Catalysts, processes and uses

Abstract

The application discloses a catalyst, a method and application, and the catalyst comprises a full-silica molecular sieve and metal nanoparticles; wherein the particle size of the metal nanoparticles is 0.5-3.5 nm; the metal nanoparticles are dispersed in the inside of the full-silica molecular sieve; the metal element in the metal nanoparticles is selected from one or more of Pd, Pt and Rh; the metal nanoparticles are 0.2-4.5 parts by weight based on 100 parts by weight of the catalyst; and the catalyst has a sheet structure. The catalyst of the application can be used as a catalyst for decarboxylation of furfural to furan, and the conversion rate of raw materials and the selectivity of the product furan are relatively high.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of catalyst and method and application, especially a kind of catalyst and method and application for furfural decarbonylation preparation furan. BACKGROUND

[0002] Furan is a valuable chemical raw material, which can be used to produce α-acetyl furan, 2,2-difuran propane, pyrrole derivatives and other pharmaceutical intermediates, and is also widely used in the synthesis of adhesives, vinyl films, glass paper and other polymers. There are several methods for synthesizing furan, among which, furfural decarbonylation method is the highest yield method for furan at present, which can realize the catalytic conversion of furfural, a biomass-derived platform product, and establish a green industrial chain for preparing furan by biomass route, which plays an important role in coping with energy crisis and environmental problems.

[0003] The method for preparing furan by furfural decarbonylation can be divided into liquid phase and gas phase decarbonylation. CN101822982A discloses a high-efficiency supported noble metal catalyst for producing furan by liquid phase decarbonylation of furfural, which uses γ-Al2O3-TiO2 as the carrier of the composite oxide, and the loading amount of palladium is 2-4wt% of the carrier. K, Cs, Ru, Li, Rh, Na, La or Ba promoters are added to the catalyst, and the content is 0.5-2.0wt%. The liquid phase decarbonylation reaction of furfural is carried out under the conditions of pressure 0-0.5MPa and temperature 180-230℃, and the conversion rate of furfural is 90-99%, the yield of furan is 80-95%, and the service life of the catalyst is 100-120h. The biggest disadvantage of liquid phase decarbonylation is that the high content of metal Pd is not uniformly dispersed on the catalyst, and the stability of the catalyst is too poor, which is easy to be deactivated.

[0004] CN1308986A discloses a high-efficiency supported noble metal catalyst for producing furan by gas phase decarbonylation of furfural, which uses Al2O3-TiO2 composite oxide as the carrier, and the loading amount of platinum is 0.4-0.7wt% of the carrier. K2O, Cs2O, MgO, CaO or BaO promoters are added to the catalyst, and the content is 0.5-2.0wt%. The reaction is carried out under the conditions of normal pressure, 280℃, furfural space velocity 0.9h -1 , and the molar ratio of furfural to hydrogen is 0.5-2.0, the conversion rate of furfural is 80-97%, and the selectivity of furan is 85-92%.

[0005] CN111298818B discloses a kind of high-efficiency supported noble metal catalyst for furfural gas-phase decarbonylation to produce furan, which is represented as A-C / B, wherein: wherein A-C is active component;A is one of metal palladium, platinum, and C is one of Li, Na, K, Mg, Ca, La carbonate;The total loading of active component A-C in the catalyst in the catalyst is 1.05-60%, the loading of A is 0.05-10wt%, and the loading of C is 1-50wt%.B is a nano-sheet structured multi-level pore carrier, which is one of nano-sheet type alumina and nano-sheet type molecular sieve.When reacting at normal pressure, 200-400 DEG C, the furan yield is higher than 73%.

[0006] The conversion rate of furfural and the selectivity of furan in the above documents still have room for further improvement. SUMMARY

[0007] Therefore, one object of the present application is to provide a catalyst containing a full-silica molecular sieve and metal nanoparticles, which can be used for catalytic decarbonylation of furfural to obtain furan, and has high conversion rate of furfural and high selectivity of furan, the conversion rate of furfural can reach 100%, and the selectivity of furan can reach 96.2%. Another object of the present application is to provide a method for preparing the catalyst. Still another object of the present application is to provide the use of the catalyst. Yet another object of the present application is to provide a method for preparing furan by decarbonylation of furfural. The above objects are achieved by the following technical solutions.

[0008] In one aspect, the present application provides a catalyst comprising a full-silica molecular sieve and metal nanoparticles;wherein,

[0009] The particle size of the metal nanoparticles is 0.5-3.5 nm;The metal nanoparticles are dispersed in the interior of the full-silica molecular sieve;

[0010] The metal element in the metal nanoparticles is selected from one or more of Pd, Pt and Rh;The metal nanoparticles are 0.2-4.5 parts by weight based on 100 parts by weight of the catalyst;The catalyst has a sheet structure. Such a catalyst can be used for catalytic decarbonylation of furfural (i.e. furfural) to obtain furan, which can improve the conversion rate of raw materials and improve the selectivity of target products.

[0011] The structural formula of furfural is shown as formula (1):

[0012]

[0013] The catalyst of the present application is a catalyst formed by encapsulating metal nanoparticles with a full-silica type thin sheet molecular sieve, wherein the metal nanoparticles are dispersed in the interior of the molecular sieve and are substantially uniformly distributed in the interior of the full-silica molecular sieve. The full-silica molecular sieve of the present application has substantially zero alumina content and can also be referred to as a Silicalite-1 molecular sieve.

[0014] The metal nanoparticles have a particle size of 0.5-3.5 nm, preferably 1-3 nm. For example, the particle size can be 0.5 nm, 1.0 nm, 1.5 nm, 2 nm, 2.5 nm or 3 nm.

[0015] The metal nanoparticles can be 0.2-4.5 parts by weight, preferably 0.2-3 parts by weight, based on 100 parts by weight of the catalyst. For example, the metal nanoparticles can be 0.2, 0.3, 0.4, 0.5, 1.0, 2.0, 3.0, 4.0 or 4.5 parts by weight. Such a catalyst can both increase the conversion of the raw material and maintain a high selectivity of the target product.

[0016] The catalyst of the present application has a sheet shape and further has a thin sheet structure with a crystal thickness of 15-30 nm, preferably 15-25 nm. For example, the crystal thickness can be 15 nm, 20 nm, 25 nm or 30 nm. The catalyst of the present application has a thin sheet structure similar to a hexagon, and preferably is composed of hexagonal thin sheets with a thickness of about 20 nm. The crystal thickness is uniform, and the catalyst has a relatively large external surface area, which is advantageous for increasing the reaction sites and reducing diffusion limitations. When the catalyst is used in the reaction of decarbonylation of furfural to furan, the catalyst has excellent catalytic activity and structural stability, and the conversion of furfural can reach 100% and the selectivity to the product furan is also very high.

[0017] The catalyst of the present application is formed from a water-soluble metal salt (i.e. a precursor of the metal nanoparticles) and a silicon-containing raw material capable of forming a full-silica molecular sieve. The water-soluble metal salt is preferably a complex of a water-soluble metal salt and ethylenediamine. The silicon-containing raw material is selected from a silicate or an alkaline silica sol.

[0018] According to the catalyst of the present application, the metal element in the metal nanoparticles is preferably selected from one of Pd, Pt and Rh. This is advantageous for increasing the conversion of the raw material and the selectivity of the target product in the reaction of decarbonylation of furfural to furan.

[0019] According to the catalyst of the present application, the catalyst preferably has a sheet structure similar to a hexagon. Such a morphology is advantageous for reducing diffusion limitations.

[0020] In another aspect, the present application also provides a method for preparing the catalyst as described above, comprising the following steps:

[0021] Step 1, mixing a silicon element-containing raw material, an alkyl ammonium hydroxide and water to obtain a first mixture; preliminarily crystallizing the obtained first mixture at 50-100°C to obtain a seed suspension; the molar ratio of silicon element in the silicon element-containing raw material, the alkyl ammonium hydroxide and water is 1:0.1-0.5:6-26;

[0022] Step 2, mixing a silicon element-containing raw material, an alkyl ammonium hydroxide, an alkyl ammonium bromide, a water-soluble metal salt and water to obtain an A solution; in the A solution, the molar ratio of silicon element in the silicon element-containing raw material, the alkyl ammonium hydroxide, the alkyl ammonium bromide, the metal element in the water-soluble metal salt solution and water is 1:0.01-0.4:0.01-0.4:0.0004-0.03:20-200;

[0023] Step 3, mixing the seed suspension in Step 1 and the A solution in Step 2 to obtain a second mixture; the molar ratio of silicon element in the seed suspension and silicon element in the A solution is 0.5-2.5:1;

[0024] Step 4, mixing a solution B containing ammonium fluoride and the second mixture to obtain a third mixture; in the solution B containing ammonium fluoride, the molar ratio of ammonium fluoride and water is 1:30-300; the molar ratio of silicon element in the second mixture and ammonium fluoride in the solution B is 1:0.05-0.8;

[0025] Step 5, crystallizing the third mixture at 150-180°C, solid-liquid separation to obtain an initial solid; washing and drying the obtained initial solid to obtain a dry solid; then reducing the dry solid in a hydrogen atmosphere at 350-450°C to obtain the catalyst.

[0026] wherein,

[0027] In Step 1, the molar ratio of silicon element in the silicon element-containing raw material and the alkyl ammonium hydroxide is preferably 1:0.1-0.4, more preferably 1:0.2-0.4. The molar ratio of silicon element in the silicon element-containing raw material and water is preferably 1:5-25, more preferably 1:5-15, and more preferably 1:5-10, for example 1:10.

[0028] According to one embodiment of the present application, the silicon element-containing raw material, the alkyl ammonium hydroxide and water are mixed and stirred at 20-45°C for 6-12h to obtain the first mixture. The mixing temperature can be 20-45°C, preferably 20-40°C, for example 30°C or 35°C. The stirring time can be 6-12h, preferably 8-10h.

[0029] In the present application, the temperature of the preliminary crystallization can be 50-100°C, preferably 50-80°C, more preferably 70-80°C. The time of the preliminary crystallization nucleation can be 24-96h, preferably 48-72h. It is found in the present application that the time of the preliminary crystallization nucleation and the temperature range need to be controlled in the step of obtaining the seed suspension, otherwise it is not conducive to form the thin sheet catalyst for the decarbonylation of furfural to furan.

[0030] In step 2, the mixing temperature can be 20-45°C, preferably 20-40°C, for example 30°C or 35°C. In the A solution, the molar ratio of the silicon element in the silicon element-containing raw material to the alkylammonium hydroxide can be 1:0.01-0.4, preferably 1:0.05-0.2. The molar ratio of the silicon element in the silicon element-containing raw material to the alkylammonium bromide can be 1:0.01-0.4, preferably 1:0.05-0.2. The molar ratio of the silicon element in the silicon element-containing raw material to water can be 1:20-200, preferably 1:20-160, more preferably 1:30-110, for example 1:100. The molar ratio of the metal element in the water-soluble metal salt to the silicon element in the silicon-containing raw material can be 0.0004-0.03:1, preferably 0.0004-0.025:1.

[0031] The silicon element-containing raw material is selected from silicate or basic silica sol, preferably silicate. The silicate is selected from one or more of methyl orthosilicate, ethyl orthosilicate, isopropyl orthosilicate, butyl orthosilicate, preferably ethyl orthosilicate. The alkylammonium hydroxide is selected from one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, dimethyldiethylammonium hydroxide, dimethyldipropylammonium hydroxide, preferably tetrapropylammonium hydroxide. The alkylammonium bromide is selected from one or more of tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, preferably tetrapropylammonium bromide. The water-soluble metal salt is a complex of a water-soluble metal salt and ethylenediamine, for example a complex of a metal chloride and ethylenediamine. The metal element in the water-soluble metal salt is consistent with the metal element in the metal nanoparticles.

[0032] In step 3, the mixing temperature can be 20-45°C, preferably 20-40°C, for example 30°C or 35°C. The mixing time can be 0.5-6h, preferably 4-6h. In the second mixture, the molar ratio of the silicon element in the seed suspension to the silicon element in the A solution can be 0.5-2.5:1, preferably 0.5-1.5:1.

[0033] In step 4, solution B is an ammonium fluoride solution. In some embodiments, the step of preparing solution B is further included, which comprises: preparing B solution by mixing ammonium fluoride and water, and stirring uniformly; the molar ratio of the ammonium fluoride to water is 1:30-300. In the B solution, the molar ratio of the ammonium fluoride to water used is preferably 1:150-300.

[0034] In step 4, the mixing temperature can be 20-45℃, preferably 20-40℃, for example 30℃ or 35℃. The mixing time can be 0.5-3h, preferably 1-3h.

[0035] The molar ratio of silicon element in the second mixture to ammonium fluoride in solution B is 1:0.05-0.8; preferably 1:0.2-0.6. The present application finds that the addition of ammonium fluoride can make the sheet grow thinner, larger, and more conducive to the catalytic performance of the catalyst. However, the amount of ammonium fluoride cannot be too much, which has an impact on the metal packaging to the sheet catalyst. The sheet post-processing process adopts a direct reduction method, and the calcination also has an impact on the metal packaging to the sheet molecular sieve catalyst.

[0036] In step 5, the crystallization temperature can be 150-180℃, preferably 170-180℃, for example 170℃ or 175℃. The stirring time can be 0.5-3h, preferably 1-3h. The solid-liquid separation can be centrifugation or suction filtration.

[0037] In the present application, the washing preferably uses water washing, and it is better to wash until the pH value of the washing liquid is 7 (i.e. neutral). The drying temperature can be 100-120℃, preferably 105-110℃. The drying time can be 2-10h, preferably 8-10h. The heating rate during reduction can be controlled to be 2-11℃ / min, preferably 3-5℃ / min. The reduction temperature in a hydrogen atmosphere can be 350-450℃, preferably 380-420℃, for example 400℃. The reduction time can be 1.5-4h, preferably 2-3h.

[0038] According to the preferred technical scheme of the present application, the present application uses a silicon element-containing raw material, tetrapropylammonium hydroxide, tetrapropylammonium bromide, ammonium fluoride, water, and a water-soluble metal salt-ethylenediamine complex, and controls the use amount of them within a specific range, and controls the temperature and the preliminary crystallization and crystallization process, so that the catalyst with a specific morphology and thickness suitable for the decarbonylation of furfural to furan can be obtained.

[0039] According to the method of the present application, preferably, the silicon element-containing raw material is selected from one or more of methyl orthosilicate, ethyl orthosilicate, isopropyl orthosilicate, and butyl orthosilicate.

[0040] According to the method of the present application, preferably, the alkylammonium hydroxide is selected from one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, dimethyldiethylammonium hydroxide, and dimethyldipropylammonium hydroxide.

[0041] According to the method of the present application, preferably, the alkylammonium bromide is selected from one or more of tetramethylammonium bromide, tetraethylammonium bromide and tetrapropylammonium bromide.

[0042] According to the method of the present application, preferably, the water-soluble metal salt is a complex of a water-soluble metal salt and ethylenediamine.

[0043] According to one embodiment of the present application, the method for preparing the catalyst of the present application comprises the following steps:

[0044] Step 1, stirring and mixing a silicon element-containing raw material, an alkylammonium hydroxide and water at 20-45℃ for 6-12h to obtain a first mixture; preliminarily crystallizing the obtained first mixture at 50-100℃ for 24-96h to obtain a seed suspension; the molar ratio of silicon element in the silicon element-containing raw material, the alkylammonium hydroxide and water is 1:0.1-0.5:6-26;

[0045] Step 2, mixing a silicon element-containing raw material, an alkylammonium hydroxide, an alkylammonium bromide, a complex of a water-soluble metal salt and ethylenediamine and water at 20-45℃ to obtain an A solution; wherein, in the A solution, the molar ratio of silicon element in the silicon element-containing raw material, the alkylammonium hydroxide, the alkylammonium bromide, the metal element in the complex of the water-soluble metal salt and ethylenediamine and water is 1:0.01-0.4:0.01-0.4:0.0004-0.03:20-200;

[0046] Step 3, continuing to stir and mix the seed suspension in Step 1 and the A solution in Step 2 at 20-45℃ for 0.5-6h to obtain a second mixture; wherein, the molar ratio of silicon element in the seed suspension and silicon element in the A solution is 0.5-2.5:1;

[0047] Step 4, stirring and mixing a solution B containing ammonium fluoride and the second mixture at 20-45℃ for 0.5-3h to obtain a third mixture; wherein, in the solution B containing ammonium fluoride, the molar ratio of ammonium fluoride and water is 1:30-300; the molar ratio of silicon element in the second mixture and ammonium fluoride in the solution B is 1:0.05-0.8;

[0048] Step 5, crystallizing the third mixture at 150-180℃ for 0.5-3h, solid-liquid separation to obtain an initial solid; washing and drying the obtained initial solid to obtain a dry solid; then reducing the dry solid under a hydrogen atmosphere at 350-450℃ for 1.5-4h to obtain the catalyst.

[0049] In still another aspect, the present application further provides the use of the catalyst as described above in the catalytic decarbonylation of furfural to prepare furan.

[0050] In another aspect, the present application also provides a method for preparing furan by catalytic decarbonylation of furfural, which uses the catalyst as described above to catalyze the decarbonylation of furfural to prepare furan, and the weight ratio of the catalyst to furfural is 1:1-20. The catalytic process conditions are as follows: the reaction pressure is normal pressure, the molar ratio of hydrogen to furfural is 50-150:1, the reaction temperature is 220-260°C, and the furfural space velocity is 0.7-0.9h -1 The weight ratio of the catalyst to furfural is preferably 1:1-10.

[0051] The molar ratio of hydrogen to furfural is preferably 70-90:1, and more preferably 75-85:1. The reaction temperature is preferably 245-250°C. The furfural space velocity is preferably 0.75-0.8h -1 Under such conditions, the catalyst is more conducive to catalyzing the decarbonylation of furfural to prepare furan.

[0052] The catalyst of the present application can be used to catalyze the decarbonylation of furfural to prepare furan, so that the selectivity of furan is higher and the conversion rate of the raw material furfural is higher. The catalyst of the present application is a sheet catalyst, which comprises a full-silica molecular sieve and metal nanoparticles, and the metal nanoparticles are dispersed in the interior of the full-silica molecular sieve. The method of the present application can obtain a catalyst with a specific morphology and thickness for the decarbonylation of furfural to prepare furan. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is the X-ray diffraction pattern of the catalyst prepared in Example 1 of the present application;

[0054] Figure 2 is the SEM image of the catalyst prepared in Example 1 of the present application;

[0055] Figure 3 is the TEM image of the catalyst prepared in Example 1 of the present application;

[0056] Figure 4 is the X-ray diffraction pattern of the catalyst prepared in Examples 3 and 4 of the present application;

[0057] Figure 5 is the SEM image of the catalyst prepared in Example 3 of the present application;

[0058] Figure 6 is the X-ray diffraction pattern of the catalyst prepared in Example 5 of the present application;

[0059] Figure 7 is the X-ray diffraction pattern of the catalyst prepared in Examples 6, 7 and Comparative Example 1 of the present application;

[0060] Figure 8is a SEM image of the catalyst prepared in Comparative Example 1 of the present application;

[0061] Figure 9 is a furfural decarbonylation to furan reactivity graph of the catalyst prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0062] <Analysis method>

[0063] The analysis method or analysis equipment used in the examples of the present application is described below:

[0064] X-ray diffraction pattern: Bruker D8 advance X-ray powder diffractometer was used.

[0065] SEM image: Regulus 8100 scanning electron microscope produced by Japan HITACHI Company was used; test conditions: after drying treatment of the sample, vacuum evaporation was used to increase the conductivity and contrast effect, the analysis electron microscope accelerating voltage was 20.0 kV, and the magnification was 30-110K.

[0066] TEM image: JEOL-JEM-2100F field emission transmission electron microscope was used; test conditions: after drying treatment of the sample, vacuum evaporation was used to increase the conductivity and contrast effect, the analysis electron microscope accelerating voltage was 20.0 kV, and the magnification was 1-20K.

[0067] Elemental analysis: the content of metal atoms in the molecular sieve was tested by using the inductively coupled plasma atomic emission spectrometer (ICP-OES) of Germany Varian Company. Before characterization, the sample was digested in an aqueous HF solution at room temperature.

[0068] Example 1

[0069] Ethyl orthosilicate, tetrapropylammonium hydroxide and water were mixed and stirred at 35℃ for 6h to obtain a first mixture; the obtained first mixture was preliminarily crystallized at 70℃ for 60h to obtain a seed suspension. The molar ratio of silicon element in ethyl orthosilicate, tetrapropylammonium hydroxide and water was 1:0.4:10.

[0070] Ethyl orthosilicate, tetrapropylammonium hydroxide, tetrapropylammonium bromide, a complex of palladium chloride-ethylenediamine and water were uniformly mixed to obtain A solution. In the A solution, the molar ratio of silicon element in ethyl orthosilicate, tetrapropylammonium hydroxide, tetrapropylammonium bromide, metal element palladium in the complex of palladium chloride-ethylenediamine and water and water was 1:0.1:0.1:0.0045:110.

[0071] The seed suspension and the A solution were stirred and mixed for 4 h to obtain a second mixture. The molar ratio of silicon in the seed suspension to silicon in the A solution was 0.8:1.

[0072] The ammonium fluoride solution (i.e., solution B) was stirred and mixed with the second mixture for 1.5 h to obtain a third mixture. In the solution B, the molar ratio of ammonium fluoride to water was 1:150; and in the second mixture, the molar ratio of silicon to ammonium fluoride was 1:0.4.

[0073] The third mixture was crystallized at 170°C for 72 h, centrifuged to obtain an initial solid; the obtained initial solid was washed with water until neutral, and dried to obtain a dry solid; and then the dry solid was placed in a reduction kettle, heated to 400°C at a heating rate of 3°C / min, and reduced at this temperature under a hydrogen atmosphere for 2 h to obtain a catalyst.

[0074] The obtained catalyst was analyzed, and the X-ray diffraction pattern thereof is shown in Figure 1 , the SEM and TEM images thereof are shown in Figure 2 and Figure 3 , respectively. As shown in Figure 1 , the diffraction pattern shows that the catalyst is a full-silica molecular sieve, and there is no characteristic diffraction peak corresponding to the palladium element, indicating that no large Pd particles are formed in the sample after synthesis. As shown in Figure 2 and Figure 3 , the morphology of the catalyst obtained in this example is uniform, and basically presents a hexagonal shape, and the average crystal thickness is 20 nm. The surface of the catalyst is smooth, and there is no obvious particulate matter. According to the elemental analysis, the metal Pd element in the catalyst is 0.91 parts by weight based on 100 parts by weight of the catalyst, which is consistent with the theoretical feeding. The metal Pd nanoparticles are uniformly encapsulated by the full-silica molecular sieve, and the particle size is 0.5-2.0 nm.

[0075] Example 2

[0076] The following parameters and settings were used in addition to those in Example 1: in the A solution, the molar ratio of silicon to palladium was 1:0.0135.

[0077] The X-ray diffraction pattern of the catalyst obtained in this example shows that it is a full-silica molecular sieve, and there is no characteristic diffraction peak corresponding to the palladium element. The morphology of the obtained catalyst is uniform, and basically presents a hexagonal shape, and the average crystal thickness is 25 nm. The surface of the catalyst is smooth, and there is no obvious particulate matter. According to the elemental analysis, the metal Pd element in the catalyst is 2.94 parts by weight based on 100 parts by weight of the catalyst, which is consistent with the theoretical feeding. The metal Pd nanoparticles are uniformly encapsulated, and the particle size is 0.7-2.1 nm.

[0078] Example 3

[0079] Except for the following parameters and settings, the rest are the same as in Example 1: the palladium chloride-ethylenediamine complex is replaced with the rhodium chloride trihydrate-ethylenediamine complex.

[0080] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 4 As shown, by Figure 4 The diffraction pattern indicates an all-silica molecular sieve, with no characteristic diffraction peaks corresponding to rhodium. Its SEM results are shown below. Figure 5 ,Depend on Figure 5 As can be seen, the catalyst obtained in this embodiment has a uniform morphology, basically exhibiting a hexagonal shape, with an average crystal thickness of 25 nm. The catalyst surface is smooth, without obvious particulate matter. Elemental analysis shows that, based on 100 parts by weight of the catalyst, the amount of metallic Rh in the catalyst is 0.79 parts by weight, which is consistent with the theoretical feed. The metallic Rh nanoparticles are uniformly encapsulated, with a particle size of 0.5–1.8 nm.

[0081] Example 4

[0082] Except for the following parameters and settings, the rest are the same as in Example 1: the palladium chloride-ethylenediamine complex is replaced with the chloroplatinic acid-ethylenediamine complex, and the molar ratio of silicon to platinum in solution A is 1:0.00135.

[0083] The X-ray diffraction pattern of the catalyst prepared in this embodiment (see...) Figure 4 In the diffraction pattern, the catalyst appears to be an all-silica molecular sieve, with no characteristic diffraction peaks corresponding to platinum. The obtained catalyst has a uniform morphology, basically hexagonal, with an average crystal thickness of 23 nm. The catalyst surface is smooth, without obvious particulate matter. Elemental analysis shows that, based on 100 parts by weight of catalyst, the amount of metallic Pt is 0.29 parts by weight, consistent with the theoretical feed. The metallic Pt nanoparticles are uniformly encapsulated, with a particle size of 0.6–1.7 nm.

[0084] Example 5

[0085] Except for the following parameters and settings, the rest are the same as in Example 1: In solution A, the molar ratio of silicon to water in tetraethyl orthosilicate is replaced with 1:30; and in solution B, the molar ratio of ammonium fluoride to water is 1:75.

[0086] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 6 As shown, by Figure 6The diffraction pattern shows that the catalyst is an all-silica molecular sieve, with no characteristic diffraction peaks corresponding to palladium. The obtained catalyst has a uniform morphology, basically hexagonal, with an average crystal thickness of 23 nm. The catalyst surface is smooth, without obvious particulate matter. Elemental analysis shows that based on 100 parts by weight of catalyst, the amount of metallic Pd in ​​the catalyst is 0.90 parts by weight, which is consistent with the theoretical feed. The metallic Pd nanoparticles are uniformly encapsulated, with a particle size of 0.5–2.5 nm.

[0087] Example 6

[0088] Except for the following parameters and settings, everything else is the same as in Example 1: tetrapropylammonium hydroxide is replaced with tetramethylammonium hydroxide.

[0089] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 7 As shown, by Figure 7 The diffraction pattern shows that the catalyst is an all-silica molecular sieve, with no characteristic diffraction peaks corresponding to palladium. The obtained catalyst has a uniform morphology, basically hexagonal, with an average crystal thickness of 23 nm. The catalyst surface is smooth, without obvious particulate matter. Elemental analysis shows that, based on 100 parts by weight of catalyst, the amount of metallic Pd in ​​the catalyst is 0.90 parts by weight, consistent with the theoretical feed. The metallic Pd nanoparticles are uniformly encapsulated, with a particle size of 0.4–2.0 nm.

[0090] Example 7

[0091] Except for the following parameters and settings, everything else is the same as in Example 1: tetrapropylammonium bromide is replaced with tetramethylammonium bromide.

[0092] The X-ray diffraction pattern of the catalyst prepared in this embodiment (see...) Figure 7 In the diffraction pattern, the catalyst appears to be an all-silica molecular sieve, with no characteristic diffraction peaks corresponding to palladium. The obtained catalyst has a uniform morphology, basically hexagonal, with an average crystal thickness of 20 nm. The catalyst surface is smooth, without obvious particulate matter. Elemental analysis shows that, based on 100 parts by weight of catalyst, the amount of metallic Pd is 0.87 parts by weight, consistent with the theoretical feed. The metallic Pd nanoparticles are uniformly encapsulated, with a particle size of 0.6–2.1 nm.

[0093] Comparative Example 1

[0094] Except for the following parameters and settings, everything else is the same as in Example 1: no ammonium fluoride solution (i.e., solution B) is added.

[0095] The X-ray diffraction pattern of the catalyst prepared in the comparative example (see...) Figure 7) shows that the diffraction pattern is of a full-silica molecular sieve without any characteristic diffraction peak corresponding to palladium element. The SEM image is shown in Figure 8 The obtained catalyst has a uniform morphology, which is slightly different from that of the catalyst of Example 1, and the average thickness of the crystal is 35 nm, which is slightly thicker. The surface of the catalyst is smooth without obvious granular substances. According to elemental analysis, the metal Pd element in the catalyst is 0.88 parts by weight based on 100 parts by weight of the catalyst, which is consistent with the theoretical feeding. The metal Pd nanoparticles are uniformly encapsulated, and the particle size is 0.7-2.6 nm.

[0096] Application Example - decarboxylation of furfural to furan

[0097] The catalyst of Example 1 above was used to catalyze the decarbonylation reaction of furfural.

[0098] The specific application conditions are as follows: the test process was carried out in a fixed bed reactor, the mass of the catalyst was 200 mg (the mass ratio to furfural was 1:5), and the catalytic process conditions were as follows: the reaction pressure was normal pressure, the molar ratio of hydrogen to furfural was 80:1, the reaction temperature was 250°C, the furfural space velocity was 0.8 h -1 -1, and the catalytic time was 8 h. Sampling was carried out every hour for analysis.

[0099] The detection method was as follows: sampling was carried out after the reaction, gas chromatography was used to analyze the product composition, and then the furfural conversion rate and the furan selectivity were calculated. The catalytic results of the catalyst of Example 1 are shown in Table 1 and Figure 9 . Figure 9 Table 1 and Table 1 have the same meaning. The calculation formula of the furfural conversion rate is as follows: furfural conversion rate = [(carbon molar number of furfural in the feed) - (carbon molar number of furfural in the discharge)] ÷ (carbon molar number of furfural in the feed) x 100%.

[0100] The calculation formula of the furan selectivity is as follows: furan selectivity = (carbon molar number of furan in the discharge) ÷ (sum of carbon molar numbers of all carbon-containing products in the discharge) x 100%.

[0101] Table 1

[0102]

[0103] As can be seen from Table 1 and Figure 9 , the catalyst obtained in Example 1 has high catalytic activity for the decarbonylation reaction of furfural to furan, the furfural conversion rate can reach 100%, the furan selectivity is 96.2%, and the selectivity for furan is high, which can reduce the cost of product separation and has obvious economic benefits.

[0104] The present application is not limited to the above-described embodiments, and any modification, improvement, replacement that can be conceived by those skilled in the art without departing from the essential content of the present application falls within the scope of the present application.

Claims

1. A catalyst for decarboxylation of furfural to furan, characterized by, The catalyst comprises a full-silica molecular sieve and metal nanoparticles; wherein, The metal nanoparticles have a particle size of 0.5-3.5 nm; the metal nanoparticles are dispersed in the interior of the full-silica molecular sieve; The metal element in the metal nanoparticles is selected from one of Pd, Pt and Rh; the metal nanoparticles are 0.2-4.5 parts by weight based on 100 parts by weight of the catalyst; The catalyst has a thin flake-like structure similar to a hexagon, and the crystal thickness is 15-25 nm; The catalyst is prepared by comprising the following steps: Step 1, mixing a silicon element-containing raw material, alkyl ammonium hydroxide and water to obtain a first mixture; preliminarily crystallizing the obtained first mixture at 50-100 ℃ to obtain a seed suspension; the molar ratio of the silicon element in the silicon element-containing raw material, the alkyl ammonium hydroxide and the water is 1:0.1-0.5:6-26; Step 2, mixing a silicon element-containing raw material, alkyl ammonium hydroxide, alkyl ammonium bromide, a water-soluble metal salt and water to obtain an A solution; wherein, in the A solution, the molar ratio of the silicon element in the silicon element-containing raw material, the alkyl ammonium hydroxide, the alkyl ammonium bromide, the metal element in the water-soluble metal salt and the water is 1:0.01-0.4:0.01-0.4:0.0004-0.03:20-200; Step 3, mixing the seed suspension in step 1 and the A solution in step 2 to obtain a second mixture; wherein, the molar ratio of the silicon element in the seed suspension to the silicon element in the A solution is 0.5-2.5:1; Step 4, mixing an ammonium fluoride-containing solution B and the second mixture to obtain a third mixture; wherein, in the ammonium fluoride-containing solution B, the molar ratio of the ammonium fluoride to the water is 1:30-300; the molar ratio of the silicon element in the second mixture to the ammonium fluoride in the solution B is 1:0.05-0.8; Step 5, crystallizing the third mixture at 150-180 ℃, solid-liquid separation to obtain an initial solid; washing and drying the obtained initial solid to obtain a dry solid; then reducing the dry solid in a hydrogen atmosphere at 350-450 ℃ to obtain the catalyst; The silicon element-containing raw material is selected from silicate; the silicate is selected from one or more of methyl orthosilicate, ethyl orthosilicate, isopropyl orthosilicate and butyl orthosilicate; The metal element in the water-soluble metal salt is consistent with the metal element in the metal nanoparticles.

2. A method for producing the catalyst for decarboxylating furfural to furan according to claim 1, characterized by, comprising the following steps: Step 1, mixing a silicon element-containing raw material, alkyl ammonium hydroxide and water to obtain a first mixture; preliminarily crystallizing the obtained first mixture at 50-100 ℃ to obtain a seed suspension; the molar ratio of the silicon element in the silicon element-containing raw material, the alkyl ammonium hydroxide and the water is 1:0.1-0.5:6-26; Step 2, mixing the silicon element-containing raw material, the alkyl ammonium hydroxide, the alkyl ammonium bromide, the water-soluble metal salt and water to obtain solution A; wherein, in the solution A, the molar ratio of the silicon element in the silicon element-containing raw material, the alkyl ammonium hydroxide, the alkyl ammonium bromide, the metal element in the water-soluble metal salt and water is 1:0.01-0.4:0.01-0.4:0.0004-0.03:20-200; Step 3, mixing the seed suspension in step 1 and the solution A in step 2 to obtain a second mixture; wherein, the molar ratio of the silicon element in the seed suspension and the silicon element in the solution A is 0.5-2.5:1; Step 4, mixing the solution B containing ammonium fluoride and the second mixture to obtain a third mixture; wherein, in the solution B containing ammonium fluoride, the molar ratio of ammonium fluoride and water is 1:30-300; the molar ratio of the silicon element in the second mixture and the ammonium fluoride in the solution B is 1:0.05-0.8; Step 5, crystallizing the third mixture at 150-180℃, solid-liquid separation to obtain an initial solid; washing and drying the obtained initial solid to obtain a dry solid; then reducing the dry solid in a hydrogen atmosphere at 350-450℃ to obtain the catalyst; wherein, the silicon element-containing raw material is selected from silicate; the silicate is selected from one or more of methyl orthosilicate, ethyl orthosilicate, isopropyl orthosilicate and butyl orthosilicate; wherein, the metal element in the water-soluble metal salt is consistent with the metal element in the metal nanoparticles.

3. The method of claim 2, wherein, The silicate is selected from one of methyl orthosilicate, ethyl orthosilicate, isopropyl orthosilicate and butyl orthosilicate.

4. The method of claim 2, wherein, The alkyl ammonium hydroxide is selected from one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, dimethyldiethylammonium hydroxide and dimethyldipropylammonium hydroxide.

5. The method of claim 2, wherein, The alkyl ammonium bromide is selected from one or more of tetramethylammonium bromide, tetraethylammonium bromide and tetrapropylammonium bromide.

6. The method of claim 2, wherein, The water-soluble metal salt is a complex of the water-soluble metal salt and ethylenediamine.

7. A method for preparing furan by catalytic decarbonylation of furfural, characterized by, The catalyst as claimed in claim 1 is used to catalytically decarbonylate furfural to prepare furan, and the weight ratio of the catalyst to furfural is 1:1-20.

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