CN116514747A - Method for directly preparing furfural by using wood fiber raw material and solvent used by method - Google Patents

Abstract

The invention discloses a method for directly preparing furfural by using a wood fiber raw material and a solvent used by the method, belonging to the technical field of clean separation and efficient utilization of the wood fiber raw material. Mixing a hydrogen bond acceptor and a hydrogen bond donor, heating after mixing, and continuously stirring until a uniform and clear liquid is formed; then mixing with an organic solvent to form a biphasic solvent system; mixing wood fiber raw materials with the biphasic solvent system for reaction, filtering after the reaction is finished, carrying out solid-liquid separation, and filtering liquid containing furfural through an organic filter membrane to obtain filtrate rich in furfural. The biphasic solvent system is utilized to pretreat the lignocellulose raw material, so that the directional conversion of hemicellulose in the lignocellulose raw material into furfural can be realized at a lower temperature, and the yield can reach 63.43%.

Description

A method for directly preparing furfural from lignocellulosic raw materials and the solvent used therefor

technical field

The invention belongs to the technical field of clean separation and high-efficiency utilization of lignocellulosic raw materials, and in particular relates to a method for directly preparing furfural from lignocellulosic raw materials and a solvent used therein.

Background technique

At present, problems such as energy crisis and environmental pollution caused by the overexploitation of fossil energy forces humans to seek new green and renewable resources. Lignocellulosic biomass has the advantages of large reserves, renewable energy, and high calorific value. Renewable energy produced from lignocellulosic biomass is considered to be an ideal option to replace petrochemical energy. Hemicellulose is one of the main components of lignocellulosic biomass, and its content is second only to cellulose. Xylan is the main component of hemicellulose, and its hydrolyzate is mainly xylose. Xylose is the carbohydrate content second only to glucose in nature, and it is also the raw material for the production of important chemical products such as furfural and γ-valerolactone. Therefore, realizing efficient conversion of xylose in lignocellulosic raw materials is beneficial to improving the utilization rate of lignocellulosic biomass.

Furfural is a heterocyclic aldehyde, which is the precursor of many fuel molecules and materials, and can replace crude oil-based compounds for the production of resins, lubricants, adhesives and plastics, etc. One of the most valuable bio-based compounds. At present, the main method of converting hemicellulose in lignocellulosic raw materials into furfural is to use a large amount of inorganic acid catalysts, resulting in serious equipment corrosion, difficulty in recycling inorganic acids, and low yield (<60%) and other series of problems severely restricted its development. The organic solvent-water dual-phase system that emerged later effectively solved the above problems, but a series of problems such as high temperature and high pressure have not been effectively solved. Therefore, there is an urgent need to seek a simpler, more efficient and milder furfural preparation method.

In recent years, deep eutectic solvents have been gradually used in the field of component separation of lignocellulosic raw materials, and they have shown exceptionally efficient performance in the degradation of hemicellulose. The deep eutectic solvent is a homogeneous solution composed of hydrogen bond donors and hydrogen bond acceptors. The hydrogen bond acceptors mainly include choline chloride, betaine, etc., while the hydrogen bond donors mainly include alcohols, organic acids, and phenolic acids. wait. Common organic acid deep eutectic solvents such as choline chloride/lactic acid, choline chloride/oxalic acid and other systems can effectively degrade hemicellulose in wood fibers, but the degraded hemicellulose is prone to a series of subsequent side effects. The reaction leads to the production of difficult-to-use condensation products such as humic acid, which greatly reduces the selectivity of furfural conversion, so furfural is often not detected in the deep eutectic solvent pretreatment solution.

Contents of the invention

Aiming at the problems of severe conditions, low yield and serious pollution in the existing furfural production methods, the present invention proposes a method for directly preparing furfural from lignocellulosic raw materials, which can quickly remove hemifibers from lignocellulosic raw materials under normal pressure and low temperature conditions. to furfural.

In order to solve the problems of the technologies described above, the technical scheme adopted in the present invention is as follows:

A kind of method utilizing lignocellulosic raw material to directly prepare furfural, comprises the following steps:

(1) Mix the hydrogen bond acceptor and the hydrogen bond donor, heat and stir continuously after mixing until a uniform and clear liquid is formed; then mix with an organic solvent to form a biphasic solvent system;

(2) The lignocellulosic raw material is mixed and reacted with the above-mentioned biphasic solvent system, filtered after the reaction, and solid-liquid separated to obtain a filtrate rich in furfural.

In the method for directly preparing furfural from lignocellulosic raw materials, the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is oxalic acid or p-toluenesulfonic acid; the organic solvent is γ-valerolactone, methyl isobutyl ketone or Any of methyl tetrahydrofuran.

In the method for directly preparing furfural from lignocellulosic raw materials, the mass ratio of the deep eutectic solvent to the organic solvent is 1:0.1˜1:10.

In the method for directly preparing furfural from lignocellulosic raw materials, the molar ratio of hydrogen bond acceptors and hydrogen bond donors is 1:0.5-1:10, heated and stirred at 60-100° C. until a uniform and transparent solvent is formed.

In the method for directly preparing furfural from lignocellulosic raw materials, the reaction temperature of lignocellulosic raw materials and the two-phase solvent system is 100-160° C., and the reaction time is 10-120 minutes.

In the method for directly preparing furfural from lignocellulosic raw materials, the mass ratio of lignocellulosic raw materials to the two-phase solvent system is 1:2˜1:50.

In the method for directly preparing furfural from lignocellulosic raw materials, the lignocellulosic raw material is any one of wheat straw, rice straw, corn straw, poplar, bamboo or eucalyptus.

Compared with the prior art, the beneficial effects of the present invention are:

In the deep eutectic solvent two-phase system proposed by the present invention, the introduction of organic solvents such as γ-valerolactone inhibits the subsequent condensation side reaction of furfural, thereby effectively increasing the yield of furfural. In addition, compared with other furfural preparation methods, the present invention can realize the large-scale preparation of furfural without adding additional catalysts. Therefore, the deep eutectic solvent two-phase system pretreatment method proposed by the present invention is a new method for producing furfural with high efficiency.

The invention utilizes a biphasic solvent system to pretreat the lignocellulosic raw material, and can realize the directional transformation of the hemicellulose in the lignocellulosic raw material into furfural at a relatively low temperature, and the yield can reach 63.43%.

Description of drawings

Fig. 1 is embodiment 1-3 hemicellulose removal rate (1a) and furfural yield (1b);

Fig. 2 is embodiment 4-6 hemicellulose removal rate (2a) and furfural yield (2b);

Figure 3 is the hemicellulose removal rate (3a) and furfural yield (3b) of Comparative Example 1-3.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Example 1

A kind of method utilizing lignocellulosic raw material to directly prepare furfural, comprises the following steps:

1) Mix choline chloride and oxalic acid in a molar ratio of 1:2, and keep stirring at 80° C. until a uniform, clear solvent is formed; then add gamma-valerolactone to the above-mentioned deep eutectic solvent, The mass ratio of γ-valerolactone to the deep eutectic solvent is 1:1 to form a biphasic solvent.

2) Mix the bamboo with the biphasic solvent system at a mass ratio of 1:10 and react at 120°C for 60 minutes. After the pretreatment is completed, filter and separate to obtain the pretreatment solution. The content of furfural was analyzed by chromatography, and the yield of furfural was calculated.

Example 2

A kind of method utilizing lignocellulosic raw material to directly prepare furfural, comprises the following steps:

1) Mix choline chloride and oxalic acid in a molar ratio of 1:2, and keep stirring at 80° C. until a uniform, clear solvent is formed; then add gamma-valerolactone to the above-mentioned deep eutectic solvent, The mass ratio of γ-valerolactone to the deep eutectic solvent is 1:1.

2) Bamboo was mixed with a two-phase solvent system at a mass ratio of 1:10 and reacted at 130° C. for 60 minutes. After the pretreatment, the furfural-rich liquid was filtered and separated, and the furfural content was analyzed by high performance liquid chromatography. And calculate the yield of furfural.

Example 3

A kind of method utilizing lignocellulosic raw material to directly prepare furfural, comprises the following steps:

1) Mix choline chloride and oxalic acid in a molar ratio of 1:2, and keep stirring at 80° C. until a uniform, clear solvent is formed; then add gamma-valerolactone to the above-mentioned deep eutectic solvent, The mass ratio of γ-valerolactone to the deep eutectic solvent is 1:1.

2) Bamboo was mixed with a biphasic solvent system at a mass ratio of 1:10 and reacted at 140°C for 60 minutes. After the pretreatment, the furfural-rich liquid was filtered and separated, and the furfural content was analyzed by high performance liquid chromatography. And calculate the yield of furfural.

Fig. 1 is embodiment 1-3 hemicellulose removal rate (1a) and furfural yield (1b); As shown in Figure 1a, hemicellulose removal rate can reach 96.26% (120 ℃) after pretreatment, shows This solvent can efficiently remove hemicellulose. As the temperature increased, the hemicellulose removal continued to increase to 98.59% (130°C) and 100% (140°C). The yield of furfural increased from 48.8% (120°C) to 61.44% (130°C), indicating that as the temperature increased, the removal rate of hemicellulose increased and the yield of furfural increased. When the temperature continues to rise to 140°C, the yield of furfural decreases significantly. This is because at high temperature, the generated furfural undergoes some side reactions and transforms into difficult-to-use condensation products such as humus, which reduces the yield of furfural.

Example 4

A kind of method utilizing lignocellulosic raw material to directly prepare furfural, comprises the following steps:

1) Mix choline chloride and p-toluenesulfonic acid in a molar ratio of 1:1, and keep stirring at 80° C. until a uniform and clear solvent is formed. Then, γ-valerolactone is added to the above-mentioned deep eutectic solvent, and the mass ratio of γ-valerolactone to the deep eutectic solvent is 1:1.

2) Mix the bamboo with the solvent at a mass ratio of 1:10 and react at 100°C for 60 minutes. After the pretreatment, filter and separate, dilute the furfural-rich liquid and use high-performance liquid chromatography to analyze the furfural content in it, and calculate the furfural content. Yield.

Example 5

A kind of method utilizing lignocellulosic raw material to directly prepare furfural, comprises the following steps:

1) Mix choline chloride and p-toluenesulfonic acid in a molar ratio of 1:1, and keep stirring at 80° C. until a uniform and clear solvent is formed. Then, γ-valerolactone is added to the above-mentioned deep eutectic solvent, and the mass ratio of γ-valerolactone to the deep eutectic solvent is 1:1.

2) Mix the bamboo with the solvent at a mass ratio of 1:10 and react at 110°C for 60 minutes. After the pretreatment, filter and separate, dilute the furfural-rich liquid and use high-performance liquid chromatography to analyze the furfural content in it, and calculate the furfural content. Yield.

Example 6

A kind of method utilizing lignocellulosic raw material to directly prepare furfural, comprises the following steps:

1) Mix choline chloride and p-toluenesulfonic acid in a molar ratio of 1:1, and keep stirring at 80° C. until a uniform and clear solvent is formed. Then, γ-valerolactone is added to the above-mentioned deep eutectic solvent, and the mass ratio of γ-valerolactone to the deep eutectic solvent is 1:1.

2) Mix the bamboo with the solvent at a mass ratio of 1:10 and react at 120°C for 60 minutes. After the pretreatment, filter and separate, dilute the furfural-rich liquid and use high-performance liquid chromatography to analyze the furfural content in it, and calculate the furfural content. Yield.

Fig. 2 is embodiment 4-6 hemicellulose removal rate (2a) and furfural yield (2b); As shown in Fig. 2a, when pretreatment temperature is 100 ℃, hemicellulose removal rate after pretreatment can be Reached 94.22%, with the extension of pretreatment time, the removal rate of hemicellulose gradually increased to 98.67% (110°C) and 99.98% (120°C). It shows that a large amount of hemicellulose can be removed at lower temperature. The yield of furfural is shown in Figure 2b. With the increase of pretreatment time, the yield of furfural increased from 43.05% (100°C) to 55.62% (110°C) and 63.43% (120°C). It shows that with the increase of pretreatment temperature, the yield of furfural increases significantly, indicating that temperature is an important condition affecting the yield of furfural.

Comparative example 1

Under conventional deep eutectic solvent system, utilize the method for preparing furfural of lignocellulosic raw material, comprise the following steps

1) Mix choline chloride and oxalic acid in a molar ratio of 1:2, and keep stirring at 80° C. until a uniform and clear solvent is formed.

2) Mix the bamboo with the solvent at a mass ratio of 1:10 and react at 120°C for 60 minutes. After the pretreatment, filter and separate, dilute the furfural-rich liquid and use high-performance liquid chromatography to analyze the furfural content in it, and calculate the furfural content. Yield.

Comparative example 2

Under conventional deep eutectic solvent system, utilize the method for preparing furfural of lignocellulosic raw material, comprise the following steps

1) Mix choline chloride and oxalic acid in a molar ratio of 1:2, and keep stirring at 80° C. until a uniform and clear solvent is formed.

2) Mix the bamboo with the solvent according to the mass ratio of 1:10 and react at 130°C for 60 minutes. After the pretreatment, filter and separate, and use high-performance liquid chromatography to analyze the furfural content in the furfural-rich liquid after dilution, and calculate the furfural content. Yield.

Comparative example 3

Under conventional deep eutectic solvent system, utilize the method for preparing furfural of lignocellulosic raw material, comprise the following steps

1) Mix choline chloride and oxalic acid in a molar ratio of 1:2, and keep stirring at 80° C. until a uniform and clear solvent is formed.

2) Mix the bamboo with the solvent at a mass ratio of 1:10 and react at 140°C for 60 minutes. After the pretreatment, filter and separate, dilute the furfural-rich liquid and use high-performance liquid chromatography to analyze the furfural content in it, and calculate the furfural content. Yield.

Figure 3 shows the hemicellulose removal rate (3a) and furfural yield (3b) of Comparative Example 1-3, as shown in Figure 3a, only using conventional deep eutectic solvent pretreatment, the hemicellulose removal rate can still reach 97.98% (120°C), indicating that the system can achieve a large amount of hemicellulose degradation and removal at a lower temperature. With the increase of temperature, the removal rate of hemicellulose continued to increase to 100% (130°C), indicating that choline chloride/oxalic acid had a prominent effect on the degradation of hemicellulose. However, the furfural yield after pretreatment was only 9.97% (120°C), and with the increase of temperature, the furfural yield only slightly increased to 12.39% (130°C) and 11.86% (140°C). It shows that although the hemicellulose in the system is severely degraded, the degraded hemicellulose is not converted into furfural in a large amount. This is because the furfural produced in this system is rapidly further converted into the condensation product—humus, which leads to a lower yield of furfural. Rate. However, in the deep eutectic solvent two-phase system proposed in this application, since the introduction of γ-valerolactone inhibits the subsequent condensation side reaction of furfural, the yield of furfural is effectively improved. Therefore, the deep eutectic solvent two-phase system pretreatment method proposed in this application is a new method for producing furfural with high efficiency.

Claims (7)

1. A method for directly preparing furfural by using wood fiber raw materials, which is characterized by comprising the following steps:

(1) Mixing a hydrogen bond acceptor and a hydrogen bond donor, heating after mixing, and continuously stirring until a uniform and clear liquid is formed; then mixing with an organic solvent to form a biphasic solvent system;

(2) And mixing the wood fiber raw material with the biphasic solvent system for reaction, filtering after the reaction is finished, and carrying out solid-liquid separation to obtain a filtrate rich in furfural.

2. The method for directly preparing furfural from lignocellulosic feedstock according to claim 1, wherein the hydrogen bond acceptor is choline chloride and the hydrogen bond donor is oxalic acid or p-toluenesulfonic acid; the organic solvent is any one of gamma-valerolactone, methyl isobutyl ketone or methyl tetrahydrofuran.

3. The method for directly preparing furfural by using wood fiber raw materials according to claim 1, wherein the mass ratio of the eutectic solvent to the organic solvent is 1:0.1-1:10.

4. The method for directly preparing furfural from lignocellulosic feedstock according to claim 1, wherein the molar ratio of hydrogen bond acceptors to hydrogen bond donors is 1:0.5-1:10, heated and stirred at 60-100 ℃ until a uniform, transparent solvent is formed.

5. The method for directly preparing furfural by using wood fiber raw materials according to claim 1, wherein the reaction temperature of the wood fiber raw materials and a biphasic solvent system is 100-160 ℃ and the reaction time is 10-120 min.

6. The method for directly preparing furfural by using wood fiber raw materials according to claim 1, wherein the mass ratio of the wood fiber raw materials to the biphasic solvent system is 1:2-1:50.

7. The method for directly preparing furfural by using wood fiber raw materials according to claim 1, wherein the wood fiber raw materials are any one of wheat straw, rice straw, corn stalk, poplar, bamboo wood or eucalyptus wood.