Dewaxing of petroleum products: Which of the following are common solvents used specifically for solvent dewaxing?
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AFurfural
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BMethyl ethyl ketone (MEK)
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CPropane
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DBoth (b) and (c)
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EToluene only
Answer
Correct Answer: Both (b) and (c)
Explanation
Introduction:Dewaxing removes high-melting waxes from lubricating oil stocks and other petroleum fractions to improve low-temperature flow properties such as pour point.
Given Data / Assumptions:
- We focus on solvents used in the dewaxing step.
- Common industrial choices include ketone-based and hydrocarbon/propane systems.
Concept / Approach:Solvent dewaxing relies on selective dissolution at low temperatures to precipitate wax. MEK (often with toluene or MIBK) and liquid propane are widely used. Furfural is a selective extraction solvent for aromatics, not a dewaxing solvent.
Step-by-Step Solution:
Step 1: Identify MEK as a classic ketone solvent for dewaxing.Step 2: Recognize propane dewaxing as an alternative process.Step 3: Exclude furfural (used in lube extraction units) and “toluene only” as incomplete.Verification / Alternative check:Process flow descriptions pair MEK with a co-solvent (often toluene) and also describe propane dewaxing units.
Why Other Options Are Wrong:
- Furfural: Extraction solvent, not for dewaxing.
- Toluene only: Common co-solvent with MEK, rarely used alone as the primary dewaxing solvent.
Common Pitfalls:Confusing extraction (furfural) with dewaxing; overlooking propane-based dewaxing.
Final Answer:Both (b) and (c)