Analysis Of Petrol-Ethanol Mixtures

Methyl tertiary butyl ether18 (MTBE), (CH3)3COCH3

E. EXPERIMENTAL WORK

The following table shows the range of petrol-ethanol mixtures used in this experiment.

Table 1: Petrol 98 and Ethanol fuel mixtures

Sample Fuel Name % composition of Petrol and Ethanol in the mixture

1 E0 100% petrol

2 E5 95% petrol and 5% ethanol

3 E10 90% petrol and 10% ethanol

4 E15 85% petrol and 15% ethanol

5 E20 80% petrol and 20% ethanol

6 E70 30% petrol and 70% ethanol

7 E75 25% petrol and 75% ethanol

8 E80 20% petrol and 80% ethanol

9 E85 15% petrol and 85% ethanol

Apparatus: Calorimeter19

It is important to have the same distance between the spirit burner and the calorimeter containing water, in order to minimize the random errors. For all experiments,

It was calculated by weighing the spirit burner before and after the experiment, using a balance. These mass losses will be used to calculate the Energy of Combustion per gram later in the calculations.

In the next step the energy of combustion of each mixture was calculated. This was done using the formula of energy of combustion

Energy of Combustion

Table 4: Theoretical value for enthalpy of combustion of pure petrol and pure ethanol20

Theoretical value for enthalpy of combustion of pure: (kJ/g)

Petrol 47.0

Ethanol 29.7

The total enthalpy change for a petrol-ethanol fuel mixture was calculated by multiplying the percentage of ethanol in a sample by the enthalpy of combustion of pure ethanol and adding that value to the value obtained by multiplying the percentage of petrol by the enthalpy of combustion of pure petrol.

For example the enthalpy of combustion of the E0 and E5 mixtures with pure petrol in it was found by:

E0 = ((100 % x 47 kJ/g) + (0 % x 29.7kJ/g)) ÷ 100 = 47.0kJ

E5 = ((95 % x 47 kJ/g) + (5 % x 29.7kJ/g)) ÷ 100 = 46.1kJ

Using these values, the total theoretical energy produced by each mixture could be

To this end, perhaps developing an internal combustion engine that is based more on ethanol combustion than on the current petrol combustion model, would overcome the energy and time inefficiencies encountered in burning high ethanol content fuels in this work.

Since bio ethanol is heavier than petrol, the petrol tends to rest on top and the ethanol sinks to the bottom of the spirit burner. Continuous stirring or agitation of the contents of the spirit burner would have perhaps lowered the inefficiencies discovered in this study, and this may also be a factor for consideration in developing a more ethanol-friendly internal combustion engine.

Since the octane rating increases as the ethanol content in petrol increases, this is another consideration that helps offset the fact that its higher content in petrol lowers the energy efficiency of the fuel, since ethanol doesn’t have the toxic impact on the environment that the current octane rating boosting additive, methyl tertiary butyl ether, (MTBE)