WO2012068327A1

WO2012068327A1 - Acid gas absorbent composition

Info

Publication number: WO2012068327A1
Application number: PCT/US2011/061118
Authority: WO
Inventors: Alan M. Blair; Keith N. Garside; William J. Andrews; Kailas B. Sawant
Original assignee: Nalco Company
Priority date: 2010-11-19
Filing date: 2011-11-17
Publication date: 2012-05-24
Also published as: CA2817549A1; US8765083B2; CA2817549C; US8765951B2; MX2013005440A; CN103221125B; AU2011329882A1; CN103221125A; BR112013012169B1; AU2011329882B2; EA024196B1; EA201390548A1; US20130240782A1; BR112013012169A2; EP2640507A1; EP2640507A4; EP2640507B1; BR112013012169B8; US20120128561A1

Abstract

This invention provides novel compositions comprising substituted polyamines as acid gas scrubbing solutions and methods of using the compositions in an industrial system. The invention relates to the use of such polyamine compounds in industrial processes to remove acidic contaminants from natural and industrial fluid streams, such as natural gas, combustion gas, natural gas, synthesis gas, biogas, and other industrial fluid streams. The compositions and methods of the invention are useful for removal, absorption, or sequestration of acidic contaminants and sulfide contaminants including CO₂, H₂S, RSH, CS₂, COS, and SO

Description

ACID GAS ABSORBENT COMPOSITION

TECHNICAL FIELD OF THE INVENTION

[001] This invention relates generally to the use of novel compounds as acid gas scrubbing solutions. More specifically, the invention relates to the use of substituted heterocyclic amines and polyamine compounds in industrial processes to remove acidic contaminants from natural and industrial fluid streams, such as natural gas, combustion gas, synthetic gas streams, and hydrocarbon fluids. The invention has particular relevance to processes for removal of carbon dioxide from gas streams having sour gas impurities.

BACKGROUND OF THE INVENTION

[002] Natural gas is a mixture of gaseous hydrocarbons and non-hydrocarbon impurities and contaminants. Removal of, for example, carbon dioxide and acidic sulfide contaminants (e.g., CO₂, H₂S, RSH, CS₂, COS, SO₂, etc.) to meet quality and regulatory requirements in natural gas that is fed into distribution pipelines is a major industrial burden. Such contaminants are often corrosive and may also impair the caloric value of the gas. In addition, increasing concerns of global warming from CO₂ and other emissions has prompted significant investments into methods of capturing such contaminants more efficiently and economically.

[003] Aqueous solutions of commonly available commodity alkanolamines are generally used as scrubbing solutions (chemical absorbents) in gas processing. The purpose of these scrubbing systems is to remove acidic contaminants from the raw gas stream. As energy sources are being depleted and environmental restrictions are tightening, the economic use of the "bottom of the barrel" in gasification processes is increasing. There are many new projects being sanctioned, most of which would need acid gas clean-up to remove contaminants during processing. Removing CO₂ from flue gases is also important for a variety of reasons, such as a secondary CO₂ market, enhanced oil recovery, and greenhouse gas reduction. [004] Weak organic bases, such as monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MD£A) comprise many of the typical alkanolamine solvents known in the art. MDEA is known to have advantages for CO₂ removal and other acid gas contaminants in high-pressure gas streams. The amount of energy required to regenerate the MDEA is low because it is a relatively weak base and therefore the chemical bond formed during the reaction with CO₂ is weaker than with other commonly used alkanolamines. A secondary benefit lies in the nature of the chemical bond formed during absorption. As a tertiary alkanolamine, MDEA reacts with CO₂ to form a bicarbonate ion rather than a carbamate, which results in a reaction ratio MDEA to CO₂ of 1 :1. In contrast, other commonly used primary and secondary alkanolamines preferentially form a carbamate and require a reaction ratio of 2: 1. The reaction between CO₂ and tertiary alkanolamines (e.g., MDEA) is typically of a greater efficiency than between CO₂ and other commonly used primary and secondary alkanolamines. These combined benefits result in a process of greater efficiency and capacity than is possible with commercial primary and secondary alkanolamines such as MBA and DBA.

[005] A disadvantage of using tertiary alkanolamines is that CO₂ is indirectly absorbed, resulting in a weak driving force and slow rate of reaction compared to other commercial alkanolamines. In high-pressure gas contacting systems the effect of the weak driving force is minimized due to the higher fraction of CO₂ that can be achieved in the liquid resulting from the high CO₂ partial pressure in the gas above it. When gasses are contacted at low pressure, the driving force is weak as the partial pressure of CO₂ is also weak. Thus, there is no beneficial effect of pressure, and the CO₂ equilibrium established between the gas and liquid is low. Tertiary alkanolamines are not normally used in low-pressure applications because of their low equilibrium loading. Other more commonly used primary and secondary amines such as MEA and DEA, which are stronger bases, are used in these applications due to their higher driving force and increased rate of reaction with CO₂. In these low-pressure situations, the disadvantage of the inefficient carbamate reaction is outweighed by the greater equilibrium liquid distribution achieved.

[006] In an effort to increase the capacity of MDEA for CO₂ at low partial pressure, a number of improvements to the basic MDEA process have been developed. These improvements typically involve the addition of small amounts of primary or secondary amines to the MDEA solution (as described in U.S. Patent Nos. 5,209,914 and 5,366,709 and PCT Application No. WO 03/013699). The resulting mixtures arc commonly described as formulated or blended MDEA with additives referred to as "catalysts," "absorption accelerators," or "activators" (e.g., U.S. Patent No. 6,740,230). These additives generally function by increasing the rate of CO₂ absorption into the MDEA blend solution at low CO₂ partial pressure thereby increasing the fraction of CO₂ in the liquid as compared to the MDEA solution alone.

[007] Although effective in the removal of CO₂ as described, the commercial application of known formulated solvents has less than ideal operating characteristics. Some of the additives used for formulating have limited solubility in MDEA, which reduces their effectiveness, and their commonly lower boiling points (some are not lower) in turn create difficulties in maintaining their concentration. Moreover, the reaction products of the additives with CO₂ are also problematic. As they are stronger organic bases than MDEA these blends have a tendency to require more energy for regeneration and their products have limited solubility, Such characteristics limit their effectiveness and the efficiency of the overall process if their concentration exceeds approximately 20% of the total amine in solution.

[008] There thus exists an industrial need for improved compositions and methods for recovering acidic contaminants from both high and low pressure systems. A particular need exists for products having the benefits of both low-pressure equilibrium capacity of primary or secondary amines and the efficiency of tertiary amines within a single compound of reduced volatility.

BRIEF SUMMARY OF THE INVENTION

[009] This invention accordingly provides novel compositions for removing carbon dioxide and acidic sulfide contaminants from fluid streams, for example, natural gas, synthesis gas, combustion gas, biogas, and other industrial fluid streams. Through this disclosure reference to gas or fluid streams is intended to encompass, without limitation, all such fluids. In a preferred embodiment, the compositions of the invention are used for removal, absorption, or sequestration of CO₂. In other preferred embodiments, the compositions are used for removal of other acidic contaminants, including, without limitation, acidic and sulfide contaminants, such as CO₂ , H₂S, RSH, CS_2, COS, and SO₂.

[0010] In an aspect, the invention is an absorbent liquid composition for absorbing acidic contaminants from fluid streams in an industrial process. The composition includes at least one absorbent component having the following general formula, structure (I).

R₁ is H, alkyl, aminoalkyl, or structure (II). Preferably, if R₁ is H, then at least one of R₁₀, R₁₁, R₁₂, or R₁₃ is not H, and if R₁ is structure (II), then at least one of R₁₀, R₁₁, R₁₂, R₁₃, R₁₄, R₁₅, R₁₆, or R₁₇ is not H. Each R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₁₀, R₁₁, R₁₂, R₁₃, R₁₄, R₁₅, R₁₆ , and R₁₇ are independently H, alkyl, or aminoalkyl, and each m, n, and o are independently 0, 1, or 2 and each p and q are independently 0, 3 , 2, 3, or 4.

[0011] In another aspect, the invention is a process for reducing acidic contaminants in an industrial fluid stream. The process includes contacting the fluid stream with the described composition to form a washed, fluid stream and a rich acid gas scrubbing liquid. At least a portion of the composition including at least a portion of the described absorbent component(s) is regenerated from the rich acid, gas scrubbing liquid.

[0012] It is an advantage of the invention to provide a novel composition having a specific molecular structure that offers reduced volatility and a working capacity for acidic contaminants greater than commonly used alkanolamine solvents in both low and high-pressure environments, [0013] It is another advantage of the invention to provide a novel composition that reduces acidic contaminants in natural synthesis, and flue gases and has an increased liquid- capacity for acidic contaminants at low gas pressure.

[0014] An additional advantage of the invention is to provide a novel composition that reduces acidic contaminants in natural, synthesis, and flue gases and has reduced energy of regeneration,

[0015] Another advantage of the invention is to provide a novel composition that reduce s acidic contaminants in natural, synthesis, and flue gases and has increased depth of removal.

[0016] It is a further advantage of the invention to provide a novel composition that reduces acidic contaminants in natural,, synthesis, and flue gases and has improved stability in the process compared to current solvents. [0017] It is an additional advantage of the invention to provide a novel composition that reduces acidic contaminants in natural, synthesis, and flue gases and has improved viscosity and regenerability in the process compared to current solvents.

[0018] It is yet another advantage of the invention to provide a novel composition that reduces acidic contaminants in natural, synthesis, and flue gases and has a higher boiling point resulting in minimized losses from the process and reduced corrosivity.

[0019] The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may he readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 illustrates a simplified process diagram demonstrating the configuration of the equipment in a typical amine solvent wash system,

[0021] Figure 2 shows the common commercially available. CO₂ absorbents used for the comparative testing discussed in Example 1.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The foliowing definitions are intended to be clarifying and are not intended to be limiting.

[0023] "Alkyl" refers to a monovalent group derived from a straight or branched chain saturated hydrocarbon by the removal of a single hydrogen atom. Representative alky! groups include methyl; ethyl; n- and wo-propyl; sec-, iso-, and tert-buiyl; C₅ to (な groups; eicosanyl (€¾>; heneicosanyl (C21); docosyl (behenyl, C22); irieosanyl (C23); tetracosanyi (C34); pentacosyl (Gas), 3-, 7-, and 13-meth I exadecaxiyl; and the like. Preferred aiky!s include methyl, ethyl, propyl isopropyl butyl, and isobutyl

[0024] "Aliphatic amine" and/or "aminoalkyl" refers to an alkyl group having one or more amino substitutions or an amino group having multiple alkyl substations. Representative aminoalkvis include aminomeihyi, dime hylaminoraethyl, diethylaminoniethyl, 2-aniinoethyl, 2- dimethylaminoeth l, 2-ethylaminoethyl, and the like.

[0025] "Amino" or "amine" refers to a group having the structure -NR'R", wherein R' and R" are independently selected from H and alkyl. as previously defined. Additionally, R' and R" taken together may optionally he -(Circle- where k is an integer of from 2 to 6. Representative amino groups include, amino (-NH2), methylamino, ethylamino, n- and iso- propylamine, dimethykmino, methylethylamino. piperidino, and the like,

[0026] "Depth of removal" refers to the amount of CO₂ that escapes the absorbent solution during peak performance (I.e., CO₂ slip), and is an approximation of the efficiency of CO₂ absorption.

[0027] "Heterocyclic amine" refers to a substituted carbocyclic structure containing at least one nitrogen member in the ring.

[0028] "Working capacity*' refers to the difference between rich loading and lean loading. [0029] This invention has application in a wide array of industrial processes including gas fields (e.g., marginal, stranded, and sour gas fields)* liquefied natural gas (LNG) liquefaction developments, gas o-liquids (GTL) developments, synthesis gas, and for the removal of 0な from combustion gases, The disclosed composition may be used in any industrial process, such as single or muUi-injection, known In the art or in any speciaiized high-pressure processes, such as those described in U.S. Patent Nos. 6,497,852, "Carbon Dioxide Recovery at High Pressure" and 7,481,988, "Method for Obtaining a H igh Pressure Acid Gas Stream by Removal of the Acid Gases from a Fluid Stream,⁵' and in PCX patent application no. WO2007077323AL "Method for Deacidifying a Gas with a Fractionally-Regenerated Absorbent Solution with Control of the Water Content of the Solution."

[0030] Referring to FIG I , an exemplary production process (typically found in natural gas processing) where this invention has utility is shown. Production process 100 includes raw gas inlet 105 where gas is contacted counter currently (typically at pressures greater than atmospheric) with a lean solvent solution (i.e., containing very low concentrations of acidic contaminants) in absorber column 1 10, The rich solvent solution (i.e., containing high concentrations of acidic contaminant(s) absorbed from the feed gas) drains out of absorber column 110 and passes via a pressure reduction valve (not shown) to rich amine flash drum 1 15 where co-absorbed volatile hydrocarbons and a portion of the absorbed acid gas contaminate is flashed from the solvent and removed into a vapor discharge stream from the drum.

[0031] Treated gas outlet 120 contains gas exiting the top of absorber column 1 10, treated and freed of acid gas contaminant(s). The rich amine solvent exits rich amine flash dram 1 15 and proceeds through rich/lean amine exchanger 125, where it is heated, and then into the top of regenerator column 130, where the acid gas contaminant(s) is separated from the rich solution at low pressure and high temperature as the solvent flows down the column. The rich solvent is stripped in the column by a countercurrent steam flow produced in amine reboiler 135 at the base of the column. The hot regenerated solvent accumulates at the base of the column and the stripped contaminants) gasses exit the top of the column with the stripping steam.

[0032] Steam and solvent vapor exiting the top of regenerator column 130 enters acid gas condenser 140. Resulting liquids are collected in reflux drum 145 for circulation back to the top of the regenerator column through reflux circulation pump 165. The regenerated hot lean sol vent is pumped from the base of regenerator column 130 via rich/lean exchanger 125 (through lean amine circulation pump 160) and lean amine cooler 1.50 back into the top of absorber column i 10 (through lean amine pressure pump 170), where the cycle is repeated. Filtration of lean solvent at lean amine filter 155 keeps il clear of solids and contaminants including degradation products caused by adverse components of the raw feed gas stream. It should be appreciated that filtration could take place in multiple and various locations in the process. [0033] In one embodiment, the composition of this invention includes at least one substituted cyclic diamine component (as shown in structure (I) above). In a preferred embodiment, the composition of this invention includes substituted piperazine moieties with substitution at the i and/or 4 nitrogen positions of the piperazine ring as well as substitution at. the 2, 3, 5, and/or 6 positions. In other embodiments, the composition includes substituted cyclic diamines having a 4- to 1 -membered ring.

[0034] Exemplary structures of typical N-tnono- or N-bi-substituted piperazines of the invention are shown as structure (ΤΪΪ) below, where is is H, alkyl aminoaikyl, or structure (IV); R is structure (I!) shown below, and Rj¾ Rao,, R:;_s Γ½, R₂3, R2 , Ras, and Rな are independently H, alkyl, or aminoaikyl.

[0035] R₂₇, R₂g, R29, R.30, R _w, Ris, is, and R,₇ are independently な alkyl, or aminoaikyl, and each in, n, o, x, y and z is independently 0, 1 , or 2. In a preferred embodiment, if Rjg is H at least one of R1 , u , Rie_> orな? is not H, and if is is structure (II) at least one of Rj_7j RJS, R2 . 30, Ri4, Ris, Rae, or R| ? is not H,

[0036] in a further embodiment, the composition of the invention includes N~mono- and N-bisubst tuted aminopiperazines, which may be substituted in the 2, 3, 5, and/or 6 positions of the piperazine ring. The substitutions are typically methyl, ethyl, propyl, isopropyi, or dimethyl. It should be appreciated that although the 2, 3, 5, and 6 unsubstituted piperazines are proficient CCな absorbents, significant advantages exist in utilizing the 2, 3, 5, and 6 substituted variants. Particularly reductions in process viscosity and improved regenerability are observed. [0037] Structure (V) below illustrates a representative structure for the bisubslftuted piperazine embodiment of the invention. R_31s R^, R_3¾ 34, R_35- R_¾¾, R₃₇, R₃₈, R39, R*:,, R41, R42, R 3, R44, R4S and R^are independently H, alkyl, or aminoalkyl. Preferred alkyls include methyl, ethyl, propyl, isopropyl, butyl, and isobutyj. Preferred aminoalkyls include 2-aminopropyi, 2- aminohutyl, aminoethyt, and ammopropyl. In a preferred embodiment, at least one of i½, R32, R33, R34, R35, な?_> or 38 s not H and at least one of R39,

is not H. The value of each s, t, and u are independently 0, 1, or 2.

[0038] Representative monosubstituted pjperazines include 2-atti mopropy 1-piperazine, 2-aminobutyl-piperazine. 1 -acety lpiperazine, and 1 -forni jpiperazine. Representative examples of typical bisubstituted piperazines include 1 , 4-bis-(2-aniinopropyi)- iperazine; 1,4-bis-(2- aniinobutyl)~piperazjne; 1 ,4-bis-(3 -am inobuty l)-piperazone; 1 ,4-bis-(N-raethyl-ammoethyl)- piperazme; i-(2-aminobutyl)-4-raeihylpiperazine; l ~(2-aminopropyl)~4-methylpiperai£ine and 1- (2-aminopropyi)-4- ethylpiperazine; 1 -aminoethyl-4-(2-aminobuty!)-piperazine; I -amsnoetnyl-4- (2-aminopropyl)-piperazine; l -aminopropyW~(3-aminobutyl)-piperazme; 1 -aminoetbyl-4-(N- methyl-aminoethyl)-piperazine; the like; and combinations thereof.

[0039] In one embodiment, the composition of the invention includes at least one absorbent component of the formulas illustrated in structures (1.-14) where — H, or more preferably R is selected from methyl, ethyl, propyl, isopropyt and combinations thereof,

[0040] in another embodiment, the composition of the invention includes at least oae absorbent component of the fonniilas illustrated in structures (15-21).

[0041] In an additional embodiment, the composition of the invention includes at least om absorbent component of the formulas illustrated in structures (22-35).

[0042] In yet another embodiment, the composition of the invention includes at least one absorbent component of the formulas illustrated in structures (36-42).

[0043] in another embodiment, the composition of the invention includes at least one absorbent component of tlie formulas illustrated in structures (43-49), where R = H, or more preferably R is selected from methyl, ethyl, propyl, isopropyl, and combinations thereof,

[0044] In another embodiment, the composition of the invention includes at least one absorbent component of the formulas illustrated in structures ⁽50-56).

[0045] n a further embodiment, the composition of the invention iiiciudes at least one absorbent component of the formulas illustrated in structures (57-63),

[0046] In one embodiment, the composition of the invention includes a least one absorbent component of the formulas illustrated in structures (64-77).

[0047] In a further embodiment, the composition of the invention includes at least one absorbent component of the formulas illustrated in structures (78-84).

[0048] In another embodiment, the composition of the invention includes at least one absorbent component of the formulas illustrated in structures (85 -91).

[0049] In another embodiment, the composition of the invention inciudes at least one- absorbent component of the formulas illustrated in structures (91-97).

[0050] The composition of the invention, may also include derivatives and/or salts of the disclosed structures. Representative derivatives include carbonates, biearboaaies, carbamates, ureas, and amides. Representative salts include all inorganic, mineral, and organic salts.

[0051] It is the intent of this invention to use the disclosed structures in a multitude of compositions including single or multiple component solutions in water or as combined with other acid gas solvent components such as tetramethylene suifone (i.e., Sulfbiane), MDBA, DBA, MEA, and the like in water and/or other mutual solvents,

[0052] For example, single and multiple component solutions range from about 0.01 to about 100 wt% actives or from about 1 to about 75 t% actives and include the use of solvents, such as water, alcohols, po!yols, other acid gas solvents, and organic solvents. In a preferred embodiment, the composition includes about 10 to about 75 wt% or from about 40 to about 50 wt% actives. Additionally, the composition generally includes an amount of solvent in the range of 0 to 99,09 wt%, depending upon the amount of actives.

[0053] The scrubbing liquid used in the composition of the invention may also include, tor example, one or more of the following components; ammoethyl-piperazine; 2-aminoetbyl- piperazine; 2-aminopropyl-piperazme; 2-aminobutyl-piperazine; 1 -acetylpiperazine; I - formy!plperazlne; 1,4-bis-arainoethyl-piperazine; 1 ,4-bis-aminopropyl-piperazine; 1,4- bisaminobutyl-piperazine; 1 ,4-bis-(2-aminopropyl)-pipera2ine; 1 ,4-bis-(2-aminobutyl)- piperazine: 1 ₍4-bis-(N-methyl-aminoethyl)-piperaz!ne; 1 -(2-amiaobutyl)-4-methylpiperazine ; 1 - (2~aminopropyl)-4-methylpipefazine; I -(2-aminopropyl)-4- ethylpiperazine; l -arainoethyl~4-(2- am inobuty l)-pipera2^*me; l-ammoethyl-4-(2-ammopropyl)-piperazine; l-aminoethyl-4-(N-methyI- aminoethy -piperazine; 2-morpholinoelhanam ine; 2-aminopropyl-morpholine; 2-( 1H-imidazol- l-yl)ethanamine; 2-aminopropyi-piperid ine; 2-aminopropyl-pyrolid ine; N 1 -(2- arainopropyl)butane- 1 ,4-diamine; N 1 -(3-aminopropyl)propane- 1 ,2~diam ine ; water; sulfolane, N- methylpyrrofidone; N-alkylated pyrrolidones, piperidones and raorp olroes corresponding to the foregoing; methanol; mixtures of dialkyl ethers of polyethylene glycols; -, lo G* dialkylether monoethy!ens glycols; Ci to C monoether tnonoethylene glycols; Ci to C4 dialkylether poly ethylene glycols; Ci to Q tnonoether polyethylene ethylene glycols; Cj to C*; ethylene glycol; diethylene glycol; triethylene glycol; NdNf-dimethyl formamide; N-acetyl morpholine; N-fortnyl morpholine; N,N -dimethyl imidazolidin-2-one; N-methyl imidazole; and the like.

[0054] In another embodiment, the composition of the invention may also include other components. Representative other components include blends of amines, activators, promoters, antifoamktg agents, co-absorbents, corrosion inhibitors, solvents, coloring agents, the like, and combinations thereof, Representative examples include alkanolamines; cyclotetramethylene su!fone and its derivatives; aliphatic acid amines such as acetyl morpholine or N-formyl morpholine; alkali metal compounds which provide alkaline hydrolysis products, such as alkali metal hydrolysis and hydrocarbonates; aliphatic and cycloaliphatic mono- and diamines, such as triethylene diamine, dicyclohexyl amine, N-ethyl-cyclobexylamine, and N,N~ diemthylcyclohexylainine; the like; and combinations thereof

[0055] In various embodiments, the absorbent of the invention ma include coabsorbeirts as disclosed in, for example, U.S. Patent Application Serial Nos, 12/494,521. "Acid Gas Scrubbing Composition," filed June 30, 2009, 12/494,533, "Acid Gas Scrubbing Composition," Hied June 30. 2009, and 12/761,939, "Composition for Treating Acid Gas," fded April 6, 2010, each of which is currently pending.

[0056] In another embodiment, coabsorbents include one or more components selected from calcium oxide, calcium ligtiosulfonate, calcium silicate hydrates, calcium hydroxide, calcium carbonate, calcium bicarbonate, sodium carboriate, sodium bicarbonate, trona, sodium sesqu (carbonate, soda ash, nacholite, sodium aluminate, metal oxides, and the like, [0057] Activators and coabsorbents are preferably present in the composition of the invention from about 0.0.1 to about 90 wt%, more preferably from about .1 to about 50 wt%, and most preferably from about 1 to about 25 wl¾ (wt% based on the weight of total actives),

[0058] In a further embodiment, the invention is a process for reducing acidic contaminants in an industrial fluid stream. The fluid stream is contacted with the disclosed composition to form a washed fluid stream and a rich acid gas scrubbing liquid. Typically, the composition is contacted with the gas stream at a temperature ranging from about 0 to about 200°C. in certain cases, this temperature range may be from about 0 to about 100°C or from about 20 to about 65°C, Industrial processes generally run at a pressure ranging from about 0 to about 200 aim, from about 0 to about 1 0 aim, from about 0 to about 70 atm, from aboui 0 to about 50 aim, from about 0 to about 25 atm, from about 0 to about 10 aim, or from about 1 to about 5 atm during the time when the composition is contacted with the fluid stream. U.S. Patent No, 4,556, "Bis Tertiary Amino Alky] Derivatives as Solvents for .Acid Gas Removal irom Gas Streams'^" discloses pressure ranges from 4 to 70 atm, Canadian patent application no. 2,651,888, "Carbon Dioxide Absorbent Requiring Less Regeneration Energy-" discloses pressures from 1 to 120 atm. It should be appreciated that this invention is operable in any of these or other pressure ranges encountered in the relevant art.

[0059] The rich acid gas scrubbing liquid is further processed through a regeneration system where at least a portion of the composition including at least a portion, of the absorbent compound(s) contacted with the fluid stream, are regenerated. The regeneration step normally takes place at a higher temperature than absorption (depending OH the particular industrial process), usually at a temperature ranging from about 0 to about 500°C, from about 20 to about 250°C, or from about 50 to about 150°C< The pressure range for the regeneration step is normally from about 0 to about 10 atm or from about 1. to about 5 aim. In certain cases, the regeneration step may be carried out via a steam-assisted reboiler. Regeneration may also be carried out via a fractional regeneration process (eg., WO 2007/077323, "Method for Deacidifying a Gas with a Fractionally-Regenerated Absorbent Solution with Control of the Water Content of the Solution").

[0060] The foregoing may be better understood by reference to the following examples, which are intended for illustrative purposes and are not intended to limit the scope of the invention.

Example I

[0061 ] The testing in this Example was used as a means of screening potential acidic contaminant scavengers and also to confirm the performance of existing commercially available scavengers. The test was designed to determine the maximum capacity of an amine solvent in absorbing acidic gases. Different amine solvents were compared. The amine solvents were saturated with acidic gases at a constant pressure and temperature until no more gas was able to be absorbed. The difference between the rich and lean loadings was used to determine ie working capacity. The test was designed to regenerate the solvent by boiling to remove the acidic gases so that the lean loading of CC¾ an amine solvent could be determined.

[0062] Solvent performance was characterized by liquid loading at equilibrium with defined composition gas mixtures at simulated amine contactor and regenerator conditions relative to industry benchmarks.

[0063] To highlight the advantages of the disclosed novel amines, several specific samples were benchmarked against common commercial C ¾ absorbents (such as 33.8/6.2 wt.%) ttiethyldlethanolamine/piperaziiie (DMDEA, a derivative of MDEA), monoethanolamine (MEA), and illustrated in FIG 2) using a laboratory-scale fixed bed absorption eel! and a batch reboiler. The "Sorbent" numbers indicated in Table I correspond to the structure numbers above and those indicated in Fig 2. The equilibrium saturation test to determine the rich loading (weight % C02 absorbed by fresh sorbeni) was rim by exposing an aqueous solution of the absorbent at 40°C to 30 psig of CO? until saturation was reached. The lean loading (weight % CO_? remaining associated with the absorbent: after regeneration) was determined by refluxmg the aqueous solution of the absorbents for two hours at atmospheric pressure. The working capacity is defined as the rich loading minus the lean loading, it is the working capacity that most accurately reflects the capacity of the chemical to absorb C⁽¼ under process conditions, The results of this evaluation are reported in Table 1 .

[0064] To determine rich loading, the equipment consisted of a high pressure gas panel that was capable of receiving supplies of 100% C<½, CO₂ N₂ mixtures and CO₂ H₂S/N₂ mixtures. The chosen gas was fed via a mass flow controller (Sierra series 100 mass flow controller, available from Sierra Instruments, Inc. in Monterey, CA) to the reaction vessel A gas totalizer (a Sierra Compod) attached to the mass flow controller measured the volume of gas used,

[0065] Once the appropriate gas cylinder valve and regulators were opened, the recirculating bath was set to a temperature of 40°C. A 200 ml glass reaction vessel was attached to the head of a Buchi Picoclave. The inlet and outlet valves to the reaction vessel were closed and the inlet pressure regulator was set to 30 psig. The gas mixture was set to 100% CC¼ and the flow rate was set to 0.5 liters/mm. After allowing the gas pressure to build to 30 psig at the reactor inlet, the amine solution was prepared at the concentration indicated in Table 1 and, after being brought to the same temperature as the reaction vessel, svas added to the reaction vessel and stirred at 1,000 rpm. [0066] The inlet valve was opened and the reactor pressure was allowed to equilibrate to 30 psig. When the pressure in the reactor reached 30 psig, the inlet valve was closed and the gas flow was shut off. The volume in the reactor vessel was recorded. Gas flow was resumed after 5 minutes and continued until the pressure equalized to 30 psig. This procedure was repeated until no additional CO?, was absorbed as measured by the final volume, The wt% rich loading of the amine was calculated from the final volume of C€½ absorbed.

[0067] To determine lean loading, the amine composition to be regenerated was poured into a 250 ml 3-neck flask equipped with mechanical stirring and a chilled condenser (8°C). The amine solution was slowly heated to reflux (about 100 to 104°C) to help avoid a sudden release of gas which would have caused the solution to foam. The solution was refJuxed for 2 hours and then cooled to room temperature. The lean loading of the amine was determined via a standard barium chloride back titration.

[0068] To determine depth of .removal, a mass flow controller (Sierra series 100 mass flow controller) was used to control the flow of gas through the reactor vessel. The chosen gas was fed via the mass flow controller to the saturation vessel (which contained detonized water) and then into the reaction vessel. From the reaction vessel, the gas was fed via a backpressure regulator through a Dreschel bottle containing ethylene glycol and a drying tube containing silica gel to the CCな analyzer. The CO₂ analyzer (Signal 7000FM CO₂ analyzer) recorded the concentration of COa flowing through it. The recirculating bath was set to the required temperature of 40°C. The 200 ml giass reaction vessel was fitted to the head of a Buchi Picoclave. A Dreschel bottle containing ethylene glycol and a drying tube containing silica gel was connected to the gas line prior to the CO₂ analyzer, and the backpressure regu lator was set to 90 psig. The gas mixture (25% C0₂/7Sな N₂) and the flow rate (0.45 liters/min) were then set and allowed to stabilize for 30 minutes. The amine solution was prepared at the concentrations indicated in Table 1 and heated as above. The amine was then added to the reaction vessel and the stirrer was set to 1,000 rpm. The downstream regulator was closed and the data recording began. The gas flow was allowed to continue until equilibrium was reached -3 hrs. At the end of the run, the gas flow was stopped, the inlet valve to the reaction vessel was closed, and the data recording was stopped. Table 1: NPX Amines ys. Common Absorbents

[0069] The tested amines on average absorbed about 1.36 moles of Ciな per mole of absorbent compared to less than 0.83 mole of €€¾ per mole of the common absorbents. Although 97 only slightly outperformed the common absorbents sorbent .1 ( = methyl) showed a significant increase in working capacity (13% increase based on MBA; 22% increase based on D DEA;). These novel amines also have a significantly lower lean loading than MEA,

[0070] The boiling points of the disclosed amines range from about 200 to about 280°C at latm (compared to MEA at 170°C and latm). Such higher boiling points help significantly reduce the losses and potential environmental releases currently associated with the volatility of MEA and also help to prevent CO₂ contamination during solvent regeneration, Initial laboratory stability testing has Indicated that unlike MEA, which is known to degrade rapidly under process condition, the disclosed amines are highly robust at simulated process conditions showing no s ign s o f degradati on .

[0071 ] To further highlight the utility of the tested amines for carbon capture, a 25% CO₂ gas stream at 90 psig was passed through the absorbents at A⁽ C until they reached saturation and the depth of removal was recorded. Importantly, the depth of removal for many of the tested amines approached 0%_» an indication that they are highly efficient at CO? capture as shown in Table 1,

Example 2

[0072] Although a reduction in the lean loading of branched compounds over linear compounds would have been expected, the select group of molecules tested also showed a unique increase in the rich mole ratio of the branched targets (Table I)). This unusual reactivity is particularly evident when comparing the linear AEP_f a promoter known in the industry, to the branched sorbents 97 and 1 (R = methyl). This increase in molar capacity is thought to occur via a change in the mechanism by which the amine reacts with C(な- Thus, the reactions between CC¾ and the branched amines are of greater efficiency.

Example 3

[0073] This Example compared the absorption Sorhents 97 and 1 (R = methyl). The two molecules are identical in molecular weight and were tested under identical conditions; however, Sorbent 1 (R = methyl) shows a 7.6% increase in working capacity, and significantly improved in process viscosity and improved process regenerabiltty. This effect has been attributed to the substitution of the piperazine ring carbon.

[0074] The rate of transfer of a solute between a gas and a liquid is proportional to the liquid film area which is the contact surface between the two phases. This contact area will be beneficially greater in a liquid which has a lower viscosity as compared against a benchmark liquid of greater viscosity due to the decrease in mean gas bubble diameter in the lower viscosity liquid and resulting increase in contact surface area as compared against the liquid of greater viscosity,

[0075] This benefit is realized in both absorption and desorption of the solute into and out of a liquid phase. In an absorption column the increase in surface contact area proportionally increases the volumetric mass transfer coefficient k¾a therefore reducing the amount of contact time required to achieve a required solute transfer fraction from gas to liquid phase. In a desorption column, the increase in surface area again benefits the mass transfer, but this time out of the liquid phase and into the stripping gas phase resulting in a reduction in contact time required to achieve the required reduction in liquid phase concentration of the solute as compared to the more viscous benchmark.

[0076] All of the compositions and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While this invention may be- embodied in many different forms, there are described in detail herein specific preferred embodiments of the invention. The present disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. In addition, unless expressly stated to the contrary, use of the term "a" is intended to include "at least one" or "one or more," For example, "a device" is intended to include "at least one device" or '"one or more devices." [0077] Any ranges given either in absolute terms or in approximate terms are intended to encompass both, and any definitions used herein are intended to be clarifying and not limiting. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges (including all fractional and whole values) subsumed therein.

[0078] Furthermore, the invention encompasses any and all possible combinations of some or all of the various embodiments described herein. Any and all patents, patent applications, scientific papers, and other references cited in this application, as well as any references cited therein, are hereby incorporated by reference in their entirety. It should also be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.

Claims

CLAIMS The claimed invention Is:

1 . A scrubbing liquid composition for absorbing acidic contaminants from fluids in an industrial process, the composition comprising:

(a) at least one absorbent component having a general formula, including carbonates, bicarbonates, carbamates, ureas, and amides thereof and salts thereof:

(i) Ri is selected from the group consisting of: H, alk L atninoa!kyl, and the following structu

(ii) eachな, R_3> Rj, R_s, R₆, R₇, R¾, and R<_? are independently H, alkyl, or aminoaiky!

(iii) each jo, Ri u Rt2, i3_> i > is= R1&. and Ri_? are independently if alkyl, or aminoalkyl; wherein if Ri is H at least one of _t¾ u, i₂. or Rj 3 is not H, and if Rj is the structure (A) at least one of Rt¾ Rt i, R12, Ri3j Rj4> R-15, i6_> or Rn is not H,

(iv) each m, n, and 0 is independently 0, 1 , or 2,

(v) p and q are independently 0, 1, 2, 3. or 4; and

(b) a solvent.

2. The composition of Claim 1. wherei n at least one of R2, R¾ ¾, R5, Re, R₇, Rg_a or Ro is not H and at least one of RJO, n, R₁₂» Ris, Ru, Ri5> Ru» or i? is not H.

3. The composition of Claim 1, wherein p and q are independently 0, i, or !

4. The composition of Claim 1 , wherein the alkyl for Rj to Rj? is independently selected from the group consisting of; methyl, ethyl, propyl, isopropyl, butyl, and isobutyl,

5. The composition of Claim 1, wherein the aminoalkyl for Ri to Rr? is selected from the group consisting of; 2-aminopropy!, 2-amiiiobutyl, aminoethyl, and aminopropyt,

6. The composition of Claim L wherein said absorbent component includes at least one selected from the group consisting of; structures 1-97, wherein R = H, methyl, ethyl, propyl, isopropyl, and combinations thereof.

7. The composition of Claim I, wherein the absorbent component includes at least one selected from the group consisting of: 2-aminopropyl-piperaz?ne; 2-ammobuiy!-piperaztoe; 1- aeetylpiperazine; 1-formylpiperazine; 1 ,4-bis-aminoethyl-piperazine; 1 ,4-bis-aroinopropyl- piperazine; 1 ,4-bisarainobutyl~piperaztite; 1 ,4-bis-(2-aminopropyl)-piperazine; L4~bis-(2- aminobutyl)-piperazine; 1 ,4-bi«-(N-rtiethyl-aiTiinoetfiyl)-piperazine; 1 -(2-aminobutyl)-4- methylpiperazine; 1 -(2-aminopropyI)-4-methylpiperazmej l-(2-aminopropyl)-4- ethylpiperazine; 1 -am3noethyl-4«(2-aminobuiyi)-piperazine; 1 -aminoethyl-4-(2-ammopropyl)-piperazine; 1 - iiminoeAyM-(N-methyl-aminoethyl)-piperazine; 2-morpholmoethanamine; 2-aminopropyl- morpholine; 2-(1H.-imida2oH-yl)ethanamIne; 2-at«jnopfopyl-piperidke; 2-arainopropyl- pyroiidine; Nl-(2-amhi0prop}d)butane~l ,4~diamine; N1 -(3"aminopropyI)propane-.l ,2-diamine; water; sulfolane, N-methylpyrroIidone; N-alkylated pyrrolidories, piperidones and morphoimes corresponding to the foregoing; methanol; mixtures of diaikyi ethers of polyethylene glycols; Cj to C₄ dialkylether moiioechyiene glycols: Cj to C₄ monoether monoethylene glycols; d to C₄ dialkylether poly ethylene glycols; Cj to C₄ monoether polyethylene ethylene glycols; Ci to C ; ethylene glycol; diethylene glycol; triethylene glycol; Ν,Ν-dimethyl formamide; N-acetyl morphoJine; N-formyl morpholiae; Ν,Ν-dimethyl imidazQlidin-2-one; N-methy! imidazole; and combinations thereof,

8. The cotBposition of Claim t, wherein said absorbeot compound is present in an amount ranging from about 0.01 to about 100 wt%.

9. The composition of Claim 1, further comprising at least one component selected from Che group consisting of: amines, activators, promoters, antifoaming agents, co-absorbents, corrosion inhibitors, coloring agents, and combinations thereof.

10. The composition of Claim 1, wherein the solvent is selected from the group consisting of: water, alcohols, polyols, other acid gas solvents, organic solvents, and combinations thereof,

11 . A process for reducing acidic contaminants in an industrial fluid stream, the process comprising: (a) contacting the fluid stream with the composition of Claim I to form a washed fluid stream and a rich add gas scrubbing liquid and (b) regenerating at least a portion of the composition including at least a portion of the absorbent compound(s) from the rich acid gas scrubbing liquid.

12. The process of Claim 1 1, wherein step (a) is carried out in a temperature range from about 0 to about 200°C and/or at a pressure range from about 0 to about 200 aim.

13, The process of Claim 11, wherein step (b) is carried out in a temperature range from about 0 to about 500°C and/or at a pressure range from about 0 to about 10 aim,

14. The process of Claim 12, wherein step (b) is carried out via a steam assisted reboiler,

15, The process of Claim 12. wherein step (b) is carried out via fractional regeneration.