In lube and wax processing, which solvent is most widely used in modern dewaxing operations to separate wax from oils and produce low-pour products?

Introduction:
Dewaxing removes higher-melting waxes from lubricating oil stocks to meet pour point and low-temperature fluidity requirements. The choice of solvent governs filtration performance, wax crystal habit, and energy use. Knowing the commonly used solvent helps understand typical refinery configurations and troubleshooting.

Given Data / Assumptions:

• Target operation: solvent dewaxing of lube distillates/deoiled stocks.
• Candidate solvents include MEK, toluene/MEK mixtures, and various light hydrocarbons.
• Question asks for the most widely used solvent choice.

Concept / Approach:
MEK, often in combination with toluene (MEK–toluene), is widely adopted because it provides favorable wax solubility contrast and efficient crystal formation/filtration at practical refrigeration temperatures. Process licensors commonly specify MEK-based systems due to their balance of selectivity, recovery ease, and operability.

Step-by-Step Solution:
1) Identify mainstream commercial solvent systems for dewaxing.2) Recognize MEK (frequently blended with toluene) as the dominant industrial choice.3) Select MEK from among the options.

Verification / Alternative check:
Industry references and licensor literature repeatedly cite MEK or MEK–toluene as standard; alternatives like propane or MIBK exist but MEK remains the most common baseline solvent in conventional trains.

Why Other Options Are Wrong:
Naphtha/petroleum ether: Too broad or insufficiently selective for dewaxing duty.Sodium plumbite: A reagent used in Doctor’s test, not a dewaxing solvent.Acetone–methanol: Used in some laboratory contexts, not the most widely used in modern refineries.

Common Pitfalls:
Assuming any light solvent works; dewaxing demands specific solvent properties to promote crystal growth and filtration without excessive refrigeration load.

Final Answer:
Methyl-ethyl-ketone (MEK)