HZSM-5 molecular sieve, preparation method and application thereof

Abstract

The application discloses HZSM-5 molecular sieve, a preparation method and application thereof, and belongs to the field of molecular sieve catalysts. The HZSM-5 molecular sieve comprises a flaky HZSM-5 molecular sieve base body and platinum nano-particles loaded on the flaky HZSM-5 molecular sieve base body; and the average thickness of the flaky HZSM-5 molecular sieve base body is 50-100 nm. The flaky HZSM-5 molecular sieve base body can provide acid centers, the platinum nano-particles can provide hydrogenation centers, and the two can cooperate to achieve good catalytic activity; and the flaky HZSM-5 molecular sieve base body has a relatively thin thickness, i.e. a relatively short b-axis channel length, which is not only beneficial to material diffusion and transmission, but also can greatly reduce the case that intermediate products contact acid sites to cause side reactions, and therefore can provide higher product selectivity. In particular, the HZSM-5 molecular sieve has a good application prospect in catalyzing bio-oil hydrodeoxygenation.

Description

Technical Field

[0001] This invention belongs to the field of organic chemical synthesis technology, and particularly relates to an HZSM-5 molecular sieve, its preparation method and application. Background Technology

[0002] Biomass, as one of the most important renewable resources on Earth and a renewable resource that can be converted into liquid fuels, has received widespread attention. The main components of biomass are cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are composed of complex polysaccharides; lignin is a highly substituted mononuclear phenolic amorphous polymer composed of phenylpropane units, and its precursors are three lignin monomers, including p-coumarol, coniferyl alcohol, and sinapyl alcohol.

[0003] Biomass conversion can be mainly divided into the following categories: (1) Direct combustion technology: Direct combustion has high requirements for raw materials, is inefficient and not environmentally friendly; (2) Bioconversion technology: Biomass is converted into ethanol, etc. by using microbial fermentation; (3) Thermal conversion technology: Generally divided into three methods: gasification, pyrolysis and liquefaction. Among them, biomass pyrolysis is the process of thermally decomposing organic compounds under anaerobic conditions to obtain coke, syngas and bio-oil. However, bio-oil contains a large amount of oxygen-containing compounds such as acids, ketones and esters, which not only have low calorific value but also unstable combustion, making it difficult to use directly. Therefore, additional bio-oil upgrading processes are needed to obtain higher quality chemicals. Hydrodeoxygenation (HDO) is considered an effective process for deoxygenating bio-oil. The HDO of bio-oil needs to be carried out in a certain temperature and hydrogen environment. The possible reactions in its catalytic process include: (1) water separation; (2) dehydration reaction caused by polycondensation reaction; (3) decarboxylation reaction, in which oxygen is removed in the form of H2O; (4) hydrogenation reaction, which may involve the saturation of unsaturated components; (5) hydrogenolysis reaction, which is related to the breaking of CO bonds, in which oxygen can be released in the form of water; (6) hydrocracking reaction, which involves the decomposition of high molecular weight components into smaller molecules.

[0004] In the field of biomass hydrogenation and deoxygenation research, transition metal or noble metal supported catalysts are the most noteworthy, and vanillin, as a highly representative simple phenolic lignin model compound, has received considerable attention and research. For example, a study reported a Ni-P amorphous alloy material synthesized by chemical reduction. After modification with Co, it not only increased the number of active sites on the catalyst but also improved the dispersibility, thermal stability, and disorder of the amorphous alloy. Under the conditions of H2 partial pressure of 2.0 MPa, reaction temperature of 150 °C, and reaction time of 3 h, the conversion rate of vanillin and the selectivity for 2-methoxy-4-methylphenol could reach 100% and 82.7%, respectively. Additionally, other studies have explored the distribution of metal-organic framework (MOF) ZIF-67 on a carbonaceous matrix (Ni... xA precursor method based on Co@NC@C was used to develop bimetallic Ni-Co nanoparticles coated with layered, flower-like nitrogen-doped carbon layers. This method is supplemented with Ni 2+ The etching ions were then subjected to hydrothermal treatment with glucose; the results showed that the defective oxygen vacancies on the catalyst and the electron-rich sites provided by Co enabled the complete conversion of vanillin under mild conditions. Furthermore, studies have shown that mesoporous ZrO2 prepared by precipitation can achieve a 99% yield of 2-methoxy-4-methylphenol in isopropanol solvent at a partial pressure of 5.0 MPa H2, a reaction temperature of 180 °C, and a reaction time of 24 h. Summary of the Invention

[0005] To overcome at least one of the problems existing in the prior art, one of the objectives of the present invention is to provide an HZSM-5 molecular sieve with a small average thickness (i.e., a small b-axis pore length), which not only facilitates the diffusion and transport of substances, but also significantly reduces the occurrence of side reactions caused by intermediate products contacting acidic sites, thus providing higher reaction selectivity; in addition, combined with the excellent hydrogenation effect of platinum, it is beneficial for the molecular sieve to achieve good hydrogenation and deoxygenation activity.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned HZSM-5 molecular sieve.

[0007] The third objective of this invention is to provide an application of the above-mentioned HZSM-5 molecular sieve in the catalytic hydrodeoxygenation of bio-oil.

[0008] The fourth objective of this invention is to provide a method for preparing 2-methoxy-4-methylphenol.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A first aspect of the present invention provides an HZSM-5 molecular sieve, comprising a sheet-like HZSM-5 molecular sieve matrix and platinum nanoparticles loaded on the sheet-like HZSM-5 molecular sieve matrix; the average thickness of the sheet-like HZSM-5 molecular sieve matrix is ​​50-100 nm.

[0011] Preferably, the average thickness of the sheet-like HZSM-5 molecular sieve matrix is ​​60–90 nm; more preferably, it is 70–85 nm.

[0012] In this invention, the thickness of the sheet-like HZSM-5 molecular sieve matrix is ​​the b-axis pore length.

[0013] Preferably, the average diameter of the platinum nanoparticles is 8–15 nm; more preferably, it is 10–12 nm.

[0014] Preferably, in the HZSM-5 molecular sieve, silicon and aluminum are measured as SiO2 and Al2O3, respectively, and the silicon-aluminum ratio is 1:(0.001-0.02) in molar ratio; more preferably 1:(0.002-0.01); and even more preferably 1:(0.003-0.007).

[0015] Preferably, the mass percentage of platinum nanoparticles in the HZSM-5 molecular sieve is 0.1-1%; more preferably 0.15-0.8%; and even more preferably 0.2-0.5%.

[0016] The second aspect of the present invention provides a method for preparing HZSM-5 molecular sieve, comprising the following steps: mixing a silicon source, an aluminum source, sodium hydroxide, a template agent, urea, isopropanol and water, and sequentially performing a crystallization reaction, a first calcination, an ammonium exchange reaction and a second calcination to obtain a sheet-like HZSM-5 molecular sieve matrix; mixing the sheet-like HZSM-5 molecular sieve matrix with a platinum source and performing a third calcination to obtain the HZSM-5 molecular sieve as described in the first aspect of the present invention.

[0017] The preparation method of this invention first synthesizes an ultrathin sheet-like HZSM-5 molecular sieve matrix, then loads it with platinum, and obtains the desired material in a simple and efficient manner. Among them, the addition of urea can achieve precise control of the b-axis pore length of the sheet-like HZSM-5 molecular sieve matrix. Isopropanol can be used as an auxiliary solvent or dispersant. Isopropanol can help to uniformly disperse the silicon source, aluminum source, template agent and urea in the system, avoid the aggregation or precipitation of components in the system, and has suitable molecular polarity and molecular size, which can promote better crystallization reaction.

[0018] Preferably, the silicon source is selected from tetraethoxysilane.

[0019] Preferably, the aluminum source is selected from aluminum nitrate nonahydrate.

[0020] Preferably, the template agent is selected from tetrapropylammonium hydroxide (TPAOH).

[0021] In the reaction system, both TPAOH and NaOH will dissociate to release OH-. - Therefore, the alkaline environment in the synthesis system is provided by TPAOH and NaOH, while the main role of NaOH is to assist in regulating alkalinity, adjusting the crystallization rate, and balancing the charge of the molecular sieve framework.

[0022] This invention, through the selection of specific silicon sources, aluminum sources, and template agents, combined with sodium hydroxide, urea, and isopropanol, carries out specific crystallization, ammonium exchange, calcination, and platinum loading processes, which can produce molecular sieves with better performance.

[0023] Preferably, the ammonium source used in the ammonium exchange reaction includes ammonium chloride, ammonium nitrate, or a combination thereof; more preferably, the ammonium source used in the ammonium exchange reaction is selected from ammonium chloride.

[0024] Preferably, the platinum source includes at least one of tetraammineplatinum nitrate, chloroplatinic acid, platinum tetrachloride, or platinum dichlorosulfite; more preferably, the platinum source includes at least one of tetraammineplatinum nitrate, platinum tetrachloride, or platinum dichlorosulfite; even more preferably, the platinum source is selected from tetraammineplatinum nitrate.

[0025] Preferably, the silicon source and the aluminum source are measured as SiO2 and Al2O3, respectively, and the molar ratio of the silicon source to the aluminum source is 1:(0.001-0.02); more preferably 1:(0.002-0.01); and even more preferably 1:(0.003-0.007).

[0026] Preferably, the silicon source is measured in SiO2, and the molar ratio of the silicon source to the sodium hydroxide is 1:(0.01-0.2); more preferably 1:(0.02-0.1); and even more preferably 1:(0.03-0.07).

[0027] Preferably, the silicon source is measured in SiO2, and the molar ratio of the silicon source to the template agent is 1:(0.1-2); more preferably 1:(0.2-1); and even more preferably 1:(0.3-0.7).

[0028] Preferably, the silicon source is measured in SiO2, and the molar ratio of the silicon source to the urea is 1:(0.3-2); more preferably 1:(0.4-1.5); and even more preferably 1:(0.5-1).

[0029] Preferably, the silicon source is measured in SiO2, and the molar ratio of the silicon source to the isopropanol is 1:(0.01-0.2); more preferably 1:(0.02-0.1); and even more preferably 1:(0.03-0.07).

[0030] Preferably, the ammonium source used in the ammonium exchange reaction is in the form of an aqueous solution; more preferably, the concentration of ammonium in the aqueous solution of the ammonium source is 0.1-2 mol / L; even more preferably, it is 0.5-1.5 mol / L.

[0031] Preferably, the ammonium source used in the ammonium exchange reaction is measured in ammonium, and the ratio of the ammonium source to the product of the first calcination is (0.001-0.02) mol: 1 g; more preferably (0.005-0.015) mol: 1 g.

[0032] Preferably, the platinum source participates in the reaction in the form of an aqueous solution; more preferably, the Pt concentration in the aqueous solution of the platinum source is 0.1-2 g / L; even more preferably, it is 0.2-1 g / L.

[0033] Preferably, the platinum source is measured in Pt, and the mass ratio of the platinum source to the sheet-like HZSM-5 molecular sieve matrix is ​​(0.0005-0.01):1; more preferably (0.001-0.007):1; and even more preferably (0.0015-0.004):1.

[0034] Preferably, in the preparation method, the mixing order of the raw materials is as follows: template agent, silicon source, isopropanol, urea, aluminum source, sodium hydroxide and water.

[0035] Preferably, the temperature of the crystallization reaction is 160–200°C; more preferably, it is 170–190°C.

[0036] Preferably, the crystallization reaction takes 24 to 72 hours; more preferably 36 to 60 hours.

[0037] Preferably, the heating rate of the crystallization reaction is 10–20 °C / h; more preferably, it is 13–17 °C / h.

[0038] In some embodiments of the present invention, the crystallization reaction is followed by a step of collecting the crystallization product. The steps of collecting the crystallization product are well known to those skilled in the art, and common operations include centrifuging, washing, and drying the crystallization product.

[0039] Preferably, the roasting temperature of the first roasting and the roasting temperature of the second roasting are each independently 500-600°C; more preferably 530-570°C.

[0040] Preferably, the holding time for the first roasting and the holding time for the second roasting are each independently 2 to 8 hours; more preferably 4 to 6 hours.

[0041] Preferably, the heating rate of the first roasting and the heating rate of the second roasting are each independently 80-120℃ / h; more preferably 90-110℃ / h.

[0042] Preferably, the reaction temperature of the ammonium exchange reaction is 60–100°C; more preferably, it is 70–90°C.

[0043] Preferably, the reaction time of the ammonium exchange reaction is 1 to 4 hours; more preferably, it is 1.5 to 3 hours.

[0044] In some embodiments of the present invention, the method of mixing the sheet-like HZSM-5 molecular sieve matrix with the platinum source is selected from the impregnation method.

[0045] Preferably, the roasting temperature of the third roasting is 300-500℃; more preferably, it is 320-450℃.

[0046] Preferably, the holding time for the third roasting is 2 to 8 hours; more preferably, it is 3 to 6 hours.

[0047] Preferably, the heating rate of the third calcination is 0.5–5 °C / min; more preferably, it is 0.8–2 °C / min.

[0048] Preferably, the third calcination includes a first stage calcination and a second stage calcination; the first stage calcination is carried out in an atmosphere containing oxygen gas; and the second stage calcination is carried out in an atmosphere containing reducing gas.

[0049] Preferably, the oxygen-containing gas includes oxygen or air; more preferably, it is air.

[0050] Preferably, the reducing gas includes at least one of hydrogen, carbon monoxide, or methane; more preferably, it is hydrogen.

[0051] Preferably, the roasting temperature of the first stage is 30-70°C higher than that of the second stage; more preferably, it is 40-60°C.

[0052] By using a specific calcination temperature, the HZSM-5 molecular sieve can be calcined completely, and the platinum nanoparticles can be evenly dispersed in the sheet-like HZSM-5 molecular sieve matrix, thus avoiding large-scale agglomeration.

[0053] Preferably, the ratio of the holding time of the first stage of roasting to the holding time of the second stage of roasting is 1:(0.5-2); more preferably, it is 1:(0.8-1.2).

[0054] Preferably, the roasting temperature in the first stage is 300–500°C; more preferably, it is 350–400°C.

[0055] Preferably, the holding time for the first stage of roasting is 1 to 4 hours; more preferably, it is 1.5 to 3 hours.

[0056] Preferably, the heating rate of the first stage of calcination is 0.1–5 °C / min; more preferably, it is 0.3–2 °C / min.

[0057] Preferably, the roasting temperature in the second stage is 300–400°C; more preferably, it is 320–350°C.

[0058] Preferably, the heat preservation time for the second stage of roasting is 1 to 4 hours; more preferably, it is 1.5 to 3 hours.

[0059] Preferably, the heating rate of the second stage of calcination is 0.1–5 °C / min; more preferably, it is 0.3–2 °C / min.

[0060] A third aspect of the present invention provides an application of the HZSM-5 molecular sieve described in the first aspect of the present invention in the catalytic hydrodeoxygenation of bio-oil.

[0061] Preferably, the bio-oil includes at least one of acids, ketones, esters, aldehydes, or phenols; more preferably, the bio-oil includes aldehydes, phenols, or combinations thereof.

[0062] In some embodiments of the present invention, the bio-oil is selected from phenolic lignin; in some specific embodiments of the present invention, the bio-oil is selected from vanillin.

[0063] Vanillin is a simple phenolic lignin. The HZSM-5 molecular sieve of this invention has a good catalytic effect, especially in the hydrogenation and deoxygenation of vanillin, and can prepare 2-methoxy-4-methylphenol with high activity and high selectivity.

[0064] The fourth aspect of the present invention provides a method for preparing 2-methoxy-4-methylphenol, comprising the following steps: using HZSM-5 molecular sieve as described in the first aspect of the present invention as a catalyst and vanillin as a substrate, performing a hydrogenation deoxygenation reaction to obtain 2-methoxy-4-methylphenol.

[0065] Preferably, the hydrodeoxygenation reaction is carried out in a hydrogen atmosphere; the partial pressure of the hydrogen is 1-3 MPa; more preferably 1.5-2.5 MPa.

[0066] Preferably, the reaction temperature of the hydrodeoxygenation reaction is 80–160°C; more preferably 100–140°C; and even more preferably 110–130°C.

[0067] Preferably, the reaction time of the hydrodeoxygenation reaction is 30 to 300 min; more preferably 50 to 200 min; and even more preferably 100 to 150 min.

[0068] Preferably, the molar ratio of vanillin to platinum nanoparticles in the HZSM-5 molecular sieve is (400-1000):1; more preferably (450-800):1; and even more preferably (480-600):1.

[0069] Preferably, the hydrodeoxygenation reaction is carried out in water; more preferably, the mass ratio of vanillin to water is 1:(100-400); even more preferably, it is 1:(200-300).

[0070] The beneficial effects of this invention are as follows: the sheet-like HZSM-5 molecular sieve matrix of this invention can provide acidic centers, and the platinum nanoparticles can provide hydrogenation centers; the combination of the two can achieve good catalytic activity. Furthermore, the sheet-like HZSM-5 molecular sieve matrix has a relatively thin thickness, i.e., a shorter b-axis pore length, which not only facilitates mass diffusion and transport but also significantly reduces the occurrence of side reactions caused by intermediate products contacting acidic sites, thus providing higher product selectivity. The HZSM-5 molecular sieve of this invention particularly exhibits excellent hydrodeoxygenation effects, and especially shows promising application prospects in the catalytic hydrodeoxygenation of bio-oils.

[0071] Specifically, compared with the prior art, the present invention has the following advantages:

[0072] 1. The HZSM-5 molecular sieve provided by this invention has a particularly good effect in catalyzing the hydrogenation and deoxygenation of vanillin to produce 2-methoxy-4-methylphenol. Specifically, the platinum nanoparticles in the HZSM-5 molecular sieve have good hydrogenation activity, which is beneficial to the conversion of vanillin to vanillyl alcohol. The sheet-like HZSM-5 molecular sieve matrix can provide acidic centers to realize the dehydroxylation process. Furthermore, the short b-axis of the sheet-like HZSM-5 molecular sieve matrix can also prevent the intermediate product from reacting with its acidic sites, thereby enabling the high-selectivity production of 2-methoxy-4-methylphenol. This achieves high activity and high selectivity in the hydrogenation and deoxygenation of vanillin to produce 2-methoxy-4-methylphenol, as well as the stability and sustainability of the catalytic system.

[0073] 2. In the preparation method of HZSM-5 molecular sieve provided by the present invention, an ultrathin sheet-like HZSM-5 molecular sieve matrix is ​​first synthesized, and then platinum is loaded onto it to obtain the required material in a simple and efficient manner. In addition, the b-axis pore length of the sheet-like HZSM-5 molecular sieve matrix can be precisely controlled mainly by adding urea and adjusting the amount of urea. This process is simple and easy to implement, and the obtained HZSM-5 molecular sieve has good catalytic activity and selectivity. Attached Figure Description

[0074] Figure 1 The XRD spectra of samples A2 and A3 in Example 1 of this invention are shown.

[0075] Figure 2 The image shows the SEM image and particle size distribution of sample A2 in Example 1 of this invention.

[0076] Figure 3The images show the TEM image and particle size distribution of sample A3 in Example 1 of this invention.

[0077] Figure 4 The image shows the SEM image and particle size distribution of sample B2 in Comparative Example 1 of this invention.

[0078] Figure 5 The TEM image and particle size distribution diagram of sample B3 in Comparative Example 1 of this invention are shown. Detailed Implementation

[0079] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the principles described herein are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0080] Example 1

[0081] This example provides an ultrathin HZSM-5 molecular sieve with platinum metal nanoclusters. The specific preparation steps are as follows:

[0082] 1) Dissolve 0.1g of isopropanol (IPA) in 2g of H2O to prepare solution A; dissolve 2g of urea in 4g of H2O to prepare solution B; dissolve 0.3g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O) in 4g of H2O to prepare solution C; dissolve 0.1g of sodium hydroxide (NaOH) in 2g of H2O to prepare solution D. Weigh 8.19g of tetrapropylammonium hydroxide (TPAOH 40wt%) and stir at room temperature. Slowly add 11.2g of tetraethoxysilane (TEOS), then add solutions A, B, C, and D in sequence, and 11.31g of H2O, and continue stirring for 2 hours to form the system for synthesizing ultrathin NaZSM-5 molecular sieves.

[0083] In the aforementioned synthetic ultrathin NaZSM-5 molecular sieve system:

[0084] The molar ratio of SiO2, Al2O3, and NaOH is 1.0:0.0042:0.046;

[0085] The molar ratio of tetrapropylammonium hydroxide, isopropanol, urea and tetraethoxysilane is 0.3:0.031:0.62:1, where tetraethoxysilane is calculated as SiO2.

[0086] 2) The above mixture was then placed in a stainless steel hydrothermal reactor lined with polytetrafluoroethylene (PTFE), and heated to 180°C at a rate of 15°C / h for static crystallization for 2 days. After crystallization, the reactor was removed and rapidly cooled to room temperature with water. The crystallized product was centrifuged, washed, and dried. The resulting sample was calcined in a muffle furnace at 550°C for 5 hours at a heating rate of 100°C / h. Sample A1 was obtained.

[0087] 3) Next, weigh out NH4Cl and dissolve it in water to prepare a 1 mol / L NH4Cl aqueous solution. Take 1 g of sample A1, heat it in a water bath at 80℃ and stir at 600 rpm, add 10 mL of NH4Cl aqueous solution, and keep it for 2 h to carry out ammonium exchange.

[0088] In the ammonium exchange system using the ultrathin NaZSM-5 molecular sieve, the mass ratio of sample A1 to the volume ratio of 1 mol / L NH4Cl aqueous solution is 1:10.

[0089] 4) After the ammonium exchange is completed, the product is centrifuged and washed, and the ammonium exchange in step 3) is repeated twice. Then the product is dried and calcined in a muffle furnace at a temperature of 550℃ for 5 hours with a heating rate of 100℃ / h to obtain sample A2, namely HZSM-5 molecular sieve.

[0090] 5) Next, using platinum tetraammine nitrate as a platinum precursor, platinum was loaded onto sample A2 using the impregnation method. 1 g of sample A2 was weighed and dispersed in 5 g of H2O and stirred continuously for 2 h. Then, 0.004 g of platinum tetraammine nitrate was dissolved in 10 mL of H2O to prepare solution E. Solution E was slowly added dropwise to a uniformly dispersed ultrathin HZSM-5 mixture under stirring at room temperature.

[0091] In the aforementioned synthetic platinum metal nanoclusters ultrathin HZSM-5 molecular sieve system:

[0092] The mass ratio of sample A2 to elemental platinum is 1.0:0.002;

[0093] The mass ratio of sample A2 to the volume ratio of the aqueous solution of tetraamminenitrate platinum was 1:15.

[0094] 6) After continuous stirring at room temperature for 4 hours, the product was evaporated and dried, then calcined in a tube furnace with flowing air at 500℃ for 2 hours at a heating rate of 1℃ / min. Reduction was then carried out in a hydrogen atmosphere at 400℃ for 2 hours at a heating rate of 1℃ / min. Sample A3 was obtained, namely, platinum metal nanoclusters ultrathin HZSM-5 molecular sieve.

[0095] Figure 1The XRD patterns of samples A2 and A3 in Example 1 of this invention are shown. As can be seen from the figure, both samples A2 and A3 are HZSM-5 molecular sieves; the peaks are sharp and free of impurities, and there are no obvious platinum characteristic peaks in the molecular sieve spectrum, indicating that the molecular sieve has high crystallinity. At the same time, in sample A3, the platinum loaded on the molecular sieve does not show obvious agglomeration.

[0096] Figure 2 The image shows the SEM image and particle size distribution of sample A2 in Example 1 of this invention. The small image in the upper right corner is the particle size distribution. It can be seen from the image that the synthesized molecular sieve crystals have a regular morphology. The particle size analysis results show that the b-axis pore length of the ultrathin HZSM-5 is about 75.8 nm.

[0097] Figure 3 The images shown are TEM images and particle size distribution diagrams of sample A3 in Example 1 of this invention. The small image in the upper left corner is the particle size distribution diagram; the dark black spots in the TEM image are platinum nanoclusters. Figure 3 It can be seen that the platinum nanoclusters are uniformly dispersed in the ultrathin HZSM-5 molecular sieve crystals, and the particle size analysis results show that the diameter distribution of the platinum nanoclusters is relatively uniform, with an average diameter of about 11.42 nm.

[0098] The silicon-to-aluminum ratio (SiO2:Al2O3) of sample A1 is 1.00:0.0042.

[0099] The mass fraction of platinum in sample A1 is approximately 0.2%.

[0100] Comparative Example 1

[0101] This example provides a platinum metal nanoclusters HZSM-5 molecular sieve. Unlike Example 1, this comparative example uses a conventional HZSM-5 molecular sieve as a support, and the platinum nanoclusters are loaded using the same impregnation method.

[0102] The difference between this comparative example and Example 1 is that platinum nanoclusters are supported on a conventional HZSM-5 molecular sieve with a longer b-axis channel length.

[0103] The specific implementation method of this comparative example is as follows:

[0104] 1) Weigh 0.13g NaOH and dissolve it in 19.45g H2O to prepare solution A. Then weigh 0.05g sodium aluminate and add it to solution A. Add 5.08g tetrapropylammonium hydroxide (TPAOH 40wt%) while stirring. Then slowly add 10.71g TEOS to the system. Stir at 600rpm for at least 4h at room temperature (25℃) to form the system for synthesizing conventional NaZSM-5 molecular sieve.

[0105] In the aforementioned synthetic NaZSM-5 molecular sieve system:

[0106] The molar ratio of SiO2, NaAlO2, NaOH, and tetrapropylammonium hydroxide is 1.0:0.0059:0.632:0.195.

[0107] 2) The above mixture was then placed in a stainless steel hydrothermal reactor lined with polytetrafluoroethylene (PTFE), and heated to 170°C at a rate of 2°C / min for static crystallization for 3 days. After crystallization, the reactor was removed after natural cooling, and the crystallized product was centrifuged, washed, and dried. The resulting sample was calcined in a muffle furnace at 550°C for 5 hours at a heating rate of 100°C / h to obtain sample B1.

[0108] 3) Next, weigh out NH4Cl and dissolve it in water to prepare a 1 mol / L NH4Cl aqueous solution. Take 1 g of sample B1, heat it in a water bath at 80℃ and stir at 600 rpm, add 10 mL of NH4Cl aqueous solution, and keep it for 2 h.

[0109] In the ammonium exchange system using NaZSM-5 molecular sieve, the mass ratio of sample B1 to the volume ratio of 1 mol / L NH4Cl aqueous solution is 1:10.

[0110] 4) After the ammonium exchange is completed, the product is centrifuged and washed, and the ammonium exchange in step 3) is repeated twice. After drying the product, it is calcined in a muffle furnace at a temperature of 550℃ for 5 hours with a heating rate of 100℃ / h to obtain sample B2.

[0111] 5) Next, using platinum tetraammine nitrate as a platinum precursor, platinum was loaded onto sample B2 using the impregnation method. 1 g of sample B2 was weighed and dispersed in 5 g of H2O and stirred continuously for 2 h. Then, 0.004 g of platinum tetraammine nitrate was dissolved in 10 mL of H2O to prepare solution B. Solution B was slowly added dropwise to a uniformly dispersed HZSM-5 mixture under stirring at room temperature.

[0112] In the aforementioned synthetic platinum metal nanoclusters HZSM-5 molecular sieve system:

[0113] The mass ratio of B2 to elemental platinum is 1.0:0.002;

[0114] The mass ratio of sample B2 to the volume ratio of the aqueous solution of tetraammine nitrate platinum was 1:15.

[0115] 6) After continuous stirring at room temperature for 4 hours, the product was evaporated and dried, then calcined in a tube furnace with flowing air at 500℃ for 2 hours at a heating rate of 1℃ / min. It was then reduced in a hydrogen atmosphere at 400℃ for 2 hours at a heating rate of 1℃ / min. Sample B3 was obtained.

[0116] Figure 4 The image shows the SEM image and particle size distribution of sample B2 in Comparative Example 1 of this invention. The smaller image in the lower left corner is the particle size distribution. It can be seen that the synthesized molecular sieve crystals have a regular morphology. The particle size analysis results show that the b-axis pore length of the HZSM-5 molecular sieve is approximately 181 nm. Figure 2 and Figure 4 As can be seen from the comparison, the b-axis channel size of sample B3 in Comparative Example 1 is significantly longer than that of ultra-thin HZSM-5 sample A3 in Example 1.

[0117] Figure 5 The image shows the TEM image and particle size distribution of sample B3 in Comparative Example 1 of this invention. The small image in the lower right corner is the particle size distribution. The dark black spots in the TEM image are platinum nanoclusters. As can be seen from the image, the platinum nanoclusters are uniformly dispersed in the HZSM-5 molecular sieve crystal. The particle size analysis results show that the diameter distribution of the platinum nanoclusters is relatively uniform, with an average diameter of about 11.74 nm.

[0118] The silicon-to-aluminum ratio (SiO2:Al2O3) of sample B1 is 1.00:0.00295.

[0119] The mass fraction of platinum in sample B1 is approximately 0.2%.

[0120] Example 2

[0121] This example provides an ultrathin HZSM-5 molecular sieve with platinum metal nanoclusters. The specific preparation steps are as follows:

[0122] 1) Dissolve 0.1g of isopropanol (IPA) in 2g of H2O to prepare solution A; dissolve 2g of urea in 4g of H2O to prepare solution B; dissolve 0.3g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O) in 4g of H2O to prepare solution C; dissolve 0.1g of sodium hydroxide (NaOH) in 2g of H2O to prepare solution D. Weigh 8.19g of tetrapropylammonium hydroxide (TPAOH 40wt%) and stir at room temperature. Slowly add 11.2g of tetraethoxysilane (TEOS), then add solutions A, B, C, and D in sequence, and 11.31g of H2O, stirring continuously for 2 hours to form the system for synthesizing ultrathin NaZSM-5 molecular sieves.

[0123] In the aforementioned synthetic ultrathin NaZSM-5 molecular sieve system:

[0124] The molar ratio of SiO2, Al2O3, and NaOH is 1.0:0.0042:0.046;

[0125] The molar ratio of tetrapropylammonium hydroxide, isopropanol, urea and tetraethoxysilane is 0.3:0.031:0.62:1, where tetraethoxysilane is calculated as SiO2.

[0126] 2) The above mixture was then placed in a stainless steel hydrothermal reactor lined with polytetrafluoroethylene (PTFE), and heated to 180°C at a rate of 15°C / h for static crystallization for 2 days. After crystallization, the reactor was removed and rapidly cooled to room temperature with water. The crystallized product was centrifuged, washed, and dried. The resulting sample was calcined in a muffle furnace at 550°C for 5 hours at a heating rate of 100°C / h. Sample C1 was obtained.

[0127] 3) Next, weigh out NH4Cl and dissolve it in water to prepare a 1 mol / L NH4Cl aqueous solution. Take 1 g of sample C1, heat it in a water bath at 80℃ and stir at 600 rpm, add 10 mL of NH4Cl aqueous solution, and keep it for 2 h.

[0128] In the ammonium exchange system of the ultrathin NaZSM-5 molecular sieve, the mass ratio of sample C1 to 1 mol / L NH4Cl aqueous solution is 1:10.

[0129] 4) After the ammonium exchange is completed, the product is centrifuged and washed, and the ammonium exchange in step 3) is repeated twice. After drying the product, it is calcined in a muffle furnace at a temperature of 550℃ for 5 hours with a heating rate of 100℃ / h to obtain sample C2.

[0130] 5) Next, using platinum tetraammine nitrate as a platinum precursor, platinum was loaded onto sample C2 using the impregnation method. 1 g of sample C2 was weighed and dispersed in 5 g of H2O and stirred continuously for 2 h. Then, 0.004 g of platinum tetraammine nitrate was dissolved in 10 mL of H2O to prepare solution E. Solution E was slowly added dropwise to a uniformly dispersed ultrathin HZSM-5 mixture under stirring at room temperature.

[0131] In the aforementioned synthetic platinum metal nanoclusters ultrathin HZSM-5 molecular sieve system:

[0132] C2, the mass ratio of elemental platinum is 1.0:0.002;

[0133] The mass ratio of sample C2 to tetraammineplatinum nitrate aqueous solution is 1:15.

[0134] 6) After continuous stirring at room temperature for 4 hours, the product was evaporated and dried, then calcined in a tube furnace with flowing air at 350℃ for 2 hours at a heating rate of 0.5℃ / min. Reduction was then carried out in a hydrogen atmosphere at 300℃ for 2 hours at a heating rate of 0.5℃ / min. Sample C3 was obtained.

[0135] The XRD pattern, SEM image, and TEM image of sample C3 are similar to those of sample A3 in Example 1, and respectively have the following characteristics: Figure 1 , Figure 2 and Figure 3 Features of [the text].

[0136] The silicon-to-aluminum ratio (SiO2:Al2O3) of sample C1 is 1.00:0.0042.

[0137] The mass fraction of platinum in sample C1 is approximately 0.2%.

[0138] Example 3

[0139] A method for preparing 2-methoxy-4-methylphenol, the specific steps of which are as follows:

[0140] Take 0.1 mmol of vanillin and add it to the molecular sieve sample A3 prepared in Example 1 at a molar ratio of vanillin to platinum in the catalyst of 500:1. Then add 3 mL of H2O, sonicate to disperse the system evenly, place it in an autoclave, replace the air in the autoclave with hydrogen three times, and catalyze the reaction for 120 min at 120 °C and 2.0 MPa H2. After extraction four times with 1 mL of dichloromethane, the sample is detected by GC.

[0141] The test results showed that the conversion rate of vanillin was approximately 100%, and the selectivity of 2-methoxy-4-methylphenol was approximately 96%.

[0142] Comparative Example 2

[0143] A method for preparing 2-methoxy-4-methylphenol, the specific steps of which are as follows:

[0144] Take 0.1 mmol of vanillin and add it to molecular sieve sample B3 prepared in Comparative Example 1 at a molar ratio of vanillin to platinum in the catalyst of 500:1. Then add 3 mL of H2O, sonicate to disperse the system evenly, place it in an autoclave, replace the air in the autoclave with hydrogen three times, and catalyze the reaction for 120 min under H2 conditions of 120℃ and 2.0 MPa. After extraction four times with 1 mL of dichloromethane, the sample is detected by GC.

[0145] The test results showed that the conversion rate of vanillin was approximately 63%, and the selectivity of 2-methoxy-4-methylphenol was approximately 77%.

[0146] It is evident that, compared to the HZSM-5 molecular sieve (sample B3) with a longer b-axis pore size in Comparative Example 1, the HZSM-5 molecular sieve (sample A3) with a longer b-axis pore size in Example 1 exhibits higher catalytic activity, especially in its ability to better catalyze the conversion of vanillin to 2-methoxy-4-methylphenol, resulting in higher conversion rate and selectivity.

[0147] The HZSM-5 molecular sieve provided in this invention has a particularly good effect on catalyzing the hydrogenation and deoxygenation of vanillin to produce 2-methoxy-4-methylphenol. Specifically, the platinum nanoparticles in the HZSM-5 molecular sieve have good hydrogenation activity, which is beneficial to the conversion of vanillin to vanillyl alcohol. The sheet-like HZSM-5 molecular sieve matrix can provide acidic centers to realize the dehydroxylation process. Furthermore, the short b-axis of the sheet-like HZSM-5 molecular sieve matrix can also prevent the intermediate product from reacting with its acidic sites, thereby enabling the high-selectivity of the product 2-methoxy-4-methylphenol. This achieves high activity and high selectivity in the hydrogenation and deoxygenation of vanillin to produce 2-methoxy-4-methylphenol, as well as the stability and sustainability of the catalytic system.

[0148] Furthermore, in the preparation method of HZSM-5 molecular sieve provided in the embodiments of the present invention, an ultrathin sheet-like HZSM-5 molecular sieve matrix is ​​first synthesized, and then platinum is loaded by impregnation method to obtain the required material in a simple and efficient manner. In addition, the b-axis pore length of the sheet-like HZSM-5 molecular sieve matrix can be precisely controlled mainly by adding urea and adjusting the amount of urea. This process is simple and easy to implement, and the obtained HZSM-5 molecular sieve has good catalytic activity and selectivity.

[0149] In summary, the sheet-like HZSM-5 molecular sieve matrix of this invention provides acidic centers, while platinum nanoparticles provide hydrogenation centers; the combination of these two components achieves excellent catalytic activity. Furthermore, the sheet-like HZSM-5 molecular sieve matrix has a relatively thin thickness, i.e., a shorter b-axis pore length, which not only facilitates mass diffusion and transport but also significantly reduces the likelihood of intermediate products contacting acidic sites and causing side reactions, thus providing higher product selectivity. The HZSM-5 molecular sieve of this invention exhibits particularly good hydrodeoxygenation effects, and especially shows promising application prospects in the catalytic hydrodeoxygenation of bio-oils.

Claims

1. Use of HZSM-5 molecular sieve in catalyzing hydrodeoxygenation of bio-oil, characterized in that, The HZSM-5 molecular sieve comprises a platy HZSM-5 molecular sieve substrate and platinum nanoparticles supported on the platy HZSM-5 molecular sieve substrate; the average thickness of the platy HZSM-5 molecular sieve substrate is 50-100 nm; the average diameter of the platinum nanoparticles is 8-15 nm; in the HZSM-5 molecular sieve, the silicon and aluminum are measured in terms of SiO2 and Al2O3 respectively, and the molar ratio of silicon to aluminum is 1: (0.001-0.02).

2. Use according to claim 1, characterized in that, The mass percentage of the platinum nanoparticles in the HZSM-5 molecular sieve is 0.1-1%.

3. Use according to claim 1, characterized in that, The HZSM-5 molecular sieve is prepared by a method comprising the following steps: mixing a silicon source, an aluminum source, sodium hydroxide, a template agent, urea, isopropyl alcohol and water, and sequentially performing a crystallization reaction, a first calcination, an ammonium exchange reaction and a second calcination to obtain a platy HZSM-5 molecular sieve substrate; mixing the platy HZSM-5 molecular sieve substrate with a platinum source and performing a third calcination to obtain the HZSM-5 molecular sieve.

4. Use according to claim 3, characterized in that, The silicon source is selected from tetraethoxysilane; and / or, the aluminum source is selected from aluminum nitrate nonahydrate; and / or, the template agent is selected from tetrapropylammonium hydroxide; and / or, the ammonium source used in the ammonium exchange reaction comprises ammonium chloride, ammonium nitrate or a combination thereof; and / or, the platinum source comprises at least one of tetraamine platinum nitrate, chloroplatinic acid, platinum tetrachloride or dichloroplatinous.

5. Use according to claim 3, characterized in that, The silicon source and the aluminum source are measured in terms of SiO2 and Al2O3 respectively, and the molar ratio of the silicon source to the aluminum source is 1: (0.001-0.02); and / or, the silicon source is measured in terms of SiO2, and the molar ratio of the silicon source to the sodium hydroxide is 1: (0.01-0.2); and / or, the silicon source is measured in terms of SiO2, and the molar ratio of the silicon source to the template agent is 1: (0.1-2); and / or, the silicon source is measured in terms of SiO2, and the molar ratio of the silicon source to the urea is 1: (0.3-2); and / or, the silicon source is measured in terms of SiO2, and the molar ratio of the silicon source to the isopropyl alcohol is 1: (0.01-0.2); and / or, the ammonium source used in the ammonium exchange reaction is measured in terms of ammonium, and the dosage ratio of the ammonium source to the product of the first calcination is (0.001-0.02) mol: 1 g; and / or, the platinum source is measured in terms of Pt, and the mass ratio of the platinum source to the platy HZSM-5 molecular sieve substrate is (0.0005-0.01):

1.

6. Use according to claim 3, characterized in that, The temperature of the crystallization reaction is 160-200℃; and / or, the time of the crystallization reaction is 24-72 h; and / or, the temperature rising rate of the crystallization reaction is 10-20℃ / h; and / or, the calcination temperature of the first calcination and the calcination temperature of the second calcination are each independently 500-600℃; and / or, the holding time of the first calcination and the holding time of the second calcination are each independently 2-8 h; and / or, the temperature rising rate of the first calcination and the temperature rising rate of the second calcination are each independently 80-120℃ / h; And / or, the reaction temperature of the ammonium exchange reaction is 60-100℃; And / or, the reaction time of the ammonium exchange reaction is 1-4h; And / or, the calcination temperature of the third calcination is 300-500℃; And / or, the holding time of the third calcination is 2-8h; And / or, the heating rate of the third calcination is 0.1-5℃ / min.

7. Use according to claim 3, characterized in that, The third calcination comprises a first stage calcination and a second stage calcination; the first stage calcination is carried out in an atmosphere containing oxygen gas; and the second stage calcination is carried out in an atmosphere of reducing gas.

8. Use according to claim 7, characterized in that, The calcination temperature of the first stage calcination is 30-70℃ higher than that of the second stage calcination; And / or, the ratio of the holding time of the first stage calcination to that of the second stage calcination is 1:(0.5-2).

9. A process for the preparation of 2-methoxy-4-methylphenol, characterized in that, The method comprises the following steps: Vanillin is used as a substrate to carry out a hydrodeoxygenation reaction by using HZSM-5 molecular sieve as a catalyst, so as to obtain 2-methoxy-4-methylphenol; the HZSM-5 molecular sieve comprises a flaky HZSM-5 molecular sieve substrate and platinum nanoparticles loaded on the flaky HZSM-5 molecular sieve substrate; the average thickness of the flaky HZSM-5 molecular sieve substrate is 50-100nm; the average diameter of the platinum nanoparticles is 8-15nm; in the HZSM-5 molecular sieve, the silicon and aluminum are measured in terms of SiO2 and Al2O3 respectively, and the molar ratio of silicon to aluminum is 1:(0.001-0.02).

10. The method of claim 9, wherein, The hydrodeoxygenation reaction is carried out in a hydrogen atmosphere; the partial pressure of the hydrogen is 1-3MPa; And / or, the reaction temperature of the hydrodeoxygenation reaction is 80-160℃; And / or, the reaction time of the hydrodeoxygenation reaction is 30-300min; And / or, the molar ratio of vanillin to platinum nanoparticles in the HZSM-5 molecular sieve is (400-1000):1; And / or, the hydrodeoxygenation reaction is carried out in water; and the mass ratio of vanillin to water is 1:(100-400).

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