Process for recovering ethylene from an olefin stream produced by a methanol to olefin reaction

• US 5,811,621 A
• Filed: 08/09/1996
• Issued: 09/22/1998
• Est. Priority Date: 08/09/1996
• Status: Expired due to Fees

• Current Assignee: Van DIJK Technologies LLC
• Original Assignee: Starchem Incorporated (Star Holdings, Inc.)
• Inventors: van Dijk, Christiaan P.
• Primary Examiner(s): Griffin, Walter D.
• Assistant Examiner(s): Dang, Thuan D.
• Application Number:
  US08/689,520
• Time in Patent Office: 774 Days
• Field of Search: 585/314, 585/316, 585/319, 585/638, 585/639, 585/640, 585/323, 585/324, 585/809, 585/446, 585/315, 203/73, 203/74, 208/347, 208/351
• US Class Current: 585/639
• CPC Class Codes: B01D 3/009 in combination with chemical reactions
• CPC Class Codes: B01D 3/146 Multiple effect distillation
• CPC Class Codes: C07C 11/04 Ethylene
• CPC Class Codes: C10G 2300/4006 Temperature
• CPC Class Codes: C10G 2300/4012 Pressure
• CPC Class Codes: C10G 2300/4081 Recycling aspects
• CPC Class Codes: C10G 2400/20 C2-C4 olefins
• CPC Class Codes: C10G 3/00 Production of liquid hydrocarbon mixtures from oxygen-containing organic materials, e.g. fatty oils, fatty acids production from non-melting solid oxygen-containing carbonaceous materials C10G1/00
• CPC Class Codes: C10G 70/041 by distillation
• CPC Class Codes: F25J 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2210/12 Refinery or petrochemical off-gas
• CPC Class Codes: F25J 2215/62 Ethane or ethylene
• CPC Class Codes: F25J 3/0219 Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
• CPC Class Codes: F25J 3/0238 separation of CnHm with 2 carbon atoms or more
• CPC Class Codes: F25J 3/0242 separation of CnHm with 3 carbon atoms or more
• CPC Class Codes: F25J 3/0252 separation of hydrogen production of hydrogen containing gas in general C01B3/00, e.g. separation of hydrogen or hydrogen containing gases form gaseous mixtures at low temperatures C01B3/506
• CPC Class Codes: Y02P 20/10 Process efficiency
• CPC Class Codes: Y02P 30/40 Ethylene production

Abstract

A polymerizable grade of ethylene is recovered from an olefin-containing composition, prepared by the conversion of a methoxy compound to olefins, by a process which significantly reduces the requirements of the demethanizer distillation column through which hydrogen and methane are eliminated as impurities from the ethylene product without suffering economically unacceptable losses of ethylene to the hydrogen-methane fraction that is separated. The invention also provides for a C-2 splitter column of simplified requirements.

Claims

1. A process for producing and recovering ethylene, comprising the steps of:

converting a methoxy composition to a mixture containing ethylene, methane and hydrogen;

feeding said ethylene containing mixture to a first distillation unit to produce

an ethylene containing condensate stream essentially free of any content of methane and hydrogen, and a vapor stream composition containing ethylene and methane in a mole ratio of ethylene to methane of at least about 1;

1.

2. The process of claim 1, further comprising the step of

separating ethylene from propylene and heavier components by feeding said ethylene containing condensate stream to a second distillation column to produce

a condensate comprising propylene and heavier components;

and

a vapor stream comprising ethylene.

3. The process of claim 2, further comprising steps of

compressing said vapor stream composition containing ethylene and methane to a pressure wherein its ethylene content has a condensation point temperature which is greater than that temperature of the ethylene containing condensate stream;

passing said compressed composition containing ethylene and methane into indirect heat exchange contact with condensate within said second distillation unit and thereafter feeding said compressed composition to a vapor-liquid separator; and

dispersing liquid taken from said vapor-liquid separator within an upper portion of said second distillation unit as liquid reflux.

4. The process of claim 3 wherein

said vapor stream composition containing ethylene and methane has a mole ratio of ethylene to methane of at least about 3:

1 and a vapor stream taken from a vapor-liquid separator has a mole ratio of ethylene to methane of 1;

1 or less.

5. The process of claim 1, wherein

the vapor stream composition containing ethylene and methane has a temperature of no lower than -40°

C.

6. The process of claim 5, where

said ethylene containing mixture feed to the first distillation unit has a temperature of no lower than -40°

C.

7. The process of claim 6, further comprising the step of

separating the ethylene containing condensate stream into a vapor stream containing ethylene and 200 ppm or less of ethane, and a condensate stream comprising ethane.

8. The process of claim 7, wherein

said condensate stream comprising ethane contains ethylene in a mole ratio to ethane of from about 0.5:

1 to about 1;

1.

9. The process of claim 8, wherein

of the ethylene containing mixture fed to said first distillation unit, at least about 93% of said ethylene is recovered in said vapor stream containing ethylene and 200 ppm or less ethane.

10. The process of claim 9, wherein said stream comprising ethane and ethylene in a mole ratio to ethane of from about 0.5:

1 to about 1;

1 is utilized as a feedstock material for supply to a reactor wherein said ethylene content is converted into ethylene dichloride or ethyl benzene.

11. The process of claim 4, further comprising the step of

recovering a quantity of ethylene from the vapor stream taken from said vapor-liquid separator by expansion cooling and liquefaction of said vapor stream, and

recycling said recovered quantity of ethylene to said first distillation unit.

12. The process of claim 11, wherein

at least about 97% of the ethylene fed to said first distillation unit is recovered in said ethylene containing condensate stream.

15. The process of claim 4, further comprising the step of

recovering a quantity of ethylene from the vapor stream taken from said vapor-liquid separator by membrane separation of said vapor stream to a methane containing permeate and an ethylene containing nonpermeate, and

recycling said recovered quantity of ethylene to said first distillation unit.

13. A process for producing and recovering ethylene, comprising the steps of:

converting a methoxy composition to an ethylene containing mixture;

separating C₂ hydrocarbons and lighter components from said mixture;

feeding said C₂ hydrocarbons and lighter components to a distillation column to produce

a column condensate stream comprising C₂ hydrocarbons essentially free of any content of methane and hydrogen, and

a column vapor stream composition comprising ethylene and methane in a mole ratio of ethylene to methane of at least about 3;

1;

compressing said column vapor stream composition to a pressure wherein its ethylene content has a condensation point temperature which is greater than that temperature of the column condensate stream;

passing said compressed composition into indirect heat exchange contact with condensate within said distillation column and thereafter feeding said compressed composition to a vapor-liquid separator; and

dispersing liquid taken from said vapor-liquid separator within an upper portion of said distillation column as reflux.

14. The process of claim 13, wherein

a vapor stream taken from a vapor-liquid separator has a mole ratio of ethylene to methane of 1:

1 or less.