CN114471636A - A kind of preparation method of supported nickel-based catalyst and application thereof - Google Patents

Abstract

The application discloses a preparation method and application of a supported nickel-based catalyst, Ca (NO) is added₃)₂·4H₂O，NH₄H₂PO₄Respectively dissolving the two solutions in deionized water, mixing the two solutions, dropwise adding 25% vol ammonia water, heating and stirring, filtering and washing the obtained suspension to be neutral, drying at 80-100 ℃, and calcining the solid in air at 400 ℃ for 3-5 hours to obtain a carrier; ni (NO)₃)₂·6H₂Dissolving O in deionized water, pouring the carrier into the nickel precursor solution, violently stirring at room temperature, dropwise adding 25% vol ammonia water, and stirring at room temperature; filtering and washing the suspension until the filtrate is neutral, drying the obtained solid at 80-100 ℃, calcining the dried solid in air at 400-500 ℃ for 3-5 hours to obtain the supported nickel-based catalyst Ni_x/Ca_10‑x(PO₄)₆(OH)₂。

Description

A kind of preparation method of supported nickel-based catalyst and application thereof

technical field

The present application relates to the technical field of preparation of nickel-based catalysts, in particular to a preparation method and application of a supported nickel-based catalyst.

Background technique

The greenhouse effect problem caused by the massive consumption of fossil energy has begun to emerge. The efficient utilization of _CO2 , which is the most important greenhouse gas, has attracted extensive attention. Among them, the dry methane reforming technology of _CO2 and _CH4 to prepare CO and _H2 has received great attention. Methane dry reforming technology not only utilizes two greenhouse gases, CH ₄ and CO ₂ at the same time, and the theoretical ratio of CO and H ₂ in its product is 1:1. It is also an ideal raw material for synthesizing liquid carbonaceous fuels through technologies such as Fischer-Tropsch synthesis. , the application potential is huge.

Methane dry reforming catalysts are mainly divided into noble metal catalysts (Ru, Pt, Pd, Rh) and non-precious metal catalysts (Ni, Co, Cu, Fe). Noble metal catalysts have excellent catalytic activity for methane dry reforming, and the catalysts have good anti-coking properties, but the expensive cost of noble metals limits large-scale industrial applications. Among the non-precious metal catalysts, nickel-based catalysts have the highest cracking activity for methane, but nickel-based catalysts still have two problems in dry reforming of methane. On the one hand, nickel-based catalysts are easily sintered and deactivated during the high-temperature reaction process (the methane dry reforming reaction usually needs to be carried out above 700°C), and on the other hand, the nickel-based active sites are easily covered by carbon deposits generated by methane cracking during the reaction process. resulting in deactivation of the catalyst. There are two reasons for these two problems. One is that the active site of nickel is not stable enough, and the aggregates migrate and sinter during the reaction process. The other is that the cracking rate of _CH4 is too fast, resulting in the formation of a large number of inert carbon species, thus covering the active site. site. Therefore, it is crucial to prepare catalysts with strong metal _- support interactions and to ensure that the CH cracking rate matches the _CO conversion rate.

In order to solve the problems of high temperature sintering and carbon deposition in the methane dry reforming reaction, the present invention intends to use calcium-deficient hydroxyapatite as a carrier to prepare a metal-support interaction, high catalytic activity, catalytic stability, and Supported nickel-based catalysts with anti-carbon deposition properties.

Application content

Technical problems solved:

The technical problem to be solved in this application is the technical problems such as high-temperature sintering and carbon deposition in the dry reforming reaction of methane in the prior art. To provide a preparation method and application of a supported nickel-based catalyst, a cationic starch-based catalyst is used. The flocculant St-CTA uses the flocculation-precipitation process to classify and precipitate the lignin of different molecular weights in the black liquor, so that the molecular weight distribution is controllable, so as to facilitate the comprehensive utilization of the resources of the subsequent lignin products.

Technical solutions:

A preparation method of a supported nickel-based catalyst, firstly prepares a calcium-deficient hydroxyapatite carrier by a co-precipitation method, and then supports active metal nickel by an impregnation method, specifically comprising the following steps:

The first step: Dissolve Ca(NO ₃ ) ₂ ·4H ₂ O and NH ₄ H ₂ PO ₄ in deionized water, respectively, and control the Ca/P molar ratio to 8-10/6. Mixing, adding 25% vol ammonia water dropwise at room temperature and vigorously stirring to adjust the pH of the mixed solution to 10±1, heating and stirring, controlling the heating temperature to 60-90 °C, and controlling the stirring time to 2-4 hours;

The second step: after the stirring is completed, the obtained suspension is filtered and washed to neutrality and then dried at 80-100 ℃, and the dried solid is calcined in the air at 300-400 ℃ for 3-5 hours to obtain calcium-deficient hydroxyapatite Carrier (chemical formula: Ca _10-x (PO ₄ ) ₆ (OH) ₂ , 0<x<2);

The third step: Dissolve Ni(NO ₃ ) ₂ ·6H ₂ O in deionized water to prepare a nickel precursor solution, pour the calcium-deficient hydroxyapatite carrier into the nickel precursor solution, and the moles of Ni and Ca are equal to each other. and is 10;

Step 4: Stir vigorously at room temperature, add 25% vol ammonia water dropwise to adjust the pH of the mixed solution to 10±1, and stir at 80°C for 2-4 hours;

The fifth step: filter and wash the suspension until the filtrate is neutral, the obtained solid is dried, and the dried solid is calcined in air at 400-500 ° C for 3-5 hours to obtain a supported nickel-based catalyst Ni _x /Ca _10-x ( PO ₄ ) ₆ (OH) ₂ ; 0<x<2.

As a preferred technical solution of the present application: in the first step, the mass ratio of calcium nitrate tetrahydrate Ca(NO ₃ ) ₂ ·4H ₂ O to deionized water is 1:1-2, respectively, ammonium dihydrogen phosphate The mass ratio of NH ₄ H ₂ PO ₄ to deionized water was 1:1-2, respectively.

As a preferred technical solution of the present application: in the second step, it is dried for 24 hours until the moisture content is less than 5%.

As a kind of preferred technical scheme of the present application: in the third step, nickel nitrate hexahydrate Ni(NO ₃ ) ₂ .6H ₂ O, deionized water and calcium-deficient hydroxyapatite mass ratio are 1:2-10: 2-10.

As a preferred technical solution of the present application: in the third step, the Ni/Ca molar ratio is controlled at 0.001-2/8-9.999.

As a preferred technical solution of the present application: the stirring speed of vigorous stirring in the fourth step is 400-600 rpm/min.

As a preferred technical solution of the present application: the drying conditions in the fifth step are drying at 80-100° C. for 24 hours until the moisture content is less than 5%.

The application also discloses the application of the supported nickel-based catalyst prepared by the above preparation method in the dry reforming of methane.

As a preferred technical solution of the present application: the specific application method is to pass the mixture of methane and carbon dioxide according to the molar ratio of 1:1 at a temperature of 800 ° C through the catalyst bed, and the obtained products are carbon monoxide and hydrogen.

Beneficial effects:

The preparation method of a supported nickel-based catalyst described in the present application and its application adopt the above technical scheme compared with the prior art, and have the following technical effects:

1. A supported nickel-based catalyst with simple preparation conditions and easy to scale up application;

2. The carrier is calcium-deficient hydroxyapatite (chemical formula: Ca _10-x (PO ₄ ) ₆ (OH) ₂ , 0<x<2), and the mass percentage of nickel is 0%-10%;

3. When the catalyst is used in the methane dry reforming reaction, the reaction temperature is 800 °C, the gas hourly space velocity is 30000 mL g _cat ^{- 1} h ^-1 , the catalyst life is as long as 200 h, and there is no deactivation trend. The TEM image of the catalyst after the reaction No carbon deposition was observed in the

4. In the supported nickel-based catalyst prepared by the method of the present invention, more than 75% of the Ni nanoparticles are dispersed in the hydroxyapatite structure. This structure ensures the stability of Ni in the high temperature reaction process, effectively prevents the sintering of the catalyst, and improves the stability of the catalyst. The reduction rate of methane conversion after 200h is less than 3%.

5. The catalyst prepared by this method has good catalytic activity and anti-carbon deposition performance for methane dry reforming, and no carbon deposition is found in the TEM image of the catalyst after the reaction.

6. In the 200h reaction of the catalyst, the methane deactivation rate is 0.008% h ^-1 , and the methane deactivation rate in the comparative example is 0.014% h ^-1 .

Description of drawings

FIG. 1 is a TEM image of the catalyst obtained in Example 1 of the application after reduction.

FIG. 2 is a graph showing the change of CH ₄ conversion rate with reaction time in the DMR lifetime investigation reaction of Example 1 and Comparative Example.

FIG. 3 is a graph showing the variation of CO ₂ conversion rate with reaction time in the DMR lifetime investigation reaction of Example 1 and Comparative Example.

FIG. 4 is a graph showing the change of H ₂ /CO conversion rate with reaction time in the DMR lifetime investigation reaction of Example 1 and Comparative Example.

FIG. 5 is a TEM image of the nickel-based catalysts prepared in Example 1 and Comparative Example after the reaction of lifetime investigation.

Figure 6 is the H ₂ -TPR characterization of the nickel-based catalysts prepared in Examples 1, 2, 3 and Comparative Example.

Figure 7 is the XPS characterization of the nickel-based catalysts prepared in Examples 1, 2, 3 and Comparative Example.

Detailed ways

The technical solution of the present invention will be clearly and completely described below by combining with the specific implementation of the present invention, but it should not be understood that the scope of the present invention is limited to the following examples. Without departing from the above-mentioned method idea of the present invention, various substitutions or changes made according to common technical knowledge in the art and conventional means should all be included within the scope of the present invention.

Embodiment 1:

A preparation method of a supported nickel-based catalyst, firstly prepares a calcium-deficient hydroxyapatite carrier by a co-precipitation method, and then supports active metal nickel by an impregnation method, specifically comprising the following steps:

The first step is to prepare calcium-deficient hydroxyapatite carrier: 44.87g Ca(NO ₃ ) ₂ ·4H ₂ O (0.19mol, molecular weight is 236.15g/mol) and 13.80g NH ₄ H ₂ PO ₄ (0.12mol, Molecular weight of 115.03g/mol) was dissolved in 50mL and 20mL of deionized water respectively, and the two solutions were mixed in a beaker after being completely dissolved; 25vol% ammonia solution was added dropwise to the above solution at room temperature and under vigorous stirring to adjust pH. is 10, and then the heating temperature is controlled to be 80°C, and stirring is continued for 2 hours;

The second step: after the stirring is completed, the obtained suspension is filtered and washed until the filtrate is neutral, and the solid obtained by filtration is dried at 80 ° C for 24 hours;

The third step: the solid obtained in the second step is calcined in a muffle furnace at 400° C. for 4 hours under an air atmosphere to obtain a calcium-deficient hydroxyapatite carrier with a molecular formula of Ca _9.5 (PO ₄ ) ₆ (OH) ₂ ;

Step 4: Dissolve 2.91g Ni(NO ₃ ) ₂ ·6H ₂ O (0.01mol, molecular weight is 290.81g/mol) in 15mL water, add 19.68g Ca _9.5 (PO ₄ ) ₆ (OH) ₂ (0.02mol , molecular weight is 984g/mol), at room temperature, under vigorous stirring, add 25vol% aqueous ammonia solution dropwise to above-mentioned solution, adjust pH to be 10, then control heating temperature to be 80 ℃, continue to stir for 2 hours;

The fifth step: filter and wash the suspension until the filtrate is neutral, and dry the solid obtained by filtration at 80 ° C for 24 hours;

The sixth step: the obtained solid was calcined in a muffle furnace at 500° C. for 4 hours under an air atmosphere to obtain a Ni _0.5 /Ca _9.5 (PO ₄ ) ₆ (OH) ₂ -D catalyst, denoted as catalyst A.

As shown in Figure 1, which is the TEM image of the catalyst of Example 1 after reduction, it can be seen from Figure 1 that the Ni dispersion in the catalyst of Example 1 is relatively uniform, and the average particle size is 15.4 nm.

The above-mentioned catalyst is reacted with the methane dry reforming reaction, the catalyst is ground to 40-80 mesh, 400 _mg of the catalyst is loaded into the constant temperature zone of the quartz tube reactor, N is first introduced to heat up, and after the temperature is raised to the reaction temperature, it is switched to The feed gas, methane, carbon dioxide, and nitrogen injection volume were 1:1:8 (20mL, 20mL, 160mL), and the test was carried out at 800 °C. The average conversions of methane and carbon dioxide were 98.7% and 98.5%, respectively. The catalyst stability test of Example 1 was carried out at 800°C, and the results are shown in Figures 2-4. After 200h of reaction, the methane deactivation rate was 0.008% h ^-1 . The carbon dioxide deactivation rate was 0.007% h ^-1 . The catalyst maintains good activity. No carbon deposition was observed in the TEM image of the catalyst after the reaction (see Figure 5).

Example 2

A preparation method of a supported nickel-based catalyst, firstly prepares a calcium-deficient hydroxyapatite carrier by a co-precipitation method, and then supports active metal nickel by an impregnation method, specifically comprising the following steps:

The first step is to prepare calcium-deficient hydroxyapatite carrier: 42.51g Ca(NO ₃ ) ₂ ·4H ₂ O (0.18mol, molecular weight is 236.15g/mol) and 13.80g NH ₄ H ₂ PO ₄ (0.12mol, Molecular weight of 115.03g/mol) was dissolved in 50mL and 20mL of deionized water respectively, and the two solutions were mixed in a beaker after being completely dissolved; 25vol% ammonia solution was added dropwise to the above solution at room temperature and under vigorous stirring to adjust pH. is 10, and then the heating temperature is controlled to be 80°C, and stirring is continued for 2 hours;

The second step: after the stirring is completed, the obtained suspension is filtered and washed until the filtrate is neutral, and the solid obtained by filtration is dried at 80 ° C for 24 hours;

The third step: the solid obtained in the second step is calcined in a muffle furnace at 400° C. for 4 hours under an air atmosphere to obtain a calcium-deficient hydroxyapatite carrier, and the molecular formula is Ca ₉ (PO ₄ ) ₆ (OH) ₂ ;

The fourth step: dissolve 5.82g Ni(NO ₃ ) ₂ ·6H ₂ O (0.02mol, molecular weight is 290.81g/mol) in 30mL water, add 19.28g Ca ₉ (PO ₄ ) ₆ (OH) ₂ (0.02mol , molecular weight is 964g/mol), at room temperature, under vigorous stirring, add 25vol% aqueous ammonia solution dropwise to above-mentioned solution, adjust pH to be 10, then control heating temperature to be 80 ℃, continue to stir for 2 hours;

The fifth step: filter and wash the suspension until the filtrate is neutral, and dry the solid obtained by filtration at 80 ° C for 24 hours;

The sixth step: the obtained solid was calcined in a muffle furnace at 500° C. for 4 hours under an air atmosphere to obtain a Ni ₁ /Ca ₉ (PO ₄ ) ₆ (OH) ₂ -D catalyst, denoted as catalyst B.

The method of Example 1 was used for its dry reforming performance of methane. The average conversions of methane and carbon dioxide were 98.8% and 98.5%, respectively.

Example 3

A preparation method of a supported nickel-based catalyst, firstly prepares a calcium-deficient hydroxyapatite carrier by a co-precipitation method, and then supports active metal nickel by an impregnation method, specifically comprising the following steps:

The first step is to prepare calcium-deficient hydroxyapatite carrier: 40.15g Ca(NO ₃ ) ₂ ·4H ₂ O (0.17mol, molecular weight is 236.15g/mol) and 13.80g NH ₄ H ₂ PO ₄ (0.12mol, Molecular weight of 115.03g/mol) was dissolved in 50mL and 20mL of deionized water respectively, and the two solutions were mixed in a beaker after being completely dissolved; 25vol% ammonia solution was added dropwise to the above solution at room temperature and under vigorous stirring to adjust pH. is 10, and then the heating temperature is controlled to be 80°C, and stirring is continued for 2 hours;

The second step: after the stirring is completed, the obtained suspension is filtered and washed until the filtrate is neutral, and the solid obtained by filtration is dried at 80 ° C for 24 hours;

The third step: the solid obtained in the second step is calcined in a muffle furnace at 400° C. for 4 hours under an air atmosphere to obtain a calcium-deficient hydroxyapatite carrier, and the molecular formula is Ca _8.5 (PO ₄ ) ₆ (OH) ₂ ;

Step 4: Dissolve 8.72g Ni(NO ₃ ) ₂ ·6H ₂ O (0.03mol, molecular weight is 290.81g/mol) in 45mL water, add 18.88g Ca _8.5 (PO ₄ ) ₆ (OH) ₂ (0.02mol) , molecular weight is 944g/mol), add 25vol% ammonia solution dropwise to above-mentioned solution under room temperature, vigorous stirring, adjust pH to be 10, then control heating temperature to be 80 ℃, continue to stir for 2 hours;

The fifth step: filter and wash the suspension until the filtrate is neutral, and dry the solid obtained by filtration at 80 ° C for 24 hours;

The sixth step: the obtained solid was calcined in a muffle furnace at 500° C. for 4 hours under an air atmosphere to obtain a Ni _1.5 /Ca _8.5 (PO ₄ ) ₆ (OH) ₂ -D catalyst, denoted as catalyst C.

The method of Example 1 was used for its dry reforming performance of methane. The average conversions of methane and carbon dioxide were 96.3% and 98.7%, respectively.

Comparative Example

A preparation method of a supported nickel-based catalyst, firstly prepares a calcium-deficient hydroxyapatite carrier by a co-precipitation method, and then supports active metal nickel by an impregnation method, specifically comprising the following steps:

The first step is to prepare calcium-deficient hydroxyapatite carrier: 47.23g Ca(NO ₃ ) ₂ ·4H ₂ O (0.2mol, molecular weight is 236.15g/mol) and 13.80g NH ₄ H ₂ PO ₄ (0.12mol, Molecular weight of 115.03g/mol) was dissolved in 50mL and 20mL of deionized water respectively, and the two solutions were mixed in a beaker after being completely dissolved; 25vol% ammonia solution was added dropwise to the above solution at room temperature and under vigorous stirring to adjust pH. is 10, and then the heating temperature is controlled to be 80°C, and stirring is continued for 2 hours;

The second step: after the stirring is completed, the obtained suspension is filtered and washed until the filtrate is neutral, and the solid obtained by filtration is dried at 80 ° C for 24 hours;

The third step: the solid obtained in the second step is calcined in a muffle furnace at 400° C. for 4 hours under an air atmosphere to obtain a calcium-deficient hydroxyapatite carrier, and the molecular formula is Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ;

The fourth step: dissolve 2.91g Ni(NO ₃ ) ₂ ·6H ₂ O (0.01mol, molecular weight is 290.81g/mol) in 30mL water, add 20.08g Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ (0.02mol) , molecular weight is 1004g/mol), add 25vol% ammonia solution dropwise to the above solution under room temperature and vigorous stirring, adjust pH to be 10, then control the heating temperature to be 80 ° C, continue stirring for 2 hours;

The fifth step: filter and wash the suspension until the filtrate is neutral, and dry the solid obtained by filtration at 80 ° C for 24 hours;

The sixth step: the obtained solid was calcined in a muffle furnace at 500° C. for 4 hours under an air atmosphere to obtain a Ni _0.5 /Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ catalyst, denoted as catalyst D.

The method of Example 1 was used for its dry reforming performance of methane. The average conversions of methane and carbon dioxide were 84.9% and 91.1%, respectively. The catalyst stability test of the comparative example was carried out at 800° C., and the results are shown in FIGS. 2 to 4 . After 118 hours of reaction, the methane deactivation rate was 0.087%, which was 10.9 times that of the catalyst in Example 1. The deactivation rate of carbon dioxide was 0.069%, which was 9.9 times that of the catalyst of Example 1. In the TEM spectrum after the reaction (see Figure 5), it was found that the metal Ni was surrounded by carbon deposits.

As shown in Figure 6, it is the H ₂ -TPR characterization of the catalysts of Examples 1, 2, 3 and Comparative Examples. It can be seen from Figure 6 that the reduction temperatures of the catalysts of Examples 1, 2, and 3 are significantly higher than those of the comparison. The examples show that in the catalysts of Examples 1, 2, and 3, the interaction between Ni and the carrier is strong, thereby increasing the stability of the catalyst, inhibiting the sintering of Ni during the reaction process, and prolonging the life of the catalyst.

As shown in Figure 7, it is the XPS characterization of the catalysts of Examples 1, 2, 3 and Comparative Examples. It can be seen from Figure 7 that in Examples 1, 2, and 3, Ni ²⁺ [I] and Ni ²⁺ [ The ratio of II] is much higher than that of the comparative example, indicating that the Ni in the catalysts of Examples 1, 2, and 3 mainly exists in the hydroxyapatite lattice, which provides the catalyst with more stable active sites and CH with higher matching degree. ₄ and _CO2 reaction rates.

Claims (9)

1. A preparation method of a supported nickel-based catalyst is characterized in that a calcium-deficient hydroxyapatite carrier is prepared by a coprecipitation method, and then active metal nickel is loaded by an impregnation method, and the preparation method specifically comprises the following steps:

the first step is as follows: ca (NO)₃)₂·4H₂O，NH₄H₂PO₄Respectively dissolving in deionized water, controlling the molar ratio of Ca/P to be 8-10/6, mixing the two solutions after the two solutions are completely dissolved, dropwise adding 25% vol ammonia water under vigorous stirring at room temperature to adjust the pH value of the mixed solution to 10 +/-1, heating and stirring, controlling the heating temperature to be 60-90 ℃, and controlling the stirring time to be 2-4 hours;

the second step is that: after stirring, filtering and washing the obtained suspension to neutrality, drying at 80-100 ℃, calcining the dried solid in air at 300-400 ℃ for 3-5 hours to prepare the calcium-deficient hydroxyapatite carrier (chemical formula: Ca)_10-x(PO₄)₆(OH)₂，0<x<2)；

The third step: ni (NO)₃)₂·6H₂Dissolving O in deionized water to prepare a nickel precursor solution, pouring the calcium-deficient hydroxyapatite carrier into the nickel precursor solution, wherein the sum of the mole numbers of Ni and Ca is 10;

the fourth step: stirring vigorously at room temperature, adding 25% vol ammonia water dropwise to adjust the pH of the mixed solution to 10 +/-1, and stirring for 2-4 hours at 80 ℃;

the fifth step: filtering and washing the suspension until the filtrate is neutral, drying the obtained solid, calcining the dried solid in air at 400-500 ℃ for 3-5 hours to obtain the supported nickel-based catalyst Ni_x/Ca_10-x(PO₄)₆(OH)₂；0<x<2。

2. The method for preparing a supported nickel-based catalyst according to claim 1, wherein: calcium nitrate tetrahydrate Ca (NO) in the first step₃)₂·4H₂The mass ratio of O to deionized water is 1:1-2 respectively, ammonium dihydrogen phosphate NH₄H₂PO₄The mass ratio of the deionized water to the deionized water is 1:1-2 respectively.

3. The method for preparing a supported nickel-based catalyst according to claim 1, wherein: and drying for 24 hours in the second step until the water content is less than 5 percent.

4. The method for preparing a supported nickel-based catalyst according to claim 1, wherein: nickel nitrate hexahydrate Ni (NO) in the third step₃)₂·6H₂The mass ratio of the O, the deionized water and the calcium-deficient hydroxyapatite is 1:2-10: 2-10.

5. The method for preparing a supported nickel-based catalyst according to claim 1, wherein: the molar ratio of Ni/Ca in the third step is controlled to be 0.001-2/8-9.999.

6. The method for preparing a supported nickel-based catalyst according to claim 1, wherein: the stirring speed of the vigorous stirring in the fourth step is 400-600 rpm/min.

7. The method for preparing a supported nickel-based catalyst according to claim 1, wherein: and in the fifth step, the drying condition is drying for 24 hours at the temperature of 80-100 ℃ until the water content is less than 5%.

8. Use of a supported nickel-based catalyst prepared by the preparation process according to any one of claims 1 to 7 in the dry reforming of methane.

9. Use of a supported nickel-based catalyst according to claim 8 in the dry reforming of methane, characterized in that: the mixed gas of methane and carbon dioxide is passed through a catalyst bed layer according to the molar ratio of 1:1 at the temperature of 800 ℃, and the obtained products are carbon monoxide and hydrogen.

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