The first processing step for crude oil in a refinery is
Answer: A
The crude is separated into fractions before anything is done to any of them, since each fraction needs different treatment. Everything downstream operates on one cut rather than on the whole crude. The tower separates by boiling range alone.
Please log in or register to report this question.
Arrange the following crude fractions in order of increasing boiling range.
1. kerosene and diesel
2. light gases and LPG
3. atmospheric residue
4. naphtha and gasoline
Answer: B
Correct answer: 2 - 4 - 1 - 3
Boiling range rises with molecular size, so the order follows the carbon number: light gases and LPG boil below ambient, naphtha and gasoline to about 200 degrees, kerosene and diesel from there to around 350, and the atmospheric residue is whatever will not distil below that. The column separates them in exactly this order, lightest at the top.
Please log in or register to report this question.
Vacuum distillation is applied to the atmospheric residue in order to
Answer: C
Correct answer: separate further fractions without cracking
Above about 350 degrees the heavier molecules begin to crack thermally, so the atmospheric column cannot be pushed further. Reducing the pressure lowers the boiling points, allowing vacuum gas oil to be taken overhead at a temperature the molecules survive. It is a physical separation throughout - nothing is converted, and the sulphur and octane options describe other units entirely.
Please log in or register to report this question.
Assertion (A): The heavy residue is distilled under vacuum rather than at atmospheric pressure.
Reason (R): At the temperature needed to boil it at atmospheric pressure the oil would crack thermally.
Answer: D
Both are true and the reason gives the constraint: reducing the pressure lowers the boiling point enough that the separation can be made without decomposing the material being separated. Vacuum residue is the bottom product of that tower.
Please log in or register to report this question.
Match each conversion process with what it does.
List I
A. Catalytic cracking
B. Catalytic reforming
C. Alkylation
D. Isomerisation
List II
1. combines light olefins into branched gasoline
2. breaks heavy gas oil into lighter products
3. rearranges straight chains into branched ones
4. converts naphtha into high octane aromatics
Answer: A
Correct answer: A-2, B-4, C-1, D-3
Four conversion processes doing four different things. Catalytic cracking breaks heavy gas oil into lighter products. Reforming rearranges naphtha into high octane aromatics. Alkylation combines light olefins with isobutane into branched gasoline. And isomerisation converts straight chain paraffins into branched ones. The last three all raise octane; only the first is about size reduction.
Please log in or register to report this question.
Fluid catalytic cracking uses a catalyst that is
Answer: B
The powder behaves as a fluid, which allows continuous circulation between reactor and regenerator. Platinum on alumina belongs to reforming and the other two to quite different industries. The fine powder is what allows continuous circulation.
Please log in or register to report this question.
Assertion (A): The catalyst in a fluid catalytic cracker is circulated continuously to a regenerator.
Reason (R): Coke deposits on the catalyst within seconds and must be burned off to restore activity.
Answer: C
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason is why the design takes the form it does. Coke lays down on the catalyst within a few seconds of contact, so a fixed bed would be dead almost at once. Fluidising the catalyst lets it circulate continuously between riser and regenerator, where the coke is burned off - and that combustion also supplies the heat the endothermic cracking reaction needs, so the two halves are thermally coupled.
Please log in or register to report this question.
Consider the following statements about catalytic reforming.
1. It converts naphthenes and paraffins into aromatics.
2. Hydrogen is a valuable by-product of the process.
3. It is a strongly exothermic reaction requiring cooling.
Answer: D
Correct answer: 1 and 2 only
Statements 1 and 2 are correct: reforming dehydrogenates naphthenes and cyclises paraffins into aromatics, and the hydrogen released is a valuable by-product that supplies the refinery’s hydrotreaters. Statement 3 is inverted - the dominant dehydrogenation reactions are strongly *endothermic*, which is why the process uses several reactors in series with a fired heater between each.
Please log in or register to report this question.
Catalytic reforming raises the octane number of naphtha chiefly by
Answer: A
Aromatics have far higher octane numbers than the straight chain paraffins they replace. The process is also the refinery's principal source of hydrogen and of benzene, toluene and xylene. Lead additives have long been withdrawn.
Please log in or register to report this question.
Octane number measures a fuel's resistance to
Answer: B
A higher octane fuel resists premature ignition and allows a higher compression ratio. Cetane number is the corresponding property for diesel and runs in the opposite direction. Higher octane permits a higher compression ratio.
Please log in or register to report this question.
