MXPA01003345A - Composition and process for removal of acid gases - Google Patents

Abstract

Alkanolamines of formula (I):R-NHCH2CH(OH)CH2CH3, or mixtures thereof wherein R is H, -CH2CH(OH)CH2CH3, an alkyl group having from 1 to 6 carbon atoms, an aryl group having from 6 to 12 carbon atoms, an aralkyl group having from 6 to 12 carbon atoms, or a cycloalkyl group having from 3 to 6 carbon atoms are effective in the removal of acidic gases from a fluid stream containing same and show superior degradation properties as compared to alkanolamines conventionally used in the gas purification applications.

Description

COMPOSITION AND PROCESS TO REMOVE ACID GAS This invention relates to a composition and method for removing acid gases such as, for example, H2S, CO2 and COS from a fluid stream containing them. The purification of fluids involves the removal of impurities from the fluid streams. Various methods for fluid purification are known and practiced. These methods for fluid purification generally fall into one of the following categories: absorption in a liquid, adsorption in a solid, penetration through a membrane, chemical conversion to another compound, and condensation. The absorption purification method involves the transfer of a component of a fluid to an absorbent liquid in which said component is soluble. If desired, the liquid containing the transferred component is subsequently stripped to regenerate the liquid. See, for example, "Gas Purification" by A. Kohl and R. Nielsen, 5th edition, Gulf Publishing, 1 997; "Gas Purification" by A. Kohl and F. C. Riesenfeld, 4th edition, Gulf Publishing, 1985; "Gas Purification" by A. Kohl and F. C. Riesenfeld, 3rd edition, Gulf Publishing, 1979; and "The Gas Conditioning Fact Book" published by The Dow Chemical of Canada, Limited, 1 962; all incorporated by reference to this. Aqueous solutions of various primary, secondary and tertiary alkanolamines, such as, for example, monoethanolamine (MEA), diethanolamine (DEA), diglycolamine (DGA), diisopropanolamine (DIPA), methyldiethanolamine (MDEA), and triethanolamine (TEA), have been used. , as absorbent liquids to remove acid gases from liquid and gaseous streams. In a regeneration method, the aqueous alkanolamine solution containing acid gas is then subjected to heating to regenerate the aqueous alkanolamine solution. Primary alkanolamines such as M EA and DGA, or secondary alkanolamines such as DEA or D I PA are generally suitable for highly exhaustive removal of CO2, however, they have the disadvantage of requiring high energy expenditure for regeneration. Tertiary alkanolamines, especially M DEA and TEA, require less energy consumption for regeneration, but since they do not react directly with CO2, they do not completely remove CO2 from the fluid stream. The tertiary alkanolamines are, however, suitable for the selective removal of H2S from a fluid containing both H2S and CO2, since the absorption rate for H2S is approximately the same for all alkanolamines. The chemistry of acid gas reactions with alkanolamine treatment solutions is well known and is described in many publications such as, for example, the aforementioned publications and references cited therein, and publications described below and references cited therein. same. Canadian Patent No. 1, 091, 429 (G. Sartori et al.) Discloses the use of aqueous solutions containing primary water-soluble monoamines having a secondary carbon atom attached to the amino group in gas purification applications. The primary monoamines having a secondary carbon atom attached to the amino group specifically mentioned in this reference as suitable are 2-amino-1-propanol, 2-amino-1-butanol, 2-amino-3-methyl-1-butanol, 2-amino-1-pentanol, 2-amino-1-hexanol and 2-aminocyclohexanol. It is noteworthy that this reference does not say anything at all about the degradation and corrosion power of these primary monoamines having a secondary carbon atom attached to the amino group. Chem. Eng. Comm. , 1996, Vol. 144, p. 103-1 12, "Effects of Composition on the Performance .. of Alcanolamine Blends for Gas Sweetening ", describes the influence of composition and mixing components on some of the parameters that can be used to monitor the performance of amines mixtures for aqueous mixtures of MDEA and MEA, MDEA and DEA, and MDEA and D IPA., Annual Laurance Reid Gas Condi- tioning Conference, March 1 -4, 1 998, p. 146-160, "Amine Degradation Chemistry in CO2 Service", describes the degradation chemistry of several ethanolamines in CO2 service. The conference promotes gas treatment solvents which are not formulated with primary or secondary ethanolamines as a solution for the loss regimes associated with the use of various ethanolamines such as MDEA, MMEA and DEA. The primary and secondary alkanolamines can also be used as activators in combination with tertiary alkanolamines to remove CO2 to as low as 100 parts per million (ppm) or less requiring less regeneration energy than is required using the primary or secondary alkanolamines alone. The Patents of E. OR . , Nos. 5,209,914 and 5,366,709 show how activators such as ethylmonoethanolamine (EMEA) or butylmonoethanolamine (BMEA) can be used with M DEA to achieve better CO2 removal than with MDEA alone. The Patent of E. U. , No. 4,336.23.3 discloses that the use of a combination of piperazine and MDEA results in an improved acid gas removal. However, a particular disadvantage of piperazine is that the piperazine carbamate formed from the reaction of piperazine and CO2 is not soluble in the aqueous solution of MDEA / piperazine. Thus, the level of additive is limited to approximately only 0.8 moles / liter, which severely limits the capacity of the solvent, or requires higher flow rates to treat the same amount of fluid as those required by other MDEA activator mixtures. alkanolamine. The main disadvantage of using primary and secondary alkanolamines such as MEA, DEA and DI PA is that the CO2 reacts with these alkanolamines to form degradation compounds such as oxazolidinones and ethylenediamines. C. J. Kim, Ind. Eng. Chem. Res. 1988, 27, and references cited in the same sample as the DEA reacts with CO2 to form 3- (2-hydroxyethyl) -2-oxazolidinone (HEO) and N, N, N'-tris (2-hydroxyethyl) ethylene diamine (THEED). This reference also shows how DI PA reacts to form 3- (2-hydroxypropyl) -5-methyl-2-oxazolidinone (HPMO).

These degradation compounds reduce the amount of alkanolamine available for acid gas removal, increase the viscosity of the solution and potentially increase the corrosion power of the solvent. It is evident that there is still a great need and interest in the gas purification industry for alkanolamine compounds that are effective in the removal of acid gases from fluid streams and that have improved degradation properties compared to alkanolamines commonly used for this purpose It has now been discovered that 1-amino-2-butanol and its derivatives are effective in removing acid gases from fluid streams and that they have superior degradation properties compared to alkanolamines conventionally used in the gas purification industry. In the context of the present invention the term "fluid stream" encompasses both a gaseous stream and a liquid stream. In one aspect the present invention is an aqueous solution adapted for use in the removal of acid gases from a fluid stream containing them, said aqueous solution comprising an effective amount of an alkanolamine of the formula: R-NHCH2CH (OH) CH2CH3 (I) or mixtures thereof wherein R is H, -CH2CH (OH) CH2CH3, an alkyl group having from 1 to 6 carbon atoms, an aryl group having from 6 to 12 carbon atoms, an aralkyl group having from 6 to 1 2 carbon atoms, or a cycloalkyl group having from 3 to 6 carbon atoms. In another aspect the present invention is a process for removing acid gases from a fluid stream containing them, said process comprising contacting said fluid stream containing acid gases with an aqueous solution comprising an effective amount of an alkanolamine of the formula: R-NHCH2CH (OH) CH2CH3 (I) or mixtures thereof wherein R is H, -CH2CH (OH) CH2CH3, an alkyl group having from 1 to 6 carbon atoms, an aryl group having from 6 to 12 carbon atoms, an aralkyl group having 6 to 12 carbon atoms, or a cycloalkyl group having from 3 to 6 carbon atoms. The alkanolamines of formula I above have been found to be effective for removing acid gases, particularly CO2, H2S, COS or mixtures thereof, from a fluid stream containing the same and still exhibit greatly improved degradation properties compared to alkanolamines conventionally used in the gas purification industry. These compounds are known and their synthesis is described in several publications such as, for example, J. Zienko, M. Stoyanowa-Antoszczyszyn and J. Myszkowski, Chemik 1/1 991, p. 8-9, and references cited therein.

The alkanolamines of the formula I in which R is H, -CH 2 CH (OH) CH 2 CH 3, or an alkyl group having 1 to 6 carbon atoms are preferred in the practice of the present invention with those in which R is H , -CH2CH (OH) CH2CH3, or an alkyl group having 1 to 4 carbon atoms being further preferred. Particularly preferred are 1-amino-2-butanol (M BA) and bis (1-hydroxybutyl) -amine (DBA), N-methyl-2-hydroxybutylamine and N-ethyl-2-hydroxybutylamine, with 1-amino-2- butanol and bis (1-hydroxybutyl) amine (DBA) with the most preferred alkanolamines being for use in the present invention. The alkyl group having from 1 to 6 carbon atoms contemplated by R in formula 1 can be a straight or branched chain alkyl group. Non-limiting examples of such alkyl groups are: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, and hexyl. The aryl group having from 6 to 12 carbon atoms contemplated by R in formula 1 can be substituted or unsubstituted. Non-limiting examples of suitable aryl groups are: phenyl and tolyl. The aralkyl group having from 6 to 12 carbon atoms contemplated by R in formula 1 can be substituted or unsubstituted. Non-limiting examples of suitable aralkyl groups are: benzyl and phenethyl. The cycloalkyl group having from 3 to 12 carbon atoms contemplated by R in formula 1 can be substituted or unsubstituted. Non-limiting examples of suitable cycloalkyl groups are: cyclohexyl and methylcyclohexyl.

In the present invention, the aqueous solution of an alkanolamine of the formula 1 can be used alone, or in combination with tertiary alkanolamines such as, for example, methyldiethanolamine (MDEA), dimethylethanolamine (DMEA) and triethanolamine (TEA) to remove acid gases from fluids The alkanolamine of the formula I is present in the aqueous solution of the present invention in an amount effective to remove acid gases from a fluid stream. When the alkanolamine of the formula I is used alone, it is typically present in an amount of from 7 to 50, preferably from 1 to 40, more preferably from 20 to 30, weight percent based on the total weight of the solution aruosa The optimum amount of the alkanolamine of the formula I will depend on the composition of the fluid stream, fluid outlet requirement, flow rate, and available energy to strip the solvent. A person of ordinary skill in the art could quickly determine the optimum amount of the alkanolamine of formula 1. When the alkanolamine of the formula I is used as an activator in combination with a tertiary alkanolamine, the amount used can vary very widely, but is generally present in an amount from 1 to 30, preferably from 5 to 20, more preferably from 7. at 1 5 percent by weight based on the total weight of the aqueous solution. The tertiary alkanolamine is generally used in an amount from 25 to 60, preferably from 25 to 40, more preferably from 30 to 40, percent by weight based on the total weight of the aqueous solution. The process of the present invention can be carried out in any conventional equipment for the removal of acid gases from fluids and detailed procedures are well known to a person of ordinary skill in the art. See, for example, the Patent of E. U. , No. 1, 783,901 (Bottoms) and subsequent improvements which are known in the art. The process according to the present invention can conveniently be carried out in any suitable absorber. The large number of absorbers used for gas purification operations include packaged, plate, or spray towers. These absorbers are interchangeable to a considerable extent even though certain specific conditions may favor one over the other. In addition to conventional packed, or spray, towers, specialized absorption towers have been developed to meet specific process requirements. Examples of these specific towers include shock dish scrubbers and turbulent contact scrubbers. The process of the present invention can be carried out on any, packed, dish or spray towers, and may contain other peripheral equipment as necessary for optimal process operation. Such peripheral equipment may include an inlet gas separator, a treated gas fusion promoter, a solvent flashing tank, a particulate filter and a carbon bed purifier. The rate of inflow of gas varies depending on the size of the equipment, but is typically between 0.141 863 and 2.837726 million standard cubic meters per day (MCSD). The solvent circulation regime will depend on the amine concentration, gas flow rate, gas composition, total pressure and specification of the treated fluid. The solvent circulation regime is typically between 1 9 and 19,000 liters per minute (Ipm). The internal pressure of the absorber can vary between 0 and 84.5 kg / cm2 man. depending on the type of fluid that is processed. The absorbers, disposers and peripheral equipment useful for carrying out the process of the present invention are well known in the art and are described in many publications including the aforementioned references. In the process of the present invention, a fluid containing an acid gas is contacted with an aqueous solution comprising an effective amount of an alkanolamine of the formula 1 at a temperature from room temperature (about 25 ° C) to 93 ° C. ° C. The temperatures inside the stripping tower, if one is used, they can vary between 82 ° C and 1 27 ° C. The pressure above the stripper is typically between 0 and 1 .40 kg / cm2 man. Optionally, corrosion inhibitors, scale inhibitors and defoamers can be employed.

The following examples are offered to illustrate, but not limit the invention. Percentages, relationships and parts are by weight unless otherwise stated.

EXAMPLES 1 TO 3 AND COMPARATIVE EXAMPLES C-1 TO C-3 Experiments with dissolved CO2 were made by spraying the compressed CO2 (Liquid Carbonic HI-DRY Grade, purity greater than 99.99 percent) through a Cole-Palmer fluidometer of 0-1 50 ml / min. at a rate of 50 ml / min. for 90 min. to an aqueous solution (200 ml) comprising MDEA (2.94 mol, 35 percent) and an additive (1.68 mol) contained in a 250 ml jacketed flask the aqueous solution was stirred with a magnetic stir bar while being sprayed continuously with CO2. The temperature of the solution (31 ° C) was adjusted using a GCA Precision R10 circulation bath and was monitored using a thermometer. A polycarbonate cover with slits for the thermometer, gas inlet and outlet, was used in the upper part of the flask to prevent CO2 from entering the atmosphere. After 90 minutes of continuous spraying, the solution was analyzed for dissolved CO2 according to ASTM Method "D513 Total CO2 and Water Dissolved". The additives used and results obtained are given in Table 1 below.

Table 1 CO2 reaction with MDEA / Additive This information shows that aqueous solutions containing MBA absorbed more CO2 than those containing DEA or EMEA. The amount of CO2 absorbed by solutions containing MBA (average: 4.13 percent by weight) is statistically similar to the amount of CO2 absorbed by the solution containing MEA (4.16 percent by weight). Similarly, the amount of CO2 absorbed by the aqueous solution containing DBA is also statistically similar to the amount of CO2 absorbed by the aqueous solutions containing DEA or EMEA.

EXAMPLES 4 AND 5 AND COMPARATIVE EXAMPLES C-4 AND C-5 Autoclave degradation tests were performed on equimolar amine solutions using 0.050 moles of CO2 per mole of amine at 126.7 ° C. An aqueous solution was added (1, 1 00 ml) containing MDEA (35 weight percent; 1.68 mole), DEA (1 7.7 weight percent; 1.68 mole) or MBA (1.5 weight percent; 1.68 mole) to an autoclave Parr of two liters. Then each solution was charged with CO2 such that the charged CO2 was 0.050 mol of CO2 per mol of total amine. The solution was then heated for 28 days at 126.7 ° C. After 28 days, the solutions were analyzed by gas chromatography (GC) and chromatography / gas mass spectrometry (GC / MS) to determine the amount of the additive amine remaining in the solution and for the presence of degradation / conversion products. The results obtained are given in Table 2 below.

Table 2 Degradation Tests This information clearly shows the unexpected advantage of MBA on EM EA and DEA. The information shows that substantially all of the MBA remains in the solution after 28 days without detection of any degradation product while during the same time substantial amount of EMEA and DEA has been lost due to its reactivity with CO2 and conversion to products of undesirable reaction.

EXAMPLES 6 AND 7 AND EXAMPLE COMPARATIVE PLATES C-6 AND C-7 Autoclave degradation tests were performed on equimolar amine solutions using 0.050 moles of CO2 per mole of amine at 26.7 ° C. An aqueous solution was added (1 , 100 ml) containing MDEA (35 weight percent), and either EMEA (15 weight percent), BMEA (1 5 weight percent), MBA (1 5 weight percent) or DBA (15 percent by weight) to a Parr two-liter autoclave. Then each solution was charged with CO2 such that the charged CO2 was 0.050 mol of CO2 per mol of total amine. The solution was then heated for 28 days at 26.7 ° C. After 28 days, the solutions were analyzed by gas chromatography (GC) and chromatography / gas mass spectrometry (GC / MS) to determine the amount of the additive amine remaining in the solution and for the presence of degradation / conversion products. The amount of EMEA, BMEA, MBA (two runs) and DBA remaining in the solution after 28 days was 1 0.6, 10.4, 15.1, 14.99 and 12.3 percent by weight, respectively. The EMEA was converted to 3 weight percent of N, N'- (2-hydroxyethyl) ethylene diamine. The BMEA was converted to 3.2 weight percent of N, N'-dibutyl-N- (2-hydroxyethyl) ethylene diamine plus a small amount (less than 0.5 weight percent) of N-butyl-2-oxazolidinone. The MBA showed very little degradation. Less than 0.2 weight percent of what is possibly an oxazolidinone or substituted ethylene diamine was detected by GC and GC / MS. The DBA was converted to 2.9 weight percent of a product that was preliminarily identified as N- (2-hydroxybutyl) -2-oxazolidinone by GC / MS analysis. The results are given in Table 3 below.

Table 3 Degradation Tests This information also shows the unexpected advantage of MBA and DBA on EMEA and BMEA. The information demonstrates that substantially all of the MBA remains in the solution after 28 days without detection of essentially any degradation product while during the same time a substantial amount of EM EA and DEA has been lost due to its reactivity with CO2 and conversion. to undesirable reaction products.

EXAMPLE 9 AND COMPARATIVE EXAMPLE C-8 Autoclave degradation tests were carried out on 2.80 mol amine solutions using 0.050 mol of CO2 per mol of amine at 126.7 ° C. An aqueous solution (1.100 ml) was added. contains M EA (1 7.7 weight percent, 2.80 mol). or MBA (25 weight percent, 2.80 mol) to a Parr two-liter autoclave. Then each solution was charged with CO2 such that the charged CO2 was 0.050 mol of CO2 per mol of total amine. The solution was then heated for 28 days at 126.7 ° C. After 28 days, the solutions were analyzed by gas chromatography (GC) and chromatography / gas mass spectrometry (GC / MS) to determine the amount of the amine. additive remaining in the solution and for the presence of degradation / conversion products. The amount of MEA and MBA remaining in the solution after 28 days was 16.47 and 24.71 weight percent, respectively. The GC and GC / MS did not positively identify any of the small degradation peaks for MEA or MBA runs. The results are given in Table 4 below.

Table 4 Degradation Tests

Claims (18)

1. CLAIMS 1. An aqueous solution adapted for use in the removal of acid gases from a fluid stream containing them, said aqueous solution comprising an effective amount of an alkanolamine of the formula: R-NHCH2CH (OH) CH2CH3 (I) or mixtures thereof wherein R is H, - CH2CH (OH) CH2CH3, an alkyl group having from 1 to 6 carbon atoms, an aryl group having from 6 to 12 carbon atoms, an aralkyl group having from 6 to 12 carbon atoms, to 12 carbon atoms, or a cycloalkyl group having from 3 to 6 carbon atoms.
2. 2. The aqueous solution according to claim 1 wherein the alkanolamine of the formula I is present in an amount of from 7 to 50 weight percent.
3. 3. The aqueous solution according to claim 1 further comprising a tertiary alkanolamine.
4. 4. The aqueous solution of claim 3 wherein the alkanolamine of the formula I is present in an amount from 1 to 30 percent and the tertiary alkanolamine is present in an amount from 25 to 60 percent.
5. 5. The aqueous solution according to claim 3 wherein the tertiary alkanolamine is selected from the group consisting of methyldiethanolamine, dimethylethanolamine and triethanolamine.
6. 6. The aqueous solution according to claim 1 or claim 3 wherein R in the formula I is H, -CH 2 CH (OH) CH 2 CH 3, or an alkyl group having from 1 to 6 carbon atoms.
7. 7. The aqueous solution according to claim 1 or claim 3 wherein the alkanolamine of the formula I is selected from the group consisting of 1-amino-2-butanol, N-methyl-2-hydroxybutylamine and N-ethyl- 2-hydroxybutylamine.
8. 8. The aqueous solution according to claim 7 wherein the alkanolamine of the formula I is present in an amount of from 1 to 30 weight percent and further containing methyldiethanolamine in an amount from 25 to 60 weight percent.
9. 9. The aqueous solution according to claim 7 wherein the alkanolamine of the formula I is a mixture of 1-amino-2-butanol and bis (1-hydroxy butyl) amine.
10. 10. A process for removing acid gases from a fluid stream containing them, said process comprising contacting said fluid stream with an aqueous solution comprising an effective amount of an alkanolamine of the formula: R-NHCH2CH (OH) CH2CH3 (I) or mixtures thereof wherein R is H, - CH2CH (OH) CH2CH3, an alkyl group having from 1 to 6 carbon atoms, an aryl group having from 6 to 12 carbon atoms, an aralkyl group having 6 to 12 carbon atoms, or a cycloalkyl group having from 3 to 6 carbon atoms. eleven .
11. The process according to claim 1 wherein the alkanolamine of the formula I is present in an amount of from 7 to 50 weight percent.
12. The process according to claim 1 wherein the aqueous solution further comprises a tertiary alkanolamine.
13. The process according to claim 12 wherein the alkanolamine of the formula I is present in an amount of from 1 to 30 percent and the tertiary alkanolamine is present in an amount of from 25 to 60 percent.
14. The process according to claim 1 wherein the tertiary alkanolamine is selected from the group consisting of methyldiethanolamine, dimethylethanolamine and triethanolamine.
15. 15. The process according to claim 10 or claim 12 wherein R in formula I is H, -CH 2 CH (OH) CH 2 CH 3, or an alkyl group having from 1 to 6 carbon atoms.
16. The process according to claim 10 or claim 12 wherein the alkanolamine of the formula I is selected from the group consisting of 1-amino-2-butanol, bis (1-hydroxybutyl) amine, N-methyl-2 -hydroxybutylamine and N-ethyl-2-hydroxybutylamine.
17. The process according to claim 16 wherein the alkanolamine of the formula I is present in an amount of from 1 to 30 weight percent and the solution further contains methyldiethanolamine in an amount of from 25 to 60 weight percent.
18. 18. The process according to claim 16 wherein the alkanolamine of the formula I is a mixture of 1-amino-2-butanol and bis (1-hydroxybutyl) amine.