A cobalt-magnesium-aluminum hydrotalcite, a preparation method and application thereof, and a method for pretreating biomass
By using a cobalt-magnesium-aluminum hydrotalcite catalyst with a specific molar ratio and structure to thermally catalytically degrade biomass under an oxidizing atmosphere, the problems of low lignin removal rate and cellulose loss were solved, achieving efficient and safe biomass pretreatment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2023-12-21
- Publication Date
- 2026-05-22
Smart Images
Figure CN117776278B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of biomass pretreatment technology, specifically relating to a cobalt-magnesium-aluminum hydrotalcite, its preparation method and application, and a method for biomass pretreatment. Background Technology
[0002] Biomass resources mainly consist of cellulose, hemicellulose, and lignin. Lignin, the second most abundant organic compound after cellulose, is widely found in plant cell walls (approximately 15-35%). Lignin is primarily composed of three phenylpropane structural units (guaiacol, syringyl, and p-hydroxyphenyl). As a crucial component of biomass, lignin is not only abundant in variety but also widely distributed, making it a versatile renewable resource. Currently, lignin is mainly degraded into monomers from biomass through thermocatalytic reduction degradation. This method requires hydrogen, is costly, and involves high-temperature and high-pressure reaction conditions, hindering its further application and industrialization. Catalytic oxidation can remove lignin from biomass and separate cellulose and hemicellulose under atmospheric conditions, solving the cost and safety issues associated with hydrogen use. However, current catalytic oxidation methods have low lignin removal rates and severe hemicellulose degradation, limiting downstream applications. The key to this problem lies in the lack of suitable catalysts. Summary of the Invention
[0003] In view of this, the present invention provides a cobalt magnesium aluminum hydrotalcite, its preparation method and application, and a method for biomass pretreatment. The cobalt magnesium aluminum hydrotalcite provided by the present invention is used to remove lignin from biomass and simultaneously carry out catalytic oxidation degradation, and achieves a high retention rate of cellulose and hemicellulose.
[0004] To address the aforementioned technical problems, this invention provides a cobalt-magnesium-aluminum hydrotalcite, wherein the molar ratio of aluminum, cobalt, and magnesium in the cobalt-magnesium-aluminum hydrotalcite is 0.6–0.8:2.2–2.4:1, and the specific surface area of the cobalt-magnesium-aluminum hydrotalcite is 280.2–291.4 m². 2 / g, the average pore size of the cobalt magnesium aluminum hydrotalcite is 1-4 nm.
[0005] This invention also provides a method for preparing the cobalt-magnesium-aluminum hydrotalcite described in the above technical solution, comprising the following steps:
[0006] A soluble aluminum salt, a soluble cobalt salt, a soluble magnesium salt, and water are mixed to obtain a mixed solution; the molar ratio of the soluble aluminum salt, the soluble cobalt salt, and the soluble magnesium salt is 0.6–0.8:2.2–2.4:1.
[0007] The mixed solution was added dropwise to a sodium carbonate solution to carry out a coprecipitation reaction, yielding a cobalt-magnesium-aluminum hydrotalcite precursor; the molar concentration of the sodium carbonate solution was 0.58–0.62 mol / L, and the volume ratio of the mixed solution to the sodium carbonate solution was 1:0.8–1.2; the pH value of the coprecipitation reaction system was 9.5–10.5.
[0008] The cobalt-magnesium-aluminum hydrotalcite precursor was calcined to obtain cobalt-magnesium-aluminum hydrotalcite.
[0009] Preferably, the coprecipitation reaction is carried out at a temperature of 55–65°C for a time of 1.8–2.2 h.
[0010] Preferably, the calcination is carried out in an air atmosphere, wherein the air introduction rate is 850-950 sccm;
[0011] The calcination temperature is 550–650℃, the time is 1.8–2.2 h, and the heating rate to the required calcination temperature is 4.8–5.2℃ / min.
[0012] The present invention also provides the application of the cobalt magnesium aluminum hydrotalcite described in the above technical solution or the cobalt magnesium aluminum hydrotalcite prepared by the preparation method described in the above technical solution in the separation of lignin in biomass pretreatment.
[0013] The present invention also provides a method for biomass pretreatment, comprising the following steps:
[0014] Biomass, catalyst, and alcohol compound are mixed and then subjected to thermocatalytic degradation in an oxidizing atmosphere to obtain a degradation product mixture system; the catalyst is the cobalt-magnesium-aluminum hydrotalcite described in the above technical solution or the cobalt-magnesium-aluminum hydrotalcite prepared by the preparation method described in the above technical solution;
[0015] The degradation product mixture was subjected to solid-liquid separation to obtain a liquid phase and a solid phase, respectively.
[0016] Preferably, the mass ratio of biomass to catalyst is 10:0.5 to 2;
[0017] The mass ratio of the biomass to the volume ratio of the alcohol compound is 1g:18-22mL.
[0018] Preferably, the volume percentage of oxygen in the oxidizing atmosphere is 5% to 30%.
[0019] Preferably, the temperature for the thermocatalytic degradation is 180–220°C, and the time is 3–4 hours.
[0020] Preferably, the solid-liquid separation process further includes:
[0021] The liquid phase is concentrated and then extracted to obtain lignin monomers; the organic phase used for extraction is dichloromethane, and the inorganic phase used for extraction is water.
[0022] This invention provides a cobalt-magnesium-aluminum hydrotalcite, wherein the molar ratio of aluminum, cobalt, and magnesium in the cobalt-magnesium-aluminum hydrotalcite is 0.6–0.8:2.2–2.4:1, and the specific surface area of the cobalt-magnesium-aluminum hydrotalcite is 280.2–291.4 m². 2 / g, the average pore size of the cobalt-magnesium-aluminum hydrotalcite is 1-4 nm. The cobalt-magnesium-aluminum hydrotalcite provided by the present invention has a specific molar ratio of aluminum, cobalt and magnesium and has a specific specific surface area and pore size. As a catalyst for the removal and depolymerization of lignin in biomass, it can improve the removal rate of lignin while retaining a high amount of cellulose and hemicellulose.
[0023] This invention also provides a method for biomass pretreatment, comprising the following steps: mixing biomass, a catalyst, and an alcohol compound, and then subjecting the mixture to thermocatalytic degradation in an oxidizing atmosphere to obtain lignin degradation products; wherein the catalyst is the cobalt-magnesium-aluminum hydrotalcite described in the above technical solution or the cobalt-magnesium-aluminum hydrotalcite prepared by the preparation method described in the above technical solution. This invention uses cobalt-magnesium-aluminum hydrotalcite as a catalyst to degrade lignin in an oxidizing atmosphere, which can improve the retention rate of hemicellulose and achieve better lignin separation and degradation. Attached Figure Description
[0024] Figure 1 The XRD pattern of the cobalt-magnesium-aluminum hydrotalcite precursor prepared in Example 1 is shown below.
[0025] Figure 2 The XRD pattern of the cobalt-magnesium-aluminum hydrotalcite prepared in Example 1 is shown below.
[0026] Figure 3 The EDS spectrum of the cobalt-magnesium-aluminum hydrotalcite prepared in Example 1 is shown below.
[0027] Figure 4 The EDS spectrum of the cobalt-magnesium-aluminum hydrotalcite prepared in Example 1 is shown below.
[0028] Figure 5 TEM image of the cobalt-magnesium-aluminum hydrotalcite prepared in Example 1;
[0029] Figure 6 The adsorption-desorption curves of the cobalt-magnesium-aluminum hydrotalcite prepared in Example 1 are shown below.
[0030] Figure 7 The image shows the GC-MS spectrum of the lignin monomer obtained by thermocatalytic degradation in Example 3. Detailed Implementation
[0031] This invention provides a cobalt-magnesium-aluminum hydrotalcite, wherein the molar ratio of aluminum, cobalt, and magnesium in the cobalt-magnesium-aluminum hydrotalcite is 0.6–0.8:2.2–2.4:1, preferably 0.6:2.4:1; and the specific surface area of the cobalt-magnesium-aluminum hydrotalcite is 280.2–291.4 m². 2 / g, preferably 285.5m 2 / g; the average pore size of the cobalt-magnesium-aluminum hydrotalcite is 1-4 nm, preferably 2-3 nm.
[0032] In this invention, cobalt is highly dispersed in cobalt-magnesium-aluminum hydrotalcite, and some cobalt is also embedded in the magnesium-aluminum oxide framework.
[0033] This invention also provides a method for preparing the cobalt-magnesium-aluminum hydrotalcite described in the above technical solution, comprising the following steps:
[0034] A soluble aluminum salt, a soluble cobalt salt, a soluble magnesium salt, and water are mixed to obtain a mixed solution; the molar ratio of the soluble aluminum salt, the soluble cobalt salt, and the soluble magnesium salt is 0.6–0.8:2.2–2.4:1.
[0035] The mixed solution was added dropwise to a sodium carbonate solution to carry out a coprecipitation reaction to obtain a cobalt-magnesium-aluminum hydrotalcite precursor; the molar concentration of the sodium carbonate solution was 0.58–0.62 mol / L, and the volume ratio of the mixed solution to the sodium carbonate solution was 1:0.8–1.2; the pH value of the coprecipitation reaction system was 9.5–10.5.
[0036] The cobalt-magnesium-aluminum hydrotalcite precursor was calcined to obtain cobalt-magnesium-aluminum hydrotalcite.
[0037] This invention involves mixing a soluble aluminum salt, a soluble cobalt salt, a soluble magnesium salt, and water to obtain a mixed solution. In this invention, the soluble aluminum salt is preferably aluminum chloride or aluminum nitrate, more preferably aluminum chloride; the soluble cobalt salt is preferably cobalt chloride or cobalt nitrate, more preferably cobalt nitrate; and the soluble magnesium salt is preferably magnesium chloride or magnesium nitrate, more preferably magnesium chloride. In this invention, the water is preferably deionized water. In this invention, the molar ratio of the soluble aluminum salt, soluble cobalt salt, and soluble magnesium salt is 0.6–0.8:2.2–2.4:1, preferably 0.6:2.4:1.
[0038] The present invention has no special requirements for the mixing, as long as the mixing is uniform.
[0039] After obtaining the mixed solution, the present invention adds the mixed solution dropwise to a sodium carbonate solution to carry out a coprecipitation reaction to obtain a cobalt-magnesium-aluminum hydrotalcite precursor. In the present invention, the molar concentration of the sodium carbonate solution is 0.58–0.62 mol / L, preferably 0.6 mol / L; the volume ratio of the mixed solution to the sodium carbonate solution is 1:0.8–1.2, preferably 1:1. In the present invention, the pH value of the coprecipitation reaction system is 9.5–10.5, preferably 10; the present invention preferably controls the pH value by adding sodium hydroxide solution to the system. In the present invention, the molar concentration of the sodium hydroxide solution is preferably 2.8–3.2 mol / L, more preferably 3 mol / L. The present invention has no special requirements on the amount of sodium hydroxide solution used, as long as the desired pH value is achieved.
[0040] In this invention, the dripping rate is preferably 1-3 drops / s, more preferably 1 drop / s; the dripping temperature is preferably 55-65°C, more preferably 60°C. This invention preferably utilizes a water bath to ensure the dripping temperature. In this invention, the dripping is preferably accompanied by stirring, and the stirring rate is preferably 700-1000 rpm, more preferably 800-900 rpm.
[0041] In this invention, the temperature of the coprecipitation reaction is preferably 55–65°C, more preferably 60°C; the time of the coprecipitation reaction is preferably 1.8–2.2 h, more preferably 2 h. In this invention, the timing of the coprecipitation reaction preferably begins after the mixed solution is added dropwise. In this invention, the coprecipitation reaction is preferably accompanied by stirring, and the stirring rate is preferably 500–1000 rpm, more preferably 700–1000 rpm. In this invention, the coprecipitation reaction preferably further includes: solid-liquid separation of the coprecipitation reaction system; drying the solid obtained from the solid-liquid separation to obtain a cobalt-magnesium-aluminum hydrotalcite precursor. In this invention, the solid-liquid separation is preferably filtration; this invention has no special requirements for the filtration, and conventional methods in the art are acceptable. In this invention, the drying temperature is preferably 75–85°C, more preferably 80°C; this invention has no special requirements for the drying time, as long as the moisture on the solid surface is removed.
[0042] After obtaining the cobalt-magnesium-aluminum hydrotalcite precursor, the present invention calcines the cobalt-magnesium-aluminum hydrotalcite precursor to obtain cobalt-magnesium-aluminum hydrotalcite. In this invention, the calcination is preferably carried out in an air atmosphere, and the air introduction rate is preferably 850–950 sccm, more preferably 900 sccm. In this invention, the calcination temperature is preferably 550–650℃, more preferably 600℃; the calcination time is preferably 1.8–2.2 h, more preferably 2 h. In this invention, the heating rate to the required calcination temperature is preferably 4.8–5.2℃ / min, more preferably 5℃ / min.
[0043] The present invention also provides the application of the cobalt magnesium aluminum hydrotalcite described in the above technical solution or the cobalt magnesium aluminum hydrotalcite prepared by the preparation method described in the above technical solution in the separation of lignin in biomass pretreatment.
[0044] The present invention also provides a method for biomass pretreatment, comprising the following steps:
[0045] Biomass, catalyst, and alcohol compound are mixed and then subjected to thermocatalytic degradation in an oxidizing atmosphere to obtain a degradation product mixture system; the catalyst is the cobalt-magnesium-aluminum hydrotalcite described in the above technical solution or the cobalt-magnesium-aluminum hydrotalcite prepared by the preparation method described in the above technical solution;
[0046] The degradation product mixture was subjected to solid-liquid separation to obtain a liquid phase and a solid phase, respectively.
[0047] This invention involves mixing biomass, a catalyst, and an alcohol compound, and then subjecting them to thermocatalytic degradation in an oxidizing atmosphere to obtain a mixed system of degradation products. In this invention, the biomass is preferably poplar wood pellets. The poplar wood pellets are preferably selected from the trunk of poplar trees. The average particle size of the biomass is preferably 40-60 mesh, more preferably 45-55 mesh. The alcohol compound is preferably methanol, ethylene glycol, or isopropanol, more preferably methanol. The mass ratio of biomass to catalyst is preferably 10:0.5-2, more preferably 10:0.5-1. The mass ratio of biomass to alcohol compound is preferably 1g:18-40mL, more preferably 1g:20-40mL.
[0048] In this invention, the volume percentage of oxygen in the oxidizing atmosphere is preferably 5-30%, more preferably 21%. In this invention, the oxidizing atmosphere is preferably air. In this invention, the pressure of the oxidizing atmosphere is preferably 1-2 MPa, more preferably 1.4-1.8 MPa, and even more preferably 1.5-1.6 MPa. This invention performs thermocatalytic degradation under an air-based oxidizing atmosphere, overcoming the shortcomings of traditional lignin degradation using a hydrogen-reducing atmosphere and improving operational safety.
[0049] In this invention, the temperature of the thermocatalytic degradation is preferably 180-220°C, more preferably 200°C; the time of the thermocatalytic degradation is preferably 3-4 hours, more preferably 4 hours.
[0050] After obtaining the degradation product mixture system, this invention performs solid-liquid separation on the degradation product mixture system to obtain a liquid phase and a solid phase respectively. This invention has no particular limitation on the solid-liquid separation, as long as the liquid and solid can be separated. In this invention, the solid phase obtained from the solid-liquid separation mainly contains catalyst and biomass residue, the biomass residue including undegraded lignin, cellulose, and hemicellulose. This invention preferably uses a 100-mesh sieve to sieve the catalyst from the solid phase, leaving the biomass residue. This invention preferably uses methanol to wash the biomass residue and then dries it to obtain undegraded lignin, cellulose, and hemicellulose. This invention preferably uses the NREL method to determine the content of undegraded lignin, cellulose, and hemicellulose in the biomass residue.
[0051] In this invention, the solid-liquid separation process preferably further includes:
[0052] The liquid phase is concentrated and then extracted to obtain lignin monomers; the organic phase used for extraction is dichloromethane, and the inorganic phase used for extraction is water.
[0053] This invention involves solid-liquid separation of a thermocatalytic degradation system to obtain a liquid phase. In this invention, the liquid phase obtained from the solid-liquid separation primarily contains lignin monomers obtained from lignin degradation. Preferably, the lignin monomers are... and One or more of them.
[0054] After obtaining the liquid phase, the present invention concentrates the liquid phase and then extracts it to obtain lignin monomers. In the present invention, the concentration is preferably performed by rotary evaporation. The present invention has no special requirements for the rotary evaporation, as long as it can remove the solvent methanol from the liquid phase. In the present invention, the organic phase used for extraction is preferably dichloromethane, and the inorganic phase used for extraction is preferably water. In the present invention, the volume ratio of the organic phase to the inorganic phase is preferably 1:0.8 to 1.2, more preferably 1:1. In the present invention, the lignin monomers will dissolve in the organic phase; the present invention preferably performs rotary evaporation on the organic phase containing dissolved lignin to obtain lignin monomers.
[0055] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0056] Preparation of cobalt magnesium aluminum hydrotalcite
[0057] Example 1
[0058] AlCl3, Co(NO3)2 and MgCl2 were dissolved in 50 mL of deionized water in a molar ratio of 0.6:2.4:1 to obtain a mixed solution;
[0059] The mixed solution was added dropwise at a rate of 1 drop / s to 50 mL of a 0.6 mol / L Na₂CO₃ solution at 60 °C (water bath heating), with stirring at 800 rpm during the addition. A 3 mol / L NaOH solution was added during the addition to maintain the pH of the system at 10. After the addition of the mixed solution was complete, a co-precipitation reaction was carried out in a 60 °C water bath (with stirring at 1000 rpm) for 2 h. The reaction system was then filtered, and the resulting solid was dried at 80 °C to obtain the cobalt-magnesium-aluminum hydrotalcite precursor.
[0060] The cobalt-magnesium-aluminum hydrotalcite precursor was placed in a tube furnace and air was introduced at 900 sccm. The temperature was increased to 600℃ at a rate of 5℃ / min and calcined for 2 hours to obtain cobalt-magnesium-aluminum hydrotalcite.
[0061] Example 2
[0062] Cobalt-magnesium-aluminum hydrotalcite was prepared according to the method in Example 1, except that the molar ratio of AlCl3, Co(NO3)2 and MgCl2 was 0.6:2.4:1.
[0063] Comparative Example 1
[0064] Cobalt-magnesium-aluminum hydrotalcite was prepared according to the method in Example 1, except that the molar ratio of AlCl3, Co(NO3)2 and MgCl2 was 0:3:1.
[0065] Comparative Example 2
[0066] Cobalt-magnesium-aluminum hydrotalcite was prepared according to the method in Example 1, except that the molar ratio of AlCl3, Co(NO3)2 and MgCl2 was 0.3:2.7:1.
[0067] Comparative Example 3
[0068] Cobalt-magnesium-aluminum hydrotalcite was prepared according to the method in Example 1, except that the molar ratio of AlCl3, Co(NO3)2 and MgCl2 was 1:2:1.
[0069] The cobalt-magnesium-aluminum hydrotalcite precursor and cobalt-magnesium-aluminum hydrotalcite prepared in Example 1 were subjected to XRD analysis, and the XRD spectra were obtained as follows. Figure 1 and Figure 2 As shown, where Figure 1 The XRD pattern of the cobalt-magnesium-aluminum hydrotalcite precursor prepared in Example 1 is shown below. Figure 2 The image shows the XRD pattern of the cobalt-magnesium-aluminum hydrotalcite prepared in Example 1. Figure 1 and Figure 2 It can be seen that the prepared catalyst precursor has the structure of cobalt magnesium aluminum hydrotalcite, and retains the structure of cobalt magnesium aluminum hydrotalcite after calcination.
[0070] The cobalt-magnesium-aluminum hydrotalcite prepared in Example 1 was analyzed using TEM and X-ray energy dispersive spectroscopy (EDS), and the electron micrographs and EDS spectra are shown below. Figure 3 As shown. Figure 3 The first two images are TEM images, and the last three are EDS spectra. (Combined) Figure 2 Peak shifts in XRD patterns of cobalt-magnesium-aluminum hydrotalcite Figure 3 The distribution of cobalt atoms shows that cobalt is highly dispersed in the magnesium-aluminum hydrotalcite framework provided by this invention.
[0071] The cobalt-magnesium-aluminum hydrotalcite prepared in Example 1 was analyzed by X-ray energy dispersive spectroscopy (EDS), and the elemental energy dispersive spectroscopy (EDS) chromatogram was obtained, as shown below. Figure 4 As shown. According to Figure 4 The data in Table 1 were obtained from quantitative analysis.
[0072] Table 1. Elemental energy dispersive spectroscopy (EDS) results
[0073]
[0074] Combination Figure 4 As can be seen from Table 1, the Co content in cobalt-magnesium-aluminum hydrotalcite is relatively high, reaching 28.02 wt%.
[0075] The cobalt-magnesium-aluminum hydrotalcite prepared in Example 1 was examined using transmission electron microscopy at different magnifications, and TEM images were obtained, as shown below. Figure 5 As shown. By Figure 5 Cobalt can be observed to be highly dispersed in magnesium aluminum hydrotalcite and has a relatively clear layered structure with octahedral coordination lattice.
[0076] Adsorption-desorption experiments were conducted on the cobalt-magnesium-aluminum hydrotalcite prepared in Example 1, and the adsorption-desorption curves were obtained, as shown below. Figure 6 As shown. According to Figure 6 The specific surface area of cobalt-magnesium-aluminum hydrotalcite was obtained, and the results are listed in Table 2. Adsorption-desorption experiments were conducted on the cobalt-magnesium-aluminum hydrotalcite prepared in Example 1 and Comparative Examples 1-3, and the adsorption-desorption curves were obtained. The specific surface area and average pore size of the cobalt-magnesium-aluminum hydrotalcite were calculated, and the results are listed in Table 2.
[0077] Table 2. Performance parameters of the cobalt-magnesium-aluminum hydrotalcites prepared in Examples 1-2 and Comparative Examples 1-3
[0078] Co:Mg:Al (molar ratio) <![CDATA[Specific surface area (m 2 / g)]]> Average pore size (nm) Comparative Example 1 CoPMO-1 0:3:1 98.5±0.6 10-40 Comparative Example 2CoPMO-2 0.3:2.7:1 196.3±0.7 5-50 Example 1 CoPMO-3 0.6:2.4:1 285.8±5.6 1-4 Comparative Example 3CoPMO-4 1:2:1 171.6±0.1 10-55
[0079] As can be seen from Table 2, the cobalt-magnesium-aluminum hydrotalcite provided by this invention has a high surface area (the specific surface area of existing magnesium-aluminum hydrotalcite catalysts is mostly 200 m²). 2 (below / g) and smaller pore size (most existing magnesium aluminum hydrotalcite catalysts have mesopores with a pore size of 10nm).
[0080] Thermocatalytic removal and degradation of lignin
[0081] Example 3:
[0082] Poplar wood powder with an average particle size of 40-60 mesh, cobalt magnesium aluminum hydrotalcite prepared in Example 1, and methanol were added to a high-temperature and high-pressure reactor, and air at a pressure of 1.5 MPa was introduced. The reactor was then subjected to thermal catalytic degradation at 200°C for 4 hours. The mass ratio of poplar wood powder to cobalt magnesium aluminum hydrotalcite was 20:1, and the mass ratio of poplar wood powder to methanol was 1 g:40 mL.
[0083] After thermocatalytic degradation, the system underwent solid-liquid separation. The solid obtained from the solid-liquid separation was washed with methanol and dried. Cobalt-magnesium-aluminum hydrotalcite was removed from the solid phase using a 100-mesh sieve. The composition of lignin, cellulose, and hemicellulose in the solid was analyzed, and the results are listed in Table 3. The liquid obtained from the solid-liquid separation was desolventized by rotary evaporation, dissolved in dichloromethane, transferred to a separatory funnel, and extracted with water (dichloromethane to water volume ratio 1:1) to obtain a dichloromethane solution of lignin monomers. This solution was again desolventized by rotary evaporation, dissolved in methanol, and the internal standard n-decane was added. The lignin monomers were then analyzed by GC-MS, and the results are shown in Table 3. Figure 7 The monomer yield of lignin was quantitatively determined to be 6.47%.
[0084] The filtered solid was dried, and the catalyst and poplar solid powder were separated by sieving through a 60-mesh sieve. The obtained poplar solid powder was analyzed for lignin, cellulose, and hemicellulose content using the NREL standard. The lignin removal rate and cellulose and hemicellulose retention rates were obtained and the results are listed in Table 3.
[0085] Example 4
[0086] The lignin was degraded according to the method of Example 3, except that the air pressure was 2 MPa.
[0087] Example 5
[0088] The lignin was degraded according to the method in Example 3, except that the thermocatalytic degradation time was 3 hours.
[0089] Comparative Example 4
[0090] The lignin was degraded according to the method in Example 3, except that the thermocatalytic degradation time was 6 hours.
[0091] Comparative Example 5
[0092] The lignin was degraded according to the method in Example 3, except that the thermocatalytic degradation time was 12 hours.
[0093] Comparative Example 6
[0094] The lignin was degraded according to the method of Example 3, except that the cobalt magnesium aluminum hydrotalcite used was the cobalt magnesium aluminum hydrotalcite (CoPMO-1) prepared in Comparative Example 1.
[0095] Comparative Example 7
[0096] The lignin was degraded according to the method of Example 3, except that the cobalt magnesium aluminum hydrotalcite used was the cobalt magnesium aluminum hydrotalcite (CoPMO-2) prepared in Comparative Example 2.
[0097] Comparative Example 8
[0098] The lignin was degraded according to the method of Example 3, except that the cobalt magnesium aluminum hydrotalcite used was the cobalt magnesium aluminum hydrotalcite (CoPMO-4) prepared in Comparative Example 3.
[0099] Comparative Example 9
[0100] The lignin was degraded according to the method of Example 3, except that the cobalt magnesium aluminum hydrotalcite used was the copper magnesium aluminum hydrotalcite (CuPMO-20) prepared in Comparative Example 3.
[0101] Table 3 Performance parameters of poplar pretreatment in Examples 3-5 and Comparative Examples 4-9
[0102]
[0103] As can be seen from Table 3, the biomass thermocatalytic removal and degradation of lignin method provided by the present invention can achieve a high retention rate of cellulose and hemicellulose, while also achieving a high removal rate of lignin.
[0104] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A cobalt-magnesium-aluminum hydrotalcite, characterized in that, The molar ratio of aluminum, cobalt, and magnesium in the cobalt-magnesium-aluminum hydrotalcite is 0.6:2.4:1, the specific surface area of the cobalt-magnesium-aluminum hydrotalcite is 280.2~291.4 m² / g, and the average pore size of the cobalt-magnesium-aluminum hydrotalcite is 1~4 nm.
2. The method for preparing the cobalt-magnesium-aluminum hydrotalcite according to claim 1, comprising the following steps: A soluble aluminum salt, a soluble cobalt salt, a soluble magnesium salt, and water are mixed to obtain a mixed solution; the molar ratio of the soluble aluminum salt, the soluble cobalt salt, and the soluble magnesium salt is 0.6:2.4:
1. The mixed solution was added dropwise to a sodium carbonate solution to carry out a coprecipitation reaction, yielding a cobalt-magnesium-aluminum hydrotalcite precursor; the molar concentration of the sodium carbonate solution was 0.58~0.62 mol / L, and the volume ratio of the mixed solution to the sodium carbonate solution was 1:0.8~1.2; the pH value of the coprecipitation reaction system was 9.5~10.
5. The cobalt-magnesium-aluminum hydrotalcite precursor was calcined to obtain cobalt-magnesium-aluminum hydrotalcite.
3. The preparation method according to claim 2, characterized in that, The coprecipitation reaction is carried out at a temperature of 55-65℃ for a time of 1.8-2.2 hours.
4. The preparation method according to claim 2, characterized in that, The calcination is carried out in an air atmosphere, and the air introduction rate is 850~950 sccm; The calcination temperature is 550~650℃, the time is 1.8~2.2h, and the heating rate to the required calcination temperature is 4.8~5.2℃ / min.
5. The application of the cobalt magnesium aluminum hydrotalcite according to claim 1 or the cobalt magnesium aluminum hydrotalcite prepared by any one of claims 2 to 4 in the separation of lignin in biomass pretreatment.
6. A method for biomass pretreatment, comprising the following steps: Biomass, catalyst, and alcohol compound are mixed and then subjected to thermocatalytic degradation in an oxidizing atmosphere to obtain a mixed system of degradation products; the catalyst is the cobalt magnesium aluminum hydrotalcite of claim 1 or the cobalt magnesium aluminum hydrotalcite prepared by the preparation method of any one of claims 2 to 4; The degradation product mixture was subjected to solid-liquid separation to obtain a liquid phase and a solid phase, respectively.
7. The biomass pretreatment method according to claim 6, characterized in that, The mass ratio of biomass to catalyst is 10:0.5~2; The mass ratio of the biomass to the volume ratio of the alcohol compound is 1g:18~22mL.
8. The biomass pretreatment method according to claim 6, characterized in that, The oxygen volume percentage in the oxidizing atmosphere is 5-30%.
9. The method for biomass pretreatment according to any one of claims 6 to 8, characterized in that, The thermocatalytic degradation is carried out at a temperature of 180~220℃ for 3~4 hours.
10. The method for biomass pretreatment according to claim 6, characterized in that, The solid-liquid separation process also includes: The liquid phase is concentrated and then extracted to obtain lignin monomers; the organic phase used for extraction is dichloromethane, and the inorganic phase used for extraction is water.