Integrated furfural oxidation and furoate carboxylation process

Abstract

An integrated process for the preparation of furan-2, 5-dicarboxylic acid (FDCA) and FDCA derivatives combines a furfural oxidation reaction, an intermediate water removal step, and a furoate carboxylation reaction. A furfural feed stream is oxidized with an alkaline solution with air as an oxidant in the presence of a catalyst and an excess of a base. The resulting furoate solution from the first process step is dried to remove water. The anhydrous solid product is passed to a carboxylation process to produce an FDCA salt, which may optionally be further reacted to form FDCA or an FDCA ester.

Description

[0001] Priority declaration

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 377,785 filed on September 30, 2022, the entire contents of which are incorporated herein by reference. Background Art

[0003] Furan-2,5-dicarboxylate (FDCA) and its derivatives can be used as starting materials for a family of bio-based plastics as alternatives to starting materials such as terephthalic acid and p-xylene.

[0004] The current process for producing FDCA converts fructose to FDCA via the intermediate hydroxymethylfurfural (HMF). This process has several disadvantages that result in an expensive product, including the fact that fructose is an expensive starting material and HMF has stability issues.

[0005] New methods for preparing FDCA would be desirable. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic representation of one embodiment of an integrated furfural oxidation and furoate carboxylation process. DETAILED DESCRIPTION

[0007] An integrated process for the preparation of furan-2,5-dicarboxylic acid (FDCA) and FDCA derivatives has been developed. The integrated process combines the furfural oxidation reaction, the intermediate water removal step and the furoate carboxylation reaction.

[0008] The oxidation process involves oxidizing a furfural feed stream with an alkaline solution using air as the oxidant in the presence of a catalyst and an excess of base. The resulting furoate solution from the first process step is dried to remove water. These anhydrous solid products are sent to a carboxylation process to produce FDCA salts.

[0009] The FDCA salt can be further reacted to form FDCA or a FDCA derivative such as an ester.

[0010] Optionally, promoters and reagents for the carboxylation reaction may be added prior to the water removal step.

[0011] The first step is to oxidize a feed stream comprising furfural. Furfural and an aqueous alkaline base stream (and optionally recycled carboxylate salts from downstream in the process) react in an oxidation reactor in the presence of a catalyst and an oxygen-containing gas to form a solution of a furoate salt.

[0012] The feed stream typically comprises greater than 0 wt% to 20 wt% furfural.In some embodiments, furfural can be produced from pentoses obtained from biomass, thereby making the process environmentally friendly.

[0013] The aqueous alkaline alkali stream typically contains greater than 0 wt % to 20 wt % of an alkaline base. Any alkaline base may be used. Suitable alkaline bases include, but are not limited to, Li, Na, K, and Cs.

[0014] Any catalyst suitable for furfural oxidation can be used. Suitable catalysts include but are not limited to copper, silver, gold or a combination thereof. The catalyst can be supported on an inert carbonaceous or ceramic material. In some embodiments, the catalyst comprises a metal oxide. In some embodiments, the catalyst comprises silver.

[0015] The oxygen-containing gas generally contains from greater than 0% to 21% oxygen. Typically, air is used.

[0016] Typical reaction conditions for the oxidation reaction include temperatures in the range of 25°C to 100°C and pressures in the range of 6.9 kPa to 3447 kPa.

[0017] The reaction product contains furoate in residual unreacted alkaline base and unreacted carboxylate from the feed stream. There may also be unreacted furfural in the alkaline solution. Air is purged from the reactor.

[0018] The reaction mixture may also contain furfuryl alcohol, which is an undesirable byproduct of the oxidation reaction. Furfuryl alcohol may be removed using any suitable method including, but not limited to, biphasic solvent extraction prior to the water removal step.

[0019] The reaction mixture is sent for liquid removal or crystallization. The feed is a solution of furoate and an alkaline solution. A promoter salt may optionally be included. Suitable promoter salts include, but are not limited to, acetates and malonates.

[0020] Liquid, typically water (possibly mixed with a small amount of methanol), is removed from the solution of the furoate salt and the alkaline solution, leaving behind the solid furoate and alkaline salts and optionally the promoter salt. Any suitable liquid removal method may be used. Suitable water removal methods include, but are not limited to, drying and crystallization.

[0021] Solid furoate and alkali salt and optional promoter salt are fed to the second reactor. In some embodiments, the furoate reacts with a CO2-containing gas to form a FDCA salt in the second reactor. The alkali salt and any promoter salt present may be recycled to the oxidation reactor.

[0022] Suitable promoter salts for reacting with CO2-containing gases include, but are not limited to, acetates and malonates. In some embodiments, the promoter salt comprises a carboxylate having at least one hydrogen on the carbon attached to the carboxylate.

[0023] Typical reaction conditions for the carboxylation reaction include temperatures ranging from 280°C to 350°C and pressures ranging from 6.9 kPa to 6900 kPa.

[0024] In other embodiments, the reaction in the second reactor is a disproportionation reaction (also known as the Henkel reaction). In this case, CO2 is not used in the second reaction. Instead, the furoate reacts with the carboxylate-containing compound. Optionally, a promoter may also be used in this reaction. Suitable promoters for reacting with carboxylate-containing compounds include, but are not limited to, cadmium salts, zinc salts, or mercury salts. In some embodiments, the carboxylate-containing compound includes acetate. In some embodiments, the promoter is recycled.

[0025] Figure 1 An embodiment of furan-2,5-dicarboxylic acid (FDCA) and FDCA derivatives of process 100 is shown. A feed stream 105 containing furfural, an aqueous alkaline base stream 110, and an oxygen-containing gas stream 115 are sent to an oxidation reactor 120 containing an oxidation catalyst. The reaction produces a solution of a furoate salt. The reaction mixture also contains an aqueous alkaline base, unreacted furfural.

[0026] The effluent stream 125 is sent to a vessel 130 where water stream 135 is removed. The water may be removed by drying and / or crystallization. Other methods may also be used.

[0027] Optionally, a promoter salt 140 may be added prior to removing the water.

[0028] The water removal step produces a solid mixture of the furoate salt and the alkali salt. If a promoter salt is added, the solid mixture will also contain the promoter salt.

[0029] The solid mixture stream 145 of the furoate and base salt is sent to a second reactor 150. In some embodiments, the furoate is reacted with a CO2-containing gas stream 155 to produce a FDCA salt. In other embodiments, the furoate is reacted with a carboxylate-containing compound 160 to produce a FDCA salt stream 165 containing the FDCA salt. In some embodiments, the FDCA salt can be recovered as a product.

[0030] In other embodiments, the FDCA salt stream 165 is sent to an acidification reactor 170, where the FDCA salt can be acidified by adding an acid to form FDCA. In another embodiment, the FDCA salt can be acidified and esterified. A product stream 175 from the acidification reactor 170 can be recovered.

[0031] In other embodiments, the FDCA salt stream 165 is sent to a carboxylate esterification reactor where the FDCA salt can be esterified with methanol and CO2 to form FDME. The FDME product stream from the esterification reactor can be recovered. Unrecovered components from the FDME product stream can be recycled to the initial oxidation reactor.

[0032] In other embodiments, the FDCA salt may be acidified and then esterified.

[0033] In some embodiments, the promoter recycle stream 180 from the second reactor 150 may be recycled to the oxidation reactor 120 to the effluent stream 125 from the oxidation reactor 120 and prior to the vessel 130 .

[0034] In some embodiments, a portion 185 of product stream 175 may be recycled to oxidation reactor 120 , to effluent stream 125 from oxidation reactor 120 and prior to vessel 130 .

[0035] Specific implementation plan

[0036] While the following is described in conjunction with specific embodiments, it should be understood that this description is intended to illustrate and not to limit the scope of the foregoing description and the appended claims.

[0037] The first embodiment of the present invention is a method for preparing furan-2,5-dicarboxylic acid (FDCA) and FDCA derivatives, the method comprising oxidizing a feed stream containing furfural and an aqueous alkaline base stream in the presence of a catalyst and an oxygen-containing gas in an oxidation reactor to form a reaction mixture containing a solution of a furoate; removing liquid from the reaction mixture to form a solid containing a furoate and an alkali salt; and reacting the furoate with a CO2-containing gas or a carboxylate-containing compound or both in a second reactor to produce an FDCA salt. An embodiment of the present invention is the first embodiment in this paragraph to one, any one, or all of the foregoing embodiments in this paragraph, wherein reacting the furoate with a CO2-containing gas or a carboxylate-containing compound comprises reacting the furoate with a CO2-containing gas. An embodiment of the present invention is the first embodiment in this paragraph to one, any one, or all of the foregoing embodiments in this paragraph, wherein the feed further comprises a first promoter, wherein the reaction mixture further comprises a first promoter salt, wherein the solid further comprises the first promoter salt, and the method further comprises recycling the first promoter salt. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, wherein the first promoter salt comprises a carboxylate having at least one hydrogen on the carbon attached to the carboxylate. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, wherein reacting the furoate with a CO2-containing gas or a carboxylate-containing compound or both comprises reacting the furoate with a carboxylate-containing compound. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, wherein the feed further comprises a second promoter, wherein the reaction mixture further comprises a second promoter salt, wherein the solid further comprises the second promoter salt, and the method further comprises recycling the second promoter salt. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, wherein the second promoter salt comprises a cadmium salt, a zinc salt or a mercury salt. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, wherein the carboxylate-containing compound comprises an acetate. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, the method further comprising acidifying the FDCA salt to form FDCA; or esterifying the FDCA salt to form the FDCA ester; or acidifying the FDCA salt to form the FDCA and esterifying the FDCA to form the FDCA ester. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, the method further comprising recycling a portion of the FDCA salt, the FDCA or the FDCA ester to the oxidation reactor, the second reactor or both.An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, wherein the reaction mixture further comprises furfuryl alcohol, and the method further comprises removing the furfuryl alcohol from the reaction mixture before removing the liquid from the reaction mixture. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, the method further comprises recycling at least a portion of the alkaline base, or at least a portion of the furoate or furoate, or at least a portion of the first promoter salt, or at least a portion of the second promoter salt, or a combination thereof to the oxidation reactor. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, wherein the catalyst comprises copper, silver, gold or a combination thereof. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, wherein the catalyst is supported on a carbonaceous or ceramic support. An embodiment of the present invention is the first embodiment in this paragraph to one, any one or all of the foregoing embodiments in this paragraph, wherein the catalyst comprises a metal oxide. An embodiment of the invention is the first embodiment in this paragraph through one, any or all of the preceding embodiments in this paragraph, wherein removing water from the reaction mixture comprises heating the reaction mixture to evaporate the water or to crystallize the reaction mixture.

[0038] Although there is no further detailed description, it is believed that those skilled in the art can utilize the present invention to the greatest extent by using the foregoing description and can easily determine the essential characteristics of the present invention without departing from the spirit and scope of the present invention to make various changes and modifications of the present invention and adapt it to various usages and conditions. Therefore, the aforementioned preferred specific embodiments should be understood as merely illustrative and not to limit the rest of the present disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0039] In the foregoing, all temperatures are set forth in degrees Celsius and all parts and percentages are by weight unless otherwise indicated.

Claims

1. A method for preparing furan-2,5-dicarboxylic acid (FDCA) and FDCA derivatives, the method comprising: oxidizing a feed stream (105) comprising furfural and an aqueous alkaline base stream (110) in an oxidation reactor (120) in the presence of a catalyst and an oxygen-containing gas (115) to form a reaction mixture (125) comprising a solution of a furoate salt; removing liquid from the reaction mixture (125) to form a solid (145) comprising the furoate salt and the base salt; The furoate salt is reacted with a CO2-containing gas (155) or a carboxylate-containing compound (160), or both, in a second reactor (150) to produce a FDCA salt (165).

2. The method of claim 1, wherein reacting the furoate with the CO2-containing gas (155) or the carboxylate-containing compound (160) comprises reacting the furoate with the CO2-containing gas (155).

3. The method of claim 2, wherein the feed further comprises a first promoter, wherein the reaction mixture (125) further comprises a first promoter salt, wherein the solid (145) further comprises the first promoter salt, and the method further comprises: The first promoter salt is recycled (180).

4. The method of claim 3, wherein the first promoter salt comprises a carboxylate having at least one hydrogen on the carbon attached to the carboxylate.

5. The method of claim 1, wherein reacting the furoate with the CO2-containing gas (155) or the carboxylate-containing compound (160), or both, comprises reacting the furoate with the carboxylate-containing compound (160).

6. The method of claim 5, wherein the feed further comprises a second promoter, wherein the reaction mixture (125) further comprises a second promoter salt, wherein the solid (145) further comprises the second promoter salt, and the method further comprises: The second promoter salt is recycled (180).

7. The method of claim 6, wherein the second promoter salt comprises a cadmium salt, a zinc salt, or a mercury salt.

8. The method according to claim 1, further comprising: acidifying the FDCA salt to form the FDCA; or esterifying the FDCA salt to form an FDCA ester; or The FDCA salt is acidified to form the FDCA and the FDCA is esterified to form the FDCA ester.

9. The method of claim 1, wherein the reaction mixture further comprises furfuryl alcohol, and the method further comprises: The furfuryl alcohol is removed from the reaction mixture (125) prior to removing the liquid (135) from the reaction mixture (145).

10. The method of claim 1, wherein the catalyst comprises copper, silver, gold, or a combination thereof.

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