Methods and apparatuses for producing low sulfur propane and butane

Patent metadata

Field	Value
Publication number	US-2015141728-A1
Application number	US-201314083116-A
Country	US
Kind code	A1
Filing date	Nov 18, 2013
Priority date	Nov 18, 2013
Publication date	May 21, 2015
Grant date	—

Abstract

Methods and apparatuses are provided for producing low sulfur propane and butane. The method includes reacting a mercaptan in a washed feed stream with a caustic stream to produce a mercaptan salt in a rich caustic stream and a hydrocarbon treated stream. The mercaptan salt in the rich caustic stream is reacted with oxygen and water to produce a mixed caustic/disulfide stream, and the caustic and disulfides in the mixed caustic/disulfide stream are separated to produce a disulfide stream and the caustic stream. The hydrocarbon treated stream is fractionated to produce a propane stream, a butane stream, and a C5+ stream.

First claim

1 . A method for producing low sulfur propane and butane, the method comprising the steps of:
reacting a mercaptan in a washed feed stream with a caustic stream to produce a mercaptan salt in a rich caustic stream and a hydrocarbon treated stream; reacting the mercaptan salt in the rich caustic stream with oxygen and water to produce a mixed caustic/disulfide stream; separating caustic and disulfides in the mixed caustic/disulfide stream to produce a disulfide stream and the caustic stream; and fractionating the hydrocarbon treated stream to produce a propane stream, a butane stream and a C5+ stream.

2 . The method of claim 1 further comprising:
prewashing the washed feed stream prior to reacting the mercaptan in the washed feed stream with the caustic stream, wherein prewashing comprises contacting the washed feed stream a prewash stream comprising sodium hydroxide.

3 . The method of claim 1 wherein fractionating the hydrocarbon treated stream further comprises:
debutanizing the hydrocarbon treated stream to produce a C3-4 stream and the C5+ stream, and
depropanizing the C3-4 stream to produce the propane stream and the butane stream.

4 . The method of claim 1 wherein reacting the mercaptan salt in the rich caustic stream with oxygen further comprises contacting the rich caustic stream with air.

5 . The method of claim 1 wherein reacting the mercaptan in the washed feed stream with the caustic stream further comprises reacting the mercaptan in the washed feed stream with the caustic stream wherein the washed feed stream is derived from hydraulic fracturing of shale.

6 . The method of claim 1 wherein reacting the mercaptan salt in the rich caustic stream further comprises adding an oxidation catalyst to the rich caustic stream.

7 . The method of claim 1 wherein reacting the mercaptan salt in the rich caustic stream further comprises adding an oxidation catalyst to the rich caustic stream wherein the oxidation catalyst is in liquid form, and wherein the oxidation catalyst comprises a metal chelate.

8 . The method of claim 1 wherein reacting the mercaptan in the washed feed stream with the caustic stream further comprises reacting the mercaptan in the washed feed stream with the caustic stream wherein 90 mass percent or more of the washed feed stream comprises hydrocarbons with 3 to 5 carbon atoms.

9 . The method of claim 1 further comprising:
replenishing the caustic stream with fresh caustic.

10 . A method of producing low sulfur propane and butane, the method comprising the steps of:
feeding a washed feed stream into an extraction unit to produce a hydrocarbon treated stream and a rich caustic stream, wherein the washed feed stream comprises a mercaptan, and wherein the mercaptan in the washed feed stream reacts with caustic to produce a mercaptan salt that remains in the rich caustic stream; removing the mercaptan salt from the rich caustic stream in a caustic regeneration unit to produce a caustic stream; and feeding the caustic stream into the extraction unit.

11 . The method of claim 10 wherein removing the mercaptan salt from the rich caustic stream further comprises:
oxidizing the mercaptan salt with oxygen and water in an oxidizer to produce a mixed caustic/disulfide stream comprising disulfides and caustic; and
separating the disulfides from the caustic in a disulfide separator.

12 . The method of claim 11 wherein oxidizing the mercaptan salt with oxygen further comprises oxidizing the mercaptan salt with oxygen in the presence of an oxidation catalyst.

13 . The method of claim 12 wherein oxidizing the mercaptan salt with oxygen further comprises adding an oxygen supply stream to the rich caustic stream, wherein the oxygen supply stream comprises air.

14 . The method of claim 10 further comprising:
fractionating the hydrocarbon treated stream to produce a propane stream, a butane stream, and a C5+ stream.

15 . The method of claim 14 wherein fractionating the hydrocarbon treated stream further comprises:
depropanizing the hydrocarbon treated stream to produce the propane stream and a C4-5+ stream; and
debutanizing the C4-5+ stream to produce the butane stream and the C5+ stream.

16 . The method of claim 14 wherein fractionating the hydrocarbon treated stream further comprises:
debutanizing the hydrocarbon treated stream to produce a C3-4 stream and the C5+ stream; and
depropanizing the C3-4 stream to produce the propane stream and the butane stream.

17 . The method of claim 10 further comprising:
prewashing a feed stream with caustic to produce the washed feed stream.

18 . The method of claim 10 wherein feeding the washed feed stream into the extraction unit further comprises feeding the washed feed stream into the extraction unit, wherein the washed feed stream is a product of hydraulic fracturing of shale.

19 . The method of claim 10 wherein feeding the washed feed stream into the extraction unit further comprises feeding the washed feed stream into the extraction unit, wherein the washed feed stream comprises 90 mass percent hydrocarbons with 3 to 5 carbon atoms.

20 . An apparatus for producing low sulfur propane and butane comprising;
an extraction unit configured to react a mercaptan with caustic to form a mercaptan salt and produce a hydrocarbon treated stream and a rich caustic stream; a caustic regeneration unit fluidly coupled to the extraction unit, wherein the caustic regeneration unit is configured to react the mercaptan salt with oxygen and water to produce a disulfide; and a hydrocarbon fractionation zone fluidly coupled to the extraction unit, wherein the hydrocarbon fractionation zone is configured to fractionate hydrocarbons with 3 to 5+ carbon atoms into a propane stream, a butane stream and a C5+ stream.

Assignees

• Uop Llc

Inventors

• Laricchia Luigi
• Tertel Jonathan Andrew

Classifications

• C07C7/10 Primary

  by extraction, i.e. purification or separation of liquid hydrocarbons with the aid of liquids · CPC title

• C07C7/005

  Processes comprising at least two steps in series · CPC title