Preparation method of Pt-based catalyst with adjustable pore diameter and limited titanium oxide nanotube and application of Pt-based catalyst prepared by preparation method
阅读说明：本技术 孔径可调氧化钛纳米管限域的Pt基催化剂的制备方法及其制备的Pt基催化剂的应用 (Preparation method of Pt-based catalyst with adjustable pore diameter and limited titanium oxide nanotube and application of Pt-based catalyst prepared by preparation method ) 是由 覃勇 王眉花 高哲 张斌 孟甜甜 于 2019-10-15 设计创作，主要内容包括：本发明提供一种孔径可调的氧化钛纳米管限域的Pt基催化剂的制备方法及其制备的Pt基催化剂的应用,属于纳米催化剂的制备方法及其应用技术领域,解决限域纳米孔材料缺乏连续可调孔径的技术问题。解决方案为：所述催化剂是以碳纳米纤维为模板,使用原子层沉积方法依次将薄氧化钛内壁层、Pt纳米粒子层、氧化铝牺牲层和厚氧化钛壳层沉积在碳纳米纤维的表面,然后采用H<Sub>3</Sub>PO<Sub>4</Sub>酸蚀选择性除去牺牲层,得到具有限域空间的Pt基催化剂。其中,限域空间可通过改变氧化铝的厚度精确调控,优化到最佳尺度。本发明制备的限域Pt基催化剂相比负载在氧化钛纳米管外壁的Pt催化剂加氢性能极大提升。(The invention provides a preparation method of a pore-size-adjustable titanium oxide nanotube confinement Pt-based catalyst and application of the prepared Pt-based catalyst, belongs to the technical field of preparation methods and application of nano-catalysts, and solves the technical problem that a confinement nano-pore material is lack of continuously adjustable pore size. The solution is as follows: the catalyst is prepared by using carbon nano fiber as a template, sequentially depositing a thin titanium oxide inner wall layer, a Pt nano particle layer, an aluminum oxide sacrificial layer and a thick titanium oxide shell layer on the surface of the carbon nano fiber by using an atomic layer deposition method, and then adopting H 3 PO 4 Selectively removing the sacrificial layer by acid etching to obtain the Pt-based catalyst with limited space. Wherein, the confinement space can be accurately regulated and controlled by changing the thickness of the alumina, and is optimized to the optimal dimension. Compared with the Pt catalyst loaded on the outer wall of the titanium oxide nanotube, the limited-area Pt-based catalyst prepared by the invention has greatly improved hydrogenation performance.)
1. A preparation method of a pore diameter adjustable titanium oxide nanotube confinement Pt-based catalyst is characterized by comprising the following steps:
s1, taking the carbon nanofiber as a template, taking titanium tetraisopropoxide and deionized water as precursors for titanium oxide film deposition, taking trimethylaluminum and deionized water as precursors for aluminum oxide film deposition, and sequentially performing the following operations on the carbon nanofiber template by utilizing an atomic layer deposition method: first, TiO is deposited on the carbon nano fiber template for 30-100 cycles2As an inner wall layer; secondly, depositing a Pt nanoparticle layer on the outer side surface of the inner wall layer; thirdly, depositing Al on the outer side surface of the nanoparticle layer for 3-100 cycles2O3As a sacrificial layer; finally, depositing TiO on the outer side surface of the sacrificial layer for 200-600 cycles2As a layer of the outer shell,preparing a Pt-based catalyst;
s2, calcining the sample prepared in the step S1 for 1-3H in an air atmosphere at the temperature of 300-400 ℃, and then calcining the calcined sample in H3PO4Soaking in the solution at 30-60 deg.C for 3-12 hr, and H3PO4The mass percent of the solution is 5-20wt%, selectively removing the aluminum oxide sacrificial layer, and reserving the titanium oxide shell layer to prepare the Pt-based catalyst with the adjustable aperture of the titanium oxide nanotube confinement.
2. The method for preparing the pore diameter adjustable titanium oxide nanotube confinement Pt-based catalyst according to claim 1, wherein the pore diameter adjustable titanium oxide nanotube confinement Pt-based catalyst comprises the following steps: by adjusting Al2O3And the thickness of the atomic layer deposition of the sacrificial layer is adjusted so as to adjust the dimension of the limited space.
3. The method for preparing the pore diameter adjustable titanium oxide nanotube confinement Pt-based catalyst according to claim 1, wherein the pore diameter adjustable titanium oxide nanotube confinement Pt-based catalyst comprises the following steps: the weight percentage content of Pt element in the prepared Pt-based catalyst of the titanium oxide nanotube confinement with adjustable aperture is 0.4-1 wt%.
4. The application of the Pt-based catalyst prepared by the preparation method of the Pt-based catalyst with adjustable pore diameter for titanium oxide nanotubes as claimed in claim 1 is characterized by comprising the following steps:
mixing a reactant phenol, a Pt-based catalyst with an adjustable pore diameter and a reaction solvent ethanol solution, adding the mixture into a reactor, wherein the volume of the ethanol solution is 20ml, the water bath temperature is 25-45 ℃, introducing hydrogen into the reactor, the hydrogen pressure is 0.5-2MPa, and stirring for reacting for a period of time to complete the hydrogenation reaction of phenol.
5. The application of the titanium oxide nanotube confinement catalyst as claimed in claim 4, wherein the mass molar ratio of the Pt-based catalyst with adjustable pore diameter to the reactant phenol is 0.1 ~ 1g:1 mmol.
Technical Field
The invention belongs to the technical field of preparation methods and application of nano catalysts, and particularly relates to a method for confining noble metal Pt nano particles in a titanium oxide nano cavity with adjustable pore diameter by using an atomic layer deposition method, and application of a catalyst prepared by the method in phenol hydrogenation reaction.
Background
The limited-domain catalysis provides an important approach for the performance regulation of the heterogeneous catalyst, and molecules or metal/oxide nanoparticles of limited domains in a nanometer space often show some specific limited-domain effects which can regulate the activity, selectivity, stability and the like of the catalyst. At present, carbon nanotubes, microporous molecular sieves and the like are often selected as carriers of the constrained-domain catalysts, and oxides are often used as carriers of the catalysts in actual industrial applications. Compared with the carbon nano tube, the oxide nano confinement carrier has more universality and is more significant for industrial production.
However, limited by the traditional preparation method, there is no effective means for embedding metal nanoparticles into oxide confinement space with spatial dimensions at the nanometer level. In addition, the size of the reactant molecules catalyzing the reaction is on the atomic level, and thus, the size of the confinement space should be controlled on the atomic/molecular level. However, current confined-nanopore materials lack continuously adjustable pore sizes, and it is difficult to optimize the confined space to an optimal scale at the atomic/molecular level.
Disclosure of Invention
In order to solve the technical problems in the prior art and solve the technical problem that a limited-area nano-pore material is lack of continuous adjustable pore diameter, the invention provides a preparation method of a pore diameter adjustable titanium oxide nano-tube limited-area Pt-based catalyst and application of the prepared Pt-based catalyst.
The design concept of the invention is as follows: the Atomic Layer Deposition (ALD) method has strong advantages in the design and preparation of the nano structure and can be used for the structural design of the nano catalyst.
The invention is realized by the following technical scheme.
The preparation method of the Pt-based catalyst with adjustable pore diameter and limited titanium oxide nanotube domain comprises the following steps:
s1, taking the carbon nanofiber as a template, taking titanium tetraisopropoxide and deionized water as precursors for titanium oxide film deposition, taking trimethylaluminum and deionized water as precursors for aluminum oxide film deposition, and sequentially performing the following operations on the carbon nanofiber template by utilizing an atomic layer deposition method: first, TiO is deposited on the carbon nano fiber template for 30-100 cycles2As an inner wall layer; secondly, depositing a Pt nanoparticle layer on the outer side surface of the inner wall layer; thirdly, depositing Al on the outer side surface of the nanoparticle layer for 3-100 cycles2O3As a sacrificial layer; finally, depositing TiO on the outer side surface of the sacrificial layer for 200-600 cycles2As an outer shell layer, a Pt-based catalyst is prepared;
s2, calcining the sample prepared in the step S1 for 1-3H in an air atmosphere at the temperature of 300-400 ℃, and then calcining the calcined sample in H3PO4Soaking in the solution at 30-60 deg.C for 3-12 hr, and H3PO4The mass percent of the solution is 5-20wt%, the sacrificial layer is selectively removed, the titanium oxide shell layer is reserved, and the Pt-based catalyst with the adjustable aperture and the titanium oxide nanotube confinement is prepared.
Further, by adjusting Al2O3And the thickness of the atomic layer deposition of the sacrificial layer is adjusted so as to adjust the dimension of the limited space.
Furthermore, the weight percentage content of Pt element in the prepared Pt-based catalyst of the titanium oxide nanotube confinement with adjustable aperture is 0.4-1 wt%.
The application of the Pt-based catalyst prepared by the preparation method of the Pt-based catalyst with the adjustable pore diameter and the limited range of the titanium oxide nanotube comprises the following steps:
mixing a reactant phenol, a Pt-based catalyst with an adjustable pore diameter and a reaction solvent ethanol solution, adding the mixture into a reactor, wherein the volume of the ethanol solution is 20ml, the water bath temperature is 25-45 ℃, introducing hydrogen into the reactor, the hydrogen pressure is 0.5-2MPa, and stirring for reacting for a period of time to complete the hydrogenation reaction of phenol.
Further, the mass molar ratio of the Pt-based catalyst with the adjustable pore diameter and the titanium oxide nanotube confinement to the reactant phenol is 0.1 ~ 1g:1 mmol.
The invention has the following beneficial effects:
1. by using the sacrificial layer concept of atomic layer deposition and controlling the thickness of the sacrificial layer, a series of oxide nanometer confinement spaces with adjustable pore diameters can be prepared, and the pore diameters are distributed from atomic scale to nanometer level. The technical difficulty that the conventional limited-domain nano-pore material is lack of continuous adjustable pore diameter is solved;
2. the template method of atomic layer deposition is used for embedding the Pt nanoparticles with small size into the limited domain nanometer space at the atomic level, thereby solving the technical difficulty that the metal nanoparticles are difficult to embed in the conventional method.
Drawings
FIG. 1 is a transmission electron micrograph of a Pt-in-TWT-12 catalyst in example 3;
FIG. 2 is a high resolution TEM image of the Pt-in-TWT-12 catalyst of example 3;
FIG. 3 is a transmission electron micrograph of the Pt-on-TNF catalyst of comparative example 1.
Detailed Description
The invention is described in further detail below with reference to the figures and examples.