Catalytic polymerisation – correctness of statements Which statement(s) about acid-catalysed polymerisation for gasoline production is/are correct?

Introduction / Context:Acid-catalysed polymerisation of light olefins (e.g., from FCC gas) produces higher olefins that, after hydrogenation or finishing, become gasoline-range blend components. Exam questions often contrast the sulphuric-acid liquid process with solid-phosphoric-acid processes and ask you to identify accurate statements.

Given Data / Assumptions:

• Liquid H2SO4 is a classic polymerisation catalyst for light olefins.
• Solid phosphoric acid (H3PO4 on support) is a different process.
• Statements mix details from different technologies.

Concept / Approach:The direct product of H2SO4 polymerisation is a mixture containing significant unsaturation (higher olefins). These are typically hydrogenated to improve stability before blending. The claim that, in H2SO4 polymerisation, H3PO4 is “always used with 2 percent steam to prevent meta & ortho H3PO4 formation” is incorrect and conflates distinct technologies; steam conditioning applies to solid phosphoric acid catalysts, not to liquid sulphuric acid systems in the manner described.

Step-by-Step Solution:

Verification / Alternative check:Process descriptions of polymer gasoline units show a hydrogenation finishing step after H2SO4 polymerisation to stabilise product by saturating double bonds.

Why Other Options Are Wrong:

• (b): Technically incorrect; wrong process attribution and unjustified “always.”
• Both / Neither: Do not match the true/false evaluation.

Common Pitfalls:Confusing polymerisation with alkylation or merging liquid sulphuric acid and solid phosphoric acid operating details.

Final Answer:H2SO4 polymerisation yields gasoline rich in unsaturates before finishing