Method for preparing aromatic compound by depolymerizing lignin
阅读说明：本技术 一种解聚木质素制备芳香族化合物的方法 (Method for preparing aromatic compound by depolymerizing lignin ) 是由 李志礼 张九冰 葛圆圆 于 2021-08-31 设计创作，主要内容包括：本发明公开了一种木质素解聚制备芳香族化合物的方法,包含以下操作步骤：(1)制备无定形地质聚合物催化剂；(2)取步骤(1)加入木质素、溶剂到反应釜中,混合均匀,置换空气,密封反应釜；(3)加热解聚,解聚结束后,温度降至室温,取出反应釜,对釜内混合物进行固液分离,即得含有芳香族化合物的液体产物。本发明方法既能够有效的利用制浆造纸过程中产生的木质素废弃物,及其他工业废弃物偏高岭土、矿渣等,将其制备成无定形地质聚合物催化剂,达到可持续利用；同时,使用的催化剂用量少,得到的产品性能好,将制备所得产品应用在木质素解聚领域,以获得成本低廉、绿色环保的解聚方法。(The invention discloses a method for preparing aromatic compounds by depolymerizing lignin, which comprises the following operation steps: (1) preparing an amorphous geopolymer catalyst; (2) adding lignin and a solvent into the reaction kettle obtained in the step (1), uniformly mixing, replacing air, and sealing the reaction kettle; (3) heating for depolymerization, cooling to room temperature after deagglomeration, taking out the reaction kettle, and performing solid-liquid separation on the mixture in the kettle to obtain a liquid product containing aromatic compounds. The method can effectively utilize lignin waste generated in the pulping and papermaking process and other industrial waste metakaolin, slag and the like to prepare the amorphous geopolymer catalyst so as to achieve sustainable utilization; meanwhile, the used catalyst is less in dosage, the obtained product has good performance, and the prepared product is applied to the field of lignin depolymerization so as to obtain a low-cost, green and environment-friendly depolymerization method.)
1. A method for preparing aromatic compounds by depolymerizing lignin is characterized by comprising the following operation steps:
(1) preparing an amorphous geopolymer catalyst;
(2) adding the amorphous geopolymer catalyst prepared in the step (1), lignin and a solvent into a reaction kettle, uniformly mixing, replacing air, and sealing the reaction kettle; wherein the mass ratio of the added lignin to the amorphous geopolymer catalyst is 1-40: 1;
(3) and (3) heating the reaction kettle in the step (2) at a certain temperature for depolymerization, cooling to room temperature after the depolymerization, taking out the reaction kettle, and carrying out solid-liquid separation on the mixture in the kettle to obtain a liquid product containing the aromatic compound.
2. The method of claim 1, further comprising: the method for preparing the amorphous geopolymer catalyst in the step (1) comprises the steps of taking aluminosilicate powder, adding modified water glass and water, stirring and mixing uniformly to obtain mixed slurry, adding H into the mixed slurry2O2Stirring with sodium dodecyl sulfate, mixing, injecting film, maintaining and polishing to obtain the amorphous geopolymer catalyst.
3. The method of claim 2, further comprising: the quality of the modified water glass and waterThe weight ratio is 2-10:1, the modulus of the modified water glass is 1.0-2.4, and the modified water glass is one of industrial sodium water glass, potassium water glass, sodium silicate or potassium silicate; the aluminosilicate powder is one or two of metakaolin, slag, fly ash or red mud; the addition amount of the aluminosilicate powder is Na according to the molar ratio2O/Al2O3＝0.5～2.0，SiO2/Al2O3＝1.0～5.0。
4. The method of claim 2, further comprising: the stirring speed is 500-3000 r/min, and the time is 0.5-5 min; the curing temperature is 20-120 ℃, and the curing time is 12-96 hours.
5. The method of claim 2, further comprising: said H2O2And the addition amount of the sodium dodecyl sulfate is 0.1-2.0% and 0.1-2.0% of the mass of the mixed slurry respectively.
6. The method of claim 1, further comprising: the mass ratio of the lignin added in the step (2) to the amorphous geopolymer catalyst is 2: 1.
7. The method of claim 1, further comprising: in the step (2), the lignin is one of alkali lignin, lignosulfonate and organic solvent lignin; the solvent is organic solvent and/or water, the organic solvent is one of methanol, ethanol, isopropanol or acetone, and the water is pure water.
8. The method of claim 1, further comprising: the volume of the solvent added in the step (2) is 20-40% of the volume of the reaction kettle.
9. The method of claim 1, further comprising: in the step (3), the heating temperature is 200-300 ℃, and the heating time is 0.5-12 h.
10. The method of claim 1, further comprising: in the step (3), two methods are adopted for separation, when an organic solvent is used as a depolymerization reaction solvent, a reaction mixture is filtered by an organic filter membrane, solid-liquid separation is carried out, and the obtained solution is a liquid product containing the phenolic compound; when water or an organic solvent/water mixed solvent is used as a depolymerization reaction solvent, the reaction mixture is extracted by ethyl acetate, and the obtained extracted ethyl acetate phase is a liquid product obtained by depolymerization.
Technical Field
The invention relates to a preparation method of aromatic compounds, in particular to a method for preparing aromatic compounds by depolymerizing lignin.
Background
With the rapid development of economy in recent years, the energy crisis is increased by the excessive utilization of fossil resources, and the problems of environmental pollution, climate damage and the like caused by the excessive utilization are frequent. Excessive exploitation and use of fossil resources cause environmental pollution phenomena such as ozone layer destruction, global warming, ecological imbalance, and excessive discharge of harmful substances. Thus, the need to develop and utilize renewable clean resources is increasing. Biomass is an extremely abundant renewable organic carbon resource, well known as abundant, clean, renewable compared to fossil fuels, and is an important candidate for the production of high quality liquid fuels and high value-added chemicals.
Lignocellulose is the most abundant component in biomass and is mainly composed of cellulose, hemicellulose and lignin. In plants, lignin is the second most abundant organic substance next to cellulose, accounting for about 25% of the total content. About 5000 ten thousand tons of lignin byproducts are separated from plants every year in the pulping and papermaking industry, but until now, more than 95 percent of lignin is directly discharged into rivers as black liquor or is burnt after being concentrated, and is rarely effectively utilized. This not only pollutes the environment but also causes a serious waste of resources. In addition, lignin, as a major component of lignocellulose, has an energy density much higher than cellulose and hemicellulose. The carbon content of lignin molecules is higher than 60%, and the oxygen content is about 25% -28%, so that lignin is the highest energy storage component in biomass, and the lignin accounts for about 20% -30% of the total components of biomass and stores 35% -45% of energy. The O/C and H/C ratio of the lignin is low, and is respectively 0.32-0.46 and 1.1-1.3, so the lignin liquefied oil has higher compatibility with crude oil and has potential to be used as a petroleum alternative fuel.
Lignin is a three-dimensional amorphous organic polymer containing three basic structural units of p-hydroxyphenyl, guaiacol and syringyl. Which are linked by a condensed bond (e.g., 5-5, beta-beta, beta-5, and beta-1) and an ether bond (e.g., alpha-O-4, 5-O-4, and beta-O-4). Due to high oxygen content, complex structure and poor thermal stability, the direct utilization of lignin is limited, and the conversion utilization rate is low. How to improve the conversion utilization rate of the chemical, and producing high value-added chemicals are the problems which are continuously concerned by a plurality of researchers.
Based on the above considerations, researchers have developed a number of lignin depolymerization processes and techniques to convert lignin into aromatic compounds, such as aromatic and phenolic compounds, to increase its utilization. The development of the depolymerization technology combining pyrolysis, hydrogenolysis, catalytic fast pyrolysis, liquid phase depolymerization and the like is more and more rapid. The fast thermal cracking process is widely researched and reaches a small test stage, but the problem of unstable feeding is also generally existed in the reaction process, and due to the fact that lignin particles have very low melting points, the lignin particles are always melted and partially reacted at the joint of a feeder and a reactor, the feeding is unstable, and even pipeline blockage occurs; secondly, the fluidized bed layer is easy to lose the fluidized state due to the melting of lignin, and the reactor fails due to coking. The hydro-depolymerization of lignin can increase the oil yield on the one hand and the combustion value of the product on the other hand. Can be classified into homogeneous catalytic hydrogenolysis, heterogeneous catalytic hydrogenolysis, and electrocatalytic depolymerization. The homogeneous catalyst has poor thermal stability, incomplete depolymerization of the product, difficult separation and recovery of the homogeneous catalyst and higher cost. The yield of the monocyclic aromatic compounds subjected to electrocatalytic hydrogenation is very limited, and a plurality of limitations exist in practical application. Heterogeneous catalysts occupy an important position in the field of catalytic hydrogenolysis, which can improve the yield of phenolic compounds, but also face the difficulty of catalyst deactivation caused by coke generation.
In the lignin depolymerization method, a mild, economic and efficient depolymerization process and method are adopted, which is beneficial to reducing energy consumption, saving energy, protecting environment, improving the yield of liquid products and reducing the yield of solid insoluble substances.
Disclosure of Invention
Aiming at the technical problems, the invention provides a method for preparing aromatic compounds by depolymerizing lignin, which utilizes amorphous geopolymer as a heterogeneous catalyst, and catalytically depolymerizes lignin biomass by controlling reaction temperature, reaction time, catalyst addition amount and solvent volume to obtain aromatic compounds, especially phenolic compounds with high added values.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
a method for preparing aromatic compounds by depolymerizing lignin comprises the following operation steps:
(1) preparing an amorphous geopolymer catalyst;
(2) adding the amorphous geopolymer catalyst prepared in the step (1), lignin and a solvent into a polytetrafluoroethylene reaction kettle, uniformly mixing, replacing air with nitrogen, and sealing the reaction kettle; wherein the mass ratio of the added lignin to the amorphous geopolymer catalyst is 1-40: 1;
(3) and (3) heating the reaction kettle in the step (2) at a certain temperature for depolymerization, cooling to room temperature after the depolymerization, taking out the reaction kettle, and carrying out solid-liquid separation on the mixture in the kettle to obtain a liquid product containing the aromatic compound.
The method for preparing the amorphous geopolymer catalyst in the step (1) comprises the steps of taking aluminosilicate powder, adding modified water glass and deionized water, mechanically stirring and uniformly mixing to obtain mixed slurry, adding H into the mixed slurry2O2Mechanically stirring with sodium dodecyl sulfate (K12), mixing, injecting film, maintaining, and grinding to obtain amorphous geopolymer catalyst; wherein, the mould used for injecting the film is a cylinder or a cube with indefinite size.
The mass ratio of the modified water glass to the deionized water is 2-10:1, the modulus of the modified water glass is 1.0-2.4, and the modified water glass is one of industrial sodium water glass, potassium water glass, sodium silicate or potassium silicate; the aluminosilicate powder is one or two of metakaolin, slag, fly ash or red mud; the addition amount of the aluminosilicate powder is Na according to the molar ratio2O/Al2O3＝0.5～2.0，SiO2/Al2O3＝1.0～5.0。
Wherein the mechanical stirring speed is 500-3000 r/min, and the time is 0.5-5 min; the curing temperature is 20-120 ℃, and the curing time is 12-96 hours.
Wherein, the H2O2And the addition amount of the sodium dodecyl sulfate (K12) is 0.1-2.0% and 0.1-2.0% of the mass of the mixed slurry respectively.
Wherein the mass ratio of the lignin added in the step (2) to the amorphous geopolymer catalyst is 2: 1.
Wherein, the lignin in the step (2) is one of alkali lignin, lignosulfonate and organic solvent lignin.
Wherein, the solvent in the step (2) is organic solvent and/or water, the organic solvent is one of methanol, ethanol, isopropanol or acetone, and the water is pure water.
Wherein, the volume of the solvent added in the step (2) is 20-40% of the volume of the polytetrafluoroethylene reaction kettle.
Wherein, in the step (3), the heating temperature is 200-300 ℃, and the heating time is 0.5-12 h.
Wherein, the separation in the step (3) has two methods, when an organic solvent is used as a depolymerization reaction solvent, a reaction mixture is filtered by an organic filter membrane with the thickness of 0.22 μm, and solid-liquid separation is carried out, and the obtained solution is a liquid product containing the phenolic compound; when water or an organic solvent/water mixed solvent is used as a depolymerization reaction solvent, the reaction mixture is extracted by ethyl acetate, and the obtained extracted ethyl acetate phase is a liquid product obtained by depolymerization.
Compared with the prior art, the invention has the following beneficial effects:
the method can effectively utilize lignin waste generated in the pulping and papermaking process and other industrial waste metakaolin, slag and the like to prepare the amorphous geopolymer catalyst so as to achieve sustainable utilization; meanwhile, the used catalyst is less in dosage, the obtained product has good performance, and the prepared product is applied to the field of lignin depolymerization so as to obtain a low-cost, green and environment-friendly depolymerization method.
Drawings
FIG. 1 is a surface topography of a geopolymer catalyst prepared in step (1) of example 1 of the present invention; wherein A is a surface topography map enlarged by 200 μm, and B is a surface topography map enlarged by 500 μm.
FIG. 2 is a pore size distribution diagram (A) and an acidity distribution diagram (B) of the geopolymer catalyst prepared in step (1) of example 1 of the present invention.
FIG. 3 is a product total ion chromatogram of the catalytic depolymerization of alkali lignin with an amorphous geopolymer according to the present invention; wherein A is a total ion chromatogram with retention time within 20 min; b is total ion chromatogram with retention time of 20-50 min.
Figure 4 is a total ion chromatogram of the product of the catalytic depolymerization of alkali lignin with an amorphous geopolymer according to the present invention.
Figure 5 is a total ion flow chromatogram of the product of the catalytic depolymerization of alkali lignin with an amorphous geopolymer according to the present invention.
Figure 6 is a product quantification plot of the catalytic depolymerization of lignosulfonate by the amorphous geopolymer of the present invention.
Detailed Description
The following detailed description is to be read in connection with the accompanying drawings, but it is to be understood that the scope of the invention is not limited to the specific embodiments. The raw materials and reagents used in the examples were all commercially available unless otherwise specified.
The amorphous geopolymer catalyst prepared in the step (1) of the method has a silicon-aluminum ratio of Na2O/Al2O3＝0.5～2.0，SiO2/Al2O31.0 to 5.0, and a specific surface area of 5 to 200m2The pore diameter is 1 nm-1 mm.
The elemental compositions of the slag and metakaolin used in the examples are shown in table 1:
example 1
A method for preparing aromatic compounds by depolymerizing lignin comprises the following operation steps:
(1) preparation of amorphous geopolymer catalyst: uniformly mixing metakaolin and slag according to the mass ratio of 1:1 to obtain mixed powder, wherein the addition amount of the metakaolin and the slag is Na2O/Al2O3＝1.0，SiO2/Al2O3Mixing the components in a ratio of 4.0, wherein the mass ratio of the modified water glass to the deionized water is 8: 1, weighing modified sodium silicate with the modulus of 1.3 and deionized water, adding the weighed modified sodium silicate and deionized water into the obtained mixed powder, mechanically stirring the mixture for 1min at the rotating speed of 1000r/min, uniformly mixing the mixture to obtain mixed slurry, and adding H into the mixed slurry according to 0.1 percent of the mass of the mixed slurry2O2Adding K12 into the mixed slurry according to 0.1% of the mass of the mixed slurry, mechanically stirring for 1min at the rotating speed of 2000R/min, uniformly mixing, casting into a round plastic mold (R is 20mm), maintaining at 60 ℃ for 12h, grinding by using sand paper with the mesh number of 100, and mechanically cutting to obtain the amorphous geopolymer catalyst, wherein the surface topography of the obtained amorphous geopolymer catalyst is shown in figure 1, the pore size distribution diagram is shown in figure 2(A), and the acidity distribution 2(B) (the acidity of the catalyst is obtained by ammonia-temperature programmed desorption (NH3-TPD) test);
(2) taking the amorphous geopolymer catalyst obtained in the step (1), cutting the amorphous geopolymer catalyst into cuboid blocks with the length, width and height of 12mm multiplied by 6mm multiplied by 1mm, adding the cuboid blocks with the mass of 0.1g, 0.2g of alkali lignin and 16mL of methanol into a polytetrafluoroethylene reaction kettle with the volume of 50mL, uniformly mixing, replacing air with nitrogen, and sealing the reaction kettle;
(3) placing the reaction kettle in the step (2) in an electric heating constant-temperature air blast drying oven, heating for 2h for depolymerization at 280 ℃, taking out the reaction kettle after depolymerization is finished, cooling the temperature to room temperature, performing solid-liquid separation on the mixture in the kettle by using a polytetrafluoroethylene membrane with the diameter of 0.22 mu m, and obtaining filtrate, namely a liquid product containing the micromolecular compound aromatic compound; and evaporating the liquid product by using the solvent to remove the methanol to obtain the methanol-solvent-free bio-oil, wherein the bio-oil is a product containing aromatic compounds.
Performing qualitative analysis on the obtained liquid product containing the small molecular compound aromatic compound by using a gas chromatography-mass spectrometer to obtain a product distribution diagram and a product distribution table (figure 3 and table 2), selecting a monophenol compound with higher yield to perform quantitative analysis, performing standard curve drawing on ten phenol compounds, namely guaiacol, 4-ethyl guaiacol, 4-methyl guaiacol, 4-methoxyphenol, isoeugenol, 3-methyl guaiacol, 4-methyl guaiacol, 2, 6-dimethoxyphenol, 2, 6-dimethoxy-4-methylphenol and 2, 4-di-tert-butylphenol, by using an external standard method, testing a sample to be tested by using a gas chromatograph, and performing quantitative analysis to determine the yield of each monophenol and the total phenol yield; as shown in fig. 3 and table 2, fig. 3 is a total ion flow chromatogram of a methanol-based liquid product (a liquid product containing a small-molecular compound aromatic compound), and a product distribution obtained by analysis based on the chromatogram is shown in table 2. From table 2, it can be seen that the obtained depolymerization products are rich in variety, including guaiacol, 4-ethylguaiacol, isovanillin, 3, 4-dimethoxybenzyl alcohol and other aromatic compounds which can be utilized later, wherein the relative selectivity of guaiacol is as high as more than 40%.
Example 2
A method for preparing aromatic compounds by depolymerizing lignin comprises the following operation steps:
(1) preparation of amorphous geopolymer catalyst: uniformly mixing metakaolin and slag according to the mass ratio of 1:1 to obtain mixed powder, wherein the addition amount of the metakaolin and the slag is Na2O/Al2O3＝1.0，SiO2/Al2O3Mixing the components in a ratio of 4.0, wherein the mass ratio of the modified water glass to the deionized water is 8: 1, weighing modified sodium silicate with the modulus of 1.3 and deionized water, adding the weighed modified sodium silicate and deionized water into the obtained mixed powder, mechanically stirring the mixture for 1min at the rotating speed of 1000r/min, uniformly mixing the mixture to obtain mixed slurry, and adding H into the mixed slurry according to 0.1 percent of the mass of the mixed slurry2O2Adding K12 into the mixed slurry according to 0.1% of the mass of the mixed slurry, mechanically stirring at the rotating speed of 2000R/min for 1min, uniformly mixing, casting into a round plastic mold (R is 20mm), maintaining at 60 ℃ for 12h, grinding by using abrasive paper with the mesh number of 100, and mechanically cutting to obtain the amorphous geopolymer catalyst;
(2) taking the amorphous geopolymer catalyst obtained in the step (1), cutting the amorphous geopolymer catalyst into cuboid blocks with the length, width and height of 12mm multiplied by 6mm multiplied by 1mm, adding the cuboid blocks with the mass of 0.1g, 0.2g of alkali lignin and 16mL of pure water into a polytetrafluoroethylene reaction kettle with the volume of 50mL, uniformly mixing, replacing air with nitrogen, and sealing the reaction kettle;
(3) placing the reaction kettle in the step (2) in an electric heating constant temperature blast drying box, heating for 2h for depolymerization at 280 ℃, cooling to room temperature after depolymerization, taking out the reaction kettle, carrying out solid-liquid separation on the mixture in the kettle, namely acidifying the mixture in the kettle by hydrochloric acid solution with the volume concentration of 37% to ensure that the pH value of the mixture in the kettle is about 1.5, then adding 30mL of ethyl acetate to separate the mixture, stirring for 10min to completely extract a liquid part from solid residues of the mixture in the kettle, then centrifuging the mixture in the kettle for 10min at the speed of 9000r/min, filtering by a Polytetrafluoroethylene (PTFE) membrane, separating a water phase and an ethyl acetate phase from the solid residues, separating the obtained liquid after separation to obtain a water phase and an ethyl acetate phase, separating the ethyl acetate phase from the water phase by a separating funnel to obtain an ethyl acetate liquid product, and finally, and (3) removing ethyl acetate by using a rotary evaporator to obtain a liquid product containing the micromolecular compound aromatic compound, namely the bio-oil containing the micromolecular compound aromatic compound.
Qualitative analysis is performed on the liquid product obtained in this example 2 by using a gas chromatography-mass spectrometer to obtain a product distribution diagram and a product distribution table (fig. 4, table 3), a monophenol compound with a high yield is selected for quantitative analysis, external standard methods are used for drawing standard curves of ten phenol compounds, namely guaiacol, 4-ethyl guaiacol, 4-methyl guaiacol, 4-methoxyphenol, isoeugenol, 3-methyl guaiacol, 4-methyl guaiacol, 2, 6-dimethoxyphenol, 2, 6-dimethoxy-4-methylphenol, and 2, 4-di-tert-butylphenol, and a sample to be tested is tested by using a gas chromatograph, and quantitative analysis is performed to obtain table 5, so as to determine the yield of each monophenol and the yield of total phenols.
Example 3
A method for preparing small molecular compounds by lignin depolymerization comprises the following operation steps:
(1) preparation of amorphous geopolymer catalyst: uniformly mixing metakaolin and slag according to the mass ratio of 1:1 to obtain mixed powder, and keeping Na of the mixed powder2O/Al2O3＝2.0，SiO2/Al2O33.5, and mixing the modified water glass and the deionized water according to the mass ratio of 10:1, weighing modified sodium silicate with the modulus of 1.4 and deionized water, adding the weighed modified sodium silicate and deionized water into the obtained mixed powder, mechanically stirring the mixture for 2min at the rotating speed of 2000r/min, uniformly mixing the mixture to obtain mixed slurry, and adding H into the mixed slurry according to 2 percent of the mass of the mixed slurry2O2Adding K12 into the mixed slurry according to 0.1% of the mass of the mixed slurry, mechanically stirring at the rotating speed of 2000R/min for 1min, uniformly mixing, casting into a round plastic mold (R is 20mm), maintaining at 120 ℃ for 12h, grinding by using abrasive paper with the mesh number of 100, and mechanically cutting to obtain the amorphous geopolymer catalyst; whether sanded or cut, is for ease of use of the catalyst.
(2) Taking the amorphous geopolymer catalyst obtained in the step (1), cutting the amorphous geopolymer catalyst into cuboid blocks with the length, width and height of 12mm multiplied by 6mm multiplied by 1mm, adding the cuboid blocks with the mass of 0.05g, 0.2g of alkali lignin and 16mL of methanol into a polytetrafluoroethylene reaction kettle with the volume of 50mL, uniformly mixing, replacing air with nitrogen, and sealing the reaction kettle;
(3) placing the reaction kettle in the step (2) in an electric heating constant temperature blast drying oven, heating for 3h for depolymerization at 290 ℃, taking out the reaction kettle after depolymerization is finished, cooling the temperature to room temperature, performing solid-liquid separation on the mixture in the kettle by using a polytetrafluoroethylene membrane with the diameter of 0.22 mu m, and evaporating the methanol-based liquid by using a solvent to obtain bio-oil without methanol solvent, wherein the bio-oil is a product containing aromatic compounds;
qualitative analysis is carried out on the obtained methanol liquid product by adopting a gas chromatography-mass spectrometer to obtain a product distribution diagram and a product distribution table (figure 5, table 4), monophenol compounds with higher yield are selected for quantitative analysis, external standard method is adopted to carry out standard curve drawing on the ten phenol compounds of guaiacol, 4-ethyl guaiacol, 4-methyl guaiacol, 4-methoxy phenol, isoeugenol, 3-methyl guaiacol, 4-methyl guaiacol, 2, 6-dimethoxy phenol, 2, 6-dimethoxy-4-methyl phenol and 2, 4-di-tert-butyl phenol, and a gas chromatograph is adopted to test and quantitatively analyze a sample to be tested to determine the yield of each monophenol and the yield of total phenol.
Example 4
A method for preparing aromatic compounds by depolymerizing lignin comprises the following operation steps:
(1) preparation of amorphous geopolymer catalyst: uniformly mixing metakaolin and slag according to the mass ratio of 1:1 to obtain mixed powder, wherein the Si/Al molar ratio is 3, and the mass ratio of the modified water glass to the deionized water is 2:1, weighing modified sodium silicate with the modulus of 1.3 and deionized water, adding the weighed modified sodium silicate and deionized water into the obtained mixed powder, mechanically stirring the mixture for 5min at the rotating speed of 2000r/min, uniformly mixing the mixture to obtain mixed slurry, and adding H into the mixed slurry according to 0.1 percent of the mass of the mixed slurry2O2Adding K12 into the mixed slurry according to 0.1% of the mass of the mixed slurry, mechanically stirring at the rotating speed of 2000R/min for 1min, uniformly mixing, casting into a round plastic mold (R is 20mm), maintaining at 60 ℃ for 24h, grinding by using abrasive paper with the mesh number of 100, and mechanically cutting to obtain the amorphous geopolymer catalyst;
(2) taking the amorphous geopolymer catalyst obtained in the step (1), cutting the amorphous geopolymer catalyst into cuboid blocks with the length, width and height of 12mm multiplied by 6mm multiplied by 1mm, adding the cuboid blocks with the mass of 0.1g, 0.2g of lignosulfonate and 16mL of pure water into a polytetrafluoroethylene reaction kettle with the volume of 50mL, uniformly mixing, replacing air with nitrogen, and sealing the reaction kettle;
(3) placing the reaction kettle in the step (2) in an electric heating constant temperature blast drying box, heating for 4h for depolymerization at 280 ℃, cooling to room temperature after depolymerization, taking out the reaction kettle, performing solid-liquid separation on the mixture in the kettle, namely acidifying the mixture in the kettle by hydrochloric acid solution with the volume concentration of 37% to enable the pH value of the mixture in the kettle to be about 1.5, then adding 30mL of ethyl acetate to separate the mixture, stirring for 10min to completely extract a liquid part from solid residues of the mixture in the kettle, centrifuging the mixture in the kettle for 10min at the speed of 9000r/min, filtering by a Polytetrafluoroethylene (PTFE) membrane to perform solid-liquid separation on the mixture in the kettle, separating a water phase and an ethyl acetate phase from the solid residues, separating the obtained liquid after separation to obtain a water phase and an ethyl acetate phase, separating the ethyl acetate phase from the water phase by a separating funnel, obtaining an ethyl acetate liquid product, and finally, removing ethyl acetate by using a rotary evaporator to obtain a liquid product containing the micromolecular compound aromatic compound, namely the bio-oil containing the micromolecular compound aromatic compound.
Adopting an external standard method to draw a standard curve for ten phenolic compounds, namely guaiacol, 4-ethyl guaiacol, 4-methyl guaiacol, 4-methoxyphenol, isoeugenol, 3-methyl guaiacol, 4-methyl guaiacol, 2, 6-dimethoxyphenol, 2, 6-dimethoxy-4-methylphenol and 2, 4-di-tert-butylphenol, and adopting a gas chromatograph to test and quantitatively analyze a sample to be tested so as to determine the yield of each monophenol and the total phenol yield (figure 6).
Carrying out qualitative and quantitative tests on the aromatic compound-containing liquid product obtained by the method to obtain the yield of the phenolic compound; qualitative gas chromatography-mass spectrometer, quantitative external standard method or internal standard method; the yield of the liquid product is 10-90% (the ratio of the mass of the liquid product to the mass of the initial lignin), and the yield of the phenolic compound is 10-300 mg/g (the mass ratio of the initial lignin).
TABLE 2 product identification distribution Table for the catalytic depolymerization of alkali lignin with amorphous geopolymer according to the invention (2h, 280 ℃, 16ml methanol)
TABLE 3 product identification distribution Table for the catalytic depolymerization of alkali lignin with amorphous geopolymer according to the invention (2h, 280 ℃, 16ml water)
TABLE 4
TABLE 5
"Ni 10 Al" in Table 52O3"data quoted from S.Cheng, C.Wilks, Z.Yuan, M.Leitch, C.xu, Hydrothermal Degradation of alkali lignin to bio-phenolic compounds in sub/supercritical ethanol and water-ethanol co-solvent, Polymer Degradation and Stabilty 97(2012) 839-;
in Table 5 "Ru/ZSM-5 + CuCl2"data quoted from M.Wang, M.Liu, H.Li, Z.ZHao, X.ZHang, F.Wang, degradation of Lignin to Phenol via Oxidation-Hydrogenation Stratagene, Acs Catalysis 8(2018) 6837-;
in Table 5 "Ru/ZSM-5 + CuCl2"data are quoted from Z.Zhang, B.Du, H.Zhu, C.Chen, Y.Sun, X.Wang, J.Zhou, facility adaptation of the registration of silicon seed to organic solvent HZSM-5zeolite catalysts for effective catalytic polymerization reaction of lignin, Biomass Conversion and Biorefinement2021)。
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.