crude oil, hydrocarbons and alkanes

what’s a hydrocarbon

compounds that contain only hydrogen and carbon atoms only

whats crude oil

• finite resource found in earths crust

• remains of organisms , mainly plankton which was buried in mud

• complex mixture of hydrocarbons

what is crude oil an important source of?

• fuels such as petrol, diesel, kerosene, heavy fuel oil and liquefied petroleum gases

• feedstock for the petrochemical industry

what is feedstock

raw material used to provide reactants for an industrial reaction.

what is a petrochemical

a substance made from crude oil using chemical reactions

e.g ethene is made from crude oil and is used as feedstock to make poly(ehene), a polymer

what are other useful solvents made from compounds found in crude oil

• solvents

• lubricants

• detergents

what is fractional distillation used for

separate crude oil into simpler, more useful mixtures.

Methods can vary because different hydrocarbons have different boiling points

what happens during fractional distillation of crude oil

heated crude oil enters a tall fractionating column, which is hot at the bottom and gets colder towards the top- longer chains are at the bottom whilst shorter hydrocarbon chains are at the top

vapours from the oil rise through the column

vapours condense when they become cold enough

liquids are leg out of the column at different heights

what forces do small hydrocarbons have

weak, intermolecular forces, so have low boiling points. They do not condense, but leave the column as gases.

what forces do

what forces do long hydrocarbons have

stronger intermolecular forces, so have high boiling points. They leave the column as hot liwuid bitumen

what are the different useful mixtures called?

fractions

• because they are only apart of the original crude oil

what are properties of fractions

the hydrocarbons in a fraction are mostly hydrocarbons called alkanes. Tney have similar:

• number of hydrogen and carbon atoms in their molecules

• boiling points

• ease of ignition

• viscosity

what is cracking

a reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated

• the original starting hydrocarbons are alkanes

• the product of cracking include alkanes and alkenes, members of a different homologous series

what is catalytic cracking

-uses a temp of approximately 550 C and a catalyst known as zeolite which contains aluminium oxide and silicon oxide

what is steam cracking

uses a higher temp of over 800 C and no catalyst

why is cracking important

1. helps match the supply of fractions with the demand for them

2. it produces alkenes which are useful to feedstock for the petrochemical industry

suply and demand

supply= how much of a fraction an oil refinery produces

demand= how much of a fraction a customer wants to by

Fractional distillation of crude oil produces more of the larger hydrocarbons than customers want

smaller hydrocarbons are useful as fuels than larger hydrocarbons. Since cracking converts larger hydrocarbons into smaller hydrocarbons, the supply is improved. This helps match with supply of demand