JP5866474B1 - Process for controlling HI concentration in residue stream - Google Patents

Abstract

[0119] A process for acetic acid production comprising providing a feed stream comprising methyl iodide, water, acetic acid, methyl acetate and at least one PRC to a distillation column comprising a distillation zone and a bottom storage zone, methyl iodide And at a pressure and temperature sufficient to produce an overhead stream comprising at least one PRC and a residue stream comprising water and HI equal to or greater than about 0.11 wt%, exiting the bottom storage zone. A process comprising distilling the feed stream is disclosed in the present invention. [Selection] Figure 1

Description

Related applications

  [0001] This application claims priority from US Provisional Application No. 62 / 112,120, filed Feb. 4, 2015, the entire disclosure of which is incorporated herein by reference.

  [0002] The production of acetic acid by carbonylation involves the continuous reaction of methanol and carbon monoxide in the presence of a catalyst in a reactor. The reaction mixture present in the reactor comprises a transition metal, which may be a group VIII metal, which may be iridium and / or rhodium or nickel, and further comprises one or more solvents, water, various stabilizers, promoters , Accelerators and the like can be included. Reaction mixtures known in the art can include acetic acid, methyl acetate, methyl iodide, hydrogen iodide, hydrogen iodide promoter, and the like.

  [0003] A complex network of interdependent equilibria involving liquid acetic acid reaction components exists in the reaction mixture in the reactor, which is directed to the production of acetic acid and the generation of various impurities in the reactor. There is something to go to. Impurities that may be present in acetic acid include permanganate reducing compounds (PRC) such as acetaldehyde.

  [0004] Hydrogen iodide (HI), whether in molecular form as hydrogen iodide or dissociated in a solvent as hydriodic acid, is present in the reaction mixture according to various production schemes. However, HI is highly corrosive to metals and presents various difficulties in acetic acid production.

  [0005] In the art, attempts have been made to minimize HI outside the reactor, and the ultimate goal is to eliminate HI outside the reactor. For example, there is a process intended to inject methanol into a distillation column and react methanol with HI present in the distillation column to produce methyl iodide and water (Japanese Patent Application No. Hei filed on Aug. 31, 1998). 10-244590 (JP 2000-72712), the entire disclosure of which application is incorporated herein by reference). However, processes that try to minimize or eliminate corrosion problems by minimizing HI have failed to realize the benefits associated with a specific concentration of HI outside the reactor. In various aspects of the acetic acid production process, the HI concentration needs to be controlled within a certain range.

  [0006] In an embodiment in accordance with the present disclosure, the method for producing acetic acid is such that the concentration of HI exceeds a minimum concentration in one or more streams outside the carbonylation reactor, particularly in a distillation column used in an aldehyde removal process. And / or processes controlled within a selected concentration range above its minimum concentration.

  [0007] In an aspect, the process provides a feed stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC to a distillation column comprising a distillation zone and a bottom sump zone. Producing an overhead stream comprising methyl iodide and at least one PRC and a residue stream comprising HI equal to or greater than about 0.11 wt% of water exiting the bottom storage zone Distilling at a pressure and temperature sufficient to do so.

[0008] In some embodiments, the process distills a portion of the reaction medium of the carbonylation reactor in a first distillation column to produce an acetic acid stream and methyl iodide, water, acetic acid, methyl acetate, and at least one A second overhead stream comprising or derived from the first overhead stream is charged to a second distillation tower comprising a distillation zone and a bottom storage zone The second column feed stream is equal to a second column overhead stream comprising methyl iodide and at least one PRC, and water and about 0.11 wt% exiting the bottom storage zone, or Distilling at a pressure and temperature sufficient to produce a second tower residue stream comprising greater HI; at least a portion of the second tower overhead stream comprising methyl iodide and at least one PRC is about 25 ℃ not And extracted with water temperature, and an aqueous waste stream containing at least one PRC, it generates a raffinate (raffinate) streams containing methyl iodide; second at least a first portion of the raffinate stream Return to the distillation column.

  [0009] In yet another aspect, the process comprises distilling a portion of the reaction medium of the carbonylation reactor in a first distillation column to produce an acetic acid stream and methyl iodide, water, acetic acid, methyl acetate, and Obtaining a first overhead stream comprising at least one PRC; a second column feed stream comprising or derived from the first overhead stream to a second distillation column comprising a distillation zone and a bottom storage zone Charging the second tower feed stream with a second tower overhead stream comprising methyl iodide, dimethyl ether, and at least one PRC, and water and about 0.11 weight out of the bottom storage zone. Distilling at a pressure and temperature sufficient to produce a second column residue stream comprising from about 0.9% to about 0.9% by weight HI; at the same time, a top flush stream comprising water is added to the second column feed stream. 0.1% of mass flow rate of Charging the distillation zone at a mass flow rate of or above; and simultaneously, distilling the bottom flush stream containing acetic acid at a mass flow rate equal to or exceeding 0.1% of the mass flow rate of the second column feed stream. Injecting into the zone and / or the bottom storage zone.

  [0010] The above summary is provided as an introduction to the selection of concepts that are further described below in the detailed description. The above summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help limit the scope of the claimed subject matter. .

[0011] FIG. 1 is a schematic diagram of a process for producing acetic acid according to one embodiment. [0012] FIG. 1 is a schematic diagram of a purification process according to one embodiment. [0013] FIG. 3 is a cross-sectional view of a second distillation column according to one embodiment. [0014] FIG. 4 is a cross-sectional view of a liquid redistributor of a second distillation column according to one embodiment. [0015] FIG. 6 is a cross-sectional view of a liquid redistributor of a second distillation column according to one embodiment. [0016] FIG. 6 is a cross-sectional view of a liquid redistributor of a second distillation column according to another embodiment.

  [0017] First, of course, in developing such an actual aspect, the developer makes a number of execution-specific decisions, such as adhering to system-related and business-related constraints that can change with execution. It is necessary to achieve these specific goals. Further, as will be apparent to those skilled in the art, the processes disclosed herein may include other than those cited or specifically mentioned.

  [0018] In the summary and detailed description of the invention, unless otherwise indicated by context, each numerical value is once modified with the term "about" (if no explicit modification has already been made). After reading, the modification should be removed and read again. In the summary and detailed description of the invention, as a matter of course, when a useful concentration range, an appropriate concentration range, and the like are described, all concentrations within the range (including the end point) are described. Should be considered. For example, a “range of 1-10” should be understood to indicate any and all possible numbers along a continuum between about 1 and about 10. Thus, even if only a few predetermined data points are shown within the range or the data points are not clearly identified, the inventors will naturally We understand that every and every data point should be considered as specified, and the inventors have knowledge of the entire range and all points within that range.

[0019] Unless stated otherwise, throughout this specification (including the claims), the following terms have the meanings set forth below.
[0020] As used herein and in the claims, "near (a value or place)" includes "(its value or place) itself". The term “and / or” means both the inclusive “and” case and the exclusive “or” case, but is used herein for the sake of brevity. For example, a mixture containing acetic acid and / or methyl acetate may contain only acetic acid, may contain only methyl acetate, or may contain both acetic acid and methyl acetate.

  [0021] Unless otherwise stated, all percentages are expressed as weight percent (wt%) relative to the total weight of the particular stream or composition present therein. Unless otherwise stated, the room temperature is 25 ° C. and the atmospheric pressure is 101.325 kPa.

[0022] In this specification,
Acetic acid is abbreviated as “AcOH”,
Acetaldehyde is abbreviated as “AcH”;
Methyl acetate is abbreviated as “MeAc”,
Methanol is abbreviated as “MeOH”,
Methyl iodide is abbreviated as “MeI”,
Carbon monoxide is abbreviated as “CO”,
Dimethyl ether may be abbreviated as “DME”.

[0023] HI means hydrogen iodide molecules or hydroiodic acid that dissociates upon at least partial ionization in a polar medium (usually a medium containing at least some water). Unless otherwise stated, the two are used interchangeably. Unless otherwise stated, HI concentration is determined by acid-base titration using potentiometric endpoint. In particular, the HI concentration is determined by titration to the potentiometric titration end point using a standard lithium acetate solution. Of course, in this specification, the concentration of HI is determined by subtracting from the total iodide present in the sample the concentration of iodide that appears to be associated with measurements of corrosive metals and other cations other than H ^+. It is not a thing.

[0024] Of course, HI concentration does not mean iodide ion concentration. Specifically, the HI concentration means the HI concentration obtained by potentiometric titration.
[0025] The above subtraction method is unreliable, and since it is estimated that all cations other than H ⁺ (eg, cations of Fe, Ni, Cr, Mo) bind only to iodide anions, An inaccurate method for determining low HI concentrations (ie, less than about 5% by weight). In practice, most of the metal cations in the process can bind to the acetate anion. In addition, many of these cations are multivalent, which makes the assumption about the amount of iodide anions that can bind to these metals increasingly less reliable. After all, considering that a simple titration that directly indicates the HI concentration can be performed, it is not reliable to determine the actual HI concentration by this method.

  [0026] As used herein, "overhead" of a distillation column refers to at least one low boiling condensable fraction that distills at or near the top of the distillation column (eg, near the top) and / or overhead. It means the condensed form of a stream or composition. In the end, it is clear that all fractions are condensable, but as those skilled in the art will readily understand, condensable fractions are condensed here under the conditions present in the process. Is possible. Examples of non-condensable fractions include nitrogen and hydrogen. Similarly, an overhead stream can be obtained just below the top outlet of the distillation column, but, as one skilled in the art can readily appreciate, for example, the lowest boiling fraction is a non-condensable stream or a slight It is a simple flow.

  [0027] Distillation column residue means one or more of the highest boiling fractions emerging at or near the bottom of the distillation column and, as used herein, flowing out from the bottom storage zone of the distillation column. Also means. It should be understood that the residue can be obtained from just above the actual bottom outlet of the distillation column, for example, the bottom fraction produced by the distillation column is , Salt, unusable tar, solid waste, or a slight stream.

  [0028] As used herein, a distillation column includes a distillation zone and a bottom storage zone. The distillation zone includes everything above the bottom storage zone, i.e. between the bottom storage zone and the top of the column. In this specification, the bottom storage zone means the lower part of the distillation column (for example, the bottom of the distillation column) where the liquid reservoir of the high boiling point component exists, from which the bottom or residue flow flows and the outside of the distillation column. To be discharged. The bottom storage zone includes a reboiler and a control device.

  [0029] The terms "passage", "flow path", "flow conduit", etc., associated with an internal component of a distillation column, refer to liquids that move from one side of the internal component to the other side of the internal component and It should be understood to mean holes, tubes, grooves, slits, drains, etc. that are arranged through and / or provide passageways for steam. Examples of passages disposed through a structure such as a liquid distributor in a distillation column include drain holes that allow liquid to flow from one side of the structure to the other side of the structure, A drain tube and drain slit are included.

  [0030] Average residence time is the total amount of total liquid volume holdup for a given phase in the distillation zone divided by the average flow rate of that phase through that distillation zone. The hold-up volume for a given phase is the volume of liquid contained in various internal components of the distillation column, including collectors, distributors, etc., as well as on the tray, in the downcomer, and / or structured. Liquids contained within the bed or randomly packed beds may also be included.

  [0031] The average total residence time of the feed stream in the distillation zone of the distillation column is necessarily less than the total residence time of the feed stream in the distillation column, and thus does not mean the total residence time of the feed stream in the distillation column. The total residence time of the feed stream in the distillation column is the sum of both the total residence time of the feed stream in the distillation zone and the total residence time of the feed stream in the bottom storage zone of the distillation column.

[0032] As used herein, internal components within the distillation zone of a distillation column include packings, liquid distributors, liquid collectors, liquid redistributors, trays, supports, and the like.
[0033] In this specification, unless otherwise stated, the mass flow rate is given in kg / hour and may be determined directly or calculated from volumetric measurements.

  [0034] As used herein, a carbonylatable reactant is acetic acid, ie, any substance that reacts with carbon monoxide under the reaction conditions to produce the desired product. Reactive substances that can be carbonylated include methanol, methyl acetate, dimethyl ether, methyl formate, and the like.

  [0035] As used herein, "part" refers to a stream or other composition that is further processed, for example, by recycling or returning to another part of the process. And should be understood to mean a portion of the composition. In other words, “part” means part of the total mass flow rate of the stream or part of the total composition. It should be understood that a “portion” of a stream or composition does not refer to optional ingredients present therein. Thus, recirculation of a portion of the flow does not include any process in which the components in the flow at the origin do not exist at the disposal point.

[0036] When a portion of the stream or composition is directly recycled or transferred to the disposal point, the mass of each component originally present in the stream is also present at the disposal point in the same relative proportions.
[0037] A portion of a stream or composition that is indirectly recirculated or directly charged may be mixed with other streams, but the absolute amount of any component present in the original stream is also at the point of disposal. The change in overall composition that exists is the result of mixing a particular stream with other streams.

  [0038] As used herein, a stream or composition "derived" from another stream, including the entire other stream, is from all of the individual components originally present in the other stream. Small components may be included. Thus, recirculation of a stream originating from another stream does not necessarily require that the amount of each component that was originally present in that other stream is also present at the disposal point. Thus, a stream or composition “derived from” a particular stream may include a stream that is subjected to further processing or purification prior to disposal. For example, the stream that is distilled and then recycled to the final disposal point originates from the stream.

  [0039] In the present specification, permanganic acid reducing compound (PRC) includes acetaldehyde, acetone, methyl ethyl ketone, butyraldehyde, crotonaldehyde, 2-ethylcrotonaldehyde, 2-ethylbutyraldehyde and the like, and aldol condensates thereof. And crossed aldol condensates. PRC is detected according to ASTM D1363. HI has physical properties that are generally considered to adversely affect various process components that are typically present in commercial acetic acid processes due to corrosion problems. In particular, the presence of HI in the distillation column is considered to adversely affect the heat exchange surface such as a reboiler. Although HI is necessarily present in carbonylation reactors used for the production of acetic acid via “Monsanto” or AO® technology processes, numerous applications in the art are found outside the carbonylation reactor. It is directed to reducing and / or eliminating the presence of HI in the stream.

  [0040] However, it has been discovered that the presence of HI at a specific concentration in one or more streams outside the acetic acid process carbonylation reactor has one or more benefits not previously known. For example, HI has been suggested to be beneficial for the production of dimethyl ether (DME) under conditions present in the distillation column of an aldehyde removal system (ARS). This dimethyl ether is surprisingly found in iodine in aqueous waste streams produced by aldehyde removal systems such as those disclosed in US Pat. No. 7,223,883, US Pat. No. 7,223,886 and US Pat. No. 8,076,507, all of which are incorporated herein by reference. Has the function of reducing the methyl chloride concentration. Thus, prior art disclosures directed to eliminating HI outside the reactor cannot benefit from the HI concentration according to the embodiments disclosed herein. Aspects disclosed herein further provide a method by which the HI concentration in the ARS distillation column reservoir can be controlled. By controlling the HI concentration in the reservoir of the ARS distillation column, the amount of DME produced in the distillation column can be controlled and the benefits derived therefrom can be obtained.

  [0041] In an aspect, the process provides a feed stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC to a distillation column comprising a distillation zone and a bottom storage zone; Sufficient to produce an overhead stream comprising methyl iodide and at least one PRC, and a residual stream comprising HI equal to or greater than about 0.11% by weight flowing out of the bottom storage zone. Distillation at moderate pressure and temperature. In some embodiments, the residue stream comprises about 0.6 wt% to about 1.2 wt% HI.

  [0042] In some embodiments, the average liquid phase residence time in the distillation zone of the process is from about 1 minute to about 60 minutes. In some embodiments, the liquid phase includes a first liquid phase that includes greater than about 50 wt% water and a second liquid phase that includes greater than about 50 wt% methyl iodide. In some embodiments, the distillation zone includes a plurality of internal components each having a component liquid retention volume, each internal component having an average residence time of the first liquid phase and the first component in each of the component liquid retention volumes. The dimensions and arrangement are such that the average residence time of the two liquid phases is less than about 30 minutes.

  [0043] In some embodiments, at least one internal component is sized and arranged such that the average residence time of the first liquid phase is equal to or exceeds the average residence time of the second liquid phase in the corresponding component liquid holding volume. Has been. In some embodiments, the first at least one internal component is sized and arranged such that the average residence time of the first liquid phase is from about 0.1 minutes to about 20 minutes in the corresponding component liquid retention volume. And / or at least one internal component is dimensioned such that the average residence time of the second liquid phase is about 0.1 minutes to about 20 minutes in the corresponding component liquid holding volume And a second plurality of channels arranged.

  [0044] In certain embodiments, the process further comprises introducing a top flush stream comprising water into the distillation zone simultaneously with distillation of the feed stream. In some embodiments, the mass flow of the top flash stream entering the distillation column is equal to or greater than about 0.1% of the mass flow of the feed stream and / or the top flash stream is about 20% by weight. Or a portion of the bottom residue stream, or a combination thereof.

  [0045] In certain embodiments, the process further comprises charging a bottom flush stream comprising acetic acid to the distillation zone, the bottom storage zone, or both simultaneously with distillation of the feed stream, the charging comprising water. It may be simultaneous with the introduction of the top flush stream containing into the distillation zone. In some embodiments, the bottom flush stream comprises acetic acid equal to or greater than about 20% by weight and / or the bottom flush stream mass flow to the distillation column is about 0.1% of the feed stream mass flow rate. Is equal to or greater than In any one of the above embodiments, the overhead stream produced by the distillation column comprises dimethyl ether.

[0046] In some embodiments, the process comprises the following steps:
a. A stream derived from the reaction medium of the carbonylation reactor is distilled in a first distillation column to form an acetic acid stream and a first overhead stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC. And a process of obtaining
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower comprising a distillation zone and a bottom storage zone;
c. HI equal to or greater than about 0.11 wt% water and a second tower overhead stream comprising methyl iodide and at least one PRC and water exiting the bottom storage zone. Distilling at a pressure and temperature sufficient to produce a second tower residue stream comprising:
d. Extracting at least a portion of the second tower overhead stream comprising methyl iodide and at least one PRC with water at a temperature of less than about 25 ° C. to obtain an aqueous waste stream comprising the at least one PRC; Obtaining a raffinate stream comprising:
e. Returning at least a first portion of the raffinate stream to the second distillation column.

  [0047] In some embodiments, the second tower residue stream comprises about 0.6 wt% to about 1.2 wt HI. In certain embodiments, the second tower overhead stream comprises dimethyl ether and may further comprise returning a second portion of the raffinate stream comprising methyl iodide and dimethyl ether to the reaction medium. In some embodiments, the mass flow rate of the first portion of the raffinate stream returned to the second distillation column is equal to or exceeds the mass flow rate of the second portion of the raffinate stream returned to the reaction medium.

[0048] In some embodiments, the bottom temperature of the second distillation column is from about 90 ° C to about 130 ° C, and the pressure of the second distillation column is from atmospheric pressure to a pressure above atmospheric pressure of about 700 kPa , or a combination thereof It is.

[0049] In some embodiments,
a. The bottom temperature of the second distillation column,
b. The pressure in the second distillation column,
c. The composition of the top flush stream (eg the concentration of water present there),
d. The top flush stream mass flow rate relative to the second column feed stream mass flow rate,
e. The composition of the bottom flush stream (eg the concentration of acetic acid therein),
f. The bottom flush stream mass flow rate relative to the second column feed stream mass flow rate,
g. The average liquid phase residence time in the distillation zone of the second distillation column, and h. An average residence time of the first liquid phase and / or the second liquid phase within each of the internal components present in the distillation zone of the second distillation column,
Is selected to produce a second tower residue stream comprising about 0.11% to 0.9% by weight of HI.

Acetic acid production system
[0050] The process of producing acetic acid by carbonylation of methanol is conveniently divided into three main regions: a reaction system, an internal purification system, and a product purification system.

[0051] The reaction system includes a carbonylation reactor, a flasher, and the like. Internal purification systems include light end recovery / acetic acid product separation systems, aldehyde removal systems, and the like.
[0052] Product purification systems include drying towers, resin beds, etc. directed to purifying acetic acid to produce the final product.

  [0053] Examples of processes suitable for producing a distillation column feed stream according to the present disclosure include US 3769329, US 3772156, US 4039395, US 42555591, US 4615806, US 5001259, US 5026908, US 5144068, US 5237097, US 5334755, US 5653895, US 5588392, US 5588392. U.S. Pat. U.S. Are incorporated herein by reference.

Reaction system and process
[0054] As shown in FIG. 1, the process 100 includes charging a methanol-containing feed stream 101 and a carbon monoxide-containing feed stream 102 to the liquid phase reaction medium 105 of the carbonylation reactor 104, where they are In the presence of a catalyst, water, methyl iodide, methyl acetate, acetic acid, iodide salt, HI, and other reaction medium components to produce acetic acid.

  [0055] A portion of the reaction medium 105 is continuously withdrawn from the reactor 104 via the line 113 to the flasher 112. This stream is subjected to flash or low pressure distillation in flasher 112 to separate acetic acid and other volatile components from non-volatile components present in the reaction medium. Non-volatile components are recycled into the reaction medium via stream 110. Volatile components of the reaction medium enter the light end tower 124 via line 122.

  [0056] As shown in FIG. 1, the process includes a number of recirculation lines through which various streams are recycled from other parts of the process to the reaction medium. The process also includes various steam purge lines and the like. All vents and other steam lines are connected to one or more scrubbers or vent systems, and all condensable components discharged to the scrubber system are eventually recycled to the carbonylation reactor. Should be understood.

  [0057] In certain embodiments, the reaction medium comprises a metal catalyst, or a Group VIII metal catalyst, or a catalyst comprising rhodium, nickel and / or iridium. In some embodiments, the reaction medium typically includes about 200 to about 5000 ppm by weight of rhodium catalyst, based on the total weight of the reaction medium.

  [0058] In certain embodiments, the reaction medium further comprises a halogen-containing catalyst promoter, typically methyl iodide (MeI). In some embodiments, the reaction medium comprises MeI equal to or greater than about 5 wt%, or about 5 wt% to about 50 wt% MeI. In some embodiments, the reaction medium comprises AcOH equal to or greater than about 50% by weight.

  [0059] In certain embodiments, the reaction medium comprises a finite concentration of water. In so-called low water processes, the reaction medium contains a finite concentration of water up to about 14% by weight. In some embodiments, the reaction medium further comprises about 0.5 wt% to less than 20 wt% methyl acetate (MeAc).

  [0060] In some embodiments, the reaction medium further comprises hydrogen iodide and one or more iodide salts, typically lithium iodide (LiI), at about 2 wt% or more and about 30 wt% of the reaction medium. In amounts sufficient to provide the following total iodide ion concentrations.

  [0061] In certain embodiments, the reaction medium may further comprise hydrogen that depends on the hydrogen partial pressure in the reactor. In some embodiments, the partial hydrogen pressure in the reactor is equal to or greater than about 1.03 MPa (0.1 psia), 3.5 kPa (0.5 psia), or 6.9 kPa (1 psia). 150 psia), 689 kPa (100 psia), 345 kPa (50 psia), or 138 kPa (20 psia).

  [0062] In certain embodiments, the reactor temperature, ie, the temperature of the reaction medium, is equal to or greater than about 150 ° C. In some embodiments, the reactor temperature is about 150 ° C. or higher and about 250 ° C. or lower. In some embodiments, the reactor temperature is about 180 ° or more and about 220 ° C. or less.

  [0063] In certain embodiments, the carbon monoxide partial pressure in the reactor is equal to or greater than about 200 kPa. In some embodiments, the CO partial pressure is about 200 kPa or more and about 3 MPa or less. In some embodiments, the CO partial pressure in the reactor is about 300 kPa, 400 kPa, or 500 kPa or more and about 2 MPa or 1 MPa or less. The total reactor pressure is the combined partial pressure of all reactants, products and by-products present in the reactor. In some embodiments, the total reactor pressure is about 1 MPa or more and about 4 MPa or less.

Light-end recovery / acetic acid product separation system and process
[0064] In one embodiment, the overhead stream from the flasher 112 is input as stream 122 to the first distillation column 124, which is also referred to as the light end column or stripper column. That is, the feed stream to the first distillation column is derived from the reaction medium because it has undergone distillation before entering the first distillation column. Distillation of the feed stream in the light end column 124 produces a low boiling first overhead vapor stream 126 (referred to herein as first overhead stream 126) and a purified acetic acid stream 128. Stream 128 is a crude acetic acid stream that is later purified. In some embodiments, the acetic acid stream 128 is withdrawn as a side stream. The light end column 124 further produces a high boiling residue stream 116 that may be subjected to further purification and / or recycled to the reaction medium.

  [0065] In an embodiment, acetic acid stream 128 is subjected to further purification in the product purification section of the process (eg, drying tower 130) to remove water. In some embodiments, the acetic acid stream 128 may be further purified in a heavy end tower (see International Publication No. WO 0216297) and / or contacted with one or more absorbents, adsorbents or purification resins in the guard tower 200 for various purposes. Impurities may be removed (see US6657078).

  [0066] In an aspect, the first overhead 126 is condensed and then injected into an overhead phase separator 134 (overhead decanter 134). The first overhead 126 includes methyl iodide, methyl acetate, acetic acid, water and at least one PRC. In some embodiments, the condensed first overhead stream 126 comprises light aqueous phase 135 comprising water, acetic acid, methyl iodide, methyl acetate and at least one PRC, and methyl iodide, methyl acetate and at least one PRC. Separate into heavy phase 137. Considering the solubility of methyl iodide in water or vice versa, the heavy phase 137 contains some water and the light phase 135 contains some methyl iodide. The exact composition of these two streams is a function of the methyl acetate, acetic acid, acetaldehyde and other components that are also present in the light end overhead stream 126.

  [0067] In some embodiments, at least a portion of the heavy phase 137, the light phase 135, or both are returned to the reaction medium via line 114. In some embodiments, essentially all the heavy phase 137 is recycled to the reactor to transfer the light phase 135 to the aldehyde removal process 108. In other embodiments, essentially all of the light phase 135 is recycled to the reactor and the heavy phase 137 is transferred to the aldehyde removal process 108. In this specification, the case where the light phase 135 is transferred to the aldehyde removal process 108 is taken as an example. However, it should be understood that only the heavy phase 137 may be transferred to the aldehyde removal process 108 and may be transferred along with the light phase 135. In some embodiments, a portion (typically about 5-40% by volume) of the heavy phase 137 may be transferred to the aldehyde removal system 108 and the remainder recycled to the reaction medium. In some embodiments, at least a portion of the condensed second tower overhead 138 is returned to the light end tower 124 via stream 140 as reflux.

  [0068] In an aspect, a stream derived from the first tower overhead 126 (ie, light phase 135) is provided as a feed stream 142 to the aldehyde removal system 108 (ARS). Feed stream 142 includes methyl iodide, water, acetic acid, methyl acetate and at least one PRC. The aldehyde removal system includes at least one distillation column 150. The distillation column 150 includes a distillation zone 312 and a bottom storage zone 314 (see FIG. 3).

  [0069] The aldehyde removal system 108 may have a single distillation column 150, as shown in FIG. In FIG. 1, a single distillation column ARS embodiment is indicated generally at 132. In this embodiment, the ARS feed stream 142 is distilled in the second distillation column 150 to remove water, acetic acid, methyl iodide and methyl acetate from the residue 154, and PRC (acetaldehyde) concentrated in methyl iodide is removed. A second overhead stream 152 containing is generated.

  [0070] As shown in FIG. 2, the aldehyde removal system 108 may include at least two distillation columns 170 and 172. This multiple tower ARS is generally designated as 133. In assembly 133, feed stream 142 is input to separation tower 170 and water and acetic acid are withdrawn as residue stream 174. Overhead 178 includes methyl iodide, methyl acetate and PRC. A portion of overhead 178 may be refluxed to the separation column as stream 181.

  [0071] Overhead stream 178 is then input to second distillation column 172 as stream 179. As used herein, stream 179 refers to another second tower feed stream 179. Feed stream 179 is distilled in a second distillation column 172 to produce a second overhead stream 152 comprising methyl iodide and at least one PRC. Distilling another second column feed stream 179 further produces a residue stream 154 that exits from the bottom storage zone of the column 172 containing HI equal to or greater than about 0.11 wt%.

  [0072] Both of these ARS systems are described herein with similar descriptions using the same representations used to describe essentially the same flow in each system. The second tower overhead 152 and second tower residue 154 generated using assembly 132 are essentially the same as the same streams 152 and 154 generated using assembly 133. That is, in the present specification, various flow rates, various flow inputs, and the like are used without being distinguished between the assemblies indicated by 132 and 133. In some embodiments, the second overhead stream 152 may further include dimethyl ether. Dimethyl ether may be intentionally added to the process such that it accumulates in the second column overhead 152 so that DME is generated in-situ in the second distillation column 150 or 172. The process may be operated.

[0073] In an aspect, the second tower overhead 152 is condensed and transferred to an overhead separator 160. A portion of the condensed second column overhead 162 may be refluxed to the second distillation column (150 or 172) via lines 167 and 164. At least a portion of the second tower overhead 162 condensed (e.g., by a heat exchanger 173) is cooled, at least one extractor 169, typically less than about 25 ° C., less than about 20 ° C., 15 ° C. The aqueous stream 166 (usually water) is contacted at an extraction temperature of less than about 10 ° C or less than about 5 ° C. Extraction of the second tower overhead 152 produces an aqueous waste stream 168 containing PRC and a small amount of methyl iodide, which is later removed from the process as waste. This extraction also produces a raffinate stream 158 containing methyl iodide. If the second tower overhead 152 includes dimethyl ether, the raffinate stream 158 also includes dimethyl ether.

  [0074] In some embodiments, at least a portion of the raffinate stream 158 is recycled to the second distillation column via line 161, which greatly improves the amount of PRC present in the second column overhead 152. To do.

  [0075] In some embodiments, the raffinate stream 158 is divided into two parts, a first part 161 and a second part 163. The first portion 161 of the raffinate stream flow is recycled to the second distillation column. A second portion 163 of the raffinate stream flow is recycled to the reaction medium via stream 155 (eg, stream 155 combined with streams 116, 118, etc.). By recycling a portion of the raffinate stream to the reaction medium, the DME present in the stream is consumed. As a result, excessive accumulation of DME in the second distillation column 150 or 172 is suppressed, and overpressure in the second distillation column 150 or 172 can be prevented (see US Pat. No. 7,228,883). As the pressure increases in column 150 or 172, an overhead separator 160 vents to scrubber system 139. This vent leads to undesirable aldehyde recirculation to the reaction medium.

  [0076] In some embodiments, the mass flow rate of the first portion 161 of the raffinate is equal to or greater than the mass flow rate of the second portion 163 of the raffinate. In some embodiments, the mass flow rate of the raffinate first portion 161 is about 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60% of the mass flow rate of the raffinate second portion 163. %, 70%, 80%, or 90%, and less than 500%. In some embodiments, the mass flow rate of the raffinate second portion 163 is about 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60% of the mass flow rate of the raffinate first portion 161. %, 70%, 80%, or 90%, and less than 500%.

  [0077] In some embodiments, the second distillation column (150 or 172) may optionally have a side stream 157 from which a stream comprising methyl acetate is produced. The optional side stream 157 allows the second distillation column to operate at conditions desirable to increase the acetaldehyde concentration in the second column overhead stream 152, while normally the center of the second distillation column. It is possible to provide a mechanism for removing methyl acetate and / or methanol that accumulates (eg, methyl acetate bulge) and eventually enters the second tower overhead stream 152 And If any side stream 157 containing methyl acetate is utilized, it is preferably recycled to the process.

  [0078] Aspects of the process may further include charging a top flash stream 164 containing water into the distillation zone of the second distillation column 150 or 172. The top flush stream 164 may contain fresh material, but is preferably generated from the stream generated by the process to control the amount of moisture in the system. In some embodiments, the top flush stream 164 includes water, acetic acid, methanol, or any combination thereof.

  [0079] In an embodiment using assembly 133, a portion of separation tower residue stream 174 may be input to another second distillation tower 172 as top flash stream 164 via streams 156 and 164. In embodiments using apparatus 132, the top flush stream may include at least a portion of residue stream 154 that is input via streams 156-164.

  [0080] In certain aspects, the mass flow rate of the top flush stream 164 is equal to about 1% of the total mass flow rate of the feed stream 142, the second column feed stream 143, or the feed stream 179, if applicable, or Exceed. In some embodiments, the mass flow rate of the top flush stream 164 is about 5%, 10%, 20%, 30% of the mass flow rate of the feed stream 142, the second column feed stream 143 or the feed stream 179, where applicable. %, 40%, 50%, 60%, 70%, 80%, 90%, 100% or 150%, and less than 500%.

  [0081] In some embodiments, the process may further comprise injecting a bottom flush stream 165 into the distillation zone of the second distillation column and / or the bottom storage zone of the second distillation column. The bottom flush stream 165 may include water, acetic acid, or both. In some embodiments, the bottom flush stream 165 includes at least 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or 95 wt% acetic acid. In some embodiments, the bottom flush stream consists of or consists essentially of acetic acid.

  [0082] In some embodiments, the mass flow rate of the bottom flush stream 165 into the second distillation column 150 or 172 is about 0.1% of the total mass flow rate of the feed stream 142, the second column feed stream 143 or 179. Is equal to or greater than In certain embodiments, the mass flow rate of bottom flush stream 165 is about 5%, 10%, 20%, 30% of the mass flow rate of feed stream 142, second column feed stream 143 or feed stream 179, as applicable. It is equal to or exceeding 40%, 50%, 60%, 70%, 80%, 90%, 100%, 150%, 200% or 300% and less than 500%.

  [0083] In certain aspects, the combined total mass flow rate of the top flash stream 164 and the bottom flash stream 165 is approximately the mass flow rate of the feed stream 142, the second tower feed stream 143, or the feed stream 179, where applicable. 1.1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 150%, 200% or 300%, 500 %.

  [0084] In some embodiments, the mass flow rate of the top flash stream 164, the mass flow rate of the bottom flash stream 165, or the combined total mass flow rate of the top flash stream 164 and the bottom flash stream 165 is about the mass flow rate of the residue stream 154. 1% to about 50%.

  [0085] In some embodiments, the second distillation column residue stream 154 comprises water, acetic acid and at least about 0.11 wt% HI. In some embodiments, the residue stream 154 is equal to or greater than about 5 wt% water, or 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or 95 wt%. Contains water. In some embodiments, the residue stream 154 is equal to or greater than about 5 wt% acetic acid, or 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or 95 wt%. Contains acetic acid. In some embodiments, the residue stream 154 is equal to or greater than about 5 wt% methyl iodide, or 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or 95 wt%. Of methyl iodide.

  [0086] In some embodiments, the second tower residue stream 154 includes HI equal to or greater than about 0.11 wt%. In one aspect, the residue stream 154 is equal to or greater than about 0.21% by weight HI, equal to or greater than about 0.25% HI, equal to or greater than about 0.3% HI, about 0.1%. HI equal to or greater than 35 wt%, HI equal to or greater than about 0.4 wt%, HI equal to or greater than about 0.5 wt%, HI equal to or greater than about 0.6 wt%, about HI equal to or greater than 0.65 wt% or HI equal to or greater than about 0.7 wt%.

  [0087] In view of corrosion, excessive amounts of HI are generally undesirable. As described above, in order to catalyze the production of DME whose amount is controlled in the distillation column, it is desirable to control the amount of HI within a predetermined range. As illustrated in US Pat. No. 7,223,883, US Pat. No. 7,223,886, and US Pat. No. 8,076,507, this DME has been shown to have a beneficial effect on phase separation in liquid-liquid extraction systems common to acetaldehyde removal systems. In some embodiments, the residue stream 154 is HI equal to or less than about 10% by weight, HI equal to or less than about 5% by weight, HI equal to or less than about 2% by weight relative to the total weight of the residue stream. HI equal to or less than about 1.5 wt%, HI equal to or less than about 1.2 wt%, HI equal to or less than about 1.1 wt%, equal to or less than about 1.0 wt% HI, HI equal to or less than about 0.9 wt%, 0.75 wt% HI, HI equal to or less than about 0.7 wt%, HI equal to or less than about 0.65 wt%, about HI equal to or less than 0.6 wt%, HI equal to or less than about 0.55 wt%, HI equal to or less than about 0.5 wt%, or HI equal to or less than about 0.45 wt% including. The maximum HI concentration in the second tower residue stream 154 may be selected according to the corrosion level allowed under the conditions present therein. That is, by selecting a specific material, the HI concentration in the residue can be made much higher than 0.11 wt%.

  [0088] In some embodiments, the residue stream 154 may further comprise methyl iodide, methanol, methyl acetate, and / or acetaldehyde. In some embodiments, a portion of the residue stream 154 may be charged to the drying tower 130, the reactor 104, or both, for example, via reflux originating from the drying tower decanter 148.

  [0089] As shown in FIG. 3, in one embodiment, the second distillation column (shown in FIG. 3 is column 150, where 150 represents one of 150 or 172 for purposes of drawing). A distillation zone 312 and a bottom storage zone 314. Distillation zone 312 refers to everything above the bottom storage zone 314 and may include various internal components such as filling sections, liquid collectors / redistributors, trays, supports, etc. For example, but not limited to.

[0090] In some embodiments, the second distillation column includes at least 100 trays and operates at a temperature in the range of about 101 ° C at the bottom to about 60 ° C at the top. In other embodiments, the second distillation column includes a structured packing instead of a tray. In some embodiments, the structured filler, random filler, or combination thereof may have an interface area of 150-400 m ² / m ³ and may include ceramic, polymer, austenite-ferrite metal alloy, or a combination thereof. In some embodiments, the bottom temperature of the second distillation column is about 90 ° C. to about 130 ° C., and the pressure of the second distillation column is atmospheric or about 150 kPa above atmospheric pressure to about 700 kPa above atmospheric pressure , Or a combination thereof.

[0091] In some embodiments, the distillation zone is sized and arranged to control the contact time between methyl iodide and water to control the HI concentration in the second distillation column residue 154.
[0092] In some embodiments, the liquid phase present in the second distillation column comprises a first liquid phase (aqueous phase) comprising greater than about 50 wt% water and greater than about 50 wt% methyl iodide. Contains a second liquid phase (methyl iodide phase).

  [0093] In some embodiments, the distillation zone 312, particularly various internal components within the distillation zone, has a HI concentration equal to or greater than about 0.11 wt% contact time between the methyl iodide phase and the aqueous phase. Are dimensioned and arranged to control the minimum amount required to produce a second tower residue stream 154 having

  [0094] In some embodiments, the internal components are designed (sized and arranged) to minimize the residence time of the liquid phase present in the distillation column under process conditions. A minimum contact time between the water phase and the methyl iodide phase in the second distillation column to produce a residue stream leaving the bottom storage zone containing water and about 0.11 wt% HI. Is known to be necessary. However, it has also been found that increasing the contact time between individual portions of the aqueous phase and the methyl iodide phase has an adverse effect on the ability to control the amount of HI in the residue stream. Such long contact times do not affect the total residence time of the liquid phase in the distillation column by storing and / or trapping individual parts of the specific phase within specific internal components of the distillation column. Can occur.

  [0095] As shown in FIG. 3, in some embodiments, the second distillation column 150 or 172 may have a plurality of internal components (eg, liquid collector 310, liquid distributor 300, etc.) These components may be disposed between a plurality of fillers 302 and 304 each having a structured filler, a random filler, or a combination thereof. In other embodiments, the internal components may be distillation plates and trays as well as various supports 308 and collectors.

  [0096] In some embodiments, the distillation zone 312 includes a vapor phase and a liquid phase, the liquid phase includes a first liquid phase 326 (see FIG. 4) and a second liquid phase 328 (see FIG. 4), and the first liquid The phase contains more than about 50% by weight water and the second liquid phase contains more than about 50% by weight methyl iodide. Apart from some internal solubility, the two liquid phases are generally immiscible.

  [0097] As shown in FIG. 4, each internal component includes an associated or corresponding liquid phase holding volume depending on the size and placement of the component. In an embodiment in which two types of liquid phases are present in the distillation column, the total retention volume of the liquid phase associated with a particular component is within the range of this particular component and the retention volume of the first liquid phase 326 is It is equal to the sum of the holding volumes of the two liquid phases 328. Thus, the liquid holdup volume of the distillation zone is equal to the sum of the liquid phase holding volumes of the components within the distillation zone plus the amount present on the side of the distillation column and other non-functional surfaces.

  [0098] The holding volume of each component has a corresponding residence time of the first liquid phase and a corresponding residence time of the second liquid phase under operating conditions. The residence time of a particular liquid phase of an internal component is equal to the average time that an individual amount of this particular liquid phase is held in the holding volume of the component under operating conditions. However, the physical properties of the two liquid phases, the location of the drains and flow paths of the internal components, and / or other sides of the internal components are one of the liquid phases within the holding volume. Can lead to storage or capture. The liquid phase trapped in the holding volume of a particular component can have an average residence time in this particular component that exceeds the average residence time of all liquid phases in the distillation zone of the distillation column.

  [0099] That is, the residence time of a specific liquid phase in the internal components of the distillation column is measured directly or calculated under operating conditions based on the physical properties of the liquid phase and the design and arrangement of the specific components. And / or need to be modeled.

  [0100] As shown in FIG. 4, because there are two liquid phases 326 and 328 during distillation, they do not include a bottom drain or a bottom drain that is not properly sized or positioned. Inside the distillation column, the heavier methyl iodide second liquid phase 328 tends to accumulate below the lighter aqueous first liquid phase 326 even if the methyl iodide phase has a lower boiling point than the aqueous phase. is there. Thereafter, the heavier methyl iodide phase tends to travel through the distillation column when transferred with the lighter aqueous phase. The heavier phase may accumulate in the holding volume and then overflow from various structures in the distillation column. Such a distillation column design increases the residence time of the individual parts of the second liquid phase and is unpredictable.

  [0101] Similarly, as shown in FIG. 4, the interior of a distillation column that includes a bottom drain but does not include a top drain, or does not include an appropriately sized or properly positioned top drain, There is a tendency to accumulate a lighter aqueous first liquid phase 326 within the holding volume of the internal component. For a heavier second liquid phase 328 that is successfully drained, the first liquid phase 326 may then be captured, the heavier second liquid phase being accumulated first liquid phase 326 and one or more bottoms. It is discharged through the drain hole 340. Thereafter, the light first liquid phase tends to travel through the distillation column only when transported with the heavy phase or only by overflowing the various structures in the distillation column. The residence time of the individual parts of the first aqueous liquid phase within the holding volume of the internal component part structure is increased.

  [0102] As shown in FIG. 4, in one aspect, the liquid redistributor, tray or other distillation column interior 300 includes one or more vapor risers 316 that allow the vapor phase to flow through the structure; One or more dripping tubes 318 may be included that allow liquid to pass through the structure from one to the other. In one aspect, each of the one or more drip tubes 318 can include at least one of the first plurality of passages 324 disposed therethrough. The passage 324 is a hole arranged to discharge the first liquid phase 326 therethrough, and the first liquid phase 326 is less dense (lighter) than the second liquid phase 328 and thus the structure Located further away from the bottom of the body. Each drip tube 318 may further include at least one of a second plurality of passages 330 disposed therethrough. It may be provided so as to penetrate the tube. The passage 330 is a hole that is located proximate to the bottom of the structure to discharge the second heavier liquid phase 328 therethrough.

  [0103] FIG. 5 illustrates an embodiment in which each of the drop tubes 320 includes at least one of the first plurality of passages, the passages being combined with a second plurality of passages in the form of slits 332. The second plurality of passages are disposed therethrough along the vertical wall of the drop tube 320, and both the first light phase 326 and the second heavy phase 328 are discharged through the structure. Make it possible.

  [0104] FIG. 6 illustrates an embodiment in which each of the dripping tubes 322 includes at least one of the first plurality of passages in the form of slits 334, the passages being only a portion of the vertical wall inside the dripping tube 322. And the passage is arranged such that the first light phase 326 is discharged through the structure, and each drip tube 322 is provided therethrough. At least one of the second plurality of passages 336, the second plurality of passages being disposed proximate to the bottom of the structure and passing the second heavy liquid phase 328 therethrough. It is a hole for discharging through.

  [0105] In certain embodiments, as shown in FIG. 4, the structure has a side height 338 that allows the lighter first phase 326 to drain by overflowing the side or A dam (e.g., the side of the liquid redistributor 300 or distillation column tray) may be included, and together with it, one or more bottom drain holes 340 may be provided with the tray to allow the heavy phase to drain therefrom. The tray may be included.

[0106] In some embodiments, as would be normally understood by one skilled in the art, if distillation column packing is present, it may be selected to reduce liquid holdup.
[0107] Experiments were performed by simulation to determine the average residence time of the aqueous phase of the second distillation column operated in the industrial acetic acid production process aldehyde removal system using a top flash stream and partial column reflux. This process produced a residue stream with a HI concentration that was difficult to control. In the comparative example, the average residence time of the aqueous phase in the distillation zone of the second distillation column provided with only the bottom drain in the liquid redistributor was determined by simulation to be about 6 hours. It was not reflected in the total residence time of the feed stream within. That is, the aqueous phase was trapped in a part of the distillation column. Next, in a separate model experiment, a distillation tower was simulated by providing a dropping pipe composed of a plurality of first and second fluid passages as shown in FIGS. Under the same conditions as in the comparative simulation, the average residence time of the aqueous phase in the distillation zone of the distillation column of the present invention was reduced from about 6 hours to about 11 minutes on average.

  [0108] A second distillation column according to embodiments disclosed herein wherein the average liquid phase residence time in the distillation zone is from about 1 minute to about 60 minutes, each of the distillation zones comprising a component liquid holding volume. A plurality of internal components, each of which has an average residence time of the first liquid phase and an average residence time of the second liquid phase in each component liquid holding volume of less than about 30 minutes. Employment of a sized and arranged distillation tower resulted in a second tower residue stream having a HI concentration of 0.11% to 0.9% by weight.

[0109] In certain embodiments, the average residence time of the feed stream in the distillation zone of the second distillation column is from about 1 minute to about 60 minutes, from about 1 minute to about 30 minutes, or from about 1 minute to about 15 minutes.
[0110] In some embodiments, the distillation zone includes a plurality of internal components, each having a component liquid retention volume. Each internal component is dimensioned such that the average residence time of the first liquid phase within the liquid holding volume of each component is less than about 30 minutes, less than about 20 minutes, less than about 10 minutes, or less than about 5 minutes. Has been placed. In certain embodiments, each internal component has an average residence time of the second liquid phase within the liquid retention volume of each component of less than about 30 minutes, less than about 20 minutes, about 10 minutes, as measured by model experiments or direct measurements. Less than or less than about 5 minutes.

  [0111] In some embodiments, at least one internal component present in the distillation zone, or all internal components, are component liquids corresponding to an average residence time of the first liquid phase as measured by model experiments or direct measurements. It is sized and arranged to be equal to or exceeding the average residence time of the second liquid phase in the holding volume.

  [0112] In some embodiments, at least one internal component, such as a distillation tray, liquid collector, distributor, or redistributor, has an average residence time of the first liquid phase as measured by model experiments or direct measurements. A first plurality of channels (e.g., 324, sized and arranged to be about 0.1 minute to about 20 minutes, about 10 minutes, or about 5 minutes in a corresponding component liquid holding volume, 322 and / or 334).

  [0113] In certain embodiments, the at least one internal component is about 0.1 minute to about 20 in a component liquid retention volume corresponding to an average residence time of the second liquid phase as measured by model experiment or direct measurement. It further includes a second plurality of channels (e.g., 330, 322, 336, and / or 340) that are dimensioned and arranged to be minutes, ˜about 10 minutes, or ˜about 5 minutes.

  [0114] In certain embodiments, various conditions associated with the second distillation column may be selected to control the HI concentration in the second column residue. In one embodiment, the distillation temperature and pressure, i.e., the bottom temperature of the second distillation column and the pressure of the second distillation column are selected so that the HI concentration in the second column residue is 0.1 wt% to 0.9 wt%. % May be controlled.

  [0115] In some embodiments, the composition of the top flash stream, the mass flow of the top flash stream, the composition of the bottom flash stream, and / or the mass flow of the bottom flash stream is selected to control the HI concentration in the second column residue. May be. For example, in order to reduce the HI concentration in the second tower residue, the bottom flush flow rate with respect to the column feed flow rate may be increased to dilute and wash away the HI present in the tower reservoir.

  [0116] In some embodiments, as described herein, an average liquid phase residence time in the distillation zone is selected and / or one or more liquid phases in the holding volume of one or more internal components. The average residence time may be controlled to control the HI concentration in the second tower residue. In addition, any combination of the above control schemes may be selected to produce a residue stream comprising about 0.11 wt% to 0.9 wt% HI.

[0117] Various aspects are contemplated, as will be apparent from the drawings and description above.
E1. Process,
Providing a feed stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC to a distillation column comprising a distillation zone and a bottom storage zone;
The feed stream produces an overhead stream comprising methyl iodide and at least one PRC, and a residue stream comprising water and HI equal to or greater than about 0.11 wt% exiting the bottom storage zone. A process involving distillation at a pressure and temperature sufficient for
E2. The process of embodiment E1, wherein the residue stream comprises about 0.6% to about 1.2% HI by weight.
E3. The process of embodiment E1 or E2, wherein the average liquid phase residence time in the distillation zone is from about 1 minute to about 60 minutes.
E4. The process of any one of aspects E1-E3, wherein the liquid phase comprises a first liquid phase comprising greater than about 50% by weight water and a second liquid phase comprising greater than about 50% by weight methyl iodide. process.
E5. The process of any one of aspects E1-E4, wherein the distillation zone includes a plurality of internal components each having a component liquid retention volume, each of the internal components being in a respective component liquid retention volume. A process sized and arranged such that the average residence time of the first liquid phase and the average residence time of the second liquid phase is less than about 30 minutes.
E6. The process of aspect E5, wherein the at least one internal component has an average residence time of the first liquid phase equal to or greater than an average residence time of the second liquid phase in a corresponding component liquid holding volume. The process that is dimensioned and arranged.
E7. The process of aspect E5 or E6, wherein the at least one internal component is such that the average residence time of the first liquid phase is about 0.1 minutes to about 20 minutes in the corresponding component liquid holding volume and A process comprising a first plurality of flow paths arranged.
E8. The process of any one of aspects E5 to E7, wherein the at least one internal component has an average residence time of the second liquid phase in the corresponding component liquid retention volume of from about 0.1 minutes to about 20 minutes. A process further comprising a second plurality of channels sized and arranged.
E9. The process of any one of embodiments E1-E8, further comprising charging a top flush stream comprising water into the distillation zone simultaneously with distillation of the feed stream.
E10. The process of embodiment E9, wherein the mass flow rate of the top flush stream is equal to or greater than about 0.1% of the mass flow rate of the feed stream.
E11. The process of embodiment E9 or E10, wherein the top flush stream comprises water equal to or greater than about 20% by weight, a portion of the bottom residue stream, or a combination thereof.
E12. The process of any one of embodiments E1-E11, further comprising charging a bottom flush stream comprising acetic acid into the distillation zone, the bottom storage zone, or both simultaneously with distillation of the feed stream.
E13. The process of embodiment E12, wherein the bottom flush stream comprises acetic acid equal to or greater than about 20% by weight.
E14. The process of embodiment E12 or 13, wherein the mass flow rate of the bottom flush stream is equal to or greater than about 0.1% of the mass flow rate of the feed stream.
E15. The process of any one of embodiments E1-E14, wherein the overhead stream comprises dimethyl ether.
E16. A process according to any one of aspects E1-E15, further comprising:
a. A portion of the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and a first overhead stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC; To get the
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower comprising a distillation zone and a bottom storage zone;
c. HI equal to or greater than about 0.11 wt% water and a second tower overhead stream comprising methyl iodide and at least one PRC and water exiting the bottom storage zone. Distilling at a pressure and temperature sufficient to produce a second tower residue stream comprising
d. Extracting at least a portion of the second tower overhead stream comprising methyl iodide and at least one PRC with water at a temperature of less than about 25 ° C., comprising an aqueous waste stream comprising at least one PRC and methyl iodide Generating a raffinate stream; and e. Returning at least a first portion of the raffinate stream to the second distillation column.
E17. Process,
a. A portion of the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and a first overhead stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC; To get the
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower comprising a distillation zone and a bottom storage zone;
c. HI equal to or greater than about 0.11 wt% water and a second tower overhead stream comprising methyl iodide and at least one PRC and water exiting the bottom storage zone. Distilling at a pressure and temperature sufficient to produce a second tower residue stream comprising
d. Extracting at least a portion of the second tower overhead stream comprising methyl iodide and at least one PRC with water at a temperature of less than about 25 ° C., comprising an aqueous waste stream comprising at least one PRC and methyl iodide Generating a raffinate stream; and e. Returning at least a first portion of the raffinate stream to the second distillation column.
E18. The process of embodiment E16 or E17, wherein the second column residue stream comprises from about 0.6% to about 1.2% by weight HI.
E19. The process of any one of embodiments E16-E18, wherein the second tower overhead stream comprises dimethyl ether.
E20. The process of any one of embodiments E16-E19, wherein the average liquid phase residence time in the distillation zone of the second distillation column is from about 1 minute to about 60 minutes.
E21. A process according to any one of aspects E16-E20, further comprising charging a top flush stream comprising water into the distillation zone of the second distillation column simultaneously with distillation of the second column feed stream. process.
E22. The process of any one of aspects E16-E21, wherein the mass flow rate of the top flush stream is equal to or greater than about 0.1% of the mass flow rate of the second column feed stream.
E23. The process of embodiment E22, wherein the top flush stream comprises water equal to or greater than about 20% by weight, a portion of the bottom residue stream, or a combination thereof.
E24. A process according to any one of aspects E16-E23, wherein a bottom flush stream comprising acetic acid is sent to the distillation zone and / or the bottom storage zone of the second distillation column simultaneously with distillation of the second column feed stream. A process that further includes throwing in.
E25. The process of embodiment E24, wherein the bottom flush stream comprises acetic acid equal to or greater than about 20% by weight.
E26. A process according to any one of aspects E16 to E25,
f. A process further comprising returning a second portion of the raffinate stream comprising methyl iodide and dimethyl ether to the reaction medium.
E27. The process of aspect E26, wherein the mass flow rate of the first portion of the raffinate stream is equal to or greater than the mass flow rate of the second portion of the raffinate stream.
E28. The process of any one of embodiments E1-E27, wherein the bottom temperature of the second distillation column is from about 90 ° C. to about 130 ° C., and the pressure of the second distillation column is from about atmospheric pressure to about atmospheric pressure. A process that is a pressure above 700 kPa , or a combination thereof.
E29. Process,
a. A portion of the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and a first overhead stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC. Getting,
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower comprising a distillation zone and a bottom storage zone;
c. The second column feed stream is divided into a second tower overhead stream comprising methyl iodide, dimethyl ether, and at least one PRC, and water and about 0.11 wt% to about 0 flowing out of the bottom storage zone. Distilling at a pressure and temperature sufficient to produce a second tower residue stream comprising 9 wt% HI;
d. At the same time, a top flush stream containing water is introduced into the distillation zone at a mass flow rate equal to or greater than 0.1% of the mass flow rate of the second column feed stream, and e. Simultaneously, introducing a bottom flush stream comprising acetic acid into the distillation zone and / or the bottom storage zone at a mass flow rate equal to or greater than 0.1% of the mass flow rate of the second column feed stream.
E30. A process according to any one of embodiments E1-E29, wherein the bottom temperature of the second distillation column, the pressure of the second distillation column, the composition of the top flash stream, the mass flow rate of the top flash stream, the bottom A residue stream comprising about 0.6 wt% to 1.2 wt% HI, selected from the composition of the flush stream, the mass flow rate of the bottom flush stream, the average liquid phase residence time in the distillation zone, or a combination thereof Process to generate.

[0118] While the embodiments have been described in detail with reference to the drawings and the foregoing description, these embodiments should be considered illustrative in nature and not limiting, and of course It is desirable that all the changes and modifications in line with the gist of these aspects be protected. Of course, terms such as ideal, desired, preferred, desirable, preferred, more preferred, and exemplary used in the above description are desirable and characteristic in describing characteristics, but are not necessarily used. Even embodiments that do not use such terms are intended to be within the scope of the present invention as defined by the claims. When terms such as “a” (an), “at least one”, “at least part”, etc. are used in the interpretation of the claims, unless there is a specific description contrary to the claims It is not intended that the claims be limited to only one item.
The following are the corrections necessary for the description of the claims at the time of filing.
[Claim 1]
Process,
a. Providing a feed stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC to a distillation column comprising a distillation zone and a bottom storage zone;
b. Producing a feed stream comprising an overhead stream comprising methyl iodide and at least one PRC, and a residue stream comprising HI equal to or greater than about 0.11 wt% exiting the bottom storage zone; Process involving distillation at sufficient pressure and temperature.
[Claim 2]
The process of claim 1, wherein the residue stream comprises about 0.6 wt% to about 1.2 wt% HI.
[Claim 3]
The process of claim 1, wherein the average liquid phase residence time in the distillation zone is from about 1 minute to about 60 minutes.
[Claim 4]
4. The process of claim 3, wherein the liquid phase comprises a first liquid phase comprising greater than about 50% by weight water and a second liquid phase comprising greater than about 50% by weight methyl iodide.
[Claim 5]
5. The process of claim 4, wherein the distillation zone includes a plurality of internal components, each having a component liquid retention volume, each of the internal components being the first in each component liquid retention volume. A process sized and arranged such that the average residence time of the liquid phase and the average residence time of the second liquid phase are less than about 30 minutes.
[Claim 6]
6. The process according to claim 5, wherein the at least one internal component has an average residence time of the first liquid phase equal to an average residence time of the second liquid phase in the corresponding component liquid holding volume, or Processes that are dimensioned and arranged to exceed.
[Claim 7]
7. The process of claim 6, wherein the at least one internal component is dimensioned such that the average residence time of the first liquid phase is from about 0.1 minutes to about 20 minutes in the corresponding component liquid holding volume. And a process further comprising a first plurality of flow paths arranged.
[Claim 8]
8. The process of claim 7, wherein the at least one internal component is dimensioned such that the average residence time of the second liquid phase is about 0.1 minutes to about 20 minutes in the corresponding component liquid holding volume. And a process further comprising a second plurality of flow paths arranged.
[Claim 9]
The process of claim 1, further comprising introducing a top flush stream comprising water into the distillation zone simultaneously with distillation of the feed stream.
[Claim 10]
The process of claim 9, wherein the mass flow rate of the top flush stream is equal to or greater than about 0.1% of the mass flow rate of the feed stream.
[Claim 11]
The process of claim 9, wherein the top flush stream comprises water equal to or greater than about 20 wt%, a portion of the bottom residue stream, or a combination thereof.
[Claim 12]
The process of claim 1, further comprising charging a bottom flush stream comprising acetic acid into the distillation zone, the bottom storage zone, or both simultaneously with distillation of the feed stream.
[Claim 13]
13. The process of claim 12, wherein the bottom flush stream comprises acetic acid equal to or greater than about 20% by weight.
[Claim 14]
13. The process of claim 12, wherein the bottom flush stream mass flow rate is equal to or greater than about 0.1% of the feed flow mass flow rate.
[Claim 15]
The process of claim 1, wherein the overhead stream comprises dimethyl ether.
[Claim 16]
Process,
a. A stream from the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and a first overhead stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC. To get the
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower comprising a distillation zone and a bottom storage zone;
c. HI equal to or greater than about 0.11 wt% water and a second tower overhead stream comprising methyl iodide and at least one PRC and water exiting the bottom storage zone. Distilling at a pressure and temperature sufficient to produce a second tower residue stream comprising
d. Extracting at least a portion of the second tower overhead stream comprising methyl iodide and at least one PRC with water at a temperature of less than about 25 ° C., comprising an aqueous waste stream comprising at least one PRC and methyl iodide Generating a raffinate stream; and e. Returning at least a first portion of the raffinate stream to the second distillation column.
[Claim 17]
The process of claim 16, wherein the second tower residue stream comprises about 0.6 wt% to about 1.2 wt% HI.
[Claim 18]
The process of claim 16, wherein the second tower overhead stream comprises dimethyl ether.
[Claim 19]
The process of claim 16, wherein the average liquid phase residence time in the distillation zone of the second distillation column is from about 1 minute to about 60 minutes.
[Claim 20]
17. The process of claim 16, further comprising introducing a top flush stream comprising water into the distillation zone of the second distillation column simultaneously with distillation of the second column feed stream.
[Claim 21]
21. The process of claim 20, wherein the mass flow rate of the top flush stream is equal to or greater than about 0.1% of the mass flow rate of the second column feed stream.
[Claim 22]
21. The process of claim 20, wherein the top flush stream comprises water equal to or greater than about 20 wt%, a portion of the bottom residue stream, or a combination thereof.
[Claim 23]
17. Process according to claim 16, wherein simultaneously with distillation of the second column feed stream, a bottom flush stream containing acetic acid is introduced into the distillation zone and / or the bottom storage zone of the second distillation column. A process further comprising:
[Claim 24]
24. The process of claim 23, wherein the bottom flush stream comprises acetic acid equal to or greater than about 20% by weight.
[Claim 25]
19. A process according to claim 18, comprising:
f. A process further comprising returning a second portion of the raffinate stream comprising methyl iodide and dimethyl ether to the reaction medium.
[Claim 26]
26. The process of claim 25, wherein the mass flow rate of the first portion of the raffinate stream is equal to or greater than the mass flow rate of the second portion of the raffinate stream.
[Claim 27]
The process of claim 16, wherein the bottom temperature of the second distillation column is from about 90 ° C to about 130 ° C and the pressure of the second distillation column is from atmospheric pressure to about 700 kPa above atmospheric pressure. A process that is or a combination thereof.
[Claim 28]
Process,
a. A stream from the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and a first overhead stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC. Getting,
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower comprising a distillation zone and a bottom storage zone;
c. The second column feed stream includes a second column overhead stream comprising methyl iodide, dimethyl ether, and at least one PRC, and water and about 0 flowing from the bottom storage zone out of the second distillation column. Distilling at a pressure and temperature sufficient to produce a second tower residue stream comprising from 11 wt% to about 0.9 wt% HI;
d. At the same time, a top flush stream containing water is introduced into the distillation zone at a mass flow rate equal to or greater than 0.1% of the mass flow rate of the second column feed stream, and e. Simultaneously, introducing a bottom flush stream comprising acetic acid into the distillation zone and / or the bottom storage zone at a mass flow rate equal to or greater than 0.1% of the mass flow rate of the second column feed stream.
[Claim 29]
29. The process of claim 28, wherein the bottom temperature of the second distillation column, the pressure of the second distillation column, the composition of the top flash stream, the mass flow of the top flash stream, the bottom flash stream The composition, the mass flow rate of the bottom flush stream, the average liquid phase residence time in the distillation zone, or a combination thereof is selected to produce a residue stream comprising about 0.11 wt% to 0.9 wt% HI process.

Claims (32)

Process,
a. A stream from the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and methyl iodide, water, acetic acid, methyl acetate, and at least one permanganate reducing compound (PRC). Obtaining a first overhead stream including
b . Providing a second column feed stream comprising or derived from the first overhead stream to a second distillation column that is an aldehyde removal distillation column comprising a distillation zone and a bottom storage zone;
c . The second tower feed stream, beyond a second tower overhead stream comprising methyl iodide and at least one PRC, and flows out of said bottom reservoir zone, or it is equal to the water and 0.11 wt% and a process comprising distillation at a sufficient pressure and temperature to produce a second residue stream, comprising a HI below or equal to 10 wt%. A process according to claim 1, the process wherein the second residue stream comprises HI 0.6 wt% to 1.2 wt%. The process according to claim 1, wherein the average liquid phase residence time in the distillation zone is from 1 minute to 60 minutes. 4. A process according to claim 3, wherein the liquid phase comprises a first liquid phase comprising more than 50 % by weight water and a second liquid phase comprising more than 50 % by weight methyl iodide. 5. The process of claim 4, wherein the distillation zone includes a plurality of internal components, each having a component liquid retention volume, each of the internal components being the first in each component liquid retention volume. A process sized and arranged such that the average residence time of the liquid phase and the average residence time of the second liquid phase are less than 30 minutes. 6. The process according to claim 5, wherein the at least one internal component has an average residence time of the first liquid phase equal to an average residence time of the second liquid phase in the corresponding component liquid holding volume, or Processes that are dimensioned and arranged to exceed that. 7. Process according to claim 6, wherein the at least one internal component is dimensioned and arranged such that the average residence time of the first liquid phase is between 0.1 and 20 minutes in the corresponding component liquid holding volume. A process further comprising a first plurality of flow paths. 8. Process according to claim 7, wherein the at least one internal component is dimensioned and arranged such that the average residence time of the second liquid phase is between 0.1 and 20 minutes in the corresponding component liquid holding volume. A process further comprising a second plurality of channels. The process of claim 1, further comprising introducing a top flush stream comprising water into the distillation zone simultaneously with distillation of the second column feed stream . A process according to claim 9, the mass flow rate of said top flash flow exceeds or equal to 0.1% of the mass flow rate of the second tower feed stream process. A process according to claim 9, process said top flash stream, containing 20 wt% and equal to or water beyond that, a part of the bottom portion residue stream, or a combination thereof. The process of claim 1, further comprising charging a bottom flush stream comprising acetic acid into the distillation zone, the bottom storage zone, or both simultaneously with distillation of the second column feed stream. . A process according to claim 12, the process said bottom flash stream comprising acetic acid of greater than or equal to 20 wt%. A process according to claim 12, process the mass flow rate of the bottom portion the flash stream in excess of or equal to 0.1% of the mass flow rate of the second tower feed stream. A process according to claim 1, the process said second tower overhead stream containing dimethyl ether. Process,
a. A stream from the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and methyl iodide, water, acetic acid, methyl acetate, and at least one permanganate reducing compound (PRC). Obtaining a first overhead stream including
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower, which is an aldehyde removal distillation tower comprising a distillation zone and a bottom storage zone;
c. The second tower feed stream, beyond a second tower overhead stream comprising methyl iodide and at least one PRC, and flows out of said bottom reservoir zone, or it is equal to the water and 0.11 wt% and second Tozan渣流including the HI below or equal to 10% by weight, distillation at a sufficient pressure and temperature to produce,
d. Extracting at least a portion of the second tower overhead stream comprising methyl iodide and at least one PRC with water at a temperature below 25 ° C. to provide an aqueous waste stream comprising at least one PRC and a raffinate comprising methyl iodide Generating a flow; and e. Returning at least a first portion of the raffinate stream to the second distillation column. The process according to claim 16, wherein the second tower residue stream comprises 0.6 wt% to 1.2 wt% HI.   The process of claim 16, wherein the second tower overhead stream comprises dimethyl ether. The process according to claim 16, wherein the average liquid phase residence time in the distillation zone of the second distillation column is from 1 minute to 60 minutes.   17. The process of claim 16, further comprising introducing a top flush stream comprising water into the distillation zone of the second distillation column simultaneously with distillation of the second column feed stream. A process according to claim 20, the mass flow rate of said top flash stream is equal to or exceeds that of 0.1% of the mass flow rate of the second tower feed stream process. A process according to claim 20, the water said top flash flow exceeding or equal to 20 wt%, a part of the bottom portion residue stream, or process combinations thereof.   17. Process according to claim 16, wherein simultaneously with distillation of the second column feed stream, a bottom flush stream containing acetic acid is introduced into the distillation zone and / or the bottom storage zone of the second distillation column. A process further comprising: A process according to claim 23, the process said bottom flash stream comprising acetic acid of greater than or equal to 20 wt%. 19. A process according to claim 18, comprising:
f. A process further comprising returning a second portion of the raffinate stream comprising methyl iodide and dimethyl ether to the reaction medium. It claims a process according to claim 25, the process mass flow rate of the first portion of the raffinate stream is more than it, or equal to the mass flow rate of the second portion of the raffinate stream. The process according to claim 16, wherein the bottom temperature of the second distillation column is 90 ° C to 130 ° C, and the pressure of the second distillation column is a pressure higher than atmospheric pressure to 700 kPa above atmospheric pressure. Or a process that is a combination thereof. Process,
a. A stream from the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and methyl iodide, water, acetic acid, methyl acetate, and at least one permanganate reducing compound (PRC). Obtaining a first overhead stream comprising
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower, which is an aldehyde removal distillation tower comprising a distillation zone and a bottom storage zone;
c. The second column feed stream comprises a second tower overhead stream comprising methyl iodide, dimethyl ether, and at least one PRC, and water and 0.02% flowing out of the second distillation column from the bottom storage zone . 11 second Tozan渣流including the HI weight% to 0.9 weight%, to distillation at a sufficient pressure and temperature to produce,
d. At the same time, by pouring water into the distillation zone top flash flow at 0.1% and equal to or mass flow rate exceeds that of the mass flow rate of the second tower feed stream containing, and e. Simultaneously, charging a bottom flush stream containing acetic acid into the distillation zone and / or the bottom storage zone at a mass flow rate equal to or greater than 0.1% of the mass flow rate of the second column feed stream. process. 29. The process of claim 28, wherein the bottom temperature of the second distillation column, the pressure of the second distillation column, the composition of the top flash stream, the mass flow of the top flash stream, the bottom flash stream Process of selecting a composition, mass flow rate of the bottom flush stream, average liquid phase residence time in the distillation zone, or a combination thereof to produce a residue stream comprising 0.11 wt% to 0.9 wt% HI . A method for producing acetic acid, comprising:
a. A stream from the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and methyl iodide, water, acetic acid, methyl acetate, and at least one permanganate reducing compound (PRC). Obtaining a first overhead stream including
b. Providing a second column feed stream comprising or derived from the first overhead stream to a second distillation column that is an aldehyde removal distillation column comprising a distillation zone and a bottom storage zone;
c. The second column feed stream is equal to or greater than 0.11% by weight of water and a second tower overhead stream comprising methyl iodide and at least one PRC and water exiting the bottom storage zone. And distilling at a pressure and temperature sufficient to produce a second residue stream comprising HI equal to or less than 10% by weight.
Including said method. A method for producing acetic acid, comprising:
a. A stream from the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and methyl iodide, water, acetic acid, methyl acetate, and at least one permanganate reducing compound (PRC). Obtaining a first overhead stream including
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower, which is an aldehyde removal distillation tower comprising a distillation zone and a bottom storage zone;
c. The second column feed stream is equal to or greater than 0.11% by weight of water and a second tower overhead stream comprising methyl iodide and at least one PRC and water exiting the bottom storage zone. And distilling at a pressure and temperature sufficient to produce a second column residue stream comprising HI equal to or less than 10% by weight,
d. Extracting at least a portion of the second tower overhead stream comprising methyl iodide and at least one PRC with water to produce an aqueous waste stream comprising at least one PRC and a raffinate stream comprising methyl iodide; as well as
e. Returning at least a first portion of the raffinate stream to the second distillation column.
Said method. A method for producing acetic acid, comprising:
a. A stream from the reaction medium of the carbonylation reactor is distilled in a first distillation column to produce an acetic acid stream and methyl iodide, water, acetic acid, methyl acetate, and at least one permanganate reducing compound (PRC). Obtaining a first overhead stream comprising
b. Charging a second tower feed stream comprising or derived from the first overhead stream into a second distillation tower, which is an aldehyde removal distillation tower comprising a distillation zone and a bottom storage zone;
c. The second column feed stream comprises a second tower overhead stream comprising methyl iodide, dimethyl ether, and at least one PRC, and water and 0.02% flowing out of the second distillation column from the bottom storage zone. Distilling at a pressure and temperature sufficient to produce a second tower residue stream comprising 11 wt% to 0.9 wt% HI;
d. At the same time, a top flush stream containing water is introduced into the distillation zone at a mass flow rate equal to or greater than 0.1% of the mass flow rate of the second column feed stream; and
e. At the same time, a bottom flush stream containing acetic acid is introduced into the distillation zone and / or the bottom storage zone at a mass flow rate equal to or greater than 0.1% of the mass flow rate of the second column feed stream.
Said method.

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