In chemical separation terminology, the raffinate (from French ''raffiner'', to refine) is a product which has had a component or components removed. The product having the removed materials is referred to as the

extract An extract (essence) is a substance made by extracting a part of a raw material, often by using a solvent such as ethanol, oil or water. Extracts may be sold as tinctures or absolutes or dried and powdered. The aromatic principles of ma ...

. For example, in solvent extraction, the raffinate is the liquid stream which remains after solutes from the original liquid are removed through contact with an

immiscible Miscibility () is the property of two chemical substance, substances to mix in all mixing ratio, proportions (that is, to fully dissolution (chemistry), dissolve in each other at any concentration), forming a homogeneity and heterogeneity, homoge ...

liquid. In metallurgy, raffinating refers to a process in which impurities are removed from liquid material. In pressure swing adsorption the raffinate refers to the gas which is not adsorbed during the high pressure stage. The species which is desorbed from the adsorbent at low pressure may be called the "extract" product.

Types

Raffinate-1 or C4R1

In naphtha cracking process, C4R1 refers to C4 residual obtained after separation of 1,3-butadiene from C4 raffinate stream and which, mainly consists of isobutylene 40~50 wt% and ''cis''- or ''trans''- 2-butene 30~35 wt%. Normally C4R1 is a side product in 1,3-butadiene plant and feed to ''tert''-butyl alcohol plant.

Raffinate-2 or C4R2

In naphtha cracking process, C4R2 refers to C4 residual obtained after separation of 1,3-butadiene and isobutylene from C4 raffinate stream and which mainly consists of ''cis''- or ''trans''-2-butene 50~60 wt%,

1-butene 1-Butene (IUPAC name: But-1-ene, also known as 1-butylene) is the organic compound with the formula CH3CH2CH=CH2. It is a colorless gas, but easily condensed to give a colorless liquid. It is classified as a linear alpha-olefin (terminal alkene). ...

10~15 wt%, and ''n''-

butane Butane () is an alkane with the formula C4H10. Butane exists as two isomers, ''n''-butane with connectivity and iso-butane with the formula . Both isomers are highly flammable, colorless, easily liquefied gases that quickly vaporize at ro ...

~20 wt%. Normally C4R2 is a side product in ''tert''-butyl alcohol plant if C4R1 is used for feed.

Raffinate-3 or C4R3

In naphtha cracking process, C4R3 refers to C4 residual obtained after separation of 1,3-butadiene, isobutylene, and 1-butene from C4 raffinate stream which mainly consists of ''cis''- or ''trans''-2-butene, ''n''-butane, and unseparated 1-butene. Normally C4R3 is being process through a selective hydrogenation unit (SHU) and CDHydro deisobutenizer unit to produce isobutylene as a feed to ''tert''-butyl alcohol plant.

Raffinate-4 or C4R4

In naphtha cracking process, C4R4 refers to C4 residual obtained after separation of 1,3-butadiene, isobutylene, 1-butene, and ''cis''- or ''trans''-2-butene from C4 raffinate stream which mainly consists of ''n''-butane. Normally C4R4 is a side product in ''tert''-butyl alcohol plant if C4R3 is used for feed.

References