Wax deoiling methods\nDeoiling of petroleum wax is accomplished by which method(s)?

Introduction / Context:
Slack wax from lube refining contains entrained oil; deoiling (dewaxing and oil removal) is needed to meet wax product specifications such as melting point, oil content, and penetration.

Given Data / Assumptions:

• Processes considered include chilling/filtration and solvent methods.

Concept / Approach:
Deoiling relies on cooling to crystallize wax and reduce oil solubility, combined with solvent extraction (e.g., MEK/toluene) to selectively dissolve oil and permit filtration or centrifugation. Heating alone would dissolve wax back into oil; vacuum flashing cannot selectively remove tightly held oil in wax crystals. Therefore, practical deoiling uses cooling plus solvent extraction.

Step-by-Step Solution:

Verification / Alternative check:
Industrial deoiling flowsheets show chilling trains with solvent addition followed by filters (rotary drum, plate-and-frame) or centrifuges.

Why Other Options Are Wrong:

• Heating reverses the separation; vacuum flashing is not selective enough.

Common Pitfalls:
Insufficient residence for crystal growth or wrong solvent ratio causing poor filtration rates.

Final Answer:
Both (b) & (c)