Composite containing zsm-5 molecular sieve, method for preparing the same, and use thereof

Abstract

The present application relates to the technical field of molecular sieve synthesis and catalysis, and discloses a composite containing ZSM-5 molecular sieve and a preparation method and application thereof.The composite comprises hydrothermal carbon and ZSM-5 molecular sieve, the mass content of the ZSM-5 molecular sieve is 97-99.5% and the mass content of the hydrothermal carbon is 0.5-3% based on the mass of the composite; wherein, the composite has a peak position in the infrared spectrum at 1500-1600 cm ‑1 and 1700-1800 cm ‑1 . Under the hydrothermal conditions of high temperature and high pressure, the present application uses sucrose and other disaccharides as carbon sources which have lower cost and better thermal stability than glucose and are converted into hydrothermal carbon in situ, effectively modulates the acidity of ZSM-5 molecular sieve at a lower cost, and finally obtains the composite containing ZSM-5 molecular sieve which is applied to the n-pentane cracking reaction and has higher activity and higher olefin selectivity.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve synthesis technology and catalysis, specifically to a composite containing ZSM-5 molecular sieve, its preparation method, and its application. Background Technology

[0002] Zeolite molecular sieves are a class of materials with regular pore structures, widely used in adsorption separation, ion exchange, and catalysis. Among them, ZSM-5 molecular sieve is a high silica-to-alumina ratio, three-dimensional through-pore molecular sieve with a unique three-dimensional pore system that facilitates the diffusion of product molecules. Due to the limitation of the ten-membered ring pore size, it exhibits strong shape selectivity, making it less prone to the formation of multi-branched isomers and large molecular products. Furthermore, the pore interior is less prone to carbon deposition, which helps maintain catalytic activity. In addition, ZSM-5 molecular sieves also possess high thermal stability, large specific surface area, and controllable strength and number of acid centers. They have very wide applications in the petrochemical and coal chemical industries, such as alkylation, aromatization, isomerization, and cracking, some of which have already been industrialized. Therefore, ZSM-5 molecular sieves hold significant importance in the petrochemical industry.

[0003] Hydrothermal carbon is a semi-carbonized material produced from monosaccharides or polysaccharides under hydrothermal conditions at relatively low temperatures (170-300℃). Compared with other carbon-based materials, hydrothermal carbon is characterized by its wide availability of carbon sources, low cost, mild reaction conditions, and green reaction process. Hydrothermal carbon is a solid and can be used as a template agent during the crystallization process of molecular sieves to regulate the pore structure of the sieves. Furthermore, the surface of hydrothermal carbon typically has a large number of oxygen-containing functional groups (hydroxyl, phenolic hydroxyl, carbonyl, and carboxyl groups), which can regulate the acidity distribution and acidity content of the material.

[0004] Acidity is fundamental to many reactions catalyzed by ZSM-5 molecular sieves, and different reactions require different acid strength and distribution from the ZSM-5 molecular sieve. Adjusting the acidity (acid quantity, acid strength, acid type, and acid distribution) of ZSM-5 molecular sieves allows for more controllable acidic sites in the catalyst, which is one method for preparing higher-performance molecular sieve catalysts. In-situ synthesis is an effective method for adjusting the acidity of ZSM-5 molecular sieves, which can be controlled by changing the type of template agent, silicon source, aluminum source, etc. With the continuous development of the chemical industry and the deepening of green chemistry, the industry's requirements for the performance of molecular sieve catalysts are becoming increasingly stringent. Introducing a carbon source during the molecular sieve synthesis process is a method for modulating acidity, which can change the physicochemical properties of the catalyst. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of existing technologies being unable to perform acid regulation in a low-cost and efficient manner, and to provide a complex containing ZSM-5 molecular sieve, its preparation method and application. The complex containing ZSM-5 molecular sieve has high catalytic performance when applied to the n-pentane cracking reaction.

[0006] To achieve the above objectives, the first aspect of the present invention provides a composite containing ZSM-5 molecular sieve, the composite comprising hydrothermal carbon and ZSM-5 molecular sieve, wherein, based on the mass of the composite, the mass content of ZSM-5 molecular sieve is 97-99.5% and the mass content of hydrothermal carbon is 0.5-3%.

[0007] The infrared spectrum of the composite is in the range of 1500-1600 cm⁻¹. -1 and 1700-1800cm -1 There is a peak at that location.

[0008] The hydrothermal carbon is provided by disaccharides, preferably by at least one of lactose, sucrose and maltose.

[0009] The second aspect of the present invention provides a method for preparing a composite containing ZSM-5 molecular sieve, the method comprising: mixing ZSM-5 seed crystals, disaccharide, aluminum source, alkali source, silicon source and water, and then crystallizing.

[0010] Preferably, the amounts of ZSM-5 seed crystals, disaccharide, aluminum source, alkali source, silicon source and water are such that the ZSM-5 molecular sieve content in the composite containing ZSM-5 molecular sieve is 97-99.5% by mass and the hydrothermal carbon content is 0.5-3% by mass.

[0011] Hydrothermal carbon can be synthesized using monosaccharides, disaccharides, or polysaccharides as precursors. During their research, the inventors of this invention discovered that, in the preparation of complexes containing ZSM-5 molecular sieves, disaccharides, compared to monosaccharides, consist of two monosaccharide molecules linked by a glycosidic bond. Hydrothermal carbon synthesized using disaccharides exhibits higher stability and potentially more uniform properties when combined with the complex formed by ZSM-5 and the molecular sieve. Furthermore, compared to monosaccharides such as glucose and fructose, sucrose, as a disaccharide, offers advantages such as a wider availability of raw materials and lower price, resulting in a greater cost advantage.

[0012] A third aspect of the present invention provides a ZSM-5 molecular sieve-containing composite obtained by the method described in the second aspect above.

[0013] The fourth aspect of the present invention provides the application of the ZSM-5 molecular sieve-containing complex described in the first or third aspect above in the n-pentane pyrolysis reaction.

[0014] The beneficial effects obtained by the present invention through the above technical solution are as follows:

[0015] (1) The ZSM-5 molecular sieve-containing composite of the present invention contains a specific amount of ZSM-5 molecular sieve and hydrothermal carbon, and the infrared spectrum is in the range of 1500-1600 cm⁻¹. -1 and 1700-1800cm -1 The presence of peak positions and ordered carbon structures allows for effective regulation of the acidity of molecular sieves.

[0016] (2) Furthermore, in the composite provided by the present invention, the molecular sieve crystal size is 500-1200 nm, which is more conducive to improving its activity and olefin selectivity in the n-pentane cracking reaction.

[0017] (3) Furthermore, the ZSM-5 molecular sieve-containing composite of the present invention possesses abundant weak acidity and limited medium-strong acidity. Compared with conventional ZSM-5 molecular sieves, the introduction of hydrothermal carbon improves the hydrothermal stability of ZSM-5 molecular sieves, and the pore structure of the molecular sieve does not change significantly.

[0018] (4) In the synthesis of the ZSM-5 molecular sieve complex in this invention, under high temperature and high pressure hydrothermal conditions, disaccharides such as sucrose, which are cheaper than glucose and have better thermal stability, are used as carbon sources and converted in situ into hydrothermal carbon. The acidity of ZSM-5 molecular sieve is effectively modulated at a lower cost. The ZSM-5 molecular sieve complex is finally obtained and applied to the n-pentane cracking reaction, exhibiting high activity and high olefin selectivity. Attached Figure Description

[0019] Figure 1 This is the XRD pattern of the ZSM-5 molecular sieve-containing composite obtained in Example 1;

[0020] Figure 2 The image shows the infrared spectrum of the ZSM-5 molecular sieve-containing complex obtained in Example 1.

[0021] Figure 3 The image shows the XRD pattern of the ZSM-5 molecular sieve-containing complex prepared in Comparative Example 1.

[0022] Figure 4 This is the XRD pattern of the ZSM-5 molecular sieve-containing complex prepared in Comparative Example 2. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The first aspect of the present invention provides a composite containing ZSM-5 molecular sieve, the composite comprising hydrothermal carbon and ZSM-5 molecular sieve, wherein, based on the mass of the composite, the mass content of ZSM-5 molecular sieve is 97-99.5% and the mass content of hydrothermal carbon is 0.5-3%.

[0025] The infrared spectrum of the composite is in the range of 1500-1600 cm⁻¹. -1 and 1700-1800cm -1 There is a peak at that location.

[0026] In this invention, the addition of hydrothermal carbon is beneficial to improving the hydrothermal stability of ZSM-5 molecular sieve, and the pore structure of the molecular sieve does not change significantly. The final composite containing ZSM-5 molecular sieve is applied to the n-pentane cracking reaction and has high activity and selectivity.

[0027] In this invention, the infrared spectrum of the complex is in the range of 1500-1600 cm⁻¹. -1 and 1700-1800cm -1 The presence of peaks at these locations, namely the C=C stretching vibration peak and the C=O stretching vibration peak, are characteristic peaks of hydrothermal carbon, indicating that the disaccharide molecule successfully crystallized during the crystallization process and transformed into structurally ordered hydrothermal carbon.

[0028] When the infrared spectrum of the complex is in the range of 3400-3500 cm⁻¹ -1 When the peak position is present, the complex exhibits high activity and high olefin selectivity in the n-pentane cracking reaction.

[0029] According to the present invention, preferably, the infrared spectrum of the composite is in the range of 3400-3500 cm⁻¹. -1 There are also peak positions at certain locations.

[0030] In this invention, the infrared spectrum of the composite is in the range of 3400-3500 cm⁻¹. -1 The peak at that location is the -OH stretching vibration peak.

[0031] In this invention, the specific operation of the infrared spectroscopy (IR) method for determining the complex includes: using a Nicolet 5700 instrument, with a test wavelength range of 400-4000 cm⁻¹. -1 The sample was ground to a fineness below 200 mesh. 10 mg of the sample was mixed with an appropriate amount of potassium bromide and ground into a tablet. The tablet was then measured using an instrument.

[0032] According to the present invention, preferably, the hydrothermal carbon is provided by a disaccharide, more preferably by at least one of lactose, sucrose, and maltose. Using the aforementioned preferred disaccharide is beneficial for improving the relative crystallinity of the ZSM-5 zeolite-containing complex and reducing preparation costs. The resulting ZSM-5 zeolite-containing complex exhibits high activity and olefin selectivity when applied in the n-pentane cracking reaction.

[0033] According to the present invention, preferably, the ZSM-5 molecular sieve in the composite has a crystal size of 500-1200 nm, more preferably 500-1000 nm. The ZSM-5 molecular sieve-containing composite prepared using the aforementioned preferred crystal size range exhibits high activity and olefin selectivity when applied to the n-pentane cracking reaction.

[0034] In this invention, the crystal size of the ZSM-5 molecular sieve in the composite was determined by electron microscopy.

[0035] According to the present invention, preferably, based on the mass of the composite, the mass content of ZSM-5 molecular sieve is 98-99%, and the mass content of hydrothermal carbon is 1-2%.

[0036] In this invention, the term "hydrothermal carbon" has the conventional meaning in the art. The mass content of ZSM-5 molecular sieve and the mass content of hydrothermal carbon in the composite are obtained by a programmed temperature-increasing oxidation method. Specifically, a certain mass of dried sample is placed in an air atmosphere and heated to 550°C at a rate of 5°C / min; the weight loss is the mass content of hydrothermal carbon.

[0037] In this invention, by using the ZSM-5 molecular sieve and hydrothermal carbon within the above-mentioned preferred range of mass content, the final ZSM-5 molecular sieve-containing composite can be applied to the n-pentane cracking reaction, exhibiting high activity and olefin selectivity.

[0038] According to the present invention, preferably, the molar ratio of SiO2 / Al2O3 in the composite is 80-200, more preferably 99-180.

[0039] In this invention, when the molar ratio of SiO2 / Al2O3 in the composite meets the above-mentioned range, the final composite containing ZSM-5 molecular sieve is applied to the n-pentane cracking reaction and has high activity and olefin selectivity.

[0040] In this invention, the SiO2 / Al2O3 molar ratio is determined by atomic absorption spectrometry (ICP). Specifically, 100 mg of finely ground sample is weighed into a crucible, 1 gram of sodium hydroxide is added, and the mixture is melted at 750°C for 15 minutes. After the melt cools, hydrochloric acid is added for neutralization, and the solution is then transferred to a 100 mL volumetric flask and diluted 10 times. The SiO2 / Al2O3 molar ratio of the molecular sieve or composite is calculated by measuring the SiO2 / Al2O3 ratio using an ICP spectrometer and comparing the results with those of a blank solution.

[0041] According to the present invention, preferably, the XRD pattern of the composite exhibits a characteristic peak at 2θ = 26.6° ± 0.2°. This characteristic peak at 2θ = 26.6° ± 0.2° is attributed to sp. 2 The characteristic peaks of carbon indicate that the disaccharide also underwent a transformation during the hydrothermal process, generating carbon with an ordered structure.

[0042] According to the present invention, preferably, the specific surface area of ​​the composite is 40-350 m². 2 / g, further preferably 150-350m 2 / g.

[0043] According to the present invention, preferably, the total pore volume of the composite is 0.29-0.35 cm³. 3 / g.

[0044] In this invention, when the specific surface area and total pore volume of the complex meet the above-mentioned range, it is beneficial to improve the selectivity in the n-pentane cracking reaction.

[0045] In this invention, the specific surface area and pore structure of the composite were determined using a nitrogen adsorption-desorption isotherm. Specifically, a Micromeritics ASAP 2020 instrument was used, and the test temperature was -196°C. Before nitrogen physical adsorption, the sample was degassed at 330°C and 1.33 Pa for 4 hours. The total specific surface area was calculated using the BET (Brunauer-Emmett-Teller) formula.

[0046] According to the present invention, preferably, in the complex, the amount of weak acid accounts for 55-65% of the total acid amount, and the amount of moderately strong acid accounts for 12-22% of the total acid amount.

[0047] More preferably, the amount of weak acid accounts for 58-63% of the total acid amount, and the amount of moderately strong acid accounts for 15-20% of the total acid amount.

[0048] In this invention, when the acid content of the weak acid and the acid content of the medium-strong acid in the complex meet the above-mentioned range, it is beneficial to improve the activity of the n-pentane cracking reaction and reduce the generation of side reactions during the reaction process.

[0049] In this invention, acid strength is determined using an ammonia-programmed temperature desorption (NH3-TPD) analysis method. The specific procedure is as follows: the sample is pressed into a pellet, crushed, and sieved. 20-40 mesh particles are dried for later use to obtain the sample to be tested. During the experiment, 150 mg of the dried sample is accurately weighed and placed in a quartz tube. The sample bed is supported by a quartz sand bed and covered by another quartz sand bed, ensuring the sample bed is positioned at the thermocouple location. The sample is activated at 550°C for 2 hours under a helium atmosphere, then cooled to room temperature to adsorb 10% ammonia for 30 minutes. The temperature is then raised to a constant 100°C until the baseline stabilizes. Finally, the temperature is increased to 650°C at a rate of 10°C / min, and the ammonia desorption signal is collected. The total acid content is obtained by integrating the NH3-TPD peak area. The contents of weak acid, moderately strong acid and strong acid were calculated by dividing NH3-TPD into peaks and then calculating the percentage of peak area. The peak position of weak acid was around 200℃, that of moderately strong acid was around 330℃, and that of strong acid was around 410℃.

[0050] According to the present invention, preferably, the relative crystallinity of the composite is 85%-110%, more preferably 85%-100%.

[0051] In this invention, the relative crystallinity is obtained by comparing the peak area of ​​the sample at 22.5°–25° with the standard peak area of ​​Acros's ZSM-5 product. The calculation formula is as follows:

[0052] R = A P / A R

[0053] Where R is the relative crystallinity, and A P A represents the peak area of ​​the sample at 22.5°–25°. R This represents the peak area of ​​the standard sample in the range of 22.5°–25°.

[0054] The second aspect of the present invention provides a method for preparing a complex containing ZSM-5 molecular sieve as described in the first aspect above, the method comprising: mixing ZSM-5 seed crystals, disaccharide, aluminum source, alkali source, silicon source and water, and then crystallizing.

[0055] According to the present invention, preferably, the amounts of ZSM-5 seed crystals, disaccharide, aluminum source, alkali source, silicon source and water are such that the mass content of ZSM-5 molecular sieve in the composite containing ZSM-5 molecular sieve is 97-99.5% and the mass content of hydrothermal carbon is 0.5-3%.

[0056] In this invention, there is no particular limitation on the source of the ZSM-5 seed crystal; it can be obtained commercially or prepared using existing methods. Preferably, the ZSM-5 seed crystal is obtained by mixing a first silicon source, a structure directing agent, and water, followed by heat treatment.

[0057] In this invention, preferably, the first silicon source is tetraethyl orthosilicate and / or tetramethyl orthosilicate, more preferably tetraethyl orthosilicate.

[0058] In this invention, preferably, the structure directing agent is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide, and more preferably tetrapropylammonium hydroxide and / or tetrabutylammonium hydroxide.

[0059] In this invention, preferably, the mass ratio of the structure-directing agent to water is 1-11:1.

[0060] In this invention, preferably, the mass ratio of the first silicon source (SiO2) to water is 0.2-2.5, more preferably 0.2-2.2.

[0061] In this invention, there is no particular limitation on the mixing temperature, but it is preferably 20-50°C.

[0062] In this invention, the mixing is carried out under stirring, and the mixing time is adjusted according to the actual conditions. Preferably, the mixing time is 6-12 hours.

[0063] In this invention, there is no particular limitation on the temperature of the heat treatment, but it is preferably 70-80°C.

[0064] In this invention, the heat treatment can be carried out under stirring, and the heat treatment time can be adjusted according to the actual conditions. Preferably, the heat treatment time is 48-72 hours.

[0065] In this invention, the disaccharide in the second aspect has the same selection range as that in the first aspect. Preferably, the disaccharide is selected from at least one of lactose, sucrose, and maltose.

[0066] According to the present invention, preferably, the mass ratio of the disaccharide to water is 0.002-0.03, more preferably 0.004-0.02.

[0067] The silicon source, aluminum source, and alkali source described in this invention can be conventional choices in the field, and this invention does not have any particular limitations on them.

[0068] According to the present invention, preferably, the aluminum source is aluminum sulfate and / or aluminum nitrate, and more preferably aluminum sulfate.

[0069] According to the present invention, preferably, the alkali source is sodium hydroxide.

[0070] According to the present invention, preferably, the silicon source is silica sol and / or silica.

[0071] According to the present invention, preferably, the mass ratio of the ZSM-5 seed crystal to water is 0.01-1, and more preferably 0.05-0.8.

[0072] In this invention, when the mass ratio of seed crystals to water meets the above-mentioned range, it is beneficial to improve the crystallinity of the composite containing ZSM-5 molecular sieve and improve the grain size of ZSM-5 molecular sieve.

[0073] According to the present invention, preferably, the mass ratio of the aluminum source to water is 0.002-0.02, more preferably 0.002-0.01.

[0074] According to the present invention, preferably, the mass ratio of the alkali source to water is 0.06-1.5, more preferably 0.06-0.6.

[0075] According to the present invention, preferably, the mass ratio of silicon source to water is 0.05-2, more preferably 0.05-1.2.

[0076] In this invention, the silicon source is calculated as SiO2 and the aluminum source is calculated as Al2O3.

[0077] According to the present invention, preferably, the molar ratio of the silicon source and the aluminum source is 50-150, wherein the silicon source is calculated as SiO2 and the aluminum source is calculated as Al2O3.

[0078] In this invention, there is no particular limitation on the crystallization temperature. Preferably, the crystallization temperature is 160-200℃, and more preferably 175-200℃. The crystallization time can be adjusted according to actual conditions, preferably 12-36 hours, and more preferably 16-28 hours.

[0079] According to the present invention, preferably, the method further includes a pre-crystallization step performed before crystallization, wherein the pre-crystallization conditions include: a temperature of 100-120°C and a time of 8-24 hours. This preferred embodiment is more advantageous for modulating the crystallite size of the ZSM-5 molecular sieve in the composite, resulting in a composite with higher activity and higher olefin selectivity when applied to the n-pentane cracking reaction.

[0080] In this invention, preferably, after crystallization is complete, the crystallization product is further subjected to steps such as centrifugation and washing, which are conventional operating procedures in the art. In a preferred embodiment of this invention, the centrifuged product is washed with deionized water until neutral.

[0081] Preferably, this invention further includes drying the washed crystallized product.

[0082] In this invention, there is no particular limitation on the drying temperature, but the preferred drying temperature is 120℃-150℃; the drying time is adjusted accordingly based on actual conditions, and is preferably 5-24h.

[0083] In this invention, the drying is carried out in conventional equipment in the art, such as an oven.

[0084] According to the present invention, preferably, the method further includes an ammonium exchange step performed after crystallization. The ammonium exchange can be performed using conventional techniques in the art, and includes contacting an ammonium salt solution with the solid product obtained after crystallization under ammonium exchange conditions.

[0085] According to the present invention, preferably, the ammonium salt is selected from ammonium nitrate and / or ammonium sulfate.

[0086] In a preferred embodiment of the present invention, the solvent of the ammonium salt solution is water.

[0087] The present invention does not particularly limit the range of concentrations of the ammonium salt solution, and can use conventional choices in the art.

[0088] In this invention, there is no particular limitation on the exchange temperature of the ammonium exchange conditions, but the preferred exchange temperature is 60-80℃; the exchange time is adjusted accordingly according to the actual conditions, and the preferred exchange time is 3-48h.

[0089] According to the present invention, preferably, the number of ammonium exchanges is 1-4 times.

[0090] In this invention, after ammonium exchange is completed, conventional operations in the art, such as centrifugation and washing, can be performed. In a preferred embodiment of this invention, the centrifuged product is washed with deionized water until the pH is neutral.

[0091] The present invention also includes drying the washed product.

[0092] In this invention, there is no particular limitation on the drying temperature, but the preferred drying temperature is 120℃-150℃; the drying time is adjusted accordingly based on actual conditions, and is preferably 6-24h.

[0093] A third aspect of the present invention provides a composite containing ZSM-5 molecular sieve prepared by the method described in the second aspect above.

[0094] The fourth aspect of the present invention provides the application of the ZSM-5 molecular sieve-containing complex described in the first or third aspect above in the n-pentane pyrolysis reaction.

[0095] In this invention, the ZSM-5 molecular sieve-containing complex can be used as a catalyst in the n-pentane cracking reaction, exhibiting excellent effects of high activity and high olefin selectivity.

[0096] This invention does not impose any particular limitation on the morphology of the ZSM-5 molecular sieve-containing composite during use, and can be adapted to the actual application scenario. Preferably, before application, the composite containing ZSM-5 molecular sieve is further shaped into a molded catalyst. The molding method includes, but is not limited to, extrusion molding. The catalyst can be a column with a length of 3-10 mm, and the cross-section of the column can be one or more of the following: circular, square, cloverleaf, and star-shaped, with a radial dimension of 0.8-3 mm.

[0097] In this invention, the conditions for the n-pentane cracking reaction can be conventionally selected in the art. Preferably, the conditions for the n-pentane cracking reaction include: a reaction temperature of 450-650℃, a reaction pressure of 0-0.2 MPa, and a n-pentane mass hourly space velocity of 5-25 h⁻¹. -1 .

[0098] The present invention will be described in detail below through examples. Unless otherwise specified, all reagents used in the following examples are commercially available.

[0099] In this invention, the specific operation methods of the relative crystallinity calculation method, X-ray diffraction method, infrared spectroscopy (IR) method, and atomic absorption spectroscopy (ICP) are as described above, and will not be repeated here.

[0100] The characterization methods for specific surface area, pore structure, and acid strength have been described above and will not be repeated here.

[0101] Example 1

[0102] (1) Weigh 27.79g of tetraethyl orthosilicate, 43.89g of tetrapropylammonium hydroxide and 20g of water, mix them and stir at 25℃ for 12h to obtain a mixed solution. Stir the mixed solution at 70℃ for 72h to obtain ZSM-5 seed crystals.

[0103] (2) Weigh 0.33g aluminum sulfate, 0.204g sucrose, 6.86g sodium hydroxide, 42g water, 12g silica sol (SiO2 mass content 45%) and 4g seed crystals, mix them, and stir at 25℃ for 1.5h to obtain a gel. Place the gel in a reaction vessel, pre-crystallize at 100℃ for 12h, then crystallize at 185℃ for 16h, then cool to room temperature, centrifuge and wash until neutral, and dry at 150℃ for 6h.

[0104] (3) Take 5g of the dried sample from step (2) and place it in 30g of 10wt% ammonium nitrate solution for ammonium exchange at 80℃ for 4h. Then cool it to room temperature, centrifuge it, wash it with deionized water until neutral, and dry it at 150℃ for 6h to obtain DZSM5-1.

[0105] Its properties are shown in Table 1, and its XRD pattern is shown in Table 1. Figure 1Infrared spectrum (see) Figure 2 .Depend on Figure 1 It can be seen that the standard XRD patterns of DZSM5-1 and ZSM-5 are consistent in peak position and intensity, and also show sp. 2 The characteristic peak of carbon (2θ = 26.6°) indicates that sucrose also underwent a transformation during the hydrothermal process, generating ordered carbon structures; from Figure 2 It can be known that 1550cm -1 1750cm -1 Two peaks appeared nearby, attributed to the C=C stretching vibration and the C=O stretching vibration, respectively, confirming the successful preparation of hydrothermal carbon from sucrose. 3450 cm⁻¹ -1 The appearance of a broad peak, attributed to the -OH vibration peak, indicates that the carbon in DZSM5-1 contains hydroxyl groups.

[0106] Example 2

[0107] (1) Weigh 27.79g of tetraethyl orthosilicate, 43.89g of tetrapropylammonium hydroxide and 4g of water, mix them, and stir at 25℃ for 12h to obtain a mixed solution. Stir the mixed solution at 70℃ for 72h to obtain ZSM-5 seed crystals.

[0108] (2) Weigh 0.25g aluminum sulfate, 0.140g lactose, 6.82g sodium hydroxide, 36g water, 5.4g silica and 4g seed crystals and mix them. Stir at 25℃ for 1.5h to obtain a gel. Place the gel in a reaction vessel and pre-crystallize at 110℃ for 10h, then crystallize at 175℃ for 18h. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150℃ for 6h.

[0109] (3) Take 5g of the dried sample from step (2) and place it in 30g of 10wt% ammonium nitrate solution for ammonium exchange at 80℃ for 4h. Then cool it to room temperature, centrifuge and wash it until neutral, and dry it at 150℃ for 6h to obtain DZSM5-2.

[0110] Example 3

[0111] (1) Weigh 13.90g of tetraethyl orthosilicate, 21.95g of tetrapropylammonium hydroxide and 20g of water, mix them and stir at 25℃ for 12h to obtain a mixed solution. Stir the mixed solution at 70℃ for 72h to obtain ZSM-5 seed crystals.

[0112] (2) Weigh 0.26g aluminum nitrate, 0.240g maltose, 6.86g sodium hydroxide, 12g water, 12g silica sol (SiO2 mass content 45%) and 16g seed crystals, mix them, and stir at 25℃ for 1.5h to obtain a gel. Place the gel in a reaction vessel, pre-crystallize at 100℃ for 16h, then crystallize at 185℃ for 16h, then cool to room temperature, centrifuge and wash until neutral, and dry at 150℃ for 6h.

[0113] (3) Take 5g of the dried sample from step (2) and place it in 30g of 10wt% ammonium nitrate solution for ammonium exchange at 80℃ for 4h. Then cool it to room temperature, centrifuge and wash it until neutral, and dry it at 150℃ for 6h to obtain DZSM5-3.

[0114] Example 4

[0115] (1) Weigh 27.79g of tetraethyl orthosilicate, 43.89g of tetrapropylammonium hydroxide and 20g of water, mix them and stir at 25℃ for 12h to obtain a mixed solution. Stir the mixed solution at 70℃ for 72h to obtain ZSM-5 seed crystals.

[0116] (2) Weigh 0.33g aluminum sulfate, 0.204g sucrose, 6.86g sodium hydroxide, 42g water, 12g silica sol (SiO2 mass content 45%) and 4g seed crystals, mix them, and stir at 25℃ for 1.5h to obtain a gel. Place the gel in a reaction vessel and crystallize at 195℃ for 12h, then cool to room temperature, centrifuge and wash until neutral, and dry at 150℃ for 6h.

[0117] (3) Take 5g of the dried sample from step (2) and place it in 30g of 10wt% ammonium nitrate solution for ammonium exchange at 80℃ for 4h. Then cool it to room temperature, centrifuge and wash it until neutral, and dry it at 150℃ for 6h to obtain DZSM5-4.

[0118] Example 5

[0119] (1) Weigh 27.79g of tetraethyl orthosilicate, 43.89g of tetrapropylammonium hydroxide and 20g of water, mix them and stir at 25℃ for 12h to obtain a mixed solution. Stir the mixed solution at 70℃ for 72h to obtain ZSM-5 seed crystals.

[0120] (2) Weigh 0.33g aluminum sulfate, 0.338g sucrose, 6.86g sodium hydroxide, 42g water, 12g silica sol (SiO2 mass content 45%) and 4g seed crystals, mix them, and stir at 25℃ for 1.5h to obtain a gel. Place the gel in a reaction vessel, pre-crystallize at 100℃ for 12h, then crystallize at 185℃ for 16h, then cool to room temperature, centrifuge and wash until neutral, and dry at 150℃ for 6h.

[0121] (3) Take 5g of the dried sample from step (2) and place it in 30g of 10wt% ammonium nitrate solution for ammonium exchange at 80℃ for 4h. Then cool it to room temperature, centrifuge and wash it until neutral, and dry it at 150℃ for 6h to obtain DZSM5-5.

[0122] Comparative Example 1

[0123] (1) Weigh 20.84g of tetraethyl orthosilicate, 29.17g of tetrapropylammonium hydroxide and 15g of water, mix them and stir at 25℃ for 12h to obtain mixture A. Stir mixture A at 70℃ for 72h to obtain seed crystals.

[0124] (2) Weigh 0.33g aluminum sulfate, 6.86g sodium hydroxide, 42g water, 12g silica sol (SiO2 mass content 45%) and 4g seed crystals, mix them, and stir at 25℃ for 1.5h to obtain a gel. Place the gel in a reaction vessel and crystallize at 185℃ for 24h, then cool to room temperature, centrifuge and wash until neutral, and dry at 150℃ for 6h.

[0125] (3) Take 5g of the dried sample from step (2) and place it in 30g of 10wt% ammonium nitrate solution for ammonium exchange at 80℃ for 4h. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150℃ for 6h to obtain product DZSM5-C1. Its properties are shown in Table 1, and its XRD pattern is shown in Table 2. Figure 3 .Depend on Figure 3 As can be seen, the sample obtained in Comparative Example 1 is consistent with the ZSM-5 standard XRD pattern in terms of peak position and intensity, and no peaks of other crystal structures appear.

[0126] Comparative Example 2

[0127] (1) Weigh 27.79g of tetraethyl orthosilicate, 43.89g of tetrapropylammonium hydroxide and 20g of water, mix them and stir at 25℃ for 12h to obtain a mixed solution. Stir the mixed solution at 70℃ for 72h to obtain seed crystals.

[0128] (2) Weigh 0.33g aluminum sulfate, 0.193g glucose, 6.86g sodium hydroxide, 42g water, 12g silica sol (SiO2 mass content 45%) and 4g seed crystals, mix them, and stir at 25℃ for 1.5h to obtain a gel. Place the gel in a reaction vessel and crystallize at 185℃ for 24h, then cool to room temperature, centrifuge and wash until neutral, and dry at 150℃ for 6h.

[0129] (3) Take 5g of sample and place it in 30g of 10wt% ammonium nitrate solution for ammonium exchange at 80℃ for 4h. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150℃ for 6h to obtain product DZSM5-C2. Its properties are shown in Table 1, and its XRD pattern is shown in Table 2. Figure 4 .Depend on Figure 4It can be seen that DZSM5-C2 also has a characteristic peak at 26.6°. Infrared characterization of DZSM5-C2 shows that it has a characteristic peak at 1750 cm⁻¹. -1 and 3440cm -1 There is a peak nearby, similar to that in Example 1, but at 1500-1600 cm⁻¹. -1 No very obvious absorption peaks were observed.

[0130] Table 1

[0131]

[0132] Test case

[0133] Catalyst evaluation was performed on a fixed-bed pulsed microdevice. Specifically, 25 mg of each catalyst prepared in the examples and comparative examples were weighed and loaded into quartz glass tubes specifically designed for the fixed-bed pulsed microdevice. The catalysts were lined with a layer of quartz wool both above and below for support and coverage, respectively. The reactants were quantitatively aspirated using a microsyringe and injected into the reaction tube through the injection port. The products were analyzed using gas chromatography. The reaction temperature was 500°C, the reactant was liquid n-pentane, and the injection volume was 1 μL. An Agilent 7890B chromatograph was used, and a flame ionization detector was employed. The reaction results for each catalyst are shown in Table 2.

[0134] Table 2

[0135]

[0136] As shown in Table 2, compared to Comparative Example 1 without the introduction of hydrothermal carbon, Example 1 showed improved n-pentane conversion and selectivity for ethylene and propylene. Comparative Example 2 shows that when the carbon source was replaced with glucose, although the conversion rate of Example 1 was lower than that of Comparative Example 2, its diene selectivity was greater, resulting in a higher diene yield.

[0137] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite containing ZSM-5 molecular sieve, characterized in that, The composite comprises hydrothermal carbon and ZSM-5 molecular sieve, wherein the mass content of ZSM-5 molecular sieve is 97-99.5% and the mass content of hydrothermal carbon is 0.5-3% based on the mass of the composite. The infrared spectrum of the composite is in the range of 1500-1600 cm⁻¹. -1 and 1700-1800cm -1 There is a peak at that location.

2. The complex according to claim 1, wherein, The infrared spectrum of the complex is in the range of 3400-3500 cm⁻¹. -1 There are also peaks at this location; Preferably, the hydrothermal carbon is provided by a disaccharide, and more preferably by at least one of lactose, sucrose, and maltose.

3. The complex according to claim 1 or 2, wherein, The ZSM-5 molecular sieve in the composite has a crystal size of 500-1200 nm, preferably 500-1000 nm.

4. The complex according to any one of claims 1-3, wherein, Based on the mass of the composite, the mass content of ZSM-5 molecular sieve is 98-99%, and the mass content of hydrothermal carbon is 1-2%. Preferably, the molar ratio of SiO2 / Al2O3 in the composite is 80-200, more preferably 99-180.

5. The complex according to any one of claims 1-4, wherein, The specific surface area of ​​the composite is 40-350 m². 2 / g, total pore volume is 0.29-0.35cm³ 3 / g; And / or, in the complex, the amount of weak acid accounts for 55-65% of the total acid amount, and the amount of moderately strong acid accounts for 12-22% of the total acid amount; preferably, the amount of weak acid accounts for 58-63% of the total acid amount, and the amount of moderately strong acid accounts for 15-20% of the total acid amount.

6. A method for preparing a composite containing ZSM-5 molecular sieve, characterized in that, The method includes: mixing ZSM-5 seed crystals, disaccharide, aluminum source, alkali source, silicon source and water, and then crystallizing them; Preferably, the amounts of ZSM-5 seed crystals, disaccharide, aluminum source, alkali source, silicon source and water are such that the ZSM-5 molecular sieve content in the composite containing ZSM-5 molecular sieve is 97-99.5% by mass and the hydrothermal carbon content is 0.5-3% by mass.

7. The method according to claim 6, wherein, The disaccharide is selected from at least one of lactose, sucrose, and maltose; Preferably, the mass ratio of the disaccharide to water is 0.002-0.03, more preferably 0.004-0.

02.

8. The method according to claim 6 or 7, wherein, The aluminum source is aluminum sulfate and / or aluminum nitrate, preferably aluminum sulfate; And / or, the alkali source is sodium hydroxide; And / or, the silicon source is silica sol and / or silica.

9. The method according to any one of claims 6-8, wherein, The mass ratio of ZSM-5 seed crystals to water is 0.01-1; And / or, the mass ratios of aluminum source, alkali source, silicon source and water are 0.002-0.02, 0.06-1.5 and 0.05-2, respectively, wherein the silicon source is calculated as SiO2 and the aluminum source is calculated as Al2O3; And / or, the molar ratio of silicon source to aluminum source is 50-150, wherein the silicon source is calculated as SiO2 and the aluminum source is calculated as Al2O3.

10. The method according to any one of claims 6-9, wherein, The crystallization conditions include: a crystallization temperature of 160-200℃ and a crystallization time of 12-36h. Preferably, the method further includes a pre-crystallization step performed before crystallization, wherein the pre-crystallization conditions include a temperature of 100-120°C and a time of 8-24 hours.

11. The method according to any one of claims 6-10, wherein, The method further includes an ammonium exchange step performed after crystallization, wherein the ammonium exchange comprises contacting an ammonium salt solution with the solid product obtained after crystallization under ammonium exchange conditions; Preferably, the ammonium salt is selected from ammonium nitrate and / or ammonium sulfate; Preferably, the ammonium exchange conditions include: an exchange temperature of 60-80℃, an exchange time of 3-48h, and 1-4 ammonium exchange cycles.

12. The ZSM-5 molecular sieve-containing complex prepared by the method according to any one of claims 6-11.

13. The use of the ZSM-5 molecular sieve-containing complex according to any one of claims 1-5 and 12 in the n-pentane cracking reaction.

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