Industrial reactor materials — photochemical chlorination of benzene In producing benzene hexachloride (BHC) via photochemical chlorination of benzene, the reactor is typically lined with which material to resist chlorine and hydrogen chloride formed during the process?

Introduction / Context:
Benzene hexachloride (BHC, also called hexachlorocyclohexane) is produced by the photochemical chlorination of benzene in the presence of light. The reaction medium contains benzene, chlorine gas, and generates hydrogen chloride. Choosing an appropriate reactor lining is vital to resist corrosion and ensure long equipment life.

Given Data / Assumptions:

• Reaction: benzene + chlorine → BHC isomers, in a photochemical reactor.
• Corrosive species: dry/wet chlorine and hydrogen chloride (HCl).
• Need: corrosion-resistant lining compatible with halogens and HCl.

Concept / Approach:
Materials selection for chlorination service favors linings that are inert to halogens and acid gases. Glass-lined steel and lead-lined equipment have a long history in handling chlorination reactions due to their excellent resistance to Cl2 and HCl at moderate temperatures typical of photochemical operations.

Step-by-Step Solution:
Identify corrosive environment: chlorine + HCl present.Screen common linings: lead and glass show strong resistance to Cl2/HCl; many refractories do not protect against acid gas permeation.Select lining used historically and industrially for BHC production: lead or glass.

Verification / Alternative check:
Corrosion charts and industry practice for chlorination reactors repeatedly recommend glass-lined steel or lead lining for durability and ease of cleaning in halogen-rich environments.

Why Other Options Are Wrong:

• Karbate: suitable for some acid services, but photochemical chlorination commonly uses lead/glass linings.
• Fireclay bricks: designed for high-temperature furnaces, not optimized for halogen acid corrosion in liquid-phase photochemical duty.
• PVC: cannot serve as a structural reactor lining under process temperatures/solvents; poor compatibility with hot aromatics.

Common Pitfalls:

• Confusing structural refractories with corrosion-resistant internal linings.
• Assuming a plastic liner can handle solvent-swelling and temperature in chlorination systems.

Final Answer:
Lead or glass