Sorption fractionation system for olefin separation

• US 4,479,812 A
• Filed: 06/29/1983
• Issued: 10/30/1984
• Est. Priority Date: 06/29/1983
• Status: Expired due to Fees

• Current Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Original Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Inventors: Owen, Hartley, Hsia, Chung H., Wright, Bernard S.
• Primary Examiner(s): Hart, Charles
• Application Number:
  US06/508,779
• Time in Patent Office: 489 Days
• Field of Search: 55/50, 55/65, 55/80, 55/88, 55/94, 55/223, 55/48, 55/51, 203/42, 208/341, 208/342, 208/349, 208/350
• US Class Current: 95/223
• CPC Class Codes: C07C 11/04 Ethylene
• CPC Class Codes: C07C 7/11 by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids
• CPC Class Codes: Y02P 30/40 Ethylene production

Abstract

A continuous fractionation technique is provided for recovering ethylene from an olefinic feedstock comprising C₃⁺ higher olefins. This technique provides methods and means for contacting the olefinic feedstock in a counter current sorption tower with a liquid sorbent stream comprising C₆⁺ gasoline range hydrocarbons under process conditions to selectively sorb substantially the entire C₃⁺ olefin components from the feedstock, withdrawing an ethylene-rich vapor stream from the sorption tower and further contacting the ethylene-rich stream with a distillate range liquid hydrocarbon stream in a sponge absorber to purify the ethylene stream. Typically, the olefinic feedstock consists essentially of volatile hydrocarbons, and preferably comprises about 10 to 50 mole % ethylene and 10 to 50 mole % propene. Purified ethylene product may be recovered having an average molecular weight not greater than 28.5 under non-cryogenic conditions.

Claims

1. A continuous fractionation process for recovering ethylene from an olefinic feedstock comprising about 10 to 50 mole % ethylene and 10 to 50 mole % propene, said olefinic feedstock consisting essentially of volatile C₂ -C₄ hydrocarbons comprising the steps of

contacting the olefinic feedstock in a countercurrent sorption tower with a liquid sorbent stream comprising C₆⁺ olefinic gasoline range hydrocarbons under process conditions to selectively sorb substantially the entire C₃⁺ olefin components from the feedstock;

withdrawing an ethylene-rich vapor stream from the sorption tower; and

further contacting the ethylene-rich stream with a distillate range liquid hydrocarbon stream in a sponge absorber to recover ethylene having an average molecular weight not greater than 28.5.

2. The process of claim 1 wherein olefinic liquid gasoline sorbent is supplied to the sorption tower as a molar ratio of about 0.2:

1 to 10;

1 based on feedstock C₃⁺ olefins.

3. The process of claim 2 wherein the distillate liquid stream is supplied to the sponge absorber at a molar ratio of about 0.1:

1 to 0.06;

1 based on ethylene whereby C₃⁺ and gasoline range hydrocarbons escaping the first sorption tower with the ethylene rich stream are absorbed by the distillate liquid.

4. The process of claim 1 wherein fractionation is conducted under non-cryogenic conditions and process pressure is maintained at about 2000 to 2200 kPa.

5. A continuous fractionation process for recovering ethylene from an olefinic feedstock comprising about 10 to 50 mole % ethylene and 10 to 50 mole % propene, said olefinic feedstock consisting essentially of volatile C₂ -C₄ hydrocarbons;

comprising the steps of

contacting the olefinic feedstock in a countercurrent sorption tower with a liquid sorbent stream comprising C₆⁺ olefinic gasoline range hydrocarbons under process conditions to selectively sorb substantially the entire C₃⁺ olefin components from the feedstock;

withdrawing an ethylene-rich vapor stream from the sorption tower;

mixing the ethylene-rich vapor with incoming liquid sorbent and passing the mixture thereof into a phase separator operatively connected between the sorption tower and a sponge absorber;

passing liquid sorbent from the phase separator to the countercurrent sorption tower; and

further contacting the ethylene-rich stream with a distillate range liquid hydrocarbon stream in the sponge absorber to recover substantially pure ethylene.