Catalyst for hydrogen production through natural gas steam reforming and preparation method and application thereof

Abstract

The invention discloses a natural gas steam reforming hydrogen production catalyst and a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: S1, alkali treatment of the beta molecular sieve; s2, preparation of a carrier: adding hexadecyl trimethyl ammonium bromide as a template agent into the reaction mixture containing the silicon source, then adding an acid solution to adjust the pH value to 9.6, then putting into a reaction kettle, carrying out hydrothermal crystallization for 24-72 hours at the temperature of 100-150 DEG C, carrying out suction filtration to obtain a solid, and washing, drying and calcining the solid to obtain the carrier; and S3, loading of a nickel-based active component: loading nickel on the carrier by using a nickel salt precursor solution and adopting an impregnation method, and then drying and calcining to obtain the catalyst for hydrogen production by natural gas steam reforming. The catalyst disclosed by the invention can realize effective utilization of natural gas resources in a catalytic conversion manner, and the natural gas resources are converted into an environment-friendly fuel or chemical raw material product, namely hydrogen, so that considerable benefits can be brought while resource utilization is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas steam reforming hydrogen production, and in particular to a catalyst for natural gas steam reforming hydrogen production, and a preparation method and application thereof. Background Art

[0002] As people's environmental awareness gradually improves, they pay more and more attention to the development of low-carbon energy. Hydrogen is widely regarded as a low-carbon energy carrier in the future due to its high specific energy and clean combustion products. Although "green hydrogen" with nearly zero carbon emissions can be obtained through offshore wind power, photovoltaics and other energy supply methods, electrolysis hydrogen production technology is still in the development stage and the price is relatively high. It currently accounts for less than 4% of the total hydrogen production. Therefore, from a cost perspective, most hydrogen is obtained through the path of hydrogen production from fossil energy.

[0003] In the global field, hydrogen production from natural gas accounts for 50% of the total annual hydrogen production, which includes thermal cracking hydrogen production, natural gas dry gas reforming, natural gas steam reforming and other routes. Natural gas steam reforming is one of the more mature fossil energy hydrogen production technologies. Compared with other processes, methane steam reforming hydrogen production has the advantage of low carbon dioxide emissions. Methane is the simplest alkane and the main component of natural gas. It is also used directly as an energy source and is one of the basic raw materials for modern chemical industry. In addition, due to the introduction of unconventional natural gas development technologies such as methane hydrate and shale gas in recent years, it has also provided a wide range of raw material sources for natural gas hydrogen production reactions. Therefore, the natural gas steam reforming process is currently the main route for hydrogen production.

[0004] Steam methane reforming (SMR) is generally considered to be a two-step reaction. First, methane reacts with water vapor to form carbon monoxide and hydrogen. The generated carbon monoxide undergoes a water gas reaction under reaction conditions. In current research, it is widely believed that the breaking of the CH bond of CH4 is the rate-controlling step in the reaction. However, under low temperature conditions of 500°C, the rate-controlling step of the reaction is transformed into a process in which carbon and oxygen active species combine to form CO. From the perspective of the thermodynamics of the reaction, the overall reaction is an endothermic reaction, so high temperature conditions of 700-850°C are required to make the reaction proceed in the forward direction.

[0005] In summary, the natural gas steam reforming reaction can achieve high-value utilization of natural gas and alleviate the difficulty of natural gas resource utilization. However, the natural gas steam reforming reaction now has problems such as easy carbon deposition and easy loss of active metals caused by water vapor. The multi-level pore structure formed by the eutectic molecular sieve can increase the carbon deposition capacity and improve the catalyst life. Therefore, the natural gas steam reforming reaction catalyzed by this catalyst has a good application prospect. Summary of the invention

[0006] The main purpose of the present invention is to provide a catalyst for hydrogen production by steam reforming of natural gas with better activity and stronger carbon deposition resistance, as well as a preparation method and application thereof.

[0007] To achieve the above object, the present invention provides a method for preparing a catalyst for hydrogen production by natural gas steam reforming, comprising the following steps:

[0008] S1: Alkali treatment of β molecular sieve

[0009] The beta molecular sieve is mixed with an alkali solution, and stirred at a temperature of 30 to 70° C. for 30 to 100 minutes to obtain a reaction mixture containing a silicon source;

[0010] S2: Preparation of vector

[0011] Adding hexadecyltrimethylammonium bromide as a template to a reaction mixture containing a silicon source, and then adding an acid solution to adjust the pH value to 9.6, and then placing it in a reaction kettle, hydrothermally crystallizing it at a temperature of 100 to 150° C. for 24 to 72 hours, filtering to obtain a solid, and washing, drying, and calcining the solid to obtain a carrier;

[0012] S3: Loading of nickel-based active components

[0013] A nickel salt precursor solution is used to load nickel on a carrier by an impregnation method, and then the catalyst for hydrogen production by steam reforming of natural gas is obtained through drying and calcination.

[0014] Furthermore, in step S1, the silicon-aluminum ratio of the β molecular sieve is 20-60, the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution with a concentration of 0.5-2.5 mol / L, and the mass volume ratio of the β molecular sieve to the alkali solution is 100 g:0.7 L.

[0015] Furthermore, in step S2, hexadecyltrimethylammonium bromide is added in a solid state or a solution state. When added in a solution state, a 25 wt% hexadecyltrimethylammonium bromide solution is prepared, and the volume mass ratio of the solution to the β molecular sieve is 0.3-0.35L:100g.

[0016] Furthermore, in step S2, the acid solution is any one of formic acid, acetic acid, oxalic acid, sulfuric acid, and hydrochloric acid, or a mixture of two or more of them in any proportion.

[0017] Furthermore, in step S2, the drying temperature is 100-120°C, the drying time is 6-12 hours, the calcination temperature is 530-570°C, and the calcination time is 6-18 hours.

[0018] Furthermore, in step S3, the concentration of the nickel salt precursor solution is 1-10 mol / L, and the nickel salt precursor is any one of nickel nitrate, nickel oxalate, nickel acetate, and nickel formate, or a mixture of two or more of them in any proportion.

[0019] Furthermore, in step S3, the immersion method uses any one of water, ethanol and methanol or a mixture of two or more of them in any proportion as a solvent, and 1 mL / L of nitric acid is added as an acidifier during the solvent preparation process.

[0020] Furthermore, in step S3, the drying temperature is 80-120°C, the drying time is 4-10 hours, the calcination temperature is 300-400°C, the calcination time is 2-8 hours, and the calcination atmosphere is any one of air, oxygen, and nitrogen, or a mixture of two or more in any proportion.

[0021] Furthermore, in step S3, the nickel loading, that is, the content of nickel atoms in the catalyst is 5-10 wt%.

[0022] The present invention also provides a catalyst for hydrogen production by steam reforming of natural gas, which is prepared according to the above preparation method.

[0023] The present invention also provides the use of the above catalyst in catalyzing the reforming reaction of natural gas and water vapor.

[0024] The beneficial effects of the present invention are embodied in:

[0025] The present invention desiliconizes the commercial β molecular sieve by alkali treatment, uses it as the silicon source for the subsequent carrier synthesis, and then uses the template agent to form a microporous-mesoporous multi-level pore zeolite as a carrier. This structure can not only ensure that the active metal is firmly loaded on the carrier, but also increase the capacity for carbon deposition and have good mass transfer capacity. The nickel active center has a high ability to catalyze the breaking of the CH bond, thereby improving the activity of the reforming reaction.

[0026] The catalyst of the present invention can realize the effective utilization of natural gas resources by catalytic conversion, and convert it into hydrogen, an environmentally friendly fuel or chemical raw material product, thereby realizing resource utilization and bringing considerable benefits. DETAILED DESCRIPTION

[0027] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0028] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods; unless otherwise specified, the methods used in the examples of the present invention are methods known to those skilled in the art. Among them, the silicon-aluminum ratio of the β molecular sieve is 30-35, and the specific surface area and other characteristics are shown in Table 1.

[0029] Example 1

[0030] Preparation of catalyst for hydrogen production from natural gas steam reforming

[0031] Preparation The preparation method is as follows:

[0032] S1: Alkali treatment of β molecular sieve

[0033] Weigh 500 g of β molecular sieve into a beaker, then add 3.5 L of 1.0 mol / L sodium hydroxide aqueous solution into the beaker, stir evenly with a mechanical stirrer, and heat to 40° C. and keep stirring for 50 min to obtain a reaction mixture containing a silicon source;

[0034] S2: Preparation of vector

[0035] 1.75 L of 25 wt% hexadecyltrimethylammonium bromide aqueous solution as a template was added to the reaction mixture containing the silicon source in a beaker, and the mixture was stirred until completely mixed, and then a 50 wt% acetic acid aqueous solution was added to adjust the pH value of the system to 9.6, and then the mixture was placed in a reactor and subjected to hydrothermal crystallization reaction at 100° C. for 48 h. After the reaction was completed, the solid was filtered to obtain a solid, which was washed with deionized water, and then dried at 100° C. for 9 h. Finally, the solid was placed in a muffle furnace and calcined at 550° C. for 6 h to remove the template, thereby obtaining a carrier, which was recorded as β / MCM-41.

[0036] S3: Loading of nickel-based active components

[0037] According to the nickel loading amount of 5wt%, an aqueous solution of nickel nitrate with a concentration of 5mol / L was used as the impregnation solution, and the carrier was added and stirred for two hours for impregnation. After the impregnation was completed, it was placed in a 100°C oven to dry for 12 hours, and finally placed in a muffle furnace at a temperature of 350°C for calcination for 4 hours to decompose the precursor salt to obtain a catalyst for hydrogen production from natural gas steam reforming.

[0038] The specific surface area, pore volume, etc. of the raw material β molecular sieve and the β / MCM-41 eutectic molecular sieve prepared in this example were tested by nitrogen adsorption method. The results are shown in Table 1 below.

[0039] Table 1

[0040]

[0041] Example 2

[0042] Preparation of catalyst for hydrogen production from natural gas steam reforming

[0043] In this example, the catalyst was prepared according to the preparation method of Example 1, except that in step S1, 3.5 L of 1.5 mol / L sodium hydroxide solution was added to beaker A, stirred evenly with a mechanical stirrer, and heated to 40° C. and stirred for 50 min.

[0044] Example 3

[0045] Preparation of catalyst for hydrogen production from natural gas steam reforming

[0046] In this embodiment, the catalyst is prepared according to the preparation method of embodiment 1, except that in step S2, 1.5 L of 25 wt% hexadecyltrimethylammonium bromide aqueous solution is added to the obtained mixture as a template.

[0047] Example 4

[0048] Preparation of catalyst for hydrogen production from natural gas steam reforming

[0049] In this embodiment, the catalyst is prepared according to the preparation method of embodiment 1, except that 50 wt % of a mixed solution of formic acid and acetic acid is added in step S2 to adjust the pH to 9.6.

[0050] Example 5

[0051] Preparation of catalyst for hydrogen production from natural gas steam reforming

[0052] In this embodiment, the catalyst is prepared according to the preparation method of embodiment 1, with the only difference being that in step S2, hydrothermal crystallization is performed at a temperature of 120° C. for 48 h.

[0053] Example 6

[0054] Preparation of catalyst for hydrogen production from natural gas steam reforming

[0055] In this embodiment, the catalyst is prepared according to the preparation method of embodiment 1, with the only difference being that in step S2, hydrothermal crystallization is performed at a temperature of 100° C. for 72 hours.

[0056] Example 7

[0057] Preparation of catalyst for hydrogen production from natural gas steam reforming

[0058] In this embodiment, the catalyst is prepared according to the preparation method of embodiment 1, with the only difference being that in step S3, a 5 mol / L nickel acetate aqueous solution is used as the impregnation solution.

[0059] Example 8

[0060] Preparation of catalyst for hydrogen production from natural gas steam reforming

[0061] In this example, the catalyst was prepared according to the preparation method of Example 1, except that the loading amount of nickel was 10 wt %.

[0062] Comparative Example 1

[0063] Preparation of catalysts for comparison

[0064] The preparation steps are as follows:

[0065] Prepare a 5 mol / L nickel nitrate aqueous solution as the impregnation solution, weigh 25 g of β molecular sieve as a carrier, add the prepared impregnation solution at a nickel loading of 5 wt%, and stir for two hours for impregnation. After the impregnation is completed, place it in a 100°C oven to dry for 12 hours, and then place it in a muffle furnace and calcine it at 350°C for 4 hours.

[0066] Comparative Example 2

[0067] Preparation of catalysts for comparison

[0068] The preparation steps are as follows:

[0069] The operation process of this comparative example is the same as that of Example 1, except that in step S2:

[0070] To the reaction mixture containing the silicon source in the beaker, add 1.75 L of a 25 wt% aqueous solution of hexadecyltrimethylammonium bromide as a template, stir until completely mixed, and then add a 50 wt% aqueous solution of acetic acid to adjust the pH value of the system to 9.6. Then, place it in a reactor and stir at 50°C for 48 hours. After the reaction is completed, filter out the solid, wash the solid with deionized water, and then dry it at 100°C for 9 hours. Finally, place it in a muffle furnace and calcine it at 550°C for 6 hours to remove the template to obtain a carrier.

[0071] Catalyst performance evaluation

[0072] The performance evaluation of the catalyst was carried out on a 30mL micro fixed bed reactor. 20g of catalyst sample and 50mL of quartz sand were weighed and loaded into the middle section of the reactor. Porcelain balls or quartz wool were used to support both ends. 25% H2 / N2 was continuously introduced under programmed temperature, and the catalyst was reduced at 700℃ for 2h. The reaction gas was introduced, the feed ratio of raw methane to hydrogen was 1:1, and the reaction gas space velocity was 80L / g cat h, and the reaction temperature was 700° C. Sampling and analysis were performed 1 h after the reaction started to ensure that the reaction operation reached stability. The experimental results of the catalysts prepared in various embodiments and comparative examples are shown in Table 2.

[0073] Table 2

[0074]

[0075]

[0076] The catalyst prepared in the following example was used for evaluation of methane-steam reforming reaction, except that the reaction gas ratio was adjusted. The evaluation process was the same as above, and the results are listed in Table 3.

[0077] Table 3

[0078]

[0079] From the above, it can be seen that the catalyst used in the present invention uses nickel as the active center and uses a microporous-mesoporous multi-level zeolite as a carrier to ensure the smooth diffusion of reactants while increasing the carbon deposition capacity, thereby improving the stability of the catalyst. The catalyst provided by the present invention has a unique multi-level pore structure, the internal nickel-based active metal is evenly distributed, and the appropriate pore structure and metal active center are conducive to improving the catalytic activity of the catalyst for the methane-steam reforming reaction.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for hydrogen production by steam reforming of natural gas, characterized in that: The following steps are involved: S1: Alkali treatment of β molecular sieve The beta molecular sieve is mixed with an alkali solution, and stirred at a temperature of 30 to 70° C. for 30 to 100 minutes to obtain a reaction mixture containing a silicon source; S2: Preparation of vector Adding hexadecyltrimethylammonium bromide as a template to a reaction mixture containing a silicon source, and then adding an acid solution to adjust the pH value to 9.6, and then placing it in a reaction kettle, hydrothermally crystallizing it at a temperature of 100 to 150° C. for 24 to 72 hours, filtering to obtain a solid, and washing, drying, and calcining the solid to obtain a carrier; S3: Loading of nickel-based active components A nickel salt precursor solution is used to load nickel on a carrier by an impregnation method, and then the catalyst for hydrogen production by steam reforming of natural gas is obtained through drying and calcination.

2. The method for preparing a catalyst for hydrogen production by steam reforming of natural gas according to claim 1, characterized in that: In step S1, the silicon-aluminum ratio of the β molecular sieve is 20-60, the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution with a concentration of 0.5-2.5 mol / L, and the mass volume ratio of the β molecular sieve to the alkali solution is 100 g:0.7 L.

3. The method for preparing a catalyst for hydrogen production by steam reforming of natural gas according to claim 1, characterized in that: In step S2, hexadecyltrimethylammonium bromide is added in a solid state or a solution state. When added in a solution state, a 25 wt% hexadecyltrimethylammonium bromide solution is prepared, and the volume mass ratio of the solution to the β molecular sieve is 0.3-0.35L:100g.

4. The method for preparing a catalyst for hydrogen production by steam reforming of natural gas according to claim 1, characterized in that: In step S2, the acid solution is any one of formic acid, acetic acid, oxalic acid, sulfuric acid, and hydrochloric acid, or a mixture of two or more of them in any proportion.

5. The method for preparing a catalyst for hydrogen production by steam reforming of natural gas according to claim 1, characterized in that: In step S2, the drying temperature is 100-120°C, the drying time is 6-12 hours, the calcination temperature is 530-570°C, and the calcination time is 6-18 hours.

6. The method for preparing a catalyst for hydrogen production by steam reforming of natural gas according to claim 1, characterized in that: In step S3, the concentration of the nickel salt precursor solution is 1-10 mol / L, and the nickel salt precursor is any one of nickel nitrate, nickel oxalate, nickel acetate, and nickel formate, or a mixture of two or more of them in any proportion.

7. The method for preparing a catalyst for hydrogen production by natural gas steam reforming according to claim 1, characterized in that: In step S3, the nickel salt precursor solution uses any one of water, ethanol and methanol or a mixture of two or more of them in any proportion as a solvent, and 1 mL / L of nitric acid is added as an acidifier during the solvent preparation process.

8. The method for preparing a catalyst for hydrogen production by steam reforming of natural gas according to claim 1, characterized in that: In step S3, the drying temperature is 80-120°C, the drying time is 4-10 hours, the calcination temperature is 300-400°C, the calcination time is 2-8 hours, and the calcination atmosphere is any one of air, oxygen, and nitrogen, or a mixture of two or more in any proportion.

9. A catalyst for hydrogen production from natural gas steam reforming, characterized in that: Prepared according to the preparation method as described in any one of claims 1 to 8.

10. Use of the catalyst according to claim 9 in catalyzing the reforming reaction of natural gas and water vapor.

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