Reactor selection – very high-pressure gas-phase reactions Which reactor configuration is most suitable for conducting very high-pressure gas-phase reactions?

Introduction / Context:
Operating at very high pressure imposes stringent mechanical and safety constraints. Reactor geometry, wall thickness, stress distribution, and mixing/heat transfer characteristics all influence the preferred design for gas-phase processes (e.g., polymerization, hydrogenation).

Given Data / Assumptions:

• Gas-phase reaction requiring very high pressure.
• Continuous operation is feasible.
• Mechanical integrity and pressure containment are primary concerns.

Concept / Approach:
For pressure vessels, the required wall thickness is proportional to diameter (for a given pressure and allowable stress). Long, small-diameter tubes can withstand high pressures with comparatively thinner walls and offer high area/volume for heat transfer. Consequently, tubular (plug-flow) reactors are favored over large-diameter stirred vessels or fluidised beds under very high pressure.

Step-by-Step Solution:

Verification / Alternative check:
Industrial practice: high-pressure synthesis (e.g., LDPE tubular reactors, certain hydrogenations) commonly use tubular configurations for pressure-holding efficiency.

Why Other Options Are Wrong:

• Batch/CSTR: Large diameters demand very thick walls and heavy construction at high pressure.
• Fluidised bed: Gas–solid contacting and bed dynamics complicate ultra-high-pressure operation and vessel design.

Common Pitfalls:
Ignoring pressure-vessel design rules and focusing only on kinetics. Mechanical constraints often dictate reactor choice at extreme pressures.

Final Answer:
Tubular flow reactor