MTW molecular sieves, their preparation methods and applications, and catalyst compositions and their applications.

Abstract

This invention relates to the field of molecular sieve preparation, specifically to an MTW molecular sieve, its preparation method and application, and a catalyst composition and its application. The MTW molecular sieve exhibits a morphology of nanoparticles agglomerated into near-ellipsoidal crystals.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve preparation, specifically to an MTW molecular sieve, its preparation method and application, and a catalyst composition and its application. Background Technology

[0002] Zeolite molecular sieves, due to their unique pore shape selectivity, distinctive solid acid properties, and excellent ion exchange properties, have a wide range of applications, demonstrating significant commercial value in adsorption, separation, and catalysis. For example, in the petroleum refining and chemical industries, the application of Y zeolite has brought about a revolutionary leap in petroleum catalytic cracking technology. Meanwhile, the application of other molecular sieve catalysts, such as ZSM-5 zeolite, mordenite, β-zeolite, MCM-22 zeolite, and SAPO-34 molecular sieves, has also brought substantial breakthroughs to important petroleum refining and chemical technologies such as cracking, reforming, isomerization, aromatic disproportionation and alkylation, and methanol conversion. Therefore, given the important role of molecular sieves in many industrial fields, research on new molecular sieves and novel synthetic methods has been abundant in literature and patents.

[0003] MTW-type molecular sieves possess one-dimensional twelve-membered ring (0.57nm × 0.61nm) straight channels, exhibiting high acid resistance, good thermal stability, and hydrothermal stability. They are a type of high-silica molecular sieve, with ZSM-12 molecular sieve being a typical example. MTW-type molecular sieves have a pore size between mesoporous and macroporous zeolites, enabling effective catalytic conversion of most organic molecules. They demonstrate excellent catalytic performance in hydrocarbon cracking, isomerization, dehydration, and reforming reactions, showing promising application prospects in the catalytic conversion of heavy components and large-molecule feedstocks in petroleum refining and chemical industries.

[0004] Methyltriethylammonium bromide is a common organic structure directing agent for the synthesis of ZSM-12 molecular sieves, but the synthesized ZSM-12 molecular sieves are generally rod-shaped or block-shaped with large crystal sizes, only reaching the micrometer scale.

[0005] CN106587102B discloses a method for synthesizing ZSM-12 type zeolite molecular sieves, which uses a gemini quaternary ammonium salt or quaternary ammonium base containing a benzene ring as an organic structure directing agent, thus solving the problem of excessive impurities in the synthesized ZSM-12 type zeolite molecular sieves.

[0006] CN112939009A discloses a solid-phase synthesis method for MTW-type molecular sieves, which involves mixing silica and sodium aluminate and calcining them at a certain temperature for a period of time to obtain a silica-alumina precursor; then mixing the silica-alumina precursor with an alkali source and an organic amine solution to obtain a solid mixture; and finally crystallizing the solid mixture at a certain temperature to obtain the MTW-type molecular sieve.

[0007] CN112939017A discloses a method for synthesizing MTW-type molecular sieves. The method involves mixing silica, sodium aluminate, alkali source, and seed crystals evenly, transferring the mixture into a reaction vessel, and heating it at a certain temperature for a period of time to obtain a silica-alumina precursor. Then, a template agent solution and a surfactant are added to the reaction vessel containing the precursor, and the mixture is crystallized at a certain temperature. This method is similar to a solid-phase synthesis method.

[0008] Different molecular sieve morphologies can significantly affect catalytic performance, making the regulation of MTW-type molecular sieve morphology of great importance.

[0009] CN103435065B discloses a method for preparing nano ZSM-12 molecular sieves. The method uses tetraethylammonium bromide as an organic structure directing agent. First, pre-crystallized seed crystals are prepared, and then the pre-crystallized seed crystals are added to a newly prepared mixed gel for crystallization.

[0010] CN106698465B discloses a method for preparing nano-ZSM-12 molecular sieves. The preparation method involves first mixing raw materials to obtain a gel, then mixing the gel with macroporous carbon and ultrasonically treating it, then completely evaporating the water, and finally loading it into a reactor and adding a certain amount of water to carry out a crystallization reaction in a closed reactor to obtain nano-ZSM-12 molecular sieves. The particle size of the synthesized nanocrystals is close to 100 nm.

[0011] The methods described above for preparing MTW molecular sieves employ expensive organic structure-directing agents, and the resulting MTW molecular sieves typically have crystallites larger than 80 nm. Furthermore, the synthesis steps are often quite complex. Therefore, developing a simple and efficient MTW molecular sieve synthesis technique that combines the high activity of nano-zeolites with easily separable micron-sized crystalline products is essential and will facilitate its industrial application. Summary of the Invention

[0012] The purpose of this invention is to overcome the problems of large crystal size, complex preparation and low activity of existing MTW molecular sieves, and to provide an MTW molecular sieve, its preparation method and application, and a catalyst composition and its application. This MTW molecular sieve has the characteristics of small crystal size, simple preparation method and high activity.

[0013] To achieve the above objectives, the first aspect of the present invention provides an MTW molecular sieve having a morphology of nanoparticles agglomerated into quasi-ellipsoidal crystals.

[0014] A second aspect of the present invention provides the application of the MTW molecular sieve described herein in the preparation of adsorbents or catalysts for the conversion of organic compounds.

[0015] A third aspect of this invention provides a method for preparing the MTW molecular sieve described herein. The method includes mixing a silicon source, sodium aluminate, sodium hydroxide, an organic structure directing agent, and water, followed by crystallization, solid-liquid separation, washing, drying, and optionally ammonium exchange and calcination to obtain the MTW molecular sieve. The sodium aluminate contains 35%-43% Al₂O₃ by weight and 25%-33% Na₂O by weight. The organic structure directing agent is selected from at least one of dimethyldiethylammonium hydroxide, dimethyldiethylammonium chloride, and dimethyldiethylammonium iodide. The molar ratio of the silicon source (SiO₂), sodium aluminate (Al₂O₃), sodium hydroxide, organic structure directing agent, and water is 1:0.008-0.020:0.07-0.14:0.13-0.26:10-50.

[0016] A fourth aspect of the present invention provides a catalyst composition in which the active component comprises the MTW molecular sieve described in the present invention.

[0017] The fifth aspect of the present invention provides the application of the catalyst composition of the present invention in the preparation of a catalyst for the cumene cracking reaction.

[0018] Through the above technical solution, the present invention has the following beneficial effects:

[0019] The MTW molecular sieve provided by this invention, comprising a morphology of nanoparticles agglomerated into near-ellipsoidal crystals, exhibits high activity. This invention also provides a simple and feasible method for preparing MTW molecular sieves, eliminating the need for seed crystals and segmented crystallization, and resulting in well-crystallized MTW molecular sieves. Attached Figure Description

[0020] Figure 1 The X-ray diffraction (XRD) pattern of the sample in Example 1;

[0021] Figure 2 The image shown is a scanning electron microscope (SEM) image of the sample in Example 1.

[0022] Figure 3 The X-ray diffraction (XRD) pattern of the sample in Example 2;

[0023] Figure 4 The image shown is a scanning electron microscope (SEM) image of the sample in Example 2.

[0024] Figure 5 The X-ray diffraction (XRD) pattern of the sample in Example 3;

[0025] Figure 6 The image shown is a scanning electron microscope (SEM) image of the sample in Example 3.

[0026] Figure 7 The X-ray diffraction (XRD) pattern of the sample in Example 7;

[0027] Figure 8 The image shown is a scanning electron microscope (SEM) image of the sample in Example 7.

[0028] Figure 9 The X-ray diffraction (XRD) pattern of the sample in Comparative Example 1 is shown.

[0029] Figure 10 The image shows a scanning electron microscope (SEM) image of the sample in Comparative Example 2.

[0030] Figure 11 The image shows the X-ray diffraction (XRD) pattern of the sample in Comparative Example 3. Detailed Implementation

[0031] 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.

[0032] The first aspect of the present invention provides an MTW molecular sieve having a morphology of nanoparticles agglomerated into quasi-ellipsoidal crystals.

[0033] The MTW molecular sieve provided by this invention, which has a morphology of nanoparticles agglomerated into quasi-ellipsoidal crystals, exhibits high activity.

[0034] According to a preferred embodiment of the present invention, the length of the quasi-ellipsoidal crystal is 150-850 nm, preferably 200-800 nm.

[0035] According to a preferred embodiment of the present invention, the width of the quasi-ellipsoidal crystal is 100-700 nm, preferably 150-600 nm.

[0036] According to a preferred embodiment of the present invention, the size of the nanoparticles is 20-60 nm, preferably 20-50 nm.

[0037] According to a preferred embodiment of the present invention, the aspect ratio of the quasi-ellipsoidal crystal is 1.1-2.5, preferably 1.2-2.2.

[0038] According to a preferred embodiment of the present invention, the number of nanoparticles with a size not exceeding 50 nm accounts for at least 60% of the total number of nanoparticles, preferably 65-90%.

[0039] According to a preferred embodiment of the present invention, the silicon-aluminum molar ratio (SiO2 / Al2O3) of the MTW molecular sieve is 50-120.

[0040] According to a preferred embodiment of the present invention, the total specific surface area of ​​the MTW molecular sieve is not less than 300 m². 2 / gram, preferably 300-450 meters 2 / gram.

[0041] According to a preferred embodiment of the present invention, the external specific surface area of ​​the MTW molecular sieve is not less than 40 m². 2 / gram, preferably 40-100 meters 2 / gram.

[0042] According to a preferred embodiment of the present invention, the total pore volume of the MTW molecular sieve is not less than 0.30 cm³. 3 / gram, preferably 0.30-0.60 cm 3 / gram.

[0043] According to a preferred embodiment of the present invention, the micropore volume of the MTW molecular sieve is not less than 0.10 cm³. 3 / gram, preferably 0.10-0.20 cm 3 / gram.

[0044] The MTW molecular sieve having the aforementioned preferred features of the present invention has higher activity.

[0045] According to a preferred embodiment of the present invention, the total acid content of the MTW molecular sieve is not less than 300 μmol / g, preferably 300-800 μmol / g. By adopting the aforementioned preferred embodiment, the activity of the MTW molecular sieve can be further improved. In the present invention, the acid content corresponding to a desorption temperature higher than 300°C is considered to be the acid content of a strong acid.

[0046] According to a preferred embodiment of the present invention, the strong acid content of the MTW molecular sieve is not less than 150 μmol / g, preferably 150-300 μmol / g. By adopting the aforementioned preferred embodiment, the activity of the MTW molecular sieve can be further improved.

[0047] The molecular sieve of this invention can be used in any physical form, such as powder, granules, or molded products (e.g., strips, clover shapes, etc.). These physical forms can be obtained in any manner conventionally known in the art, without particular limitation.

[0048] A second aspect of the present invention provides the application of the MTW molecular sieve described herein in the preparation of adsorbents or catalysts for the conversion of organic compounds.

[0049] A third aspect of this invention provides a method for preparing the MTW molecular sieve described herein. The method includes mixing a silicon source, sodium aluminate, sodium hydroxide, an organic structure directing agent, and water, followed by crystallization, solid-liquid separation, washing, drying, and optionally ammonium exchange and calcination to obtain the MTW molecular sieve. The sodium aluminate contains 35%-43% Al₂O₃ by weight, preferably 38%-43%, and 25%-33% Na₂O by weight, preferably 28%-33%. The organic structure directing agent is selected from at least one of dimethyldiethylammonium hydroxide, dimethyldiethylammonium chloride, and dimethyldiethylammonium iodide. The molar ratio of the silicon source (SiO₂), sodium aluminate (Al₂O₃), sodium hydroxide, organic structure directing agent, and water is 1:0.008-0.020:0.07-0.14:0.13-0.26:10-50.

[0050] Molecular sieves are prepared by means of the present invention. This method uses inexpensive and simple dimethyldiethylammonium ions as organic structure directing agents for direct synthesis. No seed crystals or segmented crystallization are required. It has the advantages of low cost, simple preparation, and high yield. Moreover, the prepared MTW molecular sieve has the aforementioned characteristics of the present invention, with adjustable acidity and high activity.

[0051] According to a preferred embodiment of the present invention, the yield of the MTW molecular sieve product is not less than 85%.

[0052] According to a preferred embodiment of the present invention, the MTW molecular sieve does not contain bromine.

[0053] According to a preferred embodiment of the present invention, the organic structure directing agent is dimethyldiethylammonium hydroxide. By employing the aforementioned preferred embodiment, the activity of the prepared molecular sieve can be further improved.

[0054] In this invention, the silicon source can be a conventional choice in the art. According to a preferred embodiment of the invention, the silicon source is silica sol.

[0055] In this invention, the methods and conditions for crystallization, solid-liquid separation, washing, drying, calcination, and ammonium exchange can be conventional choices in the field.

[0056] According to a preferred embodiment of the present invention, the crystallization conditions include: a crystallization temperature of 140-190°C, preferably 150-180°C; and / or a crystallization time of 1.0-9.0 days, preferably 1.5-8.0 days.

[0057] According to a preferred embodiment of the present invention, the crystallization process is dynamic crystallization by rotation or stirring, with a rotation speed of 10-60 rpm and a stirring speed of 30-300 rpm.

[0058] According to a preferred embodiment of the present invention, the solid-liquid separation can be filtration, specifically such as vacuum filtration.

[0059] According to a preferred embodiment of the present invention, the washing method may be selected from washing with deionized water and / or ethanol.

[0060] According to a preferred embodiment of the present invention, the drying conditions include: a drying temperature of 40-250°C, preferably 60-150°C; and / or a drying time of 8-30 hours, preferably 10-20 hours.

[0061] According to a preferred embodiment of the present invention, the drying can be carried out under normal pressure or under reduced pressure.

[0062] According to a preferred embodiment of the present invention, the calcination conditions include: a calcination temperature of 300-800℃, preferably 400-650℃; and / or a calcination time of 1-10h, preferably 3-6h.

[0063] According to a preferred embodiment of the present invention, the roasting is generally carried out in an oxygen-containing atmosphere, such as air or oxygen atmosphere.

[0064] According to a preferred embodiment of the present invention, the conditions for ammonium exchange include: the concentration of ammonium ions in the ammonium salt solution is 0.1-1 mol / L, the solid-liquid ratio is 1:5-1:20, the ammonium exchange temperature is 30-80℃, and the ammonium exchange time is 1-8 hours; preferably, the number of ammonium exchanges is 1-2 times, and the ammonium salt is selected from at least one of ammonium chloride, ammonium nitrate, ammonium carbonate, and ammonium sulfate.

[0065] A fourth aspect of the present invention provides a catalyst composition in which the active component comprises the MTW molecular sieve described in the present invention.

[0066] The fifth aspect of the present invention provides the application of the catalyst composition of the present invention in the preparation of a catalyst for the cumene cracking reaction.

[0067] The present invention will be described in detail below through embodiments. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0068] In the context of this specification, the structure of MTW molecular sieves is determined by X-ray diffraction (XRD), which is measured using an X-ray powder diffractometer with a Cu-Kα ray source and a nickel filter. Before sample testing, the crystallinity of the molecular sieve samples is observed using a scanning electron microscope (SEM) to confirm that the samples contain only one type of crystal, i.e., the molecular sieve samples are pure phases. XRD testing is then performed to ensure that there are no interfering peaks from other crystals in the diffraction patterns of the XRD patterns.

[0069] In the context of this specification, including in the following examples and comparative examples, the X-ray powder diffractometer used for the molecular sieves is a Panalytical X-PERPRO type X-ray powder diffractometer, used to analyze the phase composition of the samples, and a CuKα ray source. Nickel filter, 2θ scanning range 2-50°, operating voltage 40KV, current 40mA, scanning rate 10° / min.

[0070] In the context of this specification, including in the following examples and comparative examples, the scanning electron microscope (SEM) used for the molecular sieves is a model S-4800II field emission scanning electron microscope. The molecular sieves were observed using this SEM at a magnification of 40,000x. A randomly selected field of view was used to calculate the average sum of the particle sizes of all nanocrystals within that field of view. This operation was repeated 10 times, and the average sum of the 10 averages was taken as the size of the nanoparticles. Using the same method, the average length of the major axis of the nanocrystals agglomerated into ellipsoidal particles within the field of view was measured as the crystal length, and the average length of the minor axis was taken as the crystal width. Crystals with a particle size no greater than 100 nm were used as the statistical object, and the percentage of crystals with a particle size no greater than 50 nm was counted. This operation was repeated 5 times, and the average of the 5 counts was taken as the percentage of crystals with a particle size no greater than 50 nm.

[0071] In the context of this specification, including in the following examples and comparative examples, the micropore size, pore volume, specific surface area, and external specific surface area of ​​the molecular sieve were measured by the nitrogen physical adsorption-desorption method (BET method): the nitrogen physical adsorption-desorption isotherm of the molecular sieve was measured using a Micromeretic ASAP2020M physical adsorption instrument, and then calculated using the BET equation and t-plot equation. The experimental conditions for this molecular sieve were: measurement temperature -196℃, and before measurement, the molecular sieve was heat-treated at 550℃ in air for 6 hours, followed by pretreatment in vacuum at 350℃ for 4 hours.

[0072] In the context of this specification, including in the following examples and comparative examples, the molecular sieve was analyzed using an inductively coupled plasma atomic emission spectrometer (ICP) model Varian 725-ES, and the elemental content, in molar terms, was determined by dissolving the analytical sample in hydrofluoric acid.

[0073] In the context of this specification, including in the following examples and comparative examples, the acid content of the molecular sieves was determined using an Altamira AMI-3300 instrument for NH3-TPD chemisorption-desorption curve analysis. Before testing, the samples were activated at 550°C for 1 hour, ammonia was adsorbed at 100°C for 20 minutes, and then desorbed and detected at 100-600°C. Quantitative analysis was performed using a quantitative cyclic pulse of ammonia to determine the peak area. Peaks were then separated using a Gaussian distribution, and the acid content corresponding to desorption temperatures above 300°C was considered the acid content of a strong acid.

[0074] In the context of this specification, including in the following examples and comparative examples, the yield of molecular sieves refers to the percentage of the mass of the calcined sample relative to the sum of the masses of SiO2 and Al2O3 contained in the raw material.

[0075] In the context of this specification, including in the following examples and comparative examples, the catalyst is applied to the cumene cracking reaction:

[0076] The cumene cracking reaction uses cumene as a raw material and cracks it into products such as propylene and benzene under the action of a catalyst.

[0077] The conversion rate of cumene is % = (molar amount of cumene in the feed - molar amount of cumene in the product) / (molar amount of cumene in the feed) × 100%.

[0078] Selectivity of benzene % = (molar amount of benzene in the product) / (total molar amount of aromatics in the product) × 100%;

[0079] The aromatic hydrocarbons in the products do not include the raw material cumene.

[0080] Example 1

[0081] A mixture was prepared by stirring 4.94 g of deionized water, 0.195 g of sodium aluminate (containing 40.5 wt% Al₂O₃ and 30.6 wt% Na₂O), 0.225 g of sodium hydroxide, 5.32 g of dimethyl diethyl ammonium hydroxide solution (containing 25.00 wt% dimethyl diethyl ammonium hydroxide) (organic structure directing agent R), and 9.31 g of silica sol (containing 40.0 wt% SiO₂) at room temperature for 3 hours. The final material ratio (molar ratio) was as follows:

[0082] SiO2 / Al2O3 = 80;

[0083] NaOH / SiO2 = 0.12;

[0084] R / SiO2 = 0.18;

[0085] H2O / SiO2 = 13.

[0086] The mixture was placed in a stainless steel reactor and heated at 175°C and 20 rpm for 1.5 days to crystallize. After crystallization, the mixture was filtered, washed, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours. The XRD pattern of the product is shown below. Figure 1 The image shows a molecular sieve with an MTW structure. The yield of the molecular sieve was 90 wt%. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 79.7 using inductively coupled plasma atomic emission spectrometry (ICP). The SEM image of the sample is shown below. Figure 2 The image shows the morphology of nanoparticles agglomerated into ellipsoidal crystals. The crystal length is 220 nm, the nanoparticle size is 25 nm, the width is 170 nm, the aspect ratio is 1.3, and nanoparticles with a size not exceeding 50 nm account for 70% of the total. The specific surface area of ​​the molecular sieve is 366 m². 2 / gram, with an external specific surface area of ​​54 m² measured by the BET method. 2 / g; Total pore volume 0.47cm 3 / gram, micropore volume is 0.13 cm³ 3 / g. Sodium-type nano-MTW molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 65℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 4 hours to obtain hydrogen-type nano-MTW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 561 μmol / g, and the strong acid content was 229 μmol / g.

[0087] Example 2

[0088] A mixture was prepared by stirring 7.56 g of deionized water, 0.175 g of sodium aluminate (containing 40.5 wt% Al₂O₃ and 30.6 wt% Na₂O), 0.158 g of sodium hydroxide, 6.64 g of dimethyl diethyl ammonium hydroxide solution (containing 25.00 wt% dimethyl diethyl ammonium hydroxide), and 10.46 g of silica sol (containing 40.0 wt% SiO₂) at room temperature for 3 hours. The final material ratio (molar ratio) was as follows:

[0089] SiO2 / Al2O3 = 100;

[0090] NaOH / SiO2 = 0.08;

[0091] R / SiO2 = 0.20;

[0092] H2O / SiO2 = 15.

[0093] The mixture was placed in a stainless steel reactor and heated at 165°C and 15 rpm for 3.5 days to crystallize. After crystallization, the mixture was filtered, washed, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours. The XRD pattern of the product is shown below. Figure 3 The image shows a molecular sieve with an MTW structure. The yield of the molecular sieve was 86 wt%. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 101.1 using inductively coupled plasma atomic emission spectrometry (ICP). The SEM image of the sample is shown below. Figure 4 The image shows the morphology of nanoparticles agglomerated into ellipsoidal crystals. The crystal length is 320 nm, the width is 240 nm, and the aspect ratio is 1.3. The nanoparticle size is 30 nm, and nanoparticles with a size not exceeding 50 nm account for 70% of the total. The specific surface area of ​​the molecular sieve is 348 m². 2 / gram, with an external specific surface area of ​​49 m² measured by the BET method. 2 / g; Total pore volume 0.50cm 3 / gram, micropore volume is 0.13 cm³ 3 / g. Sodium-type nano-MTW molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 65℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 4 hours to obtain hydrogen-type nano-MTW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 336 μmol / g, and the strong acid content was 170 μmol / g.

[0094] Example 3

[0095] A mixture was prepared by stirring 46.62 g of deionized water, 0.392 g of sodium aluminate (containing 40.5 wt% Al₂O₃ and 30.6 wt% Na₂O), 0.334 g of sodium hydroxide, 9.80 g of dimethyl diethyl ammonium hydroxide solution (containing 25.00 wt% dimethyl diethyl ammonium hydroxide), and 12.86 g of silica sol (containing 40.0 wt% SiO₂) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0096] SiO2 / Al2O3 = 55;

[0097] NaOH / SiO2 = 0.14;

[0098] R / SiO2 = 0.24;

[0099] H2O / SiO2 = 40.

[0100] The mixture was placed in a stainless steel reactor and heated at 155°C and 10 rpm for 6 days to crystallize. After crystallization, the mixture was filtered, washed, dried overnight in a 100°C oven, and then calcined in air at 550°C for 6 hours. The XRD pattern of the product is shown below. Figure 5 The image shows a molecular sieve with an MTW structure. The yield of the molecular sieve was 92 wt%. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 56.0 using inductively coupled plasma atomic emission spectrometry (ICP). The SEM image of the sample is shown below. Figure 6 The image shows the morphology of nanoparticles agglomerated into ellipsoidal crystals. The crystal length is 620 nm, the width is 480 nm, the aspect ratio is 1.3, and the nanoparticle size is 50 nm. Nanoparticles with a size not exceeding 50 nm account for 75% of the total count. The specific surface area of ​​the molecular sieve is 361 m². 2 / gram, with an external specific surface area of ​​47 m² measured by the BET method. 2 / g; Total pore volume 0.44cm 3 / gram, micropore volume is 0.13 cm³ 3 / g. Sodium-type nano-MTW molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 65℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 4 hours to obtain hydrogen-type nano-MTW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 768 μmol / g, and the strong acid content was 277 μmol / g.

[0101] Example 4

[0102] A mixture was prepared by stirring 14.95 g of deionized water, 0.218 g of sodium aluminate (containing 40.5 wt% Al₂O₃ and 30.6 wt% Na₂O), 0.231 g of sodium hydroxide, 8.16 g of dimethyldiethylammonium chloride solution (containing 25.00 wt% dimethyldiethylammonium chloride), and 11.71 g of silica sol (containing 40.0 wt% SiO₂) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0103] SiO2 / Al2O3 = 90;

[0104] NaOH / SiO2 = 0.10;

[0105] R / SiO2 = 0.19;

[0106] H2O / SiO2 = 20.

[0107] The mixture was placed in a stainless steel reactor and heated to crystallize at 165°C and 50 rpm for 3 days. After crystallization, it was filtered, washed, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours. The XRD pattern of the product obtained was similar to... Figure 1 Similarly, this is a molecular sieve with an MTW structure. The yield of the molecular sieve is 91 wt%. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 89.6 using inductively coupled plasma atomic emission spectrometry (ICP). The SEM image of the sample is similar to... Figure 2 Similarly, the morphology of nanoparticles agglomerated into ellipsoidal crystals is shown, with a crystal length of 300 nm, a width of 170 nm, an aspect ratio of 1.8, and a nanoparticle size of 25 nm. Nanoparticles with a size not exceeding 50 nm account for 65% of the total count. The specific surface area of ​​the molecular sieve is 403 m². 2 / gram, with an external specific surface area of ​​66 m² measured by the BET method. 2 / g; Total pore volume 0.43cm 3 / gram, micropore volume is 0.13 cm³ 3 / g. Sodium-type nano-MTW molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 65℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 4 hours to obtain hydrogen-type nano-MTW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 454 μmol / g, and the strong acid content was 204 μmol / g.

[0108] Example 5

[0109] A mixture was prepared by stirring 30.26 g of deionized water, 0.356 g of sodium aluminate (containing 40.5 wt% Al₂O₃ and 30.6 wt% Na₂O), 0.309 g of sodium hydroxide, 6.54 g of dimethyldiethylammonium chloride solution (containing 25.00 wt% dimethyldiethylammonium chloride), and 12.75 g of silica sol (containing 40.0 wt% SiO₂) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0110] SiO2 / Al2O3 = 60;

[0111] NaOH / SiO2 = 0.13;

[0112] R / SiO2 = 0.14;

[0113] H2O / SiO2 = 28.

[0114] The mixture was placed in a stainless steel reactor and heated to crystallize at 175°C and 15 rpm for 2 days. After crystallization, it was filtered, washed, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours. The XRD pattern of the product obtained was similar to... Figure 1 Similarly, this is a molecular sieve with an MTW structure. The yield of the molecular sieve is 89 wt%. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 60.6 using inductively coupled plasma atomic emission spectrometry (ICP). The SEM image of the sample is similar to... Figure 2 Similarly, the morphology of nanoparticles agglomerated into ellipsoidal crystals is shown, with a crystal length of 440 nm, a width of 260 nm, an aspect ratio of 1.7, and a nanoparticle size of 30 nm. Nanoparticles with a size not exceeding 50 nm account for 65% of the total count. The specific surface area of ​​the molecular sieve is 342 m². 2 / gram, with an external specific surface area of ​​53 m² measured by the BET method. 2 / g; Total pore volume 0.36cm 3 / gram, micropore volume is 0.14 cm³ 3 / g. Sodium-type nano-MTW molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 65℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 4 hours to obtain hydrogen-type nano-MTW molecular sieve. NH3-TPD analysis showed that the total acid content of the molecular sieve was 750 μmol / g, and the strong acid content was 263 μmol / g.

[0115] Example 6

[0116] A mixture was prepared by stirring 34.49 g of deionized water, 0.265 g of sodium aluminate (containing 40.5 wt% Al₂O₃ and 30.6 wt% Na₂O), 0.204 g of sodium hydroxide, 10.83 g of dimethyl diethyl ammonium hydroxide solution (containing 25.00 wt% dimethyl diethyl ammonium hydroxide), and 14.21 g of silica sol (containing 40.0 wt% SiO₂) at room temperature for 3 hours. The final material ratio (molar ratio) was as follows:

[0117] SiO2 / Al2O3 = 90;

[0118] NaOH / SiO2 = 0.08;

[0119] R / SiO2 = 0.24;

[0120] H2O / SiO2 = 30.

[0121] The mixture was placed in a stainless steel reactor and heated to crystallize at 160°C and 40 rpm for 4 days. After crystallization, it was filtered, washed, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours. The XRD pattern of the product obtained was similar to... Figure 1 Similarly, this is a molecular sieve with an MTW structure. The yield of the molecular sieve is 88 wt%. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 91.2 using inductively coupled plasma atomic emission spectrometry (ICP). The SEM image of the sample is similar to... Figure 8 Similarly, the morphology of nanoparticles agglomerated into ellipsoidal crystals is shown, with a crystal length of 560 nm, a width of 330 nm, an aspect ratio of 1.7, and a nanoparticle size of 35 nm. Nanoparticles with a size not exceeding 50 nm account for 75% of the total count. The specific surface area of ​​the molecular sieve is 395 m². 2 / gram, with an external specific surface area of ​​42 m² measured by the BET method. 2 / g; Total pore volume 0.38cm 3 / gram, micropore volume is 0.13 cm³ 3 / g. Sodium-type nano-MTW molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 65℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 4 hours to obtain hydrogen-type nano-MTW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 445 μmol / g, and the strong acid content was 192 μmol / g.

[0122] Example 7

[0123] A mixture was prepared by stirring 15.38 g of deionized water, 0.357 g of sodium aluminate (containing 40.5 wt% Al₂O₃ and 30.6 wt% Na₂O), 0.208 g of sodium hydroxide, 6.09 g of dimethyl diethyl ammonium hydroxide solution (containing 25.00 wt% dimethyl diethyl ammonium hydroxide), and 12.79 g of silica sol (containing 40.0 wt% SiO₂) at room temperature for 3 hours. The final material ratio (molar ratio) was as follows:

[0124] SiO2 / Al2O3 = 60;

[0125] NaOH / SiO2 = 0.10;

[0126] R / SiO2 = 0.15;

[0127] H2O / SiO2 = 18.

[0128] The mixture was placed in a stainless steel reactor and heated at 170°C and 20 rpm for 3 days to crystallize. After crystallization, the mixture was filtered, washed, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours. The XRD pattern of the product is shown below. Figure 7 The image shows a molecular sieve with an MTW structure. The yield of the molecular sieve was 87 wt%. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 60.3 using inductively coupled plasma atomic emission spectrometry (ICP). The SEM image of the sample is shown below. Figure 8 The image shows the morphology of nanoparticles agglomerated into ellipsoidal crystals. The crystal length is 240 nm, the width is 120 nm, the aspect ratio is 2.0, and the nanoparticle size is 30 nm. Nanoparticles with a size not exceeding 50 nm account for 75% of the total. The specific surface area of ​​the molecular sieve is 378 m². 2 / gram, with an external specific surface area of ​​62 m² measured by the BET method. 2 / g; Total pore volume 0.53cm 3 / gram, micropore volume is 0.14 cm³ 3 / g. Sodium-type nano-MTW molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 65℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 4 hours to obtain hydrogen-type nano-MTW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 743 μmol / g, and the strong acid content was 268 μmol / g.

[0129] Example 8

[0130] A mixture was prepared by stirring 44.70 g of deionized water, 0.297 g of sodium aluminate (containing 40.5 wt% Al₂O₃ and 30.6 wt% Na₂O), 0.191 g of sodium hydroxide, 6.33 g of dimethyl diethyl ammonium hydroxide solution (containing 25.00 wt% dimethyl diethyl ammonium hydroxide), and 13.30 g of silica sol (containing 40.0 wt% SiO₂) at room temperature for 3 hours. The final material ratio (molar ratio) was:

[0131] SiO2 / Al2O3 = 75;

[0132] NaOH / SiO2 = 0.085;

[0133] R / SiO2 = 0.15;

[0134] H2O / SiO2 = 36.

[0135] The mixture was placed in a stainless steel reactor and heated at 160°C and 25 rpm for 4.5 days to crystallize. After crystallization, it was filtered, washed, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours. The XRD pattern of the product obtained was similar to... Figure 1 Similarly, this is a molecular sieve with an MTW structure. The yield of the molecular sieve is 89 wt%. The SiO2 / Al2O3 molar ratio of the molecular sieve was determined to be 75.5 using inductively coupled plasma atomic emission spectrometry (ICP). The SEM image of the sample is similar to... Figure 2 Similarly, the morphology of nanoparticles agglomerated into ellipsoidal crystals is shown, with a crystal length of 380 nm, a width of 200 nm, an aspect ratio of 1.9, and a nanoparticle size of 45 nm. Nanoparticles with a size not exceeding 50 nm account for 65% of the total count. The specific surface area of ​​the molecular sieve is 332 m². 2 / gram, with an external specific surface area of ​​55 m² measured by the BET method. 2 / g; Total pore volume 0.59cm 3 / gram, micropore volume is 0.12 cm³ 3 / g. Sodium-type nano-MTW molecular sieve was subjected to ammonium ion exchange with 0.2 mol / L NH4NO3 solution (mass ratio 1:20) at 65℃ for 2 hours, followed by centrifugation and washing. The ammonium ion exchange was repeated twice. The resulting sample was dried overnight at 100℃ and calcined in air at 550℃ for 4 hours to obtain hydrogen-type nano-MTW molecular sieve sample. NH3-TPD analysis showed that the total acid content of the molecular sieve was 589 μmol / g, and the strong acid content was 239 μmol / g.

[0136] Comparative Example 1

[0137] Same as Example 7, except that more aluminum source is added, and the final material ratio (molar ratio) is:

[0138] SiO2 / Al2O3 = 30;

[0139] NaOH / SiO2 = 0.10;

[0140] R / SiO2 = 0.15;

[0141] H2O / SiO2 = 18.

[0142] Other conditions are the same as in Example 7, and the XRD pattern of the obtained product is as follows. Figure 9 As shown, it has not crystallized and is an amorphous substance, not an MTW molecular sieve.

[0143] Comparative Example 2

[0144] Same as Example 7, except that the content of Al2O3 and Na2O in the added sodium aluminate is different. The sodium aluminate composition is 50.6% by weight of Al2O3 and 45.2% by weight of Na2O. The raw materials are prepared in the same amount of substances, and the final material ratio (molar ratio) is:

[0145] SiO2 / Al2O3 = 60;

[0146] NaOH / SiO2 = 0.10;

[0147] R / SiO2 = 0.15;

[0148] H2O / SiO2 = 18.

[0149] Other conditions are the same as in Example 7, and the XRD pattern of the obtained product is... Figure 7 Similarly, for MTW molecular sieves, the SEM image of the sample is as follows: Figure 10 As shown, it has a rod-like morphology, not the morphology of nanoparticles agglomerated into ellipsoidal crystals.

[0150] Comparative Example 3

[0151] Same as Example 7, except that tetraethylammonium hydroxide is added as the organic structure directing agent R, and the final material ratio (molar ratio) is:

[0152] SiO2 / Al2O3 = 60;

[0153] NaOH / SiO2 = 0.10;

[0154] R / SiO2 = 0.15;

[0155] H2O / SiO2 = 18.

[0156] Other conditions are the same as in Example 7, and the XRD pattern of the obtained product is as follows. Figure 11 The image shows a MOR molecular sieve, not an MTW molecular sieve.

[0157] Comparative Example 4

[0158] Same as Example 7, except that methyltriethylammonium bromide is added as the organic structure directing agent R, and the final material ratio (molar ratio) is:

[0159] SiO2 / Al2O3 = 60;

[0160] NaOH / SiO2 = 0.10;

[0161] R / SiO2 = 0.15;

[0162] H2O / SiO2 = 18.

[0163] Other conditions are the same as in Example 7, and the XRD pattern of the obtained product is... Figure 7 Similarly, for MTW molecular sieves, the SEM image of the sample is similar to... Figure 10 Similarly, it has a rod-shaped morphology, not the morphology of nanoparticles agglomerated into ellipsoidal crystals.

[0164] Comparative Example 5

[0165] Same as Example 7, except that Al2O3 and Na2O are added separately, and the raw materials are prepared in the same amount of each substance. The final material ratio (molar ratio) is:

[0166] SiO2 / Al2O3 = 60;

[0167] NaOH / SiO2 = 0.16;

[0168] R / SiO2 = 0.10;

[0169] H2O / SiO2 = 18.

[0170] Other conditions are the same as in Example 7, and the XRD pattern of the obtained product is... Figure 9 Similarly, it did not crystallize and is an amorphous substance, not an MTW molecular sieve.

[0171] Examples 9-16

[0172] The hydrogen-form MTW molecular sieve powder samples synthesized in Examples 1-8 were crushed, and 0.5 g of the 20-40 mesh particle size fraction was sieved and placed into a fixed-bed reactor for cumene pyrolysis. The reaction conditions were: reaction temperature 270-350℃, reaction pressure atmospheric pressure, and cumene weight hourly space velocity 3-6 h⁻¹. -1 The specific reaction conditions for each embodiment are shown in Table 1. The products, catalyst activity, and product selectivity were analyzed using an Agilent GC-8890 gas chromatograph, as shown in Table 1.

[0173] Comparative Examples 6-7

[0174] Similar to Examples 9-16, the hydrogen-type molecular sieves obtained by ammonium exchange treatment of the molecular sieves synthesized in Comparative Examples 2 and 4 were used as catalysts for the reaction. The catalyst activity and product selectivity are shown in Table 1.

[0175] Table 1

[0176]

[0177]

[0178] As can be seen from the results in Table 1, the nano-MTW molecular sieve of the present invention has a significantly better effect on the catalytic cracking of cumene compared with the rod-shaped MTW molecular sieve.

[0179] 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 combining the 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. An MTW molecular sieve, characterized in that, The MTW molecular sieve has a morphology in which nanoparticles are aggregated into ellipsoidal crystals; The size of the nanoparticles is 20-60 nm; the number of nanoparticles with a size not exceeding 50 nm accounts for at least 60% of the total number of nanoparticles.

2. The MTW molecular sieve according to claim 1, wherein, The length of the ellipsoidal crystal is 150-850 nm; and / or The width of the ellipsoidal crystal is 100-700 nm; and / or The nanoparticles have a size of 20-50 nm.

3. The MTW molecular sieve according to claim 2, wherein, The length of the ellipsoidal crystal is 200-800 nm; and / or The width of the ellipsoidal crystal is 150-600 nm.

4. The MTW molecular sieve according to claim 1, wherein, The aspect ratio of the ellipsoidal crystal is 1.1-2.

5.

5. The MTW molecular sieve according to claim 4, wherein, The aspect ratio of the ellipsoidal crystal is 1.2-2.

2.

6. The MTW molecular sieve according to claim 1, wherein, The MTW molecular sieve has a silicon-to-aluminum molar ratio of SiO2 / Al2O3 of 50-120; and / or The total specific surface area of ​​the MTW molecular sieve is not less than 300 m². 2 / gram; and / or The specific surface area of ​​the MTW molecular sieve is not less than 40 m². 2 / gram; and / or The total pore volume of the MTW molecular sieve is not less than 0.30 cm³. 3 / gram; and / or The micropore volume of the MTW molecular sieve is not less than 0.10 cm³. 3 / gram.

7. The MTW molecular sieve according to claim 6, wherein, The total specific surface area of ​​the MTW molecular sieve is 300-450 m². 2 / gram; and / or The specific surface area of ​​the MTW molecular sieve is 40-100 m². 2 / gram; and / or The total pore volume of the MTW molecular sieve is 0.30-0.60 cm³. 3 / gram; and / or The MTW molecular sieve has a micropore volume of 0.10-0.20 cm³. 3 / gram.

8. The MTW molecular sieve according to any one of claims 1-7, wherein, The total acid content of the MTW molecular sieve is not less than 300 μmol / g; and / or The strong acid content of the MTW molecular sieve is not less than 150 μmol / g.

9. The MTW molecular sieve according to claim 8, wherein, The total acidity of the MTW molecular sieve is 300-800 μmol / g; and / or The strong acid content of the MTW molecular sieve is 150-300 μmol / g.

10. The use of the MTW molecular sieve according to any one of claims 1-9 in the preparation of adsorbents or catalysts for the conversion of organic compounds.

11. The method for preparing MTW molecular sieve according to any one of claims 1-9, characterized in that, This method involves mixing a silicon source, sodium aluminate, sodium hydroxide, an organic structure-directing agent, and water, followed by crystallization, solid-liquid separation, washing, drying, ammonium exchange, and calcination to obtain MTW molecular sieves; wherein, The sodium aluminate contains 35%-43% Al2O3 and 25%-33% Na2O by weight. The organic structure directing agent is selected from at least one of dimethyl diethyl ammonium hydroxide, dimethyl diethyl ammonium chloride, and dimethyl diethyl ammonium iodide; The molar ratio of the silicon source (SiO2), sodium aluminate (Al2O3), sodium hydroxide, organic structure directing agent, and water is 1:0.008-0.020:0.07-0.14:0.13-0.26:10-50.

12. The preparation method according to claim 11, wherein, The sodium aluminate contains 38%-43% Al2O3 and 28%-33% Na2O by weight.

13. The preparation method according to claim 11, wherein, The organic structure directing agent is dimethyldiethylammonium hydroxide.

14. The preparation method according to any one of claims 11-13, wherein, The crystallization conditions include: a crystallization temperature of 140-190℃; and / or a crystallization time of 1.0-9.0 days; and / or The drying conditions include: a drying temperature of 40-250℃; and / or a drying time of 8-30 hours; and / or The calcination conditions include: a calcination temperature of 300-800℃; and / or a calcination time of 1-10 hours; and / or The conditions for ammonium exchange include: an ammonium ion concentration of 0.1-1 mol / L in the ammonium salt solution, a solid-liquid ratio of 1:5-1:20, an ammonium exchange temperature of 30-80℃, and an ammonium exchange time of 1-8 hours.

15. The preparation method according to claim 14, wherein, The crystallization conditions include: a crystallization temperature of 150-180℃; and / or a crystallization time of 1.5-8.0 days; and / or The drying conditions include: a drying temperature of 60-150℃; and / or a drying time of 10-20 hours; and / or The calcination conditions include: a calcination temperature of 400-650℃; and / or a calcination time of 3-6 hours; and / or The conditions for the ammonium exchange include: the number of ammonium exchanges is 1-2 times, and the ammonium salt is selected from at least one of ammonium chloride, ammonium nitrate, ammonium carbonate and ammonium sulfate.

16. A catalyst composition, characterized in that, The active component of the catalyst composition includes the MTW molecular sieve as described in any one of claims 1-9.

17. The use of the catalyst composition of claim 16 in the preparation of a catalyst for the cumene cracking reaction.

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