Patent GB-858917-A (GB)
Title: Molecular sieve separation process for organic substances, particularly hydrocarbons
IPC: C10G25/03
Filed: 1958-03-26
Abstract: <PICT:0858917/IV(b)/1> Straight chain hydrocarbons are separated from mixtures thereof with branched chain or cyclic hydrocarbons, using a zeolite molecular sieve as absorbant in three stages, viz.: desorbtion, cooling and absorbtion, in which the raffinate from the absorption stage is used to cool the hot desorbant and the hot raffinate then used to pre-heat the initial feed.  For example, vessel C (Fig. 1) at the desorbtion stage is treated with propane admitted through a pipe 3, the desorbate produced is heated to about 600 DEG  F. in a heater 4 and recycled to the top of the vessel.  A heat front at 600 DEG  F. moves downwards through the vessel previously at 250 DEG  F. When the outlet temperature reaches 600 DEG F. desorbtion is complete, and the vessel becomes Vessel B which requires cooling to 250 DEG  F.  Vessel B is coupled to Vessel A which is an absorbant stage.  The feed material is fed through a line 20 and heat exchanger 21 which raises the feed temperature to 250 DEG F., and this passes downwards through the zeolite absorbant in Vessel A to a line 22, and a part of the outflow is cooled in an exchanger 17 (part of the element 21 at the top) and is then withdrawn at 17 as raffinate.  A portion of the raffinate passes from line 22 to the bottom of Vessel B and used to cool the zeolite therein from 600 to 250 DEG  F. ready for use as absorber, while the raffinate warms the input feed in a Vessel 13.  A modification of the apparatus provides a heat-reservoir filled with lead shot and is alternately charged with heat (and the vapour cooled) and the reverse in sequence.ALSO:<PICT:0858917/III/1> In the separation of hydrocarbons and like organic substances by a 3-stage process using a zeolite molecular sieve absorbent and consisting of desorbtion cooling and absorbtion, the raffinate from the absorbtion stage is used to cool the hot desorbent and the hot raffinate then used to pre-heat the feed to the absorbtion stage.  The hot raffinate may be cycled in a heat exchanger with the feed, or used in a separate heat reservoir charged with inert solids.  For example, vessel C, Fig. 1, at the desorbtion stage is treated with propane admitted through a pipe 3, the desorbate produced is heated to about 600 DEG F. in a heater 4 and recycled to the top of the vessel.  A heat front at 600 DEG F. moves downward through the vessel previously at 250 DEG F.  When the outlet temperature reaches 600 DEG F. desorption is complete, and the vessel becomes vessel B which requires cooling to 250 DEG F.  Vessel B is coupled to vessel A which is an absorbent stage.  The feed material is fed through a line 20 and heat exchanger 21 which raises the feed temperature to 250 DEG F., and this passes downwards through zeolite absorbent in vessel A to a line 22, and a part of the outflow is cooled in exchanger 17 (associated with element 21 at the top) and is then withdrawn at 17 as raffinate.  A portion of the raffinate passes from line 22 to the bottom of vessel B and used to cool the zeolite therein from 600 DEG  to 250 DEG F. ready for use as absorber, while the raffinate warms the input feed in a vessel 13. The process may be applied to separating straight chain hydrocarbons from mixtures thereof with cyclic or aromatic hydrocarbons.  A modification of the apparatus provides a heat reservoir filled for example with lead shot, which is alternately charged with heat (and the vapour is cooled) and the reverse in sequence.