ABU GODWIN ITAKPE PSC0904473 TOPIC: DESULPHURIZATION OF KEROSENE LITERATURE REVIEW INTRODUCTION Refining of crude oil to final products requires desulphurization of the oil. Fuel specifications that govern transportation fuels have over the years become increasingly stringent with respect to sulphur content. Many petrochemical products are likewise
produced to be almost sulphur-free. The removal of sulphur from oil is consequently one of the central conversion requirements in most refineries and the price (and processing cost) of a crude oil is influential by its sulphur content. Kerosene is a clear, oily highly flammable liquid with strong odour, usually obtained by distillation of ...view middle of the document...
Dissolved free sulphides (HS- and S2-) are very aggressive species for the corrosion of many metals such as steel, stainless steel and copper (Vaughan and Craig, 1978). Sulphides and its corrosive properties is reduced by oxidation of the sulphide which forms thiosulphate as intermediate (S2O32-) while the medium is also acidified by production of sulphuric acid when the oxidation is more advanced (Greenwood and Earnshaw 1997). The general formular of sulphides is RSR Structural examples of Sulphides in kerosene CH3 – S – CH3 H–S–H C2H5 – S – C2H5 Diethyl sulphide
Dimethy sulphides Hydrogen sulphide
Disulphides refers to the structural unit composed of linked pair of sulphur atoms (Greenwood and Earnshaw, 1997). Disulphides are
(hydrogenation) to give hydrogen sulphide and hydrocarbons as products. Structural examples of Disulphides in kerosene CH3 – S – S – CH3 Dimethy disulphide NITROGEN COMPOUNDS In crude oil distillates both basic and non-basic nitrogen C3H7 – S – S – C3H7 Dipropyl disulphide
compounds in kerosene appear and they usually have low nitrogen content. The occurrence of nitrogen compounds in kerosene degrades the colour of the product on exposure to sunlight. The nitrogen is easily removed by stripping or fractionation method. The basic nitrogen are nitrogens with alkyl substituted quinoline, pyridines, isoquinoline and its methyl derivative. The non-basic nitrogen are indoles, pyroles and carbozoles. They appear in kerosene but in trace amount. Structure of Basic Nitrogen Compounds
Non-Basic Nitrogen Compounds
OXYGEN COMPOUNDS (ACID COMPOUNDS) The oxygen compounds present in crude oil exists as organic acids or phenols. They are mostly concentrated in the gas oil fraction of the crude. The organic oxygen compounds are converted into water and hydrocarbons in a desulphurizer plant as show in the reaction below (William, 1994).
Example of acid compounds in kerosine
ORGANIC COMPOUND (OIL) Sulphur in organic materials is conveniently determined by burning the sample in a stream of oxygen. The sulphur dioxide (as well as the sulphur trioxide) formed during the oxidation is collected by distillation into a dilute solution of hydrogen peroxide (Douglas, 2001) SO2(g) + H2O2 ® H2SO4
The sulphuric acid is then titrated with standard base (e.g. NaOH). Alternatively, sulphur in inorganic compound can be detected or determined by adding freshly prepared sodium nitroprusside [Na2Fe(CN)5NO] (Wilson,1992 ). The fading of the deep violet colour of the salts shows that sulphur is present.
WAYS OF REMOVAL OF SULPHUR (OR DESULPHURIZATION) OF PETROLEUM FRACTION (KEROSENE)
kerosene: Hydrodesulphurization is most commonly used method in the petroleum industry to reduce the sulphur content of crude oil as well as its fraction. In most cases...