Preparation method of cello-oligosaccharide

Abstract

The invention discloses a preparation method of cellooligosaccharide, which is characterized by comprising the following steps: mixing lignocellulose biomass with an L molecular sieve, carrying out ball milling, adding a solvent for dissolving, carrying out solid-liquid separation on the L molecular sieve, and drying to obtain the cellooligosaccharide, the chemical composition of the L molecular sieve is as follows: 1 to 5 percent of K2O, 1.0 percent of Al2O3, 5 to 10 percent of SiO2 and 1 to 5 percent of H2O, and the L molecular sieve has a straight pore channel. The L molecular sieve prepared by the method can selectively shear glucosidic bonds of cellulose to prepare cello-oligosaccharide, is higher in catalytic efficiency, and can be repeatedly used; on one hand, a large amount of water or other solvents are not needed to participate in reaction, and the advantages of environment friendliness, low cost and the like are achieved; on the other hand, the original ecological lignocellulose biomass is directly used as a raw material, and the hydrogen bond is more efficiently destroyed and the hydrolysis is rapid by utilizing an intertwining structure of cellulose and lignin in the original ecological lignocellulose biomass.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass conversion and utilization, and specifically relates to a method for preparing cellooligosaccharides from lignocellulosic biomass or cellulose. Background Art

[0002] Cello-oligosaccharides are oligosaccharides formed by glucose linked by β-1,4 glycosidic bonds, with a degree of polymerization of 2-10. Cello-oligosaccharides have a variety of biological activities, including inducing plant disease resistance, promoting plant growth, and resisting stress; they also have physiological activities and functions such as lowering blood sugar and blood lipids, and regulating the balance of beneficial intestinal microorganisms. They can be used in the fields of biological pesticides, health foods, food additives, etc.

[0003] At present, cellooligosaccharides are generally prepared by hydrolysis of cellulose, mainly including chemical degradation and enzymatic degradation. Chemical degradation generally uses concentrated acid hydrolysis. Although the degradation efficiency is high, it has the disadvantages of harsh reaction conditions, difficult control, low product quality, high equipment requirements and environmental pollution. Enzymatic degradation is a mild method, but it has problems such as insufficient enzyme activity and low enzyme yield. Since lignocellulose is insoluble in water and most solvents, lignocellulose requires complex pre-treatment, long production cycle and high cost.

[0004] The reason why cellulose is difficult to degrade is that a large number of hydrogen bonds are formed between its sugar chains, resulting in high crystallinity and structural density; in addition, the cellulose in lignocellulosic biomass is also interlocked with lignin, hemicellulose, etc., which affects the contact of macromolecules such as enzymes, resulting in low hydrolysis efficiency. Ball milling is a method that can assist polysaccharide molecules to open some hydrogen bonds and reduce crystallinity, but it cannot degrade polysaccharide chains to prepare oligosaccharides; it is mostly used as an auxiliary tool and used in conjunction with other polysaccharide hydrolysis methods, such as ball milling before enzymatic hydrolysis to improve the enzyme hydrolysis efficiency. Despite this, the efficiency of cellulose hydrolysis to prepare cellooligosaccharides still needs to be improved and currently cannot meet production needs. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing cellooligosaccharides to solve the technical problem of low efficiency in preparing cellooligosaccharides by hydrolysis of cellulose in the prior art.

[0006] To achieve the above object, the present invention provides a method for preparing cellooligosaccharides, comprising the following steps: mixing lignocellulosic biomass with L molecular sieve, grinding with ball mill, adding solvent to dissolve, separating the L molecular sieve from solid and liquid, and drying to obtain cellooligosaccharides.

[0007] Preferably, the lignocellulosic biomass includes wood, bamboo, and crop straw.

[0008] Preferably, the mass ratio of the lignocellulosic biomass to the L molecular sieve is 20:1 to 1:1; the mass ratio of cellulose in the lignocellulosic biomass to the L molecular sieve is 10:1 to 1:1.

[0009] Preferably, the ball milling beads used in ball milling are one or more of zirconia ball milling beads, alumina ball milling beads, and agate ball milling beads; the diameter of the ball milling beads is 1 to 10 mm; the mass ratio of the lignocellulosic biomass to the ball milling beads is 1:1 to 1:20.

[0010] Preferably, the ball milling time is 1 to 10 hours, the grinding speed is 100 to 1000 rpm; the temperature is maintained at 25 to 60°C; the solvent is water, and the amount of water added is 2 to 10 times the mass of the chitin biomass; the solid-liquid separation method includes centrifugation and filtration; the drying method includes rotary evaporation drying, spray drying, and oven drying.

[0011] The invention provides an L molecular sieve, whose chemical composition is: xK2O·1.0Al2O3·ySiO2·zH2O, and has straight pores; wherein x ranges from 1 to 5; y ranges from 5 to 10; and z ranges from 1 to 5.

[0012] Preferably, the straight pore size is 0.71 nm, and the topological structure is LTL L-type zeolite molecular sieve.

[0013] The invention provides a method for preparing L molecular sieve, which is characterized by taking a silicon source and a potassium source, mixing them and grinding them for the first time, then adding an aluminum source and grinding them for the second time, crystallizing at 150-200° C., and directly calcining at 400-600° C. in an air atmosphere to obtain the L molecular sieve.

[0014] Preferably, the molar ratio of silicon source: potassium source: aluminum source is 5-20:1-10:0.1-2.0; the first grinding time is 10-120 minutes, and the second grinding time is 5-60 minutes; the crystallization time is 4-24 hours; the calcination time is 1-5 hours; the silicon source is one or a mixture of fumed silica, potassium silicate, and sodium silicate; the potassium source is one or a mixture of potassium hydroxide and potassium bromide; the aluminum source is one or a mixture of aluminum hydroxide, sodium aluminate, and aluminum sulfate.

[0015] The present invention provides an application of an L molecular sieve for preparing a catalyst for cellooligosaccharides.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] Based on a large number of experiments, this patent has developed an L molecular sieve with straight pores, and the size of the pores just matches the size of the cellulose sugar chain, which can selectively shear the glycosidic bonds of cellulose to prepare cello-oligosaccharides; based on the solid structure characteristics of the molecular sieve, combined with the ball milling method, this patent has developed a technology that uses L molecular sieve as a catalyst to ball-mill lignocellulosic biomass or cellulose with L molecular sieve, which can efficiently prepare cello-oligosaccharides, not only with higher catalytic efficiency, but also reusable. On the one hand, this technical solution does not require a large amount of water or other solvents to participate in the reaction, and has the advantages of being environmentally friendly and low cost; on the other hand, the present invention uses native lignocellulosic biomass directly as raw material, and utilizes the intertwined structure of cellulose and lignin in the native lignocellulosic biomass to more efficiently destroy hydrogen bonds and quickly hydrolyze. Compared with existing reports, the technology described in this patent has obvious advantages and is more conducive to industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The XRD pattern of the L molecular sieve prepared by the present invention;

[0019] Figure 2 The mass spectrum of cellooligosaccharides obtained by ball-milling cellulose with the L molecular sieve prepared in the present invention;

[0020] Figure 3 This is the XRD diagram of L molecular sieve prepared by the hydrothermal method in the prior art. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0022] The instruments, reagents, materials, etc. involved in the following examples, unless otherwise specified, are all conventional instruments, reagents, materials, etc. in the prior art and can be obtained through regular commercial channels. The experimental methods, detection methods, etc. involved in the following examples, unless otherwise specified, are all conventional experimental methods, detection methods, etc. in the prior art.

[0023] The invention discloses a method for preparing cellooligosaccharides, comprising the following steps: mixing lignocellulosic biomass or cellulose with L molecular sieve, adding ball milling beads, grinding with a ball mill, adding water to dissolve the cellooligosaccharides, separating the molecular sieve from the solid and liquid, and drying the solution to obtain the cellooligosaccharides.

[0024] Wherein, the lignocellulosic biomass is wood, bamboo, crop straw; the mass ratio of lignocellulosic biomass to molecular sieve is 20:1 to 1:1. The mass ratio of cellulose to molecular sieve is 10:1 to 1:1; the ball milling beads are zirconia ball milling beads, alumina ball milling beads and / or agate ball milling beads; the diameter of the ball milling beads is 1 to 10 mm; the amount of ball milling beads added is: the mass ratio of lignocellulosic biomass and / or cellulose to ball milling beads is 1:1 to 1:20; the ball mill grinding time is 1 to 10 hours, preferably 1 to 4 hours; the grinding speed is 100 rpm-1000 rpm; the temperature is maintained at 25°C to 60°C, preferably 30°C to 40°C; the amount of water added is 2-10 times the mass of lignocellulosic biomass and / or cellulose.

[0025] The solid-liquid separation method includes centrifugation at 5000 rpm and filtration; the drying method includes rotary evaporation drying, spray drying and oven drying.

[0026] The degree of polymerization of the cellooligosaccharide is 2-10.

[0027] The preparation method of L molecular sieve of the present invention comprises the following steps: taking silicon source and potassium source, grinding them for the first time after mixing, adding aluminum source, grinding them for the second time, crystallizing at 150-200° C., and calcining them directly at 400-600° C. in air atmosphere to obtain L molecular sieve.

[0028] Among them, the molar ratio of silicon source: potassium source: aluminum source is 5-20:1-10:0.1-2.0; the first grinding time is 10-120 minutes, and the second grinding time is 5-60 minutes; the crystallization time is 4-24 hours; the calcination time is 1-5 hours; the silicon source is one or a mixture of fumed silica, potassium silicate, and sodium silicate; the potassium source is one or a mixture of potassium hydroxide and potassium bromide; the aluminum source is one or a mixture of aluminum hydroxide, sodium aluminate, and aluminum sulfate.

[0029] The chemical composition of the L molecular sieve of the present invention is: xK2O·1.0Al2O3·ySiO2·zH2O, with straight channels; wherein x ranges from 1 to 5; y ranges from 5 to 10; z ranges from 1 to 5; the pore size of the straight channels is 0.71 nm, and the topological structure is LTL, an L-type zeolite molecular sieve.

[0030] Example 1: Preparation of L molecular sieve by solvent-free method

[0031] Weigh 3.60g of fumed silica and 3.366g of potassium hydroxide as solid raw materials, pour them into a mortar and grind for 10 minutes, then add 0.468g of aluminum hydroxide and grind for another 5 minutes, add the reaction raw materials into a polytetrafluoroethylene stainless steel reactor, crystallize at 170°C for 24h, and the obtained product does not need to be filtered or washed, but is directly calcined at 550°C for 4h in an air atmosphere to obtain the final L molecular sieve. The ratio of the reaction raw materials is as follows:

[0032] 10K2O:1Al2O3:20SiO2.

[0033] X-ray diffraction analysis showed that the structure was L zeolite molecular sieve. Figure 1 The XRD pattern synthesized by this method is consistent with the typical XRD peaks of L molecular sieve.

[0034] By adding different amounts of aluminum hydroxide, L molecular sieves with different Si / Al ratios can be prepared, for example: L molecular sieve with Si / Al=2.5, L molecular sieve with Si / Al=5, and L molecular sieve with Si / Al=20.

[0035] Preparation of cellooligosaccharides by ball-milling and hydrolyzing cellulose using L molecular sieve prepared by the present invention

[0036] Add 2.0g of cellulose, different masses of solid catalysts (L molecular sieves with different Si / Al, activated carbon, oxidized activated carbon, ZSM-5 molecular sieves with Si / Al=10, Hβ molecular sieves with Si / Al=10, nano-silica), 10.0g of zirconium oxide ball milling beads (Ф=5mm), and 0.2g of water to the ball milling jar of the high-energy planetary ball mill F-P2000, and mill for different times at 500rpm and 1000rpm; the temperature of the ball milling chamber is controlled at 40℃. After the ball milling, add 50.0mL of water, stir at 200rpm for 30min, filter, and rotary evaporate the filtrate to dry to obtain cellooligosaccharides. The cellooligosaccharide yield is calculated based on the mass of cellulose added; the product is analyzed by ESI-MS to analyze the degree of polymerization of cellooligosaccharides.

[0037] Table 1. Preparation of cellooligosaccharides by ball-milling hydrolysis of cellulose using different solid catalysts

[0038]

[0039]

[0040] Preparation of cello-oligosaccharides by ball-milling hydrolysis of wood cellulose using L molecular sieve prepared by the present invention

[0041] Add 8.0g of dry poplar wood powder (including 43.7% cellulose by mass), solid catalysts of different masses (L molecular sieves with different Si / Al, activated carbon, oxidized activated carbon, ZSM-5 molecular sieves with Si / Al=10, Hβ molecular sieves with Si / Al=10, nano-silica), 10.0g of zirconium oxide ball milling beads (Ф=5mm), and 0.2g of water into the ball milling jar of the high-energy planetary ball mill F-P2000, and mill for different times at 500rpm and 1000rpm; the temperature of the ball milling chamber is controlled at 40°C. After the ball milling, add 50.0mL of water, stir at 200rpm for 30min, filter, and rotary evaporate the filtrate to dry to obtain cellooligosaccharides. Calculate the yield of cellooligosaccharides based on the mass of cellulose added; perform ESI-MS analysis on the product to analyze the degree of polymerization of cellooligosaccharides.

[0042] Table 2. Preparation of cello-oligosaccharides by ball-milling hydrolysis of lignocellulose using different solid catalysts

[0043]

[0044]

[0045] Preparation of cellooligosaccharides by ball-milling and hydrolyzing straw using L molecular sieve prepared by the present invention

[0046] 8.0 g of dry wheat straw (including 37.5% cellulose by mass), solid catalysts of different masses (L molecular sieves with different Si / Al, activated carbon, oxidized activated carbon, ZSM-5 molecular sieves with Si / Al=10, Hβ molecular sieves with Si / Al=10, nano-silica), 10.0 g of zirconium oxide ball milling beads (Ф=5 mm), and 0.2 g of water were added to the ball milling jar of the high-energy planetary ball mill F-P2000, and ball milled at 500 rpm and 1000 rpm for different times; the temperature of the ball milling chamber was controlled at 40°C. After the ball milling, 50.0 mL of water was added, stirred at 200 rpm for 30 min, filtered, and the filtrate was rotary evaporated and dried to obtain cellooligosaccharides. The cellooligosaccharide yield was calculated based on the mass of cellulose added; the product was analyzed by ESI-MS to analyze the degree of polymerization of cellooligosaccharides.

[0047] Table 3. Preparation of cellooligosaccharides by ball milling and hydrolysis of straw using different solid catalysts

[0048]

[0049]

[0050] Life experiment of preparing cellooligosaccharides by ball-milling and hydrolyzing cellulose with L molecular sieve prepared by the present invention

[0051] Add 2.0g cellulose, 0.4g L molecular sieve with Si / Al of 10, 10.0g zirconium oxide ball milling beads (Ф=5mm), and 0.2g water to the ball milling jar of high-energy planetary ball mill F-P2000, and ball mill for 2h at 500rpm; the temperature of the ball milling chamber is controlled at 40℃. After the ball milling, add 50.0mL water, stir at 200rpm for 30min, filter, and rotary evaporate the filtrate to obtain cello-oligosaccharides. The yield of cello-oligosaccharides is 85.4% based on the mass of cellulose added; the L molecular sieve obtained by filtration is repeatedly used in the above process four times, and the yields of cello-oligosaccharides are 85.7%, 84.9%, 83.5% and 83.8% respectively, indicating that the catalyst activity has not decreased significantly and can be reused. The product is analyzed by ESI-MS, and the degree of polymerization of cello-oligosaccharides is 2-10.

[0052] It can be seen from the above examples that L molecular sieves with different Si / Al can efficiently hydrolyze cellulose and lignocellulose biomass to prepare cello-oligosaccharides under different ball milling parameters, and the degree of polymerization is 2-10; other solid acid catalysts, including ZSM-5 molecular sieve, Hβ molecular sieve, activated carbon, oxidized activated carbon and nano-silica, can also catalyze the hydrolysis of cellulose to prepare cello-oligosaccharides, but the efficiency is not high, and the degree of polymerization of oligosaccharides is either low or contains monosaccharides, which affects the quality of cello-oligosaccharides. The L molecular sieve ball milling catalyzed cellulose and lignocellulose biomass to prepare cello-oligosaccharides has significant technical advantages.

[0053] Comparative Example:

[0054] Compared with the traditional hydrothermal method for synthesizing L molecular sieve:

[0055] According to the reference (Catalysts 2019,9,1073; doi:10.3390 / catal9121073), L molecular sieve was prepared by traditional hydrothermal method. The specific synthesis process is as follows:

[0056] Weigh 3.018g potassium hydroxide and 1.442g aluminum sulfate, pour them into a beaker filled with 18.208g deionized water, stir at room temperature for 10 minutes to form a slightly turbid solution, namely liquid A; weigh 6.875g HS-40 silica sol, pour it into a beaker filled with 9.958g deionized water, stir at room temperature for 5 minutes, namely liquid B; add liquid B dropwise into liquid A and stir well for 10 minutes to obtain liquid C, which is transferred to a polytetrafluoroethylene stainless steel reactor and crystallized at 180°C for 72 hours. The obtained product is washed with deionized water until neutral and dried, and then calcined at 480°C for 4 hours in an air atmosphere to obtain the final L molecular sieve.

[0057] The ratio of the reaction materials is as follows:

[0058] 10K2O:1Al2O3:20SiO2:800H2O.

[0059] X-ray diffraction analysis showed that the structure was L zeolite molecular sieve. Figure 3 The XRD pattern synthesized by this method is consistent with the typical XRD peaks of L molecular sieve.

[0060] Table 4 shows the pyridine-infrared analysis characterization results of L molecular sieves synthesized by solvent-free method and traditional hydrothermal method. Compared with L molecular sieves synthesized by traditional hydrothermal method, L molecular sieves synthesized by solvent-free method in the present invention contain higher Lewis acid / The acid ratio is 5.961, which is significantly higher than 0.86 prepared by traditional hydrothermal method.

[0061] Table 4. Pyridine-IR analysis characterization results of L molecular sieves prepared by traditional hydrothermal method and solvent-free method

[0062]

[0063] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing cellooligosaccharides, characterized in that: The following steps are involved: The lignocellulosic biomass is mixed with L molecular sieve, ball-milled, and then dissolved in a solvent, and then the L molecular sieve is separated from the solid and liquid, and dried to obtain cellooligosaccharides.

2. The method for preparing cellooligosaccharides according to claim 1, characterized in that: The lignocellulosic biomass includes wood, bamboo, and crop straw.

3. The method for preparing cellooligosaccharides according to claim 1, characterized in that: The mass ratio of the lignocellulosic biomass to the L molecular sieve is 20:1 to 1:1; the mass ratio of cellulose in the lignocellulosic biomass to the L molecular sieve is 10:1 to 1:

1.

4. The method for preparing cellooligosaccharides according to claim 1, characterized in that: The ball milling beads used in ball milling are one or more of zirconium oxide ball milling beads, aluminum oxide ball milling beads and agate ball milling beads; the diameter of the ball milling beads is 1 to 10 mm; the mass ratio of the lignocellulosic biomass to the ball milling beads is 1:1 to 1:

20.

5. The method for preparing cellooligosaccharides according to claim 1, characterized in that: The ball milling time is 1 to 10 hours, the grinding speed is 100 to 1000 rpm; the temperature is maintained at 25 to 60° C.; the solvent is water, and the amount of water added is 2 to 10 times the mass of the chitin biomass; the solid-liquid separation method includes centrifugation and filtration; the drying method includes rotary evaporation drying, spray drying, and oven drying.

6. An L molecular sieve, characterized in that Its chemical composition is: xK2O·1.0Al2O3·ySiO2·zH2O, with straight channels; wherein x ranges from 1 to 5; y ranges from 5 to 10; and z ranges from 1 to 5.

7. The L molecular sieve according to claim 6, characterized in that The straight pores have a pore size of 0.71 nm and a topological structure of an LTL L-type zeolite molecular sieve.

8. A method for preparing L molecular sieve, characterized in that: The following steps are involved: Take a silicon source and a potassium source, mix them and grind them for the first time, then add an aluminum source and grind them for the second time, crystallize at 150-200° C., and calcine at 400-600° C. in an air atmosphere to obtain the product.

9. The method for preparing L molecular sieve according to claim 8, characterized in that: The molar ratio of silicon source: potassium source: aluminum source is 5-20:1-10:0.1-2.0; the first grinding time is 10-120 minutes, and the second grinding time is 5-60 minutes; the crystallization time is 4-24 hours; the calcination time is 1-5 hours; the silicon source is one or a mixture of fumed silica, potassium silicate, and sodium silicate; the potassium source is one or a mixture of potassium hydroxide and potassium bromide; the aluminum source is one or a mixture of aluminum hydroxide, sodium aluminate, and aluminum sulfate.

10. Use of the L molecular sieve according to any one of claims 6 to 9, characterized in that: Catalysts for the preparation of cellooligosaccharides.

Images