Branched high-solid-content 4-dimethylaminopyridine catalyst and preparation method thereof
阅读说明：本技术 一种枝化型高固载4-二甲氨基吡啶催化剂及其制备方法 (Branched high-solid-content 4-dimethylaminopyridine catalyst and preparation method thereof ) 是由 张小里 唐凯 刘力 舒文芳 卫龙辉 张甜甜 李冰麟 赵彬侠 于 2020-06-02 设计创作，主要内容包括：本发明公开了一种枝化型高固载4-二甲氨基吡啶催化剂及其制备方法,通过对多羟基硅基载体进行环氧-醇加成反应得到多烷氯基硅基载体,在反应催化剂存在的前提下,对多烷氯基硅基载体和4-甲氨基吡啶进行N-烷基化反应,制备得到枝化型高固载4-二甲氨基吡啶催化剂；多羟基硅基载体是硅烷偶联剂对硅基载体表面进行修饰得到环氧化硅基载体,再利用枝化剂在二甲基甲酰胺中对环氧化硅基载体的环氧基末端进行枝化制得；本发明的方法通过枝化的方式提高了硅基载体表面的羟基含量,使得4-二甲氨基吡啶在枝化型硅基载体上的固载量显著提升,4-二甲氨基吡啶是以共价结合的形式固定在硅基载体上,因此性质稳定,易于分离,无4-二甲氨基吡啶残留。(The invention discloses a branched high-solid-content 4-dimethylaminopyridine catalyst and a preparation method thereof, wherein a poly-alkyl-chloro-silicon-based carrier is obtained by performing an epoxy-alcohol addition reaction on a polyhydroxy-silicon-based carrier, and the branched high-solid-content 4-dimethylaminopyridine catalyst is prepared by performing an N-alkylation reaction on the poly-alkyl-chloro-silicon-based carrier and 4-methylaminopyridine in the presence of a reaction catalyst; the polyhydroxy silicon-based carrier is prepared by modifying the surface of a silicon-based carrier by using a silane coupling agent to obtain an epoxy silicon-based carrier, and then branching the epoxy end of the epoxy silicon-based carrier in dimethylformamide by using a branching agent; the method improves the hydroxyl content on the surface of the silicon-based carrier in a branching mode, so that the solid carrying capacity of the 4-dimethylamino pyridine on the branched silicon-based carrier is obviously improved, and the 4-dimethylamino pyridine is fixed on the silicon-based carrier in a covalent bonding mode, so the method has stable property, is easy to separate and has no 4-dimethylamino pyridine residue.)
1. A preparation method of a branched high-solid-content 4-dimethylaminopyridine catalyst is characterized in that a multi-alkyl chloride-based silicon-based carrier is obtained by performing an epoxy-alcohol addition reaction on a polyhydroxy silicon-based carrier, and the N-alkylation reaction is performed on the multi-alkyl chloride-based silicon-based carrier and 4-methylaminopyridine in the presence of a reaction catalyst to prepare the branched high-solid-content 4-dimethylaminopyridine catalyst;
the polyhydroxy silicon-based carrier is prepared by modifying the surface of a silicon-based carrier by using a silane coupling agent to obtain an epoxy silicon-based carrier and branching the epoxy end of the epoxy silicon-based carrier in dimethylformamide by using a branching agent;
the reaction catalyst for the N-alkylation reaction is K2CO3、Na2CO3、KHCO3、NaHCO3、KI、KOH、NaOH、Ca(OH)2、C2H5ONa, triethylamine or pyridine.
2. The preparation method according to claim 1, comprising the specific steps of:
modifying the surface of a silicon-based carrier by using a silane coupling agent in an anhydrous solvent 1 to obtain an epoxy silicon-based carrier, and branching the epoxy group tail end of the epoxy silicon-based carrier in dimethylformamide by using a branching agent to obtain a polyhydroxy silicon-based carrier;
carrying out epoxy-alcohol addition reaction on the obtained polyhydroxy silicon-based carrier and epoxy chloropropane in dimethylformamide to obtain a polyalkyl chloride-based silicon-based carrier;
then 4-methylaminopyridine is fully dissolved in an anhydrous solvent 2 to obtain a solution, and the solution is dissolved in N2Carrying out N-alkylation reaction under protection: and sequentially adding a poly-alkyl chloro-silicon-based carrier and a reaction catalyst into the solution, stirring, separating out solids after the reaction is finished, and washing and drying to obtain the branched high-solid-supported 4-dimethylaminopyridine catalyst.
3. The method according to claim 2, wherein the silane coupling agent is γ - (2, 3-epoxypropoxy) propyltrimethoxysilane, γ -aminopropyltriethoxysilane, or γ -chloropropyltriethoxysilane;
the silicon-based carrier is a natural or artificially synthesized silicon-containing material.
4. The method of claim 2, wherein the branching agent is glycerol, xylitol or sorbitol.
5. The method of claim 2, wherein the reaction conditions for preparing the silica-based carrier are dry condensation reflux at 95 ℃ for 18 h.
6. The preparation method of claim 2, wherein the reaction conditions for preparing the polyhydroxy silicon-based carrier are 30-70 ℃ for 2-12 h, and 50 μ L of boron trifluoride ethyl ether solution is added every 2h for catalysis.
7. The preparation method of claim 2, wherein the reaction conditions for preparing the polyalkylchlorosilane-based carrier are 60 ℃ for 2-12 h and 50 μ L of boron trifluoride ethyl ether solution is added every 2h for catalysis.
8. The preparation method according to claim 2, wherein the addition amount of the reaction catalyst is 0.1 to 4.5 times of the molar mass of the 4-methylaminopyridine, the stirring rate is 300 to 700rpm, the N-alkylation reaction temperature is 90 to 140 ℃, and the reaction is carried out for 1 to 25 hours.
9. The method according to claim 2, wherein the anhydrous solvent 1 and the anhydrous solvent 2 are both aromatic hydrocarbons.
10. The branched high-solid-content 4-dimethylaminopyridine catalyst is characterized by being prepared by the preparation method of any one of claims 1-9.
Technical Field
The invention belongs to the technical field of chemical material preparation, and particularly relates to a branched high-solid-content 4-dimethylaminopyridine catalyst and a preparation method thereof.
Background
DMAP (4-dimethylaminopyridine) is a super-nucleophilic catalyst, has the characteristics of good solubility, small using amount, high catalytic activity, mild reaction conditions and the like, and is widely used for synthesis of spices, dyes, pesticides, medicines, high molecular compounds and the like. Homogeneous DMAP is not easily separated from the product, is difficult to recycle, increases cost, affects product purity, and has subsequent problems of waste treatment and environmental pollution, and attempts to immobilize DMAP on chemically stable supports have been chosen to solve the above problems.
There are four currently reported methods for DMAP immobilization:
(1) physical adsorption, which utilizes inorganic porous materials, such as molecular sieves, diatomaceous earth, neutral aluminum oxide, activated carbon, and the like, to fix DMAP onto a solid surface by physical adsorption to achieve the loading of DMAP.
(2) The polymer combination method realizes the covalent combination immobilization of DMAP by carrying out N-alkylation on DMAP through halogenated olefin monomers or halogen-containing polymers.
(3) Silane coupling method. 4-methylamino pyridine is N-alkylated by a haloalkane silane coupling agent and is bonded to a silicon-based carrier through silane coupling.
(4) Improved silane coupling processes. Silanization is carried out on a silicon-based carrier by using a haloalkylsilane coupling agent to obtain a coupled carrier, and then N-alkylation reaction is carried out on the coupled carrier and 4-methylamino pyridine, or N-alkylation reaction is carried out on the 4-methylamino pyridine by using the haloalkylsilane coupling agent to obtain a silane coupling agent-DMAP intermediate, and then silane coupling is carried out on the silicon-based carrier by using the silane coupling agent to obtain the immobilized DMAP acylation catalyst.
DMAP immobilized by a physical adsorption method is not firm, and the supported catalyst is easy to fall off, so that the product is polluted, and the performance of the immobilized catalyst is reduced. The second and third immobilization processes require halogen-containing compounds to carry out N-alkylation on 4-methylaminopyridine, and severe dangerous substances such as NaH, N-butyllithium and the like are used as catalysts, so that the whole operation process is complex, the safety guarantee is low according to experimenters, and industrialization is difficult to realize.
The fourth method abandons the use of severe dangerous substances such as NaH, n-butyllithium and the like, but is limited by the hydroxyl content on the surface of the silicon-based carrier, and the prepared immobilized catalyst has less active molecules DMAP, so that the immobilized DMAP catalyst has lower catalytic activity, thereby influencing the reaction effect. In summary, the existing methods can realize the immobilization of the DMAP catalyst, but due to the limitation of the surface hydroxyl content of the adopted carrier, the prepared catalyst has low immobilization capacity and cannot meet the actual production requirements.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a branched high-solid-content 4-dimethylaminopyridine catalyst and a preparation method thereof, and solves the technical problems that the catalyst prepared by the preparation method in the prior art is low in catalytic activity and repeatability, so that the reaction effect is influenced, the solid content of the prepared catalyst is low, and the actual production requirement cannot be met.
In order to solve the problems, the technical scheme adopted by the invention is as follows: a preparation method of a branched high-solid-content 4-dimethylamino pyridine catalyst comprises the steps of carrying out epoxy-alcohol addition reaction on a polyhydroxy silicon-based carrier to obtain a poly-alkyl-chloro-silicon-based carrier, and carrying out N-alkylation reaction on the poly-alkyl-chloro-silicon-based carrier and 4-methylamino pyridine in the presence of a reaction catalyst to prepare the branched high-solid-content 4-dimethylamino pyridine catalyst;
the polyhydroxy silicon-based carrier is prepared by modifying the surface of a silicon-based carrier by using a silane coupling agent to obtain an epoxy silicon-based carrier and branching the epoxy end of the epoxy silicon-based carrier in dimethylformamide by using a branching agent;
the reaction catalyst for the N-alkylation reaction is K2CO3、Na2CO3、KHCO3、NaHCO3、KI、KOH、NaOH、Ca(OH)2、C2H5ONa, triethylamine or pyridine.
The invention also comprises the following technical characteristics:
the preparation method comprises the following specific steps:
modifying the surface of a silicon-based carrier by using a silane coupling agent in an anhydrous solvent 1 to obtain an epoxy silicon-based carrier, and branching the epoxy group tail end of the epoxy silicon-based carrier in dimethylformamide by using a branching agent to obtain a polyhydroxy silicon-based carrier;
carrying out epoxy-alcohol addition reaction on the obtained polyhydroxy silicon-based carrier and epoxy chloropropane in dimethylformamide to obtain a polyalkyl chloride-based silicon-based carrier;
then 4-methylaminopyridine is fully dissolved in an
The silane coupling agent is silane such as gamma- (2, 3-epoxypropoxy) propyl trimethoxy silane (KH-560), gamma-aminopropyl triethoxy silane (KH-550) or gamma-chloropropyl triethoxy silane (KH-430).
The silicon-based carrier is a natural or artificially synthesized silicon-containing material.
The reaction branching agent is polyhydroxy compounds such as glycerol, xylitol, sorbitol and the like.
The reaction condition for preparing the silicon epoxide-based carrier is drying, condensing and refluxing for 18h at 95 ℃.
The reaction condition for preparing the polyhydroxy silicon-based carrier is that the polyhydroxy silicon-based carrier is reacted for 2-12 hours at the temperature of 30-70 ℃, and 50 mu L of boron trifluoride ethyl ether solution is added every 2 hours for catalysis.
The reaction conditions for preparing the polyalkyl chloride-based silicon carrier are that the reaction is carried out for 2-12 h at the temperature of 60 ℃, and 50 mu L of boron trifluoride ethyl ether solution is added every 2h for catalysis.
The addition amount of the reaction catalyst is 0.1-4.5 times of the molar mass of the 4-methylamino pyridine.
The stirring speed is 300-700 rpm, the temperature of the N-alkylation reaction is 90-140 ℃, and the reaction lasts for 1-25 h.
The anhydrous solvent 1 and the
The branched high-solid-content 4-dimethylaminopyridine catalyst is prepared by the preparation method.
The invention has the beneficial effects that:
the invention provides a preparation method of a branched high-solid-content 4-dimethylaminopyridine catalyst. The hydroxyl content on the surface of the silicon-based carrier is improved in a branching mode, so that the solid loading capacity of the 4-dimethylamino pyridine on the branched silicon-based carrier is obviously improved.
The 4-dimethylamino pyridine is fixed on the silicon-based carrier in a covalent bonding mode, so that the catalyst is stable in property and easy to separate from a reaction system, and 4-dimethylamino pyridine residues are not left in a reaction product.
(III) the immobilization method is simple and convenient to operate, avoids the use of dangerous reagents, and is easy to realize large-scale production.
Drawings
FIG. 1 is a graph showing the results of experiments conducted in example 5 of the present invention and comparative example 1;
FIG. 2 is a graph showing the results of experiments conducted in example 1 and comparative example 2 of the present invention;
FIG. 3 is a graph showing the results of experiments conducted in example 5 of the present invention and comparative example 3
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto. The invention is intended to cover alternatives, modifications and equivalents, which may be included within the scope of the invention as defined by the appended claims.
The kind of the silica-based carrier used in the present invention is not particularly limited, and natural or artificial silicon-containing substrates may be used, such as silica gel, glass, silica, diatomaceous earth, molecular sieves, montmorillonite, zeolite, etc.
The silane coupling agent used in the present invention is not particularly limited, and examples thereof include γ - (2, 3-epoxypropoxy) propyltrimethoxysilane (KH560), γ -aminopropyltriethoxysilane (KH-550), and γ -chloropropyltriethoxysilane (KH-430).
The N-alkylation reaction of DMAP is carried out in a solvent, the type of the solvent is not particularly limited, and the anhydrous solvent is only required to be capable of dissolving DMAP, has a boiling point higher than 80 ℃ and is stable under reaction conditions, such as toluene, xylene, o-xylene and the like.
The branching agent used in the present invention is not particularly limited, and examples thereof include glycerin, xylitol, and sorbitol.
The reaction catalyst used for promoting the reaction of the invention is inorganic salt, inorganic base, organic base and the like, and the inorganic salt is K2CO3、Na2CO3、KHCO3、NaHCO3KI, etc., inorganic bases such as KOH, NaOH, Ca (OH)2Etc., organic bases such as triethylamine, pyridine, sodium ethoxide, etc., with KI, K2CO3The effect is optimal.
The preparation of the epoxysilicon-based carrier mentioned in the present invention can be carried out by referring to the conventional method since the silane coupling to the silicon-based carrier is not a subject of the present invention.
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