In the Udex (glycol) extraction process for removing light aromatics from cracked naphtha, which solvent formulation is used as the selective extractant?

Introduction:
Udex is a classic liquid–liquid extraction process used to separate aromatics from light hydrocarbon streams like cracked naphtha. Correct identification of the solvent system is essential for understanding selectivity and phase behavior in the extractor.

Given Data / Assumptions:

• Target: preferentially extract benzene, toluene, and other light aromatics.
• Process: countercurrent extraction with a polar solvent.
• Options include hydrocarbons and polar solvents; only one matches Udex practice.

Concept / Approach:
Udex employs diethylene glycol (DEG) with controlled water content to tune selectivity and viscosity. The common formulation is DEG with about 10% water, which enhances aromatic solubility differentials and aids solvent recovery/phase disengagement.

Step-by-Step Solution:
Identify Udex solvent family → glycols.Selectivity tuning → add ~10% water to DEG.Therefore choose the aqueous DEG option.

Verification / Alternative check:
Process descriptions for Udex list DEG with controlled water; hydrocarbons like propane or ketones like MEK are not the Udex extractant.

Why Other Options Are Wrong:
Propane/MEK: Not the Udex aromatic extractant.DEG neat: Lacks the typical water content used to optimize selectivity.Formamide: Used in other extractive systems, not the standard Udex solvent.

Common Pitfalls:
Confusing Udex with Sulfolane or other solvent extraction technologies; each uses distinct solvents and conditions.

Final Answer:
Aqueous solution (about 10% water) of diethylene glycol