C4 Raffinate I & II

C4 Raffinate I & II


This is a colorless gas at ambient temperature and atmospheric pressure made from the remaining mixture after separating 1,3-butadiene from mixed C4 produced in the ethylene plant (NCC).

CAS number : – / Molecular formula : Mixture

Plant processes

C4 Raffinate is the remaining mixture following the extraction of 1,3-Bitadene from Mixed C4, and utilized as the raw material for MTBE and polybutene plant.

  • First Extractive Distillation Unit
    This unit fractionates acetylenes, that dissolve well in DMF (Dimethyl Formamide), an extractant, among mixed C4, butane that does not dissolve in BD, and C4 Raffinate-1 containing butene.
  • Second Extractive Distillation Unit
    This unit uses the extractant (DMF) to fractionate crude BD and acetylene from the BD and acetylenes fractionated along with solvents in the first extractive distillation unit.
  • BD Fractionation Unit
    This unit produces high-purity 1,3-butadiene in the two continuous separation columns using the differences in boiling points. Light acetylene is recovered as Off Gas and used as fuel, while heavy butene-2 and acetylene are fractionated as C4 Raffinate-2.
Product uses

Utilized as the raw material for MTBE and polybutene plant.

  • MTBE Plant
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C4 Raffinate II.

which is used to produce M.E.K, Butadiene1.3 and Butene-1. Raffinate-2 can be regarded as stages in the processing of Crude C4s streams. The first stage of the process is to remove, by solvent extraction, the valuable butadiene which may be 40-45% of the stream. What is left is Raffinate-1. It consists of Isobutylene, the two normal isomers, butene-1 and butene-2 and small quantities of butanes and other compounds. Removal of the isobutylene, usually by reaction with Methanol to produce MTBE, leaves Raffinate-2.


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