Carbon compounds as fuels and feedstock

• Crude oil is a finite resource found in rocks, the remains of an ancient biomass consisting mainly of plankton that was buried in mud, and is a mixture of a very large number of compounds.
• A mixture is defined as two or more elements that are not chemically combined, with the chemical properties of each substance in the mixture unchanged.
• It is possible to separate the substances in the mixture by physical methods including distillation.
• Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon only (hydrocarbons).
• Most of these saturated hydrocarbons are alkanes.
• Hydrocarbons have the general formula: C n H 2n+2.
• Alkane molecules can be represented in the following forms: MEPB (Monkeys Eat Peanut Butter).
• The molecular formula of butane is C4H10.
• The first 4 alkanes are methane, ethane, propane and butane.
• The oil is heated in the fractionating column and the oil evaporates and condenses at a number of different temperatures.
• The many hydrocarbons in crude oil can be separated into fractions each of which contains molecules with a similar number of carbon atoms.
• The fractionating column works continuously, heated crude oil is piped in at the bottom.
• The vaporised oil evaporates and rises up the column and the various fractions are constantly tapped off at the different levels where they condense.
• The fractions can be processed to produce fuels and feedstock for the petrochemical industry.
• Many of the fuels on which we depend for our modern lifestyle, such as petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases, are produced from crude oil.
• Many useful materials on which modern life depends are produced by the petrochemical industry, such as solvents, lubricants, polymers, and detergents.
• The vast array of natural and synthetic carbon compounds occur due to the ability of carbon atoms to form families of similar compounds.
• Alkenes are used for producing other chemicals, such as polymers.
• Unsaturated carbons can be represented in the following forms:
• The shorter the molecules, the lower the temperature at which that fraction is vaporised or condensed, and the lower its boiling point.
• The shorter the molecules, the more flammable it is, making it a better fuel.
• The processes for cracking hydrocarbons include passing them over a hot catalyst (catalytic cracking) and mixing them with steam and heated to a very high temperature so that thermal decomposition reactions can occur (steam cracking).
• The first two alkenes are ethene and propene.
• The longer the molecules, the more viscous it is, making it harder to pour.
• If you had to add the other product to this reaction equation: C 6 H 14 → C 2 H 4 + ?, you simply calculate how many carbons and hydrogens are left over.
• Hydrocarbons can be cracked to produce smaller, more useful molecules, a process that involves heating the hydrocarbons to vaporise them.
• In cracking reactions, you must make sure there are the same number of carbons and hydrogens on each side of the equation, and remember you are going from a bigger molecule to usually 2 smaller molecules.
• Alkenes react with bromine water, turning it from orange to colourless, alkanes do not, because an alkene’s double bond makes them more reactive than alkanes.
• Shorter the molecules, the less viscous it is, making it more runny.
• The products of cracking include alkanes and unsaturated hydrocarbons called alkenes, which have the general formula C n H 2n and have at least one double carbon-carbon bond.
• Some of the products made from cracking are useful as fuels, since they have shorter chains than the alkanes you started with, making them more flammable so a better fuel.
• Hydrocarbons are burnt so that they can be used as fuel, since the reaction produces energy.
• Some properties of hydrocarbons depend on the size of their molecules, influencing their use as fuels.