Spheroidal zsm-48 molecular sieve, preparation method and application thereof, and method for hydroisomerization of n-heptane

Abstract

The application relates to the field of molecular sieves, and discloses a spherical ZSM-48 molecular sieve, a preparation method and application thereof, and a method for n-heptane hydroisomerization. The molecular sieve has a spherical agglomerate morphology formed by agglomeration of nanoparticle crystals, the length of the nanoparticle crystals is 20-50 nm, and the width is 8-40 nm. The ZSM-48 molecular sieve has a spherical morphology formed by agglomeration of nanoparticles, has a wide silicon-aluminum ratio range and adjustable acid properties, has good accessibility, and can be used as an adsorbent or a catalyst for organic compound conversion, and has good catalytic performance.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, specifically to a spherical ZSM-48 molecular sieve, its preparation method and application, and a method for the hydroisomerization of n-heptane. Background Technology

[0002] Molecular sieves are a class of inorganic microporous crystalline materials with high specific surface area, controllable pore structure and framework composition, and excellent hydrothermal stability. They have wide applications in petrochemical, coal chemical, industrial separation processes, and ion exchange industries. Common industrial molecular sieves often have a micrometer size, while their pores are in the micropore range (<2nm). Therefore, the diffusion and mass transfer of molecules within the micropores is slow, easily leading to mass transfer resistance. When used as catalysts, the slow diffusion and mass transfer rate of molecules within molecular sieves can easily lead to reduced catalyst utilization, easy side reactions of products resulting in reduced selectivity, and easy carbon deposition and deactivation of the catalyst. Nanosheet molecular sieves, due to their larger specific surface area, shorter pores, and more exposed acidic sites, can solve a series of problems caused by the above-mentioned mass transfer difficulties and the inaccessibility of acidic sites.

[0003] ZSM-48 molecular sieves possess one-dimensional 10-membered ring channels with a *MRE topology. Structure-directing agents commonly used in the synthesis of ZSM-48 molecular sieves include 1,6-hexanediamine (HDA) and hexamethylammonium bromide (HMBr2). However, these synthesis processes easily generate competing phases such as EUO, MWW, or MTW, and the synthesized ZSM-48 samples typically have a silica-to-alumina ratio higher than 100, resulting in low acid density and limiting their catalytic applications. Hong et al. successfully synthesized ZSM-48 molecular sieves with a low silica-to-alumina ratio (Si / Al = 30) using pentamethylammonium bromide (PMBr2) as a structure-directing agent, but the low Brønsted acid density was unfavorable for catalytic applications [Suk Bong Hong et al., Microporous and Mesoporous Materials, 2004, 68, 97-104]. Furthermore, the molecular sieve crystals in ZSM-48 synthesized by the above methods typically grow into needle-like or rod-like structures along the one-dimensional channel direction, but their catalytic performance is poor. Summary of the Invention

[0004] The purpose of this invention is to overcome the poor catalytic performance of ZSM-48 in existing technologies, and to provide a spherical ZSM-48 molecular sieve, its preparation method and application, and a method for the hydroisomerization of n-heptane. This ZSM-48 molecular sieve can be used as an adsorbent or a catalyst for the conversion of organic compounds.

[0005] The first aspect of the present invention provides a spherical ZSM-48 molecular sieve, wherein the molecular sieve has a spherical aggregate morphology formed by the agglomeration of nanoparticle crystals, and the length of the nanoparticle crystals is 20-50 nm and the width is 8-40 nm.

[0006] A second aspect of the present invention provides a method for preparing the ZSM-48 molecular sieve described in the first aspect of the present invention, wherein the preparation method includes:

[0007] A mixture of raw materials containing silicon source, quaternary ammonium cationic polymer, alkali source and aluminum source is subjected to crystallization treatment;

[0008] Among them, the quaternary ammonium cationic polymer is composed of structural unit a as shown in formula (I).

[0009]

[0010] In formula (I), p and q are each independent integers between 2 and 4, R1 and R2 are each independent methyl or ethyl, and X is halogen or OH.

[0011] The third aspect of the present invention provides the application of the ZSM-48 molecular sieve described in the first aspect of the present invention in adsorption treatment and / or organic compound conversion reactions.

[0012] The fourth aspect of the present invention provides a method for the hydroisomerization of n-heptane, wherein the method comprises: using the ZSM-48 molecular sieve described in the first aspect of the present invention and / or the hydrogen form ZSM-48 molecular sieve obtained after hydrogen modification of the ZSM-48 molecular sieve described in the first aspect of the present invention as a catalyst, and in the presence of hydrogen, n-heptane undergoes an isomerization reaction.

[0013] Through the above technical solution, the ZSM-48 molecular sieve of the present invention has a spherical morphology formed by the aggregation of nanoparticles, and also has a wide range of silicon-aluminum ratio and adjustable acid properties. It has good accessibility and can be used as an adsorbent or a catalyst for the conversion of organic compounds, and has good catalytic performance. Attached Figure Description

[0014] Figure 1 This is the X-ray diffraction pattern of the molecular sieve sample in Example 1;

[0015] Figure 2 This is a SEM image of the molecular sieve sample from Example 1 at 10,000x magnification;

[0016] Figure 3 This is a SEM image of the molecular sieve sample in Example 1 at a magnification of 20,000.

[0017] Figure 4 This is the X-ray diffraction pattern of the molecular sieve sample in Example 4;

[0018] Figure 5 This is a SEM image of the molecular sieve sample in Example 4 at 10,000x magnification;

[0019] Figure 6 This is a SEM image of the molecular sieve sample in Example 4 at a magnification of 40,000.

[0020] Figure 7 This is the X-ray diffraction pattern of the molecular sieve sample in Example 6;

[0021] Figure 8 This is a SEM image of the molecular sieve sample in Example 6 at a magnification of 40,000.

[0022] Figure 9 This is a SEM image of the molecular sieve sample in Example 6 at 80,000x magnification;

[0023] Figure 10 This is a SEM image of the molecular sieve sample in Comparative Example 1. Detailed Implementation

[0024] 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.

[0025] In this invention, quasi-spherical ZSM-48 molecular sieve refers to ZSM-48 molecular sieve aggregates having an approximately spherical morphology, and / or having some minor defects on the surface of the spherical aggregates.

[0026] The first aspect of the present invention provides a spherical ZSM-48 molecular sieve, wherein the molecular sieve has a spherical aggregate morphology formed by the aggregation of nanoparticle crystals; the length of the nanoparticle crystals is 20-50 nm and the width is 8-40 nm.

[0027] The ZSM-48 molecular sieve in this invention has a morphology of spherical agglomerates formed by the aggregation of nanoparticles, and the nanoparticles are in close contact when agglomerated. The spherical agglomerates formed by the agglomeration of nanoparticles with specific length and width give the molecular sieve good molecular diffusion and adsorption properties. The molecular sieve has good accessibility when used and has good catalytic performance for organic conversion reactions.

[0028] In this invention, the structure of the molecular sieve is determined to be ZSM-48 molecular sieve by X-ray diffraction (XRD). The X-ray diffraction (XRD) is measured by an X-ray powder diffractometer. Before determining the structure of the molecular sieve, the crystallization of the molecular sieve sample is observed using a scanning electron microscope (SEM) to confirm that the sample contains only one type of crystal, i.e., the molecular sieve sample is a pure phase. Based on this, XRD testing is then performed to ensure that there are no interfering peaks from other crystals in the diffraction peaks of the XRD pattern. The X-ray diffraction (XRD) is performed using an X-ray powder diffractometer (model D / MAX 2550VB / PC from Rigaku Corporation, Japan), analyzing the phase composition of the sample using a CuKα ray source. Measurements were taken using a nickel filter, with a 2θ scanning range of 5-50°, an operating voltage of 40KV, a current of 40mA, and a scanning rate of 10° / min.

[0029] According to the present invention, in some preferred embodiments, the length of the nanoparticle crystals is 25-50 nm, for example, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm. The molecular sieves described in the foregoing embodiments exhibit better adsorption and catalytic properties during use.

[0030] According to some preferred embodiments of the present invention, the width of the nanoparticle crystals is 10-35 nm, for example, 10 nm, 12 nm, 13 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 30 nm, or 35 nm. The molecular sieves described in the foregoing embodiments exhibit excellent performance when used as adsorbents or catalysts for the conversion of organic compounds.

[0031] According to the present invention, in some preferred embodiments, the size of the aggregates is 2-10 μm, for example 2 μm, 2.5 μm, 2.8 μm, 3.5 μm, 4.1 μm, 6 μm, 7 μm, 7.5 μm, 7.8 μm, 7.9 μm, 8.5 μm, or 9 μm, preferably 2.5-9 μm. The molecular sieves in the foregoing embodiments have a short-axis structure, resulting in low resistance to molecules and good diffusivity and catalytic activity.

[0032] According to the present invention, in some preferred embodiments, the aspect ratio of the nanoparticle crystals is 1.2-5, for example 1.2, 1.3, 1.5, 2, 2.8, 3, 3.1, 3.5, 3.8, 4, 4.5 or 5, preferably 1.3-4.5. The molecular sieves in the aforementioned embodiments have good accessibility and exhibit good catalytic performance in organic conversion reactions.

[0033] In this invention, the morphology of ZSM-48 molecular sieve is observed using a scanning electron microscope (SEM, model NOVA Nano SEM 450 field emission scanning electron microscope from FEI, USA). The molecular sieve is observed at a certain magnification using this SEM. A field of view is randomly selected, and the average length and width of all nanoparticles in that field of view are calculated. This operation is repeated 10 times, and the average of the sum of the 10 measurements is taken as the length and width of the nanoparticle crystal. The size of all aggregates in the field of view is measured using the same method, and this operation is repeated 5 times. The nanoparticle crystal is a three-dimensional crystal, and its maximum outer diameter is the length of the nanoparticle crystal. The maximum diameter of the cross-section with the largest area perpendicular to this length is defined as the width, and the minimum diameter as the thickness. This invention only describes the length and width, which are relatively larger than the thickness, and does not impose excessive restrictions on the thickness.

[0034] According to the present invention, the molecular sieve with a specific morphology has a certain pore volume. In some embodiments, the total pore volume of the molecular sieve is not less than 0.2 cm³. 3 / g. The molecular sieves described in the above embodiments exhibit good adsorption and diffusion properties.

[0035] According to some preferred embodiments of the present invention, the total pore volume of the molecular sieve is 0.2-0.6 cm. 3 / gram, for example, 0.2 cm 3 / gram, 0.25cm 3 / gram, 0.3cm 3 / gram, 0.35cm 3 / gram, 0.36cm 3 / gram, 0.37cm 3 / gram, 0.38cm 3 / gram, 0.39cm 3 / gram, 0.4cm 3 / gram, 0.5cm 3 / gram or 0.6cm 3 / g. The molecular sieves described in the above embodiments have good adsorption and diffusion properties, and exhibit good catalytic performance when used for organic matter conversion reactions.

[0036] According to the present invention, the molecular sieve with a specific morphology has a certain number of micropores. In some embodiments, the micropore volume of the molecular sieve is not less than 0.05 cm³. 3 / g. The molecular sieves described in the above embodiments exhibit good adsorption and diffusion properties.

[0037] According to some preferred embodiments of the present invention, the micropore volume of the molecular sieve is 0.05-0.15 cm³. 3 / gram, for example, 0.05 cm 3 / gram, 0.06cm 3 / gram, 0.07cm 3 / gram, 0.08cm 3 / gram, 0.09cm 3 / gram, 0.1cm 3 / gram, 0.12cm 3 / gram or 0.15cm 3 / g. The molecular sieves described in the above embodiments have good adsorption and diffusion properties, and exhibit good catalytic performance when used for organic matter conversion reactions.

[0038] According to the present invention, the molecules with specific morphologies have high specific surface areas. In some embodiments, the total specific surface area of ​​the molecular sieve is not less than 300 m². 2 / g. The molecular sieves described in the above embodiments have good accessibility and exhibit good catalytic performance in organic conversion reactions.

[0039] According to some preferred embodiments of the present invention, the total specific surface area of ​​the molecular sieve is 300-450 m². 2 / gram, for example, 300 meters 2 / gram, 310 meters 2 / gram, 319 meters 2 / gram, 329 meters 2 / gram, 331 meters 2 / gram, 334 meters 2 / gram, 336 meters 2 / gram, 341 meters 2 / gram, 345 meters 2 / gram, 352 meters 2 / gram, 360 meters 2 / gram, 370 meters 2 / gram, 370 meters 2 / gram, 400 meters 2 / gram, 420 meters 2 / gram or 450 meters 2 / g. The aforementioned molecular sieves exhibit good catalytic performance in organic conversion reactions.

[0040] According to the present invention, in some embodiments, the external specific surface area of ​​the molecular sieve is not less than 100 m². 2 / g. The molecular sieves described in the above embodiments exhibit good catalytic performance in organic conversion reactions.

[0041] According to some preferred embodiments of the present invention, the molecular sieve has an external specific surface area of ​​100-200 m². 2 / gram, for example, 100 meters 2 / gram, 120 meters 2 / gram, 130 meters2 / gram, 149 meters 2 / gram, 154 meters 2 / gram, 156 meters 2 / gram, 157 meters 2 / gram, 161 meters 2 / gram, 166 meters 2 / gram, 172 meters 2 / gram, 178 meters 2 / gram, 185 meters 2 / gram, 195 meters 2 / gram or 200 meters 2 / g. The aforementioned molecular sieves exhibit good catalytic performance in organic conversion reactions.

[0042] In this invention, the total pore volume, micropore volume, total specific surface area, and external specific surface area of ​​the molecular sieve were measured using the nitrogen physical adsorption-desorption method (BET method). The nitrogen physical adsorption-desorption isotherm of the molecular sieve was measured using a physical adsorption instrument (Beijing Best Instrument Technology Co., Ltd. 3H-2000PS4 model), 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 atmosphere for 6 hours, followed by vacuum pretreatment at 350℃ for 4 hours.

[0043] According to the present invention, the molecular sieves with specific morphologies of the present invention have a wide range of silicon-to-aluminum ratios. In some embodiments, the SiO2 / Al2O3 molar ratio of the molecular sieve is 40-350, for example, 40, 50, 57, 60, 75, 105, 116, 191, 200, 246, 300, or 350, preferably 50-300. The molecular sieves of the aforementioned embodiments have a wide range of silicon-to-aluminum ratios, and their acidity is tunable and readily available, exhibiting good catalytic performance when used for organic matter conversion reactions.

[0044] In this invention, the SiO2 / Al2O3 molar ratio of the molecular sieve is obtained by measuring an inductively coupled plasma atomic emission spectrometer (ICP) model Varian 710-ES, and the element content is determined by dissolving the analytical sample in hydrofluoric acid.

[0045] A second aspect of the present invention provides a method for preparing the ZSM-48 molecular sieve described in the first aspect of the present invention, wherein the preparation method includes:

[0046] A mixture of raw materials containing silicon source, quaternary ammonium cationic polymer, alkali source and aluminum source is subjected to crystallization treatment;

[0047] Among them, the quaternary ammonium cationic polymer is composed of structural unit a as shown in formula (I).

[0048]

[0049] In formula (I), p and q are each independent integers between 2 and 4, R1 and R2 are each independent methyl or ethyl, and X is halogen or OH.

[0050] In this invention, halogens that can be listed include fluorine, chlorine, bromine and iodine.

[0051] In this invention, the quaternary ammonium cationic polymer is formed by the repeated linkage of the same structural unit 'a'. Those skilled in the art will understand that the polymerization products obtained from the polymerization reaction generally exist in the form of a mixture, where the molecular chains of each polymer contain different numbers of monomers, i.e., a mixture composed of polymers with different degrees of polymerization. In some embodiments, the average degree of polymerization of the quaternary ammonium cationic polymer is 2-20, preferably 3-13. That is, the average degree of polymerization mentioned in this invention refers to the average number of structural units 'a' contained in the quaternary ammonium cationic polymer.

[0052] According to the present invention, R1 and R2 may be the same or different. Based on the consideration of readily available raw materials, in some embodiments, R1 and R2 are the same in formula (I).

[0053] According to the present invention, in some preferred embodiments, the quaternary ammonium cationic polymer is selected from one or more of the following: quaternary ammonium cationic polymer A1 composed of structural unit a1, quaternary ammonium cationic polymer A2 composed of structural unit a2, quaternary ammonium cationic polymer A3 composed of structural unit a3, and quaternary ammonium cationic polymer A4 composed of structural unit a4, wherein: in structural unit a1, p is 4, q is 3, and R1 and R2 are methyl; in structural unit a2, p is 4, q is 3, and R1 and R2 are ethyl; in structural unit a3, p is 4, q is 4, and R1 and R2 are methyl; and in structural unit a4, p is 4, q is 4, and R1 and R2 are ethyl. The molecular sieve obtained by the foregoing embodiments has good diffusivity and adsorption properties.

[0054] According to the present invention, as long as the objective of the present invention can be achieved, there are no special restrictions on the amount of raw materials used in preparing molecular sieves. In some embodiments, the silicon source is calculated as SiO2, and the quaternary ammonium cationic polymer is calculated as structural unit a. The molar ratio of the silicon source to the quaternary ammonium cationic polymer is 1:(0.1-0.4), for example 1:0.1, 1:0.15, 1:0.2, 1:0.33, 1:0.35, or 1:0.4, preferably 1:(0.1-0.35). The molecular sieves obtained by the foregoing embodiments have special morphologies that are conducive to molecular diffusion.

[0055] According to the present invention, it is understood that the quaternary ammonium cationic polymer refers to the total amount of structural unit a contained in the reaction raw material system, calculated as structural unit a.

[0056] According to the present invention, in some embodiments, the silicon source is SiO2 and the alkali source is cations, and the molar ratio of the silicon source to the alkali source is 1:(0.15-0.5), preferably 1:(0.2-0.45). The foregoing embodiments facilitate the crystallization process and better form the molecular sieve with the special morphology of the present invention.

[0057] In this invention, it is understood that the mixture formed by the raw materials containing silicon source, quaternary ammonium cationic polymer, alkali source and aluminum source refers to the mixture obtained by mixing the raw materials (including silicon source, quaternary ammonium cationic polymer, alkali source and aluminum source) in the presence of a solvent. The solvent can be selected as needed, such as water. As long as it can be mixed evenly, there are no special restrictions on the mixing method, such as stirring at room temperature (20-30°C) for 12-36 hours.

[0058] According to the present invention, in some embodiments, the silicon source is SiO2, and the aluminum source is Al2O3, wherein the molar ratio of the silicon source to the aluminum source is 1:(0-0.025), and not 0, preferably 1:(0-0.02), and not 0. The foregoing embodiments can obtain molecular sieves with a wide silicon-to-aluminum ratio, and the molecular sieves have good accessibility.

[0059] According to the present invention, in some embodiments, the silicon source is SiO2, and the molar ratio of the silicon source to the solvent in the mixture is 1:(10-100), preferably 1:(12-90). The foregoing embodiments enable the crystallization process to be performed better.

[0060] According to the present invention, those skilled in the art will understand that the silicon source is a raw material that provides silicon element in molecular sieves. As long as the purpose of the present invention can be achieved, there is no special limitation on the type of silicon source. In some embodiments, the silicon source is selected from one or more of tetraethyl orthosilicate, fumed silica, silica sol and silica.

[0061] According to the present invention, those skilled in the art will understand that the alkali source is a raw material that provides alkali metals in molecular sieves. As long as the purpose of the present invention can be achieved, there is no special limitation on the type of alkali source. In some embodiments, the alkali source is selected from one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0062] According to the present invention, those skilled in the art will understand that the aluminum source is a raw material that provides aluminum element in molecular sieves. As long as the purpose of the present invention can be achieved, there is no special limitation on the type of aluminum source. In some embodiments, the aluminum source is selected from one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum hydroxide, sodium aluminate, boehmite and aluminum isopropoxide.

[0063] According to the present invention, the conditions for crystallization treatment are not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the conditions for crystallization treatment include: a crystallization temperature of 30-190°C, for example, 30°C, 50°C, 100°C, 140°C, 160°C, 170°C, 180°C, or 190°C, preferably 140-180°C. The foregoing embodiments can better obtain molecular sieves with a morphology of near-spherical aggregates formed by the aggregation of nanoparticle crystals.

[0064] According to the present invention, in some preferred embodiments, the crystallization treatment conditions include a crystallization time of 2-12 days, for example 2 days, 3 days, 4 days, 7 days, 9 days, 10 days, or 12 days, preferably 3-10 days. The aforementioned embodiments can better ensure the crystallization treatment proceeds, resulting in molecular sieves with specific morphologies exhibiting better catalytic performance.

[0065] According to some embodiments of the present invention, the preparation method further includes: solid-liquid separation and heat treatment after crystallization treatment.

[0066] According to the present invention, solid-liquid separation is for separating solid substances from materials obtained by crystallization treatment. During the solid-liquid separation process, washing may also be performed as needed, wherein washing may be performed using water and / or ethanol.

[0067] According to the present invention, the purpose of heat treatment is to remove substances such as solvents and template agents from the solid obtained by solid-liquid separation. In some embodiments, the heat treatment conditions include drying followed by calcination.

[0068] According to the present invention, there are no special restrictions on the drying conditions, and conventional drying methods in the art can be used, such as drying at 40-250°C, preferably at 60-150°C for 8-30 hours, and more preferably for 10-20 hours; wherein, drying can be carried out under normal pressure or under reduced pressure.

[0069] According to some preferred embodiments of the present invention, the calcination conditions include a calcination temperature of 300-800°C, preferably 400-650°C.

[0070] According to some preferred embodiments of the present invention, the calcination conditions include a calcination time of 1-10 hours, preferably 3-6 hours.

[0071] According to some preferred embodiments of the present invention, the calcination conditions include being carried out in an oxygen-containing atmosphere. Examples of such oxygen-containing atmospheres include air or oxygen.

[0072] The third aspect of the present invention provides the application of the ZSM-48 molecular sieve described in the first aspect of the present invention in adsorption treatment and / or organic compound conversion reactions.

[0073] In this invention, the ZSM-48 molecular sieve with a specific morphology can better adsorb organic molecules, for example, in the adsorption and utilization of organic waste gas; and the ZSM-48 molecular sieve with a specific morphology also has good molecular diffusivity, and has good catalysis and stability when used in organic compound conversion reactions.

[0074] In this invention, ZSM-48 molecular sieves can be used directly or modified using conventional methods in the art, depending on the need. In some embodiments, the ZSM-48 molecular sieve is used directly as an active component and / or the hydrogen form ZSM-48 molecular sieve obtained by hydrogen modification of the ZSM-48 molecular sieve is used as an active component.

[0075] In this invention, those skilled in the art can choose to use either the hydrogen-modified ZSM-48 molecular sieve or the unmodified ZSM-48 molecular sieve, depending on the actual application. Alternatively, they can choose to use a combination of the hydrogen-modified ZSM-48 molecular sieve and the unmodified ZSM-48 molecular sieve.

[0076] In this invention, the hydrogen form modification of ZSM-48 molecular sieve is a conventional modification method in the art, namely, ammonium exchange of ZSM-48 molecular sieve with ammonium salt aqueous solution, followed by centrifugation, washing, drying, and calcination to prepare hydrogen form ZSM-48 molecular sieve. The number of ammonium exchange and centrifugation / washing cycles can be selected as needed, and the methods and conditions for ammonium exchange, centrifugation / washing, drying, and calcination are conventional methods in the art. In this invention, the advantages of the invention are illustrated by the following hydrogen form modification method, but the invention is not limited thereto:

[0077] The hydrogen form of ZSM-48 molecular sieve was obtained by ammonium ion exchange at 65°C for 3 hours, followed by centrifugation and washing, repeating the above steps twice, drying overnight at 100°C (8-12 hours), and then calcining in air at 550°C for 4 hours.

[0078] In this invention, ammonium exchange utilizes ammonium ions to exchange the alkali metal atoms attached to O adjacent to Al in the ZSM-48 molecular sieve framework with NH4 ions in the solution, converting the ZSM-48 molecular sieve into NH4-type ZSM-48. Then, through methods including calcination, it is finally converted into hydrogen-type ZSM-48 molecular sieve. Those skilled in the art will understand that the hydrogen-type ZSM-48 molecular sieve obtained after ammonium exchange and calcination is only a change in acidity. The specific surface area, pore volume, SiO2 / Al2O3 molar ratio, structure, and crystal morphology of the hydrogen-type ZSM-48 molecular sieve are the same as those without ammonium exchange and calcination treatment.

[0079] According to the present invention, in some embodiments, the total acid content of the hydrogen-form ZSM-48 molecular sieve is not higher than 1000 μmol / g. The molecular sieves of the aforementioned embodiments exhibit good catalytic performance in organic conversion reactions.

[0080] According to some preferred embodiments of the present invention, the total acidity of the hydrogen-form ZSM-48 molecular sieve is 50-1000 μmol / g, for example, 50 μmol / g, 100 μmol / g, 294 μmol / g, 357 μmol / g, 476 μmol / g, 493 μmol / g, 579 μmol / g, 621 μmol / g, 633 μmol / g, 645 μmol / g, 691 μmol / g, 750 μmol / g, 850 μmol / g, 950 μmol / g, or 1000 μmol / g. The molecular sieves of the aforementioned embodiments exhibit good catalytic performance.

[0081] According to the present invention, in some embodiments, the strong acid content of the hydrogen-form ZSM-48 molecular sieve is not higher than 400 μmol / g. The molecular sieves of the aforementioned embodiments have good catalytic performance, and when used in organic conversion reactions, the target product has a high yield.

[0082] According to some preferred embodiments of the present invention, the strong acid content of the hydrogen-form ZSM-48 molecular sieve is 20-400 μmol / g, for example, 20 μmol / g, 79 μmol / g, 123 μmol / g, 172 μmol / g, 192 μmol / g, 209 μmol / g, 224 μmol / g, 230 μmol / g, 300 μmol / g, 350 μmol / g, or 400 μmol / g. The molecular sieves of the aforementioned embodiments exhibit high yields of the target product when used in organic conversion reactions.

[0083] In this invention, the total acid content and strong acid content of the hydrogen-form ZSM-48 molecular sieve were determined using a Micrometer Chemisorb 2720 instrument via NH3-TPD chemical adsorption-desorption curve analysis. Before testing, the sample was activated at 550℃ for 1 hour, ammonia gas was adsorbed at 100℃ for 20 minutes, and then desorbed and detected at 100-600℃. The peak area was quantified using a quantitative cyclic pulse of ammonia gas, and the peaks were separated using a Gaussian distribution. The acid content corresponding to a desorption temperature higher than 300℃ was considered the strong acid content.

[0084] In this invention, using ZSM-48 molecular sieve directly as an active component or hydrogen-form ZSM-48 molecular sieve as an active component means that the corresponding molecular sieve can be used directly as a catalyst as needed. Alternatively, the molecular sieve can be prepared into strip-shaped or clover-shaped molded products as a catalyst as needed. Other methods can also be used to prepare the corresponding molecular sieve into corresponding catalyst products for application. This invention has no special limitations on this.

[0085] According to the present invention, the organic compound transformation reactions involve various types of carbon-carbon bond breaking and recombination and / or carbon-hydrogen bond breaking and recombination reactions. In some embodiments, the organic compound transformation reactions include isomerization reactions, hydroisomerization reactions, and hydrogenolysis reactions. The molecular sieves with special morphologies of the present invention have good accessibility and exhibit good catalytic activity in the reactions used in the aforementioned embodiments.

[0086] The fourth aspect of the present invention provides a method for the hydroisomerization of n-heptane, wherein the method comprises: using the ZSM-48 molecular sieve described in the first aspect of the present invention and / or the hydrogen form ZSM-48 molecular sieve obtained after hydrogen modification of the ZSM-48 molecular sieve described in the first aspect of the present invention as a catalyst, and in the presence of hydrogen, n-heptane undergoes an isomerization reaction.

[0087] In this invention, when using the ZSM-48 molecular sieve with special morphology or the hydrogen-form ZSM-48 molecular sieve obtained by modification of the present invention for the hydroisomerization of n-heptane, it not only has good catalytic performance, but also yields high yields of single-branched alkanes and double-branched alkane isomers.

[0088] According to the present invention, the conditions for the isomerization reaction are not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the conditions for the isomerization reaction include a mass hourly space velocity (HHSV) of 0.5-3.5 h⁻¹. -1 .

[0089] According to some embodiments of the present invention, the conditions for the isomerization reaction include a reaction temperature of 200-400°C.

[0090] According to some embodiments of the present invention, the molar ratio of hydrogen to n-heptane is 10-40.

[0091] The present invention will be described in detail below through embodiments. The following embodiments include:

[0092] Quaternary ammonium cationic polymers (SDA) are composed of structural unit a as shown in formula (I):

[0093]

[0094] In the following examples and comparative examples, the prepared molecular sieves were modified with hydrogen form to obtain hydrogen-form molecular sieves. The method of hydrogen form modification is as follows: the molecular sieves were subjected to ammonium ion exchange at 65°C for 3 hours, then centrifuged and washed, the above steps were repeated twice, dried overnight at 100°C, and then calcined in air at 550°C for 4 hours to obtain hydrogen-form molecular sieves.

[0095] Hydrogen-form molecular sieves were used as catalysts in the hydroisomerization reaction of n-heptane. The reaction conditions were as follows: catalyst loading of 0.4 g, particle size of 20-40 mesh, hydrogen to n-heptane molar ratio of 2:6, reaction temperature of 200-400 °C, and mass hourly space velocity of 1 h⁻¹. -1 The yield of the isomer is determined by measuring the highest yield of the isomer product obtained as the reaction time progresses.

[0096] Isomer yield % = (mass of isomers in the product) / (total mass of carbon-containing products) × 100%;

[0097] The isomer products are single-branched and double-branched alkane isomers, and the carbon-containing byproducts are mainly cracked products, excluding the feedstock n-heptane.

[0098] Example 1

[0099] A mixture was prepared by stirring 4.30 g of deionized water, 0.48 g of SDA (p = 4, q = 3, R1 and R2 are methyl groups, X is Br, and the average degree of polymerization is 3.1), 0.045 g of aluminum nitrate nonahydrate, 0.08 g of sodium hydroxide, and 1.27 g of tetraethyl orthosilicate at room temperature for 24 hours.

[0100] The mixture was placed in a stainless steel reactor and crystallized at 180°C for 7 days. After crystallization, the mixture was filtered, washed with water, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours to obtain the molecular sieve sample.

[0101] Figure 1 The X-ray diffraction pattern of the molecular sieve sample indicates that the sample is ZSM-48 molecular sieve.

[0102] Figure 2 and Figure 3 The images show SEM images of the molecular sieve sample at 10,000x and 20,000x magnification, respectively. The morphology of the molecular sieve sample is a spherical aggregate formed by the agglomeration of nanoparticle crystals. The length of the nanoparticle crystals is 45 nm, the width is 15 nm, the aspect ratio is 3, and the size of the aggregates is 7.5 μm.

[0103] The SiO2 / Al2O3 molar ratio of the molecular sieve sample was determined to be 91 using inductively coupled plasma atomic emission spectrometry (ICP).

[0104] The total specific surface area of ​​the molecular sieve sample was 345 m². 2 / gram, external specific surface area 156 m² 2 / g, total pore volume 0.39cm 3 / gram, micropore volume is 0.06 cm³ 3 / gram;

[0105] The prepared molecular sieve sample was modified with hydrogen form to obtain hydrogen form ZSM-48 molecular sieve. The total acid content of the ZSM-48 molecular sieve sample was 493 μmol / g, the strong acid content was 149 μmol / g, and the strong acid content accounted for 30% of the total acid content.

[0106] Using hydrogen-form ZSM-48 molecular sieve as a catalyst for the hydroisomerization of n-heptane, the yield of the isomer product reached a maximum of 70%.

[0107] Example 2

[0108] A mixture was prepared by stirring 5.40 g of deionized water, 0.60 g of SDA (p = 4, q = 3, R1 and R2 are methyl groups, X is Br, average degree of polymerization = 3.1), 0.09 g of aluminum nitrate nonahydrate, 0.09 g of sodium hydroxide, and 1.13 g of silica sol (40% mass concentration) at room temperature for 24 hours.

[0109] The mixture was placed in a stainless steel reactor and crystallized at 180°C for 7 days. After crystallization, the mixture was filtered, washed with water, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours to obtain the molecular sieve sample.

[0110] X-ray diffraction pattern of molecular sieve sample and Figure 1 Similarly, the molecular sieve sample can be identified as ZSM-48 molecular sieve;

[0111] SEM images of molecular sieve samples and Figure 2 Similarly, the morphology of the molecular sieve sample can be obtained as a spherical aggregate formed by the agglomeration of nanoparticle crystals. The length of the nanoparticle crystals is 45 nm, the width is 12 nm, the aspect ratio is 3.8, and the size of the aggregates is 6.2 μm.

[0112] The SiO2 / Al2O3 molar ratio of the molecular sieve sample was determined to be 56 using inductively coupled plasma atomic emission spectrometry (ICP).

[0113] The total specific surface area of ​​the molecular sieve sample was 352 m². 2 / gram, external specific surface area 166 m² 2 / gram, total pore volume 0.40 cm³ 3 / gram, micropore volume is 0.06 cm³ 3 / gram;

[0114] The prepared molecular sieve sample was modified with hydrogen form to obtain hydrogen form ZSM-48 molecular sieve. The total acid content of hydrogen form ZSM-48 molecular sieve is 633 μmol / g, the strong acid content is 209 μmol / g, and the strong acid content accounts for 33% of the total acid content.

[0115] Using hydrogen-form ZSM-48 molecular sieve as a catalyst for the hydroisomerization of n-heptane, the yield of the isomer product reached a maximum of 66%.

[0116] Example 3

[0117] A mixture was prepared by stirring 5.70 g of deionized water, 0.60 g of SDA (p = 4, q = 3, R1 and R2 are methyl groups, X is OH, and the average degree of polymerization is 5.2), 0.11 g of aluminum nitrate nonahydrate, 0.11 g of sodium hydroxide, and 1.80 g of tetraethyl orthosilicate at room temperature for 24 hours.

[0118] The mixture was placed in a stainless steel reactor and crystallized at 180°C for 7 days. After crystallization, the mixture was filtered, washed with water, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours to obtain the molecular sieve sample.

[0119] X-ray diffraction pattern of molecular sieve sample and Figure 1 Similarly, the molecular sieve sample can be identified as ZSM-48 molecular sieve;

[0120] SEM images of molecular sieve samples and Figure 2 Similarly, the morphology of the molecular sieve sample can be obtained as a spherical aggregate formed by the agglomeration of nanoparticle crystals. The length of the nanoparticle crystals is 40 nm, the width is 11 nm, the aspect ratio is 3.6, and the size of the aggregates is 7.0 μm.

[0121] The SiO2 / Al2O3 molar ratio of the molecular sieve sample was determined to be 57 using inductively coupled plasma atomic emission spectrometry (ICP).

[0122] The total specific surface area of ​​the molecular sieve sample was 336 m². 2 / gram, external specific surface area 172 m² 2 / g, total pore volume 0.39cm 3 / gram, micropore volume is 0.07 cm³ 3 / gram;

[0123] The prepared molecular sieve sample was modified with hydrogen form to obtain hydrogen form ZSM-48 molecular sieve. The total acid content of hydrogen form ZSM-48 molecular sieve is 621 μmol / g, the strong acid content is 230 μmol / g, and the strong acid content accounts for 37% of the total acid content.

[0124] Using hydrogen-form ZSM-48 molecular sieve as a catalyst for the hydroisomerization of n-heptane, the yield of the isomer product reached a maximum of 70%.

[0125] Example 4

[0126] A mixture was prepared by stirring 6.00 g of deionized water, 0.60 g of SDA (p = 4, q = 4, R1 and R2 are methyl groups, X is Br, and the average degree of polymerization is 7.9), 0.08 g of aluminum nitrate nonahydrate, 0.09 g of sodium hydroxide, and 1.42 g of tetraethyl orthosilicate at room temperature for 24 hours.

[0127] The mixture was placed in a stainless steel reactor and crystallized at 160°C for 7 days. After crystallization, the mixture was filtered, washed with water, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours to obtain the molecular sieve sample.

[0128] Figure 4 The X-ray diffraction pattern of the molecular sieve sample indicates that the sample is ZSM-48 molecular sieve.

[0129] Figure 5 and Figure 6 The images show SEM images of the molecular sieve sample at magnifications of 10,000 and 40,000, respectively. The morphology of the molecular sieve sample is a spherical aggregate formed by the agglomeration of nanoparticle crystals. The length of the nanoparticle crystals is 50 nm, the width is 13 nm, the aspect ratio is 3.8, and the size of the aggregates is 4.1 μm.

[0130] The SiO2 / Al2O3 molar ratio of the molecular sieve sample was determined to be 61 using inductively coupled plasma atomic emission spectrometry (ICP).

[0131] The total specific surface area of ​​the molecular sieve sample was 342 m². 2 / gram, external specific surface area 161 m² 2 / g, total pore volume 0.38cm 3 / gram, micropore volume is 0.05 cm³ 3 / gram;

[0132] The prepared molecular sieve sample was modified with hydrogen form to obtain hydrogen form ZSM-48 molecular sieve. The total acid content of hydrogen form ZSM-48 molecular sieve is 645 μmol / g, the strong acid content is 224 μmol / g, and the strong acid content accounts for 35% of the total acid content.

[0133] Using hydrogen-form ZSM-48 molecular sieve as a catalyst for the hydroisomerization of n-heptane, the yield of the isomer product reached a maximum of 64%.

[0134] Example 5

[0135] A mixture was prepared by stirring 6.90 g of deionized water, 0.36 g of SDA (p = 4, q = 4, R1 and R2 are methyl groups, X is Br, average degree of polymerization 3.1), 0.05 g of aluminum nitrate nonahydrate, 0.12 g of sodium hydroxide, and 1.30 g of silica sol (40% mass concentration) at room temperature for 24 hours.

[0136] The mixture was placed in a stainless steel reactor and crystallized at 160°C for 7 days. After crystallization, the mixture was filtered, washed with water, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours to obtain the molecular sieve sample.

[0137] X-ray diffraction pattern of molecular sieve sample and Figure 3 Similarly, the molecular sieve sample can be identified as ZSM-48 molecular sieve;

[0138] SEM images of molecular sieve samples and Figure 4 Similarly, the morphology of the molecular sieve sample can be obtained as a spherical aggregate formed by the agglomeration of nanoparticle crystals. The length of the nanoparticle crystals is 45 nm, the width is 12 nm, the aspect ratio is 3.8, and the size of the aggregates is 6 μm.

[0139] The SiO2 / Al2O3 molar ratio of the molecular sieve sample was determined to be 105 using inductively coupled plasma atomic emission spectrometry (ICP).

[0140] The total specific surface area of ​​the molecular sieve sample was 319 m². 2 / gram, external specific surface area 178 m² 2 / g, total pore volume 0.37cm 3 / gram, micropore volume is 0.06 cm³ 3 / gram;

[0141] The prepared molecular sieve sample was modified with hydrogen form to obtain hydrogen form ZSM-48 molecular sieve. The total acid content of hydrogen form ZSM-48 molecular sieve is 357 μmol / g, the strong acid content is 123 μmol / g, and the strong acid content accounts for 34% of the total acid content.

[0142] Using hydrogen-form ZSM-48 molecular sieve as a catalyst for the hydroisomerization of n-heptane, the yield of the isomer product reached a maximum of 62%.

[0143] Example 6

[0144] The method of Example 1 is followed, except that SDA (p = 4, q = 3, R1 and R2 are ethyl, X is OH, average degree of polymerization 3.1) (50% aqueous solution) is used instead of SDA (p = 4, q = 3, R1 and R2 are methyl, X is Br, average degree of polymerization 3.1), while the amount of raw materials added is controlled so that the molar ratio of the final mixture is the same as in Example 1;

[0145] Crystallize at 180℃ for 3 days.

[0146] Figure 7 The X-ray diffraction pattern of the molecular sieve sample indicates that the sample is ZSM-48 molecular sieve.

[0147] Figure 8 and Figure 9 The images show SEM images of the molecular sieve sample at magnifications of 40,000 and 80,000, respectively. The morphology of the molecular sieve sample is that of a spherical aggregate formed by the agglomeration of nanoparticle crystals. The length of the nanoparticle crystals is 50 nm, the width is 15 nm, the aspect ratio is 3.3, and the size of the aggregates is 2.8 μm.

[0148] The SiO2 / Al2O3 molar ratio of the molecular sieve sample was determined to be 116 using inductively coupled plasma atomic emission spectrometry (ICP).

[0149] The total specific surface area of ​​the molecular sieve sample was 334 m². 2 / gram, external specific surface area 149 m² 2 / gram, total pore volume 0.35 cm³ 3 / gram, micropore volume is 0.06 cm³ 3 / gram;

[0150] The prepared molecular sieve sample was modified with hydrogen form to obtain hydrogen-form ZSM-48 molecular sieve. The total acid content of ZSM-48 molecular sieve was 294 μmol / g, the strong acid content was 79 μmol / g, and the strong acid content accounted for 27% of the total acid content.

[0151] Using hydrogen-form ZSM-48 molecular sieve as a catalyst for the hydroisomerization of n-heptane, the yield of the isomer product reached a maximum of 65%.

[0152] Example 7

[0153] A mixture was prepared by stirring 5.40 g of deionized water, 0.36 g of SDA (p = 4, q = 3, R1 and R2 are methyl groups, X is Br, average degree of polymerization 3.1), 0.018 g of aluminum nitrate nonahydrate, 0.08 g of sodium hydroxide, and 0.37 g of silica at room temperature for 24 hours.

[0154] The mixture was placed in a stainless steel reactor and crystallized at 170°C for 5 days. After crystallization, the mixture was filtered, washed with water, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours to obtain the molecular sieve sample.

[0155] X-ray diffraction pattern of molecular sieve sample and Figure 1 Similarly, the molecular sieve sample can be identified as ZSM-48 molecular sieve;

[0156] SEM images of molecular sieve samples and Figure 2 Similarly, the morphology of the molecular sieve sample can be obtained as a spherical aggregate formed by the agglomeration of nanoparticle crystals. The length of the nanoparticle crystals is 45 nm, the width is 20 nm, the aspect ratio is 2.3, and the size of the aggregates is 7.9 μm.

[0157] The SiO2 / Al2O3 molar ratio of the molecular sieve sample was determined to be 246 using inductively coupled plasma atomic emission spectrometry (ICP).

[0158] The total specific surface area of ​​the molecular sieve sample was 341 m². 2 / gram, external specific surface area 157 m² 2 / g, total pore volume 0.36cm 3 / gram, micropore volume is 0.07 cm³ 3 / gram;

[0159] The prepared molecular sieve sample was modified with hydrogen form to obtain hydrogen form ZSM-48 molecular sieve. The total acid content of hydrogen form ZSM-48 molecular sieve is 119 μmol / g, the strong acid content is 48 μmol / g, and the strong acid content accounts for 40% of the total acid content.

[0160] Using hydrogen-form ZSM-48 molecular sieve as a catalyst for the hydroisomerization of n-heptane, the yield of the isomer product reached a maximum of 61%.

[0161] Example 8

[0162] A mixture was prepared by stirring 4.30 g of deionized water, 0.36 g of SDA (p = 4, q = 3, R1 and R2 are methyl groups, X is Br, and the average degree of polymerization is 3.1), 0.025 g of aluminum nitrate nonahydrate, 0.12 g of potassium hydroxide, and 1.27 g of tetraethyl orthosilicate at room temperature for 24 hours.

[0163] The mixture was placed in a stainless steel reactor and crystallized at 160°C for 9 days. After crystallization, the mixture was filtered, washed with water, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours to obtain the molecular sieve sample.

[0164] X-ray diffraction pattern of molecular sieve sample and Figure 1 Similarly, the molecular sieve sample can be identified as ZSM-48 molecular sieve;

[0165] SEM images of molecular sieve samples and Figure 2 Similarly, the morphology of the molecular sieve sample can be obtained as a spherical aggregate formed by the agglomeration of nanoparticle crystals. The length of the nanoparticle crystals is 45 nm, the width is 22 nm, the aspect ratio is 2.0, and the size of the aggregates is 3.5 μm.

[0166] The SiO2 / Al2O3 molar ratio of the molecular sieve sample was determined to be 191 using inductively coupled plasma atomic emission spectrometry (ICP).

[0167] The total specific surface area of ​​the molecular sieve sample was 329 m². 2 / gram, external specific surface area 170 m² 2 / g, total pore volume 0.42cm 3 / gram, micropore volume is 0.08 cm³ 3 / gram;

[0168] The prepared molecular sieve sample was modified with hydrogen form to obtain hydrogen form ZSM-48 molecular sieve. The total acid content of hydrogen form ZSM-48 molecular sieve is 216 μmol / g, the strong acid content is 82 μmol / g, and the strong acid content accounts for 38% of the total acid content.

[0169] Using hydrogen-form ZSM-48 molecular sieve as a catalyst for the hydroisomerization of n-heptane, the yield of the isomer product reached a maximum of 65%.

[0170] Example 9

[0171] A mixture was prepared by stirring 4.30 g of deionized water, 0.36 g of SDA (p = 4, q = 3, R1 and R2 are methyl groups, X is Br, and the average degree of polymerization is 3.1), 0.012 g of sodium aluminate, 0.08 g of sodium hydroxide, and 1.27 g of tetraethyl orthosilicate at room temperature for 24 hours.

[0172] The mixture was placed in a stainless steel reactor and heated to crystallize at 170°C for 4 days. After crystallization, it was filtered, washed with water, dried overnight in an oven at 100°C, and then calcined in air at 550°C for 6 hours to obtain the molecular sieve sample.

[0173] X-ray diffraction pattern of molecular sieve sample and Figure 1 Similarly, the molecular sieve sample can be identified as ZSM-48 molecular sieve;

[0174] SEM images of molecular sieve samples and Figure 2 Similarly, the morphology of the molecular sieve sample can be obtained as a spherical aggregate formed by the agglomeration of nanoparticle crystals. The length of the nanoparticle crystals is 50 nm, the width is 18 nm, the aspect ratio is 2.8, and the size of the aggregates is 6.4 μm.

[0175] The SiO2 / Al2O3 molar ratio of the molecular sieve sample was determined to be 75 using inductively coupled plasma atomic emission spectrometry (ICP).

[0176] The total specific surface area of ​​the molecular sieve sample was 331 m². 2 / gram, external specific surface area 163 m² 2 / gram, total pore volume 0.40 cm³3 / gram, micropore volume is 0.05 cm³ 3 / gram;

[0177] The prepared molecular sieve sample was modified with hydrogen form to obtain hydrogen form ZSM-48 molecular sieve. The total acid content of hydrogen form ZSM-48 molecular sieve is 483 μmol / g, the strong acid content is 146 μmol / g, and the strong acid content accounts for 30% of the total acid content.

[0178] Using hydrogen-form ZSM-48 molecular sieve as a catalyst for the hydroisomerization of n-heptane, the yield of the isomer product reached a maximum of 66%.

[0179] Comparative Example 1

[0180] The method of Example 1 was followed, except that 1,6-hexanediamine was used as the structure-directing agent (SDA), and the amount of each raw material added was controlled so that the molar ratio of the final mixture was the same as in Example 1.

[0181] The final mixture was placed in a stainless steel reactor and heated to crystallize at 180℃ for 7 days under static crystallization conditions. After crystallization, the mixture was filtered, washed with water, dried overnight in an oven at 100℃, and then calcined in air at 550℃ for 6 hours to obtain the molecular sieve sample. The X-ray diffraction pattern of the molecular sieve sample is similar to... Figure 1 Similarly, the molecular sieve sample was identified as ZSM-48 molecular sieve; the SEM image of the molecular sieve sample is shown below. Figure 10 As shown, it has a rod-shaped morphology, not a spherical aggregate morphology formed by the aggregation of nanoparticle crystals.

[0182] The prepared molecular sieve sample was modified with hydrogen to obtain hydrogen-form ZSM-48 molecular sieve. The hydrogen-form ZSM-48 molecular sieve was used as a catalyst for the hydroisomerization reaction of n-heptane, and the yield of the isomer product reached the highest of 49%.

[0183] The results from the above examples and comparative examples show that using the hydrogen-form modified ZSM-48 molecular sieve obtained in the embodiments of the present invention as a catalyst for the hydroisomerization reaction of n-heptane has good catalytic effect and can obtain high yields of isomer products.

[0184] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A spherical ZSM-48 molecular sieve, characterized in that, The molecular sieve has a spherical aggregate morphology formed by the aggregation of nanoparticle crystals; the length of the nanoparticle crystals is 20-50 nm, and the width is 8-40 nm; the external specific surface area of ​​the molecular sieve is not less than 100 m². 2 / gram; the total pore volume of the molecular sieve is not less than 0.2 cm. 3 / gram; the micropore volume of the molecular sieve is not less than 0.05 cm³. 3 / gram; The aspect ratio of the nanoparticle crystals is 1.2-5.

2. The molecular sieve according to claim 1, wherein, The length of the nanoparticle crystals is 25-50 nm; and / or The width of the nanoparticle crystals is 10-35 nm; and / or The size of the aggregates is 2-10 μm.

3. The molecular sieve according to claim 2, wherein, The size of the aggregates is 2.5-9 μm.

4. The molecular sieve according to claim 1, wherein, The aspect ratio of the nanoparticle crystals is 1.3-4.

5.

5. The molecular sieve according to claim 1, wherein, The total pore volume of the molecular sieve is 0.2-0.6 cm. 3 / gram; and / or The molecular sieve has a micropore volume of 0.05-0.15 cm³. 3 / gram.

6. The molecular sieve according to claim 1, wherein, The total specific surface area of ​​the molecular sieve is not less than 300 m². 2 / gram; and / or The molecular sieve has an external specific surface area of ​​100-200 m². 2 / gram; and / or The SiO2 / Al2O3 molar ratio of the molecular sieve is 40-350.

7. The molecular sieve according to claim 6, wherein, The total specific surface area of ​​the molecular sieve is 300-450 m². 2 / gram; and / or; The SiO2 / Al2O3 molar ratio of the molecular sieve is 50-300.

8. A method for preparing the ZSM-48 molecular sieve according to any one of claims 1-7, characterized in that, The preparation method includes: A mixture of raw materials containing silicon source, quaternary ammonium cationic polymer, alkali source and aluminum source is subjected to crystallization treatment; Among them, the quaternary ammonium cationic polymer is composed of structural unit a as shown in formula (I), Equation (I), In formula (I), p and q are each an integer between 2 and 4, R1 and R2 are each methyl or ethyl, and X is a halogen or OH.

9. The preparation method according to claim 8, wherein, The quaternary ammonium cationic polymer has an average degree of polymerization of 2-20; and / or R1 and R2 are the same.

10. The preparation method according to claim 8, wherein, The quaternary ammonium cationic polymer has an average degree of polymerization of 3-13; and / or The quaternary ammonium cationic polymer is selected from one or more of the following: quaternary ammonium cationic polymer A1 composed of structural unit a1, quaternary ammonium cationic polymer A2 composed of structural unit a2, quaternary ammonium cationic polymer A3 composed of structural unit a3, and quaternary ammonium cationic polymer A4 composed of structural unit a4, wherein: In structural unit a1, p is 4, q is 3, and R1 and R2 are methyl groups; In structural unit a2, p is 4, q is 3, and R1 and R2 are ethyl groups; In structural unit a3, p is 4, q is 4, and R1 and R2 are methyl groups; In structural unit a4, p is 4, q is 4, and R1 and R2 are ethyl groups.

11. The preparation method according to claim 8, wherein, The silicon source is calculated as SiO2, and the quaternary ammonium cationic polymer is calculated as structural unit a, wherein the molar ratio of the silicon source to the quaternary ammonium cationic polymer is 1:(0.1-0.4); and / or The silicon source is calculated as SiO2, and the alkali source is calculated as cations, wherein the molar ratio of the silicon source to the alkali source is 1:(0.15-0.5); and / or The silicon source is calculated as SiO2 and the aluminum source as Al2O3, wherein the molar ratio of the silicon source to the aluminum source is 1:(0-0.025), and not 0; and / or The silicon source is SiO2, and the molar ratio of the silicon source to the solvent in the mixture is 1:(10-100).

12. The preparation method according to claim 11, wherein, The silicon source is calculated as SiO2, and the quaternary ammonium cationic polymer is calculated as structural unit a, wherein the molar ratio of the silicon source to the quaternary ammonium cationic polymer is 1:(0.1-0.35); and / or The silicon source is calculated as SiO2, and the alkali source is calculated as cations, wherein the molar ratio of the silicon source to the alkali source is 1:(0.2-0.45); and / or The silicon source is calculated as SiO2 and the aluminum source as Al2O3, wherein the molar ratio of the silicon source to the aluminum source is 1:(0-0.02), and not 0; and / or The silicon source is SiO2, and the molar ratio of the silicon source to the solvent in the mixture is 1:(12-90).

13. The preparation method according to claim 8, wherein, The silicon source is selected from one or more of tetraethyl orthosilicate, silica sol, and silica; and / or The alkali source is selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide; and / or The aluminum source is selected from one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum hydroxide, sodium aluminate, boehmite, and aluminum isopropoxide.

14. The preparation method according to claim 8, wherein, The conditions for crystallization treatment include: Crystallization temperature is 30-190℃; and / or Crystallization time is 2-12 days; And / or, The preparation method also includes: solid-liquid separation after crystallization treatment and heat treatment.

15. The preparation method according to claim 14, wherein, The conditions for crystallization treatment include: The crystallization temperature is 140-180℃; and / or Crystallization time is 3-10 days; And / or, The conditions for heat treatment include drying followed by calcination.

16. The preparation method according to claim 15, wherein, The calcination conditions include: a calcination temperature of 300-800℃; and / or a calcination time of 1-10 hours; and / or calcination under an oxygen-containing atmosphere.

17. The use of the ZSM-48 molecular sieve according to any one of claims 1-7 in adsorption treatment and / or organic compound conversion reactions.

18. The application according to claim 17, wherein, The ZSM-48 molecular sieve is used directly as an active component and / or the hydrogen-form ZSM-48 molecular sieve obtained by hydrogen modification of the ZSM-48 molecular sieve is used as an active component; and / or The organic compound transformation reactions include isomerization, hydroisomerization, and hydrogenolysis.

19. A method for the hydroisomerization of n-heptane, characterized in that, The method includes: Using the ZSM-48 molecular sieve of any one of claims 1-7 and / or the hydrogen-form ZSM-48 molecular sieve obtained by hydrogen modification of the ZSM-48 molecular sieve of any one of claims 1-7 as a catalyst, and in the presence of hydrogen, n-heptane undergoes an isomerization reaction.

20. The method according to claim 19, wherein, The conditions for the isomerization reaction include: Mass hourly space velocity (MHSV) is 0.5-3.5 h⁻¹. -1 ; and / or The reaction temperature is 200-400℃; and / or The molar ratio of hydrogen to n-heptane is 10-40.

Images