Raffinate 1 and 2 are the streams produced from the processing of crude C4 olefins made as a by-product of ethylene manufacture from the steam cracking of liquid hydrocarbons such as naphtha and gas oil. Crude C4s typically contain butadiene, isobutene (isobutylene), butene-1, butene-2 and butane.
After butadiene is extracted from the crude C4 olefins, the remaining mixture of products (isobutene, butene-1, butene-2 and butane) is called Raffinate 1. After isobutene is removed from the Raffinate 1 stream, the remaining mixture of products is called Raffinate 2.
Isobutene from the Raffinate 1 stream is used in the manufacture of a variety of polymers such as polyisobutene (PIB) and butyl rubber, and fuel components such as methyl tert-butyl ether (MTBE) and gasoline alkylate.
Major polymer end uses include sealing compounds and adhesives for plastic products, protective coatings and cable insulating materials.
The n-butene from the Raffinate 2 stream can be used in the manufacture methyl ethyl ketone (MEK). Butene-1 is used as a comonomer in the production of linear low density polyethylene (LLDPE). Butene-2 can be converted to propylene in a metathesis (olefins conversion) plant.