Lamia Dahmash and Shinhoo Lee

The Oil Industry

C.2.1 Compare the use of Oil as an energy source and as a chemical Feedstock.

Crude oil (or petroleum) was formed over the course of millions of years from the decay of marine organisms.

Crude oil is a mixture of different hydrocarbons and they can be separated or refined, and most of the crude oil is used for sources of energy such as petrol, other fuels for transport (diesel), and oil heating systems..

Only 10% of crude oil is used as chemical feedstock.Chemical feedstock is used to manufacture products

such as polymers, drugs, cosmetics, paints, fertilizers, pesticides, detergents and dyes.

Importance of Oil as a Chemical Feedstock

C.2.2 Compare catalytic cracking, thermal cracking and steam cracking.

Cracking is the process conducted at high temperatures whereby large hydrocarbons are broken down into smaller, more useful molecules. The products are usually alkanes and alkenes. For example, decane can be broken down from octane to ethene.

C10+ H22 (g) C8H18(g) + C2H4 (g)

The alkanes are usually branched isomers (eg.2,2,4 trimethyl pentane) and are added to gasoline (petrol) to improve the octane rating. The alkanes are used to make other chemicals, particularly addition polymers.

Cracking

The use of a Silica/ alumina Catalyst enables the cracking to take place at relatively low temperature of between 500- 800°C. Products are branched alkanes and alkenes. An example is high grade gasoline, since branched alkanes increase the fuel octane rating

Catalytic Cracking

The feedstock preheated, vaporized, and mixed with steam and then converted to low molecular mass alkenes at 800-900°C. These are used in manufacturing of polymers (i.e. polyethene)

Steam Cracking

Temperatures range from 500-750°C, and a high pressure of 70 atm is required. This process creates branched alkanes and alkenes, but smaller hydrocarbons than those produced by catalytic cracking. Used for kerosene, jet fuel.

Thermal Cracking

The number of Carbon atoms, boiling ranges, and the uses of different fractions summarized in the table:

Composition and Characterisitcs of Crude Oil Fractions

Fraction Carbon Chain Length

Boiling Range / °C Main Uses

Refinery Gas 1-4 <30 Used as fuel on site, gaseous cooking fuel, and as feedstock for chemicals, e.g.. Methane is used to provide hydrogen gas for the Haber process.

Gasoline 5-10 40-180 Gasoline (petrol) for cars. Feedstock for organic chemicals (by steam cracking).

Kerosine 11-12 160-250 Fuel for jet engines. Domestic heating cracked to provide extra gasoline (petrol).

Gas oil (Diesel oil) 13-25 220-350 Diesel engines and industrial heating; cracked to produce extra gasoline (petrol).

Residue > 20 >350 Fuel for large furnaces; vacuum distilled to make lubricating oils and waxes. Residue of Bitumen and asphalt used to surface roads and waterproof roofs.

Environmental Impact of the Process and the Products.

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LamiaShinhoo