Engineering Chemistry S Datta

410 ENGINEERING CHEMISTRY
Q. 17. What is oil gas?
Ans. Oil gas is mainly obtained by cracking of kerosene oil. But other oils like diesel and
heavy oils and petrol may also be used for cracking. A device is set up where a plate is heated
specially electrically and the oil is allowed to drop on the hot plate. The oil is cracked to lower
gaseous hydrocarbons.
C 12
H 26
⎯⎯→ CH 4
+ C 2
H 6
+ C 2
H 4
+ C 2
H 2
+ etc. + tar
The resulting gases are passed generally through a hydraulic main and collected in a
gas holder by displacement of water.
The composition of oil gas is
CH 4
= 25-30%, H 2
= 50-55%, CO = 10-12%, CO 2
= 3%,
Calorific value = 54000 kcal/m 3 .
The gas is mainly generated for laboratory use.
Q. 18. What are the advantages of a gaseous fuel?
Ans.
• Can be distributed over a wide area by pipeline.
• Smooth combustion without smoke and ash.
• The temperature of heating can be controlled by controlling the gas flow to the burner.
• Higher calorific values.
Q. 19. Mention the disadvantages of a gaseous fuel.
Ans.
• Danger of explosion
• Larger scale fire risk.
Q. 20. What is an anti-knocking agent?
Ans. The organometallic compounds like TEL or TML, which increase octane number of
a fuel.
Q. 21. What is an aviation gasoline?
Ans. The variety of gasoline specially suitable for aircraft having octane number well
over 100.
Q. 22. Why is sulphur content controlled below 0.1%?
Ans. Sulphur and sulphur compounds greatly reduce effectiveness of TEL to increase
the octane number of a fuel.
Q. 23. What is a natural gasoline?
Ans. A mixture of butane, pentane, and hexane obtained from natural gas.
Q. 24. What is HDA process?
Ans. Gasoline produced, for the manufacture of ethene, as a byproduct is known as
pyrolysis gasoline. This gasoline is mainly used to produce benzene by Hydro-DeAlkylation
(HDA) process.
700 K
CH 3
(CH 2
) 8
CH 3 ⎯⎯→
HDA
C 8
H 18 ⎯⎯→
C 8
H 18
+ CH 2
= CH 2
octane ethene
C 6
H 6