chemistry 6.5 - crude oil

What is petroleum?

Crude oil - mixture of hydrocarbons, mainly alkanes

what are the steps of fractional distillation?

1. Crude oil vaporised at 350 degrees Celsius

2. The vapour goes into the fractional column and rises through the trays. They biggest hydrocarbons didn’t vaporise as the boiling points are too high

3. As the vapour rises it gets cooler and each fraction condenses at different points due to the different chain lengths so the fractions are drawn off at different levels of the column

4. The lowest boiling point hydrocarbons don’t condense

What fraction doesn’t condense, how many carbons do the container and what are their uses?

Gases

1-4 Cs

Liquified petroleum has (LPG), camping gas

What fraction condenses at 40 degrees Celsius, how many carbons do the container and what are their uses?

Petrol (gasoline)

5-12 Cs

Petrol

What fraction condenses at 110 degrees Celsius, how many carbons do the container and what are their uses?

Naphtha

7-14 Cs

Processed to make petrochemical

What fraction condenses at 180 degrees Celsius, how many carbons do the container and what are their uses?

Kerosine (paraffin)

11-15 Cs

Jet fuel, petrochemicals, central heating fuels

What fraction condenses at 250 degrees Celsius, how many carbons do the container and what are their uses?

Gas oil (diesel)

15-19 Cs

Diesel fuel, central heating fuel

What fraction condenses at 340 degrees Celsius, how many carbons do the container and what are their uses?

Mineral oil

20 - 30 Cs

Lubricating oil

What fraction never evaporated (is the residue), how many carbons do the container and what are their uses?

Fuel oil, wax/grease, bitumen

30-40 Cs, 40-50 Cs, 50+ Cs

Ships/power stations, candles/lubrication, roofing/road surfacing

What is cracking and what does it produce?

Breaks the C-C bond and makes an alkene and an alkane

What is thermal cracking?

When alkanes are cracked at 1000 degrees Celsius and 70 atm. It results in lots of alkenes

What is catalytic cracking?

When a zeolite catalyst (hydrated alluminosilicate) is used at a slight pressure and 45 degrees Celsius. It produces aromatic hydrocarbons (cyclic with delocalised pi electrons) and motor fuels. It saves money and time

What is knocking?

When alkanes explode of their own accord when fuel / air mixture is compressed in an engine. It is more likely to happen in straight chain hydrocarbons

How does the cyclic/branched chain hydrocarbons in petrol make its combustion more efficient?

Less chance of knocking

What is reforming?

Using a catalyst (e.g. Pt stuck on Al2O3) to make straight chain hydrocarbons into branched / cyclic hydrocarbons (e.g. hexane → cyclohexane + H2