A method for modifying a mordenite molecular sieve and use thereof
By treating sodium-type mordenite molecular sieves with low-temperature plasma technology, combined with ammonium ion exchange and calcination, the problems of insufficient catalytic activity and stability of mordenite molecular sieves were solved, and a highly efficient catalytic effect for the conversion of dimethyl ether to methyl acetate was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YANCHANG ZHONGKE (DALIAN) ENERGY TECH CO LTD
- Filing Date
- 2023-12-25
- Publication Date
- 2026-06-26
Smart Images
Figure CN117861712B_ABST
Abstract
Description
Technical Field
[0001] This application relates to a method for modifying mordenite molecular sieves and its application, belonging to the field of industrial catalysis technology. Background Technology
[0002] Ethanol is a basic chemical raw material widely used in chemical, pharmaceutical, food, and military industries. As a clean and pollution-free green energy source, ethanol can also serve as an excellent vehicle fuel and fuel additive. To ensure energy and food security, developing non-petroleum, non-grain routes for ethanol production, utilizing my country's abundant coal resources, is of great significance for the clean and efficient conversion of coal.
[0003] Currently, the green ethanol synthesis route, which utilizes raw materials such as coal, biomass, and shale gas to synthesize dimethyl ether (DME), prepares methyl acetate (MA) via carbonylation, and then hydrogenates methyl acetate to produce ethanol, holds significant promise for industrial applications and has attracted widespread attention. Developing highly active and stable DME carbonylation catalysts is one of the key challenges in this process. Although mordenite (H-MOR) exhibits good activity in DME carbonylation, it still suffers from low catalytic activity, poor stability, and a limited number of active sites, which restricts its commercial application.
[0004] In the synthesis of mordenite, organic materials are often required as templates. In the initially synthesized molecular sieves, the organic template fills the channels, which can only be opened after the template is removed. Although there are reports of template-free methods for preparing mordenite, industrial synthesis still largely relies on template methods. Traditional methods for removing templates often involve high-temperature calcination, which is effective in removing templates, but the excessively high temperatures often cause the molecular sieve framework to undergo transformation or shrinkage. In addition, aluminum atoms in the molecular sieve framework are frequently removed, thus affecting the catalytic performance of the molecular sieve. Summary of the Invention
[0005] Plasma is the fourth state of matter, on the same level as solid, liquid, and gas. Low-temperature plasma is rich in electrons, ions, free radicals, and excited-state molecules. Electrons and ions exhibit high reactivity, enabling chemical reactions that are difficult or slow to occur under normal conditions to proceed very rapidly. Based on energy state and particle density, plasma can be divided into high-temperature and low-temperature plasmas, with low-temperature plasmas further subdivided into hot and cold plasmas. Cold plasma is characterized by high electron temperature and low overall temperature, making it widely applicable in fields such as semiconductor manufacturing, waste gas treatment, metallurgy, and chemical reactions. In the 1980s, Maesen et al. (Chemical Communications, 1987, 1284-1285) explored the use of air radio frequency discharge plasma to remove organic templates from MFI-type molecular sieves. This method has the advantage of operating at low temperatures, avoiding problems that may arise from high-temperature calcination. However, this method uses radio frequency discharge plasma operated under vacuum, resulting in a limited concentration of reactive oxygen species, thus restricting the rate of organic template removal. CN106145142A discloses a method for removing template agents from ZSM-5, Beta, and MCM series molecular sieves. This method uses dielectric barrier discharge technology to remove template agents from molecular sieves containing organic template agents, selecting O2 as the plasma working gas. After removing the template agent using this method, the crystal structure of the molecular sieve remains unaffected. Kim et al. (IEEE Transactions on Plasma Science, 2006, 34(3): 984-995) used dielectric barrier discharge plasma to assist oxides and molecular sieve catalysts in decomposing benzene. When the molecular sieve was used as a catalyst, it exhibited a considerable decomposition rate and excellent carbon balance. Due to its high efficiency, energy saving, and low temperature characteristics, low-temperature plasma technology has significant application potential and broad development prospects in the field of catalysis. However, none of the above methods can solve the problem of the catalytic performance of sodium-type mordenite containing template agents and not calcined.
[0006] According to one aspect of this application, a method for modifying mordenite molecular sieves is provided. This method, for a specific sodium-type mordenite, uses a specific gradient voltage, along with an appropriate amount of plasma generating gas and voltage treatment time, to make the mordenite exhibit higher acid density.
[0007] A method for modifying mordenite molecular sieves includes:
[0008] Sodium-type mordenite molecular sieve containing a template agent was placed in a low-temperature plasma and modified under preset conditions to obtain a modified sodium-type mordenite molecular sieve.
[0009] The modified sodium-type mordenite molecular sieve was subjected to ammonium ion exchange treatment to obtain ammonium-type mordenite molecular sieve.
[0010] The ammonium-type mordenite molecular sieve was calcined to obtain hydrogen-type mordenite molecular sieve.
[0011] The preset conditions include:
[0012] The plasma generator uses an oxygen-containing gas.
[0013] Modification is performed under gradient voltage;
[0014] The modification treatment time is 1-120 min.
[0015] Optionally, under preset conditions, the modification treatment under gradient voltage includes treatment under two or more different voltages, wherein the voltage is between 5-50KV.
[0016] Optionally, the modification process under gradient voltage includes:
[0017] Set up voltages U1, U2, ..., Un, with processing times T1, T2, ..., Tn for each voltage;
[0018] Wherein, 20 ≥ n ≥ 2;
[0019] 50KV≥Un>……>U2>U1≥5KV;
[0020] T1, T2, ..., Tn are independently 0.5 min to 100 min.
[0021] Optionally, 15KV≥U n -U n-1 ≥2KV;
[0022] T1 = T2 = ... = T n .
[0023] Preferably, 5 ≥ n ≥ 2.
[0024] Preferably, 10KV≥U n -U n-1 ≥5KV.
[0025] Preferably, T1, T2, ..., Tn are independently 10 min to 90 min.
[0026] Optionally, under preset conditions, the volume percentage of oxygen in the plasma generating gas containing oxygen is 10%-100%.
[0027] Optionally, the flow rate of the plasma generating gas is 500–1200 ml / min.
[0028] Optionally, in the step of placing the sodium-type mordenite molecular sieve containing the template agent into a low-temperature plasma, the method for generating the low-temperature plasma includes at least one of glow discharge, corona discharge, dielectric barrier discharge, radio frequency discharge, sliding arc discharge, jet discharge, atmospheric pressure glow discharge, and sub-atmospheric pressure glow discharge.
[0029] Optionally, in the step of placing the sodium-type mordenite molecular sieve containing the template agent in a low-temperature plasma, the sodium-type mordenite molecular sieve is an uncalcined sodium-type mordenite molecular sieve.
[0030] According to a second aspect of this application, a catalyst for the carbonylation of dimethyl ether to produce methyl acetate is provided.
[0031] A catalyst for the carbonylation of dimethyl ether to produce methyl acetate, obtained by the modification method described above.
[0032] Optionally, the acid density of the catalyst is 917-1260 μmol / g.
[0033] According to a third aspect of this application, the use of a catalyst in the carbonylation of dimethyl ether to produce methyl acetate is provided.
[0034] The application of a catalyst in the carbonylation of dimethyl ether to produce methyl acetate, wherein the catalyst is selected from the hydrogen-form mordenite molecular sieve obtained by the modification method described above or the catalyst described above.
[0035] Optionally, at 180°C, the highest conversion rate of dimethyl ether is 55%-80%.
[0036] Optionally, the conversion rate of dimethyl ether is 50%-80% after reacting at 180°C for 100 h.
[0037] The beneficial effects that this application can produce include:
[0038] 1) The method for modifying mordenite molecular sieve provided in this application involves generating low-temperature plasma by using a specific gradient voltage, along with an appropriate amount of plasma generating gas and voltage treatment time during the preparation of mordenite. This removes the template agent from the mordenite, increases the acid density of the mordenite, and exhibits higher catalytic activity and stability in the reaction of dimethyl ether carbonylation to methyl acetate.
[0039] 2) The catalyst for the carbonylation of dimethyl ether to produce methyl acetate provided in this application has an acid density of 917-1260 μmol / g, which can improve the activity and stability of the catalyst.
[0040] 3) The application of the catalyst provided in this application in the carbonylation of dimethyl ether to produce methyl acetate shows that the highest conversion rate of dimethyl ether can reach 78% at 180°C, and the conversion rate of dimethyl ether can reach 76% after 100 h of reaction at 180°C. Attached Figure Description
[0041] Figure 1 Infrared pyridine adsorption diagrams of the hydrogen-type mordenite molecular sieves prepared in Example 7 and Comparative Example 1. Detailed Implementation
[0042] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0043] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially. The sodium-type mordenite molecular sieve containing the template agent was prepared using the template method disclosed in patent CN 111087002 A, specifically:
[0044] Step 1: Mix 1.5g sodium aluminate, 79.6g sodium silicate, 0.5g NaCl, 3.5g NaOH, 4.7g CTMAB, and 100.0g deionized water to obtain a silica-alumina gel with the following composition: n(SiO2) / n(Al2O3) = 30.63, n(Na2O) / n(SiO2) = 1.17, n(CTMAB) / n(Al2O3) = 1.41, n(NaCl) / n(SiO2) = 0.03, and n(H2O) / n(SiO2) = 20. Divide the gel into two equal parts. Add 25g of deionized water to component one and stir well. The resulting diluted gel has an n(H2O) / n(SiO2) ratio of 30. Transfer component two to a tetrafluoroethylene liner and precrystallize at 110℃ for 24 hours. Cool to obtain the precrystallized mother liquor.
[0045] Step 2: Slowly add the diluted component 1 to the pre-crystallization mother liquor from Step 1 and mix well. Then, in the reactor, the temperature is programmed to rise to 170℃ at a rate of 1℃ / min and crystallize for 48 hours. After crystallization, the product is washed with deionized water until neutral and dried at 120℃ for 12 hours to obtain Na-MOR containing the template agent, named M-Na-MOR.
[0046] The analytical methods used in the embodiments and comparative examples of this application are as follows:
[0047] Elemental composition (XRF): Measured using a Rigaku ZSX PrimusⅢ+ X-ray fluorescence spectrometer with a power of 3KW.
[0048] Product analysis: Performed on a Fuli GC9790 gas chromatograph with an HP-PLOT / Q column and an FID detector; the conversion rate of dimethyl ether (DME) and the selectivity of methyl acetate (MA) were calculated using the area normalization method.
[0049] Ammonia desorption-programmed temperature-programmed desorption (NH3-TPD) analysis: An AMI300 chemisorption analyzer from AMI Corporation (USA) was used. 0.1 g of molecular sieve sample was placed in a U-shaped quartz tube and pretreated at 600℃ in a He atmosphere for 1 h. The temperature was then lowered to 100℃, and an NH3 / He mixture was introduced for adsorption for 0.5 h. The sample was then purged under a He atmosphere for 0.5 h to remove physically adsorbed NH3. After baseline stabilization, the temperature was increased to 700℃ at a rate of 10℃ / min. The desorbed NH3 was recorded using a thermal conductivity detector (TCD).
[0050] Thermogravimetric analysis (TG): The sample was thermally analyzed using a Mettler Toledo TGA / DSC 3+ / 1100LF analyzer. The analysis conditions were: approximately 10 mg of sample was heated to 800 °C at a rate of 10 °C / min in air.
[0051] Fourier transform infrared spectroscopy (Py-IR): The pyridine adsorption infrared spectroscopy experiment of the sample was performed on a TENSOR II infrared spectroscopy characterization system from Bruker GmbH, Germany. First, 5 mg of powder sample was pressed into a self-supporting disc with a diameter of 7 mm, then placed in an in-situ infrared cell. It was then pretreated at 400 °C (heating rate 2 °C / min) under vacuum for 1 h, and then cooled to below 45 °C for scanning. Next, the temperature was increased to 150 °C at a rate of 5 °C / min, and pyridine vapor was adsorbed at this temperature for 5 min. After adsorption saturation, a vacuum was applied for 30 min to remove weakly adsorbed pyridine, and infrared spectroscopy was performed in the range of 4000-1000 cm⁻¹. -1 The number of scans was 32, and the resolution was 4cm. -1 .
[0052] In the examples and comparative examples, the conversion rate of dimethyl ether and the selectivity of methyl acetate were calculated based on the number of carbon moles of dimethyl ether:
[0053] 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%);
[0054] 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%).
[0055]
Preparation Method
[0056] A method for modifying mordenite molecular sieves includes:
[0057] S1: Sodium-type mordenite molecular sieve containing a template agent is placed in a low-temperature plasma and modified under preset conditions to obtain a modified sodium-type mordenite molecular sieve; S2: The modified sodium-type mordenite molecular sieve is subjected to ammonium ion exchange treatment to obtain an ammonium-type mordenite molecular sieve; S3: The ammonium-type mordenite molecular sieve is calcined to obtain a hydrogen-type mordenite molecular sieve; wherein, the preset conditions include: using an oxygen-containing gas as the plasma generating gas; performing the modification treatment under a gradient voltage; and the modification treatment time being 1-120 min. Here, the treatment time corresponds to the treatment time for 1 g of sodium-type mordenite molecular sieve containing the template agent. Optionally, the treatment time is independently selected from any value or a range between 1 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, and 120 min.
[0058] According to one embodiment of this application, under preset conditions, the modification treatment under gradient voltage includes treatment at two or more different voltages, wherein the voltage is between 5 and 50 kV. The gradient voltage treatment can be performed by setting 2-20 different pressure gradients, gradually increasing from low to high pressure. For example, treatment can be performed at 5 kV for 20 minutes, then at 10 kV for 20 minutes, and finally at 15 kV for 20 minutes. Optionally, the voltage is independently selected from any value or a range between 5 kV, 10 kV, 15 kV, 20 kV, 25 kV, 30 kV, 35 kV, 40 kV, 45 kV, and 50 kV.
[0059] According to one embodiment of this application, under preset conditions, the volume percentage of oxygen in the plasma generating gas containing oxygen is 10%-100%. Here, volume percentage refers to the percentage of oxygen in the volume of the plasma generating gas. The plasma generating gas also includes nitrogen. The flow rate of the plasma generating gas can be 900-1100 ml / min. Optionally, the volume percentage of oxygen is independently selected from any value or a range between 10%, 21%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%.
[0060] According to one embodiment of this application, in the step of placing a sodium-type mordenite molecular sieve containing a template agent in a low-temperature plasma, the method for generating the low-temperature plasma includes at least one of glow discharge, corona discharge, dielectric barrier discharge, radio frequency discharge, sliding arc discharge, jet discharge, atmospheric pressure glow discharge, and sub-atmospheric pressure glow discharge. During the generation of the low-temperature plasma, the sample to be processed is placed in the plasma discharge region or downstream region of the low-temperature plasma generator.
[0061] According to one embodiment of this application, in the step of placing a sodium-type mordenite molecular sieve containing a template agent in a low-temperature plasma, the sodium-type mordenite molecular sieve is an uncalcined sodium-type mordenite molecular sieve.
[0062] According to one embodiment of this application, in step S2, the ammonium ion exchange treatment of the modified sodium-type mordenite molecular sieve includes: reacting a mixture containing the modified sodium-type mordenite molecular sieve and an ammonium source at 50-90°C for 1-8 hours, repeating the reaction 2-4 times to obtain ammonium-type mordenite. The ammonium source is selected from at least one of ammonium chloride, ammonium nitrate, and ammonium sulfate. Optionally, the concentration of the ammonium source is 0.1-1 mol / L, wherein the concentration of the ammonium source is expressed in terms of ammonium ions. Optionally, the concentration of the ammonium source is independently selected from any value or a range between any two of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, and 1.0 mol / L.
[0063] According to one embodiment of this application, in step S3, the temperature and time of the calcination treatment are those disclosed in the prior art, and the temperature and time of the calcination treatment can be 500-600℃ and 3-4h.
[0064]
catalyst
[0065] A catalyst for the carbonylation of dimethyl ether to produce methyl acetate, obtained by the modification method described above.
[0066] According to one embodiment of this application, the acid density of the catalyst is 917-1260 μmol / g. Optionally, the acid density of the catalyst is independently selected from any value or a range between 917 μmol / g, 1000 μmol / g, 1050 μmol / g, 1100 μmol / g, 1150 μmol / g, 1200 μmol / g, 1250 μmol / g, and 1260 μmol / g.
[0067] Application in the carbonylation of dimethyl ether to produce methyl acetate
[0068] The application of a catalyst in the carbonylation of dimethyl ether to produce methyl acetate, wherein the catalyst is selected from the hydrogen-form mordenite molecular sieve obtained by the modification method described above or the catalyst described above.
[0069] According to one embodiment of this application, the highest conversion rate of dimethyl ether at 180°C is 55%-80%. Optionally, the highest conversion rate of dimethyl ether is independently selected from any value of 55%, 60%, 65%, 70%, 75%, 80%, or a range between any two.
[0070] According to one embodiment of this application, the conversion rate of dimethyl ether after 100 h at 180°C is 50%-80%. Optionally, the conversion rate of dimethyl ether after 100 h is independently selected from any value of 50%, 55%, 60%, 65%, 70%, 75%, 80% or a range between any two.
[0071] Example 1
[0072] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was placed in the discharge area of the low-temperature plasma generator and placed evenly. Air was introduced into the device at a flow rate of 1000ml / min, a frequency of 2kHz, a pulse width of 600ns, a pulse rise time of 50ns, and was treated at 5kV for 20min, 10kV for 20min, and 15kV for 20min to obtain modified Na-MOR molecular sieve.
[0073] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0074] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0075] Example 2
[0076] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was placed in the discharge area of the low-temperature plasma generator and placed evenly. Air was introduced into the device at a flow rate of 1000ml / min, a frequency of 2kHz, a pulse width of 600ns, a pulse rise time of 50ns, and was treated at 5kV for 30min, 10kV for 30min, and 15kV for 30min to obtain modified Na-MOR molecular sieve.
[0077] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0078] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0079] Example 3
[0080] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed in the discharge area of the low-temperature plasma generator. The catalyst was placed evenly and air was introduced into the device. The air flow rate was 1000ml / min, the frequency was 2kHz, the pulse width was 600ns, the pulse rise time was 50ns, and the treatment was carried out at 5kV for 30min, 10kV for 30min, and 20kV for 30min to obtain modified Na-MOR molecular sieve.
[0081] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0082] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0083] Example 4
[0084] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was placed in the discharge area of the low-temperature plasma generator and placed evenly. Air was introduced into the device at a flow rate of 1000ml / min, a frequency of 2kHz, a pulse width of 600ns, and a pulse rise time of 50ns. The device was treated at 10kV for 30min and at 15kV for 60min to obtain modified Na-MOR molecular sieve.
[0085] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0086] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0087] Example 5
[0088] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed in the discharge area of the low-temperature plasma generator. The catalyst was placed evenly and air was introduced into the device. The air flow rate was 1000ml / min, the frequency was 2kHz, the pulse width was 600ns, the pulse rise time was 50ns, and the treatment was carried out at 5kV for 30min, 10kV for 30min, and 20kV for 30min to obtain modified Na-MOR molecular sieve.
[0089] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0090] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0091] Example 6
[0092] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was placed in the discharge area of the low-temperature plasma generator and placed evenly. Oxygen was introduced into the device at an air flow rate of 1000ml / min, a frequency of 2kHz, a pulse width of 600ns, a pulse rise time of 50ns, and was treated at 5kV for 30min, 10kV for 30min, and 15kV for 30min to obtain modified Na-MOR molecular sieve.
[0093] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0094] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0095] Example 7
[0096] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed in the discharge area of the low-temperature plasma generator. The catalyst was placed evenly and air was introduced into the device. The air flow rate was 1000ml / min, the frequency was 2kHz, the pulse width was 600ns, the pulse rise time was 50ns, and the treatment was carried out at 5kV for 30min, 10kV for 30min, and 20kV for 30min to obtain modified Na-MOR molecular sieve.
[0097] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0098] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0099] Example 8
[0100] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed in the discharge area of the low-temperature plasma generator. The catalyst was placed evenly and air was introduced into the device. The air flow rate was 1000ml / min, the frequency was 2kHz, the pulse width was 600ns, the pulse rise time was 50ns, and the treatment was carried out at 5kV for 30min, 10kV for 50min, and 20kV for 60min to obtain modified Na-MOR molecular sieve.
[0101] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0102] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0103] Example 9
[0104] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was placed in the discharge area of the low-temperature plasma generator and placed evenly. 10% oxygen and nitrogen balance gas was introduced into the device. The gas flow rate was 1200ml / min, the frequency was 2kHz, the pulse width was 600ns, the pulse rise time was 50ns, and the treatment was carried out at 5kV for 30min, 10kV for 50min, and 20kV for 60min to obtain modified Na-MOR molecular sieve.
[0105] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0106] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0107] Example 10
[0108] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was placed in the discharge area of the low-temperature plasma generator and placed evenly. 50% oxygen and nitrogen balance gas was introduced into the device. The gas flow rate was 800ml / min, the frequency was 2kHz, the pulse width was 600ns, the pulse rise time was 50ns, and the treatment was carried out at 5kV for 30min, 10kV for 50min, and 20kV for 60min to obtain modified Na-MOR molecular sieve.
[0109] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0110] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0111] Example 11
[0112] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed in the discharge area of the low-temperature plasma generator. The catalyst was placed evenly and 100% oxygen was introduced into the device. The gas flow rate was 500ml / min, the frequency was 2kHz, the pulse width was 600ns, the pulse rise time was 50ns, and the treatment was carried out at 5kV for 30min, 10kV for 50min, and 20kV for 60min to obtain modified Na-MOR molecular sieve.
[0113] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0114] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0115] Comparative Example 1
[0116] (1) M-Na-MOR is tableted, crushed and sieved, and 1g of 20-40 mesh catalyst is weighed and loaded into a tube furnace and treated in an oxygen atmosphere at 500℃ for 12 hours.
[0117] (2) The Na-MOR molecular sieve treated in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0118] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0119] The acid properties of the catalyst were characterized using pyridine infrared spectroscopy (Py-IR). Figure 1 This is the infrared spectrum of the catalyst after adsorbing pyridine, where 1455 cm⁻¹... -1 The peak at 1545 cm⁻¹ is attributed to the characteristic absorption peak of pyridine adsorbed on the Lewis acid site. -1 The peak at that point is pyridine and The characteristic peak of proton formation of pyridine cation, and 1490 cm⁻¹ -1 Characteristic peaks are formed by The absorption peak is caused by the combined effect of acid sites and Lewis acid sites. It can be seen that, compared to Comparative Example 1, Example 7 shows... Higher acidity, Lewis lower acidity.
[0120] Comparative Example 2
[0121] (1) M-Na-MOR is tableted, crushed and sieved, and 1g of 20-40 mesh catalyst is weighed and loaded into a tube furnace and treated in an oxygen atmosphere at 550℃ for 8 hours.
[0122] (2) The Na-MOR molecular sieve treated in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0123] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0124] Comparative Example 3
[0125] (1) M-Na-MOR is tableted, crushed and sieved, and 1g of 20-40 mesh catalyst is weighed and loaded into a tube furnace and treated in an oxygen atmosphere at 550℃ for 10 hours.
[0126] (2) The Na-MOR molecular sieve after the previous step was placed in a beaker and ammonium ion exchanged with 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8 at 80℃ for 3 h. After repeating the ammonium ion exchange 3 times, it was dried at 120℃ for 12 h to obtain the NH4-MOR molecular sieve catalyst.
[0127] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0128] Comparative Example 4
[0129] (1) M-Na-MOR was tableted, crushed and sieved, and 1g of 20-40 mesh catalyst was placed in the discharge area of the low-temperature plasma generator and placed evenly. Air was introduced into the device at a flow rate of 1000ml / min, a frequency of 2kHz, a pulse width of 600ns, a pulse rise time of 50ns, and treated at 15kV for 90min to obtain modified Na-MOR molecular sieve.
[0130] (2) The modified Na-MOR molecular sieve prepared in step (1) was placed in a beaker and subjected to ammonium ion exchange for 3 hours at 80°C with a 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120°C for 12 hours to obtain the NH4-MOR molecular sieve catalyst.
[0131] (3) The NH4-MOR molecular sieve catalyst prepared in step (2) was calcined at 550℃ for 4h to obtain hydrogen-type mordenite molecular sieve.
[0132] Comparative Example 5
[0133] (1) M-Na-MOR was tableted, crushed and sieved, placed in a beaker, and subjected to ammonium ion exchange for 3 hours at 80℃ with 1 mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8. After repeating the ammonium ion exchange 3 times, it was dried at 120℃ for 12 hours to obtain NH4-MOR molecular sieve catalyst containing template agent.
[0134] (2) The NH4-MOR molecular sieve catalyst containing template agent prepared in step (1) is dried, crushed and sieved. 1g of 20-40 mesh catalyst is weighed and placed in the discharge area of the low-temperature plasma generator and placed evenly. 100% oxygen is introduced into the device at a gas flow rate of 500ml / min, a frequency of 2kHz, a pulse width of 600ns, and a pulse rise time of 50ns. The device is treated at 5kV for 30min, 10kV for 50min, and 20kV for 60min to obtain H-MOR molecular sieve.
[0135] Carbonylation of dimethyl ether to produce methyl acetate:
[0136] The H-MOR obtained by the above method was loaded into a fixed-bed reactor and pretreated in situ at 250°C for 3 hours. The temperature was then lowered to 180°C, and the reaction pressure was adjusted to 2.0 MPa for activity evaluation. The feed volume ratio was DME:N2:CO = 1:13:7, and the volume hourly space velocity was 1800 h⁻¹. -1 Product analysis was performed on a Fuli GC9790 gas chromatograph with an HP-PLOT / Q column and an FID detector; the conversion rate of dimethyl ether (DME) and the selectivity of methyl acetate (MA) were calculated using the area normalization method.
[0137] In the examples and comparative examples, the conversion rate of dimethyl ether and the selectivity of methyl acetate were calculated based on the number of carbon moles of dimethyl ether:
[0138] 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%);
[0139] 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%).
[0140] The test results are shown in the table below:
[0141] Table 1. Catalyst evaluation and characterization results determined in Examples 1-11 and Comparative Examples 1-5.
[0142]
[0143]
[0144] As shown in the table above, compared with the traditional hot calcination method, the hydrogen-form mordenite obtained by the modification method of this application has a higher acid density and exhibits better catalytic activity and stability in the reaction of dimethyl ether carbonylation to prepare methyl acetate.
[0145] As can be seen from Example 1 and Comparative Example 5, the modification method of this application requires first modifying the sodium-type mordenite molecular sieve containing the template agent, then performing ammonium ion exchange treatment, and finally calcining. In Comparative Example 5, if the sodium-type mordenite molecular sieve containing the template agent is first subjected to ammonium ion exchange treatment and then modified, the modification effect cannot be achieved.
[0146] 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 modifying mordenite molecular sieves, characterized in that, include: Sodium-type mordenite molecular sieve containing a template agent was placed in a low-temperature plasma and modified under preset conditions to obtain a modified sodium-type mordenite molecular sieve. The modified sodium-type mordenite molecular sieve was subjected to ammonium ion exchange treatment to obtain ammonium-type mordenite molecular sieve. The ammonium-type mordenite molecular sieve was calcined to obtain hydrogen-type mordenite molecular sieve. The preset conditions include: The plasma generator uses an oxygen-containing gas. Modification is performed under gradient voltage; The modification treatment time is 1-120 min; Under the preset conditions, the modification treatment under gradient voltage includes treatment under two or more different voltages, wherein the voltage is between 5-50 kV; The modification process under gradient voltage includes: Set U1, U2, ..., U n There are 1 voltage, and the processing time for each voltage is T1, T2, ..., Tn. n ; Wherein, 20 ≥ n ≥ 2; 50KV≥U n >...>U2>U1≥5KV; T1, T2, ..., T n Independently, the time is 0.5 min to 100 min.
2. The modification method according to claim 1, characterized in that, 15KV≥U n -IN n-1 ≥2KV; T1=T2=……=T n 。 3. The modification method according to claim 1, characterized in that, Under the preset conditions, the volume percentage of oxygen in the plasma generating gas containing oxygen is 10%-100%.
4. The modification method according to claim 1, characterized in that, The flow rate of the plasma generating gas is 500~1200 ml / min.
5. The modification method according to claim 1, characterized in that, In the step of placing sodium-type mordenite molecular sieves containing template agents into a low-temperature plasma, the method for generating the low-temperature plasma includes at least one of dielectric barrier discharge, radio frequency discharge, sliding arc discharge, atmospheric pressure glow discharge, and sub-atmospheric pressure glow discharge.
6. The modification method according to claim 1, characterized in that, In the step of placing the sodium-type mordenite molecular sieve containing the template agent in a low-temperature plasma, the sodium-type mordenite molecular sieve is an uncalcined sodium-type mordenite molecular sieve.
7. A catalyst for the carbonylation of dimethyl ether to produce methyl acetate, characterized in that, Obtained by the modification method according to any one of claims 1-6.
8. The catalyst according to claim 7, characterized in that, The acid density of the catalyst is 917-1260 μmol / g.
9. The application of a catalyst in the carbonylation of dimethyl ether to methyl acetate, characterized in that, The catalyst is selected from the hydrogen-type mordenite molecular sieve obtained by the modification method of any one of claims 1-6 or the catalyst of any one of claims 7-8.
10. The application according to claim 9, characterized in that, At 180 °C, the conversion rate of dimethyl ether after 100 h is 50%-80%.