Preparation method and application of Mo2C supported catalyst

Abstract

The invention provides a preparation method and application of a Mo2C supported catalyst. The preparation method comprises the following steps: adding quantitative noble metal Ru salt, molybdenum salt and an organic carbon source into a solvent, stirring for dissolving, stirring for reaction, and drying in vacuum overnight to obtain a catalyst sample precursor; pure H2 is introduced into a catalyst sample precursor for reduction, after reduction is completed, 1% O2-Ar mixed gas is introduced for passivation, and the loaded Ru-based catalyst is obtained. Compared with a traditional industrial catalyst, the Ru-based catalyst disclosed by the invention is relatively low in noble metal content and has a good cost advantage, and certain possibility is provided for subsequent industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and particularly relates to a preparation method of a Mo2C supported catalyst and application of the catalyst in a reaction of partially hydrogenating benzene to produce cyclohexene. Background Art

[0002] Cyclohexene is an important organic chemical raw material, often used as an intermediate for petrochemicals, medicines, pesticides and dyes, and is widely used in the fields of petroleum and fine chemicals. In the production of caprolactam, cyclohexene can be hydrated to produce cyclohexanol, cyclohexanol is oxidized and dehydrated to produce cyclohexanone, cyclohexanone is ammoximated to produce cyclohexanone oxime, and then the molecules are rearranged to produce caprolactam. At present, the production methods of cyclohexene include partial hydrogenation of benzene to produce cyclohexene, cyclohexanol dehydration, cyclohexane dehydrogenation and Birch reduction. Since the partial hydrogenation of benzene to produce cyclohexene is simple and has low production cost, it is often used in industrial production of cyclohexene.

[0003] The difficulty of partial hydrogenation of benzene to produce cyclohexene is that the C=C double bond in the product cyclohexene is active, and it is easy to deeply hydrogenate to produce cyclohexane, and it is thermodynamically easier to produce cyclohexane. Therefore, to achieve efficient cyclohexene production, it is necessary to select a suitable reaction system to avoid excessive hydrogenation of the product to produce cyclohexane. In this regard, a large number of documents and patents have been systematically studied. For example, patent CN1984712A discloses a catalyst for partial hydrogenation of benzene to produce cyclohexene. In this patent, the proportion of catalyst pore size in the range of 2~15 nm should be greater than 50%, otherwise it will be detrimental to the production of cyclohexene. Patent CN106140154B puts forward a completely opposite conclusion, believing that the proportion of catalyst pore size in the range of 2~15 nm should be less than 50%, which can be conducive to the production of cyclohexene and improve the stability of the catalyst. Patent CN102264471A proposes that reducing a Ru-based catalyst in an aqueous solution containing a metal salt can increase the cyclohexene yield to a certain extent. Patent CN108409520B proposes to treat RuZn catalyst with alkali, which can improve catalyst stability and cyclohexene yield. Its catalytic activity test shows that the cyclohexene yield of the catalyst can still reach 41.2% after 200 hours of continuous operation (i.e., benzene conversion rate is 48.5%, cyclohexene selectivity is 84.9%). Summary of the invention

[0004] In order to solve the above problems, the present invention aims to provide a method for preparing a Mo2C supported catalyst and its application in the reaction of partial hydrogenation of benzene to cyclohexene.

[0005] The technical solution of the present invention is as follows: (1) adding Ru salt, molybdenum salt and organic carbon source into a solvent, stirring to dissolve, stirring to react, and vacuum drying overnight to obtain a catalyst sample precursor; (2) The catalyst sample precursor was reduced by introducing pure H2. After the reduction was completed, 1% O2-Ar mixed gas was introduced for passivation to obtain the supported Ru-based catalyst Ru-Mo2C.

[0006] In some preferred embodiments, the metal Ru salt in step (1) is one or more of RuCl3, Ru(acac)3, tris(triphenylphosphine)ruthenium chloride, and Ru(NO)(NO3)3.

[0007] In some preferred embodiments, the molybdenum salt in step (1) is one or more of sodium molybdate, ammonium molybdate, ammonium phosphomolybdate, molybdenum acetylacetonate, molybdenum chloride or molybdenum hexacarbonyl.

[0008] In some preferred embodiments, the organic carbon source in step (1) is one or more of sugars, organic amines, and amides.

[0009] In some preferred embodiments, the mass ratio of the molybdenum salt to the organic carbon source in step (1) is (1-100): (1-100).

[0010] In some preferred embodiments, the solvent in step (1) is one or more of ammonia water, deionized water and ethanol.

[0011] In some preferred embodiments, the stirring reaction conditions in step (1) are 70-90 °C for 10-15 h, and then vacuum drying at 100 °C overnight; preferably, stirring at 80 °C for 12 h, and then vacuum drying at 100 °C overnight.

[0012] In some preferred embodiments, the reduction temperature in step (2) is 200°C to 1000°C.

[0013] In some preferred embodiments, the Ru loading in step (2) is 1.0 wt% to 5.0 wt%.

[0014] The present invention provides a method for preparing the Mo2C supported catalyst described in the above technical solution, and application of the catalyst in the reaction of partially hydrogenating benzene to produce cyclohexene.

[0015] The advantages of the present invention are: The present invention provides a method for preparing a Mo2C supported catalyst and its application in the reaction of preparing cyclohexene by partial hydrogenation of benzene. Since Mo2C has a strong interaction with metal Ru, the noble metal Ru can be better dispersed, thereby exposing more Ru active sites on the catalyst surface, so that a higher cyclohexene yield can be obtained under a lower loading amount, and the amount of zinc sulfate used in the reaction can be greatly reduced from the traditional 10g addition amount to 2g. In addition, Mo2C has a noble metal-like property and has a certain performance of preparing cyclohexene by partial hydrogenation of benzene. Under the synergistic effect of the noble metal Ru, the Ru-Mo2C catalyst obtains a higher cyclohexene yield.

[0016] It is difficult to prepare a catalyst with a low loading of Ru. The present invention achieves a lower loading of 1.5%-5% by simultaneously feeding the materials and combining the screening of carbon sources and solvent types.

[0017] Compared with existing industrial catalysts (metal Ru content of about 10 wt%), the catalyst provided by the present invention has the advantages of low metal Ru content, low cost burden and high cyclohexene yield, and has a price advantage in large-scale industrial applications. DETAILED DESCRIPTION

[0018] The following will be combined with the specific embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0019] In the context of this specification, except for the contents explicitly described, any matters or items not mentioned directly use the technology known in the art. Moreover, any embodiment described in this patent can be freely combined with one or more other embodiments described in this patent, and the technical solutions or technical ideas formed thereby are regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed in this patent, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0020] The data points disclosed in this patent include not only the specific disclosed numerical points, but also the endpoints of each numerical range. Any combination of these data points should be regarded as the scope disclosed or recorded in the present invention, regardless of whether these numerical points are disclosed one by one in this article.

[0021] In the present invention, the catalytic performance evaluation device used is a kettle reactor. Unless otherwise specified, the evaluation method for preparing cyclohexene by partial hydrogenation of benzene is as follows: weigh a quantitative catalyst and add it into the reactor. After multiple pressure charging and pressure relief, the air in the reactor is exhausted, and the pressure is held to check for leaks. After the pressure is normal, the reaction temperature is started to rise. After the temperature reaches the target temperature, benzene is added and the reaction timing is started.

[0022] In the present invention, unless otherwise specified, the reaction conditions are 5.0 MPa, 155°C, rotation speed 1000 r / min, catalyst 1 g, benzene 50 mL, water 100 mL, and 2 g ZnSO4.

[0023] In the present invention, unless otherwise specified, the benzene conversion rate and cyclohexene selectivity listed in Table 1 are obtained under the condition of the highest cyclohexene yield.

[0024] To further illustrate the present invention, the following embodiments are described in detail, but the protection scope of the present invention is not limited to the following embodiments.

[0025] Example 1 Weigh 8.65 g (NH4)6Mo7O 24 •4H2O (abbreviated as AHM), 0.21 g RuCl3 and 7.84 g hexamethylenetetramine (abbreviated as HMT) were dissolved in 150 ml deionized water, stirred at 80 °C for 12 h, and then vacuum dried at 100 °C overnight. The obtained sample was the catalyst sample precursor. The loading amount of precious metal Ru was 2 wt%, and the molar ratio of AHM and HMT was 1:8.

[0026] The sample obtained above was reduced at 700 °C for 2 h under a hydrogen flow rate. After the reduction was completed, Ar gas was introduced to cool it down. After cooling to room temperature, 1% O2-N2 was introduced for passivation for 12 h, and the obtained catalyst was Ru-Mo2C.

[0027] Example 2 The Ru-Mo2C catalyst was prepared with reference to Example 1. The difference from Example 1 was that the loading amount of the precious metal Ru in this example was 5 wt%.

[0028] Example 3 The Ru-Mo2C catalyst was prepared with reference to Example 1. The difference from Example 1 was that the molar ratio of AHM to HMT in this example was 1:4.

[0029] Example 4 The Ru-Mo2C catalyst was prepared with reference to Example 1. The difference from Example 1 is that the solvent in this example is ethylene glycol.

[0030] Example 5 The Ru-Mo2C catalyst was prepared with reference to Example 1, except that the organic carbon source in this example was sucrose, wherein the molar ratio of AHM to sucrose was 1:10.

[0031] Example 6 The Ru-Mo2C catalyst was prepared with reference to Example 5. The difference from Example 5 was that the molar ratio of AHM to sucrose in this example was 1:5.

[0032] Example 7 The Ru-Mo2C catalyst was prepared with reference to Example 5. The difference from Example 5 was that the loading amount of the precious metal Ru in this example was 5 wt%.

[0033] Example 8 The Ru-Mo2C catalyst was prepared with reference to Example 1. The difference from Example 1 is that the molybdenum source in this example is molybdenum acetylacetonate.

[0034] Example 9 The Ru-Mo2C catalyst was prepared with reference to Example 1. The difference from Example 1 is that the reduction temperature in this example is 500 °C.

[0035] Comparative Example 1 Weigh 10 g ZrOCl2•8H2O, add it to 100 ml water, stir mechanically until it is completely dissolved, add ammonia water to adjust the solution pH to 10, and then reflux at 80 °C for 12 h to completely hydrolyze ZrOCl2•8H2O. After hydrolysis, centrifuge to separate the product. In order to ensure that the Cl ions are completely washed out, the product needs to be stirred and dispersed-centrifuged several times until the upper separation droplets are in the AgNO3 solution without precipitation. Finally, the washed precipitate is dried at 130 °C overnight, calcined at 800 °C for 5 h, and marked as ZrO2.

[0036] Weigh 2 g ZrO2, add it to 40 ml water, stir it with a magnetic stirrer until it is evenly dispersed, then add 0.21 g RuCl3, stir it at 80 °C, and then add 2 mol / L KBH4 solution dropwise. 3+ The molar ratio of Ru to ZrO2 is 4:1, the metal is reduced, and finally, after multiple centrifugal washings, the precipitate is dried overnight at 130 °C to obtain the catalyst Ru / ZrO2. The loading amount of Ru in this example is 5.0 wt%. Comparative Example 2 The Ru-Mo2C catalyst was prepared with reference to Example 1. The difference from Example 1 is that the present embodiment does not contain the precious metal Ru.

[0037] The above samples were subjected to partial hydrogenation activity evaluation of benzene. The evaluation conditions were as described above. The catalytic activity test results are listed in Table 1. From the implementation results, the activity of partial hydrogenation of benzene to cyclohexene by Mo2C alone is weak, but after loading with metal Ru, its catalytic performance is significantly increased. The cyclohexene yield of the best Ru-Mo2C catalyst is much higher than that of comparative sample 1. This is mainly due to the strong interaction between Ru and Mo2C, which is conducive to the dispersion of metal Ru, thereby forming more Ru active sites on the catalyst surface. In addition, Mo2C has precious metal-like properties and can be used as a catalyst promoter to promote the formation of cyclohexene. Compared with common Ru / ZrO2, Ru-Mo2C has a higher cyclohexene yield.

[0038] Table 1 Example Benzene Partial Hydrogenation Performance Results

[0039] The technical solution of the present invention is explained through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above specific embodiments to be implemented. Any improvements made by technicians in the relevant field based on the present invention, or equivalent replacement of the materials selected by the present invention, etc., fall within the scope of protection of the patent.

Claims

1. A method for preparing a Mo2C supported catalyst, characterized in that: The method comprises the following steps: (1) adding Ru salt, molybdenum salt and organic carbon source into a solvent, stirring to dissolve, stirring to react, and vacuum drying overnight to obtain a catalyst sample precursor; (2) The catalyst sample precursor was reduced by introducing pure H2. After the reduction was completed, 1% O2-Ar mixed gas was introduced for passivation to obtain the supported Ru-based catalyst Ru-Mo2C.

2. The method for preparing the Mo2C supported catalyst according to claim 1, characterized in that: The metal Ru salt in step (1) is one or more of RuCl3, Ru(acac)3, tris(triphenylphosphine)ruthenium chloride, and Ru(NO)(NO3)3; The molybdenum salt is one or more of sodium molybdate, ammonium ... phosphomolybdate, molybdenum acetylacetonate, molybdenum chloride or molybdenum hexacarbonyl.

3. The method for preparing the Mo2C supported catalyst according to claim 1, characterized in that: In the step (1), the organic carbon source is one or more of sugars, organic amines and amides.

4. The method for preparing the Mo2C supported catalyst according to claim 1, characterized in that: In the step (1), the mass ratio of the molybdenum salt to the organic carbon source is (1-100): (1-100).

5. The method for preparing the Mo2C supported catalyst according to claim 1, characterized in that: The solvent in step (1) is one or more of ethylene glycol, deionized water and ethanol.

6. The method for preparing the Mo2C supported catalyst according to claim 1, characterized in that: The stirring reaction conditions in step (1) are 70-90 ° C for 10-15 h, and then vacuum drying at 100 ° C overnight; preferably, stirring at 80 ° C for 12 h, and then vacuum drying at 100 ° C overnight.

7. The method for preparing the Mo2C supported catalyst according to claim 1, characterized in that: The reduction temperature in step (2) is 200°C to 1000°C.

8. The method for preparing the Mo2C supported catalyst according to claim 1, characterized in that: The Ru loading amount in step (2) is 1.0 wt% to 5.0 wt%.

9. Use of the Mo2C supported catalyst prepared by the preparation method according to any one of claims 1 to 8 in the reaction of partial hydrogenation of benzene to produce cyclohexene.

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