.

The reaction mixture was cooled and the residual coal was filtered and washed with excess of hot distilled water and dried in vacuum oven set at 40˚C over night. The experiment was repeated at various reaction temperatures of 50 and 104˚C (refluxing temperature).

The reaction was also conducted with various acids to peroxide volume ratio of 50:50, 30:70 and 60:20 and with 30% hyrogen peroxide concentration.

III.By Physical Adsorption Of Sulphur Oxide:

One of the more promising processes for removal of S02 and NO, simultaneously is the Bergbau-Forschung process that involves S02 adsorption and catalytic NO, reduction with ammonia by using carbonaceous adsorbents 1281.

The mechanism and kinetics of adsorption of S02 fiom flue gas on carbon is very complex due to the presence of water vapour and oxygen, which leads to the formation of sulphuric acid. The adsorption capacity for S02 is much greater than that of physical adsorption because of the formation of H2S04.

Lu and Do studied the use of coal reject - a coal mine waste - as an adsorbent. They found that the coal reject, when previously treated by pyrolysis and activation, possessed considerable adsorption capacities for both SO2 and NO.

This process presents the advantages of simultaneous removal of S02 and NO, and utilization of solid waste.