Catalytic reforming chemistry — undesirable pathway: Identify the reaction that is undesirable during catalytic reforming aimed at producing high-octane gasoline.

Introduction / Context:
Catalytic reforming upgrades naphtha to high-octane reformate by increasing aromatics and isoparaffins while producing hydrogen. Not all dehydrogenation/isomerization reactions are beneficial to gasoline yield and octane objectives.

Given Data / Assumptions:

• Typical Pt/acid bifunctional catalysts.
• Feed: paraffinic/naphthenic naphtha boiling range.
• Goal: raise octane, maintain gasoline-range yield.

Concept / Approach:
Desired reactions include dehydrogenation of naphthenes to aromatics, isomerization of paraffins, and dehydrocyclization of suitable higher paraffins—each boosts octane and often generates hydrogen. In contrast, dehydrogenating lower paraffins tends to form light olefins/hydrogen that can over-crack or exit as gas, lowering liquid yield and not directly enhancing octane of the gasoline pool; thus it is undesirable.

Step-by-Step Solution:

Verification / Alternative check:
Process texts emphasize minimizing C1–C4 gas make; reactions that increase light ends at the expense of C5+ liquid are detrimental.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming “any” dehydrogenation is good; the molecular size and pathway to light ends matters.

Final Answer:
Dehydrogenation of lower paraffins