阅读说明：本技术 溴化锂熔盐水合物-丙酮体系催化碳水化合物一锅法制备5-羟甲基糠醛的方法 (Method for preparing 5-hydroxymethylfurfural by using lithium bromide molten salt hydrate-acetone system to catalyze carbohydrate through one-pot method ) 是由 马巧智 官铭钊 刘启予 林健颖 梁皓童 蒋恩臣 于 2021-08-02 设计创作，主要内容包括：本发明公开了溴化锂熔盐水合物-丙酮体系催化碳水化合物一锅法制备5-羟甲基糠醛的方法。该方法包括以下步骤：将碳水化合物、溴化锂熔盐水合物和丙酮混合后进行水热反应,充分反应后即可得到高产率的还原糖和5-羟甲基糠醛反应液。反应过程中还加入磷酸或氯化铝。本发明通过溴化锂熔盐水合物和丙酮构建的双相体系可以高效的一锅法催化转化纤维素,并在氯化铝的催化作用下获得了高产率的5-羟甲基糠醛。而且,本发明具有工艺简单,成本低,转化速度快,高选择性转化的优势。(The invention discloses a method for preparing 5-hydroxymethylfurfural by a one-pot method by catalyzing carbohydrate with a lithium bromide molten salt hydrate-acetone system. The method comprises the following steps: mixing carbohydrate, lithium bromide molten salt hydrate and acetone, carrying out hydrothermal reaction, and fully reacting to obtain the reaction solution of reducing sugar and 5-hydroxymethylfurfural with high yield. Phosphoric acid or aluminum chloride is also added in the reaction process. According to the invention, a two-phase system constructed by lithium bromide molten salt hydrate and acetone can be used for efficiently catalyzing and converting cellulose by a one-pot method, and high-yield 5-hydroxymethylfurfural is obtained under the catalysis of aluminum chloride. Moreover, the method has the advantages of simple process, low cost, high conversion speed and high selectivity conversion.)

1. The method for preparing 5-hydroxymethylfurfural by using a lithium bromide molten salt hydrate-acetone system to catalyze carbohydrate through a one-pot method is characterized by comprising the following steps of:

mixing carbohydrate, lithium bromide molten salt hydrate and acetone, and then carrying out hydrothermal reaction to obtain the 5-hydroxymethylfurfural.

2. The method according to claim 1, wherein phosphoric acid or aluminum chloride is further added to perform the hydrothermal reaction.

3. The method according to claim 2, wherein the mass ratio of the carbohydrate, the lithium bromide molten salt hydrate, the phosphoric acid and the acetone is 0.1: 6: 0-1.73: 24.

4. the method according to claim 2, wherein the mass ratio of the carbohydrate, the lithium bromide molten salt hydrate, the aluminum chloride and the acetone is 0.1: 6: 0.005-0.02: 24.

5. the method according to claim 4, wherein the mass ratio of the carbohydrate, the lithium bromide molten salt hydrate, the aluminum chloride and the acetone is 0.1: 6: 0.005-0.0125: 24.

6. the method according to claim 5, wherein the mass ratio of the carbohydrate, the lithium bromide molten salt hydrate, the aluminum chloride and the acetone is 0.1: 6: 0.01: 24.

7. the method according to any one of claims 1 to 6, wherein the molar ratio of salt to water in the lithium bromide molten salt hydrate is 2 to 6: 1.

8. the method as claimed in any one of claims 1 to 6, wherein the hydrothermal reaction is carried out at a temperature of 160 ℃ and 190 ℃ for a period of 10 to 50 min.

9. The method according to any one of claims 1 to 6, wherein the molar ratio of salt to water in the lithium bromide molten salt hydrate is 3.2: 1; the temperature of the hydrothermal reaction is 180 ℃ and the time is 20 min.

10. The method of any one of claims 1-6, wherein the carbohydrate is one or more of cellulose, cellobiose, and fructose.

Technical Field

The invention relates to the field of preparation of 5-hydroxymethylfurfural from carbohydrate, and particularly relates to a method for preparing 5-hydroxymethylfurfural from carbohydrate by a one-pot method under catalysis of lithium bromide molten salt hydrate-acetone system.

Background

With the continuous consumption of non-renewable fossil energy, people are keenly expected to utilize biomass such as cellulose to produce high value-added chemicals and fuels. Meanwhile, lignocellulose is the most abundant natural resource, has the characteristics of sustainability, biodegradability, biocompatibility and the like, and is considered as the most promising raw material for producing oil refining chemicals and fuels.

In which 5-hydroxymethylfurfural (5-HMF) is regarded as an important bridge between carbohydrates and high value-added chemicals, a variety of high value-added chemicals, such as gamma-valerolactone, 2, 5-furandicarboxylic acid, and dimethylfuran, can be synthesized using 5-hydroxymethylfurfural as a precursor. Currently, the preparation of 5-hydroxymethylfurfural mainly utilizes monosaccharide (glucose or fructose) as a raw material, but the utilization of glucose or fructose as a starting substrate for synthesizing refined chemicals limits the cost competitiveness thereof on an industrial scale and competes with the food industry. Therefore, methods for synthesizing high value-added chemicals using more abundant, cheaper cellulose as a substrate are more attractive.

The conversion of cellulose to 5-hydroxymethylfurfural involves three steps: (1) cellulose is hydrolyzed to form glucose, (2) the glucose is isomerized into fructose, and (3) the fructose is dehydrated into 5-hydroxymethyl furfural. However, in the cascade reaction process for converting cellulose into high value-added chemicals, due to the stable and compact structure of cellulose and the high degree of crystallinity polymerization, the catalyst is difficult to act on the connecting bonds between cellulose monomers, so that the depolymerization difficulty of cellulose is extremely high, and in addition, 5-hydroxymethylfurfural generated in the aqueous phase is easy to decompose and the yield is low.

Although there have been some reports on the production of 5-hydroxymethylfurfural using cellulose, the results are not optimistic. For example, one widely reported and potentially developing method is to catalyze cellulose to prepare 5-hydroxymethylfurfural by combining ionic liquid and organic phase to form a two-phase system. Wherein the ionic liquid can dissolve cellulose and drive the cellulose to be efficiently hydrolyzed into glucose, and the 5-hydroxymethylfurfural generated by conversion can be extracted by an organic phase and is protected from further degradation. However, ionic liquids are subject to scaling due to their costly synthetic route and the disadvantage that most are toxic. Compared with the ionic liquid, the fused salt hydrate has the advantages of simpler structure, simpler preparation and wider applicable temperature range. In recent years, a process for preparing high value-added chemicals by directionally converting cellulose by virtue of the characteristic of dissolving cellulose by virtue of a molten salt hydrate and constructing an adaptive two-phase system by coupling an organic phase has been occasionally reported. For example, the professor of easy maintenance of Shandong theory of science, in a biphasic system of lithium chloride molten salt hydrate in combination with methyl isobutyl ketone, catalyzed by cellulose with a solid acid catalyst, gave 94% of levulinic acid. However, the process for selectively preparing 5-hydroxymethylfurfural by a system like this is still rarely reported. Therefore, the design of a high-efficiency cellulose catalytic reaction system to realize the directional conversion of low-value cellulose to high-value 5-hydroxymethylfurfural has important significance.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a method for preparing 5-hydroxymethylfurfural by a one-pot method by catalyzing carbohydrate through a lithium bromide molten salt hydrate-acetone system.

The object of the present invention is achieved by the following means.

The method for preparing 5-hydroxymethylfurfural by using a lithium bromide molten salt hydrate-acetone system to catalyze carbohydrate through a one-pot method comprises the following steps:

mixing carbohydrate, lithium bromide molten salt hydrate and acetone, and then carrying out hydrothermal reaction to obtain the 5-hydroxymethylfurfural.

Preferably, phosphoric acid or aluminum chloride is also added to carry out hydrothermal reaction.

Preferably, the phosphoric acid is 85 wt% phosphoric acid.

Preferably, the mass ratio of the carbohydrate, the lithium bromide molten salt hydrate, the phosphoric acid and the acetone is 0.1: 6: 0-1.73: 24.

preferably, the mass ratio of the carbohydrate to the lithium bromide molten salt hydrate to the aluminum chloride to the acetone is 0.1: 6: 0.005-0.02: 24.

preferably, the mass ratio of the carbohydrate to the lithium bromide molten salt hydrate to the aluminum chloride to the acetone is 0.1: 6: 0.005-0.0125: 24.

preferably, the mass ratio of the carbohydrate to the lithium bromide molten salt hydrate to the aluminum chloride to the acetone is 0.1: 6: 0.01: 24.

preferably, the molar ratio of salt to water in the lithium bromide molten salt hydrate is 2-6: 1.

preferably, the temperature of the hydrothermal reaction is 160-190 ℃ and the time is 10-50 min.

Preferably, the molar ratio of salt to water in the lithium bromide molten salt hydrate is 3.2: 1; the temperature of the hydrothermal reaction is 180 ℃ and the time is 20 min.

Preferably, the carbohydrate is one or more of cellulose, cellobiose and fructose.

The reaction solution containing glucose and 5-hydroxymethylfurfural is prepared by the invention, and the glucose can be further converted into the 5-hydroxymethylfurfural by utilizing the prior art.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention utilizes the lithium bromide molten salt hydrate-acetone system to catalyze the carbohydrate, can prepare the 5-hydroxymethylfurfural by a one-pot method, does not need post-treatment, and has simple operation process and low cost.

(2) The method for preparing 5-hydroxymethylfurfural by catalyzing carbohydrate with the lithium bromide molten salt hydrate-acetone system has the characteristics of high catalytic activity, high reaction speed and high yield.

(3) The invention utilizes the lithium bromide molten salt hydrate-acetone system to catalyze the cellulose to prepare the 5-hydroxymethylfurfural, and the conversion rate of the cellulose is high.

Drawings

FIG. 1 is a schematic synthesis of the present invention; wherein, Cellulose-Cellulose, oligose, Lewis acid-Lewis acid, Glucose-Glucose, Fructose-Fructose, 5-HMF-5-hydroxymethyl furfural and MSH-molten salt system.

FIG. 2 is a graph showing the yields of 5-hydroxymethylfurfural obtained by the methods of example 1 (corresponding to a), example 2 (corresponding to b), and example 3 (corresponding to c) according to the present invention.

Detailed Description

The following detailed description will be given with reference to the accompanying drawings, but the embodiments of the present invention are not limited by the following examples.

The synthesis of the invention is schematically shown in FIG. 1.

Example 1

Preparing a reaction solution of glucose and 5-hydroxymethylfurfural: 0.1g of cellulose, 6g of lithium bromide molten salt hydrate (the molar ratio of water to salt is 3.2: 1) and 24g of acetone are weighed in a hydrothermal reaction kettle, sealed and heated in a heating jacket, cooling circulating water is continuously introduced, the stirring speed is 300rad/min, the heating rate is 4.6 ℃/min, and the mixture is kept at 180 ℃ for 20 min. After the reaction is finished, stopping stirring and introducing cooling circulating water, taking the reaction kettle out to ice water for cooling, opening the kettle for collection to obtain reaction liquid of glucose and 5-hydroxymethylfurfural, and measuring the contents of the glucose and the 5-hydroxymethylfurfural in the reaction liquid to be 55.1 percent and 37.1 percent respectively by adopting a high performance liquid chromatograph (see a in figure 2).

Example 2

Preparing a reaction solution of glucose and 5-hydroxymethylfurfural: 0.1g of cellulose, 6g of lithium bromide molten salt hydrate (the molar ratio of water to salt is 3.2: 1), 0.6g of phosphoric acid (85 wt%) and 24g of acetone are weighed into a hydrothermal reaction kettle, sealed and heated in a heating jacket, cooling circulating water is continuously introduced, the stirring speed is 300rad/min, the heating rate is 4.6 ℃/min, and the temperature is kept at 180 ℃ for 20 min. And after the reaction is finished, stopping stirring and introducing cooling circulating water, taking the reaction kettle out to ice water for cooling, opening the kettle for collection to obtain reaction liquid of glucose and 5-hydroxymethylfurfural, and determining the contents of the glucose and the 5-hydroxymethylfurfural in the reaction liquid to be 51.9 percent and 44.1 percent respectively by adopting a high performance liquid chromatograph (see b in figure 2).

Example 3

Preparing a reaction solution with high yield of 5-hydroxymethylfurfural: 0.1g of cellulose and 6g of lithium bromide molten salt hydrate (the molar ratio of water to salt is 3.2: 1), aluminum chloride with the dosage shown in table 1 and 24g of acetone are weighed in a hydrothermal reaction kettle, sealed and heated in a heating jacket, cooling circulating water is continuously introduced, the stirring speed is 300rad/min, the heating rate is 4.6 ℃/min, and the temperature is kept at 180 ℃ for 20 min. And after the reaction is finished, stopping stirring and introducing cooling circulating water, taking the reaction kettle out to ice water for cooling, opening the kettle for collection to obtain a reaction solution of the high-yield 5-hydroxymethylfurfural, and determining the content of the 5-hydroxymethylfurfural in the reaction solution by using a high performance liquid chromatograph.

TABLE 1

As can be seen from Table 1, the yield of 5-HMF increased and then decreased with increasing amount of aluminum chloride, and when the amount of aluminum chloride was 0.01g, a higher yield of 5-HMF (75.1%, see c in FIG. 2) was obtained.

Example 4

Weighing 0.1g of carbohydrate shown in Table 2, 6g of lithium bromide molten salt hydrate (the molar ratio of water to salt is 3.2: 1), 0.01g of aluminum chloride and 24g of acetone in a hydrothermal reaction kettle, sealing, heating in a heating jacket, continuously introducing cooling circulating water, stirring at a rotation speed of 300rad/min and a temperature rise rate of 4.6 ℃/min, and keeping at 180 ℃ for 20 min. And after the reaction is finished, stopping stirring and introducing cooling circulating water, taking the reaction kettle out to ice water for cooling, opening the kettle for collection to obtain a reaction solution of glucose and 5-hydroxymethylfurfural, and measuring the content of the glucose and the 5-hydroxymethylfurfural in the reaction solution by using a high performance liquid chromatograph.

TABLE 4

As can be seen from Table 2, microcrystalline cellulose, cellobiose, and fructose all served as carbohydrate feedstocks in the present system to achieve higher yields of 5-HMF.

Comparative example 1

0.1g of cellulose, 6g of lithium bromide molten salt hydrate (the molar ratio of water to salt is 3.2: 1) and 31.2g of gamma-valerolactone are weighed in a hydrothermal reaction kettle, sealed and heated in a heating jacket, and continuously introduced with cooling circulating water, the stirring speed is 300rad/min, the heating rate is 4.6 ℃/min, and the temperature is kept for 20min at 180 ℃. And after the reaction is finished, stopping stirring and introducing cooling circulating water, taking the reaction kettle out to ice water for cooling, opening the kettle to collect reaction liquid, and measuring the reaction liquid by using a high performance liquid chromatograph, wherein the generation of the 5-hydroxymethylfurfural is not measured. Therefore, the preparation of 5-hydroxymethylfurfural is difficult to realize by adopting the lithium bromide molten salt hydrate-gamma-valerolactone system to catalyze the cellulose.

Comparative example 2

0.1g of cellulose, 6g of lithium bromide molten salt hydrate (the molar ratio of water to salt is 3.2: 1) and 29.4g of tetrahydrofuran are weighed in a hydrothermal reaction kettle, sealed and heated in a heating jacket, cooling circulating water is continuously introduced, the stirring speed is 300rad/min, the heating rate is 4.6 ℃/min, and the temperature is kept at 180 ℃ for 20 min. And after the reaction is finished, stopping stirring and introducing cooling circulating water, taking the reaction kettle out to ice water for cooling, opening the kettle to collect reaction liquid, and measuring the content of the 5-hydroxymethylfurfural in the reaction liquid to be 16.2% by using a high performance liquid chromatograph. Therefore, the yield of 5-hydroxymethylfurfural prepared by catalyzing cellulose by using the lithium bromide molten salt hydrate-tetrahydrofuran system is lower.

Finally, it should be noted that the above list is only a few specific embodiments of the present invention. It is obvious that the invention is not limited to the above embodiment examples, but that many variations are possible. All modifications which can be derived or suggested directly from the disclosure of the present invention by a person skilled in the art are considered to be within the scope of the present invention.