Magnesium aluminate spinel catalyst, its preparation method, and method for catalytically reforming the pyrolysis gas of lignocellulose in a targeted manner to prepare aldehyde compounds

Abstract

The present invention discloses a magnesium aluminate spinel catalyst, a preparation method thereof, and a method for the catalytic reforming of pyrolysis gas of lignocellulose for the preparation of aldehyde compounds, comprising the following steps: mixing a magnesium salt, an aluminum salt and water to obtain a mixed salt solution, adding an ammonia water solution, reacting to generate a white flocculent precipitate, collecting the precipitate by filtration, adding a solution of polyethylene glycol, stirring evenly, drying, calcining, and ball-milling the calcined product to obtain a magnesium aluminate spinel powder; mixing the magnesium aluminate spinel powder with a metal compound evenly, and then performing roasting to obtain a magnesium aluminate spinel catalyst loaded with a double metal oxide. The magnesium aluminate spinel of the present invention is very suitable for pyrolysis catalysts, which can not only avoid the deactivation of metal components due to carbon deposition and sintering, but also load active metals on a carrier with a specific structure, and obtain good catalytic performance with a small amount of active metals by means of the carrier effect. Its properties will have uniqueness in activity due to the intervention of metal components.

Description

Technical Field

[0001] The invention relates to the technical field of wood biomass conversion, and in particular to a magnesium aluminum spinel catalyst and a preparation method thereof, and a method for preparing aldehyde compounds by pyrolysis of wood biomass and gas-phase directional catalytic reforming. Background Art

[0002] The biomass pyrolysis process is extremely complex, including a variety of physical and chemical processes, such as the diffusion and flow of substances, the condensation of bio-oil and other physical processes, as well as the depolymerization or ring opening of macromolecular compounds, the reaction between the functional groups of the products and other chemical processes. Adjusting pyrolysis factors, such as pyrolysis time, heating rate, adding directional catalysts and other factors, can improve the yield of the target product. In today's situation where fossil non-renewable resources are becoming increasingly scarce, early research on the technology of preparing compounds from renewable biomass pyrolysis will help alleviate the pressure on fossil resources, and at the same time can achieve high-value and efficient renewable utilization of biomass in my country, which has important practical significance.

[0003] However, in the prior art, in the process of preparing aldehyde compounds by pyrolysis and catalytic reforming of woody biomass, the pyrolysis temperature of woody biomass is relatively high and biochar is generated during the pyrolysis process, which easily causes the catalyst to be carbonized and deactivated, so the thermal stability and catalytic activity sustainability of the catalyst are required to be relatively high. Therefore, how to overcome the shortcomings of the prior art is an urgent problem to be solved in the field of biomass energy utilization technology. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing aldehyde compounds by pyrolysis and gas-phase directional catalytic reforming of woody biomass, which mainly solves the technical problem that in the process of preparing aldehyde compounds by pyrolysis and catalytic reforming of woody biomass, conventional catalysts are easily deactivated due to carbon deposition.

[0005] To achieve the above object, the present invention is achieved through the following technical solutions:

[0006] A method for preparing a magnesium-aluminum spinel catalyst comprises the following steps: (1) mixing a magnesium salt, an aluminum salt and water to obtain a mixed salt solution, adding an ammonia solution to react to generate a white flocculent precipitate, collecting the precipitate by filtration, adding a polyethylene glycol solution, stirring evenly, drying and calcining, and ball-milling the calcined product to obtain a magnesium-aluminum spinel powder; (2) mixing the magnesium-aluminum spinel powder and a metal compound evenly, and then calcining to obtain a magnesium-aluminum spinel catalyst loaded with a bimetallic oxide, wherein the metal compound is any two combinations of ferric nitrate, zinc nitrate, zirconium nitrate and n-butyl titanate.

[0007] Further, in step (1), the magnesium salt and aluminum salt are mixed according to a molar ratio of MgO∶Al2O3 of 1:1-2; optionally, in step (1), the polyethylene glycol accounts for 1-5% of the total mass of the precipitate, and the polyethylene glycol is any 2 of polyethylene glycol-2000, polyethylene glycol 70000, polyethylene glycol 100000, and polyethylene glycol 130000; preferably, the polyethylene glycol is pre-dissolved in ethanol and then mixed with the precipitate; optionally, in step (1), the calcination temperature is 800-1000°C and the time is 1-3 h.

[0008] Further, in step (2), the magnesium aluminate spinel is uniformly mixed with any one of metal compounds such as ferric nitrate, zinc nitrate, zirconium nitrate, and tetrabutyl titanate, then ethanol is added and uniformly dispersed in ultrasonic for 3-5 hours, and then a metal compound different from the one added previously is selected from ferric nitrate, zinc nitrate, zirconium nitrate, and tetrabutyl titanate and added to the mixed solution. After continuing to be uniformly dispersed in ultrasonic for 3-5 hours, the solvent is evaporated under constant temperature stirring at 40-60°C. After the material is completely dried, it is placed in an oven and dried at 95-105°C for 10 hours to obtain a uniformly mixed powder; optionally, in step (2), the calcination temperature is 400-900°C and the calcination time is 3-5 hours.

[0009] Based on the same inventive concept, the present invention also provides a magnesium aluminate spinel catalyst prepared by any of the above preparation methods. Among them, the magnesium aluminate spinel catalyst is TiO2-ZrO2-MAS, TiO2-ZnO-MAS, TiO2-Fe2O3-MAS, ZrO2-ZnO-MAS, ZrO2-Fe2O3-MAS, or ZnO-Fe2O3-MAS with hierarchical pore sizes, where MAS represents magnesium aluminate spinel. The magnesium aluminate spinel serves as a matrix to support the double metal oxide, and the magnesium aluminate spinel has pores with different pore sizes, including pores with at least two of the pore sizes of 2-10 nm, 10-15 nm, and 15-25 nm.

[0010] Further, in the magnesium aluminate spinel catalyst, the ratio of the total mass of the double metal oxide to the mass of the magnesium aluminate spinel is 0.005-0.1.

[0011] In the present invention, the support of the supported magnesium aluminate spinel catalyst is synthesized from MgO and Al2O3. It not only has the advantages of MgO and Al2O3, but also has two active centers of acidity and basicity, and has a pore structure. The saturated structure of magnesium aluminate spinel gives it high thermal stability. Its crystal phase structure can remain unchanged at high temperatures, and its melting point is 2135 °C. Magnesium aluminate spinel has a catalytic effect. After loading metal oxides, its thermal stability remains unchanged, and it has high catalytic efficiency and selectivity for target products. Therefore, spinel is very suitable for pyrolysis catalysts, especially as the support of supported metal catalysts. It can not only prevent the metal components from deactivating due to carbon deposition and sintering, but also load the active metals on the support with a specific structure, and rely on the support effect to obtain good catalytic performance with a small amount of active metals. Its properties will make its activity unique due to the intervention of metal components. In addition, in the present invention, by using a magnesium aluminate spinel catalyst with multi-stage pore sizes (2 - 25 nm) to load double metal oxides such as TiO2, ZrO2, ZnO, and Fe2O3, when pyrolysis products with different molecular sizes and structures pass through the catalyst, they are continuously and directionally catalyzed through pores of different diameters. Compared with catalysts with a single-diameter pore structure, the gas-phase reforming efficiency and the yield of target products are further improved.

[0012] Based on the same inventive concept, the present invention also provides a method for the preparation of aldehyde compounds by gas-phase directional catalytic reforming of pyrolysis of lignocellulose biomass. The above-mentioned magnesium aluminate spinel catalyst is used for multi-stage pore size continuous directional catalytic pyrolysis gas-phase reforming of lignocellulose biomass to obtain a liquid product containing aldehyde compounds. Preferably, it includes the following steps: S1, loading granular lignocellulose biomass and the catalyst into a pyrolysis reaction device, wherein the catalyst is a supported magnesium aluminate spinel catalyst, and the mass ratio of lignocellulose biomass to the catalyst is 1:1 - 1:5; S2, using an isolation structure to separate the lignocellulose biomass and the catalyst; S3, carrying out a directional catalytic pyrolysis reforming reaction under a nitrogen atmosphere to obtain a pyrolysis catalytic gas; S4, the pyrolysis catalytic gas is condensed to obtain a liquid product containing aldehyde compounds. In the present invention, the mass ratio of the lignocellulose biomass to the catalyst is 1:1 to 1:5. Exceeding this ratio, that is, the dosage of the catalyst is too high, it is difficult to collect the liquid substance after condensation, and most of it is enriched on the surface of the catalyst. If the ratio is lower than this ratio, the content of aldehyde compounds in the condensed liquid substance is relatively low.

[0013] Furthermore, the lignocellulose biomass is any one or more of poplar powder particles, elm powder particles, manchurian ash powder particles, oak powder particles, birch powder particles, and maple particles.

[0014] Furthermore, the particle size of the lignocellulose biomass is 0.2 - 0.5 μm.

[0015] Further, in step S3, the pyrolysis reaction device is heated to 400-600 °C at a heating rate of 10-50 K / min; preferably, the catalytic pyrolysis reforming reaction time is 20-50 min.

[0016] Further, in step S2, asbestos is used to separate the lignocellulose biomass from the catalyst.

[0017] The above technical solution has the following advantages or beneficial effects:

[0018] In the method for preparing aldehyde compounds by catalytic gas-phase directional reforming of lignocellulose biomass pyrolysis according to the present invention, the multi-stage pore-size supported magnesium aluminate spinel catalyst is used to perform multi-stage pore-size continuous directional catalytic gas-phase reforming of lignocellulose biomass at a relatively high temperature, which can effectively change the pyrolysis reaction pathway of lignocellulose biomass, greatly promote the formation of aldehyde compounds, and at the same time inhibit the formation of other organic liquid by-products. In the present invention, the aldehyde compounds account for more than 60% of the yield of bio-oil from pyrolysis products, which is much higher than the proportion under the conditions of non-catalytic (about 12%) or other catalysts (about 30%) of lignocellulose biomass. More importantly, furfural, an important variety among the aldehyde compounds, accounts for up to more than 50% of the bio-oil from pyrolysis products. Description of the Drawings

[0019] Figure 1 is the scanning electron microscope image of the ZrO2-Fe2O3-MAS catalyst of the embodiment of the present invention.

[0020] Figure 2 is the scanning electron microscope image of the TiO2-ZnO-MAS catalyst of the embodiment of the present invention. Detailed Embodiments

[0021] The present invention will be further described below in conjunction with embodiments.

[0022] Those skilled in the art should understand that the following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those without specific technical or conditions noted in the embodiments, the techniques or conditions described in the literature in the art or according to the product specifications are followed. Those reagents or instruments without the manufacturer noted are all conventional products that can be obtained by purchase.

[0023] The preparation method of the supported double metal oxide magnesium aluminate spinel catalyst with a pore size of 2-25 nm of the present invention is specifically as follows:

[0024] Preparation of magnesium aluminate spinel support:

[0025] Prepare a mixed salt solution with a concentration of 0.5 mol / L by mixing MgCl₂·6H₂O and AlCl₃·6H₂O according to MgO∶Al₂O₃ (molar ratio) = 1:1.5. Slowly drip ammonia water into it under rapid stirring, and keep the solution pH between 11 and 12. The generated white flocculent precipitate is filtered and washed with water to remove impurities. After filtration and washing with water, add a certain amount of polyethylene glycol (any 2 of polyethylene glycol - 2000, polyethylene glycol 70000, polyethylene glycol 100000, 130000 with a total mass of MgO and Al₂O₃ of 1 - 5%). The polyethylene glycol needs to be fully dissolved in ethanol in advance. Then dry at 90 °C and calcine (800 - 1000 °C, 1 - 3 h), and ball - mill and disperse to obtain MgAl₂O₄ powder with different pore size distributions.

[0026] Preparation method of a supported bimetallic oxide magnesium - aluminum spinel catalyst:

[0027] Uniformly mix magnesium - aluminum spinel with a metal compound (one of ferric nitrate, zinc nitrate, zirconium nitrate, tetrabutyl titanate), then add ethanol and disperse uniformly in ultrasonic for 3 - 5 hours. Then add a second metal compound (one of ferric nitrate, zinc nitrate, zirconium nitrate, tetrabutyl titanate, and different from the metal compound added for the first time), and continue to disperse uniformly in ultrasonic for 3 - 5 hours. Then evaporate the solvent under constant temperature stirring at 40 - 60 °C. After the material is completely dried, put it into an oven and dry at 95 - 105 °C for 10 hours to obtain a uniformly mixed powder; then carry out calcination, the calcination temperature is 400 - 900 °C, and the calcination time is 3 - 5 hours, correspondingly preparing TiO₂ - ZrO₂ - MAS, TiO₂ - ZnO - MAS, TiO₂ - Fe₂O₃ - MAS, ZrO₂ - ZnO - MAS, ZrO₂ - Fe₂O₃ - MAS, ZnO - Fe₂O₃ - MAS catalysts with hierarchical pore sizes.

[0028] The present invention will be further described in detail below with reference to the embodiments. (If not otherwise specified in the present invention, the percentage is the mass percentage.)

[0029] Example 1

[0030] According to MgO:Al2O3 (molar ratio) = 1:1.5, weigh 4.04 g of MgCl2·6H2O and 14.44 g of AlCl3·6H2O. Prepare a mixed salt solution with a concentration of 0.5 mol / L from MgCl2·6H2O and AlCl3·6H2O. Slowly drop ammonia water solution under rapid stirring, and keep the solution pH between 11 and 12. The generated white flocculent precipitate is filtered and washed with water to remove impurities. After filtration and washing with water, add 0.019 g of polyethylene glycol 70000 and 0.019 g of polyethylene glycol 130000, then dry at 90 °C, calcine (900 °C, 1 h), and ball-mill and disperse to obtain MgAl2O4 powder with a multi-level pore size distribution.

[0031] Take 2 g of the above MgAl2O4 powder, uniformly mix it with 0.022 g of the metal compound tetrabutyl titanate, then add ethanol and uniformly disperse it in ultrasonic for 5 hours. Then add 0.014 g of the second metal compound zirconium nitrate, and continue to uniformly disperse it in ultrasonic for 5 hours. Then evaporate the solvent under slow stirring at a constant temperature of 40 °C. After the material is completely dried, put it into an oven and dry at 95 °C for 10 hours. Take it out and put it into a muffle furnace and calcine at 900 °C for 3 hours to obtain a TiO2-ZrO2-MAS catalyst with a multi-level pore size.

[0032] Example 2

[0033] According to MgO:Al2O3 (molar ratio) = 1:2, weigh 4.04 g of MgCl2·6H2O and 19.24 g of AlCl3·6H2O. Prepare a mixed salt solution with a concentration of 0.5 mol / L from MgCl2·6H2O and AlCl3·6H2O. Slowly drop ammonia water solution under rapid stirring, and keep the solution pH between 11 and 12. The generated white flocculent precipitate is filtered and washed with water to remove impurities. After filtration and washing with water, add 0.1 g of polyethylene glycol 2000 and 0.14 g of polyethylene glycol 100000, then dry at 90 °C, calcine (800 °C, 3 h), and ball-mill and disperse to obtain MgAl2O4 powder with a multi-level pore size distribution.

[0034] Take 2 g of the above MgAl2O4 powder, uniformly mix it with 0.215 g of the metal compound tetrabutyl titanate, then add ethanol and uniformly disperse it in ultrasonic for 3 hours. Then add 0.152 g of the second metal compound iron nitrate, and continue to uniformly disperse it in ultrasonic for 3 hours. Then evaporate the solvent under slow stirring at a constant temperature of 60 °C. After the material is completely dried, put it into an oven and dry at 105 °C for 10 hours. Take it out and put it into a muffle furnace and calcine at 400 °C for 5 hours to obtain a TiO2-Fe2O3-MAS catalyst with a multi-level pore size.

[0035] Example 3

[0036] According to MgO:Al2O3 (molar ratio) = 1:1, weigh 4.04 g of MgCl2·6H2O and 9.62 g of AlCl3·6H2O. Prepare a mixed salt solution with a concentration of 0.5 mol / L from MgCl2·6H2O and AlCl3·6H2O. Slowly drip ammonia water solution under rapid stirring, keeping the solution pH between 11 - 12. The generated white flocculent precipitate is filtered and washed with water to remove impurities. After filtration and washing with water, add 0.05 g of polyethylene glycol 2000 and 0.09 g of polyethylene glycol 130000, then dry at 90 °C, calcine (at 1000 °C for 1.5 h), and ball-mill and disperse to obtain MgAl2O4 powder with a multi-level pore size distribution.

[0037] Take 2 g of the above-mentioned MgAl2O4 powder, uniformly mix it with 0.431 g of the metal compound tetrabutyl titanate, then add ethanol and uniformly disperse it in ultrasonic for 4 hours. Then add 0.233 g of the second metal compound zinc nitrate, and continue to uniformly disperse it in ultrasonic for 4 hours. Then evaporate the solvent under slow stirring at a constant temperature of 50 °C. After the material is completely dried, put it into an oven and dry at 100 °C for 10 hours. Take it out and put it into a muffle furnace and calcine at 600 °C for 4 hours to prepare a TiO2-ZnO-MAS catalyst with a multi-level pore size.

[0038] Example 4

[0039] According to MgO:Al2O3 (molar ratio) = 1:2, weigh 4.04 g of MgCl2·6H2O and 19.24 g of AlCl3·6H2O. Prepare a mixed salt solution with a concentration of 0.5 mol / L from MgCl2·6H2O and AlCl3·6H2O. Slowly drip ammonia water solution under rapid stirring, keeping the solution pH between 11 - 12. The generated white flocculent precipitate is filtered and washed with water to remove impurities. After filtration and washing with water, add 0.08 g of polyethylene glycol 2000 and 0.16 g of polyethylene glycol 130000, then dry at 90 °C, calcine (at 850 °C for 2 h), and ball-mill and disperse to obtain MgAl2O4 powder with a multi-level pore size distribution.

[0040] Take 2 g of the above-mentioned MgAl2O4 powder, uniformly mix it with 0.279 g of the metal compound zirconium nitrate, then add ethanol and uniformly disperse it in ultrasonic for 5 hours. Then add 0.186 g of the second metal compound zinc nitrate, and continue to uniformly disperse it in ultrasonic for 3 hours. Then evaporate the solvent under slow stirring at a constant temperature of 60 °C. After the material is completely dried, put it into an oven and dry at 100 °C for 10 hours. Take it out and put it into a muffle furnace and calcine at 700 °C for 3.5 hours to prepare a ZrO2-ZnO-MAS catalyst with a multi-level pore size.

[0041] Example 5

[0042] Weigh 4.04 g of MgCl₂·6H₂O and 14.44 g of AlCl₃·6H₂O according to MgO:Al₂O₃ (molar ratio) = 1:1.5. Prepare a mixed salt solution with a concentration of 0.5 mol / L from MgCl₂·6H₂O and AlCl₃·6H₂O. Slowly drip ammonia water solution under rapid stirring, and keep the pH of the solution between 11 and 12. The generated white flocculent precipitate is filtered and washed with water to remove impurities. After filtration and washing with water, add 0.05 g of polyethylene glycol 2000 and 0.10 g of polyethylene glycol 130000, then dry at 90 °C, calcine (800 °C, 2.5 h), and ball-mill and disperse to obtain MgAl₂O₄ powder with a multi-level pore size distribution.

[0043] Take 2 g of the above MgAl₂O₄ powder, uniformly mix it with 0.349 g of the metal compound zirconium nitrate, then add ethanol and disperse it uniformly in ultrasonic for 5 hours. Then add 0.304 g of the second metal compound iron nitrate, and continue to disperse it uniformly in ultrasonic for 3.5 hours. Then evaporate the solvent under constant temperature and slow stirring at 60 °C. After the material is completely dried, put it into an oven and dry at 100 °C for 10 hours. Take it out and put it into a muffle furnace and calcine at 650 °C for 4 hours to prepare a ZrO₂-Fe₂O₃-MAS catalyst with a multi-level pore size.

[0044] Example 6

[0045] Weigh 4.04 g of MgCl₂·6H₂O and 9.62 g of AlCl₃·6H₂O according to MgO:Al₂O₃ (molar ratio) = 1:1. Prepare a mixed salt solution with a concentration of 0.5 mol / L from MgCl₂·6H₂O and AlCl₃·6H₂O. Slowly drip ammonia water solution under rapid stirring, and keep the pH of the solution between 11 and 12. The generated white flocculent precipitate is filtered and washed with water to remove impurities. After filtration and washing with water, add 0.08 g of polyethylene glycol 2000 and 0.06 g of polyethylene glycol 70000, then dry at 90 °C, calcine (900 °C, 2.5 h), and ball-mill and disperse to obtain MgAl₂O₄ powder with a multi-level pore size distribution.

[0046] Take the above 2 g of MgAl2O4 powder, mix it evenly with 0.163 g of metal compound zinc nitrate, then add ethanol and disperse it evenly in ultrasonic for 4.5 hours. Then add 0.212 g of the second metal compound iron nitrate, and continue to disperse it evenly in ultrasonic for 4 hours. Then evaporate the solvent under slow stirring at a constant temperature of 60 °C. After the material is completely dried, put it into an oven and dry it at 100 °C for 10 hours. After taking it out, put it into a muffle furnace and calcine it at 650 °C for 3.5 hours to obtain the ZnO2-Fe2O3-MAS catalyst with hierarchical pore sizes.

[0047] Example 7

[0048] Load 0.2 g of poplar powder into a pyrolysis reaction device pre-filled with 0.2 g of TiO2-ZrO2-MAS catalyst (pore sizes 2.0 - 5.63 nm, 12.37 - 14.52 nm), and separate the poplar powder from the catalyst with asbestos. In the magnesium aluminate spinel catalyst, the ratio of the total mass of the two metal oxides loaded to the mass of the carrier (magnesium aluminate spinel) is 0.005. Heat it to 400 °C at a heating rate of 10 K / min under a nitrogen atmosphere and carry out the catalytic pyrolysis reforming reaction for 20 min. The pyrolysis catalytic gas obtained is condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehyde compounds in the liquid product is 65.73%, and the mass percentage of furfural in the liquid product is 50.38%.

[0049] Example 8

[0050] Load 0.2 g of elm powder into a pyrolysis reaction device pre-filled with 1.0 g of TiO2-ZnO-MAS catalyst (pore sizes 4.70 - 10.0 nm, 11.83 - 14.65 nm), and separate the elm powder from the catalyst with asbestos. In the magnesium aluminate spinel catalyst, the ratio of the total mass of the two metal oxides loaded to the mass of the carrier (magnesium aluminate spinel) is 0.05. Heat it to 600 °C at a heating rate of 50 K / min under a nitrogen atmosphere and carry out the catalytic pyrolysis reforming reaction for 50 min. The pyrolysis catalytic gas obtained is condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehyde compounds in the liquid product is 72.61%, and the mass percentage of furfural in the liquid product is 55.37%.

[0051] Example 9

[0052] 0.2 g of Manchurian ash wood powder was loaded into a pyrolysis reaction device pre-filled with 0.6 g of TiO2-Fe2O3-MAS catalyst (pore sizes 10.0 - 13.50 nm, 15.0 - 19.28 nm), and asbestos was used to separate the Manchurian ash wood powder from the catalyst. In the magnesium aluminate spinel catalyst, the ratio of the total mass of the two metal oxides loaded to the mass of the carrier (magnesium aluminate spinel) was 0.1. Under a nitrogen atmosphere, the temperature was raised to 450 °C at a heating rate of 15 K / min, and the catalytic pyrolysis reforming reaction was carried out for 40 min. The pyrolysis catalytic gas obtained was condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehyde compounds in the liquid product was 78.71%, and among them, the mass percentage of furfural in the liquid product was 64.88%.

[0053] Example 10

[0054] 0.2 g of oak wood powder was loaded into a pyrolysis reaction device pre-filled with 0.4 g of ZrO2-ZnO-MAS catalyst (pore sizes 12.07 - 15.0 nm, 18.47 - 23.61 nm), and asbestos was used to separate the oak wood powder from the catalyst. In the magnesium aluminate spinel catalyst, the ratio of the total mass of the two metal oxides loaded to the mass of the carrier (magnesium aluminate spinel) was 0.02. Under a nitrogen atmosphere, the temperature was raised to 500 °C at a heating rate of 20 K / min, and the catalytic pyrolysis reforming reaction was carried out for 30 min. The pyrolysis catalytic gas obtained was condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehyde compounds in the liquid product was 60.69%, and among them, furfural accounted for 57.88%.

[0055] Example 11

[0056] 0.2 g of birch wood powder was loaded into a pyrolysis reaction device pre-filled with 0.8 g of ZrO2-Fe2O3-MAS catalyst (pore sizes 4.06 - 6.35 nm, 15.87 - 25.0 nm), and asbestos was used to separate the birch wood powder from the catalyst. In the magnesium aluminate spinel catalyst, the ratio of the total mass of the two metal oxides loaded to the mass of the carrier (magnesium aluminate spinel) was 0.04. Under a nitrogen atmosphere, the temperature was raised to 450 °C at a heating rate of 30 K / min, and the catalytic pyrolysis reforming reaction was carried out for 25 min. The pyrolysis catalytic gas obtained was condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehyde compounds in the liquid product was 67.93%, and among them, the mass percentage of furfural in the liquid product was 56.28%.

[0057] Example 12

[0058] 0.2 g of maple wood powder was loaded into a pyrolysis reaction device pre-filled with 0.2 g of ZnO-Fe2O3-MAS catalyst (pore sizes 3.81 - 9.42 nm, 12.63 - 25.0 nm), and asbestos was used to separate the maple wood powder from the catalyst. In the magnesium aluminate spinel catalyst, the ratio of the total mass of the two metal oxides loaded to the mass of the carrier (magnesium aluminate spinel) was 0.07. Under a nitrogen atmosphere, the temperature was raised to 550 °C at a heating rate of 40 K / min, and catalytic pyrolysis reforming reaction was carried out for 35 min. The pyrolysis catalytic gas obtained was condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehyde compounds in the liquid product was 65.82%, and among them, the mass percentage of furfural in the liquid product was 59.04%.

[0059] Example 13

[0060] 0.2 g of elm wood powder was loaded into a pyrolysis reaction device pre-filled with 0.6 g of ZrO2-Fe2O3-MAS catalyst (pore sizes 6.32 - 9.40 nm, 15.77 - 23.81 nm), and asbestos was used to separate the elm wood powder from the catalyst. In the magnesium aluminate spinel catalyst, the ratio of the total mass of the two metal oxides loaded to the mass of the carrier (magnesium aluminate spinel) was 0.1. Under a nitrogen atmosphere, the temperature was raised to 500 °C at a heating rate of 15 K / min, and catalytic pyrolysis reforming reaction was carried out for 30 min. The pyrolysis catalytic gas obtained was condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehyde compounds in the liquid product was 83.14%, and among them, the mass percentage of furfural in the liquid product was 75.59%.

[0061] Example 14

[0062] 0.2 g of maple wood powder was loaded into a pyrolysis reaction device pre-filled with 0.5 g of ZrO2-ZnO-MAS catalyst (pore sizes 4.06 - 7.25 nm, 10.36 - 13.18 nm), and asbestos was used to separate the maple wood powder from the catalyst. In the magnesium aluminate spinel catalyst, the ratio of the total mass of the two metal oxides loaded to the mass of the carrier (magnesium aluminate spinel) was 0.06. Under a nitrogen atmosphere, the temperature was raised to 500 °C at a heating rate of 20 K / min, and catalytic pyrolysis reforming reaction was carried out for 25 min. The pyrolysis catalytic gas obtained was condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehyde compounds in the liquid product was 67.04%, and among them, the mass percentage of furfural in the liquid product was 56.64%.

[0063] Comparative Example 1

[0064] 0.2 g of Manchurian ash powder was loaded into a pyrolysis reaction device pre-filled with 1.0 g of MgAl2O4 catalyst (pore sizes 4.17 - 9.35 nm, 12.72 - 15.46 nm), and the Manchurian ash powder was separated from the catalyst by asbestos. Under a nitrogen atmosphere, the temperature was raised to 500 °C at a heating rate of 15 K / min, and the catalytic pyrolysis reforming reaction was carried out for 40 min. The pyrolysis catalytic gas obtained was condensed to obtain a liquid product. Among them, the mass percentage of aldehyde compounds in the liquid product was 22.05%, and the mass percentage of furfural in the liquid product was 16.80%.

[0065] As described above, the embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. Therefore, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Claims

1. A method for the preparation of aldehyde compounds by catalytic reforming of pyrolysis gas of lignocellulose biomass in a directed manner, characterized in that: The multi-stage pore continuous directional catalytic pyrolysis gas reforming of lignocellulose is carried out using a magnesium aluminate spinel catalyst to obtain a liquid product containing aldehyde compounds; The magnesium aluminate spinel catalyst is TiO2-ZrO2-MAS, TiO2-ZnO-MAS, TiO2-Fe2O3-MAS, ZrO2-ZnO-MAS, ZrO2-Fe2O3-MAS or ZnO-Fe2O3-MAS with multi-stage pores, where MAS represents magnesium aluminate spinel. Magnesium aluminate spinel is used as a matrix to support bimetallic oxides. Magnesium aluminate spinel has pores with different pore sizes, including pores with at least two of the pore sizes of 2-10 nm, 10-15 nm, and 15-25 nm; The preparation method of the magnesium aluminate spinel catalyst includes the following steps: (1) Mix magnesium salts, aluminum salts and water to obtain a mixed salt solution, add an ammonia water solution, react to form a white flocculent precipitate, collect the precipitate by filtration, add a solution of polyethylene glycol, stir evenly, dry, calcine, and ball-mill the calcined product to obtain magnesium aluminate spinel powder; (2) Mix the magnesium aluminate spinel powder with metal compounds evenly, and then calcine to obtain a magnesium aluminate spinel catalyst supporting bimetallic oxides, where the metal compounds are any two combinations of ferric nitrate, zinc nitrate, zirconium nitrate, and tetrabutyl titanate.

2. The method for preparing aldehyde compounds by catalytic reforming of pyrolysis gas of woody biomass according to claim 1, wherein: It includes the following steps: S1, Load granular lignocellulose and the catalyst into a pyrolysis reaction device, where the catalyst is a supported magnesium aluminate spinel catalyst, and the mass ratio of lignocellulose to the catalyst is 1:1 - 1:5; S2, Use an isolation structure to separate the lignocellulose and the catalyst; S3, Carry out a directional catalytic pyrolysis reforming reaction under a nitrogen atmosphere to obtain a pyrolysis catalytic gas; S4, The pyrolysis catalytic gas is condensed to obtain a liquid product containing aldehyde compounds.

3. The method for preparing aldehyde compounds by catalytic reforming of pyrolysis gas phase of lignocellulose biomass according to claim 2, wherein: The lignocellulose is any one or more of poplar powder particles, elm powder particles, manchurian ash powder particles, oak powder particles, birch powder particles, and maple particles.

4. The method for preparing aldehyde compounds by the gas-phase directional catalytic reforming of woody biomass pyrolysis according to claim 3, characterized in that: The particle size of the lignocellulose is 0.2 - 0.5 μm.

5. The method for the preparation of aldehyde compounds by the catalytic reforming of the pyrolysis gas phase of lignocellulose biomass according to claim 2, characterized in that: In step S3, the pyrolysis reaction device is heated to 400 - 600 °C at a heating rate of 10 - 50 K / min; The catalytic pyrolysis reforming reaction time is 20 - 50 min.

6. The method for preparing aldehyde compounds by catalytic reforming of pyrolysis gas phase of lignocellulose biomass according to claim 2, wherein: In step S2, asbestos is used to separate the lignocellulose and the catalyst.

7. The method for preparing aldehyde compounds by the gas-phase directional catalytic reforming of pyrolyzed woody biomass according to claim 1, wherein: In step (1), the magnesium salts and aluminum salts are mixed according to a molar ratio of MgO∶Al2O3 of 1:1 - 2; In step (1), polyethylene glycol accounts for 1 - 5% of the total mass of the precipitate. The polyethylene glycol is any two of polyethylene glycol - 2000, polyethylene glycol 70000, polyethylene glycol 100000, and polyethylene glycol 130000; Polyethylene glycol is pre-dissolved in ethanol and then mixed with the precipitate; In step (1), the calcination temperature is 800 - 1000 °C and the time is 1 - 3 h.

8. The method for preparing aldehyde compounds by catalytic reforming of pyrolysis gas of woody biomass according to claim 1, characterized in that: In step (2), magnesium aluminate spinel is uniformly mixed with any one of metal compounds such as iron nitrate, zinc nitrate, zirconium nitrate, and tetrabutyl titanate, then ethanol is added and uniformly dispersed in ultrasonic waves for 3-5 hours. Then, a metal compound different from the one added previously is selected from iron nitrate, zinc nitrate, zirconium nitrate, and tetrabutyl titanate and added to the mixed solution. After continuing to be uniformly dispersed in ultrasonic waves for 3-5 hours, the solvent is evaporated under constant temperature stirring at 40-60 °C. After the material is completely dried, it is placed in an oven and dried at 95-105 °C for 10 hours to obtain a uniformly mixed powder; In step (2), the calcination temperature is 400-900 °C and the calcination time is 3-5 hours.

9. The method for preparing aldehyde compounds by the gas-phase directional catalytic reforming of pyrolyzed woody biomass according to claim 1, wherein: In the magnesium aluminate spinel catalyst, the ratio of the total mass of the double metal oxide to the mass of the magnesium aluminate spinel is 0.005-0.1.

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