12.2 FRACTIONAL DISTILLATION OF CRUDE OIL Flashcards
What is crude oil at present the world’s main source?
main source of organic chemicals
Why is crude oil called a fossil fuel?
as it was formed millions of years ago by temperatures deep below the Earth’s surface
Why is crude oil non-renewable?
it forms very slowly
What is crude oil a mixture of?
mixture of mostly alkanes, both unbranched and branched
Do crude oil from different sources have different compositions?
yes
What does crude oil also contain?
small amounts of other compounds dissolved in it
Where does the small amount of other compounds dissolved in crude oil come from?
come from other elements in the original plants and animals the oil was formed from
Example of compound dissolved in crude oil?
sulphur
What does sulphur produce when burnt?
sulphur dioxide, SO2
What does sulphur dioxide cause?
acid rain
How does sulphur dioxide cause acid rain? (2)
sulphur dioxide reacts with oxygen high in the atmosphere to form sulphur trioxide
sulphur trioxide reacts with water in the atmosphere to form sulfuric acid
What must be done to convert crude oil into useful products?
have to separate the mixture
How is crude oil separated?
done by heating and collecting the fractions that boil over different ranges of temperatures
What is each fraction from crude oil? (hint- mixture of what)
mixture of hydrocarbons of similar chain length and so similar properties
What is the process of how crude oil is separated into its fractions called?
fractional distillation
Where is fractional distillation done?
in a fractionating tower
What is first done to crude oil before its fractionated?
heated in a furnace
What happens after the crude oil is heated in a furnace?
mixture of liquid and vapour passes into a tower that’s cooler at the top than at the bottom
What happens after the mixture of liquid and vapour passes into a tower?
vapour passes up the tower via a series of trays containing bubble caps until they arrive at a tray that’s sufficiently cool (lower temp than their boiling pt.). then they condense to liquid
What happens after the fractions have condensed on each tray?
they’re piped off
At which trays do shorter chain hydrocarbons condense?
trays closer to the top of the tower, where it’s cooler
Why do shorter chain hydrocarbons condense at trays closer to the top?
because they have lower boiling points
What is collected at the base of the tower?
thick residue
What is the thick residue collected at the base of the tower called?
tar or bitumen
What can tar/ bitumen be used for?
road surfacing
What happens to tar/ bitumen?
as supply often exceeds demands, this fraction often further processed to give more valuable products
