Syngas purification — In naphtha steam reforming, the CO2 present in the reformed gas is typically removed by absorption into which solvent?

Introduction:
Steam reforming of naphtha produces a synthesis gas containing H2, CO, CO2, CH4, and impurities. Downstream processes (e.g., ammonia synthesis) require CO2 removal to protect catalysts and meet composition targets. Identifying the standard solvent is a core process design decision.

Given Data / Assumptions:

• Post-shift gas contains significant CO2.
• Solvent absorption is used prior to methanation or cryogenic steps.
• Common industrial choices include amines and hot carbonate systems.

Concept / Approach:

MEA (monoethanolamine) is a primary amine widely used for chemical absorption of CO2 via reversible carbamate/bicarbonate formation. It offers fast kinetics and established regeneration practice. Alternatives like hot potassium carbonate, DEA, MDEA, or physical solvents may also be used, but in many classical plant designs the baseline answer is MEA. Slaked lime is suited to fixed chemical scrubbing and not standard for continuous syngas purification; ammoniacal liquor and MEK are not mainstream CO2 solvents in reformer trains.

Step-by-Step Solution:

Verification / Alternative check:

Process schematics for ammonia plants show amine absorbers and strippers in the CO2 removal section, with MEA or DEA commonly specified.

Why Other Options Are Wrong:

B: Lime would produce solids and is unsuitable for cyclic solvent systems. C: Ammoniacal liquor is not a standard CO2 solvent here. D: MEK is an organic solvent, not used for CO2 chemical absorption. E: Propylene carbonate is a physical solvent used at high pressures; not the canonical answer versus MEA.

Common Pitfalls:

Overlooking that solvent selection depends on pressure and composition; MEA remains a standard textbook answer.

Final Answer:

mono-ethanolamine (MEA)