C4 separation technology

C4 separation, or C4 fractionation, is the process of separating the C4 fraction into individual components. The C4 fraction has a complex composition, with similar boiling points and the tendency to form azeotropes; therefore, ordinary distillation methods cannot yield products of high purity, and solvent extraction distillation as well as chemical methods must be used for separation. The extraction distillation methods for separating dienes from the C4 fraction include the furfural method, acetonitrile method, V-methylpyrrolidone method, dimethylformamide method, etc. Methods for separating isobutylene include: the sulfuric acid extraction method, in which the isobutylene-butane mixture is first converted into a tertiary alcohol and then hydrolyzed to yield isobutylene; the catalytic hydrolysis method; the isobutylene hydration method; the isobutylene etherification separation method; the isobutylene isomerization separation method; the isobutylene oligomerization separation method; and the molecular sieve adsorption separation method. The C4 fraction from which butadiene and isobutylene have been extracted can be further separated into isobutane, 1-butene, n-butane, etc., using distillation and extractive distillation methods.