Process for separating propylene mixed with propane by adsorption in a simulated moving bed

Abstract

A process for separating propylene mixed with propane by adsorption in a simulated moving bed is described. The process operates in the gaseous phase or in the liquid phase, and it uses a 13X faujasite-type zeolite as adsorbent solid and butene-1 or isobutane or any mixture of these 2 components as desorbent.

1 . Process for separating propylene by adsorption from a hydrocarbon mixture that contains at least 90% by weight of propylene and propane, whereby the addition consists of other hydrocarbons, whereby said process is implemented in a simulated moving bed in the gaseous phase or the liquid phase and uses a 13X faujasite-type zeolite as an adsorbent solid and either butene-1, or isobutane, or any mixture of these two components as desorbent, whereby said process comprises the succession of following stages:
 a) A stage for bringing the feedstock into contact with an adsorbent bed that contains 13X zeolite so as to preferably adsorb the propylene;   b) A stage for bringing the adsorbent bed into contact with the desorbent,   c) A stage for drawing off from the adsorbent bed a flow that contains desorbent and the least selectively adsorbed products of the feedstock,   d) A stage for drawing off from the adsorbent bed a flow that contains desorbent and propylene.   
   
   
       2 . Process for separating propylene according to  claim 1 , in which the
 desorbent that is used is isobutane.   
   
   
       3 . Process for separating propylene according to  claim 1 ,
 whereby said process operates in the gaseous phase, whereby the temperature is between 20° C. and 150° C., and the pressure is between 0.1 and 1 MPa.   
   
   
       4 . Process for separating propylene according to  claim 1 ,
 whereby said process operates in the liquid phase, whereby the temperature is between 0° C. and 60° C., and the pressure is between 0.8 and 2 MPa.   
   
   
       5 . Process for separating propylene according to  claim 3 , in which the adsorbent solid is in the form of extrudates with a diameter of between 1.0 and 2.0 mm, and with a length of between 2.0 and 16.0 mm 
   
   
       6 . Process for separating propylene according to  claim 4 , in which the adsorbent solid that is used is shaped like balls with a diameter of between 0.6 and 2.0 mm 
   
   
       7 . Process for separating propylene according to  claim 1 , also comprising, following stage c), a stage e) for separating the flow from said stage c) into a first flow that contains the desorbent and a second flow that contains the least selectively adsorbed feedstock products, whereby the desorbent is recycled at the inlet of the simulated moving bed unit. 
   
   
       8 . Process for separating propylene according to  claim 1 , also comprising, following stage d), a stage f) for separating the flow from said stage d) into a first flow that contains the desorbent and a second flow that contains high-purity propylene, whereby the desorbent is recycled at the inlet of the simulated moving bed unit.