CN101792495A - Method for ultrasonically catalyzing and extracting hemicellulose, cellulose and lignin from plant straws - Google Patents

Abstract

The invention discloses a method for ultrasonically catalyzing and extracting hemicellulose, cellulose and lignin from plant straws. The method comprises the following steps of: (1) airing plant straws and then mechanically crushing, collecting plant straw powder, fully drying and removing moisture; (2) dispersing the dried plant straw powder into a water solution and then carrying out ultrasonic treatment, dissolving the hemicellulose into the water solution, then separating the water solution, and carrying out photocatalytic decomposition on the separated plant straw residuals by taking nano Fe3O4-TiO2 as a photocatalyst with a core-shell structure; (3) separating and extracting lignin from the residuals subjected to the photocatalytic decomposition by using an organic solvent in an extraction way, wherein the extracted residuals are a mixture of the cellulose and the photocatalyst; and (4) putting the extracted residuals under a magnetic field to separate the cellulose from the photocatalyst to obtain the cellulose. The invention successfully realizes the separation and the full utilization of the hemicellulose, the cellulose and the lignin in the plant straws and improves the utilization ratio of renewable resources.

Description

Method for Ultrasonic Catalytic Extraction of Hemicellulose, Cellulose and Lignin from Plant Straw

Technical field:

The invention relates to a method for ultrasonically catalyzing and extracting hemicellulose, cellulose and lignin from plant straws. The invention belongs to a pretreatment method of organic chemical plant stalks.

Background technique

It is becoming increasingly apparent that we face an unprecedented challenge to meet growing energy demands and protect the environment. Naturally attracting attention as the planet's premier and yearly renewable plant fiber resource. Plant fiber resources mainly include crop straw and forestry waste. The amount of straw raw materials produced in my country every year is huge, and it is estimated that there are as many as one billion tons. Most of these resources are not used efficiently, and converting plant fibers into industrial products represents a sustainable way to meet the growing demand for fuel and chemical products, especially in view of the limited supply of mineral resources, and the dwindling oil resources. and concern for the environment.

At present, it is still a difficult problem to efficiently extract these three main chemical components from plant fibers as high-value-added raw materials. This is due to the complex chemical structure of plant fibers and the difficulty in technologically obtaining sufficient yield and commercial value of products. For example, in the paper industry, the value of hemicellulose and lignin is not fully utilized, and only about 40% of the material is recovered in a usable form. Many separation processes for lignocellulosic feedstock used to produce cellulosic ethanol ignore other possible uses of lignin and instead suggest incinerating it for heat recovery. These modes of producing a single bulk product, due to the lack of full utilization of plant fiber raw materials, result in low economic benefits, thereby limiting the development of related industries. Biorefining is similar to petroleum refining. It is a process of comprehensively utilizing various components of plant fiber raw materials. Through processing, grading and transforming plant fiber raw materials to produce a series of high value-added products, biorefining is a promising way to make the plant fiber industry more commercially attractive. However, for a long time, the traditional plant fiber extraction method generally adopts strong acid and strong alkali process, which not only consumes high energy, causes large pollution, but also has low extraction rate, resulting in a serious waste of resources. Therefore, it is necessary to establish a process that is easy to industrialize. Separating the three main components of plant fibers, minimizing the degradation of hemicellulose and lignin, and recycling them in useful forms has become a hot spot in the research of comprehensive utilization of plant fibers at home and abroad.

The main components of plant straw are mainly composed of three components: cellulose, hemicellulose and lignin. A complex of cross-linked hemicellulose and lignin glues the cellulose fibers together to form a composite material, lignocellulose. Generally, there are two main methods for separating the three main components of plant fibers: biological method and chemical method. The biological method mainly uses cellulase to convert fiber raw materials into usable sugars, which are further used to produce lactic acid and other products. However, due to the slow hydrolysis speed and low efficiency of enzymatic hydrolysis, which are restricted by various factors, the cost of enzymatic hydrolysis is too high, thus hindering the industrial scale of cellulase hydrolysis of plant fiber materials. The chemical method is to use certain chemical reagents to treat plant fibers under certain conditions, and use the differences in chemical properties of the three main components of plant fibers to gradually separate them. However, these methods generally require high temperature and high pressure, harsh reaction and extraction conditions, and the use of organic solvents is also likely to cause environmental pollution, which is not suitable for industrial promotion and production. Therefore, to make full use of the three main components in plant fibers, especially to meet the standards of medicinal or food additives, it is necessary to research and develop a pollution-free, low-consumption and high-efficiency separation technology and craft.

Contents of the invention

The object of the present invention is to provide a method for ultrasonically catalytically extracting hemicellulose, cellulose and lignin from plant straws, which has simple production process, low cost, wide application range and is convenient for large-scale industrial production.

In order to achieve the above purpose, the present invention comprehensively utilizes the excellent properties of ultrasonic waves and nanometer _TiO2 . Ultrasound, as a method of injecting energy at room temperature, has been widely used in the fields of physics, biology, and chemistry in recent years. Impact, shear, heat and free radicals generated by cavitation can degrade macromolecules. Some studies have shown that ultrasonic treatment of mixed office waste paper and kraft pulp has found that ultrasonic waves can open the crystallization area of cellulose, which can significantly change the morphology and ultrastructure of wood pulp fibers, which is helpful for improving the accessibility of cellulase. The degree and chemical reactivity are very favorable. In addition, under the irradiation of light with a certain energy, the photosensitive semiconductor nano TiO ₂ is excited to generate electron-hole pairs, and the water molecules adsorbed on the surface of the semiconductor accept the photogenerated electron-hole pairs, thus a series of redox reactions occur. The reaction can break the connection between lignin and cellulose, and also break the bonds inside cellulose, and the reaction process does not involve any chemicals that pollute the environment. The present invention develops a new method for extracting hemicellulose, cellulose and lignin from plant fibers on the basis of comprehensively utilizing the excellent properties of ultrasonic waves and nanometer _TiO2 .

The technical scheme that the present invention realizes its object to take is:

The method that the present invention extracts hemicellulose from plant stalk ultrasonic catalysis mainly comprises the following steps:

(1) the plant stalk is dried first, then the plant stalk is mechanically pulverized, and the plant stalk powder is collected through a sieve, and the collected plant stalk powder is fully dried to remove moisture;

(2) Disperse the dried plant stalk powder in the aqueous solution and carry out ultrasonic treatment, so that the hemicellulose in the plant stalk is dissolved in the aqueous solution, and then the aqueous solution is separated, and the hemicellulose aqueous solution is collected, and the hemicellulose Drying of plain aqueous solution yielded hemicellulose solid.

Further, in the step (2) of the present invention, the pH of the aqueous solution used for the ultrasonic treatment is 4-10, the ultrasonic temperature is 30-50°C, the ultrasonic time is 20-60 minutes, and the ultrasonic power is 200 -800 watts, ultrasonic frequency is 20~25KHz.

Further, in the step (2) of the present invention, the drying treatment of the hemicellulose aqueous solution to obtain the hemicellulose solid is a freeze-drying method or a vacuum drying method.

The method for extracting lignin from plant straw ultrasonic catalysis of the present invention mainly comprises the following steps:

(1) the plant stalk is dried first, then the plant stalk is mechanically pulverized, and the plant stalk powder is collected through a sieve, and the collected plant stalk powder is fully dried to remove moisture;

(2) disperse the dried plant stalk powder in the aqueous solution and carry out ultrasonic treatment, so that the hemicellulose in the plant stalk is dissolved in the aqueous solution, and then the aqueous solution is separated, and the separated plant stalk residue is obtained with Nano-Fe ₃ O ₄ @TiO ₂ with "core-shell" structure is used as photocatalyst for photocatalytic decomposition;

(3) Separating and extracting lignin from the residue after photocatalytic decomposition by means of extraction with an organic solvent.

Further, in the step (2) of the present invention, the pH of the aqueous solution used for the ultrasonic treatment is 4-10, the ultrasonic temperature is 30-50°C, the ultrasonic time is 20-60 minutes, and the ultrasonic power is 200 -800 watts, ultrasonic frequency is 20~25KHz.

Further, in the step (2) of the present invention, the particle size of the nano-Fe ₃ O ₄ @TiO ₂ particles is 30-50nm; wherein, the nano-Fe ₃ O ₄ is the core, and the particle size of the nano-Fe ₃ O ₄ 20nm; TiO ₂ is the shell, the thickness of the TiO ₂ is 10-30nm.

Further, in the present invention, when performing the photocatalytic decomposition in step (2), the photocatalytic temperature is 20-50° C. and the time is 30-60 minutes.

The method for extracting cellulose from plant straw ultrasonic catalysis of the present invention mainly comprises the following steps:

(1) plant stalks are first dried, then plant stalks are mechanically crushed, plant stalk powders are collected, and the collected plant stalk powders are fully dried to remove moisture;

(2) disperse the dried plant stalk powder in the aqueous solution and carry out ultrasonic treatment, so that the hemicellulose in the plant stalk is dissolved in the aqueous solution, and then the aqueous solution is separated, and the separated plant stalk residue is obtained with Nano-Fe ₃ O ₄ @TiO ₂ with "core-shell" structure is used as photocatalyst for photocatalytic decomposition;

(3) Using an organic solvent to separate and extract lignin from the residue after photocatalytic decomposition, the residue after extraction is a mixture of cellulose and photocatalyst;

(4) Putting the extracted residue under a magnetic field to separate the cellulose from the photocatalyst to obtain cellulose.

Further, in the step (2) of the present invention, the pH of the aqueous solution used for the ultrasonic treatment is 4-10, the ultrasonic temperature is 30-50°C, the ultrasonic time is 20-60 minutes, and the ultrasonic power is 200 -800 watts, ultrasonic frequency is 20~25KHz.

Further, in the step (2) of the present invention, the particle size of the nano-Fe ₃ O ₄ @TiO ₂ particles is 30-50nm; wherein, the nano-Fe ₃ O ₄ is the core, and the particle size of the nano-Fe ₃ O ₄ 20nm; TiO ₂ is the shell, the thickness of the TiO ₂ is 10-30nm.

The plant stalk used in the present invention can be any one or two or more of corn stalks, sorghum stalks, wheat stalks, rice stalks, rape stalks and sawdust.

The present invention can use 200-400 mesh sieves to collect and obtain plant straw powder.

When the present invention separates and extracts the lignin from the residue after photocatalytic decomposition by means of extraction, the organic solvent used can be methanol, ethanol, ethylene glycol, propylene glycol, butanediol, phenols, ketones , tetrahydrofuran, and benzene-based solutions, or any two or more of them.

In the present invention, when the separated plant straw residue is photocatalytically decomposed using nano Fe ₃ O ₄ @TiO ₂ with a "core-shell" structure as a photocatalyst, the light used can be a high-pressure light with a wavelength of 365nm Mercury lamp.

Compared with prior art, the advantage of the present invention is:

(1) The present invention greatly reduces the possibility of environmental pollution due to the adoption of ultrasonic and catalytic technologies;

(2) The present invention successfully realizes the separation of hemicellulose, cellulose and lignin in the plant straw, and makes full use of each, further improving the utilization rate of renewable resources.

(3) The method of the present invention is simple, can reduce cost and energy consumption, and is convenient for industrial scale production.

Description of drawings

Fig. 1 is a summary diagram of the technological process for extracting hemicellulose, cellulose and lignin from plant stalks by ultrasonic catalysis in the present invention.

Detailed ways

Example 1:

(1) First dry the corn stalks in the sun, then mechanically pulverize the corn stalks, collect the corn stalk powder through a 200-mesh sieve, and fully dry the collected corn stalk powders to remove moisture.

(2) Weigh 0.50 g of the collected dry corn stalk powder and disperse it in 40 mL of aqueous solution with pH=4 adjusted by 1 M HCl for ultrasonic treatment, and control the ultrasonic temperature at 30° C., and the ultrasonic time for 40 minutes, The ultrasonic power is 200 watts, the ultrasonic frequency is 20KHz, the hemicellulose in the corn stalk is dissolved in the aqueous solution, the hemicellulose aqueous solution is collected by separation, and the hemicellulose aqueous solution is freeze-dried to obtain 0.08 g of hemicellulose solid.

(3) the stalk residue obtained by separation in the previous step is treated with 10mg nano Fe ₃ O ₄ @TiO ₂ (wherein, nano Fe ₃ O ₄ is the nucleus, and the particle diameter of the nano Fe ₃ O ₄ is 20nm; TiO ₂ is the shell , the thickness of the TiO ₂ is 10nm) as a photocatalyst for photocatalytic decomposition (light wavelength is 365nm). The photocatalytic temperature is 50° C. and the time is 30 minutes.

(4) The residue after photocatalysis in the previous step was extracted with ethanol to separate and extract lignin, and 0.11 g of lignin was obtained after removing ethanol and drying.

(5) The residue after extraction is a mixture of cellulose and photocatalyst, which can be completely separated from the photocatalyst under a certain external magnetic field, and finally 0.30 g of cellulose is obtained by vacuum drying.

Example 2:

(1) After the wheat straw is dried in the sun, the wheat straw is mechanically pulverized, and the wheat straw powder is collected through a 200-mesh sieve, and the collected wheat straw powder is fully dried to remove moisture.

(2) Weigh 0.50 g of the collected dry wheat straw powder and disperse it in a certain 40 mL of water with pH=7 for ultrasonic treatment, and control the ultrasonic temperature at 40° C., ultrasonic time of 30 minutes, ultrasonic power of 200 watts, and ultrasonic frequency of 20 KHz, The hemicellulose in the wheat straw is dissolved in the aqueous solution, and the hemicellulose aqueous solution is collected by separation, and the hemicellulose aqueous solution is rotary evaporated to remove water, and then vacuum-dried to 0.06 g of hemicellulose solid.

(3) the stalk residue obtained by separation in the previous step is treated with 10mg nano Fe ₃ O ₄ @TiO ₂ (wherein, nano Fe ₃ O ₄ is the nucleus, and the particle diameter of the nano Fe ₃ O ₄ is 20nm; TiO ₂ is the shell , the thickness of the TiO ₂ is 10nm) as a photocatalyst for photocatalytic decomposition (light wavelength is 365nm). The photocatalytic temperature is 20° C. and the time is 30 minutes.

(4) The residue after the photocatalysis in the previous step was extracted with acetone to separate and extract the lignin, and 0.09 g of lignin was obtained after removing the acetone and drying.

(5) The residue after extraction is a mixture of cellulose and photocatalyst, which can be completely separated from the photocatalyst under a certain external magnetic field, and vacuum dried to finally obtain 0.31 g of cellulose.

Example 3:

(1) The rape straw is first dried in the sun, then the rape straw is mechanically pulverized, and the rape straw powder is collected through a 400-mesh sieve, and the collected rape straw powder is fully dried to remove water.

(2) Weigh 0.50 g of the collected dry rape stalk powder and disperse it in a certain 40 mL aqueous solution with a concentration of 1 M NaOH to adjust pH=10 for ultrasonic treatment, and control the ultrasonic temperature at 50 ° C, ultrasonic time for 20 minutes, ultrasonic With a power of 400 watts and an ultrasonic frequency of 25KHz, the hemicellulose in the rape straw is dissolved in the aqueous solution, the hemicellulose aqueous solution is collected by separation, and the hemicellulose aqueous solution is freeze-dried to obtain 0.11 g of hemicellulose solid.

(3) the stalk residue obtained by separation in the previous step is treated with 10mg nano Fe ₃ O ₄ @TiO ₂ (wherein, nano Fe ₃ O ₄ is the nucleus, and the particle diameter of the nano Fe ₃ O ₄ is 20nm; TiO ₂ is the shell , the thickness of the TiO ₂ is 20nm) as a photocatalyst for photocatalytic decomposition (light wavelength is 365nm). The photocatalytic temperature is 50° C. and the time is 60 minutes.

(4) The residue after the photocatalysis in the previous step was extracted with toluene to separate and extract the lignin, and 0.10 g of lignin was obtained after removing the toluene and drying.

(5) The residue after extraction is a mixture of cellulose and photocatalyst, which can be completely separated from the photocatalyst under a certain external magnetic field, and finally 0.27 g of cellulose is obtained by vacuum drying.

Example 4:

(1) First dry the corn stalks in the sun, then mechanically pulverize the plant stalks, and collect the corn stalk powder through a 400-mesh sieve, and fully dry the collected plant stalk powders to remove moisture.

(2) Weigh 0.50 g of the collected dry corn stalk powder and disperse it in a certain amount of 40mL water for ultrasonic treatment, and control the ultrasonic temperature at 50°C, ultrasonic time for 60 minutes, ultrasonic power of 500 watts, and ultrasonic frequency of 25KHz to make the corn stalk The hemicellulose in the rod is dissolved in the aqueous solution, and the hemicellulose aqueous solution is collected by separation, and the hemicellulose aqueous solution is freeze-dried to obtain 0.10 g of hemicellulose solid.

(3) the stalk residue obtained by separation in the previous step is treated with 10mg nano Fe ₃ O ₄ @TiO ₂ (wherein, nano Fe ₃ O ₄ is the nucleus, and the particle diameter of the nano Fe ₃ O ₄ is 20nm; TiO ₂ is the shell , the thickness of the TiO ₂ is 20nm) as a photocatalyst for photocatalytic decomposition (light wavelength is 365nm). The photocatalytic temperature is 20° C. and the time is 60 minutes.

(4) The lignin was separated and extracted from the residue after the photocatalysis in the previous step by extraction with tetrahydrofuran, and 0.12 g of lignin was obtained after removal of tetrahydrofuran and drying.

(5) The residue after extraction is a mixture of cellulose and photocatalyst, which can be completely separated from the photocatalyst under a certain magnetic field, and vacuum dried to finally obtain 0.25 g of cellulose.

Example 5:

(1) First dry the corn stalk and the sorghum stalk, then mechanically pulverize the plant stalk, and collect the corn stalk powder through a 400-mesh sieve, and fully dry the collected plant stalk powder to remove moisture.

(2) Weigh 0.25 g of the collected dry corn stalk and sorghum stalk powder respectively and disperse them in a certain 40 mL of water for ultrasonic treatment, and control the ultrasonic temperature at 50 ° C, ultrasonic time for 30 minutes, ultrasonic power of 800 watts, ultrasonic frequency 25KHz, the hemicellulose in the corn stalk was dissolved in the aqueous solution, and the hemicellulose aqueous solution was collected by separation, and the hemicellulose aqueous solution was rotary evaporated to remove water and then vacuum-dried to obtain 0.12 g of hemicellulose solid.

(3) the stalk residue obtained by separation in the previous step is treated with 10mg nano Fe ₃ O ₄ @TiO ₂ (wherein, nano Fe ₃ O ₄ is the nucleus, and the particle diameter of the nano Fe ₃ O ₄ is 20nm; TiO ₂ is the shell , the thickness of the TiO ₂ is 30nm) as a photocatalyst for photocatalytic decomposition (light wavelength is 365nm). The photocatalytic temperature is 20° C. and the time is 60 minutes.

(4) The residue after photocatalysis in the previous step was extracted with phenol to separate and extract lignin, and 0.14 g of lignin was obtained after removing phenol and drying.

(5) The residue after extraction is a mixture of cellulose and photocatalyst, which can be completely separated from the photocatalyst under a certain magnetic field, and vacuum dried to finally obtain 0.22 g of cellulose.

Claims (10)

1. the method from plant straw ultrasonically catalyzing and extracting hemicellulose is characterized in that comprising the steps:

(1) earlier the plant straw is dried, after with plant straw mechanical disintegration, and sift out and collect the plant stalk powder end, with collected plant stalk powder end thorough drying to remove moisture;

(2) dried plant stalk powder end is dispersed in carries out supersound process in the aqueous solution, hemicellulose in the plant straw is dissolved in the aqueous solution, separate the aqueous solution back, collects the hemicellulose aqueous solution wherein, and hemicellulose aqueous solution drying treatment is obtained the hemicellulose solid.

2. according to the described method of claim 1 from plant straw ultrasonically catalyzing and extracting hemicellulose, its feature in: in described step (2), the pH=4-10 of aqueous solutions employed when carrying out described supersound process, ultrasonic temperature is that 30-50 ℃, ultrasonic time are that 20-60 minute, ultrasonic power are that 200-800 watt, ultrasonic frequency are 20～25KHz.

3. according to the described method of claim 1 from plant straw ultrasonically catalyzing and extracting hemicellulose, its feature in: in step (2), describedly hemicellulose aqueous solution drying treatment obtained the hemicellulose solid be to use freeze-drying or boulton process.

4. the method from plant straw ultrasonically catalyzing extraction xylogen is characterized in that comprising the steps:

(1) earlier the plant straw is dried, after with plant straw mechanical disintegration, and sift out and collect the plant stalk powder end, with collected plant stalk powder end thorough drying to remove moisture;

(2) dried plant stalk powder end is dispersed in carries out supersound process in the aqueous solution, hemicellulose in the plant straw is dissolved in the aqueous solution, separate the aqueous solution back, and the plant straw residue that separation is obtained is to have the nanometer Fe of " nuclear-shell " structure ₃O ₄@TiO ₂Photocatalyst carries out photocatalysis Decomposition;

(3) residue after the photocatalysis Decomposition is with an organic solvent gone out wherein xylogen by extractive mode separation and Extraction.

5. according to the described method of extracting xylogen from plant straw ultrasonically catalyzing of claim 4, its feature in: in described step (2), the pH=4-10 of aqueous solutions employed when carrying out described supersound process, ultrasonic temperature is that 30-50 ℃, ultrasonic time are that 20-60 minute, ultrasonic power are that 200-800 watt, ultrasonic frequency are 20～25KHz.

6. according to the described method of claim 4, it is characterized in that from plant straw ultrasonically catalyzing extraction xylogen: in described step (2), nanometer Fe ₃O ₄@TiO ₂The particle diameter of particle is 30-50nm; Wherein, nanometer Fe ₃O ₄Be nuclear, this nanometer Fe ₃O ₄Particle diameter be 20nm; TiO ₂Be shell, this TiO ₂Thickness be 10-30nm.

7. extract the method for xylogen according to claim 4 is described from plant straw ultrasonically catalyzing, it is characterized in that: when carrying out described photocatalysis Decomposition in step (2), light-catalysed temperature is that 20-50 ℃, time are 30-60 minute.

8. one kind is extracted cellulosic method from plant straw ultrasonically catalyzing, it is characterized in that comprising the steps:

(1) earlier the plant straw is dried, after with plant straw mechanical disintegration, collect the plant stalk powder end, with collected plant stalk powder end thorough drying to remove moisture;

(2) dried plant stalk powder end is dispersed in carries out supersound process in the aqueous solution, hemicellulose in the plant straw is dissolved in the aqueous solution, separate the aqueous solution back, and the plant straw residue that separation is obtained is to have the nanometer Fe of " nuclear-shell " structure ₃O ₄@TiO ₂Photocatalyst carries out photocatalysis Decomposition;

(3) residue after the photocatalysis Decomposition is with an organic solvent gone out wherein xylogen by extractive mode separation and Extraction, the residue after the extracting is the mixture of Mierocrystalline cellulose and photocatalyst;

(4) residue after the extracting is placed Mierocrystalline cellulose is separated with photocatalyst, obtain Mierocrystalline cellulose.

9. extract cellulosic method according to claim 8 is described from plant straw ultrasonically catalyzing, its feature in: in described step (2), the pH=4-10 of aqueous solutions employed when carrying out described supersound process, ultrasonic temperature is that 30-50 ℃, ultrasonic time are that 20-60 minute, ultrasonic power are that 200-800 watt, ultrasonic frequency are 20～25KHz.

10. extract cellulosic method according to claim 8 is described from plant straw ultrasonically catalyzing, it is characterized in that: in described step (2), nanometer Fe ₃O ₄@TiO ₂The particle diameter of particle is 30-50nm; Wherein, nanometer Fe ₃O ₄Be nuclear, this nanometer Fe ₃O ₄Particle diameter be 20nm; TiO ₂Be shell, this TiO ₂Thickness be 10-30nm.

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