CN116603515A - Magnesia-alumina spinel catalyst and preparation method thereof, and method for preparing aldehyde compound by pyrolysis gas-phase directional catalytic reforming of woody biomass - Google Patents

Abstract

The invention discloses a magnesia-alumina spinel catalyst and a preparation method thereof, and a method for preparing aldehyde compounds by pyrolysis gas phase directional catalytic reforming of woody biomass, comprising the following steps: mixing magnesium salt and aluminum salt with water to obtain a mixed salt solution, adding an ammonia water solution, reacting to generate white flocculent precipitate, filtering, collecting precipitate, adding a polyethylene glycol solution, uniformly stirring, drying, calcining, and ball-milling a calcined product to obtain magnesia-alumina spinel powder; and uniformly mixing the magnesia-alumina spinel powder with a metal compound, and roasting to obtain the magnesia-alumina spinel catalyst loaded with the bimetallic oxide. The aluminum magnesium spinel is very suitable for pyrolysis catalysts, not only can avoid deactivation of metal components caused by carbon deposition and sintering, but also can load active metals on a carrier with a specific structure, and obtains better catalytic performance with less active metal amount by means of carrier effect, wherein the activity of the aluminum magnesium spinel is unique due to the intervention of the metal components.

Description

Magnesium aluminum spinel catalyst and its preparation method and woody biomass pyrolysis gas phase orientation Method for preparing aldehyde compounds by catalytic reforming

technical field

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

Background technique

The biomass pyrolysis process is extremely complex, including a variety of physical and chemical processes, such as physical processes such as diffusion and flow of substances, condensation of bio-oil, depolymerization or ring opening of macromolecular compounds, and reactions between functional groups of products. and other chemical processes. Adjusting pyrolysis factors, such as pyrolysis time, heating rate, adding directional catalyst and other factors, can increase the yield of the target product. In today's situation where fossil non-renewable resources are becoming increasingly tense, early research on the technology of pyrolysis of renewable resources to prepare compounds will help alleviate the pressure on fossil resources, and at the same time realize the efficient and sustainable development of high-value biomass in my country. Recycling has important practical significance.

However, in the prior art, in the process of using woody biomass pyrolysis catalytic reforming to prepare aldehyde compounds, due to the high pyrolysis temperature of woody biomass and the generation of biochar during the pyrolysis process, it is easy to cause carbon deposition in the catalyst and cause loss of energy. Therefore, the requirements for the thermal stability and catalytic activity of the catalyst are relatively high. Therefore, how to overcome the deficiencies of the prior art is an urgent problem to be solved in the field of biomass energy utilization technology.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a method for preparing aldehyde compounds by pyrolysis gas-phase directional catalytic reforming of woody biomass, which mainly solves the problem of preparing aldehyde compounds by pyrolysis catalytic reforming of woody biomass The technical problem that its conventional catalyst is easily deactivated due to carbon deposition in the process.

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

A preparation method of magnesium aluminum spinel catalyst, comprising the following steps: (1) mixing magnesium salt, aluminum salt and water to obtain mixed salt solution, adding ammonia solution, reacting to generate white flocculent precipitate, and collecting the precipitate by filtration , adding a solution of polyethylene glycol, stirring evenly, drying and calcining, and ball milling the calcined product to obtain magnesium-aluminum spinel powder; (2) mixing the magnesium-aluminum spinel powder and the metal compound uniformly, and then performing calcining to obtain a magnesium-aluminum spinel catalyst loaded with bimetallic oxides, wherein the metal compound is any combination of two of iron nitrate, zinc nitrate, zirconium nitrate and n-butyl titanate.

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

Further, in step (2), the magnesium-aluminum spinel is uniformly mixed with any metal compound in iron nitrate, zinc nitrate, zirconium nitrate, and n-butyl titanate, and then ethanol is added and uniformly dispersed in ultrasonic for 3-5 hours, and then choose a metal compound different from the previous addition from ferric nitrate, zinc nitrate, zirconium nitrate, and n-butyl titanate to add to the mixed solution, continue to disperse uniformly in the ultrasonic wave for 3-5 hours, and then Evaporate the solvent under constant temperature stirring at 40-60°C, place the material in an oven after it is completely dry, and dry it at 95-105°C for 10 hours to obtain a uniformly mixed powder; optional, as described in step (2) The firing temperature is 400-900° C., and the firing time is 3-5 hours.

Based on the same inventive concept, the present invention also provides a magnesium-aluminum spinel catalyst prepared by any of the above-mentioned preparation methods, wherein the magnesium-aluminum spinel catalyst is TiO ₂ -ZrO ₂ with multi-level pores -MAS, TiO ₂ -ZnO-MAS, TiO ₂ -Fe ₂ O ₃ -MAS, ZrO ₂ -ZnO-MAS, ZrO ₂ -Fe ₂ O ₃ -MAS or ZnO-Fe ₂ O ₃ -MAS, where MAS stands for Magnesium Aluminum spinel, magnesia-aluminum spinel is used as a matrix to support bimetallic oxides, and magnesia-alumina spinel has holes of different pore sizes, including holes with pore sizes of at least two of 2-10nm, 10-15nm, and 15-25nm .

Further, in the magnesium-aluminum spinel catalyst, the ratio of the total mass of bimetallic oxides to the mass of the magnesium-aluminum spinel is 0.005-0.1.

In the present invention, the carrier of the supported magnesium aluminum spinel catalyst is synthesized by MgO and Al ₂ O ₃ , which not only has the advantages of MgO and Al ₂ O ₃ , but also has two active centers, acidic and alkaline, and has pores structure. The saturated structure of magnesium aluminum spinel makes it have high thermal stability, its crystal phase structure can remain unchanged at high temperature, and its melting point is 2135°C. Magnesia-aluminum spinel has a catalytic effect, and after loading metal oxides, its thermal stability remains unchanged, and it has high-efficiency catalytic effect and selectivity for the target product. Therefore, spinel is very suitable for pyrolysis catalysts, especially as a support for supported metal catalysts, which can avoid the deactivation of metal components due to carbon deposition and sintering, and can support active metals on supports with specific structures , with the help of the support effect to obtain better catalytic performance with less active metal, its properties will make its activity unique due to the intervention of metal components. In addition, the present invention supports bimetallic oxides such as TiO ₂ , ZrO ₂ , ZnO, and Fe ₂ O ₃ by using magnesium-aluminum spinel catalysts with multi-level apertures (2-25nm), so that pyrolysis products of different molecular sizes and structures When passing through the catalyst, the pores of different diameters are continuously and directionally catalyzed, which further improves the efficiency of gas phase reforming and the yield of target products compared with catalysts with a single diameter pore structure.

Based on the same inventive concept, the present invention also provides a method for preparing aldehyde compounds by pyrolysis gas-phase directional catalytic reforming of woody biomass, using the above-mentioned magnesium-aluminum spinel catalyst to carry out multi-level aperture continuous directional catalytic pyrolysis of woody biomass Gas-phase reforming to obtain liquid products containing aldehyde compounds. Preferably, the following steps are included: S1, loading granular woody biomass and a catalyst into a pyrolysis reaction device, wherein the catalyst is a loaded magnesium-aluminum spinel catalyst, and the mass ratio of woody biomass to the catalyst is 1 :1-1:5; S2, using an isolation structure to separate the woody biomass from the catalyst; S3, performing a directional catalytic pyrolysis reforming reaction in a nitrogen atmosphere to obtain a pyrolysis catalytic gas; S4, condensing the pyrolysis catalytic gas A liquid product containing aldehydes is obtained. In the present invention, the mass ratio of the woody biomass to the catalyst is 1:1 to 1:5. If this ratio is exceeded, the amount of the catalyst is too high, and it is difficult to collect liquid substances after condensation, and most of them are concentrated on the surface of the catalyst. , and if it is lower than this ratio, the content of aldehyde compounds in the liquid substance obtained by condensation is low.

Further, the woody biomass is any one or more of poplar wood powder particles, elm wood powder particles, ash wood powder particles, oak wood powder particles, birch wood powder particles and maple wood particles.

Further, the particle size of woody biomass is 0.2-0.5um.

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

Further, in step S2, asbestos is used to separate the woody biomass from the catalyst.

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

In the method for preparing aldehyde compounds by gas-phase directional catalytic reforming of woody biomass pyrolysis according to the present invention, the multi-stage pore size loaded magnesium-aluminum spinel catalyst is used to carry out multi-stage processing of woody biomass at a relatively high temperature Continuous and directional catalytic pyrolysis gas-phase reforming with pore size can effectively change the pyrolysis reaction pathway of woody biomass, greatly promote the formation of aldehyde compounds, and at the same time inhibit the formation of other organic liquid by-products. The aldehyde compounds of the present invention account for more than 60% of the bio-oil yield of the pyrolysis product, which is much higher than the proportion of woody biomass without catalysis (about 12%) or other catalysts (about 30%), and more importantly, aldehydes Furfural, an important kind of compound, accounts for more than 50% of pyrolysis product bio-oil.

Description of drawings

Fig. 1 is a scanning electron micrograph of the ZrO ₂ -Fe ₂ O ₃ -MAS catalyst of the embodiment of the present invention.

Fig. 2 is a scanning electron micrograph of the TiO ₂ -ZnO-MAS catalyst of the embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with embodiment.

Those skilled in the art should understand that the following examples are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. If no specific technique or condition is indicated in the examples, it shall be carried out according to the technique or condition described in the literature in this field or according to the product specification. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased.

The preparation method of the magnesium-aluminum spinel catalyst with a pore diameter of 2-25nm loaded with double metal oxides according to the present invention is specifically:

Preparation of magnesium aluminum spinel carrier:

According to MgO:Al ₂ O ₃ (molar ratio) = 1:1.5, MgCl ₂ 6H ₂ O and AlCl ₃ 6H ₂ O are prepared into a mixed salt solution with a concentration of 0.5mol/L, and ammonia is slowly dropped into it under rapid stirring Aqueous solution, keep the solution pH=11-12. The resulting white flocculent precipitate was filtered and washed with water to remove impurities. After filtering and washing with water, add a certain amount of polyethylene glycol (MgO and Al _{2 O} The total mass of 1-5% polyethylene glycol-2000, polyethylene glycol 70000, polyethylene glycol 100000, 130000 Any 2 kinds), polyethylene glycol needs to be fully dissolved in ethanol in advance. Then it is dried at 90°C, calcined (800-1000°C, 1-3h), and ball-milled to disperse to obtain MgAl ₂ O ₄ powders with different pore size distributions.

The preparation method of the magnesia-aluminum spinel catalyst supporting double metal oxide:

Mix magnesium aluminum spinel with metal compound (one of iron nitrate, zinc nitrate, zirconium nitrate, n-butyl titanate) evenly, then add ethanol and disperse evenly in ultrasonic for 3-5 hours, then add the second A metal compound (one of iron nitrate, zinc nitrate, zirconium nitrate, n-butyl titanate, and different from the metal compound added for the first time), continued to disperse uniformly in the ultrasonic wave for 3-5 hours, and then at 40 Evaporate the solvent under constant temperature stirring at -60°C. After the material is completely dry, put it in an oven and dry it at 95-105°C for 10 hours to obtain a uniformly mixed powder; then roast it at 400-900°C. The calcination time is 3-5 hours, and TiO ₂ -ZrO ₂ -MAS, TiO ₂ -ZnO-MAS, TiO ₂ -Fe ₂ O ₃ -MAS, ZrO ₂ -ZnO-MAS, ZrO ₂ -Fe ₂ O ₃ -MAS, ZnO-Fe ₂ O ₃ -MAS catalysts.

The present invention will be further described in detail below in conjunction with the examples. (if there are no special instructions in the present invention, the percentage sign is a mass percentage.)

Example 1

According to MgO:Al ₂ O ₃ (molar ratio) = 1:1.5, weigh 4.04g of MgCl ₂ ·6H ₂ O, 14.44g of AlCl ₃ ·6H ₂ O, MgCl ₂ ·6H ₂ O and AlCl ₃ ·6H ₂ O was prepared into a mixed salt solution with a concentration of 0.5 mol/L, and the ammonia solution was slowly added dropwise under rapid stirring to keep the pH of the solution between 11-12. The resulting white flocculent precipitate was filtered and washed with water to remove impurities. After filtering and washing with water, add 0.019g polyethylene glycol 70000 and 0.019g polyethylene glycol 130000, then dry at 90°C, calcinate (900°C, 1h), and disperse by ball milling to obtain MgAl ₂ O with multi-level pore size distribution. ₄ powder.

Take the above 2g of MgAl ₂ O ₄ powder, mix it evenly with 0.022g of metal compound n-butyl titanate, then add ethanol and disperse evenly in ultrasonic for 5 hours, then add 0.014g of the second metal compound zirconium nitrate, continue to After dispersing uniformly in the medium for 5 hours, evaporate the solvent under constant temperature and slow stirring at 40°C. After the material is completely dry, put it in an oven, dry it at 95°C for 10 hours, take it out, put it in a muffle furnace and bake it at 900°C for 3 hours. , to prepare TiO ₂ -ZrO ₂ -MAS catalyst with multi-level pore diameter.

Example 2

According to MgO:Al ₂ O ₃ (molar ratio ₎ = 1:2, weigh 4.04g of MgCl ₂ ·6H ₂ O, 19.24g of AlCl 3 ·6H ₂ O, MgCl ₂ ·6H ₂ O and AlCl ₃ ·6H ₂ O was prepared into a mixed salt solution with a concentration of 0.5 mol/L, and the ammonia solution was slowly added dropwise under rapid stirring to keep the pH of the solution between 11-12. The resulting white flocculent precipitate was filtered and washed with water to remove impurities. After filtering and washing with water, add 0.1g polyethylene glycol 2000 and 0.14g polyethylene glycol 100000, then dry at 90°C, calcinate (800°C, 3h), and disperse by ball milling to obtain MgAl ₂ O with multi-level pore size distribution. ₄ powder.

Take the above 2g of MgAl ₂ O ₄ powder, mix it evenly with 0.215g of metal compound n-butyl titanate, then add ethanol and disperse in ultrasonic for 3 hours, then add 0.152g of the second metal compound, ferric nitrate, and continue to After dispersing uniformly in the medium for 3 hours, evaporate the solvent under constant temperature and slow stirring at 60°C. After the material is completely dry, put it in an oven, dry it at 105°C for 10 hours, take it out, put it in a muffle furnace and bake it at 400°C for 5 hours. , to prepare TiO ₂ -Fe ₂ O ₃ -MAS catalyst with multi-level pore diameter.

Example 3

According to MgO:Al ₂ O ₃ (molar ratio) = 1:1, weigh 4.04g of MgCl ₂ ·6H ₂ O, 9.62g of AlCl ₃ ·6H ₂ O, MgCl ₂ ·6H ₂ O and AlCl ₃ ·6H ₂ O was prepared into a mixed salt solution with a concentration of 0.5 mol/L, and the ammonia solution was slowly added dropwise under rapid stirring to keep the pH of the solution between 11-12. The resulting white flocculent precipitate was filtered and washed with water to remove impurities. After filtering and washing with water, add 0.05g polyethylene glycol 2000 and 0.09g polyethylene glycol 130000, then dry at 90°C, calcinate (1000°C, 1.5h), and disperse by ball milling to obtain _MgAl2 with multi-level pore size distribution. O ₄ powder.

Take the above 2g of MgAl ₂ O ₄ powder, mix it evenly with 0.431g of metal compound n-butyl titanate, then add ethanol and disperse in ultrasonic for 4 hours, then add 0.233g of the second metal compound zinc nitrate, continue to After dispersing uniformly in the medium for 4 hours, evaporate the solvent under constant temperature and slow stirring at 50°C. After the material is completely dry, put it in an oven, dry it at 100°C for 10 hours, take it out, put it in a muffle furnace and bake it at 600°C for 4 hours. , to prepare a TiO ₂ -ZnO-MAS catalyst with multi-level pore diameter.

Example 4

According to MgO:Al ₂ O ₃ (molar ratio) = 1:2, weigh 4.04g of MgCl ₂ ·6H ₂ O, 19.24g of AlCl ₃ ·6H ₂ O, MgCl ₂ ·6H ₂ O and AlCl ₃ ·6H ₂ O was prepared into a mixed salt solution with a concentration of 0.5 mol/L, and the ammonia solution was slowly added dropwise under rapid stirring to keep the pH of the solution between 11-12. The resulting white flocculent precipitate was filtered and washed with water to remove impurities. After filtering and washing with water, add 0.08g polyethylene glycol 2000 and 0.16g polyethylene glycol 130000, then dry at 90°C, calcinate (850°C, 2h), and disperse by ball milling to obtain MgAl ₂ O with multi-level pore size distribution. ₄ powder.

Take the above 2g of MgAl ₂ O ₄ powder, mix it with 0.279g of metal compound zirconium nitrate evenly, then add ethanol and disperse evenly in ultrasonic for 5 hours, then add 0.186g of the second metal compound zinc nitrate, continue to disperse evenly in ultrasonic After 3 hours, evaporate the solvent under constant temperature and slow stirring at 60°C. After the material is completely dry, put it in an oven, dry it at 100°C for 10 hours, take it out, put it in a muffle furnace and bake it at 700°C for 3.5 hours to obtain ZrO ₂ -ZnO-MAS catalyst with multi-level pore diameter.

Example 5

According to MgO:Al ₂ O ₃ (molar ratio) = 1:1.5, weigh 4.04g of MgCl ₂ ·6H ₂ O, 14.44g of AlCl ₃ ·6H ₂ O, MgCl ₂ ·6H ₂ O and AlCl ₃ ·6H ₂ O was prepared into a mixed salt solution with a concentration of 0.5 mol/L, and the ammonia solution was slowly added dropwise under rapid stirring to keep the pH of the solution between 11-12. The resulting white flocculent precipitate was filtered and washed with water to remove impurities. After filtering and washing with water, add 0.05g polyethylene glycol 2000 and 0.10g polyethylene glycol 130000, then dry at 90°C, calcinate (800°C, 2.5h), and disperse by ball milling to obtain _MgAl2 with multi-level pore size distribution. O ₄ powder.

Take the above 2g of MgAl ₂ O ₄ powder, mix it with 0.349g of metal compound zirconium nitrate evenly, then add ethanol and disperse evenly in ultrasonic for 5 hours, then add 0.304g of the second metal compound ferric nitrate, continue to disperse evenly in ultrasonic After 3.5 hours, evaporate the solvent under constant temperature and slow stirring at 60°C. After the material is completely dry, put it in an oven, dry it at 100°C for 10 hours, take it out, put it in a muffle furnace and bake it at 650°C for 4 hours to obtain ZrO ₂ -Fe ₂ O ₃ -MAS catalyst with multi-level pore diameter.

Example 6

According to MgO:Al ₂ O ₃ (molar ratio) = 1:1, weigh 4.04g of MgCl ₂ ·6H ₂ O, 9.62g of AlCl ₃ ·6H ₂ O, MgCl ₂ ·6H ₂ O and AlCl ₃ ·6H ₂ O was prepared into a mixed salt solution with a concentration of 0.5 mol/L, and the ammonia solution was slowly added dropwise under rapid stirring to keep the pH of the solution between 11-12. The resulting white flocculent precipitate was filtered and washed with water to remove impurities. After filtering and washing with water, add 0.08g polyethylene glycol 2000 and 0.06g polyethylene glycol 70000, then dry at 90°C, calcinate (900°C, 2.5h), and disperse by ball milling to obtain _MgAl2 with multi-stage pore size distribution. O ₄ powder.

Take the above 2g of MgAl ₂ O ₄ powder, mix it with 0.163g of metal compound zinc nitrate evenly, then add ethanol and disperse evenly in ultrasonic for 4.5 hours, then add 0.212g of the second metal compound ferric nitrate, continue to disperse evenly in ultrasonic After 4 hours, evaporate the solvent under constant temperature and slow stirring at 60°C. After the material is completely dry, put it in an oven, dry it at 100°C for 10 hours, take it out, put it in a muffle furnace and bake it at 650°C for 3.5 hours to obtain ZnO ₂ -Fe ₂ O ₃ -MAS catalyst with multi-level pore diameter.

Example 7

Put 0.2g poplar wood powder into the pyrolysis reaction device with 0.2g TiO ₂ -ZrO ₂ -MAS catalyst (pore diameter 2.0-5.63nm, 12.37-14.52nm) in advance, and use asbestos to separate the poplar wood powder from the catalyst Open, and in the magnesium-aluminum spinel catalyst, the ratio of the total mass of the two metal oxides to the mass of the support (magnesium-aluminum spinel) is 0.005, and the temperature rises to 400 °C at a heating rate of 10K/min under a nitrogen atmosphere. The catalytic pyrolysis reforming reaction is carried out for 20 minutes, and the obtained pyrolysis catalytic gas is condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehydes in the liquid product is 65.73%, and the mass percentage of furfural in the liquid product is 50.38%.

Example 8

Put 0.2g of elm powder into the pyrolysis reaction device with 1.0g of TiO ₂ -ZnO-MAS catalyst (pore size 4.70-10.0nm, 11.83-14.65nm) in advance, and use asbestos to separate the elm powder from the catalyst , and in the magnesium-aluminum spinel catalyst, the ratio of the total mass of the two metal oxides to the mass of the support (magnesia-alumina spinel) is 0.05, and the heating rate is raised to 600°C at a rate of 50K/min under a nitrogen atmosphere, and the Catalytic pyrolysis and reforming reaction for 50 minutes, the obtained pyrolysis catalytic gas is condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehydes in the liquid product was 72.61%, and the mass percentage of furfural in the liquid product was 55.37%.

Example 9

Put 0.2g ash wood powder into the pyrolysis reaction device with 0.6g TiO ₂ -Fe ₂ O ₃ -MAS catalyst (pore size 10.0-13.50nm, 15.0-19.28nm) in advance, and use asbestos to ash wood The powder is separated from the catalyst, and in the magnesium-aluminum spinel catalyst, the ratio of the total mass of the two metal oxides to the mass of the carrier (magnesia-alumina spinel) is 0.1, and the temperature rises at a rate of 15K/min under a nitrogen atmosphere. To 450°C, carry out the catalytic pyrolysis reforming reaction for 40 minutes, and the obtained pyrolysis catalytic gas is condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehyde compounds in the liquid product is 78.71%, and the mass percentage of furfural in the liquid product is 64.88%.

Example 10

Put 0.2g oak wood powder into the pyrolysis reaction device with 0.4g ZrO ₂ -ZnO-MAS catalyst (pore size 12.07-15.0nm, 18.47-23.61nm) in advance, and use asbestos to separate the oak wood powder from the catalyst , and in the magnesium-aluminum spinel catalyst, the ratio of the total mass of the two metal oxides to the mass of the carrier (magnesia-alumina spinel) is 0.02, and the heating rate is raised to 500 °C at a rate of 20K/min under a nitrogen atmosphere, and the Catalyzed pyrolysis reforming reaction for 30 minutes, the obtained pyrolysis catalytic gas is condensed to obtain a liquid product rich in aldehyde compounds. Aldehyde compounds accounted for 60.69% by mass of the liquid product, of which furfural accounted for 57.88%.

Example 11

Put 0.2g birch powder into the pyrolysis reaction device with 0.8g ZrO ₂ -Fe ₂ O ₃ -MAS catalyst (aperture 4.06-6.35nm, 15.87-25.0nm) in advance, and use asbestos to separate the birch powder from the catalyst Open, and in the magnesium-aluminum spinel catalyst, the ratio of the total mass of the two metal oxides to the mass of the support (magnesium-aluminum spinel) is 0.04, and the temperature rises to 450°C at a rate of 30K/min under a nitrogen atmosphere. The catalytic pyrolysis reforming reaction is carried out for 25 minutes, and the obtained pyrolysis catalytic gas is condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehydes in the liquid product is 67.93%, and the mass percentage of furfural in the liquid product is 56.28%.

Example 12

Put 0.2g maple powder into the pyrolysis reaction device with 0.2g ZnO-Fe ₂ O ₃ -MAS catalyst (pore size 3.81-9.42nm, 12.63-25.0nm) in advance, and use asbestos to mix the maple powder with the catalyst Separated, and in the magnesium-aluminum spinel catalyst, the ratio of the total mass of the two metal oxides to the mass of the support (magnesium-aluminum spinel) is 0.07, and the temperature rises to 550°C at a rate of 40K/min under a nitrogen atmosphere , carry out the catalytic pyrolysis reforming reaction for 35 minutes, and the obtained pyrolysis catalytic gas is condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehydes in the liquid product is 65.82%, and the mass percentage of furfural in the liquid product is 59.04%.

Example 13

Put 0.2g elm powder into the pyrolysis reaction device with 0.6g ZrO ₂ -Fe ₂ O ₃ -MAS catalyst (aperture 6.32-9.40nm, 15.77-23.81nm) in advance, and use asbestos to mix the elm powder and The catalyst is separated, and in the magnesium-aluminum spinel catalyst, the ratio of the total mass of the two metal oxides to the mass of the carrier (magnesia-alumina spinel) is 0.1, and the temperature rises to 500 at a heating rate of 15K/min under a nitrogen atmosphere. ℃, carry out the catalytic pyrolysis reforming reaction for 30 minutes, and the obtained pyrolysis catalytic gas is condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehydes in the liquid product was 83.14%, and the mass percentage of furfural in the liquid product was 75.59%.

Example 14

Put 0.2g maple wood powder into the pyrolysis reaction device with 0.5g ZrO ₂ -ZnO-MAS catalyst (pore size 4.06-7.25nm, 10.36-13.18nm) in advance, and use asbestos to separate the maple wood powder from the catalyst , and in the magnesium-aluminum spinel catalyst, the ratio of the total mass of the two metal oxides to the mass of the support (magnesia-alumina spinel) is 0.06, and the temperature is raised to 500 °C at a rate of 20K/min under a nitrogen atmosphere. The catalytic pyrolysis reforming reaction was carried out for 25 minutes, and the obtained pyrolysis catalytic gas was condensed to obtain a liquid product rich in aldehyde compounds. The mass percentage of aldehydes in the liquid product is 67.04%, and the mass percentage of furfural in the liquid product is 56.64%.

Comparative example 1

Put 0.2g of ash powder into the pyrolysis reaction device with 1.0g of MgAl ₂ O ₄ catalyst (aperture 4.17-9.35nm, 12.72-15.46nm) in advance, and use asbestos to separate the ash powder from the catalyst , under a nitrogen atmosphere at a heating rate of 15K/min to 500°C, and carry out a catalytic pyrolysis reforming reaction for 40 minutes, and the obtained pyrolysis catalytic gas is condensed to obtain a liquid product. The mass percentage of aldehyde compounds in the liquid product is 22.05%, and the mass percentage of furfural in the liquid product is 16.80%.

As mentioned above, the embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; 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: it can still be used for the foregoing implementation Modifications to the technical solutions described in the examples, or equivalent replacements for some of the technical features; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, so those of ordinary skill in the art All other embodiments obtained under the premise of no creative work belong to the protection scope of the present invention.

Claims (10)

1. The preparation method of the magnesia-alumina spinel catalyst is characterized by comprising the following steps of: the method comprises the following steps:

(1) Mixing magnesium salt and aluminum salt with water to obtain a mixed salt solution, adding an ammonia water solution, reacting to generate white flocculent precipitate, filtering, collecting precipitate, adding a polyethylene glycol solution, uniformly stirring, drying, calcining, and ball-milling a calcined product to obtain magnesia-alumina spinel powder;

(2) Uniformly mixing the magnesia-alumina spinel powder with a metal compound, and roasting to obtain the magnesia-alumina spinel catalyst loaded with the bimetallic oxide, wherein the metal compound is any two of ferric nitrate, zinc nitrate, zirconium nitrate and n-butyl titanate.

2. The method for preparing the magnesia-alumina spinel catalyst according to claim 1, wherein: in the step (1), magnesium salt and aluminum salt are mixed according to MgO to Al ₂ O ₃ The molar ratio is 1:1-2, mixing;

optionally, in the step (1), polyethylene glycol accounts for 1-5% of the total mass of the precipitate, wherein the polyethylene glycol is any 2 of polyethylene glycol-2000, polyethylene glycol 70000, polyethylene glycol 100000 and polyethylene glycol 130000; preferably, polyethylene glycol is dissolved in ethanol in advance and then mixed with the precipitate;

optionally, the calcination in step (1) is carried out at a temperature of 800-1000 ℃ for a time of 1-3 hours.

3. The method for preparing the magnesia-alumina spinel catalyst according to claim 1, wherein: uniformly mixing magnesia-alumina spinel with any one of metal compounds of ferric nitrate, zinc nitrate, zirconium nitrate and n-butyl titanate, adding ethanol, uniformly dispersing in ultrasound for 3-5 hours, then adding one metal compound different from the metal compound added in the previous time into the mixed solution, continuously uniformly dispersing in ultrasound for 3-5 hours, then evaporating the solvent under constant temperature stirring at 40-60 ℃, putting the materials into an oven after the materials are completely dried, and drying for 10 hours at 95-105 ℃ to obtain uniformly mixed powder;

optionally, the roasting temperature in the step (2) is 400-900 ℃ and the roasting time is 3-5 hours.

4. A magnesia alumina spinel catalyst, characterized by: prepared by the preparation method of the magnesia-alumina spinel catalyst of any one of claims 1 to 3, wherein the magnesia-alumina spinel catalyst is TiO with multi-stage pore diameter ₂ -ZrO ₂ -MAS、TiO ₂ -ZnO-MAS、TiO ₂ -Fe ₂ O ₃ -MAS、ZrO ₂ -ZnO-MAS、ZrO ₂ -Fe ₂ O ₃ MAS or ZnO-Fe ₂ O ₃ -MAS, wherein MAS stands for magnesium aluminate spinel, which serves as matrix-supported bimetallic oxide, with pores of different pore sizes, including pores of at least two pore sizes of 2-10nm, 10-15nm, 15-25 nm.

5. The magnesia alumina spinel catalyst as claimed in claim 4, wherein: in the magnesium aluminate spinel catalyst, the ratio of the total mass of the bimetallic oxide to the mass of the magnesium aluminate spinel is 0.005-0.1.

6. A method for preparing aldehyde compounds by pyrolysis gas-phase directional catalytic reforming of woody biomass is characterized by comprising the following steps: multistage pore diameter continuous directional catalytic pyrolysis gas phase reforming of woody biomass using the magnesia-alumina spinel catalyst of claim 4 or 5 to obtain a liquid product containing aldehyde compounds.

7. The method for preparing aldehyde compounds by pyrolysis gas phase directional catalytic reforming of woody biomass according to claim 6, wherein the method comprises the following steps: the method comprises the following steps:

s1, loading granular woody biomass and a catalyst into a pyrolysis reaction device, wherein the catalyst is a supported magnesia-alumina spinel catalyst, and the mass ratio of the woody biomass to the catalyst is 1:1-1:5;

s2, separating the woody biomass from the catalyst by using a separation structure;

s3, carrying out directional catalytic pyrolysis reforming reaction in a nitrogen atmosphere to obtain pyrolysis catalytic gas;

s4, condensing the pyrolysis catalytic gas to obtain a liquid product containing aldehyde compounds.

8. The method for preparing aldehyde compounds by pyrolysis gas phase directional catalytic reforming of woody biomass according to claim 7, wherein the method comprises the following steps: the woody biomass is any one or more of poplar powder particles, elm powder particles, ash powder particles, oak powder particles, birch powder particles and maple particles.

9. The method for preparing aldehyde compounds by pyrolysis gas phase directional catalytic reforming of woody biomass according to claim 8, wherein the method comprises the following steps: the particle size of the woody biomass is 0.2-0.5um.

10. The method for preparing aldehyde compounds by pyrolysis gas phase directional catalytic reforming of woody biomass according to claim 7, wherein the method comprises the following steps: in the step S3, the pyrolysis reaction device is raised to 400-600 ℃ at a heating rate of 10-50K/min;

optionally, the catalytic pyrolysis reforming reaction time is 20-50min;

optionally, in step S2, asbestos is used to separate the woody biomass from the catalyst.