Reaction method for preparing dimethyl ether from methanol

Abstract

The invention relates to the technical field of preparation of dimethyl ether from methanol, in particular to a reaction method for preparation of dimethyl ether from methanol, the reaction method is carried out in a reactor, the reactor comprises: a reaction tube with a cavity; the molecular sieve membrane tube is positioned in the cavity, and an interlayer between the periphery of the molecular sieve membrane tube and the reaction tube is filled with a catalyst; the molecular sieve membrane tube comprises a porous material matrix and a molecular sieve membrane formed on the porous material matrix, water can selectively pass through the molecular sieve membrane, methanol and dimethyl ether cannot pass through the molecular sieve membrane, and the molecular sieve membrane is used for in-situ separation of water generated by interlayer reaction; the reaction method comprises the following steps: under the reaction condition of preparing dimethyl ether from methanol, a methanol-containing raw material and the catalyst are subjected to reaction contact in the interlayer, and generated water is separated by the molecular sieve membrane, enters the molecular sieve membrane tube and is taken away by purging gas. By adopting the method, the conversion rate of methanol can be increased, the stability of the catalyst is ensured, and the cost is saved for subsequent dimethyl ether rectification.

Description

Technical Field

[0001] The invention relates to the technical field of preparing dimethyl ether from methanol, and in particular to a reaction method for preparing dimethyl ether from methanol. Background Art

[0002] Energy provides an important material basis for human survival and social development. With the continuous development of society, human demand for energy has increased, but the total amount of energy is limited, making it a major problem that troubles countries around the world. Methanol is an important energy substitute and basic chemical raw material in my country. Alcohol ether fuels represented by methanol and dimethyl ether can effectively alleviate the shortage of oil resources and optimize the energy structure. Among them, dimethyl ether is considered to be a clean energy second only to hydrogen energy: it has safe storage and processing capabilities, combustion products such as carbon monoxide emissions are much lower than natural gas, and it has a higher cetane number. In addition, ether can not only be directly used as a foaming agent for foam plastic products, but also as a refrigerant to replace Freon, making up for the environmental problem of ozone holes caused by Freon.

[0003] In the conventional process of preparing dimethyl ether from methanol, a large amount of water is produced, which is conducive to the reverse reaction and reduces the conversion rate of methanol. At the same time, the water produced causes the catalyst pores to collapse and the active sites to decrease, which greatly reduces the reaction activity, stability and service life of the catalyst. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems in the prior art that a conventional reactor for preparing dimethyl ether from methanol does not contain a separation unit, the catalyst bed is affected by the reaction product water for a long time and its life is shortened, and the excess water will produce a large amount of by-products causing waste of methanol, and the subsequent distillation operation cost of the water-containing methanol is high. A reaction method for preparing dimethyl ether from methanol is provided. The reaction method can selectively remove water, which can not only increase the conversion rate of methanol and ensure the stability of the catalyst, but also save costs for subsequent dimethyl ether distillation.

[0005] In order to achieve the above object, the present invention provides a reaction method for preparing dimethyl ether from methanol, the reaction method is carried out in a reactor, and the reactor comprises:

[0006] A reaction tube having a cavity;

[0007] A molecular sieve membrane tube is located in the cavity, and the interlayer between the outer periphery of the molecular sieve membrane tube and the reaction tube is filled with a catalyst; the molecular sieve membrane tube comprises a porous material matrix and a molecular sieve membrane formed on the porous material matrix, the molecular sieve membrane can selectively pass water but cannot pass methanol and dimethyl ether, and is used to separate water generated by the interlayer reaction in situ;

[0008] The reaction method comprises: under the reaction conditions of methanol to dimethyl ether, reacting and contacting the methanol-containing raw material with the catalyst in an interlayer, and generating water separated by a molecular sieve membrane into a molecular sieve membrane tube and carried away by a purge gas.

[0009] Through the above technical scheme, the reaction method of the present invention adds the molecular sieve membrane tube of the present invention to the reactor, and removes water in situ through the molecular sieve membrane tube during the reaction process of preparing dimethyl ether from methanol, which not only can improve the conversion rate of methanol and ensure the stability of the catalyst, but also save costs for subsequent dimethyl ether distillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the structure of a reactor provided by a preferred embodiment of the present invention;

[0011] Figure 2 It is the XRD spectrum of the Na-type A-type molecular sieve provided by the present invention.

[0012] Description of Reference Numerals

[0013] 1—reaction tube; 2—catalyst; 3—membrane tube. DETAILED DESCRIPTION

[0014] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0015] The present invention provides a reaction method for preparing dimethyl ether from methanol. The reaction method is carried out in a reactor, and the reactor comprises:

[0016] A reaction tube having a cavity;

[0017] A molecular sieve membrane tube is located in the cavity, and the interlayer between the outer periphery of the molecular sieve membrane tube and the reaction tube is filled with a catalyst; the molecular sieve membrane tube comprises a porous material matrix and a molecular sieve membrane formed on the porous material matrix, the molecular sieve membrane can selectively pass water but cannot pass methanol and dimethyl ether, and is used to separate water generated by the interlayer reaction in situ;

[0018] The reaction method comprises: under the reaction conditions of methanol to dimethyl ether, reacting and contacting the methanol-containing raw material with the catalyst in an interlayer, and generating water separated by a molecular sieve membrane into a molecular sieve membrane tube and carried away by a purge gas.

[0019] The reaction method of the present invention adds the molecular sieve membrane tube of the present invention to the reactor, and removes water in situ through the molecular sieve membrane tube during the reaction process of preparing dimethyl ether from methanol, which can not only improve the conversion rate of methanol and ensure the stability of the catalyst, but also save costs for subsequent dimethyl ether distillation.

[0020] According to a preferred embodiment of the present invention, the reactor further comprises: an air inlet and an air outlet respectively disposed at both ends of the reaction tube and connected to each other, for inputting a methanol-containing raw material and outputting a dimethyl ether-containing logistics respectively;

[0021] One end of the molecular sieve membrane tube is provided with a purge gas inlet for introducing purge gas to bring out the water vapor inside the molecular sieve membrane tube; the other end is provided with a water vapor outlet for discharging the purge gas carrying water vapor.

[0022] In the present invention, there is no particular limitation on the shape of the reaction tube. According to a preferred embodiment of the present invention, the reaction tube is columnar.

[0023] According to a preferred embodiment of the present invention, the molecular sieve membrane tube runs through the reaction tube along the length direction of the reaction tube to separate the purge gas flow carrying water vapor from the flow containing the dimethyl ether product.

[0024] According to a preferred embodiment of the present invention, the thickness of the molecular sieve membrane is 0.1-20 μm.

[0025] In the present invention, in the molecular sieve membrane tube, the molecular sieve layer is used to selectively separate water, which enters the molecular sieve membrane tube through the molecular sieve layer. According to a preferred embodiment of the present invention, the molecular sieve membrane is a type A molecular sieve membrane; preferably, the molecular sieve membrane is a sodium type A molecular sieve membrane.

[0026] According to a preferred embodiment of the present invention, the molecular sieve membrane is formed on the inner wall and / or outer wall of the membrane tube, and preferably the molecular sieve layer is formed on the outer wall of the membrane tube.

[0027] According to a preferred embodiment of the present invention, the porous material matrix is ​​selected from one or more of an alumina hollow fiber tube, a porous silicon nitride ceramic tube and a magnesium aluminum spinel porous ceramic tube, preferably an alumina hollow fiber tube.

[0028] In the present invention, a method for preparing the molecular sieve membrane tube of the present invention is exemplarily provided, and the method comprises:

[0029] 1) Applying the seed crystals to obtain a carrier loaded with type A molecular sieve seed crystals;

[0030] 2) a step of contacting the carrier loaded with type A molecular sieve seed crystals with the gel for crystallization,

[0031] The gel is prepared by aging raw materials of type A molecular sieve and water.

[0032] According to a preferred embodiment of the present invention, in step 1), the seed coating is to dissolve commercially available high-quality molecular sieve seeds in deionized water, soak the carrier in a dispersion containing type A molecular sieve seeds for 10s to 30s, coat evenly, and then dry in an oven at 150°C-250°C for 6h-15h.

[0033] Preferably, the soaking time is 15s-20s; the drying temperature is 180°C-200°C, and the drying time is 10h-12h.

[0034] According to a preferred embodiment of the present invention, in step 2), the gel is prepared with Al 2 O 3 Aluminum source, SiO 2 Silicon source, Na 2 The molar ratio of sodium source and water is 1:0.1-1:2-5:100-200. Prepare liquid A and liquid B according to the synthesis ratio. Liquid A: add aluminum source and sodium source to deionized water in sequence; liquid B: add silicon source and sodium source to deionized water in sequence; mix liquid A and liquid B and age them at 80-110°C for 1-10h.

[0035] According to a preferred embodiment of the present invention, in step 2), the carrier loaded with type A molecular sieve seed crystals is completely immersed in the gel, crystallized at 80°C to 120°C for 3h to 5h, washed with deionized water several times after the crystallization is completed, and dried at 50°C to 100°C for 12h. After drying, the molecular sieve membrane tube is obtained.

[0036] In the present invention, there is no particular limitation on the aluminum source, and any conventional aluminum source in the art can be used in the present invention, for example, pseudo-boehmite.

[0037] In the present invention, there is no particular limitation on the silicon source, and any conventional silicon source in the art can be used in the present invention, such as silica sol.

[0038] In the present invention, there is no particular limitation on the Na source, and any conventional Na source in the art can be used in the present invention, for example, it can be sodium hydroxide.

[0039] In the present invention, the amount of the alkali source in liquid A and liquid B is not particularly limited. In terms of mass ratio, the amount ratio of the alkali source in liquid A to liquid B is 1-5:1.

[0040] In the present invention, there is no particular limitation on the type of the catalyst. Any catalyst conventionally used in the art for preparing dimethyl ether from methanol can be used in the present invention. According to a preferred embodiment of the present invention, the catalyst comprises γ-Al2 O 3 and loaded on γ-Al 2 O 3 The silicon-aluminum molecular sieve and / or silicon-aluminum phosphate molecular sieve is selected from HZSM-5 and / or ZSM-5; the silicon-aluminum phosphate molecular sieve is HSAPO-34 molecular sieve.

[0041] According to a preferred embodiment of the present invention, the weight of the silicon aluminum molecular sieve and / or the silicon aluminum phosphate molecular sieve is γ-Al 2 O 3 2-20wt%.

[0042] In the present invention, there is no particular limitation on the preparation method of the catalyst. An exemplary method for preparing the catalyst of the present invention is provided, which comprises:

[0043] According to the mass ratio, the weight of the silicon aluminum molecular sieve and / or the silicon aluminum phosphate molecular sieve is γ-Al 2 O 3 2-20wt%, the silicon aluminum molecular sieve and / or the silicon aluminum phosphate molecular sieve and γ-Al 2 O 3 Mix, add acid solution, knead into shape, dry and roast. Preferably, the acid solution is nitric acid with a mass fraction of 1-7%; dry at 90-130°C and roast at 500-650°C.

[0044] In the present invention, there is no particular limitation on the reaction conditions for preparing dimethyl ether from methanol. The reaction conditions for preparing dimethyl ether from methanol in the art are all applicable to the present invention. According to a preferred embodiment of the present invention, the reaction conditions for preparing dimethyl ether from methanol include: a temperature of 200°C-450°C, preferably 250°C-370°C, and a pressure of 1Mpa-10Mpa, preferably 3-5Mpa.

[0045] In the present invention, there is no particular limitation on the type of the purge gas, as long as it does not participate in the reaction of preparing dimethyl methyl ether from methanol. Preferably, the purge gas is nitrogen.

[0046] According to a preferred embodiment of the present invention, the ratio of the membrane tube radius to the catalyst layer thickness is 1:1-2.5, preferably 1:1.6-2; in the present invention, regulating the membrane tube radius and the catalyst layer thickness at 1:1.6-2 is beneficial to improving the methanol conversion rate.

[0047] The catalyst layer thickness refers to the thickness of the catalyst filled between the outer periphery of the molecular sieve membrane tube and the reaction tube along the radial direction of the reaction tube.

[0048] The membrane tube radius refers to the radius of the inner diameter of the membrane tube.

[0049] In the present invention, there is no special limitation on the setting position of the molecular sieve membrane tube, as long as the catalyst is filled between the periphery of the molecular sieve membrane tube and the reaction tube. According to a preferred embodiment of the present invention, the molecular sieve membrane tube is arranged in the middle position of the cavity, so that on the cross-section obtained by cutting along the diameter direction of the cavity, the periphery of the cavity and the periphery of the molecular sieve membrane tube are distributed in concentric circles.

[0050] The number of molecular sieve membrane tubes in the present invention can be selected in a wide range and can be reasonably selected according to the diameter of the reaction tube, as long as the catalyst is filled between adjacent molecular sieve membrane tubes and between the molecular sieve membrane tube and the reaction tube.

[0051] In the present invention, a schematic diagram of a reactor structure is exemplarily provided, such as Figure 1 As shown, the reactor comprises:

[0052] A cylindrical reaction tube 1 having a cavity; an air inlet and an air outlet respectively disposed at both ends of the reaction tube 1 and connected;

[0053] The molecular sieve membrane tube 3 is arranged in the middle of the cavity, so that in the cross section obtained by cutting along the diameter direction of the cavity, the periphery of the cavity and the periphery of the molecular sieve membrane tube 3 are distributed in concentric circles, and the molecular sieve membrane tube 3 runs through the reaction tube 1; one end of the molecular sieve membrane tube 3 is provided with a purge gas inlet, and the other end is provided with a water vapor outlet;

[0054] The catalyst 2 is filled between the outer periphery of the molecular sieve membrane tube 3 and the reaction tube 1 .

[0055] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0056] In order to more clearly explain the present invention, the following embodiments are given, but the present invention can be implemented in a manner not limited to the scope of the embodiments.

[0057] Preparation Example 1

[0058] 1) Mixing type A molecular sieve seed crystals with deionized water at a weight ratio of 1:80, and then sealing both ends of the alumina hollow fiber tube with polytetrafluoroethylene stoppers, and then soaking the alumina hollow fiber tube in the solution containing the molecular sieve seed crystals for 20 seconds, taking it out and drying it in an oven at 200° C. for 12 hours; obtaining an alumina hollow fiber tube loaded with seed crystals;

[0059] 2) According to the molar ratio of Al 2 O 3 :Na 2 O:H2 O=1:2:64, pseudo-boehmite, sodium hydroxide and water are mixed to obtain liquid A; according to the molar ratio of SiO 2 :Na 2 O:H 2 O=0.3:1.16:64. Silica sol, sodium hydroxide and water are mixed to obtain liquid B; liquids AB are mixed and aged at 100°C for 4 hours. After the aging is completed, the gel liquid is added into the hydrothermal reactor.

[0060] 3) The alumina hollow fiber tube loaded with the seed crystals was immersed in the gel solution, crystallized at 110° C. for 5 h, washed with deionized water several times after the crystallization was completed, and dried at 100° C. for 12 h. After the drying was completed, a molecular sieve membrane tube with a Na-type A-type molecular sieve membrane grown on the outer wall was obtained; the thickness of the Na-type A-type molecular sieve membrane was 4 μm, and the XRD spectrum of the molecular sieve in the Na-type A-type molecular sieve membrane was as follows: Figure 2 shown.

[0061] Preparation Example 2

[0062] 1) Mixing type A molecular sieve seed crystals with deionized water at a weight ratio of 1:150, and then sealing both ends of the alumina hollow fiber tube with polytetrafluoroethylene stoppers, and then soaking the alumina hollow fiber tube in a solution containing the molecular sieve seed crystals for 20 seconds, taking it out and drying it in an oven at 200° C. for 12 hours; obtaining an alumina hollow fiber tube loaded with seed crystals;

[0063] 2) According to the molar ratio of Al 2 O 3 :Na 2 O:H 2 O=1:2:64, pseudo-boehmite, sodium hydroxide and water are mixed to obtain liquid A; according to the molar ratio of SiO 2 :Na 2 O:H 2 O=0.3:1.16:64. Silica sol, sodium hydroxide and water are mixed to obtain liquid B; liquids AB are mixed and aged at 90°C for 2h. After aging, the gel liquid is added into a hydrothermal reactor.

[0064] 3) Immerse the alumina hollow fiber tube loaded with seed crystals in the gel solution, crystallize at 100°C for 4 hours, wash with deionized water several times after crystallization, and dry at 100°C for 12 hours. After drying, a molecular sieve membrane tube with a Na-type A-type molecular sieve membrane grown on the outer wall is obtained; the thickness of the Na-type A-type molecular sieve membrane is 2.7 μm.

[0065] Preparation Example 3

[0066] 1) Mixing type A molecular sieve seed crystals with deionized water at a weight ratio of 1:298, and then sealing both ends of the alumina hollow fiber tube with polytetrafluoroethylene stoppers, and then soaking the alumina hollow fiber tube in a solution containing the molecular sieve seed crystals for 20 seconds, taking it out and drying it in an oven at 200° C. for 12 hours; obtaining an alumina hollow fiber tube loaded with seed crystals;

[0067] 2) According to the molar ratio of Al 2 O 3 :Na 2 O:H 2 O=1:2:64, pseudo-boehmite, sodium hydroxide and water are mixed to obtain liquid A; according to the molar ratio of SiO 2 :Na 2 O:H 2 O=0.3:1.16:64. Silica sol, sodium hydroxide and water are mixed to obtain liquid B; liquids AB are mixed and aged at 80°C for 1 hour. After the aging is completed, the gel liquid is added into a hydrothermal reactor.

[0068] 3) Immerse the alumina hollow fiber tube loaded with seed crystals in the gel solution, crystallize at 80°C for 4 hours, wash with deionized water several times after crystallization, and dry at 100°C for 12 hours. After drying, a molecular sieve membrane tube with a Na-type A-type molecular sieve membrane grown on the outer wall is obtained; the thickness of the Na-type A-type molecular sieve membrane is 2 μm.

[0069] Preparation Example 4

[0070] Commercially available pseudo-boehmite powder was mixed with ZSM-5 powder accounting for 15% of the mass of the pseudo-boehmite powder, and 5% by mass of nitric acid was added, extruded into spheres with a diameter of 3 mm, dried at 100°C, and calcined at 550°C to obtain a methanol to dimethyl ether catalyst.

[0071] Preparation Example 5

[0072] Commercially available pseudo-boehmite powder was mixed with ZSM-5 powder accounting for 10% of the mass of the pseudo-boehmite powder, and 5% by mass of nitric acid was added, extruded into spheres with a diameter of 3 mm, dried at 100°C, and calcined at 550°C to obtain a methanol to dimethyl ether catalyst.

[0073] Preparation Example 6

[0074] Commercially available pseudo-boehmite powder was mixed with ZSM-5 powder accounting for 7% of the mass of the pseudo-boehmite powder, and 5% by mass of nitric acid was added, extruded into spheres with a diameter of 3 mm, dried at 100°C, and calcined at 550°C to obtain a methanol to dimethyl ether catalyst.

[0075] Examples 1-3

[0076] The molecular sieve membrane tubes prepared in Preparation Examples 1-3 and the catalysts prepared in Preparation Examples 4-6 were prepared according to Figure 1 The reactor is assembled in the manner shown, wherein the radius of the membrane tube is 4 mm and the thickness of the catalyst layer is 7.5 mm.

[0077] At the inlet of the reactor, a space velocity of 4 h -1 Methanol at a temperature of 200°C produces dimethyl ether and water under the action of a catalyst at a temperature of 300°C and a pressure of 3Mpa. The produced water passes through the pervaporation membrane tube, enters the inner side of the membrane tube, and is taken away by the nitrogen purge gas. The water vapor is continuously taken away, and the product dimethyl ether is collected at the reactor outlet. After 0.5h of reaction, the conversion rate of methanol is tested.

[0078] The conversion rate of methanol was calculated by the following formula, where the amounts of methanol and dimethyl ether were measured by gas chromatography.

[0079]

[0080] Among them, N in is the raw gas flow rate;

[0081] N g,out is the product tail gas flow rate;

[0082] y M,out is the molar fraction of methanol in the tail gas. The test results are shown in Table 1.

[0083] Comparative Example 1

[0084] The method of Example 1 was followed, except that the alumina hollow fiber tube described in Preparation Example 1 was used instead of the molecular sieve membrane tube prepared in Preparation Example 1, and the other conditions were the same as in Example 1; the test results are shown in Table 1.

[0085] Table 1

[0086] serial number Source of molecular sieve membrane tube Catalyst source Methanol conversion rate (%) Example 1 Preparation Example 1 Preparation Example 4 92.3 Example 2 Preparation Example 2 Preparation Example 5 90.6 Example 3 Preparation Example 3 Preparation Example 6 87.9 Comparative Example 1 / Preparation Example 4 79.7

[0087] Example 4

[0088] The method of Example 1 was followed, except that the radius of the membrane tube was 4 mm and the thickness of the catalyst layer was 10 mm; the other conditions were the same as those of Example 1, and the methanol conversion rate was measured to be 87.3%.

[0089] Example 5

[0090] The method of Example 1 was followed, except that the radius of the membrane tube was 4 mm and the thickness of the catalyst layer was 5 mm; the other conditions were the same as those of Example 1, and the methanol conversion rate was measured to be 86.2%.

[0091] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A reaction method for preparing dimethyl ether from methanol, It is characterized in that The reaction method is carried out in a reactor, which comprises: A reaction tube having a cavity; A molecular sieve membrane tube is located in the cavity, and the interlayer between the outer periphery of the molecular sieve membrane tube and the reaction tube is filled with a catalyst; the molecular sieve membrane tube comprises a porous material matrix and a molecular sieve membrane formed on the porous material matrix, the molecular sieve membrane can selectively pass water but cannot pass methanol and dimethyl ether, and is used to separate water generated by the interlayer reaction in situ; The reaction method comprises: under the reaction conditions of methanol to dimethyl ether, reacting and contacting the methanol-containing raw material with the catalyst in an interlayer, and generating water separated by a molecular sieve membrane into a molecular sieve membrane tube and carried away by a purge gas.

2. The reaction method according to claim 1, in, The thickness of the molecular sieve membrane is 0.1-20 μm.

3. The reaction method according to claim 1 or 2, in, The reaction tube is columnar; preferably, along the length direction of the reaction tube, the molecular sieve membrane tube runs through the reaction tube.

4. The reaction method according to claim 1 or 2, in, The molecular sieve membrane is a type A molecular sieve membrane; preferably, the molecular sieve membrane is a sodium type type A molecular sieve membrane.

5. The reaction method according to claim 1 or 2, in, The molecular sieve membrane is formed on the inner wall and / or outer wall of the membrane tube, and preferably the molecular sieve layer is formed on the outer wall of the membrane tube; More preferably, the porous material matrix is ​​selected from one or more of an alumina hollow fiber tube, a porous silicon nitride ceramic tube and a magnesium aluminum spinel porous ceramic tube, preferably an alumina hollow fiber tube.

6. The reaction method according to claim 1 or 2, in, The catalyst includes γ-Al 2 O 3 and loaded on γ-Al 2 O 3 Silica-alumina molecular sieve and / or silico-aluminophosphate molecular sieve; The silicon-aluminum molecules are selected from HZSM-5 and / or ZSM-5; The silicoaluminophosphate molecular sieve is HSAPO-34 molecular sieve.

7. The reaction method according to claim 6, in, The weight of the silicon aluminum molecular sieve and / or the silicon aluminum phosphate molecular sieve is γ-Al 2 O 3 2-20wt%.

8. The reaction method according to claim 1 or 2, in, The reaction conditions for methanol to dimethyl ether include: temperature of 200°C-450°C, preferably 250°C-370°C, pressure of 0.1Mpa-10Mpa, preferably 3-5Mpa, and space velocity of 0.4-8h -1 , preferably 0.9-3.0h -1 .

9. The reaction method according to claim 1 or 2, in, The purge gas is nitrogen; and / or The ratio of the radius of the molecular sieve membrane tube to the thickness of the catalyst layer is 1:1-2.5, preferably 1:1.6-2.

10. The reaction method according to claim 1 or 2, in, The molecular sieve membrane tube is arranged in the middle of the cavity, so that in a cross section taken along the diameter direction of the cavity, the periphery of the cavity and the periphery of the molecular sieve membrane tube are distributed in concentric circles.

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