Crude oil

• Crude oil 


  Dark , smelly liquid

  Finite resource found in rocks

  Remains of an ancient biomass consisting mainly of plankton that was buried in mud

  Made from bodies of plants and animals that have decayed over millions of year

  In some places rock traps oil so it can’t escape. Oil wells are drilled through the rock and oil is pumped up to the surface.
• Crude oil


  Mixture of compounds that can be separated. When dead matter decays it is turned by bacteria in the absence of oxygen into crude oil. As the mud layers build up high temperature and pressure was created. This converted the material slowly into gas and oil. Earth movements caused the rock to split and the oil and gas was trapped beneath the layers of non porous rocks. Gas and oil move upwards through porous rocks. Oil wells can be found under the North Sea.
• Hydrocarbons


  Nearly all the substances found in crude oil are hydrocarbons

  A hydrocarbon contains only carbon and hydrogen

  Most hydrocarbons is crude oil are alkanes
• Alkanes


  Contain only one carbon and hydrogen, bonded together by single bonds

  Alkane are saturated which means that all the atoms are held together by single bonds

  Formula - C(n)H(2n+2)

  First 4 alkanes - methane, ethane, propane and butane
• Alkanes


  Diagram

  
• Alkanes


  Diagram

  
• What is combustion

  3 things are needed for a combustion reaction: fuel, oxygen and heat

  Combustion is an oxidation reaction - loses electrons

  During a combustion reaction, the atoms of carbon and oxygen are rearranged

  When a hydrocarbon burns in the presence of lots of oxygen, the only products are carbon dioxide and water
• Combustion of methane

  The reaction for a complete combustion of methane is:

  Methane + oxygen - carbon dioxide + water + energy

  CH4 + 2O2 - CO2 + 2H2O + energy
• Incomplete combustion


  Occurs when there isn't enough oxygen - causes the formation of carbon monoxide or the carbon doesn't burn (soot)

  Methane + oxygen - carbon monoxide + water

  2CH4 + 302 - 2CO + 4H20
• Issues of incomplete combustion

  CO2 causes global warming - greenhouse gases

  Carbon monoxide stops red blood cells carrying oxygen

  Carbon monoxide is toxic - can lead to death

  Soot causes global dimming

  Acid rain

  Carbon (soot) can cause breathing difficulties
• Properties of hydrocarbons


  Crude oil, when first obtained from earth - mixture of hydrocarbons: length of hydrocarbon chain affects properties of substance

  More carbon in hydrocarbons - higher boiling point

  Hydrocarbons with small molecules make better fuels than hydrocarbons with large molecules

  As you go up the fractioning columns i fractional distillation:

  Lower boiling points (liquid to gas)

  Lower viscosity (flows easier)

  Higher flammability (ignites more easily)
• Fractional Distillation


  The hydrocarbons in crude oil are split into fractions, each having molecules with similar number of carbon atoms. The fractions are processed to produce fuels and feedstock for the petrochemical industry. Many fuels for our modern lifestyle like petrol, diesel, kerosene, heavy fuel and liquefied petroleum gases, are produced from crude oil. Many useful materials for modern life are made by petrochemical industry like solvents, lubricants, polymers, detergents. The range of natural + synthetic carbon compounds occur as carbon atoms form families of similar compounds
• Fractional distillation


  Distillation is the process of heating a liquid to form vapours and condensing those vapours to form a liquid - relies on the fact that components of the mixture have sufficient difference in their boiling points. As the number of carbon atoms increase, the molecules become larger and have higher boiling points. They also become darker in colour, more viscous (flows easier), less flammable and less volatile (doesn't evaporate as easily)
• Process of fractional distillation

  1 - Crude oil is extracted from oil fields underground

  2 - Crude oil is heated in a fractioning tower

  3 - The liquid evaporates and the vapours condense at different temperatures

  4 - The light fraction, which are usually liquids, have lower boiling points and come out first at the top of the tower

  5 - The fraction with the highest boiling point comes at the bottom of the tower

  6 - This produces a range of useful fuels and oils
• Fractioning tower


  Diagram

  
• Fractioning Distillation


  At top of the fractioning column:

  Small molecules

  Low boiling point

  Very volatile

  Flows easily

  Lights easily

  At bottom of fractioning column:

  Large molecules

  High boiling point

  Not very volatile

  Doesn't flow easily

  Doesn't ignite easily
• Atmospheric pollutants from fuel


  The combustion of fuels is a major source of atmospheric pollutants. Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur.

  The gases released into the atmosphere when a fuel is burned may include carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen.

  Solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere
• Properties and effects of atmospheric pollutants

  Carbon monoxide is a toxic gas.

  It is colourless and odourless and so is not easily detected.

  Sulfur dioxide and oxides of nitrogen cause respiratory problems in humans and cause acid rain.

  Particulates cause global dimming and health problems for humans.