Crude oil and Hydrocarbons.

The octane rating refers to fuels with high octane levels are high performance fuel and it is represented by stars.

Fossil fuels provide over 90% of the energy consumed in most developed countries, encouraging great demand for smaller alkane chains, which satisfy the majotiry of the properties associated with an ideal fuel. All fuels follow the same basic equation, which creates energy.

Fuel + Oxygen (or other oxidiser) Oxidation products + Energy

They oxidise fairly easily, ignite quickly and sustain without further intervention, most of these properties derive form the small hydrocarbon volatile nature as gases react more readily with oxygen. Fuel must also be easily transported and stored and as clean as possible, not creating polluting or harmful substances that are hard to dispose of, however, this is where hydrocarbons fall down in that it produces extensive carbon dioxide which at one time was considered pretty harmless until it was created in such an excess it began to affect the global climate. Hydrocarbons can also create carbon monoxide if it does not react in it's entirety normally due to a limited supply of oxygen.

C(s) + O2(g) CO2

C(s) + O2 (g) CO

Nitrogen and sulphur oxides can also be created due to the impurities of oil, which can fall as acid rain.

Hydrocarbons can be manipulated in various ways to make them more valuable, either by cracking, reforming or isomerisation.

Cracking breaks molecules down into smaller carbon chains. This is a starting point for the manufacture of many organics, including polymers and petrol.

There are two types of cracking thermal and catalytic cracking. Thermal cracking heats the naphtha fraction, with steam at high temperature of around 800 OC and high pressure. This process creates a mixture of straight chain alkanes and alkenes, mostly ethane, creating minor proportions of branched and cyclic structures and H2 gas.

Thermal cracking breaks C-C bonds by homolytic fission, forming free radicals.

C10 H22 C8H18 + C2H4

C10 H22 C6H14 + 2C2H4

Alkane Alkane + Alkene

Catalytic cracking processes heavy long chain fractions obtained in larger quantities than required. A mixture of vaporised fraction and a zeolite catalyst are reacted using slight pressure at 450 oC. Used in petrol this process forms higher amounts of branched and cyclic hydrocarbons.

Reforming is a process by which unbranched fractions are converted into cycloalkanes and arenas; uses include pharmaceuticals and drugs. Increased demands for branched alkanes followed the removal of lead petrol form the UK market to aid effective combustion of petroleum.

The struggle to find an effective and viable substitute to fossil fuels has become an increasing necessary as the oil reserves deplete. Various suggestions include biofuels, solar power, hydrogen and the more controversial nuclear power.

Biofuel is renewable and energy can be gained from burning plants directly or converting into other forms. Ethanol can be brewed from sugar can and act as an alternative or to dilute petrol. It had recently become popular to use natural oils within diesel fuels and the only waste product being the carbon dioxide being utilized for plant growth. The only unfortunate disadvantage is this method alone would not substitute all the energy we take from oil and it uses a lot of land.

Solar power is utilized by exposing solar panels to the suns rays to heat water in the pipes beneath. The disadvantage is that it will only work where the sun is plentiful for most of the year for them to be worth installing due to initial cost. Photovoltaic cells create electricity from the suns energy. Scientists have considered the placement of such devices in space via satellite, which would microwave the energy back to earth.

Nuclear power, which is probably the major contender for taking over oil, creates energy by nuclear fission, which is released when the nuclei of atoms of uranium U- 235 undergoes splitting in a chain reaction. This immense power is used to drive water and turbines to generate electricity. There is no carbon or carbon related pollutants but the storage and treatment of radioactive waste is difficult and costly disasters are possible despite contentious safety controls.

Personally I feel that the government or the general will only take action public when they are forced to by the oil reserves running out. To have a dramatic effect on the environment we must all make a conscious effort to reduce our energy wastage, but as the U.S have proved with their refusal to cut emissions along with Europe, some people refuse to comply. Recycling oil product will also preserve the oil reserves for a bit longer, although ultimately we must find other energy sources. I fear that it will be

Chemistry 1

inevitable that this will contain nuclear power, despite its drawbacks. But still nuclear power is non renewable and surely the only way forward is to develop clean renewable fuel.

Bibliography

www.news.bbc.co.uk

Energy review urges greener focus

Chemistry 1

pages 100,106 and 107,108

Letts Revise As chemistry

page 118 and 119

G.C.S.E Double Science Chemistry revision guide

page 18

http://www.schoolscience.co.uk/content/4/chem

Crude oil