A biochar-supported aluminum-zirconium diacid type solid acid catalyst and its preparation method and application

Abstract

The present invention discloses a biochar-supported aluminum-zirconium dual acid type solid acid catalyst and a preparation method and application thereof, belonging to the technical field of heterogeneous solid acid catalysts. 3 ) 3 and CO 4 Zr is used as raw material, and a full solid phase method strategy of mechanical activation treatment combined with high temperature calcination is adopted to construct a biochar-loaded aluminum-zirconium double acid type solid acid catalyst. The catalyst is a double acid type solid acid catalyst of green economy, stable performance and directional catalysis, and the acid content thereof is about 3.6 μmol / g, and the Lewis acid content is about 47.7 μmol / g. The preparation method of the catalyst of the present invention is simple to operate, the raw materials are easy to obtain, the conditions are simple and mild, and the production cost is low. The catalyst of the present invention is applied to catalyze cellulose to prepare levulinic acid, the conversion rate of cellulose can reach 97.5%, and the yield of levulinic acid can reach 67.5%, which has a good application prospect for efficiently converting cellulose to prepare levulinic acid, and has important research significance for effectively promoting the high value utilization of cellulose resources.

Description

Technical Field

[0001] The invention belongs to the technical field of heterogeneous solid acid catalysts, and specifically relates to a biochar-loaded aluminum-zirconium diacid type solid acid catalyst, and a preparation method and application thereof. Background Art

[0002] Cellulose is the main component of lignocellulosic biomass and is widely present in various plant cells, such as wood, cotton, agricultural straw, algae, etc., which can be used as raw materials for cellulose extraction. As the plant biomass with the largest total amount in nature, cellulose plays an important role in the development of human society. Cellulose can be effectively converted to produce glucose, sorbitol, ethylene glycol, synthesis gas, aromatic hydrocarbons, levulinic acid (LA), furan compounds, etc. through hydrolysis, hydrogenation, pyrolysis, dehydration and other reactions. LA molecules contain carboxyl and carbonyl groups and have good chemical reactivity. They can undergo chemical reactions such as esterification, halogenation, hydrogenation, oxidative dehydrogenation, condensation, and salt formation. They can also be used as intermediates to synthesize a series of high-value-added chemicals and new polymer materials.

[0003] The catalytic conversion of cellulose to 5-hydroxymethylfurfural (5-HMF) and LA is a cascade process, including cellulose hydrolysis to glucose, glucose isomerization to fructose, fructose dehydration to 5-HMF, and 5-HMF rehydration to LA and formic acid (FA). Different types of acid sites are required to promote the main reaction and inhibit the formation of by-products. Isomerization is mainly promoted by Lewis acid sites, and pyridine nitrogen (N) also shows outstanding catalytic performance for isomerization, which can assist Lewis acid sites to improve the isomerization efficiency. Hydrolysis, dehydration and rehydration are mainly promoted by Bronsted acid sites. site promotion. Therefore, The synergistic effect of the Lewis acid sites is beneficial to enhance the main reaction, inhibit the side reactions, and contribute to the direct conversion of cellulose into 5-HMF and LA.

[0004] Catalytic conversion of cellulose to LA requires The combined effect of acid and Lewis acid, traditional homogeneous catalysts (inorganic, organic liquid phase The problems of Lewis acid and metal chloride salts (Lewis acid) are many by-products, low selectivity and recovery rate, difficulty in effectively separating the final product, high equipment requirements, and large amount of acid waste liquid, which restrict the development of homogeneous catalytic conversion of cellulose. Therefore, heterogeneous catalysts that are easy to separate from the reaction mixture and have good recyclability are gaining more and more attention. Solid acid, as a kind of heterogeneous acid catalyst, is widely used in the catalytic conversion of cellulose due to its adjustable acidity, reusability, durability and high selectivity. Metal oxides, as a kind of catalyst with both Lewis acidity and Acidic solid acids not only have the advantages of solid catalysts, but also have the advantages of high catalytic activity and good thermal stability compared with other solid acids. However, when bare metal oxides are used as catalysts, harsh reaction conditions will change the structure and composition of metal particles, causing metal leaching, sintering and coking, leading to serious deactivation of metal catalysts. Therefore, it is necessary to load them on a suitable carrier to solve these problems. The metal-carrier interaction formed by the supported solid acid catalyst prepared by the traditional method is weak, which makes the active components easy to be leached under hydrothermal conditions, reducing the reaction activity.

[0005] Mechanical activation (MA) is an intense ball milling process that destroys the dense crystalline structure of solid materials through the impact, shear, friction and other forces generated by the high-speed movement of the ball milling medium, and forms a close interaction between the components. Mechanical activation changes the apparent structure, physicochemical properties and reactivity of solid materials, which in turn has a positive impact on subsequent processes and product characteristics. It is considered to be a simple and environmentally friendly pretreatment method for preparing functional composite materials. For starch as a biochar (BC) precursor, the strong mechanical action can effectively promote the uniform dispersion and embedding of metal salts in starch, which is conducive to the formation of strong interactions between metals and starch-derived BC after calcination. The resulting structurally stable BC-supported metal composite has excellent reusability, thereby improving the efficiency and economic feasibility of practical applications. MA has the advantages of high efficiency, simplicity, high reproducibility and high stability. It shows excellent characteristics in the preparation of composite materials, especially effectively promoting the formation of strong metal-support interactions in composite materials, which undoubtedly provides a new strategy for the preparation of highly stable and active biochar-based composite materials. Summary of the invention

[0006] In view of the above problems, the present invention provides a biochar-supported aluminum-zirconium diacid type solid acid catalyst and its preparation method and application to solve the problems of low activity, difficult separation, easy deactivation and poor stability of traditional heterogeneous solid acid catalysts. The present invention adopts a full solid phase method strategy of mechanical treatment combined with high-temperature calcination to prepare a biochar-supported aluminum-zirconium diacid type solid acid catalyst with strong metal-carrier interaction, which is used to efficiently catalyze the conversion of cellulose into levulinic acid.

[0007] The present invention is achieved through the following technical solutions:

[0008] A biochar-supported aluminum-zirconium diacid solid acid catalyst for the synthesis of starch, Al(NO 3 ) 3 , CO 4Zr and urea are mixed and mechanically activated, and then calcined at high temperature under the protection of inert gas to obtain a biochar-supported aluminum-zirconium double acid type solid acid catalyst; the biochar-supported aluminum-zirconium double acid type solid acid catalyst contains Al-Zr components formed by Al 0.08 Zr 0.92 O 0.196 Solid solution.

[0009] Furthermore, the biochar-supported aluminum-zirconium diacid-type solid acid catalyst has a Bronsted acid content of 3.5 to 4 μmol / g and a Lewis acid content of 47 to 48 μmol / g.

[0010] A method for preparing the biochar-supported aluminum-zirconium diacid type solid acid catalyst as described above comprises the following steps:

[0011] (1) Pretreatment: starch, Al(NO 3 ) 3 , CO 4 Zr and urea are mixed and dried, the obtained mixture and ball milling media are added into a mechanically activated solid phase reactor for pretreatment, the ball milling media are separated by sieving, and a pretreated mixture is obtained;

[0012] (2) calcining: calcining the pretreated mixture under nitrogen or argon protection to obtain a calcined product;

[0013] (3) Activation: The calcined product is activated with a hydrochloric acid solution, then washed to neutrality, and vacuum dried to obtain a biochar-supported aluminum-zirconium diacid type solid acid catalyst.

[0014] Furthermore, in step (1), the starch, Al(NO 3 ) 3 , CO 4 The mass ratio of Zr to urea is 10:2 to 5:3 to 5:1.

[0015] Furthermore, in step (1), the mass ratio of the mixture to the ball milling medium is 1:15-20; and the ball milling medium is zirconium dioxide.

[0016] Furthermore, in step (1), the pretreatment is ball milling at a rotation speed of 400 to 500 rpm for 50 to 60 minutes.

[0017] Furthermore, in step (2), the calcination temperature is 700-800° C. and the calcination time is 1.5-2 h.

[0018] Furthermore, in step (3), the mass ratio of the calcined product to the hydrochloric acid solution is 100-120 mg:1 mL; and the concentration of the hydrochloric acid solution is 1-1.2 mol / L.

[0019] Furthermore, in step (3), the activation time is 0.5 to 1 h; the vacuum drying temperature is 70 to 80° C., and the time is 10 to 12 h.

[0020] A use of the biochar-supported aluminum-zirconium diacid type solid acid catalyst as described above in catalyzing cellulose to prepare levulinic acid.

[0021] Furthermore, the application is specifically as follows: cellulose, deionized water and the catalyst are added into a hydrothermal reactor in a ratio of 0.1 g:10 mL:0.1-0.25 g, and reacted for 2-6 hours under an oil bath condition of 160-180° C. After the reaction is completed, the obtained reaction solution is cooled and filtered through a 0.25 μm filter membrane to obtain levulinic acid.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0023] 1. The present invention uses starch, urea, Al(NO 3 ) 3 and CO 4 Zr is used as raw material, and a full solid phase method strategy of mechanical activation treatment combined with high temperature calcination is adopted to construct a biochar-supported aluminum-zirconium dual acid type solid acid catalyst. The present invention effectively strengthens the interface interaction between Al and Zr-based components, Al-Zr components and biochar through mechanical activation treatment, so that the catalyst has a stable bimetallic-support structure and efficiently catalyzes cellulose to prepare levulinic acid. The present invention successfully constructs a green, economical, stable, and directional catalytic catalyst through a full solid phase method strategy. -Lewis double acid type solid acid catalyst provides a new method strategy for the design and development of functional catalysts, which has important research significance for effectively promoting the high-value utilization of cellulose resources.

[0024] 2. The present invention uses mechanical activation to effectively refine the particles of each component and destroy their crystal structure, thereby making Al(NO 3 ) 3 , CO 4 The close interaction between Zr and starch is conducive to the formation of a mutually nested structure after high-temperature calcination, thereby constructing a stable bimetallic-support strong interaction structure, reducing the leaching of active components, and improving the stability of the catalyst; mechanical activation treatment promotes the Al(NO 3 ) 3 and CO 4 Zr undergoes surface complexation with the -OH of starch, strengthening the interaction between the metal salt and starch, thereby presenting a mutually embedded structure, which is beneficial to the stable immobilization of the active components on the biochar carrier, so as to construct a supported solid acid catalyst with strong bimetallic-carrier interaction.

[0025] 3. The present invention can refine the catalyst particles through mechanical activation treatment, effectively improving the dispersibility of the metal-based components; the Al-Zr component in the catalyst forms Al 0.08 Zr 0.92 O 0.196 Solid solution, indicating that the Al-based component and the Zr-based component are embedded in each other's lattices and embedded in the biochar carrier with a regular crystal structure, successfully constructing a stable bimetallic-carrier structure; mechanical activation treatment strengthens the interface interaction between the Al-Zr components, changes the electron cloud density between them, promotes the surface hydroxylation of the catalyst, thereby significantly increasing the Lewis acid content of the catalyst and improving the catalytic conversion efficiency of cellulose. The catalyst of the present invention has both A double acid type solid acid catalyst with Lewis acid sites and The acid content is about 3.6 μmol / g, and the Lewis acid content is about 47.7 μmol / g.

[0026] 4. The preparation method of the catalyst of the present invention is simple to operate, the raw materials are readily available, the conditions are simple and mild, and the production cost is low. The catalyst of the present invention has a good catalytic conversion efficiency for cellulose. When the catalyst is applied to the process of catalyzing cellulose to prepare levulinic acid, the conversion rate of cellulose and the yield of levulinic acid are high. The conversion rate of cellulose can reach 97.5%, and the yield of levulinic acid can reach 67.5%. It has a good application prospect for the efficient conversion of cellulose to prepare levulinic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The untreated raw starch and the starch-urea-Al (NO 3 ) 3 -CO 4 Zr, MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 SEM images of Zr, AZ / N-BC and MA-AZ / N-BC prepared in Example 1.

[0028] Figure 2 The Starch-urea, Starch-urea-Al(NO 3 ) 3 -CO 4 Zr, MA-treated starch-urea-Al(NO 3 ) 3 -CO 4XRD patterns of Zr, MA-N-BC, MA-A-BC, MA-Z-BC, AZ-BC and MA-AZ / N-BC prepared in Example 1.

[0029] Figure 3 The Starch-urea, Starch-urea-Al(NO 3 ) 3 -CO 4 Zr, MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 FT-IR graphs of Zr, AZ / N-BC, MA-N-BC and MA-AZ / N-BC prepared in Example 1.

[0030] Figure 4 The XPS spectra of AZ / N-BC prepared in Comparative Example 4 and MA-AZ / N-BC prepared in Example 1 are shown.

[0031] Figure 5 Py-IR graphs of AZ / N-BC prepared in Comparative Example 4 and MA-AZ / N-BC prepared in Example 1 analyzed at 100, 200 and 350°C. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below by way of examples. These examples are only used to illustrate the present invention and do not limit the protection scope of the present invention.

[0033] Example 1

[0034] Preparation of biochar-supported aluminum-zirconium diacid type solid acid catalyst:

[0035] 30g starch, 9.4g Al(NO 3 ) 3 , 12.5 g CO 4 Zr and 3.0g urea were mixed and dried at 80°C for 5h. The resulting mixture and 1000g ball-milling medium zirconium dioxide were added to a ball mill for mechanical activation treatment, and ball milled at a rotation speed of 400rpm for 60min. After the ball milling was completed, the ball milling medium was separated by sieving to obtain a pretreated mixture. The obtained pretreated mixture was calcined at 700°C under nitrogen protection for 2h to obtain a calcined product. The obtained calcined product was activated with 50mL 1mol / L hydrochloric acid solution for 1h, then washed with deionized water to neutrality, and dried in a vacuum oven at 70°C for 12h to obtain a biochar-supported aluminum-zirconium diacid type solid acid catalyst (denoted as MA-AZ / N-BC).

[0036] Example 2

[0037] Preparation of biochar-supported aluminum-zirconium diacid type solid acid catalyst:

[0038] 30g starch, 7.5g Al(NO 3 ) 3 , 13.4 g CO 4 Zr and 3.0g urea were mixed and dried at 80°C for 5h. The resulting mixture and 1000g ball-milling medium zirconium dioxide were added to a ball mill for mechanical activation treatment, and ball milled at a rotation speed of 400rpm for 60min. After the ball milling was completed, the ball milling medium was separated by sieving to obtain a pretreated mixture. The obtained pretreated mixture was calcined at 700°C under nitrogen protection for 2h to obtain a calcined product. The obtained calcined product was activated with 50mL 1mol / L hydrochloric acid solution for 1h, then washed with deionized water to neutrality, and dried in a vacuum oven at 70°C for 12h to obtain a biochar-supported aluminum-zirconium diacid type solid acid catalyst (denoted as MA-AZ / N-BC).

[0039] Example 3

[0040] Preparation of biochar-supported aluminum-zirconium diacid type solid acid catalyst:

[0041] 30g starch, 6.3g Al(NO 3 ) 3 , 13.9 g CO 4 Zr and 3.0g urea were mixed and dried at 80°C for 5h. The resulting mixture and 1000g ball-milling medium zirconium dioxide were added to a ball mill for mechanical activation treatment, and ball milled at a rotation speed of 500rpm for 50min. After the ball milling was completed, the ball milling medium was separated by sieving to obtain a pretreated mixture. The obtained pretreated mixture was calcined at 800°C under nitrogen protection for 1.5h to obtain a calcined product. The obtained calcined product was activated with 50mL1mol / L hydrochloric acid solution for 0.5h, then washed with deionized water to neutrality, and dried in a vacuum oven at 80°C for 10h to obtain a biochar-loaded aluminum-zirconium diacid type solid acid catalyst (denoted as MA-AZ / N-BC).

[0042] Example 4

[0043] Preparation of biochar-supported aluminum-zirconium diacid type solid acid catalyst:

[0044] 30g starch, 12.4g Al(NO 3 ) 3 , 11.2 g CO 4Zr and 3.0g urea were mixed and dried at 80°C for 5h. The resulting mixture and 1000g ball-milling medium zirconium dioxide were added to a ball mill for mechanical activation treatment and ball milled at a rotation speed of 500rpm for 60min. After the ball milling was completed, the ball milling medium was separated by sieving to obtain a pretreated mixture. The obtained pretreated mixture was calcined at 700°C under argon protection for 2h to obtain a calcined product. The obtained calcined product was activated with 50mL 1mol / L hydrochloric acid solution for 1h, then washed with deionized water to neutrality, and dried in a vacuum oven at 70°C for 12h to obtain a biochar-supported aluminum-zirconium diacid type solid acid catalyst (denoted as MA-AZ / N-BC).

[0045] Comparative Example 1

[0046] 30 g of starch and 3 g of urea were simply mixed to obtain a simple mixture of starch-urea (denoted as Starch-urea).

[0047] Comparative Example 2

[0048] 30g starch, 9.4g Al(NO 3 ) 3 , 12.5 g CO 4 Zr and 3.0 g urea were simply mixed to obtain starch-urea-Al(NO 3 ) 3 -CO 4 A simple mixture of Zr (denoted as Starch-urea-Al(NO 3 ) 3 -CO 4 Zr).

[0049] Comparative Example 3

[0050] 30g starch, 9.4g Al(NO 3 ) 3 , 12.5 g CO 4 Zr and 3.0 g urea were mixed and dried at 80 °C for 5 h. The resulting mixture and 1000 g zirconium dioxide as a ball milling medium were added to a ball mill for mechanical activation treatment. The ball milling was performed at a speed of 400 rpm for 60 min. After the ball milling was completed, the ball milling medium was separated by sieving to obtain starch-urea-Al(NO 3 ) 3 -CO 4 Zr mixture (denoted as MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 Zr).

[0051] Comparative Example 4

[0052] The difference between Comparative Example 4 and Example 1 is that the mixture in Comparative Example 4 is not subjected to mechanical activation treatment, and the other preparation conditions are the same as those in Example 1, thereby obtaining a biochar-loaded aluminum-zirconium diacid type solid acid catalyst (denoted as AZ / N-BC) that is not treated with MA.

[0053] Comparative Example 5

[0054] The difference between Comparative Example 5 and Example 1 is that the mixture in Comparative Example 5 does not contain Al(NO 3 ) 3 and CO 4 Zr, and the other preparation conditions were the same as those in Example 1, to obtain a biochar solid acid catalyst (denoted as MA-N-BC).

[0055] Comparative Example 6

[0056] The difference between Comparative Example 6 and Example 1 is that the mixture in Comparative Example 6 does not contain CO 4 Zr and urea, and the other preparation conditions were the same as those in Example 1, to obtain a biochar-supported aluminum solid acid catalyst (denoted as MA-A-BC).

[0057] Comparative Example 7

[0058] The difference between Comparative Example 7 and Example 1 is that the mixture in Comparative Example 7 does not contain Al(NO 3 ) 3 and urea, and the other preparation conditions were the same as those in Example 1, to obtain a biochar-supported zirconium solid acid catalyst (denoted as MA-Z-BC).

[0059] Comparative Example 8

[0060] The difference between Comparative Example 8 and Example 1 is that the mixture in Comparative Example 8 does not contain urea and the mixture is not subjected to mechanical activation treatment, and the other preparation conditions are the same as those in Example 1, thereby obtaining a biochar-loaded aluminum-zirconium diacid type solid acid catalyst (denoted as AZ-BC) that is not doped with urea.

[0061] Material Characterization Analysis

[0062] (I) SEM analysis

[0063] Scanning electron microscopy (SEM) was used to characterize and analyze different samples. Figure 1 As shown, Figure 1 The untreated raw starch and the starch-urea-Al (NO 3 ) 3 -CO 4Zr, MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 SEM images of Zr, AZ / N-BC and MA-AZ / N-BC prepared in Example 1. Figure 1 middle, Figure 1 (a) is the SEM image of untreated native starch. Figure 1 (b) is Starch-urea-Al(NO 3 ) 3 -CO 4 SEM image of Zr, Figure 1 (c) is MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 SEM image of Zr, Figure 1 (de) is the SEM image of AZ / N-BC, Figure 1 (fh) are SEM images of MA-AZ / N-BC.

[0064] Depend on Figure 1 (a) It can be seen that the original starch without any treatment presents smooth surface, regular shape, and dispersed spheres; Figure 1 (b) It can be seen that the starch-urea-Al (NO 3 ) 3 -CO 4 In a simple mixture of Zr, the four components of the precursor are simply stacked, and agglomeration occurs between the metal salts and between the metal salts and urea. The catalyst prepared by calcining with this as the precursor is prone to metal agglomeration, which makes the metal active sites easily leached into the reaction solution, thereby affecting the activity of the catalyst. Figure 1 (c) It can be seen that the starch treated with MA in Comparative Example 3, Al(NO 3 ) 3 , CO 4 In the mixture of Zr and urea, the intact starch particles were completely destroyed, the particle size was significantly reduced, and the four components of the precursor were tightly combined and embedded in each other, indicating that the strong mechanical force during the MA treatment effectively destroyed the crystalline structure of starch and embedded the metal salt into its structure. The two metal salts were also embedded in each other, forming a stable solid acid catalyst after calcination, thus laying the foundation for constructing a stable bimetallic-carrier strong interaction structure.

[0065] Depend on Figure 1 (de) It can be seen that the surface of the biochar-supported aluminum-zirconium diacid solid acid catalyst of Comparative Example 4 without MA treatment presents irregular blocks, and small spherical particles are simply accumulated on the surface of the block; Figure 1 (fh) It can be seen that in the MA-treated biochar-loaded aluminum-zirconium dual acid solid acid catalyst of Example 1, the smaller spheres are embedded in the larger flake stacking structure, presenting a mutually nested structure, and the overall particles are generally smaller than those of AZ / N-BC. This may be because after the MA treatment, the precursor components are effectively refined, so that the prepared catalyst presents relatively small particles; the Al and Zr components, and the Al and Zr components and BC are embedded in each other to form a tightly bound interaction. This interactive precursor is conducive to the formation of a mutually nested structure after high-temperature calcination, thereby constructing a stable bimetallic-carrier strong interaction structure, reducing the leaching of active components, and improving the stability of MA-AZ / N-BC.

[0066] (ii) XRD analysis

[0067] X-ray diffractometer (XRD) was used to characterize and analyze different samples. Figure 2 As shown, Figure 2 The Starch-urea, Starch-urea-Al(NO 3 ) 3 -CO 4 Zr, MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 XRD patterns of Zr, MA-N-BC, MA-A-BC, MA-Z-BC, AZ-BC and MA-AZ / N-BC prepared in Example 1. Figure 2 middle, Figure 2 (a) is Starch-urea, Starch-urea-Al (NO 3 ) 3 -CO 4 Zr, MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 XRD pattern of Zr, Figure 2 (b) is the XRD pattern of MA-N-BC, MA-A-BC, MA-Z-BC, AZ-BC, and MA-AZ / N-BC.

[0068] Depend on Figure 2 (a) It can be seen that the diffraction peak of the simple mixture of starch and urea in Comparative Example 1 is clearly visible, and the diffraction peak of the simple mixture of starch and urea in Comparative Example 2 is clearly visible. 3 ) 3 and CO 4After simple stirring and mixing of starch and urea, Al(NO 3 ) 3 and CO 4 After the mixed material of Zr was treated with MA, no crystal diffraction peaks of starch, metal salt and other components were detected, indicating that starch, urea, Al(NO 3 ) 3 and CO 4 The crystal structures of the four Zr components were all destroyed by mechanical forces, and Al salts, Zr salts, bimetallic salts and starch were easily embedded in each other's lattices, laying the foundation for building a structurally stable catalyst, which was consistent with the results of SEM analysis.

[0069] Depend on Figure 2 (b) It can be seen that in the MA-N-BC catalyst, broad diffraction peaks attributed to the (002) and (101) crystal planes of graphite carbon were observed, indicating that MA-N-BC is an amorphous structure; no crystalline diffraction peaks of any Al species were detected in the MA-A-BC catalyst, indicating that the Al species in MA-A-BC exists in an amorphous form; tetragonal and monoclinic ZrO were detected in the MA-Z-BC catalyst. 2 Crystal phase, indicating that the single metal Zr salt mainly forms two crystal forms of ZrO after calcination. 2 crystals; for AZ / N-BC and MA-AZ / N-BC catalysts, all diffraction peaks at 2θ = 30.5° (101), 35.4° (110), 50.9° (112), 60.5° (211), 63.5° (202) and 74.9° (220) are attributed to Al 0.08 Zr 0.92 O 0.196 (PDF#54-1134) solid solution. The formation of solid solution indicates that the MA treatment causes the metal Al and Zr to be embedded in each other's lattices, forming an interface coupling effect, which effectively improves the interface compatibility. 2 With only weak Lewis sites, the Al-based component is incorporated into the Zr-based component to form a solid solution, which can effectively enrich the acidity type of the catalyst. Figure 2 It can be clearly seen in (b) that the diffraction peak of MA-AZ / N-BC is significantly broader and weaker than that of AZ / N-BC. This is because the lattice breakage and lattice defects caused by MA treatment are conducive to the close bonding between crystal particles and further solid diffusion.

[0070] (III) FT-IR analysis

[0071] Fourier transform infrared spectrometer (FT-IR) was used to characterize and analyze different samples. Figure 3 As shown, Figure 3 The Starch-urea, Starch-urea-Al(NO 3 ) 3 -CO 4 Zr, MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 FT-IR graphs of Zr, AZ / N-BC, MA-N-BC and MA-AZ / N-BC prepared in Example 1. Figure 3 middle, Figure 3 (a) is Starch-urea, Starch-urea-Al (NO 3 ) 3 -CO 4 Zr, MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 FT-IR image of Zr, Figure 3 (b) FT-IR graphs of AZ / N-BC, MA-N-BC, and MA-AZ / N-BC.

[0072] Depend on Figure 3 (a) It can be seen that starch-urea-Al(NO 3 ) 3 -CO 4 Zr and MA-treated starch-urea-Al(NO 3 ) 3 -CO 4 The infrared spectra of Zr are similar, except for the intensity of each absorption peak, indicating that MA treatment can change the functional group content of the material. 3 ) 3 -CO 4 Compared with Zr, the starch-urea-Al(NO 3 ) 3 -CO 4 The absorption peak of -OH of Zr became narrower and steeper, indicating that MA treatment can induce more -OH to complex with metal salts on the surface. 3 ) 3 -CO 4 The -OH absorption peak of Zr (3427 cm -1) compared to the -OH absorption peak (3477 cm -1 ) showed an obvious negative shift, which further demonstrated that MA treatment could strengthen the surface complexation between -OH in starch and metal salts, enhance the interaction between metal salts and starch, and thus improve the stability of the prepared catalyst.

[0073] Depend on Figure 3 (b) It can be seen that the FT-IR spectra of MA-N-BC, AZ / N-BC and MA-AZ / N-BC catalysts show similar peaks located at 3200-3700 cm -1 The band at 1650 cm-1 is attributed to the stretching vibration of -OH and NH. -1 The nearby spectral bands are attributed to the stretching vibration of C=O. From the figure, it can be seen that the stretching vibration peaks of -OH and C=O in MA-AZ / N-BC are stronger than those of AZ / N-BC, indicating that the MA-AZ / N-BC catalyst has more oxygen-containing functional groups. This is because the MA treatment of the precursor can promote the formation of free radicals on the surface of the prepared MA-AZ / N-BC, resulting in the cleavage of the C=C bond and the formation of active species (free radicals, anions and cations), promoting the combination of oxygen species and the formation of more oxygen-containing functional groups, which will also show stronger reactivity in the catalytic reaction.

[0074] (IV) XPS analysis

[0075] X-ray photoelectron spectroscopy (XPS) was used to characterize and analyze the surface chemical state and elemental composition of different samples. Figure 4 As shown, Figure 4 The XPS spectra of AZ / N-BC prepared in Comparative Example 4 and MA-AZ / N-BC prepared in Example 1 are shown. Figure 4 middle, Figure 4 (a) is the full XPS spectrum of AZ / N-BC and MA-AZ / N-BC. Figure 4 (bf) XPS spectra of AZ / N-BC and MA-AZ / N-BC in C1s, N 1s, O 1s, Al 2p, and Zr 3d regions, respectively.

[0076] Depend on Figure 4 (a) It can be seen that AZ / N-BC and MA-AZ / N-BC catalysts have C, N, O, Al and Zr elements at the same time. Figure 4 (b) It can be seen that the C1s of AZ / N-BC and MA-AZ / N-BC can be well fitted into three peaks, and the 284.36 eV of MA-AZ / N-BC (AZ / N-BC is located at 284.41 eV) belongs to the SP of CC. 2hybridization, 286.28 eV (AZ / N-BC is located at 286.28 eV) is attributed to C-OH or CN, and 288.44 eV (AZ / N-BC is located at 284.44 eV) is attributed to C=O or C=N, indicating that the AZ / N-BC and MA-AZ / N-BC catalysts contain abundant oxygen- and nitrogen-containing functional groups on their surfaces, which will provide the required oxygen- and nitrogen-containing functional groups for the catalytic conversion of cellulose. Acid sites, while nitrogen-containing functional groups have Alkalinity can also provide more catalytic active sites for the isomerization of glucose by assisting Lewis acid sites. The contents of C-OH and C=O in AZ / N-BC are 9.55% and 6.34%, respectively, and the contents of C-OH and C=O in MA-AZ / N-BC are 11.51% and 6.75%, respectively. The contents of C-OH and C=O in MA-AZ / N-BC are higher than those in AZ / N-BC, indicating that MA-AZ / N-BC prepared from MA-treated precursors has more oxygen-containing functional groups. The bridging strategy of Zr-based components and Al-based components is conducive to the hydroxylation of the MA-AZ / N-BC surface, thereby increasing the content of -OH species, which is an important factor in improving the reaction activity of the catalyst.

[0077] Figure 4 (c) It can be seen that the N1s spectra of AZ / N-BC and MA-AZ / N-BC can be fitted into three peaks, corresponding to pyridinic N (397.54 eV for MA-AZ / N-BC and 397.36 eV for AZ / N-BC), pyrrole N (399.53 eV for MA-AZ / N-BC and 399.21 eV for AZ / N-BC) and N-oxide (402.64 eV for MA-AZ / N-BC and 401.45 eV for AZ / N-BC), indicating that there are multiple forms of N species in AZ / N-BC and MA-AZ / N-BC catalysts. Previous studies have shown that pyridinic N exhibits excellent catalytic activity and high selectivity in the process of glucose isomerization to fructose, because the lone electron pair in pyridine is delocalized and can donate electrons in the reaction, which is different from the fully delocalized five-atom state of pyrrole. The contents of pyridinic N in AZ / N-BC and MA-AZ / N-BC were 14.88% and 16.58%, respectively. The proportion of pyridinic N in MA-AZ / N-BC was higher than that in AZ / N-BC, indicating that MA-Al / N-BC showed stronger activity in the glucose isomerization reaction, and pyridinic N could synergize with Lewis acid sites to significantly improve the catalytic conversion efficiency of cellulose.

[0078] Depend on Figure 4(d) It can be seen that the fitting peak of the binding energy of AZ / N-BC and MA-AZ / N-BC at around 530 eV (529.71 eV for MA-AZ / N-BC and 529.93 eV for AZ / N-BC) is attributed to the surface lattice oxygen (Lattice O) of Zr-based oxides or Al-based oxides, while that near 531 eV (531.57 eV for MA-AZ / N-BC and 531.76 eV for AZ / N-BC) is attributed to C-OH, and that near 533 eV is attributed to OC=O (533.04 eV for MA-AZ / N-BC and 533.25 eV for AZ / N-BC). Compared with the lattice oxygen in AZ / N-BC, the binding energy of lattice oxygen in MA-AZ / N-BC undergoes a significant negative shift. This is because after MA treatment, the Al-based components and the Zr-based components are embedded in each other, which improves the interfacial compatibility of the composite catalyst and enhances the interfacial interaction between the two components. The solid solution formed can stably exist in the biochar carrier, thereby improving the stability of the catalyst.

[0079] Depend on Figure 4 (e) It can be seen that the main peak of AZ / N-BC is located at 73.86eV, while the main peak of MA-AZ / N-BC is located at 73.45eV. In contrast, the Al 2p peak of MA-N-BC moves to a lower binding energy, which indicates that the MA-AZ / N-BC catalyst has a higher electron cloud density, so MA-AZ / N-BC will have more Lewis acid sites and will show better catalytic performance in the catalytic conversion of cellulose.

[0080] Depend on Figure 4 (f) It can be seen that the two peaks of MA-AZ / N-BC at 181.72 and 184.12 eV (AZ / N-BC at 180.99 and 183.39 eV) correspond to Zr 4+ Zr 3d 5 / 2 and Zr 3d 3 / 2 It can be clearly seen from the figure that the diffraction peak of Zr 3d of MA-AZ / N-BC moves to a higher binding energy. This is because the MA treatment of the precursor effectively strengthens the interface interaction of the prepared catalyst, resulting in the formation of interface coupling between the Al-based and Zr-based components, causing the electron cloud between Al and Zr atoms to change. The high electronegativity formed by the increase in the electron cloud near the Al atom leads to an increase in the positive charge of the Zr atom, which ultimately increases the number and intensity of Lewis sites of MA-AZ / N-BC.

[0081] (V) Py-IR analysis

[0082] Pyridine adsorption infrared spectrometer (Py-IR) was used to characterize and analyze the surface chemical state and elemental composition of different samples. Figure 5 As shown, Figure 5 Py-IR graphs of AZ / N-BC prepared in Comparative Example 4 and MA-AZ / N-BC prepared in Example 1 analyzed at 100, 200 and 350°C. Figure 5 middle, Figure 5 (ac) are Py-IR spectra of AZ / N-BC and MA-AZ / N-BC analyzed at 100, 200 and 350 °C.

[0083] The acid site type of the catalyst plays an important role in the catalytic conversion reaction of cellulose, so FT-IR spectroscopy was performed after evacuation of pyridine adsorption at different temperatures (100, 200 and 350 °C) to distinguish the Lewis and Acid sites, from Figure 5 The Lewis acid sites (indicated by L in the figure) and Acid sites (indicated by B in the figure). According to the literature, the absorption bands in the sample spectrum are assigned at 1540 and 1640 cm -1 The spectral band table at can be summarized as Acid sites, Lewis acid sites are located at 1440 and 1570 cm -1 1490cm -1 The spectral bands show that AZ / N-BC and MA-AZ / N-BC exist simultaneously. and Lewis acid sites.

[0084] Obviously, Lewis and The acid sites all occupy the surface of AZ / N-BC and MA-AZ / N-BC. The acid sites are likely to come from the oxygen-containing functional groups (-OH and -COOH) on the surface of the biochar support and metal oxides, and may also come from the bridging -OH between Al and Zr. The acid contents were 2.7 and 3.6 μmol / g, and the Lewis acid contents were 35.3 and 47.7 μmol / g, respectively. MA-AZ / N-BC showed more The acid sites are mainly due to the fact that MA treatment can promote the formation of oxygen-containing acid functional groups, which is consistent with the results of FT-IR and XPS. The Lewis acid sites are attributed to the unsaturated coordinated Zr 4+ 、A1 3+ The number of Lewis acid sites of MA-AZ / N-BC catalyst is significantly greater than that of AZ / N-BC catalyst, which is consistent with the analysis results of Al 2p and Zr 3d in the XPS spectrum.

[0085] Application Example 1

[0086] Take the biochar-supported aluminum-zirconium bis-acid solid acid catalyst prepared in Example 1, put 0.1g cellulose, 10mL deionized water and 0.1g catalyst into a hydrothermal reactor lined with polytetrafluoroethylene (25mL), and then place the reactor in a 160°C oil bath. After reacting for 4h, take the reactor out of the oil bath, quickly cool it in a water bath to stop the reaction, and cool the obtained reaction solution and filter it through a filter membrane with a pore size of 0.25μm to obtain levulinic acid. It was determined that the conversion rate of cellulose was 77.1% and the yield of levulinic acid was 21.3%.

[0087] Application Example 2

[0088] The difference between Application Example 2 and Application Example 1 is that the oil bath temperature in Application Example 2 is 170° C., and the other preparation conditions are the same as those in Application Example 1. It was determined that the conversion rate of cellulose was 88.1%, and the yield of levulinic acid was 44.3%.

[0089] Application Example 3

[0090] The difference between Application Example 3 and Application Example 1 is that the oil bath temperature in Application Example 3 is 180° C., and the other preparation conditions are the same as those in Application Example 1. It was determined that the conversion rate of cellulose was 97.5%, and the yield of levulinic acid was 67.1%.

[0091] Application Example 4

[0092] The difference between Application Example 4 and Application Example 1 is that the oil bath temperature in Application Example 4 is 190° C., and the other preparation conditions are the same as those in Application Example 1. It was determined that the conversion rate of cellulose was 98.0%, and the yield of levulinic acid was 65.1%.

[0093] Application Example 5

[0094] The difference between Application Example 5 and Application Example 1 is that the oil bath temperature in Application Example 5 is 200° C., and the other preparation conditions are the same as those in Application Example 1. It was determined that the conversion rate of cellulose was 97.3%, and the yield of levulinic acid was 63.9%.

[0095] Application Example 6

[0096] The difference between Application Example 6 and Application Example 3 is that the reaction time in Application Example 6 is 2 hours, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 82.1%, and the yield of levulinic acid was 25.3%.

[0097] Application Example 7

[0098] The difference between Application Example 7 and Application Example 3 is that the reaction time in Application Example 7 is 3 hours, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 86.5%, and the yield of levulinic acid was 45.3%.

[0099] Application Example 8

[0100] The difference between Application Example 8 and Application Example 3 is that the reaction time in Application Example 8 is 5 hours, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 97.0%, and the yield of levulinic acid was 66.1%.

[0101] Application Example 9

[0102] The difference between Application Example 9 and Application Example 3 is that the reaction time in Application Example 9 is 6 hours, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 99.0%, and the yield of levulinic acid was 62.2%.

[0103] Application Example 10

[0104] The difference between Application Example 10 and Application Example 3 is that the amount of catalyst used in Application Example 10 is 0.05 g, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 78.5%, and the yield of levulinic acid was 21.1%.

[0105] Application Example 11

[0106] The difference between Application Example 11 and Application Example 3 is that the amount of catalyst used in Application Example 11 is 0.15 g, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 90.2%, and the yield of levulinic acid was 51.0%.

[0107] Application Example 12

[0108] The difference between Application Example 12 and Application Example 3 is that the amount of catalyst used in Application Example 12 is 0.20 g, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 92.3%, and the yield of levulinic acid was 54.0%.

[0109] Application Example 13

[0110] The difference between Application Example 13 and Application Example 3 is that the amount of catalyst used in Application Example 13 is 0.25 g, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 95.4%, and the yield of levulinic acid was 51.4%.

[0111] Application Comparative Example 1

[0112] The difference between Application Example 1 and Application Example 3 is that the catalyst used in Application Example 1 is the catalyst prepared in Comparative Example 4, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 35.2%, and the yield of levulinic acid was 0.3%.

[0113] Application Comparative Example 2

[0114] The difference between Application Example 2 and Application Example 3 is that the catalyst used in Application Example 2 is the catalyst prepared in Comparative Example 5, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 91.5%, and the yield of levulinic acid was 46.1%.

[0115] Application Comparative Example 3

[0116] The difference between Application Example 3 and Application Example 3 is that the catalyst used in Application Example 3 is the catalyst prepared in Comparative Example 6, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 95.3%, and the yield of levulinic acid was 38.4%.

[0117] Application Comparative Example 4

[0118] The difference between Application Example 4 and Application Example 3 is that the catalyst used in Application Example 4 is the catalyst prepared in Comparative Example 7, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 94.9%, and the yield of levulinic acid was 14.1%.

[0119] Application Comparative Example 5

[0120] The difference between Application Example 5 and Application Example 3 is that the catalyst used in Application Example 5 is the catalyst prepared in Comparative Example 8, and the other preparation conditions are the same as those in Application Example 3. It was determined that the conversion rate of cellulose was 94.3%, and the yield of levulinic acid was 40.0%.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A biochar-supported aluminum-zirconium diacid type solid acid catalyst, It is characterized in that Starch, Al(NO 3 ) 3 , CO 4 Zr and urea are mixed and dried, and then subjected to ball milling mechanical activation treatment, and then calcined under the protection of inert gas to obtain a biochar-supported aluminum-zirconium double acid type solid acid catalyst; the biochar-supported aluminum-zirconium double acid type solid acid catalyst contains Al formed by Al-Zr components 0.08 Zr 0.92 O 0.196 Solid solution; the biochar-supported aluminum-zirconium double acid type solid acid catalyst has a Bronsted acid content of 3.5 to 4 μmol / g and a Lewis acid content of 47 to 48 μmol / g.

2. A method for preparing the biochar-supported aluminum-zirconium diacid type solid acid catalyst as claimed in claim 1, It is characterized in that The following steps are involved: (1) Pretreatment: starch, Al(NO 3 ) 3 , CO 4 Zr and urea are mixed and dried, the obtained mixture and ball milling media are added into a mechanically activated solid phase reactor for pretreatment, the ball milling media are separated by sieving, and a pretreated mixture is obtained; (2) Calcination: calcining the pretreated mixture under nitrogen or argon protection to obtain a calcined product; (3) Activation: The calcined product is activated with a hydrochloric acid solution, then washed to neutrality, and vacuum dried to obtain a biochar-supported aluminum-zirconium diacid type solid acid catalyst.

3. The method for preparing the biochar-supported aluminum-zirconium dual acid type solid acid catalyst according to claim 2, It is characterized in that In step (1), the starch, Al(NO 3 ) 3 , CO 4 The mass ratio of Zr to urea is 10:2 to 5:3 to 5:

1.

4. The method for preparing the biochar-supported aluminum-zirconium double acid type solid acid catalyst according to claim 2, It is characterized in that In step (1), the mass ratio of the mixture to the ball milling medium is 1:15-20.

5. The method for preparing the biochar-supported aluminum-zirconium dual acid type solid acid catalyst according to claim 2, It is characterized in that In step (1), the pretreatment is ball milling at a rotation speed of 400 to 500 rpm for 50 to 60 min.

6. The method for preparing the biochar-supported aluminum-zirconium bis-acid type solid acid catalyst according to claim 2, It is characterized in that In step (2), the calcination temperature is 700-800° C. and the calcination time is 1.5-2 h.

7. The method for preparing the biochar-supported aluminum-zirconium diacid type solid acid catalyst according to claim 2, It is characterized in that In step (3), the mass ratio of the calcined product to the hydrochloric acid solution is 100-120 mg: 1 mL.

8. The method for preparing the biochar-supported aluminum-zirconium bis-acid type solid acid catalyst according to claim 2, It is characterized in that In step (3), the activation time is 0.5 to 1 h; the vacuum drying temperature is 70 to 80° C., and the time is 10 to 12 h.

9. Use of the biochar-supported aluminum-zirconium diacid type solid acid catalyst as claimed in claim 1 in catalyzing cellulose to prepare levulinic acid.

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