Refining separation — dewaxing know-how: In the Barisol solvent dewaxing process used to lower the pour point of waxy distillates, which solvent system is employed as the characteristic dewaxing medium?

Introduction / Context:
Dewaxing is a key refining step to improve low-temperature flow properties of middle distillates and lube base stocks. Several named processes exist, each defined by its solvent system and operating method. The Barisol process is a classic solvent dewaxing route historically highlighted in petroleum exam questions.

Given Data / Assumptions:

• Objective: identify the solvent pair specific to the Barisol dewaxing process.
• Feed: waxy petroleum fractions requiring pour point reduction.
• Context: comparison against other common solvents (MEK/toluene, propane, furfural, hexane).

Concept / Approach:
Solvent dewaxing relies on selective dissolution and crystallization. A characteristic signature of the Barisol process is its use of benzol (benzene) together with ethylene dichloride as the mixed solvent. Other solvent systems correspond to different proprietary processes (e.g., MEK + toluene for modern solvent dewaxing, liquid propane for propane dewaxing; furfural is an extraction solvent for aromatics, not a dewaxing solvent).

Step-by-Step Solution:

Verification / Alternative check:
Cross-references of historical process names consistently tie “Barisol” to the benzene + ethylene dichloride mixture for promoting wax crystal formation and filtration at low temperatures.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing solvent extraction names (Edeleanu/furfural) with dewaxing names, or assuming any low-boiling solvent implies Barisol.

Final Answer:
benzol (benzene) and ethylene dichloride