阅读说明：本技术 一种分子筛表面有机碱刻蚀及负载Pt催化剂的制备方法 (Preparation method of molecular sieve surface organic base etching and Pt-loaded catalyst ) 是由 周仁贤 王佳露 石壹军 于 2020-05-27 设计创作，主要内容包括：本发明提供了一种分子筛表面有机碱刻蚀及负载Pt催化剂的制备方法,以廉价的ZSM-5等分子筛和少量的氯铂酸为原料,先使用有机碱溶液对分子筛表面进行溶硅刻蚀处理,然后采用乙二醇液相还原法负载Pt制得Pt/分子筛催化剂。使用适量的有机碱对分子筛表面进行溶硅刻蚀处理,在不破坏分子筛骨架的基础上形成丰富的多级孔结构,有利于Pt纳米颗粒分散和稳定,并改善大分子反应物和产物的传质性质。此外,分子筛表面丰富的酸性位与高分散的Pt纳米颗粒氧化中心之间的催化协同作用,可显著提高催化剂对各类VOCs污染物的低温氧化性能,苯和乙酸乙酯的完全氧化温度(99％的转化率时)分别仅为130℃和190℃。该Pt/分子筛催化剂特别适用于工业排放的二氯乙烷等含氯VOCs、苯和乙酸乙酯等非含氯VOCs的低温催化燃烧,有良好的应用前景。(The invention provides a preparation method of a molecular sieve surface organic alkali etching and Pt-loaded catalyst, which takes a cheap molecular sieve such as ZSM-5 and a small amount of chloroplatinic acid as raw materials, firstly uses an organic alkali solution to carry out silicon dissolving etching treatment on the surface of the molecular sieve, and then adopts a glycol liquid phase reduction method to load Pt to prepare the Pt/molecular sieve catalyst. And a proper amount of organic alkali is used for carrying out silicon dissolving etching treatment on the surface of the molecular sieve, so that a rich hierarchical pore structure is formed on the basis of not damaging the framework of the molecular sieve, the dispersion and the stability of Pt nano particles are facilitated, and the mass transfer properties of macromolecular reactants and products are improved. In addition, the catalytic synergistic effect between the abundant acid sites on the surface of the molecular sieve and the highly dispersed Pt nanoparticle oxidation center can obviously improve the low-temperature oxidation performance of the catalyst on various VOCs pollutants, and the complete oxidation temperatures (at 99% conversion rate) of benzene and ethyl acetate are only 130 ℃ and 190 ℃ respectively. The Pt/molecular sieve catalyst is particularly suitable for low-temperature catalytic combustion of chlorine-containing VOCs such as dichloroethane and the like and non-chlorine-containing VOCs such as benzene, ethyl acetate and the like which are discharged industrially, and has good application prospect.)

1. A process for preparing the catalyst used to etch the surface of molecular sieve by organic alkali and load Pt features that the molecular sieve and chloroplatinic acid (H)₂PtCl₆) Firstly, etching the surface of a molecular sieve by using an organic alkali solution, and then loading Pt by adopting a glycol liquid phase reduction method to prepare a Pt/molecular sieve catalyst, wherein the preparation method comprises the following specific steps:

adding 3g of powder molecular sieve into 50m L organic alkali aqueous solution, stirring and treating for 6-10 hours at 50-80 ℃, then filtering, washing for multiple times by deionized water until filtrate is neutral, dispersing the molecular sieve subjected to organic alkali etching treatment in 50m L ethylene glycol solution, and stirring uniformlyPost addition of H₂PtCl₆The pH value of the mixed solution is 5.0-7.0, the mixed solution is continuously stirred for more than 2 hours under the protection of nitrogen, the temperature is raised to 160 ℃, the mixed solution is filtered and washed by deionized water for many times after being refluxed for 4-6 hours until no Cl exists in the filtrate^-Ionic drying at 100 ℃.

2. The method for preparing the molecular sieve surface organic base etching and Pt-loaded catalyst according to claim 1, wherein the molecular sieve is one of a ZSM-5 molecular sieve or an S-1 type molecular sieve.

3. The method for preparing the molecular sieve surface organic base etching and Pt-loaded catalyst according to claim 2, wherein the Si/Al molar ratio of the ZSM-5 molecular sieve is 25-130.

4. The method for preparing the molecular sieve surface organic base etching and Pt-loaded catalyst according to claim 3, wherein the optimum Si/Al molar ratio of the ZSM-5 molecular sieve is 38-46.

5. The method for etching the surface of the molecular sieve with the organic base and preparing the supported Pt catalyst according to claim 1, 2, 3 or 4, wherein the organic base is tetrapropylammonium hydroxide (TPAOH), and the optimal concentration of the aqueous solution of the organic base is 0.05-0.2M.

6. The method for preparing the molecular sieve surface organic base etching and Pt-loaded catalyst according to claim 1, wherein the ethylene glycol liquid phase reduction method for loading Pt is to etch the surface of the molecular sieve with organic base before loading Pt, and then to react with H₂PtCl₆Blending and adsorbing for more than 2 hours, adjusting the pH value of the mixed solution to 5.0-7.0, and performing high-temperature reduction treatment to obtain the Pt/molecular sieve catalyst.

Technical Field

The invention relates to a preparation method of a catalyst, in particular to a preparation method of a molecular sieve surface organic base etching and Pt-loaded catalyst.

Background

Volatile Organic Compounds (VOCs) mainly come from waste gas emission in industries such as petrochemical production, printing and coating, food and rubber production and the like, are complex in components and large in exhaust amount, and have serious harm to the natural environment and human health. The catalytic combustion technology is one of important and effective means for purifying VOCs pollutants, and the development of a catalyst with low cost, high efficiency, stability and good broad spectrum is the key for realizing the application of the technology. Molecular sieves such as ZSM-5, BETA or USY and the like have larger specific surface area and regular pore channel structure, contain rich acid sites, and are widely applied to the fields of separation, adsorption, catalysis and the like. However, the microporous structure of molecular sieves such as ZSM-5 and the like significantly influences the mass transfer of reactants and products, the macromolecular reactants are difficult to enter a pore channel, the diffusion resistance is high, the products formed in the pore channel cannot rapidly escape, and the application of the products in the macromolecular catalytic reaction is greatly limited. Therefore, in order to improve the pore structure, inorganic or organic alkali is usually used for carrying out silicon-dissolving etching treatment on molecular sieves such as ZSM-5 and the like, a multi-level pore structure is formed on the basis of not damaging the original framework of the molecular sieve, the mass transfer of macromolecular reactants and products is promoted, and the adsorption, desorption and catalytic performances of the molecular sieves can be obviously improved. In addition, molecular sieves such as ZSM-5 and the like are also commonly used as carriers of supported catalysts, but the surfaces of the microporous molecular sieves are smooth, so that the microporous molecular sieves are not beneficial to high-dispersion loading of active components such as noble metals and the like, and the wide application of the microporous molecular sieves is limited, therefore, the pore structure and the surface property of the microporous molecular sieves are improved, and the high dispersion of the active components is promoted, and the catalytic performance of the microporous molecular sieves is improved. At present, the supported noble metal catalyst still remains a mainstream catalyst for industrial application due to high activity and broad spectrum on the oxidative degradation of VOCs. The method improves the pore structure and surface property of microporous molecular sieves such as ZSM-5 and the like, promotes high dispersion and stability of active components such as noble metal and the like, and can ensure that the supported catalyst has good acidity and oxidability, thereby realizing low-temperature oxidation of industrial discharged VOCs, which has important significance for wide application of catalytic combustion technology.

Disclosure of Invention

The invention relates to a preparation method of a high-activity VOCs oxidative degradation catalyst, in particular to a preparation method of a molecular sieve surface organic base etching and Pt-loaded catalyst, which is realized by the following technical scheme:

the invention discloses a method for preparing a molecular sieve surface organic alkali etching and Pt-loaded catalyst, which comprises a molecular sieve and chloroplatinic acid (H)₂PtCl₆) Firstly, etching the surface of a molecular sieve by using an organic alkali solution, and then loading Pt by adopting a glycol liquid phase reduction method to prepare a Pt/molecular sieve catalyst, wherein the preparation method comprises the following specific steps:

adding 3g of powder molecular sieve into 50m L organic alkali aqueous solution, stirring and treating for 6-10 hours at 50-80 ℃, then filtering, washing for multiple times by deionized water until filtrate is neutral, dispersing the molecular sieve subjected to organic alkali etching treatment into 50m L ethylene glycol solution, stirring uniformly, and adding H₂PtCl₆The pH value of the mixed solution is 5.0-7.0, the mixed solution is continuously stirred for more than 2 hours under the protection of nitrogen, the temperature is raised to 160 ℃, the mixed solution is filtered and washed by deionized water for many times after being refluxed for 4-6 hours until no Cl exists in the filtrate^-Ionic drying at 100 ℃.

As a further improvement, the molecular sieve is one of a ZSM-5 molecular sieve or an S-1 type molecular sieve.

As a further improvement, the Si/Al molar ratio of the ZSM-5 molecular sieve is 25-130.

As a further improvement, the optimum Si/Al molar ratio of the ZSM-5 molecular sieve is 38-46.

As a further improvement, the organic base is tetrapropylammonium hydroxide (TPAOH), and the optimal concentration of the aqueous solution is 0.05-0.2M.

As a further improvement, the method for loading Pt by the ethylene glycol liquid phase reduction method is that before loading Pt, the surface of the molecular sieve is etched by organic alkali, and then the molecular sieve and H are mixed₂PtCl₆Blending and adsorbing for more than 2 hours, adjusting the pH value of the mixed solution to 5.0-7.0, and performing high-temperature reduction treatment to obtain the Pt/molecular sieve catalyst.

The preparation method of the molecular sieve surface organic base etching and Pt-loaded catalyst provided by the invention has the following beneficial effects: the method comprises the steps of taking cheap molecular sieves such as ZSM-5 and the like which are industrially produced at present and a small amount of chloroplatinic acid as raw materials, firstly carrying out silicon dissolving etching treatment on the surfaces of the molecular sieves by using an organic alkali solution, then loading Pt by using a glycol liquid phase reduction method to prepare a Pt/molecular sieve catalyst, wherein the optimal treatment concentration of tetrapropylammonium hydroxide (TPAOH) aqueous solution is 0.05-0.2M. And a proper amount of organic alkali is used for carrying out silicon dissolving etching treatment on the surface of the molecular sieve, so that a rich hierarchical pore structure is formed on the basis of not damaging the framework of the molecular sieve, the dispersion and the stability of Pt nano particles are facilitated, and the mass transfer properties of macromolecular reactants and products are improved. In addition, the catalytic synergistic effect between the abundant acid sites on the surface of the molecular sieve and the highly dispersed Pt nanoparticle oxidation center can remarkably improve the low-temperature oxidation performance of the catalyst on various VOCs pollutants, such as the complete oxidation temperatures (at 99% conversion rate) of benzene and ethyl acetate which are only 130 ℃ and 190 ℃ respectively. The Pt/molecular sieve catalyst prepared by the invention is particularly suitable for low-temperature catalytic combustion of chlorine-containing VOCs such as dichloroethane and the like and non-chlorine-containing VOCs such as benzene, ethyl acetate and the like which are discharged industrially, and has good application prospect.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples: