CN113121333A - Process for recovering aromatic monocarboxylic acids - Google Patents
Process for recovering aromatic monocarboxylic acids Download PDFInfo
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- CN113121333A CN113121333A CN202110421294.5A CN202110421294A CN113121333A CN 113121333 A CN113121333 A CN 113121333A CN 202110421294 A CN202110421294 A CN 202110421294A CN 113121333 A CN113121333 A CN 113121333A
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- C—CHEMISTRY; METALLURGY
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- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
- C07C51/265—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting having alkyl side chains which are oxidised to carboxyl groups
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- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/47—Separation; Purification; Stabilisation; Use of additives by solid-liquid treatment; by chemisorption
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/48—Separation; Purification; Stabilisation; Use of additives by liquid-liquid treatment
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Abstract
The present invention provides a process and apparatus for recovering aromatic monocarboxylic acid from a residue stream in which a first solids extraction is performed followed by a second extraction.
Description
This application is a divisional application of an application having an international application date of 2015, 8/12, international application numbers of PCT/EP2015/068593, national application number of 201580043210.1 and an invention name of "method for recovering aromatic monocarboxylic acid".
Technical Field
The present invention relates to a process and apparatus for recovering aromatic monocarboxylic acids from a residue stream.
Background
Aromatic polycarboxylic acids are typically produced by the liquid phase oxidation of alkyl-substituted aromatic starting materials, typically methyl-substituted benzene and naphthalene starting materials, in which the position of the methyl substituent corresponds to the position of the formic acid substituent in the desired end product. For example, Terephthalic Acid (TA), which is widely used in polyester manufacture, is manufactured by subjecting p-xylene to a liquid-phase oxidation reaction with air or another oxygen source using a bromine-promoted catalyst (bromine-promoted catalyst) containing cobalt and manganese and using acetic acid as a solvent. Generally, a feed mixture containing paraxylene, acetic acid, and cobalt-manganese-bromine catalyst (typical ratios of these compounds are 1: 2) is fed to an oxidation reactor containing compressed air and reacted at 150 ℃ and 230 ℃.
The reaction mixture containing the crude TA and various byproducts, such as p-toluic acid and 4-carboxybenzaldehyde (4-CBA), was cooled to produce TA crystals, which were separated from the mother liquor by filtration. The mother liquor typically comprises water, acetic acid, organic impurities and by-products (e.g., isophthalic acid, benzoic acid, p-toluic acid, and trimellitic acid) as well as the TA itself, as well as inorganic components (e.g., cobalt, manganese, and bromine compounds). While a portion of the mother liquor is returned directly or indirectly to the oxidation reactor to recycle these materials, another portion of the mother liquor is flushed to a solvent recovery system to maintain the levels of impurities, byproducts, and water in the oxidation reactor within acceptable limits.
A portion of the acetic acid and a portion of the water are vaporized from the rinse stream to leave the residue stream. Typical compositions of such residue streams are 2 to 25 weight percent (wt%) acetic acid, 10 to 50 wt% water, 50 to 60 wt% organic components including 20 to 40 wt% benzoic acid, 5 to 20 wt% isophthalic acid and 4 to 5 wt% phthalic acid and a catalyst component comprising 0.2 to 1.5 wt% cobalt, 0.2 to 2 wt% manganese and 2 to 5 wt% hydrobromic acid (or its sodium salt).
The amount of these residues produced in TA manufacture is estimated to be on the order of hundreds of thousands of metric tons per year. Thus, although these residues have previously been eliminated as waste (e.g., by combustion), the recovery of useful chemicals present in these residues can bring significant environmental and financial benefits.
WO 2011/119395 a1, incorporated herein by reference in its entirety, describes a system for recovering aromatic monocarboxylic acid and catalyst components from this residual stream using a single extraction step, a simplified schematic of which is shown in figure 1. The residue stream is fed to a collection vessel and combined with organic and aqueous solvents. The mixture is passed to a filtration unit to produce a filter cake and a filtrate that will separate into an organic layer and an aqueous layer. The aqueous layer is passed to a concentrator and the aqueous solvent obtained from this unit is recycled to a collection vessel. The organic layer is passed to a solvent recovery zone and the organic solvent obtained from this zone is recycled to the collection vessel. The bottoms from the solvent recovery zone are fed to a fractionation unit where benzoic acid is recovered from the overhead product and para-toluic acid is recovered from the bottoms product by another distillation column.
However, the present inventors have found that even where good washing of the filter cake is achieved, typical single-stage extraction processes are unable to recover a substantial portion of the aromatic carboxylic acid in the organic phase. In particular, the inventors have found that for a typical residual stream from a process for the manufacture of terephthalic acid, although most of the benzoic acid is extracted in the organic phase, about 11% of the benzoic acid is extracted in the aqueous phase (the other component of the benzoic acid is still in the solid phase). This constitutes a significant loss of valuable benzoic acid production and a significant effluent disposal requirement.
It is therefore an object of the present invention to provide a process and apparatus which provides for enhanced recovery of organic components, particularly aromatic monocarboxylic acids such as benzoic acid and p-toluic acid, from these residues.
Disclosure of Invention
In a first aspect of the invention, there is provided a process and apparatus for recovering aromatic monocarboxylic acid from a residue stream, said first aspect comprising first performing a solids extraction followed by an aqueous extraction. Accordingly, this aspect of the invention provides a process for recovering aromatic monocarboxylic acid from a residue stream, said process comprising the steps of:
(i) mixing a residue stream comprising aromatic monocarboxylic acid with an aqueous liquid and an organic liquid to produce a first mixture comprising dissolved material and suspended material, wherein the dissolved material comprises aromatic monocarboxylic acid,
(ii) (ii) filtering the first mixture from step (i) to produce a filtrate and a solid,
(iii) (iii) separating the filtrate from step (ii) into a first aqueous phase and a first organic phase, and
(iv) (iv) recovering the aromatic monocarboxylic acid from the first organic phase from step (iii), characterized in that the process further comprises the steps of:
(v) (iv) mixing the first aqueous phase from step (iii) with an organic liquid to produce a second mixture, and
(vi) (vi) separating the second mixture from step (v) into a second aqueous phase and a second organic phase, wherein the second organic phase comprises the aromatic monocarboxylic acid.
The aromatic monocarboxylic acid is preferably recovered from the second organic phase of step (vi). Preferably, this is achieved by recycling the second organic phase of step (vi) to step (i), thereby providing a counter current flow (relative to the residual stream) of organic liquid in the process. Thus, preferably, the organic liquid in step (i) comprises (and preferably consists of) the second organic phase from step (vi). It will be appreciated that the start-up of the process requires the addition of fresh make-up organic liquid to step (i), but in steady state operation fresh organic liquid is preferably introduced only to step (v). Whereby the aromatic monocarboxylic acid from the second organic phase of step (vi) is recovered in step (iv).
The first aspect of the present invention further provides an apparatus for recovering an aromatic monocarboxylic acid from a residue stream, the apparatus comprising:
(a) a mixer configured to receive and mix a residue stream comprising an aromatic monocarboxylic acid with an aqueous liquid and an organic liquid to produce a first mixture comprising dissolved material and suspended material, wherein the dissolved material comprises an aromatic monocarboxylic acid,
(b) a filtration unit in fluid communication with the mixer (a) configured to receive the first mixture from the mixer (a) and produce a solid and a filtrate,
(c) a separator in fluid communication with the filtration unit (b) configured to receive the filtrate from the filtration unit (b) and produce a first aqueous phase and a first organic phase, and
(d) a recovery unit in fluid communication with separator (c) configured to receive the first organic phase from separator (c) and recover aromatic monocarboxylic acid from the first organic phase from separator (c),
characterized in that the apparatus further comprises:
(e) a mixer in fluid communication with the separator (c) configured to receive and mix the first aqueous phase and the organic liquid from the separator (c) to produce a second mixture, and
(f) a separator in fluid communication with mixer (e) configured to receive the second mixture from mixer (e) and produce a second aqueous phase and a second organic phase, wherein the second organic phase comprises an aromatic monocarboxylic acid.
The aromatic monocarboxylic acid is preferably recovered from the second organic phase from separator (f). Preferably, this is achieved by the mixer (a) being in fluid communication with the separator (f) and being configured to receive the second organic phase from the separator (f), thereby providing a counter current flow (relative to the residue stream) of organic liquid such that organic liquid is recycled from the separator (f) to the mixer (a). Thus, preferably, mixer (a) is configured to receive an organic liquid comprising (and preferably consisting of) the second organic phase from separator (f). It will be appreciated that starting the process for using the apparatus will require fresh make-up organic liquid to be added to mixer (a), but under steady state operation fresh organic liquid is preferably only introduced into mixer (e). Whereby the aromatic monocarboxylic acid from the second organic phase of separator (f) is recovered in recovery unit (d). The mixer (e) is preferably an in-line mixer. The separator (f) is preferably a decanter.
Preferably, the organic liquid introduced in step (v) and/or mixer (e) is a clean organic solvent. Preferably, the aqueous liquid introduced in step (i) and/or mixer (a) is a clean aqueous solvent.
The residue stream is preferably derived from a process for the manufacture of aromatic polycarboxylic acids, typically dicarboxylic acids such as terephthalic acid. Typically, the residue stream is derived from the mother liquor from the separation step. The aromatic monocarboxylic acid may be dissolved in the residual stream, suspended in the residual stream or present in the residual stream as a melt phase. The aromatic monocarboxylic acid is preferably selected from the group consisting of benzoic acid, p-toluic acid and mixtures thereof.
Accordingly, the first aspect of the present invention further provides a process for the production of an aromatic polycarboxylic acid by the liquid phase oxidation of an alkyl-substituted aromatic starting material, wherein the improvement comprises:
(i) mixing a residue stream comprising aromatic monocarboxylic acid with an aqueous liquid and an organic liquid to produce a first mixture comprising dissolved material and suspended material, wherein the dissolved material comprises aromatic monocarboxylic acid,
(ii) (ii) filtering the first mixture from step (i) to produce a filtrate and a solid,
(iii) (iii) separating the filtrate from step (ii) into a first aqueous phase and a first organic phase,
(iv) (iv) recovering the aromatic monocarboxylic acid from the first organic phase from step (iii),
(v) (iv) mixing the first aqueous phase from step (iii) with an organic liquid to produce a second mixture, and
(vi) (vi) separating the second mixture from step (v) into a second aqueous phase and a second organic phase, wherein the second organic phase comprises the aromatic monocarboxylic acid.
The present inventors have found that the first aspect of the present invention comprising water extraction in addition to the solid extraction step increases the recovery of aromatic monocarboxylic acid without increasing the amount of solvent used. For example, depending on the process for making terephthalic acid, the recovery of benzoic acid from the residue stream in the organic phase can be increased up to 95%. Furthermore, this significant increase in benzoic acid recovery is achieved with relatively small capital investment (e.g., in-line mixers and small decanter vessels) and relatively small process complexity increases. Thus, the efficiency and economy of the overall manufacturing process are significantly improved.
A second aspect of the invention provides a process and apparatus for recovering aromatic monocarboxylic acid from a residue stream, the second aspect comprising first solids extraction followed by second solids extraction. Accordingly, this aspect of the invention provides a process for recovering aromatic monocarboxylic acid from a residue stream, said process comprising the steps of:
(I) mixing a residue stream comprising aromatic monocarboxylic acid with an aqueous liquid and an organic liquid to produce a first mixture comprising dissolved material and suspended material, wherein the dissolved material comprises aromatic monocarboxylic acid,
(II) filtering the first mixture from step (I) to produce a first filtrate and a first solid,
(III) separating the first filtrate from step (II) into a first aqueous phase and a first organic phase, and
(IV) recovering the aromatic monocarboxylic acid from the first organic phase from step (III), characterized in that the process further comprises the steps of:
(V) mixing the first aqueous phase from step (III) with an organic liquid and the first solid from step (II) to produce a second mixture, and filtering the second mixture to produce a second filtrate and a second solid, and
(VI) separating the second filtrate from step (V) into a second aqueous phase and a second organic phase, wherein the second organic phase comprises the aromatic monocarboxylic acid.
The aromatic monocarboxylic acid is preferably recovered from the second organic phase of step (VI). Preferably, this is achieved by recycling the second organic phase of step (VI) to step (I), thereby providing a counter-current flow (with respect to the residue stream) of organic liquid in the process. Thus, preferably, the organic liquid in step (I) comprises (and preferably consists of) the second organic phase from step (VI). It will be appreciated that the process requires fresh make-up organic liquid to be added to step (I) to begin, but that under steady state operation fresh organic liquid is preferably introduced only into step (V). Whereby the aromatic monocarboxylic acid from the second organic phase of step (VI) is recovered in step (IV).
The second aspect of the present invention further provides an apparatus for recovering an aromatic monocarboxylic acid from a residue stream, the apparatus comprising:
(A) a mixer configured to receive and mix a residue stream comprising an aromatic monocarboxylic acid with an aqueous liquid and an organic liquid to produce a first mixture comprising dissolved material and suspended material, wherein the dissolved material comprises an aromatic monocarboxylic acid,
(B) a filtration unit in fluid communication with the mixer (A) configured to receive the first mixture from the mixer (A) and produce a first solid and a first filtrate,
(C) a separator in fluid communication with the filtration unit (B) configured to receive the first filtrate from the filtration unit (B) and produce a first aqueous phase and a first organic phase, and
(D) a recovery unit in fluid communication with the separator (C) configured to receive the first organic phase from the separator (C) and to recover the aromatic monocarboxylic acid from the first organic phase from the separator (C),
characterized in that the apparatus further comprises:
(E) a mixer in communication with the filtration unit (B) and in fluid communication with the separator (C) configured to receive and mix the first solid from the filtration unit (B), the first aqueous phase from the separator (C), and the organic liquid to produce a second mixture,
(F) a filtration unit in fluid communication with the mixer (E) configured to receive the second mixture from the mixer (E) and produce a second solid and a second filtrate, an
(G) A separator in fluid communication with the filtration unit (F) configured to receive the second filtrate from the filtration unit (F) and produce a second aqueous phase and a second organic phase, wherein the second organic phase comprises the aromatic monocarboxylic acid.
The aromatic monocarboxylic acid is preferably recovered from the second organic phase from separator (G). Preferably, this is achieved by the mixer (a) being in fluid communication with the separator (G) and being configured to receive the second organic phase from the separator (G), thereby providing a counter current flow (relative to the residue stream) of organic liquid such that organic liquid is recycled from the separator (G) to the mixer (a). Thus, preferably, mixer (a) is configured to receive an organic liquid comprising (and preferably consisting of) the second organic phase from separator (G). It will be appreciated that starting the process for using the apparatus will require fresh make-up organic liquid to be added to mixer (a), but under steady state operation fresh organic liquid is preferably only introduced into mixer (E). Whereby the aromatic monocarboxylic acid from the second organic phase of separator (G) is recovered in recovery unit (D). The separator (G) is preferably a decanter.
Preferably, the organic liquid introduced in step (V) and/or mixer (E) is a clean organic solvent. Preferably, the aqueous liquid introduced in step (I) and/or mixer (a) is a clean aqueous solvent.
The residue stream is preferably derived from a process for the manufacture of aromatic polycarboxylic acids, typically dicarboxylic acids such as terephthalic acid. Typically, the residue stream is derived from the mother liquor from the separation step. The aromatic monocarboxylic acid may be dissolved in the residual stream, suspended in the residual stream or present in the residual stream as a melt phase. The aromatic monocarboxylic acid is preferably selected from the group consisting of benzoic acid, p-toluic acid and mixtures thereof.
Accordingly, the second aspect of the present invention further provides a process for the production of an aromatic polycarboxylic acid by the liquid phase oxidation of an alkyl-substituted aromatic starting material, wherein the improvement comprises:
(I) mixing a residue stream comprising aromatic monocarboxylic acid with an aqueous liquid and an organic liquid to produce a first mixture comprising dissolved material and suspended material, wherein the dissolved material comprises aromatic monocarboxylic acid,
(II) filtering the first mixture from step (I) to produce a first filtrate and a first solid,
(III) separating the first filtrate from step (II) into a first aqueous phase and a first organic phase,
(IV) recovering the aromatic monocarboxylic acid from the first organic phase from step (III),
(V) mixing the first aqueous phase from step (III) with an organic liquid and the first solid from step (II) to produce a second mixture, and filtering the second mixture to produce a second filtrate and a second solid, and
(VI) separating the second filtrate from step (V) into a second aqueous phase and a second organic phase, wherein the second organic phase comprises the aromatic monocarboxylic acid.
The inventors have found that the process of this second aspect of the invention comprising a second solid extraction in addition to the first solid extraction can increase the recovery of aromatic monocarboxylic acid without increasing the amount of solvent used. For example, depending on the process for making terephthalic acid, the recovery of benzoic acid from the residue stream in the organic phase can be significantly increased.
A third aspect of the present invention provides a process for producing purified terephthalic acid, the process comprising a catalytic oxidation reaction of a hydrocarbon precursor in a reaction solvent, the process comprising the steps of:
oxidizing a hydrocarbon precursor in a reaction solvent in the presence of a metal catalyst to produce crude terephthalic acid; and
purifying the crude terephthalic acid to produce a purified terephthalic acid,
wherein the process further comprises the step of recovering the aromatic monocarboxylic acid from the residue stream by the process of the first aspect of the present invention or the process of the second aspect of the present invention.
Drawings
FIG. 1 is a schematic of a conventional single stage solids extraction according to the background art.
Fig. 2 is a schematic illustration of solid extraction combined with water extraction according to the first aspect of the present invention.
Figure 3 is a schematic of a two-step solids extraction according to a second aspect of the invention.
Fig. 4 and 5 are graphs showing the percent recovery of benzoic acid and p-toluic acid in the total organic phase (including organic liquid in the wet cake), aqueous phase, and solid phase after a single stage solids extraction process.
Figures 6 and 7 are graphs showing the mass transfer of benzoic acid and p-toluic acid from the aqueous phase to the organic phase in an extraction carried out in a water to toluene weight ratio of 1.9 in a process according to the first aspect of the invention.
Fig. 8 and 9 are water showing the ratio between water: graph of the mass transfer of benzoic acid from aqueous to organic phase in the extraction with toluene weight ratio.
Fig. 10 and 11 are graphs showing the mass transfer of p-toluic acid from the aqueous phase to the organic phase in extractions performed at a water to toluene weight ratio of 0.92 and 6, respectively, in the process according to the first aspect of the present invention.
Detailed Description
Various embodiments of the invention are described herein. It is to be understood that the features specified in each embodiment can be combined with other specified features to provide further embodiments.
The weight ratio of aqueous liquid to organic liquid used in step (V)/(V) may be optimized to maximize the final recovery of the aromatic monocarboxylic acid. This weight ratio of aqueous liquid to organic liquid may be between 0.05: 1 and 50: 1, more suitably between 0.1: 1 and 25: 1, between 0.25: 1 and 20: 1, between 0.5: 1 and 15: 1, between 0.75: 1 and 10: 1, between 0.8: 1 and 7.5: 1 or between 0.9: 1 and 6: 1. Thus, suitable weight ratios of aqueous liquid to organic liquid include about 1: 1, about 2: 1, about 3: 1, about 4: 1, and about 5: 1. The solvent of the aqueous liquid (aqueous solvent) is preferably water. The solvent (or organic solvent) of the organic liquid may be selected from toluene, benzene, methanol, cyclohexane, petroleum ether and mixtures thereof. Preferably, the solvent of the organic liquid is toluene. The mixture of aqueous liquid and organic liquid may be heated in steps (I) and/or (V)/(I) and/or (V) (i.e. in mixers (a) and/or (E)/(a) and/or (E)) to a temperature of, for example, up to 75 ℃ to 80 ℃ to facilitate dissolution of the solids. As mentioned above, the aqueous and organic solvents may be, and preferably are, "clean" when introduced into (V)/(V) of the process of the present invention. By "clean" is meant that the aqueous and organic solvents are not used elsewhere in the process (e.g., in the extraction), i.e., fresh or make-up solvents are used. The duration of step (V)/(V) can be optimized to maximize the final recovery of the aromatic monocarboxylic acid while minimizing the increase in the duration of the overall process. Thus, the duration of step (V)/(V) may suitably be from 5 seconds to 60 minutes, or from 5 seconds to 30 minutes, or from 5 seconds to 15 minutes, or from 5 seconds to 5 minutes, or from 10 seconds to 150 seconds. Typical duration of step (V)/(V) may be about 15 seconds or about 30 seconds.
The method of the first aspect of the invention comprises water extraction in steps (v) and (vi). In one embodiment, the process further comprises subjecting the second aqueous phase from step (vi) to one or more additional aqueous extractions. The one or more additional aqueous extractions may comprise mixing the second aqueous phase from step (vi) with an organic liquid to produce a further mixture, and separating the further mixture into a further aqueous phase and a further organic phase, wherein the further organic phase comprises the aromatic monocarboxylic acid. The other organic phase may be recycled to step (i). Similarly, the apparatus of the first aspect of the invention is adapted to perform a first water extraction in the mixer (e) and the separator (f). In one embodiment, the apparatus is adapted to perform one or more additional aqueous extractions of the second aqueous phase from separator (f). Thus, the apparatus may further comprise a further mixer in fluid communication with the separator (f) configured to receive and mix the second aqueous phase and the organic liquid from the separator (f) to produce a further mixture, and a further separator in fluid communication with the further mixer configured to receive the further mixture from the further mixer and produce a further aqueous phase and a further organic phase, wherein the further organic phase comprises the aromatic monocarboxylic acid. Mixer (a) may be in fluid communication with the other separator and configured to receive another organic phase from the other separator.
The process of the second aspect of the invention comprises a first solids extraction carried out in steps (I), (II) and (III) and a second solids extraction carried out in steps (V) and (VI). In one embodiment, the process further comprises subjecting the second aqueous phase from step (VI) to one or more additional solid extractions. The one or more additional solid extractions can comprise mixing the second aqueous phase from step (VI) with an organic liquid and the second solid from step (V) to produce another mixture, filtering the other mixture to produce another filtrate and another solid, and separating the other filtrate into another aqueous phase and another organic phase, wherein the another organic phase comprises the aromatic monocarboxylic acid. The other organic phase may be recycled to step (I). Similarly, the apparatus of the second aspect of the invention is adapted to perform a first solids extraction in the mixer (a), the filtration unit (B) and the separator (C) and a second solids extraction in the mixer (E), the filtration unit (F) and the separator (G). In one embodiment, the apparatus is adapted to perform one or more additional solid extractions on the second aqueous phase from separator (G). Thus, the apparatus may further comprise a further mixer in communication with the filtration unit (F) and in fluid communication with the separator (G) configured for receiving and mixing the second solids from the filtration unit (F), the second aqueous phase from the separator (G) and the organic liquid to produce a further mixture; a further filtration unit in fluid communication with the further mixer configured to receive a further mixture from the further mixer and produce a further solid and a further filtrate; and a further separator in fluid communication with the further filtration unit configured to receive a further mixture from the further filtration unit and produce a further aqueous phase and a further organic phase, wherein the further organic phase comprises an aromatic monocarboxylic acid. Mixer (a) may be in fluid communication with the other separator and configured to receive another organic phase from the other separator.
The mixing of the residue stream from step (I)/(I) with the aqueous liquid and the organic liquid may be carried out simultaneously or sequentially. For example, the residue stream may be mixed with an organic liquid, and then followed by the addition of an aqueous liquid. Alternatively, the residue stream may be mixed with an aqueous liquid and then followed by the addition of an organic liquid. Alternatively, the aqueous liquid may be mixed with the organic liquid and the residue stream then added to this mixture. Alternatively, the residue stream, the aqueous liquid and the organic liquid may be mixed simultaneously.
The initial contacting of the streams may be carried out in the mixer (a)/(a) or in a line or vessel upstream of the mixer (a)/(a). Thus, the mixer (a)/(a) may independently receive the residue stream, the aqueous liquid and the organic liquid or two or more of these streams may be contacted prior to being received by the mixer (a)/(a). For example, the residue stream may be contacted with the organic liquid before the residue stream and the organic liquid are received by the mixer (a)/(a). Alternatively, the residue stream may be contacted with the aqueous liquid before the residue stream and the aqueous liquid are received by the mixer (a)/(a). Alternatively, the aqueous liquid may be contacted with the organic liquid and the residue stream before the aqueous liquid, the organic liquid and the residue stream are received by the mixer (a)/(a).
The weight ratio of the residue stream to the organic liquid to water may suitably be in the range 0.25-1.5: 0.5-3: 0.75-7.5, or 0.5-1: 0.7-2: 1-5.
As mentioned above, the residue stream is preferably derived from a process for the manufacture of aromatic polycarboxylic acids, typically dicarboxylic acids, such as terephthalic acid.
Terephthalic acid is typically produced by a process comprising the catalytic oxidation of a hydrocarbon precursor in a reaction solvent. Hydrocarbon precursors are compounds that can be oxidized to form terephthalic acid. Thus, the hydrocarbon precursor is typically substituted with a substituent such as C at the position of the formic acid substituent in the terephthalic acid1-6Alkyl, formyl or acetyl substituted benzene. Preferred hydrocarbon precursors are C1-6Alkyl-substituted benzenes, especially p-xylene. The reaction solvent is typically an aliphatic carboxylic acid (such as acetic acid) or a mixture of such an aliphatic carboxylic acid and water. The oxidation reaction may be carried out under any conditions where oxygen is available, for example the reaction may be carried out in air. The reaction catalyst typically comprises a soluble form of cobalt and/or manganese (e.g. its acetate salt) with a bromine source (such as hydrobromic acid) acting as a promoter. The temperature of the oxidation reaction is generally in the range of about 100 ℃ to 250 ℃, preferably about 150 ℃ to 220 ℃. Any conventional pressure may be used for the reaction, suitably to maintain the reaction mixture in a liquid state.
The oxidation reaction step serves to catalytically oxidize the hydrocarbon precursor in the reaction solvent, thereby forming a product stream and an exhaust gas. The product stream is typically transferred to a crystallization step to form a first slurry of crude terephthalic acid crystals and an overhead vapor. The first slurry of crude terephthalic acid crystals is typically passed to a separation step wherein a mother liquor is separated from the crude terephthalic acid crystals, which may then be mixed with an aqueous liquid to form a second slurry of crude terephthalic acid crystals. This second slurry of crude terephthalic acid crystals is typically transferred to a purification step, heated and hydrogenated before being cooled to form a slurry of purified terephthalic acid crystals.
The off-gas from the oxidation reaction step will typically be separated in a distillation step into an organic solvent rich stream and a water rich vapour stream. The organic solvent rich stream from the distillation step typically comprises 80-95% w/w of the reaction solvent and is typically returned to the oxidation reaction step. The water-rich vapour stream from the distillation step typically comprises from 0.1 to 5.0% w/w of reaction solvent and is typically condensed in a condensation step to form a condensate stream and an overhead gas. A portion of the condensate stream is typically used as a source of aqueous liquid for forming the second slurry of crude terephthalic acid crystals as described above. A portion of the condensate stream preferably forms part of the wash fluid for the purified terephthalic acid crystals from the purification apparatus.
Typically, the residue stream is derived from the mother liquor separated from the crude terephthalic acid crystals in the separation step (i.e. from the first slurry of terephthalic acid crystals). While a portion of the mother liquor is returned directly or indirectly to the oxidation reactor to recycle these materials, another portion of the mother liquor is flushed to a solvent recovery system to maintain the levels of impurities, byproducts, and water in the oxidation reactor within acceptable limits. A portion of the reaction solvent and a portion of the water evaporate from the flush stream leaving the residue stream. Thus, the recovered aromatic monocarboxylic acid is preferably selected from benzoic acid, p-toluic acid and mixtures thereof. More preferably, the aromatic monocarboxylic acid is benzoic acid. However, other monocarboxylic acids, such as m-toluic acid and o-toluic acid, may be recovered. Thus, the aromatic monocarboxylic acid may be selected from benzoic acid, m-toluic acid, o-toluic acid, p-toluic acid and mixtures thereof. In the case where the aromatic monocarboxylic acid comprises a mixture of two or more aromatic monocarboxylic acids, the step of recovering the aromatic monocarboxylic acid, step (IV)/(IV), may comprise one or more distillation processes, such as those described in WO 2011/119395 a 1. For example, a first distillation process may be used to remove the organic solvent in the form of an overhead product, a second distillation process may be used to remove the first aromatic monocarboxylic acid (e.g., benzoic acid) in the form of an overhead product, and a third distillation may be used to remove the second aromatic monocarboxylic acid (e.g., p-toluic acid) in the form of an overhead product. Thus, the recovery unit (D)/(D) may comprise one or more distillation columns.
The solid obtained in the filtration step (steps (II)/(II) and step (IV)) of the present invention may be further treated to recover a dicarboxylic acid as described in 2011/119395 a 1. The dicarboxylic acid typically comprises terephthalic acid, isophthalic acid, or mixtures thereof.
The aqueous liquor obtained in the final separation step, step (VI)/(VI), may also be further treated to recover catalyst metals (e.g. cobalt and manganese carbonates, preferably by precipitation with sodium hydroxide and/or sodium carbonate) and/or tricarboxylic acid (e.g. trimellitic acid) as described in WO 2011/119395 a 1.
The process and apparatus of the first and second aspects of the present invention provide significantly improved recovery of aromatic monocarboxylic acids, such as benzoic acid and p-toluic acid, from the production of aromatic polycarboxylic acids. The process and apparatus according to the first aspect of the invention is particularly advantageous over the process and apparatus of the second aspect of the invention in that it provides improved recovery of aromatic monocarboxylic acids (such as benzoic acid and p-toluic acid) in a comparable manner, but in a more efficient and cost effective manner involving fewer unit operations.
The invention will be further described with reference to the drawings.
Figure 1 shows a conventional single stage solids extraction. Residue stream 1, organic solvent stream 3, and water stream 4 are combined in an extractor (although either or both of organic solvent stream 3 and water stream 4 may be combined with residue stream 1 upstream of the extractor as indicated by the dashed lines). The resulting mixture was passed to a filter. The solid phase separates into a solid stream 6 and the liquid phase is passed to a decanter. The organic liquid separates into stream 8 and the aqueous liquid separates into stream 9.
Fig. 2 is a schematic diagram of a method according to a preferred embodiment of the first aspect of the present invention, comprising solid extraction in combination with water extraction. The residue stream 1, the aqueous stream 4 and the organic liquid recycled from the downstream processing step are combined in an extractor (although as indicated by the dashed line either or both of the organic liquid and the aqueous stream 4 may be combined with the residue stream 1 upstream of the extractor). The resulting mixture was passed to a filter. The solid phase separates into a solid stream 6 and the liquid phase is passed to a decanter. The organic liquid is separated into stream 8 and the aqueous liquid is passed to a mixer and combined with organic solvent stream 3. The resulting mixture was transferred to a decanter. The aqueous liquid is separated into stream 9 and the organic liquid is recycled in a counter current manner to mix with the residue stream 1 in the extractor.
Fig. 3 is a schematic diagram of a process according to a preferred embodiment of the second aspect of the present invention, comprising two stages of solids extraction. The residue stream 1, aqueous stream 4 and organic liquid recycled from downstream processing steps are combined in a first extractor (although as indicated by the dashed line either or both of the organic liquid and aqueous stream 4 may be combined with the residue stream 1 upstream of the extractor). The resulting mixture was passed to a filter. The solid phase is separated and the liquid phase is passed to a decanter. The organic liquid is separated into stream 8 and the aqueous liquid is passed to a second extractor and recombined with the solid phase from the previous separation and combined with organic solvent stream 3. The resulting mixture was passed to a filter. The solid phase separates into a solid stream 6 and the liquid phase is passed to a decanter. The aqueous liquid is separated into stream 9 and the organic liquid is recycled in a counter current manner to mix with the residue stream 1 in the first extractor.
The invention is further illustrated by the following examples. As noted above, the examples are not intended to limit the invention. Modifications in detail may be made without departing from the scope of the invention.
Examples of the invention
Comparative example 1
Single stage solids extraction was investigated by extracting the residue (from a typical residue stream 1 derived from the liquid phase oxidation of para-xylene to terephthalic acid) with toluene for a series of batch times (fig. 1). The slurry was filtered and the filter cake was washed with water. Samples of the wet cake, organic layer and aqueous layer were taken and analyzed to assess the extent of extraction.
The recovery of benzoic acid in the organic liquid was found to vary little with increasing batch time, indicating that the extraction was completed in a very short time.
The concentration of organic liquid in the wet cake can be calculated from the toluene concentration in the cake. From this calculation it was found that benzoic acid present as a solid in the wet cake was significantly reduced between 5 and 10 minutes and then remained fairly constant, indicating that the extraction was complete within 10 minutes. It was also found that most of the benzoic acid in the wet cake was present as an organic liquid. The benzoic acid recovery data was then adjusted to account for the organic liquid in the wet cake. These data are shown in fig. 4. From these data, it can be seen that after 10 minutes, approximately 86% benzoic acid was extracted in the organic phase and 11% remained in the aqueous phase and 3% remained in the solid phase.
The recovery of p-toluic acid was evaluated in a similar manner. These data are shown in fig. 5. Approximately 54% p-toluic acid was recovered in the organic phase and approximately equal amounts in the solid and aqueous phases.
Example 1
An artificial aqueous feed (500g) was prepared to simulate the composition of the aqueous phase from the solids extraction step, i.e. the aqueous phase from step (III)/(III) of the process of the invention (in other words stream 9 from comparative example 1 and figure 1). The feed was heated to 80 ℃ and any undissolved solids were filtered off.
The filtrate was then mixed with hot toluene (200 g). Samples of the aqueous and organic layers were taken at regular intervals and analyzed by HPLC to find mass transfer of benzoic acid and p-toluic acid from the aqueous to the organic phase. These data are shown in fig. 6 and 7. The data show the extraction in organic liquids of organic by-products derived from the aqueous stream of the solids extraction step.
The water to toluene weight ratio in the above experiment was 1.9. In practice, the amount of water present may vary depending on the amount of water added to the residue and the amount of water used to wash the filter cake in the first solids extraction step. The effect of the water to toluene ratio was assessed by performing two additional experiments.
Example 2
The first experiment simulated a process with a water to toluene weight ratio of 0.92. The results are shown in fig. 8 and 10.
Example 3
The second experiment simulated a process with a water to toluene weight ratio of 6. The results are shown in fig. 9 and 11.
Recovery data for benzoic acid and p-toluic acid in each of the experiments of examples 1 to 3 showed that extraction was complete within 30 seconds. These 30 seconds consisted of 15 seconds of mixing and 15 seconds of resting, so it can be concluded that a simple in-line mixer with 15 seconds residence time followed by a decanter would be far enough to complete the extraction.
Under normal conditions (example 1), 70% benzoic acid (fig. 6) and 90% p-toluic acid (fig. 7) were extracted in the organic phase. Thus, in conjunction with the single stage solids extraction of comparative example 1, this equates to an overall recovery over two steps of approximately 94% benzoic acid and 68% p-toluic acid.
At reduced water content (example 2), the benzoic acid recovery increased to about 80% (fig. 8), while at increased water content (example 3), the benzoic acid recovery decreased to 50% (fig. 9). Similarly, at reduced water content, the p-toluic acid recovery increased slightly to 92% (fig. 10), while at increased water content, the p-toluic acid recovery decreased to 75% (fig. 11).
These results indicate that it is advantageous to minimize the relative water content of the feed, but that an increase in aromatic monocarboxylic acid recovery is still achieved at both low and high water content.
Claims (20)
1. A process for recovering aromatic monocarboxylic acid from a residue stream, said process comprising the steps of:
(i) mixing a residue stream comprising an aromatic monocarboxylic acid with water and an organic liquid selected from the group consisting of toluene, benzene, methanol, cyclohexane, petroleum ether, or mixtures thereof to produce a first mixture comprising dissolved material and suspended material, wherein the dissolved material comprises the aromatic monocarboxylic acid,
(ii) (ii) filtering the first mixture from step (i) to produce a filtrate and a solid,
(iii) (iii) separating the filtrate from step (ii) into a first aqueous phase and a first organic phase, and
(iv) (iv) recovering the aromatic monocarboxylic acid from the first organic phase from step (iii), characterized in that the process further comprises the steps of:
(v) (iv) mixing the first aqueous phase from step (iii) with an organic liquid selected from toluene, benzene, methanol, cyclohexane, petroleum ether or mixtures thereof to produce a second mixture, and
(vi) (vi) separating the second mixture from step (v) into a second aqueous phase and a second organic phase, wherein the second organic phase comprises the aromatic monocarboxylic acid.
2. A process for recovering aromatic monocarboxylic acid from a residue stream, said process comprising the steps of:
(I) mixing a residue stream comprising an aromatic monocarboxylic acid with water and an organic liquid selected from the group consisting of toluene, benzene, methanol, cyclohexane, petroleum ether, or mixtures thereof to produce a first mixture comprising dissolved material and suspended material, wherein the dissolved material comprises the aromatic monocarboxylic acid,
(II) filtering the first mixture from step (I) to produce a first filtrate and a first solid,
(III) separating the first filtrate from step (II) into a first aqueous phase and a first organic phase, and
(IV) recovering the aromatic monocarboxylic acid from the first organic phase from step (III), characterized in that the process further comprises the steps of:
(V) mixing the first aqueous phase from step (III) with an organic liquid selected from toluene, benzene, methanol, cyclohexane, petroleum ether, or mixtures thereof, and the first solid from step (II) to produce a second mixture, and filtering the second mixture to produce a second filtrate and a second solid, and
(VI) separating the second filtrate from step (V) into a second aqueous phase and a second organic phase, wherein the second organic phase comprises the aromatic monocarboxylic acid.
3. The process of claim 1 or claim 2, wherein the aromatic monocarboxylic acid is recovered from the second organic phase from step (VI) or step (VI).
4. The process of any one of claims 1-3, further comprising the step of recycling the second organic phase from step (VI) or step (VI) to step (I) or step (I).
5. A process according to claim 4, wherein in the process organic liquid flows counter-currently to the residual stream.
6. The process of any preceding claim, wherein the organic liquid in step (I) or step (I) comprises the second organic phase from step (VI) or step (VI).
7. The process of any preceding claim, wherein step (IV) or step (IV) comprises one or more distillation processes.
8. The process according to any preceding claim, wherein the weight ratio of the first aqueous phase to the organic liquid used in step (V) or step (V) is in the range of from 0.05: 1 and 50: 1, 0.1: 1 and 25: 1 or 0.25: 1 and 20: 1.
9. The process of any preceding claim, wherein the process further comprises subjecting the second aqueous phase from step (VI) or step (VI) to one or more additional extractions.
10. An apparatus for recovering aromatic monocarboxylic acid from a residue stream comprising:
(a) a mixer configured to receive and mix a residue stream comprising an aromatic monocarboxylic acid with water and an organic liquid selected from toluene, benzene, methanol, cyclohexane, petroleum ether, or mixtures thereof to produce a first mixture comprising dissolved species and suspended species, wherein the dissolved species comprises the aromatic monocarboxylic acid,
(b) a filtration unit in fluid communication with mixer (a) configured to receive the first mixture from mixer (a) and produce a solid and a filtrate,
(c) a separator in fluid communication with filtration unit (b) configured to receive the filtrate from filtration unit (b) and produce a first aqueous phase and a first organic phase, and
(d) a recovery unit in fluid communication with separator (c) configured to receive the first organic phase from separator (c) and recover aromatic monocarboxylic acid from the first organic phase from separator (c),
characterized in that the apparatus further comprises:
(e) a mixer in fluid communication with separator (c) configured to receive and mix the first aqueous phase from separator (c) with an organic liquid selected from toluene, benzene, methanol, cyclohexane, petroleum ether, or mixtures thereof to produce a second mixture, and
(f) a separator in fluid communication with mixer (e) configured to receive the second mixture from mixer (e) and produce a second aqueous phase and a second organic phase, wherein the second organic phase comprises the aromatic monocarboxylic acid.
11. An apparatus for recovering aromatic monocarboxylic acid from a residue stream comprising:
(A) a mixer configured to receive and mix a residue stream comprising an aromatic monocarboxylic acid with water and an organic liquid selected from toluene, benzene, methanol, cyclohexane, petroleum ether, or mixtures thereof to produce a first mixture comprising dissolved species and suspended species, wherein the dissolved species comprises the aromatic monocarboxylic acid,
(B) a filtration unit in fluid communication with mixer (A) configured to receive the first mixture from mixer (A) and produce a first solid and a first filtrate,
(C) a separator in fluid communication with filtration unit (B) configured to receive the first filtrate from filtration unit (B) and produce a first aqueous phase and a first organic phase, and
(D) a recovery unit in fluid communication with separator (C) configured to receive the first organic phase from separator (C) and to recover aromatic monocarboxylic acid from the first organic phase from separator (C),
characterized in that the apparatus further comprises:
(E) a mixer in communication with filtration unit (B) and in fluid communication with separator (C) configured to receive and mix the first solid from filtration unit (B), the first aqueous phase from separator (C), and an organic liquid selected from toluene, benzene, methanol, cyclohexane, petroleum ether, or mixtures thereof to produce a second mixture,
(F) a filtration unit in fluid communication with the mixer (E) configured to receive the second mixture from the mixer (E) and produce a second solid and a second filtrate, and
(G) a separator in fluid communication with filtration unit (F) configured to receive the second filtrate from filtration unit (F) and produce a second aqueous phase and a second organic phase, wherein the second organic phase comprises the aromatic monocarboxylic acid.
12. The apparatus according to claim 10 or claim 11, wherein the aromatic monocarboxylic acid is recovered from the second organic phase from separator (f) or separator (G).
13. The apparatus of any one of claims 10-12, wherein mixer (a) or mixer (a) is in fluid communication with separator (f) or separator (G) and is configured to receive the second organic phase from separator (f) or separator (G).
14. The apparatus of any one of claims 10-13, wherein recovery device (D) or (D) comprises one or more distillation columns.
15. The process or apparatus of any preceding claim, wherein the organic liquid introduced in step (V), mixer (E) or mixer (E) is a clean organic solvent.
16. The method or apparatus of any preceding claim, wherein the water introduced in step (I), mixer (a) or mixer (a) is clean water.
17. The process or apparatus of any preceding claim, wherein the residue stream is from a process for the manufacture of an aromatic polycarboxylic acid.
18. The process or apparatus of claim 17 wherein the aromatic polycarboxylic acid is terephthalic acid.
19. The process or apparatus of any preceding claim, wherein the aromatic monocarboxylic acid is selected from benzoic acid, p-toluic acid and mixtures thereof.
20. A process for the manufacture of purified terephthalic acid, said process comprising C1-6A catalytic oxidation reaction of an alkyl-substituted benzene precursor in a reaction solvent, the process comprising the steps of:
oxidizing said C in said reaction solvent in the presence of a metal catalyst1-6An alkyl-substituted benzene precursor to produce crude terephthalic acid, wherein the metal catalyst is selected from the group consisting of soluble forms of cobalt and/or manganese; and
purifying the crude terephthalic acid to produce a purified terephthalic acid,
wherein the process further comprises the step of recovering aromatic monocarboxylic acid from the residue stream by the process of any one of claims 1 to 9, 15, 16 and 19.
Applications Claiming Priority (3)
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| GBGB1414292.1A GB201414292D0 (en) | 2014-08-12 | 2014-08-12 | Process |
| GB1414292.1 | 2014-08-12 | ||
| CN201580043210.1A CN106660926A (en) | 2014-08-12 | 2015-08-12 | Process for recovering aromatic monocarboxylic acid |
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| CN201580043210.1A Division CN106660926A (en) | 2014-08-12 | 2015-08-12 | Process for recovering aromatic monocarboxylic acid |
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| CN201580043210.1A Pending CN106660926A (en) | 2014-08-12 | 2015-08-12 | Process for recovering aromatic monocarboxylic acid |
| CN202110421294.5A Pending CN113121333A (en) | 2014-08-12 | 2015-08-12 | Process for recovering aromatic monocarboxylic acids |
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| CN114478234A (en) * | 2022-02-09 | 2022-05-13 | 河北海力香料股份有限公司 | Refining method of 4-chlorophthalic acid monosodium salt crude product |
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| CN115867683A (en) | 2020-08-14 | 2023-03-28 | 科氏技术英国有限公司 | Recovery of metal catalyst from an oxidizer purge stream |
| WO2023021347A1 (en) | 2021-08-20 | 2023-02-23 | Koch Technology Solutions UK Limited | Nickel and cobalt separation in a pta process |
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| CN101255107A (en) * | 2008-04-03 | 2008-09-03 | 沈福昌 | Resourceful treatment method of purified terephthalic acid waste residue |
| WO2009064037A1 (en) * | 2007-11-12 | 2009-05-22 | Ant (Asian New Tech) Corporation | Recovery of catalysts, benzoic acid and aromatic acid |
| CN102199082A (en) * | 2010-03-26 | 2011-09-28 | 英威达技术有限公司 | Recovery of aromatic carboxylic acids and oxidation catalyst |
| CN102786412A (en) * | 2012-09-03 | 2012-11-21 | 绍兴汉青环保科技有限公司 | Extraction method for extracting benzoic acid, p-toluic acid, terephthalic acid and isophthalic acid from pure terephthalic acid (PTA) oxidation residues |
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2014
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- 2015-08-12 WO PCT/EP2015/068593 patent/WO2016023958A1/en active Application Filing
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009064037A1 (en) * | 2007-11-12 | 2009-05-22 | Ant (Asian New Tech) Corporation | Recovery of catalysts, benzoic acid and aromatic acid |
| CN101255107A (en) * | 2008-04-03 | 2008-09-03 | 沈福昌 | Resourceful treatment method of purified terephthalic acid waste residue |
| CN102199082A (en) * | 2010-03-26 | 2011-09-28 | 英威达技术有限公司 | Recovery of aromatic carboxylic acids and oxidation catalyst |
| CN102786412A (en) * | 2012-09-03 | 2012-11-21 | 绍兴汉青环保科技有限公司 | Extraction method for extracting benzoic acid, p-toluic acid, terephthalic acid and isophthalic acid from pure terephthalic acid (PTA) oxidation residues |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114478234A (en) * | 2022-02-09 | 2022-05-13 | 河北海力香料股份有限公司 | Refining method of 4-chlorophthalic acid monosodium salt crude product |
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| WO2016023958A1 (en) | 2016-02-18 |
| CN106660926A (en) | 2017-05-10 |
| GB201414292D0 (en) | 2014-09-24 |
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