Carbon compounds as fuels and feedstock

What is crude oil?

A finite resource found in rocks; the remains of an ancient biomass consisting mainly of plankton that was buried in mud.

What are most of the compounds in crude oil?

Hdrocarbons, which are molecules made up of hydrogen and carbon atoms only.

What are most of the hydrocarbons in crude oil called?

Alkanes

What are alkanes?

• The simplest type of hydrocarbon.

• Saturated compounds - each carbon atom forms 4 single covalent bonds.

What are the first four members of the alkanes?

Methane, ethane, propane and butane.

What is the general formula for the homologous series of alkane?

CnH2n+2

What can the many hydrocarbons in crude oil may be separated into?

Fractions, each of which contains molecules with a similar number of carbon atoms, by fractional distillation.

What can the fractions be processed to produce?

Fuels and feedstock for the petrochemical industry.

What are some of the fuels on which we depend for our modern lifestyle?

Petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases; produced from crude oil.

What are many useful materials on which modern life depends are produced by?

The petrochemical industry, such as solvents, lubricants, polymers, detergents.

What does the vast array of natural and synthetic carbon compounds occur due to?

The ability of carbon atoms to form families of similar compounds.

How does fractional distillation?

1. The oil is heated is heated until most of it is turned into gas, the gases enter a fractionating column.

2. In the column, there is a natural gradient (hot at the bottom and gets cooler as you go up)

3. The longer hydrocarbons have high boiling points, they condense back into liquids and drain out of the column early on.

4. The shorter hydrocarbons have lower boiling points, they condense and drain out much later.

5. You end up eith the crude oil mixture seperated out into different fractions. Each fraction contains a mixture of hydrocarbons that al contain a similar number of carbon atoms, so have similar boiling points.

What properties influence how hydrocarbons are used as fuels?

The size of their molecules, including boiling point, viscosity and flammability.

What happens as the length of the carbon chain changes?

The properties of the hydrocarbon change.

How does the length of the carbon chain effect the properties of the hydrocarbon?

The shorter the chain:

• The more runny (less viscous) it is.

• The more flammable it is.

• The lower the boiling point.

What does the combustion of hydrocarbon fuels release?

Energy; during combustion, the carbon and hydrogen in the fuels are oxidised. The complete combustion of a hydrocarbon produces carbon dioxide and water.

What can hydrocarbons can be broken down (cracked) to produce?

Smaller, more useful molecules.

How can cracking be done?

By various methods including catalytic cracking and steam cracking.

What is catalytic cracking?

Catalytic cracking involves an aluminium oxide catalyst. The long chain hydrocarbon is turned into a gas, which then passes over a hot, powdered aluminium oxide catalyst at a temperature of about 550°C.

What is steam cracking?

Steam cracking simply involves heat and steam. In steam cracking, the long chain hydrocarbon is turned into a gas, then mixed with steam. At very high temperatures, over 850 °C, and under pressure, the long chain hydrocarbon will split into shorter chain hydrocarbons and lots of small alkenes.

What do the products of cracking include?

Alkanes and Alkenes.

What are alkenes?

more reactive than alkanes and react with bromine water, which is used as a test for alkenes.

• Another type of hydrocarbon.

• More reactive than alkanes and react with bromine water, which is used as a test for alkenes.

• Unsaturated - adouble carbon carbon bond.

What are alkenes used to produce?

Polymers and as starting materials for the production of many other chemicals.