Carbon-based M-N-C catalyst and preparation method and application thereof

Abstract

The invention discloses a carbon-based M-N-C catalyst as well as a preparation method and application thereof. According to the catalyst, mesoporous carbon particles serve as a carrier, an active component is an M-N-C site formed by coordination of a nitrogen element and transition metal, and the transition metal is at least one of Mn, Fe, Co, Ni and Cu. The catalyst can be applied to an olefin epoxidation reaction in which olefin and peroxide react to generate an epoxy compound, and has the advantages of low cost, favorable hydrophobicity, favorable activity and stability and favorable industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and specifically, to a carbon-based M-N-C catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Epoxides represented by propylene oxide, epichlorohydrin, butylene oxide, etc. are widely used in the fields of chemical materials such as polyurethanes and epoxy resins. The traditional production method of epoxides is the chlorohydrin method, which has a short process and is mature, but inorganic salt waste residues and chlorine-containing wastewater will be generated during the production process, the equipment corrosion is serious, and the environmental pollution is large.

[0003] In recent years, an epoxidation process using titanium silicalite as a catalyst and organic peroxides as oxidants has been developed and applied. Organic peroxides such as tert-butyl hydroperoxide, ethylbenzene hydroperoxide, and cumene hydroperoxide are widely used in the preparation and production of epoxides such as propylene oxide and butylene oxide. The related process system has less pollution and is more environmentally friendly.

[0004] In these reaction systems using organic peroxides as oxidants, in order to avoid the hydrolysis ring-opening of the epoxidation product and improve the service life of the titanium silicalite catalyst, the catalyst needs to be hydrophobically treated, and usually a silanization reagent is used for post-modification of the molecular sieve.

[0005] Patent CN104437636A discloses a titanium-containing porous silica catalyst for producing propylene oxide and a preparation method thereof, which makes the titanium-loaded precursor contact with an organic silicon at 25-500°C to obtain a superhydrophobic catalyst modified by silanization, inhibits the ring-opening hydrolysis of propylene oxide, reduces the occurrence of side reactions and the formation of polymers, and improves the selectivity of propylene oxide.

[0006] For the titanium-containing mesoporous catalyst applied to the epoxidation reaction, on the one hand, the silanization treatment has a high cost, and on the other hand, the service life after silanization modification is also short. As the catalyst is used, the post-modification groups on the surface are gradually damaged and fall off, the product selectivity begins to decline, and the catalyst quickly reaches the end of its life and needs to be replaced again. In the process of producing epoxides, the catalyst urgently needs to be improved and innovated to reduce costs and increase the service life. Summary of the Invention

[0007] The technical problem to be solved by the present invention is aimed at the technical defects of the complex hydrophobization treatment and poor stability of the epoxidation catalyst used in the prior art. The present invention provides a novel carbon-based M-N-C catalyst with good hydrophobicity and stability and an application for catalyzing the conversion of olefins to synthesize epoxides. It shows good activity and stability in the reaction of oxidizing cyclohexene to prepare cyclohexene oxide.

[0008] One of the objectives of the present invention is to provide a carbon-based M-N-C catalyst, where the catalyst uses mesoporous carbon particles as the carrier, and the active component is the M-N-C site formed by coordinating transition metals with nitrogen element, and among them, the transition metal is at least one of Mn, Fe, Co, Ni, and Cu.

[0009] In the catalyst of the present invention, N and C are the nitrogen element and carbon element doped in the carbon carrier.

[0010] According to a preferred embodiment of the present invention, in terms of elemental mass in the catalyst, M:N:C = (0.0005 - 0.1):(0.005 - 0.2):1, and more preferably, M:N:C = (0.001 - 0.01):(0.01 - 0.1):1.

[0011] According to a preferred embodiment of the present invention, the catalyst has a signal peak of N element in the range of 365 - 405 eV of X-ray photoelectron spectroscopy.

[0012] According to a preferred embodiment of the present invention, the transition metal in the catalyst can be two or more of Mn, Fe, Co, Ni, and Cu.

[0013] According to a preferred embodiment of the present invention, the specific surface area of the catalyst is 200 - 2000 m 2 / g, and more preferably 200 - 800 m 2 / g.

[0014] According to a preferred embodiment of the present invention, the pore size range of the catalyst is 10 - 80 nm, and more preferably 10 - 50 nm.

[0015] Another objective of the present invention is to provide a preparation method of the carbon-based M-N-C catalyst, including the following steps:

[0016] (1) Dissolve the transition metal salt in a solvent, and add a nitrogen-containing compound;

[0017] (2) Add a carbon source to the solution obtained in step (1) until the solution is absorbed by the carbon source, and dry the obtained mixture;

[0018] (3) Heat the dried mixture and then cool it.

[0019] According to a preferred embodiment of the present invention, the transition metal is one, two or more of Mn, Fe, Co, Ni, and Cu.

[0020] According to a preferred embodiment of the present invention, the transition metal salt is at least one of the chloride, sulfate, and nitrate of the transition metal.

[0021] According to a preferred embodiment of the present invention, the nitrogen-containing compound is at least one of urea, dicyandiamide, and melamine.

[0022] According to a preferred embodiment of the present invention, the carbon source is at least one of coconut shell carbon and activated carbon.

[0023] According to a preferred embodiment of the present invention, the pore size range of the carbon source is 10-100 nm.

[0024] According to a preferred embodiment of the present invention, the solvent is at least one of water, ethanol, and methanol.

[0025] According to a preferred embodiment of the present invention, in step (1), the mass ratio of the transition metal salt to the nitrogen-containing compound is (0.001-1):1, preferably (0.01-0.1):1.

[0026] According to a preferred embodiment of the present invention, in step (2), the drying temperature is 60-120 °C, preferably 90-110 °C.

[0027] According to a preferred embodiment of the present invention, in step (3), the heating temperature is 450-650 °C, and the heating time is 30 min-20 h.

[0028] According to a more preferred embodiment of the present invention, in step (3), the heating temperature is 500-550 °C, and the heating time is 1 h-10 h.

[0029] According to a preferred embodiment of the present invention, in step (3), the heating is carried out in a nitrogen atmosphere.

[0030] The carbon-based M-N-C catalyst support of the present invention is synthesized in a high-temperature nitrogen atmosphere, and the catalyst synthesis also undergoes high-temperature treatment, with good hydrophobicity.

[0031] The third object of the present invention is to provide the application of the carbon-based M-N-C catalyst or the carbon-based M-N-C catalyst obtained by the preparation method in the epoxidation reaction of olefins.

[0032] The olefin epoxidation reaction includes the oxidation reaction of an olefin with a peroxide as an oxidant to form an epoxide.

[0033] According to a preferred embodiment of the present invention, the olefin is at least one of cyclohexene ring, cyclopentene, 1-hexene, 2-hexene, and 1-methylcyclopentene.

[0034] According to a more preferred embodiment of the present invention, the catalyst is used for the oxidation of cyclohexene to prepare cyclohexene oxide.

[0035] According to a preferred embodiment of the present invention, the mass space velocity of the catalyst relative to the peroxide is 0.08 - 5.00 h -1 , preferably 0.1 - 1.0 h -1 .

[0036] According to a preferred embodiment of the present invention, in the epoxidation reaction of olefins, the reaction temperature is 40 - 130 °C and the reaction pressure is 0.01 - 10.00 MPa.

[0037] According to a more preferred embodiment of the present invention, in the epoxidation reaction of olefins, the reaction temperature is 70 - 110 °C and the reaction pressure is 0.10 - 1.00 MPa.

[0038] The M-N-C catalyst is a type of catalyst with a nitrogen-coordinated transition metal as the active center. By means of in-situ doping carbonization or post-loading, a nitrogen-coordinated carbon support can be obtained, which can coordinate well with the transition metal to form a type of catalyst with M-N-C as the active center.

[0039] The inventors found that the M-N-C catalyst also has a certain catalytic effect on the epoxidation of olefins. The M-N-C catalyst obtained by the post-loading method inherits the hydrophobicity of the carbon support obtained by high-temperature carbonization treatment, has good hydrophobicity, good activity and stability.

[0040] The catalyst of the present invention is easy to prepare, has good hydrophobicity, and can be used in the application of catalytic olefin conversion to synthesize epoxides, especially suitable for the reaction of oxidizing cyclohexene to prepare cyclohexene oxide. Because it does not require complex hydrophobic treatment, the catalyst cost is low, and it has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is the N1s XPS energy spectrum diagram of the catalysts obtained in Examples 1 - 3. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention will be specifically described below in conjunction with specific examples. It is necessary to point out here that the following examples are only for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the content of the present invention still fall within the protection scope of the present invention.

[0043] In addition, it should be noted that in the following specific embodiments, the various specific technical features described can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0044] In addition, any combination can be made among various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions formed thereby belong to a part of the original disclosure content of this specification and also fall within the protection scope of the present invention.

[0045] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0046] The raw materials used in the examples and comparative examples, if not specifically defined, are those disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0047]

Example 1

[0048] Under room temperature and stirring conditions, 5.0 g of urea was added to a beaker containing 10 mL of ethanol and stirred evenly. 0.5 g of nickel chloride hexahydrate solid was weighed and added to the mixed solution and stirred evenly.

[0049] 13.5 g of activated carbon with a pore size range of 10 - 100 nm was washed with water, dried at 110 °C for standby. The dried activated carbon was added to the mixed solution to ensure that the activated carbon particles covered the mixed solution and there was no excess liquid residue, and then stirred evenly and dried at 110 °C.

[0050] The dried solid was added to a crucible and placed in a muffle furnace. The temperature was programmed to rise to 550 °C under a nitrogen atmosphere. After heating for 5 hours, it was naturally cooled, and the sample was taken out to obtain the Ni-N-C catalyst. When the catalyst particles were put into water, a slight gas film on the surface of the catalyst particles could be observed, indicating that the catalyst had hydrophobicity.

[0051] Through inductively coupled plasma atomic emission spectrometry (ICP-AES) test and elemental analysis test, the mass ratio of Ni:N:C in the obtained catalyst was 0.005:0.02:1, the specific surface area of the catalyst was 762 m 2 / g, and the pore size range was 20 - 80 nm.

[0052] 10 g of the Ni-N-C catalyst and 33 g of cyclohexene were added to 200 g of a 40% cumene hydroperoxide / cumene solution. The mass space velocity of the catalyst relative to the peroxide was 0.1 h -1, the reaction pressure was 0.1 MPa, and the reaction was carried out at 80 °C for 5 hours. At the end of the reaction, the conversion rate calculated based on the product cyclohexene oxide was 89%. The catalyst was filtered, washed with water, and dried from the reaction system. The recovered catalyst was reused in the same epoxidation reaction. After 3 recycling runs, the conversion rate was 83%, and the activity was basically maintained stable.

[0053]

Example 2

[0054] Under room temperature and stirring conditions, 1.0 g of dicyandiamide was added to a beaker containing 20 mL of H 2 O, and stirred evenly. 0.1 g of ferric chloride hexahydrate solid was weighed and added to the mixed solution, and stirred evenly.

[0055] 39.6 g of activated carbon with a pore size range of 10 - 100 nm was washed with water and dried at 110 °C for standby. The dried activated carbon was added to the mixed solution to ensure that the activated carbon particles covered the mixed solution and there was no excess liquid residue, and stirred evenly, then dried at 110 °C.

[0056] The dried solid was added to a crucible and placed in a muffle furnace. The temperature was programmed to rise to 550 °C under a nitrogen atmosphere. After heating for 5 hours, it was cooled naturally, and the sample was taken out to obtain the Fe-N-C catalyst.

[0057] Through inductively coupled plasma optical emission spectrometry (ICP-OES) testing and elemental analysis testing, the mass ratio of Fe:N:C in the obtained catalyst was 0.007:0.02:1, the specific surface area of the catalyst was 683 m 2 / g, and the pore size range was 20 - 80 nm. When the catalyst particles were put into water, a slight gas film on the surface of the catalyst particles could be observed, indicating that the catalyst had hydrophobicity.

[0058] 10 g of the Fe-N-C catalyst and 33 g of cyclohexene were added to 200 g of a 40% cumene hydroperoxide / cumene solution. The mass space velocity of the catalyst relative to the peroxide was 0.1 h -1 , the reaction pressure was 0.1 MPa, and the reaction was carried out at 85 °C for 10 hours. At the end of the reaction, the conversion rate calculated based on the product cyclohexene oxide was 82%. The catalyst was filtered, washed with water, and dried from the reaction system. The recovered catalyst was reused in the same epoxidation reaction. After 3 recycling runs, the conversion rate was 75%, and the activity was basically maintained stable.

[0059]

Example 3

[0060] Under room temperature and stirring conditions, 5.0 g of urea was added to a beaker containing 10 mL of ethanol, and stirred evenly. 0.25 g of nickel chloride hexahydrate and 0.25 g of cobalt chloride hexahydrate solids were weighed and added to the mixed solution, and stirred evenly.

[0061] Weigh 13.5 g of activated carbon with a pore size range of 10 - 100 nm, wash it with water, and dry it at 110 °C for later use. Add the dried activated carbon to the mixed solution, ensuring that the activated carbon particles cover the mixed solution with no excess liquid remaining. Stir evenly and dry at 110 °C.

[0062] Add the dried solid to a crucible, place it in a muffle furnace, and increase the temperature to 550 °C at a programmed rate. The atmosphere is nitrogen. After heating for 5 hours, let it cool naturally. Take out the sample to obtain the Co-Ni-N-C catalyst. When the catalyst particles are put into water, a slight gas film on the surface of the catalyst particles can be observed, indicating that the catalyst is hydrophobic.

[0063] Through inductively coupled plasma optical emission spectrometry (ICP-OES) testing and elemental analysis, the mass ratio of Co:Ni:N:C in the obtained catalyst is 0.003:0.003:0.02:1, and the specific surface area of the catalyst is 719 m 2 / g, and the pore size ranges from 20 - 80 nm.

[0064] Add 10 g of the Co-Ni-N-C catalyst and 33 g of cyclohexene to 200 g of a 40% cumene hydroperoxide / cumene solution. The mass space velocity of the catalyst relative to the peroxide is 0.1 h -1 , the reaction pressure is 0.1 MPa, and react at 80 °C for 5 hours. At the end of the reaction, the conversion rate calculated based on the product cyclohexene oxide is 92%. Filter the catalyst from the reaction system, wash it with water, and dry it. The recovered catalyst is reused in the same epoxidation reaction. After recycling 3 times, the conversion rate is 85%, and the activity remains basically stable.

[0065]

Example 4

[0066] Under room temperature and stirring conditions, add 1.0 g of urea to a beaker containing 10 mL of ethanol and stir evenly. Weigh 0.1 g of nickel chloride hexahydrate solid and add it to the mixed solution, then stir evenly.

[0067] Weigh 13.5 g of activated carbon with a pore size range of 10 - 100 nm, wash it with water, and dry it at 110 °C for later use. Add the dried activated carbon to the mixed solution, ensuring that the activated carbon particles cover the mixed solution with no excess liquid remaining. Stir evenly and dry at 110 °C.

[0068] Add the dried solid to a crucible, place it in a muffle furnace, and increase the temperature to 550 °C at a programmed rate. The atmosphere is nitrogen. After heating for 5 hours, let it cool naturally. Take out the sample to obtain the Ni-N-C catalyst. When the catalyst particles are put into water, a slight gas film on the surface of the catalyst particles can be observed, indicating that the catalyst is hydrophobic.

[0069] After plasma emission spectroscopy testing and elemental analysis testing, the mass ratio of Ni:N:C in the obtained catalyst is 0.0005:0.005:1, and the specific surface area of the catalyst is 691 m 2 / g, and the pore size range is 20 - 80 nm.

[0070] 10 g of the Co-Ni-N-C catalyst and 33 g of cyclohexene were added to 200 g of a 40% cumene hydroperoxide / cumene solution. The mass space velocity of the catalyst relative to the peroxide is 0.1 h -1 , the reaction pressure is 0.1 MPa, and the reaction is carried out at 80 °C for 5 hours. At the end of the reaction, the conversion rate calculated based on the product cyclohexene oxide is 66%. The catalyst was filtered, washed with water, and dried from the reaction system, and the recovered catalyst was reused in the same epoxidation reaction. After 3 recycling runs, the conversion rate was 43%.

[0071]

Comparative Example 1

[0072] Under room temperature and stirring conditions, 5.0 g of urea was added to a beaker containing 10 mL of ethanol and stirred evenly. 0.5 g of titanium chloride solid was weighed and added to the solution and stirred evenly.

[0073] 19.8 g of activated carbon with a pore size range of 10 - 100 nm was washed with water and dried at 110 °C for standby. The dried activated carbon was added to the mixed solution to ensure that the activated carbon particles covered the mixed solution with no excess liquid remaining, and it was stirred evenly and dried at 110 °C.

[0074] The dried solid was added to a crucible and placed in a muffle furnace. The temperature was programmed to rise to 550 °C, the atmosphere was nitrogen, and after heating for 5 hours, it was cooled naturally. The sample was taken out to obtain the Ti-N-C catalyst.

[0075] After plasma emission spectroscopy testing and elemental analysis testing, the mass ratio of Ti:N:C in the obtained catalyst is 0.005:0.02:1, and the specific surface area of the catalyst is 708 m 2 / g, and the pore size range is 20 - 80 nm.

[0076] 10 g of the Ti-N-C catalyst and 33 g of cyclohexene were added to 200 g of a 40% cumene hydroperoxide / cumene solution. The mass space velocity of the catalyst relative to the peroxide is 0.1 h -1 , the reaction pressure is 0.1 MPa, and the reaction is carried out at 80 °C for 5 hours. At the end of the reaction, the conversion rate calculated based on the product cyclohexene oxide is 7%.

[0077]

Comparative Example 2

[0078] At room temperature and under stirring conditions, 5.0 g of urea was added to a beaker containing 10 mL of ethanol and stirred evenly. 0.5 g of nickel chloride hexahydrate solid was weighed and added to the mixed solution and stirred evenly.

[0079] 87.4 g of commercial conductive carbon black was washed with water and dried at 110 °C for standby. The dried carbon black was added to the mixed solution to ensure that the carbon black particles covered the mixed solution and there was no excess liquid residue, and then stirred evenly and dried at 110 °C.

[0080] The dried solid was added to a crucible and placed in a muffle furnace. The temperature was raised to 550 °C at a programmed rate under a nitrogen atmosphere. After heating for 5 hours, it was cooled naturally, and the sample was taken out to obtain the Ni-N-C catalyst.

[0081] Plasma emission spectroscopy test and elemental analysis test showed that the mass ratio of Ni:N:C in the catalyst was 0.0002:0.01:1, and the specific surface area of the catalyst was 43 m 2 / g.

[0082] 10 g of the Ni-N-C catalyst and 33 g of cyclohexene were added to 200 g of a 40% cumene hydroperoxide / cumene solution. The mass space velocity of the catalyst relative to the peroxide was 0.1 h -1 , the reaction pressure was 0.1 MPa, and the reaction was carried out at 80 °C for 5 hours. The conversion rate calculated based on the product cyclohexene oxide at the end of the reaction was 3%.

[0083] All publications, patent applications, patents, and other references mentioned in this specification are hereby incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0084] When this specification uses prefixes such as "well-known to those skilled in the art", "prior art", or their similar terms to derive materials, substances, methods, steps, devices, or components, etc., the objects derived by such prefixes cover those commonly used in the art at the time when this application is filed, but also include those that are not commonly used at present but will become recognized by the art as suitable for similar purposes.

[0085] In the context of this specification, any matter or thing not mentioned, except as expressly stated, shall directly apply those known in the art without any change. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas thus formed shall be regarded as part of the original disclosure or original record of the present invention, and shall not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider such combination to be obviously unreasonable.

Claims

1. A carbon-based MNC catalyst, wherein the catalyst uses mesoporous carbon particles as a carrier, and the active component is an MNC site formed by nitrogen coordinated with a transition metal, wherein: The transition metal is at least one of Mn, Fe, Co, Ni and Cu.

2. The carbon-based MNC catalyst according to claim 1, characterized in that: In the catalyst, by mass, M:N:C=(0.0005-0.1):(0.005-0.2):1, preferably, M:N:C=(0.001-0.01):(0.01-0.1):

1.

3. The carbon-based MNC catalyst according to claim 1, characterized in that: The catalyst has a signal peak of N element in the range of 365 to 405 eV of X-ray photoelectron spectrum; and / or, The specific surface area of ​​the catalyst is 200 to 2000 m 2 / g, preferably 200 to 800 m 2 / g; and / or, The pore size of the catalyst is in the range of 10 to 80 nm, preferably 10 to 50 nm.

4. The method for preparing the carbon-based MNC catalyst according to any one of claims 1 to 3, comprising the following steps: (1) dissolving a transition metal salt in a solvent and adding a nitrogen-containing compound; (2) adding a carbon source to the solution obtained in step (1) until the solution is absorbed by the carbon source, and drying the obtained mixture; (3) The dried mixture is heated and cooled.

5. The preparation method according to claim 4, characterized in that: The transition metal salt is at least one of chloride, sulfate and nitrate of a transition metal; and / or, The nitrogen-containing compound is at least one of urea, dicyandiamide and melamine; and / or, The carbon source is at least one of coconut shell carbon and activated carbon; and / or, The solvent is at least one of water, ethanol and methanol.

6. The preparation method according to claim 4, characterized in that: In step (1), the mass ratio of the transition metal salt to the nitrogen-containing compound is (0.001-1):1, preferably (0.01-0.1):1; and / or, In step (2), the drying temperature is 60 to 120° C., preferably 90 to 110° C.; and / or, In step (3), the heating temperature is 450-650° C., preferably 500-550° C.; the heating time is 30 min-20 h, preferably 1-10 h.

7. Use of the carbon-based MNC catalyst according to any one of claims 1 to 3 or the carbon-based MNC catalyst obtained by the preparation method according to any one of claims 4 to 6 in olefin epoxidation reaction.

8. The use according to claim 7, characterized in that: The olefin epoxidation reaction comprises an olefin and a peroxide undergoing an oxidation reaction to generate an epoxy compound; Preferably, the olefin is selected from at least one of cyclohexene, cyclopentene, 1-hexene, 2-hexene, and 1-methylcyclopentene.

9. The use according to claim 8, characterized in that: The mass space velocity of the catalyst relative to the peroxide is 0.08 to 5.00 h -1 , preferably 0.1~1.0h -1 .

10. The use according to claim 7, characterized in that: In the olefin epoxidation reaction, the reaction temperature is 40 to 130° C., preferably 70 to 110° C.; the reaction pressure is 0.01 to 10.00 MPa, preferably 0.10 to 1.00 MPa.

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