Spherical nano ZSM-35 molecular sieve as well as preparation method and application thereof

Abstract

The invention provides a spherical nano ZSM-35 molecular sieve as well as a preparation method and application thereof. The spherical nano ZSM-35 molecular sieve disclosed by the invention is formed by self-assembling a plurality of long-strip rod-shaped nano ZSM-35 molecular sieves; the grain size of the spherical nano ZSM-35 molecular sieve is 40 to 100 nm, and the length of the long-strip rod-shaped nano ZSM-35 molecular sieve is preferably within 100 nm. The spherical nano ZSM-35 molecular sieve obtained by the preparation method disclosed by the invention has smaller grain size, higher specific surface area and higher external specific surface area, and has the advantages of high diffusion and high activity in applications such as catalysis, adsorption separation and the like.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, specifically to a spherical nano ZSM-35 molecular sieve, its preparation method, and its application. Background Technology

[0002] In the mid-to-late 1970s, Mobil Corporation in the United States developed a molecular sieve with a FER topology, which possesses a vertically intersecting two-dimensional pore system. The ten-membered ring pores parallel to the

[001] plane have a size of 0.42 × 0.54 nm, while the eight-membered ring pores parallel to the

[010] plane have a size of 0.35 × 0.48 nm. ZSM-35 molecular sieves are widely used in catalytic reactions of hydrocarbon conversion, such as isomerization, polymerization, aromatization, and cracking of straight-chain olefins.

[0003] Currently, the main synthesis method for ZSM-35 molecular sieves relies on organic template agents (common template agents include ethylenediamine, cyclohexylamine, n-butylamine, pyridine, pyrrolidine, etc.) as template agents, and the crystal size of these molecular sieves is generally in the micrometer range. However, with the upgrading of oil quality, the disadvantages of micrometer-sized molecular sieves have gradually become apparent, such as high diffusion resistance and easy coking and deactivation of the catalyst. Small-crystal catalytic materials, especially nanoscale molecular sieve catalysts, can effectively alleviate the above problems. Typically, the crystal size of nanoscale molecular sieves is within 100 nm. Due to the small crystal size, nanoscale molecular sieves have a large external surface area, increasing the number of exposed effective active sites and exhibiting higher activity. In addition, the diffusion path is shortened, which is more advantageous for dealing with carbon deposition and deactivation caused by diffusion limitation.

[0004] Compared to the synthesis of conventional micron-sized ZSM-35 molecular sieves, the synthesis of nano-sized ZSM-35 molecular sieves is much more difficult, often requiring expensive surfactants and other template agents, resulting in high costs. Furthermore, filtration of the molecular sieves presents a significant challenge. For example, Hu et al. synthesized nanosheet-stacking ZSM-35 molecular sieves using Pi and TEAOH under dynamic conditions (Designing ferrierite-based catalysts with improved properties for skeletalisomerization of n-butene to isobutene; Rsc Advances), obtaining ZSM-35 molecular sieve nanocrystals with a length of approximately 120 nm and a thickness of 30 nm. Although a molecular sieve with a small crystal size was synthesized, its crystallization temperature is low, the crystallization time is long, and the economic benefits are low. Therefore, nano-sized ZSM-35 molecular sieves currently have few industrial applications.

[0005] Existing research reports on the preparation of nano-sized ZSM-35 molecular sieves mainly focus on adding organic surfactants and organic templates to prepare small-crystal ZSM-35 molecular sieves. These organic surfactants are not only expensive but also present significant challenges in the filtration and separation processes of the molecular sieves, thus increasing the preparation cost. Therefore, finding a simple and efficient synthetic method to prepare nano-sized ZSM-35 molecular sieves is crucial for their industrial application. Summary of the Invention

[0006] In order to solve one of the above-mentioned technical problems in the prior art, the present invention provides a spherical nano ZSM-35 molecular sieve, its preparation method and application.

[0007] The first aspect of the present invention provides a spherical nano ZSM-35 molecular sieve, which is formed by the self-assembly of multiple long rod-shaped nano ZSM-35 molecular sieves.

[0008] According to some embodiments of the present invention, the grain size of the spherical nano-ZSM-35 molecular sieve is 40–100 nm. According to some embodiments of the present invention, the length of the elongated rod-shaped nano-ZSM-35 molecular sieve is less than 100 nm.

[0009] According to some embodiments of the present invention, the grain size of the spherical nano-ZSM-35 molecular sieve is 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value between them. According to some embodiments of the present invention, the length of the elongated rod-shaped nano-ZSM-35 molecular sieve is 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value between them.

[0010] According to some embodiments of the present invention, the specific surface area of ​​the spherical nano ZSM-35 molecular sieve is not less than 310 m². 2 ·g -1 Preferably, it is 310–330m 2 ·g -1 .

[0011] According to some embodiments of the present invention, the external specific surface area of ​​the spherical nano ZSM-35 molecular sieve is not less than 35 m². 2 ·g -1 Preferably 35-45m 2 ·g -1 .

[0012] According to some embodiments of the present invention, the total pore volume of the spherical nano ZSM-35 molecular sieve is 0.15–0.25 cm³.3 / g.

[0013] According to some embodiments of the present invention, the average pore size of the spherical nano ZSM-35 molecular sieve is 2-3 nm, for example, 2-2.5 nm.

[0014] A second aspect of the present invention provides a method for preparing spherical nano ZSM-35 molecular sieves, comprising the following steps:

[0015] A mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent, and sodium oleate is subjected to a crystallization reaction to obtain the spherical nano ZSM-35 molecular sieve.

[0016] According to some embodiments of the present invention, the alkali source includes an inorganic alkali source, such as hydroxides comprising alkali metals or alkaline earth metals. The alkali source in this invention includes, but is not limited to, one or more of sodium hydroxide, potassium hydroxide, and magnesium hydroxide.

[0017] According to some embodiments of the present invention, the aluminum source includes one or more of sodium aluminate, aluminum sulfate, aluminum chloride, and aluminum nitrate.

[0018] According to some embodiments of the present invention, the silicon source includes one or more of silica, silica gel, silica sol, and water glass.

[0019] According to some embodiments of the present invention, the template agent includes an organic amine template agent, preferably including cyclohexylamine and / or ethylenediamine.

[0020] According to some embodiments of the present invention, in the mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent and sodium oleate, the molar ratio of MxO to Al2O3 is (1-2):1, for example, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1 or any value between them; M represents an alkali metal or an alkaline earth metal, and x is 1 or 2.

[0021] According to some embodiments of the present invention, in the mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent and sodium oleate, the molar ratio of Al2O3 to SiO2 is 1:(20-35), for example 1:20, 1:22, 1:25, 1:28, 1:30, 1:32, 1:35 or any value between them.

[0022] According to some embodiments of the present invention, in the mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent and sodium oleate, the molar ratio of Al2O3 to the template agent is 1:(4-8), for example, 1:4, 1:5, 1:6, 1:7, 1:8 or any value between them.

[0023] According to some embodiments of the present invention, in the mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent and sodium oleate, the molar ratio of Al2O3 to sodium oleate is 1:(0.05 to 0.2), for example 1:0.05, 1:0.08, 1:0.1, 1:0.12, 1:0.15, 1:0.18, 1:0.2 or any value between them.

[0024] According to some embodiments of the present invention, in the mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent and sodium oleate, the molar ratio of Al2O3 to water is 1:(400-800), for example 1:400, 1:450, 1:500, 1:550, 1:600, 1:650, 1:700, 1:750, 1:800 or any value between them.

[0025] According to some embodiments of the present invention, in the mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent and sodium oleate, the molar ratio MxO:Al2O3:SiO2:template agent:sodium oleate:water = (1~2):1:(20~35):(4~8):(0.05~0.2):(400~800); M represents an alkali metal or an alkaline earth metal, and x is 1 or 2.

[0026] In this invention, the crystallization temperature and time affect the success of crystallization. When the crystallization temperature is too low, crystallization is difficult; when the crystallization time is too short, the product will not crystallize completely, containing a large amount of amorphous material. When the temperature is higher, the crystallization time can be appropriately shortened. For example, at 190°C, crystallization can be completed in 36 hours. Within a suitable crystallization temperature range, the lower the temperature, the smaller the crystal size of the molecular sieve. According to some embodiments of the invention, the crystallization temperature is 150°C to 200°C, for example, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, or any value between them. In some embodiments, the crystallization temperature is 180°C to 200°C. According to some embodiments of the invention, the crystallization time is 36 hours to 96 hours, for example, 36 hours, 48 ​​hours, 60 hours, 72 hours, 84 hours, 96 hours, or any value between them, preferably 48 hours to 72 hours.

[0027] According to some embodiments of the present invention, the crystallization is static crystallization.

[0028] According to some embodiments of the present invention, the mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent, and sodium oleate is prepared by a method comprising the following steps:

[0029] The alkali source, aluminum source, and solvent are mixed (preferably at 10°C to 80°C), and then a template agent and sodium oleate are added. Finally, a silicon source is added to obtain the mixed solution containing the alkali source, aluminum source, silicon source, template agent, and sodium oleate.

[0030] In the preparation method of the spherical nano ZSM-35 molecular sieve of the present invention, after the crystallization step is completed, the solid phase can be separated from the obtained reaction mixture as a product by any conventionally known separation method, thereby obtaining the spherical nano ZSM-35 molecular sieve of the present invention. Examples of such separation methods include filtering, washing, and drying the obtained reaction mixture. The filtration, washing, and drying can be performed in any manner conventionally known in the art. Specifically, for example, the filtration can be performed by simply vacuum filtering the obtained reaction mixture. For example, washing can be performed using deionized water. For example, the drying temperature can be 60–150°C, preferably 80–120°C. For example, the drying time can be 6–30 hours, preferably 10–20 hours. The drying can be performed under normal pressure or under reduced pressure.

[0031] In the preparation method of the spherical nano ZSM-35 molecular sieve of the present invention, the solid product obtained according to the aforementioned preparation method may be calcined as needed to remove the organic template agent and any possible moisture, thereby obtaining the calcined spherical nano ZSM-35 molecular sieve. The calcination can be carried out in any manner conventionally known in the art; for example, the calcination temperature is generally 300–800°C, preferably 400–650°C, and the calcination time is generally 1–10 hours, preferably 3–6 hours. Furthermore, the calcination is generally carried out in an oxygen-containing atmosphere, such as air or an oxygen atmosphere.

[0032] According to some embodiments of the present invention, the method further includes: after the crystallization reaction is completed, performing solid-liquid separation to obtain a solid product, and washing, drying and calcining the solid product to obtain the spherical nano ZSM-35 molecular sieve.

[0033] Preferably, the drying temperature is 80℃~120℃;

[0034] Preferably, the roasting temperature is 450℃~650℃.

[0035] According to some embodiments of the present invention, the method for preparing spherical nano ZSM-35 molecular sieves includes:

[0036] Step A: Dissolve the inorganic alkali and aluminum source in water, then add the template agent and surfactant sodium oleate, and then mix with the silicon source to obtain the initial gel; wherein the molar ratio of the materials is MxO:Al2O3:SiO2:template agent:surfactant:water = (1~2):1:(20~35):(4~8):(0.05~0.2):(400~800); M represents alkali metal or alkaline earth metal, and x is 1 or 2;

[0037] Step B: Transfer the initial gel obtained in Step A to a stainless steel crystallization vessel with a polytetrafluoroethylene liner, and statically crystallize at 150℃~200℃ for 36h~96h.

[0038] Step C: After crystallization in step B, the product is filtered and washed, the filter cake is dried at 80-120°C, and then calcined at 450-650°C in an oxygen or air atmosphere to obtain the spherical nano ZSM-35 molecular sieve.

[0039] A third aspect of the present invention provides the application of the above-described spherical nano ZSM-35 molecular sieve, or the spherical nano ZSM-35 molecular sieve prepared by the above method, in the catalytic carbonylation reaction of dimethyl ether.

[0040] The dimethyl ether carbonylation reaction described in this invention includes the reaction of producing methyl acetate by carbonylation of dimethyl ether.

[0041] In some embodiments, the dimethyl ether carbonylation reaction comprises: reacting dimethyl ether and CO under the catalysis of the mordenite molecular sieve described above. In some embodiments, the reaction temperature is 150–250°C. In some embodiments, the reaction pressure is 1–5 MPa. In some embodiments, the dimethyl ether feed rate is 0.1–1.0 Whsv. In some embodiments, the CO feed rate is 150–300 mL / min.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The ZSM-35 molecular sieve of the present invention has a small crystal size, below 100 nm, and a large external specific surface area, increasing the number of exposed effective active sites and thus having higher activity. In addition, the diffusion path is shortened, diffusion is faster, carbon deposition is less likely, and catalyst life is longer. The ZSM-35 molecular sieve of the present invention has a special spherical morphology structure composed of numerous rod-shaped small nanocrystals self-assembled, which has advantages such as high diffusion and high activity in the catalytic reaction process.

[0044] (2) The method for preparing ZSM-35 molecular sieves of the present invention can obtain ZSM-35 molecular sieves with smaller crystal size and special morphology by selecting sodium oleate instead of conventional surfactants (such as CTAB, TEAOH, etc.) in the prior art. Furthermore, sodium oleate is cheap and readily available, which can significantly reduce industrial production costs. Attached Figure Description

[0045] Figure 1 The XRD pattern of the molecular sieve prepared in Example 1 is shown.

[0046] Figure 2 The XRD pattern of the molecular sieve prepared in Example 2 is shown.

[0047] Figure 3 SEM images of the molecular sieves prepared in Examples 1, 2, and 2 are shown. Figure a is an SEM image of the molecular sieve prepared in Example 1, Figure b is an SEM image of the molecular sieve prepared in Example 2, Figure c is an SEM image of the molecular sieve prepared in Comparative Example 1, and Figure d is an SEM image of the molecular sieve prepared in Comparative Example 2.

[0048] Figure 4 The results of the evaluation of the dimethyl ether carbonylation catalytic activity of the molecular sieves prepared in Example 2 and Comparative Example 1 are shown. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0050] Unless otherwise specified, all reagents used in the following experiments of this invention are commercially available products or reagents prepared according to conventional methods. Unless otherwise specified, all methods used in the experiments are conventional experimental methods. Unless otherwise specified, all instruments used in the experiments are commercially available.

[0051] The molecular sieve prepared in this invention was analyzed for phase composition using an X-ray powder diffractometer (model D8 Advance SS) with a CuKα ray source. Nickel filter, 2θ scanning range 20-50°, operating voltage 40KV, current 40mA, scanning rate 10° / min.

[0052] The scanning electron microscope (SEM) used to prepare the molecular sieve in this invention is a model S-4800II field emission scanning electron microscope. Using this SEM, the molecular sieve precursor was observed at a magnification of 40,000x. A randomly selected field of view was used to calculate the average sum of the thicknesses of all crystals within that field of view. This operation was repeated 10 times. The average sum of the 10 measurements was taken as the crystal thickness. The size of all aggregates within the same field of view was then measured using the same method.

[0053] In this invention, "specific surface area" refers to the total area per unit mass of sample, including internal and external surface areas. Non-porous samples only have external surface area, such as silicate cement and some clay mineral powders; porous and multi-porous samples have both external and internal surface areas, such as asbestos fibers, diatomaceous earth, and molecular sieves. In porous and multi-porous samples, the surface area of ​​pores with a diameter less than 2 nanometers is the internal surface area, and the surface area after deducting the internal surface area is called the external surface area. The external surface area per unit mass of sample is the external specific surface area.

[0054] In this invention, "total pore volume" refers to the volume of all pores per unit mass of molecular sieve (generally only pores with a diameter less than 50 nanometers are included). "Average adsorption pore size" is the average pore size calculated from the total adsorption pore volume and the BET specific surface area.

[0055] Example 1

[0056] Step A: First, add 2.7 g of sodium aluminate (51 wt% Al2O3) and 1.8 g of sodium hydroxide to 120 g of deionized water at room temperature and stir for 10 minutes. After the sodium aluminate and sodium hydroxide are completely dissolved, add 9.6 g of cyclohexylamine (99%) and 0.41 g of sodium oleate to the solution and stir thoroughly for another 20 minutes. Then add 60 g of silica sol (40 wt%) and stir for 60 minutes to form a silica-alumina mixed solution. The molar composition of the silica-alumina mixed solution is Na2O:Al2O3:SiO2:cyclohexylamine:sodium oleate:water = 1.5:1:30:7:0.1:640.

[0057] Step B: Transfer the silicon-aluminum mixed solution obtained in Step A into a stainless steel crystallization vessel with a polytetrafluoroethylene liner, and then place the stainless steel crystallization vessel in an oven at 180°C for static crystallization for 72 hours.

[0058] Step C: After the crystallization in step B is complete, filter and wash the solid product, place the filter cake in an oven at 120°C overnight to dry, and then calcine it in air at 550°C to obtain nano ZSM-35 molecular sieve.

[0059] The molecular sieves obtained above were subjected to X-ray diffraction and SEM measurements, and the results are as follows: Figure 1 and Figure 3As shown in Figure a, the synthesized molecular sieve has an FER structure and is a ZSM-35 molecular sieve. Its morphology is a spherical structure assembled from multiple nanorods, with a grain size between 40 and 100 nm and a rod length of less than 100 nm.

[0060] Example 2

[0061] The difference from Example 1 lies in the amount of sodium oleate added in step A, resulting in a different molar composition of the resulting silica-alumina mixed solution: Na₂O:Al₂O₃:SiO₂:cyclohexylamine:sodium oleate:water = 1.5:1:30:7:0.2:640. All other synthesis conditions remained the same. The resulting molecular sieve was characterized by XRD and SEM, confirming it to be ZSM-35 with a size below 100 nm (see XRD details). Figure 2 See SEM Figure 3 b).

[0062] Example 3

[0063] The difference from Example 1 lies in the amount of sodium oleate added in step A, resulting in a silica-alumina mixed solution with a molar composition of Na₂O:Al₂O₃:SiO₂:cyclohexylamine:sodium oleate:water = 1.5:1:30:7:0.4:640. All other synthesis conditions remained the same. XRD and SEM characterization of the obtained molecular sieves revealed that they failed to completely transform into crystals.

[0064] Example 4

[0065] The difference from Example 1 lies in the amount of sodium hydroxide added in step A, resulting in a silicon-aluminum mixed solution with a molar composition of Na₂O:Al₂O₃:SiO₂:cyclohexylamine:sodium oleate:water = 2:1:30:7:0.1:640. The obtained molecular sieve was characterized by XRD as ZSM-35 and by SEM, exhibiting a spherical structure composed of multiple nanorods with a grain size between 40 and 100 nm and a nanorod length less than 100 nm.

[0066] Example 5

[0067] The difference from Example 1 lies in the amount of silica sol added in step A, resulting in a silica-alumina mixed solution with a molar composition of Na₂O:Al₂O₃:SiO₂:cyclohexylamine:sodium oleate:water = 1.5:1:20:7:0.1:640. The obtained molecular sieve was characterized by XRD as ZSM-35 and by SEM, exhibiting a spherical structure composed of multiple nanorods assembled together, with a grain size between 40 and 100 nm and a nanorod length less than 100 nm.

[0068] Example 6

[0069] The difference from Example 1 lies in the amount of template agent added in step A, resulting in a silica-alumina mixed solution with a molar composition of Na₂O:Al₂O₃:SiO₂:cyclohexylamine:sodium oleate:water = 1.5:1:30:4:0.1:640. The obtained molecular sieve was characterized by XRD as ZSM-35 and by SEM, exhibiting a spherical structure composed of multiple nanorods with a grain size between 40 and 100 nm and a nanorod length less than 100 nm.

[0070] Example 7

[0071] The difference from Example 1 lies in the amount of deionized water added in step A, resulting in a silica-alumina mixed solution with a molar composition of Na₂O:Al₂O₃:SiO₂:cyclohexylamine:sodium oleate:water = 1.5:1:30:7:0.1:400. The obtained molecular sieve was characterized by XRD as ZSM-35 and by SEM, exhibiting a spherical structure composed of multiple nanorods assembled together, with a grain size between 40 and 100 nm and a nanorod length less than 100 nm.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that the surfactant sodium oleate is not added in step A, while the other steps are the same. The resulting molecular sieve is characterized by XRD as ZSM-35 molecular sieve, and SEM characterization shows that the molecular sieve synthesized by this method has a plate-like structure with a crystal size of 0.5-1 μm (see SEM). Figure 3 c).

[0074] Comparative Example 2

[0075] The difference from Example 1 is that in step A, the surfactant "sodium oleate" was replaced with an equimolar amount of "cetylammonium bromide (CTAB)," while all other synthesis conditions remained the same. The resulting molecular sieve was characterized by XRD and SEM, confirming that the molecular sieve synthesized using this method was ZSM-35, exhibiting a blocky structure of plate-like aggregates (see SEM image). Figure 3 d).

[0076] Comparative Example 3

[0077] The difference from Example 1 is that in step A, the surfactant "sodium oleate" was replaced with an equimolar amount of "sodium petroleum sulfonate". All other synthesis conditions were the same. The molecular sieves obtained were characterized by XRD and SEM and it was found that they failed to completely transform into crystals.

[0078] I. Characterization of catalyst structure and physical properties

[0079] The molecular sieves prepared in Examples 1-7, Comparative Examples 1 and 2 were characterized by nitrogen adsorption, and the specific methods are as follows:

[0080] The nitrogen physical adsorption-desorption isotherms of the molecular sieve were measured using a physical adsorption instrument (such as the TriStar 3000 physical adsorption instrument from Micron Instruments, USA). The specific surface area of ​​the sample was calculated using the Brunauer-Emmett-Teller equation, the pore size distribution was calculated using the BJH model, and the micropore size and surface area were calculated using t-plot technology. The experimental conditions for nitrogen physical adsorption-desorption were: measurement temperature -169℃, and the molecular sieve was pretreated in a vacuum at 350℃ for 16 hours before measurement.

[0081] The molecular sieve pore structure parameters and specific surface area parameters are shown in Table 1.

[0082] Table 1

[0083]

[0084] As can be seen from Table 1, in Examples 1-7 of this application, sodium oleate was used as a surfactant, which not only prepared spherical nano ZSM-35 molecular sieves assembled from nanorod structures, but also significantly improved the specific surface area and external specific surface area compared with molecular sieves obtained without surfactants and compared with molecular sieves obtained by using other conventional surfactants (CTAB) in the prior art.

[0085] II. Characterization of Catalyst Performance

[0086] The catalytic performance of the ZSM-35 molecular sieves prepared in Example 2 and Comparative Example 1 in the dimethyl ether carbonylation to methyl acetate reaction was evaluated under the following conditions:

[0087] ZSM-35 molecular sieves prepared in Example 1 and Comparative Example 1 were weighed and packed into a high-pressure fixed bed. The experimental process parameters were: reaction temperature 200℃, reaction pressure 2.0MPa, dimethyl ether feed rate 0.5Whsv, CO feed rate 200mL / min, and the reaction gas products were analyzed by online analytical chromatography.

[0088] The results of the 45-hour evaluation are as follows Figure 4 As shown, the spherical nano ZSM-35 molecular sieve catalyst prepared in Example 2 exhibits higher reactivity in the dimethyl ether carbonylation reaction. Furthermore, due to its rod-like morphology and smaller crystal size, the catalyst activity decreases more slowly and has a longer lifespan compared to Comparative Example 1.

[0089] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A spherical nano-ZSM-35 molecular sieve, characterized in that, The spherical nano ZSM-35 molecular sieve is self-assembled from multiple long rod-shaped nano ZSM-35 molecular sieves; the grain size of the spherical nano ZSM-35 molecular sieve is preferably 40-100 nm, and the length of the long rod-shaped nano ZSM-35 molecular sieve is preferably within 100 nm.

2. The spherical nano ZSM-35 molecular sieve according to claim 1, characterized in that, The specific surface area of ​​the spherical nano ZSM-35 molecular sieve is not less than 310 m². 2 ·g -1 Preferably, it is 310–330m 2 ·g -1 ; and / or, The spherical nano ZSM-35 molecular sieve has an external specific surface area of ​​not less than 35m². 2 ·g -1 Preferably 35-45m 2 ·g -1 ; and / or, The total pore volume of the spherical nano ZSM-35 molecular sieve is 0.15–0.25 cm³. 3 / g; and / or, The average pore size of the spherical nano ZSM-35 molecular sieve is 2-3 nm.

3. A method for preparing spherical nano-ZSM-35 molecular sieves, comprising the following steps: A mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent, and sodium oleate is subjected to a crystallization reaction to obtain the spherical nano ZSM-35 molecular sieve.

4. The method according to claim 3, characterized in that, The alkali source includes an inorganic alkali source, preferably including hydroxides of alkali metals or alkaline earth metals, more preferably including one or more of sodium hydroxide, potassium hydroxide, and magnesium hydroxide; and / or, The aluminum source includes one or more of sodium aluminate, aluminum sulfate, aluminum chloride, and aluminum nitrate; and / or, The silicon source includes one or more of silica, silica gel, silica sol, and water glass; and / or, The template agent includes organic amine template agents, preferably including cyclohexylamine and / or ethylenediamine.

5. The method according to claim 3 or 4, characterized in that, In the mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent, and sodium oleate, the molar ratio of MxO to Al2O3 is (1-2):1, where M represents an alkali metal or an alkaline earth metal, and x is 1 or 2; and / or, The molar ratio of Al2O3 to SiO2 is 1:(20–35); and / or, The molar ratio of Al2O3 to the template agent is 1:(4–8); and / or, The molar ratio of Al2O3 to sodium oleate is 1:(0.05–0.2); and / or, The molar ratio of Al2O3 to water is 1:(400-800).

6. The method according to any one of claims 3-5, characterized in that, In the mixed solution containing alkali source, aluminum source, silicon source, template agent and sodium oleate, the molar ratio MxO:Al2O3:SiO2:template agent:sodium oleate:water = (1~2):1:(20~35):(4~8):(0.05~0.2):(400~800); M represents alkali metal or alkaline earth metal, and x is 1 or 2.

7. The method according to any one of claims 3-6, characterized in that, The crystallization temperature is 150℃~200℃, preferably 180℃~200℃, and / or the crystallization time is 36h~96h, preferably 48h~72h; and / or the crystallization is static crystallization.

8. The method according to any one of claims 3-7, characterized in that, The mixed solution containing an alkali source, an aluminum source, a silicon source, a template agent, and sodium oleate is prepared by a method comprising the following steps: The alkali source, aluminum source, and solvent are mixed, and then a template agent and sodium oleate are added. Finally, a silicon source is added to obtain the mixed solution containing the alkali source, aluminum source, silicon source, template agent, and sodium oleate. Preferably, the mixing temperature is 10℃~80℃.

9. The method according to any one of claims 3-8, characterized in that, The method further includes: after the crystallization reaction is completed, solid-liquid separation is performed to obtain a solid product, and the solid product is washed, dried and calcined to obtain the spherical nano ZSM-35 molecular sieve; Preferably, the drying temperature is 80℃~120℃; Preferably, the roasting temperature is 450℃~650℃.

10. The application of the spherical nano ZSM-35 molecular sieve as described in claim 1 or 2, or the spherical nano ZSM-35 molecular sieve prepared by the method described in any one of claims 3-9, in the catalytic carbonylation reaction of dimethyl ether; Preferably, the dimethyl ether carbonylation reaction includes the reaction of dimethyl ether carbonylation to produce methyl acetate.

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