In catalytic alkylation (e.g., isobutane with C3–C4 olefins), how does increasing the iso-butane-to-olefin (I/O) ratio affect product properties and yields?

Introduction:
Alkylation combines isobutane with light olefins in a strong acid medium to make high-octane, low-endpoint alkylate. The iso-butane-to-olefin (I/O) ratio is a critical severity knob that shapes selectivity, endpoint, and yield.

Given Data / Assumptions:

• Reaction: isobutane + olefins → branched C7–C9 isoparaffins (alkylate).
• Variables: I/O ratio adjusted at constant temperature and acid strength.
• Targets: maximize yield and lower final boiling point (better product quality).

Concept / Approach:
A higher I/O ratio supplies excess isobutane, suppressing oligomerization/polymer gasoline formation, reducing heavy-end side reactions, and driving cleaner C7–C9 isoparaffin production. This typically lowers final boiling point and raises alkylate yield and quality.

Step-by-Step Solution:
Increase I/O → carbocation reactions favor desired alkylation over polymerization.Desired outcome → lower endpoint (final boiling point) and higher liquid yield.Therefore, both statements (a) and (b) are correct.

Verification / Alternative check:
Operating guidelines for H2SO4/HF alkylation units recommend high I/O ratios to improve selectivity and product quality, evidenced by lower endpoint and higher yields.

Why Other Options Are Wrong:
a or b alone: Incomplete; both are observed.d: Contradicts established practice.e: Higher I/O actually suppresses polymer gasoline formation.

Common Pitfalls:
Confusing alkylation with polymerization units; in alkylation, excess isobutane is beneficial.

Final Answer:
Both (a) and (b).