what are the major composition(hydrocarbon) present in LPG,CNG,petrol& diesel?

The normal components of LPG are propane (C₃H₈) and butane (C₄H₁₀). Small concentrations of other hydrocarbons may also be present.

CNG mainly contains: 

Methane [CH4]

82.0 - 94.0

Ethane [C2H6]

3.0 - 6.0

Natural gas consists mostly of methane and is drawn from gas wells or in conjunction with crude oil production.  As delivered through the pipeline system, it also contains hydrocarbons such as ethane and propane as well as other gases such as nitrogen, helium, carbon dioxide, sulphur compounds, and water vapour. 

 

Diesel is composed of about 75% saturated hydrocarbons (primarily paraffins including n, iso, and cycloparaffins), and 25% aromatic hydrocarbons (including naphthalenes and alkylbenzenes). 

 

Petrol consists of hydrocarbons with between 5 and 12 carbon atoms per molecule but then it is blended for various uses. Overall a typical petrol sample is predominantly a mixture of paraffins (alkanes), naphthenes (cycloalkanes), aromatics and olefins (alkenes). The ratios vary based on a variety of factors.