Adsorption-desorption separation process with integrated light and heavy desorbents

Claim 1

In an adsorption-desorption process for separating close boiling materials or isomers in which a liquid desorbent is used to produce an extract of desired materials in said desorbent and also a raffinate of byproduct materials in said desorbent, the improvement which comprises: carrying out an adsorption-desorption step in a first unit with a desorbent lower boiling than the feedstream to be separated to obtain a light extract and a light raffinate; carrying out an adsorption-desorption step in a second unit with a desorbent higher boiling than said feedstream to obtain a heavy extract and a heavy raffinate; passing light raffinate and heavy raffinate into a fractionating column and separating the same by fractionation into light desorbent, heavy desorbent and byproduct raffinate materials; passing light extract and heavy extract into a second fractionating column and separating the same by fractionation into light desorbent, heavy desorbent and product extracted materials; and recycling light desorbent streams from both fractionators to said first unit and recycling heavy desorbent streams from both fractionators to said second unit.