Exhibit 2004
`E.I. du Pont de Nemours & Co. and
`Acher-Daniels-Midland Co. v. Furanix Technologies BV
`IPR2015-01838
`
`

`
`n0.UacHbUD1n0.UaC.__II__WAtnBtaD1
`
`US 2015/0183755 A1
`
`

`
`US 2015/0183755 A1
`
`Jul. 2, 2015
`
`SPRAY OXIDATION PROCESS FOR
`PRODUCING 2,5-FURANDICARBOXYLIC
`ACID FROM HYDROXYMETHYLFURFURAL
`
`BACKGROUND
`
`[0001] The use of natural products as starting materials for
`the manufacture of various large-scale chemical and fuel
`products which are presently made from petroleum- or fossil
`fuel-based starting materials, or for the manufacture of bio-
`based equivalents or analogs thereto, has been an area of
`increasing importance. For example, a great deal of research
`has been conducted into the conversion of natural products
`into fuels, as a cleaner and, certainly, as a more sustainable
`alternative to fossil-fuel based energy sources.
`
`[0002] Agricultural raw materials such as starch, cellulose,
`sucrose or inulin are inexpensive and renewable starting
`materials for the manufacture ofhexoses, such as glucose and
`fructose. It has long been appreciated in turn that glucose and
`other hexoses, in particular fructose, may be converted into
`other useful materials, such as 2-hydroxymethyl-5-furfural-
`dehyde, also known as 5-hydroxymethylfurfural or simply
`hydroxymethylfurfural (HMF):
`
`O
`
`Hydroxymethylfurfural
`
`The sheer abundance ofbiomass carbohydrates available pro-
`vides a strong renewable resource base for the development of
`commodity chemical and fuel products based on HMF. For
`example, U.S. Pat. No. 7,385,081, issued in June 2008 to
`Gong, estimates, for example, that of the approximately 200
`billion tons of biomass produced amrually, 95% was in the
`form of carbohydrates, and only 3 to 4% of the total carbo-
`hydrates were then used for food and other purposes.
`
`In view of this fact, and due to HMF’s various func-
`[0003]
`tionalities, it has been proposed that the HMF thus obtainable
`from hexoses such as fructose and glucose, could be utilized
`to produce a wide range of products derived from renewable
`resources, such as polymers, solvents, surfactants, pharma-
`ceuticals, and plant protection agents. HMF has in this regard
`been proposed, as either a starting material or intermediate, in
`the synthesis of a wide variety of compounds, such as furfuryl
`dialcohols, dialdehydes, esters, ethers, halides andcarboxylic
`acids.
`
`[0004] A number of the products discussed in the literature
`derive from the oxidation of HMF. Included are hydroxym-
`ethylfurancarboxylic acid (HmFCA), fonnylfurancarboxylic
`acid (FFCA), 2,5-furandicarboxylic acid (FDCA, also known
`as dehydromucic acid), and diformylfuran
`Of these,
`FDCA has been discussed as a biobased, renewable substitute
`in the production of such multi-megaton polyester polymers
`as poly(ethylene terephthalate) or poly(butylene terephtha-
`late). Derivatives such as FDCA can be made from 2,5-dih '-
`droxymethylfuran and 2,5-bis(hydroxymethyl)tetrahydrofu-
`ran and used to make polyester polymers. FDCA esters have
`also recently been evaluated as replacements for phthalate
`plasticizers for PVC, see, e.g., WO 2011/023491A1 and WO
`
`2011/023590A1, both assigned to Evonik Oxeno GmbH, as
`well as R.D. Sanderson et al., Journal ofAppl. Pol. Sci. 1994,
`vol. 53, pp. 1785-1793.
`[0005] While FDCA and its derivatives have attracted a
`great deal of recent commercial interest, with FDCA being
`identified, for instance, by the United States Department of
`Energy i11 a 2004 study as one of 12 priority chemicals for
`establishing the “green” chemical industry of the future, the
`potential of FDCA (due to its structural similarity to tereph-
`thalic acid) to be used in making polyesters has been recog-
`nized at least as early as 1946, see GB 621,971 to Drewitt et
`al, “Improvements in Polymer”.
`[0006] Unfortunately, while HMF and its oxidation-based
`derivatives such as FDCA have thus long been considered as
`promising biobased starting materials,
`intermediates and
`final products for a variety of applications, viable commer-
`cial-scale processes have proven elusive. Acid-based dehy-
`dration methods have long been known for making HMF,
`being used at least as of 1895 to prepare HMF from levulose
`G)ull, Chem. Ztg., 19, 216) and from sucrose (Kiermayer,
`Chem. Ztg., 19, 1003). However, these initial syntheses were
`not practical methods for producing HMF due to low conver-
`sion ofthe starting material to product. Inexpensive inorganic
`acids such as HZSO4, H3PO4, and HCI have been used, but
`these are used in solution and are difficult to recycle. In order
`to avoid the regeneration and disposal problems, solid sul-
`fonic acid catalysts have also been used. The solid acid resins
`have not proven entirely successful as alternatives, however,
`because of the formation of deactivating humin polymers on
`the surface of the resins. Still other acid-catalyzed methods
`for forming HMF from hexose carbohydrates are described i11
`Zhao et al., Science, Jun. 15, 2007, No. 316, pp. 1597-1600
`and in Bicker et al., Green Chemistry, 2003, no. 5, pp. 280-
`284. In Zhao et al., hexoses are treated with a metal salt such
`as chromium (II) chloride in the presence of an ionic liquid, at
`100 degrees Celsius for three hours to result in a 70% yield of
`HM3, whereas in Bicker et al., sugars are dehydrocyclized to
`HM? at nearly 70% reported selectivity by the action of
`sub-or super-critical acetone and a sulfuric acid catalyst.
`[0007]
`In the acid-based dehydration methods, additional
`complications arise from the rehydration of HMF, which
`yields by-products such as levulimc and formic acids.
`Another unwanted side reaction includes the polymerization
`of HMF and/or fructose resulting in humin polymers, which
`are solid waste products and act as catalyst poisons where
`solid acid resin catalysts are employed, as just mentioned.
`Further complications may arise as a result of solvent selec-
`tion. Water is easy to dispose of and dissolves fructose, but
`unfortunately, low selectivity and the formation of polymers
`and humin increases under aqueous conditions.
`[0008]
`In consideration of these difficulties and in further
`consideration of previous efforts toward a commercially
`viable process for making HMF, Sanborn et al. in US Pub-
`lished Patent Application 2009/0156841A1 (Sanborn et al)
`describe a method for producing “substantially pure” HMF
`by heating a carbohydrate starting material (preferably fruc-
`tose) in a solvent in a column, continuously flowing the
`heated carbohydrate and solvent through a solid phase cata-
`lyst (preferably an acidic ion exchange resin) and using dif-
`ferences in the elution rates ofHMF and the other constituents
`
`ofthe product mixture to recover a “substantially pure” HMF
`product, where “substantially pure” is described as meaning a
`purity of about 70% or greater, optionally about 80% or
`greater, or about 90% or greater. An alternative method for
`
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`US 2015/0183755 A1
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`Jul. 2, 2015
`
`producing HMF esters performs the conversion in the pres-
`ence of an organic acid, which can also serve as the solvent.
`Acetic acid is mentioned in particular as a solvent for fruc-
`tose. The resulting acetylated HMF product is reported to be
`“more stable” than HMF, because upon heating HMF is
`described as decomposing and producing byproducts “that
`are not easily isolated or removed,” page 4, paragraph 0048.
`[0009]
`Further, the acetylated HMF is said to be more easily
`recovered by distillation or by extraction, though filtration,
`evaporation and combinations of methods for isolating the
`HMF esters are also described (page 2, para. 0017). The
`product, HMF ester which may include some residual HMF,
`can then be mixed in one embodiment with organic acid,
`cobalt acetate, manganese acetate and sodium bromide and
`oxidized to FDCA in the presence of oxygen and at elevated
`temperatures and pressures. In the examples, a Parr reactor is
`used for performing the oxidation.
`[001 0] Those familiar with the manufacture of terephthalic
`acid will appreciate the fact that the same Co/Mn/Br catalyst
`system conventionally used in the Mid-Century Process, for
`liquid-phase oxidation of para-xylene to terephthalic acid,
`was thus shown to be useful in the oxidation of HMF esters
`
`and residual HMF to TPA’s biobased analog FDCA. The
`capacity to source and use, for converting biobased materials,
`the same catalyst as used predominantly in the processing of
`petroleum-derived materials is a valuable and desirable fea-
`ture.
`
`[0011] Very recently published WO 2011/043661 (herein-
`after, “WO’661”) describes continuing efforts to produce
`FDCA commercially from carbohydrates such as fructose
`and glucose through HMF and HMF derivatives as interme-
`diates. After summarizing their view or interpretation of pre-
`viously published methods for the oxidation of HMF to
`FDCA in an aqueous medium using a Pt-group catalyst or
`involving the oxidation of HMF over a gold-based catalyst,
`the inventors in WO’661 contend that Sanbom et al. failed in
`
`fact to produce FDCA from the 5-(acetoxymethyl)furfural
`(AMF) ester formed through the reaction of HMF with the
`acetic acid solvent. “Surprisingly” the inventors in WO’661
`find that when using an oxidation catalyst based on cobalt and
`manganese and containing a bromide, various firran-based
`materials inclusive of 5-(acetoxymethyl)furfural and other
`like ester derivatives of HMF can provide FDCA in “high
`yields” provided reaction temperatures higher than 140
`degrees Celsius are employed.
`[0012] The HMF ester starting materials common to both
`Sanbom et al. and WO’661 are indicated in WO’661 as pro-
`ceeding from known methods, wherein a carbohydrate source
`is converted in the presence of an alkyl carboxylic acid into
`products comprising an HMF ester and optionally HMF.
`Then a11 HMF ester and optional HMF feed is isolated from
`the products for subsequent oxidation at the greater than 140
`degree Fahrenheit, alleged critical temperatures. While batch,
`semi-continuous and continuous processes are contemplated
`generally, “operation in the batch mode with increasing tem-
`perature at specific times,
`increasing pressure at specific
`times, variation of the catalyst concentration at the beginning
`of the reaction, and variation of the catalyst composition
`during the reaction” is indicated as preferred (pg 4, lines
`28-32). And, while the pressure in the oxidation process of
`WO’661 is expressly observed to be dependent on the solvent
`pressure, page 4, last line to page 5, li11e 1, the preference is
`that the pressure should be such that the solvent is “mainly in
`the liquid phase”, page 5, line 2.
`
`SUMMARY OF THE INVENTION
`
`In contrast, the present invention, in one aspect,
`[0013]
`relates to a process for carrying out an oxidation of a spray-
`able feed comprising a catalytically effective combination of
`cobalt, manganese and bromide components with a furanic
`substrate to be oxidized, wherein the feed is sprayed into a
`reactor, combined and reacted with an oxidant therein. Fur-
`ther, the exothermic temperature rise within the reactor is
`limited at least in part by selection and control of the pressure
`within the reactor.
`
`is
`the pressure within the reactor
`Preferably,
`[0014]
`selected and controlled so that the boiling point of a liquid
`present in the reactor as the highly exothermic oxidation
`proceeds (whichboiling point will of course vary based on the
`pressure acting on the liquid) is only from 10 to 30 degrees
`Celsius greater than the temperature at the start of the oxida-
`tion. By selecting and controlling the pressure so that the
`boiling point of a liquid does not significantly exceed the
`temperature at the start ofthe oxidation, a portion of the heat
`generated from the oxidation process is accounted for in
`vaporizing the liquid and so the exothermic temperature rise
`within the reactor can be limited. It will be appreciated that in
`limiting the exothermic temperature rise, yield losses due to
`higher temperature byproducts and degradation products, as
`well as to due to solvent burning, can correspondingly be
`reduced.
`
`In the HMF to FDCA process, conveniently, the
`[0015]
`same acetic acid solvent/carrier used for the HMF and the
`
`Co/Mn/Br catalyst in the W0’ 661 reference, in Sanbom et al.,
`and in the Partenheimer (Adv. Synth. Catal. 2001, vol. 343,
`pp. 102-111) and Grushin (WO 01/72732)
`references
`described in WO’661's background can serve as the liquid,
`having a boiling point at modest pressures that corresponds
`closely to the typically desired oxidation temperatures. The
`vaporization of acetic acid in this case offers a further benefit,
`as well. While the various components of the feed and while
`intermediates in the conversion of HMF to its oxidized
`
`derivative FDCA remain soluble i11 the acetic acid, FDCA is
`minimally soluble ir1 acetic acid and thus can precipitate out
`(either in the reactor itself and/or upon cooling the reaction
`mixture exiting the reactor) and be recovered as a substan-
`tially pure solid product.
`[0016]
`In a second aspect, the present invention provides a
`frmdamental improvement in the oxidation of a biobased
`furanic substrate to produce FDCA as variously addressed in
`the past by Sanbom et al., by WO’661, by the Partenheimer
`and Grushin references, as well as WO 2010/ 132740 to San-
`born. As discussed above, the tendency of HMF to self-poly-
`merize and degrade in acidic environments and at elevated
`temperatures has led to efforts in recent years to derivatize
`HMF to a more stable intermediate that can still be oxidized
`
`to produce FDCA. In this second aspect, a process is provided
`for making FDCA from fructose, glucose or a combination
`thereof, based upon the discovery that in the context of the
`inventive spray oxidation process using a Co/Mn/Br Mid-
`Century Process-type oxidation catalyst, the crude dehydra-
`tion product mixture resulting from a conventional acid dehy-
`dration of the carbohydrate can be directly solubilized in the
`solvent, sprayed into the reactor and oxidized with subse-
`quent recovery ofthe FDCA product in an unexpectedly high
`yield. No isolation or purification ofthe HMF is required, and
`no derivatization of the HMF is needed (though the present
`invention extends to such HMF derivatives as furanic sub-
`
`strates that can be oxidized). In fact, as established in the
`
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`US 20l5/0l83755 Al
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`Jul. 2, 2015
`
`Examples below, use of a crude dehydration product (crude
`HMF) can provide greater than 100 percent yield of FDCA
`based on the HMF content of the feed coming into the oxi-
`dation process.
`
`DESCRIPTION OF THE FIGURE
`
`FIG. 1 is a schematic diagram of an illustrative
`[0017]
`embodiment of an oxidation reaction system.
`
`DETAILED DESCRIPTION OF CERTAIN
`EMBODIMENTS
`
`[0018] The present invention may be more completely
`understood by describing certain embodiments in greater
`detail. These embodiments are not to be taken as limiting the
`scope and breadth of the current invention as more particu-
`larly defined in the claims that follow, but are illustrative of
`the principles behind the invention and demonstrate various
`ways a11d options for how those principles can be applied in
`carrying out the invention.
`[0019] One embodiment of a process for canying out an
`oxidation of a sprayable feed which comprises a catalytically
`effective combination of cobalt, manganese and bromide
`components with a furanic substrate to be oxidized, involves
`spraying the feed into a reactor and combining and reacting
`the furanic substrate in the feed with an oxidant (such as an
`oxidizing gas), while managing and limiting the exothermic
`temperature rise within the reactor by selection and control of
`the pressure within the reactor.
`[0020] While a variety of furanic substrates can be contem-
`plated for oxidation according to the inventive process, pref-
`erably the furanic substrates are those derived in whole or in
`significant part from renewable sources and that can be con-
`sic ered as “biobased” or “bioderived”, These terms may be
`Jsed herein identically to refer to materials whose carbon
`co item is shown by ASTM D6866, in whole or in significant
`oart (for example, at least about 20 percent or more), to be
`de*ived from or based upon biological products or renewable
`agxicultural materials (including but not limited to plant, ani-
`nal and marine materials) or forestry materials. In this
`‘espect ASTM Method D6866, similar to radiocarbon dating,
`co npares how much of a decaying carbon isotope remains in
`a sample to 110w much would be in the same sample if it were
`nade of entirely recently grown materials. The percentage is
`ca led the biobased content of the product. Samples are com-
`Justed in a quartz sample tube and the gaseous combustion
`oroducts are transferred to a borosilicate break seal tube. In
`
`one method, liquid scintillation is used to count the relative
`amounts of carbon isotopes in the carbon dioxide in the gas-
`eous con1bustion products. In a second method, l3C/12C and
`l4C/ 12C isotope ratios are counted (l4C) and measured
`(l3C/ 1 2C) using accelerator mass spectrometry. Zero percent
`l4C indicates the entire lack of 14C atoms in a material, thus
`indicating a fossil (for example, petroleum based) carbon
`source. One hundred percent 14C, after correction for the
`post-1950 bomb injection of 14C into the atmosphere, indi-
`cates a modern carbon source. ASTM D6866 effectively dis-
`tinguishes between biobased materials andpetroleum derived
`materials in part because isotopic fractionation due to physi-
`ological processes, such as, for example, carbon dioxide
`transport within plants during photosynthesis, leads to spe-
`cific isotopic ratios in natural or biobased compounds. By
`contrast, the l3C/ l 2C carbon isotopic ratio of petroleun1 and
`petroleum derived products is different from the isotopic
`
`ratios in natural or bioderived compounds due to different
`chemical processes andisotopic fractionation during the gen-
`eration of petroleum. In addition, radioactive decay of the
`unstable l4C carbon radioisotope leads to different isotope
`ratios in biobased products compared to petroleum products.
`[0021] More particularly, preferred furanic substrates are
`those which can be derived from readily available carbohy-
`drates from agricultural raw materials such as starch, cellu-
`lose, sucrose or inulin, especially fructose, glucose or a com-
`bination of
`fructose and glucose,
`though any such
`carbohydrate source can be used generally. Examples of suit-
`able carbohydrate sources that can be used to provide the
`furanic substrates of interest include, but are 11ot lin1ited to,
`hexose, fructose syrup, crystalline fructose, and process
`streams from the crystallization of fructose. Suitable mixed
`carbohydrate sources may comprise any industrially conve-
`nient carbohydrate source, such as con1 syrup. Other mixed
`carbohydrate sources include, but are not limited to, hexoses,
`fructose syrup, crystalline fructose, high fructose corn syrup,
`crude fructose, purified fructose,
`fructose corn syrup
`refinery intermediates and by-products, process streams from
`crystallizing fructose or glucose or xylose, and molasses,
`such as soy molasses resulting from production of soy protein
`concentrate, or a mixture thereof.
`[0022] Especially of interest are the furanic substrates of
`this natural carbohydrate-derived character, which can be
`spray oxidized in the presence of a homogeneous oxidation
`catalyst contained in a sprayable feed including the furanic
`substrate, to provide products of commercial interest such as
`2,5-furandicarboxylic
`acid (FDCA).
`In WO’66l,
`for
`example, a variety of furanic substrates are identified whicl1
`can be oxidized in the presence of mixed metal bromide
`catalysts, such as Co/Mn/Br catalysts,
`to provide FDCA
`5-hydroxyn1ethylfurfural (HMF), esters of HMF, 5-methyl-
`furfural,
`5-(chlorometl1yl)furfural,
`5-methylfuroic
`acid,
`5-(chloromethyl)furoic acid and 2,5-dimethylfuran (as well
`as mixtures of any of these) being named.
`[0023] Most preferably, however, the furanic substrates
`which are fed to the process are simply those which are
`formed by an acid-catalyzed dehydration reaction from fruc-
`tose, glucose or a combination of these according to the
`various well-known methods of this character, principally
`comprising HMF and the esters of HMF formed with an
`organic acid or organic acid salt.
`[0024] As has been indicated previously, one such organic
`acid, acetic acid, has been found especially useful as a solvent
`for the subsequent Co/Mn/Br-catalyzed oxidation of HMF
`and HMF esters, such as the 5-(acetoxymethyl)furfural
`(ACHMF) ester of HMF and acetic acid. Acetic acid as noted
`in the WO’66l
`reference is helpfully regenerated from
`ACHMF through the oxidation step, and is a good solvent for
`the HMF and its derivatives but is not a good solvent for
`FDCA—substantially simplifying separation and recovery of
`a substantially pure FDCA solidproduct. Further, as noted by
`Sanborn et al., ACHMF and HMF can be oxidized together to
`yield the single FDCA product in reasonable yields. In the
`context ofthe present invention, acetic acidhas the still added
`beneficial attribute of having a boiling point at reasonable
`pressures that is within the desired range of 10 degrees to 30
`degrees Celsius above the preferred temperature range for
`carrying out the Co/Mn/Br-catalyzed oxidation of the HMF
`and HMF esters to FDCA, so that by selecting an operating
`pressure and also controlling the system pressure to maintain
`the acetic acid solvent’s boiling point in this range, an evapo-
`
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`US 2015/0183755 A1
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`Jul. 2, 2015
`
`rative heat sink can be provided in the reaction system to limit
`the exothermic heat rise that ensues as the HMF and HMF
`
`esters are oxidized. Temperature-related yield losses of sub-
`strate to byproducts and solvent loss to buming can accord-
`ingly be limited by this means and by further optimization of
`catalyst composition, water concentration and substrate addi-
`tion modes (as demonstrated below).
`[0025] Given the usefulness of acetic acid for the subse-
`quent oxidation step, the acid dehydration of carbohydrates
`would in one embodiment be accomplished simply through
`the use of acetic acid in a concentrated, preferably highly
`concentrated form, an elevated temperature consistent with a
`preheating to the oxidation temperatures used thereafter and
`a sufficient residence time in a first, dehydration reactor to
`substantially fully convert all of the carbohydrates before the
`crude dehydration product mix would be combined with the
`Co/Mn/Br catalyst components and made into a sprayable
`feed composition. Alternatively, a solid phase acid catalyst
`could also be used in the first dehydration reactor to assist in
`converting the carbohydrates in a feed wherein the crude
`dehydration product mix from a first reactor is made into a
`sprayable feed for a subsequent spray oxidation reactor. It
`will be appreciated that other organic acids and even the
`strong inorganic acids that have been traditionally used for
`making HMF from fructose, for example, could equally be
`used for the dehydration, so that any acid or combination of
`acids is generally contemplated, provided that the oxidation
`step to come thereafter is not materially adversely affected by
`the selection—for example, by deactivation of the Co/Mn/Br
`catalyst or other effects. It is expected however that a useful
`approach would be to use a concentrated acetic acid solution
`and a solid acid catalyst in the first reactor for performing the
`dehydration step.
`[0026]
`For example, a continuous process can be envi-
`sioned wherein a fructose]acetic acid mixture is supplied to a
`reactor vessel containing a solid acid catalyst at 150 degrees
`Celsius. The fructose is dehydrated to HMF and the HMF
`substantially completely converted to AcHMF ester with
`excess acetic acid, and then the crude dehydration mixture is
`made into a sprayable feed with the Co/Mn/Br catalyst in a
`subsequent vessel.
`[0027] The resulting sprayable feed is then continuously
`supplied to the second, oxidation step. The acetic acid would
`preferably be sufficiently concentrated so that, given the
`amount of water produced in the dehydration step, the crude
`dehydration product mix contains not more than 10 weight
`percent of water and preferably contains not more than 7
`weight percent of water.
`[0028] The solid phase acid catalysts useful for the dehy-
`dration step in such a scenario include acidic resins such as
`Amberlyst 35, Amberlyst 15, Amberlyst 36, Amberlyst 70,
`Amberlyst 131 (Rolnn and Haas); Lewatit 52328, Lewatit
`K2431, Lewatit 52568, Lewatit K2629 (Bayer Company);
`and Dianion SK104, PK228, RCP160, Relite RAD/F (Mit-
`subishi Chemical America, Inc .). Other solid phase catalysts
`such as clays and zeolites such as CBV 3024 and CBV 5534G
`(Zeolyst Intemational), T-2665, T-4480 (United Catalysis,
`Inc), LZY 64 (Union Carbide), H-ZSM-5 (PQ Corporation)
`may also be useful, along with sulfonated zirconia or a Nafion
`sulfonated tetrafluoroethylene resin. Acidic resins such as
`Amberlyst 35 are cationic, while catalysts such as zeolite,
`alumina, and clay are porous particles that trap small mol-
`ecules. Because the dehydration step will produce water, a
`cation exchange resin having a reduced water content is pre-
`
`ferred for carrying out the dehydration step. A number of
`commercially available solid phase catalysts, such as dry
`Amberlyst 35, have approximately 3% water content and are
`considered preferable for this reason.
`[0029] The crude dehydration product mix thus generated
`is then input as part of a sprayable feed to a spray oxidation
`process of a type described i11WO 2010/1 1 1288 to Subrama-
`niam et al. (WO’288), which published application is hereby
`incorporated by reference herein. In one embodiment, the
`sprayable feed—in addition to containing the ACHMF esters
`and potentially some residual HMF, but containing substan-
`tially no unreacted carbohydrates, comprises acetic acid and
`preferably no more than 10 weight percent of water as
`described above, as well as a homogeneous oxidation catalyst
`dissolved in the sprayable feed. In other embodiments, more
`generally, the sprayable feed comprises one or more furanic
`substrate species to be oxidized, a homogeneous oxidation
`catalyst, a solvent for the furanic substrate species and the
`homogeneous oxidation catalyst, a limited amount of water
`and optionally other materials for improving the spraying or
`processing characteristics ofthe sprayable feed, for providing
`additional evaporative cooling or other purposes.
`[0030] The sprayable feed can include at least one liquid
`whose boiling point under normal operating pressures is from
`10 to 30 degrees Celsius greater than the temperature at which
`the oxidation reaction is begun. The liquid i11 question may
`be, or include, the solvent, or optionally other liquids can be
`selected to provide the evaporative cooling for limiting the
`exothermic temperature rise in the reactor as the reaction
`proceeds. Preferably acetic acid functions both as a solvent
`and as a vaporizable liquid for providing evaporative cooling
`as the reaction proceeds.
`[0031] As described in the WO’288 reference, the spray
`process is configured to produce a high number of small
`droplets into which oxygen (from an oxygen-containing gas
`used as the oxidant) is able to permeate and react with the
`AcI-IMF esters therein, the droplets functioning essentially
`as micro-reactors and with the substrate oxidation to FDCA
`
`substantially occurring within the droplets.
`[0032] The spray oxidation process is operated in a manner
`to avoid combustion of the solvent to the extent possible, as
`well as to avoid the temperature-related formation of yield-
`reducing byproducts, in part by selection of and management
`of the “normal operating pressures” just referenced so as to
`limit the exothermic temperature rise in the reactor through
`evaporative cooling. Preferably, consistent evaporative cool-
`ing control is enabled in respect of the exothermic tempera-
`ture rise by maintaining a Vapor/liquid equilibrium for the
`solvent in the reactor. In practice, this can be done by main-
`taining a substantially constant liquid level in the reactor, so
`that the rate of evaporation of acetic acid and water is matched
`by the rate at which condensed acetic acid and water vapor are
`returned to the reactor. Additional heat removal devices, such
`as internal cooling coils and the like, can also be used. Pref-
`erably, the sprayable feed is sprayed into a reactor containing
`02 in an inert background gas in the form of fine droplets
`(e.g., as a mist). The droplets can be formed as small as
`possible from a spray nozzle, such as a nebulizer, mister, or
`the like. Smaller droplets containing the furanic substrate(s)
`to be oxidized result in an increased interfacial surface area of
`
`contact between the liquid droplets and gaseous 02. The
`increased interfacial surface area can lead to improved reac-
`tion rates and product quality (e.g., yield and purity) . Also, the
`droplets are sufiiciently small such that the O2 penetrates the
`
`

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`US 2015/0183755 Al
`
`Jul. 2, 2015
`
`entire volume of the droplets by diffusion and is available at
`stoichiometric amounts throughout the droplet for the selec-
`tive oxidation to proceed to the desired product. As well,
`smaller droplets are more readily vaporized to provide efli-
`cient evaporative cooling of the highly exothermic oxidation
`reaction. Preferably, the sprayable feed is supplied to the
`reactor in the form of droplets having a mean droplet size of
`from 300 microns to 1000 microns, more preferably from 100
`microns to 300 microns, and still more preferably from 10 to
`100 microns.
`
`FIG. 1 shows a diagram of an embodiment of the
`[0033]
`illustrative oxidation system 100 which can include a source
`102 of the sprayable feed, an oxygen or oxygen containing-
`gas (for example, air and oxygen-enriched air) source 104,
`and a diluent gas (e.g., noble gases, nitrogen, carbon dioxide)
`source 106, iii fluid communication with a reactor 108, such
`as through fluid pathways 110. Fluidpathways 110 are shown
`by the tubes that connect the various components together,
`such as, for example, sprayable feed source 102 which is
`fluidly coupled to a pump 114, splitter 118 and heater 122, all
`before the sprayable feed is passed through the nozzles 128.
`The fluid pathways 110 can include one or more valves 112,
`pumps 114, junctions 116, and splitters 118 to allow fluid
`flow through the fluid pathways 110. Accordingly,
`the
`arrangement can be configured to provide for selectively
`transferring a sprayable feed, oxygen or oxygen-containing
`gases (oxygen by itself being preferred), a11d one or more
`diluent gases to the reactor 108 so that an oxidation reaction
`can be performed as described.
`[0034] Additionally, the oxidation system 100 can include
`a computing system 120 that can be operably coupled with
`any of the components of the oxidation system 100. Accord-
`ingly, each component, such as the valves 112 and/or pumps
`114 can receive instructions from the computing system 120
`with regard to fluid flow through the fluid pathways 110.
`General cormnunication between the computing system 120
`and oxidation system components 100 is represented by the
`dashed-line box around the oxidation system 100. The com-
`puting system 120 can be any type of computing system
`ranging from personal-type computers to industrial scale
`computing systems. Also, the computing system can include
`a storage medium, such as a disk drive, that can store com-
`puter-executable instructions (e.g., software) for performing
`the oxidation reactions and controlling the oxidation system
`100 components.
`[0035] The fluid pathway 110 that fluidly couples the
`sprayable feed source 102 may include aheater 122 as shown.
`The heater 122 can pre-heat the sprayable feed to a desired
`temperature before the feed is introduced into the reactor 1 08.
`As shown, the fluid pathway 110 that fluidly couples any of
`the gas sources 104, 106 to the reactor 108 can similarly
`include a heater 122 to heat the gases to a temperature before
`these are introduced into the reactor 108. Any of the heaters
`122 can be operably coupled with the computing system 120
`so that the computing system 120 can provide operation
`instructions to the heater 122, and/or the heater 122 can
`provide operation data back to the computing system 120.
`Thus, the heaters 122, as well as any of the components, can
`be outfitted with data transmitters/receivers (not shown) as
`well as control modules (not shown).
`[0036] The fluid pathways 110 can be fluidly coupled with
`one or more nozzles 128 that are configured to spray the
`sprayable feed (and optionally including the oxygen-contain-
`ing and/or diluent gases from 104 and 106, if nozzles 128 are
`
`employed for injecting both gases and liquids or a mixture of
`gases and liquids) into the reactor 108. The nozzles 128 in any
`such arrangements can be configured to provide liq