Supported nickel cobalt-metal hydroxide core-shell catalyst and application thereof

Abstract

The invention relates to a supported nickel-cobalt-metal hydroxide core-shell catalyst which is prepared by taking nickel-cobalt metal salt as a metal source, taking an organic carbon-containing compound as a carrier precursor or a commercial carrier and uniformly dispersing active metal on the carrier by adopting a hydrothermal-carbonization method or a precipitation-reduction method. The nickel-cobalt metal salt is selected from one or more than two of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate, cobalt sulfate heptahydrate, nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate and nickel sulfate hexahydrate. Meanwhile, the invention also discloses application of the core-shell catalyst. According to the invention, the supported nickel cobalt-metal hydroxide core-shell catalyst is utilized to directly react with morpholine to prepare N-formylmorpholine from CO2 and H2, and the obtained product N-formylmorpholine not only has higher selectivity and yield, but also is easy to separate, and is suitable for industrial production. And meanwhile, the adopted supported nickel cobalt-metal hydroxide core-shell catalyst has relatively good cycling stability and has good application potential.

Description

Technical Field

[0001] This invention relates to the field of fine chemical synthesis, and more particularly to a supported nickel-cobalt-metal hydroxide core-shell catalyst and its applications. Background Technology

[0002] CO2 is both a greenhouse gas and a cheap, safe, and abundant renewable C1 resource. In recent years, how to utilize carbon dioxide as a C1 resource to convert it into high-value chemicals has attracted widespread attention from governments and researchers around the world.

[0003] N-Formylmorpholine is an important formamide compound with wide industrial applications. It can be used as a solvent in organic synthesis, and is also a key solvent for aromatic hydrocarbon extraction, butene concentration, and natural gas desulfurization. Its efficient synthesis is of great significance to the petrochemical industry. Due to its high selectivity, low toxicity, and chemical stability, it is widely used in aromatic hydrocarbon separation processes (such as the Morphysorb technology) and syngas purification.

[0004] However, existing synthesis processes still face challenges such as low catalyst efficiency, harsh reaction conditions, and numerous byproducts. Currently, common production methods for formamide mainly include the formic acid method, the methyl formate method, and the CO carbonylation synthesis method. Chinese patent CN1345723A uses a homogeneous acidic catalyst to prepare N-formylmorpholine using the formic acid method. This method corrodes equipment and produces numerous byproducts (such as formic acid and unreacted amines), which are difficult to completely separate, affecting the industrial quality of N-formylmorpholine. Chinese patent CN100548999C reports a method for preparing N-formylmorpholine using a methyl formate method with a homogeneous transesterification catalyst. This method suffers from drawbacks such as non-recoverable catalyst and cumbersome separation steps.

[0005] In addition, CO2 hydrogenation can also directly prepare formamide compounds. Chinese patent CN105985254B discloses a method for preparing formamide compounds, using a homogeneous noble metal pincer complex catalyst. Shi Feng and Ma Ding et al. prepared formamide compounds using supported Ir and Pd catalysts respectively via CO2 hydrogenation. Chin. J. Catal. 2019, 40 , 1141-1146, Angew. Chem. Int. Ed. 2022, 61 (e202202654.), but there are few reports on the preparation of formamide compounds using non-precious metals with this method. Milstein and Bernskoetter et al. respectively reported the preparation of N-formylmorpholine ( ) using Fe-based and Co-based homogeneous complex catalysts via CO2 hydrogenation. ACS Catal. 2017,7 2500-2504 ACS Catal. 2018, 8 Although the catalyst used is a non-precious metal catalyst, this method has limitations such as the instability and easy deactivation of homogeneous complex catalysts and the inability to recycle homogeneous catalysts.

[0006] Therefore, there is an urgent need to develop a simple, readily available, highly active, highly selective, and recyclable heterogeneous nickel-cobalt metal hydroxide core-shell catalyst to achieve a green and efficient preparation process of N-formylmorpholine under mild reaction conditions. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a simple and readily available supported nickel-cobalt metal hydroxide core-shell catalyst with high activity and high selectivity.

[0008] Another technical problem to be solved by the present invention is to provide the application of this supported nickel-cobalt-metal hydroxide core-shell catalyst.

[0009] To address the aforementioned problems, the present invention provides a supported nickel-cobalt metal hydroxide core-shell catalyst, characterized in that: the core-shell catalyst is prepared by using a nickel-cobalt metal salt as the metal source and an organic carbon-containing compound as the precursor or commercial support, and by employing a hydrothermal-carbonization method or a precipitation-reduction method to uniformly disperse the active metal on the support; the nickel-cobalt metal salt is selected from one or more of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate, cobalt sulfate heptahydrate, nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate, and nickel sulfate hexahydrate.

[0010] The active component of the core-shell catalyst is a nickel-cobalt metal core and a metal hydroxide shell.

[0011] The active metal component in the core-shell catalyst refers to cobalt and nickel with a content of 5 wt.% to 95 wt.%, and the active metal hydroxide with a content of 5 wt.% to 45 wt.%.

[0012] The carrier is selected from at least one of carbon-based carriers, silicon dioxide, molecular sieves, zirconium dioxide, titanium dioxide, aluminum oxide, magnesium oxide, and cerium oxide.

[0013] In the hydrothermal-carbonization method, the hydrothermal temperature is 60~240 ℃ and the hydrothermal time is 4~48 h; the carbonization or heat treatment temperature is 350~600 ℃ and the heating rate is 3~20 ℃ / min; and the treatment atmosphere used for carbonization or heat treatment is a mixture of hydrogen and inert gas of different concentrations.

[0014] The precipitant used in the precipitation-reduction method is one or more of the following: NaOH, KOH, NH3·H2O, K2CO3, Na2CO3, and urea.

[0015] The application of the supported nickel-cobalt-metal hydroxide core-shell catalyst as described above is characterized in that: the supported nickel-cobalt-metal hydroxide core-shell catalyst is used as a catalyst for preparing N-formylmorpholine from CO2 and H2 and morpholine as raw materials.

[0016] The N-formylmorpholine is prepared by the following method: using CO2 and H2 and morpholine as raw materials, in a suitable solvent, under the action of a supported nickel-cobalt-metal hydroxide core-shell catalyst and an alkaline auxiliary agent, the reaction conditions are CO2 / H2=1.0~5.0, the reaction temperature is 60~200 ℃, the reaction pressure is 1~10 MPa, the molar ratio of alkaline auxiliary agent to morpholine is 0.2~5, and the mass ratio of solvent to reactants is 5~50; the reaction is carried out for 2~48 hours, the catalyst is separated, the solvent is distilled off, and the target product N-formylmorpholine is obtained.

[0017] Its compound formula is as follows: The solvent is at least one selected from methanol, anhydrous ethanol, water, toluene, isopropanol, toluene, 1,4-dioxane, tetrahydrofuran, and ethyl acetate.

[0018] The alkali additive is one or two of potassium hydroxide, sodium hydroxide, potassium tert-butoxide, sodium tert-butoxide, sodium phosphate, sodium carbonate, potassium carbonate, potassium bicarbonate, and potassium phosphate.

[0019] Compared with the prior art, the present invention has the following advantages: 1. The supported nickel-cobalt-metal hydroxide core-shell catalyst of the present invention has multiple catalytic active sites, and there is a significant synergistic effect among the functional sites. The bimetallic nickel-cobalt alloy metal core formed by the nickel-cobalt bimetal in the catalyst component provides a highly efficient hydrogen activation site, and the shell structure formed by the nickel-cobalt hydroxide is conducive to promoting the adsorption and activation of CO2 and reactant morpholine by the catalyst, thereby improving the catalytic performance of the catalyst in the reaction of CO2 and H2 with morpholine to prepare N-formylmorpholine.

[0020] 2. This invention utilizes a supported non-precious metal nickel-cobalt-metal hydroxide core-shell catalyst to directly prepare N-formylmorpholine from CO2 and H2 with morpholine. The process is simple, convenient, and the synthesis conditions are mild and the cost is low. The obtained N-formylmorpholine not only has high selectivity and yield, but the product is also easy to separate. At the same time, the heterogeneous nickel-cobalt-metal hydroxide core-shell catalyst used in this method has good cycle stability and good application potential. Attached Figure Description

[0021] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0022] Figure 1 This is a TEM image of the supported nickel-cobalt-metal hydroxide core-shell catalyst prepared in Example 1 of the present invention.

[0023] Figure 2 This is a gas chromatogram of the synthesis of N-formylmorpholine by the reaction of CO2 and H2 with morpholine using the NiCo-450 core-shell catalyst prepared in Example 2 of the present invention. Detailed Implementation

[0024] A supported nickel-cobalt metal hydroxide core-shell catalyst is prepared by uniformly dispersing the active metal on a support using a nickel-cobalt metal salt as the metal source and an organic carbonaceous compound as the precursor or commercial support, via a hydrothermal-carbonization method or a precipitation-reduction method. The nickel-cobalt metal salt is selected from one or more of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate, cobalt sulfate heptahydrate, nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate, and nickel sulfate hexahydrate.

[0025] The active component of the core-shell catalyst is a nickel-cobalt metal core and a metal hydroxide shell.

[0026] The active metal component in the core-shell catalyst refers to cobalt and nickel with a content of 5 wt.% to 95 wt.%, and the active metal hydroxide with a content of 5 wt.% to 45 wt.%.

[0027] The support is selected from at least one of carbon-based supports, silica, molecular sieves, zirconium dioxide, titanium dioxide, alumina, magnesium oxide, and cerium oxide. The carbon-based support is one of activated carbon, graphene, or carbon nanotubes. Al2O3 or graphene is preferred as the support.

[0028] In the hydrothermal-carbonization method, the hydrothermal temperature is 60~240 ℃ and the hydrothermal time is 4~48 h; the carbonization or heat treatment temperature is 350~600 ℃ and the heating rate is 3~20 ℃ / min. The treatment atmosphere used for carbonization or heat treatment is a mixture of hydrogen and inert gases such as argon, nitrogen or helium of different concentrations.

[0029] The precipitant used in the precipitation-reduction method is one or more of the following: NaOH, KOH, NH3·H2O, K2CO3, Na2CO3, and urea.

[0030] Application of a supported nickel-cobalt-metal hydroxide core-shell catalyst: This supported nickel-cobalt-metal hydroxide core-shell catalyst is used as a catalyst for the preparation of N-formylmorpholine from CO2 and H2 and morpholine.

[0031] N-Formylmorpholine is prepared by the following method: using CO2 and H2 and morpholine as raw materials, in a suitable solvent, under the action of a supported nickel-cobalt-metal hydroxide core-shell catalyst and an alkaline auxiliary agent, the reaction conditions are CO2 / H2=1.0~5.0, the reaction temperature is 60~200 ℃, the reaction pressure is 1~10 MPa, the molar ratio of alkaline auxiliary agent to morpholine is 0.2~5, and the mass ratio of solvent to reactants is 5~50; the reaction is carried out for 2~48 hours, the catalyst is separated, the solvent is distilled off, and the target product N-formylmorpholine is obtained.

[0032] The solvent is at least one of methanol, anhydrous ethanol, water, toluene, isopropanol, toluene, 1,4-dioxane, tetrahydrofuran, and ethyl acetate.

[0033] The alkali additive is one or two of the following: potassium hydroxide, sodium hydroxide, potassium tert-butoxide, sodium tert-butoxide, sodium phosphate, sodium carbonate, potassium carbonate, potassium bicarbonate, and potassium phosphate.

[0034] Example 1 Preparation of supported nickel-cobalt-metal hydroxide core-shell catalysts: 3.8402 g of cobalt nitrate hexahydrate, 3.8411 g of nickel nitrate hexahydrate, and 7.0246 g of disodium ethylenediaminetetraacetate dihydrate were added to a 100 mL round-bottom flask, followed by 20 mL of deionized water. The mixture was stirred for 30 min, then 20 mL of 1 M NaOH was added, and stirring was continued for another 30 min. The mixture was then transferred to a hydrothermal reactor lined with tetrafluoroethylene and placed in an oven at 200 °C for 24 h. After the hydrothermal reactor cooled down, the resulting sample solution was centrifuged and washed twice with deionized water and twice with methanol. The resulting solid sample was then dried at 80 °C for 12 h. Finally, the sample was carbonized at 350 °C under a nitrogen atmosphere for 3 h to obtain the NiCo-NiCo(OH)x@C-350 core-shell catalyst (x=1~3).

[0035] Preparation of N-formylmorpholine: 0.15 g of the prepared NiCo-NiCo(OH)x@C-350 core-shell catalyst, 1.32 g of K2CO3, and 0.82 g of morpholine were placed in a high-pressure reactor. The reactor was purged with CO2 three times until the final CO2 pressure was 3 MPa. Then, hydrogen was introduced to 6 MPa, and the reactor was placed in a heated aluminum block. The reaction was carried out at 160 °C and 600 rpm for 24 hours with stirring. The reactor was cooled to room temperature with water, the gas was slowly discharged, and the catalyst was separated by centrifugation. The resulting liquid was analyzed by gas chromatography. The conversion rate of morpholine was 95%, and the selectivity of N-formylmorpholine was 91%.

[0036] Example 2 Preparation of supported nickel-cobalt-metal hydroxide core-shell catalysts: 5.238 g of cobalt nitrate hexahydrate, 1.740 g of nickel nitrate hexahydrate, and 6.386 g of tetrasodium ethylenediaminetetraacetate dihydrate were added to a 100 mL round-bottom flask, followed by 20 mL of deionized water. The mixture was stirred for 30 min, then 20 mL of 1 M NaOH was added, and stirring continued for another 30 min. The mixed solution was transferred to a hydrothermal reactor lined with tetrafluoroethylene and placed in an oven at 200 °C for 24 h. After the hydrothermal reactor cooled down, the resulting sample solution was centrifuged and washed twice with deionized water and twice with methanol. The resulting solid sample was then dried at 80 °C for 12 h. Finally, the sample was carbonized at 450 °C under a nitrogen atmosphere for 3 h to obtain the NiCo-NiCo(OH)x@C-450 core-shell catalyst (x=1~3).

[0037] Preparation of N-formylmorpholine: 0.10 g of the prepared NiCo-NiCo(OH)x@C-450 core-shell catalyst, 0.72 g of K2CO3, and 0.52 g of morpholine were placed in a high-pressure reactor. The reactor was purged with CO2 three times until the final CO2 pressure was 3 MPa. Then, hydrogen was introduced to 6 MPa, and the reactor was placed in a heated aluminum block. The reaction was carried out at 160 °C and 600 rpm for 24 hours with stirring. The reactor was cooled to room temperature with water, the gas was slowly discharged, and the catalyst was separated by centrifugation. The resulting liquid was analyzed by gas chromatography. The conversion rate of morpholine was 100%, and the selectivity of N-formylmorpholine was 97%.

[0038] Example 3 Preparation of supported nickel-cobalt-metal hydroxide core-shell catalysts: 3.491 g of cobalt nitrate hexahydrate, 3.490 g of nickel nitrate hexahydrate, and 6.386 g of disodium ethylenediaminetetraacetate dihydrate were added to a 100 mL round-bottom flask, followed by 20 mL of deionized water. The mixture was stirred for 30 min, then 20 mL of 1 M NaOH was added, and stirring continued for another 30 min. The mixture was transferred to a hydrothermal reactor lined with tetrafluoroethylene and placed in an oven at 200 °C for 24 h. After the hydrothermal reactor cooled down, the resulting sample solution was centrifuged and washed twice with deionized water and twice with methanol. The resulting solid sample was then dried at 80 °C for 12 h. Finally, the sample was carbonized at 500 °C under a nitrogen atmosphere for 1 h to obtain the NiCo-NiCo(OH)x@C-500 core-shell catalyst (x=1~3).

[0039] Preparation of N-formylmorpholine: 0.10 g of the prepared NiCo-NiCo(OH)x@C-500 core-shell catalyst, 1.27 g of K3PO4, and 0.52 g of morpholine were placed in a high-pressure reactor. The reactor was purged with CO2 three times until the final CO2 pressure was 3 MPa. Then, hydrogen was introduced to 6 MPa, and the reactor was placed in a heated aluminum block. The reaction was carried out at 160 °C and 600 rpm for 24 hours with stirring. The reactor was cooled to room temperature with water, the gas was slowly discharged, and the catalyst was separated by centrifugation. The resulting liquid was analyzed by gas chromatography. The conversion rate of morpholine was 100%, and the selectivity of N-formylmorpholine was 94%.

[0040] Example 4 Preparation of supported nickel-cobalt-metal hydroxide core-shell catalysts: 0.3491 g of cobalt nitrate hexahydrate, 0.3490 g of nickel nitrate hexahydrate, and 0.152 g of magnesium oxide were added to a 100 mL round-bottom flask, along with 20 mL of deionized water. The pH of the solution was adjusted to 9-10 with 1 M NaOH, and the mixture was stirred for 12 h. The mixture was then filtered, washed with deionized water and anhydrous ethanol, and the resulting solid sample was dried at 120 ℃ for 12 h. The sample was then pretreated at 400 ℃ under a 5% hydrogen / argon atmosphere for 3 h to obtain the NiCo-NiCo(OH)x / MgO-400 core-shell catalyst (x=1~3).

[0041] Preparation of N-formylmorpholine: 0.10 g of the prepared NiCo-NiCo(OH)x / MgO-400 core-shell catalyst, 0.276 g of K2CO3, and 0.52 g of morpholine were placed in a high-pressure reactor. The reactor was purged with CO2 three times until the final CO2 pressure was 3 MPa. Then, hydrogen was introduced to 6 MPa, and the reactor was placed in a heated aluminum block. The reaction was carried out at 160 °C and 600 rpm for 24 hours with stirring. The reactor was cooled to room temperature with water, and the gas was slowly discharged. The catalyst was separated by centrifugation, and the resulting liquid was analyzed by gas chromatography. The conversion rate of morpholine was 98%, and the selectivity of N-formylmorpholine was 95%.

[0042] Example 5 Preparation of supported nickel-cobalt-metal hydroxide core-shell catalysts: 0.2793 g of cobalt chloride, 0.2790 g of nickel nitrate hexahydrate, and 0.3 g of magnesium oxide were added to a 100 mL round-bottom flask, followed by 20 mL of deionized water. The pH of the solution was adjusted to 9-10 with 1 M NaOH, and the mixture was stirred for 12 h. The solution was then washed with deionized water and anhydrous ethanol. The resulting solid sample was dried at 120 °C for 12 h, and then pretreated at 400 °C under a 5% hydrogen / nitrogen atmosphere for 3 h to obtain the NiCo-NiCo(OH)x / MgO-400 core-shell catalyst (x=1-3).

[0043] Preparation of N-formylmorpholine: 0.10 g of the prepared NiCo-NiCo(OH)x / MgO-400 core-shell catalyst, 0.63 g of Na2CO3, and 0.52 g of morpholine were placed in a high-pressure reactor. The reactor was purged with CO2 three times until the final CO2 pressure was 3 MPa. Then, hydrogen was introduced to 6 MPa, and the reactor was placed in a heated aluminum block. The reaction was carried out at 160 °C and 600 rpm for 24 hours with stirring. The reactor was cooled to room temperature with water, the gas was slowly discharged, and the catalyst was separated by centrifugation. The resulting liquid was analyzed by gas chromatography. The conversion rate of morpholine was 95%, and the selectivity of N-formylmorpholine was 93%.

[0044] Example 6 Preparation of supported nickel-cobalt-metal hydroxide core-shell catalysts: 0.4189 g of cobalt nitrate hexahydrate, 0.4193 g of nickel chloride, and 0.3 g of Al2O3 were added to a 100 mL round-bottom flask, followed by 20 mL of deionized water. The pH of the solution was adjusted to 9-10 with 1 M NaOH, and the mixture was stirred for 12 h. The solution was then washed with deionized water and anhydrous ethanol. The resulting solid sample was dried at 120 °C for 12 h, and then reduced at 400 °C under a 5% hydrogen / argon atmosphere for 2 h to obtain the NiCo-NiCo(OH)x / Al2O3-400 core-shell catalyst (x=1-3).

[0045] Preparation of N-formylmorpholine: 0.20 g of the prepared NiCo-NiCo(OH)x / Al2O3-400 core-shell catalyst, 0.8 g of KOH, and 1.6 g of morpholine were placed in a high-pressure reactor. The reactor was purged with CO2 three times until the final CO2 pressure was 2 MPa. Then, H2 was introduced to 6 MPa, and the reactor was placed in a heated aluminum block. The reaction was carried out at 160 °C and 600 rpm for 24 hours with stirring. The reactor was cooled to room temperature with water, the gas was slowly discharged, and the catalyst was separated by centrifugation. The resulting liquid was analyzed by gas chromatography. The conversion rate of morpholine was 95%, and the selectivity of N-formylmorpholine was 93%.

[0046] Example 7 Preparation of supported nickel-cobalt-metal hydroxide core-shell catalysts: 0.3491 g of cobalt chloride hexahydrate, 0.3490 g of nickel chloride hexahydrate, and 0.151 g of coconut shell activated carbon were added to a 100 mL round-bottom flask, along with 20 mL of deionized water. The pH of the solution was adjusted to 9-10 with 1 M NaOH, and the mixture was stirred for 12 h. The sample was then washed with deionized water and anhydrous ethanol. The resulting solid sample was dried at 60 °C for 12 h, and then pretreated at 400 °C under a 5% hydrogen / argon atmosphere for 3 h to obtain the NiCo-NiCo(OH)x / AC-400 core-shell catalyst (x=1-3).

[0047] Preparation of N-formylmorpholine: 0.20 g of the prepared NiCo-NiCo(OH)x / AC-400 core-shell catalyst, 0.48 g of NaOH, and 0.88 g of morpholine were placed in a high-pressure reactor. The reactor was purged with CO2 three times until the final CO2 pressure was 2 MPa. Then, hydrogen was introduced to 6 MPa, and the reactor was placed in a heated aluminum block. The reaction was carried out at 160 °C and 600 rpm for 24 hours with stirring. The reactor was cooled to room temperature with water, the gas was slowly discharged, and the catalyst was separated by centrifugation. The resulting liquid was analyzed by gas chromatography. The conversion rate of morpholine was 96%, and the selectivity of N-formylmorpholine was 94%.

[0048] Example 8 Preparation of supported nickel-cobalt-metal hydroxide core-shell catalysts: 0.2742 g of cobalt nitrate hexahydrate, 0.2739 g of nickel nitrate hexahydrate, and 0.2 g of ZrO2 were added to a 100 mL round-bottom flask, followed by 20 mL of deionized water. The pH of the solution was adjusted to 9-10 with 1 M KOH, and the mixture was stirred for 12 h. The solution was then washed with deionized water and anhydrous ethanol. The resulting solid sample was dried at 60 °C for 12 h, and then pretreated at 400 °C under a 5% hydrogen / nitrogen atmosphere for 3 h to obtain the NiCo-NiCo(OH)x / ZrO2-400 core-shell catalyst (x=1-3).

[0049] Preparation of N-formylmorpholine: 0.15 g of the prepared NiCo-NiCo(OH)x / ZrO2-400 core-shell catalyst, 0.56 g of KOH, and 0.89 g of morpholine were placed in a high-pressure reactor. The reactor was purged with CO2 three times until the final CO2 pressure was 3 MPa. Then, hydrogen was introduced to 6 MPa, and the reactor was placed in a heated aluminum block. The reaction was carried out at 150 °C and 600 rpm for 12 hours with stirring. The reactor was cooled to room temperature with water, the gas was slowly discharged, and the catalyst was separated by centrifugation. The resulting liquid was analyzed by gas chromatography. The conversion rate of morpholine was 98%, and the selectivity of N-formylmorpholine was 97%.

[0050] Example 9 Preparation of supported nickel-cobalt-metal hydroxide core-shell catalysts: 0.2371 g of cobalt acetate, 0.3490 g of nickel acetate, and 0.5 g of SiO2 were added to a 100 mL round-bottom flask, followed by 20 mL of deionized water. The pH of the solution was adjusted to 9-10 with 1 M KOH, and the mixture was stirred for 12 h. The solution was then washed with deionized water and anhydrous ethanol. The resulting solid sample was dried at 60 °C for 12 h, and then pretreated at 400 °C under a 5% hydrogen / nitrogen atmosphere for 3 h to obtain the NiCo-NiCo(OH)x / SiO2-400 core-shell catalyst (x=1-3).

[0051] Preparation of N-formylmorpholine: 0.15 g of the prepared NiCo-NiCo(OH)x / SiO2-400 core-shell catalyst, 0.56 g of KOH, and 0.89 g of morpholine were placed in a high-pressure reactor. The reactor was purged with CO2 three times until the final CO2 pressure was 3 MPa. Then, hydrogen was introduced to 6 MPa, and the reactor was placed in a heated aluminum block. The reaction was carried out at 160 °C and 600 rpm for 12 hours with stirring. The reactor was cooled to room temperature with water, and the gas was slowly discharged. The catalyst was separated by centrifugation, and the resulting liquid was analyzed by gas chromatography. The conversion rate of morpholine was 98%, and the selectivity of N-formylmorpholine was 95%.

[0052] The reaction results of Examples 1 to 9 are compared in Table 1.

[0053] Table 1 Comparison of reaction results under different reaction conditions As shown in Table 1, the present invention has good technical effects, with ideal conversion rates of the raw material morpholine and selectivity of the target product N-formylmorpholine. Furthermore, the carbon-supported nickel-cobalt-metal hydroxide core-shell catalyst prepared by the hydrothermal-carbonization method exhibits superior catalytic performance compared to the supported nickel-cobalt-metal hydroxide core-shell catalyst prepared by the precipitation-reduction method.

Claims

1. A supported nickel cobalt-metal hydroxide core-shell catalyst characterized by: The core-shell catalyst is prepared by hydrothermal-carbonization or deposition-reduction method using nickel-cobalt metal salt as metal source, organic carbon-containing compound as carrier precursor or commercial carrier, and making active metal uniformly dispersed on the carrier; the nickel-cobalt metal salt is selected from one or more of the following: cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate, cobalt sulfate heptahydrate, nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate, and nickel sulfate hexahydrate.

2. A supported nickel cobalt-metal hydroxide core-shell catalyst according to claim 1, characterized in that: The active component of the core-shell catalyst is a nickel-cobalt metal core-metal hydroxide shell.

3. The supported nickel cobalt-metal hydroxide core-shell catalyst of claim 1, wherein: The active metal component in the core-shell catalyst refers to cobalt and nickel in an amount of 5 wt.% to 95 wt.%, and the content of active metal hydroxide is 5 wt.% to 45 wt.%.

4. The supported nickel cobalt-metal hydroxide core-shell catalyst of claim 1, wherein: The carrier is selected from at least one of the following: carbon-based carrier, silicon dioxide, molecular sieve, zirconium dioxide, titanium dioxide, aluminum oxide, magnesium oxide, and cerium oxide.

5. The supported nickel-cobalt-metal hydroxide core-shell catalyst as described in claim 1, characterized in that: In the hydrothermal-carbonization method, the hydrothermal temperature is 60 to 240 ℃, the hydrothermal time is 4 to 48 h; the carbonization or heat treatment temperature is 350 to 600 ℃, the heating rate is 3 to 20 ℃ / min, and the treatment atmosphere for carbonization or heat treatment is a mixture of hydrogen gas with different concentrations and inert gas.

6. The supported nickel cobalt-metal hydroxide core-shell catalyst of claim 1, wherein: In the deposition-reduction method, the precipitant used is one or more of the following: NaOH, KOH, NH3·H2O, K2CO3, Na2CO3, and urea.

7. Use of a supported nickel cobalt-metal hydroxide core-shell catalyst according to any one of claims 1 to 6, characterized in that: The supported nickel-cobalt-metal hydroxide core-shell catalyst is used as a catalyst for preparing N-formylmorpholine from CO2 and H2 and morpholine as raw materials.

8. Use of a supported nickel cobalt-metal hydroxide core-shell catalyst according to claim 7, characterized in that: The N-formylmorpholine is prepared by using CO2 and H2 and morpholine as raw materials, in a suitable solvent, under the action of the supported nickel-cobalt-metal hydroxide core-shell catalyst and an alkali aid, and under the following reaction conditions: CO2 / H2=1.0 to 5.0, reaction temperature of 60 to 200 ℃, reaction pressure of 1 to 10 MPa, molar ratio of alkali aid to morpholine of 0.2 to 5, and mass ratio of solvent to reactants of 5 to 50; the reaction is carried out for 2 to 48 hours, the catalyst is separated, the solvent is distilled out, and the target product N-formylmorpholine is obtained.

9. Use of a supported nickel cobalt-metal hydroxide core-shell catalyst according to claim 8, characterized in that: The solvent is at least one of the following: methanol, anhydrous ethanol, water, toluene, isopropyl alcohol, toluene, 1,4-dioxane, tetrahydrofuran, and ethyl acetate.

10. Use of a supported nickel cobalt-metal hydroxide core-shell catalyst according to claim 8, characterized in that: The alkali aid is one or more of the following: potassium hydroxide, sodium hydroxide, potassium tert-butoxide, sodium tert-butoxide, sodium phosphate, sodium carbonate, potassium carbonate, potassium bicarbonate, and potassium phosphate.

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