CN-121972210-A - Preparation method and application of multi-metal supported molecular sieve catalyst

CN121972210ACN 121972210 ACN121972210 ACN 121972210ACN-121972210-A

Abstract

The invention relates to the technical field of catalysts, in particular to a preparation method and application of a multi-metal supported molecular sieve catalyst, wherein an isovolumetric impregnation method or an ion exchange method is adopted to load a metal precursor solution on the surface of a molecular sieve carrier to obtain a wet precursor, the wet precursor is pre-frozen for 6-24 hours at a temperature of 50 ℃ below zero to 10 ℃ below zero and is transferred to a vacuum freeze dryer, the dried precursor is dried for 12-36 hours at a pressure of less than 10Pa and a temperature of 80 ℃ below zero to 30 ℃ below zero, and a third metal element is impregnated into the dehydrated precursor by adopting a surface organic chemical method to serve as a structural auxiliary agent to obtain the multi-metal supported molecular sieve catalyst. In addition, the catalyst prepared by the preparation method provided by the invention has 32% conversion rate and 96% selectivity index in the application of methane anaerobic coupling reaction at the advanced level in the field.

Inventors

WANG PENGZHAO
Zhang Shuiyao
ZHENG HANGBIN
LIU HUIYONG
WANG ZIRUI

Assignees

福州大学

Dates

Publication Date: 20260505
Application Date: 20260123

Claims (7)

1. A preparation method of a multi-metal supported molecular sieve catalyst is characterized by comprising the following steps: S1, loading a metal precursor solution on the surface of a molecular sieve carrier by adopting an isovolumetric impregnation method or an ion exchange method to obtain a wet precursor; S2, pre-freezing the wet precursor for 6-24 hours at the temperature of-50 to-10 ℃, transferring to a vacuum freeze dryer, and drying for 12-36 hours at the temperature of-80 to-30 ℃ under the pressure of less than 10Pa to obtain a dehydrated precursor; S3, the dehydration precursor is impregnated with a third metal element by adopting a surface organic chemistry method as a structure auxiliary agent, and the multi-metal supported molecular sieve catalyst is obtained.
2. The method of preparing a multi-metal supported molecular sieve catalyst of claim 1, wherein the metal in the metal precursor solution comprises a first active metal comprising at least one of a group VIII metal element and a second active metal comprising at least one of a group IB metal element, and the structure aid metal comprises at least one of a group IVA metal element.
3. The method of preparing a multi-metal supported molecular sieve catalyst according to claim 2, wherein the first active metal comprises Pt and/or Fe, the second active metal comprises Au and/or Cu, and the structure promoter metal comprises Sn and/or Ge.
4. The preparation method of the multi-metal supported molecular sieve catalyst according to claim 2, wherein the mass loading of the first active metal is Pt, the mass loading of Pt is 0.1-5%, the mass loading of the second active metal is Au, the mass loading of Au is 0.1-5%, the mass loading of the structure aid metal is Sn, and the mass loading of Sn is 0.1-5%, and the loading is calculated by taking the total weight of the catalyst as 100%.
5. The method of preparing a multi-metal supported molecular sieve catalyst according to claim 1, wherein the precursor impregnated by the organic chemical method in step S3 comprises an organic acid metal salt (such as stannous octoate), an alkyl tin compound (such as tetrabutyl metal) or acetylacetone metal.
6. The method of claim 1, wherein the molecular sieve carrier in the step S1 is one of a silica-alumina molecular sieve, an all-silica molecular sieve, a silica-alumina phosphate molecular sieve, and a mesoporous molecular sieve, or a composite carrier obtained by compositing two or more materials.
7. Use of a multimetal supported molecular sieve catalyst prepared by the preparation method of any one of claims 1 to 6 in a methane anaerobic coupling reaction.

Description

Preparation method and application of multi-metal supported molecular sieve catalyst Technical Field The invention relates to the technical field of catalysts, in particular to a preparation method and application of a multi-metal supported molecular sieve catalyst. Background In heterogeneous catalytic reactions, multi-metal active component supported catalysts often exhibit better reaction performance than single metal catalysts due to the synergistic effect between the metals, and the distribution form of the multi-metal components on the surface of the support has a significant impact on the reaction performance of the catalyst. Surface organic chemical impregnation is also an important way to impregnate the structure aid. For example, in reactions involving two or more reactants that follow the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism, the different metal components may each be responsible for the activation of a different reactant molecule, taking the methane and carbon dioxide dry reforming reaction as an example, the intermediate product formed after activation of the two reactants by different metals may further react, while the situation is more complicated for a reaction process in which only one reactant molecule is involved. Taking methane anaerobic direct coupling reaction as an example, the reaction path mainly depends on the activation mode of methane molecules, wherein if the methane molecules are activated to form methyl free radicals (CH 3), two methyl free radicals can be combined to generate ethane, the ethane can be partially dehydrogenated to generate ethylene under the thermal reaction condition of more than 700 ℃, and if the methane molecules are activated to form methylene free radicals (CH 2), the two methylene free radicals can be directly coupled to generate ethylene, and then the two methylene free radicals can be further coupled to generate propylene. Ethylene and propylene are important basic organic chemical raw materials, and the market demand is large, so that the design and preparation of the catalyst which can efficiently adsorb and activate methane molecules and promote the methane molecules to preferentially form methylene free radicals (CH 2) have important significance for improving the selectivity of target products of the anaerobic coupling reaction of methane. In the prior art, long et al report that a bimetallic supported catalyst is used for the anaerobic coupling reaction of methane (Long Y, et al APPLIED CATALYSIS B: environmental, 2020, 264: 118502), and the catalyst can realize the coupling conversion of methane, but the product is mainly ethane, the total selectivity of ethylene and propylene is lower, and the industrial application requirement is difficult to meet. Therefore, providing a preparation method of a novel multi-metal supported molecular sieve catalyst applicable to a methane anaerobic coupling reaction has become a technical problem to be solved in the field. Disclosure of Invention The invention aims to provide a preparation method of a multi-metal supported molecular sieve catalyst applicable to a methane anaerobic coupling reaction. In order to achieve the above purpose, the present invention provides the following technical solutions: The invention provides a preparation method of a multi-metal supported molecular sieve catalyst, which comprises the following steps: S1, loading a metal precursor solution on the surface of a molecular sieve carrier by adopting an isovolumetric impregnation method or an ion exchange method to obtain a wet precursor; S2, pre-freezing the wet precursor for 6-24 hours at the temperature of-50 to-10 ℃, transferring to a vacuum freeze dryer, and drying for 12-36 hours at the temperature of-80 to-30 ℃ under the pressure of less than 10Pa to obtain a dehydrated precursor; S3, the dehydration precursor is impregnated with a third metal element by adopting a surface organic chemistry method as a structure auxiliary agent, and the multi-metal supported molecular sieve catalyst is obtained. Firstly, dipping a metal component on the surface of a catalyst body, then overcoming the problem of uneven distribution of the metal component caused by migration and agglomeration of the metal component due to conventional drying operation in the traditional catalyst preparation process by a freeze-drying method, preparing the alloy catalyst uniformly distributed among nano particles, and then dipping a metal element serving as a structure auxiliary agent by adopting an organic chemical method to inhibit agglomeration of the metal nano alloy particles under the high-temperature reaction condition. Further, the metal in the metal precursor solution comprises a first active metal comprising at least one of a group VIII metal element and a second active metal comprising at least one of a group IB metal element, and the structure aid metal comprises at least one of a group IVA metal element. Firstly, two metal components (a