There are specifications for over 2000 individual refinery products. Intermediate feed stocks can be routed to various units to produce different blend products depending on market demand. Figure. shows typical refinery products with their carbon atom contents and boiling ranges. The specifications of each product are discussed in detail in the coming subsections
Figure. Principal petroleum products with carbon numbers and boiling ranges
1. Liquefied Petroleum Gas (LPG)
Liquified petroleum gas is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation. They include ethane, ethylene, propane, propylene, normal butane, butylene, isobutane and isobutylene. For convenience of transportation, these gases are liquefied through pressurization.
2. Gasoline
Gasoline is classified by octane ratings (conventional, oxygenated and reformulated) into three grades: Regular, Midgrade and Premium.
- Regular gasoline: Gasoline having an antiknock index, i.e. octane rating, greater than or equal to 85 and less than 88.
- Mid-grade gasoline: Gasoline having octane rating, greater than or equal to 88 and less than or equal to 90.
- Premium gasoline: Gasoline having octane rating greater than 90.
Premium and regular grade motor gasoline are used depending on the octane rating. In addition, aviation gasoline, which is a complex mixture of relatively volatile hydrocarbons, is blended with additives to form suitable fuel for aviation engines.
3. Kerosene
Kerosene is a light petroleum distillate that is used in space heaters, cook stoves and water heaters and which is suitable for use as a light source. Kerosene has a maximum distillation temperature of 204 C (400 F) at the 10% recovery point, a final boiling point of 300 C (572 F), and a minimum flash point of 37.8 C (100 F). The two grades are recognized by ASTM Specification D3699. A kerosene-type jet fuel-based product is having a maximum distillation temperature of 204 C (400 F) at the 10% recovery point and a final maximum boiling point of 300 C (572 F) and meeting ASTM Specification D1655.
4. Jet Fuel
This category comprises both gasoline and kerosene and meets specifications for use in aviation turbine power units.
5. Diesel Fuel
The quality of diesel fuels can be expressed as cetane number or cetane index. The cetane number (CN) is expressed in terms of the volume percent of cetane (C16H34) which has high ignition (CN = 100) in a mixture with alpha-methyl-naphthalene (C11H10) which has low ignition quality (CN = 0). Diesel fuel includes No.1 diesel (Super-diesel) which has cetane number of 45 and it is used in high speed engines, trucks and buses. No. 2 diesel has 40 cetane number. Railroad diesel fuels are similar to the heavier automotive diesel fuels, but have higher boiling ranges upto 400C (750 F) and lower cetane numbers (CN = 30).
6. Fuel Oil
The fuel oils are mainly used in space heating and thus the market is quite high specially in cold climates. No. 1 fuel oil is similar to kerosene and No. 2 fuel oil is very similar to No. 2 diesel fuel. Heavier grades of No. 3 and 4 are also available.
7. Residual Fuel Oil
It is mainly composed of vacuum residue. Critical specifications are viscosity and sulphur content. Low sulphur residues are in more demand in the market.
8. Lube Oil
Lubricants are based on the viscosity index. Paraffinic and naphthenic lubricants have a finished viscosity index of more than 75.
9. Asphalt
Asphalt is an important product in the construction industry and comprises upto 20% of products. It can be produced only from crude containing asphaltenic material.
10. Petroleum Coke
Carbon compounds formed from thermal conversion of petroleum containing resins and asphaltenes are called petroleum cokes. Fuel grade coke contains about 85% carbon and 4% hydrogen. The balance is made up of sulphur, nitrogen, oxygen, vanadium and nickel.