CN113856726B - Efficient low-cost heterogeneous catalyst suitable for beta-nitroalcohol preparation - Google Patents

Abstract

The invention relates to preparation of a novel single-atom dispersed heterogeneous catalyst and application thereof in catalytic synthesis, belongs to the field of materials and catalytic science, and discloses preparation of a single-atom dispersed heterogeneous catalyst prepared by a surface fixing method and application thereof in beta-nitroalcohol synthesis. Compared with the traditional method for synthesizing the beta-nitroalcohol through the Henry reaction, the heterogeneous catalyst disclosed by the invention has the advantages of simple method, mild condition, high economy of reaction atoms, high raw material conversion rate, good product regioselectivity, and easiness in separation, recovery and recycling of the catalyst after the reaction is finished. Meanwhile, the catalyst has the advantages of simple preparation method, low-cost and easily available raw materials, easy mass preparation and excellent application prospect.

Description

A high-efficiency and low-cost heterogeneous catalyst suitable for the preparation of β-nitroalcohols

Technical field:

The invention relates to the preparation of a heterogeneous catalyst and its application in Henry reaction, belonging to the field of material and catalysis science.

Background technique:

The 1,2-addition reaction of nitroalkanes to the carbonyl of aldehydes or ketones can produce β-nitroalcohol compounds, which is called Henry reaction. The nitroalcohol product can be converted into compounds for various purposes, such as amino alcohols can be obtained by reduction, alcohols can be obtained by denitrogenation, nitroalkenes can be obtained by dehydration, nitroketones can be obtained by oxidation, etc. It is a synthesis of various natural products and Organic intermediates of important compounds in medicine. However, there are many shortcomings in the current method of synthesizing β-nitroalcohol compounds. Usually, it is necessary to use a strong base to promote the reaction and the reaction is reversible. The generated β-nitroalcohol compounds can be further dehydrated into nitroalkenes under this condition. , other side reactions such as the Cannizzaro reaction may also occur, which makes the synthesis yield of β-nitroalcohols lower and greatly increases the production cost. When the substrate is a multi-carbon nitroalkane such as nitroethane, there are also various cis-trans isomerization products in the reaction product. The use of other homogeneous metal catalysts will result in the residue of heavy metals in the β-nitroalcohol product, seriously affecting the product quality, and the efficiency is low. Therefore, the development of highly efficient and highly selective heterogeneous catalysts is an important solution to realize the economical industrial production of β-nitroalcohols. In recent years, single-atom dispersed heterogeneous catalysts have attracted extensive attention due to their excellent catalytic activity and selectivity, high atom utilization, and easy separation. Therefore, efficient and low-cost single-atom dispersed heterogeneous catalysts have been developed It is the key to realize the economical and efficient production of β-nitroalcohols. At the same time, heterogeneous catalysis can also make the products have special regioselectivity, which is a difficult problem that needs to be solved in the large-scale preparation of such compounds.

Invention content:

Aiming at many problems existing in the catalytic preparation of β-nitroalcohol at present, the purpose of the present invention is to provide a high-efficiency and low-cost single-atom dispersed heterogeneous catalyst, which can improve the conversion efficiency and regioselectivity of the β-nitroalcohol preparation reaction. At the same time, the product and catalyst can be separated quickly and efficiently, reducing the cost of product separation and purification.

Furthermore, the present invention discloses for the first time the application of a monoatomic dispersed heterogeneous catalyst synthesized by a surface immobilization method in catalyzing the Henry reaction. The catalyst has good reactivity and selectivity, high regioselectivity, and is easy to recycle. It has great application value in the industrial preparation of β-nitro alcohol.

In order to achieve the above object, the present invention adopts the following technical solutions:

The present invention discloses for the first time a method for catalyzing the preparation of β-nitroalcohols by using the single-atom dispersed heterogeneous catalyst prepared by the surface immobilization method. In the mixed solution, the reaction can be catalyzed to generate β-nitroalcohol at room temperature, and high conversion efficiency and regioselectivity can be realized. After the reaction, the catalyst in the reaction system can be effectively removed by filtration. After the catalyst is recycled for many times, its catalytic performance can still be maintained.

Furthermore, the preparation method of the single-atom dispersed heterogeneous catalyst in the present invention is to load the pre-organized MN _x O _y complex precursor on the surface of the substrate material in a homogeneous solution system. Carbon bond bonding and reconstruction reactions occur through high-temperature treatment at 200-400 °C, thereby immobilizing the MN _x O _y complex precursor to the surface of the substrate material to form a single-atom dispersed heterogeneous catalyst.

Further, the metal atoms in the MN _x O _y structure complex precursor fixed on the surface of the single-atom dispersed heterogeneous catalyst used in the present invention can be Mn, Fe, Cu, Co, Ni, Ru, Rh, Pd, etc. , the ligands are bidentate or multidentate ligands containing coordination sites such as amine groups, imines, phenolic hydroxyl groups, and nitrogen-containing aromatic rings. A complex precursor of a single metal atom or a complex precursor of multiple metal atoms can be added on the surface of the substrate.

Further, the substrate material used in the present invention is a frame structure material (such as MOF, COF, etc.) or a two-dimensional lamellar material with a large specific surface area, which is a pure organic or organic-inorganic hybrid material, in a homogeneous solution system In this method, the precursor molecules can be uniformly dispersed on the surface of the substrate material to form a monomolecular dispersion.

Further, the single-atom dispersed heterogeneous catalyst used in the present invention is prepared by heating the surface-dispersed MN _x O _y precursor to the substrate at 200-400°C, and adding different proportions of MN on the surface of the substrate. Catalysts with different concentrations of surface active species can be obtained from _x O _y precursors.

Furthermore, the content of metal atoms in the single-atom dispersed heterogeneous catalyst used in the present invention for catalyzing the preparation of β-nitro alcohol is 2-20 mol%, preferably 5-15 mol%.

Furthermore, the monoatomic dispersed heterogeneous catalyst used in the present invention is easy to recover and can be recycled.

Further, the substrate suitable for preparing β-nitroalcohols in the present invention is various aromatic aldehydes or ketones, and the aromatic rings can have different numbers of different substituents, etc., and the aromatic rings can be benzene rings, pyridine rings, Pyrimidine ring, pyridazine, pyrazine, imidazole, quinoline, etc., the conversion rate of different reaction substrates is different.

Further, the nitroalkanes suitable for the preparation of β-nitroalcohols in the present invention include nitromethane, nitroethane and other linear nitroalkanes, and the conversion rates of the corresponding reactions are different.

Further, the solvent used for the Henry reaction in the present invention can be alcohol (other alcohols such as methanol, ethanol, isopropanol), N,N-dimethylformamide, N,N-dimethylacetamide, N , N-diethylformamide, N,N-diethylacetamide, dimethyl sulfoxide, tetrahydrofuran, ether in any one or a mixture of solvents.

Furthermore, in the present invention, the reaction temperature range for the preparation of β-nitroalcohol is 20°C-150°C, and the reaction time is 2-100h.

The invention adopts the surface immobilization method to prepare the single-atom dispersed heterogeneous catalyst with low raw material cost, easy mass preparation and high yield. When the catalyst is used to catalyze the preparation of β-nitroalcohol, the reaction conditions are mild, the reaction conversion rate is high, the regioselectivity is good, and it is easy to recover and can be recycled. After being used for 10 times, its catalytic performance still has no obvious decline, and it has good performance. The method has economic benefits and has very good application prospects in the large-scale preparation of β-nitroalcohols.

Description of drawings:

Fig. 1 is the XRD schematic diagram of the FeN single _- atom dispersed heterogeneous catalyst (Fe-SAC) described in Example 2 of the present invention

Fig. 2 is the HAADF-STEM image of the FeN _x single-atom dispersed heterogeneous catalyst described in Example 2 of the present invention

Detailed ways:

In order to make the present invention more clear and definite, the present invention will be further described in detail below. The described embodiments are only some of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other examples obtained by those skilled in the art without creative work belong to the present invention protected range.

Example 1: Preparation of single-atom dispersed heterogeneous catalysts with surface-immobilized NiN _x

①In a 1000ml reaction bottle, add 500mg of cobalt nitrate hexahydrate, 35mg of ethylenediamine nickel and 1000mg of surfactant SAAS, and add 200ml of deionized water. After the reactants were completely dispersed and dissolved, 200ml of dichloromethane was added, and the mixed solution was vigorously stirred for 10 minutes to form a uniform emulsion. Subsequently, 300 mg of dimethylimidazole was dissolved in 30 ml of dichloromethane, and slowly added dropwise into the emulsion system. At room temperature, the mixed solution was vigorously stirred for 12 h. After the reaction was completed, the water layer was removed through a separatory funnel, and the organic layer was dried by a vacuum rotary evaporator and an oven.

②Place the sample obtained after the above post-treatment in a muffle furnace for calcination. The calcination procedure is as follows: the heating rate is 5° C. per minute, and when it rises to 350° C., it is kept for 1 hour. Finally, it was naturally cooled to room temperature to obtain a gray foamy powder material, which was fully ground and used in subsequent experiments.

Example 2: Preparation of single-atom dispersed heterogeneous catalysts with surface-immobilized _FeNx

①In a 1000ml reaction bottle, add 500mg of cobalt nitrate hexahydrate, 35mg of 1,4,7,10-tetraazacyclododecylamine complex iron and 1000mg of surfactant SAAS, and add 200ml of ionized water. After the reactants were completely dispersed and dissolved, 200ml of dichloromethane was added, and the mixed solution was vigorously stirred for 10 minutes to form a uniform emulsion. Subsequently, 300 mg of dimethylimidazole was dissolved in 30 ml of dichloromethane, and slowly added dropwise into the emulsion system. At room temperature, the mixed solution was vigorously stirred for 12 h. After the reaction was completed, the water layer was removed through a separatory funnel, and the organic layer was dried by a vacuum rotary evaporator and an oven.

②Place the sample obtained after the above post-treatment in a muffle furnace for calcination. The calcination procedure is as follows: the heating rate is 5° C. per minute, and when it rises to 350° C., it is kept for 1 hour. Finally, it was naturally cooled to room temperature to obtain a gray foamy powder material, which was fully ground and used in subsequent experiments.

Example 3: Preparation of a single-atom dispersed heterogeneous catalyst of _FeNx / _NiNx fixed on the surface

①In a 1000ml reaction bottle, add 500mg of cobalt nitrate hexahydrate, 17.5mg of 1,4,7,10-tetraazacyclododecylamine complex iron, 17.5mg of ethylenediamine nickel and 1000mg of surface active agent SAAS, and add 200ml of deionized water. After the reactants were completely dispersed and dissolved, 200ml of dichloromethane was added, and the mixed solution was vigorously stirred for 10 minutes to form a uniform emulsion. Subsequently, 300 mg of dimethylimidazole was dissolved in 30 ml of dichloromethane, and slowly added dropwise into the emulsion system. At room temperature, the mixed solution was vigorously stirred for 12 h. After the reaction was completed, the water layer was removed through a separatory funnel, and the organic layer was dried by a vacuum rotary evaporator and an oven.

②Place the sample obtained after the above post-treatment in a muffle furnace for calcination. The calcination procedure is as follows: the heating rate is 5° C. per minute, and when it rises to 350° C., it is kept for 1 hour. Finally, it was naturally cooled to room temperature to obtain a gray foamy powder material, which was fully ground and used in subsequent experiments.

Example 4: Preparation of single-atom dispersed heterogeneous catalysts with CuN _x immobilized on the surface

①In a 1000ml reaction bottle, add 500mg of cobalt nitrate hexahydrate, 35mg of ethylenediamine copper and 1000mg of surfactant SAAS, and add 200ml of deionized water. After the reactants were completely dispersed and dissolved, 200ml of dichloromethane was added, and the mixed solution was vigorously stirred for 10 minutes to form a uniform emulsion. Subsequently, 300 mg of dimethylimidazole was dissolved in 30 ml of dichloromethane, and slowly added dropwise into the emulsion system. At room temperature, the mixed solution was vigorously stirred for 12 h. After the reaction was completed, the water layer was removed through a separatory funnel, and the organic layer was dried by a vacuum rotary evaporator and an oven.

②Place the sample obtained after the above post-treatment in a muffle furnace for calcination. The calcination procedure is as follows: the heating rate is 5° C. per minute, and when it rises to 350° C., it is kept for 1 hour. Finally, it was naturally cooled to room temperature to obtain a gray foamy powder material, which was fully ground and used in subsequent experiments.

Example 5:

In a 20ml high-pressure reaction flask, add 2ml methanol, 0.1ml benzaldehyde, 0.5ml nitromethane and 50mg of the Ni single-atom dispersed heterogeneous catalyst prepared in Example 1, ultrasonically treat the mixed solution, and use a vacuum pump to remove the high pressure The air in the reaction bottle was stirred at room temperature, and the reaction time was 72h. For post-treatment, add ethyl acetate to the mixed solution, and then simply filter with filter paper to obtain the product. At a temperature of 50°C, use a vacuum rotary evaporator to remove the solvent and put it in an oven overnight. Finally a yellow liquid was obtained. After instrumental characterization, the conversion rate of the reaction was 98%.

Embodiment 6:

In a 20ml high-pressure reaction bottle, add 2ml N,N-dimethylformamide, 0.1ml benzaldehyde, 0.5ml nitromethane and 50mg Ni single-atom dispersed heterogeneous catalyst prepared in Example 1, and mix with ultrasonic treatment solution, and use a vacuum pump to remove the air in the high-pressure reaction bottle, and stir at room temperature, and the reaction time is 72h. For post-treatment, add ethyl acetate to the mixed solution, and then simply filter with filter paper to obtain the product. At a temperature of 50°C, use a vacuum rotary evaporator to remove the solvent and put it in an oven overnight. Finally a yellow liquid was obtained. After instrumental characterization, the conversion rate of the reaction was 95%.

Embodiment 7:

In a 20ml high-pressure reaction flask, add 2ml methanol, 150mg p-nitrobenzaldehyde, 0.5ml nitromethane and 50mg of the Fe single-atom dispersed heterogeneous catalyst prepared in Example 2, ultrasonically process the mixed solution, and use a vacuum pump to extract Remove the air in the high-pressure reaction bottle, stir at room temperature, and the reaction time is 72h. For post-treatment, add ethyl acetate to the mixed solution, and then simply filter with filter paper to obtain the product. At a temperature of 50°C, use a vacuum rotary evaporator to remove the solvent and put it in an oven overnight. Finally a yellow liquid was obtained. After instrumental characterization, the conversion rate of the reaction was 99%.

Embodiment 8:

In a 20ml high-pressure reaction flask, add 2ml methanol, 150mg p-nitrobenzaldehyde, 0.5ml nitromethane and 50mg of the Cu single-atom dispersed heterogeneous catalyst prepared in Example 4, ultrasonically process the mixed solution, and use a vacuum pump to extract Remove the air in the high-pressure reaction bottle, stir at room temperature, and the reaction time is 72h. For post-treatment, add ethyl acetate to the mixed solution, and then simply filter with filter paper to obtain the product. At a temperature of 50°C, use a vacuum rotary evaporator to remove the solvent and put it in an oven overnight. Finally a yellow liquid was obtained. After instrumental characterization, the conversion rate of the reaction was 94%.

Embodiment 9:

In a 20ml high-pressure reaction flask, respectively add 2ml methanol, 0.12ml p-methoxybenzaldehyde, 0.5ml nitromethane and 50mg of the Ni single-atom dispersed heterogeneous catalyst prepared in Example 1, ultrasonically process the mixed solution, and utilize The air in the high-pressure reaction bottle was sucked out by a vacuum pump, and stirred at room temperature, and the reaction time was 72 hours. For post-treatment, add ethyl acetate to the mixed solution, and then simply filter with filter paper to obtain the product. At a temperature of 50°C, use a vacuum rotary evaporator to remove the solvent and put it in an oven overnight. Finally a yellow liquid was obtained. After instrumental characterization, the conversion rate of the reaction was 92%.

Example 10:

In a 20ml high-pressure reaction flask, respectively add 2ml methanol, 150mg p-nitrobenzaldehyde, 0.5ml nitromethane and 50mg example 3 prepared Fe/Ni single-atom dispersed heterogeneous catalyst, sonicate the mixed solution, and utilize The air in the high-pressure reaction bottle was sucked out by a vacuum pump, and stirred at room temperature, and the reaction time was 72 hours. For post-treatment, add ethyl acetate to the mixed solution, and then simply filter with filter paper to obtain the product. At a temperature of 50°C, use a vacuum rotary evaporator to remove the solvent and put it in an oven overnight. Finally a yellow liquid was obtained. After instrumental characterization, the conversion rate of the reaction was 99%.

Example 11:

In a 20ml high-pressure reaction flask, add 2ml methanol, 150mg p-nitrobenzaldehyde, 0.5ml nitroethane and 50mg of the Ni single-atom dispersed heterogeneous catalyst prepared in Example 1, ultrasonically process the mixed solution, and use a vacuum pump The air in the high-pressure reaction bottle was pumped out, and stirred at room temperature, and the reaction time was 72 hours. For post-treatment, add ethyl acetate to the mixed solution, and then simply filter with filter paper to obtain the product. At a temperature of 50°C, use a vacuum rotary evaporator to remove the solvent and put it in an oven overnight. Finally a yellow liquid was obtained. After instrumental characterization, the conversion rate of the reaction was 99%, and the cis-trans isomerism selectivity of the product reached 15:1.

Example 12:

In a 20ml high-pressure reaction flask, add 2ml methanol, 0.1ml benzaldehyde, 0.5ml nitroethane and 50mg of the Ni single-atom dispersed heterogeneous catalyst prepared in Example 1, ultrasonically treat the mixed solution, and use a vacuum pump to remove The air in the high-pressure reaction bottle was stirred at room temperature, and the reaction time was 72h. For post-treatment, add ethyl acetate to the mixed solution, and then simply filter with filter paper to obtain the product. At a temperature of 50°C, use a vacuum rotary evaporator to remove the solvent and put it in an oven overnight. Finally a yellow liquid was obtained. After instrumental characterization, the conversion rate of the reaction was 97%, and the cis-trans isomerism selectivity of the product reached 15:1.

Claims (3)

1. a high-efficiency low-cost monoatomic dispersion heterogeneous catalyst suitable for preparing beta-nitroalcohol is characterized in that MNx complex precursors are loaded on the surface of a substrate material in a homogeneous solution system, and carbon bonding and reconstruction reaction are carried out under the condition of 200-400 ℃, so that the MNx complex precursors are fixed on the surface of the substrate material; the MNx precursor can form a single-atom dispersed active catalytic site after being fixed, the metal atoms are one or more of Fe, cu, co, ni, and the ligand is a bidentate or polydentate ligand containing amino and imine sites; preparing a catalyst of a single metal or multi-metal site by loading a complex of single or multiple metal atoms on the surface of a substrate material, wherein the loading is 5-15mol%; the substrate material is a two-dimensional lamellar material prepared from cobalt nitrate and dimethyl imidazole by taking SAAS as a surfactant, mixing cobalt nitrate and SAAS to form uniform emulsion, then slowly dripping dimethyl imidazole, carrying out vigorous stirring reaction at room temperature for 12 hours, and evaporating to remove a solvent to obtain the two-dimensional lamellar material; under mild reaction conditions, other additives are not needed, the catalyst is applied to catalyzing the reaction of the reactant aromatic aldehyde and the reactant nitroalkane to prepare the beta-nitroalcohol, or catalyzing the reaction of the reactant aromatic ketone and the reactant nitroalkane to prepare the beta-nitroalcohol, the catalyst has high catalytic reaction activity and selectivity, the reaction product and the catalyst are easy to separate, and the catalyst can be recycled.

2. A high efficiency low cost single atomic dispersion heterogeneous catalyst for the preparation of β -nitroalcohols as claimed in claim 1 wherein the substrate is various aromatic aldehydes or ketones, nitroalkanes having different numbers of various substituents on the aromatic aldehydes or ketones, the aromatic rings including benzene rings, pyridine rings, pyrimidine rings, pyridazines, pyrazines, imidazoles, quinolines, and nitroalkanes being nitromethane, nitroethane and other linear nitroalkanes.

3. A high efficiency low cost single atom dispersed heterogeneous catalyst for beta-nitroalcohol preparation as claimed in claim 1, wherein the solvent used in the preparation of beta-nitroalcohol is any one or more of methanol, ethanol, isopropanol, N-dimethylformamide, N-dimethylacetamide, N-diethylformamide, N-diethylacetamide, dimethylsulfoxide, tetrahydrofuran, diethyl ether; the reaction temperature is 20-150 ℃ and the reaction time is 2-100h.

Images