Amino polycarboxylates as rate accelerators in glacial acetic acid processes

Abstract

A process for the production and recovery of acetic acid in an acetic acid production system is disclosed, the process comprising contacting methanol, methyl acetate, or a mixture of both with carbon monoxide in the presence of a reaction mixture comprising iodide under carbonylation conditions sufficient to form acetic acid. The reaction mixture comprises a carbonylation catalyst, water, and one or more promoters selected from the group consisting of Group I amino polycarboxylates and Group II amino polycarboxylates, and mixtures of the Group I amino polycarboxylates and the Group II amino polycarboxylates. One aspect of the process includes a method for reducing water in the acetic acid production process.

Description

[0001] Cross-references to related applications

[0002] This application is filed pursuant to the Patent Cooperation Treaty and claims priority to U.S. Provisional Patent Application No. 63 / 535,875, filed August 31, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the production of glacial acetic acid (GAA). More specifically, this disclosure relates to rate-accelerating compounds in the production of acetic acid. Background Technology

[0004] The carbonylation process of methanol is a promising commercial route for the synthesis of acetic acid. In this process, methanol, methyl acetate, or any mixture of both are reacted with carbon monoxide in the presence of a homogeneous catalyst, such as a rhodium-based catalyst, at, for example, 150 to 200 °C. o Under elevated pressure and at high temperatures, the reaction proceeds in the liquid phase to produce acetic acid, typically with a selectivity up to 95% and a byproduct of 5%. Methyl iodide (CH3I or MeI) is commonly used as a promoter in the carbonylation step of this process. This commercial reaction uses a homogeneous catalyst and is carried out in the liquid phase with solvents such as methyl acetate. The controlled amount of water required for the reaction is added and / or generated in situ via the reaction of methanol with HI or via the esterification of methanol with acetic acid. Given that water must be separated from acetic acid during recovery, it is desirable to use even less water in the carbonylation process.

[0005] In carbonylation processes, homogeneous catalysts are preferably cyclicated between oxidation states. For example, for rhodium-based catalysts, the catalytically active species can be the tetracoordinate anion [Rh(CO)₂I₂]. − This is commonly referred to as "Rh I". The first organometallic step will be the reaction of methyl iodine with [Rh(CO)₂I₂]. − Oxidative addition forms a six-coordinate anion [(CH3)Rh(CO)2I3]. − The anion rapidly transforms through the migration of the methyl group to the adjacent carbonyl ligand, yielding the five-coordinate acetyl anion [(CH3CO)Rh(CO)I3]. − The five-coordinate complex then reacts with carbon monoxide to form a six-coordinate dicarbonyl complex, which subsequently undergoes reductive elimination to produce acetyl iodide (CH3C(O)I). This catalytic cycle also includes two non-organometallic steps: the conversion of methanol or methyl acetate to methyl iodide, and the hydrolysis of acetyl iodide to acetic acid and hydrogen iodide. This reaction has been shown to be effective for methyl iodide and [Rh(CO)2I2]. − It is a first-order reaction. The first step of the catalytic cycle is the oxidative addition of methyl iodine.

[0006] The aim is to improve this carbonylation process by accelerating or "promoting" the formation rate of acetic acid, such as by accelerating the rate of methyl iodide oxidative addition. Furthermore, it is possible to inhibit the reaction of HI with [Rh(CO)₂I₂]. − Undesirable oxidative addition and methods to support water reduction in the process are also desirable. To investigate the potential benefits of rate-accelerating compounds (“accelerators”) in the acetic acid process, it is advantageous to study the subsequent rate-determining steps.

[0007] Specifically, the two oxidative addition reactions that control the pathways leading to the desired methanol carbonylation (A) and the undesirable water-gas shift (B) are shown below:

[0008] MeI + Rh I → GAA(A)

[0009] HI + RhI → H2 + CO2(B)

[0010] Therefore, any new GAA production method is expected to accelerate the oxidative addition of MeI and / or inhibit the oxidative addition of HI. Ideally, the optimal production method will both accelerate the oxidative addition of MeI to RhI and inhibit the oxidative addition of HI to RhI. Inhibiting the oxidative addition of HI to RhI will release more RhI for the oxidative addition of MeI. Summary of the Invention

[0011] A process for producing and recovering acetic acid in an acetic acid production system is disclosed. The process includes contacting methanol and / or methyl acetate with carbon monoxide under carbonylation conditions sufficient to form acetic acid, in the presence of a reaction mixture containing an iodide. The reaction mixture comprises a carbonylation catalyst, water, and one or more rate-promoting compounds (“promoters”), selected from the group consisting of Group I aminopolycarboxylates and Group II aminopolycarboxylates, and mixtures of the Group I and Group II aminopolycarboxylates.

[0012] Embodiments of this disclosure include a process for producing acetic acid, which comprises (or consists of, or substantially consists of):

[0013] a) Combining methanol, methyl acetate, or any mixture thereof with carbon monoxide in the presence of a reaction mixture containing:

[0014] i) Carbonylation catalysts, selected from the group consisting of rhodium catalysts, iridium catalysts, palladium catalysts and cobalt catalysts;

[0015] ii) Water, present in the range of 0.1% to 10% by weight, based on the weight of the reaction mixture; and

[0016] iii) one or more accelerators selected from the group consisting of Group I amino polycarboxylates and Group II amino polycarboxylates, and mixtures of the Group I amino polycarboxylates and Group II amino polycarboxylates; and

[0017] iv) Iodides; and

[0018] b) Recover acetic acid.

[0019] Embodiments of this disclosure also include methods for reducing water in an acetic acid production process, the method comprising (or consisting of, or substantially consisting of):

[0020] a) Under carbonylation conditions sufficient to form acetic acid at a first rate, methanol, methyl acetate, or any mixture thereof is combined with carbon monoxide in the presence of a reaction mixture containing an iodide, wherein the reaction mixture comprises:

[0021] i) A carbonylation catalyst, selected from the group consisting of rhodium, iridium, palladium, and cobalt catalysts; and

[0022] ii) A first amount of water, wherein the water is present in the range of 0.1% to 10% by weight, based on the weight of the reaction mixture; and

[0023] b) Incorporating one or more accelerators into the reaction mixture at a molar ratio of iodide to accelerator greater than 2, wherein the one or more accelerators are selected from the group consisting of Group I aminopolycarboxylates and Group II aminopolycarboxylates, and mixtures of the Group I aminopolycarboxylates and the Group II aminopolycarboxylates; and

[0024] c) Reduce the weight percentage of water in the reaction mixture to a second water amount, while maintaining a second acetic acid production rate that is the same as or higher than the first acetic acid production rate.

[0025] While the disclosed process allows for various modifications and alternatives, the accompanying drawings illustrate specific embodiments described in detail herein by way of example. However, it should be understood that the description of specific embodiments herein is not intended to limit the invention to the disclosed specific embodiments; rather, the invention is intended to cover all modifications, equivalents, and substitutions falling within the spirit and scope of the invention as defined by the appended claims.

[0026] Brief description of the attached figures

[0027] The claimed subject matter can be understood by referring to the following description in conjunction with the accompanying drawings, in which the same reference numerals identify the same elements, and wherein:

[0028] Figure 1This is a schematic diagram of an exemplary acetic acid production system based on the embodiments and / or technologies disclosed herein;

[0029] Figure 2 To show the FTIR superimposed spectra of the oxidative addition of MeI to RhI carbonylation catalyst over time under different H2 concentrations;

[0030] Figure 3 In response to Figure 2 A graph showing the first-order rate constant of the data as a function of H2O concentration;

[0031] Figure 4 The graph shows the first-order rate constant as a function of the accelerator concentration.

[0032] Figure 5 The image shows the FTIR superimposed spectra of the oxidative addition of MeI to Rh I carbonylation catalyst in the presence of LiOAc (top superimposed spectrum) and DTPA-Na3Ca (bottom superimposed spectrum);

[0033] Figure 6 To compare the FTIR superimposed spectra of the oxidative addition of MeI to the Rh I carbonylation catalyst in the presence of 0.5M LiOAc (bottom superimposed spectrum) and 0.033M DTPA-Na5 (top superimposed spectrum) from 0 to 120 minutes;

[0034] Figure 7 FTIR stacked spectra to show the effect of different DTPA-Na3Ca concentrations on the oxidative addition kinetics of MeI;

[0035] Figure 8 First-order rate constant curves for the oxidative addition rate constants of various common and novel accelerators;

[0036] Figure 9 To display the FTIR superimposed spectra of the oxidative addition of 0.25M HI to 0.015M Rh I at different H2O concentrations from 0 to 60 minutes;

[0037] Figure 10 In response to Figure 9 The relevant rate constant curves of the middle part of the dynamics experiment;

[0038] Figure 11 The graph shows the relevant rate constants from some kinetic experiments with relatively low water concentrations.

[0039] Figure 12 The graph shows the relevant rate constants from some kinetic experiments with relatively high water concentrations.

[0040] Figure 13The graphs of the rate constants for the oxidative addition of HI and MeI, estimated for low-speed, high-H2O experiments, are shown. All rate constants are plotted as a function of H2O concentration.

[0041] Figure 14 The above are FTIR superimposed spectra in the presence of the novel accelerator DTPA-Na3Ca and HI.

[0042] Figure 15 The above are FTIR superimposed spectra in the presence of the novel accelerator DTPA-Na3Ca and HI.

[0043] Figure 16 According to Figure 14 and Figure 15 Time-varying curves plotted from the data

[0044] Figure 17 According to Figure 14 and Figure 15 The data was plotted as a time-varying curve; and

[0045] Figure 18 The graph shows the first-order rate constant curves for the oxidative addition of HI to RhI under different HI / accelerator ratios. Detailed Implementation

[0046] The designation of groups in the periodic table used herein is in accordance with current IUPAC convention. The expression “MeI” is used herein as an abbreviation for methyl iodine. The expression “HI” is used herein as an abbreviation for hydrogen iodide. The expression “acac” is used herein as an abbreviation for acetoacetate anion, i.e., H3CC(═O)CH2C(═O)O−. Unless otherwise specifically indicated, the expression “wt%” as used herein refers to the weight percentage of a specific component in the reference composition. The expression “LiOAc” is an abbreviation for lithium acetate.

[0047] The term "alkyl" refers to a monovalent group consisting of carbon and hydrogen (such as C1 to C2). 30 Such as C1 to C 12 Alkyl groups in a compound are typically bonded directly to the compound via carbon atoms. Unless otherwise specified, alkyl groups can be straight-chain (i.e., unbranched) or branched, and can be cyclic, acyclic, or partially cyclic / acyclic. In one embodiment, the alkyl group includes straight-chain or branched acyclic alkyl groups. Representative examples of alkyl groups include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, dimethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, nonadecanyl, eicosyl, and triacontyl.

[0048] The disclosed process and system implementation scheme involves the production of acetic acid by carbonylating methanol in a carbonylation reaction. The carbonylation reaction can be represented as: CH3OH + CO → CH3COOH

[0049] Figure 1 This is a schematic diagram of an exemplary acetic acid production system 100 that performs a carbonylation reaction. In some embodiments, the acetic acid system 100 may include a reaction zone 102, a light distillation zone 104, a purification zone 106, and a recycling zone 108. The reaction zone 102 may include a reactor 110, a flash vessel 120, and associated equipment. The reactor 110 is a reactor or vessel in which methanol is carbonylated at elevated pressure and temperature in the presence of a catalyst to form acetic acid. Note that the “stream” discussed herein may be part of more than one functional zone. A “reaction mixture” is present in the reactor 110, a portion of which may be withdrawn, and components such as catalysts, chemical reactants, promoters, diluents, etc., may be introduced into, combined, and mixed in the reactor to achieve a desired concentration; and the reaction proceeds and / or is maintained at the desired concentration.

[0050] Reaction zone 102 may include reactor 110, flash vessel 120, equipment associated with reactor 110 and flash vessel 120, and streams associated with reactor 110 and flash vessel 120. For example, reaction zone 102 may include reactor 110, flash vessel 120, and streams (or portions of streams) 111, 112, 114, 121, 126, 131, 160, 138, 139, 148. Reactor 110 is a reactor or vessel in which methanol is carbonylated at elevated pressure and temperature in the presence of a catalyst to form acetic acid. Flash vessel 120 is a tank or vessel in which the reaction mixture obtained in the reactor (e.g., reactor 110) is at least partially depressurized and / or cooled to form a vapor stream and a liquid stream. The vapor stream is a product or composition containing gaseous components under the conditions of the processing step that forms the stream. The liquid stream may be a product or composition containing liquid components under the conditions of the processing step that forms the stream.

[0051] Light distillation section 104 may include a separation column (e.g., light distillation column 130), equipment associated with light distillation column 130, and streams associated with light distillation column 130. For example, light distillation section 104 may include light distillation column 130, decanter 134, and streams 126, 131, 132, 133, 135, 136, 138, and 139. Light distillation column 130 is a fractionation column or distillation column and includes any equipment associated with that column, including but not limited to heat exchangers, decanters, pumps, compressors, valves, etc.

[0052] Purification zone 106 may include a drying column 140, an optional heavy distillation column 150, equipment associated with the drying column 140 and the heavy distillation column 150, and streams associated with the drying column 140 and the heavy distillation column 150. For example, purification zone 106 may include drying column 140, heavy distillation column 150, and streams 136, 141, 142, 145, 148, 151, 152, and 156. Heavy distillation column 150 is a fractionating column or distillation column and includes any equipment associated with that column, including but not limited to heat exchangers, decanters, pumps, compressors, valves, etc.

[0053] The recirculation zone 108 may include process streams (not shown) that are recirculated to the reaction zone 102 and / or the light distillation zone 104. For example, in Figure 1 In the middle, the recirculation area 108 may include streams 121, 138, 139, and 148.

[0054] In one embodiment, reactor 110 may be configured to receive a carbon monoxide feed stream 114 and a methanol feed stream 112. Feed stream 112 may include a methanol feed stream, a methyl acetate feed stream, or any mixture of both. In the illustrated embodiment, feed stream 112 is a mixed stream. The reaction mixture in stream 111 may be removed from the reactor. Other streams may be included, such as streams that can recycle the bottom mixture of reactor 110 back into reactor 110, or streams that release gas from reactor 110. Stream 111 may include at least a portion of the reaction mixture.

[0055] In one embodiment, flash vessel 120 may be configured to receive stream 111 from reactor 110. Within flash vessel 120, stream 111 may be separated into vapor stream 126 and liquid stream 121. Vapor stream 126 may be fed to light fractionation column 130, and liquid stream 121 may be fed to reactor 110. In one embodiment, stream 126 may contain acetic acid, water, methyl iodide, methyl acetate, HI, or mixtures thereof.

[0056] In one embodiment, the light distillation column 130 may be a distillation column and associated equipment such as a decanter 134, pumps, compressors, valves, and other related equipment. The light distillation column 130 may be configured to receive stream 126 from flash vessel 120. In the illustrated embodiment, stream 132 is the overhead product from the light distillation column 130, and stream 131 is the bottom product from the light distillation column 130. As indicated, the light distillation column 130 may include a decanter 134, and stream 132 may enter the decanter 134.

[0057] Stream 135 may be discharged from decanter 134 and recycled back to light fractionation column 130. Stream 138 may be discharged from decanter 134 and may be recycled back to reactor 110 via, for example, stream 112, or combined with any other stream fed to the reactor. Stream 139 may recycle a portion of the light phase from decanter 134 back to reactor 110 via, for example, stream 112. Stream 136 may be discharged from light fractionation column 130. Other streams may be included, such as streams that may recycle the bottom mixture of light fractionation column 130 back into light fractionation column 130. Streams received by or discharged from light fractionation column 130 may pass through pumps, compressors, heat exchangers, etc., as is common in the art.

[0058] In one embodiment, drying column 140 may be a container and associated equipment such as a heat exchanger, decanter, pump, compressor, valve, etc. Drying column 140 may be configured to receive stream 136 from light fractionation column 130. Drying column 140 may separate the components of stream 136 into streams 142 and 141.

[0059] Stream 142 may be discharged from drying tower 140, recycled back to drying tower 140 via stream 145, and / or recycled back to reactor 110 via stream 148 (e.g., via stream 112). Stream 141 may be discharged from drying tower 140 and may include dehydrated crude acetic acid product. Stream 142 may pass through equipment, such as, for example, a heat exchanger or separation vessel, before the components of stream 142 are recycled to stream 145 or 148. Other streams may be included, such as those that may recycle the bottom mixture of drying tower 140 back into drying tower 140. Streams received by or discharged from drying tower 140 may pass through pumps, compressors, heat exchangers, separation vessels, etc., as is common in the art.

[0060] The heavy distillation column 150 can be a distillation column and associated equipment such as heat exchangers, decanters, pumps, compressors, valves, etc. The heavy distillation column 150 can be configured to receive stream 141 from the drying column 140. The heavy distillation column 150 can separate the components from stream 141 into streams 151, 152, and 156. Streams 151 and 152 can be sent to additional processing equipment (not shown) for further processing. Stream 152 can also be recycled, for example, to the light distillation column 130. Stream 156 may contain acetic acid product.

[0061] A single column (not depicted) can be used instead of the combination of light fraction distillation column 130 and drying column 140. The diameter / height ratio and number of stages of the single column can be varied depending on the composition of the vapor stream from the flash separation and the desired product quality. For example, single-column distillation is disclosed in U.S. Patent No. 5,416,237 (the teachings of which are incorporated herein by reference).

[0062] Alternative embodiments of the acetic acid production system 100 can also be found in U.S. Patent Nos. 6,552,221, 7,524,988 and 8,076,512, the entire contents of which are incorporated herein by reference.

[0063] In one embodiment, the carbonylation reaction in reactor 110 of system 100 can be carried out in the presence of a carbonylation catalyst. The catalyst may include, for example, a rhodium catalyst and an iridium catalyst.

[0064] Suitable rhodium catalysts are taught, for example, by U.S. Patent No. 5,817,869, which is incorporated herein by reference. Rhodium catalysts may comprise rhodium metal and rhodium compounds. In one embodiment, the rhodium compound may be selected from the group consisting of: rhodium salts, rhodium oxide, rhodium acetate, organorhodium compounds, rhodium coordination compounds, and mixtures thereof. In one embodiment, the rhodium compound may be selected from the group consisting of: Rh₂(CO)₄I₂, Rh₂(CO)₄Br₂, Rh₂(CO)₄Cl₂, Rh(CH₃CO₂)₂, Rh(CH₃CO₂)₃, [H]Rh(CO)₂I₂, and mixtures thereof. In one embodiment, the rhodium compound may be selected from the group comprising: [H]Rh(CO)₂I₂, Rh(CH₃CO₂)₂, and mixtures thereof.

[0065] Suitable iridium catalysts include, for example, those disclosed in U.S. Patent No. 5,932,764, which is incorporated herein by reference. Iridium catalysts may include iridium metal and iridium compounds. Examples of suitable iridium compounds include IrCl3, IrI3, IrBr3, [Ir(CO)2I]2, [Ir(CO)2Cl]2, [Ir(CO)2Br]2, [Ir(CO)4I2]-H+, [Ir(CO)2Br2]-H+, [IR(CO)2I2]-H+, [Ir(CH3)I3(CO)2]-H+, Ir4(CO)12, IrCl3.4H2O, IrBr3.4H2O, Ir3(CO)12, Ir2O3, IrO2, Ir(acac)(CO)2, Ir(acac)3, Ir(OAc)3, [Ir3O(OAc)6(H2O)3][OAc], H2[IrCl6], and mixtures thereof. In one embodiment, the iridium compound may be selected from acetates, oxalates, acetoacetates, and mixtures thereof. In one embodiment, the iridium compound may be one or more acetates.

[0066] In one embodiment, the catalyst may be used in conjunction with a co-catalyst. In one embodiment, the co-catalyst may comprise metals and metal compounds selected from the group consisting of osmium, rhenium, ruthenium, cadmium, mercury, zinc, gallium, indium, and tungsten, compounds thereof, and mixtures thereof. In one embodiment, the co-catalyst may be selected from ruthenium compounds and osmium compounds. In one embodiment, the co-catalyst may be one or more ruthenium compounds. In one embodiment, the co-catalyst may be one or more acetates.

[0067] The reaction rate depends on the concentration of the carbonylation catalyst in the reaction mixture in reactor 110. In some embodiments, the catalyst concentration is at least 2 mmol / L, or at least 3 mmol / L, or at least 5 mmol / L. In some embodiments, the catalyst concentration is at most 150 mmol / L, or at most 100 mmol / L, or at most 25 mmol / L. In a specific embodiment, the catalyst concentration is about 2 to about 150 mmol / L, or about 3 to about 100 mmol / L, or about 5 to about 25 mmol / L.

[0068] In one embodiment, the carbonylation reaction in reactor 110 of system 100 can be carried out in the presence of a catalyst stabilizer. Suitable catalyst stabilizers include at least two types. The first type of catalyst stabilizer can be a metal iodide salt, such as lithium iodide. The second type of catalyst stabilizer can be a non-salt stabilizer. In one embodiment, the non-salt stabilizer can be a pentavalent group 15 oxide, such as those disclosed in U.S. Patent No. 9,790,159, which is incorporated herein by reference. The pentavalent group 15 oxide is soluble in acetic acid and, in one embodiment, comprises bidentate phosphine dioxide, tertiary arsine oxide, the like, or combinations thereof. Non-limiting examples of bidentate phosphine dioxides suitable as pentavalent group 15 oxides include, but are not limited to: bis(diphenylphosphine)methane dioxide (bis-DPPMeO2), bis(diphenylphosphine)propane dioxide (bis-DPPPrO2), bis(diphenylphosphine)pentane dioxide (bis-DPPPeO2), and combinations thereof. Non-limiting examples of phosphine oxides suitable for use as pentavalent group 15 oxides include, but are not limited to, triphenylarsine oxide (TPAsO), triethylarsine oxide (TEtAsO), and combinations thereof. In one embodiment, the catalyst stabilizer may be one or more phosphine oxides.

[0069] In one embodiment, hydrogen may also be fed into reactor 110. The addition of hydrogen can improve carbonylation efficiency. In one embodiment, the concentration of hydrogen in reactor 110 may be in the range of about 0.1 mol% to about 5 mol% of carbon monoxide. In another embodiment, the concentration of hydrogen in reactor 110 may be in the range of about 0.3 mol% to about 3 mol% of carbon monoxide.

[0070] In one embodiment, the carbonylation reaction in reactor 110 of system 100 can be carried out in the presence of water. In one embodiment, the concentration of water is from about 0.1 wt% to about 10.0 wt%, from about 0.2 wt% to about 6.0 wt%, from about 0.3 wt% to about 4.5 wt%, or from about 0.4 wt% to about 2 wt%, based on the total weight of the reaction mixture.

[0071] In one embodiment, the carbonylation reaction can be carried out in the presence of methyl acetate. Methyl acetate can be formed in situ. In one embodiment, methyl acetate can be added to the reaction mixture as a starting material. In one embodiment, the concentration of methyl acetate can be from about 2% by weight to about 20% by weight, based on the total weight of the reaction mixture. In one embodiment, the concentration of methyl acetate can be from about 2% by weight to about 16% by weight. In one embodiment, the concentration of methyl acetate can be from about 2% by weight to about 8% by weight. Alternatively, methyl acetate from a methanol decomposition byproduct stream of polyvinyl acetate or ethylene-vinyl acetate copolymer, or a mixture of methyl acetate and methanol, can be used for the carbonylation reaction.

[0072] In one embodiment, the carbonylation reaction can be carried out in the presence of methyl iodine, which is added to reactor 110, to generate MeI in the reactor, or both. In one embodiment, the concentration of MeI can be from about 0.6 wt% to about 36 wt% based on the total weight of the reaction mixture. In one embodiment, the concentration of MeI can be from about 4 wt% to about 24 wt%. In one embodiment, the concentration of MeI can be from about 6 wt% to about 20 wt%. Alternatively, MeI can be generated in reactor 110 by adding HI.

[0073] In one embodiment, methanol and carbon monoxide can be fed into reactor 110 in the form of streams 112 and 114, respectively. The methanol feed stream to reactor 110 can be from a syngas-methanol facility or any other source. Methanol does not react directly with carbon monoxide to form acetic acid. It is converted to MeI by HI present in reactor 110, and then reacts with carbon monoxide and water to give acetic acid and regenerate HI. Therefore, in any embodiment, based on the total weight of the reaction mixture, the concentration of HI present in the reactor is about 0.1 wt% to about 10.0 wt%, about 0.2 wt% to about 6.0 wt%, about 0.3 wt% to about 4.5 wt%, or about 0.4 wt% to about 2 wt%.

[0074] In any embodiment, MeI reacts with a carbonylation catalyst in the rate-limiting step of the acetic acid production process to form an active catalyst species. HI may be added to the reaction mixture to generate MeI; however, its presence is desired to be modulated, as HI is believed to inhibit the carbonylation catalyst. Therefore, in any embodiment, a promoter compound is added to the reaction mixture in an amount beneficial to both.

[0075] In any embodiment, in any part of the acetic acid production system 100, preferably upstream of the purification zone 106, one or more promoters are incorporated and maintained in the reaction mixture, wherein the one or more promoters are selected from the group consisting of Group I aminopolycarboxylates and Group II aminopolycarboxylates, and mixtures of the Group I aminopolycarboxylates and the Group II aminopolycarboxylates. In any embodiment, the aminopolycarboxylate comprises two, three, or more carboxyl groups. In another embodiment, the aminopolycarboxylate comprises two, three to five, eight, or ten carboxyl groups. In yet another embodiment, the aminopolycarboxylate comprises at least one amino group and at least three or four carboxyl groups. In still another embodiment, the aminopolycarboxylate comprises at least two amino groups and at least two carboxyl groups.

[0076] In any embodiment, the one or more promoters are selected from the group consisting of: amino polycarboxylate salts containing at least one amine group and at least three or four carboxylate groups, and amino polycarboxylate salts containing at least two amine groups and at least two carboxylate groups.

[0077] In any embodiment, the amino polycarboxylate described herein may be represented by the general formula [(COO)RNR') representing the anionic moiety. - ] xThis indicates that the accelerator compound may contain units in the number of "x", such as 2, 3, 4 or more; and each R group may be the same or different, and may be a straight-chain, branched or cyclic alkyl or alkylene group, and preferably ethylene (–CH2–); and each R' group may be the same or different, and may be a straight-chain, branched or cyclic alkyl or alkylene group; wherein when R' is an alkylene group, it may be attached to another [(COO)RNR'). - The unit is preferably connected to "x" units.

[0078] Non-limiting examples of promoters include dialkyltriamine pentacarboxylate salts, such as pentasodium diethylenetriaminepentaacetate, trisodium diethylenetriaminepentaacetate calcium, trisodium hypotriacetate, tetrasodium N,N-bis(carboxymethyl)-L-glutamate, and carboxylate-substituted glutamate salts, such as tetrasodium N,N-bis(carboxymethyl)-L-glutamate and trisodium hypotriacetate. Exemplary structures are shown in structural formulas (1) to (4) below, wherein different molar equivalents of hydrated water may be present:

[0079]

[0080] Wherein (1) is pentasodium diethylenetriaminepentaacetate (DTPA-Na5), and (2) is trisodium calcium diethylenetriaminepentaacetate (DTPA-Na3Ca). Structural formula (3) is trisodium hypoazinetriacetate (NTA-Na3), and (4) is tetrasodium N,N-bis(carboxymethyl)-L-glutamic acid. Other alkyl and carboxylate-substituted variants of these salts, in any combination with Group I and Group II cations, are possible promoters as disclosed herein.

[0081] In any embodiment, Group I amino polycarboxylates and Group II amino polycarboxylates can be completely ionized to form complete salts, or can be partially ionized to form salts (e.g., Na+). + or Ca 2+ A mixture of ) and acid (H+).

[0082] In any embodiment, glutamate (C5H8O4N) and dicarboxymethyl alanine (C7H8NO6) are absent from the reaction mixture, meaning they are not added to the reaction mixture and are expected to be absent (0 ppm), or if present, in amounts less than 0.2 ppm or 0.1 ppm. However, substituted variants of glutamate as described herein may be present as one or more promoters, such as tetrasodium N,N-bis(carboxymethyl)-L-glutamate (GLDA-Na4) and trisodium hypotriacetate (NTA-Na)3.

[0083] Therefore, in any embodiment, there is a process for producing acetic acid, the process comprising (or consisting of, or substantially consisting of): a) combining methanol and carbon monoxide in the presence of a reaction mixture comprising: i) a carbonylation catalyst selected from the group consisting of rhodium, iridium, palladium and cobalt catalysts; ii) water, which is present in the range of 0.1% to 10% by weight based on the weight of the reaction mixture; and iii) one or more promoters selected from the group consisting of Group I aminopolycarboxylates and Group II aminopolycarboxylates and mixtures thereof; and iv) iodide; and b) recovering acetic acid.

[0084] Similarly, in any embodiment, there is a method for reducing water in an acetic acid production process, the method comprising (or consisting of, or substantially consisting of): a) combining methanol and carbon monoxide in the presence of a reaction mixture containing an iodide under carbonylation conditions sufficient to form acetic acid at a first rate, wherein the reaction mixture comprises: i) a carbonylation catalyst selected from the group consisting of rhodium, iridium, palladium, and cobalt catalysts; and ii) a first water amount, wherein the water is present in the range of 0.1 wt% to 10 wt% based on the weight of the reaction mixture; and b) incorporating one or more promoters into the reaction mixture at a molar ratio of iodide to promoter greater than 2, wherein the one or more promoters are selected from the group consisting of Group I aminopolycarboxylates and Group II aminopolycarboxylates and mixtures thereof; and c) reducing the wt% of water in the reaction mixture to a second water amount while maintaining a second acetic acid production rate that is the same as or higher than the first acetic acid production rate.

[0085] In any embodiment, the amount of promoter maintained in the reaction mixture is such that its molar ratio to the carbonylation catalyst is greater than about 0.5:1. In some embodiments, the molar ratio of promoter to rhodium is about 0.5:1 to about 100:1. In some embodiments, the reaction mixture may contain about 0.005 to about 2.0 M of promoter. In some embodiments, the reaction mixture may contain about 0.01 to about 1.5 M, or 0.025 to 1.2 M of promoter.

[0086] In any embodiment, the amount of accelerator maintained in the reaction mixture is such that the molar ratio of iodide to accelerator is greater than 2:1, or greater than 3:1, or greater than 4:1, or greater than 6:1. In some embodiments, the molar ratio of iodide to accelerator is 2:1 to 40:1, or 3:1 to 35:1, or 4:1 to 30:1, or 6:1 to 25:1. Similarly, in any embodiment, one or more accelerators are maintained at a molar ratio of accelerator to carbonylation catalyst of 0.005:1 to 4:1, or 0.01:1 to 3:1, or 0.02:1 to 2:1.

[0087] In one embodiment, the rate at which the promoter is introduced into system 100 may be adjusted according to the water content, the carbonylation catalyst content, and / or the HI content. In some embodiments, the promoter may be maintained at at least about 0.1 mol per mole of HI. In some embodiments, the promoter may be maintained at at least about 0.5 mol, or at least about 1 mol, or at least about 1.5 mol per mole of HI. In some embodiments, the promoter may be maintained at about 0.1 to about 10 mol per mole of HI. In some embodiments, the amount of promoter is about 0.25 to about 7.5 mol per mole of HI, or about 0.5 to about 5 mol, or about 0.75 to about 1.5 mol per mole of HI.

[0088] In other embodiments, the amount of the promoter is about 1 to about 10 moles of HI, or about 1 to about 7.5 moles, or about 1 to about 5 moles. In some embodiments, the promoter may be maintained at about 0.1 to about 1.5 moles of HI. In some embodiments, the maintenance amount of the promoter may be about 0.1 to about 1.3 moles of HI, or about 0.1 to about 1.1 moles. In further embodiments, the amount of the promoter is about 0.5 to about 3 moles of HI, or about 0.5 to about 2 moles, or about 0.5 to about 1.5 moles.

[0089] In one embodiment, the carbonylation reaction in reactor 110 of system 100 can occur at a temperature ranging from about 120°C to about 250°C, alternatively from about 150°C to about 250°C, and alternatively from about 150°C to about 200°C. In one embodiment, the carbonylation reaction in reactor 110 of system 100 can be carried out at a pressure ranging from about 200 psia (1.38 MPa-a) to 2,000 psia (13.8 MPa-a), alternatively from about 200 psia (1.38 MPa-a) to about 1,000 psia (6.9 MPa-a), and alternatively from about 300 psia (2.1 MPa-a) to about 500 psia (3.4 MPa-a).

[0090] In one embodiment, the reaction mixture can be drawn from reactor 110 via stream 111 and flashed in flash vessel 120 to form vapor stream 126 and liquid stream 121. The reaction mixture in stream 111 may include acetic acid, methanol, methyl acetate, methyl iodine, carbon monoxide, carbon dioxide, water, HI, heavy impurities, catalyst, or combinations thereof. Flash vessel 120 may include any configuration for separating the vapor and liquid components via reduced pressure. For example, flash vessel 120 may include a flash tank, nozzle, valve, or combinations thereof.

[0091] The flash vessel 120 may have a lower pressure than the reactor 110. In one embodiment, the flash vessel 120 may have a pressure from about 10 psig (69 kPa-g) to 100 psig (689 kPa-g). In one embodiment, the flash vessel 120 may have a temperature from about 100°C to 160°C.

[0092] Vapor stream 126 may include acetic acid and other volatile components such as methanol, methyl acetate, methyl iodine, carbon monoxide, carbon dioxide, water, entrained HI, complexed HI, and mixtures thereof. Liquid stream 121 may include acetic acid, methanol, methyl acetate, methyl iodine, carbon monoxide, carbon dioxide, water, complexed HI, HI, HI and water azeotropes, and mixtures thereof. Specifically, the liquid stream may include a catalyst, complexed HI, HI, HI and water azeotropes, and mixtures thereof. Liquid stream 121 may also include sufficient amounts of water and acetic acid to carry and stabilize the catalyst, non-volatile catalyst stabilizers, or combinations thereof. Liquid stream 121 may be recycled to reactor 110. Vapor stream 126 may be fed to light fractionation column 130 for distillation.

[0093] In one embodiment, vapor stream 126 can be distilled in light fractionation column 130 to form overhead stream 132, crude acetic acid product stream 136, and bottom stream 131. In one embodiment, light fractionation column 130 can have at least 10 theoretical stages or 16 actual stages. In an alternative embodiment, light fractionation column 130 can have at least 14 theoretical stages. In an alternative embodiment, light fractionation column 130 can have at least 18 theoretical stages. In one embodiment, one actual stage can be equal to about 0.6 theoretical stages. The actual stage can be a tray or packing. The reaction mixture can be fed into light fractionation column 130 via stream 126 at the bottom of column 130 or as a first-stage feed.

[0094] The overhead stream 132 may include acetaldehyde, water, carbon monoxide, carbon dioxide, methyl iodine, methyl acetate, methanol, and acetic acid, one or more promoters, and (if present) catalyst stabilizers and mixtures thereof. The bottom stream 131 may contain acetic acid, methyl iodine, methyl acetate, HI, water, and mixtures thereof. Stream 136 may contain acetic acid, HI, water, heavy impurities, and mixtures thereof. Streams 132, 131, and 136, as well as other streams discussed herein, may also contain varying concentrations of catalyst stabilizers and / or promoters, depending on where the catalyst stabilizers and / or promoters are added to the system.

[0095] In one embodiment, the light distillation column 130 can be operated at a top pressure ranging from 20 psia (138 kPa-a) to 40 psia (276 kPa-a), or alternatively, from 30 psia (207 kPa-a) to 35 psia (241 kPa-a). In one embodiment, the top temperature can be ranging from 95°C to 135°C, or alternatively, from 110°C to 135°C, or alternatively, from 125°C to 135°C. In one embodiment, the light distillation column 130 can be operated at a bottom pressure ranging from 25 psia (172 kPa-a) to 45 psia (310 kPa-a), or alternatively, from 30 psia (207 kPa-a) to 40 psia (276 kPa-a).

[0096] In one embodiment, the bottom temperature of the light distillation column 130 can be in the range of 115°C to 155°C, or alternatively, in the range of 125°C to 135°C. In one embodiment, crude acetic acid in stream 136 can be discharged from the light distillation column 130 as a liquid-side fraction. Stream 136 can be operated at a pressure in the range of 25 psia (172 kPa-a) to 45 psia (310 kPa-a), or alternatively, at a pressure in the range of 30 psia (207 kPa-a) to 40 psia (276 kPa-a). In one embodiment, the temperature of stream 136 can be in the range of 110°C to 140°C, or alternatively, at a temperature in the range of 125°C to 135°C. Stream 136 can be obtained between the fifth and eighth actual stages of the light distillation column 130.

[0097] The overhead vapor from stream 132 of the light fractionation column 130 can be condensed and separated in decanter 134 to form a light aqueous phase and a heavy organic phase. For example, the heavy organic phase can be recycled to reactor 110 via stream 112 in stream 138. Stream 138 may include acetic acid, methanol, methyl acetate, methyl iodine, carbon monoxide, carbon dioxide, water, HI, heavy impurities, one or more promoters, catalyst stabilizers (optionally), and mixtures thereof.

[0098] For example, the light aqueous phase can be recycled to the light fractionation column 130 in stream 135, or it can be recycled to the reactor 110 via stream 112 in stream 139. Stream 135 may include acetic acid, methanol, methyl acetate, methyl iodine, carbon monoxide, carbon dioxide, water, HI, heavy impurities, one or more promoters, catalyst stabilizers (optionally), and mixtures thereof. The heavy organic phase in stream 138 may contain methyl iodine and methyl acetate, and mixtures thereof. The light aqueous phases in streams 136 and 139 may contain water (greater than 50%), acetic acid, methanol, methyl acetate, methyl iodine, carbon monoxide, carbon dioxide, heavy impurities, one or more promoters, catalyst stabilizers (optionally), and mixtures thereof. Make-up water may be introduced into decanter 134 via stream 133. Streams 139 and 138 can be considered to be located in the light fractionation zone 104 and the recirculation zone 108.

[0099] In one or more embodiments, the crude acetic acid in stream 136 may optionally be further purified, such as, but not limited to, dry distillation, such as in a drying column 140, to remove water, and to remove water and heavy distillate from stream 141. Stream 141 may be fed to a heavy distillation column 150, where heavy impurities (such as propionic acid) may be removed, and the final acetic acid product may be recovered in stream 156.

[0100] In one embodiment, the promoter can be continuously introduced into system 100 via stream 160 and can be added in any form, such as solid, liquid, or solution (such as acetic acid solution). Figure 1 In this process, stream 160 mixes with the vapor from flash vessel 120 to continuously introduce the promoter into the components of the vapor stream 126 of flash vessel 120. In an alternative embodiment (not shown), stream 160 may continuously introduce the promoter into any device or stream of reaction zone 102, light distillation section 104, recirculation zone 108, or combinations thereof. For example, stream 160 may continuously introduce the promoter into flash vessel 120, light distillation column 130, reactor 110, streams 111, 112, 114, 121, 126, 131, 132, 133, 135, 136, 138, 139, or combinations thereof. Therefore, although Figure 1The diagram shows stream 160 being mixed with a vapor stream exiting from flash vessel 120, but it is conceivable that alternative embodiments may include mixing stream 160 with any device or stream in reaction zone 102, light distillation zone 104, recirculation zone 108, or combinations thereof.

[0101] In some embodiments, one or more promoters disclosed herein may be continuously introduced as a solution comprising the promoter and a solvent in the form of stream 160. In one embodiment, the promoter solution may include an acetic acid solution. The nature of the solvent or diluent is generally not critical, as long as the solvent or diluent does not interfere with the carbonylation reaction or the purification of acetic acid in purification zone 106.

[0102] Those skilled in the art of homogeneous processes, particularly those skilled in processes requiring a flash evaporation step to separate non-volatile catalysts and accelerators, will understand that the loss rates of catalysts and accelerators, which are solely related to entrainment, will be a function of several variables. These variables include reactor size, feed rate, flash vessel size, and flash rate. They will also understand that the replenishment solution of one or more accelerators disclosed herein in acetic acid can be concentrated to a concentration permissible by the solubility limit of the accelerators disclosed herein in acetic acid, i.e., about 50% by weight, or diluted to a few ppm.

[0103] The primary consideration is that the flow rate and concentration of the one or more promoters disclosed herein must be matched to allow the promoters in the reactor to reach a steady-state concentration. This concentration typically varies by up to 1.5 wt% from its high to low point between batch additions and is controlled within a target range of ±0.5 wt% in one embodiment, or within ±0.2 wt% in another embodiment. Therefore, for example, in a process with a monthly loss rate of 1 wt% in the reactor, monthly batch additions can be replaced with a continuous metering flow, corresponding to an average daily addition of approximately 0.03 wt% of the promoters disclosed herein.

[0104] In one embodiment, a solvent or diluent may not be used. When a solvent or diluent is used in one embodiment, it is one or more components of the liquid composition of the reaction mixture in reactor 110, such as acetic acid, methanol, methyl iodine, water, or combinations thereof. In one embodiment, the solvent or diluent may be acetic acid, methanol, or both. Similarly, the amount of solvent or diluent used in this context is not critical and can be widely adjusted according to process economics. The use of a solvent or diluent can help ensure rapid and uniform distribution and contact of the promoter with HI.

[0105] In one embodiment, it may be advantageous to use a solvent or diluent when introducing one or more promoters separately and independently from the reaction mixture and any recirculation stream into system 100. Such a “recirculation stream” may be a product or composition recovered from a downstream processing step of the flash vessel and recycled back to the reactor, flash vessel, or light fractionation column. In an alternative embodiment, when one or more promoters are contacted with the reaction mixture in flash vessel 120, for example by adding one or more promoters to stream 131 before introducing stream 131 into flash vessel 120, the promoters may be introduced in physical form (i.e., in undiluted form), as the liquid component of stream 131 acts as a solvent or diluent.

[0106] In any embodiment, the rate of acetic acid production is increased by more than 5, 10, or 16 times in the presence (or in combination with) one or more of the promoters disclosed herein. While not wishing to be bound by theory, it is believed that some kind of concerted interaction exists among the amine groups in the promoters. These groups are likely to undergo quaternization with MeI to form the corresponding ammonium iodide, thereby creating an electronic environment that may be significantly different from the parent molecule that promotes oxidative addition with the carbonylation catalyst.

[0107] Furthermore, while not wishing to be bound by theory, it is believed that as the amount of water in the reaction mixture is advantageously reduced, HI will increasingly exist in the covalent HI form rather than the dissociated H+--I- or H3O+--I- forms, and the promoter will push this equilibrium towards the dissociated form. Primarily only the covalent form can undergo oxidative addition, in which the following initial reaction (C) occurs:

[0108] [Rh(CO)2I2)] - + 2HI → [Rh(CO)2I4] - + H2(C)

[0109] The second part of the cycle involves the interaction of the formed Rh III species with H2O and CO (D):

[0110] [Rh(CO)2I4] - + H2O + CO → [Rh(CO)2I2] - + CO + 2HI(D)

[0111] At low water concentrations and when HI is primarily covalent, the rate-limiting step is likely the second step as described above; while at high water concentrations, the first step is likely the rate-limiting step. Therefore, it is believed that one or more promoters inhibit the oxidative addition of HI to the carbonylation catalyst.

[0112] In one embodiment, the continuous introduction of one or more promoters may include continuously or alternately metering the promoter in a solution (e.g., an acetic acid solution) using gas or liquid metering techniques known in the art (such as turbine flow meters, Coriolis flow meters, ultrasonic flow meters, volumetric flow meters, or combinations thereof). Continuous or alternate metering may include uniformly injecting a promoter solution (e.g., an acetic acid solution) of a known concentration, or adjusting the injection rate up or down to meet desired requirements.

[0113] In one embodiment, the reaction mixture in reactor 110 does not contain any promoter other than the promoter that is continuously introduced into system 100 and has been recycled back to reactor 110.

[0114] In one embodiment, the amount of promoter in contact with HI, the carbonylation catalyst, and / or water is generally not critical, as long as the promoter is provided in an effective amount. In this context, an effective amount refers to the amount of promoter capable of increasing the rate of acetic acid production in system 100. The amount of promoter added is preferably determined by the rate of promoter loss from the reactor rather than by the HI concentration.

[0115] Generally, if the molar amount of one or more promoters exceeds the molar amount required to promote the acetic acid reaction, it is not detrimental to the subsequent separation and purification of the final acetic acid product, provided that the boiling point of the promoter is sufficiently higher than that of the vapor stream 126 discharged from flash vessel 120 and / or the stream 136 discharged from light fractionation column 130. For example, the boiling point of the additive is sufficiently high when the boiling point of the promoter is at least 15°C higher than that of crude acetic acid in stream 136, alternatively at least 30°C, or alternatively at least 50°C.

[0116] In any embodiment, one or more accelerators may be maintained in the flash vessel 120 at an amount of about 0.1 to about 1.5 moles per mole of HI. In some embodiments, the amount of accelerator is about 0.1 to about 1.3 moles per mole of HI, or about 0.1 to about 1.1 moles per mole of HI. In some embodiments, the amount of accelerator is about 0.5 to about 3 moles per mole of HI, or about 0.5 to about 2 moles per mole of HI, or about 0.5 to about 1.5 moles per mole of HI.

[0117] In a further embodiment, the accelerator may be maintained in the flash vessel 120 at an amount sufficient to establish a concentration of no more than about 20% by weight of the accelerator in the liquid stream 121. In other embodiments, the accelerator may be maintained at a concentration of no more than about 15% by weight, or no more than about 12% by weight, or no more than about 10% by weight of the accelerator in the liquid stream 121. In other embodiments, the accelerator may be maintained at an amount sufficient to establish a concentration of at least about 0.5% by weight of the accelerator in the liquid stream 121. In some embodiments, the accelerator may be maintained at an amount sufficient to establish a concentration of at least about 1% by weight, or at least about 2.5% by weight, or at least about 4% by weight of the accelerator in the liquid stream 121. In a specific embodiment, the accelerator may be maintained at an amount sufficient to establish a concentration of from about 0.5% by weight to about 20% by weight of the accelerator in the liquid stream 121.

[0118] In other embodiments, the promoter may be maintained at an amount sufficient to establish a concentration of about 1% to about 20% by weight, or about 2.5% to about 20% by weight, or about 4% to about 20% by weight in the liquid stream 121. In some embodiments, the promoter may be maintained at an amount sufficient to establish a concentration of about 0.5% to about 15% by weight, or about 1% to about 15% by weight, or about 2.5% to about 15% by weight, or about 4% to about 15% by weight in the liquid stream 121. In some embodiments, one or more promoters may be maintained at an amount sufficient to establish a concentration of about 0.5% to about 12% by weight, or about 1% to about 12% by weight, or about 2.5% to about 12% by weight, or about 4% to about 12% by weight in the liquid stream 121.

[0119] Liquid stream 121 can be recycled back to reactor 110. The recycled liquid stream 121 can introduce one or more promoters into reactor 110, and thus into the reaction mixture in reactor 110.

[0120] In some embodiments, the amount of one or more accelerators maintained in the flash vessel 120 can be adjusted to establish a steady-state concentration of the accelerator in the reaction mixture of no more than about 20% by weight. In alternative embodiments, the accelerator can be maintained in the flash vessel 120 at an amount sufficient to establish a steady-state concentration of the accelerator of no more than about 17%, or no more than about 15%, or no more than about 12% by weight in the reaction mixture. In other embodiments, the accelerator can be maintained in the flash vessel 120 at an amount sufficient to establish a steady-state concentration of the accelerator of at least about 2% by weight in the reaction mixture. In alternative embodiments, the accelerator can be maintained in the flash vessel 120 at an amount sufficient to establish a steady-state concentration of the accelerator of at least about 5% by weight or at least about 7% by weight in the reaction mixture.

[0121] In a specific embodiment, the one or more accelerators may be maintained in the flash vessel 120 at an amount sufficient to establish a steady-state concentration of about 2% to about 20% by weight of the accelerator in the reaction mixture. In an alternative embodiment, the accelerator may be maintained in the flash vessel 120 at an amount sufficient to establish a steady-state concentration of about 5% to about 20% by weight, or about 7% to about 20% by weight of the accelerator in the reaction mixture. In an alternative embodiment, the accelerator may be maintained in the flash vessel 120 at an amount sufficient to establish a steady-state concentration of about 2% to about 17% by weight, or about 5% to about 17% by weight, or about 7% to about 17% by weight of the accelerator in the reaction mixture.

[0122] In some embodiments, the one or more accelerators may be maintained in the flash vessel 120 at an amount sufficient to establish a steady-state concentration of about 2% to about 15% by weight, or about 5% to about 15% by weight, or about 7% to about 15% by weight in the reaction mixture. In some embodiments, the accelerators may be maintained in the flash vessel 120 at an amount sufficient to establish a steady-state concentration of about 2% to about 12% by weight, or about 5% to about 12% by weight, or about 7% to about 12% by weight in the reaction mixture.

[0123] Residual HI that may reach the light fraction column 130 can be easily separated as the bottom product stream 131 of the light fraction section 104. Furthermore, since HI is removed from the product stream at the earliest stage of acetic acid post-treatment, HI-induced side reactions (i.e., the formation of undesirable long-chain alkyl iodine contaminants in the product stream downstream of the flash vessel) are significantly reduced. Additionally, the reduced amount of HI in the product stream downstream of the flash vessel 120 mitigates corrosion and engineering problems.

[0124] The beneficial effects of one or more promoters are not limited to their location of introduction into system 100. Rather, as one or more promoters circulate within system 100 by circulating liquid stream 121 from flash vessel 120 to reactor 110, the presence of these promoters in the reaction mixture helps to promote the rate-limiting step in the acetic acid process and / or inhibit the reaction of HI with the carbonylation catalyst. Therefore, in the case of continuous process operation, the amount of promoter in contact with the reaction mixture in flash vessel 120 can typically be reduced when steady-state conditions are reached. Under steady-state conditions, the amount of promoter in contact with the reaction mixture in flash vessel 120 can typically be reduced to the amount necessary to maintain the desired steady-state concentration of promoter.

[0125] After describing various aspects of the process of the present invention, the following are presented in the form of numbered paragraphs (P):

[0126] P1. A process for producing acetic acid, the method comprising: a) combining methanol, methyl acetate, or any mixture thereof with carbon monoxide in the presence of a reaction mixture comprising: i) a carbonylation catalyst selected from the group consisting of rhodium, iridium, palladium, and cobalt catalysts; ii) water present in the range of 0.1% to 10% by weight based on the weight of the reaction mixture; and iii) one or more promoters selected from the group consisting of Group I aminopolycarboxylates and Group II aminopolycarboxylates and mixtures thereof; and iv) iodide; and b) recovering acetic acid.

[0127] P2. The process described in paragraph 1, wherein the amino polycarboxylate contains two, three or more carboxylate groups.

[0128] P3. The process described in paragraph 1 or 2, wherein the amino polycarboxylate contains 2, or 3 to 5, or 8, or 10 carboxylate groups.

[0129] P4. The process according to any one of paragraphs 1 to 3, wherein the amino polycarboxylate contains at least one amine group and at least three carboxylate groups.

[0130] P5. The process according to any one of paragraphs 1 to 4, wherein the amino polycarboxylate contains at least two amine groups and at least two carboxylate groups.

[0131] P6. The process according to any one of paragraphs 1 to 5, wherein the iodide is in the form of HI, CH3I, or both.

[0132] P7. The process according to any one of paragraphs 1 to 6, wherein the one or more accelerators are continuously added to the reaction mixture as an acetic acid solution.

[0133] P8. The process according to any one of paragraphs 1 to 6, wherein the process is carried out in an acetic acid system comprising a reaction zone, a light distillation zone, a purification zone and a circulation zone, wherein the reaction zone comprises a reactor and a flash vessel.

[0134] P9. The process described in paragraph 8, wherein one or more accelerators are added to the flash vessel.

[0135] P10. The process described in paragraph 8, wherein the combination is carried out in the reactor at a temperature ranging from about 120°C to about 250°C and a pressure ranging from about 200 psia (1.38 MPa-a) to 2,000 psia (13.8 MPa-a).

[0136] P11. The process according to any one of paragraphs 1 to 10, wherein the one or more accelerators are maintained at a molar ratio of iodide to accelerator of 2:1 to 40:1.

[0137] P12. The process according to any one of paragraphs 1 to 11, wherein the one or more promoters are maintained at a molar ratio of promoter to carbonylation catalyst of 0.005:1 to 4:1.

[0138] P13. According to the process described in paragraph 12, the weight percentage of water can be reduced as the molar ratio of the one or more promoters increases.

[0139] P14. The process according to any one of paragraphs 1 to 13, wherein there are no salts of glutamate and dicarboxymethylalanine.

[0140] P15. A method for reducing water in an acetic acid production process, the method comprising: a) combining methanol, methyl acetate, or any mixture thereof with carbon monoxide in the presence of a reaction mixture containing an iodide under carbonylation conditions sufficient to form acetic acid at a first rate, wherein the reaction mixture comprises: i) a carbonylation catalyst selected from the group consisting of rhodium, iridium, palladium, and cobalt catalysts; and ii) a first water amount, wherein the water is present in the range of 0.1 wt% to 10 wt% based on the weight of the reaction mixture; and b) combining one or more promoters into the reaction mixture at a molar ratio of iodide to promoter greater than 2, wherein the one or more promoters are selected from the group consisting of Group I aminopolycarboxylates and Group II aminopolycarboxylates and mixtures of the Group I aminopolycarboxylates and Group II aminopolycarboxylates; and c) reducing the wt% of water in the reaction mixture to a second water amount while maintaining a second acetic acid production rate that is the same as or higher than the first acetic acid production rate.

[0141] P16. The process described in paragraph 15, wherein the amino polycarboxylate contains two, three or more carboxylate groups.

[0142] P17. The process described in paragraph 15 or 16, wherein the amino polycarboxylate contains 2, or 3 to 5, or 8, or 10 carboxylate groups.

[0143] P18. The process according to any one of paragraphs 15 to 17, wherein the amino polycarboxylate comprises at least one amine group and at least three carboxylate groups.

[0144] P19. The process according to any one of paragraphs 15 to 18, wherein the amino polycarboxylate comprises at least two amine groups and at least two carboxylate groups.

[0145] P20. The process according to any one of paragraphs 15 to 19, wherein the iodide is in the form of HI, CH3I, or both.

[0146] P21. The process according to any one of paragraphs 15 to 20, wherein the one or more accelerators are continuously added to the reaction mixture as an acetic acid solution.

[0147] P22. The process according to any one of paragraphs 15 to 21, wherein the process is carried out in an acetic acid system comprising a reaction zone, a light distillation zone, a purification zone and a circulation zone, wherein the reaction zone comprises a reactor and a flash vessel.

[0148] P23. The process according to paragraph 22, wherein one or more accelerators are added to the flash evaporator.

[0149] P24. The process described in paragraph 22, wherein the combination is carried out in the reactor at a temperature ranging from about 120°C to about 250°C and a pressure ranging from about 200 psia (1.38 MPa-a) to 2,000 psia (13.8 MPa-a).

[0150] P25. The process according to any one of paragraphs 15 to 24, wherein the one or more accelerators are maintained at a molar ratio of iodide to accelerator of 2:1 to 40:1.

[0151] P26. The process according to any one of paragraphs 15 to 25, wherein the one or more promoters are maintained at a molar ratio of promoter to carbonylation catalyst of 0.005:1 to 4.

[0152] P27. In any of the processes described in paragraphs 15 to 26, there are no salts of glutamate and dicarboxymethylalanine.

[0153] Example

[0154] The following studies and embodiments are merely illustrative and are not intended to limit the scope of the invention in any way, nor should they be construed as limiting the scope of the invention.

[0155] A 3000 ppm stock solution of [Rh(CO)₂I₂]Li (commonly referred to as "Rh I") in glacial acetic acid was prepared as follows: 0.12 g of rhodium dicarbonyl(I) chloride dimer (CAS# 14523-22-9) was added to 20 mL of previously purged glacial acetic acid in a 30 mL vial. The vial was sealed with a septum and, while stirring at room temperature, gently purged with N₂ at one atmosphere. After 10 minutes, the septum was removed, 0.21 g of lithium iodide was quickly added, the septum was replaced, and the mixture was continued to be stirred and purged for another 10 minutes, at which point complete dissolution had occurred. The active Rh I catalyst was now formed and could be stored indefinitely under an N₂ atmosphere without decomposition. FTIR analysis of aliquots confirmed that 100% of the catalyst was formed in each batch. To begin the kinetic experiments, 1.5 mL of this stock solution was injected into a stirred, septum-sealed vial purged with N2 containing 1.5 mL of the other components (accelerator, MeI or HI, H2O, glacial acetic acid). Thus, the initial Rh concentration was 1500 ppm or 0.015 M. Typical conditions for the MeI oxidation experiments are shown in Table 1. The high concentration of MeI used ensured that all experiments were pseudo-first-order conditions; it should be understood that the term "rate constant" used in the text and figures refers to the pseudo-first-order rate constant. Table 1 also includes comparative conditions for similar experiments reported in US Patent 9,580,377.

[0156] Table 1. Experimental conditions

[0157]

[0158] In the kinetic experiments, a constant H2O concentration of approximately 1.3 M (2 wt%) was maintained whenever possible. For HI oxidative addition experiments, a 0.1 M HI concentration was chosen for most experiments. A 57% HI aqueous solution contributed 0.53 M of H2O to each kinetic experiment, with the remainder (totaling 1.3 M) related to the H2O content in the concentrated accelerator solution. The various novel accelerators studied are listed in Table 2. DTPA-Na5 was only commercially available in a 40 wt% (1 M) aqueous solution. DTPA-Na3Ca and NTA-Na3 were available as solids. The various total aqueous solutions and GAA / H2O solutions prepared are listed in the table. Density measurements were performed in all cases to calculate molar concentration. All materials were soluble in H2O at >40 wt% and in GAA containing 10 wt% H2O at >20 wt%.

[0159] Table 2. Characteristics and concentrations of exemplary accelerators

[0160]

[0161] Since DTPA-Na5 can only be obtained as an aqueous solution, the highest molar concentration that can be used in kinetic experiments while maintaining a 1.3 M H2O concentration is 0.033 M. Therefore, most kinetic studies have used a similar DTPA-Na3Ca, because in this case, molar concentrations up to about 0.15 M can be used without exceeding the target H2O concentration.

[0162] FTIR spectroscopy analysis was performed as follows: FTIR spectra were acquired using an iS50 FTIR spectrometer equipped with a Thermo Scientific DTGS detector. The sample chamber could optionally be equipped with a transmission cell accessory or an attenuated total reflectance (ATR) accessory. The transmission cell, purchased from Harrick Scientific, was equipped with a sapphire window and had a path length of 0.1 mm. The ATR cell, purchased from Pike Technologies, was equipped with a three-reflection zinc selenide (ZnSe) crystal. For the FTIR measurements in this disclosure, the rhodium carbonyl band in the 1950–2100 cm⁻¹ region was measured, and the two cells were largely interchangeable in terms of spectral acquisition time, signal quality, etc. The sample volume required for FTIR analysis depends on the sample cell used. When using a transmission cell, approximately 0.3 mL of sample was drawn from a septum-sealed reaction flask (initially containing 3 mL) using a 1 mL syringe with a needle. The sample was then loaded into the transmission cell, which was placed in the spectrometer sample chamber, and the spectrum was recorded. When using the ATR cell, the ATR attachment is fixed in the sample chamber, and a much smaller sample volume (approximately 0.05 mL, obtained using a 100 μL microsyringe) is added to the ATR cell. For both cells, the sample is isolated from the atmosphere during spectral acquisition to avoid oxidation of the rhodium carbonyl compounds caused by any trace amounts of air.

[0163] Effect of H2O concentration on the oxidation rate of MeI to RhI

[0164] In all these examples, glassware kinetics were studied by tracking the FTIR spectra of the Rh carbonylation catalysts. While the H₂O concentration was maintained at 1.3 M (approximately 2 wt%) in most cases, higher concentrations, up to 3.9 M (6 wt%), were observed in some instances using rate promoters. Therefore, the focus was on determining the effect of H₂O concentration (if present) on the oxidative addition of MeI (in the absence of other rate promoters). Three experiments were conducted, with the H₂O concentration varying in 1.3 M increments. The superimposed FTIR spectra of the three experiments within the 0–240 minute time window are shown below. Figure 2 As shown. Qualitatively, the rate difference appears to be very small. This is due to... Figure 3This is confirmed by the first-order rate curve and the rate constant (k) in Table 3. Note that the rate increases by only 12% over this broad H₂O concentration range. This is consistent with the measurements in US 9,580,377.

[0165] Table 3. Variation of first-order rate constant with water concentration

[0166]

[0167] Effects of LiOAc, LiI, and Cytop™ 503 on the oxidative addition rate of MeI to RhI

[0168] The rate-promoting effect of LiOAc was compared with similar promoting effects of exemplary novel promoters, and with LiI and Cytop™ 503 (a liquid phosphine oxide-based extractant from Solvay) to confirm the trends of LiOAc and LiI obtained in glassware at N2 atmospheres as disclosed in US9,580,377.

[0169] Kinetic data were obtained for the following ranges: LiOAc 0.17 to 0.93 M, LiI 0.32 to 0.98 M, and Cytop™ 503 0.25 to 0.75 M. The resulting pseudo-first-order rate constants were first plotted based on the molar concentration of the promoter, including the zero-point rate constant k = 4.0 min for the absence of a promoter. -1 Since zero points can have an undesirable impact on linear fitting, they are removed. The corresponding linear fitting curve is shown below. Figure 4 As shown, a good R was obtained. 2 The values ​​and the directional trends of LiOAc and LiI, as well as Cytop™ 503, are disclosed in US 9,580,377. Those familiar with kinetic measurements will understand that while the directionality and relative trends of the rate constant are expected to remain consistent across laboratories, the absolute values ​​may vary slightly due to factors such as FTIR signal quality, the batch of Rh I commercial precursor dimer used, etc.

[0170] Effect of potential novel promoters on the oxidative addition rate of MeI to RhI

[0171] A new class of potential rate enhancers is based on amino acid salts. A limited selection of compounds was investigated, and some relevant structures are detailed above.

[0172] Several novel promoters resulted in extremely rapid oxidative addition rates of MeI. This is first visually demonstrated in the following figures using FTIR superimposed spectra. Figure 5The spectra of 0.93M LiOAc from 0 to 180 minutes and 0.16M DTPA-Na3Ca from 0 to 60 minutes were included. Although the molar concentration of DTPA-Na3Ca was almost 6 times lower, the MeI oxidative addition was essentially completed at 60 minutes, while the solution containing LiOAc required 180 minutes.

[0173] Figure 6 A similar comparison is shown, this time for 0.5M LiOAc and 0.033M DTPA-Na5, displaying the spectra at 0 minutes and 120 minutes, respectively. Although the molar concentration of the DTPA-Na5 solution is 15 times lower, the extent of the reaction is visually observed to be greater than that of the 0.5M LiOAc solution. The effect of different concentrations of DTPA-Na3Ca on the oxidative addition rate of MeI is shown below. Figure 7 As shown, the spectral sets associated with four different experiments are superimposed. The complete rate data obtained are shown in Tables 4 and 5.

[0174] Table 4. Rate constants of common accelerators

[0175]

[0176] Table 5. Rate constants of exemplary novel accelerators

[0177]

[0178]

[0179] The data in Tables 4 and 5 show that, except for a few experiments using high concentrations of the novel rate enhancer, the target concentration of 1.3 M H₂O (2 wt%) was largely maintained. However, as mentioned above and as shown in Table 4, the effect of H₂O on the rate was minimal. This is further supported by the NTA-Na₃ data in Table 5, where essentially identical experiments were performed, except that the H₂O concentration was doubled in the second experiment. Similar rates were obtained within the experimental error range. In all cases, the data in Table 5 show that the rates were very high at H₂O concentrations of 1.3 M or close to 1.3 M.

[0180] The selected corresponding curves associated with these tables are as follows: Figure 8 As shown, the relative promoting effects are summarized in Table 6. Figure 8The rate equations in the table correspond to the slopes of the curves in Table 6. The slopes of these curves are particularly valuable for reference. If one were to assume that the various new pentaacetic and triacetic salts should result in proportionally increased rates due to their acetate (carboxylate) molar concentrations being 5 times and 3 times higher than LiOAc, respectively, then the slope of the pentaacetic salt curve should be 5 times steeper than that of LiOAc, and the slope of the triacetic salt curve should be 3 times steeper. However, as shown in Table 6, pentaacetic and triacetic salts unexpectedly exhibited rate-promoting growth increases of 16 to 18 times and 6 times, respectively.

[0181] Table 6. Summary of the promoting effects of the novel accelerators

[0182]

[0183] Effect of H2O concentration on the oxidation rate of HI to RhI

[0184] The effect of H2O concentration on the oxidative addition rate of HI to RhI and its entry into the water-gas shift (WGS) cycle is a question in glacial acetic acid processing. The theory is that as the H2O content decreases, HI will increasingly exist as covalent HI rather than dissociated H+. + --I - or H3O + --I - The covalent form of HI exists. As discussed above, it is believed that the covalent form of HI can undergo an undesirable oxidative addition reaction with the carbonylation catalyst, thereby inhibiting the desired oxidative addition reaction of MeI. At low H2O concentrations and when HI is mainly present in the covalent form, the rate-limiting step may be the second step as shown above; while at high H2O concentrations, the first step may be the rate-limiting step.

[0185] To verify and quantify this effect, a series of kinetic experiments were conducted at room temperature, with an initial HI concentration of 0.25 M and H₂O concentrations varying from 1.3 M to 3.9 M (2 to 6 wt%). An initial Rh I concentration of 0.015 M and a 16-fold molar excess of HI were assumed to be sufficient to achieve pseudo-first-order conditions for determining the rate constant. Since 0.25 M HI contains 1.3 M H₂O, this is the highest usable HI concentration. While the results were in line with expectations in terms of direction, the magnitude of the variation was surprising. FTIR stacked spectra for time windows from 0 to 60 minutes at four different H₂O concentrations are shown below. Figure 9 As shown in the figure, the superimposed spectrum indicates that the reaction rate decreases in the range of 1.3 M to 2.6 M H2O.

[0186] The relevant rate constant curves of some of these experiments are as follows: Figure 10 As shown, the reaction proceeded almost completely at 1.3 M H₂O, while almost no reaction occurred at 3.0 M H₂O. Figure 10The data were examined more carefully, including the rate curves from the three lowest H2O experiments, as shown in the figure. Figure 11 As shown, the rate curves for higher H2O experiments were plotted on [date missing]. Figure 12 middle. Figure 11 The three experiments followed pseudo-first-order kinetics, but even within this narrow H2O range of 1.3 to 2.1 M (2 to 3.2 wt%), R could be observed. 2 It gradually decreases as the pseudo-first-order dynamics become more unstable. Figure 12 In the higher H2O experiments shown, the kinetics are clearly no longer pseudo-first-order. These data suggest that the gradual decrease in the percentage of covalent HI leads to a significant drop in rate, transitioning from pseudo-first-order kinetics to second- or third-order kinetics.

[0187] By estimating the rate constants of low-speed, high-H2O experiments, all rate constants can be plotted as a function of H2O concentration, such as... Figure 13 As shown in the figure. For comparison, the graph also includes the corresponding data for the oxidative addition of MeI to RhI. A power function fit was applied to closely fit all the HI data points. From this graph, the effect of H2O concentration changing from 2 wt% to only 3 wt% can be observed, which contrasts with the relatively small dependence of MeI oxidative addition on H2O concentration.

[0188] Figure 13 The data tend to confirm and quantify the working theory regarding undesirable water-gas shift (SFS). Low H2O conditions may represent an undesirable situation where the HI oxidative addition step is accelerated, while the formed Rh III stagnates due to insufficient H2O to drive the SFS completion. Therefore, the reduced shift rate comes at the cost of higher steady-state Rh III, reduced catalyst stability, and a lower carbonylation rate without Rh addition. These data suggest that binding or ionizing covalent HI at low H2O concentrations to prevent its entry into the SFS cycle is crucial.

[0189] Inhibition of HI-to-RhI oxidative addition

[0190] From the perspective of carbonylation for the production of glacial acetic acid, the remarkably large rate-enhancing effect of the amino polycarboxylate described in this paper is encouraging. However, if the undesirable HI oxidative addition (initiating water-gas shift) also exhibits a similar rate-enhancing effect, it may weaken or even negate the rate advantage of carbonylation. Therefore, a similar kinetic study was conducted, except that 0.1 M HI was used instead of 2 M MeI. In all cases, the concentration was maintained at 1.3 M H₂O.

[0191] In the initial study, two parallel experiments were conducted using 0.1 M HI, with one set of sample vials additionally containing 0.007 M DTPA-Na3Ca. The superimposed spectra of the two sets of experiments during a 5-hour monitoring period are shown below. Figure 14 As shown, even with only 1 / 14 the molar amount of HI (i.e., insufficient accelerator), the oxidative addition reaction was essentially suppressed compared to experiments without a rate accelerator. These preliminary data spurred further investigation into the kinetics of HI at even lower accelerator concentrations.

[0192] Figure 15 Spectral data associated with three 0.1 M HI kinetic experiments are shown. Each experiment was followed up for 5 hours. The top set of superimposed spectra corresponds to the 0.1 M HI / 0.0037 M DTPA-Na3Ca combination. The middle set of spectra corresponds to experiments where the DTPA-Na3Ca concentration was doubled, and the bottom set of spectra corresponds to experiments where the concentration was doubled again. In this way, the molar equivalent ratio of HI to DTPA-Na3Ca varied from a minimum of 6 to a maximum of 27. It can be observed that the addition of HI to Rh I is suppressed; in fact, at 0.016 M DTPA-Na3Ca (the highest molar concentration tested), the HI reaction essentially did not occur.

[0193] Spectral data were acquired for three other 0.1 M HI experiments using LiOAc as a promoter. Compared to the DTPA-Na3Ca case, the molar equivalence ratio of HI to LiOAc was significantly reduced, with ratios of 1, 2, and 6 in the three experiments, respectively. The quantitative data from the obtained FTIR spectra are presented as time-varying curves. Figure 16 and Figure 17 .right Figure 16 and Figure 17 Qualitative and intuitive comparisons showed that, compared to LiOAc, the reaction between HI and Rh I was inhibited in the presence of DTPA-Na3Ca at a concentration several times lower. From the perspective of the rate equation, this is likely quite complex, therefore no attempt was made to determine the rate constant.

[0194] The oxidative addition of HI to Rh I was also investigated in the presence of different concentrations of Cytop™ 503. Significant Rh III formation was only observed during the 3-hour monitoring period when HI was in a four-fold molar excess. As an alternative rate constant comparison tool, the percentage of unreacted Rh I after 250 minutes was used to compare the extent of HI oxidative addition in all experiments. The complete dataset is shown in Table 7.

[0195] Table 7. Relative oxidative addition of HI with or without novel accelerators.

[0196]

[0197] The data in Table 7 were plotted on Figure 18 All four sets of data showed reasonable linear fit. While these comparative equations may only be semi-quantitative, the data indicate that Cytop™ 503 is twice as superior to LiOAc in inhibiting HI oxidative addition. Additional inhibition of 3 to 5 times was achieved for the two novel promoters tested.

[0198] The inhibition slopes and corresponding relative rates of HI oxidative addition are shown in Table 8. As shown in Table 5 for the corresponding MeI oxidative addition promotion rates, the ability of these amino polycarboxylate salts to exert a favorable influence on the reaction rate is demonstrated. In summary, the data disclosed above demonstrate the dual effect of a novel class of promoter compounds in promoting the first step of methanol carbonylation and inhibiting the undesirable first step of water-gas shift reaction. In experiments conducted under the same conditions, these effects were up to 20-fold and 11-fold greater, respectively, than those observed with LiOAc.

[0199] Table 8. Inhibition of water-gas shift reaction by novel accelerators

[0200]

[0201] Consistent with Table 7 of the concurrently filed patent application entitled "Polyphosphates and Polyphosphonates as Rate Promoters in Glacial Acetic Acid Processes," a summary table of novel oxidative addition rate promoter compounds is provided. While not wishing to be bound by theory, it is speculated that these novel rate promoters possess at least two properties that enable them to induce novel and unexpected increases in the oxidative addition rate of MeI. First, there is their high concentration of intramolecular salt groups (phosphonate or phosphate groups), which are not present in salts such as LiI and LiOAc. In these novel promoters, the proximity of the salt groups, combined with their known chelating abilities, likely plays a role in their rate-promoting effect. The second characteristic of these promoters relates to the presence of an amino skeleton in most of them. In glacial acetic acid media rich in iodides (MeI or HI), quaternization reactions almost certainly occur, even at room temperature, to produce the corresponding ammonium acetate, ammonium iodide, or a mixture of both.

[0202] The scope of this application is not intended to be limited to the specific embodiments of the accelerators, processes, equipment, methods, and / or steps described in the specification. The specific embodiments disclosed above are merely illustrative, as those skilled in the art can modify and practice the processes and systems in different but equivalent ways with the benefit of the teachings herein.

[0203] For the sake of brevity, this document only explicitly discloses certain ranges. However, in addition to the ranges listed, any lower bound can be combined with any upper bound to list ranges not explicitly listed, and a range from any lower bound can be combined with any other lower bound to list ranges not explicitly listed, just as a range from any upper bound can be combined with any other upper bound to list ranges not explicitly listed. Additionally, even if not explicitly stated, a range includes every point or individual value between its endpoints. Therefore, each point or individual value can be combined as its own lower or upper bound with any other point or individual value or any other lower or upper bound to list ranges not explicitly listed.

[0204] All patents, test procedures and other documents referenced in this application are incorporated herein by reference in their entirety to allow for all jurisdictions to be permitted by such reference. In the event of any conflict between one or more incorporated patents or publications and this disclosure, this specification (including definitions) shall prevail.

Claims

1. A process for producing acetic acid, the process comprising: a) Combining methanol, methyl acetate, or any mixture thereof with carbon monoxide in the presence of a reaction mixture containing: i) A carbonylation catalyst, wherein the carbonylation catalyst is selected from rhodium catalysts, iridium catalysts, palladium catalysts and cobalt catalysts; ii) Water, which is present in the range of 0.1% to 10% by weight, based on the weight of the reaction mixture; and iii) one or more accelerators, said accelerators being selected from the group consisting of Group I amino polycarboxylates and Group II amino polycarboxylates, and mixtures of said Group I amino polycarboxylates and said Group II amino polycarboxylates; and iv) Iodides; and b) Recover acetic acid.

2. The process according to claim 1, wherein the amino polycarboxylate comprises two or more carboxylate groups.

3. The process according to claim 1, wherein the amino polycarboxylate contains 2 to 10 carboxylate groups.

4. The process according to claim 1, wherein the amino polycarboxylate comprises at least one amine group and at least three carboxylate groups.

5. The process according to claim 1, wherein the amino polycarboxylate comprises at least two amine groups and at least two carboxylate groups.

6. The process according to claim 1, wherein the iodide is in the form of HI, CH3I, or both.

7. The process according to claim 1, wherein the one or more promoters are continuously added to the reaction mixture as an acetic acid solution.

8. The process according to claim 1, wherein the process is carried out in an acetic acid system comprising a reaction zone, a light distillation zone, a purification zone and a circulation zone, wherein the reaction zone comprises a reactor and a flash evaporation vessel.

9. The process of claim 8, wherein one or more accelerators are added to the flash evaporation vessel.

10. The process of claim 8, wherein the combination is carried out in the reactor at a temperature ranging from about 120°C to about 250°C and a pressure ranging from about 200 psia (1.38 MPa-a) to 2,000 psia (13.8 MPa-a).

11. The process according to claim 1, wherein the one or more accelerators are maintained at a molar ratio of iodide to accelerator of 2:1 to 40:

1.

12. The process according to claim 1, wherein the one or more promoters are maintained at a molar ratio of promoter to carbonylation catalyst of 0.005:1 to 4:

1.

13. The process according to claim 11, wherein the weight percentage of water can be reduced as the molar ratio of the one or more promoters increases.

14. The process according to claim 1, wherein no salts of glutamate and dicarboxymethylalanine are present.

15. A method for reducing water in an acetic acid production process, the method comprising: a) Under carbonylation conditions sufficient to form acetic acid at a first rate, methanol, methyl acetate, or any mixture thereof is combined with carbon monoxide in the presence of a reaction mixture containing an iodide, wherein the reaction mixture comprises: i) a carbonylation catalyst, wherein the carbonylation catalyst is selected from the group consisting of rhodium catalysts, iridium catalysts, palladium catalysts, and cobalt catalysts; and ii) A first water content, based on the weight of the reaction mixture, wherein the water is present in the range of 0.1% to 10% by weight; and b) Incorporating one or more accelerators into the reaction mixture at a molar ratio of iodide to accelerator greater than 2, wherein the one or more accelerators are selected from the group consisting of Group I aminopolycarboxylates and Group II aminopolycarboxylates, and mixtures of the Group I aminopolycarboxylates and the Group II aminopolycarboxylates; and c) Reduce the weight percentage of water in the reaction mixture to a second water amount, while maintaining a second acetic acid production rate that is the same as or higher than the first acetic acid production rate.

16. The process of claim 15, wherein the amino polycarboxylate comprises two or more carboxylate groups.

17. The process of claim 15, wherein the amino polycarboxylate comprises 2 to 10 carboxylate groups.

18. The process according to claim 15, wherein the amino polycarboxylate comprises at least one amine group and at least three carboxylate groups.

19. The process according to claim 15, wherein the amino polycarboxylate comprises at least two amine groups and at least two carboxylate groups.

20. The process according to claim 15, wherein the iodide is in the form of HI, CH3I, or both.

21. The process of claim 15, wherein the one or more promoters are continuously added to the reaction mixture as an acetic acid solution.

22. The process of claim 15, wherein the process is carried out in an acetic acid system comprising a reaction zone, a light distillation zone, a purification zone, and a circulation zone, wherein the reaction zone comprises a reactor and a flash evaporator.

23. The process of claim 22, wherein one or more accelerators are added to the flash evaporation vessel.

24. The process of claim 22, wherein the combination is carried out in the reactor at a temperature ranging from about 120°C to about 250°C and a pressure ranging from about 200 psia (1.38 MPa-a) to 2,000 psia (13.8 MPa-a).

25. The process of claim 15, wherein the one or more accelerators are maintained at a molar ratio of iodide to accelerator of 2:1 to 40:

1.

26. The process according to claim 15, wherein the one or more promoters are maintained at a molar ratio of promoter to carbonylation catalyst of 0.005:1 to 4:

1.

27. The process according to claim 15 does not contain salts of glutamate and dicarboxymethylalanine.

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