Gas separation: processes – Solid sorption – Inorganic gas or liquid particle sorbed
Reexamination Certificate
2002-05-01
2004-05-18
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
Solid sorption
Inorganic gas or liquid particle sorbed
C095S121000, C095S135000, C095S136000, C095S139000
Reexamination Certificate
active
06736879
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a novel process to remove a portion of acid gas from a sulfur compound stream to produce a low acid gas sulfur product. More specifically, this invention relates to a novel process to remove a portion of acid gas from the sulfur compound stream by adsorption on an adsorption media followed by regeneration of the adsorption media when the adsorption capacity has been reached.
BACKGROUND OF THE INVENTION
Generally, when a sulfur compound stream such as dimethylsulfide (DMS) or methyl mercaptan, is produced, it can contain carbon disulfide (CS
2
) in the range of 0 to about 0.5 wt %. Various methods for removing CS
2
from DMS and mercaptans are known in the art. Treatment with aqueous caustic for CS
2
removal is a possible route for producing a low CS
2
DMS. In this process, aqueous caustic is added to the sulfur compound stream in a tank to form a mixture. The mixture is circulated through a roll pump. Subsequently, the mixing is stopped and two phases, an aqueous phase and a an organic phase are formed. The two phases are allowed to separate, and the aqueous phase is drained off the bottom of the tank.
However in this process, it is necessary to add a phase transfer agent such as methanol or trimethyl amine, in order to provide adequate contact between the aqueous phase and the organic phase. Subsequent draining of the aqueous caustic can cause a high total organic carbon (TOC) count at plant wastewater systems if this route is employed. There is a need for an efficient, environmental-friendly process to remove acid gas from a sulfur compound stream.
Alternatively, the acid gas can be removed via distillation. However, CS
2
and DMS form an azeotrope that limits the ultimate purity of DMS that can be obtained via distillation.
Other markets for high purity DMS (low CS
2
) may become available in the future. Dimethyl sulfoxide (DMSO), which is produced via partial oxidation of high purity DMS, is one possibility. Another market opportunity is low CS
2
DMS for ethylene furnace treatment. High CS
2
content in the DMS for treatment of the cracking furnace tubes can result in off specification C
5
+ streams which in turn cause a number of unfavorable consequences in downstream processes. The inventors provide such a process in this patent application.
A novel method to remove acid gas from a sulfur compound stream is disclosed. The acid gas consists of at least one compound selected from the group consisting of carbon disulfide (CS
2
), carbonyl sulfide (COS), carbon dioxide (CO
2
), or hydrogen sulfide (H
2
S). The sulfur compound stream is selected from a group consisting of sulfides, disulfides, or thiols (mercaptans). Preferably, the S compound stream is selected from one or more of the following: DMS, diethylsulfide (DES), dimethyldisulfide (DMDS), methyl ethyl sulfide (MES), methyl isopropyl sulfide, methyl mercaptan, or ethyl mercaptan. Specifically, the method relates to a novel process to remove CS
2
from a sulfur containing stream by adsorption on an adsorption media comprising an activated alumina adsorbent followed by regeneration of the activated alumina after adsorption capacity has been reached. The adsorption media comprises an activated alumina, which has been previously treated with one or more alkali metal compounds, one or more alkaline earth metal compounds, or a mixture thereof; then regenerating the adsorbent after the adsorption capacity has been reached. Specifically, the adsorption media comprises an activated alumina, which has been previously treated with caustic; then regenerating the adsorbent after the adsorption capacity has been reached. Preferably, the caustic used in the treatment of the activated alumina is sodium hydroxide (NaOH). The activated alumina will adsorb acid gases (CO
2
, COS, H
2
S and CS
2
) from liquid hydrocarbon streams. The process to adsorb acid gas with activated alumina from a liquid hydrocarbon stream is disclosed in U.S. Pat. Nos. 4,835,338 and 4,493,715 herein incorporated by reference. However, using the alumina impregnated with caustic or other adsorbent medias to remove acid gas from a sulfur containing stream would not be readily apparent by one skilled in the art. One skilled in the art may believe that cleaving of sulfur compounds in the sulfur compound stream could occur thus making the ability of the adsorbent to remove acid gas ineffective. However, a new use and a process have been developed to use activated alumina to remove acid gas from the sulfur compound stream.
SUMMARY OF THE INVENTION
An object of this invention is to remove a portion of acid gas from a sulfur compound stream to produce a low acid gas sulfur product.
Another object of this invention is to remove a portion of the acid gas from a wet sulfur compound stream to produce a low acid gas sulfur product.
Another object of this invention is to provide a process for the removal of a portion of CS
2
from a sulfur compound stream by adsorption on an adsorption media comprising an activated alumina adsorbent followed by regeneration of the activated alumina after the adsorption capacity has been reached.
Another object of this invention is to provide an improved process for removal of a portion of CS
2
from a sulfur compound stream by adsorption on a an adsorption media comprising an activated alumina which has been previously treated with one or more alkali metal compounds, alkaline earth metal compounds, or a mixture thereof, and then regenerating the adsorbent after the adsorption capacity has been reached.
Another object of this invention is to provide an improved process for removal of a portion of CS
2
from a sulfur compound stream by adsorption on a adsorption media comprising an activated alumina which has been previously treated with caustic.
Another object of this invention is to provide a process to remove CS
2
from a DMS stream by adsorption on a an adsorption media comprising adsorbing said CS
2
in an adsorption zone to remove a portion of said CS
2
from said DMS stream to produce a low CS
2
DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been previously treated with one or more alkali metal compounds, one or more alkaline earth metal compounds, or a mixture thereof.
Another object of this invention is to provide a process to remove CS
2
from a DMS stream by adsorption on a an adsorption media comprising adsorbing said CS
2
in an adsorption zone to remove a portion of said CS
2
from said DMS stream to produce a low CS
2
DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been treated with caustic.
Another object of this invention is to provide a process to remove CS
2
from a DMS stream by adsorption on a an adsorption media comprising adsorbing said CS
2
in an adsorption zone to remove a portion of said CS
2
from said DMS to produce a low CS
2
DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been previously treated with one or more alkali metal compounds, one or more alkaline earth metal compounds, or a mixture thereof, wherein said adsorber is operated at a temperature in a range of −25° C. to about 100° C.; wherein said adsorber is operated to its adsorption capacity and regenerated with nitrogen or natural gas at a temperature in a range of 235° C. to 300° C.
Another object of this invention is to provide a process to remove CS
2
from a DMS stream by adsorption on a an adsorption media comprising adsorbing said CS
2
in an adsorption zone to remove a portion of said CS
2
from said DMS to produce a low CS
2
DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been treated with caustic; wherein said adsorber is operated at a temperature in a range of −25° C. to about 100° C.; wherein said adsorber is operated
Hasenberg Dan M.
Refvik Mitchell D.
Zisman Stan A.
Chevron Phillips Chemical Company LP
Jenkens & Gilchrist
Spitzer Robert H.
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