Catalyst for preparing nano carbon material from methane and preparation method of catalyst

Abstract

The invention discloses a catalyst for preparing a nano carbon material from methane and a preparation method of the catalyst, a hydroxycarboxylic acid chelating agent and polyhydroxy alcohol are added into an active component solution of various active metal salt components at one time to obtain a precursor, and then the precursor is dried and roasted to obtain the catalyst. The catalyst with multiple active components is prepared by adopting a polymer precursor method, and perovskite type metal oxide is selected as a carrier of an active substance, so that relatively strong interaction between metal and the carrier exists between the active components and the metal oxide carrier, and uniform dispersion and size control of catalyst particles are realized; the low-temperature activity and the carbon deposition resistance of the catalyst are improved, so that the low-temperature preparation of the nano carbon material is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of heterogeneous catalysis, and specifically relates to a catalyst for preparing nano-carbon materials from methane and a preparation method thereof. Background Art

[0002] Nanocarbon materials refer to carbon materials with at least one dimension of the dispersed phase smaller than 100nm. Nanocarbon materials mainly include three types: carbon nanotubes, carbon nanofibers and nanocarbon balls. Nanocarbon materials are a new type of carbon material with excellent physical and chemical properties. They can be widely used in many fields such as electricity, electronics, super-lubricating materials, ultra-high-strength materials, electrode materials, protective coatings, catalyst carriers, etc., and have broad development and application prospects.

[0003] At present, there are three most commonly used methods for preparing nanocarbon materials, namely arc discharge method, laser evaporation method and catalytic cracking method. Arc discharge method and laser evaporation method both use graphite as raw material, which is expensive, has poor controllability over the microstructure of nanocarbon materials, and has insufficient product output and quality; catalytic cracking method uses methane and other carbon-containing gases as raw materials, and is a process of gradual dehydrogenation, mainly including methane activation, carbon nucleus generation, and carbon nanotube / fiber growth. To achieve the maximum conversion rate, the temperature needs to be raised to 1300°C. If a suitable catalyst is used, the optimal reaction temperature can be greatly reduced, while the reaction efficiency can be improved. The feasibility of methane catalytic cracking process depends largely on the efficiency and durability of the catalyst. At present, a lot of work is focused on the selection of catalyst carriers and the preparation of catalysts. Summary of the invention

[0004] The present invention is proposed to solve the problem of low low temperature activity of the catalyst for preparing nano-carbon materials by catalytic cracking of methane prepared by the existing preparation method, and its purpose is to provide a catalyst for preparing nano-carbon materials from methane and a preparation method thereof.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing a catalyst for preparing nano-carbon materials from methane comprises the following steps:

[0007] (I) Weighing an active component salt and adding it to deionized water to prepare an active component solution;

[0008] (II) adding a hydroxycarboxylic acid chelating agent to the active component solution, stirring and dissolving the mixture at room temperature to obtain a mixed solution;

[0009] (III) adding a polyhydric alcohol to the mixed solution obtained in step (II), stirring and dissolving the mixture at room temperature to obtain a precursor;

[0010] (IV) After the precursor obtained in step (III) is fully dried, it is calcined to obtain a catalyst for preparing nano-carbon materials using methane.

[0011] In the above technical solution, the active component salt includes multiple types of soluble lanthanum salts, soluble nickel salts, soluble magnesium salts, soluble cobalt salts and soluble iron salts.

[0012] In the above technical solution, the mass concentration of the active component salt in the active component solution is 4% to 10%.

[0013] In the above technical solution, the hydroxycarboxylic acid chelating agent is any one or more of citric acid, tartaric acid or gluconic acid.

[0014] In the above technical solution, the molar amount of the hydroxycarboxylic acid chelating agent is 1 to 2 times the molar amount of the total cations.

[0015] In the above technical solution, the polyhydric alcohol is ethylene glycol and / or propylene glycol.

[0016] In the above technical solution, the molar amount of the polyhydric alcohol is 1 to 2 times the molar amount of the total cations.

[0017] In the above technical solution, the drying temperature in step (IV) is 90°C to 120°C; the calcination condition in step (IV) is calcination at 700°C to 900°C for 4 hours.

[0018] A catalyst for preparing nano-carbon materials from methane is a perovskite catalyst whose active components are La-Ni-Mg-B.

[0019] In the above technical solution, the chemical formula of the catalyst is La 2-x Mg x NiBO 6 , where: B = Co or Fe, x = 0, 0.5, 1 or 1.5.

[0020] The beneficial effects of the present invention are:

[0021] The present invention provides a multi-metal catalyst for preparing nano-carbon materials from methane with high activity at low temperature and a preparation method thereof. A polymer precursor method is adopted to prepare catalysts with multiple active components, and a perovskite-type metal oxide is selected as a carrier of the active substance. During preparation, the metal oxide enters the main lattice of the perovskite and is dissolved onto the surface of the perovskite during reduction in a hydrogen atmosphere. In this way, a strong metal-carrier interaction is achieved between the active component and the metal oxide carrier. After pre-reduction, highly dispersed catalyst metal particles with uniform particle size can be obtained, thereby achieving uniform dispersion and size control of the catalyst particles, improving the low-temperature activity and carbon deposition resistance of the catalyst, and thus achieving low-temperature preparation of the nano-carbon material. DETAILED DESCRIPTION

[0022] In order to enable persons skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below through specific implementation methods.

[0023] Example 1

[0024] A method for preparing a catalyst for preparing nano-carbon materials from methane comprises the following steps:

[0025] (I) 4.86 g of lanthanum nitrate, 1.83 g of nickel nitrate, 1.83 g of cobalt nitrate, and 0.74 g of magnesium nitrate were added to a certain amount of deionized water to prepare a 100 g active component solution;

[0026] (II) adding 7.68 g of citric acid to aqueous solution A and stirring and dissolving the mixture at room temperature to obtain a mixed solution;

[0027] (III) adding 5 g of ethylene glycol to the mixed solution and stirring and dissolving the mixture at room temperature to obtain a precursor;

[0028] (IV) After the precursor is fully dried at 100°C, the temperature is raised to 750°C and calcined for 4 hours to obtain the catalyst.

[0029] Example 2

[0030] A method for preparing a catalyst for preparing nano-carbon materials from methane comprises the following steps:

[0031] (I) 3.24 g of lanthanum nitrate, 1.83 g of nickel nitrate, 2.41 g of ferrous nitrate, and 1.48 g of magnesium nitrate were added to a certain amount of deionized water to prepare a 100 g active component solution;

[0032] (II) adding 8.9 g of citric acid to aqueous solution A and stirring and dissolving the mixture at room temperature to obtain a mixed solution;

[0033] (III) adding 5 g of propylene glycol to the mixed solution and stirring and dissolving the mixture at room temperature to obtain a precursor;

[0034] (IV) After the precursor is fully dried at 110°C, the temperature is raised to 800°C and calcined for 4 hours to obtain the catalyst.

[0035] Example 3

[0036] A method for preparing a catalyst for preparing nano-carbon materials from methane comprises the following steps:

[0037] (I) 5.48 g of lanthanum nitrate, 1.83 g of nickel nitrate, and 1.41 g of ferrous nitrate were added to a certain amount of deionized water to prepare a 100 g active component solution;

[0038] (II) adding 9 g of citric acid to aqueous solution A and stirring and dissolving the mixture at room temperature to obtain a mixed solution;

[0039] (III) adding 5 g of propylene glycol to the mixed solution and stirring and dissolving the mixture at room temperature to obtain a precursor;

[0040] (IV) After the precursor is fully dried at 110°C, the temperature is raised to 900°C and calcined for 4 hours to obtain the catalyst.

[0041] Example 4

[0042] A method for preparing a catalyst for preparing nano-carbon materials from methane comprises the following steps:

[0043] (I) 1.62 g of lanthanum nitrate, 1.83 g of nickel nitrate, 1.83 g of cobalt nitrate, and 2.22 g of magnesium nitrate were added to a certain amount of deionized water to prepare a 100 g active component solution;

[0044] (II) adding 10 g of citric acid to aqueous solution A and stirring and dissolving the mixture at room temperature to obtain a mixed solution;

[0045] (III) adding 3 g of ethylene glycol to the mixed solution and stirring and dissolving the mixture at room temperature to obtain a precursor;

[0046] (IV) After the precursor is fully dried at 110°C, the temperature is raised to 900°C and calcined for 4 hours to obtain the catalyst.

[0047] Performance testing:

[0048] The catalysts prepared in Examples 1 to 4 were crushed, and 0.5 g of the catalysts for preparing nano-carbon materials from methane with a mesh size of 80 to 100 were weighed and loaded into the constant temperature zone of the CVD horizontal quartz tube reactor. After the air tightness test, the catalysts for preparing nano-carbon materials from methane were first placed in a hydrogen atmosphere at 700 °C (50 cm 3 / min) for 2h, cooled to room temperature after reduction, and then heated to 20cm 3 Methane was decomposed at a flow rate of 1 / min, and the solid carbon after the reaction was collected and calculated.

[0049] Catalyst carbon yield = mass of generated carbon material / (CH 4 Volume flux × reaction time ÷ 1000 ÷ 22.4 × 12)

[0050] Table 1 Catalytic effect of catalysts in Examples 1-4

[0051] Example Catalyst carbon yield Example 1 <![CDATA[1.42g / gcath -1 ]]> Example 2 <![CDATA[1.15g / gcath -1 ]]> Example 3 <![CDATA[1.08g / gcath -1 ]]> Example 4 <![CDATA[1.35g / gcath -1 ]]>

[0052] It can be seen from Table 1 that the catalysts for preparing nano-carbon materials from methane prepared in Examples 1 to 4 of the present invention have high low-temperature activity and can meet the requirements for efficient conversion of methane to prepare nano-carbon materials.

[0053] Principle of the present invention:

[0054] The active component in the catalyst prepared by the method of the present invention is La-Ni-Mg-B (B is Fe or Co). Due to the unique 3d orbital properties of Fe, Co and Ni, they exhibit high catalytic activity and low cost, and are ideal active components. Various metal active components are introduced into the perovskite structure through the polymer precursor method. The special structure and the synergy between the metals make the active metals reach a highly dispersed state and have high low-temperature activity. At the same time, the introduction of Mg element into the perovskite can generate more oxygen vacancies, so that the active metal reduction is more complete, and the low-temperature activity of the catalyst is improved.

[0055] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a catalyst for preparing nano-carbon materials from methane, characterized in that: The following steps are involved: (I) Weighing an active component salt and adding it to deionized water to prepare an active component solution; (II) adding a hydroxycarboxylic acid chelating agent to the active component solution, stirring and dissolving the mixture at room temperature to obtain a mixed solution; (III) adding a polyhydric alcohol to the mixed solution obtained in step (II), stirring and dissolving the mixture at room temperature to obtain a precursor; (IV) After the precursor obtained in step (III) is fully dried, it is calcined to obtain a catalyst for preparing nano-carbon materials using methane.

2. The method for preparing a catalyst for preparing nano-carbon materials from methane according to claim 1, characterized in that: The active component salt includes multiple types of soluble lanthanum salts, soluble nickel salts, soluble magnesium salts, soluble cobalt salts and soluble iron salts.

3. The method for preparing a catalyst for preparing nano-carbon materials from methane according to claim 1, characterized in that: The mass concentration of the active component salt in the active component solution is 4% to 10%.

4. The method for preparing a catalyst for preparing nano-carbon materials from methane according to claim 1, characterized in that: The hydroxycarboxylic acid chelating agent is any one or more of citric acid, tartaric acid or gluconic acid.

5. The method for preparing a catalyst for preparing nano-carbon materials from methane according to claim 1, characterized in that: The molar amount of the hydroxycarboxylic acid chelating agent is 1 to 2 times the total molar amount of cations in the active component salt.

6. The method for preparing a catalyst for preparing nano-carbon materials from methane according to claim 1, characterized in that: The polyhydric alcohol is ethylene glycol and / or propylene glycol.

7. The method for preparing a catalyst for preparing nano-carbon materials from methane according to claim 1, characterized in that: The molar amount of the polyhydric alcohol is 1 to 2 times the total molar amount of cations in the active component salt.

8. The method for preparing a catalyst for preparing nano-carbon materials from methane according to claim 1, characterized in that: The drying temperature in the step (IV) is 90°C to 120°C; the calcination condition in the step (IV) is calcination at 700°C to 900°C for 4 hours.

9. A catalyst for preparing nano-carbon materials from methane prepared by the method according to any one of claims 1 to 8, characterized in that: The catalyst is a perovskite catalyst whose active component is La-Ni-Mg-B.

10. The catalyst for preparing nano-carbon materials from methane according to claim 9, characterized in that: The chemical formula of the catalyst is La 2-x Mg x NiBO6, wherein: B = Co or Fe, x = 0, 0.5, 1 or 1.5.