In metallurgy, raffinating refers to a process in which impurities are removed from liquid material.
The species which is desorbed from the adsorbent at low pressure may be called the "extract" product.
Normally C4R2 is a side product in tert-butyl alcohol plant if C4R1 is used for feed.
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.
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.