It is estimated that a Explain the process by which gasoline is obtained from cr

Question

It is estimated that a Explain the process by which gasoline is obtained from crude oil. b Octane numbers are often stated on petrol pumps in petrol stations 2 there are over 1 billion cars in the world and the majority of these use petrol/gasoline as fuel. [41 i State what is meant by the octane number of a fuel. i Explain how cracking can be used to improve the octane number of fuels. 131 c Transport contributes a great deal to an individual's carbon footprint. i Use the data below to calculate the carbon footprint per person for an aeroplane journey from 131 London to New York. distance from London to New York fuel consumption of aircraft number of passengers +crew carbon dioxide produced per dm3 of fuel consumed 5570km 14.0dm3km- 500 2.00kg ii The Ferrari 458 Italia has a fuel consumption of approximately 13.0dm per 100km. Calculate the carbon footprint per person for two people travelling 5570 km in a Ferrari 458. Assume that the fuel has the same molecular formula as octane (C8H18) and a density of 0.700 gcm. [5

Explanation / Answer

2.a)Gasoline is separated from Crude Oil by using Fractional Distillation Process.

Fractional Distillation occurs in a tower known as Fractional Distillation Tower.A fractional distillation tower is a huge unit that may hold up to 200,000 barrels of crude oil. The oil is first pumped into a furnace and heated to over 600°F (316°C), causing all but the largest molecules to evaporate. The vapors rise into the fractionating column, which may be as tall as 150 feet (46 m). The vapors cool as they rise through the column. Since the boiling points of all the fractions differ, the larger, heavier molecules will condense first lower in the tower and the shorter, lighter molecules will condense higher in the tower. Natural gases, gasoline, and kerosene are released near the top. Heavier compounds used in the manufacture of plastics and lubricants are removed lower in the tower.

Fractional distillation itself does not produce gasoline from crude oil, it just removes the gasoline from other compounds in crude oil. Further refining processes will be used to improve the quality of the fuel.

Refining of Gasoline

Catalytic cracking is used to refine gasoline. This process uses a catalyst, high temperature, and increased pressure to affect chemical changes in petroleum. Catalysts such as aluminum, platinum, processed clay, and acids are added to petroleum to break down larger molecules so that it will possess the desired compounds of gasoline.

After refining of gasoline, chemicals are added to reduce knocking and prevent the formation of gum in the engine.

2.b)i)The octane number of a gasoline is a measure of knocking tendency of a fuel. Octane number is determined by comparing the performance of a model fuel and the gasoline under test in a standard engine in a laboratory. The model fuel is prepared by mixing iso-octane (2,2,4 trimethyl pentane) whose octane number is assumed to be 100 and n-heptane, whose octane number is assumed to be zero. So, the octane number of a gasoline sample is defined as the percent by volume of iso-octane in a model fuel (a mixture of iso-octane and n-heptane) whose knocking performance matches with the test gasoline. Hence, a gasoline with octane number 90 means, its knocking tendency matches with a model fuel having 90 vol% isooctane.

2.b)ii.)Cracking is a secondary process in the refinery where a change in the composition of the petroleum fractions is done by the action of heat alone (thermal cracking) or heat in presence of a catalyst (catalytic cracking). Cracking is the decomposition of the C-C bond of hydrocarbon molecules.

In cracking the long straight chain Hydrocarbons are converted to branched-chain hydrocarbons which have higher octane number than the initial feedstock of straight chain hydrocarbons by reactions like isomerization, cyclisation, polymerization etc.

So, in the way described above Cracking is used to improve Octane number of fuels.

2.c.i)Carbon footprint per person is the amount of Carbon dioxide released into the atmosphere by a person.

Total Fuel Consumed during the flight from London to New York= 5570 x 14= 77980 dm3

Total Carbon dioxide produced= 77980 x 2=155960 kg

Carbon footprint per person= 155960/500=311.92 kg per person

2.c.ii)Carbon footprint per person is the amount of Carbon dioxide released into the atmosphere by a person.

Fuel Consumption of Ferrari 458= 5570 x13 /100=724.1 dm3

Mass of fuel consumed= 724.1 x 700=506870g

Molecular weight of octane=(12x8+18x1)=114

Moles of Octane released=506870/114=4446.22 moles

Reaction of combustion of fuel(C8H18):

C8H18 + 12.5 O2 ---> 8CO2 + 9H2O

so 1 mole of octane produces 8 moles of CO2

4446.22 moles of octane produces=4446.22x8=35569.76 moles of CO2 produced

Mass of CO2 produced in kg = 35569.76x44/1000=1565.069 kg

Carbon footprint per person= 1565.069/2= 782.5345 kg of CO2 per person

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