A kind of eggshell silver catalyst and its preparation method and application

Abstract

The invention provides an eggshell-type silver catalyst and a preparation method and application thereof. The steps of the preparation method include: mixing a silver-containing solution, an alkali metal or alkaline earth metal-containing auxiliary agent and a dispersant, adding a carrier and immersing it for 20-60 minutes under normal pressure. , dried to obtain the first impregnated substance; the first impregnated substance was added to the precipitant solution, firstly impregnated under vacuum for 30-60 min, then released the vacuum, continued to impregnate for 30-60 min, and dried to obtain the second impregnated substance; the second impregnation After calcination and reduction, the eggshell silver catalyst was obtained. The preparation method of the invention has the advantages of simple process and mild conditions, the prepared eggshell-shaped silver catalyst in which the silver particles are evenly distributed on the surface of the carrier, realizes the technical effect that the loading amount and the thickness of the eggshell can be controlled at the same time, and has excellent catalytic performance and good catalyst life. , suitable for the oxidative dehydrogenation of alcohols to aldehydes and epoxidation reactions, especially the reaction of catalyzing the oxidative dehydrogenation of prenol to prepare prenaldehyde.

Description

technical field [0001] The invention belongs to the technical field of catalyst and prenaldehyde preparation, and relates to an eggshell-type silver catalyst and a preparation method and application thereof. Background technique [0002] The chemical name of prenaldehyde is 3-methyl-2-butene-1-aldehyde. It is an intermediate for the continuous synthesis of citral with high atomic economy, and citral is a food and daily chemical fragrance, and citral is used as raw material. It can synthesize citral nitrile, damascenone flavor and ionone, the latter can also be used to synthesize vitamin A, E and carotene. [0003] According to relevant literature reports, DSM (Netherlands), Xinhecheng, BASF and Adisseo (France) account for about 90% of the global supply of vitamins. Major domestic manufacturers Xinhecheng, Zhejiang Medicine and Jindawei The total output is about 7000t / a. The domestic demand for citral is at least 3500t / a, and the citral currently used to produce vitamin A ...

AI Technical Summary

Problems solved by technology

This method uses a solid gold catalyst, which is expensive

[0005] Patent CN102470346B discloses a supported noble metal-containing catalyst for oxidative dehydrogenation or epoxidation. The silver source used is a colloidal silver solution. The preparation of the silver solution is complicated, and there are few manufacturers in China. Not easy to get

[0006] Patent CN101977684B discloses the use of a supported catalyst in the preparation of ethylenically unsaturated carbonyl compounds, wherein the catalyst is prepared by applying a refractory metal compound on the surface of the carrier by flame spraying. The preparation of the catalyst The technology is complex and the active components of the catalyst are not evenly distributed

[0007] Patent CN104507575A discloses a supported noble metal-containing catalyst for oxidative dehydrogenation or epoxidation. The preparation method of the catalyst is to repeatedly mix noble metal compounds, promoters and reducing agents to the carrier to prepare multilayer silver Catalyst, complex operation, not easy for industrial application

[0008] In addition, the Research Institute of Beijing Yanshan Branch of China Petroleum & Chemical Co., Ltd. has published many articles about catalysts related to the preparation of ethylene oxide by epoxidation of ethylene, such as CN105618036A, CN102527384A, CN104549543A and other patents. The catalyst is a A uniformly loaded catalyst with a large loading capacity, and the raw materials are prone to side reactions inside the catalyst

[0009] Since the active centers of eggshell catalysts are concentrated on the surface of the catalyst, they have the advantages of high utilization of active components and fast heat transfer, and are more economical than the above-mentioned supported catalysts. However, there are few researches on the preparation methods of eggshell catalysts. , the traditional impregnation method is mostly used. This method is affected by many factors such as pH value, concentration of metal ions in the impregnation solution, viscosity, carrier, impregnation method, drying process, etc. The parameters such as the thickness of the catalyst shell, metal loading, and dispersibility are not easy. control

For example, in the eggshell-type catalyst preparation method disclosed in the patent CN107051428A, an aqueous solution of a soluble metal salt is added to the glue to obtain a precursor solution of the active component, and then the precursor solution is impregnated or sprayed on a spherical carrier, Then dry and roast to obtain an eggshell catalyst. Although this method is simple to operate, the active component is attached to the surface of the carrier by cohesive force and is easy to fall off, resulting in a decrease in catalyst activity.

CN105879862A discloses a method in which a carrier is added to a platinum metal salt solution, through rapid reduction reaction, and solution viscosity is controlled, platinum nanoparticles are deposited on the carrier surface, filtered, washed, heated and dried in an inert atmosphere to form an eggshell catalyst method, but the preparation process of this method is complicated, and it is not easy to scale up production

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