Solid acid catalyst for micropacked bed reactor and preparation method thereof

Abstract

The invention discloses a solid acid catalyst for a micropacked bed reactor and a preparation method of the solid acid catalyst, and relates to the field of catalysts. The preparation method of the solid acid catalyst comprises the following steps: (1) providing a porous carrier, and modifying the porous carrier by adopting an acid solution so as to load hydroxyl on the surface of the porous carrier to obtain a modified carrier; (2) mixing the modified carrier with a solution containing silane, and reacting at 50-200 DEG C for 0.5-36 hours to obtain a first basic catalyst; wherein the silane has a carbon chain length greater than or equal to 3; (3) mixing the first base catalyst with an oxidizing solution, and reacting at 30-100 DEG C for 0.5-36 hours to obtain a second base catalyst; and (4) mixing the second basic catalyst with a solution containing a sulfonic acid group, and reacting at 30-100 DEG C for 0.5-36 hours to obtain a reinforced solid acid catalyst finished product.

Description

Technical Field

[0001] The invention relates to the field of catalysts, and in particular to a solid acid catalyst for a micro-packed bed reactor and a preparation method thereof. Background Art

[0002] As a cornerstone compound for biomass value-added, 5-hydroxymethylfurfural (HMF) can be further prepared into 2,5-furandicarboxylic acid, 2,5-dimethylfuran, cyclohexanol, levulinic acid, sorbitol and other substances through oxidation, hydrogenation, hydration and other reaction pathways, which is of great significance to the development of biomass resources. HMF is mainly derived from hexose sugars such as glucose and fructose. Among them, fructose is considered to be the most ideal substrate for the preparation of HMF due to its advantages such as mild reaction conditions and short reaction path. Therefore, the efficient preparation of HMF from fructose and the catalysts and process conditions involved have become the focus of attention in the scientific and industrial communities. At present, the preparation of HMF from fructose is usually carried out in intermittent reactors such as stirred tanks and three-necked flasks. Intermittent reactors are usually limited by mass transfer and heat transfer, and usually have problems such as long reaction time, many by-products, low yield of target products, cumbersome intermittent operation, and complex scale-up. In addition, under the reaction conditions of high temperature and high pressure (100-200℃, 0-5MPa), intermittent reactors also have potential safety risks. Micro-packed beds are widely used in catalytic conversion processes due to their high mass and heat transfer efficiency, easy catalyst immobilization, plug flow characteristics, easy automation and scale-up, and inherent safety. They have great potential in the preparation of 5-HMF.

[0003] On the other hand, the reaction of fructose to produce HMF requires the presence of Acid site catalysts are used to promote the dehydration of fructose to produce HMF. In the early days, homogeneous catalysts including inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid were often used to participate in the reaction, but there were problems such as reactor corrosion, difficulty in catalyst separation and circulation, and environmental pollution. At present, catalysts such as zeolites, metal oxides, and functional organic frameworks commonly used in intermittent reactors have problems such as loss of active sites and poor stability, and most of them are in powder form. Direct use in micro-packed bed reactors may cause excessive pressure drop, leading to reactor blockage and high energy consumption of injection pumps. Commercial ion exchange resin catalysts have problems such as catalyst deformation and rapid performance decay at high temperatures (greater than 120°C), and there is also the problem of difficulty in catalyst circulation. Since the specific surface area of ​​the catalyst will decrease significantly as the catalyst particle size increases, the direct use of the powder solid acid catalyst preparation process for carriers with a particle size greater than 1 mm will significantly reduce the active site loading density, which will lead to the prepared catalysts having problems such as poor catalytic performance and insufficient stability.

[0004] In addition, the reaction process of fructose to prepare HMF mainly involves: (1) adsorption of fructose on the catalyst surface; (2) the adsorption of fructose on the catalyst surface. The acid sites are dehydrated to form HMF, and (3) HMF is desorbed from the catalyst. Although the catalyst has a large number of acid sites, it has a weak adsorption capacity for fructose, so it still has problems such as low efficiency in catalyzing fructose dehydration and poor catalytic performance. Even if the traditional catalyst is made into granules by tableting and other methods in a micro-packed bed reactor, there is still a problem of low HMF yield. At the same time, fructose will remove 3 molecules of water when forming HMF, and HMF will further combine with water on the catalyst surface in the presence of water to form a by-product, levulinic acid. Therefore, even if the reaction of fructose dehydration to prepare HMF is carried out in a pure organic solvent, it is difficult to avoid the formation of by-products. Especially in a micro-packed reactor, mass transfer is greatly enhanced, which means that fructose is easy to dehydrate to form HMF, and it also means that HMF is easy to combine with water to form by-products. Therefore, regulating the hydrophobicity of the catalyst and preventing HMF on the catalyst surface from contacting water and continuing to react is an effective means to improve the yield of HMF. Therefore, it is necessary to develop a high-performance, stable, relatively hydrophobic solid acid catalyst, and combined with a micro-packed bed reactor, it can quickly convert high-concentration fructose to prepare HMF in a short time, further approaching the needs of industrial production. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a solid acid catalyst for a micro-packed bed reactor and a preparation method thereof, which can improve the catalytic efficiency and have strong stability.

[0006] The technical problem that the present invention also aims to solve is to provide a method for preparing 5-hydroxymethylfurfural, which has high yield and high synthesis efficiency.

[0007] In order to solve the above technical problems, the present invention provides a method for preparing a solid acid catalyst for a micro-packed bed reactor, which comprises the following steps:

[0008] (1) providing a porous support, and modifying the porous support with an acidic solution to load hydroxyl groups on the surface of the porous support to obtain a modified support;

[0009] The porous carrier may be activated carbon or molecular sieve, but is not limited thereto. The acidic solution may be hydrochloric acid solution, nitric acid solution, sulfuric acid solution, phosphoric acid solution or acetic acid solution, but is not limited thereto. The modification by the acidic solution can not only increase the specific surface area of ​​the porous carrier, but also increase the surface hydroxyl content, which can significantly enhance the subsequent grafting of functional groups.

[0010] (2) mixing the modified support with a solution containing silane, and reacting at 50 to 200° C. for 0.5 to 36 hours to obtain a first base catalyst; wherein the silane has a carbon chain length greater than or equal to 3;

[0011] Among them, the silane can be mercaptosilane, methoxysilane, ethoxysilane, but is not limited thereto. The silane contains a carbon chain, and the number of carbon molecules in the carbon chain is greater than or equal to 3, so as to give the first base catalyst a modified group with a longer chain length. Specifically, taking mercaptosilane as an example, its general formula is HS-(CH2) n -Si-X3, then n is greater than or equal to 3. In the above general formula, X is methoxy, ethoxy, methyl or ethyl, but not limited thereto. By using a solution containing silane for modification, -Si bonds, mercapto or methoxy, ethoxy, etc. can be loaded on the surface of the modified carrier, laying a good foundation for improving the reaction activity. In addition, the long-chain active functional group grafting also improves the hydrophobicity of the catalyst.

[0012] (3) mixing the first base catalyst with an oxidizing solution and reacting at 30 to 100° C. for 0.5 to 36 hours to obtain a second base catalyst;

[0013] The oxidizing solution includes, but is not limited to, a hydrogen peroxide solution, a sulfuric acid solution or a potassium permanganate solution. Through the treatment with the oxidizing solution, the hydroxylation on the surface of the modified support can be further enhanced, and the sulfhydryl groups previously loaded can also be oxidized to form sulfonic acid groups, which become acidic sites.

[0014] (4) Mixing the second base catalyst with the solution containing the sulfonic acid group, reacting at 30 to 100° C. for 0.5 to 36 hours, and obtaining a finished reinforced solid acid catalyst.

[0015] The solution containing sulfonic acid groups is selected from chlorosulfonic acid or concentrated sulfuric acid, but is not limited thereto. By treating with the solution containing sulfonic acid groups, sulfonic acid groups can be directly loaded on the surface of the modified carrier to form modified groups with shorter chain lengths.

[0016] As an improvement of the above technical solution, in step (1), 1 to 10 g of the porous carrier is mixed with 10 to 200 mL of the acidic solution, stirred and condensed under reflux at 30 to 150° C. for 0.5 to 36 h, and washed and dried to obtain a modified carrier;

[0017] The acidic solution is selected from one or more of hydrochloric acid solution, nitric acid solution, sulfuric acid solution and phosphoric acid solution, and the volume concentration of the acidic solution is 10-100% v / v.

[0018] As an improvement of the above technical solution, step (2) includes:

[0019] (2.1) adding the modified support obtained in step (1) into 50-200 mL of toluene, and then adding 5-70 mL of silane;

[0020] (2.2) stirring and condensing the mixture under reflux at 80 to 200° C. for 10 to 36 hours, washing and drying to obtain a first base catalyst;

[0021] Wherein, the silane is selected from γ-mercaptopropyltrimethoxysilane and / or trimethoxy[3-(methylamino)propyl]silane,

[0022] As an improvement of the above technical solution, in step (3), the first base catalyst obtained in step (2) is mixed with 100 to 300 mL of an oxidizing solution, stirred at 30 to 60° C. for 10 to 36 hours, washed and dried to obtain a second base catalyst;

[0023] Wherein, the oxidizing solution is selected from one or more of hydrogen peroxide solution, sulfuric acid solution or potassium permanganate solution; the volume concentration of the oxidizing solution is 10-100% v / v.

[0024] As an improvement of the above technical solution, step (4) includes:

[0025] (4.1) mixing the second base catalyst obtained in step (3) with 50 to 200 mL of an organic solvent, and then adding 5 to 70 mL of a solution containing sulfonic acid groups;

[0026] (4.2) reacting at 30-60° C. for 10-36 hours, washing and drying to obtain a finished enhanced solid acid catalyst;

[0027] Wherein, the organic solvent is selected from one or more of dichloromethane, chloroform, dichloroethane, dichloropropane, and dibromomethane;

[0028] The solution containing sulfonic acid groups is selected from chlorosulfonic acid or concentrated sulfuric acid.

[0029] As an improvement of the above technical solution, the porous carrier is selected from one or more of alumina, zirconia, silicon oxide, and activated carbon;

[0030] The particle size of the porous carrier is 20nm-1mm.

[0031] As an improvement of the above technical solution, step (1) includes:

[0032] (1.1) providing a porous support, heating it to 400-600° C. at a heating rate of 2-10° C. / min, and calcining it for 2-5 hours;

[0033] (1.2) The calcined porous carrier is modified with an acidic solution to obtain a modified carrier.

[0034] Correspondingly, the present invention also discloses a solid acid catalyst, which is prepared by the above-mentioned preparation method of the solid acid catalyst for a micro-packed bed reactor.

[0035] Correspondingly, the present invention also discloses a method for preparing 5-hydroxymethylfurfural, which comprises: adding the above-mentioned solid acid catalyst into a micro-packed bed reactor, introducing a fructose aqueous solution with a concentration of 1 to 40 wt%, and reacting at 70 to 200° C. and 0 to 3 MPa for 20 to 500 seconds.

[0036] As an improvement of the above technical solution, the micro packed bed reactor is a long cylindrical structure, and its aspect ratio is greater than 30. Specifically, in some embodiments of the present invention, the packed bed reactor is a long cylindrical structure, its diameter is 2.38-6.4 mm, its length is 100-300 mm, and its aspect ratio is 30.5-35, but it is not limited thereto.

[0037] The implementation of the present invention has the following beneficial effects:

[0038] 1. In the preparation method of the solid acid catalyst for the micro-packed bed in one embodiment of the present invention, the hydroxyl groups are first loaded on the surface of the porous carrier using an acidic solution, and then the silane groups are grafted using a silane solution, and then the surface hydroxylation is enhanced by an oxidizing solution, and finally the sulfonic acid functional groups are bonded. Based on the above technical scheme, firstly, the powdered solid acid is loaded on the surface of the porous carrier, which solves the problems of reactor blockage and high energy consumption of the syringe. Secondly, the porous carrier is a porous structure with adsorption effect, which can promote the rapid binding of fructose at the acid site, synergistically enhance the effect, and enhance the catalyst performance; thirdly, through a specific preparation process, two kinds of acids with different volumes and different chain lengths are bonded to the surface of the solid acid catalyst. Acid sites, which not only enhance the acid density of the solid acid catalyst, but also the two acid sites simultaneously bind to a fructose molecule, coordinating the rapid dehydration of fructose to prepare HMF, that is, while increasing the catalyst particle size, it also ensures a higher catalytic reaction efficiency. Fourth, the active sites of the solid acid catalyst are chemically bonded to the porous carrier, which has high stability and can react stably for a long time, thereby extending the service life of the catalyst. Fifth, the surface of the base catalyst of this embodiment is grafted with silane with a longer carbon chain length, which effectively improves the hydrophobic properties, reduces the contact between the water molecules generated in the reaction and the catalyst, and effectively prevents HMF from further reacting on the catalyst surface to generate by-products, thereby improving the yield of the target product HMF.

[0039] 2. In the preparation method of the solid acid catalyst for the micro-packed bed in one embodiment of the present invention, the porous carrier is pre-calcined, which effectively adjusts the pore structure of the porous carrier and increases the specific surface area, which not only strengthens the adsorption of the reactant fructose on the catalyst surface, but also allows the HMF produced by the reaction to be desorbed through appropriate pores in a timely manner, effectively reducing the generation of by-products and improving the reaction efficiency.

[0040] 3. In the preparation method of 5-hydroxymethylfurfural in one embodiment of the present invention, the above-mentioned solid acid catalyst is used to catalyze the reaction of fructose. First, this solid acid catalyst can make the reactor dominated by capillary force, significantly improving the mass transfer capacity; second, through the synergistic effect of the micro-packed bed and the solid acid catalyst, the reaction time is greatly shortened. Specifically, in this embodiment, the reaction time can be shortened from the traditional several hours to a minimum of less than 1 minute, and a high conversion rate (≥92%, up to 99%) and a high yield (≥86%, up to 97.5%) can also be guaranteed. Third, through the synergistic effect of the micro-packed bed and the solid acid catalyst, high-concentration fructose can be continuously converted to prepare HMF. In this embodiment, the fructose concentration can reach more than 100g / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The double structure in Example 1 Electron microscopy image and EDS Mapping scan of the acid site activated carbon solid acid catalyst;

[0042] Figure 2 The double structure in Example 1 FT-IR image of the acid site activated carbon solid acid catalyst. In the figure, the reinforced solid acid is the double structure prepared in this example. Acid site activated carbon solid acid catalyst, the carrier is an activated carbon carrier that has not been subjected to calcination and hydroxylation treatment, the modified carrier is an activated carbon carrier that has been subjected to calcination and hydroxylation treatment, and the basic solid acid is a basic solid acid catalyst that has not been loaded;

[0043] Figure 3 The double structure in Example 1 XPS spectrum of acid site activated carbon solid acid catalyst;

[0044] Figure 4 The double structure in Example 1 NMR spectrum of acid site activated carbon solid acid catalyst;

[0045] Figure 5 The double structure in Example 1 Contact angle diagram of activated carbon solid acid catalyst at acid site In the figure, the carrier is an activated carbon carrier that has not been calcined or hydroxylated, the modified carrier is an activated carbon carrier that has been calcined or hydroxylated, the basic solid acid is an unloaded basic solid acid catalyst, and the enhanced solid acid is the dual-structured solid acid catalyst prepared in this example. Acid site activated carbon solid acid catalyst. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0047] Example 1

[0048] (1) 5 g of an activated carbon support with a particle size of 0.8 mm was heated to 500° C. at a rate of 2° C. / min in nitrogen and calcined for 2 h, then added to 100 mL of an 80% v / v nitric acid aqueous solution, stirred and refluxed at 80° C. for 24 h, washed and dried to obtain a surface-modified activated carbon support;

[0049] (2) adding the surface-modified activated carbon support obtained in step (1) into 100 mL of toluene solution, adding 50 mL of γ-mercaptopropyltrimethoxysilane after uniform dispersion, stirring and condensing and reflux at 120° C. for 24 h, washing and drying to obtain a basic activated carbon catalyst;

[0050] (3) The basic activated carbon catalyst obtained in step (2) was added to 200 mL of a 50% v / v H2O2 aqueous solution, and stirred at 30°C for 24 h to obtain a single structure Acid site activated carbon solid acid catalyst;

[0051] (4) The single structure obtained in step (3) The acid site activated carbon solid acid catalyst was added to 100 mL of dichloromethane, and after being evenly dispersed, 20 mL of chlorosulfonic acid was added, and the mixture was stirred and refluxed at 30 ° C for 24 h. After washing and drying, a dual structure was obtained. Acid site activated carbon solid acid catalyst.

[0052] The double structure obtained in this embodiment The acid site activated carbon solid acid catalyst was characterized, and the results were as follows Figure 1 to Figure 5 As shown. Among them, Figure 1 It is a double structure Electron microscope image and EDS Mapping scan of the acid site activated carbon solid acid catalyst. It can be seen from the figure that elements such as Si, S, and Cl are evenly dispersed on the catalyst surface, proving that the active sites are successfully grafted. Figure 2 It is a double structure FT-IR image of the acid site activated carbon solid acid catalyst. In the figure, the reinforced solid acid is the double structure prepared in this example. Acid site activated carbon solid acid catalyst, the carrier is an activated carbon carrier that has not been calcined or hydroxylated, the modified carrier is an activated carbon carrier that has been calcined and hydroxylated, and the basic solid acid is an unloaded basic solid acid catalyst. As can be seen from the figure, the peak intensity of the surface hydroxyl group of the catalyst increases significantly after surface modification and hydroxylation, proving that the catalyst treatment method is feasible. Figure 3 It is a double structure The XPS spectrum of the acid site activated carbon solid acid catalyst also proves that elements such as Si, S, C, and O are loaded on the surface of the carrier, indicating that the catalyst was successfully prepared. Figure 4 It is a double structure The NMR spectrum of the acid site activated carbon solid acid catalyst shows the characteristic peaks of silanesulfonic acid and chlorosulfonic acid, proving that there are two structures in the catalyst. Acid sites. Figure 5 It is a double structure Contact angle diagram of acid site activated carbon solid acid catalyst. In the figure, the carrier is an activated carbon carrier that has not been calcined or hydroxylated, the modified carrier is an activated carbon carrier that has been calcined and hydroxylated, and the basic solid acid is an unloaded basic solid acid catalyst. It can be seen from the figure that with the grafting of active functional groups, the catalyst contact angle increases, proving that its hydrophobicity has been effectively improved.

[0053] The double structure prepared in this example The acid-site activated carbon solid acid catalyst was filled into a micro-packed bed reactor (6.4 mm in diameter and 200 mm in length), and a 40 wt % fructose aqueous solution and a 100 % v / v dimethyl sulfoxide aqueous solution were introduced at the same time. The reaction was carried out at a flow rate of 0.1 mL / min at 150 ° C and 0.5 MPa for 60 s, resulting in a fructose conversion rate of 99% and an HMF yield of 97.5%.

[0054] Example 2

[0055] (1) adding 5 g of an activated carbon carrier having a particle size of 0.8 mm into 100 mL of an aqueous solution of nitric acid having a concentration of 80 v / v%, stirring and condensing the solution under reflux at 80° C. for 24 h, washing the solution and drying the solution to obtain a surface-modified activated carbon carrier;

[0056] (2) adding the surface-modified activated carbon support obtained in step (1) into 100 mL of toluene solution, adding 50 mL of γ-mercaptopropyltrimethoxysilane after uniform dispersion, stirring and condensing and reflux at 120° C. for 24 h, washing and drying to obtain a basic activated carbon catalyst;

[0057] (3) The basic activated carbon catalyst obtained in step (2) was added to 200 mL of a 50% v / v H2O2 aqueous solution, and stirred at 30°C for 24 h to obtain a single structure Acid site activated carbon solid acid catalyst;

[0058] (4) The single structure obtained in step (3) The acid site activated carbon solid acid catalyst was added to 100 mL of dichloromethane, and after being evenly dispersed, 20 mL of chlorosulfonic acid was added, and the mixture was stirred and refluxed at 30 ° C for 24 h. After washing and drying, a dual structure was obtained. Acid site activated carbon solid acid catalyst.

[0059] The double structure prepared in this example The acid-site activated carbon solid acid catalyst was filled into a micro-packed bed reactor (diameter 6.4 mm, length 200 mm), and a 40 wt % fructose aqueous solution and a 100 % v / v dimethyl sulfoxide aqueous solution were introduced at a flow rate of 0.1 mL / min at 150 ° C and 0.5 MPa for 60 s to obtain a fructose conversion rate of 96.8% and an HMF yield of 90.3%.

[0060] Example 3

[0061] (1) 5 g of an alumina carrier with a particle size of 20 nm was heated to 500° C. in hydrogen at a rate of 2° C. / min and calcined for 2 h, then added to 100 mL of a 90% v / v nitric acid solution and stirred and refluxed at 80° C. for 24 h, washed and dried to obtain a surface-modified alumina carrier;

[0062] (2) adding the surface-modified alumina support obtained in step (1) into 100 mL of toluene solution, adding 30 mL of trimethoxy[3-(methylamino)propyl]silane after uniform dispersion, stirring and reflux under condensation at 100° C. for 12 h, washing and drying to obtain a basic alumina catalyst;

[0063] (3) The base alumina catalyst obtained in step (2) was added to 150 mL of a 10% v / v sulfuric acid aqueous solution, and stirred at 30° C. for 12 h to obtain a single structure Acid site alumina solid acid catalyst;

[0064] (4) The single structure obtained in step (3) The acid site alumina solid acid catalyst was added to 70 mL of chloroform, and after being evenly dispersed, 10 mL of chlorosulfonic acid was added, and the mixture was stirred and refluxed at 30 ° C for 18 h. After washing and drying, a dual structure was obtained. Acid site alumina solid acid catalyst;

[0065] The above double structure The acid site alumina solid acid catalyst was filled into a micro-packed bed reactor (6.4 mm in diameter and 200 mm in length), and a 40 wt % fructose aqueous solution and a 100 % v / v dimethyl sulfoxide aqueous solution were introduced at a flow rate of 0.1 mL / min at 150 ° C and 4 MPa for 60 s, resulting in a fructose conversion rate of 92.6% and an HMF yield of 86.5%.

[0066] Example 4

[0067] (1) 5 g of silicon oxide with a particle size of 0.5 mm was heated to 500° C. at a rate of 5° C. / min in helium and calcined for 2 h, then added to 150 mL of a 70% nitric acid aqueous solution, stirred and condensed under reflux at 120° C. for 12 h, washed and dried to obtain a surface-modified silicon oxide carrier;

[0068] (2) adding the surface-modified silica support obtained in step (1) into 120 mL of toluene solution, adding 70 mL of γ-mercaptopropyltrimethoxysilane after uniform dispersion, stirring and condensing and reflux at 140° C. for 24 h, washing and drying to obtain a basic silica catalyst;

[0069] (3) The silicon oxide catalyst obtained in step (2) was added to 200 mL of 80% v / v sulfuric acid aqueous solution, and stirred at 50° C. for 12 h to obtain a single structure Acid site silica solid acid catalyst;

[0070] (4) The single structure obtained in step (3) The acid site silica solid acid catalyst was added to 120 mL of dibromomethane, and after being evenly dispersed, 40 mL of chlorosulfonic acid was added, and the mixture was stirred and condensed at 50 ° C for 12 h, and then dried to obtain a dual structure Acid site silica solid acid catalyst;

[0071] The above double structure The acid-site silica solid acid catalyst was filled into a micro-packed bed reactor (6.4 mm in diameter and 200 mm in length), and a 40 wt % fructose aqueous solution and a 100 % v / v dimethyl sulfoxide aqueous solution were introduced at a flow rate of 0.1 mL / min at 150 ° C and 0.5 MPa for 84 s, resulting in a fructose conversion rate of 95.3% and an HMF yield of 88.6%.

[0072] Comparative Example 1

[0073] (1) 5 g of an activated carbon support with a particle size of 0.8 mm was heated to 500° C. at a rate of 2° C. / min in nitrogen and calcined for 2 h, then added to 100 mL of an 80% v / v nitric acid aqueous solution, stirred and refluxed at 80° C. for 24 h, washed and dried to obtain a surface-modified activated carbon support;

[0074] (2) adding the surface-modified activated carbon support obtained in step (1) into 100 mL of toluene solution, adding 50 mL of γ-mercaptopropyltrimethoxysilane after uniform dispersion, stirring and condensing and reflux at 120° C. for 24 h, washing and drying to obtain a basic activated carbon catalyst;

[0075] (3) The basic activated carbon catalyst obtained in step (2) was added to 200 mL of a 50% v / v H2O2 aqueous solution, and stirred at 30°C for 24 h to obtain a single structure Acid site activated carbon solid acid catalyst.

[0076] The single structure prepared in this comparative example The acid-site activated carbon solid acid catalyst was filled into a micro-packed bed reactor (6.4 mm in diameter and 200 mm in length), and a 40 wt % fructose aqueous solution and a 100 % v / v dimethyl sulfoxide aqueous solution were introduced at a flow rate of 0.1 mL / min at 150 ° C and 0.5 MPa for 60 s, obtaining a fructose conversion rate of 82% and an HMF yield of 72.3%.

[0077] Comparative Example 2

[0078] (1) 5 g of an activated carbon support with a particle size of 0.8 mm was heated to 500° C. at a rate of 2° C. / min in nitrogen and calcined for 2 h, then added to 100 mL of an aqueous solution of 80 / 20 v / v % nitric acid, stirred and refluxed at 80° C. for 24 h, washed and dried to obtain a surface-modified activated carbon support;

[0079] (3) The single activated carbon carrier obtained in step (1) was added to 100 mL of dichloromethane, and after being evenly dispersed, 20 mL of chlorosulfonic acid was added, and the mixture was stirred, condensed and refluxed at 30° C. for 24 h. After washing and drying, an activated carbon solid acid catalyst was obtained.

[0080] The activated carbon solid acid catalyst prepared in this comparative example was filled into a micro-packed bed reactor (diameter 6.4 mm, length 200 mm), and a 40 wt % fructose aqueous solution and a 100 % v / v dimethyl sulfoxide aqueous solution were introduced at the same time. The reaction was carried out at a flow rate of 0.1 mL / min at 150 ° C and 0.5 MPa for 60 s to obtain a fructose conversion rate of 79% and an HMF yield of 53%.

[0081] Comparative Example 3

[0082] (1) 5 g of an activated carbon support with a particle size of 0.8 mm was heated to 500° C. at a rate of 2° C. / min in nitrogen and calcined for 2 h, then added to 100 mL of an 80% v / v nitric acid aqueous solution, stirred and refluxed at 80° C. for 24 h, washed and dried to obtain a surface-modified activated carbon support;

[0083] (2) adding the surface-modified activated carbon support obtained in step (1) into 100 mL of toluene solution, adding 50 mL of mercaptomethyltriethoxysilane after uniform dispersion, stirring, condensing and reflux at 120° C. for 24 h, washing and drying to obtain a basic activated carbon catalyst;

[0084] (3) The basic activated carbon catalyst obtained in step (2) was added to 200 mL of a 50% v / v H2O2 aqueous solution, and stirred at 30°C for 24 h to obtain a single structure Acid site activated carbon solid acid catalyst;

[0085] (4) The single structure obtained in step (3) The acid site activated carbon solid acid catalyst was added to 100 mL of dichloromethane, and after being evenly dispersed, 20 mL of chlorosulfonic acid was added, and the mixture was stirred and refluxed at 30 ° C for 24 h. After washing and drying, a dual structure was obtained. Acid site activated carbon solid acid catalyst.

[0086] The double structure prepared in this comparative example The acid-site activated carbon solid acid catalyst was filled into a micro-packed bed reactor (6.4 mm in diameter and 200 mm in length), and a 40 wt % fructose aqueous solution and a 100 % v / v dimethyl sulfoxide aqueous solution were introduced at a flow rate of 0.1 mL / min at 150 ° C and 0.5 MPa for 60 s to obtain a fructose conversion rate of 94.3% and an HMF yield of 61.8%.

[0087] Comparative Example 4

[0088] Commercial solid acid HND8 particles (average particle size 50 μm) were filled into a micropacked bed reactor (diameter 6.4 mm, length 200 mm), and a 10 wt % fructose aqueous solution and a 100 % v / v dimethyl sulfoxide aqueous solution were introduced at a flow rate of 0.1 mL / min at 150 ° C and 5 MPa for 60 s, obtaining a fructose conversion rate of 83% and an HMF yield of 62%.

[0089] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A method for preparing a solid acid catalyst for a micro-packed bed reactor, characterized in that: The following steps are involved: (1) providing a porous support, and modifying the porous support with an acidic solution to load hydroxyl groups on the surface of the porous support to obtain a modified support; (2) mixing the modified support with a solution containing silane, and reacting at 50 to 200° C. for 0.5 to 36 hours to obtain a first base catalyst; wherein the silane has a carbon chain length greater than or equal to 3; (3) mixing the first base catalyst with an oxidizing solution and reacting at 30 to 100° C. for 0.5 to 36 hours to obtain a second base catalyst; (4) Mixing the second base catalyst with the solution containing the sulfonic acid group, reacting at 30 to 100° C. for 0.5 to 36 hours, and obtaining a finished reinforced solid acid catalyst.

2. The method for preparing a solid acid catalyst for a micro-packed bed reactor according to claim 1, characterized in that: In step (1), 1 to 10 g of the porous carrier is mixed with 10 to 200 mL of an acidic solution, stirred and condensed under reflux at 30 to 150° C. for 0.5 to 36 h, and then washed and dried to obtain a modified carrier; The acidic solution is selected from one or more of hydrochloric acid solution, nitric acid solution, sulfuric acid solution and phosphoric acid solution, and the volume concentration of the acidic solution is 10-100% v / v.

3. The method for preparing a solid acid catalyst for a micro-packed bed reactor according to claim 1, characterized in that: Step (2) comprises: (2.1) adding the modified support obtained in step (1) into 50-200 mL of toluene, and then adding 5-70 mL of silane; (2.2) stirring and condensing the mixture under reflux at 80 to 200° C. for 10 to 36 hours, washing and drying to obtain a first base catalyst; Wherein, the silane is selected from γ-mercaptopropyltrimethoxysilane and / or trimethoxy[3-(methylamino)propyl]silane.

4. The method for preparing a solid acid catalyst for a micro-packed bed reactor according to claim 1, characterized in that: In step (3), the first base catalyst obtained in step (2) is mixed with 100 to 300 mL of an oxidizing solution, stirred at 30 to 60° C. for 10 to 36 hours, and washed and dried to obtain a second base catalyst; Wherein, the oxidizing solution is selected from one or more of hydrogen peroxide solution, sulfuric acid solution or potassium permanganate solution; the volume concentration of the oxidizing solution is 10-100% v / v.

5. The method for preparing a solid acid catalyst for a micro-packed bed reactor according to claim 1, characterized in that: Step (4) comprises: (4.1) mixing the second base catalyst obtained in step (3) with 50 to 200 mL of an organic solvent, and then adding 5 to 70 mL of a solution containing sulfonic acid groups; (4.2) reacting at 30-60° C. for 10-36 hours, washing and drying to obtain a finished enhanced solid acid catalyst; Wherein, the organic solvent is selected from one or more of dichloromethane, chloroform, dichloroethane, dichloropropane, and dibromomethane; The solution containing sulfonic acid groups is selected from chlorosulfonic acid or concentrated sulfuric acid.

6. The method for preparing a solid acid catalyst for a micro-packed bed reactor according to any one of claims 1 to 5, characterized in that: The porous carrier is selected from one or more of alumina, zirconia, silicon oxide, and activated carbon; The particle size of the porous carrier is 20nm-1mm.

7. The method for preparing a solid acid catalyst for a micro-packed bed reactor according to claim 6, characterized in that: Step (1) comprises: (1.1) providing a porous support, heating it to 400-600° C. at a heating rate of 2-10° C. / min, and calcining it for 2-5 hours; (1.2) The calcined porous carrier is modified with an acidic solution to obtain a modified carrier.

8. A solid acid catalyst, characterized in that The solid acid catalyst is prepared by the method for preparing a solid acid catalyst for a micro-packed bed reactor as described in any one of claims 1 to 7.

9. A method for preparing 5-hydroxymethylfurfural, characterized in that: The solid acid catalyst as claimed in claim 8 is added into a micro-packed bed reactor, and a fructose aqueous solution with a concentration of 1 to 40 wt% is introduced, and the reaction is carried out at 70 to 200° C. and 0 to 3 MPa for 20 to 500 seconds.

10. The method for preparing 5-hydroxymethylfurfural as claimed in claim 9, characterized in that: The micro-packed bed reactor is a long cylindrical structure with an aspect ratio of >30.

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