CN111393279A - A kind of method that cellulose catalytic degradation is converted into levulinic acid - Google Patents

Abstract

The invention discloses a method for converting cellulose into levulinic acid through catalytic degradation, and belongs to the technical field of biomass resource utilization. Adding cellulose into a reaction vessel filled with a solvent, and reacting under the synergistic action of Amberlyst15 and a composite solvent in a certain gas environment to realize the degradation of the cellulose. A cellulose conversion of at least 90%; the yield of the product levulinic acid reaches 75 percent. The method is green and efficient, and the catalyst after reaction can be recycled and reused and still maintains higher activity. The method provides a new technical scheme for effectively utilizing cellulose to produce high value-added chemicals.

Description

A kind of method that cellulose catalytic degradation is converted into levulinic acid

technical field

The invention belongs to the technical field of biomass resource utilization, and in particular relates to a method for converting cellulose into levulinic acid by catalytic degradation.

Background technique

Cellulose, hemicellulose and lignin are the three main structural components in the vascular tissue of higher terrestrial plants. Among them, cellulose is the most widely distributed and most abundant polysaccharide in nature, accounting for more than 50% of the carbon content in the plant kingdom. Cellulose is a macromolecular polysaccharide composed of glucose.

The structure of cellulose is a homogeneous polymer in which glucose units are linearly connected by β-1,4 glycosidic bonds, and crystalline regions and amorphous regions can be formed between celluloses through the interaction of hydrogen bonds. Cellulose molecules are usually composed of several hundred to several thousand glucose units. Unbranched cellulose chains are tightly packed by interchain hydrogen bonds. Cellulose is an important structural component of the primary cell wall of green plants (many algae), and it is also the most widely distributed and most abundant polysaccharide in nature. Its content varies according to the woody biomass raw materials. Generally speaking Usually 30-50wt%, wherein the cellulose content of cotton fiber is 90%, the cellulose content of wood is 40-50%, and the cellulose content of dry hemp is about 45%. Cellulose has a high degree of polymerization and molecular weight, and is difficult to dissolve in water. At the same time, due to the existence of intermolecular hydrogen bonds, hydrophobic layers on the surface and van der Waals forces between crystal layers, the molecular chains of cellulose are arranged in a tight and orderly manner, which also causes cellulose to be insoluble in water and most organic solvents.

At present, domestic and foreign scholars have made great breakthroughs in cellulose research, which are mainly reflected in: (1) modern advanced analytical instruments have been widely used and played an important role in cellulose research; (2) biomass raw materials There has been some progress in the utilization of cellulose resources. Because of its definite structure and function, its degradation mechanism is easier to study than cellulose, which can provide a theoretical basis for the study of cellulose degradation mechanism. It aims to provide more reference and theoretical basis for the conversion of cellulose into high value-added chemicals and high-quality energy in the future.

酸作为催化剂。糠醇催化水解法是以糠醇为原料，糠醇在液体酸催化下，通过水解、开环、重排反应生成LA；生物质直接水解法是生物质原料中的纤维素首先生成单糖，单糖在酸的催化下脱水生成5-羟甲基糠醛(5-HMF)等化合物，其中5-HMF可进一步水解生成LA和甲酸。玉米等淀粉类、甘蔗汁等糖类及秸秆等纤维素类生物质都可作为生物质直接水解法的原料，但由于糖类及淀粉类生物质原料数量及经济性不能得到保障，因此木质纤维素类生物质被认为是生产LA的理想原料。纤维素生产LA包括纤维素解聚成单糖，单糖水解成5-HMF，5-HMF脱羧生成LA三步过程，过程复杂且副反应较多，限制了LA的产率，因此如何提高LA产率是近年来的主要研究内容。Levulinic acid (LA), also known as 4-oxopentanoic acid, fructonic acid or leuconic acid, etc., is a new type of green platform compound and a widely used fine chemical product in the production of medicines, fuels, pesticides, etc. , food, ink, fragrance, plasticizer, cosmetics, electronic products and fabric treatment have important uses, is a chemical intermediate capable of synthesizing liquid fuels and chemicals. At present, the production methods of LA are roughly divided into two categories, namely the catalytic hydrolysis of furfuryl alcohol and the direct hydrolysis of biomass.

acid as a catalyst. The furfuryl alcohol catalytic hydrolysis method uses furfuryl alcohol as raw material, and furfuryl alcohol is catalyzed by liquid acid to generate LA through hydrolysis, ring opening and rearrangement; Dehydration under the catalysis of acid generates compounds such as 5-hydroxymethylfurfural (5-HMF), of which 5-HMF can be further hydrolyzed to generate LA and formic acid. Starch such as corn, sugars such as sugarcane juice, and cellulosic biomass such as straw can be used as raw materials for the direct hydrolysis of biomass. Vegetarian biomass is considered as an ideal raw material for the production of LA. The production of LA from cellulose includes depolymerization of cellulose into monosaccharides, hydrolysis of monosaccharides to 5-HMF, and decarboxylation of 5-HMF to form LA. The process is complex and has many side reactions, which limit the yield of LA. Therefore, how to improve the yield of LA It is the main research content in recent years.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for converting cellulose into levulinic acid by catalytic degradation. The compound solvent system is adopted to provide a new technical route for effectively utilizing cellulose to produce high value-added chemicals.

Technical scheme: in order to solve the above problems, the technical scheme adopted in the present invention is as follows:

A method for converting cellulose into levulinic acid by catalytic degradation, adding cellulose into a reaction vessel containing a solvent, and reacting under the synergistic effect of Amberlyst15 and a composite solvent under a certain gas environment to realize the degradation of cellulose; The mass volume ratio of cellulose to solvent is 20mg/mL; the volume ratio of distilled water to polar aprotic solvent is 1:1; the solvent is any one of distilled water and tetrahydrofuran, dioxane, DMSO, GVL or sulfolane. The composite solvent; the reaction temperature is 180-220 ℃, and the reaction time is 2-4h.

The method for converting cellulose into levulinic acid by catalytic degradation, the cellulose is 20 μm microcrystalline cellulose.

In the method for converting cellulose into levulinic acid by catalytic degradation, the reaction temperature is 200° C. and the reaction time is 3 hours.

In the method for converting cellulose into levulinic acid by catalytic degradation, the mass ratio of cellulose to Amberlyst15 is 1:3.

In the method for converting cellulose into levulinic acid by catalytic degradation, the composite solvent system is distilled water and GVL.

In the method for the catalytic degradation of cellulose into levulinic acid, the gas environment is 4MPa nitrogen.

A method for catalyzing degradation of cellulose into levulinic acid, dissolving cellulose in a reaction vessel filled with distilled water and GVL, adding Amberlyst15, and reacting at 200° C. for 3 hours under a nitrogen atmosphere of 4 MPa, the cellulose and solvent are mixed together. The mass-volume ratio is 20 mg/mL, the mass ratio of cellulose to Amberlyst15 is 1:3, and the mass ratio of distilled water to GVL is 1:1; the conversion rate of cellulose is at least 90%, and the yield of levulinic acid is 75%.

Beneficial effects: Compared with the existing technology, the advantages of the present invention include:

(1) Compared with the current cellulose degradation method, the present invention can obtain high product yield under the synergistic effect of Amberlyst15 and composite solvent, and provides a new technical route for effectively utilizing cellulose to produce high value-added chemicals .

(2) The catalytic degradation system of the present invention directly degrades the unpretreated cellulose without any pretreatment of the cellulose, the operation method is simple, the reaction conditions are controllable, the degradation of the cellulose is achieved, and the obtained degradation The product can be used as an important high value-added platform compound.

(3) The solvent of the present invention is green and harmless, effectively reducing the toxicity of the reaction; and the catalyst can be recycled and still has high reactivity.

Description of drawings

Fig. 1 is the reaction process flow chart that embodiment 1 cellulose degradation is converted into levulinic acid;

Fig. 2 is that embodiment 7 is applied to the high performance liquid chromatography (HPLC) figure of reaction liquid of cellulose;

Fig. 3 is the infrared spectrogram of the solid residue after the reaction of Example 7 applied to cellulose.

Detailed ways

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below with reference to specific embodiments.

Product yield calculation method in the present invention: first, according to the standard sample of levulinic acid, draw the standard curve of levulinic acid by high-phase liquid chromatography (HPLC), then the peak area of the reaction solution at the corresponding peak position is in the standard Calculate the concentration of the available product on the curve, and then obtain the quality of the product levulinic acid, and the molar percentage of the product and the raw material is the yield of the product. The conversion rate is obtained by the percentage of the raw material to remove the solid residue from the original mass.

Example 1

The flow chart of the catalytic degradation of cellulose into levulinic acid is shown in Figure 1.

Dissolve 240 mg of cellulose raw material in an autoclave filled with 12 mL of distilled water, add 720 mg of Amberlyst15, and react at 180 °C for 3 h in an air environment. The reaction solution is filtered and centrifuged to obtain a supernatant, which is quantitatively characterized by HPLC. The test results show that when the solvent is distilled water, the conversion rate of cellulose is 71.29%, the yield of levulinic acid is 41.77%, and the degradation effect of catalyst Amberlyst15 is better.

Example 2

The method for catalyzing degradation of cellulose into levulinic acid is the same as that in Example 1, and the solvent is a composite solvent composed of distilled water and tetrahydrofuran, dioxane, DMSO, GVL or sulfolane in a volume ratio of 1:1.

The reaction solution was filtered and centrifuged to obtain a supernatant, which was quantitatively characterized by HPLC. The experimental results are shown in Table 1. Combined with the experimental results of Example 1, it can be seen from Table 1 that the water/tetrahydrofuran, water/dioxane, and water/GVL composite solvent systems can effectively improve the degradation level of cellulose, promote the generation of levulinic acid, and the intermediate products are also extremely low.

Product yield results in Example 2 of Table 1

Example 3

The method for catalytic degradation of cellulose into levulinic acid is the same as that in Example 1, the solvents are distilled water and GVL, and the reaction temperatures are 180, 200, and 220° C., respectively.

The reaction solution was filtered and centrifuged, and the obtained supernatant was quantitatively characterized by HPLC. The detection results are shown in Table 2. It can be seen from Table 2 that the change of reaction temperature has a great influence on the conversion rate and product yield. When the reaction temperature is 200°C, the conversion rate and product yield are the highest, which is the optimal reaction temperature.

Product yield result in the embodiment 3 of table 2

Example 4

The method for catalytic degradation of cellulose into levulinic acid is the same as that in Example 1, the solvent is distilled water and GVL, the reaction temperature is 200° C., and the reaction time is 2, 3 and 4 h, respectively.

The reaction solution was filtered and centrifuged, and the obtained supernatant was quantitatively characterized by HPLC. The detection results are shown in Table 3. It can be seen from Table 3 that the conversion rate of cellulose and the yield of levulinic acid will show a trend of first increase and then decrease with the increase of reaction time, and reach the maximum value when the reaction time is 3h, which are 83.54% and 65.09%, respectively. %.

Product yield result in the embodiment 4 of table 3

Example 5

The method for converting cellulose into levulinic acid by catalytic degradation is the same as that in Example 1, the solvent is distilled water and GVL, the reaction temperature is 200° C., and the gas environment is 4MPa nitrogen.

The reaction solution was filtered and centrifuged, and the obtained supernatant was quantitatively characterized by HPLC. The detection results showed that when the gas environment was 4MPa nitrogen, the conversion rate of cellulose was 97.17%, and the yield of levulinic acid was 75.69%. Under nitrogen pressure, the contact between cellulose and the composite solvent is enhanced, the association between reactants and protons is increased to enhance the reaction activity, and the carbon transition state in the acid-catalyzed reaction is stabilized, thereby improving the conversion rate of cellulose and the conversion of levulinic acid. Yield.

Example 6

The catalyst after the first reaction of the water/GVL composite solvent system in Example 2 was collected, washed with distilled water (5*10mL) and dried, and then used in the second catalytic reaction again, and the method was the same as in Example 2, The solvent is a composite solvent of distilled water and GVL. The conversion rate of cellulose can still reach 82.78%, and the yield of levulinic acid is both 58.74%, indicating that the catalyst of the present invention can be reused and still has high reactivity.

Example 7

The method for catalyzing degradation of cellulose into levulinic acid is the same as that in Example 1, and the solvents are distilled water and GVL.

The reaction solution was filtered and centrifuged, and quantitatively characterized by HPLC. The detection results are shown in Figure 2. It can be seen from Figure 2 that the components in the reaction solution can be separated by high performance liquid chromatography (each peak is relatively independent), wherein the retention time of 13.593min is formic acid (45.3%), and 14.691min is acetic acid (16.56%) , 15.303min is levulinic acid (51.52%), after 30min the peak is the solvent.

The obtained solid residue is subjected to infrared detection, and the detection result is shown in Figure 3. It can be seen from Figure 3 that the strong absorption peak of cellulose raw material -OH appears at 3500-3250 cm-1, mainly from the cellulose of biomass raw materials to form the basic glucose unit; the strong absorption peak at 3000-2750 cm-1 is mainly Stretching vibration of C—H bonds in methyl and methylene; strong absorption peaks at 1100-1000 cm-1 represent the stretching vibration of C—O, which are alkyl ethers and primary and secondary alcohols; in alkyl ethers and secondary alcohols The strong absorption peak of C—O stretching vibration appears at 1050cm-1.

Claims (7)

1. a method for converting cellulose catalytic degradation into levulinic acid, is characterized in that, cellulose is added in the reaction vessel that solvent is housed, under certain gas environment, reacts under the synergy of Amberlyst15 and composite solvent, Realize the degradation and conversion of cellulose; the mass-volume ratio of cellulose and solvent is 20 mg/mL, the volume ratio of distilled water and polar aprotic solvent is 1:1, and the solvent is water and tetrahydrofuran, dioxane, DMSO, The composite solvent composed of either GVL or sulfolane has a reaction temperature of 180-220° C. and a reaction time of 2-4h. 2 . The method for converting cellulose into levulinic acid by catalytic degradation according to claim 1 , wherein the cellulose is 20 μm microcrystalline cellulose. 3 . 3 . The method for converting cellulose into levulinic acid by catalytic degradation according to claim 1 , wherein the reaction temperature is 200° C. and the reaction time is 3 h. 4 . 4. The method for converting cellulose catalytic degradation into levulinic acid according to claim 1, wherein the mass ratio of cellulose to Amberlyst15 is 1:3. 5. cellulose catalytic degradation according to claim 1 is converted into the method for levulinic acid, it is characterised in that the composite solvent system is distilled water and GVL. 6. The method for converting cellulose catalytic degradation into levulinic acid according to claim 1, wherein the gas environment is 4MPa nitrogen. 7. cellulose catalytic degradation according to claim 1 is converted into the method for levulinic acid, it is characterized in that, get cellulose and be dissolved in the reaction vessel that distilled water and GVL are housed, add Amberlyst15, under 4MPa nitrogen environment, in Reaction at 200°C for 3h, the mass volume ratio of cellulose to solvent is 20mg/mL, the mass ratio of cellulose to Amberlyst15 is 1:3, the volume ratio of distilled water to GVL is 1:1; the conversion rate of cellulose is at least 90% , the yield of levulinic acid was 75%.

Images