A method for preparing a graphene-supported molybdenum catalyst

Abstract

The application discloses a method for preparing a graphene supported molybdenum catalyst, which comprises the following steps: (1) dispersing graphene oxide in concentrated phosphoric acid; (2) dispersing phosphomolybdic acid molecules in concentrated phosphoric acid; (3) mixing the dispersions obtained in steps (1) and (2) and stirring and heating; and (4) standing the dispersion obtained in step (3) and removing the concentrated phosphoric acid to obtain a graphene supported molybdenum catalyst. In the method, the graphene and the phosphomolybdic acid are easily compounded, the phosphomolybdic acid is saved, and the required equipment is relatively simple.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts, more particularly, to the preparation of graphene supported catalysts, in particular to a method for preparing graphene supported molybdenum catalysts. BACKGROUND

[0002] Graphene is an excellent support for molybdenum catalysts (Seok, Ki, Kim, et al. Mo2C / Graphene Nanocomposite As a Hydrodeoxygenation Catalyst for the Production of Diesel Range Hydrocarbons [J]. Acs Catalysis, 2015.). Oxidized graphene and phosphomolybdic acid can be directly compounded in an aqueous solution to form a corresponding catalyst (Qu Jiangying, Wang Bohui, Gao Feng, et al. Preparation and Liquid Crystal Properties of Oxidized Graphene / Phosphomolybdic Acid Composite [J]. Journal of Liaoning Normal University: Natural Science Edition, 2012, 35(3): 4.). Both the highly dispersed oxidized graphene and the phosphomolybdic acid molecules generate negative colloids in water. Due to the same electric repulsion, it is difficult to form an ideal structure of oxidized graphene adsorbing phosphomolybdic acid molecules in an aqueous solution, and a large amount of phosphomolybdic acid needs to be added to saturate the sites on the surface of graphene, resulting in waste of molybdenum elements. Another method is to use the electrochemical activity of oxidized graphene and phosphomolybdic acid molecules to make them compound in an aqueous solution under the action of an electric current (Wang Jiajun, Huang Zhihai, Sun Ting, et al. Preparation of Electrochemically Reduced Oxidized Graphene / Phosphomolybdic Acid Nanocomposite and Its Electro-catalytic Performance for Bromate [J]. Guangdong Chemical Industry, 2016, 43(10): 2.). This method is more suitable for preparing a sensitized electrode or a catalyst coating, and the mass of catalyst generated by each electrochemical reaction is small.

[0003] In view of the problem that the colloids formed by oxidized graphene and phosphomolybdic acid molecules in an aqueous solution are negatively charged and are not easy to compound, a method for preparing graphene supported molybdenum catalysts is invented. SUMMARY

[0004] In view of the problem that the colloids formed by oxidized graphene and phosphomolybdic acid molecules in an aqueous solution are negatively charged and are not easy to compound, the present application aims to provide a method for preparing graphene supported molybdenum catalysts.

[0005] The purpose of the present application is achieved by the following scheme: a method for preparing graphene supported molybdenum catalysts, comprising the following steps:

[0006] (1) Disperse the oxidized graphene in concentrated phosphoric acid.

[0007] (2) Disperse the phosphomolybdic acid molecules in concentrated phosphoric acid.

[0008] (3) Mix and stir the dispersion obtained in step (1) and step (2) and heat.

[0009] (4) Let the reaction solution obtained in step (3) stand and remove the concentrated phosphoric acid to obtain a graphene supported molybdenum catalyst.

[0010] Preferably, the step (1) and step (2) use commercially available 85% concentrated phosphoric acid.

[0011] Preferably, the heating temperature in step (3) is 75 degrees Celsius.

[0012] In the present application, the composite process occurs in concentrated phosphoric acid, avoiding the problem that graphene oxide and phosphomolybdic acid repel each other because they have the same charge. Similarly to the Hummers method (Ren Xiaomeng, Wang Yuansheng, He Te. Key technology and reaction mechanism of graphene synthesis by Hummers method [J]. Materials Engineering, 2013 (1)), graphene oxide can be intercalated by phosphoric acid molecules to form a relatively stable dispersion, and phosphomolybdic acid molecules can be stably dispersed in cold concentrated phosphoric acid, and have strong oxidizing properties in hot concentrated phosphoric acid and react with graphene oxide, the two are combined by reaction to form a composite and settle from the concentrated phosphoric acid, which can be easily separated from the generated composite by the method of standing.

[0013] Advantages of the present application:

[0014] (1) In the present method, graphene and phosphomolybdic acid are easily compounded, saving phosphomolybdic acid.

[0015] (2) The required equipment is relatively simple. DETAILED DESCRIPTION

[0016] The present application will be further described below in conjunction with specific examples. In the following examples, the experimental methods used are conventional methods unless otherwise specified. In the following examples, the materials, reagents, etc. used are commercially available unless otherwise specified. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application.

[0017] Example 1.

[0018] A graphene supported molybdenum catalyst was prepared as follows:

[0019] (1) Disperse graphene oxide in concentrated phosphoric acid:

[0020] Add 500 mg of commercially available graphene oxide and 20 mL of commercially available concentrated phosphoric acid (85%) to a 50 mL beaker, add a magnetic stirrer and stir for 20 minutes, ultrasonic treatment for 5 minutes, and then stir for 20 minutes to obtain a dispersion of graphene oxide in concentrated phosphoric acid;

[0021] (2) Disperse the phosphomolybdic acid molecules in concentrated phosphoric acid:

[0022] In a 50 mL beaker, add 50 mg of commercially available yellow phosphomolybdic acid powder, 10 mL of commercially available concentrated phosphoric acid (85%), and add a magnetic stirrer for rapid stirring for 1 h;

[0023] (3) React and compound the graphene oxide and phosphomolybdic acid in the concentrated phosphoric acid:

[0024] Immediately add the dispersion obtained in step (2) into the dispersion obtained in step (1) and stir rapidly for 4 h; keep stirring and heat the solution to 75°C and maintain the temperature for 4 h;

[0025] (4) Separate the compound: cool the reaction solution obtained in step (3), stand for 24 h; the product is settled at the bottom, use a dropper to remove the upper concentrated phosphoric acid, wash the product with a little water, and dry at 80°C to obtain a graphene supported molybdenum catalyst.

[0026] The above examples are merely examples for clearly illustrating the present application, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing a graphene-supported molybdenum catalyst, characterized in that, Includes the following steps: (1) Disperse graphene oxide in concentrated phosphoric acid; (2) Disperse phosphomolybdic acid molecules in concentrated phosphoric acid; (3) Mix the dispersions obtained in steps (1) and (2) and stir and heat them; (4) The dispersion obtained in step (3) was allowed to stand and concentrated phosphoric acid was removed to obtain a graphene-supported molybdenum catalyst; wherein, 85% concentrated phosphoric acid is used in steps (1) and (2); The reaction temperature in step (3) is 75 degrees Celsius.

2. The method for preparing a graphene-supported molybdenum catalyst according to claim 1, characterized in that, A graphene-supported molybdenum catalyst was prepared according to the following steps: (1) Disperse graphene oxide in concentrated phosphoric acid: Add 500 mg of commercially available graphene oxide and 20 mL of commercially available concentrated phosphoric acid (85% concentration) to a 50 mL beaker, add a magnetic stir bar and stir rapidly for 20 minutes, sonicate for 5 minutes, and then stir for another 20 minutes to obtain a dispersion of graphene oxide in concentrated phosphoric acid. (2) Disperse phosphomolybdic acid molecules in concentrated phosphoric acid: Add 50 mg of commercially available yellow phosphomolybdic acid powder and 10 mL of commercially available concentrated phosphoric acid (85% concentration) to a 50 mL beaker, and stir rapidly with a magnetic stir bar for 1 h. (3) Graphene oxide and phosphomolybdic acid react to form a composite in concentrated phosphoric acid: Immediately add all of the dispersion obtained in step (2) to the dispersion obtained in step (1) and stir rapidly for 4 h; keep stirring and heat the solution to 75°C and maintain this temperature for 4 h. (4) Separation of the complex: Cool the reaction solution obtained in step (3) and let it stand for 24 h; the product settles to the bottom, and the upper layer of concentrated phosphoric acid is removed with a dropper. Add a little water to wash the product and dry it at 80°C to obtain the graphene-supported molybdenum catalyst.