Alkanes
- Created by: maira842
- Created on: 27-02-22 13:37
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- ALKANES
- General formula- Cn H2n+2
- Saturated hydrocarbons.
- Cycloalkanes- Cn H2n. still saturated
- Fractional Distillation.
- Uses Petroleum (crude oil)
- Mixture of hydrocarbons- mostly made up of alkanes. Short and long chains.
- How its done- crude oil is vaporized at 350°C.
- vaporized crude oil goes into fractionating column and rises up through trays.
- Largest hydrocarbons don't vaporise at all as there boiling points are too high, produces gooey residue and runs at the bottom.
- As crude oil travels up fractionating column, it gets cooler. Each fraction condenses at different temperatures, shorter chain lengths towards the top.
- Hydrocarbons with lowest boiling points don't condense. there draw on as gases at the top of the column.
- As crude oil travels up fractionating column, it gets cooler. Each fraction condenses at different temperatures, shorter chain lengths towards the top.
- Largest hydrocarbons don't vaporise at all as there boiling points are too high, produces gooey residue and runs at the bottom.
- vaporized crude oil goes into fractionating column and rises up through trays.
- Uses Petroleum (crude oil)
- CRACKING
- Light fractions of crude oil is in high demand. Such as naphtha. Bitumen is not in high in demand. To meet this demand heavier fraction are cracked.
- Long hydrocarbon chains broken into smaller chains. involves breaking C-C
- Thermal Cracking
- Takes place at high temps up to 1000°C
- Takes place at high pressure up to 70atm.
- Produces a high percentage of alkenes.
- Alkenes are used to make valuable products such as polymers- plastics. Eg polyethene.
- Catalytic Cracking
- Takes place at lower temp. 450°C
- Takes place at slight pressure.
- Uses a zeolite catalyst. they have a honeycomb structure giving in a large SA.
- This form of cracking produces aromatic hydrocarbons and motor fuels,
- products are mostly branched alkanes, cycloalkanes, and aromatic compounds.
- Catalysts cut costs as the reaction can be done at low temp and pressure. it also speeds up reaction.
- combustion of ALKANES.
- Complete combustion
- alkanes burnt completely in oxygen producing water and carbon dioxide
- Alkanes are used as fuels.
- Incomplete combustion
- happens when there isn't enough oxygen. soot produced
- 2 different types of products are produced;
- CO and H2O
- C and H2O
- CO, H2O AND CO2
- CO is a poisonous gas. binds to heamoglobin as oxygen molecules stopping from oxygen to go around body.
- CATALYTIC CONVERTER
- The internal combustion engine produces pollutants such as NOx, CO and unburned hydrocarbons.
- the gaseous pollutants of internal combustion engines can be removed using catalytic converters.
- honey comb structure made of ceramic material coated with platinum and rhodium metals-catalysts.
- less harmful products produced as polluting gases pass over catalyst- these are CO2 H2O
- Flue gas desulfurisation.
- electricity is generate from power stations using fuels such as coal and natural gases. one of the products is SO2 which reacts with oxygen and water in the atmosphere producing acid rain.
- such gases are called flue gases.
- method- a slurry of calcium oxide and water is sprayed into the flue gas which reacts with and water to form calcium sulfite, which can further oxidised to calcium sulfate, also called gypsum. Alternative process uses calcium CARBONATE
- electricity is generate from power stations using fuels such as coal and natural gases. one of the products is SO2 which reacts with oxygen and water in the atmosphere producing acid rain.
- Complete combustion
- Chlorination of ALKANES
- free radical substitution,
- INITIATION.
- Breaking Cl bond using UV light, one quantum of UV light is greater than Cl-Cl bond energy .
- Propagation
- 2 steps
- Termination.
- removal of free radicals. 3 ways
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