CN114478225B

CN114478225B - Method for preparing levulinic acid by synergistically promoting cellulose conversion through alkyl ammonium halide and sodium halide

Info

Publication number: CN114478225B
Application number: CN202210142280.4A
Authority: CN
Inventors: 祝良芳; 胡平; 胡常伟; 刘忠宝; 王科; 王晓光
Original assignee: Qingdao Sanli Bennuo New Materials Ltd By Share Ltd; Sichuan University
Current assignee: Qingdao Sanli Bennuo New Materials Ltd By Share Ltd; Sichuan University
Priority date: 2022-02-16
Filing date: 2022-02-16
Publication date: 2023-01-31
Anticipated expiration: 2042-02-16
Also published as: CN114478225A

Abstract

A method for preparing levulinic acid by synergistically promoting cellulose conversion by using alkyl ammonium halide and sodium halide comprises the steps of synthesizing the levulinic acid in a microwave reactor or a high-pressure reaction kettle by using microcrystalline cellulose or crop straws as raw materials, 2-methyltetrahydrofuran and water as a two-phase solvent, benzenesulfonic acid as a catalyst and the alkyl ammonium halide and the sodium halide as auxiliaries. The method avoids using high-corrosivity inorganic acid and toxic metal salt, has low corrosivity to equipment and low environmental toxicity; high-concentration cellulose can be efficiently converted into levulinic acid, and the synthesis efficiency is high; no solid humin is generated, and the atom utilization rate of the raw material carbon is high; the method is suitable for preparing the levulinic acid by converting the crop straws from which the hemicellulose and the lignin components are separated in advance through solvent heat treatment, and has low risk of equipment blockage and low energy consumption for levulinic acid separation.

Description

Method for preparing levulinic acid by synergistically promoting cellulose conversion through alkyl ammonium halide and sodium halide

Technical Field

The invention belongs to the field of chemistry, and particularly relates to a method for preparing levulinic acid by synergistically promoting cellulose conversion through alkyl ammonium halide salt and sodium halide salt.

Background

Levulinic acid is a lower fatty acid containing carbonyl and alpha-H, has good reaction performance, and is an important chemical raw material. Various high value-added chemicals and liquid fuels can be prepared through reactions such as esterification, halogenation, hydro-dehydration, condensation, ammoniation and the like, and chiral products can also be prepared through asymmetric reduction reactions, so that the method has important applications in various aspects such as bulk chemicals, foods, medicines, pesticides, printing ink, rubber, plastics, plastic auxiliaries, lubricants, adsorbents, coatings, batteries, electronic products, bioactive materials and the like, and is one of twelve important biomass-based platform chemicals identified by the U.S. department of energy in 2004.

As an important biomass-based platform chemical, levulinic acid can be produced from lignocellulosic biomass or feedstocks derived therefrom. Mao bamboo, poplar, pine, crop straw and the like all belong to lignocellulose biomass, and the main components of the lignocellulose biomass are cellulose, hemicellulose and lignin, wherein the cellulose and hemicellulose components can be used for synthesizing levulinic acid. In the hemicellulose path, hemicellulose components in lignocellulose are firstly hydrolyzed into xylose, the xylose is then dehydrated into furfural, the furfural generates furfuryl alcohol through hydrogenation reaction, and finally the furfuryl alcohol is subjected to hydration decomposition reaction to prepare levulinic acid; in the cellulose path, the cellulose component in lignocellulose is hydrolyzed into glucose, the glucose is dehydrated to generate 5-hydroxymethyl furfural, and the latter is subjected to hydration decomposition reaction to prepare levulinic acid. Compared with a hemicellulose pathway, the cellulose pathway involves fewer reaction steps and is the most promising method for synthesizing levulinic acid in industrial application.

The "Biofine process" for realizing industrial production in 1998 is a typical method for synthesizing levulinic acid by a cellulose route, and the operation flow of the method mainly comprises the following two steps: (1) Mixing lignocellulose raw materials (poplar, miscanthus, switchgrass and the like) ground to 0.5-1.0 cm with 1.5-3.0% sulfuric acid aqueous solution, and reacting at 210-220 ℃ for 12 seconds to obtain a mixture obtained by hydrolyzing cellulose and hemicellulose and undissolved lignin; (2) The reaction mixture enters the next reactor and reacts for 20 minutes at 190-200 ℃ to obtain a mixed product containing levulinic acid, furfural, formic acid, humins and undissolved lignin. The levulinic acid can be separated after the mixed product is subjected to reduced pressure distillation and concentration and solid humins and undissolved lignin are separated at the same time. The method has multiple separation steps and high energy consumption; the sulfuric acid has great corrosion to equipment and serious environmental pollution; the generation of the solid humins not only has the risk of blocking equipment, but also seriously reduces the atom utilization rate of the biomass raw material carbon and the product yield.

Qing et al reported in Bioresource Technology 260 (2018) 150-156 a reaction for the preparation of levulinic acid from corn stover (32.6 wt.% cellulose, 31.7wt.% hemicellulose, and 16.9wt.% lignin) by a further conversion catalyzed by tin tetrachloride. Under the optimal reaction conditions, the corn straw with the mass percent concentration of 5.0 wt% (wherein the cellulose content is 1.6 wt%) is reacted for 17 minutes at 193 ℃, the yield of the levulinic acid reaches 76.0mol%, and xylose, furfural, solid humins and undissolved lignin are associated. Although tin tetrachloride itself has low toxicity and little corrosion of equipment, the energy consumption for separation between the product after conversion of the hemicellulose component and the undissolved lignin component and levulinic acid is high.

Reactions for the direct conversion of microcrystalline cellulose to levulinic acid are reported by Girisuta et al in Industrial & Engineering Chemistry Research 46 (2007) 1696-1708. 1.7wt.% of microcrystalline cellulose is used as a raw material, water is used as a solvent, 1.0mol/L sulfuric acid is used as a catalyst, the reaction is carried out for 120 minutes at 150 ℃, and the yield of the levulinic acid can reach 60.0mol%; under the same reaction conditions, the cellulose concentration was increased to 7.7wt.% and 14.0wt.%, respectively, and the levulinic acid yield was decreased to-50.0 mol% and-40.0 mol%, respectively. The method directly takes the microcrystalline cellulose as the raw material, avoids the separation step between furfural obtained by conversion of hemicellulose components in the lignocellulose raw material and undissolved lignin components and a product levulinic acid, but in a high-concentration microcrystalline cellulose conversion system, the generation condition of solid humins is very serious, the atom utilization rate of raw material carbon and the synthesis efficiency of the levulinic acid are low, and the problem of corrosion of sulfuric acid to equipment is not effectively solved.

Jung et al reported in ACS Sustainable Chemistry & Engineering 4 (2016) 4146-4155 the concerted catalysis of microcrystalline cellulose conversion to levulinic acid using carbonic acid generated by the reaction of carbon dioxide in water with chromium trichloride. The carbonic acid can catalyze the conversion and dissolution of cellulose to obtain a mixture of oligosaccharide and glucose, and the chromium trichloride can catalyze the further hydrolysis, dehydration and hydration decomposition of oligosaccharide and glucose to generate levulinic acid. The higher concentration of microcrystalline cellulose (10.0 wt.%) was reacted in water at 180 ℃ for 90 minutes with a levulinic acid yield of 32.0mol%. Although carbonic acid is nontoxic and does not easily corrode equipment, chromium trichloride is required to be used together, and the latter is toxic and pollutes the environment; in addition, since a large amount of solid humins is produced in the reaction system, the atom utilization rate of the raw material and the synthesis efficiency of levulinic acid are still very low.

From the current reports, the main problems faced by synthesizing levulinic acid by using lignocellulose biomass or microcrystalline cellulose as raw materials are as follows: (1) the inorganic acid/salt catalyst has high toxicity and high corrosivity, (2) the cellulose concentration is generally low, and (3) the intermediate and the product levulinic acid and the like after the cellulose is depolymerized are easy to repolymerize to generate solid humins, so the atom utilization rate of the biomass raw material carbon and the synthesis efficiency of the levulinic acid are low. The organic acid has low toxicity and low corrosivity, and is expected to replace inorganic acid/salt with high toxicity and high corrosivity to be used for preparing the levulinic acid by the catalytic conversion of the cellulose. Because the organic acid is relatively weak in acidity, a non-toxic and low-corrosivity auxiliary agent needs to be added to synergistically promote depolymerization of high-concentration cellulose and further convert the cellulose into levulinic acid, and meanwhile, generation of solid humin is inhibited. When the lignocellulose biomass such as crop straws and the like is directly used as a raw material, the production energy consumption is reduced by reducing the separation steps between a product obtained by converting a hemicellulose component and an undissolved lignin component and a product levulinic acid.

Disclosure of Invention

The invention aims to provide a method for preparing levulinic acid by synergistically promoting cellulose conversion from alkyl ammonium halide and sodium halide.

The invention is characterized in that: synthesizing levulinic acid in a microwave reactor or a high-pressure reaction kettle by using microcrystalline cellulose or crop straws as a raw material, 2-methyltetrahydrofuran and water as a two-phase solvent, benzenesulfonic acid as a catalyst and alkyl ammonium halide and sodium halide as auxiliaries. The concentration of the microcrystalline cellulose or the cellulose in the crop straws in water is 2.0-50.0 wt.%, the volume ratio of 2-methyltetrahydrofuran to water is 8.

The crop straws of the invention refer to rice straw, corn straw, sorghum straw and wheat straw; the alkyl ammonium halide refers to tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrapropyl ammonium bromide, octyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, hexadecyl ethyl dimethyl ammonium bromide, octadecyl trimethyl ammonium bromide and hexadecyl trimethyl ammonium chloride; the sodium halide refers to sodium bromide and sodium chloride.

The concentration of cellulose in water in the invention is preferably 2.0-20.0 wt.%, the volume ratio of 2-methyltetrahydrofuran to water is preferably 4.

The invention has the following characteristics: (1) The benzenesulfonic acid is used as a catalyst, so that strong corrosive inorganic acid and toxic metal salt are avoided, and the equipment corrosivity and the environmental toxicity are low; (2) The alkyl ammonium halide and the sodium halide are used for synergistically promoting the conversion of the high-concentration cellulose to prepare the levulinic acid, and the synthesis efficiency of the levulinic acid is high; (3) No solid humin is generated, and the atom utilization rate of the raw material carbon is high; (4) The method is suitable for preparing the levulinic acid by converting the crop straws subjected to the thermal pretreatment of the solvent and pre-separation of hemicellulose and lignin components, and has low equipment blockage risk and low levulinic acid separation energy consumption.

Drawings

FIG. 1 structural formula of levulinic acid.

FIG. 2 scheme for the synthesis of levulinic acid.

FIG. 3 shows a formula for calculating the yield of levulinic acid.

Detailed Description

Example 1:

a magnetic stirrer, 750.0mg (15.0 wt.%) of microcrystalline cellulose, 5mL of water, 10mL of 2-methyltetrahydrofuran, 237.3mg (100.0 mmol/L) of benzenesulfonic acid, 500.0mg (91.3 mmol/L) of cetyltrimethylammonium bromide, and 80.0mg (91.3 mmol/L) of sodium chloride were sequentially added to a microwave reaction tube, the reaction tube was sealed with a reaction cap having a polytetrafluoroethylene membrane, and the reaction tube was heated to 180 ℃ by microwave for 120 minutes. After the reaction is finished, the reaction tube is purged by using compressed air, after the reaction tube is cooled to room temperature, solid residues are centrifugally separated, an organic layer and a water layer in the solution are respectively taken out, and the product is quantitatively analyzed by using high performance liquid chromatography, wherein the yield of the levulinic acid is 60.8mol%.

Examples 2 to 6:

the reaction was carried out according to the method of example 1 using microcrystalline cellulose at different mass percent concentrations, the reaction conditions and results being shown in table 1.

TABLE 1

Example number	Cellulose concentration (wt%)	Levulinic acid yield (mol%)
			2	2.0	80.2
3	5.0	69.0
			4	10.0	60.0
5	20.0	55.2
			6	50.0	50.0

Examples 7 to 10:

the process of example 1 was followed using 2-methyltetrahydrofuran and water as reaction solvents in different volume ratios, and the reaction conditions and results are shown in Table 2.

TABLE 2

Examples 11 to 15:

the reaction was carried out according to the procedure of example 1, using benzenesulfonic acid at various concentrations, and the reaction conditions and results are shown in Table 3:

TABLE 3

Example number	Concentration of benzenesulfonic acid (mmol/L)	Levulinic acid yield (mol%)
			11	33.3	42.9
12	50.0	53.3
			13	150.0	59.7
14	200.0	56.0
			15	250.0	50.0

Examples 16 to 20:

the reaction was carried out according to the procedure of example 1, using various concentrations of cetyltrimethylammonium bromide, the reaction conditions and results being shown in Table 4:

TABLE 4

Example number	Hexadecyl trimethyl ammonium bromide concentration (mmol/L)	Levulinic acid yield (mol%)
			16	25.0	54.3
17	50.0	56.6
			18	150.0	58.7
19	200.0	57.4
			20	600.0	52.8

Examples 21 to 25:

the reaction was carried out according to the procedure of example 1, using sodium chloride at various concentrations for 60 minutes, and the reaction conditions and results are shown in Table 5:

TABLE 5

Example number	Concentration of sodium chloride (mmol/L)	Levulinic acid yield (mol%)
			21	45.7	51.9
22	91.3	56.5
			23	365.3	56.2
24	731.0	57.2
			25	2054.1	49.2

Examples 26 to 28:

the reaction was carried out according to the procedure of example 1, using different reaction temperatures, the reaction conditions and results being shown in Table 6:

TABLE 6

Example number	Reaction temperature (. Degree.C.)	Levulinic acid yield (mol%)
			26	160	35.6
27	170	56.5
			28	190	52.6

Examples 29 to 32:

the reaction was carried out according to the procedure of example 1, using different reaction times, the reaction conditions and results are shown in Table 7:

TABLE 7

Example number	Reaction time (minutes)	Levulinic acid yield (mol%)
			29	30	50.4
30	60	56.5
			31	90	57.5
32	150	51.4

Examples 33 to 40:

the procedure of example 1 was followed, using different alkylammonium halides, under the conditions and with the results shown in table 8:

TABLE 8

Example 41:

following the procedure of example 1, substituting sodium chloride for sodium bromide, the levulinic acid yield was 56.3mol%.

Example 42:

following the procedure of example 2, the microwave reactor was replaced with an autoclave and the levulinic acid yield was 46.6mol%.

Examples 43 to 46:

adding 5g of crop straw, 40mL of tetrahydrofuran and 60mL of water into a 200mL reaction kettle with a mechanical stirring and heating jacket, purging with nitrogen for 5 minutes to remove air, pressurizing with nitrogen to 2MPa, heating to 200 ℃ for reaction for 60 minutes, purging with air, cooling to room temperature, and separating out a solid product by reduced pressure suction filtration. The reaction was carried out in the same manner as in example 1 using the solid obtained above as a starting material, and the reaction starting material (cellulose component concentration in the starting material: 15.0 wt.%) and the results are shown in Table 9:

TABLE 9

Example number	Reaction raw material	Levulinic acid yield (mol%)
			43	Straw stalk	68.1
44	Corn stalk	73.8
			45	Sorghum stalk	64.2
46	Wheat straw	81.0

Claims

1. A process for the preparation of levulinic acid from cellulose conversion synergistically promoted by an alkylammonium halide and a sodium halide, characterized in that: synthesizing levulinic acid in a microwave reactor or a high-pressure reaction kettle by using microcrystalline cellulose or crop straws as a raw material, 2-methyltetrahydrofuran and water as a two-phase solvent, benzenesulfonic acid as a catalyst and alkyl ammonium halide and sodium halide as auxiliaries, wherein the concentration of cellulose in microcrystalline cellulose or crop straws in water is 2.0-50.0 wt.%, the volume ratio of 2-methyltetrahydrofuran to water is (8-1-8); the alkyl ammonium halide is tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrapropyl ammonium bromide, octyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, hexadecyl ethyl dimethyl ammonium bromide, octadecyl trimethyl ammonium bromide and hexadecyl trimethyl ammonium chloride; the sodium halide is sodium bromide or sodium chloride.

2. The method of claim 1, wherein: the crop straw is rice straw, corn straw, sorghum straw and wheat straw.

3. The method of claim 1, wherein: the cellulose concentration is 2.0-20.0 wt.%.

4. The method of claim 1, wherein: the volume ratio of 2-methyltetrahydrofuran/water is 4.

5. The method of claim 1, wherein: the concentration of the benzenesulfonic acid is 100.0-200.0 mmol/L.

6. The method of claim 1, wherein: the concentration of the alkyl ammonium halide is 50.0-200.0 mmol/L.

7. The method of claim 1, wherein: the concentration of the sodium halide is 91.3-731.0 mmol/L.

8. The method of claim 1, wherein: the reaction temperature is 170-180 ℃.

9. The method of claim 1, wherein: the reaction time is 60 to 120 minutes.