Hydrothermal carbon / ZSM-5 molecular sieve composite and synthesis method and application thereof

Abstract

The application discloses a hydrothermal carbon / ZSM-5 molecular sieve composite and a synthesis method and application thereof. The hydrothermal carbon / ZSM-5 molecular sieve composite comprises hydrothermal carbon and ZSM-5 molecular sieve, wherein the hydrothermal carbon is obtained by in-situ conversion of a small-molecule carbon source under hydrothermal conditions, is SP2O with 2theta=26.6°, and has a mass content of 0.5% to 5% in the composite. 2 The hydrothermal carbon / ZSM-5 molecular sieve composite has high activity and low deactivation rate when used as a catalyst in an isopropyl benzene cracking reaction.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve synthesis technology and catalysis, specifically relating to a hydrothermal carbon / ZSM-5 molecular sieve complex and its synthesis method, as well as the application of the complex in the cumene cracking reaction. Background Technology

[0002] ZSM-5 molecular sieve is a high silica-to-alumina ratio, three-dimensional through-channel molecular sieve. Its unique three-dimensional channel system is highly favorable for the diffusion of product molecules, and due to the limitation of the ten-membered ring channel size, it exhibits strong shape selectivity, making it less prone to the formation of multi-branched isomers and large molecular products. Furthermore, it is less prone to carbon deposition within the channels, which helps maintain catalytic activity. In addition, ZSM-5 molecular sieve also possesses high thermal stability, a large specific surface area, and adjustable strength and number of acidic centers. ZSM-5 molecular sieve has a wide range of applications in the petrochemical and coal chemical industries, with potential applications in alkylation, aromatization, isomerization, and cracking, some of which have already been industrialized. Therefore, ZSM-5 molecular sieve holds significant importance in the petrochemical industry.

[0003] Acidity is fundamental to many reactions catalyzed by ZSM-5 molecular sieves. Different reactions require different acid strength and distribution from ZSM-5 molecular sieves. Modulating 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, making it 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 increasing emphasis on green chemistry, the industry's requirements for the performance of molecular sieve catalysts are becoming increasingly stringent. Therefore, it is necessary to continuously explore more effective and economical acidity modulation methods to prepare molecular sieve catalysts with superior catalytic performance. Summary of the Invention

[0004] The purpose of this invention is to provide a hydrothermal carbon / ZSM-5 molecular sieve composite, its synthesis method, and its application. This hydrothermal carbon / ZSM-5 molecular sieve composite exhibits high activity and low deactivation rate when applied in the cumene cracking reaction.

[0005] The first aspect of the present invention provides a hydrothermal carbon / ZSM-5 molecular sieve composite (C / ZSM-5), comprising: hydrothermal carbon and ZSM-5 molecular sieve, wherein, based on the mass of the composite, the mass of ZSM-5 molecular sieve is 95% to 99.5%, preferably 97.5% to 99.0%, and the hydrothermal carbon content is 0.5% to 5.0%, preferably 1.0% to 2.5%.

[0006] In the above technical solution, the hydrothermal carbon is obtained by in-situ conversion of a small molecule carbon source under hydrothermal conditions. The hydrothermal carbon is SP with a 2θ = 26.6°. 2 carbon.

[0007] In the above technical solution, the SiO2 / Al2O3 molar ratio measured by atomic absorption spectrometry (ICP) in the hydrothermal carbon / ZSM-5 molecular sieve composite is 80-200, preferably 99-180.

[0008] In the above technical solution, the amount of weak acid in the hydrothermal carbon / ZSM-5 molecular sieve composite is 50% to 60% of the total acid amount, and the amount of medium-strong acid is 15% to 25% of the total acid amount. Preferably, the amount of weak acid is 53% to 58% of the total acid amount, and the amount of medium-strong acid is 15% to 20% of the total acid amount.

[0009] In the above technical solution, the specific surface area of ​​the hydrothermal carbon / ZSM-5 molecular sieve composite is 250-500 m². 2 / g, preferably 280-350m 2 / g.

[0010] In the above technical solution, the relative crystallinity of the hydrothermal carbon / ZSM-5 molecular sieve composite is 80% to 110%, preferably 85% to 100%.

[0011] A second aspect of this invention provides a method for synthesizing a hydrothermal carbon / ZSM-5 molecular sieve composite, comprising:

[0012] (1) Mix the first silicon source, the structure guiding agent and water, and heat treat them to obtain seed crystals;

[0013] (2) Mix the seed crystals, small molecule carbon source, aluminum source, alkali source, second silicon source and water obtained in step (1), crystallize and dry to obtain the material;

[0014] (3) The material obtained in step (2) is subjected to ammonium exchange to obtain hydrothermal carbon / ZSM-5 molecular sieve composite.

[0015] In the above technical solution, in step (1), the first silicon source is at least one of tetraethyl orthosilicate or tetramethyl orthosilicate, preferably tetraethyl orthosilicate; in step (2), the second silicon source is at least one of silica sol or silica, preferably silica sol.

[0016] In the above technical solution, in step (2), the small molecule carbon source is at least one of glucose and fructose.

[0017] In the above technical solution, the mass ratio of the first silicon source (SiO2) to water is 0.2 to 2.5, preferably 0.4 to 2.2.

[0018] In the above technical solution, in step (1), the structure directing agent is one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide, preferably at least one of tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

[0019] In the above technical solution, in step (1), the mass ratio of the structure guiding agent to water is 0.1 to 10.0.

[0020] In the above technical solution, the mixing conditions in step (1) include: a mixing temperature of 20-50°C and a stirring time of 6-12 hours; the heat treatment conditions include: a temperature of 70-80°C and a stirring time of 48-72 hours.

[0021] In the above technical solution, in step (2), the mass ratio of seed crystal to water is 0.01 to 1.00.

[0022] In the above technical solution, in step (2), the mass ratio of small molecule carbon source to water is 0.002 to 0.03.

[0023] In the above technical solutions, the silicon source is SiO2, and the molar ratio of small molecule carbon source to total silicon source (the sum of the first silicon source and the second silicon source) is 0.005 to 0.020.

[0024] In the above technical solution, in step (2), the aluminum source is one or more of aluminum sulfate and aluminum nitrate, preferably aluminum sulfate.

[0025] In the above technical solution, in step (2), the alkali source is sodium hydroxide.

[0026] In the above technical solution, in step (2), the mass ratios of aluminum source, alkali source, second silicon source and water are 0.005-0.10, 0.02-2.0 and 0.05-5.0, respectively. The second silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the SiO2 / Al2O3 molar ratio is 30-105.

[0027] In the above technical solution, the mixing conditions in step (2) include: a temperature of 20 to 60°C and a stirring time of 1 to 48 hours.

[0028] In the above technical solution, the crystallization conditions in step (2) include: a crystallization temperature of 180 to 200°C and a crystallization time of 12 to 36 hours.

[0029] In the above technical solution, after crystallization in step (2), conventional steps such as separation and washing can be performed. The drying conditions include: a drying temperature of 120℃~150℃ and a drying time of 5~24 hours. The drying equipment can be a conventional oven or the like.

[0030] In the above technical solution, in step (3), the catalyst is prepared by ammonium exchange, as follows: the material obtained in step (2) is subjected to ion exchange with an ammonium salt solution, and after separation, washing and drying, the catalyst is obtained.

[0031] In the above technical solution, the ammonium exchange uses an ammonium salt solution, wherein the ammonium salt is one or a mixture of ammonium nitrate, ammonium sulfate, and ammonium chloride. The mass concentration of the ammonium salt solution is 5% to 15%. The ammonium exchange conditions include: an exchange temperature of 60 to 80°C and an exchange time of 3 to 48 hours. The number of ammonium exchanges is 1 to 4.

[0032] In the above technical solution, separation, washing, drying, and calcination are conventional steps. The drying conditions include: a drying temperature of 120℃~150℃ and a drying time of 12 hours~24 hours. The drying equipment can be a conventional oven or similar device used in the art.

[0033] A third aspect of the present invention provides the application of the above-mentioned hydrothermal carbon / ZSM-5 molecular sieve composite as a catalyst in the cumene cracking reaction.

[0034] In the above technical solution, the hydrothermal carbon / ZSM-5 molecular sieve can be made into a catalyst by extrusion molding. The length of the catalyst can be a column of 3.0 to 10.0 mm. The cross-section of the column is circular, square, clover-shaped or star-shaped, and the maximum radial dimension of the cross-section is 0.8 to 3.0 mm.

[0035] In the above technical solution, the reaction conditions for cumene cracking are as follows: reaction temperature is 300–350℃, reaction pressure is 0–0.5 MPa, and cumene mass hourly space velocity is 30–200 h⁻¹. -1 .

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] 1. The hydrothermal carbon / ZSM-5 molecular sieve composite of the present invention has a large amount of weak acid and a small amount of medium-strong acid. Compared with ZSM-5 molecular sieve, the hydrothermal stability and pore structure do not change significantly after the introduction of hydrothermal carbon. Therefore, the hydrothermal carbon / ZSM-5 molecular sieve composite has good comprehensive performance and is particularly suitable for cumene cracking reaction.

[0038] 2. In the hydrothermal synthesis of the carbon / ZSM-5 molecular sieve composite in this invention, SP is obtained by in-situ conversion of inexpensive small-molecule carbon sources under high-temperature and high-pressure hydrothermal conditions. 2Hybrid carbon, with a certain ordered structure and relatively uniform bulk distribution, utilizes the unique physicochemical properties of hydrothermal carbon to effectively modulate the acidity of ZSM-5 molecular sieve at a low cost, thereby giving the hydrothermal carbon / ZSM-5 molecular sieve composite good comprehensive performance, and making it particularly suitable for cumene cracking reaction.

[0039] 3. When the hydrothermal carbon / ZSM-5 molecular sieve composite of the present invention is used as a catalyst in the cumene cracking reaction, it has high activity and selectivity, long catalyst lifetime, and strong comprehensive reaction performance. Attached Figure Description

[0040] Figure 1 The image shows the XRD pattern of the hydrothermal carbon / ZSM-5 molecular sieve composite obtained in Example 1.

[0041] Figure 2 The XRD pattern of the ZSM-5 molecular sieve obtained in Comparative Example 1 is shown.

[0042] Figure 3 The XRD pattern of the ZSM-5 molecular sieve obtained in Comparative Example 2 is shown.

[0043] Figure 4 The NH3-TPD diagram of the hydrothermal carbon / ZSM-5 molecular sieve composite obtained in Example 1 is shown.

[0044] Figure 5 The image shows the NH3-TPD of the ZSM-5 molecular sieve obtained in Comparative Example 1. Detailed Implementation

[0045] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0046] The testing method of this invention is as follows:

[0047] (1) Calculation method for relative crystallinity. Relative crystallinity is obtained by comparing the peak area of ​​the sample at 22.5°–25° with the standard peak area of ​​commercial product ZSM-5. The calculation formula is as follows:

[0048] R = A P / A R

[0049] 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 at 22.5°–25°.

[0050] (2) X-ray diffraction method. The phase composition (XRD) of the sample was determined using a Bruker D8 X-ray powder diffractometer. Measurements were taken using a scanning diffractometer. The instrument used was a Cu target with a graphite monochromatic filter. The slit angle (SS / DS) was 1°, the RS was 0.15 mm, the operating voltage was 40 kV, and the current was 30 mA.

[0051] (3) Specific surface area was determined using a nitrogen adsorption-desorption isotherm. The specific procedure was as follows: the instrument used was a Micromeritics ASAP2020, and the test temperature was -196℃. Before nitrogen physical adsorption, the sample was degassed at 330℃ and 1.33 Pa for 4 hours. The total specific surface area was calculated using the BET (Brunauer-Emmett-Teller) formula.

[0052] (4) Acid strength was determined by ammonia-programmed temperature desorption (NH3-TPD) analysis. The specific procedure was as follows: the molecular sieve sample was pressed into tablets, crushed, and sieved. 20-40 mesh particles were dried for later use to obtain the sample to be tested. During the experiment, 150 mg of the dried sample was accurately weighed and placed in a quartz tube. A quartz sand bed supported the zeolite bed and covered it with a quartz sand bed, positioning the zeolite bed at the thermocouple position. The sample was activated at 550℃ for 2 hours under a helium atmosphere, then cooled to room temperature, adsorbed 10% ammonia for 30 minutes, and then heated to a constant temperature of 100℃. After baseline stabilization, the temperature was increased to 650℃ at a rate of 10℃ / min, and the ammonia desorption signal was collected. The total acid content was 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℃.

[0053] (5) The SiO2 / Al2O3 molar ratio of the catalyst was measured using atomic absorption spectrometry (ICP). 100 mg of the finely ground sample was weighed into a crucible, 1 g of sodium hydroxide was added, and the mixture was melted at 750 °C for 15 minutes. After the melt cooled, hydrochloric acid was added to neutralize it. The solution was then transferred to a 100 mL volumetric flask and diluted 10 times. The SiO2 / Al2O3 molar ratio of the molecular sieve or composite was calculated by measuring the results using an ICP spectrometer and comparing them with the results of a blank solution.

[0054]

Example 1

[0055] This embodiment provides a method for synthesizing hydrothermal carbon / ZSM-5 molecular sieve composites, which includes the following steps:

[0056] (1) Weigh 20.84 g of tetraethyl orthosilicate, 29.17 g of tetrapropylammonium hydroxide and 15 g of water, mix them and stir at 25 °C for 12 hours to obtain a mixed solution. Stir the mixed solution at 70 °C for 72 hours to obtain seed crystals.

[0057] (2) Weigh 0.33 g of aluminum sulfate, 0.203 g of glucose, 6.86 g of sodium hydroxide, 42 g of water, 12 g of silica sol (SiO2 content 45%, SiO2 / Al2O3 molar ratio 100) and 4 g of seed crystals, mix them, and stir at 25°C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185°C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150°C for 6 hours.

[0058] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM-5-1. Its properties are shown in Table 1, and its XRD pattern is shown in Table 2. Figure 1 .Depend on Figure 1 It can be seen that the C / ZSM-5-1 and ZSM-5 standard XRD patterns are consistent in peak position and intensity, and also show sp. 2 The characteristic peak of carbon (2θ = 26.6°) indicates that glucose also underwent transformation during the hydrothermal process, resulting in an ordered structure.

[0059]

Example 2

[0060] This embodiment provides a method for synthesizing hydrothermal carbon / ZSM-5 molecular sieve composites, which includes the following steps:

[0061] (1) Weigh 20.84 g of tetraethyl orthosilicate, 38 g of tetrabutylammonium hydroxide and 15 g of water, mix them and stir at 25 °C for 12 hours to obtain a mixed solution. Stir the mixed solution at 70 °C for 72 hours to obtain seed crystals.

[0062] (2) Weigh 0.33 g aluminum sulfate, 0.203 g fructose, 6.86 g sodium hydroxide, 42 g water, 12 g silica sol (SiO2 mass content 45%, SiO2 / Al2O3 molar ratio 99) and 4 g seed crystals, mix them, and stir at 25 °C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185 °C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours.

[0063] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM-5-2. Its properties are shown in Table 1, and its XRD pattern is similar to... Figure 1 Similarly, the C / ZSM-5-2 and ZSM-5 standard XRD patterns are consistent in peak position and intensity, and sp also appears at 2θ = 26.6°. 2 The characteristic peaks of carbon indicate that fructose also underwent transformation during the hydrothermal process, resulting in an ordered structure.

[0064]

Example 3

[0065] This embodiment provides a method for synthesizing hydrothermal carbon / ZSM-5 molecular sieve composites, which includes the following steps:

[0066] (1) Weigh 20.84 g of tetraethyl orthosilicate, 29.17 g of tetrapropylammonium hydroxide and 15 g of water, mix them and stir at 25 °C for 12 hours to obtain a mixed solution. Stir the mixed solution at 70 °C for 72 hours to obtain seed crystals.

[0067] (2) Weigh 0.411 g of aluminum nitrate, 0.203 g of glucose, 6.86 g of sodium hydroxide, 48.6 g of water, 5.4 g of silica (SiO2 content 100%, SiO2 / Al2O3 molar ratio 100), and 4 g of seed crystals, mix them, and stir at 25°C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185°C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150°C for 6 hours.

[0068] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM-5-3. Its properties are shown in Table 1, and its XRD pattern is similar to... Figure 1 Similarly, the C / ZSM-5-3 and ZSM-5 standard XRD patterns are consistent in peak position and intensity, and sp also appears at 2θ = 26.6°. 2 The characteristic peaks of carbon indicate that glucose also underwent a transformation during the hydrothermal process under these conditions, resulting in an ordered structure.

[0069]

Example 4

[0070] This embodiment provides a method for synthesizing hydrothermal carbon / ZSM-5 molecular sieve composites, which includes the following steps:

[0071] (1) Weigh 20.84 g of tetraethyl orthosilicate, 24.79 g of tetrapropylammonium hydroxide and 3 g of water, mix them and stir at 25 °C for 12 hours to obtain a mixed solution. Stir the mixed solution at 70 °C for 72 hours to obtain seed crystals.

[0072] (2) Weigh 0.381 g of aluminum sulfate, 0.135 g of glucose, 7.85 g of sodium hydroxide, 41.04 g of water, 13.74 g of silica sol (SiO2 content 45%, SiO2 / Al2O3 molar ratio 104) and 6 g of seed crystals, mix them, and stir at 25°C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185°C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150°C for 6 hours.

[0073] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM-5-4. Its properties are shown in Table 1, and its XRD pattern is similar to... Figure 1 Similarly, the C / ZSM-5-4 and ZSM-5 standard XRD patterns are consistent in peak position and intensity, and sp also appears at 2θ = 26.6°. 2 The characteristic peaks of carbon indicate that glucose also underwent a transformation during the hydrothermal process under these conditions, resulting in an ordered structure.

[0074]

Example 5

[0075] This embodiment provides a method for synthesizing hydrothermal carbon / ZSM-5 molecular sieve composites, which includes the following steps:

[0076] (1) Weigh 20.84 g of tetraethyl orthosilicate, 29.17 g of tetrapropylammonium hydroxide and 15 g of water, mix them and stir at 25 °C for 12 hours to obtain a mixed solution. Stir the mixed solution at 70 °C for 72 hours to obtain seed crystals.

[0077] (2) Weigh 0.329 g of aluminum nitrate, 0.135 g of glucose, 6.86 g of sodium hydroxide, 5 g of water, 18 g of silica sol (SiO2 content 45%, SiO2 / Al2O3 molar ratio 100) and 4 g of seed crystals, mix them, and stir at 25°C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185°C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150°C for 6 hours.

[0078] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM-5-5. Its properties are shown in Table 1, and its XRD pattern is similar to... Figure 1 Similarly, the C / ZSM-5-5 and ZSM-5 standard XRD patterns are consistent in peak position and intensity, and sp also appears at 2θ = 26.6°. 2 The characteristic peaks of carbon indicate that glucose also underwent a transformation during the hydrothermal process under these conditions, resulting in an ordered structure.

[0079]

Example 6

[0080] This embodiment provides a method for synthesizing hydrothermal carbon / ZSM-5 molecular sieve composites, which includes the following steps:

[0081] (1) Weigh 20.84 g of tetraethyl orthosilicate, 29.17 g of tetrapropylammonium hydroxide and 7.5 g of water, mix them and stir at 25 °C for 12 hours to obtain a mixed solution. Stir the mixed solution at 70 °C for 72 hours to obtain seed crystals.

[0082] (2) Weigh 0.33 g aluminum sulfate, 0.305 g glucose, 6.86 g sodium hydroxide, 24 g water, 12 g silica sol (SiO2 mass content 45%, SiO2 / Al2O3 molar ratio 101) and 4 g seed crystals, mix them, and stir at 25 °C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185 °C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours.

[0083] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM-5-6. Its properties are shown in Table 1, and its XRD pattern is similar to... Figure 1 Similarly, the C / ZSM-5-6 and ZSM-5 standard XRD patterns are consistent in peak position and intensity, and sp also appears at 2θ = 26.6°. 2 The characteristic peaks of carbon indicate that glucose also underwent a transformation during the hydrothermal process under these conditions, resulting in an ordered structure.

[0084]

Example 7

[0085] This embodiment provides a method for synthesizing a hydrothermal carbon / ZSM-5 molecular sieve composite, wherein the mass ratio of the first silicon source (SiO2) to water is 0.2, and the method includes the following steps:

[0086] (1) Weigh 10.42 g of tetraethyl orthosilicate, 15.26 g of tetrapropylammonium hydroxide and 15 g of water, mix them and stir at 25 °C for 12 hours to obtain a mixed solution. Stir the mixed solution at 70 °C for 72 hours to obtain seed crystals.

[0087] (2) Weigh 0.33 g aluminum sulfate, 0.203 g glucose, 6.86 g sodium hydroxide, 42 g water, 12 g silica sol (SiO2 mass content 45%) and 4 g seed crystals and mix them. Stir at 25°C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185°C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150°C for 6 hours.

[0088] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM-5-4. Its properties are shown in Table 1, and its XRD pattern is similar to... Figure 1 Similarly, the C / ZSM-5-4 and ZSM-5 standard XRD patterns are consistent in peak position and intensity, and sp also appears at 2θ = 26.6°. 2 The characteristic peaks of carbon indicate that glucose also underwent a transformation during the hydrothermal process under these conditions, resulting in an ordered structure.

[0089] Comparative Example 1

[0090] This comparative example serves as a reference for Example 1. No small molecule carbon source was added during synthesis. The synthesis method includes the following steps:

[0091] (1) Weigh 20.84 g of tetraethyl orthosilicate, 29.17 g of tetrapropylammonium hydroxide and 15 g of water, mix them and stir at 25 °C for 12 hours to obtain mixture A. Stir mixture A at 70 °C for 72 hours to obtain seed crystals.

[0092] (2) Weigh 0.33 g of aluminum sulfate, 6.86 g of sodium hydroxide, 42 g of water, 12 g of silica sol (SiO2 mass content 45%) and 4 g of seed crystals and mix them. Stir at 25 °C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185 °C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours.

[0093] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM5-C1. Its properties are shown in Table 1, and its XRD pattern is shown in Table 2. Figure 2 .Depend on Figure 2As 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.

[0094] Comparative Example 2

[0095] This comparative example serves as a reference for Example 1. The silicon source is SiO2, and the molar ratio of glucose to total silicon source is 0.075. The synthesis method includes the following steps:

[0096] (1) Weigh 20.84 g of tetraethyl orthosilicate, 29.17 g of tetrapropylammonium hydroxide and 15 g of water, mix them and stir at 25 °C for 12 hours to obtain a mixed solution. Stir the mixed solution at 70 °C for 72 hours to obtain seed crystals.

[0097] (2) Weigh 0.33 g aluminum sulfate, 1.3 g glucose, 6.86 g sodium hydroxide, 42 g water, 12 g silica sol (SiO2 mass content 45%, SiO2 / Al2O3 molar ratio 100) and 4 g seed crystals, mix them, and stir at 25 °C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185 °C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours.

[0098] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM-5-C2. Its properties are shown in Table 1, and its XRD pattern is shown in the figure. Figure 3 As shown, sp also appears at 2θ = 26.6°. 2 It has characteristic peaks for carbon, but the peak width is relatively large.

[0099] Comparative Example 3

[0100] This comparative example serves as a reference for Example 1. The carbon source used is starch, and its synthesis method includes the following steps:

[0101] (1) Weigh 20.84 g of tetraethyl orthosilicate, 29.17 g of tetrapropylammonium hydroxide and 15 g of water, mix them and stir at 25 °C for 12 hours to obtain a mixed solution. Stir the mixed solution at 70 °C for 72 hours to obtain seed crystals.

[0102] (2) Weigh 0.33 g aluminum sulfate, 0.203 g starch, 6.86 g sodium hydroxide, 42 g water, 12 g silica sol (SiO2 content 45%, SiO2 / Al2O3 molar ratio 100) and 4 g seed crystals, mix them, and stir at 25°C for 1.5 hours to obtain a gel. Place the gel in a reaction vessel and crystallize at 185°C for 24 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150°C for 6 hours.

[0103] (3) Take 5 g of sample and place it in 30 g of 10 wt% ammonium nitrate solution for ammonium exchange at 80 °C for 4 hours. Then cool to room temperature, centrifuge and wash until neutral, and dry at 150 °C for 6 hours to obtain product C / ZSM-5-C3. Its properties are shown in Table 1. As can be seen from Table 1, the weak acid content of Comparative Example 3 is significantly lower than that of Example 1, while the medium-strong acid content is similar to that of Comparative Example 1 without a carbon source, indicating that the introduction of starch has limited effect on the acidity regulation of the catalyst.

[0104] [Test Example]

[0105] Catalyst evaluation was performed on a fixed-bed pulsed microdevice. Specifically, 20 mg of each catalyst from Examples 1-7 and Comparative Examples 1-3 were accurately weighed and placed 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 tubes through the injection port. The products were analyzed using gas chromatography. The reaction temperature was 250℃-350℃, the reactant was liquid cumene, and the injection volume was 1 μL. The chromatograph used was an Agilent 7890B, and the detector used was a flame ionization detector. The reaction results for each catalyst are shown in Table 2.

[0106] Figure 4 and Figure 5 The NH3-TPD curves for Example 1 (C / ZSM-5-1) and Comparative Example 1 (C / ZSM-5-C1) are shown in Table 1. It can be seen that the relative weak acid content of CZSM-5-1 is about 10% higher than that of CZSM-5-C1 (Table 1), indicating that the introduction of hydrothermal carbon significantly increases the content of the weak acid in the catalyst, which is beneficial to the cumene cracking reaction. On the other hand, the content of the strong acid in C / ZSM-5-1 is about 10% lower than that in C / ZSM-5-C1, which can reduce side reactions; while the strong acid content remains basically unchanged, indicating that the weak acid is mainly obtained by suppressing the formation of medium-strong acids. Table 1 also shows that the specific surface area increases to some extent after the introduction of hydrothermal carbon, from 273 m² / m². 2 / g increased to 296m 2 / g, which may help with diffusion during the reaction process.

[0107] As shown in Table 2, compared to C / ZSM-5-C1 without the introduction of hydrothermal carbon, the benzene selectivity of C / ZSM-5-1 is improved, which may be related to the reduction of moderately strong acid. Table 2 also shows that in the catalyst lifetime test for cumene cracking in Example 1 and Comparative Example 1, after 16 repeated injections, the activity of C / ZSM-5-1 decreased by only 0.7%, while the activity of C / ZSM-5-C1 decreased by 3.7%. Comparative Example 2 shows that when too much glucose is added, the activity of the composite catalyst decreases significantly, possibly due to blockage of the molecular sieve pores. Comparative Example 3 added starch; although the selectivity improved, the activity was not as good as Comparative Example 1 without glucose. Furthermore, although the activity and selectivity of Example 7 are higher than those of the comparative examples, the overall performance is not as good as Examples 1 to 6 because the mass ratio of the first silicon source to water is not within the preferred range.

[0108] Table 1

[0109]

[0110] Table 2

[0111]

[0112]

[0113] The embodiments described above are merely detailed descriptions of the technical solutions of this invention, but the invention is not limited to the above embodiments; that is, the invention does not depend on the steps described in the above embodiments for implementation. In summary, any improvements made to this invention by those skilled in the art, including substitutions for the raw materials and additives described in this invention, and selections of specific implementation methods, all fall within the protection and disclosure scope of this invention.

Claims

1. A hydrothermal carbon / ZSM-5 molecular sieve composite comprising: The composite contains hydrothermal carbon and ZSM-5 molecular sieve, with ZSM-5 molecular sieve comprising 95%–99.5% by mass and hydrothermal carbon comprising 0.5%–5.0% by mass, wherein the hydrothermal carbon is SP with 2θ = 26.6°. 2 In the hydrothermal carbon / ZSM-5 molecular sieve composite, the amount of weak acid accounts for 50% to 60% of the total acid amount, and the amount of medium-strong acid accounts for 15% to 25% of the total acid amount.

2. The composite according to claim 1, characterized in that Based on the mass of the composite, the ZSM-5 molecular sieve has a mass of 97.5%~99.0% and a hydrothermal carbon content of 1.0%~2.5%.

3. The composite of claim 1, wherein In the hydrothermal carbon / ZSM-5 molecular sieve composite, the molar ratio of SiO2 / Al2O3 is 80~200.

4. The composite of claim 3, wherein In the hydrothermal carbon / ZSM-5 molecular sieve composite, the molar ratio of SiO2 / Al2O3 is 99~180.

5. The composite of claim 1, wherein In the hydrothermal carbon / ZSM-5 molecular sieve composite, the amount of weak acid accounts for 53% to 58% of the total acid content, and the amount of medium-strong acid accounts for 15% to 20% of the total acid content.

6. The composite of claim 1, wherein The water heat carbon / ZSM-5 molecular sieve composite has a specific surface area of 250-500 m 2 / g. And / or, the relative crystallinity of the hydrothermal carbon / ZSM-5 molecular sieve composite is 80%~110%.

7. The composite of claim 1, wherein The water hydrocarbon / ZSM-5 molecular sieve composite has a specific surface area of 280-350 m 2 / g; And / or, the relative crystallinity of the hydrothermal carbon / ZSM-5 molecular sieve composite is 85%~100%.

8. A method for synthesizing the hydrothermal carbon / ZSM-5 molecular sieve composite according to any one of claims 1-7, comprising: (1) The first silicon source, the structure guiding agent and water are mixed and heat-treated to obtain seed crystals; (2) The seed crystals, small molecule carbon source, aluminum source, alkali source, second silicon source and water obtained in step (1) are mixed, crystallized and dried to obtain the material; (3) The material obtained in step (2) is subjected to ammonium exchange to obtain hydrothermal carbon / ZSM-5 molecular sieve composite.

9. The method of synthesis according to claim 8, wherein, In step (1), the first silicon source is at least one of tetraethyl orthosilicate or tetramethyl orthosilicate; in step (2), the second silicon source is at least one of silica sol or silica.

10. The method of synthesis according to claim 9, wherein, In step (1), the first silicon source is tetraethyl orthosilicate; in step (2), the second silicon source is silica sol.

11. The method of synthesis according to claim 8, wherein, In step (2), the small molecule carbon source is at least one of glucose and fructose.

12. The method of synthesis according to claim 8, wherein, In step (1), the mass ratio of the first silicon source (SiO2) to water is 0.2~2.5; And / or, in step (1), the structure directing agent is one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; And / or, in step (1), the mass ratio of the structure-directing agent to water is 0.1 to 10.0; And / or, in step (1), the mixing conditions include: a temperature of 20°C to 50°C and a mixing time of 6 to 12 hours; And / or, in step (1), the conditions for the heat treatment include: a temperature of 70~80℃ and a time of 48~72 hours.

13. The method of synthesis according to claim 12, wherein, In step (1), the mass ratio of the first silicon source (SiO2) to water is 0.4 to 2.

2.

14. The method of synthesis according to claim 8, wherein, In step (2), the mass ratio of the small molecule carbon source to water is 0.002~0.03; And / or, in step (2), the aluminum source is one or more of aluminum sulfate and aluminum nitrate; the alkali source is sodium hydroxide; And / or, in step (2), the mass ratio of seed crystals to water is 0.01~1.0; And / or, in step (2), the mass ratios of aluminum source, alkali source, second silicon source and water are 0.005~0.10, 0.02~2.0 and 0.05~2.0, respectively, wherein the second silicon source is SiO2, the aluminum source is Al2O3, and the molar ratio of SiO2 / Al2O3 is 30~105; And / or, in step (2), the mixing conditions include: a mixing temperature of 20~60℃ and a mixing time of 1~48 hours; And / or, in step (2), the crystallization conditions include: a crystallization temperature of 180~200℃ and a crystallization time of 12~36 hours.

15. The method of synthesis according to claim 14, wherein, In step (2), the aluminum source is aluminum sulfate.

16. The method of synthesis according to claim 8, wherein, The silicon source is SiO2, and the molar ratio of the small molecule carbon source to the total silicon source, including the sum of the first silicon source and the second silicon source, is 0.005~0.

020.

17. The method of synthesis according to claim 8, wherein, In step (3), the ammonium exchange uses an ammonium salt solution, wherein the ammonium salt is one or a mixture of ammonium nitrate and ammonium sulfate; the mass concentration of the ammonium salt solution is 5% to 15%; the ammonium exchange conditions include: an exchange temperature of 60 to 80°C, an exchange time of 3 to 48 hours, and 1 to 4 ammonium exchanges.

18. The application of the hydrothermal carbon / ZSM-5 molecular sieve composite according to any one of claims 1 to 7 or the hydrothermal carbon / ZSM-5 molecular sieve composite synthesized by any one of claims 8 to 17 as a catalyst in the cumene cracking reaction.

Images