Method for preparing silicide catalyst by pyrolyzing metal organic polymer
阅读说明：本技术 一种金属有机聚合物热解制备硅化物催化剂的方法 (Method for preparing silicide catalyst by pyrolyzing metal organic polymer ) 是由 梁长海 韩树华 陈霄 李闯 于 2019-12-09 设计创作，主要内容包括：本发明属于精细化工领域,公开了一种金属有机聚合物热解制备硅化物催化剂的方法。利用金属盐在分子水平上修饰改性含硅有机聚合物,将Fe、Co、Ni等过渡金属元素引入到热解前体的骨架中。在一定还原温度下,可制备得到粒子大小均一,分散性良好,具有较高催化选择性和催化稳定性的金属硅化物催化剂。本方法制备工艺简单安全,催化剂粒径较小且分布均一,所得硅化物催化剂对串联催化制备芳香亚胺及其衍生物具有较高的催化活性和稳定性。(The invention belongs to the field of fine chemical engineering, and discloses a method for preparing a silicide catalyst by pyrolyzing a metal organic polymer. Modifying and modifying the silicon-containing organic polymer on a molecular level by utilizing metal salt, and introducing transition metal elements such as Fe, Co, Ni and the like into a framework of the pyrolysis precursor. Under a certain reduction temperature, the metal silicide catalyst with uniform particle size, good dispersibility, higher catalytic selectivity and catalytic stability can be prepared. The preparation method is simple and safe in preparation process, the catalyst is small in particle size and uniform in distribution, and the obtained silicide catalyst has high catalytic activity and stability for preparing the aromatic imine and the derivative thereof through series catalysis.)
1. A method for preparing a silicide catalyst by pyrolyzing a metal organic polymer is characterized by comprising the following steps:
(1) dissolving metal salt and silicon-containing organic polymer in tetrahydrofuran or xylene solvent according to the mass ratio of 1:2.5-1:20, heating and stirring for 2-15 h at the temperature of 50-180 ℃, and removing the solvent by adopting a vacuum pumping or high-temperature blowing method to obtain a corresponding metal organic polymer pyrolysis precursor;
(2) crosslinking and curing the metal organic polymer pyrolysis precursor at 100-220 ℃ for 1-8 h, and then mixing the metal organic polymer pyrolysis precursor with a solvent in a volume ratio of 1: 2H2And (3) carrying out temperature programmed pyrolysis at 400-1000 ℃ at the temperature rise rate of 5 ℃/min under the mixed gas of Ar to obtain the silicide catalyst.
2. The method for preparing silicide catalyst by pyrolysis of organometallic polymer according to claim 1 wherein the metal salt is one of ferric chloride, cobalt chloride, nickel chloride, ferric acetylacetonate, cobalt acetylacetonate, nickel acetylacetonate, cobalt acetate and nickel acetate.
3. The method for preparing silicide catalyst by pyrolysis of organometallic polymer according to claim 1 or 2 wherein the silicon-containing organic polymer is polysilazane or polydimethylsilane.
4. The method for preparing silicide catalyst by pyrolysis of metal organic polymer according to claim 1 or 2, wherein the prepared silicide catalyst is Fe3Si/SiC、Ni2Si/SiC、CoSi/SiC、Ni2Si/SiCN, CoSi/SiCN and Fe3Si/SiCN.
5. The method for preparing silicide catalyst by pyrolysis of metal organic polymer as claimed in claim 3, wherein the prepared silicide catalyst is Fe3Si/SiC、Ni2Si/SiC、CoSi/SiC、Ni2Si/SiCN, CoSi/SiCN and Fe3Si/SiCNOne kind of (1).
Technical Field
The invention belongs to the field of fine chemical engineering, and relates to a preparation method of a silicide catalyst prepared by pyrolysis of a metal organic polymer and application of the silicide catalyst in series catalytic reaction of nitroaromatic hydrocarbon and ketone or aldehyde serving as raw materials to obtain aromatic imine and derivatives thereof.
Background
The aromatic imine and the derivative thereof play a central role in organic synthesis, and various surfactants, detergents and dyes which are common in daily life and various additives in the petrochemical industry can not leave the figure of the aromatic imine and the derivative thereof. Generally, aromatic imines and their derivatives are prepared by the condensation of ketones or aldehydes with amines, which are often based on the selective reduction of nitroarenes. The aromatic imine and the derivative thereof are prepared by directly taking nitroaromatic and ketone or aldehyde as raw materials through series catalysis, thereby avoiding the separation and purification of intermediate products and greatly improving the chemical synthesis efficiency.
In the past, some noble metal (Au, Pt, Ru, Ir-Pd) catalysts for preparing aromatic imine and derivatives thereof by serial catalysis using nitroaromatic hydrocarbons and ketone or aldehyde as raw materials have been reported, but with the increasing exhaustion of earth resources, the widespread use of noble metal catalysts does not conform to the green chemical concept of sustainable development, and therefore, the development of a non-noble metal catalyst with high activity and high stability is urgently needed.
Transition metal silicide catalysts are the most promising alternatives to noble metal catalysts. The metal silicide is a substance formed by entering silicon atoms into metal lattices, and the insertion of the silicon atoms can adjust the electronic structure and the geometric structure of metal active sites, improve the catalytic selectivity and the stability of the metal silicide and enable the metal silicide to show the properties similar to noble metals.
Typical production methods include liquid phase sintering, powder metallurgy, ultra-high pressure hot isostatic pressing, spark plasma sintering, etc., but these methods require extremely high temperatures and pressures to achieve highly dispersed, dense nanostructured catalytic materials, and further, these methods often require the use of nano-sized ceramic powders as starting materials, which introduce undesirable contaminants.
Disclosure of Invention
The invention provides a method for preparing a silicide catalyst by pyrolyzing a metal organic polymer. Aiming at the synthesis of the prior non-noble metal catalyst, a simple and effective preparation method is provided, and the metal salt is utilized to modify and modify the silicon-containing organic polymer on the molecular level, so that transition metal elements such as Fe, Co, Ni and the like are introduced into the framework of the pyrolysis precursor. Under a certain reduction temperature, the metal silicide catalyst with uniform particle size, good dispersibility, higher catalytic selectivity and catalytic stability can be prepared. Compared with other methods, the method has the advantages of relatively mild preparation conditions, safe, simple and convenient operation, and can realize in-situ reduction of the catalyst and overcome the defect that the catalyst is oxidized after contacting with air so as to lose catalytic activity.
The technical scheme of the invention is as follows:
a method for preparing a silicide catalyst by pyrolyzing a metal organic polymer comprises the following steps:
(1) dissolving metal salt and silicon-containing organic polymer in tetrahydrofuran or xylene solvent according to the mass ratio of 1:2.5-1:20, heating and stirring for 2-15 h at the temperature of 50-180 ℃, and removing the solvent by adopting a vacuum pumping or high-temperature blowing method to obtain a corresponding metal organic polymer pyrolysis precursor;
(2) crosslinking and curing the metal organic polymer pyrolysis precursor at 100-220 ℃ for 1-8 h, and then mixing the metal organic polymer pyrolysis precursor with a solvent in a volume ratio of 1: 2H2And (3) carrying out temperature programmed pyrolysis at 400-1000 ℃ at the temperature rise rate of 5 ℃/min under the mixed gas of Ar to obtain the silicide catalyst.
The metal salt is one of ferric chloride, cobalt chloride, nickel chloride, ferric acetylacetonate, cobalt acetylacetonate, nickel acetylacetonate, cobalt acetate and nickel acetate.
The silicon-containing organic polymer is polysilazane or polydimethylsilane.
The silicide catalyst is Fe3Si/SiC、Ni2Si/SiC、CoSi/SiC、Ni2Si/SiCN, CoSi/SiCN and Fe3Si/SiCN.
The prepared silicide catalyst is mainly used for preparing aromatic imine and derivatives thereof by directly taking nitroaromatic and ketone or aldehyde as raw materials and carrying out serial catalytic reaction.
The invention has the beneficial effects that: the preparation method is safe and simple in preparation process, the catalyst is small in particle size and uniform in distribution, and the prepared silicide catalyst has high selective hydrogenation performance and hydrogenation stability for preparing the aromatic imine and the derivative thereof through series catalysis.
Drawings
FIG. 1 shows Ni as a product of the present invention2XRD analysis result pattern of Si/SiCN.
FIG. 2 shows Ni2The product selectivity diagram of aromatic imine and its derivatives prepared by Si/SiCN serial catalysis.
FIG. 3 shows Ni2And (3) a stability chart of series coupling of nitrobenzene and benzaldehyde catalyzed by Si/SiCN.
Detailed Description
The present invention will be described in detail below by way of examples, which are illustrative only and are not intended to limit the present invention thereto.