CONVENTIONAL TRANSPORT FUELS (GASOLINE/DIESEL)

2.0 CONVENTIONAL TRANSPORT FUELS (GASOLINE/DIESEL)

Since the birth of automotives in the 19th century, diesel and gasoline are used as the primary source of energy for the vehicles, though many alternate fuels like CNG, LPG, alcohol, dimethylether, biodiesel, methanol, etc. are emerging in the market. The conventional fuels are basically derived from crude oil, where crude oil is fractioned by continuous distillation into several fractions: Petrol (gasoline), kerosene (kerosene, paraffin oil), gas oil (heavy oil), vacuum gas oil, naphtha, lubricating oil and residue. These fractions are further processed through conversion, reforming and treatment processes to increase the yields and adjust the chemical composition of transport fuels and to remove the trace impurities. Finally, several streams are blended to produce transport fuels with the desired specifications. The composition of crude oil varies with the locality of occurrence, but all contains alkanes (straight and branched chain from about C1 to C40), cycloalkanes or napthenes, and aromatic hydrocarbons. The low -boiling fraction of almost all petroleum products are composed of alkanes; it is the composition of the higher boiling fraction, which differ according to the source of the petroleum. In addition to hydrocarbons, there are also present compounds containing oxygen, nitrogen, sulphur and metallic constituents.

Codes, standards or specifications for the gasoline and diesel have been laid down in different countries. National or other legally enforceable specifications represent the minimum quality that must be supplied and it is implicit that engine designers should ensure that their vehicles will run satisfactorily on such a quality of fuel. In India, the Bureau of Indian Standards (BIS) notifies the requisite specifications for petrol and diesel. Annexure I & II show BIS specifications for diesel & gasoline that are being implemented all over the country except in four metros, while in four metro cities Bharat stage-II fuel specifications are implemented.