Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/48—Sulfur compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
  • B01D53/1493—Selection of liquid materials for use as absorbents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/30—Sulfur compounds
  • B01D2257/308—Carbonoxysulfide COS
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Definitions

• the present invention relates to an improved composition for selective removal of carbonyl sulfide (COS) with minimal absorption of carbon dioxide (CO 2 ) from an acid gas containing COS and CO 2 , and also to a method for selective removal of COS from an acid gas containing COS and CO using this improved composition.
• COS carbonyl sulfide
• CO 2 carbon dioxide
• Natural and synthesis gas streams derived from natural gas reservoirs, petroleum or coal, often contain a significant amount of carbonyl sulfide (COS) in addition to other impurities such as carbon dioxide (CO 2 ), hydrogen sulfide (H S), sulfur dioxide (SO 2 ), carbon disulfide (CS 2 ), and mercaptans.
• COS carbonyl sulfide
• H S hydrogen sulfide
• SO 2 sulfur dioxide
• CS 2 carbon disulfide
• mercaptans mercaptans
• Certain physical solvents have been widely used for the selective removal of H 2 S from gas streams containing H 2 S, CO and optionally, other components.
• dialkyl ethers of polyalkylene glycols are commonly specified for this purpose.
• Typical of the numerous disclosures of such solvents in the art is European Patent Application No. EP 0770420 A2 and U.S. Patent Nos. 3,737,392; 3,824,766; 3,837,143; 4,044,100; 4,336,233; 4,581,154; 4,741,745; and 4,946,620, among others. According to such references, it is well known that the solubility of H 2 S in these glycols is much higher than the solubility of CO 2 .
• tertiary alkanolamines methyldiethanolamine and triethanolamine for example
• tertiary alkanolamines have been widely used for the selective removal of H 2 S from gas streams which also contain CO . Users of these amines exploit the rapid reaction with H 2 S and the slow reaction with CO 2 to allow selective removal of H 2 S.
• the reaction of these amines with COS is about 100 times slower than the reaction with CO 2 .
• tertiary amines are relatively ineffective at separating COS or COS and H 2 S from CO 2 containing streams.
• Certain primary and secondary amines have been widely used for the simultaneous removal of H 2 S and CO 2 . These amines react rapidly with both H 2 S and CO 2 and are well suited for simultaneous removal of H 2 S and CO 2 . Although the reaction of COS with these amines is also about 100 times slower than the reaction with CO 2 , appreciable amounts of CO 2 and COS can be removed. Unfortunately, since COS reacts much more slowly with these amines than does CO 2 , selective removal of COS or COS and H 2 S with primary or secondary amines has proved difficult.
• U.S. Patent No. 3,989,811 discloses a multi-step process for removal of acid gases, that is, H 2 S, CO 2 , and sulfur containing compounds including CS 2 , COS, and various mercaptans from sour gases.
• acid gases that is, H 2 S, CO 2 , and sulfur containing compounds including CS 2 , COS, and various mercaptans from sour gases.
• H 2 S, CO 2 and COS are absorbed in a nonselective alkanolamine.
• the regenerated acid gases are then contacted with a selective amine to produce an H 2 S rich stripper off gas and a low pressure CO 2 rich stream.
• Suitable alkanolamines include methyldiethanolamine, triethanolamine, or one or more di- propanolamines, such as di-n-propanolamine or diisopropanolamine.
• the preferred absorbent for treatment of COS containing gas streams also contains a significant amount of a tetramethylene sulfone (the unsubstituted compound is known as sulfolane).
• sulfolane tetramethylene sulfone
• U.S. Patent No. 4,482,529 discloses a single step process for the selective removal of COS from a gas stream containing CO 2 .
• Small amounts of bicyclo tertiary amine are added to a physical solvent already known to be selective for H 2 S in the presence of CO 2 .
• addition of the bicyclo tertiary amine encourages hydrolysis of the COS to H 2 S and CO 2 .
• the net effect is to improve the absorption of COS without substantially increasing the absorption of CO .
• Applicable physical solvents include SELEXOLTM solvent (a blend of polyethylene glycol dimethyl ethers sold by Union Carbide Corporation under the trademark SELEXOL), sulfolane, methanol and others.
• U.S. Patent No. 4,524,050 (Chen et al.) discloses a process for hydrolyzing COS in gas streams to H 2 S and CO 2 using solid supported bicyclo tertiary amine catalyst.
• U.S. Patent No. 4,504,449 discloses a process for selective removal of H 2 S and possibly COS from a CO 2 containing gas stream using highly volatile secondary amines in an organic solvent. A complex regeneration scheme is required.
• Applicable secondary amines are diethyl amine, diisopropyl amine, methyl isopropyl amine, ethyl isopropyl amine, dipropyl amine, methyl n-butylamine, methyl isobutyl amine and methyl sec-butyl amine.
• Applicable organic solvents include alkylated polyethylene glycol ethers, tetrahydrothiophene dioxide etc.
• U.S. Patent No. 4,532,116 discloses a process for the removal of H 2 S and/or COS from synthesis gas using at least one secondary amine and an organic solvent. Although the process is selective for H S and COS in the presence of CO 2 , the process is complex. Two scrubbing zones are required - a preliminary desulfurizing zone using a conventional circulated and regenerated solution and a fine desulfurizing or scrubbing zone using unregenerated solvent. The fine desulfurizing zone contains a heat exchanger to condense the unregenerated solvent.
• Applicable organic solvents are methanol, ethanol and isopropanol.
• Applicable secondary amines are N-ethylethaneamine, N-(l- methylethyl)propaneamine, N-methyl-2-propanamine, N-ethyl-2-propanamine, N-propyl-1- propanamine, N-methyl- 1 -butanamine, N-2-dimethyl- 1 -propanamine, N-methyl-2- butanamine.
• U.S. Patent No. 4,749,555 discloses a process for selective removal of H 2 S and COS without absorbing CO 2 from a gas stream having a relatively large concentration of CO using bridgehead amines (bicyclotertiary amine or bicyclo amidine), tertiary amine, physical solvent and water.
• Applicable physical solvents include sulfolane, polyethylene glycol dimethyl ethers and others.
• U.S. Patent No. 4,980,140 discloses a process for selective removal of COS from H S using a solvent comprising a tertiary amine, a physical co-solvent and a minor amount of water.
• the useful physical co-solvent includes sulfones, sulfoxides, glycols and the mono and diethers thereof, 1,3-dioxo heterocyclic compounds (dioxane and dioxolane), aromatic ethers, aromatic hydrocarbons and N-alkylated lactams of gamma or omega amino acids.
• U.S. Patent No. 5,413,627 discloses the selective removal of H 2 S and COS from CO 2 using a physical scrubbing agent comprising a heterocycle having five or more ring atoms, which contains two heteroatoms, one of which is nitrogen and the other of which is oxygen or nitrogen.
• the nitrogen atom present in the ring is/are either double bonded or single bonded but, if single bonded, the nitrogen is organo-substituted.
• scrubbing agents are disclosed, including l,3-dimethyl-3,4,5,6-tetrahydro-2(lH)- pyrimidinone (DMTP).
• U.S. Patent No. 5,589,149 discloses absorption solvents for removing mercaptans from gas streams without the use of iodine.
• the solvent comprises alkyl ether of a polyalkylene glycol and a secondary monoalkanolamine and, optionally, other amines, such as dialkanolamines.
• U.S. Patent No. 6,277,345 Bl discloses the use of absorption liquid comprising at least one dialkanolamine, at least one polyalkylene glycol alkyl ether, and water for nonselective removal of CO 2 , H 2 S, COS and other acidic gases from a gaseous stream.
• U.S. Patent No. 6,102,987 discloses a process for removal of CO 2 and sulfur compounds from natural gas and raw synthesis gas with a mixture of N- formylmorpholine and N-acetylmorpholine at temperatures between -20 °C and +40 °C at pressure of 10 to 150 bar in absorbing operation.
• One aspect of the present invention concerns a solvent composition for removal of m a gas stream containing same, said composition comprising
• Ri is an alkyl group having from 1 to 6 carbon atoms
• R 2 is hydrogen or an alkyl group having from 1 to 4 carbon atoms
• Alk is an alkylene group, branched or unbranched, having from 2 to 4 carbon atoms, and n is from 1 to 10;
• R 3 is hydrogen, an alkyl group having from 1 to 6 carbon atoms, or the RjOH group; t is a branched or unbranched alkylene group having from 1 to 6 carbon atoms; R 5 , independently in each occurrence, is hydrogen or an hydroxyalkyl group having from 1 to 4 carbon atoms; and R 6 is hydrogen, an alkyl group having from 1 to 6 carbon atoms or an hydroxyalkyl group having from 1 to 4 carbon atoms.
• compositions for removal of m a gas stream containing same comprising a) l,3-dimethyl-3,4,5,6-tetrahydro-2(lH)-pyrimidinone;
• R 3 is hydrogen, an alkyl group having from 1 to 6 carbon atoms, or the RiOH group; Ri is a branched or unbranched alkylene group having from 1 to 6 carbon atoms; R 5 , independently in each occurrence, is hydrogen or an hydroxyalkyl group having from 1 to 4 carbon atoms; and R 6 is hydrogen, an alkyl group having from 1 to 6 carbon atoms or an hydroxyalkyl group having from 1 to 4 carbon atoms.
• the present invention concerns a process for selective removal of COS from a gas stream containing same, said process comprising treating the gas stream with a solvent composition comprising
• Ri is an alkyl group having from 1 to 6 carbon atoms
• R 2 is hydrogen or an alkyl group having from 1 to 4 carbon atoms
• Alk is an alkylene group, branched or unbranched, having from 2 to 4 carbon atoms
• n is from 1 to 10; and b) at least one alkanolamine compound of the formula
• R 3 is hydrogen, an alkyl group having from 1 to 6 carbon atoms, or the R OH group
• Ri. is a branched or unbranched alkylene group having from 1 to 6 carbon atoms
• R 5 independently in each occurrence, is hydrogen or an hydroxyalkyl group having from 1 to 4 carbon atoms
• R 6 is hydrogen, an alkyl group having from 1 to 6 carbon atoms or an hydroxyalkyl group having from 1 to 4 carbon atoms.
• the present invention concerns a process for selective removal of COS from a gas stream containing same, said process comprising treating the gas stream with a solvent composition comprising
• R 3 is hydrogen, an alkyl group having from 1 to 6 carbon atoms, or the RiOH group
• Rt is a branched or unbranched alkylene group having from 1 to 6 carbon atoms
• R 5 independently in each occurrence, is hydrogen or an hydroxyalkyl group having from 1 to 4 carbon atoms
• R 6 is hydrogen, an alkyl group having from 1 to 6 carbon atoms or an hydroxyalkyl group having from 1 to 4 carbon atoms.
• the present invention concerns a solvent composition for removal of COS from a gas stream containing same, said composition comprising
• R 3 is hydrogen, an alkyl group having from 1 to 6 carbon atoms, or the R 4 OH group
• R 4 is a branched or unbranched alkylene group having from 1 to 6 carbon atoms
• R 5 independently in each occurrence, is hydrogen or an hydroxyalkyl group having from 1 to 4 carbon atoms
• R 6 is hydrogen, an alkyl group having from 1 to 6 carbon atoms or an hydroxyalkyl group having from 1 to 4 carbon atoms.
• the present invention concerns a process for selective removal of COS from a gas stream containing same, said process comprising treating the gas stream with a solvent composition comprising
• R 3 is hydrogen, an alkyl group having from 1 to 6 carbon atoms, or the RtOH group;
• R4 is a branched or unbranched alkylene group having from 1 to 6 carbon atoms;
• R 5 independently in each occurrence, is hydrogen or an hydroxyalkyl group having from 1 to 4 carbon atoms;
• R 6 is hydrogen, an alkyl group having from 1 to 6 carbon atoms or an hydroxyalkyl group having from 1 to 4 carbon atoms.
• gas As used herein, the terms "gas”, “acid gas”, and “gaseous stream” are intended to refer to natural gas, hydrocarbon gas, synthesis gas, steam reformer-type gases, and any other gas containing COS, CO 2 and other gaseous components such as hydrogen sulfide, methane, ethane, propane, hydrogen, carbon monoxide, mercaptans etc.
• minimal additional removal of CO 2 means additional CO 2 absorption due to the presence of the amine additive is less than one third of the CO 2 present in the feed gas, all other factors being the same.
• the solvent compositions of the present invention have excellent selectivity for the removal of COS from a gaseous stream containing same with minimal additional removal of CO 2 .
• polyalkylene alkyl ethers of formula I suitable in the practice of the present invention are well known and include, without any limitation, diethylene glycol dimethyl ether, diethylene glycol diisopropyl ether, triethylene glycol dimethyl ether, triethylene glycol diisopropyl ether, tefraethylene glycol dimethyl ether, tefraethylene glycol diisopropyl ether, pentaethylene glycol dimethyl ether, pentaethylene glycol diisopropyl ether, hexaethylene glycol dimethyl ether, hexaethylene glycol diisopropyl ether, heptaethylene glycol
• Preferred polyethylene glycol alkyl ether is a mixture consisting of a dimethyl ethers of polyethylene glycols of formula CH 3 O(C 2 H O) n CH 3 wherein n is from 2 to 10.
• Particularly preferred polyethylene glycol alkyl ether is the mixture of dimethyl ethers of polyethylene glycols sold under the trademark SELEXOL by Union Carbide Corporation.
• SELEXOLTM solvent is a mixture of dimethyl ethers of polyethylene glycols comprising from 0 to 0.5 wt percent of diethylene glycol dimethyl ether, from 5 to 7 wt percent of triethylene glycol dimethyl ether, from 16 to 18 wt percent tefraethylene glycol dimethyl ether, from 23 to 25 wt percent of pentethylene glycol dimethyl ether, from 22 to 24 wt percent of hexaethylene glycol dimethyl ether, from 15 to 17 wt percent of heptaethylene glycol dimethyl ether, from 8 to 10 wt percent of octaethylene glycol dimethyl ether, from 3 to 5 wt percent of nonaethylene glycol dimethyl ether, and from 1 to 2 wt percent of decaethylene glycol dimethyl ether.
• SELEXOLTM solvent is widely used in gas treating applications for the removal of acidic gases.
• solvent factors low solubility
• applications specific factors low COS partial pressure
• Certain amine additives such as bicyclic tertiary amines and tertiary amines have been used, with some success, to improve removal of COS by SELEXOLTM solvent.
• the SELEXOLTM solvent containing alkanolamines of formula II hereinbefore or a piperazine compound of formula III hereinabove is surprisingly selective in removing COS in the presence of CO from gases.
• Alkanolamine compounds of formula II usefull in the practice of the present invention are well known compounds and include both primary and secondary alkanolamines.
• Preferred alkanolamine compounds of formula II are primary alkanolamines.
• Non-limiting examples of alkanolamine compounds are monoethanolamine (MEA), diethanolamine (DEA), methylethanolamine (NMEA), dusopropanolamine (DIP A), and 2-(2-aminoethoxy)ethanol (AEE) also known as diethylene glycolamine (available from Huntsman Corporation under the trademark DGA).
• the present invention is particularly useful in the desulfurization portion of an Integrated Combined Cycle Gasification (IGCC) process using an IGCC system consisting of a conventional SELEXOLTM solvent acid gas removal unit, a fixed bed catalytic converter for reducing the gas phase concentration of carbonyl sulfide (COS), and heat exchanger equipment upstream of the SELEXOLTM solvent unit.
• IGCC Integrated Combined Cycle Gasification
• the operating conditions of the process are those of the IGCC process. These operating conditions are well known to a person of an ordinary skill in the art.
• MEA is monoethanolamine
• DEA diethanolamine
• TEA triethanolamine
• NMEA methylethanoalmine
• DIPA dusopropanolamine
• HEP hydroxyethylpiperazine
• MDEA methyldiethanolamine
• DMEA dimethyethanolamine
• DBU l,8-diazabicyclo[5.4.0]undec-7-ene
• DBN is l,5-diazabicyclo[4.3.0]non-5-ene
• DABCO is l,4-diazabicyclo[2.2.2]octane, sold by Air Products and Chemicals, Inc. under the trademark DABCO;
• DMTP is l,3-dimethyl-3,4,5,6-tetrahydro-2(lH)-pyrimidinone
• Quinuclidine is 1,4-ethanolpiperidine
• AEE is 2-(2-aminoethoxy)ethanol.
• the SELEXOL TM solvent alone removes about 10 percent of the COS from the feed gas while the addition of about 3 wt percent of HEP or AEE to the SELEXOLTM solvent improves COS removal to 60-70 percent. Removal of CO 2 increases from 0 to 12-14 percent.
• DMTP solvent alone removes about 8 percent of the COS from the feed gas while the addition of about 3 wt percent of HEP or NMEA to the DMTP solvent improves COS removal to about 69-100 percent. Removal of CO 2 increases from 3 to 6-10 percent.
• the solvent compositions of the present invention showed a marked improvement in COS removal with minimal additional CO 2 removal.
• the solvent compositions of the present invention comprising the SELEXOLTM solvent and the alkanolamine of formula II or piparazine compound of formula III removed COS in an amount of from 17 percent to 52 percent as compared to the SELEXOLTM solvent alone which removed COS in an amount of only about 1 percent.
• the solvent composition of the present invention comprising DMTP and the alkanolamine of formula II removed COS in an amount of 40 - 100 percent as compared to DMTP alone which removed COS in an amount of from 3 - 8 percent.
• Such magnitude of improved removal of COS by the solvent compositions of the present invention is completely unexpected and unpredictable.

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