Petroleum

Question 1

What are the key impurities in crude oil that must be removed during refining?

Answer 1

Crude oil impurities include water, inorganic salts (e.g., calcium, sodium, magnesium chlorides), suspended solids, and trace metals. These are removed to avoid equipment corrosion, plugging, fouling, and catalyst poisoning.

Question 2

What are the two main steps in crude oil pretreatment?

Answer 2

1. Field Separation: Removes gases, water, and dirt by gravity separation.
2. Crude Desalting: Uses water washing to remove water-soluble minerals and solids.

Question 3

What is fractional distillation, and why is it important in refining?

Answer 3

Fractional distillation separates crude oil into components based on boiling points. It is the first step in refining, crucial for producing specific fractions like gasoline, jet fuel, and road tar.

Question 4

What are the primary aims of petroleum refining?

Answer 4

1. Producing high-octane compounds for gasoline.
2. Converting hydrocarbons outside the C4–C10 range into usable chemical substances.

Question 5

What is catalytic reforming?

Answer 5

Catalytic reforming restructures hydrocarbons in naphtha to produce aromatics (e.g., benzene, toluene, xylene) with high octane numbers.

Question 6

What catalysts are used in catalytic reforming?

Answer 6

Platinum-based catalysts, often combined with alumina or zeolite, are used.

Question 7

What are the key reactions in catalytic reforming?

Answer 7

1. Dehydrogenation of naphthenes to aromatics.
2. Isomerization of paraffins to isoparaffins.
3. Dehydrocyclization of paraffins to aromatics.
4. Hydrocracking of paraffins.

Question 8

What is alkylation, and why is it performed?

Answer 8

Alkylation reacts olefins (e.g., isobutene) with isoparaffins (e.g., isobutane) to produce branched hydrocarbons, increasing gasoline’s octane number.

Question 9

What catalysts are used in alkylation?

Answer 9

Sulfuric acid (H₂SO₄) and hydrofluoric acid (HF) are commonly used.

Question 10

What is polymerization in refining?

Answer 10

Polymerization converts light olefins (e.g., ethylene, propylene) into higher molecular weight hydrocarbons, used as gasoline blending stocks.

Question 11

What catalysts are used in polymerization?

Answer 11

Solid phosphoric acid is commonly used for catalytic polymerization.

Question 12

What is isomerization, and what does it achieve?

Answer 12

Isomerization converts straight-chain paraffins (e.g., n-pentane) into branched isomers (e.g., isopentane) with higher octane numbers, improving fuel quality.

Question 13

What are the two isomerization processes?

Answer 13

Butane isomerization: Produces feedstock for alkylation.
Pentane/hexane isomerization: Improves octane numbers of straight-run fractions.

Question 14

What is hydrotreating, and what are its goals?

Answer 14

Hydrotreating removes contaminants (e.g., sulfur, nitrogen, metals) to protect catalysts and improve product quality.

Question 15

What is the Claus process used for?

Answer 15

The Claus process recovers sulfur from hydrogen sulfide (H₂S) produced during hydrotreating.

Question 16

Compare cracking and reforming.

Answer 16

1. Cracking: Breaks large hydrocarbons into smaller ones (e.g., gasoline, alkenes).
2. Reforming: Rearranges hydrocarbon structures to improve octane numbers (e.g., aromatics).

Question 17

Compare alkylation and polymerization

Answer 17

1. Alkylation: Combines small olefins and isoparaffins to create high-octane products.
2. Polymerization: Combines olefins into larger molecules for blending stocks.