Selected routes of C4 hydrocarbons processing | Source: T. Streich et al., Hydrocarbon Processing (July 2016).

Raffinate-2 is the residual C₄ stream obtained after extraction or selective hydrogenation of 1,3-butadiene from steam-cracker or FCC-derived crude C₄ (yielding raffinate-1) followed by removal of isobutylene via MTBE/ETBE etherification, hydration into TBA, or an equivalent conversion route. RAF-2 typically emerges as the unreacted C₄ side-stream from a tert-Butyl Alcohol (TBA) unit or an MTBE/ETBE unit processing raffinate-1.  It is a mixed olefin/paraffin liquefied gas consists mainly of cis- and trans-2-butene (50–60 wt%), 1-butene (10–15 wt%), n-butane (~20 wt%), and minor isobutane. When raffinate-1 is fed to a tert-Butyl Alcohol unit, RAF-2 is produced as the unreacted C₄ side-stream.

Read the full RAF-2 product profile here.

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