Crude oils and fuels Crude oil and fuels Click to continue

Overview — crude oil Crude oil is derived from an ancient biomass found in rocks. Many useful materials can be produced from crude oil. Crude oil can be fractionally distilled. Some of the fractions can be used as fuels. What useful materials can be made from crude oil? Click to continue

Overview — biofuels Biofuels are produced from plant material. There are advantages and disadvantages to their use as fuels. Fuels can come from renewable or non-renewable resources. What are the advantages and disadvantages of biofuels? Click to continue

Crude oil Crude oil is a mixture of a large number of compounds. A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged. It is possible to separate the substances in a mixture by physical methods, including distillation. Why does crude oil have so many different compounds in it? Click to continue

Hydrocarbons 1 Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only (hydrocarbons). Most of these are saturated hydrocarbons called alkanes, which have the general formula CnH2n+2. What would a model of ethane (two carbons) look like? A molecular model of methane and its structural formula Click to continue

Hydrocarbons 2 The many hydrocarbons in crude oil may be separated into fractions by evaporating the oil and allowing it to condense at a number of different temperatures. Each fraction contains molecules with a similar number of carbon atoms. This process is called fractional distillation. Click to continue

Fractional distillation Explain how the fractionating column works. Click to continue

Properties 1 Some properties of hydrocarbons depend on the size of their molecules. Look at the table below and on the next slide. What patterns do you notice? Fraction Carbon atoms in the molecule Description Boiling point (C) Flammability Uses Petroleum gas 1–4 Colourless gas Less than 40 Explodes if mixed with air and lit Used as a fuel in the refinery Bottled and sold as LPG Naphtha 5–10 Yellowish liquid, flows easily 25–175 Evaporates easily, vapour mixed with air is explosive Petrol Used for making other chemicals Kerosene 10–14 Yellowish liquid, flows like water 150–260 Burns when heated Aircraft fuel Click to continue

Properties 2 Fraction Carbon atoms in molecule Description Boiling point (C) Flammability Uses Light gas oil 14–20 Yellow liquid, thicker than water 235–360 Only burns when soaked onto a wick or other material Diesel fuel Heavy gas oil 20–50 Yellow brown liquid 330–380 Only burns when soaked onto a wick — very smoky Used in the catalytic cracker Lubricants (car engine oils) 50–60 Thick brown syrup-like liquid 340–575 Only burns when hot and soaked onto a wick Grease for lubrication Catalytic cracker Fuel oil 60–80 Thick brown sticky liquid Above 490 Fuel oil for power stations and ships Bitumen More than 80 Black semi-solid Above 580 Only burns if very hot Road and roof surfaces Click to continue

Hydrocarbon fuels 1 Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur. The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide, sulfur dioxide and oxides of nitrogen. Solid particles (particulates) may also be released. What problems do carbon dioxide, sulfur dioxide and particulates cause? (Answers on the next slide.) Click to continue

Hydrocarbon fuels 2 The combustion of hydrocarbon fuels releases heat. During combustion, the carbon and hydrogen in the fuels are oxidised. Sulfur dioxide causes acid rain. Carbon dioxide causes global warming. Solid particles cause global dimming. How can these effects be reduced? (Answers on the next slide.) Click to continue

Hydrocarbon fuels 3 Sulfur can be removed from fuels before they are burned, for example in vehicles. Sulfur dioxide can be removed from the waste gases after combustion, for example in power stations using scrubbers. Catalytic converters in the exhausts of vehicles reduce the release of nitrogen oxides. Click to continue

Biofuels Biofuels, including biodiesel and ethanol, are produced from plant material, e.g palm oil. There are economic, ethical and environmental issues surrounding their use. What are the issues with biofuels? Shariff Che’Lah/Fotolia Click to continue