Raffinate-1 and 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.
Raffinate-1 is a chemical building block used in the manufacture of methyl tertiary butyl ether (MTBE) and diisobutylene (DIB). MTBE is a liquid added to petroleum to reduce emissions, and DIB is an intermediate in the production of alcohols and solvents.
Raffinate-2 is a chemical building block used in the manufacture of secondary butyl alcohol (SBA) and methyl ethyl ketone (MEK). SBA is an intermediate in the production of industrial cleaning compounds, oil treating chemicals and paint removers, and MEK is an intermediate in the production of surface coatings, adhesives, thinners, printing inks and cleaning agents.