9. Alkylation

Question 1

■ Objective and description of Alkylation process?
■ How to achieve (Isoheptane and Isooctane)? How do the called?
■ Main Units?

Answer 1

■ The objective was to maximize the volume of gasoline being produced, but butylenes and propylene were too volatile and plentiful to stay dissolved in the gasoline blends. So they devised a process that was the inverse of cracking, alkylation, which starts with small molecules and ends up with
larger ones.

▪ Sulphuric acid catalysts used

■
▪ Isobutane (C4H10) [Parafine] + Propylene (C3H6) (Olefin) = Isoheptane (С7H16) — high octane gasoline blending component (alkylate)
▪ Isobutane (C4H10) + Butylene (C4H8) = Isooctane (C8H18) — high octane gasoline blending component (alkylate)

■ 
▪ The chiller
▪ The Reactors
▪ The Acid separator (cat)
▪ The caustic wash
▪ three distilling columns

Question 2

■ Feedstock (sources), output & disposition?

Answer 2

■ Feedstock:
▪ Propylene (C3H6)
▪ Butylene (C4H8)
▪ Isobutane (C4H10)
│
■ Output:
▪ Propane (C3H8) — too volatile so used in refinery fuel system
▪ N-Butane (C4H10) — gasoline blending
▪ Alkylate (Isoheptane (C7H16) & Isooctane (C8H18) — high octane gasoline blending component

Question 3

■ Poly Plant or Dimer plant?

Answer 3

■
▪ If refinery does not have enough isobutane (C4H10) to alkylate all their propylene (C3H6) and butylene (C4H8)
▪ then they direct all butylene in an alky plant and utilize all isobutane
▪ and build a polymerization plant for the propylene.
▪ propylene reacts with itself with catalyst (phosphoric acid or liquid catalyst based on nickel carboxylate or ethyl aluminium dichloride)
▪ results in forming Isohexane (C6H12) also called dimate
▪ which is used as gasoline blending component with poorer octane number than propylene alkylate (88 versus 92)