text: 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.