Preparation method of catalytic membrane
阅读说明：本技术 一种催化膜的制备方法 (Preparation method of catalytic membrane ) 是由 陈日志 路佳 吴员鸿 陈思百 唐文麒 邢卫红 于 2019-11-27 设计创作，主要内容包括：本发明涉及一种催化膜制备方法,属于催化剂制备技术领域。将陶瓷膜放入原子层沉积设备反应腔内,在陶瓷膜上沉积二氧化钛涂层,放入管式炉内煅烧,放入原子层沉积设备反应腔内,沉积Pd纳米颗粒,得到Pd催化膜。本发明采用原子层沉积技术沉积TiO<Sub>2</Sub>对陶瓷膜表面及孔道进行修饰,随后将修饰后的陶瓷膜煅烧,调控陶瓷膜表面特性,有利于后续Pd活性组分的沉积,制备出的催化膜可以用于流通式膜反应装置,实现催化剂与反应物的反应分离耦合,催化膜重复性使用效果好,只需简单冲洗即可,催化膜重复使用多次,活性无明显下降。采用陶瓷膜作为载体,经过处理,提高了单位质量Pd的催化效率,提高了重金属Pd的利用率。(The invention relates to a preparation method of a catalytic membrane, belonging to the technical field of catalyst preparation. Putting a ceramic membrane into a reaction cavity of an atomic layer deposition device, depositing a titanium dioxide coating on the ceramic membrane, putting the ceramic membrane into a tube furnace for calcination, putting the ceramic membrane into the reaction cavity of the atomic layer deposition device, and depositing Pd nanoRice particles to obtain the Pd catalytic membrane. The invention adopts the atomic layer deposition technology to deposit TiO 2 The surface and the pore channels of the ceramic membrane are modified, the modified ceramic membrane is calcined, the surface characteristics of the ceramic membrane are regulated and controlled, the subsequent deposition of Pd active components is facilitated, the prepared catalytic membrane can be used for a flow-through membrane reaction device, the reaction separation coupling of a catalyst and a reactant is realized, the catalytic membrane is good in repeated use effect and can be simply washed, the catalytic membrane is repeatedly used for multiple times, and the activity is not obviously reduced. The ceramic membrane is used as a carrier, and the catalytic efficiency of Pd per unit mass is improved and the utilization rate of heavy metal Pd is improved through treatment.)
1. A preparation method of a catalytic membrane is characterized by comprising the following steps:
the method comprises the following steps: putting a ceramic membrane into a reaction cavity of the atomic layer deposition equipment, and depositing a titanium dioxide coating on the ceramic membrane to prepare TiO2A modified ceramic membrane;
step two: adding TiO into the mixture2Calcining the modified ceramic membrane in a tubular furnace to prepare TiO2Calcining the modified ceramic membrane;
step three: adding TiO into the mixture2And placing the calcined and modified ceramic membrane into a reaction cavity of atomic layer deposition equipment, and depositing Pd nano particles to obtain the Pd catalytic membrane.
2. A catalytic membrane preparation method according to claim 1, wherein the ceramic membrane is a sheet alumina ceramic membrane having a pore size of 1 to 3.5 μm and a thickness of 1.5 to 3 mm.
3. The method of claim 1, wherein the deposition temperature of titania on the ceramic membrane in the first step is 100-150 ℃; titanium tetrachloride and water are used as precursors, the pulse time of the titanium tetrachloride is 0.03-0.06 s, the exposure time is 10-30 s, and the cleaning time is 20-60 s; the pulse time of water is 0.06-0.12 s, the exposure time is 10-30 s, and the cleaning time is 20-60 s; the cycle number is 10-50.
4. A catalytic membrane preparation process according to claim 1 wherein the calcination conditions in step two are: under the hydrogen-argon mixed atmosphere with the hydrogen volume fraction of 10%, the temperature rise rate is increased to 400-475 ℃ at the speed of 2-3 ℃/min, and the calcination is carried out for 120-210 min.
5. The method of claim 1, wherein the Pd active component is deposited at a temperature of 200 ℃ in step III; the precursors used for depositing the active component Pd were palladium hexafluoroacetylacetonate and formalin solution with a formaldehyde concentration of 37%.
6. The method of claim 5, wherein the temperature of the hexafluoroacetylacetonatopalladium is 80 ℃, formalin is normal temperature, the pulse time of the hexafluoroacetylacetonatopalladium is 0.3-1 s, the exposure time is 80-150 s, and the cleaning time is 100-150 s; the pulse time of the formalin precursor is 0.6-2 s, the exposure time is 80-150 s, and the cleaning time is 100-150 s; the cycle number is 2-80.
7. The catalytic membrane preparation method according to claim 1, wherein the ceramic membrane has a thickness of 1.75 mm and a pore size of 2.5 μm, normal-temperature titanium tetrachloride and water are used for depositing titanium dioxide, the pulse time, the exposure time and the cleaning time of titanium tetrachloride are respectively 0.06 s, 10 s and 20 s, and the pulse time, the exposure time and the cleaning time of water are respectively 0.12s, 10 s and 20 s; the titanium dioxide cycle number is 10; through TiO 22The modified ceramic membrane is calcined in a TL1200 tubular furnace at the calcining temperature of 450 ℃ and the heating rate of 2 ℃/minThe burning time is 120 min; the deposition temperature of the Pd active component is 200 ℃, the precursor for depositing the Pd active component is hexafluoroacetylacetone palladium with the temperature of 80 ℃ and normal-temperature formalin solution, the pulse time, the exposure time and the cleaning time of the hexafluoroacetylacetone palladium are respectively 0.5 s, 120 s and 100 s, and the pulse time, the exposure time and the cleaning time of the formalin are respectively 1 s, 120 s and 100 s; the number of cycles was 64.
8. Use of a catalysed membrane prepared by the process according to any one of claims 1 to 7 in a flow-through membrane reactor.
9. The use of claim 8, wherein the catalytic membrane is a catalyst recovered after the reaction is completed, and the recovery method is to wash the catalytic membrane with clean water for more than 5 seconds.
Technical Field
The invention relates to a process for preparing a catalytic film by an atomic layer deposition method, belonging to the technical field of preparation of catalytic films.
Background
Membrane catalysis is an important branch in the membrane process and is an important field influencing the development of chemical and petrochemical industries. The membrane catalysis technology has the advantages of breaking the chemical equilibrium limitation, improving the reaction conversion rate, realizing in-situ separation of products and catalysts, realizing the coupling of separation and reaction processes and the like, and has attracted extensive attention of people.
The catalytic membrane is a core component constituting the membrane catalytic reactor. Researchers have focused on improving catalytic membrane performance in terms of membrane surface characteristics, membrane configuration, preparation methods, etc., however, few studies have been made on the effect of catalytic membrane active components themselves on catalytic membrane performance. The method for loading active components on the catalytic membrane mainly comprises the following steps: organometallic chemical vapor deposition, ion exchange, in situ growth, surface impregnation, phase inversion, and the like. Compared with the method that the microscopic size of the active component can not be accurately regulated and controlled by the method for loading the active component, the atomic layer deposition technology has the unique advantage of accurately regulating the deposited object, can theoretically regulate and control the microscopic size of the deposited object at the atomic level, has good conformality and basically has no influence on the specific surface area of the film carrier before and after deposition. Researchers have conducted some research work utilizing the characteristics of atomic layer deposition techniques. The patent (CN 110042365A) reports an atomic layer deposition method for growing alumina on the surface of a two-dimensional material, the atomic layer deposition method is used to grow alumina on the surface of the two-dimensional material, and the alumina is deposited on the surface of the two-dimensional material by physical adsorption, so that not only impurities and defects are prevented from being introduced on the surface of the two-dimensional material, but also the intrinsic characteristics of the two-dimensional material are maintained. Patent (CN 109675609A) reports a preparation method and application of a nanoporous gold-based catalyst modified by atomic layer deposition of ultrathin titanium oxide, and the method of atomic layer deposition is adopted to deposit ultrathin titanium oxide on the nanoporous gold-based catalyst, thereby greatly improving the catalytic performance of the nanoporous gold-based catalyst. At present, no report of preparing a catalytic film by adopting an atomic layer deposition technology is found.
The present invention is directed to a method for preparing a catalytic film by atomic layer deposition, which is used to prepare a high performance catalytic film.
Disclosure of Invention
The invention aims to modify the surface of a ceramic membrane by adopting an atomic layer deposition technology, then load Pd nano-particles to prepare a Pd catalytic membrane, and develop a novel catalytic membrane preparation method.
The technical scheme of the invention is as follows: a Pd catalytic membrane prepared by an atomic layer deposition technology comprises the following steps:
the method comprises the following steps: putting a ceramic membrane into a reaction cavity of the atomic layer deposition equipment, and depositing a titanium dioxide coating on the ceramic membrane to prepare TiO2A modified ceramic membrane;
step two: adding TiO into the mixture2Calcining the modified ceramic membrane in a tube furnace with model number of TL1200 to prepare TiO2Calcining the modified ceramic membrane;
step three: adding TiO into the mixture2And placing the calcined and modified ceramic membrane into a reaction cavity of atomic layer deposition equipment, and depositing Pd nano particles to obtain the Pd catalytic membrane.
Preferably, the ceramic membrane is a sheet type alumina ceramic membrane, the aperture is 1-3.5 mu m, and the thickness is 1.5-3 mm.
Preferably, the deposition temperature of the titanium dioxide on the ceramic membrane in the first step is 100-150 ℃; titanium tetrachloride and water are used as precursors, the pulse time of the titanium tetrachloride is 0.03-0.06 s, the exposure time is 10-30 s, and the cleaning time is 20-60 s; the pulse time of water is 0.06-0.12 s, the exposure time is 10-30 s, and the cleaning time is 20-60 s; the cycle number is 10-50.
Preferably, the calcination conditions in step two are: under the hydrogen-argon mixed atmosphere with the hydrogen volume fraction of 10%, the temperature rise rate is increased to 400-475 ℃ at the speed of 2-3 ℃/min, and the calcination is carried out for 120-210 min.
Preferably, the deposition temperature of the Pd active component in the step three is 200 ℃; the precursors used for depositing the active component Pd were palladium hexafluoroacetylacetonate and formalin solution with a formaldehyde concentration of 37%.
Preferably, the temperature of the hexafluoroacetylacetone palladium is 80 ℃ to ensure that enough vapor pressure exists in the steel cylinder, formalin is at normal temperature, the pulse time of the hexafluoroacetylacetone palladium is 0.3-1 s, the exposure time is 80-150 s, and the cleaning time is 100-150 s; the pulse time of the formalin precursor is 0.6-2 s, the exposure time is 80-150 s, and the cleaning time is 100-150 s; the cycle number is 2-80.
Preferably, the optimal parameters for preparing the catalytic membrane are as follows: the thickness of the ceramic film is 1.75 mm, the aperture is 2.5 mu m, two precursors for depositing titanium dioxide are titanium tetrachloride and water, the two precursors are kept at normal temperature in a steel cylinder, the pulse time, the exposure time and the cleaning time of the titanium tetrachloride are respectively 0.06 s, 10 s and 20 s, and the pulse time, the exposure time and the cleaning time of the water are respectively 0.12s, 10 s and 20 s; the number of titanium dioxide cycles was 10. The calcination temperature of the ceramic membrane modified by titanium dioxide in a TL1200 tubular furnace is 450 ℃, the heating rate is 2 ℃/min, and the calcination time is 120 min; the deposition temperature of the Pd active component is 200 ℃, the steel cylinder of the precursor of the hexafluoroacetylacetone palladium is maintained at 80 ℃, the formalin solution is maintained at normal temperature, the pulse time, the exposure time and the cleaning time of the hexafluoroacetylacetone palladium are respectively 0.5 s, 120 s and 100 s, and the pulse time, the exposure time and the cleaning time of the formalin precursor are respectively 1 s, 120 s and 100 s; the number of Pd cycles was 64.
The catalytic membrane prepared by the method is applied to a flow-through membrane reaction device.
The catalyst recovered after the reaction can be used as the catalytic membrane, and the recovery method is to wash the catalytic membrane for more than 5 seconds by using clean water without obvious reduction of activity.
Has the advantages that:
1. the invention adopts the atomic layer deposition technology to deposit TiO2Modifying the surface and the pore channel of the ceramic membrane, and then putting the modified ceramic membrane at 10% H2Calcining is carried out, the surface characteristics of the ceramic membrane are regulated, and the subsequent deposition of Pd active components is facilitated, so that the catalytic membrane with excellent catalytic performance is prepared.
2. The catalytic membrane prepared by the invention can be used for a flow-through membrane reaction device, realizes the reaction separation coupling of a catalyst and a reactant, has good repeated use effect, only needs simple washing, can be repeatedly used for many times, and has no obvious reduction of activity.
3. According to the invention, the ceramic membrane is used as a carrier, and the catalytic efficiency of Pd per unit mass is improved and the utilization rate of heavy metal Pd is improved through treatment.
Drawings
FIG. 1 is a schematic view of an atomic layer deposition apparatus.
FIG. 2 is a schematic of a flow-through catalytic membrane reactor.
FIG. 3 shows the results of the catalytic performance of each catalytic membrane prepared in example 1 in the reaction of preparing p-aminophenol by catalytic reduction of p-nitrophenol.
The reference number is 1 reaction cavity, 2 air inlet pipeline, 3 ALD valve, 4 manual valves, 5 precursor steel bottle, 6 carrier gas flowmeter, 7 carrier gas inlet, 8 vacuum gauge, 9 tail valve, 10 tail gas outlet, 11 vacuum pump, A constant temperature water bath, B storage tank, C membrane module, D peristaltic pump.
Detailed Description
The method and the effect of using the catalyst of the present invention will be specifically described below by way of examples. The following examples are provided only for illustrating the present invention and are not intended to limit the scope of the present invention.
The atomic layer deposition apparatus used in this embodiment has a model number E100-M6, and a schematic diagram of the apparatus is shown in fig. 1, which mainly includes: the device comprises a reaction chamber 1, an
In the embodiment, sodium borohydride is used as a reducing agent, and p-aminophenol prepared by catalyzing reduction of p-nitrophenol is used as a model reaction to evaluate the catalytic performance of the prepared catalytic membrane. The p-nitrophenol reduction reaction was carried out in a flow-through catalytic membrane reactor as shown in figure 2. The reactor consists of a membrane component C, a storage tank B, a peristaltic pump D and a temperature-controlled water bath A. Firstly, preparing 60 mL of reaction solution (0.45 g of p-nitrophenol is dissolved in 10 mL of absolute ethyl alcohol, then adding 50mL of deionized water to reach a constant volume of 60 mL, and then adding 0.65 g of sodium borohydride to stir uniformly) and adding the reaction solution into a storage tank B; then starting a peristaltic pump D, and reacting the reaction liquid with the loaded active component by flowing through the surface and pore channels of the membrane catalyst through the peristaltic pump D; and returning the reaction liquid passing through the membrane catalyst from the bottom end of the membrane component C to the storage tank B for circular reaction for 60 min. Analyzing the content of p-nitrophenol in the reaction solution by adopting high performance liquid chromatography, calculating the conversion rate of the p-nitrophenol, and evaluating the catalytic activity of the catalytic membrane by using the conversion rate of the p-nitrophenol.
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