Petroleum Products and Refining Questions and Answers

Answer: C

Both are true and the reason gives the inversion: a diesel engine relies on the fuel igniting readily under compression, which is exactly what a high octane fuel is formulated to resist. The two scales measure opposite tendencies.

Answer: D

Correct answer: hydrotreating of the kerosene cut

Hydrotreating removes sulphur and nitrogen; it does not raise octane, and kerosene is not a gasoline component in any case. The other three are the refinery’s three octane units, and they attack the problem from different directions - aromatics from reforming, branched alkylate from light olefins, and branched isomers from light paraffins.

Answer: A

Correct answer: isobutane with light olefins

Alkylation reacts isobutane with propylene or butylenes over a strong acid catalyst to give a branched paraffin of high octane and low volatility. Its value is that it converts two low-value light streams into a premium gasoline blendstock with no aromatics and no olefins - which is exactly what tightening fuel specifications have made scarce.

Answer: B

Correct answer: True

Hydrotreating passes the feed with hydrogen over a catalyst so that sulphur leaves as hydrogen sulphide and nitrogen as ammonia. It also saturates olefins and improves stability and colour, but sulphur removal is the driver: fuel specifications now demand ten parts per million or less, and downstream catalysts are poisoned by sulphur, so nearly every stream in a modern refinery is hydrotreated.

Answer: C

Correct answer: elemental sulphur in a Claus plant

The Claus process burns a third of the hydrogen sulphide to sulphur dioxide and reacts that with the remainder over a catalyst to give elemental sulphur and water. It recovers well over 95 per cent, rising above 99 with a tail gas unit, and it turns an environmental liability into a saleable product - refineries are among the world’s largest sulphur producers as a result.

Answer: D

Correct answer: atmospheric distillation of the crude

Distillation separates what is already there; it converts nothing. The other three all change the molecules - catalytic cracking and hydrocracking break large ones into smaller, and delayed coking rejects carbon from the residue to yield lighter products and petroleum coke. That distinction, separation against conversion, is the basic division of a refinery’s units.

Answer: A

The first two are correct and are why hydrocrackers are built where diesel is wanted. The third is quite wrong, since hydrocracking is a large net consumer of hydrogen. Its hydrogen demand is the main cost of the unit.

Answer: B

It is the refinery's way of dealing with the bottom of the barrel, converting material that nothing else will take. The coke is sold as fuel or, if the feed is clean enough, for anodes. It is the last resort for the heaviest material.

Answer: C

Correct answer: 40 per cent

\[ 100 - (20+15+25) = 100 - 60 = 40\%. \] A residue of this size is why conversion units exist: two fifths of the barrel is worth less than the crude it came from unless it is cracked, hydrocracked or coked into lighter products, and refinery economics turn largely on how much of that residue can be upgraded.

Answer: D

Both are true and the reason gives the driver: light products are what the market wants, so the more residue a crude gives the more must be converted and the more the refinery costs to build. Coking and hydrocracking are the usual answers.