Supported catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a supported catalyst as well as a preparation method and application thereof. The preparation method of the supported catalyst provided by the invention comprises the following steps: mixing soluble transition metal salt, a carrier, an alkaline aqueous solution and water, and dipping to obtain a primary catalyst; the soluble transition metal salt comprises transition metal oxalate, transition metal formate or transition metal citrate; and carrying out microwave roasting on the primary catalyst to obtain the supported catalyst. According to the method, the transition metal salt is used as a roasting precursor, the transition metal is subjected to in-situ reduction in the reducing atmosphere generated during thermal decomposition of the transition metal salt in the roasting process, roasting and reduction are completed through microwave roasting one-step heating, the preparation steps are simplified, and meanwhile energy consumption is reduced. The supported catalyst is used in a catalytic condensation coupling hydrogen transfer reaction, has high conversion rate and coupling product selectivity, and can stably operate for a long time.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a supported catalyst and a preparation method and application thereof. Background Art

[0002] The carbon chain growth reaction (coupling reaction) of small organic molecules is an important step in realizing the transformation and synthesis of organic molecules, and plays a key role in the synthesis of complex or high-value organic molecules. For example, the condensation coupling hydrogen transfer reaction of ketones and small molecule alcohols (after dehydrogenation, Aldol condensation reaction, dehydration, hydrogenation) can obtain high-carbon ketones; most of the existing condensation coupling hydrogen transfer reactions need to be carried out under the conditions of catalysts, and the catalysts used for hydrogen transfer reactions are mostly supported catalysts. The preparation process of traditional supported catalysts is mainly: adding a porous catalyst carrier to a transition metal salt solution, and obtaining a catalyst through impregnation, drying, calcination, reduction, etc.; its preparation steps are complicated and need to be carried out under high temperature conditions, and the energy consumption is high. Summary of the invention

[0003] In view of this, the present invention provides a supported catalyst and a preparation method and application thereof. The preparation method provided by the present invention has simple steps, less energy consumption, improves production efficiency and reduces production costs.

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a supported catalyst, comprising the following steps: A soluble transition metal salt, a carrier, an alkaline aqueous solution and water are mixed and then impregnated to obtain a primary catalyst; the soluble transition metal salt includes a transition metal oxalate, a transition metal formate or a transition metal citrate; The primary catalyst is subjected to microwave calcination to obtain the supported catalyst.

[0005] Preferably, the transition metal in the soluble transition metal salt includes one or more of Mn, Ni, Co, Fe, Zn and Cu; The carrier includes porous carbon material, carbon nanotube, alkaline earth oxide, aluminum oxide, silicon oxide, silicon aluminum oxide or silica.

[0006] Preferably, the molar ratio of the soluble transition metal salt to the carrier is 1:5-40.

[0007] Preferably, the alkaline aqueous solution comprises an inorganic alkali aqueous solution and / or an organic alkali aqueous solution; The inorganic alkali aqueous solution includes aqueous ammonia; The organic base in the organic base aqueous solution includes urea, methylamine, ethylamine, ethanolamine, ethylenediamine or dimethylamine.

[0008] Preferably, the molar ratio of the soluble transition metal salt to the nitrogen element in the alkaline aqueous solution is 1:3-10.

[0009] Preferably, the power of the microwave used in the microwave roasting is 800-4000 W, and the time of the microwave roasting is 30-300 min.

[0010] Preferably, the microwave roasting is carried out in a vacuum or inert atmosphere; The vacuum degree of the vacuum is 1×10 -2 ~1×10 2 Pa; The inert atmosphere includes argon.

[0011] The present invention also provides a supported catalyst prepared according to the preparation method described in the above technical scheme, comprising a support and a transition metal supported on the surface or in the pores of the support.

[0012] The present invention also provides the use of the supported catalyst described in the above technical solution as a catalyst for condensation coupling hydrogen transfer reaction.

[0013] Preferably, the condensation coupling hydrogen transfer reaction includes an alcohol-ketone condensation coupling hydrogen transfer reaction or an alcohol-amine condensation coupling hydrogen transfer reaction.

[0014] The present invention provides a method for preparing a supported catalyst, comprising the following steps: mixing a soluble transition metal salt, a carrier, an alkaline aqueous solution and water and then impregnating the mixture to obtain a primary catalyst; the soluble transition metal salt comprises a transition metal oxalate, a transition metal formate or a transition metal citrate; and subjecting the primary catalyst to microwave roasting to obtain the supported catalyst. The present invention uses transition metal oxalate, transition metal formate or transition metal citrate as a roasting precursor of the catalyst, and in the roasting process, utilizes the reducing atmosphere (hydrogen and / or carbon monoxide) generated when the transition metal salt is thermally decomposed to in-situ reduce the transition metal, combines the two high-temperature steps of roasting and reduction into one, and obtains a reduced transition metal catalyst in one step, thereby simplifying the preparation steps and reducing energy consumption. At the same time, the present invention uses microwave roasting to further reduce production energy consumption and reduce preparation costs. The catalyst prepared according to the preparation method provided by the present invention is used to catalyze alcohol-ketone condensation coupling hydrogen transfer reaction or alcohol-amine condensation coupling hydrogen transfer reaction, and C- or N-alkyl grafting can be completed without adding an external solvent and a hydrogen source. It has a high conversion rate and coupling product selectivity, can operate stably for a long time, and has good industrial application prospects. DETAILED DESCRIPTION

[0015] The present invention provides a method for preparing a supported catalyst, comprising the following steps: A soluble transition metal salt, a carrier, an alkaline aqueous solution and water are mixed and then impregnated to obtain a primary catalyst; the soluble transition metal salt includes a transition metal oxalate, a transition metal formate or a transition metal citrate; The primary catalyst is subjected to microwave calcination to obtain the supported catalyst.

[0016] In the present invention, unless otherwise specified, all materials are conventional commercially available products.

[0017] The present invention mixes a soluble transition metal salt, a carrier, an alkaline aqueous solution and water and then impregnates them to obtain a primary catalyst. As a specific embodiment of the present invention, the mixing may include the following steps: first mixing the soluble transition metal salt, the carrier and water and then adding the alkaline aqueous solution.

[0018] As a specific embodiment of the present invention, the soluble transition metal salt includes transition metal oxalate, transition metal formate or transition metal citrate; the transition metal in the soluble transition metal salt may include one or more of Mn, Ni, Co, Fe, Zn and Cu, and may be specifically one of Mn, Ni, Co, Fe, Zn and Cu. As a specific embodiment of the present invention, the soluble transition metal salt may be specifically nickel oxalate, iron oxalate, cobalt oxalate, manganese oxalate, zinc oxalate, copper oxalate, copper formate or zinc citrate. The metal in the soluble transition metal salt used in the present invention is a non-precious metal, and the catalyst raw material used is easy to obtain, which significantly reduces the catalyst cost.

[0019] As a specific embodiment of the present invention, the carrier may include porous carbon material, carbon nanotube (CNT), alkaline earth oxide, aluminum oxide, silicon oxide, silicon aluminum oxide or silicate; the porous carbon material may be activated carbon (AC).

[0020] As a specific embodiment of the present invention, the alkaline aqueous solution may include an inorganic alkali aqueous solution and / or an organic alkali aqueous solution, which may be specifically an inorganic alkali aqueous solution and an organic alkali aqueous solution; the inorganic alkali aqueous solution may include ammonia water; the mass concentration of the ammonia water may be 15-25%, which may be specifically 15%, 20% or 25%. As a specific embodiment of the present invention, the organic alkali in the organic alkali aqueous solution may include urea, methylamine, ethylamine, ethanolamine, ethylenediamine or dimethylamine; the mass concentration of the organic alkali aqueous solution may be 15-25%, which may be specifically 15%, 20% or 25%. The addition of an alkaline aqueous solution to the reaction system of the present invention can increase the solubility of the soluble transition metal salt, and at the same time, it is also beneficial to the uniform dispersion of the transition metal in the carrier and provide alkaline sites, thereby helping to promote the catalysis of the condensation coupling hydrogen transfer reaction and improve the catalytic performance.

[0021] As a specific embodiment of the present invention, the molar ratio of the soluble transition metal salt to the carrier can be 1:5-40, specifically 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35 or 1:40; the molar ratio of the soluble transition metal salt to the nitrogen element in the alkaline aqueous solution can be 1:3-10, specifically 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10.

[0022] The present invention has no particular limitation on the amount of water used, as long as the materials can be mixed evenly.

[0023] As a specific embodiment of the present invention, the first mixing can be performed under stirring conditions; the present invention has no special limitation on the stirring, as long as the mixing is uniform. As a specific embodiment of the present invention, the process of adding the alkaline aqueous solution can be accompanied by stirring; the present invention has no special limitation on the stirring, as long as the mixing is uniform.

[0024] As a specific embodiment of the present invention, the immersion time may be 1.5 to 2.5 hours, specifically 1.5 hours, 2 hours or 2.5 hours. As a specific embodiment of the present invention, the immersion process may be accompanied by stirring; the present invention has no special limitation on the stirring.

[0025] As a specific embodiment of the present invention, the impregnation may further include: filtering the impregnated system, and drying the filtered solid to obtain the primary catalyst. The present invention has no special limitation on the filtration, and a conventional method in the art may be used. As a specific embodiment of the present invention, the drying temperature may be 80-120°C, or 100-110°C. The present invention has no special limitation on the drying time, as long as constant weight can be achieved.

[0026] After obtaining the primary catalyst, the present invention performs microwave roasting on the primary catalyst to obtain the supported catalyst. As a specific embodiment of the present invention, the power of the microwave used for the microwave roasting can be 800-4000W, and can be specifically 800W, 1000W, 1500W, 2000W, 2500W, 3000W, 3500W or 4000W; the time of the microwave roasting can be 30-300min, and can be specifically 30min, 50min, 100min, 120min, 150min, 180min, 200min, 230min, 250min or 300min.

[0027] As a specific embodiment of the present invention, the microwave roasting can be carried out in a microwave oven; the microwave roasting can be carried out in a vacuum or inert atmosphere; the vacuum degree of the vacuum can be 1×10-2 ~1×10 2 Pa, can also be 0.1~10Pa, and can further be 1~8Pa; the inert atmosphere can include argon.

[0028] As a specific embodiment of the present invention, the microwave roasting may further include: cooling the microwave roasted product to room temperature; the room temperature may be 20-35° C., or 25-30° C. In the present invention, the cooling may be furnace cooling.

[0029] The present invention also provides a supported catalyst prepared according to the preparation method described in the above technical scheme, comprising a support and a transition metal supported on the surface or in the pores of the support.

[0030] As a specific embodiment of the present invention, the transition metal in the supported catalyst can be Ni, Fe, Co, Cu, Zn or Mn; the carrier in the supported catalyst can be activated carbon, carbon nanotubes, silicon dioxide, magnesium oxide or aluminum oxide.

[0031] In the present invention, the connecting holes between the pores in the carrier are relatively small, and the transition metal is confined in the pores after being loaded, and is not easy to agglomerate, thereby significantly improving the life of the catalyst.

[0032] The present invention also provides the use of the supported catalyst described in the above technical solution as a coupling reaction catalyst. As a specific embodiment of the present invention, the coupling reaction may include an alcohol-ketone condensation coupling hydrogen transfer reaction or an alcohol-amine condensation coupling hydrogen transfer reaction.

[0033] As a specific embodiment of the present invention, the reaction materials of the alcohol-ketone condensation coupling hydrogen transfer reaction include α-H ketone compounds and a first alcohol compound; the α-H ketone compound may include aliphatic ketones, aromatic ketones, alicyclic ketones or ketones containing heteroatom substituents; specifically acetone, butanone, pentanone, acetophenone or cyclohexanone; the first alcohol compound may include aliphatic alcohols, aromatic alcohols, alicyclic alcohols or alcohols containing heteroatom substituents, specifically ethanol, n-propanol, isopropanol, ethylene glycol, phenylethyl alcohol, cyclohexanol or ethanolamine. As a specific embodiment of the present invention, the molar ratio of the α-H ketone compound to the first alcohol compound may be 1:2~2:1; the added amount of the supported catalyst may be 0.2~0.3g supported catalyst per 1mol of the α-H ketone compound. As a specific embodiment of the present invention, the temperature of the alcohol-ketone condensation coupling hydrogen transfer reaction can be 120~250°C, or 150~200°C; the time of the alcohol-ketone condensation coupling hydrogen transfer reaction can be 10~1000min, or 100~600min; the alcohol-ketone condensation coupling hydrogen transfer reaction can be carried out in a tank reactor, a fixed bed or a fluidized bed.

[0034] As a specific embodiment of the present invention, the reaction materials of the alcohol-amine condensation coupling hydrogen transfer reaction include an amine compound and a second alcohol compound; the amine compound may include a primary amine or a secondary amine, which may be specifically methylamine, ethylamine, propylamine, aniline, dimethylamine, diethylamine, diphenylamine, ethylenediamine, cyclohexylamine or 1-amino-2-propanone; the second alcohol compound may include a fatty alcohol, an aromatic alcohol, an alicyclic alcohol or an alcohol containing a heteroatom substituent, which may be specifically ethanol, n-propanol, isopropanol, ethylene glycol, phenylethyl alcohol, cyclohexanol or ethanolamine. As a specific embodiment of the present invention, the molar ratio of the amine compound to the second alcohol compound may be 1:2~2:1; the added amount of the supported catalyst may be 0.2~0.3g of supported catalyst per 1mol of the amine compound. As a specific embodiment of the present invention, the temperature of the alcohol-amine condensation coupling hydrogen transfer reaction can be 160-210°C, or 180-200°C; the time of the alcohol-amine condensation coupling hydrogen transfer reaction can be 30-300 min, or 80-200 min; the alcohol-amine condensation coupling hydrogen transfer reaction can be carried out in a tank reactor, a fixed bed, or a fluidized bed.

[0035] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0036] Example 1 21.3 g of nickel oxalate dihydrate and 20 g of activated carbon were added to water, stirred for 0.5 h, and then 56.7 g of 20 wt% ammonia water and 50 g of 20 wt% urea aqueous solution were added while stirring, and stirring was continued for 2 h. After filtering, the obtained solid was placed in an oven and dried at 90° C. to constant weight to obtain a primary catalyst; the molar ratio of nitrogen, activated carbon and water in the nickel oxalate, ammonia water and urea aqueous solution was 5:1:10:50:250; the primary catalyst was calcined in a microwave oven at 3000 W for 120 min under a vacuum condition of 0.1 Pa, and cooled to 30° C. with the furnace to obtain a supported catalyst, recorded as Ni5 / AC.

[0037] Embodiments 2 to 8 The supported catalyst was prepared according to the method of Example 1, and the differences are shown in Table 1.

[0038] Comparative Example 1~2 The supported catalyst was prepared according to the method of Example 1, except that no alkaline aqueous solution was added during the preparation process, see Table 1 for details.

[0039] Table 1: Conditions for preparing supported catalysts in Examples 1 to 10

[0040] The supported catalyst provided by the invention is used to catalyze alcohol-ketone condensation coupling hydrogen transfer reaction or alcohol-amine condensation coupling hydrogen transfer reaction, has high conversion rate and coupling product selectivity, and can operate stably for a long time.

[0041] Test Example 1 In a 100mL high-pressure reactor, 0.05g of catalyst Ni5 / AC, 20mL of ethanol and 20mL of acetone were added in sequence, and the coupling reaction was carried out at a temperature of 200℃ and a rotation speed of 500r / min for 10h to obtain 2-pentanone; the reaction products were analyzed by gas chromatography, and the results showed that the conversion rate of ethanol was 90%, the conversion rate of acetone was 91%, and the selectivity of 2-pentanone was 88%.

[0042] Test cases 2 to 20 According to the method of Test Example 1, the catalysts prepared in Examples 1 to 10 were used to catalyze the coupling reaction. The reaction conditions and catalytic performance are listed in Table 2.

[0043] Table 2 Reaction conditions and catalytic performance results of condensation coupling hydrogen transfer reaction

[0044] The subscript of the metal element in the abbreviation of the supported catalyst prepared in the example represents the molar percentage of the metal in the carrier; taking Ni5 / AC as an example, the molar percentage of Ni in the carrier AC is 5%.

[0045] When the supported catalyst provided by the present invention is used to catalyze the condensation coupling carbon chain growth reaction of ketone or amine with alcohol, no external solvent or high-pressure hydrogen is required, the reaction process is easy to implement, and the preparation method is simple; during the preparation, an inorganic metal-free alkaline aqueous solution and an organic alkaline aqueous solution containing N components are used to promote the dissolution of metal salts, and the introduced N is helpful for metal dispersion and providing alkaline sites, which is helpful for promoting the reaction of condensation coupling hydrogen transfer reaction, so that its catalytic performance is better than that of samples prepared by not adding alkaline aqueous solution to promote dissolution; in addition, the supported catalyst provided by the present invention has a high conversion rate for condensation coupling hydrogen transfer reaction, is applicable to a wide range of alcohol categories, has a conversion rate of alcohol and ketone of up to 91%, and has a selectivity of target high-carbon ketone of up to 92%, and can operate stably for a long time, and has a good industrial application prospect.

[0046] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a supported catalyst, characterized in that: The following steps are involved: A soluble transition metal salt, a carrier, an alkaline aqueous solution and water are mixed and then impregnated to obtain a primary catalyst; the soluble transition metal salt includes a transition metal oxalate, a transition metal formate or a transition metal citrate; The primary catalyst is subjected to microwave calcination to obtain the supported catalyst.

2. The preparation method according to claim 1, characterized in that: The transition metal in the soluble transition metal salt includes one or more of Mn, Ni, Co, Fe, Zn and Cu; The carrier includes porous carbon material, carbon nanotube, alkaline earth oxide, aluminum oxide, silicon oxide, silicon aluminum oxide or silica.

3. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the soluble transition metal salt to the carrier is 1:5-40.

4. The preparation method according to claim 1, characterized in that: The alkaline aqueous solution includes an inorganic alkali aqueous solution and / or an organic alkali aqueous solution; The inorganic alkali aqueous solution includes aqueous ammonia; The organic base in the organic base aqueous solution includes urea, methylamine, ethylamine, ethanolamine, ethylenediamine or dimethylamine.

5. The preparation method according to claim 1 or 4, characterized in that: The molar ratio of the soluble transition metal salt to the nitrogen element in the alkaline aqueous solution is 1:3-10.

6. The preparation method according to claim 1, characterized in that: The microwave power used in the microwave roasting is 800-4000W, and the microwave roasting time is 30-300min.

7. The preparation method according to claim 1 or 6, characterized in that: The microwave roasting is carried out in a vacuum or inert atmosphere; The vacuum degree of the vacuum is 1×10 -2 ~1×10 2 Pa; The inert atmosphere includes argon.

8. A supported catalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that: It comprises a carrier and a transition metal loaded on the surface or in the pores of the carrier.

9. Use of the supported catalyst according to claim 8 as a catalyst for condensation coupling hydrogen transfer reaction.

10. The use according to claim 9, characterized in that: The condensation coupling hydrogen transfer reaction includes an alcohol-ketone condensation coupling hydrogen transfer reaction or an alcohol-amine condensation coupling hydrogen transfer reaction.

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