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9- Alkylation
1). Purpose : use light olefins and light iso-paraffins to produce high octane gasoline. Basically, the reverse of cracking; small molecules are combined to produce larger molecules in the gasoline boiling range.
2). Reactions and Mechanism
Principal Reactions
3). Feedstock Olefins and isobutane are used as alkylation unit feedstocks *Chief sources of olefins are catalytic cracking and coking operations - most common olefins used are butenes and propene
*Isobutane is produced by hydrocrackers and catalytic crackers - Catalytic reformers, crude disillation and natural gas processors also produce some isobutane fed to the alkylation unit 4). Products: LPG grade propane liquid, Normal butane liquid, C5 + alkylate and Tar 5). Cataltst Only two catalysts are used commercially today to produce high octane alkylate gasoline: Concentrated Sulfuric Acid -more widely used Concentrated Hydrofluoric Acid - more risky
* Strong acids can catalyze the alkylation reaction, but weaker acids can cause polymerization to take place, therefore, the acid strengths must be kept above 88% by weight H2SO4 or HF
Some polymerization is desirabe because it increases the solubility of isobutane in the acid phase.
1). Purpose: Propene and butenes can be polymerized to form a high-octane roduct boiling in the gasoline boiling range 2).Reaction:
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