Abstract:
Disclosed is an oxidation process to produce a crude carboxylic acid product carboxylic acid product. The process comprises oxidizing a feed stream comprising at least one oxidizable compound to generate a crude carboxylic acid slurry comprising furan-2,5-dicarboxylic acid (FDCA) and compositions thereof. Also disclosed is a process to produce a dry purified carboxylic acid product by utilizing various purification methods on the crude carboxylic acid.

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This Application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/990,140 filed May 8, 2014, the entire disclosure of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid or their di-esters, dimethyl terephthalate as for example, are used to produce a variety of polyester products, important examples of which are poly (ethylene terephthalate) and its copolymers. The aromatic dicarboxylic acids are synthesized by the catalytic oxidation of the corresponding dialkyl aromatic compounds which are obtained from fossil fuels (US 2006/0205977 A1). Esterification of these diacids using excess alcohol produces the corresponding di-esters (US2010/0210867A1). There is a growing interest in the use of renewable resources as feed stocks for the chemical industries mainly due to the progressive reduction of fossil reserves and their related environmental impacts. 
     Furan-2,5-dicarboxylic acid (FDCA) is a versatile intermediate considered as a promising closest biobased alternative to terephthalic acid and isophthalic acid. Like aromatic diacids, FDCA can be condensed with diols such as ethylene glycol to make polyester resins similar to polyethylene terephthalate (PET) (Gandini, A.; Silvestre, A. J; Neto, C. P.; Sousa, A. F.; Gomes, M.,  J. Poly. Sci. A  2009, 47, 295). FDCA has been prepared by oxidation of 5-(hydroxymethyl) furfural (5-HMF) under air using homogenous catalysts (US2003/0055271 A1 and Partenheimer, W.; Grushin, V. V.,  Adv. Synth. Catal.  2001, 343, 102-111.) but only a maximum of 44.8% yield using a Co/Mn/Br catalyst system and a maximum of 60.9% yield was reported using Co/Mn/Br/Zr catalysts combination. Recently, we reported a process for producing furan-2,5-dicarboxylic acid (FDCA) in high yields by liquid phase oxidation of 5-HMF or its derivatives using a Co/Mn/Br catalyst system that minimizes solvent and starting material loss through carbon burn (U.S. patent application Ser. Nos. 13/228,803, 13/228,809, 13/228,816, and 13/228,799, herein incorporated by reference). 
     Disclosed is a method for recovering a portion of oxidation solvent, a portion of oxidation catalyst, and removing a portion of oxidation by-products and raw material impurities from a solvent stream generated in a process to make furan-2,5-dicarboxylic acid (FDCA). The process comprises oxidizing a feed stream comprising at least one oxidizable compound selected from the following group: 5-(hydroxymethyl)furfural (5-HMF), 5-HMF esters (5-R(CO)OCH 2 -furfural where R=alkyl, cycloalkyl and aryl), 5-HMF ethers (5-R′OCH 2 -furfural, where R′=alkyl, cycloalkyl and aryl), 5-alkyl furfurals (5-R″-furfural, where R″=alkyl, cycloalkyl and aryl), mixed feed-stocks of 5-HMF and 5-HMF esters and mixed feed-stocks of 5-HMF and 5-HMF ethers and mixed feed-stocks of 5-HMF and 5-alkyl furfurals to generate a crude carboxylic acid slurry comprising furan-2,5-dicarboxylic acid (FDCA) in an oxidation zone, cooling a crude carboxylic acid slurry in a cooling zone to generate a cooled crude carboxylic acid slurry, removing impurities from a cooled crude carboxylic acid slurry in a solid-liquid separation zone to form a low impurity carboxylic acid stream and a mother liquor stream, routing at least a portion of the mother liquor stream to a mother liquor purge zone to generate a recycle oxidation solvent stream, a recycle catalyst rich stream, a raffinate stream, and an impurity rich waste stream. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates different embodiments of the invention wherein a process to produce a dried carboxylic acid 410 is provided. 
         FIG. 2  illustrates an embodiment of the invention, wherein an purge stream is created. This figure is a detailed illustration on zone  700  in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood that the following is not intended to be an exclusive list of defined terms. Other definitions may be provided in the foregoing description, such as, for example, when accompanying the use of a defined term in context. 
     As used herein, the terms “a,” “an,” and “the” mean one or more. 
     As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination, B and C in combination; or A, B, and C in combination. 
     As used herein, the terms “comprising,” “comprises,” and “comprise” are open-ended transition terms used to transition from a subject recited before the term to one or more elements recited after the term, where the element or elements listed after the transition term are not necessarily the only elements that make up the subject. 
     As used herein, the terms “having,” “has,” and “have” have the same open-ended meaning as “comprising,” “comprises,” and “comprise” provided above. 
     As used herein, the terms “including,” “includes,” and “include” have the same open-ended meaning as “comprising,” “comprises,” and “comprise” provided above. 
     The present description uses numerical ranges to quantify certain parameters relating to the invention. It should be understood that when numerical ranges are provided, such ranges are to be construed as providing literal support for claim limitations that only recite the lower value of the range as well as claim limitations that only recite the upper value of the range. For example, a disclosed numerical range of 10 to 100 provides literal support for a claim reciting “greater than 10” (with no upper bounds) and a claim reciting “less than 100” (with no lower bounds). 
     The present description uses specific numerical values to quantify certain parameters relating to the invention, where the specific numerical values are not expressly part of a numerical range. It should be understood that each specific numerical value provided herein is to be construed as providing literal support for a broad, intermediate, and narrow range. The broad range associated with each specific numerical value is the numerical value plus and minus 60 percent of the numerical value, rounded to two significant digits. The intermediate range associated with each specific numerical value is the numerical value plus and minus 30 percent of the numerical value, rounded to two significant digits. The narrow range associated with each specific numerical value is the numerical value plus and minus 15 percent of the numerical value, rounded to two significant digits. For example, if the specification describes a specific temperature of 62° F., such a description provides literal support for a broad numerical range of 25° F. to 99° F. (62° F.+/−37° F.), an intermediate numerical range of 43° F. to 81° F. (62° F.+/−19° F.), and a narrow numerical range of 53° F. to 71° F. (62° F.+/−9° F.). These broad, intermediate, and narrow numerical ranges should be applied not only to the specific values, but should also be applied to differences between these specific values. Thus, if the specification describes a first pressure of 110 psia and a second pressure of 48 psia (a difference of 62 psi), the broad, intermediate, and narrow ranges for the pressure difference between these two streams would be 25 to 99 psi, 43 to 81 psi, and 53 to 71 psi, respectively 
     One embodiment of the present invention is illustrated in  FIGS. 1 and 2 . The present invention provides a process for recovering a portion of oxidation solvent, a portion of oxidation catalyst, and removing a portion of oxidation by-products and raw material impurities from a solvent stream generated in a process to make furan-2,5-dicarboxylic acid (FDCA). Step (a) comprises feeding oxidation solvent, a catalyst system, a gas stream comprising oxygen, and oxidizable raw material comprising at least one compound selected from the group of formula: 5-(hydroxymethyl)furfural (5-HMF), 5-HMF esters (5-R(CO)OCH 2 -furfural where R=alkyl, cycloalkyl and aryl), 5-HMF ethers (5-R′OCH 2 -furfural, where R′=alkyl, cycloalkyl and aryl), 5-alkyl furfurals (5-R″-furfural, where R″=alkyl, cycloalkyl and aryl), mixed feed-stocks of 5-HMF and 5-HMF esters, mixed feed-stocks of 5-HMF and 5-HMF ethers, and mixed feed-stocks of 5-HMF and 5-alkyl furfurals to an oxidation zone  100  to generate a crude carboxylic acid slurry  110  comprising furan-2,5-dicarboxylic (FDCA). 
     Structures for the preferred oxidizable raw material compounds are outlined below: 
     
       
                 
         
             
             
         
      
     
     5-HMF feed is oxidized with elemental O 2  in a multi-step reaction to form FDCA with 5-formyl furan-2-carboxyic acid (FFCA) as a key intermediate (Eq 1). Oxidation of 5-(acetoxymethyl)furfural (5-AMF), which contains an oxidizable ester and aldehydes moieties, produces FDCA, FFCA, and acetic acid (Eq 2). Similarly, oxidation of 5-(ethoxymethyl)furfural (5-EMF) produces FDCA, FFCA, 5-(ethoxycarbonyl)furan-2-carboxylic acid (EFCA) and acetic acid (Eq 3). 
     
       
                 
         
             
             
         
      
     
     Streams routed to the primary oxidation zone  100  comprise gas stream  10  comprising oxygen, and stream  30  comprising oxidation solvent, and stream  20  comprising oxidizable raw material. In another embodiment, streams routed to the oxidization zone  100  comprise gas stream  10  comprising oxygen and stream  20  comprising oxidation solvent, catalyst, and oxidizable raw material. In yet another embodiment, the oxidation solvent, gas comprising oxygen, catalyst system, and oxidizable raw materials can be fed to the oxidization zone  100  as separate and individual streams or combined in any combination prior to entering the oxidization zone  100  wherein said feed streams may enter at a single location or in multiple locations into oxidizer zone  100 . 
     Suitable catalyst systems is at least one compound selected from, but are not limited to, cobalt, bromine, and manganese compounds, which are soluble in the selected oxidation solvent. The preferred catalyst system comprises cobalt, manganese and bromine wherein the weight ratio of cobalt to manganese in the reaction mixture is from about 10 to about 400 and the weight ratio of cobalt to bromine is from about 0.7 to about 3.5. Data shown in Tables 1 to 3 demonstrate that very high yield of FDCA can be obtained using 5-HMF or its derivatives using the catalyst composition described above. 
     Suitable oxidation solvents include, but are not limited to, aliphatic mono-carboxylic acids, preferably containing 2 to 6 carbon atoms, and mixtures thereof, and mixtures of these compounds with water. In one embodiment, the oxidation solvent comprises acetic acid wherein the weight ° A) of acetic acid in the oxidation solvent is greater than 50%, greater than 75%, greater than 85%, and greater than 90%. In another embodiment, the oxidation solvent comprises acetic acid and water wherein the proportions of acetic acid to water is greater than 1:1, greater than 6:1, greater than 7:1, greater than 8:1, and greater than 9:1. 
     The temperature in oxidation zone can range from 100° C. to 220° C., or 100° C. to 200° C., or 130° C. to 180° C., or 100° C. to 180° C. and can preferably range from 110° C. to 160° C. In another embodiment, the temperature in oxidation zone can range from 105° C. to 140° C. 
     One advantage of the disclosed oxidation conditions is low carbon burn as illustrated in Tables 1 to 3. Oxidizer off gas stream  120  is routed to the oxidizer off gas treatment zone  800  to generate an inert gas stream  810 , liquid stream  820  comprising water, and a recovered oxidation solvent stream  830  comprising condensed solvent. In one embodiment, at least a portion of recovered oxidation solvent stream  830  is routed to wash solvent stream  320  to become a portion of the wash solvent stream  320  for the purpose of washing the solids present in the solid-liquid separation zone. In another embodiment, the inert gas stream  810  can be vented to the atmosphere. In yet another embodiment, at least a portion of the inert gas stream  810  can be used as an inert gas in the process for inerting vessels and or used for convey gas for solids in the process. In another embodiment, at least a portion of the energy in stream  120  is recovered in the form of steam and or electricity. 
     In another embodiment of the invention, a process is provided for producing furan-2,5-dicarboxylic acid (FDCA) in high yields by liquid phase oxidation that minimizes solvent and starting material loss through carbon burn. The process comprises oxidizing at least one oxidizable compound in an oxidizable raw material stream  30  in the presence of an oxidizing gas stream  10 , oxidation solvent stream  20 , and at least one catalyst system in a oxidation zone  100 ; wherein the oxidizable compound is 5-(hydroxymethyl)furfural (5-HMF); wherein the solvent stream comprises acetic acid with or without the presence of water; wherein the catalyst system comprising cobalt, manganese, and bromine, wherein the weight ratio of cobalt to manganese in the reaction mixture is from about 10 to about 400. In this process, the temperature can vary from about 100° C. to about 220° C., from about 105° C. to about 180° C., and from about 110° C. to about 160° C. The cobalt concentration of the catalyst system can range from about 1000 ppm to about 6000 ppm, and the amount of manganese can range from about 2 ppm to about 600 ppm, and the amount of bromine can range from about 300 ppm to about 4500 ppm with respect to the total weight of the liquid in the reaction medium. 
     Step (b) comprises routing the crude carboxylic acid slurry  110  comprising FDCA to cooling zone  200  to generate a cooled crude carboxylic acid slurry stream  210  and a 1 st  vapor stream  220  comprising oxidation solvent vapor. The cooling of crude carboxylic slurry stream  110  can be accomplished by any means known in the art. Typically, the cooling zone  200  comprises a flash tank. In another embodiment, a portion up to 100% of the crude carboxylic acid slurry stream  110  is routed directly to solid-liquid separation zone  300 , thus said portion up to 100% is not subjected to cooling in cooling zone  200 . The temperature of stream  210  can range from 35° C. to 210° C., 55° C. to 120° C., and preferably from 75° C. to 95° C. 
     Step (c) comprises isolating, washing, and dewatering solids present in the cooled crude carboxylic acid slurry stream  210  in the solid-liquid separation zone  300  to generate a crude carboxylic acid wet cake stream  310  comprising FDCA. These functions may be accomplished in a single solid-liquid separation device or multiple solid-liquid separation devices. The solid-liquid separation zone comprises at least one solid-liquid separation device capable of separating solids and liquids, washing solids with a wash solvent stream  320 , and reducing the % moisture in the washed solids to less than 30 weight %, less than 20 weight %, less than 15 weight ° A), and preferably less than 10 weight %. 
     Equipment suitable for the solid liquid separation zone can typically be at least one of the following types of devices: centrifuge, cyclone, rotary drum filter, belt filter, pressure leaf filter, candle filter, and the like. The preferred solid liquid separation device for the solid liquid separation zone is a rotary pressure drum filter. 
     The temperature of cooled crude carboxylic acid slurry steam  210  which is routed to the solid-liquid separation zone  300  can range from 35° C. to 210° C., 55° C. to 120° C., and is preferably from 75° C. to 95° C. Wash solvent stream  320  comprises a liquid suitable for displacing and washing mother liquor from the solids. In one embodiment, a suitable wash solvent comprises acetic acid. In another embodiment, a suitable wash solvent comprises acetic acid and water. In yet another embodiment, a suitable wash solvent comprises water and can be 100% water. The temperature of the wash solvent can range from 20° C. to 160° C., 40° C. to 110° C., and preferably from 50° C. to 90° C. 
     The amount of wash solvent used is defined as the wash ratio and equals the mass of wash divided by the mass of solids on a batch or continuous basis. The wash ratio can range from about 0.3 to about 5, about 0.4 to about 4, and preferably from about 0.5 to 3. After solids are washed in the solid liquid separation zone, they are dewatered. Dewatering involves reducing the mass of moisture present with the solids to less than 30% by weight, less than 25% by weight, less than 20% by weight, and most preferably less than 15% by weight resulting in the generation of a crude carboxylic acid wet cake stream  310  comprising FDCA. 
     In one embodiment, dewatering is accomplished in a filter by passing a stream comprising gas through the solids to displace free liquid after the solids have been washed with a wash solvent. In an embodiment, dewatering of the wet cake solids in solid-liquid separation zone  300  can be implemented before washing and after washing the wet cake solids in zone  300  to minimize the amount of oxidizer solvent present in the wash liquor stream  340 . In another embodiment, dewatering is achieved by centrifugal forces in a perforated bowl or solid bowl centrifuge. 
     The mother liquor steam  330  generated in solid-liquid separation zone  300  comprises oxidation solvent, catalyst, and impurities. From 5 wt % to 95 wt %, from 30 wt % to 90 wt %, and most preferably from 40 wt % to 80 wt % of mother liquor present in the crude carboxylic acid slurry  110  is isolated in solid-liquid separation zone  300  to generate mother liquor stream  330  resulting in dissolved matter comprising impurities present in mother liquor stream  330  not going forward in the process. 
     In one embodiment, a portion of mother liquor stream  330  is routed to a mother liquor purge zone  700 , wherein a portion is at least 5 weight %, at least 25 weight %, at least 45 weight %, at least 55 weight % at least 75 weight %, or at least 90 weight %. In another embodiment, at least a portion of the mother liquor stream  330  is routed back to the oxidation zone  100 , wherein a portion is at least 5 weight %. In yet another embodiment, at least a portion of mother liquor stream  330  is routed to a mother liquor purge zone  700  and to the oxidation zone  100  wherein a portion is at least 5 weight %. In one embodiment, the mother liquor purge zone  700  comprises an evaporative step to separate oxidation solvent from stream  330  by evaporation. Solids can be present in mother liquor stream  330  ranging from about 5 weight % to about 0.5 weight %. In yet another embodiment, any portion of mother liquor stream  330  routed to a mother liquor purge zone is first subjected to a solid liquid separation device to control solids present in stream  330  to less than 1 wt %, less than 0.5 wt %, less than 0.3 wt %, or less than 0.1% by weight. Suitable solid liquid separation equipment comprise a disc stack centrifuge and batch pressure filtration solid liquid separation devices. A preferred solid liquid separation device for this application comprises a batch candle filter. 
     Wash liquor stream  340  is generated in the solid-liquid separation zone  300  and comprises a portion of the mother liquor present in stream  210  and wash solvent wherein the ratio of mother liquor mass to wash solvent mass is less than 3 and preferably less than 2. In an embodiment, at least a portion of wash liquor stream  340  is routed to oxidation zone  100  wherein a portion is at least 5 weight %. In an embodiment, at least a portion of wash liquor stream is routed to mother liquor purge zone  700  wherein a portion is at least 5 weight %. In another embodiment, at least a portion of wash liquor stream  340  is routed to oxidation zone  100  and mother liquor purge zone  700  wherein a portion is at least 5 weight %. 
     In another embodiment, at least a portion of the crude carboxylic acid slurry stream  110  up to 100 weight % is routed directly to the solid-liquid separation zone  300 , thus this portion will bypass the cooling zone  200 . In this embodiment, feed to the solid-liquid separation zone  300  comprises at least a portion of the crude carboxylic acid slurry stream  110  and wash solvent stream  320  to generate a crude carboxylic acid wet cake stream  310  comprising FDCA. Solids in the feed slurry are isolated, washed, and dewatered in solid-liquid separation zone  300 . These functions may be accomplished in a single solid-liquid separation device or multiple solid-liquid separation devices. The solid-liquid separation zone comprises at least one solid-liquid separation device capable of separating solids and liquids, washing solids with a wash solvent stream  320 , and reducing the % moisture in the washed solids to less than 30 weight %, less than 20 weight %, less than 15 weight %, and preferably less than 10 weight %. Equipment suitable for the solid liquid separation zone can typically be at least one of the following types of devices: centrifuge, cyclone, rotary drum filter, belt filter, pressure leaf filter, candle filter, and the like. The preferred solid liquid separation device for the solid liquid separation zone  300  is a continuous rotary pressure drum filter. The temperature of the crude carboxylic acid slurry stream, which is routed to the solid-liquid separation zone  300  can range from 40° C. to 210° C., 60° C. to 170° C., ° C. and is preferably from 80° C. to 160° C. The wash stream  320  comprises a liquid suitable for displacing and washing mother liquor from the solids. In one embodiment, a suitable wash solvent comprises acetic acid and water. In another embodiment, a suitable wash solvent comprises water up to 100% water. The temperature of the wash solvent can range from 20° C. to 180° C., 40° C. and 150° C., and preferably from 50° C. to 130° C. The amount of wash solvent used is defined as the wash ratio and equals the mass of wash divided by the mass of solids on a batch or continuous basis. The wash ratio can range from about 0.3 to about 5, about 0.4 to about 4, and preferably from about 0.5 to 3. 
     After solids are washed in the solid liquid separation zone, they are dewatered. Dewatering involves reducing the mass of moisture present with the solids to less than 30% by weight, less than 25% by weight, less than 20% by weight, and most preferably less than 15% by weight resulting in the generation of a crude carboxylic acid wet cake stream  310 . In one embodiment, dewatering is accomplished in a filter by passing a gas stream through the solids to displace free liquid after the solids have been washed with a wash solvent. In another embodiment, the dewatering of the wet cake in solid-liquid separation zone  300  can be implemented before washing and after washing the solids in zone  300  to minimize the amount of oxidizer solvent present in the wash liquor stream  340  by any method known in the art. In yet another embodiment, dewatering is achieved by centrifugal forces in a perforated bowl or solid bowl centrifuge. 
     Mother liquor steam  330  generated in the solid-liquid separation zone  300  comprising oxidation solvent, catalyst, and impurities. From 5 wt % to 95 wt %, from 30 wt % to 90 wt %, and most preferably from 40 wt % to 80 wt % of mother liquor present in the crude carboxylic acid slurry stream  110  is isolated in solid-liquid separation zone  300  to generate mother liquor stream  330  resulting in dissolved matter comprising impurities present in mother liquor stream  330  not going forward in the process. In one embodiment, a portion of mother liquor stream  330  is routed to a mother liquor purge zone  700 , wherein a portion is at least 5 weight %, at least 25 weight %, at least 45 weight %, at least 55 weight % at least 75 weight %, or at least 90 weight %. In another embodiment, at least a portion is routed back to the oxidation zone  100 , wherein a portion is at least 5 weight %. In yet another embodiment, at least a portion of mother liquor stream  330  is routed to a mother liquor purge zone and to the oxidation zone  100  wherein a portion is at least 5 weight %. In one embodiment, mother liquor purge zone  700  comprises an evaporative step to separate oxidation solvent from stream  330  by evaporation. 
     Wash liquor stream  340  is generated in the solid-liquid separation zone  300  and comprises a portion of the mother liquor present in stream  210  and wash solvent wherein the ratio of mother liquor mass to wash solvent mass is less than 3 and preferably less than 2. In an embodiment, at least a portion of wash liquor stream  340  is routed to oxidation zone  100  wherein a portion is at least 5 weight %. In an embodiment, at least a portion of wash liquor stream  340  is routed to mother liquor purge zone  700  wherein a portion is at least 5 weight %. In another embodiment, at least a portion of wash liquor stream is routed to oxidation zone  100  and mother liquor purge zone  700  wherein a portion is at least 5 weight %. 
     Mother liquor stream  330  comprises oxidation solvent, catalyst, soluble intermediates, and soluble impurities. It is desirable to recycle directly or indirectly at least a portion of the catalyst and oxidation solvent present in mother liquor stream  330  back to oxidation zone  100  wherein a portion is at least 5% by weight, at least 25%, at least 45%, at least 65%, at least 85%, or at least 95%. Direct recycling at least a portion of the catalyst and oxidation solvent present in mother liquor stream  330  comprises directly routing a portion of stream  330  to oxidizer zone  100 . Indirect recycling at least a portion of the catalyst and oxidation solvent present in mother liquor stream  330  to oxidation zone  100  comprises routing at least a portion of stream  330  to at least one intermediate zone wherein stream  330  is treated to generate a stream or multiple streams comprising oxidation solvent and or catalyst that are routed to oxidation zone  100 . 
     Step (d) comprises separating components of mother liquor stream  330  in mother liquor purge zone  700  for recycle to the process while also isolating those components not to be recycled comprising impurities. Impurities in stream  330  can originate from one or multiple sources. In an embodiment of the invention, impurities in stream  330  comprise impurities introduced into the process by feeding streams to oxidation zone  100  that comprise impurities. Mother liquor impurities comprise at least one impurity selected from the following group: 2,5-diformylfuran in an amount ranging from about 5 ppm to 800 ppm, 20 ppm to about 1500 ppm, 100 ppm to about 5000 ppm, 150 ppm to about 2.0 wt %; levulinic acid in an amount ranging from about 5 ppm to 800 ppm, 20 ppm to about 1500 ppm, 100 ppm to about 5000 ppm, 150 ppm to about 2.0 wt %; succinic acid in an amount ranging from about 5 ppm to 800 ppm, 20 ppm to about 1500 ppm, 100 ppm to about 5000 ppm, 150 ppm to about 2.0 wt %; acetoxy acetic acid in an amount ranging from about 5 ppm to 800 ppm, 20 ppm to about 1500 ppm, 100 ppm to about 5000 ppm, 150 ppm to about 2.0 wt % 
     An impurity is defined as any molecule not required for the proper operation of oxidation zone  100 . For example, oxidation solvent, a catalyst system, a gas comprising oxygen, and oxidizable raw material comprising at least one compound selected from the group of formula: 5-(hydroxymethyl)furfural (5-HMF), 5-HMF esters (5-R(CO)OCH 2 -furfural where R=alkyl, cycloalkyl and aryl), 5-HMF ethers (5-R′OCH 2 -furfural, where R′=alkyl, cycloalkyl and aryl), 5-alkyl furfurals (5-R″-furfural, where R″=alkyl, cycloalkyl and aryl), mixed feed-stocks of 5-HMF and 5-HMF esters, mixed feed-stocks of 5-HMF and 5-HMF ethers, and mixed feed-stocks of 5-HMF and 5-alkyl furfurals are molecules required for the proper operation of oxidation zone  100  and are not considered impurities. Also, chemical intermediates formed in oxidation zone  100  that lead to or contribute to chemical reactions that lead to desired products are not considered impurities. Oxidation by-products that do not lead to desired products are defined as impurities. Impurities may enter oxidation zone  100  through recycle streams routed to the oxidation zone  100  or by impure raw material streams fed to oxidation zone  100 . 
     In one embodiment, it is desirable to isolate a portion of the impurities from oxidizer mother liquor stream  330  and purge or remove them from the process as purge stream  751 . In an embodiment of the invention, from 5 to 100% by weight, of mother liquor stream  330  generated in solid-liquid separation zone  300  is routed to mother liquor purge zone  700  wherein a portion of the impurities present in stream  330  are isolated and exit the process as purge stream  751 . The portion of stream  330  going to the mother liquor purge zone  700  can be 5% by weight or greater, 25% by weight or greater, 45% by weight or greater, 65% by weight or greater, 85% by weight or greater, or 95% by weight or greater. Recycle oxidation solvent stream  711  comprises oxidation solvent isolated from stream  330  and can be recycled to the process. The raffinate stream  742  comprises oxidation catalyst isolated from stream  330  which can optionally be recycled to the process. In one embodiment, the raffinate stream  742  is recycled to oxidation zone  100  and contains greater than 30 wt %, greater than 50 wt %, greater than 80 wt %, or greater than 90 wt % of the catalyst that entered the mother liquor purge zone  700  in stream  330 . In another embodiment, at least a portion of mother liquor stream  330  is routed directly to oxidation zone  100  without first being treated in mother liquor purge zone  700 . In one embodiment, mother liquor purge zone  700  comprises an evaporative step to separate oxidation solvent from stream  330  by evaporation. 
     One embodiment of mother liquor purge zone  700  comprises routing at least a portion of oxidizer mother liquor stream  330  to solvent recovery zone  710  to generate a recycle oxidation solvent stream  711  comprising oxidation solvent and an impurity rich waste stream  712  comprising oxidation by products and catalyst. Any technology known in the art capable of separating a volatile solvent from stream  330  may be used. Examples of suitable unit operations include, but are not limited to, batch and continuous evaporation equipment operating above atmospheric pressure, at atmospheric pressure, or under vacuum. A single or multiple evaporative steps may be used. In an embodiment of the invention, sufficient oxidation solvent is evaporated from stream  330  to result in stream  712  being present as a slurry having a weight percent solids greater than 10 weight percent, 20 weight percent, 30 weight percent, 40 weight percent, or 50 weight percent. At least a portion of impurity rich stream  712  can be routed to catalyst recovery zone  760  to generate catalyst rich stream  761 . Examples of suitable unit operations for catalyst recovery zone  760  include, but are not limited to, incineration or burning of the stream to recover noncombustible metal catalyst in stream  761 . 
     Another embodiment of mother liquor purge zone  700  comprises routing at least a portion of mother liquor stream  330  to solvent recovery zone  710  to generate a recycle oxidation solvent stream  711  comprising oxidation solvent and an impurity rich waste stream  712  comprising oxidation by products and catalyst. Any technology known in the art capable of separating a volatile solvent from stream  330  may be used. Examples of suitable unit operations include but are not limited to batch and continuous evaporation equipment operating above atmospheric pressure, at atmospheric pressure, or under vacuum. A single or multiple evaporative steps may be used. Sufficient oxidation solvent is evaporated from stream  330  to result in impurity rich waste stream  712  being present as slurry with weight % solids greater than 5 weight percent, 10 weight percent, 20 weight percent, and 30 weight percent. At least a portion of the impurity rich waste stream  712  is routed to a solid liquid separation zone  720  to generate a purge mother liquor stream  723  and a wet cake stream  722  comprising impurities. In another embodiment of the invention, all of stream  712  is routed to the solid liquid separation zone  720 . Stream  722  may be removed from the process as a waste stream. Wash stream  721  may also be routed to solid-liquid separation zone  720  which will result in wash liquor being present in stream  723 . It should be noted that zone  720  is a separate and different zone from zone  300 . 
     Any technology known in the art capable of separating solids from slurry may be used. Examples of suitable unit operations include, but are not limited to, batch or continuous filters, batch or continuous centrifuges, filter press, vacuum belt filter, vacuum drum filter, continuous pressure drum filter, candle filters, leaf filters, disc centrifuges, decanter centrifuges, basket centrifuges, and the like. A continuous pressure drum filter is a preferred device for solid-liquid separation zone  720 . 
     Purge mother liquor stream  723  comprising catalyst and impurities, and stream  731  comprising a catalyst solvent are routed to mix zone  731  to allow sufficient mixing to generate extraction feed stream  732 . In one embodiment, stream  731  comprises water. Mixing is allowed to occur for at least 30 seconds, 5 minutes, 15 minutes, 30 minutes, or 1 hour. Any technology know in the art may be used for this mixing operation including inline static mixers, continuous stirred tank, mixers, high shear in line mechanical mixers and the like. 
     Extraction feed stream  732 , recycle extraction solvent stream  752 , and fresh extraction solvent stream  753  are routed to liquid-liquid extraction zone  740  to generate an extract stream  741  comprising impurities and extract solvent, and a raffinate stream  742  comprising catalyst solvent and oxidation catalyst that can be recycled directly or indirectly to the oxidation zone  100 . Liquid-liquid extraction zone  740  may be accomplished in a single or multiple extraction units. The extraction units can be batch and or continuous. An example of suitable equipment for extraction zone  740  includes multiple single stage extraction units. Another example of suitable equipment for extraction zone  740  is a single multi stage liquid-liquid continuous extraction column. Extract stream  741  is routed to distillation zone  750  where extraction solvent is isolated by evaporation and condensation to generate recycle extract solvent stream  752 . The purge stream  751  is also generated and can be removed from the process as a waste purge stream. Batch or continuous distillation may be used in distillation zone  750 . 
     In another embodiment, the source for oxidizer mother liquor stream  330  feeding mother liquor purge zone  700  may originate from any mother liquor stream comprising oxidation solvent, oxidation catalyst, and impurities generated in process to make furan-2,5-dicarboxylic acid (FDCA). For example, a solvent swap zone downstream of oxidation zone  100  that isolates at least a portion of the FDCA oxidation solvent from stream  110  can be a source for stream  330 . Suitable equipment for a solvent swap zone comprises solid-liquid separation devices including centrifuges and filters. Examples of suitable equipment for the solvent swap include, but is not limited to, a disc stack centrifuge or a continuous pressure drum filter. 
     Examples 
     This invention can be further illustrated by the following examples of embodiments thereof, although it will be understood that these examples are included merely for the purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated. 
     Air oxidation of 5-HMF/5-AMF/5-EMF using cobalt, manganese and ionic bromine catalysts system in acetic acid solvent were conducted. After reaction the heterogeneous mixture was filtered to isolate the crude FDCA. The crude FDCA was washed with acetic acid two times and then twice with DI water. The washed crude FDCA was oven dried at 110° C. under vacuum overnight. The solid and the filtrate were analyzed by Gas Chromatography using BSTFA derivatization method. b* of the solid was measured using a Hunter Ultrascan XE instrument. As shown in Tables 1 to 3 we have discovered conditions that to generate yields of FDCA up to 89.4%, b*&lt;6, and low carbon burn (&lt;0.00072 mol/min CO+CO 2 ) 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Results from semi-batch reactions using 5-HMF feed.* 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                 yield 
                 yield 
                   
                   
                   
                   
               
               
                   
                   
                   
                 Co 
                 Mn 
                 Br 
                 of 
                 of 
                 CO 
                 CO 2   
                   
                   
               
               
                   
                   
                 Bromide 
                 conc 
                 conc 
                 conc 
                 FDCA 
                 FFCA 
                 (total 
                 (total 
                 CO x   
                 color 
               
               
                 Note-Book No. 
                 Example 
                 source 
                 (ppm) 
                 (ppm) 
                 (ppm) 
                 (%) 
                 (%) 
                 mol) 
                 mol) 
                 (mol/min) 
                 (b*) 
               
               
                   
               
             
          
           
               
                 Ex-000250-187 
                 1a 
                 solid 
                 2000 
                 93.3 
                 3000 
                 81.6 
                 0.81 
                 0.013 
                 0.078 
                 0.000758 
                 13.91 
               
               
                   
                   
                 NaBr 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Ex-000186-019 
                 1b 
                 solid 
                 2000 
                 93.3 
                 3000 
                 82.6 
                 0.87 
                 0.013 
                 0.092 
                 0.000875 
                 14.14 
               
               
                   
                   
                 NaBr 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Ex-000186-004 
                 2a 
                 aqueous 
                 2000 
                 93.3 
                 3000 
                 89.4 
                 0.58 
                 0.003 
                 0.061 
                 0.000533 
                 5.845 
               
               
                   
                   
                 HBr 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Ex-000186-016 
                 2b 
                 aqueous 
                 2000 
                 93.3 
                 3000 
                 88.6 
                 0.8 
                 0.0037 
                 0.061 
                 0.000539 
                 6.175 
               
               
                   
                   
                 HBr 
               
               
                   
               
               
                 *P = 130 psig, CO x  (mol/min) = CO (mol/min) + CO2 (mol/min). 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Results from semi-batch reactions using 5-AMF feed.* 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                 % 
                 % 
                   
                   
                   
                   
               
               
                   
                   
                 Co 
                 Mn 
                 Br 
                   
                 yield 
                 yield 
                 CO 
                 CO2 
                   
                   
               
               
                   
                   
                 conc 
                 conc 
                 conc 
                 Temperature 
                 of 
                 of 
                 (total 
                 (total 
                 CO x   
                 color 
               
               
                 Note Book # 
                 Example 
                 (ppmw) 
                 (ppmw) 
                 (ppmw) 
                 (° C.) 
                 FDCA 
                 FFCA 
                 mol) 
                 mol) 
                 (mol/min) 
                 (b*) 
               
               
                   
               
             
          
           
               
                 186-026 
                 2a 
                 2500 
                 116.8 
                 2500 
                 130 
                 88.2 
                 0.25 
                 0.0052 
                 0.08 
                 0.00071 
                 4.4 
               
               
                 186-044 
                 2b 
                 2000 
                 93.5 
                 3000 
                 130 
                 90.2 
                 0.16 
                 0.005 
                 0.046 
                 0.000425 
                 6.8 
               
               
                   
               
               
                 *P = 130 psig, CO x  (mol/min) = CO (mol/min) + CO2 (mol/min). 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Results from semi-batch reactions using 5-EMF feed.* 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                 % 
                 % 
                 % 
                   
                   
                   
                   
               
               
                   
                   
                 Co 
                 Mn 
                 Br 
                   
                 yield 
                 yield 
                 yield 
                 CO 
                 CO2 
                   
                   
               
               
                   
                   
                 conc 
                 conc 
                 conc 
                 Temperature 
                 of 
                 of 
                 of 
                 (total 
                 (total 
                 CO x   
                 color 
               
               
                 Note Book # 
                 Example 
                 (ppmw) 
                 (ppmw) 
                 (ppmw) 
                 (° C.) 
                 FDCA 
                 FFCA 
                 EFCA 
                 mol) 
                 mol) 
                 (mol/min) 
                 (b*) 
               
               
                   
               
             
          
           
               
                 186-028 
                 3a 
                 2500 
                 116.8 
                 2500 
                 130 
                 88.8 
                 0.02 
                 0.225 
                 0.008 
                 0.068 
                 0.00063333 
                 3.97 
               
               
                 186-031 
                 3b 
                 2000 
                 93.5 
                 3000 
                 130 
                 88.0 
                 0.09 
                 0.43 
                 0.008 
                 0.078 
                 0.00071667 
                 2.48 
               
               
                 186-034 
                 3c 
                 2000 
                 93.5 
                 3000 
                 105 
                 86.0 
                 2.92 
                 1.4 
                 0.005 
                 0.046 
                 0.000425 
                 6.66 
               
               
                 186-038 
                 3d 
                 2500 
                 116.8 
                 2500 
                 130 
                 87.4 
                 0.42 
                 1.3 
                 0.009 
                 0.064 
                 0.00060833 
                 2.74 
               
               
                   
               
               
                 *P = 130 psig, CO x  (mol/min) = CO (mol/min) + CO2 (mol/min). 
               
             
          
         
       
     
     Claims not Limited to Disclosed Embodiments 
     The preferred forms of the invention described above are to be used as illustration only, and should not be used in a limiting sense to interpret the scope of the present invention. Modifications to the exemplary embodiments, set forth above, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
     The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as it pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.