Separation of linear from branched hydrocarbons using a carbon membrane

• US 5,914,434 A
• Filed: 09/29/1997
• Issued: 06/22/1999
• Est. Priority Date: 01/16/1995
• Status: Expired due to Fees

• Current Assignee: Carbon Membranes Limited
• Original Assignee: Carbon Membranes Limited
• Inventors: Cohen, Haim, Soffer, Abraham, Gilron, Jack
• Primary Examiner(s): GRIFFIN, WALTER DEAN
• Application Number:
  US08/875,006
• Time in Patent Office: 631 Days
• Field of Search: 585/818, 96/4, 96/10, 423/445 R, 423/447.1, 210/651, 210/652, 210/653
• US Class Current: 585/818
• CPC Class Codes: B01D 2325/20 Specific permeability or cut-off range
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 67/0067 by carbonisation or pyrolysis
• CPC Class Codes: B01D 71/021 Carbon
• CPC Class Codes: C07C 7/144 using membranes, e.g. selective permeation
• CPC Class Codes: C10G 31/11 by dialysis

Abstract

In a process for separating linear from branched hydrocarbons, the feed is brought in contact with a carbon membrane with critical size from 0.39 to 0.55 nm. The isomer with the larger size remains on the feed side. A membrane can be produced by activating a membrane by reacting it with oxygen and then with hydrogen.

Claims

1. A method for the separation of linear from branched hydrocarbon isomers, comprising the steps of:

selecting a carbon membrane having a pore size, comprised in the range 3.9 Å

to 5.5 Å

;

providing a separating means between the two sides of the membrane, so that hydrocarbon molecules cannot move from one side of the membrane to the other, save through the membrane;

providing a mixture of two isomers to be separated and bringing the said mixture into contact with a mixture feed side of the membrane;

applying a driving force across the membrane;

collecting a permeate richer in the isomer having the smaller size from a permeate side of the membrane opposite to said mixture feed side; and

collecting a retentate richer in the isomer having the larger size from said mixture feed side of the membrane.

2. A process according to claim 1, wherein the feed mixture of isomers is kept in the gaseous state.

3. A process according to claim 1, wherein a concentration difference of one or all the isomers in the feed is maintained by applying a partial or complete vacuum at the permeate side of the membrane.

4. A process according to claim 1, wherein the isomers to be separated are selected from normal hydrocarbons and hydrocarbons containing secondary, tertiary or ternary carbon atoms.

5. A method for the separation of linear from branched hydrocarbon isomers, comprising the steps of:

selecting a carbon membrane having a pore size, comprised in the range 3.9 Å

to 5.5 Å

;

providing separating means between the two sides of the membrane, so that hydrocarbon molecules cannot move from one side of the membrane to the other, save through the membrane;

providing a mixture of two isomers to be separated and bringing the said mixture into contact with a mixture feed side of the membrane;

providing a pressure drop across the membrane, the higher pressure being on the mixture side thereof;

collecting a permeate richer in the isomer having the smaller size from the permeate side of the membrane opposite to said mixture feed side; and

collecting a retentate richer in the isomer having the larger size from said mixture feed side of the membrane.