阅读说明：本技术 膜催化剂前驱体、膜催化剂、其制备方法及应用 (Film catalyst precursor, film catalyst, preparation method and application thereof ) 是由 李义涛 张宏清 唐火强 钟颖贤 余航 邓龙辉 胡为晴 吴慧娟 于 2019-08-28 设计创作，主要内容包括：本发明涉及催化剂技术领域,具体涉及一种膜催化剂前驱体、膜催化剂、其制备方法及应用。所述前驱体的制备方法包括：向极性有机溶剂中缓慢滴加酸溶剂,得到混合溶剂；向混合溶剂中分别加入醇铝、金属助剂盐、氯钯酸溶液和表面活性剂,恒温水浴回流得到含钯复合溶胶；将多孔陶瓷置于所述含钯复合溶胶中浸渍、干燥、焙烧。本发明的膜催化剂及其制备方法通过制备比表面积较大的含钯复合氟化铝膜层,提高了催化剂的催化活性；通过添加表面活性剂,使催化剂表面金属离子分散更均匀,减少活性金属钯烧结；通过添加金属助剂以改善膜催化剂表面酸碱性,使得反应底物更易在膜催化剂表面富集,提高了膜催化剂的转化效率。(The invention relates to the technical field of catalysts, in particular to a membrane catalyst precursor, a membrane catalyst, and preparation methods and applications thereof. The preparation method of the precursor comprises the following steps: slowly dripping an acid solvent into the polar organic solvent to obtain a mixed solvent; respectively adding aluminum alkoxide, metal additive salt, chloropalladate solution and surfactant into the mixed solvent, and refluxing in a constant-temperature water bath to obtain palladium-containing composite sol; and (3) placing the porous ceramic into the palladium-containing composite sol for dipping, drying and roasting. According to the membrane catalyst and the preparation method thereof, the palladium-containing composite aluminum fluoride membrane layer with larger specific surface area is prepared, so that the catalytic activity of the catalyst is improved; by adding the surfactant, metal ions on the surface of the catalyst are dispersed more uniformly, and active metal palladium sintering is reduced; the metal auxiliary agent is added to improve the surface acidity and alkalinity of the membrane catalyst, so that a reaction substrate is easier to enrich on the surface of the membrane catalyst, and the conversion efficiency of the membrane catalyst is improved.)

1. Pd/AlF₃A film catalyst precursor, wherein the catalyst precursor comprises: the composite coating comprises a porous ceramic layer and a porous composite layer laminated on the surface of the porous ceramic layer, wherein the porous composite layer comprises aluminum oxide, metal auxiliary oxide and palladium oxide, and the metal auxiliary oxide comprises at least two of zinc oxide, chromium oxide, nickel oxide or tin oxide.

2. Pd/AlF according to claim 1₃A precursor of a film catalyst, characterized in that the ratio of the mass of aluminum in the alumina to the mass of each metal promoter in the metal promoter oxide is 100: (0.5 to 3);

and/or the thickness of the porous composite layer is 440-560 μm.

3. Pd/AlF₃A method of preparing a precursor for a film catalyst, the method comprising:

slowly dripping an acid solvent into the polar organic solvent under the condition that the pH value is 6.5-7.5 to obtain a mixed solvent;

respectively adding aluminum alkoxide, metal additive salt, chloropalladate solution and surfactant into the mixed solvent, and refluxing in a constant-temperature water bath at 50-70 ℃ to obtain palladium-containing composite sol;

placing the porous ceramic in the palladium-containing composite sol for dipping, drying and roasting to obtain Pd/AlF₃A film catalyst precursor;

wherein the metal additive salt comprises at least two of chloride or nitrate of zinc, chromium, nickel and tin.

4. Pd/AlF according to claim 3₃The preparation method of the film catalyst precursor is characterized in that the mass ratio of the mass of aluminum in the aluminum alkoxide to the mass of each metal auxiliary in the metal auxiliary salt is 100: (0.5 to 3);

and/or the ratio of the molar amount of the metallic palladium in the chloropalladate to the molar amount of the surfactant is 1: (50-80);

and/or, the polar organic solvent is absolute ethyl alcohol;

and/or the acid solvent is one of hydrochloric acid, nitric acid or acetic acid, and the mass percentage of the acid solvent is 36-70%;

and/or the aluminum alkoxide is aluminum isopropoxide or aluminum butoxide;

and/or the surfactant is cetyl trimethyl ammonium bromide;

and/or the refluxing time of the constant-temperature water bath is 10-15 hours;

and/or, the steps of immersing, drying and roasting the porous ceramic in the palladium-containing composite sol are repeated for a plurality of times;

and/or the dipping temperature is 50-60 ℃, and the dipping time is 10-15 hours;

and/or the roasting temperature is 300-550 ℃.

5. Pd/AlF₃The membrane catalyst is characterized by comprising a porous ceramic layer, a porous palladium-containing composite alumina layer stacked on the surface of the porous ceramic layer and a porous palladium-containing composite aluminum fluoride layer stacked on the surface of the porous palladium-containing composite alumina layer, wherein the porous palladium-containing composite alumina layer comprises alumina, a metal assistant oxide and metal palladium, the porous palladium-containing composite aluminum fluoride layer comprises aluminum fluoride, a metal assistant oxide and metal palladium, and the porous palladium-containing composite alumina layer or the metal assistant oxide in the porous palladium-containing composite aluminum fluoride layer comprises at least two of zinc oxide, chromium oxide, nickel oxide or tin oxide.

6. Pd/AlF according to claim 5₃Membrane catalyst, characterized in that the Pd/AlF₃The surface area of the membrane catalyst is 180-220 m²/g；

Or the thickness of the porous palladium-containing composite aluminum oxide layer is 220-280 μm, and the thickness of the porous palladium-containing composite aluminum fluoride layer is 220-280 μm;

or, the Pd/AlF₃The palladium loading capacity of the membrane catalyst is 1-5%;

or in the porous palladium-containing composite aluminum oxide layer, the mass ratio of the aluminum in the aluminum oxide to the metal additives in the metal additive oxide is 100: (0.5 to 3); in the porous palladium-containing composite aluminum fluoride layer, the mass ratio of aluminum in the aluminum fluoride to each metal auxiliary in the metal auxiliary oxide is 100: (0.5 to 3).

7. Pd/AlF₃The preparation method of the membrane catalyst is characterized by comprising the following steps:

Pd/AlF₃Placing the precursor of the membrane catalyst in a hydrogen fluoride solution, soaking for 0.5-2 hours in a water bath at 50-70 ℃, and then carrying out Pd/AlF₃Washing the film catalyst precursor to be neutral and drying;

introducing hydrogen at 380-400 ℃ to react the Pd/AlF₃Reduction of film catalyst precursor to obtain Pd/AlF₃A membrane catalyst;

wherein, the Pd/AlF₃The precursor of the film catalyst is Pd/AlF as described in claim 1 or 2₃Film catalyst precursor or Pd/AlF prepared according to the preparation method of claim 3 or 4₃A film catalyst precursor.

8. Pd/AlF according to claim 7₃The preparation method of the membrane catalyst is characterized in that the mass percentage content of the hydrogen fluoride solution is 30-40%;

or the drying condition is a vacuum environment at 50-70 ℃.

9. The Pd/AlF as set forth in claim 5 or 6₃Membrane catalyst or Pd/AlF prepared according to the preparation process of claim 7 or 8₃The membrane catalyst is applied to catalyzing the hydrodechlorination reaction of chlorine-containing organic matters.

10. The use according to claim 9, wherein the concentration of the chlorine-containing organic substance is 1000 to 5000 ppm.

Technical Field

The invention relates to the technical field of catalysts, in particular to a membrane catalyst precursor, a membrane catalyst, and preparation methods and applications thereof.

Background

R125 is also called pentafluoroethane, is a chlorine-free Freon substitute, can be used as a refrigerant, a foaming agent, a fire extinguishing agent, a propellant, a carrier gas of a disinfectant and the like, and the application requires that the R125 does not contain other chlorinated hydrocarbon impurities and has higher purity. However, in the current several production methods, the crude product can not meet the requirements, and besides R115, the crude product also contains byproducts such as R113, R114, R115, R123 and the like to different degrees according to different synthesis methods. These by-products, with the exception of R115, can be separated from R125 by conventional fractional distillation techniques, however, R115, because of its relatively close boiling points (R115 has a boiling point of-38.7 ℃ C. and R125 has a boiling point of-48.5 ℃ C.), and an azeotrope exists at 21% by weight of R125 in R115, which has a boiling point of-48.5 ℃ at 1 atm, which is very close to the boiling point of-48.1 ℃ C. of R125, adding considerable difficulty to the production of high purity R125.

The R115 separation method in R125 mainly reduces the content of R115 in the R125 product in the reaction stage, the purification stage and the rectification stage. By using a specific catalyst and specific reaction conditions, the production of R115 is reduced in the reaction stage, but excessively reducing the content of R115 results in a decrease in the yield of R125.

A purification stage: mainly converting R115 in R125 into R125 and R116, or adsorbing R115 by using an adsorbent to remove R115. The conversion of R115 into R116 easily causes the decomposition of R125 at a too high temperature and other impurities are obtained, so that the method has severe requirements on reaction conditions, is high in cost and can cause the loss of pentafluoroethane due to the reaction. The catalyst used for converting R115 into R125 is high in requirement, volatile and active, and needs a large amount of hydrogen, so that the enterprise cost is increased. The adsorbent method requires that R115 is periodically desorbed from the adsorbent, requires a plurality of units for continuous operation, and is complicated in production process.

A rectification stage: and removing R115 by adopting an unconventional extraction rectification method to obtain a high-purity R125 product. The process requires the use of specific extractants and has limitations for extremely low levels of R115.

The existing method for producing high-purity R125 mainly adopts a specific catalyst to reduce the content of R115 in a reaction stage, if the content of R115 is too high, a post-treatment system needs to be correspondingly adjusted, and the adjustment and the modification of the post-treatment system inevitably cause the increase of the production cost.

In view of the above, it is a technical problem to be solved in the art to provide a new membrane catalyst capable of providing trace amount of R115 conversion.

Disclosure of Invention

The present invention aims to overcome the above defects of the prior art and provide a membrane catalyst precursor, a membrane catalyst, and preparation methods and applications thereof.

The object of the invention can be achieved by the following technical measures:

the invention provides a Pd/AlF₃A film catalyst precursor, the catalyst precursor comprising: the composite coating comprises a porous ceramic layer and a porous composite layer laminated on the surface of the porous ceramic layer, wherein the porous composite layer comprises aluminum oxide, metal auxiliary oxide and palladium oxide, and the metal auxiliary oxide comprises at least two of zinc oxide, chromium oxide, nickel oxide or tin oxide.

Preferably, the mass ratio of the aluminum in the aluminum oxide to each metal promoter in the metal promoter oxide is 100: (0.5 to 3);

and/or the thickness of the porous composite layer is 440-560 μm.

The invention also provides Pd/AlF₃A method of preparing a precursor for a film catalyst, the method comprising:

slowly dripping an acid solvent into the polar organic solvent under the condition that the pH value is 6.5-7.5 to obtain a mixed solvent;

respectively adding aluminum alkoxide, metal additive salt, chloropalladate solution and surfactant into the mixed solvent, and refluxing in a constant-temperature water bath at 50-70 ℃ to obtain palladium-containing composite sol;

placing the porous ceramic in the palladium-containing composite sol for dipping, drying and roasting to obtain Pd/AlF₃A film catalyst precursor;

wherein the metal additive salt comprises at least two of chloride or nitrate of zinc, chromium, nickel and tin.

Preferably, the mass ratio of the aluminum in the aluminum alkoxide to each metal promoter in the metal promoter salt is 100: (0.5 to 3);

and/or the ratio of the molar amount of the metallic palladium in the chloropalladate to the molar amount of the surfactant is 1: (50-80);

and/or, the polar organic solvent is absolute ethyl alcohol;

and/or the acid solvent is one of hydrochloric acid, nitric acid or acetic acid, and the mass percentage of the acid solvent is 36-70%;

and/or the aluminum alkoxide is aluminum isopropoxide or aluminum butoxide;

and/or the surfactant is cetyl trimethyl ammonium bromide;

and/or the refluxing time of the constant-temperature water bath is 10-15 hours;

and/or, the steps of immersing, drying and roasting the porous ceramic in the palladium-containing composite sol are repeated for a plurality of times;

and/or the dipping temperature is 50-60 ℃, and the dipping time is 10-15 hours;

and/or the roasting temperature is 300-550 ℃.

The invention also provides Pd/AlF₃The membrane catalyst comprises a porous ceramic layer, a porous palladium-containing composite alumina layer stacked on the surface of the porous ceramic layer and a porous palladium-containing composite aluminum fluoride layer stacked on the surface of the porous palladium-containing composite alumina layer, wherein the porous palladium-containing composite alumina layer comprises alumina, a metal assistant oxide and metal palladium, the porous palladium-containing composite aluminum fluoride layer comprises aluminum fluoride, a metal assistant oxide and metal palladium, and the metal assistant oxide in the porous palladium-containing composite alumina layer or the porous palladium-containing composite aluminum fluoride layer comprises at least two of zinc oxide, chromium oxide, nickel oxide or tin oxide.

Preferably, the Pd/AlF₃The surface area of the membrane catalyst is 180-220 m²/g；

Or the thickness of the porous palladium-containing composite aluminum oxide layer is 220-280 μm, and the thickness of the porous palladium-containing composite aluminum fluoride layer is 220-280 μm;

or, the Pd/AlF₃The palladium loading capacity of the membrane catalyst is 1-5%;

or in the porous palladium-containing composite aluminum oxide layer, the mass ratio of the aluminum in the aluminum oxide to the metal additives in the metal additive oxide is 100: (0.5 to 3); in the porous palladium-containing composite aluminum fluoride layer, the ratio of the mass of aluminum in the aluminum fluoride to the mass of metal in the metal auxiliary oxide is 100: (0.5 to 3).

The invention also provides Pd/AlF₃A method for preparing a membrane catalyst, the method comprising:

Pd/AlF₃Placing the precursor of the membrane catalyst in a hydrogen fluoride solution, soaking for 0.5-2 hours in a water bath at 50-70 ℃, and then carrying out Pd/AlF₃Washing the film catalyst precursor to be neutral and drying;

introducing hydrogen at 380-400 ℃ to react the Pd/AlF₃Reduction of film catalyst precursor to obtain Pd/AlF₃A membrane catalyst;

wherein, the Pd/AlF₃The precursor of the film catalyst is the Pd/AlF₃Film catalyst precursor or Pd/AlF prepared according to the precursor preparation method₃A film catalyst precursor.

Preferably, the mass percentage content of the hydrogen fluoride solution is 30-40%;

or the drying condition is a vacuum environment at 50-70 ℃.

The invention also provides the Pd/AlF₃Membrane catalyst or Pd/AlF prepared according to the preparation method₃The membrane catalyst is applied to catalyzing the hydrodechlorination reaction of chlorine-containing organic matters.

Preferably, the concentration of the chlorine-containing organic matters is 1000-5000 ppm.

According to the membrane catalyst and the preparation method thereof, the palladium-containing composite aluminum fluoride membrane layer with larger specific surface area is prepared, so that the catalytic activity of the catalyst is improved; active metal palladium is added when the film catalyst precursor is prepared, and a surfactant is added, so that metal ions on the surface of the catalyst are dispersed more uniformly, and active metal palladium sintering is reduced; the metal auxiliary agent is added to improve the surface acidity and alkalinity of the membrane catalyst, so that the catalytic performance is improved, a reaction substrate R115 is easier to enrich on the surface of the membrane catalyst, better conditions are provided for converting subsequent reaction into R125, conversion of trace R115 can be catalyzed, and purification of R125 gas containing trace R115 becomes possible.

Drawings

FIG. 1 is a schematic macrostructure diagram of a porous ceramic in an example of the present invention.

FIG. 2 is a schematic view showing the microstructure of a porous ceramic according to an embodiment of the present invention.

Fig. 3 is a schematic structural view of a membrane catalyst according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In order to make the description of the present disclosure more complete and complete, the following description is given for illustrative purposes with respect to the embodiments and examples of the present invention; it is not intended to be the only form in which the embodiments of the invention may be practiced or utilized. The embodiments are intended to cover the features of the various embodiments as well as the method steps and sequences for constructing and operating the embodiments. However, other embodiments may be utilized to achieve the same or equivalent functions and step sequences.

In the specification, R115 is CFC-115, pentafluoro-monochloroethane; r125 is CFC-125, pentafluoroethane.

Precursor preparation examples

The embodiment of the invention provides Pd/AlF₃The preparation method of the film catalyst precursor comprises the following steps:

s101, slowly and dropwise adding an acid solvent into the polar organic solvent under the condition that the pH value is 6.5-7.5 to obtain a mixed solvent.

The polar organic solvent can be absolute ethyl alcohol, the acid solvent is one of hydrochloric acid, nitric acid or acetic acid, and the mass percentage of the acid solvent is 36-70%. Preferably, the acid solvent is concentrated nitric acid with the mass percentage of 67%.

S102, respectively adding aluminum alkoxide, metal additive salt, chloropalladate solution and surfactant into the mixed solvent, and refluxing in a constant-temperature water bath at 50-70 ℃ to obtain the palladium-containing composite sol.

Wherein the aluminum alkoxide is aluminum isopropoxide or aluminum butoxide, and the metal auxiliary salt comprises at least two of chloride or nitrate of zinc, chromium, nickel and tin; preferably, the aluminum alkoxide is aluminum isopropoxide and the metal promoter salt comprises two of zinc chloride, chromium chloride, nickel chloride, and tin chloride.

Wherein the mass ratio of the aluminum in the aluminum alkoxide to the metal additives in the metal additive salt is 100: (0.5 to 3), wherein the ratio of the molar amount of palladium in the chloropalladate solution to the molar amount of the surfactant is 1: (50-80). Preferably, the concentration of the metal palladium in the chloropalladate solution is 0.010g/mL, and the addition volume of the chloropalladate solution is 2mL to 10 mL.

Wherein the surfactant is Cetyl Trimethyl Ammonium Bromide (CTAB); and the refluxing time of the constant-temperature water bath is 10-15 hours.

S103, placing the porous ceramic in the palladium-containing composite sol for dipping, drying and roasting to obtain Pd/AlF₃A film catalyst precursor.

The porous ceramic material with the pore diameter and the high open porosity is prepared by taking high-quality raw materials such as corundum, silicon carbide and cordierite as main materials and through molding and a special high-temperature sintering process, has the advantages of high temperature resistance, high pressure resistance, acid corrosion resistance, alkali corrosion resistance and organic medium corrosion resistance, good biological inertia, controllable pore structure, high open porosity, long service life, good product regeneration performance and the like. In addition, the base material has stable property, so that the coating can be recycled and regenerated repeatedly even if the coating falls off. Specifically, the structure and SEM images of the porous ceramic are shown in FIGS. 1 and 2.

Wherein the dipping temperature is 50-60 ℃, and the dipping time is 10-15 hours.

Wherein the steps of immersing, drying and calcining the porous ceramic in the palladium-containing composite sol are repeated for a plurality of times, for example, for six times.

Wherein the roasting temperature is 300-550 ℃.

Pd/AlF obtained according to the above preparation method₃The film catalyst precursor contains active metal palladium, and in order to prevent the palladium-containing composite sol supported on the porous ceramic by impregnation from being sintered at the time of firing, it is necessary to further disperse the active metal palladium on the porous ceramic, and therefore, a surfactant is added in the embodiment of the present invention.

The surfactant is decomposed in the roasting process, the metal auxiliary agent forms corresponding metal auxiliary agent oxide in the roasting process, and the palladium chloride acid forms palladium oxide in the roasting process.

Pd/AlF obtained according to the above preparation method₃Use of film catalyst precursor in further preparation of Pd/AlF₃A membrane catalyst.

Pd/AlF prepared according to the above method₃The film catalyst precursor includes: the composite coating comprises a porous ceramic layer and a porous composite layer laminated on the surface of the porous ceramic layer, wherein the porous composite layer comprises aluminum oxide, metal auxiliary oxide and palladium oxide, and the metal auxiliary oxide comprises at least two of zinc oxide, chromium oxide, nickel oxide or tin oxide.

Specifically, the mass ratio of the aluminum in the aluminum oxide to each metal additive in the metal additive oxide is 100: (0.5-3), and the thickness of the porous composite layer is 440-560 μm.

Preparation examples of Membrane catalysts

The embodiment of the invention also provides Pd/AlF₃The preparation method of the membrane catalyst comprises the following steps:

s201, preparing Pd/AlF₃A film catalyst precursor.

The preparation method of the precursor is specifically referred to the above embodiments, and is not described in detail herein.

S202, the obtained Pd/AlF₃Placing the film catalyst precursor into a hydrogen fluoride solution, soaking for 0.5-2 hours in a water bath at 50-70 ℃, and then carrying outPd/AlF₃The film catalyst precursor is washed to neutrality and dried.

Wherein the mass percentage of the hydrogen fluoride solution is 30-40%, and the drying condition is a vacuum environment at 50-70 ℃.

S203, introducing hydrogen to the Pd/AlF at the temperature of 380-400 DEG C₃Reduction of film catalyst precursor to obtain Pd/AlF₃A membrane catalyst.

Pd/AlF obtained according to the above preparation method₃The structure of the membrane catalyst is shown in fig. 3, and the membrane catalyst comprises a porous ceramic layer 1, a porous palladium-containing composite alumina layer 2, and a porous palladium-containing composite alumina layer 3, which are sequentially laminated.

Pd/AlF obtained according to the above preparation method₃The surface area of the membrane catalyst is 180-220 m²/g。

Measured by an ICP emission spectrometer (inductively coupled plasma spectrometer), and the Pd/AlF obtained by the preparation method₃The palladium loading capacity of the membrane catalyst is 1-5%, preferably, the palladium loading capacity is 1-3%.

Pd/AlF prepared according to the above method₃The membrane catalyst comprises a porous ceramic layer 1, a porous palladium-containing composite alumina layer 2 stacked on the surface of the porous ceramic layer 1, and a porous palladium-containing composite aluminum fluoride layer 3 stacked on the surface of the porous palladium-containing composite alumina layer 2, wherein the porous palladium-containing composite alumina layer 2 comprises alumina, a metal assistant oxide and metal palladium, the porous palladium-containing composite aluminum fluoride layer 3 comprises aluminum fluoride, a metal assistant oxide and metal palladium, and the porous palladium-containing composite alumina layer 2 or the metal assistant oxide in the porous palladium-containing composite aluminum fluoride layer 3 comprises at least two of zinc oxide, chromium oxide, nickel oxide and tin oxide.

Wherein, the Pd/AlF₃The surface area of the membrane catalyst is 180-220 m²(ii)/g; the thickness of the porous palladium-containing composite aluminum oxide layer 2 is 220-280 μm, and the thickness of the porous palladium-containing composite aluminum fluoride layer 3 is 220-280 μm; the Pd/AlF₃The palladium loading capacity of the membrane catalyst is 1-5%; in a porous palladium-containing composite alumina layerThe mass ratio of the aluminum in the aluminum oxide to the metal additives in the metal additive oxide is 100: (0.5 to 3); in the porous palladium-containing composite aluminum fluoride layer, the mass ratio of aluminum in the aluminum fluoride to each metal auxiliary in the metal auxiliary oxide is 100: (0.5 to 3).

Compared with the prior art, the membrane catalyst and the preparation method thereof provided by the embodiment of the invention have the following differences: (1) porous ceramic is used as a carrier, and the catalytic activity of the catalyst is improved by preparing a palladium-containing composite aluminum fluoride membrane layer with a large specific surface area; (2) compared with the prior art that a composite sol without active metal palladium and a precursor without metal palladium are prepared, and the precursor is soaked in a hydrogen fluoride solution and dried and then placed in a chloropalladate solution to adsorb metal palladium, the membrane catalyst provided by the embodiment of the invention is added with active metal palladium in the process of preparing the composite sol, and the prepared composite sol and the precursor both contain metal palladium, so that each metal can be uniformly distributed on a catalyst membrane layer, more active sites are provided, a foundation is provided for improving the performance, and the surface tension among metal ions is increased and the agglomeration is reduced by adding a surfactant, so that the sintering phenomenon of the active metal palladium in the roasting process is reduced, and the effect of the traditional hydrogenation dechlorination catalyst can be achieved by using a small amount of palladium; (3) the novel metal auxiliary agent is adopted, and the acid-base property of the surface of the membrane catalyst is improved by adding the novel metal auxiliary agent (comprising at least two of chloride or nitrate of zinc, chromium, nickel and tin), so that a reaction substrate is easier to enrich on the surface of the membrane catalyst, and the conversion efficiency of the membrane catalyst is improved.