Filtering and catalyzing integrated membrane reactor and preparation method thereof

Abstract

The invention discloses a filtration and catalysis integrated membrane reactor and a preparation method, and relates to the field of fluid filtration and reaction coupling. The stability and the service life of the membrane reactor can be improved. The membrane reactor comprises a filter layer and a catalyst layer covering the filter layer; the filter layer is a stainless steel filter membrane prepared by adopting a powder metallurgy method; the catalytic layer is a metal oxide particle layer which covers the surface of the stainless steel filter membrane and has octahedral crystal morphology, and the metal oxide particle layer is formed by in-situ reaction in an alkaline solution after the stainless steel filter membrane is subjected to acid pickling pretreatment.

Description

Technical Field

[0001] This application relates to the field of fluid filtration and reaction coupling, and more particularly to a membrane reactor integrating filtration and catalysis and its preparation method. Background Technology

[0002] With the escalating global energy crisis and environmental pollution, achieving efficient and green separation and catalysis processes has become a critical technical challenge in the fields of chemical engineering, energy, and environmental engineering. To address this issue, membrane reactors, as a novel device integrating filtration and catalysis, can complete separation and conversion within a single unit, significantly reducing process steps and improving mass transfer efficiency. They show broad application prospects in water treatment, organic pollutant degradation, and hydrogen production via water electrolysis.

[0003] Currently, common membrane reactor substrates often employ materials such as ceramics, polymers, and porous carbon. While these materials can achieve filtration and catalysis to some extent, several insurmountable problems remain. For example, ceramic membranes are strong but brittle, difficult to process, and have limited interfacial adhesion to the active layer; polymer membranes lack sufficient temperature and corrosion resistance, making them prone to failure in harsh environments; and porous carbon membranes, while conductive, suffer from poor mechanical strength and stability, making long-term stable use difficult. More critically, the substrate and catalyst layer of these membrane reactors are often bonded through coating, impregnation, or deposition, resulting in poor adhesion of the active layer. This leads to the easy detachment or deactivation of active components during long-term use, thus affecting the overall performance and lifespan of the membrane reactor. Summary of the Invention

[0004] This application provides an integrated filtration and catalysis membrane reactor and its preparation method, which can improve the stability and service life of the membrane reactor.

[0005] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application provides a membrane reactor integrating filtration and catalysis, the membrane reactor comprising: a filter layer and a catalytic layer covering the filter layer; The filter layer is a stainless steel filter membrane prepared by powder metallurgy. The catalyst layer is a layer of metal oxide particles with an octahedral crystal morphology covering the surface of the stainless steel filter membrane. The metal oxide particle layer is formed by in-situ reaction in an alkaline solution after the stainless steel filter membrane has undergone acid washing pretreatment.

[0006] In one embodiment, the metal oxide particles are one or more mixtures of Fe-Cr-O, Fe-Ni-O, Fe-Cr-Ni-O, and Fe-O with a spinel or anti-spinel structure, the particle size of the metal oxide particles is 1~10µm, and the alkaline solution is a solution containing NaOH and NaNO3.

[0007] In one embodiment, the concentration of NaOH in the alkaline solution is 2.0~6.0M, and the concentration of NaNO3 is 0.05~0.5M.

[0008] In one embodiment, the filter layer comprises: a tubular, plate-shaped, sheet-shaped, or cup-shaped stainless steel filter membrane prepared by powder metallurgy, wherein the stainless steel filter membrane has an average pore size of 0.1~5µm and a porosity of 20%~70%.

[0009] A second aspect of this application provides a method for preparing a membrane reactor integrating filtration and catalysis, the method comprising: Stainless steel filter membranes undergo acid pickling pretreatment to remove surface oxides; The treated stainless steel filter membrane is placed in an alkaline solution for hydrothermal reaction to carry out in-situ reaction on the surface of the stainless steel filter membrane, and a metal oxide particle layer covering the surface of the stainless steel filter membrane is generated to obtain a filtration catalytic structure. After cleaning and drying the filtration catalytic structure, a membrane reactor is obtained.

[0010] In one embodiment, the metal oxide particles are one or more mixtures of Fe-Cr-O, Fe-Ni-O, Fe-Cr-Ni-O, and Fe-O with a spinel or anti-spinel structure, the particle size of the metal oxide particles is 1~10µm, and the alkaline solution is an aqueous solution containing NaOH and NaNO3, wherein the concentration of NaOH is 2.0~6.0M and the concentration of NaNO3 is 0.05~0.5M.

[0011] In one embodiment, the method further includes controlling the type, size, and distribution density of the metal oxide by adjusting the concentration of the NaNO3 and the reaction time.

[0012] In one embodiment, the acidic solution used in the pickling pretreatment includes hydrochloric acid, nitric acid, or a mixed acidic solution, wherein the concentration of the acidic solution is 0.1~3.0M, and the pickling time is 5~30 minutes.

[0013] In one embodiment, the temperature of the hydrothermal reaction is 120~200°C, and the time of the hydrothermal reaction is 5~12 hours.

[0014] In one embodiment, the container for the hydrothermal reaction is a stainless steel reactor lined with polytetrafluoroethylene, and the ratio of the volume of the hydrothermal reaction solution to the total volume of the container is 30-70%.

[0015] In one embodiment, the cleaning and drying process of the filter catalyst structure includes: The filtration catalyst structure is rinsed sequentially with deionized water and ethanol, and then dried under vacuum or inert atmosphere to obtain the membrane reactor.

[0016] The beneficial effects of the technical solutions provided in this application include at least the following: The membrane reactor integrating filtration and catalysis provided in this application includes: a filter layer and a catalytic layer covering the filter layer; the filter layer is a stainless steel filter membrane prepared by powder metallurgy; the catalytic layer is a metal oxide particle layer covering the surface of the stainless steel filter membrane, and the metal oxide particle layer is formed by in-situ reaction in an alkaline solution after acid washing pretreatment of the stainless steel filter membrane.

[0017] This application forms a catalytic layer by pre-treating a stainless steel filter membrane with acid washing and then reacting it in situ in an alkaline solution. This eliminates the need for an external precursor and avoids complex processes such as coating, impregnation, or deposition, making the preparation process simple and efficient.

[0018] Secondly, the metal oxide particle layer is tightly bonded to the stainless steel filter membrane, and the catalyst layer is stably attached, which can effectively prevent the active components from falling off or becoming deactivated. Moreover, there is no need to recover the catalyst separately after the catalytic reaction is completed, thus significantly improving the long-term stability and service life of the membrane reactor.

[0019] Furthermore, the membrane reactor of this application possesses three functions: mechanical strength, filtration, and catalysis. The stainless steel filter membrane provides mechanical strength and stable filtration capacity, while the surface metal oxide particle layer provides highly efficient catalytic performance, achieving functional integration and improving mass transfer efficiency and overall process performance.

[0020] Furthermore, this application allows for the control of the type, size, and distribution density of metal oxide particles by adjusting the NaNO3 concentration and reaction time.

[0021] Furthermore, the catalyst layer of this application has the characteristics of large specific surface area and abundant active sites, and can be widely used in water treatment, degradation of organic pollutants, water electrolysis and chemical reaction enhancement, etc. It has excellent catalytic performance and broad application prospects. Attached Figure Description

[0022] Figure 1 A flowchart illustrating a method for preparing an integrated filtration and catalysis membrane reactor, as provided in this application embodiment; Figure 2A schematic diagram of a hydrothermal reaction process provided for an embodiment of this application; Figure 3 A locally magnified scanning electron microscope of a catalyst layer provided in an embodiment of this application. Figure 1 ; Figure 4 A locally magnified scanning electron microscope of a catalyst layer provided in an embodiment of this application. Figure 2 . Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0025] In addition, the use of “based on” or “according to” implies openness and inclusivity, because processes, steps, calculations or other actions “based on” or “according to” one or more conditions or values ​​can in practice be based on additional conditions or values ​​beyond those conditions.

[0026] This application provides a membrane reactor integrating filtration and catalysis, the membrane reactor comprising: a filter layer and a catalytic layer covering the filter layer; The filter layer is a stainless steel filter membrane prepared by powder metallurgy. The catalyst layer is a layer of metal oxide particles with an octahedral crystal morphology covering the surface of the stainless steel filter membrane. The metal oxide particle layer is formed by in-situ reaction in an alkaline solution after the stainless steel filter membrane has undergone acid washing pretreatment.

[0027] Of course, the structure of the membrane reactor integrating filtration and catalysis also includes the reactor shell, inlet and outlet, etc., which will not be described in detail here. This application mainly describes and defines the characteristics and preparation methods of the filter layer and catalyst layer in the membrane reactor.

[0028] Optionally, the filter layer includes: tubular, plate-shaped, sheet-shaped, and cup-shaped stainless steel filter membranes prepared by powder metallurgy, wherein the average pore size of the stainless steel filter membrane is 0.1~5µm and the porosity is 20%~70%.

[0029] Stainless steel filter membranes are ideal materials for constructing membrane reactors due to their low cost, high mechanical strength, good corrosion resistance, adjustable pore structure, and the presence of metal sources such as Fe, Ni, and Cr. Stainless steel filter membranes can serve as a stable filtration layer and also provide a good bonding interface for the subsequent construction of the catalytic layer.

[0030] Optionally, the metal oxide particles are one or more mixtures of Fe-Cr-O, Fe-Ni-O, Fe-Cr-Ni-O, and Fe-O with a spinel or anti-spinel structure, and the particle size of the metal oxide particles is 1~10µm. The alkaline solution is a solution containing NaOH and NaNO3, wherein the concentration of NaOH in the alkaline solution is 2.0~6.0M and the concentration of NaNO3 is 0.05~0.5M.

[0031] It should be noted that stainless steel filter membranes are mainly composed of metallic elements such as Fe, Cr, and Ni. The surface of stainless steel is rich in Cr, which easily forms a passivation layer, hindering electron transport and the exposure of active sites, thus affecting catalytic performance. However, when stainless steel filter membranes are exposed to strongly alkaline solutions, Cr oxides have high solubility under alkaline conditions and readily react with OH-. - The reaction produces a soluble complex [Cr(OH)4]. - This reaction leads to the selective dissolution of Cr elements from the surface layer, creating locally Cr-depleted regions. At this point, Fe, Ni, and other atoms are gradually oxidized in the oxidizing environment of the solution, forming metal oxide particles.

[0032] The metal oxide particle layer generated in this application can be tightly bonded to the stainless steel filter membrane, and the catalyst layer is stably attached, which can effectively prevent the active components from falling off or becoming deactivated. Moreover, there is no need to recover the catalyst separately after the catalytic reaction is completed, thereby significantly improving the long-term stability and service life of the membrane reactor.

[0033] This application provides an integrated filtration and catalysis membrane reactor. The reactor uses a stainless steel filter membrane as its framework. Through acidic solution treatment and surface activation and elemental reconstruction under alkaline conditions, a uniformly distributed layer of metal oxide particles is formed in situ on the substrate surface. The stainless steel filter membrane provides excellent mechanical strength and porous channels, enabling effective filtration and separation of liquids or gases. Under alkaline conditions, elemental migration and reconstruction occur on the surface of the stainless steel filter membrane, forming a high specific surface area active layer structure, which is firmly bonded to the surface of the stainless steel filter membrane and serves as a catalytic layer. The resulting membrane reactor combines mechanical support, filtration separation, and catalytic conversion, enabling simultaneous filtration and catalytic conversion of target components during continuous reactions. The preparation process of this application is simple, requiring no external catalytic precursor. The resulting membrane reactor has a stable structure and tight interfacial bonding, making it suitable for continuous filtration-catalysis integrated systems in water treatment, organic pollutant degradation, and chemical processes.

[0034] This application also provides a method for preparing an integrated filtration and catalysis membrane reactor, used to prepare such a reactor. Figure 1 As shown, the method includes the following steps: Step 101: Perform acid washing pretreatment on the stainless steel filter membrane to remove surface oxides.

[0035] Optionally, the acidic solution used in the pickling pretreatment includes hydrochloric acid, nitric acid, or a mixed acidic solution; the concentration of the acidic solution is 0.1~3.0M, and the pickling time is 5~30 minutes.

[0036] Step 102: The treated stainless steel filter membrane is placed in an alkaline solution for hydrothermal reaction to carry out an in-situ reaction on the surface of the stainless steel filter membrane, thereby generating a layer of metal oxide particles covering the surface of the stainless steel filter membrane and obtaining a filtration catalytic structure.

[0037] Optionally, the metal oxide particles are one or more mixtures of Fe-Cr-O, Fe-Ni-O, Fe-Cr-Ni-O, and Fe-O with spinel or anti-spinel structures, the particle size of the metal oxide particles is 1~10µm, and the alkaline solution is an aqueous solution containing NaOH and NaNO3, wherein the concentration of NaOH is 2.0~6.0M and the concentration of NaNO3 is 0.05~0.5M.

[0038] Optionally, the method further includes controlling the type, size, and distribution density of the metal oxide particles by adjusting the concentration of the NaNO3 and the reaction time.

[0039] The hydrothermal reaction temperature is 120~200℃, and the hydrothermal reaction time is 5~12 hours.

[0040] The hydrothermal reaction vessel is a stainless steel reactor lined with polytetrafluoroethylene (PTFE), and the ratio of the solution volume to the total volume of the vessel is 30-70%. Figure 2 The diagram shown is a schematic of the hydrothermal reaction process, in which... Figure 2 The image shows a stainless steel high-pressure reactor used for hydrothermal reactions, a polytetrafluoroethylene liner, and a 316L stainless steel tubular filter membrane.

[0041] Step 103: After cleaning and drying the filter catalytic structure, a membrane reactor is obtained.

[0042] The filtration catalyst structure is rinsed sequentially with deionized water and ethanol, and then dried under vacuum or inert atmosphere to obtain the membrane reactor.

[0043] For details on the preparation method of a membrane reactor integrating filtration and catalysis, please refer to the definition of a membrane reactor integrating filtration and catalysis in this application, which will not be elaborated further here.

[0044] The preparation method of the integrated filtration and catalysis membrane reactor provided in the above embodiments is as follows. This application also provides some specific embodiments. The following embodiments describe the technical solutions of this application in more detail. These embodiments are for illustrative purposes only, as various modifications and variations within the scope of the disclosure of this application will be apparent to those skilled in the art. The reagents and raw materials used in the embodiments are commercially available or synthesized using conventional methods and can be used directly without further processing. The instruments and apparatus used in the embodiments are also commercially available.

[0045] Example 1: Step 11: Select a 316L stainless steel tubular filter membrane (outer diameter 2.0 mm, wall thickness 0.5 mm, length 50 mm, average pore size 1.2 µm). Place the sample in a 1.0 M hydrochloric acid solution and ultrasonically clean for 20 min to remove the surface oxide layer and impurities. Then rinse with deionized water and ethanol in sequence and vacuum dry at 60 °C.

[0046] Step 12: Place the stainless steel tubular filter membrane in a polytetrafluoroethylene-lined reactor, add 50 mL of alkaline solution, and then place the reactor in a constant temperature oven at 175°C for 12 hours. The alkaline solution is a mixture of 0.4 M NaNO3 and 4.0 M NaOH.

[0047] Step 13: After natural cooling, remove the stainless steel tubular filter membrane, wash it sequentially with deionized water and ethanol, and dry it under a nitrogen atmosphere to obtain a stainless steel tubular filter membrane with a uniformly distributed metal oxide particle layer on its surface. Scanning electron microscopy reveals that octahedral metal oxide particles are uniformly attached to the outer surface of the stainless steel filter membrane, with a particle size of approximately 1µm to 5µm. The surface roughness of the membrane reactor is significantly increased, which is beneficial for providing more active sites, and the active layer is tightly bonded to the filter membrane, making it difficult to peel off.

[0048] A locally magnified scanning electron microscope image of the catalyst layer prepared in Example 1 is shown below. Figure 3 As shown.

[0049] Example 2 Step 21: Cut the 316L stainless steel sheet filter membrane into 20mm × 10mm samples, and ultrasonically clean them in 1.0M hydrochloric acid solution for 15 minutes to remove the surface oxide layer. After cleaning, the samples are washed sequentially with deionized water and ethanol, and then vacuum dried at 50℃ for 12 hours.

[0050] Step 22: Place the pretreated stainless steel sheet filter membrane into a 100 mL polytetrafluoroethylene-lined reactor, and add 50 mL of a mixed solution containing 0.3 M NaNO3 and 4.5 M NaOH. Place the reactor in an oven and maintain the temperature at 180 °C for 10 hours.

[0051] Step 23: After naturally cooling to room temperature, take out the sample and wash it with deionized water and ethanol in sequence, and vacuum dry it at 50°C to obtain a stainless steel sheet filter membrane with a metal oxide particle layer on the surface.

[0052] Example 3 Step 31: Select a 316L stainless steel tubular filter membrane (outer diameter 17.0 mm, wall thickness 2.0 mm, length 50 mm, average pore size 4.7 µm). Place the sample in a 1.0 M hydrochloric acid solution and ultrasonically clean for 20 min to remove the surface oxide layer and impurities. Then rinse with deionized water and ethanol in sequence and vacuum dry at 60 °C.

[0053] Step 32: Place the stainless steel tubular filter membrane in a polytetrafluoroethylene-lined reactor, and add 50 mL of a solution consisting of 0.2 M NaNO3 and 4.0 M NaOH. Place the reactor in a constant temperature oven and react at 180°C for 10 h.

[0054] Step 33: After natural cooling, remove the stainless steel tubular filter membrane, wash it sequentially with deionized water and ethanol, and dry it under a nitrogen atmosphere to obtain a stainless steel filter membrane with a uniformly distributed metal oxide particle layer on its surface. Scanning electron microscopy reveals that octahedral metal oxide particles are uniformly attached to the outer surface of the stainless steel tube, with a particle size of approximately 5µm~10µm.

[0055] A locally magnified scanning electron microscope image of the catalyst layer prepared in Example 3 is shown below. Figure 4 As shown.

[0056] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A membrane reactor integrating filtration and catalysis, characterized in that, The membrane reactor includes: a filter layer and a catalyst layer covering the filter layer; The filter layer is a stainless steel filter membrane prepared by powder metallurgy. The catalyst layer is a layer of metal oxide particles with an octahedral crystal morphology covering the surface of the stainless steel filter membrane. The metal oxide particle layer is formed by in-situ reaction in an alkaline solution after the stainless steel filter membrane has undergone acid washing pretreatment.

2. The membrane reactor according to claim 1, characterized in that, The metal oxide particles are one or more mixtures of Fe-Cr-O, Fe-Ni-O, Fe-Cr-Ni-O, and Fe-O with spinel or anti-spinel structures, and the particle size of the metal oxide particles is 1~10µm. The alkaline solution is a solution containing NaOH and NaNO3.

3. The membrane reactor according to claim 1, characterized in that, The alkaline solution contains NaOH at a concentration of 2.0–6.0 M and NaNO3 at a concentration of 0.05–0.5 M.

4. The membrane reactor according to claim 1, characterized in that, The filter layer includes tubular, plate-shaped, sheet-shaped, and cup-shaped stainless steel filter membranes prepared by powder metallurgy, wherein the average pore size of the stainless steel filter membrane is 0.1~5µm and the porosity is 20%~70%.

5. A method for preparing a membrane reactor integrating filtration and catalysis, characterized in that, The method includes: Stainless steel filter membranes undergo acid pickling pretreatment to remove surface oxides; The treated stainless steel filter membrane is placed in an alkaline solution for hydrothermal reaction to carry out in-situ reaction on the surface of the stainless steel filter membrane, and a metal oxide particle layer covering the surface of the stainless steel filter membrane is generated to obtain a filtration catalytic structure. After cleaning and drying the filtration catalytic structure, a membrane reactor is obtained.

6. The method according to claim 5, characterized in that, The metal oxide particles are one or more mixtures of Fe-Cr-O, Fe-Ni-O, Fe-Cr-Ni-O, and Fe-O with spinel or anti-spinel structures, and the particle size of the metal oxide particles is 1~10µm. The alkaline solution is an aqueous solution containing NaOH and NaNO3, wherein the concentration of NaOH is 2.0~6.0M and the concentration of NaNO3 is 0.05~0.5M.

7. The method according to claim 6, characterized in that, The method further includes controlling the type, size, and distribution density of the metal oxide particles by adjusting the concentration of the NaNO3 and the reaction time.

8. The method according to claim 5, characterized in that, The acidic solution used in the pickling pretreatment includes hydrochloric acid, nitric acid, or a mixture of acids. The concentration of the acidic solution is 0.1~3.0M, and the pickling time is 5~30 minutes; The hydrothermal reaction temperature is 120~200℃, and the hydrothermal reaction time is 5~12 hours.

9. The method according to claim 5, characterized in that, The container for the hydrothermal reaction is a stainless steel reactor lined with polytetrafluoroethylene, and the ratio of the volume of the hydrothermal reaction solution to the total volume of the container is 30-70%.

10. The method according to claim 5, characterized in that, The cleaning and drying process of the filter catalyst structure includes: The filtration catalyst structure is rinsed sequentially with deionized water and ethanol, and then dried under vacuum or inert atmosphere to obtain the membrane reactor.

Images