Method for increasing the acid amount of a mordenite molecular sieve and use thereof

Abstract

The application discloses a method for increasing the acid amount of mordenite molecular sieves and application thereof, and belongs to the technical field of industrial catalysis. The method for increasing the acid amount of mordenite molecular sieves comprises the following steps: placing ammonium type mordenite molecular sieves without a template into a low-temperature plasma, and performing modification treatment under preset conditions to obtain hydrogen type mordenite molecular sieves; the generation method of the low-temperature plasma comprises dielectric barrier discharge; wherein the preset conditions comprise the following steps: using a gas containing oxygen as plasma generation gas; performing the modification treatment under a voltage of 5-50 KV; and the time for the modification treatment is 1-100 min. The treatment method in the application can improve the acid density of the mordenite, and the mordenite has higher catalytic activity and stability in the reaction of dimethyl ether carbonylation for preparing methyl acetate.

Description

Technical Field

[0001] This application relates to a method for increasing the acid content of 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] The preparation of mordenite typically involves either a templated or template-free method to synthesize sodium mordenite. Products synthesized via the templated method require calcination to remove the organic template, while those synthesized via the template-free method do not require calcination. Subsequently, sodium mordenite undergoes an ion exchange reaction to obtain ammonium mordenite, which is then calcined to transform into hydrogen mordenite. This preparation process usually employs hot calcination; however, it is important to note that excessively high temperatures can reduce the acid density of mordenite, leading to a decrease in its catalytic activity in the carbonylation of dimethyl ether to methyl acetate. Summary of the Invention

[0005] According to the first aspect of this application, a method for increasing the acid content of mordenite molecular sieves is provided. This method, for a specific ammonium-type mordenite, improves the acid density of the mordenite by using a specific voltage intensity and a low-temperature plasma generation method, along with an appropriate amount of plasma generating gas and voltage treatment time.

[0006] A method for increasing the acid content of mordenite molecular sieves includes:

[0007] Ammonium-type mordenite molecular sieves without template agents were placed in low-temperature plasma and modified under preset conditions to obtain hydrogen-type mordenite molecular sieves.

[0008] The method for generating the low-temperature plasma includes dielectric barrier discharge;

[0009] The preset conditions include:

[0010] The plasma generator uses an oxygen-containing gas.

[0011] Modification treatment is carried out under voltages of 5-50KV;

[0012] The modification treatment time is 1-100 min.

[0013] Optionally, under preset conditions, the frequency of the voltage is 50-5000Hz.

[0014] Optionally, the modification treatment time is 20-60 minutes.

[0015] Optionally, under preset conditions, the volume percentage of oxygen in the plasma generating gas containing oxygen is 10%-100%.

[0016] Optionally, under preset conditions, the flow rate of the plasma generating gas is 500-1000 ml / min.

[0017] According to a second aspect of this application, a catalyst for the carbonylation of dimethyl ether to produce methyl acetate is provided.

[0018] A catalyst for the carbonylation of dimethyl ether to produce methyl acetate, obtained by the method described above.

[0019] Optionally, the acid density of the catalyst is 1400-1460 μmol / g.

[0020] 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.

[0021] The application of a catalyst in the carbonylation of dimethyl ether to produce methyl acetate, wherein the catalyst is selected from the hydrogen-type mordenite molecular sieve obtained by the method described above or the catalyst described above.

[0022] Optionally, at 180°C, the highest conversion rate of dimethyl ether is 71%-80%.

[0023] Optionally, at 180°C, the conversion rate of dimethyl ether after 100 h is 69%-80%.

[0024] The beneficial effects that this application can produce include:

[0025] 1) The method for increasing the acid content of mordenite molecular sieve provided in this application adopts dielectric barrier discharge technology, uses O2 gas as discharge gas to generate cold plasma, and modifies ammonium mordenite into hydrogen mordenite, thereby increasing the acid density of hydrogen mordenite, which exhibits higher catalytic activity and stability in the reaction of dimethyl ether carbonylation to methyl acetate.

[0026] 2) The catalyst for the carbonylation of dimethyl ether to produce methyl acetate provided in this application has an acid density of 1400-1460 μmol / g, which can improve the activity and stability of the catalyst.

[0027] 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 is 71%-80% at 180°C, and the conversion rate of dimethyl ether after 100 h of reaction at 180°C is 69%-80%. Detailed Implementation

[0028] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0029] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially. The ammonium-type mordenite molecular sieve (NH4-MOR) was prepared using the method disclosed in patent CN 111087002 A, specifically:

[0030] Step 1: Weigh 1.5g sodium aluminate, 14g silica, 1.2g NaCl, 7.8g NaOH, 4.7g CTMAB, and 50g deionized water and mix them to obtain a silica-alumina gel with the following composition: n(SiO2) / n(Al2O3) = 25.81, n(Na2O) / n(SiO2) = 1.16, (CTMAB) / n(Al2O3) = 1.34, n(NaCl) / n(SiO2) = 0.09, n(H2O) / n(SiO2) = 12. Divide the gel into two equal parts. Add 27g deionized water to component one and stir well. The resulting diluted gel has n(H2O) / n(SiO2) = 25. Transfer component two to a tetrafluoroethylene liner and precrystallize at 110℃ for 24h. Cool down to obtain the precrystallized mother liquor.

[0031] Step 2: Slowly add the diluted component 1 to the pre-crystallization mother liquor from Step 1 and mix well. Then, in a 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, dried at 120℃ for 12 hours, and calcined in a muffle furnace at 550℃ for 4 hours to obtain Na-MOR.

[0032] Step 3: Weigh a certain amount of the above Na-MOR molecular sieve and place it in a beaker. At 80℃, perform ammonia ion exchange with a 2mol / L ammonium nitrate solution at a solid-liquid mass ratio of 1:8 for 3 hours. Repeat the ammonia ion exchange 3 times. After drying at 120℃ for 12 hours, NH4-MOR is obtained.

[0033] The analytical methods used in the embodiments and comparative examples of this application are as follows:

[0034] Elemental composition (XRF): Measured using a Rigaku ZSX PrimusⅢ+ X-ray fluorescence spectrometer with a power of 3KW.

[0035] 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.

[0036] 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).

[0037] 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:

[0038] 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%);

[0039] 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%).

[0040]

Preparation Method

[0041] A method for increasing the acidity of mordenite molecular sieves includes: placing ammonium-type mordenite molecular sieves without template agents in a low-temperature plasma and modifying them under preset conditions to obtain hydrogen-type mordenite molecular sieves (H-MOR); the method for generating the low-temperature plasma includes dielectric barrier discharge; wherein the preset conditions include: using an oxygen-containing gas as the plasma generating gas; performing the modification treatment at a voltage of 5-50KV; and the modification treatment time being 1-100min. Here, the modification treatment time corresponds to the treatment time corresponding to the modification of 1g of ammonium-type mordenite molecular sieves without template agents. Dielectric barrier discharge includes dual dielectric barrier discharge (DDBD), which can generate large-volume, high-energy-density low-temperature plasma at atmospheric pressure, obtaining the active particles required for chemical reactions at room temperature or near room temperature without the need for vacuum equipment. Because dielectric barrier discharge generates a large number of electrons, free radicals, and excimers during the discharge process, these particles are chemically very reactive and readily react with other atoms, molecules, or free radicals. For example, oxygen atoms and ozone molecules are formed in air plasma, and these reactive oxygen species play a key role in the removal of organic matter from molecular sieves by the DDBD method. Furthermore, DDBD technology has advantages such as high controllability and low energy consumption, making it widely applicable in environmental remediation and industrial production. Optionally, the modification 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, and 100 min. 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.

[0042] According to one embodiment of this application, under preset conditions, the frequency of the voltage is 50-5000Hz. Optionally, the frequency of the voltage is independently selected from any value or a range between any two of 50Hz, 60Hz, 70Hz, 80Hz, 90Hz, 100Hz, 200Hz, 300Hz, 400Hz, 500Hz, 600Hz, 700Hz, 800Hz, 900Hz, 1000Hz, 2000Hz, 3000Hz, 4000Hz, and 5000Hz.

[0043] According to one embodiment of this application, the modification treatment time is 20-60 minutes. A modification treatment time within this range allows for better modification of ammonium-type mordenite to hydrogen-type mordenite, thereby increasing the acid density of the hydrogen-type mordenite.

[0044] According to one embodiment of this application, the preset conditions further include performing the modification treatment at standard atmospheric pressure and room temperature. The room temperature is 20°C-30°C.

[0045] 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. 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%.

[0046] According to one embodiment of this application, under preset conditions, the flow rate of the plasma generating gas is 500-1000 ml / min. Optionally, the flow rate of the plasma generating gas is independently selected from any value or a range between any two of 500 ml / min, 600 ml / min, 700 ml / min, 800 ml / min, 900 ml / min, and 1000 ml / min.

[0047] According to one embodiment of this application, when ammonium-type mordenite molecular sieve (NH4-MOR) is placed in a dielectric barrier discharge reactor, the placement position is either in the plasma discharge zone or the downstream region of the plasma.

[0048]

catalyst

[0049] A catalyst for the carbonylation of dimethyl ether to produce methyl acetate, obtained by the method described above.

[0050] According to one embodiment of this application, the acid density of the catalyst is 1400-1460 μmol / g. Optionally, the acid density of the catalyst is independently selected from any value or a range between 1400 μmol / g, 1410 μmol / g, 1420 μmol / g, 1430 μmol / g, and 1450 μmol / g.

[0051] Application in the carbonylation of dimethyl ether to produce methyl acetate

[0052] The application of a catalyst in the carbonylation of dimethyl ether to produce methyl acetate, wherein the catalyst is selected from the hydrogen-type mordenite molecular sieve obtained by the method described above or the catalyst described above.

[0053] According to one embodiment of this application, the highest conversion rate of dimethyl ether at 180°C is 71%-80%. Optionally, the highest conversion rate of dimethyl ether is independently selected from any value of 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or a range between any two.

[0054] According to one embodiment of this application, the conversion rate of dimethyl ether after 100 h at 180°C is 69%-80%. Optionally, the conversion rate of dimethyl ether after 100 h is independently selected from any value or a range between any two of 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, and 80%.

[0055] Example 1

[0056] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​the dielectric barrier discharge device. 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 5kV for 20min to obtain H-MOR.

[0057] Example 2

[0058] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​the dielectric barrier discharge device. Air was introduced into the device at a flow rate of 500ml / min, a frequency of 2kHz, a pulse width of 600ns, and a pulse rise time of 50ns. The device was treated at 5kV for 20min to obtain H-MOR.

[0059] Example 3

[0060] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​the dielectric barrier discharge device. Oxygen was introduced into the device at a flow rate of 500ml / min, a frequency of 2kHz, a pulse width of 600ns, and a pulse rise time of 50ns. The device was treated at 8kV for 30min to obtain H-MOR.

[0061] Example 4

[0062] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​the dielectric barrier discharge device. Air was introduced into the device at a flow rate of 500ml / 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 to obtain H-MOR.

[0063] Example 5

[0064] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​the dielectric barrier discharge device. Nitrogen gas containing 10% oxygen was introduced into the device at a flow rate of 500ml / min, a frequency of 2kHz, a pulse width of 600ns, and a pulse rise time of 50ns. The device was treated at 5kV for 30min to obtain H-MOR.

[0065] Example 6

[0066] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​the dielectric barrier discharge device. Air was introduced into the device at a flow rate of 500ml / min, a frequency of 2kHz, a pulse width of 600ns, and a pulse rise time of 50ns. The device was treated at 5kV for 40min to obtain H-MOR.

[0067] Example 7

[0068] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​the dielectric barrier discharge device. 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 5kV for 50min to obtain H-MOR.

[0069] Example 8

[0070] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​the dielectric barrier discharge device. Air was introduced into the device at a flow rate of 500ml / min, a frequency of 2kHz, a pulse width of 600ns, and a pulse rise time of 50ns. The device was treated at 5kV for 60min to obtain H-MOR.

[0071] Example 9

[0072] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​a dielectric barrier discharge device. Nitrogen gas containing 50% oxygen was introduced into the device at a flow rate of 500ml / 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 to obtain H-MOR.

[0073] Example 10

[0074] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​the dielectric barrier discharge device. Air was introduced into the device at a flow rate of 500ml / min, a frequency of 2kHz, a pulse width of 600ns, and a pulse rise time of 50ns. The device was treated at 8kV for 50min to obtain H-MOR.

[0075] Example 11

[0076] NH4-MOR was tableted, crushed and sieved. 1g of 20-40 mesh catalyst was weighed and placed evenly in the discharge area of ​​a dielectric barrier discharge device. A gas with an oxygen content of 90% was introduced into the device at a flow rate of 1000ml / min. The device was operated at 30kV, with a pulse width of 600ns, a pulse rise time of 50ns, and a frequency of 2000Hz for 80min to obtain H-MOR molecular sieve.

[0077] Example 12

[0078] NH4-MOR is compressed into tablets, 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 450℃ for 12 hours to obtain H-MOR.

[0079] Weigh 1g of 20-40 mesh catalyst and place it evenly in the discharge area of ​​the dielectric barrier discharge device. Then, introduce air 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. Treat the device at 5kV for 20min to obtain the modified H-MOR.

[0080] Comparative Example 1

[0081] NH4-MOR is compressed into tablets, 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 450℃ for 12 hours to obtain H-MOR.

[0082] Comparative Example 2

[0083] NH4-MOR was compressed into tablets, crushed and sieved, and 1g of 20-40 mesh catalyst was weighed and loaded into a tube furnace and treated in an oxygen atmosphere at 500℃ for 8 hours to obtain H-MOR.

[0084] Comparative Example 3

[0085] NH4-MOR is compressed into tablets, 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 10 hours to obtain H-MOR.

[0086] Comparative Example 4

[0087] (1) Weigh 1.5g of sodium aluminate, 14g of silica, 1.2g of NaCl, 7.8g of NaOH, 4.7g of CTMAB, and 50g of deionized water to obtain a silica-alumina gel with the following composition: n(SiO2) / n(Al2O3) = 25.81, n(Na2O) / n(SiO2) = 1.16, (CTMAB) / n(Al2O3) = 1.34, n(NaCl) / n(SiO2) = 0.09, and n(H2O) / n(SiO2) = 12. Divide the gel into two equal parts. Add 27g of deionized water to component one and stir well. The dilute gel has n(H2O) / n(SiO2) = 25. Transfer component two to a tetrafluoroethylene liner and precrystallize at 110℃ for 24h. Cool down to obtain the precrystallized mother liquor.

[0088] (2) Slowly add the diluted component one to the pre-crystallization mother liquor of step one and mix well. Then, in the reactor, the temperature is increased to 170°C at a rate of 1°C / min and crystallized for 48 hours. After crystallization, the product is washed with deionized water until neutral and dried at 120°C for 12 hours to obtain sodium-type mordenite molecular sieve containing template agent.

[0089] (3) Weigh a certain amount of the above molecular sieve and place it in a beaker. Under the condition of 80℃, 2 mol / L ammonium nitrate solution is used for ammonia ion exchange at a solid-liquid mass ratio of 1:8 for 3 hours. After repeating the ammonia ion exchange 3 times, it is dried at 120℃ for 12 hours to obtain NH4-MOR containing template agent.

[0090] (4) The NH4-MOR molecular sieve catalyst containing template agent prepared in step (3) 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. The catalyst is placed evenly and a gas with an oxygen content of 90% is introduced into the device. The gas flow rate is 1000ml / min. The voltage is 30KV, the pulse width is 600ns, the pulse rise time is 50ns, and the frequency is 2000Hz. The treatment lasts for 80min to obtain H-MOR molecular sieve.

[0091] The carbonylation of dimethyl ether to prepare methyl acetate is as follows:

[0092] 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.

[0093] 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:

[0094] 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%);

[0095] methyl acetate selectivity = (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%). The results are shown in the table below:

[0096] Table 1. Catalyst evaluation and characterization results determined in Examples 1-10 and Comparative Examples 1-3.

[0097]

[0098]

[0099] As shown in the table above, compared with the traditional thermal calcination method, the hydrogen-form mordenite obtained by the dielectric barrier discharge technology has a higher acid density and exhibits better catalytic activity and stability in the reaction of dimethyl ether carbonylation to prepare methyl acetate.

[0100] As can be seen from Example 12 and Comparative Example 1, by treating H-MOR with dielectric barrier discharge technology, the amount of strong acid and the total amount of acid in H-MOR can be increased.

[0101] 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. The application of a catalyst in the carbonylation of dimethyl ether to methyl acetate, characterized in that, The catalyst is a hydrogen-type mordenite molecular sieve, and the acid density of the catalyst is 1400-1460 μmol / g; The catalyst was prepared by a method comprising the following steps: Ammonium-type mordenite molecular sieves without template agents are placed in low-temperature plasma and modified under preset conditions to obtain hydrogen-type mordenite molecular sieves. The method for generating the low-temperature plasma includes dielectric barrier discharge; The preset conditions include: The plasma generating gas is an oxygen-containing gas; the volume percentage of oxygen in the plasma generating gas is 10%-100%. Modification treatment is carried out at voltages of 5-50 kV; The modification treatment time is 1-100 min.

2. The application according to claim 1, characterized in that, Under the preset conditions, the frequency of the voltage is 50-5000Hz.

3. The application according to claim 1, characterized in that, The modification treatment time is 20-60 min.

4. The application according to claim 1, characterized in that, Under the preset conditions, the flow rate of the plasma generating gas is 500-1000 ml / min.

5. The application according to claim 1, characterized in that, At 180 °C, the highest conversion rate of dimethyl ether is 71%-80%.

6. The application according to claim 1, characterized in that, At 180 °C, the conversion rate of dimethyl ether after 100 h is 69%-80%.

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