Purpose of Mercapsol and Unisol: Mercapsol and Unisol are refinery treating processes designed primarily for which objective?

Introduction:
Refinery product quality depends on removing corrosive and odorous compounds. Mercaptans (thiols) are particularly problematic in light distillates due to their strong odour and corrosivity. Several named treating processes target them, including Mercapsol and Unisol, which are often grouped as solutizer-based systems.

Given Data / Assumptions:

• Mercapsol/Unisol are not distillation or cracking processes; they are finishing/treating steps.
• They use co-solvents (solutizers) to facilitate mercaptan transfer and reaction.
• Goal is to convert or remove mercaptans to achieve “sweet” product.

Concept / Approach:
Both processes focus on mercaptan removal/neutralisation, either by facilitating extraction of mercaptans into an alkaline phase (forming mercaptides) or by improving subsequent conversion pathways to less odorous species. They are distinct from dearomatisation (which targets aromatic hydrocarbons) and from dewaxing (which targets paraffinic wax components).

Step-by-Step Solution:

Verification / Alternative check:
Training notes on product sweetening list Mercapsol/Unisol alongside Merox and caustic wash methods, all aimed at reducing mercaptan sulphur.

Why Other Options Are Wrong:

• Dearomatisation: Targets aromatics, not sulphur species.
• Dewaxing: Targets wax; different equipment and solvents.
• Decoloration/Desalting: Different contaminants (colour bodies/salts and water).

Common Pitfalls:
Confusing “sweetening” with colour improvement; sweetening relates to sulphur odour/corrosivity.

Final Answer:
Removal of mercaptans