Carbonate-promoted carboxylation at high rates
Inventors
Kanan, Matthew W. • Banerjee, Aanindeeta • FRANKHOUSER, Amy Delano
Assignees
Leland Stanford Junior University
Publication Number
US-12358882-B2
Publication Date
2025-07-15
Expiration Date
2041-02-05
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Abstract
A method for synthesizing furan-2, 5-dicarboxylate (FDCA2−) is provided. Furan-2-carboxylate is provided with an inorganic base in the form of an inorganic base salt, wherein the furan-2-carboxylate and the inorganic base salt form a mixture. A CO2 gas is provided to the mixture. The mixture is heated to a temperature to at least partially melt the mixture, wherein the heating of the mixture causes the synthesizing of a MxFDCA solid, wherein MxFDCA denotes a salt comprising furan-2,5-dicarboxylate (FDCA2−) and cation M+ and/or M2+, where x is a number between 1 and 2, inclusive. The mixture containing furan-2-carboxylate is mechanically agitated, wherein the mechanically agitating breaks up the MxFDCA solid.
Core Innovation
The invention provides a method for synthesizing furan-2,5-dicarboxylate (FDCA2−) by reacting furan-2-carboxylate with an inorganic base salt in the presence of CO2 gas. The mixture of furan-2-carboxylate and the inorganic base salt is heated to partially melt the mixture, which results in the formation of a solid salt comprising furan-2,5-dicarboxylate and cations M+ and/or M2+. Mechanical agitation is applied to the mixture to break up this solid product, thereby facilitating the reaction.
The method addresses the problem of slow reaction rates and poor mass transport arising from the unusual phase behavior of the reaction mixture. As the furan-2,5-dicarboxylate product precipitates as a solid, it can encapsulate the molten phase, limiting contact between reactants and the gaseous CO2, causing stalling or decomposition. Mechanical agitation that breaks up the accumulating solid product improves contact between phases, enabling high yields of FDCA2− in shorter reaction times.
The background emphasizes that previous methods of producing FDCA from biomass or furan derivatives faced challenges such as multiple oxidation steps, use of hazardous or expensive reagents, catalyst contamination, and low yields limited by disproportionation reactions. The invention utilizes carbonate-promoted C—H carboxylation in a solvent- and catalyst-free molten salt system to efficiently produce FDCA at elevated temperatures, overcoming these limitations.
Claims Coverage
The patent contains two independent claims focusing on methods of synthesizing furan-2,5-dicarboxylate (FDCA2−) involving the provision of furan-2-carboxylate, inorganic base salts, CO2, heating to partially melt the mixture, and mechanical agitation or particle size reduction.
Method of synthesizing FDCA2− with mechanical agitation during molten phase
Providing furan-2-carboxylate and an inorganic base salt to form a mixture; exposing this mixture to CO2 gas; heating the mixture to at least partially melt it to synthesize a solid MxFDCA salt comprising FDCA2− and cations M+ or M2+, where x is between 1 and 2; mechanically agitating the mixture such that the MxFDCA solid is broken up.
Use of carbonate salts and alkali/alkaline earth cations in synthesis
Using inorganic base salts that are carbonate salts, with cations M+ being alkali cations (e.g., Cs+) or M2+ being alkaline earth cations, for the reaction mixture.
Mechanical agitation methods for breaking up solid product
Mechanical agitation performed by means such as an impeller with appropriate speed and geometry, extruders with screws, or ball mills to break up the MxFDCA solid formed during the reaction.
Substantially catalyst-free reaction conditions
The reaction mixture and heating step are substantially free of metal catalysts, including zinc, cadmium, mercury, and iron compounds typically used in Henkel reactions.
Method including cooling and particle size reduction cycle
A method variant wherein after synthesizing the solid MxFDCA salt by heating and partial melting, the mixture is cooled to solidify, particle sizes are reduced mechanically, and then the mixture is reheated under CO2 atmosphere to partially melt the mixture, optionally repeating the cycle.
Preparation of solid mixtures by solvent removal
Providing furan-2-carboxylate and inorganic base salt as solutions, mixing, and removing the solvent to form a solid mixture before heating.
The claims cover methods of synthesizing FDCA2− via carbonate-promoted carboxylation of furan-2-carboxylate under substantially catalyst-free conditions, emphasizing the step of mechanically breaking up the solid FDCA product to maintain reaction efficiency. The claims also cover various mechanical agitation techniques and include embodiments with cyclic heating and cooling to facilitate product formation.
Stated Advantages
High reaction yields of over 80% FDCA2− production can be achieved in less than an hour, improving throughput.
The method eliminates the need for toxic or expensive metal-based catalysts, producing substantially metal-free product.
The reaction is performed under solvent-free and catalyst-free conditions, reducing complexity and environmental impact.
Mechanical agitation prevents reaction stalling by maintaining effective mass transport between solid, molten, and gas phases.
The process avoids the formation of challenging impurities present in other FDCA synthesis methods.
Documented Applications
Synthesis of furan-2,5-dicarboxylic acid salts for producing performance-advantaged bio-based polymers, as alternatives to PET plastics.
Use in high-volume commercial applications requiring polymers with superior gas barrier, thermal, and mechanical properties.
Conversion of lignocellulosic biomass-derived furfural into valuable FDCA products via oxidation and carbonate-promoted carboxylation.
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