Synthesis method and application of hydrogen-type high-silicon small-grain MOR zeolite molecular sieve

Abstract

The invention provides a synthesis method and application of a hydrogen-type high-silicon small-grain MOR zeolite molecular sieve, and belongs to the technical field of molecular sieve synthesis and application. The preparation method comprises the following steps: preparing a mixed solution containing an alkali source, an azabicyclo-containing organic matter, an amino-containing piperidine organic matter and water, adding an aluminum source to form slurry, adding a silicon source and an MOR zeolite molecular sieve seed crystal into the slurry, and uniformly mixing to obtain silicon-aluminum sol; and aging the silica-alumina sol, and carrying out crystallization synthesis reaction and ammonium exchange to obtain the hydrogen-type high-silicon small-grain MOR zeolite molecular sieve. According to the synthesized hydrogen-type high-silicon small-grain MOR zeolite molecular sieve, the Al element is enriched in an eight-membered ring of an MOR zeolite molecular sieve skeleton structure, the number of B acid in the eight-membered ring is increased, the molecular sieve has a small-grain morphology feature structure, acid sites in side reaction in HMOR can be effectively shielded, the molecular sieve is applied to a reaction for synthesizing methyl acetate through dimethyl ether carbonylation, and the yield of methyl acetate is increased. The catalyst has the advantages of high catalytic activity, good product selectivity, simple preparation process and easy industrial amplification.

Description

Technical Field

[0001] This invention relates to a method for synthesizing hydrogen-form high-silica small-crystal MOR zeolite molecular sieves and their applications. Specifically, it relates to the preparation of hydrogen-form high-silica small-crystal MOR molecular sieves as catalysts for use in the carbonylation reaction to produce methyl acetate, belonging to the field of molecular sieve synthesis and application technology. Background Technology

[0002] Mordenite (MOR) is a type of macroporous zeolite with an orthorhombic crystal form (Cmcm, a=1.83nm, b=2.05nm, c=0.75nm). It consists of 12-membered rings (0.65×0.70nm), 8-membered rings (0.26×0.57nm), and 8-membered ring side pockets (0.34×0.48nm) connecting the 12-MR and 8-MR rings. Its 8MR and other pore structures and special topology give it unique catalytic activity for carbonylation reactions. References (Angew. Chem. Int. Ed. 45 (2006) 1, J. Catal. 245 (2007) 110, J. Am. Chem. Soc. 129 (2007) 4919) reported the carbonylation reaction of dimethyl ether in molecular sieve systems with 8-membered and 12 or 10-membered ring structures, such as Mordenite and Ferrierite. The carbonylation reaction was carried out using a mixture of methanol and dimethyl ether. The results showed that the active center for catalytic carbonylation was at the Brønsted acid site of the 8-membered ring, and the reaction achieved a selectivity of over 99% for methyl acetate. Methyl acetate is widely used in the textile, fragrance, and pharmaceutical industries and is an important organic raw material intermediate. Downstream products mainly include acetic acid, acetic anhydride, methyl acrylate, vinyl acetate, and acetamide.

[0003] Hydrogen-form mordenite zeolite (HMOR) molecular sieves possess unique pore structures, large specific surface areas, and strong acidity, making them valuable for industrial applications in the carbonylation of dimethyl ether. Mordenite zeolite exhibits straight channels with 8-membered and 12-membered rings along the

[001] direction, and between the 8-membered and 12-membered rings, there are also straight channels with 8-membered rings along the

[010] direction. For the carbonylation reaction of dimethyl ether, the 8-membered ring provides the active sites, while the active sites of the 12-membered ring are related to the deactivation of the molecular sieve. To improve the conversion rate of dimethyl ether and the selectivity of methyl acetate, it is necessary to selectively increase the active sites of the 8-membered rings of the molecular sieve and weaken the role of the active sites of the 12-membered rings in the reaction. Chinese invention patent CN101613274B utilizes organic amines such as pyridine to modify mordenite molecular sieve catalysts. After modification, pyridine substances are saturated and adsorbed in the channels of the molecular sieve, which can poison the acidic sites in the 12-ring channels of mordenite, inhibit the formation of carbon deposits, and thus improve the stability of the catalyst. However, at the same time, it will reduce its catalytic activity by about 40% to 50%.

[0004] In summary, the ultimate goal of developing highly active and stable molecular sieve catalysts for the carbonylation of dimethyl ether largely depends on two aspects: first, how to regulate active sites and eliminate carbon deposition sites; and second, how to improve mass transfer rates. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies. The synthesized MOR molecular sieve provides more acidic sites in the side-bag 8-membered ring and has a pore structure with better proximity of active sites. The main feature is the use of nitrogen-containing heterocyclic organic molecules as template agents to enrich Al elements in the 8-membered ring of the MOR zeolite molecular sieve structure, increasing the number of Brønsted acid in the 8-membered ring. Secondly, the use of aminopiperidine-containing organic compounds as organic structural aids results in a small crystallite morphology structure, effectively shielding acidic sites in the HMOR from side reactions. The prepared HMOR zeolite molecular sieve is applied to the dimethyl ether carbonylation to synthesize methyl acetate, exhibiting high catalytic activity, good product selectivity, simple preparation process, and easy industrial scale-up.

[0006] The organic template agent selected in this invention is inexpensive and has advantages in terms of cost. The obtained high-silica small-crystal MOR zeolite molecular sieve also forms abundant hierarchical pores, which is conducive to the transport of substances. The raw materials used in this preparation method have great potential in the industrial application of catalytic reactions.

[0007] This invention provides a novel method for synthesizing high-silica small-crystal MOR zeolite molecular sieves. It employs a nitrogen-containing heterobicyclic compound as an organic template agent, increasing the density of 8-membered ring acidic sites in the molecular sieve structure. Using an aminopiperidine-containing organic compound as a crystallization aid facilitates the synthesis of small-crystal MOR zeolite molecular sieves, improves the kinetic diffusion effect of reactant molecules, enhances reaction stability, reduces irreversible adsorption, and extends the lifetime of the molecular sieve catalyst. The obtained catalyst exhibits excellent catalytic activity enhancement in the dimethyl ether carbonylation reaction, with both catalytic activity and stability improved.

[0008] This invention provides a novel template agent for the synthesis of MOR zeolite molecular sieves. The activity is enhanced by enriching the Al sites in the 8-MR pores during the hydrothermal synthesis process. The stability is improved by repositioning the Al atoms in the 8-MR and 12-MR pores. Quantum chemical studies have shown that the T3-O33 site in the 8-MR side pocket is the only active site for DME carbonylation.

[0009] This invention provides a method for synthesizing hydrogen-form high-silica small-crystal MOR zeolite molecular sieves, the synthesis method comprising: (1) Prepare a mixed solution containing an alkaline source, a nitrogen-containing bicyclic organic compound, an aminopiperidine-containing organic compound and water, add an aluminum source to form a slurry, add a silicon source and MOR zeolite molecular sieve seed crystals to the slurry, and mix evenly to obtain a silica-alumina sol. (2) After aging the silica-alumina sol, a crystallization synthesis reaction and ammonium exchange were carried out to obtain hydrogen-type high-silica small-crystal MOR zeolite molecular sieve.

[0010] Further, the nitrogen-containing heterobicyclic organic compound is selected from at least one of 2-azabicyclo[2,2,1]heptane, 7-azabicyclo[2.2.1]heptane, 8-azabicyclo[3.2.1]octane, 1,5-diazabicyclo[3.2.2]nonane, and 1,3-diazabicyclo[3.2.2]nonane.

[0011] Further, the aminopiperidine-containing organic compound is selected from at least one of N-methyl-4-aminopiperidine, 4-dimethylaminopiperidine, N-benzyl-4-aminopiperidine, N-ethoxycarbonyl-4-aminopiperidine, 4-(N-methyl-N-benzyl)aminopiperidine, 1-tert-butoxycarbonyl-4-aminopiperidine, 3-tert-butoxycarbonylaminopiperidine, 4-(N-benzyloxycarbonyl)-aminopiperidine, 1-tert-butoxycarbonyl-3-aminopiperidine, 1-tert-butoxycarbonyl-3-methylaminopiperidine, N-tert-butoxycarbonyl-4-dimethylaminopiperidine, 3-acetaminopiperidine, 1-benzyl-4-aminopiperidine, and 1-aminopiperidine.

[0012] Furthermore, in the silica-alumina sol, the alkali source is calculated as M2O, the silicon source as SiO2, the aluminum source as Al2O3, OSDA is a nitrogen-containing heterocyclic organic compound, SA is an aminopiperidine-containing organic compound, and the molar ratio of each component is 0.04~0.15M2O:SiO2:0.02~0.08Al2O3:0.02~1.0OSDA:0.02~0.25SA:8~40H2O; the amount of MOR zeolite molecular sieve seed crystals added is 1wt%~10wt% of the mass of SiO2, preferably 1wt%~5wt%.

[0013] Furthermore, the aging treatment temperature is 40~130℃, and the aging treatment time is 12~72 hours.

[0014] Furthermore, the aging treatment temperature is 80~120℃, and the aging treatment time is 12~48 hours.

[0015] Furthermore, the temperature of the crystallization synthesis reaction is 140~200℃, and the time of the crystallization synthesis reaction is 12~120 hours.

[0016] Furthermore, the temperature of the crystallization synthesis reaction is 160~190℃, and the time of the crystallization synthesis reaction is 12~72 hours.

[0017] Further, the slurry after the crystallization synthesis reaction is washed with water until the pH is 7-8, dried at 100-120℃ for 4-12 hours, and then calcined at 450-650℃ for 4-12 hours at a heating rate of 1-3℃ / min to obtain molecular sieve raw powder.

[0018] Further, the ammonium exchange involves exchanging calcined molecular sieve powder with a soluble ammonium salt aqueous solution at 60-90°C at a solid-liquid mass ratio of 1:(5-30) for 1-6 hours, and repeating the exchange 1-3 times. The concentration of the soluble ammonium salt aqueous solution is 0.1~1.0 mol / L, and the soluble ammonium salt is selected from at least one of ammonium nitrate, ammonium chloride and ammonium sulfate.

[0019] Furthermore, the ammonium exchange is followed by drying and calcination. The drying temperature is 100~150℃ and the time is 2~24 hours. The calcination temperature is 450~600℃ and the time is 1~12 hours.

[0020] Furthermore, the silicon source is selected from at least one of silica sol, water glass, silica gel, type C silica gel, fumed silica, chromatography silica gel, methyl orthosilicate, and tetraethyl orthosilicate; the aluminum source is selected from at least one of sodium aluminate, sodium aluminate, aluminum hydroxide, boehmite, aluminum nitrate, aluminum chloride, aluminum powder, aluminum isopropoxide, and aluminum sulfate; and the alkali source is selected from at least one of NaOH, Na2O, Na2O2, Na2CO3, and metallic Na.

[0021] The present invention also provides a hydrogen-form high-silica small-crystal MOR zeolite molecular sieve prepared by the above synthesis method, wherein the Si / Al molar ratio of the hydrogen-form high-silica small-crystal MOR zeolite molecular sieve is 30:1 to 5:1; and the primary grain size of the hydrogen-form high-silica small-crystal MOR zeolite molecular sieve is <500 nm.

[0022] Furthermore, the Si / Al molar ratio of the hydrogen-form high-silica small-crystal MOR zeolite molecular sieve is 20:1 to 7:1; the primary grain size of the hydrogen-form high-silica small-crystal MOR zeolite molecular sieve is ≤200nm.

[0023] The present invention also provides an application of the above-mentioned hydrogen-type high-silica small-crystal MOR zeolite molecular sieve in the carbonylation reaction to prepare methyl acetate, wherein methanol carbonylation reaction is carried out with methanol and carbon monoxide, or dimethyl ether carbonylation reaction is carried out with dimethyl ether and carbon monoxide.

[0024] Furthermore, methyl acetate is synthesized by reacting a feed gas containing dimethyl ether, carbon monoxide and hydrogen through a catalyst bed supported by hydrogen-type high-silica small crystallite MOR zeolite molecular sieve at a reaction temperature of 180~280℃, a reaction pressure of 0.5~6.0 MPa and a gas hourly space velocity of 1000~6000 mL / (gcat•h). The molar ratio of dimethyl ether, carbon monoxide and hydrogen in the raw gas is 1:(4~10):(3~15), and a dry inert gas is used as the pretreatment gas.

[0025] Furthermore, the reaction temperature is 180~240℃, the reaction pressure is 2.0~5.0 MPa, and the gas hourly space velocity is 1500~4000 mL / (gcat•h).

[0026] Compared with existing technologies, the advantages of this invention are that the prepared MOR mordenite zeolite molecular sieve has a typical mordenite crystal phase and maintains high crystallinity, without containing amorphous substances or other impurities. Due to the use of a dual-template agent in the synthesis process, compared with traditional H-type catalysts, the aluminum element distribution of the mordenite zeolite molecular sieve can be effectively controlled, allowing aluminum to selectively enter the eight-membered ring, thereby improving the activity of the dimethyl ether carbonylation to methyl acetate reaction. Furthermore, compared with samples synthesized using tetraethylammonium hydroxide as a template agent, this method results in lower silicon loss in the feed solution, facilitates the synthesis of MOR with a higher silicon-to-aluminum ratio, and exhibits higher catalytic activity, thus improving economic efficiency.

[0027] The beneficial effects that this invention can produce include, but are not limited to, the following aspects: 1) Compared with the prior art, the technical solution of the present invention obtains high-silica small-crystal high-crystallinity mordenite MOR molecular sieve, and the molar ratio of Si and Al elements in the molecular sieve framework is adjustable between 10 and 30.

[0028] 2) This invention can directionally regulate the acid distribution in the pores of HMOR molecules. It can selectively shield acidic sites in the twelve-membered ring of HMOR molecular sieve that are prone to carbon deposition while introducing mesopores, and retain active sites with carbonylation function in the eight-membered ring. It has the dual function of improving the mass transfer rate of dimethyl ether carbonylation reaction and shielding active sites that cause side reactions. It can significantly improve the conversion rate and catalytic lifetime of HMOR-catalyzed dimethyl ether carbonylation at the same time.

[0029] 3) The preparation method of mordenite provided by the present invention is simple and conducive to large-scale industrial production; the catalytic effect of the prepared hierarchical porous mordenite molecular sieve on the carbonylation reaction of dimethyl ether is further improved, and the conversion rate of dimethyl ether is increased while maintaining high selectivity.

[0030] 4) This invention provides a catalyst for the production of methyl acetate from dimethyl ether. This catalyst has advantages such as high activity, high space-time yield of methyl acetate, and good stability. It not only ensures high product yield and long lifespan, but also offers a wide range of adjustable reaction conditions, making this invention universally applicable and suitable for a broad range of industrial applications. Attached Figure Description

[0031] Figure 1 The image shows the XRD diffraction pattern of the MOR molecular sieve HMR-1 sample synthesized in Example 1.

[0032] Figure 2 The image shows the SEM morphology of the MOR molecular sieve HMR-1 sample synthesized in Example 1.

[0033] Figure 3 The image shows the XRD diffraction pattern of the MOR molecular sieve HMR-2 sample synthesized in Example 2.

[0034] Figure 4 The image shows the SEM morphology of the MOR molecular sieve HMR-2 sample synthesized in Example 2.

[0035] Figure 5 The image shows the XRD diffraction pattern of the MOR molecular sieve HMR-3 sample synthesized in Example 3.

[0036] Figure 6 The image shows the SEM morphology of the MOR molecular sieve HMR-3 sample synthesized in Example 3.

[0037] Figure 7 The image shows the XRD diffraction pattern of the MOR molecular sieve HMR-4 sample synthesized in Example 4.

[0038] Figure 8 The image shows the SEM morphology of the MOR molecular sieve HMR-4 sample synthesized in Example 4.

[0039] Figure 9 The image shows the XRD diffraction pattern of the MOR molecular sieve HMR-5 sample synthesized in Example 5.

[0040] Figure 10 This is a SEM image of the MOR molecular sieve HMR-5 sample synthesized in Example 5.

[0041] Figure 11 The image shows the XRD diffraction pattern of the MOR molecular sieve HMR-6 sample synthesized in Example 6.

[0042] Figure 12 The image shows the SEM morphology of the MOR molecular sieve HMR-6 sample synthesized in Example 6.

[0043] Figure 13 The image shows the XRD diffraction pattern of the MOR molecular sieve VS-1 sample synthesized in Comparative Example 1.

[0044] Figure 14 The image shows the SEM morphology of the MOR molecular sieve VS-1 sample synthesized in Comparative Example 1.

[0045] Figure 15 The image shows the XRD diffraction pattern of the MOR molecular sieve VS-2 sample synthesized in Comparative Example 2.

[0046] Figure 16 The image shows the SEM morphology of the MOR molecular sieve VS-2 sample synthesized in Comparative Example 2. Detailed Implementation

[0047] The embodiments and comparative examples further illustrate the implementation methods and effects of the present invention, but the scope of protection of the present invention is not limited to the contents listed in the embodiments.

[0048] 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.

[0049] In this embodiment, the sample was characterized by XRD using a PANalytical Xpert Pro diffractometer with Cu Kα rays (λ = 0.15406 nm), tube voltage 45 kV, tube current 40 mA, scanning range 5°~55°, step 0.026°, and each step 17.34 ms. The relative crystallinity was calculated by summing the XRD diffraction peak areas at the five highest characteristic peaks at 2θ = 9.8±0.1°, 19.6±0.1°, 22.3±0.1°, 25.7±0.1°, and 26.3°±0.1°, corresponding to the (200), (330), (150), (202), and (350) crystal planes.

[0050] The detection was performed using a Hitachi SU5000 thermal field emission scanning electron microscope in backscatter mode, with the beam current adjusted to "standard", the accelerating voltage selected as 10kV, and the magnification of 5k~50k.

[0051] In this embodiment, the in-situ infrared spectroscopy used was a Thermo Scientific Nicolet 6700. The specific procedure was as follows: degassing at 450°C under vacuum for 60 minutes, cooling to 150°C, then introducing a 10% NH3 / Ar mixture. After adsorption saturation, vacuum was applied for 30 minutes to remove gaseous and physically adsorbed ammonia molecules. The spectrum was then recorded, starting from 1540 cm⁻¹. -1 The total amount of Brønsted acid in the sample can be calculated from the peak intensity at 1540 cm⁻¹. The amount of Brønsted acid within the twelve-membered ring of the molecular sieve was characterized using pyridine adsorption-infrared spectroscopy. The specific procedure was as follows: degassing at 450℃ under vacuum for 30 min, cooling to 150℃, introducing saturated pyridine vapor, and after static adsorption saturation, evacuating under vacuum for 30 min to remove gaseous and physically adsorbed pyridine molecules. The spectrum was then recorded. -1 The amount of Brønsted acid in the twelve-membered ring can be calculated from the peak area at the peak (Applied Catalysis A: General 417-418 (2012) 236-242). Finally, the total amount of Brønsted acid is subtracted from the amount of Brønsted acid in the twelve-membered ring to obtain the amount of Brønsted acid in the eight-membered ring.

[0052] The seed crystals described in this embodiment of the invention are commercially available MOR zeolite molecular sieves synthesized without template agents. Example 1

[0053] 1) Deionized water, NaOH (purity 99%), and sodium aluminate (Na2O content: 30.62wt%, Al2O3 content: 38.50wt%) were mixed into a homogeneous solution and stirred continuously for 30 min. Then, 2-aza-bicyclo[2,2,1]heptane (purity 99%, denoted as OSDA) and N-methyl-4-aminopiperidine (purity 99%, denoted as SA) were added. Subsequently, silica sol (SiO2 content: 29.19wt%, Na2O content: 0.07wt%) was added to the above mixed solution. Seed crystals were added, and the mixture was stirred vigorously at room temperature for 30 min to obtain a crystallized slurry precursor with the following molar ratio: 0.067Na2O: SiO2: 0.02632Al2O3: 0.08OSDA: 0.023SA: 20H2O. The amount of seed crystals added was 2% of the total weight of SiO2 in the synthesized slurry.

[0054] 2) The gelling slurry was transferred to the inner liner of a hydrothermal crystallization autoclave and placed in a constant temperature oven for static aging at 100℃ for 12 hours, followed by dynamic crystallization at 170℃ for 36 hours. After hydrothermal crystallization, the product slurry was removed and filtered. The filter cake was repeatedly washed with deionized water and dried in a 120℃ oven for 8 hours. It was then calcined in a muffle furnace at 550℃ (3℃ / min heating) for 4 hours to obtain Na-type MOR zeolite molecular sieve with a silicon-to-aluminum ratio of nSiO2 / nAl2O3 = 30.90 and a relative crystallinity of 100%.

[0055] 3) The Na-type MOR zeolite molecular sieve sample powder was dissolved in 0.5 mol / L ammonium nitrate solution, and ion exchange was carried out at 80℃ for 3 h at a solid-liquid mass ratio of 1:25. This process was repeated twice. The obtained NH4-type MOR was recovered by filtration, dried, and then calcined in a muffle furnace at 500℃ for 4 h to obtain H-type MOR, which was labeled as HMR-1. Example 2

[0056] 1) Deionized water, Na2O2 (purity 99%), and boehmite (Al2O3 content: 78wt%) were mixed into a homogeneous solution and stirred continuously for 30 min. Then, 7-azabicyclo[2.2.1]heptane (purity 99%, denoted as OSDA) and N-benzyl-4-aminopiperidine (purity 99%, denoted as SA) were added. Subsequently, water glass (SiO2 content: 29.92wt%, Na2O content: 10.76wt%) was added to the above mixed solution. Seed crystals were added, and the mixture was stirred vigorously at room temperature for 30 min to obtain a crystallized slurry precursor with the following molar ratio: 0.105Na2O: SiO2: 0.02786Al2O3: 0.133OSDA: 0.09SA: 16.7H2O. The amount of seed crystals added was 5% of the total weight of SiO2 in the synthesized slurry.

[0057] 2) The gelling slurry was transferred to the inner liner of a hydrothermal crystallization autoclave and placed in a constant temperature oven for static aging at 80℃ for 24 hours, followed by dynamic crystallization at 190℃ for 15 hours. After hydrothermal crystallization, the product slurry was removed and filtered. The filter cake was repeatedly washed with deionized water and dried in a 105℃ oven for 12 hours. It was then calcined in a muffle furnace at 540℃ (3℃ / min heating) for 6 hours to obtain Na-type MOR zeolite molecular sieve with a silicon-to-aluminum ratio of nSiO2 / nAl2O3 = 26.70 and a relative crystallinity of 101%.

[0058] 3) The Na-type MOR zeolite molecular sieve sample powder was dissolved in 1.0 mol / L ammonium chloride solution, and ion exchange was carried out at 90℃ for 3 h at a solid-liquid mass ratio of 1:10. The process was repeated once. The obtained NH4-type MOR was recovered by filtration, dried, and then calcined in a muffle furnace at 550℃ for 4 h to obtain H-type MOR, which was labeled as HMR-2. Example 3

[0059] 1) Deionized water, NaOH (99% purity), Na2CO3 (99% purity), and aluminum hydroxide (99wt% purity) were mixed into a homogeneous solution and stirred continuously for 30 min. Then, 8-azabicyclo[3.2.1]octane (99% purity, denoted as OSDA) and 4-dimethylaminopiperidine (99% purity, denoted as SA) were added. Subsequently, silica (SiO2 content: 93.09wt%) was added to the aforementioned mixed solution. Seed crystals were added, and the mixture was stirred vigorously at room temperature for 30 min to obtain a crystallized slurry precursor. The molar ratio of its components was: 0.111Na2O:SiO2: 0.03623Al2O3: 0.384OSDA: 0.15SA: 25H2O. The amount of seed crystals added was 3% of the total weight of SiO2 in the synthesized slurry.

[0060] 2) The gelling slurry was transferred to the inner liner of a hydrothermal crystallization autoclave and placed in a constant temperature oven for static aging at 120℃ for 24 hours, followed by dynamic crystallization at 150℃ for 72 hours. After hydrothermal crystallization, the product slurry was removed and filtered. The filter cake was repeatedly washed with deionized water and dried in an oven at 110℃ for 12 hours. It was then calcined in a muffle furnace at 500℃ (3℃ / min heating) for 6 hours to obtain Na-type MOR zeolite molecular sieve with a silicon-to-aluminum ratio of nSiO2 / nAl2O3 = 22.40 and a relative crystallinity of 103%.

[0061] 3) The Na-type MOR zeolite molecular sieve sample powder was dissolved in 1.5 mol / L ammonium sulfate solution, and ion exchange was carried out at 60℃ for 3 h at a solid-liquid mass ratio of 1:5. This process was repeated twice. The obtained NH4-type MOR was recovered by filtration, dried, and then calcined in a muffle furnace at 520℃ for 6 h to obtain H-type MOR, which was labeled as HMR-3. Example 4

[0062] 1) Deionized water, NaOH (purity 99%), and sodium aluminate (Na2O content: 39.38wt%, Al2O3 content: 49.95wt%) were mixed into a homogeneous solution and stirred continuously for 30 min. Then, 1,3-diazabicyclo[3.2.2]nonane (purity 99%, denoted as OSDA) and 1-tert-butoxycarbonyl-3-aminopiperidine (purity 99%, denoted as SA) were added. Subsequently, C-type silica gel (SiO2 content: 91.54wt%) was added to the aforementioned mixed solution. Seed crystals were added, and the mixture was stirred vigorously at room temperature for 30 min to obtain a crystallized slurry precursor with the following molar ratio: 0.052Na2O: SiO2: 0.04444Al2O3: 0.04OSDA: 0.22SA: 30H2O. The amount of seed crystals added was 2% of the total weight of SiO2 in the synthesized slurry.

[0063] 2) The gelling slurry was transferred to the inner liner of a hydrothermal crystallization autoclave and placed in a constant temperature oven for static aging at 60℃ for 48 hours, followed by dynamic crystallization at 140℃ for 90 hours. After hydrothermal crystallization, the product slurry was removed and filtered. The filter cake was repeatedly washed with deionized water and dried in a 130℃ oven for 4 hours. It was then calcined in a muffle furnace at 500℃ (3℃ / min heating) for 8 hours to obtain Na-type MOR zeolite molecular sieve with a silicon-to-aluminum ratio of nSiO2 / nAl2O3 = 14.50 and a relative crystallinity of 105%.

[0064] 3) The Na-type MOR zeolite molecular sieve sample powder was dissolved in 1.0 mol / L ammonium nitrate solution, and ion exchange was carried out at 90℃ for 2 h at a solid-liquid mass ratio of 1:10. This process was repeated 3 times. The obtained NH4-type MOR was recovered by filtration, dried, and then calcined in a muffle furnace at 560℃ for 4 h to obtain H-type MOR, which was labeled as HMR-4. Example 5

[0065] 1) Deionized water, Na2O (99% purity), and aluminum isopropoxide (99wt% purity) were mixed into a homogeneous solution and stirred continuously for 30 min. Then, 1,5-diazabicyclo[3.2.2]nonane (99% purity, denoted as OSDA) and 1-aminopiperidine (99% purity, denoted as SA) were added. Subsequently, methyl orthosilicate (99wt% purity) was added to the aforementioned mixed solution. Seed crystals were added, and the mixture was stirred vigorously at room temperature for 30 min to obtain a crystallized slurry precursor. The molar ratio of its components was: 0.132Na2O: SiO2: 0.02268Al2O3: 0.107OSDA: 0.05SA: 35H2O. The amount of seed crystals added was 1% of the total weight of SiO2 in the synthesized slurry.

[0066] 2) The gelling slurry was transferred to the inner liner of a hydrothermal crystallization autoclave and placed in a constant temperature oven for static aging at 130℃ for 24 hours, followed by dynamic crystallization at 150℃ for 72 hours. After hydrothermal crystallization, the product slurry was removed and filtered. The filter cake was repeatedly washed with deionized water and dried in an oven at 105℃ for 12 hours. It was then calcined in a muffle furnace at 550℃ (3℃ / min heating) for 6 hours to obtain Na-type MOR zeolite molecular sieve with a silicon-to-aluminum ratio of nSiO2 / nAl2O3 = 34.60 and a relative crystallinity of 98%.

[0067] 3) The Na-type MOR zeolite molecular sieve sample powder was dissolved in 0.5 mol / L ammonium chloride solution, and ion exchange was carried out at 60℃ for 3 h at a solid-liquid mass ratio of 1:15. This process was repeated twice. The obtained NH4-type MOR was recovered by filtration, dried, and then calcined in a muffle furnace at 550℃ for 6 h to obtain H-type MOR, which was labeled as HMR-5. Example 6

[0068] 1) Deionized water, NaOH (99% purity), and aluminum nitrate (99wt% purity) were mixed into a homogeneous solution and stirred continuously for 30 min. Then, 2-aza-bicyclo[2,2,1]heptane (99% purity, denoted as OSDA) and N-ethoxycarbonyl-4-aminopiperidine (99% purity, denoted as SA) were added. Subsequently, tetraethyl orthosilicate (99wt% purity) was added to the aforementioned mixed solution. Seed crystals were added, and the mixture was stirred vigorously at room temperature for 30 min to obtain a crystallized slurry precursor. The molar ratio of its components was: 0.055Na2O: SiO2:0.02212Al2O3: 0.148OSDA: 0.11SA: 40H2O. The amount of seed crystals added was 8% of the total weight of SiO2 in the synthesized slurry.

[0069] 2) The gelling slurry was transferred to the inner liner of a hydrothermal crystallization autoclave and placed in a constant temperature oven for static aging at 60℃ for 24 hours, followed by dynamic crystallization at 170℃ for 24 hours. After hydrothermal crystallization, the product slurry was removed and filtered. The filter cake was repeatedly washed with deionized water and dried in a 125℃ oven for 12 hours. It was then calcined in a muffle furnace at 540℃ (3℃ / min heating) for 4 hours to obtain Na-type MOR zeolite molecular sieve with a silicon-to-aluminum ratio of nSiO2 / nAl2O3 = 38.80 and a relative crystallinity of 96%.

[0070] 3) The Na-type MOR zeolite molecular sieve sample powder was dissolved in 1.0 mol / L ammonium nitrate solution, and ion exchange was carried out at 70℃ at a solid-liquid mass ratio of 1:10 for 4 h. The process was repeated twice. The obtained NH4-type MOR was recovered by filtration, dried, and then calcined in a muffle furnace at 550℃ for 6 h to obtain H-type MOR, which was labeled as HMR-6. Example 7

[0071] 1) Deionized water, NaOH (99% purity), and aluminum sulfate octadecyl water (99wt% purity) were mixed into a homogeneous solution and stirred continuously for 30 min. Then, 8-azabicyclo[3.2.1]octane (99% purity, denoted as OSDA) and 1-benzyl-4-aminopiperidine (99% purity, denoted as SA) were added. Subsequently, water glass (SiO2 content: 29.92wt%, Na2O content: 10.76wt%) was added to the above mixed solution. Seed crystals were added, and the mixture was stirred vigorously at room temperature for 30 min to obtain a crystallized slurry precursor. The molar ratio of its components was: 0.045Na2O: SiO2: 0.03623Al2O3: 0.182OSDA: 0.25SA: 32H2O. The amount of seed crystals added was 10% of the total weight of SiO2 in the synthesized slurry.

[0072] 2) The gelling slurry was transferred to the inner liner of a hydrothermal crystallization autoclave and placed in a constant temperature oven for static aging at 120℃ for 24 hours, followed by dynamic crystallization at 180℃ for 32 hours. After hydrothermal crystallization, the product slurry was removed and filtered. The filter cake was repeatedly washed with deionized water and dried in a 120℃ oven for 12 hours. It was then calcined in a muffle furnace at 550℃ (3℃ / min heating) for 6 hours to obtain Na-type MOR zeolite molecular sieve with a silicon-to-aluminum ratio of nSiO2 / nAl2O3 = 18.40 and a relative crystallinity of 104%.

[0073] 3) The Na-type MOR zeolite molecular sieve sample powder was dissolved in 1.5 mol / L ammonium nitrate solution, and ion exchange was carried out at 90℃ for 3 h at a solid-liquid mass ratio of 1:15. This process was repeated twice. The obtained NH4-type MOR was recovered by filtration, dried, and then calcined in a muffle furnace at 500℃ for 6 h to obtain H-type MOR, which was labeled as HMR-7. Example 8

[0074] 1) Mix deionized water, NaOH (99% purity) and aluminum powder (99wt% purity) into a homogeneous solution, and stir continuously for 30 min. Then add 7-azabicyclo[2.2.1]heptane (99% purity, denoted as OSDA) and 3-acetaminopiperidine (99% purity, denoted as SA). Subsequently, add silica gel (95wt% dry basis) to the above mixed solution, add seed crystals, and stir vigorously at room temperature for 30 min to obtain a crystallized slurry precursor with the following molar ratio: 0.142Na2O: SiO2: 0.0295Al2O3: 0.409OSDA: 0.25SA: 12.5H2O. The amount of seed crystals added is 6% of the total weight of SiO2 in the synthesized slurry.

[0075] 2) The gelling slurry was transferred to the inner liner of a hydrothermal crystallization autoclave and placed in a constant temperature oven for static aging at 115℃ for 36 hours, followed by dynamic crystallization at 180℃ for 28 hours. After hydrothermal crystallization, the product slurry was removed and filtered. The filter cake was repeatedly washed with deionized water and dried in a 115℃ oven for 24 hours. It was then calcined in a muffle furnace at 550℃ (3℃ / min heating) for 8 hours to obtain Na-type MOR zeolite molecular sieve with a silicon-to-aluminum ratio of nSiO2 / nAl2O3 = 28.50 and a relative crystallinity of 106%.

[0076] 3) The Na-type MOR zeolite molecular sieve sample powder was dissolved in 0.5 mol / L ammonium sulfate solution, and ion exchange was carried out at 90℃ for 2 h at a solid-liquid mass ratio of 1:30. This process was repeated twice. The obtained NH4-type MOR was recovered by filtration, dried, and then calcined in a muffle furnace at 540℃ for 6 h to obtain H-type MOR, which was labeled as HMR-8. Example 9

[0077] 1) Deionized water, NaOH (99% purity), and aluminum chloride (99wt% purity) were mixed into a homogeneous solution and stirred continuously for 30 min. Then, 1,3-diazabicyclo[3.2.2]nonane (99% purity, denoted as OSDA) and 1-tert-butoxycarbonyl-3-methylaminopiperidine (99% purity, denoted as SA) were added. Subsequently, silica sol (SiO2 content: 29.19wt%, Na2O content: 0.07wt%) was added to the aforementioned mixed solution. Seed crystals were added, and the mixture was stirred vigorously at room temperature for 30 min to obtain a crystallized slurry precursor with the following molar ratio: 0.089Na2O: SiO2: 0.03937Al2O3: 0.125OSDA: 0.12SA: 18.5H2O. The amount of seed crystals added was 7% of the total weight of SiO2 in the synthesized slurry.

[0078] 2) The gelling slurry was transferred to the inner liner of a hydrothermal crystallization autoclave and placed in a constant temperature oven for static aging at 50℃ for 48 hours, followed by dynamic crystallization at 170℃ for 96 hours. After hydrothermal crystallization, the product slurry was removed and filtered. The filter cake was repeatedly washed with deionized water and dried in a 110℃ oven for 12 hours. It was then calcined in a muffle furnace at 520℃ (3℃ / min heating) for 6 hours to obtain Na-type MOR zeolite molecular sieve with a silicon-to-aluminum ratio of nSiO2 / nAl2O3 = 20.4 and a relative crystallinity of 102%.

[0079] 3) The Na-type MOR zeolite molecular sieve sample powder was dissolved in 0.8 mol / L ammonium nitrate solution, and ion exchange was carried out at 70℃ for 3 h at a solid-liquid mass ratio of 1:15. This process was repeated twice. The obtained NH4-type MOR was recovered by filtration, dried, and then calcined in a muffle furnace at 550℃ for 6 h to obtain H-type MOR, which was labeled as HMR-9.

[0080] Comparative Example 1 0.8 g NaOH and 1.457 g NaAlO2 were mixed, and 24 g water was added and stirred to dissolve. Then, 5 g piperazine and 5 g triethylenediamine were added as template agents and dissolved evenly. 3 g γ-aminobutyric acid was added and stirred evenly. 20 g silica sol containing 40% silica (by mass) was added and stirred evenly to form a gel precursor. The precursor was aged at 80 °C for 2 days, then transferred to an oven and crystallized at 170 °C for 3 days. After cooling, filtration, washing, and drying, the product was calcined at 550 °C and then added to a 2.0 mol / L NH4Cl solution. The molecular sieve mass to NH4Cl solution volume ratio was 1:30, and the temperature was 80 °C for 6 hours. The mixture was filtered and washed, and this process was repeated three times. Then, it was calcined at 540 °C for 5 hours in air to obtain the corresponding hydrogen-form mordenite with a relative crystallinity of 88%, denoted as VS-1.

[0081] Comparative Example 2 Weigh 24g of silica sol (SiO2 content 20wt%), 0.82g of sodium aluminate, and 0.96g of sodium hydroxide into a plastic beaker, mix them thoroughly, and stir at room temperature for 4 hours to obtain a homogeneous sol. Weigh cycloheximine and tetraethylammonium hydroxide as dual template agents, such that the molar ratio of cycloheximine to silica is 0.05 and the molar ratio of tetraethylammonium hydroxide to silica is 0.23. After they are thoroughly mixed, add them to the above sol, and continue stirring at room temperature (25℃) for 1.5 hours for aging. Then, pack the mixture into a reactor and begin crystallization at 180℃ for 48 hours. After crystallization, the sample was filtered, washed with water until pH < 10, calcined at 550℃ in air for 5 h to remove the template agent, exchanged twice in a 0.2 mol / L ammonium nitrate solution, and calcined at 500℃ in air for 4 h to remove ammonia, yielding hydrogen-form mordenite with a relative crystallinity of 93%, labeled as sample VS-2.

[0082] Table 1. Brønsted acid site content of 8-membered and 12-membered rings in the synthesized MOR molecular sieves from the examples.

[0083] As shown in Table 1, the analysis of catalyst samples VS-1 and VS-2 in Comparative Examples 1 and 2 revealed that the eight-membered ring accounted for 55%–60% of the total Brønsted acid content. In contrast, catalyst samples HMR-1–HMR-9 in Examples 1–9 used nitrogen-containing bicyclic basic molecules as organic templates. During hydrothermal synthesis, due to molecular size limitations, these molecules preferentially occupied the twelve-membered ring channels, making it easier for Al atoms to insert into the eight-membered ring. Furthermore, the use of aminopiperidine-containing organic compounds as organic structure-directing agents during the synthesis process enabled the rapid achievement of high crystallinity and controlled the placement of Al atoms within the eight-membered ring, leading to Al enrichment and an increase in the amount of Brønsted acid within the eight-membered ring. Ultimately, this resulted in a catalyst more favorable for the dimethyl ether / methanol carbonylation reaction.

[0084] Examples 10-20 Catalyst samples from Examples 1-9 and Comparative Examples 1-2 were prepared into catalyst particles for evaluation of dimethyl ether carbonylation reaction. 1) A fixed-bed reactor tube with an inner diameter of 10mm and a length of 530mm is used. The reactor is 400mm long. 4g of molded catalyst (20~40 mesh) is loaded into the constant temperature section of the reactor. Quartz sand is filled above and below the catalyst.

[0085] 2) The catalyst was heated according to the following program conditions at a flow rate of 50 ml / min of N2: room temperature → 5 h → 560 ℃ → 6 h → 560 ℃ → stop heating → purge and reduce to 230 ℃.

[0086] 3) Pyridine is introduced via nitrogen gas: 230℃→3h→280℃→3h→280℃→Stop pyridine introduction. Switch to using high-purity N2 to purge excess pyridine adhering to the catalyst.

[0087] 4) The feedstock is a mixture of dimethyl ether (DME), carbon monoxide (CO), and hydrogen (H2), with a DME / CO / H2 ratio of 5 / 35 / 60 (volume ratio), a volume hourly space velocity (GHSV) of 3000 mL / (gcat•h), a reaction pressure of 4.5 MPa, and an initial reaction temperature of 200 °C. The reaction proceeds from top to bottom through the catalyst bed. The reaction is continuously run, and the results are monitored after 50 hours and 200 hours. The gaseous products are analyzed online using an Agilent Technologies 7890A gas chromatograph. The reactor effluent is analyzed online using a gas chromatograph equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID).

[0088] The conversion of dimethyl ether (DME) and the selectivity of methyl acetate (MA) are both calculated based on the number of carbon moles of dimethyl ether: Dimethyl ether conversion rate = [(number of carbon moles of dimethyl ether in feed gas) - (number of carbon moles of dimethyl ether in product)] ÷ (number of carbon moles of dimethyl ether in feed gas) × (100%); Selectivity of methyl acetate = (2 / 3) × (number of carbon moles of methyl acetate in the product) ÷ [(number of carbon moles of dimethyl ether in the feed gas) - (number of carbon moles of dimethyl ether in the product)] × (100%).

[0089] Table 2. Results of the H-MOR zeolite molecular sieve-catalyzed dimethyl ether carbonylation to methyl acetate synthesis in the examples and comparative examples.

[0090] As shown in Table 2, the MOR molecular sieve catalyst prepared by the method of the present invention exhibits a dimethyl ether carbonylation reaction conversion rate (TOS=50h) of over 50% and a methyl acetate selectivity >90%. In contrast, the catalysts VS-1 and VS-2 prepared by the comparative method show conversion rates of <35% and methyl acetate selectivity of <98% at TOS=50h, respectively. This indicates that the catalyst provided by the present invention possesses excellent catalytic activity and selectivity in the dimethyl ether carbonylation reaction to produce methyl acetate.

[0091] The MOR zeolite molecular sieve catalyst prepared by the method of the present invention exhibits a dimethyl ether carbonylation conversion rate of >45% and a methyl acetate selectivity of >99% at TOS=100 h, while the conversion rate and methyl acetate selectivity of catalysts VS-1 and VS-2 prepared by the comparative method are <33% and <97.5%, respectively, at TOS=100 h. At TOS=200 h, the dimethyl ether carbonylation conversion rate and methyl acetate selectivity are >40% and >99%, respectively, while the conversion rate and methyl acetate selectivity of catalysts VS-1 and VS-2 prepared by the comparative method are <31% and <97.0%, respectively, at TOS=200 h. This demonstrates that the catalyst provided by the present invention possesses excellent catalytic activity and deactivation resistance.

[0092] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for synthesizing hydrogen-form high-silica small-crystal MOR zeolite molecular sieves, characterized in that, The synthesis method includes: (1) Prepare a mixed solution containing an alkaline source, a nitrogen-containing bicyclic organic compound, an aminopiperidine-containing organic compound and water, add an aluminum source to form a slurry, add a silicon source and MOR zeolite molecular sieve seed crystals to the slurry, and mix evenly to obtain a silica-alumina sol. (2) After aging the silica-alumina sol, a crystallization synthesis reaction is carried out, followed by ammonium exchange, to obtain hydrogen-type high-silica small-crystal MOR zeolite molecular sieve.

2. The synthesis method according to claim 1, characterized in that, The nitrogen-containing heterobicyclic organic compound is selected from at least one of 2-azabicyclo[2,2,1]heptane, 7-azabicyclo[2.2.1]heptane, 8-azabicyclo[3.2.1]octane, 1,5-diazabicyclo[3.2.2]nonane, and 1,3-diazabicyclo[3.2.2]nonane; And / or, the aminopiperidine-containing organic compound is selected from at least one of N-methyl-4-aminopiperidine, 4-dimethylaminopiperidine, N-benzyl-4-aminopiperidine, N-ethoxycarbonyl-4-aminopiperidine, 4-(N-methyl-N-benzyl)aminopiperidine, 1-tert-butoxycarbonyl-4-aminopiperidine, 3-tert-butoxycarbonylaminopiperidine, 4-(N-benzyloxycarbonyl)-aminopiperidine, 1-tert-butoxycarbonyl-3-aminopiperidine, 1-tert-butoxycarbonyl-3-methylaminopiperidine, N-tert-butoxycarbonyl-4-dimethylaminopiperidine, 3-acetaminopiperidine, 1-benzyl-4-aminopiperidine, and 1-aminopiperidine.

3. The synthesis method according to claim 1 or 2, characterized in that, In the silica-alumina sol, the alkali source is calculated as M2O, the silicon source as SiO2, the aluminum source as Al2O3, OSDA is a nitrogen-containing heterocyclic organic compound, SA is an aminopiperidine-containing organic compound, and the molar ratio of each component is 0.04~0.15M2O:SiO2:0.02~0.08Al2O3:0.02~1.0OSDA:0.02~0.25SA:8~40H2O; the amount of MOR zeolite molecular sieve seed crystals added is 1wt%~10wt% of the mass of SiO2, preferably 1wt%~5wt%.

4. The synthesis method according to any one of claims 1 to 3, characterized in that, The aging process is carried out at a temperature of 40~130℃, preferably 80~120℃, and the aging process is carried out for a time of 12~72 hours, preferably 12~48 hours. And / or, the temperature of the crystallization synthesis reaction is 140~200℃, preferably 160~190℃, and the time of the crystallization synthesis reaction is 12~120 hours, preferably 12~72 hours; And / or, the slurry after the crystallization synthesis reaction is washed with water until the pH is 7-8, dried at 100-120℃ for 4-12h, and then calcined at 450-650℃ for 4-12h at a heating rate of 1-3℃ / min to obtain molecular sieve raw powder.

5. The synthesis method according to any one of claims 1 to 4, characterized in that, The ammonium exchange involves exchanging calcined molecular sieve powder with a soluble ammonium salt aqueous solution at 60-90°C at a solid-liquid mass ratio of 1:(5-30) for 1-6 hours, and repeating the exchange 1-3 times. The concentration of the soluble ammonium salt aqueous solution is 0.1~1.0 mol / L, and the soluble ammonium salt is selected from at least one of ammonium nitrate, ammonium chloride and ammonium sulfate.

6. The synthesis method according to any one of claims 1 to 5, characterized in that, After ammonium exchange, the mixture is dried and calcined. The drying temperature is 100~150℃ and the time is 2~24 hours. The calcination temperature is 450~600℃ and the time is 1~12 hours.

7. The synthesis method according to any one of claims 1 to 6, characterized in that, The silicon source is selected from at least one of silica sol, water glass, silica gel, type C silica gel, fumed silica, chromatography silica gel, methyl orthosilicate, and tetraethyl orthosilicate; the aluminum source is selected from at least one of sodium aluminate, sodium aluminate, aluminum hydroxide, boehmite, aluminum nitrate, aluminum chloride, aluminum powder, aluminum isopropoxide, and aluminum sulfate; the alkali source is selected from at least one of NaOH, Na2O, Na2O2, Na2CO3, and metallic Na.

8. A hydrogen-form high-silica small-crystal MOR zeolite molecular sieve prepared by the synthesis method according to any one of claims 1 to 7, characterized in that, The Si / Al molar ratio of the hydrogen-form high-silica small-crystal MOR zeolite molecular sieve is 30:1~5:1, preferably 20:1~7:1; the primary grain size of the hydrogen-form high-silica small-crystal MOR zeolite molecular sieve is <500nm, preferably ≤200nm.

9. The application of the hydrogen-form high-silica small-crystal MOR zeolite molecular sieve of claim 8 in the carbonylation reaction to prepare methyl acetate, characterized in that, Methanol carbonylation can be carried out using methanol and carbon monoxide, or dimethyl ether carbonylation can be carried out using dimethyl ether and carbon monoxide.

10. The application according to claim 9, characterized in that, Methyl acetate is synthesized by reacting a feed gas containing dimethyl ether, carbon monoxide, and hydrogen through a catalyst bed supported on a hydrogen-type high-silica small-crystal MOR zeolite molecular sieve. The reaction temperature is 180~280℃, preferably 180~240℃, the reaction pressure is 0.5~6.0 MPa, preferably 2.0~5.0 MPa, and the gas hourly space velocity is 1000~6000 mL / (gcat•h), preferably 1500~4000 mL / (gcat•h). The molar ratio of dimethyl ether, carbon monoxide and hydrogen in the raw gas is 1:(4~10):(3~15), and a dry inert gas is used as the pretreatment gas.

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