A highly crystalline, high-silica mordenite zeolite, its preparation method and applications

Abstract

This invention relates to the field of artificial synthesis of mordenite zeolite, providing a highly crystalline, high-silica mordenite zeolite, its preparation method, and its applications. The highly crystalline, high-silica mordenite zeolite has a Si / Al ratio > 15 and a relative crystallinity > 75%. Addressing the technical challenge of forming a high-silica framework in mordenite zeolite, this invention achieves control over the framework composition of mordenite zeolite through a second crystallization process after adding a second silicon source, a structure-directing agent, and a solvent. This allows for precise construction of highly crystalline, high-silica mordenite zeolite, overcoming the technical bottleneck of direct synthesis of high-silica mordenite through a single gelation crystallization process, as well as the problems of low crystallization activity and poor uniformity under excessively high or low alkalinity conditions. It breaks through the upper limit of the Si / Al ratio phase region in the artificial in-situ synthesis of mordenite zeolite, effectively controlling crystal parameters and improving product yield, thereby enhancing the microporous crystallinity of the zeolite, greatly optimizing the distribution of metastable surface-active acid centers in the zeolite, and exhibiting excellent aromatic hydrocarbon conversion performance.

Description

Technical Field

[0001] This invention relates to the field of artificially synthesized mordenite technology, and more specifically, to a highly crystalline, high-silica mordenite, its preparation method, and its applications. Background Technology

[0002] Mordenite is a common natural zeolite mineral with a pore structure consisting of one-dimensional 12-membered ring channels and one-dimensional 8-membered ring channels. It has been widely used and studied as an adsorbent. In recent years, mordenite has attracted widespread attention as a catalytic material. Whether naturally formed or artificially synthesized, the MOR topology typically has an aluminum-rich framework and contains high levels of... The / Lewis acid center ratio facilitates the electrophilic activation of the benzene ring and the formation of carbocations. It has shown high catalytic activity and stability in catalytic hydrocarbon reactions and is a promising catalytic material. It has been industrialized in reactions such as toluene disproportionation and has also been extensively studied in many chemical fields such as methanol amination.

[0003] The catalytic active centers of molecular sieves are affected by many factors. It is generally believed that they are closely related to the composition, structure and surface properties of the molecular sieve framework. The number of active centers is generally proportional to the aluminum atom content of the framework. In particular, the quantitative information of the T sites in the framework crystallography and the coordination chemical environment largely determine the type and properties of solid acid centers with catalytic activity.

[0004] Therefore, for catalytic reactions requiring specific acid strength, it is necessary to develop mordenite zeolites with corresponding silicon content. However, literature reports that the Si / Al molar ratio (Si / Al) of in-situ synthesized mordenite is typically below 10. This framework composition affects the acid strength of the hydrogen-form zeolite. Adjusting the gel chemistry of the mixture has limited effect on broadening the Si / Al ratio range of the aforementioned molecular sieve products. The yield and crystallinity are easily and significantly affected by the high silicon composition, and dense-phase impurities are easily generated in strong base synthesis systems. At the same time, the controllability of additives and other control methods is poor, making it difficult to achieve stable industrial production. Limited by the high nucleation activation energy, adding an appropriate amount of structure-directing agent to form a charge density mismatch system can increase the framework Si / Al ratio of the mordenite product, but it is still difficult to break through the bottleneck of Si / Al>15. Seed crystal method or directing agent method cannot fundamentally improve the above problems.

[0005] In summary, due to limitations in the effective activation of silicon atoms under high-silicon composition and the stability factors such as bond angle and bond energy of the aluminum-containing framework, excessively high or low alkalinity is extremely unfavorable for the synthesis of highly crystalline, high-silicon mordenite with a one-dimensional porous framework. In-situ direct synthesis of high-silicon (Si / Al>15) mordenite is a recognized challenge in both research and industry, and a key technical challenge that urgently needs to be addressed for efficient solid acid catalysis applications. If the silicon content of the mordenite framework can be increased without avoiding the loss of silicon and aluminum atoms or the formation of impurities, providing a more suitable active acid catalytic center, it will have great potential for industrial application. Summary of the Invention

[0006] The purpose of this invention is to provide a high-crystallinity, high-silica zeolite, its preparation method and application, so as to solve the technical problem that it is difficult to prepare high-crystallinity, high-yield high-silica zeolite in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a mordenite zeolite having a Si / Al ratio >15 and a relative crystallinity >75%.

[0009] It should be noted that the Si / Al used in this invention refers to the molar ratio of Si and Al elements.

[0010] According to some embodiments of the present invention, in the mordenite, 15 < Si / Al ≤ 20.

[0011] According to some embodiments of the present invention, in the mordenite, 15 < Si / Al ≤ 18.

[0012] According to some embodiments of the present invention, the relative crystallinity of the mordenite is >80%.

[0013] According to some embodiments of the present invention, the acid strength of the mordenite is shown as a desorption peak temperature >355°C for temperature-programmed ammonia desorption (NH3-TPD).

[0014] According to some embodiments of the present invention, the acid strength of the mordenite is shown to be the peak temperature of the desorption peak of temperature-programmed ammonia desorption (NH3-TPD) at 380–550 °C.

[0015] According to some embodiments of the present invention, the acid strength of the mordenite is shown to be the peak temperature of the desorption peak of temperature-programmed ammonia desorption (NH3-TPD) at 400-515°C.

[0016] To understand the acidity of solid acid catalysis, temperature-programmed desorption (NH3-TPD) of ammonia is commonly used for characterization. For example, it can be measured on an Altamira AMI-3300 chemisorption analyzer manufactured by Micrometrics Instruments, Inc. The obtained temperature-programmed ammonia desorption curves show characteristic peaks at different desorption temperatures, corresponding to different acid strengths; the higher the desorption temperature corresponding to the characteristic peak, the greater the acid strength.

[0017] According to some embodiments of the present invention, the specific surface area S of the mordenite zeolite BET ≥400m 2 / g, micropore volume V micro >0.15cm 3 / g.

[0018] According to some embodiments of the present invention, the specific surface area S of the mordenite zeolite BET 400-500m 2 / g, micropore volume V micro The value is 0.19–0.25 cm. 3 / g.

[0019] The mordenite provided by this invention, through the regulation of the distribution of silicon and aluminum atoms in the framework, breaks through the existing silicon-aluminum ratio, and has the characteristics of high acid strength and high crystallinity. It also improves the diffusion, mass transfer and reaction performance of the micropore channels of high-silicon mordenite.

[0020] Secondly, the present invention provides a method for preparing mordenite zeolite, comprising:

[0021] S1. Obtain a colloid comprising a first silicon source, an aluminum source, an alkali source, a template agent R, and a solvent I; wherein the molar ratio of silicon in the first silicon source to aluminum in the aluminum source is not greater than 15 (Si / Al≤15), preferably 5 to 15 (Si / Al=5 to 15);

[0022] S2. The colloid is crystallized once to obtain a crystallized slurry;

[0023] S3. Add a second silicon source and structure directing agent SDA to the crystallization slurry so that the molar ratio of silicon to aluminum in the entire reaction system is greater than 15 (Si / Al>15);

[0024] S4. Perform secondary crystallization to obtain the mordenite zeolite;

[0025] Optionally, it also includes S5. subjecting the mordenite to a first calcination, followed by ion exchange, and then a second calcination.

[0026] The method for preparing mordenite provided by this invention involves first mixing an aluminum source, an alkali source, a first silicon source, a template agent, and a solvent, and then performing a first crystallization according to a conventional low Si / Al ratio to obtain any one of high-crystallinity mordenite, ZSM-5 molecular sieve, MCM-22 molecular sieve, or β molecular sieve. Next, a second silicon source and a structure directing agent are added, and if necessary, an appropriate amount of solvent can be added to enhance atomic coordination and bonding capabilities. A second crystallization is then performed to obtain high-crystallinity, high-silicon mordenite.

[0027] In step S3, it can be determined whether an appropriate amount of solvent I needs to be added to the crystallization slurry based on its state. Whether solvent I needs to be added and the specific amount of solvent I to be added are readily available to those skilled in the art.

[0028] In the preparation method provided by this invention, the selection of raw material composition and conditions in the first crystallization, as well as the addition of a second silicon source and structure directing agent SDA, have a significant impact on the degree of crystallization of mordenite. By optimizing the synthesis ratio, improving the activity of the second silicon source, and selecting a suitable structure directing agent SDA, the degree of crystallization of mordenite can be improved.

[0029] According to some embodiments of the present invention, the first silicon source and the second silicon source may be the same or different, and each is independently selected from at least one of silicon powder, silicon balls, silica gel, silica sol, sodium silicate (sodium silicate / water glass), aluminosilicate, silicate esters (such as methyl silicate, ethyl silicate, propyl silicate, etc.), silicon tetrachloride, silanes (such as tetramethylsilane, methyltrimethoxysilane, isobutylenetriethoxysilane, trichlorosilane, tetraethoxysilane, etc.), silica, and diatomaceous earth.

[0030] According to some embodiments of the present invention, the second silicon source is selected from at least one of silica gel, silica sol, sodium silicate (sodium silicate / water glass), aluminosilicate, silicate esters (such as methyl silicate, ethyl silicate, propyl silicate, etc.), silicon tetrachloride, silanes (such as tetramethylsilane, methyltrimethoxysilane, isobutylenetriethoxysilane, trichlorosilane, tetraethoxysilane, etc.), and silica.

[0031] According to some embodiments of the present invention, the aluminum source includes at least one of aluminum hydroxide, aluminum isopropoxide, aluminum sec-butoxide, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride, and aluminum oxide.

[0032] According to some embodiments of the present invention, the alkali source includes alkali metal hydroxide and / or ammonia; preferably, the alkali metal includes at least one of Li, Na, K, Rb, and Cs.

[0033] According to some embodiments of the present invention, the template agent R comprises at least one selected from ammonia, cyclohexylimine (HMI), piperidine, N,N,N-trimethyl-1-adamantylammonium bromide, pyridine, cyclopropylamine, cyclobutylamine, cyclooctylamine, cyclohexylmethylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, n-butylamine, hexamethyleneimine, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, tetrapropylammonium iodide, tetraethylammonium iodide, tetrapropylammonium bromide, tetraethylammonium bromide, tetraethylammonium chloride, or tetramethylammonium chloride.

[0034] According to some embodiments of the present invention, solvent I includes at least one of deionized water, alcohol solvents, and imidazole ionic liquids.

[0035] According to some embodiments of the present invention, solvent I includes at least one selected from deionized water, ethanol, isopropanol, glycerol, acetone, and n-butanol.

[0036] According to some embodiments of the present invention, the structure-directing agent SDA includes at least one of tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, and tetraethylammonium iodide.

[0037] According to some embodiments of the present invention, the molar ratio of the alkaline source to the silicon element in the first silicon source is: OH - / Si = 0.01 to 1, for example, it can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.33, 0.35, 0.38, 0.41, 0.45, 0.50, 0.6, 0.65, 0.7, 0.8, 0.85, 0.9, 0.95, 1, etc.

[0038] According to some embodiments of the present invention, the molar ratio of solvent I to silicon in the first silicon source is I / Si = 5 to 50, for example, it can be 5, 6, 8, 10, 13, 15, 16, 19, 20, 23, 25, 26, 28, 30, 35, 38, 40, 44, 46, 50, etc.

[0039] According to some embodiments of the present invention, the molar ratio of the template agent R to the silicon element in the first silicon source is: R / Si = 0.01 to 0.5, for example, it can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.15, 0.2, 0.21, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.41, 0.45, 0.47, 0.5, etc.

[0040] According to some embodiments of the present invention, the molar ratio of the structure directing agent SDA to the sum of silicon elements in the first silicon source and the second silicon source is: SDA / Si = 0.001 to 0.5, for example, it can be 0.001, 0.002, 0.003, 0.005, 0.007, 0.008, 0.009, 0.01, 0.015, 0.03, 0.05, 0.065, 0.08, 0.1, 0.15, 0.2, 0.21, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.41, 0.45, 0.47, 0.5, etc.

[0041] According to some embodiments of the present invention, the ion exchange includes ammonium exchange.

[0042] According to some embodiments of the present invention, the ammonium exchange reagent includes at least one of ammonium nitrate, ammonium chloride, ammonium oxalate, and ammonium sulfate.

[0043] According to some embodiments of the present invention, the ammonium exchange is carried out at a temperature of 10 to 120°C for 0.1 to 1000 hours, preferably at a temperature of 50 to 80°C for 0.5 to 5 hours.

[0044] According to some embodiments of the present invention, the concentration of the ammonium exchange reagent aqueous solution is 0.01 to 5 mol / L.

[0045] According to some embodiments of the present invention, the volume-to-mass ratio of the ammonium exchange reagent aqueous solution to mordenite is 4-10 mL: 1 g.

[0046] According to some embodiments of the present invention, the number of ion exchanges is 1 to 20 times, preferably 2 to 6 times.

[0047] According to some embodiments of the present invention, after ion exchange, the material is first filtered, washed and dried, and then calcined a second time; preferably, the drying temperature is 30-200°C, more preferably 80-120°C, and the drying time is 0.1-1000h, more preferably 0.5-10h.

[0048] According to some embodiments of the present invention, the stirring speed of the first crystallization is 0 to 6000 rpm, preferably 10 to 100 rpm, the crystallization temperature is 80 to 200°C, preferably 120 to 180°C, and the crystallization time is 2 to 2000 hours, preferably 100 to 300 hours.

[0049] According to some embodiments of the present invention, a pre-crystallization is performed before the primary crystallization, and the pre-crystallization temperature is 70-140°C and the time is 2-10 hours.

[0050] According to some embodiments of the present invention, the stirring speed of the secondary crystallization is 0 to 6000 rpm, preferably 10 to 100 rpm, the crystallization temperature is 80 to 200°C, preferably 120 to 180°C, and the crystallization time is 2 to 2000 hours, preferably 100 to 300 hours.

[0051] According to some embodiments of the present invention, a pre-crystallization is performed before the secondary crystallization, and the pre-crystallization temperature is 70-140°C and the time is 2-10 hours.

[0052] According to some embodiments of the present invention, after the secondary crystallization, the process further includes filtration, washing, and drying steps; preferably, the drying temperature is 30-200°C, more preferably 80-120°C, and the time is 0.1-1000h, more preferably 0.5-10h.

[0053] According to some embodiments of the present invention, the temperature of the first roasting is 200-980°C, preferably 400-650°C, and the time of the first roasting is 0.1-250h, preferably 1-10h.

[0054] According to some embodiments of the present invention, the temperature of the second roasting is 400-650°C, preferably 500-550°C; the time of the second roasting is 1-10 hours.

[0055] According to some embodiments of the present invention, the second calcination is carried out in a segmented calcination manner, including: calcination at a temperature of 150-200°C for 0.5-3 hours, calcination at a temperature of 250-350°C for 0.5-3 hours, calcination at a temperature of 400-500°C for 0.5-3 hours, and finally calcination at a temperature of 200-900°C for 0.1-100 hours.

[0056] Thirdly, the present invention provides a mordenite zeolite prepared by the preparation method described in the second aspect.

[0057] Fourthly, the present invention provides the application of the mordenite described in the first aspect or the mordenite described in the third aspect in the conversion of aromatics.

[0058] According to some embodiments of the present invention, the aromatic weight space velocity in the aromatic conversion is 0.01 to 50 h⁻¹. -1 The hydrogen-to-oil molar ratio is 0–300.

[0059] The mordenite provided by this invention has the characteristics of high crystallinity and high silicon content. It is a solid acid catalytic material with a unique structure, a large specific surface area and strong acidic external surface active centers. It exhibits excellent adsorption and activation performance for aromatic molecules, and can provide more suitable active sites for aromatic conversion. It has the characteristics of high selectivity, high activity and high stability when used to catalyze aromatic conversion.

[0060] According to some embodiments of the invention, the application includes applications in aromatic dealkylation reactions, such as in the selective dealkylation reaction of tricresyl.

[0061] According to some embodiments of the present invention, the selective dealkylation reaction of tricresyl is carried out at a temperature of 250–650°C and a pressure of 0–20 MPa.

[0062] Fifthly, the present invention provides an aromatics conversion catalyst, the catalyst comprising the mordenite described in the first aspect or the mordenite described in the third aspect.

[0063] According to some embodiments of the present invention, the catalyst further includes an active component.

[0064] According to some embodiments of the present invention, the active component includes at least one of Group IIIA bauxite metals, Group IVA metals, Group VA metals, and transition metals (including Group IB to VIIB metals and Group VIII metals).

[0065] According to some embodiments of the present invention, the active component is selected from at least one of Y, La, Ce, Pr, Nd, Fe, Co, and Ni.

[0066] According to some embodiments of the present invention, the catalyst includes a reduction step prior to the reaction.

[0067] According to some embodiments of the present invention, the reduction is carried out using hydrogen reduction, wherein the hydrogen flow rate is 8-800 mL / min; during the reduction, the temperature is first increased to 100-280°C at a rate of 0.1-20°C / min and held at that temperature for 0-48 h, and then increased to 300-750°C at a rate of 0.1-50°C / min and held at that temperature for 0-48 h.

[0068] The beneficial effects of this invention are at least as follows:

[0069] This invention addresses the technical challenge of forming a high-silicon framework in mordenite zeolite. By adding a second silicon source and a structure-directing agent, followed by a second crystallization, it achieves control over the framework composition of mordenite zeolite, expands the flexibility of the high-silicon framework, optimizes the framework bending force constant, reduces structural stress, and achieves coordination stabilization. It solves the problem of silicon atom-induced activation, enabling the precise construction of highly crystalline, high-silicon mordenite zeolite. It overcomes the technical bottleneck of directly synthesizing high-silicon mordenite zeolite through a single gel crystallization process, as well as the problems of low crystallization activity and poor uniformity under excessively high or low alkalinity conditions. It breaks through the upper limit of the Si / Al phase ratio region in the artificial in-situ synthesis of mordenite zeolite, effectively controls crystal parameters, and improves product yield, thereby enhancing the microporous crystallinity of zeolite, greatly optimizing the distribution of metastable surface-active acid centers in zeolite, and exhibiting excellent aromatic hydrocarbon conversion performance. Attached Figure Description

[0070] Figure 1 The XRD pattern of the highly crystalline, high-silica mordenite prepared in Example 1 of this invention;

[0071] Figure 2 SEM image of the highly crystalline, high-silica mordenite zeolite prepared in Example 1 of this invention;

[0072] Figure 3 The image shows an HR-TEM image of the high-silica mordenite obtained in Example 1 of this invention.

[0073] Figure 4 The NH3-TPD curve of the high-silica mordenite prepared in Example 1 of this invention is shown.

[0074] Figure 5 The N2 adsorption-desorption curve of the high-silica mordenite prepared in Example 1 of this invention is shown. Detailed Implementation

[0075] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0076] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0077] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0078] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0079] In the various embodiments and comparative examples of the present invention, the performance data were tested according to the following test methods:

[0080] (1) Phase analysis (XRD pattern): The phase analysis was performed using a Bruker D8 Focus diffractometer with a graphite monochromator, a Cu target Kα light source, a wavelength λ of 0.154 nm, a tube voltage of 40 kV, a tube current of 40 mA, and the diffraction signal was recorded in the 2θ range of 3-90° (scanning speed of 2° / min).

[0081] (2) Scanning electron imaging (SEM) images: taken using a FEI Nova Nano SEM 450 microscope.

[0082] (3) Spherical aberration transmission imaging (TEM) images: taken using a FEI Tecnai 20S-Twin microscope.

[0083] (4) The signal information of the ammonia temperature-programmed desorption (NH3-TPD) curve was collected using an Altamira AMI-3300 chemisorption analyzer manufactured by Micrometrics.

[0084] (5) The molecular sieve samples were characterized by low-temperature N2 adsorption-desorption using a Micrometrics 3Flex-Physisorption analyzer at a test temperature of 77K. The specific surface area and pore structure parameters were calculated by analyzing the isotherms using the BET method and the BJH method, respectively.

[0085] (6) Silicon-to-aluminum ratio of the test sample: The test sample was dissolved in HF aqueous solution at room temperature and then quantitatively analyzed on a PerkinElmer Optima 3300DV inductively coupled plasma emission spectrometer (ICP).

[0086] In the various embodiments and comparative examples of the present invention, the polytetrafluoroethylene-lined pressure steel autoclave used was purchased from Shandong Yantai Muping Shuguang Precision Instrument Factory, with a specification of 100mL; the rotary oven was purchased from Beijing Keruishi Company as a 200L space rotary oven.

[0087] Example 1

[0088] A highly crystalline, high-silica mordenite is synthesized as follows:

[0089] First, dissolve NaOH and sodium aluminate in deionized water. Then, add hexamethyleneimine (template agent R, 25 wt% aqueous solution). Finally, add methyl silicate, a silicon source. The components are: silicon source (based on Si content), template agent R, aluminum source (based on Al content), and alkali source (based on OH content). - The molar ratio of PTFE (polytetrafluoroethylene) and deionized water was 25:5:4:0.75:250. After stirring evenly, a milky white gelling solution was obtained. The gelling solution was then placed in a pressure steel autoclave lined with polytetrafluoroethylene and pre-crystallized at 90℃ for 6 hours. After that, it was placed in a rotary oven at 150℃ and 20 rpm for 200 hours of hydrothermal crystallization. Then, it was cooled to room temperature with tap water to obtain a crystallized slurry of highly crystalline pure phase MCM-22 (MWW configuration).

[0090] Add appropriate amounts of silicon source ethyl silicate, tetraethylammonium hydroxide (structure directing agent SDA, 25wt% aqueous solution) and deionized water to the crystallization slurry to make the molar ratio of silicon source (based on Si content), R+SDA, aluminum source (based on Al content), alkali source (based on OH-) and deionized water in the reaction system 66:8:4; 0.75:680; repeat the above crystallization procedure for secondary crystallization, cool to room temperature with tap water, filter and wash the obtained product, and dry it in an oven at 100℃ for 2 hours to obtain zeolite raw powder.

[0091] The zeolite powder was tested, and the XRD test results are shown below. Figure 1 It can be seen that this is a pure-phase MOR configuration with a relative crystallinity of 83%. SEM and TEM images are shown below. Figure 2 and Figure 3 The Si / Al ratio of this sample is 16.3, and its specific surface area is S0. BET 442m 2 / g, micropore volume V micro It is 0.19cm 3 / g.

[0092] Zeolite powder was calcined at 550℃ for 2 hours and then cooled. The zeolite powder was then subjected to ion exchange and a second calcination treatment. Specifically, the calcined zeolite powder and a 1 mol / L ammonium chloride aqueous solution were mixed evenly at a solid-to-liquid ratio of 1:6, and heated in a water bath to 65℃ for 1 hour for ion exchange. The mixture was then filtered and washed with deionized water. This process was repeated four times to obtain a filter cake, which was dried in an oven at 100℃ for 2 hours to obtain NH4. + The molecular sieve was calcined at 520℃ for 3 hours to obtain the hydrogen-type molecular sieve, and the resulting mordenite zeolite was designated GM1. The temperature-programmed ammonia desorption (NH3-TPD) curve showed that the peak temperature of the desorption peak of the sample was 491.5℃.

[0093] Example 2

[0094] A highly crystalline, high-silica mordenite is synthesized as follows:

[0095] First, CsOH and sodium aluminate were dissolved in deionized water. Then, tetraethylammonium hydroxide (template agent R, 25 wt% aqueous solution) was added. Finally, methyl silicate, a silicon source, was added. The molar ratio of silicon source (based on Si content), template agent R, aluminum source (based on Al content), alkali source (based on OH-) and deionized water was 25:12:2:1.25:200. After stirring evenly, a milky white gelling solution was obtained. Then, the gelling solution was placed in a polytetrafluoroethylene-lined pressure steel autoclave and pre-crystallized at 90℃ for 6 hours. After that, it was placed in a rotary oven at 150℃ and 20 rpm for 200 hours of hydrothermal crystallization. Finally, it was cooled to room temperature with tap water to obtain a crystallization slurry of highly crystalline β-molecular sieve.

[0096] Add appropriate amounts of silicon source silica, tetraethylammonium chloride (structure directing agent SDA, 25wt% aqueous solution) and deionized water to the crystallization slurry to make the molar ratio of silicon source (based on Si content), R+SDA, aluminum source (based on Al content), alkali source (based on OH-) and deionized water in the reaction system 35:14:2; 1.25:500; repeat the above crystallization procedure for secondary crystallization, cool to room temperature with tap water, filter and wash the obtained product, and dry it in an oven at 100℃ for 2 hours to obtain zeolite raw powder.

[0097] Tests were conducted on the raw zeolite powder.

[0098] XRD results showed that the obtained sample exhibited a pure-phase MOR configuration with a relative crystallinity of 81%. SEM and TEM images revealed good microporous crystallinity in this high-silica molecular sieve sample. The Si / Al ratio of this sample was 15.9, and the specific surface area was S0. BET 405m 2 / g, micropore volume V micro It is 0.21cm3 / g.

[0099] Zeolite powder was calcined at 550℃ for 2 hours and then cooled. The zeolite powder was then subjected to ion exchange and a second calcination treatment. Specifically, the calcined zeolite powder and a 1 mol / L ammonium chloride aqueous solution were mixed evenly at a solid-to-liquid ratio of 1:5, and heated in a water bath to 65℃ for 1 hour for ion exchange. The mixture was then filtered and washed with deionized water. This process was repeated four times to obtain a filter cake, which was dried in an oven at 100℃ for 2 hours to obtain NH4. + The molecular sieve was calcined at 520℃ for 3 hours to obtain the hydrogen-type molecular sieve, and the resulting mordenite zeolite was designated GM2. The temperature-programmed ammonia desorption (NH3-TPD) curve showed that the desorption peak temperature of the sample was 450℃.

[0100] Example 3

[0101] A highly crystalline, high-silica mordenite is synthesized as follows:

[0102] First, add KOH and ammonia (K + NH4 + Molar ratio 2) and aluminum isopropoxide are dissolved in deionized water, followed by the addition of tetrapropylammonium bromide (template agent R, 25 wt% aqueous solution), and finally the addition of silicon source trichlorosilane, wherein the silicon source (based on Si content), R, aluminum source (based on Al content), and alkali source (based on OH content) are present. - The molar ratio of ZSM-5 and deionized water was 16:5:2:5:450. After stirring evenly, a milky white gelling solution was obtained. The gelling solution was then placed in a pressure steel autoclave lined with polytetrafluoroethylene and pre-crystallized at 90°C for 6 hours. After that, it was placed in a rotary oven at 150°C and 20 rpm for 160 hours of hydrothermal crystallization. Then, it was cooled to room temperature with tap water to obtain a crystallized slurry of ZSM-5 and mordenite symbiotic molecular sieve.

[0103] Add appropriate amounts of silicon source methyl silicate, tetraethylammonium iodide (structural directing agent SDA, 25wt% aqueous solution), and deionized water to the crystallization slurry to make the reaction system contain silicon source (based on Si content), R+SDA, aluminum source (based on Al content), and alkali source (based on OH content). - The molar ratio of zeolite powder to deionized water was 40:8:2:5:780; the above crystallization procedure was repeated for secondary crystallization, and the product was cooled to room temperature with tap water. The obtained product was filtered, washed, and dried in an oven at 100°C for 2 hours to obtain zeolite powder.

[0104] The zeolite powder was tested, and XRD results showed that the sample exhibited a pure-phase MOR configuration with a relative crystallinity of 87%. SEM and TEM images showed that the high-silica molecular sieve sample displayed good microporous crystallinity. The sample had a Si / Al ratio of 16.5 and a specific surface area of ​​S0.05. BET 435m 2 / g, micropore volume V micro 0.20cm 3 / g.

[0105] The process for preparing mordenite from zeolite powder was as described in Example 1, and the resulting mordenite was designated GM3. The temperature-programmed ammonia desorption (NH3-TPD) curve showed that the peak temperature of the desorption peak was 455℃.

[0106] Example 4

[0107] A highly crystalline, high-silica mordenite is synthesized as follows:

[0108] First, dissolve RbOH and aluminum sec-butoxide in deionized water, then add n-butylamine (template agent R), and finally add the silicon source isobutylenetriethoxysilane. The silicon source (based on Si content), R, the aluminum source (based on Al content), and the alkali source (based on OH content) are all present in the solution. - The molar ratio of α-hydroxyl group (Tf) and deionized water is 20:4:3.5:1.4:900. After stirring evenly, a milky white gelling solution is obtained. The gelling solution is then placed in a pressure steel autoclave lined with polytetrafluoroethylene and pre-crystallized at 90℃ for 6 hours. After that, it is placed in a rotary oven at 150℃ and 20 rpm for 160 hours of hydrothermal crystallization. Then, it is cooled to room temperature with tap water to obtain the crystallization slurry of ZSM-5 molecular sieve.

[0109] Add appropriate amounts of silicon tetrachloride (a silicon source), tetraethylammonium hydroxide (SDA, a structure-directing agent, 25 wt% aqueous solution), and deionized water to the crystallization slurry to make the reaction system contain silicon source (based on Si content), R+SDA, aluminum source (based on Al content), and alkali source (based on OH content). - The molar ratio of zeolite powder to deionized water was 56:5:3.5:2:1400; the above crystallization procedure was repeated for secondary crystallization, and the product was cooled to room temperature with tap water. The obtained product was filtered, washed, and dried in an oven at 100°C for 2 hours to obtain zeolite powder.

[0110] The zeolite powder was tested, and XRD results showed that the sample exhibited a pure-phase MOR configuration with a relative crystallinity of 82%. SEM and TEM images showed that the high-silica molecular sieve sample displayed good microporous crystallinity. The sample had a Si / Al ratio of 15.2 and a specific surface area of ​​S0.05. BET 409m 2 / g, micropore volume V microIt is 0.21cm 3 / g.

[0111] Zeolite powder was calcined at 550℃ for 2 hours and then cooled. The zeolite powder was then subjected to ion exchange and a second calcination treatment. Specifically, the calcined zeolite powder and a 1 mol / L ammonium chloride aqueous solution were mixed evenly at a solid-to-liquid ratio of 1:4 (mass, g) and heated in a water bath to 65℃ for 1 hour for ion exchange. The mixture was then filtered and washed with deionized water. This process was repeated four times to obtain a filter cake. The filter cake was dried in an oven at 100℃ for 2 hours to obtain an NH4+ type molecular sieve, which was then calcined at 520℃ for 3 hours to obtain a hydrogen-type molecular sieve. The resulting mordenite zeolite was designated GM4. The temperature-programmed ammonia desorption NH3-TPD curve showed that the peak temperature of the desorption peak was 515℃.

[0112] Example 5

[0113] A highly crystalline, high-silica mordenite is synthesized using the same method as in Example 1, except that the ethyl silicate added to the slurry is replaced with an equimolar amount (calculated in terms of Si element) of diatomaceous earth.

[0114] Secondary crystallization was performed, and the resulting product was filtered, washed, and dried to obtain molecular sieve powder. The molecular sieve powder was tested, and XRD results showed that the sample exhibited a pure-phase MOR configuration with a relative crystallinity of 78%. SEM and TEM images showed that the molecular sieve sample possessed good microporous crystallinity. The Si / Al ratio was 9.9, and the specific surface area S0 was [missing information]. BET 416m 2 / g, micropore volume V micro It is 0.18cm 3 / g.

[0115] The process for preparing mordenite from zeolite powder was as described in Example 1, and the resulting mordenite was designated GM5. The temperature-programmed ammonia desorption (NH3-TPD) curve showed that the peak temperature of the desorption peak was 450℃.

[0116] Example 6

[0117] A highly crystalline, high-silica mordenite zeolite is synthesized using the same method as in Example 2, except that the silica added to the slurry is replaced with an equimolar amount (calculated in terms of Si element) of silicon powder.

[0118] Secondary crystallization was performed, and the resulting product was filtered, washed, and dried to obtain molecular sieve powder. The molecular sieve powder was tested, and XRD results showed that the sample exhibited a pure-phase MOR configuration with a relative crystallinity of 80%. SEM and TEM images showed that the molecular sieve sample possessed good microporous crystallinity. The Si / Al ratio was 14.6, and the specific surface area S0 was [missing information]. BET401m 2 / g, micropore volume V micro It is 0.17cm 3 / g.

[0119] The process for preparing mordenite from zeolite powder was as described in Example 2, and the resulting mordenite was designated GM6. The temperature-programmed ammonia desorption (NH3-TPD) curve showed that the peak temperature of the desorption peak was 425℃.

[0120] Example 7

[0121] A highly crystalline, high-silica mordenite was synthesized using the same method as in Example 1, except that tetraethylammonium hydroxide was replaced with an equimolar amount of hexamethyleneimine.

[0122] Secondary crystallization was performed, and the resulting product was filtered, washed, and dried to obtain molecular sieve powder. The molecular sieve powder was tested, and XRD results showed that the sample exhibited a pure-phase MOR configuration with a relative crystallinity of 79%. SEM and TEM images showed that the molecular sieve sample possessed good microporous crystallinity. The Si / Al ratio was 15.9, and the specific surface area S0 was [missing information]. BET 428m 2 / g, micropore volume V micro It is 0.19cm 3 / g.

[0123] The process for preparing mordenite from zeolite powder was as described in Example 1, and the resulting mordenite was designated GM7. The temperature-programmed ammonia desorption (NH3-TPD) curve showed that the peak temperature of the desorption peak was 390℃.

[0124] Comparative Example 1

[0125] A type of mordenite zeolite was synthesized using the same method as in Example 1, except that only one feeding was used, and the molar ratio of silicon source (methyl silicate + ethyl silicate, based on Si content), R+SDA, aluminum source (based on Al content), (NaOH and sodium bromide) and deionized water in the reaction system was 66:8:4; 0.75:680, and only one crystallization was used. The resulting mordenite zeolite is denoted as DM1.

[0126] The zeolite powder of this comparative example was tested, and the results showed that it was a pure-phase MOR configuration; the Si / Al ratio was 7, the crystallinity was low, and the specific surface area S BET 195m 2 / g, micropore volume V micro It is 0.11cm 3 / g, with low specific surface area and micropore volume, and irregular large morphology.

[0127] Catalytic performance evaluation

[0128] The mordenite zeolite prepared in each example and comparative example was used as a catalyst, and its catalytic performance was tested.

[0129] The mordenite zeolite prepared in each embodiment and comparative example was shaped into φ1mm×1mm particles; 800g was weighed and stirred evenly with 8g of an active component solution with a mass concentration of 5%, and then allowed to stand and impregnate at room temperature for 12h; then the impregnated mordenite zeolite was transferred to an oven and dried at a temperature of 110℃ for 3h; then the dried mordenite zeolite was calcined in air at a temperature of 500℃ for 3h to obtain a catalyst.

[0130] Each of the above catalysts (5g) was loaded into a stainless steel fixed-bed tubular reactor and reduced with pure hydrogen. The reduction conditions were: hydrogen flow rate 80 mL / min, temperature increased at 2℃ / min to 180℃ and held for 2 h, then increased at 2.5℃ / min to 375℃ and held for 2 h. Trimethylbenzene was then added for selective dealkylation. The products were analyzed by an HP6890 gas chromatograph. Reaction conditions: reaction temperature 375℃, reaction pressure 0.6 MPa, feed weight hourly space velocity (WHSV) 3.35 h⁻¹. -1 The hydrogen-to-oil molar ratio was 3. The statistical results of the online 100-hour reaction are shown in Table 1.

[0131] Activity (conversion rate C) and BTX selectivity (yield of high-quality low-carbon aromatics) were used as performance evaluation indicators for catalysts.

[0132]

[0133] (TMB stands for trimethylbenzene, including 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, and mixtures thereof)

[0134] S BTX = (BTX in the product / Σ product) × 100%

[0135] (B represents benzene, T represents toluene, and X represents xylene)

[0136] Table 1

[0137]

[0138]

[0139] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A type of mordenite zeolite, characterized in that, The mordenite has a Si / Al ratio of 15 < to 20 and a relative crystallinity > 75%. The acid strength is shown as the desorption peak temperature of ammonia desorption under programmed temperature rise >355℃; The specific surface area S of the mordenite zeolite BET ≥400m 2 / g, micropore volume V micro >0.15cm 3 / g.

2. A method for preparing mordenite, characterized in that, include: S1. Obtain a colloid comprising a first silicon source, an aluminum source, an alkali source, a template agent R, and a solvent I; the molar ratio of silicon in the first silicon source to aluminum in the aluminum source is not greater than 15; S2. The colloid is crystallized once to obtain a crystallized slurry; S3. Add a second silicon source and structure directing agent SDA to the crystallization slurry so that the molar ratio of silicon to aluminum in the entire reaction system is greater than 15; S4. Perform secondary crystallization to obtain the mordenite zeolite; Optionally, it also includes S5. The mordenite is first calcined, then ion-exchanged, and then calcined a second time.

3. The preparation method according to claim 2, characterized in that, The molar ratio of silicon in the first silicon source to aluminum in the aluminum source is 5 to 15.

4. The preparation method according to claim 2, characterized in that, The first silicon source and the second silicon source may be the same or different, and each is independently selected from at least one of silicon powder, silicon balls, silica gel, silica sol, sodium silicate, aluminosilicate, silicate ester, silicon tetrachloride, silane, and silica.

5. The preparation method according to claim 4, characterized in that, The second silicon source is selected from at least one of silica gel, silica sol, sodium silicate, aluminosilicate, silicate ester, silicon tetrachloride, silane, and silica.

6. The preparation method according to any one of claims 2-5, characterized in that, The aluminum source includes at least one of aluminum hydroxide, aluminum isopropoxide, aluminum sec-butoxide, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride, and aluminum oxide. And / or, the alkali source includes alkali metal hydroxides and / or ammonia; And / or, the template agent R comprises at least one of ammonia, cyclohexylimine, piperidine, N,N,N-trimethyl-1-adamantylammonium bromide, pyridine, cyclopropylamine, cyclobutylamine, cyclooctylamine, cyclohexylmethylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, n-butylamine, hexamethyleneimine, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, tetrapropylammonium iodide, tetraethylammonium iodide, tetrapropylammonium bromide, tetraethylammonium bromide, tetraethylammonium chloride, or tetramethylammonium chloride; And / or, the solvent I includes at least one of deionized water, alcohol solvents, and imidazole ionic liquids; And / or, the structure-directing agent SDA includes at least one of tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, and tetraethylammonium iodide.

7. The preparation method according to claim 6, characterized in that, The alkali metal includes at least one of Li, Na, K, Rb, and Cs; And / or, the solvent I includes at least one of deionized water, ethanol, isopropanol, glycerol, acetone, and n-butanol.

8. The preparation method according to any one of claims 2-5, characterized in that, The molar ratio of the alkaline source to the silicon element in the first silicon source is: OH - / Si=0.01~1; And / or, the molar ratio of solvent I to silicon in the first silicon source is: I / Si = 5~50; And / or, the molar ratio of the template agent R to the silicon element in the first silicon source is: R / Si = 0.01~0.5; And / or, the molar ratio of the structure directing agent SDA to the sum of silicon elements in the first silicon source and the second silicon source is: SDA / Si = 0.001~0.

5.

9. The preparation method according to any one of claims 2-5, characterized in that, The ion exchange includes ammonium exchange.

10. The preparation method according to claim 9, characterized in that, Ammonium exchange reagents include at least one of ammonium nitrate, ammonium chloride, ammonium oxalate, and ammonium sulfate; And / or, the ammonium exchange is performed at a temperature of 10–120°C for 0.1–1000 h; And / or, the concentration of the ammonium exchange reagent aqueous solution is 0.01~5 mol / L; And / or, the volume-to-mass ratio of the ammonium exchange reagent aqueous solution to mordenite zeolite is 4-10 mL: 1 g.

11. The preparation method according to any one of claims 2-5, characterized in that, The number of ion exchanges is 1 to 20. And / or, after ion exchange, the process involves filtration, washing, and drying, followed by a second calcination. And / or, the stirring speed for the first crystallization is 0~6000 rpm, the crystallization temperature is 80~200℃, and the crystallization time is 2~2000 hours; And / or, the stirring speed for the secondary crystallization is 0~6000 rpm, the crystallization temperature is 80~200℃, and the crystallization time is 2~2000 hours; And / or, after the secondary crystallization, the process further includes filtration, washing, and drying steps; And / or, the temperature of the first calcination is 200–980°C, and the time of the first calcination is 0.1–250 h; And / or, the temperature of the second roasting is 400-650°C, and the time of the second roasting is 1-10 hours.

12. The preparation method according to claim 11, characterized in that, After ion exchange, the drying temperature is 30~200℃; And / or, after the secondary crystallization, the drying temperature is 30~200℃.

13. The application of the mordenite according to claim 1 or the mordenite prepared by any one of claims 2-12 in the conversion of aromatic hydrocarbons.

14. An aromatic hydrocarbon conversion catalyst, characterized in that, The catalyst comprises the mordenite according to claim 1 or the mordenite prepared by any one of claims 2-12.

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