दमन कंपाउंड ऑफ फॉसिल फ्यूल्स 10
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This last post in our series on Vehicle Fuels and Technology gives an overview of fossil fuels and their alternatives. You will see how crude oil pumped from the ground is transformed into everything from solvents to street tar. And you’ll learn which biofuels can be substituted for fossil fuels.
Petroleum, coal, and natural gas are the three main fossil fuels – that is, the fossilized remains of dead plants and animals created before dinosaurs walked the Earth, up to 300 million years ago. Chemically, all fossil fuels are "hydrocarbons", meaning their molecules contain hydrogen and carbon atoms. Different types of fossil fuels have different numbers of carbon atoms, and the atoms are linked together in different ways.
The vast majority of vehicles on the road today use combustion engines powered by petroleum fuels, though all three types of fossil fuels can power cars. Coal can be converted to liquid fuel (a bad idea), petroleum produces both gasoline and diesel fuel, and compressed natural gas (CNG) also can power cars.
Petroleum, or "crude oil", is the black liquid pumped out of the ground. It’s composed of simple hydrocarbons called "alkanes" that, for every n carbon atoms, have 2n+2 hydrogen atoms. For example, methane has one carbon atom, and four (2*1 + 2) hydrogen atoms.
At one carbon atom, methane is the alkane with the shortest chain of atoms. The shorter the chain, the lighter the molecule, so alkanes with four or fewer carbon atoms are gaseous. Methane is lighter than air. Alkanes with 5-19 carbon atoms are liquid at room temperature; those with 20 or more carbon atoms are solid.
Alkanes of different weights have different uses. Solvents and dry-cleaning fluids are made from alkanes with 5 to 7 carbon atoms. Gasoline is a blend of alkanes with 5 to 10 carbon atoms. Next, as the molecules get heavier, is kerosene (9-16 carbon atoms), then diesel fuel, jet fuel, home heating oil, and lubricating oil. The lightest of the solid chains (20 carbon atoms and higher) is used to make paraffin wax. Then you get tar, and finally asphaltic bitumen, which is used in asphalt roads.