C1.4- Crude oils and Fuels

Crude oil;

• a mixture of different chemical compunds
• used as fuel for cars, heating and electricity
• straight from ground = not much use
• distillation seperates it into fractions
• contains mainly alkanes (hydrocarbons)

Hydrocarbons = compunds composed of hydrogen and carbon

Alkane = saturated hydrocarbon

            = CnH2n+2

            = methane, ethane, propane, butane, pentane

saturated compund = as many atoms as possible in each molecule

short chain alkanes = more useful (burn more easily, less smoke - cleaner)

short - INCREASES flammablility

         - INCREASES volatility

         - DECREASES viscosity

         - DECREASES boiling point

fractional distillation; (continuous process)

1) crude oil is vaporised before going into the fractionating column

2) gas condenses as it reaches its boiling point

3) fractions collected as liquids at different levels

Lighter hydrocarbons are used as fuels and they combust (in sufficient oxygen) to produce energy.

fuel + oxygen ---> carbon dioxide + water

• the fuel has been completely oxidised
• this means that hydrogen and carbon have had oxygen added to them

All fuels (oil, coal, gas) combust to produce CO2 and H2O, however they sometimes contain impurities; such as sulphur. This is bad, as when it burns it is oxidised to create sulphur dioxide, which is posionous, and acidic. It can create acid rain and engine corrosion.

In a car engine more pollution occurs;

• Carbon monoixde (CO) in incomplete combustion. Posionous.
• Nitrogen oxides, in high temperatures, nitrogen in the air reacts with oxygen. Posionous and acid rain.
• Particulates, in diesel engines (with bigger molecules) they do not burn completely. Tiny solid particles in the air. Damage cells.

Products from fuel combustion can be bad for the environment and for our health.They spread out through the atmosphere.

carbon dioxide = main greenhouse gas

                        = causes climate change

carbon monoxide = red blood cell ***** it up, so affects the amount of oxygen we                                      can carry

particulates = causes global dimming

                   = reflects light back into space

                   = made from carbon (soot) and hydrocarbons

sulphur dioxide & = dissolves into droplets in the air and fall as acid rain

nitrogen oxides    = reacts in air with oxygen to form acids

                             = lowered pH (in rain) harms animals and plants

Solutions;

Catalytic converter = fitted to the cars

                               = very expensive (contain precious metal catalysts)

                               = carbon monoxide+nitrogen oxides---> CO2 + nitrogen

Filters = fitted to diesel cars

           = traps particulates

Sulphur can be removed before it is burnt, or it can be removed from the waste gases by adding calcium oxide to create calcium hydroxide (alkaline)

biofuel = a fuel made from the products of plants and animals

biodiesel = a biofuel made from plant oils

'+' (of biodiesel)

• breaks down faster (less harmul to plants and animals)
• burns more cleanly, less pollutants
• cheaper (as crude oils run out)
• carbon nuetral
• makes other products (glycerine for soap)

'-' (of biodiesel)

• uses land which could be used for food
• destroys habitats (endangers species)
• freezes faster than diesel in cold climates and gets sticky in hot climates

ethanol = another biofuel

             = made from sugar beet or sugar cane

             = can be added to petrol

             = carbon nuetral

             = uses food space

Hydrogen for the Future

• 2H2 + O2 ---> 2H2O
• no carbon dioxide produced
• extremely explosive in the air
• needs more space in cars than liquid (more storage)
• high pressure cylinders dangerous in crashes

• hydrocarbons
• mixture
• distillation
• fractions
• alkane
• saturated
• condensing
• vaporising
• combustion
• posionous
• acid rain
• global dimming
• gloabal warming (climate change?)
• biofuel
• biodiesel
• particulates
• catalytic converter
• calcium hydroxide