A distillation column for separating components of a feed stream is described herein. The distillation column has a top end; a bottom end spaced from the top end; a set of trays dispersed along a length of the distillation column between the top end and the bottom end; and a dividing wall extending between the top end and the bottom end to divide the distillation column into a pre-fractionation zone, a top zone, a bottom zone and an outflow zone. The feed stream includes a most volatile component, a first intermediate volatile component, a second intermediate volatile component and a least volatile component.

A distillation apparatus of the present invention includes high-pressure column 1 corresponding to a region above a heat exchanging section located at a lowermost part of a region including a trayed section or a packed bed section, which is used as a rectifying section; and low-pressure column 2 that is located above as seen from high-pressure column 1, which integrates a region including a trayed section or a packed bed section which is used as a stripping section, with rectifying section corresponding portion 2g that corresponds to a region locating below the heat exchanging section located at the lowermost part in the rectifying section. Rectifying section corresponding portion 2g is located on top 2c of the stripping section in low-pressure column 2 so that rectifying section corresponding portion 2g continues to the stripping section.

Systems and methods for carrying out metathesis reaction by utilizing one or more side reactors to a reactive distillation column is disclosed. The one or more side reactors is used to effect a reactive pump-around process. The systems and methods are used for equilibrium limited reactions such as the metathesis of C.sub.4 olefins.