Feedstocks for SBR (Buna-S) manufacture: which of the following starting materials are industrial precursors for the monomers used to produce SBR?

Introduction:
SBR (Buna-S) is a copolymer of styrene and butadiene. The question probes understanding of upstream petrochemical routes that supply these monomers in different regions and eras (e.g., alcohol-to-butadiene processes and ethylene-based styrene chains).

Given Data / Assumptions:

• SBR requires styrene + butadiene.
• Butadiene can be produced from ethanol (historical/alternative route) or from naphtha/steam cracker C4 cuts.
• Styrene is typically produced from ethylbenzene (benzene + ethylene).

Concept / Approach:
Industrial flexibility allows multiple monomer routes. Ethyl alcohol can be transformed to butadiene via catalytic dehydrogenation/dehydration sequences (legacy processes). Ethylene is a key feed for ethylbenzene synthesis, which dehydrogenates to styrene. Both feedstocks thus link to SBR monomer supply chains.

Step-by-Step Solution:
Map ethanol → butadiene: catalytic pathways yield the diene monomer.Map ethylene → ethylbenzene → styrene: alkylation of benzene followed by dehydrogenation.Since SBR needs both butadiene and styrene, and (a) and (b) each provide one, choose “Both (a) and (b)”.

Verification / Alternative check:
Chemical process texts describe the Lebedev and related processes (ethanol to butadiene) and standard ethylbenzene–styrene routes from ethylene.

Why Other Options Are Wrong:

• Neither (a) nor (b): incorrect; both feedstocks connect to SBR monomers.
• Propylene only: relates more to acrylonitrile (ABS/SAN routes), not directly to SBR's primary monomers.

Common Pitfalls:
Assuming only modern steam-cracking routes count; older or alternative alcohol-based routes are valid and historically significant.

Final Answer:
Both (a) and (b)