Method and apparatus for producing aromatic dicarboxylic acids

Abstract

The present invention provides a method for producing both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA), comprising: a) producing a first stream comprising recycled aromatic dicarboxylic acid by a first process, the first process comprising depolymerization of a polymer feedstock comprising polymers of said aromatic dicarboxylic acid in a first reaction system; b) producing a second stream comprising aromatic dicarboxylic acid by a second process, the second process comprising oxidation of aromatic hydrocarbons in a second reaction system; c) purifying both the first stream and the second stream in a common purification system, thereby producing both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA). The present invention also provides an apparatus for producing both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA).

Description

[Technical field]

[0001] This application claims priority to U.S. Provisional Application No. 63 / 323,208, filed March 24, 2022, and UK Patent Application No. 2205016.5, filed April 6, 2022, each of which is incorporated by reference in its entirety. The present invention relates to a process and apparatus for producing both recycled and "virgin" aromatic carboxylic acids, particularly aromatic dicarboxylic acids. [Background technology]

[0002] Several methods are known for producing aromatic carboxylic acids, such as terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. These products themselves are useful for the production of polymers. For example, terephthalic acid can be polymerized with ethylene glycol to produce polyethylene terephthalate, commonly known as PET. Recycling polymers in general, and polyesters such as PET in particular, is desirable for environmental reasons. Current techniques are capable of economically recycling clear, colorless poly(ethylene terephthalate) (PET) containers, such as soft drink bottles. In the recycling process, PET containers are sorted and consolidated by color. The consolidated containers based on clear, green PET are washed, flaked and dried to form clean PET flakes. If necessary, the clean, clear PET flakes may be processed to remove any impurities (i.e., any components other than the clean, clear PET flakes and / or the green / blue PET flakes). Recycling of the clean PET flakes may include depolymerization, which breaks the ester bonds of PET to reduce the polymer to its monomeric components. Depolymerization can be carried out using several known reaction routes, including, for example, by methanolysis or ethanolysis.

[0003] WO 2015 / 103178 describes a method of forming an aromatic diacid and / or an aromatic diacid precursor from a polyester-containing feedstock, the polyester-containing feedstock comprising an amount of at least one secondary material, the at least one secondary material being not a polyester. The method includes contacting the polyester-containing feedstock with water or alcohol to depolymerize the polyester, thereby forming an aromatic diacid and / or an aromatic diacid precursor. The formed recycled terephthalic acid (rTA) can be utilized to form additional polyethylene terephthalate polymer. Recycled polymers usually have inferior properties to those of the corresponding virgin materials. Therefore, commercial products are commonly made from a mixture of virgin and recycled materials to ensure that the desired final properties are achieved. It is becoming more and more common for customers to want to know the exact percentage of recycled material contained in such products. This can be difficult with traditional methods where the percentage of virgin and recycled materials is not continuously tracked, thus making the percentage in individual batches unknown, even when the average percentage of recycled material is known. Summary of the Invention

[0004] It is an object to provide an improved process for the recycling of polyesters and other polymers made from aromatic carboxylic acids. The inventors have now found that both recycled aromatic carboxylic acids (rCA) and "virgin" aromatic carboxylic acids (vCA) can be advantageously co-produced from the same process in a manner that allows easy control and measurement of the proportion or recycled material in the stream. Thus, in a first aspect, the present invention provides a method for producing both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA), comprising the steps of: a) producing a first stream comprising recycled aromatic dicarboxylic acids by a first process, the first process comprising depolymerizing a polymer feedstock comprising polymers of said aromatic dicarboxylic acids in a first reaction system; b) producing a second stream comprising aromatic dicarboxylic acids by a second process, the second process comprising oxidation of aromatic hydrocarbons in a second reaction system; c) purifying both the first stream and the second stream in a common purification system, thereby producing both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA); The present invention provides a method comprising:

[0005] A particular feature of the present invention is that both purified recycled aromatic dicarboxylic acids (rCA) and purified aromatic dicarboxylic acids (vCA) are produced from the process by a common purification system. Thus, both the stream containing recycled aromatic dicarboxylic acids produced in the first process and the stream containing aromatic dicarboxylic acids produced in the second process are purified in a common purification system. A further advantage is that the present invention makes it possible to always perfectly control, and easily measure, the proportion of rCA in the final product. For ease of reference, we sometimes use the term "recycle" to refer to the aromatic dicarboxylic acid produced by the first process and sometimes use the term "virgin" to refer to the aromatic dicarboxylic acid produced by the second process. The process of the present invention has several advantages in recycling polymers of aromatic dicarboxylic acids. First, the "conventional" process for producing virgin aromatic dicarboxylic acids can be improved by adding a process that produces a recycled ("unrefined") stream of aromatic dicarboxylic acids.

[0006] Second, the claimed "combined" process allows for significantly greater flexibility in the production of aromatic dicarboxylic acids. When polymeric sources of aromatic dicarboxylic acids are abundant (or "cheap"), the overall process can be operated to produce recycled aromatic dicarboxylic acids (from the first process) as a higher percentage of the total production. In other situations, the overall process can be operated to produce virgin aromatic dicarboxylic acids (from the second process) as a higher percentage of the total production, or even with low or no recycle content. The purification step can also be operated according to such requirements. For example, if a quantity of virgin aromatic dicarboxylic acid with low or zero recycle content is required, the process can be operated such that the first and second streams are purified separately, in particular consecutively, in a purification system to produce separately purified virgin aromatic dicarboxylic acid (vCA) and purified recycled aromatic dicarboxylic acid (rCA).

[0007] In an embodiment, the process may be operated to produce a mixture of recycled and virgin aromatic dicarboxylic acids, where: - the purification steps may be operated in succession, and at least a portion of the purified recycled aromatic dicarboxylic acid (rCA) is blended with at least a portion of the purified aromatic dicarboxylic acid (vTA) after the purification step, or The first and second streams, or at least a portion of both, may be co-fed to a purification system and refined together to produce a blended product.

[0008] If necessary, one or more feed silos may be provided before the purification system to help feed either or both of the first and second streams to the purification system, especially for separate (continuous) purification. If it is then desired to carry out continuous purification, the product that is not purified at a particular time can be collected and / or stored in the feed silos until its purification is required / scheduled. In a preferred embodiment, at least one first feed silo for recycled aromatic dicarboxylic acid produced in the first process and at least one second feed silo for aromatic dicarboxylic acid produced in the second process are provided. To further support the flexibility of the present invention, one or more storage silos may also be provided downstream of the purification system to which the purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA) are sent for storage after purification. In a preferred embodiment, at least two storage silos may be provided downstream of the purification system. For example, when the first stream and the second stream are continuously fed to the purification system, it is preferred to provide at least one first storage silo that is used to store the purified recycled aromatic dicarboxylic acid (rCA) and at least one second storage silo that is used to store the purified aromatic dicarboxylic acid (vCA). If desired, the products from these silos can be blended, for example, in a downstream blending or mixing step.

[0009] It may be noted that even if the purification system is operated to produce purified virgin aromatic dicarboxylic acid (vCA) and purified recycled aromatic dicarboxylic acid (rCA) separately (continuously), there may be a transition phase during which the purification system is switched from purifying a first stream (i.e., producing purified recycled aromatic dicarboxylic acid (rCA)) to purifying a second stream (i.e., producing purified virgin aromatic dicarboxylic acid (vCA)) or vice versa. During the transition phase, a mixed product stream may be produced that includes a mixture of purified recycled aromatic dicarboxylic acid and purified virgin aromatic dicarboxylic acid. One or more storage silos may be provided that are separate from any storage silos used to store purified recycled aromatic dicarboxylic acid (rCA) or to store purified aromatic dicarboxylic acid (vCA), and that are used to store a mixed stream that includes both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA).

[0010] The aromatic dicarboxylic acid may be any suitable aromatic dicarboxylic acid (for clarity, the first stream and the second stream will generally comprise the same aromatic dicarboxylic acid, i.e., the recycled aromatic dicarboxylic acid produced by the first process and the aromatic dicarboxylic acid produced by the second process are the same aromatic dicarboxylic acid). In a preferred embodiment, the aromatic dicarboxylic acid may be benzenedicarboxylic acid, naphthalenedicarboxylic acid or furandicarboxylic acid. Particularly preferably, the aromatic dicarboxylic acid is benzenedicarboxylic acid. Of these, isophthalic acid (benzene-1,3-dicarboxylic acid) and terephthalic acid (benzene-1,4-dicarboxylic acid) are particularly preferred.

[0011] Most preferably, the aromatic dicarboxylic acid is terephthalic acid. In this case, a particularly preferred embodiment is a process for producing both purified recycled terephthalic acid (rTA) and purified terephthalic acid (vTA), comprising: a) producing a first stream comprising recycled terephthalic acid by a first process, the first process comprising depolymerizing a polymer feedstock comprising polymers of terephthalic acid in a first reaction system; b) producing a second stream comprising terephthalic acid by a second process, the second process comprising oxidation of aromatic hydrocarbons in a second reaction system; c) purifying both the first stream and the second stream in a common purification system, thereby producing both purified recycled terephthalic acid (rTA) and purified terephthalic acid (vTA). The present invention provides a method comprising:

[0012] The polymer feedstock for the first process may generally be any suitable polymer feedstock containing a polymer of an aromatic dicarboxylic acid. The polymer-containing raw material is usually a polyester (containing an aromatic carboxylic acid). The polyester may be selected from the group consisting of, for example, polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PETG), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polypropylene-terephthalate (PPT), polyethylene furanoate (PEF), and combinations thereof. In a preferred embodiment, when the aromatic dicarboxylic acid is terephthalic acid or other benzene dicarboxylic acid, the polymer feedstock is preferably a polyalkylene terephthalate, most preferably polyethylene terephthalate (PET).

[0013] The first process may include any suitable reaction(s) capable of depolymerizing the polymer feedstock and producing a first stream of aromatic dicarboxylic acids. Suitable depolymerization reactions may include, for example, alkanolysis, hydrolysis or glycolysis reactions. Combinations of reactions such as alkanolysis / hydrolysis, glycolysis / hydrolysis or even glycolysis / alkanolysis / hydrolysis may also be used. Other depolymerization processes / reactions such as salt formation followed by acidification may also be used. For example, when the feedstock is a polyester, a preferred first process may include a hydrolysis or alkanolysis reaction. Particularly preferred methods include, for example, those described in WO 2015 / 103178, WO 2021257920 or US Pat. No. 7,462,649, as specified above.

[0014] The depolymerization generally uses a suitable depolymerization catalyst, which may include zinc chloride, zinc acetate, magnesium chloride, magnesium acetate, ammonium chloride, boron trifluoride, boron trichloride, boron tribromide, titanium chloride, sodium acetate, lithium acetate, manganese acetate, cobalt acetate, palladium acetate, copper acetate, or titanium oxyacetylacetonate. The depolymerization reaction is generally carried out at elevated temperatures, such as in the range of 100-350° C., and at elevated pressures, such as in the range of 5-60 bar, as known in the art.

[0015] A preferred method for the first process includes 1 -C 6 Alkanolysis using alcohols, especially methanol, ethanol, propanol, isopropanol or combinations thereof, most preferably methanol, is mentioned. The reaction may include the use of an acid or an acid precursor. Such a method, which is advantageous when water is present, is described, for example, in WO 2021 / 257920. Preferred acids, when used, are organic and mineral acids. Most preferred are organic acids, especially C 2 -C 7 Alkyl carboxylic acids, which have the structure (C1 -C 6 At least one organic acid selected from the group consisting of alkyl (meaning an acid of alkyl-COOH), aryl carboxylic acid, citric acid and fumaric acid. Most preferred is at least one C 2 -C 7 Carboxylic acids, especially acetic acid.

[0016] This first process may also include one or more further steps or reactions conventionally known in the art (i.e., other than the depolymerization reaction(s)). Examples include steps or reactions to purify the polymer feedstock, e.g., to remove impurities, and conventional separation steps to separate the aromatic dicarboxylic acid from the unreacted polymer feedstock. The second process includes any suitable reaction or reactions for oxidizing an aromatic hydrocarbon to produce an aromatic dicarboxylic acid. In this process, "aromatic hydrocarbon" generally refers to a monomer rather than a polymer. In a preferred embodiment, the aromatic hydrocarbon may be, for example, dimethylbenzene, dimethylnaphthalene, or dimethylfuran. As a specific example, when the aromatic dicarboxylic acid is terephthalic acid, the aromatic hydrocarbon is usually 1,4-dimethylbenzene (para-xylene). As another specific example, when the aromatic dicarboxylic acid is isophthalic acid, the aromatic hydrocarbon is usually 1,3-dimethylbenzene (meta-xylene).

[0017] The preparation of such compounds by oxidation of aromatic hydrocarbons is well known and may be carried out in the present invention by any suitable route, see for example US 9394223, US 8173834 or US 5723656. The second process may also include one or more additional steps or reactions (i.e., other than the oxidation reaction) conventionally known in the art. Examples include the conventional separation step of separating the aromatic dicarboxylic acid from the unreacted aromatic hydrocarbon. The purification of aromatic dicarboxylic acids is generally well known in the art, for example as described in the references already mentioned for the first and second processes, respectively, or in US Pat. No. 9,422,219.

[0018] The purification in the common purification system according to the present invention, particularly when applied to the purification of benzenedicarboxylic acids, most specifically terephthalic acid, can be achieved by the following: i) dissolving aromatic dicarboxylic acids (either rCA or vCA, or a mixture) in water at elevated temperature and pressure; ii) passing the solution into one or more crystallizers connected in series; iii) separating the solid aromatic dicarboxylic acid from the remaining solution in a solid / liquid separation step and / or by a washing step; and iv) Drying step The method may include the successive steps of:

[0019] The above purification steps, if used, generally apply regardless of whether a first stream, a second stream, or a mixture is purified. In particular, the first stream may contain different impurities than the second stream, but all typical impurities in the first stream are expected to be more soluble in water than the recycled aromatic dicarboxylic acid, and therefore are also effectively removed in the purification process. For example, in the preparation of recycled terephthalic acid, typical impurities include residual monomethyl terephthalate (MMT), dimethyl terephthalate (DMT), isophthalic acid (IA), its monoesters and dimethyl esters (MMI and DMI), and cyclohexanedimethanol (CHDM), all of which are more soluble than terephthalic acid. Therefore, all of these impurities are removed to acceptable levels without additional treatment. Nevertheless, in some embodiments, a purification step may be provided that is applied only when one or the other of the first or second streams is purified (alone or together with the other stream). For example, in some embodiments, a hydrogenation step may be applied when purifying the recycled aromatic dicarboxylic acid, either when purifying "only" the first stream, or when purifying the first and second streams (or parts thereof) together. This may be utilized, for example, when it is desired to improve the color of the purified recycled aromatic dicarboxylic acid. Hydrogenation of such streams is described, for example, in US Pat. No. 5,095,145 or US Pat. No. 5,473,102. However, the inventors have found that in the present invention, a hydrogenation step is not essential when the first rCA stream is purified. Thus, in one embodiment of the present invention, the first rCA stream is purified separately without a hydrogenation step. In another embodiment of the present invention, when a mixed stream of rCA and vCA is purified, the amount of hydrogen used in the hydrogenation reactor is equal to or less than the amount required to hydrogenate only vCA.

[0020] A further step in the above purification process may be applied when the first rCA stream is being purified (either alone or together with the second stream), which is to remove organic impurities including methanol. Methanol is formed by hydrolysis of monomethyl terephthalate and / or dimethyl terephthalate (MMT and DMT) when aromatic dicarboxylic acids are dissolved in water. Methanol is therefore present in any vapor effluents released, especially during the solid / liquid separation (recrystallization) step (iii) and the drying step (iv). If methanol is not removed or at least not significantly reduced in amount, it may contribute to volatile organic compound (VOC) emissions problems.

[0021] Such further steps to remove organic impurities include: Separating the vapor effluent released during any of steps (i)-(iv); scrubbing the vapor effluent to form a scrubber effluent; treating the scrubber effluent vapor to form a treated scrubber effluent and a treated scrubber effluent gas; removing at least a portion of the organic impurities from the treated scrubber effluent, optionally by recovering and / or decomposing said organic impurities. may include:

[0022] The scrubber effluent may be treated by condensing in at least one heat exchanger to form a treated scrubber effluent and a treated scrubber effluent vapor. In such a case, the treated scrubber effluent gas may be further thermally oxidized. Alternatively, the scrubber effluent may be treated by scrubbing with a caustic material to form a treated scrubber effluent and a treated scrubber effluent vapor. In such a case, the treated scrubber effluent gas may be further cooled and thermally oxidized. A further alternative is to heat the scrubber effluent and then treat it by oxidation in a thermal oxidizer to form a treated scrubber effluent and a treated scrubber effluent vapor. Use of the above methanol removal step allows the use of rCA containing up to 10% by weight (solids) of MMT and DMT in total. Further details of the methanol removal step can be found in US Patent No. 10,399,921.

[0023] In some embodiments, there may be other steps upstream of the purification system (or what is normally considered a purification system) that are applied to products from both the first and second processes and can be combined in a common step / system for the method of the present invention. For example, in some methods, both the first and second reactions may include a hydrolysis step / system and / or a drying step / system, and in some embodiments, these may be combined, i.e., there may be a common hydrolysis step and / or there may be a common drying step. As a further example, if both rCA and vCA are stored separately in silos in dry form, they are usually reslurried before being fed into the purification system. Both reslurries may be carried out in a common reslurry drum.

[0024] In a further aspect, there is provided an apparatus suitable for operating the process of the first aspect, in particular for producing both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA), comprising: a) a first reaction system for producing a first stream comprising recycled aromatic dicarboxylic acids, the first reaction system comprising a depolymerization reactor for depolymerization of a polymer feedstock comprising polymers of said aromatic dicarboxylic acids; b) a second reaction system for producing a second stream comprising aromatic dicarboxylic acids, the second reaction system comprising an oxidation reactor for the oxidation of aromatic hydrocarbons; c) a purification system downstream of and fluidly connected to both the first and second reaction systems for purifying the first and second streams to produce both a purified recycled aromatic dicarboxylic acid (rCA) and a purified aromatic dicarboxylic acid (vCA). An apparatus is also provided, comprising: DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Preferred embodiments of the apparatus are as already described with respect to the preferred methods / method steps of the first aspect. For example, the first reaction system may comprise one or more reactors for carrying out an alkanolysis, hydrolysis and / or glycolysis reaction, i.e., the first reaction system may comprise one or more of an alkanolysis reactor, a hydrolysis reactor and a glycolysis reactor. As another example, the apparatus may include one or more feed silos for one or both of the first vapor and the second stream, the one or more feed silos being located downstream of the respective reaction systems and upstream of the purification system, for example, at least a first feed silo for the first stream and at least a second feed silo for the second stream.

[0026] In other embodiments, the apparatus may include a mixing system in which the first and second streams, or at least a portion of both, are mixed before being fed together to the purification system. The apparatus may include one or more storage silos downstream of the purification system to which the purified recycled aromatic dicarboxylic acid (rCA) and the purified aromatic dicarboxylic acid (vCA) are sent for storage after purification. For example, at least a first storage silo utilized for storing the recycled aromatic dicarboxylic acid (rCA) and at least a second storage silo utilized for storing the purified aromatic dicarboxylic acid (vCA) may be provided. The apparatus may include a blending system downstream of the purification system, in which at least a portion of the resulting purified recycled aromatic dicarboxylic acid (rCA) is blended with at least a portion of the purified aromatic dicarboxylic acid (vCA).

[0027] Additionally, the apparatus may include a polymer preparation unit upstream of the depolymerization reactor, which may be used to process the polymer feedstock prior to the depolymerization reactor. Such a unit may be considered part of the first reaction system or may be upstream of it. In yet a further aspect, the produced purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA) may be utilized to produce polymers of aromatic dicarboxylic acids. That is, in such a further aspect, a method for producing polymers of aromatic dicarboxylic acids comprising the steps of: i) producing both a recycled aromatic dicarboxylic acid (rCA) purified by the method of the first aspect and a purified aromatic dicarboxylic acid (vCA); and ii) polymerizing the purified recycled aromatic dicarboxylic acid (rCA) and the purified aromatic dicarboxylic acid (vCA). A method is provided, comprising:

[0028] A preferred embodiment of this aspect is as presented for the first aspect. In particular, the aromatic dicarboxylic acid is preferably benzene carboxylic acid, naphthalene carboxylic acid or furan carboxylic acid. Particularly preferably, the aromatic dicarboxylic acid is benzene dicarboxylic acid. Of these, isophthalic acid (benzene-1,3-dicarboxylic acid) and terephthalic acid (benzene-1,4-dicarboxylic acid) are particularly preferred. Most preferably, the aromatic carboxylic acid is terephthalic acid. The polymer product in this aspect can be any suitable polymer of an aromatic dicarboxylic acid, but in a preferred embodiment is a polyester.

[0029] In one embodiment, the polymerization in step (ii) is carried out by polymerizing a mixture comprising both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA), thereby producing a polymer comprising recycled aromatic dicarboxylic acid. In other embodiments, the purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA) streams can be polymerized separately to produce separate "virgin" and "recycled" polymer products ("vP" and "rP"). In a particularly preferred embodiment, the purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA) are polymerized separately, and then at least a portion of the polymer obtained from the polymerization of the purified recycled aromatic dicarboxylic acid is blended with at least a portion of the polymer obtained from the polymerization of the purified aromatic dicarboxylic acid. The invention will now be illustrated with reference to the following examples. EXAMPLES

[0030] Example processes produce recycled purified terephthalic acid and virgin purified terephthalic acid, and include, among others: - a first process adapted to depolymerize polyethylene terephthalate. The process includes transesterification followed by hydrolysis resulting in a crude recycled terephthalic acid stream and a methanol stream that is recycled to the reactor. The crude recycled terephthalic acid is dissolved in water to remove methanol and other impurities, then crystallized and dried to remove the water (and any residual methanol) before being sent to a first feed silo. The first feed silo has a capacity of 2000 units of recycled terephthalic acid. Downstream of the first feed silo is a first reslurry tank. Crude recycled terephthalic acid is produced continuously at a rate of 10 units / hour. - a second process configured to oxidize para-xylene to produce a crude virgin terephthalic acid stream. The crude virgin terephthalic acid in a dry solid state is optionally passed to a second reslurry vessel via a second feed silo discussed below. The second feed silo has a capacity of 2500 units of virgin terephthalic acid. The crude virgin terephthalic acid is produced continuously at a rate of 40 units / hour. - A purification system in which a slurry of terephthalic acid (virgin or recycled) is recrystallized from water in a series of crystallizers, subjected to solid-liquid separation and then dried to obtain purified (virgin or recycled) terephthalic acid. The purification system has a capacity of 50 units / hour. - Downstream of the purification system there is a first storage silo for purified recycled terephthalic acid (rTA), a second storage silo for purified virgin terephthalic acid (vTA), and a third storage silo for material containing both rTA and vTA.

[0031] During all stages of operation, both the first and second processes are operated continuously to produce respective crude virgin terephthalic acid and crude recycled terephthalic acid streams.

[0032] In this example, during the first stage, the crude recycled terephthalic acid from the first process is sent to the first feed silo. At the same time, 50 units / hour of crude virgin terephthalic acid from the second process is sent to the second slurry tank and from there to the purification section to produce purified vTA. In particular, the crude virgin terephthalic acid sent to the second slurry tank in this stage constitutes 40 units / hour of crude virgin terephthalic acid continuously produced by the second process, supplemented by 10 units / hour of crude virgin terephthalic acid from the second feed silo previously collected (which will be discussed further below). During this first stage of operation, the purified vTA is sent to a secondary storage silo where it is stored until needed for further use, e.g., either "directly" if available on-site, or after transportation / shipment to the polymerization process. This first stage of operation continues for approximately eight days from initiation, during which time 1,920 units of crude recycled terephthalic acid from the first process are collected in a first storage silo, and simultaneously 9,600 units of crude virgin terephthalic acid are refined to produce an equivalent amount of refined virgin terephthalic acid (vTA).

[0033] After 8 days, the first feed silo is nearly full, so that both feeds to the second reslurry tank are stopped and the crude virgin terephthalic acid stream obtained from the second process is redirected to and collected in the second feed silo. At the start of this second stage, the second feed silo still contains about 500 units of crude virgin terephthalic acid, maintained as a buffer, to which 40 units / hour from the continuous production of the second process are then added. During this second stage, the feed to the purification section is switched to be from the first feed silo instead of the second feed silo, specifically the first feed silo which delivers crude recycled terephthalic acid at a rate of 50 units / hour to the first reslurry vessel from which it is delivered to the purification section to produce purified rTA (it should be noted that the feed to the first reslurry vessel is started before the end of the first stage, so that there is slurry in the first reslurry vessel in preparation for the start of the second stage).

[0034] During the first stage after switching the feed to the purification section (from the second reslurry vessel to the first reslurry vessel), the stream exiting the purification section still initially contains substantially purified vTA, which then transitions to a stream containing substantially rTA. This may take, for example, about 1-4 hours. During this time, or at least until a sufficiently pure purified vTA and purified rTA is obtained, the stream exiting the purification section is sent to a third storage silo. Once a sufficiently pure purified rTA is obtained, this product is then sent to the first storage silo. (The purified rTA is also stored until needed for further use, e.g., sent to the polymerization process either "directly" if available on-site, or after transportation / shipment). This second stage lasts approximately 48 hours, during which the purification section is fed with 1920 units of crude recycled terephthalic acid present in the first feed silo at the start of this second stage, and 480 units produced during this time from the first process. During this time, approximately 1920 units of crude virgin terephthalic acid are collected in the second feed silo. At the end of this second stage, the first feed silo is substantially empty, while the second silo contains approximately 2420 units of crude virgin terephthalic acid.

[0035] The operation is then switched back to the first "operation" (first stage) already described. In particular, the feed from the first silo to the first reslurry tank is stopped, both feeds to the second reslurry tank (40 units / h of crude virgin terephthalic acid continuously produced by the second process and 10 units / h of crude virgin terephthalic acid from the second feed silo) are resumed, and the feed to the purification zone is switched to be fed from the second feed silo (via the second reslurry tank). Thus, 50 units / h of crude virgin terephthalic acid are again sent from the second process to the second slurry tank and from there to the purification zone to produce purified vTA. (It should be noted that the feed to the second reslurry tank is started before the end of the second stage, so that there is slurry in the second reslurry tank in preparation for the resumption of the first stage). (In this example, the inventors indicate that the 50 units / hour to the second reslurry tank includes 40 units / hour of crude virgin terephthalic acid continuously produced by the second process and 10 units / hour of crude virgin terephthalic acid from the second feed silo, but it should still be noted that in reality, the 40 units / hour produced in the second process does not have to be sent "directly" to the second reslurry tank, but can continue to be sent to the second feed, and the 50 units / hour is sent from the second feed silo to the second reslurry tank. This also has the effect of reducing inventory in the second feed silo. This has the advantage that the stream from the second process is always sent to the second feed silo and does not need to be redirected again when switching.)

[0036] It should be noted that during the initial stage after switching the feed to the purification section, the stream leaving the purification section initially still contains substantially purified rTA and then transitions to a stream containing substantially vTA. This may occur, for example, over a period of about 1-4 hours. During this time, or at least until a sufficiently pure purified rTA and purified vTA is obtained, the stream leaving the purification section is sent to a third storage silo. Once a sufficiently pure purified vTA is obtained, this product is then sent to the second storage silo already described.

[0037] In some embodiments, a hydrogenation step can be performed in the purification section to remove impurities and improve the color of the purified vTA, the purified rTA, or both (i.e., this hydrogenation step can be performed during the first stage, the second stage, or both stages). For example, depending on the polyethylene terephthalate source fed to the first process, a hydrogenation step can be performed in the purification section during the second stage to remove impurities and improve the color of the purified rTA. If hydrogenation is typically only applied to the second stage and not to the first stage, hydrogenation is typically also performed during changeover, i.e., when a mixture of products is formed. In this embodiment, the process may be able to switch between stages as needed to keep all products purified and separated. Nonetheless, if desired, the products can be mixed after purification or a mixture of the first and second streams can be sent to a purification section.

Claims

1. A method for producing both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA), a) A step of generating a first stream containing recycled aromatic dicarboxylic acid by a first process, wherein the first process includes depolymerization of a polymer feedstock containing the aromatic dicarboxylic acid polymer in a first reaction system, b) A step of generating a second stream containing an aromatic dicarboxylic acid by a second process, wherein the second process includes the oxidation of an aromatic hydrocarbon in a second reaction system, c) In a common purification system, purify both the first stream and the second stream to produce both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA). The method, including the method described above.

2. The method according to claim 1, wherein the aromatic carboxylic acid is benzenedicarboxylic acid, naphthalenedicarboxylic acid, or frangic acid.

3. The method according to claim 1, wherein the aromatic dicarboxylic acid is terephthalic acid.

4. The method according to any one of claims 1 to 3, wherein the first and second streams are successively purified in a purification system to successively produce purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA).

5. The method according to claim 4, wherein at least a portion of the purified recycled aromatic dicarboxylic acid (rCA) is then blended with at least a portion of the purified aromatic dicarboxylic acid (vTA).

6. The method according to any one of claims 1 to 3, wherein the first and second streams, or at least a portion of both, are supplied together to the purification system.

7. The method according to any one of claims 1 to 3, wherein one or more feed silos for one or both of the first stream and the second stream are provided positioned in front of the purification system.

8. The method according to claim 7, wherein at least one first feed silo for a first stream and at least one second feed silo for a second stream are provided.

9. The method according to any one of claims 1 to 3, further comprising one or more storage silos downstream of the purification system for receiving purified recycled aromatic dicarboxylic acids (rCA) and purified aromatic dicarboxylic acids (vCA) after purification.

10. The method according to claim 9, wherein a first stream and a second stream are supplied in succession to a purification system, and the system is provided with at least one first storage silo for storing purified recycled aromatic dicarboxylic acids (rCA) and at least one second storage silo for storing purified aromatic dicarboxylic acids (vCA).

11. The purification process (c) is (i) A step of dissolving an aromatic dicarboxylic acid (either rCA or vCA, or a mixture thereof) in water at high temperature and high pressure, (ii) A step of sending this solution to one or more crystallization apparatuses connected in series, (iii) A step of separating a solid aromatic dicarboxylic acid from a residual solution in a solid / liquid separation step and / or a washing step, and (iv) Drying process The method according to any one of claims 1 to 3, including the method described in any one of claims 1 to 3.

12. A step of separating the steam effluent released during any of steps (i) to (iv), Steps include scrubbing the steam effluent to form scrubber effluent, The steps include treating scrubber effluent vapor to form treated scrubber effluent and treated scrubber effluent gas, and A step of removing at least a portion of organic impurities from the treated scrubber effluent, wherein the removal may be carried out by recovering and / or decomposing the organic impurities. The method according to claim 11, further comprising:

13. The method according to any one of claims 1 to 3, wherein the first stream (rCA) is purified separately without a hydrogenation step, or a mixed stream of rCA and vCA is purified, and the amount of hydrogen used in the hydrogenation reactor is less than or equal to the amount required to hydrogenate only vCA.

14. Apparatus for producing both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA), a) A first reaction system for generating a first stream containing recycled aromatic dicarboxylic acids, the first reaction system comprising a depolymerization reactor for depolymerizing a polymer feedstock containing the aromatic dicarboxylic acid polymer, b) A second reaction system for producing a second stream containing aromatic dicarboxylic acids, the second reaction system comprising an oxidation reactor for the oxidation of aromatic hydrocarbons, c) A purification system located downstream of the first and second reaction systems and fluidly connected to both, in order to purify the first and second streams to produce both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA), The apparatus comprising the above.

15. The apparatus according to claim 14, wherein a blending system is provided downstream of the purification system, and in this apparatus, at least a portion of the obtained purified recycled aromatic dicarboxylic acid (rCA) is blended with at least a portion of the purified aromatic dicarboxylic acid (vCA).

16. The apparatus according to claim 14, comprising a mixing system in which the first and second streams, or at least a portion of both, are mixed before being supplied together to a purification system.

17. The apparatus according to any one of claims 14 to 16, further comprising a polymer preparation unit upstream of the depolymerization reactor for processing the polymer feedstock before the depolymerization reactor.

18. A method for producing polymers of aromatic dicarboxylic acids, i) the step of producing both purified recycled aromatic dicarboxylic acid (rCA) and purified aromatic dicarboxylic acid (vCA) by the method according to any one of claims 1 to 3, and ii) A step of polymerizing the purified recycled aromatic dicarboxylic acid (rCA) and the purified aromatic dicarboxylic acid (vCA), The method, including the method described above.

19. The method according to claim 18, wherein the aromatic dicarboxylic acid is benzenedicarboxylic acid, naphthalenedicarboxylic acid, or frangic acid.

20. The method according to claim 18, wherein the aromatic dicarboxylic acid is terephthalic acid.