Method for producing furfural from biomass

Abstract

A process for preparing furfural, furfural derivatives, or both from biomass is described. The biomass feed is optionally adjusted to obtain a moisture content of 25 wt% or less. The biomass feed is ground to form particles having a particle size in the range of 0.02 mm to 7 mm and having an average aspect ratio of 0.4 or greater, wherein 5 wt% or less is 75 microns or less. The ground biomass feed is covered with an inert gas having an oxidant or oxygen content of 5 mol% or less. The ground biomass feed is reacted in the presence of water, a water-immiscible organic solvent, and an acid catalyst to form a reaction product mixture comprising furfural, a furfural derivative, or both.

Description

[0001] Priority Declaration

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 377,728, filed on September 30, 2022, the entire contents of which are incorporated herein by reference. Background Art

[0003] Furfural is produced commercially from lignocellulose, which is found in a variety of herbaceous and woody biomass sources. Lignocellulose is a structural component of plant cell walls and is a complex mixture of three main components: cellulose, hemicellulose, and lignin.

[0004] Cellulose is a linear chain of several hundred to several thousand beta-linked D-glucose units. Hemicellulose is a heteropolymer (arabinan) that, along with cellulose, is present in the cell walls of almost all terrestrial plants. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure and very little strength. Lignin is a polymeric material that is a cross-linked component of three monolignols: coumaroyl alcohol, coniferyl alcohol, and sinapyl alcohol. It is therefore a highly aromatic polymer. Different polymers exhibit different reactivity to thermal, chemical, and biological processing.

[0005] The conventional method for producing furfural by biomass comprises hot acid digestion, in order to hydrolyze hemicellulose to release C5 sugar, subsequently C5 sugar acid catalysis isomerization and dehydration are turned into furfural.However, due to the complex structure and acidic environment of lignocellulose, many side reactions may occur.Except the isomerization and dehydration of C5 sugar, similar methods can be with the C6 sugar component of hemicellulose or possibly even some from cellulose C6 sugar isomerization into 5-hydroxymethylfurfural (5-HMF), and this 5-hydroxymethylfurfural (5-HMF) can experience further hydrolysis to form levulinic acid and formic acid.Acetic acid is also produced by the acetyl group on hemicellulose.In addition, furfural and 5-hydroxymethylfurfural both also can experience subsequent polymerization to form humin, and this humin is the highly cross-linked chain of furans and hexose ring.

[0006] However, commercial processes for producing furfural have yields of only 50% of the theoretical value, resulting in high production costs.

[0007] Therefore, there is a need for improved processes for producing furfural from biomass. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic representation of one embodiment of a process for producing furfural from biomass. DETAILED DESCRIPTION

[0009] The present method involves the appropriate selection and pretreatment of biomass prior to the hydrolysis and dehydration reactions. By appropriately selecting the acid catalyst, solvent, and reaction conditions, the yield of furfural, furfural derivatives, or both can be increased to 80%, resulting in a more economically attractive process. Furfural derivatives include, but are not limited to, 5-hydroxymethylfurfural and 5-halomethylfurfural, where the halogen comprises a chloride, bromide, fluoride, or iodide moiety.

[0010] The first step is to select the biomass feed. Furfural is a 5-carbon product. The components of lignocellulose, which is the direct precursor of furfural, are 5-carbon sugars found in hemicellulose containing 80% C5 sugars, such as xylose and arabinose. Therefore, biomass with a high hemicellulose content and a low lignin content is an ideal raw material for producing furfural. Herbaceous materials tend to be the richest in hemicellulose, while trees (especially softwoods) have a small amount of hemicellulose and a higher amount of lignin. Examples of biomass with high hemicellulose and low lignin include corn cobs, corn stover, corn bran, oat hulls, and wheat straw. Commercial furfural processes use corn cobs and bagasse because they are rich in C5 sugars and are abundant agricultural waste. However, biomass from other sources can also be used.

[0011] Handling biomass feedstock presents a challenge not encountered in traditional refining operations: combustible dust. This dust issue requires specialized procedures to prevent explosions and / or fires within the reactor's solid feed system. The physical specifications of the biomass, including particle size, particle size distribution, and moisture content, must be controlled. Furthermore, the oxidant or oxygen content in biomass conversion processes must be controlled due to the combustible dust hazard.

[0012] The initial moisture content of original biomass can be up to 30 % by weight or more.The expected moisture content of the method relates to the expectation of the risk that balance alleviates combustible dust and the moisture content in the biomass feed that minimizes entry into reactor.The moisture content of the biomass that is used for this method is generally 25 % by weight or lower or 20 % by weight or lower or 15 % by weight or lower or 5 % by weight to 15 % by weight.Therefore, it may be necessary to regulate the original biomass to obtain the moisture content of expectation.Usually, this regulation will relate to dry original biomass.In other cases, the moisture content of biomass may need to use humidification to increase.

[0013] The granularity and the shape of the biomass feed that also should be controlled to be sent to reactor.Grind biomass to obtain the biomass feed through grinding with the mean particle size in the scope of 0.02mm to 10mm or 0.02mm to 9mm or 0.02mm to 8mm or 0.02mm to 7mm or 0.02mm to 6mm or 0.02mm to 5mm or 0.02mm to 4mm or 0.02mm to 3mm or 0.02mm to 2mm or 0.02mm to 1mm.In addition, the biomass feed through grinding should have 5 % by weight or still less or 3 % by weight or still less or 1 % by weight or still less particle of a size of 75 microns or less.The biomass particles through grinding have various shapes, for example circle, elongated, irregular shape etc., and this shape affects aspect ratio.Lower aspect ratio is corresponding to the irregular shape of higher concentration.These irregularly shaped particles have brought problems to reactor internals and downstream equipment. Therefore, the aspect ratio of the ground biomass feed should be controlled to be 0.4 or greater, or 0.45 or greater, or 0.5 or greater, or 0.55 or greater, or 0.6 or greater, or within the range of 0.4 to 1.0, or 0.45 to 1.0, or 0.5 to 1.0, or 0.55 to 1.0, or 0.6 to 1.0.

[0014] The ground biomass feed should be covered with an inert gas having 5 mol % or less, or 3 mol % or less, or 1 mol % or less of an oxidant or oxygen. This helps to reduce the risk of explosion and / or fire. Limiting the amount of oxidant and / or oxygen also reduces furfural oligomerization / polymerization side reactions, which can occur after they are formed in the reactor, resulting in yield loss and fouling in downstream separation processes (such as fractionation).

[0015] The ground biomass feed may be contained in a holding tank with an inert gas blanket before being sent to the reactor.

[0016] The reactor contains a ground biomass feed, a solvent, and an acid catalyst.

[0017] The solvent may comprise water and / or a water-immiscible organic solvent. The use of a water-immiscible organic solvent improves furfural yield by extracting furfural from the aqueous acidic environment in the reactor. By extracting furfural as it forms, the chance of it reacting with other furfural derivatives and biomass by-products in the presence of an acid catalyst is greatly reduced. Suitable water-immiscible organic solvents include, but are not limited to, aromatic hydrocarbons and alkyl ketones. Suitable aromatic hydrocarbons include, but are not limited to, benzene, toluene, xylene, tetralin, alkyltetralins, alkylnaphthalenes, aromatic alcohols, alkylphenols, or combinations thereof. Suitable alkyl ketones include, but are not limited to, methyl isobutyl ketone.

[0018] The reaction is catalyzed using an acid catalyst. Any suitable acid catalyst may be used. The acid catalyst may include a mineral acid, a solid acid, an organic acid, or a combination thereof. Suitable mineral acids include, but are not limited to, sulfuric acid, hydrochloric acid, nitric acid, or a combination thereof. Suitable solid acids include, but are not limited to, AlCl 3 , CrCl 3 , CrCl 2 , an acidic zeolite, or a combination thereof. Suitable organic acids include, but are not limited to, carboxylic acids such as acetic acid, formic acid, propionic acid, butyric acid, or a combination thereof. Longer chain carboxylic acids may also be used.

[0019] The hydrolysis reaction involves hydrolyzing the bound C5 sugars in the biomass to produce xylose. The xylose is then dehydrated in a separate reactor or in the same reactor as the hydrolysis reaction to produce furfural and / or furfural derivatives.

[0020] The method can utilize a single reactor to carry out both the hydrolysis reaction and the dehydration reaction. Alternatively, there can be two (or more) reactors, which can be arranged in series or in parallel. The oxidant and / or oxygen content in the reactor should be controlled to prevent the furfural reaction that is subsequently caused by oxygen and results in a reduction in furfural yield. The oxidant and / or oxygen content in the reactor should be 5 mol % or less, or 3 mol % or less, or 1 mol % or less of the oxidant or oxygen.

[0021] Typical reaction conditions for a single reactor include temperatures ranging from 50°C to 300°C, pressures ranging from 0.3 MPa to 35 MPa, and reaction times ranging from 10 minutes to 60 hours.

[0022] In a two (or more) reactor process, typical reaction conditions for the hydrolysis and dehydrogenation reactors include temperatures in the range of 50° C. to 300° C., pressures in the range of 0.3 MPa to 35 MPa, and reaction times in the range of 10 minutes to 60 hours. The reactors may utilize the same catalyst, or the catalyst may be different in the different reactors.

[0023] Figure 1 An embodiment of the furfural process 100 is illustrated. Biomass feed 105 is fed to an optional conditioning unit 110. Conditioning unit 110 may be required to obtain a moisture content within a desired range. If the moisture content of the biomass feed is too high, conditioning unit 110 is typically a dryer. If the moisture content is too low, the conditioning unit may be injected with steam, soaked in water, placed in a humidifier, or subjected to other suitable treatments. If the moisture content of the biomass feed is acceptable, conditioning unit 110 is not required.

[0024] The conditioned feed 115 is fed to a grinder 120 to reduce particle size. The introduced biomass feed 105 is typically sieved through a three-inch US sieve. The biomass feed is ground to an average particle size in the range of 0.02 mm to 10 mm, with 5% by weight or less having a particle size of 75 microns or less. The particles typically have an aspect ratio of 0.4 or greater.

[0025] The ground biomass feed 125 can be sent to an optional collection tank 130 where it is blanketed with an inert gas 135. The inert gas has an oxidant or oxygen content of 5 mol% or less. Alternatively, the collection tank 130 can be omitted. In this case, the inert gas is added to the transfer line of the reactor.

[0026] The covered ground biomass feed 140 is sent to a reaction zone 145 where it reacts in the presence of water, a water-immiscible organic solvent, and an acid catalyst. The reaction zone 145 may include one or more reactors.

[0027] The reaction product mixture 150 is separated in separation zone 155 into a furfural product stream 160 and a solvent stream 165 .

[0028] Example

[0029] Example 1

[0030] Corncobs were purchased from AGSCO, Inc., Warrenville, IL. The C5 sugar content of AGSCO corncobs is 34.4% (31.7% xylan, 2.7% arabinan). Since each C5 sugar molecule can be converted into one furfural molecule, the theoretical maximum yield of furfural is easily calculated once the C5 sugar content is known. The molecular weights of furfural and xylose / arabinose are 96.08 g / mol and 150.13 g / mol, respectively. Therefore, the maximum mass yield of furfural from corncobs is 22% of the starting mass of the corncobs.

[0031]

[0032] Example 2: 1-step hydrolysis

[0033] Test was carried out in a 300cc Hastelloy Parr autoclave. Ground corncob was added to the reactor vessel, followed by 100ml of deionized (DI) water, then 7% formic acid, and finally 100ml of toluene as the extraction solvent. The amount of corncob was 20g, the reaction temperature was 170°C, and the reaction time was 2 hours. After the reaction, the contents of the reactor were taken out and centrifuged or filtered to separate the aqueous phase, organic phase, and solid phase. Samples of the aqueous and organic phases were filtered through a 0.2 μm PVDF filter for analysis. Sugars and organic acids were measured only in the aqueous phase by liquid chromatography (e.g., as shown in ASTM E1758-01). Furans (e.g., as shown in ASTM D5769) were analyzed simultaneously in the aqueous phase by liquid chromatography and in the organic phase by gas chromatography.

[0034] Converting biomass to furfural using sulfuric acid

[0035] solvent Feed Observed mass yield % Toluene corn cob 16.8

[0036] Example 3: 2-step hydrolysis

[0037] 4 wt% ground corn cob feedstock, 7% formic acid, and 40 mL of DI water solution were charged to the same 75 cc autoclave from Example 2. The reactor was operated at a temperature of 120° C. for 6 hours. After that, the biomass was removed from the reactor, but the product aqueous portion and a fresh water and toluene solution (water:toluene weight ratio = 1.3:1) were added back to the reactor.

[0038] The second stage reaction was conducted at 170°C for a shorter period of 2 hours. Products from the second reaction were recovered for analysis. Under these conditions, the conversion of hydrolyzed xylose was 100%, and the mass yield of furfural from biomass C5 sugars was 18.3%. The amount of levulinic acid and 5-hydroxymethylfurfural produced was less than 5 mol% of furfural.

[0039] Specific implementation plan

[0040] 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.

[0041] A first embodiment of the present invention is a method for producing furfural or a furfural derivative, or both, comprising: providing a biomass feed having a moisture content of 25 wt % or less; grinding the biomass feed to form a ground biomass feed having a particle size in the range of 0.02 mm to 10 mm and 5 wt % or less having a particle size of 75 microns or less, and having an average aspect ratio of 0.4 or greater; blanketing the ground biomass feed with an inert gas to produce an oxidant or oxygen content of 5 mol % or less; reacting the ground biomass feed in a reaction zone comprising a reactor in the presence of a solvent and an acid catalyst to form a reaction product mixture comprising the furfural, the furfural derivative, or both, wherein the solvent comprises water and optionally a solvent immiscible with water; and separating the furfural, the furfural derivative, or both from the reaction product mixture. An embodiment of the present invention is one, any one or all of the first embodiment of this paragraph to the foregoing embodiments of this paragraph, wherein covering the ground biomass feed with the inert gas comprises: covering the ground biomass feed in a collection container, and the method further comprises: transferring the covered ground biomass feed to the reactor. An embodiment of the present invention is one, any one or all of the first embodiment of this paragraph to the foregoing embodiments of this paragraph, wherein the moisture content of the biomass feed is 15 weight % or less. An embodiment of the present invention is one, any one or all of the first embodiment of this paragraph to the foregoing embodiments of this paragraph, the method further comprises: adjusting the biomass feed to obtain the moisture content of 25 weight % or less. An embodiment of the present invention is one, any one or all of the first embodiment of this paragraph to the foregoing embodiments of this paragraph, wherein adjusting the biomass feed comprises: drying the biomass feed. An embodiment of the present invention is one, any one or all of the first embodiment of this paragraph to the foregoing embodiments of this paragraph, wherein the ground biomass feed has 1 weight % or less of particles of 75 microns or less in size. Embodiments of the present invention are one, any or all of the first embodiment of this paragraph to the preceding embodiments of this paragraph, wherein the oxygen content is 1 mol % or lower. Embodiments of the present invention are one, any or all of the first embodiment of this paragraph to the preceding embodiments of this paragraph, wherein the acid catalyst comprises a mineral acid, a solid acid, an organic acid or a combination thereof. Embodiments of the present invention are one, any or all of the first embodiment of this paragraph to the preceding embodiments of this paragraph, wherein the water-immiscible organic solvent exists and comprises benzene, toluene, xylene, tetralin, alkyltetralin, alkylnaphthalene, aromatic alcohol, dialkyl ketone, alkylphenol or a combination thereof.An embodiment of the present invention is one, any one or all of the embodiments from the first embodiment of this paragraph to the preceding embodiments of this paragraph, wherein the ground biomass feed is reacted to include a hydrolysis reaction and a dehydration reaction. An embodiment of the present invention is one, any one or all of the embodiments from the first embodiment of this paragraph to the preceding embodiments of this paragraph, wherein there are two or more reactors. An embodiment of the present invention is one, any one or all of the embodiments from the first embodiment of this paragraph to the preceding embodiments of this paragraph, wherein the furfural derivative includes 5-hydroxymethylfurfural, 5-halomethylfurfural, wherein the halogen includes a chloride, bromide, fluoride or iodide moiety or a combination thereof.

[0042] A second embodiment of the present invention is a method for producing furfural, furfural derivatives, or both, comprising: providing a biomass feed having a moisture content of 5 wt % to 15 wt %; grinding the biomass feed to form a ground biomass feed having an average particle size in the range of 0.02 mm to 10 mm and 5 wt % or less having a particle size of 75 microns or less, and having an average aspect ratio of 0.4 or greater; covering the ground biomass feed with an inert gas having an oxidant or oxygen content of 5 mol % or less; transferring the covered ground biomass feed to a reaction zone comprising a reactor; reacting the ground biomass feed in the reactor in the presence of a solvent and an acid catalyst to form a reaction product mixture comprising the furfural, the furfural derivative, or both, wherein the solvent comprises water and optionally a solvent immiscible with water; and separating the furfural, the furfural derivative, or both from the reaction product mixture. An embodiment of the present invention is one, any or all of the second embodiment of this paragraph to the preceding embodiment of this paragraph, the method further comprising: drying the biomass feed to obtain the biomass feed having a moisture content of 5% to 15% by weight; an embodiment of the present invention is one, any or all of the second embodiment of this paragraph to the preceding embodiment of this paragraph, wherein the ground biomass feed has 1% by weight or less of particles 75 microns or less in size. An embodiment of the present invention is one, any or all of the second embodiment of this paragraph to the preceding embodiment of this paragraph, wherein the oxygen content is 1 mol% or less. An embodiment of the present invention is one, any or all of the second embodiment of this paragraph to the preceding embodiment of this paragraph, wherein the acid catalyst comprises a mineral acid, a solid acid, an organic acid, or a combination thereof. An embodiment of the present invention is one, any or all of the second embodiment of this paragraph to the preceding embodiment of this paragraph, wherein the water-immiscible organic solvent is present and comprises benzene, toluene, xylene, tetralin, alkyltetralin, alkylnaphthalene, aromatic alcohol, dialkyl ketone, alkylphenol, or a combination thereof. An embodiment of the present invention is one, any one or all of the second embodiment of this paragraph to the aforementioned embodiment of this paragraph, wherein the ground biomass feed is reacted to include a hydrolysis reaction and a dehydration reaction. An embodiment of the present invention is one, any one or all of the second embodiment of this paragraph to the aforementioned embodiment of this paragraph, wherein there are two or more reactors.

[0043] Although there are no further detailed descriptions, it is believed that one skilled in the art can utilize the present invention to its fullest extent by using the foregoing description and can easily ascertain the essential characteristics of the present invention without departing from the spirit and scope of the present invention to make various changes and modifications to the present invention and adapt it to various usages and conditions. Therefore, the foregoing preferred specific embodiments should be construed as merely illustrative and not limiting the remainder 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.

[0044] 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 producing furfural or a furfural derivative or both, the method comprising: providing a biomass feed (105) having a moisture content of 25 wt% or less; grinding the biomass feed (105) to form a ground biomass feed (125), the ground biomass feed having a particle size in a range of 0.02 mm to 10 mm and 5% by weight or less having a particle size of 75 microns or less, and having an average aspect ratio of 0.4 or greater; blanketing the ground biomass feed (125) with an inert gas (135) to produce an oxidant or oxygen content of 5 mol% or less; reacting the ground biomass feed (125) in a reaction zone (145) comprising a reactor in the presence of a solvent and an acid catalyst to form a reaction product mixture (150) comprising the furfural or the furfural derivative, or both; and The furfural or the furfural derivative or both are separated from the reaction product mixture (150).

2. The method of claim 1, wherein blanketing the ground biomass feed (125) with the inert gas comprises: covering the ground biomass feed in a collection container, and the method further comprises: The covered ground biomass (140) feed is transferred to the reactor.

3. The method according to any one of claims 1 to 2, wherein the moisture content of the biomass feed (105) is 15 wt% or less.

4. The method according to any one of claims 1 to 2, further comprising: The biomass feed (125) is adjusted to obtain the moisture content of 25 wt% or less.

5. The method of claim 4, wherein conditioning the biomass feed (105) comprises: The biomass feed is dried (125).

6. The method according to any one of claims 1 to 2, wherein the ground biomass feed (125) has 1 wt% or less of particles having a size of 75 microns or less.

7. The method of any one of claims 1 to 2, wherein the acid catalyst comprises a mineral acid, a solid acid, an organic acid, or a combination thereof.

8. The method of any one of claims 1 to 2, wherein the water-immiscible organic solvent is present and comprises benzene, toluene, xylene, tetralin, alkyltetralins, alkylnaphthalenes, aromatic alcohols, dialkyl ketones, alkylphenols, or combinations thereof.

9. The method according to any one of claims 1 to 2, wherein reacting the ground biomass feed (125) comprises a hydrolysis reaction and a dehydration reaction.

10. The process according to any one of claims 1 to 2, wherein two or more reactors are present.

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