Process Technology Quick Reference Cards
Alkylation
Chapter from the Process Technology Quick Reference Cards.
ALKYLATION
Process Objective
Combine isobutane with light olefins (propylene, butylene) to produce alkylate — a high-octane, low-RVP gasoline blending component.
Key Operating Variables
| Variable | Typical Range | Effect / Notes |
|---|---|---|
| Temperature | 40-100°F (HF), 35-55°F (H2SO4) | Lower T → better quality, fewer side reactions |
| Isobutane/Olefin Ratio | 5-15:1 (external) | Higher ratio → better quality, less polymerization |
| Acid Strength | 85-92% HF, 88-99% H2SO4 | Below minimum → acid-soluble oil formation |
| Contact Time | 10-30 min (HF), 15-30 min (H2SO4) | Sufficient for complete reaction |
| Olefin Space Velocity | 0.1-0.5 vol/vol/hr | Lower → better product quality |
Process Configurations
HF Alkylation: liquid HF catalyst, settler-reactor, lower investment but HF hazard
Sulfuric Acid Alkylation: H2SO4 catalyst (autorefrigeration or effluent refrigeration)
Autorefrigeration: olefin feed vaporization controls temperature
Effluent refrigeration: external chillers cool reactor effluent
Ionic Liquid / Solid Acid: emerging alternatives to avoid HF/H2SO4 hazards
Products & Yields
Alkylate: 90-100 vol% yield, 93-97 RON, low RVP, zero sulfur/aromatics/olefins
n-Butane: co-product (debutanizer bottoms)
Propane: if propylene in feed — depropanizer overhead
Common Troubleshooting
Low octane: check i-C4/olefin ratio, acid strength, temperature
High acid consumption (H2SO4): water in feed, butadiene, acid-soluble oils
Corrosion (HF): check inhibitor, acid purity, materials of construction
Emulsion problems: fine solids, trace contaminants
Source: Process_Tech_Quick_Reference_Cards_v1.xlsx · sheet “Alkylation”
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