CN114308093A

CN114308093A - High-load nickel-based carbide catalyst and preparation method and application thereof

Info

Publication number: CN114308093A
Application number: CN202111633121.6A
Authority: CN
Inventors: 闫晓亮; 王倩倩; 李莎; 曹敏; 邱丽; 李瑞丰
Original assignee: Taiyuan University of Technology
Current assignee: Taiyuan University of Technology
Priority date: 2021-12-29
Filing date: 2021-12-29
Publication date: 2022-04-12

Abstract

The invention discloses a high-load nickel-based carbide catalyst, which is a coated interstitial carbide alloy catalyst; the molecular formula of the nickel-based catalyst is Ni₃MC_x/N_yO_zWherein M is metal, x is more than 0 and less than or equal to 1, and metal oxide N_yO_zIs a carrier; the metal M is alloyed with the metal Ni, C is an interstitial carbon atom, Ni₃MC_xThe carrier is a gap carbide alloy, and the gap carbide alloy is coated by the carrier. The high-load nickel-based carbide catalyst has good activity, stability and anti-carbon deposition performance. The invention also provides a preparation method and application of the high-load nickel-based carbide catalyst.

Description

High-load nickel-based carbide catalyst and preparation method and application thereof

Technical Field

The invention relates to the field of catalysts, in particular to a high-load nickel-based carbide catalyst and a preparation method and application thereof.

Background

In the face of the energy and environmental problems faced by the world at present, new energy is vigorously developed, and the reduction of carbon emission is the direction of effort in our country in the aspects of environmental protection and energy application.

Methane (CH)₄) And carbon dioxide (CO)₂) The recycling and conversion of two main greenhouse gases and carbon-containing resources have received wide social attention in recent years. On the one hand, the natural gas, coal bed gas and biogas which can be directly obtained contain CH₄In addition, it also contains a relatively high proportion of CO₂. The traditional process removes CO through a pre-decarbonization step before methane enrichment₂The process steps are complex, and the economic cost is high. On the other hand, with the development of modern industry, the concentration of carbon dioxide in the atmosphere is continuously increased, and the carbon dioxide breaks through 400ppm from 280ppm before the industrial revolution to 2013, and reaches 415ppm even in 2019, and CO is generated₂Global climate change due to the continuous increase in concentration has become one of the problems facing mankind. Taking the steel industry as an example, the carbon emission accounts for 7-9% of the direct global carbon emission, wherein the carbon emission accounts for CH in tail gases of coke oven gas, blast furnace gas, basic oxygen furnace gas and the like₄And CO₂The content difference is large, and how to compound and utilize the gases becomes a key for reducing the carbon emission of the steel industry (Angew. chem. int. Ed.,2021,60: 11852-11857).

Methane Dry Reforming (DRM) technology can simultaneously utilize CH₄And CO₂These two gases, and the ability to convert these two typical greenhouse gases into the ideal raw gas syngas for fischer-tropsch synthesis, have been widely studied. DRM is a strong endothermic reaction, which needs to be carried out at a higher temperature, while CH is at a higher temperature₄The progress of side reactions such as cracking and carbon monoxide (CO) disproportionation often leads to deactivation of the catalyst. On the other hand, rich in CO₂Especially CO₂/CH₄When the content exceeds the stoichiometric ratio of 1/1, the metal catalyst is easily exposed to CO₂Oxidation, leading to a reduction in catalyst activity and even deactivation.

Nickel-based catalysts have been widely studied due to their higher catalytic activity and low price, compared to noble metal catalysts. However, the nickel-based catalyst is prone to carbon deposition under the reaction conditions, which results in the reduction of the catalyst activity and the blockage of the reactor, thereby causing the increase of the production cost and increasing the potential safety hazard (appl.Catal.A: Gen.,2015,495: 141-151; J.Am.chem.Soc.,017,139: 1937-1949; appl.Catal.B: environ.,2019,246: 221-231). Studies have shown that transition metal carbides, such as Mo₂The transition metal carbide catalyst such as C has good anti-carbon deposition performance in methane dry reforming because the electronic and geometric properties of metal atoms are changed by doping carbon atoms. However, in the presence of CO₂In the reaction gas of (2), these metal carbides are rapidly oxidized to thereby deactivate the catalyst (Nat. Commun.,2020,11: 4072; Phys. chem. Phys.,2020,4: 4549-. Thus, the use of metal carbides for dry reforming of methane often requires either higher pressures or the addition of CO gas to the reaction gas. On the other hand, like raney nickel, high-loading nickel-based catalysts have unique advantages in industrial applications, whereas for conventional supported catalysts, the loading is generally controlled to be less than 20 wt% in order to ensure the dispersibility of the active metal of the catalyst to maintain its catalytic performance. Thus, a catalyst useful for CO enrichment was synthesized₂Raw material gas, high-load Ni-based catalyst with good anti-carbon deposition performance and oxidation resistance in CH₄And CO₂The direct conversion and utilization field has very important significance.

Disclosure of Invention

Therefore, the present invention aims to solve the above problems and provide a high-loading nickel-based carbide catalyst, and a preparation method and applications thereof.

The invention provides a high-load nickel-based carbide catalyst, which is a coated interstitial carbide alloy catalyst;

the molecular formula of the high-load nickel-based carbide catalyst is Ni₃MC_x/N_yO_zWherein M is metal, x is more than 0 and less than or equal to 1, and metal oxide N_yO_zIs a carrier;

the metal M is alloyed with the metal Ni, C is an interstitial carbon atom, Ni₃MC_xThe carrier is a gap carbide alloy, and the gap carbide alloy is coated by the carrier.

Further, x is more than or equal to 0.25 and less than or equal to 0.8.

Further, the Ni content is 40-60 wt%.

Further, M is at least one of Al, Zn, In, Ga, Mg and Ca;

the metal oxide N_yO_zIs Al₂O₃、ZrO₂、Fe₂O₃、CeO₂At least one of (1).

Further, the carrier fully or partially coats the interstitial carbide alloy.

The invention also provides a preparation method of the high-load nickel-based carbide catalyst, which comprises the following steps:

preparing a metal M precursor: mixing soluble salt containing metal element M, solvent and organic ligand, and then stirring and centrifuging to obtain a metal M precursor;

synthesizing a metal oxide precursor: will contain Ni²⁺Mixing the soluble salt and the soluble salt containing the metal element N to obtain a solution A, dissolving the metal M precursor to obtain a solution B, mixing the solution A and the solution B, carrying out hydrothermal reaction to obtain a hydrothermal product, and washing and roasting the hydrothermal product to obtain the metal oxide precursor;

reduction: reducing the oxide precursor by using hydrogen to obtain a reduction product; and

carbonizing: the reduction product is treated with CH₄And CO₂The mixed gas is carbonized to obtain the needed catalyst.

Further, the M is Al, the solvent is at least one of methanol solution, urea solution and ammonia water solution, and the organic ligand is at least one of 2-methylimidazole, ethylenediamine tetraacetic acid, 2-mercaptosuccinic acid and terephthalic acid.

Further, the temperature of the hydrothermal reaction is 100-150 ℃, and the time is 12-36 h.

Further, the reduction temperature is 400-600 ℃, and the carbonization temperature is 450-650 ℃.

The invention also provides an application of the high-load nickel-based carbide catalyst, and the high-load nickel-based carbide catalyst is applied to dry reforming of methane.

The technical scheme of the invention can synthesize the high-load core-shell nickel-based carbide catalyst, which not only solves the problem that the catalyst is rich in CO₂The problem of easy oxidation inactivation in gas is solved, the stability and the practicability of the catalyst are improved, higher methane and carbon dioxide activation capability is ensured, and the catalyst can well adapt to various proportions of rich CO₂The reaction environment of the methane-carbon dioxide mixed gas atmosphere and the high-temperature reaction environment are particularly suitable for being applied to methane dry reforming. In addition, the C atoms generated by methane cracking are stored in the metal alloy interstitial sites, and carbon monoxide is generated through the reaction with carbon dioxide, so that the coupling of carbon-carbon bonds is avoided, the carbon deposition path of the dry reforming reaction of methane is avoided, and the catalyst has good carbon deposition resistance.

Drawings

In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which

Fig. 1 is an XRD pattern of Al precursor in experimental group 1.

Fig. 2 is an SEM image of the Al precursor in experimental group 1.

FIG. 3 shows NiO/Al in Experimental group 2₂O₃XRD pattern of (a).

FIG. 4 shows NiO/Al in Experimental group 2₂O₃BET diagram (b).

FIG. 5 shows Ni in Experimental group 3₃AlC_0.5/Al₂O₃XRD pattern of (a).

FIG. 6 shows Ni in Experimental group 3₃AlC_0.5/Al₂O₃A TEM image of (a).

Fig. 7 is a catalyst stability test chart of the

test groups

1,6, and 7.

Figure 8 is an XRD pattern of the catalyst after the stability test of test group 1.

Fig. 9 is a graph of air TG of the catalyst after the stability test of test group 1.

Detailed Description

The following examples are only preferred embodiments of the present invention and are not intended to limit the present invention in any way. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Example one

The preparation method of the high-load nickel-based carbide catalyst comprises the following steps:

step S1: preparing a metal M precursor: mixing soluble salt containing metal element M, solvent and organic ligand, and then stirring and centrifuging to obtain a metal M precursor;

step S2: synthesizing a metal oxide precursor: will contain Ni²⁺Mixing the soluble salt and the soluble salt containing the metal element N to obtain a solution A, dissolving the metal M precursor to obtain a solution B, mixing the solution A and the solution B, carrying out hydrothermal reaction to obtain a hydrothermal product, and washing and roasting the hydrothermal product to obtain the metal oxide precursor;

step S3: reduction: reducing the oxide precursor by using hydrogen to obtain a reduction product; and

step S4: carbonizing: the reduction product is treated with CH₄And CO₂The mixed gas is carbonized to obtain the needed catalyst.

The preparation method of the nickel-based catalyst realizes that C atoms generated by methane cracking are stored in metal alloy interstitial sites and react with carbon dioxide to generate carbon monoxideThereby avoiding the coupling of carbon-carbon bonds and avoiding the carbon deposition path of the dry reforming reaction of methane, and leading the prepared nickel-based catalyst to have good carbon deposition resistance. And well solves the problem that the catalyst is rich in CO₂The problem of easy oxidation inactivation in gas is solved, the stability and the practicability of the catalyst are improved, higher methane and carbon dioxide activation capability is ensured, and the catalyst can well adapt to various proportions of rich CO₂The methane-carbon dioxide mixed gas atmosphere and the high-temperature reaction environment.

In step S1, the metal element M may be at least one of Al, Zn, In, Ga, Mg, Ca, preferably Al.

The soluble salt containing the metal element M can be at least one of a nitrate solution, an acetate solution and a sulfate solution, namely when the M is Al, the soluble salt can be one or a mixture of more of aluminum nitrate, aluminum acetate and aluminum sulfate; the solubility of the soluble salt is preferably 0.1 to 0.5 mol/L.

The solvent may be at least one of methanol solution, urea solution, and ammonia solution. The organic ligand can be at least one of 2-methylimidazole, ethylenediamine tetraacetic acid, 2-mercaptosuccinic acid and terephthalic acid. When M is Al, the solvent is preferably methanol solution and the organic ligand is preferably terephthalic acid.

Step S1 may specifically be mixing the aluminum nitrate solution, the methanol solution, and the phthalic acid, stirring for 12 hours, and then obtaining the metal Al precursor by centrifugation and filtration.

In step S2, Ni²⁺The soluble salt can be at least one of nitrate solution, acetate solution and sulfate solution, the metal element N can be at least one of Al, Zr, Fe and Ce, and the soluble salt of the metal element N can be at least one of nitrate solution, acetate solution and sulfate solution. It is understood that when M is Al, N is preferably Al, which not only can reduce the kinds of raw materials and ensure the stability of the final catalyst, but also the molar ratio of nickel ions to aluminum ions is 1 to 5:1, the total concentration is preferably 0.5 to 1.5 mol/L.

The metal M precursor is preferably dissolved with a sodium carbonate solution, further with a concentration of 0.5-1.5 mol/L.

The temperature of the hydrothermal reaction is preferably 100-150 ℃, and the hydrothermal time is preferably 12-36 h.

The roasting temperature is preferably 400-800 ℃, and the time is preferably 3-8 h.

Step S2 may specifically be mixing a nickel nitrate solution and an aluminum nitrate solution to obtain a solution a, dissolving the metal Al precursor to obtain a solution B, then uniformly mixing the solution a and the solution B, stirring for 30min, performing a hydrothermal reaction at 120 ℃ for 12h to obtain a hydrothermal product, centrifuging and washing the obtained hydrothermal product, and calcining at 600 ℃ for 5h to obtain a metal oxide precursor NiO/Al₂O₃。

In step S3, the reduction temperature is preferably 400-600 ℃, and the reduction time is preferably 1-5 h. Further, the reduction temperature is 550 ℃, and the reduction time is 2 hours. The hydrogen concentration in the reducing environment is preferably 10% to 100%.

In step S4, the carbonization temperature is preferably 450-650 ℃, and the carbonization time is preferably 1-5 h. Further, the carbonization temperature is 500 ℃, and the carbonization time is preferably 2 h.

Example two

A nickel-based catalyst, which can be prepared by the preparation method of the nickel-based catalyst provided in the first embodiment, wherein the nickel-based catalyst is a coated interstitial carbide alloy catalyst;

As a coated catalyst, the coating form of the catalyst may be fully coated or partially coated, that is, the carrier fully coats or partially coats the interstitial carbide alloy, and preferably, the coating form of the nickel-based catalyst is fully coated. Preferably, the coating thickness is 2-10nm, and the grain size of the interstitial carbide alloy is 5-100 nm.

Preferably, x is more than or equal to 0.25 and less than or equal to 0.8, and the Ni content is 40-60 wt%.

The M may be at least one of Al, Zn, In, Ga, Mg, and Ca, and is more preferably Al. The metal oxide N_yO_zMay be Al₂O₃、ZrO₂、Fe₂O₃、CeO₂More preferably Al₂O₃。

In some embodiments, the nickel-based catalyst has the formula Ni₃AlC_0.5/Al₂O₃。

EXAMPLE III

The application of the high-load nickel-based carbide catalyst provided in the second embodiment is applied to the dry reforming of methane.

Example four

Under the condition of preparing the synthesis gas by dry reforming of methane, the methane and the carbon dioxide are in contact reaction with the high-load nickel-based carbide catalyst provided in the second embodiment.

Preferably, the contacting reaction is carried out in a fixed bed reactor. The reaction condition is CH₄With CO₂The ratio of (1): 1-4, the reaction temperature is 450-650 ℃, and the reaction pressure is normal pressure. Atmospheric pressure here means one atmosphere, i.e. 1 bar.

Some specific experimental groups and test/characterization results are provided below

Experimental group 1

1.02g of terephthalic acid and 1.20g of Al (NO) were taken₃)₃·9H₂Dissolving O in 40mL of methanol solution, washing the wall of the beaker by 32mL of terephthalic acid solution, stirring at room temperature for 12h, and then obtaining the Al precursor by centrifuging and washing.

Experimental group 2

Mixing 5.81g Ni (NO)₃)₂·6H₂O and 1.88g Al (NO)₃)₃·9H₂Dissolving O in 20mL of distilled water and stirring for 20 min; dissolving 2g of Al precursor prepared in the experimental group 1 in 0.75M sodium carbonate solution; and the two solutions were mixed well and stirred at room temperature for 30 min. Subsequently, the above solution was transferred to a 100mL autoclave and reacted at 120 ℃ for 12 hours to obtain a product. Centrifuging and washing the product, and roasting at 600 ℃ for 5h to obtain a metal oxide precursor NiO/Al₂O₃。

Experimental group 3

NiO/Al obtained from experiment group 2₂O₃Reduction with hydrogen at 550 ℃ for 2h and CH at 500 ℃₄/CO₂The mixed gas is carbonized for 2 hours to obtain the metal alloy interstitial carbide catalyst Ni₃AlC_0.5/Al₂O₃。

The following tests/characterizations were performed for the above experimental groups

1. Al precursor obtained for Experimental group 1

Fig. 1 is an XRD pattern of Al precursor in experimental group 1. This indicates that Al has reacted with the organic framework and that a precursor to Al was successfully prepared.

Fig. 2 is an SEM image of the Al precursor in experimental group 1. This indicates the morphological characteristics of the Al precursor.

2. NiO/Al metal oxide precursor obtained by aiming at experimental group 2₂O₃。

FIG. 3 shows NiO/Al in Experimental group 2₂O₃XRD pattern of (a). The figure illustrates NiO/Al after firing₂O₃The catalyst mainly comprises NiO and amorphous Al₂O₃。

FIG. 4 shows NiO/Al in Experimental group 2₂O₃BET diagram (b). The figure illustrates the channel structure and specific surface area of the catalyst. The pore size distribution diagram shows that the catalyst has rich mesoporous structure.

Table 1 shows the specific surface area, average pore diameter, and pore volume of the metal oxide precursors in experimental group 2.

TABLE 1

Table 2 shows the metal contents of the metal oxide precursors in experimental group 2.

TABLE 2

3. Metal alloy interstitial carbide catalyst Ni obtained by aiming at experimental group 3₃AlC_0.5/Al₂O₃

FIG. 5 shows Ni in Experimental group 3₃AlC_0.5/Al₂O₃XRD pattern of (a). As can be seen in this figure, Ni appears at 43.3 °, 50.4 ° and 74.0 ° 2 θ₃AlC_0.5Characteristic diffraction peak of (A) indicates that the catalyst Ni is successfully prepared₃AlC_0.5/Al₂O₃. Al is not obtained₂O₃The characteristic diffraction peak of (2) is due to the low crystallinity of the oxide, which cannot be detected by XRD.

FIG. 6 shows Ni in Experimental group 3₃AlC_0.5/Al₂O₃A TEM image of (a). As can be seen from the figure, the catalysis is of a core-shell structure, i.e., about 2nm of Al₂O₃The shell is wrapped with about 80nm of Ni₃AlC_0.5。

Stability testing was performed on the catalysts:

test set 1

The performance of the catalyst prepared in experimental group 3 was investigated using a fixed bed reactor. The fixed bed reactor had an outer diameter of 12mm, an inner diameter of 8mm and a length of 450 mm. The reactants and products were detected by gas chromatography with a TCD detector and a soap bubble flow meter.

Reaction conditions are as follows: 0.1g of catalyst mixed with 1g of quartz sand is filled in a constant temperature area of a fixed bed reactor, and after the temperature is raised to 500 ℃ under Ar, the constant temperature area is switched to CH₄/CO₂The flow rate of the mixed gas was 60mL/min, and the reaction pressure was normal pressure, 1/1. Atmospheric pressure here means one atmosphere, i.e. 1 bar.

Test groups 2 to 5

The differences from test set 1 are: the temperature is raised to 450 ℃, 550 ℃, 600 ℃ and 650 ℃ under Ar.

Test set 6

The difference from test set 1 is: CH (CH)₄/CO₂＝1/2。

Test group 7

The difference from test set 1 is: CH (CH)₄/CO₂＝1/4。

Test groups 8 to 11

The difference from test group 7 is: the temperature is raised to 450 ℃, 550 ℃, 600 ℃ and 650 ℃ under Ar.

Fig. 7 is a catalyst stability test chart of the

test groups

1,6, and 7. The catalyst did not significantly deactivate in the 100h test, indicating that the catalyst is in CH₄/CO₂The stability of the product is good in 1/1, 1/2 and 1/4 atmosphere.

The test data from test groups 1 to 5 were collated to give Table 3:

TABLE 3CH₄/CO ₂1/1 time difference in reaction temperature versus Ni₃AlC_0.5/Al₂O₃Effect of Metal alloy interstitial carbide catalyst on methane Dry reforming

As can be seen from Table 3, the catalyst synthesized by the present invention has good conversion of methane and carbon dioxide at a relatively low temperature. The methane conversion and carbon dioxide conversion can reach 57.1% and 69.2% conversion respectively at 650 ℃.

Table 4 was obtained by collating the test data from test groups 7-11:

TABLE 4 CH₄/CO ₂1/4 time difference in reaction temperature versus Ni₃AlC_0.5/Al₂O₃Effect of Metal alloy interstitial carbide catalyst on methane Dry reforming

As can be seen from table 4, the catalysts synthesized in the examples of the present invention have good conversion rates of methane and carbon dioxide at lower temperatures. The methane conversion and carbon dioxide conversion can reach 91.6% and 42.5% conversion respectively at 650 ℃.

Further characterization was performed for the catalysts after stability testing in test group 1

FIG. 8 is an XRD pattern of the catalyst after stability test of test group 1, Al₂O₃Is an amorphous substance. The spectrum shows that no diffraction peak of carbon species appears, which indicates that the catalyst has good anti-carbon deposition performance. And the comparison with the XRD pattern (figure 6) of the catalyst before the stability test shows that the two are consistent, which indicates that the catalyst has high stability.

Fig. 9 is a graph of air TG of the catalyst after the stability test of test group 1. The atlas shows that the catalyst has obvious weight loss peak at the temperature of less than 200 ℃, which is because the water absorbed by the catalyst is removed; the increase in mass at 200-400 ℃ is attributed to the oxidation of the carbide metal in the catalyst; the weight loss above 400 ℃ is due to mass loss caused by oxidation of the liberated carbon species in the alloy catalyst. Thus, the data also show that the catalyst has good resistance to carbon deposition.

In conclusion, the nickel-based metal carbide interstitial catalyst prepared by the method can be well suitable for dry reforming reaction of methane, and can adapt to different reactant proportions, namely CH₄/CO₂The range is 1: 1-1: 4. The catalyst has good activity, stability and anti-carbon deposition performance. In addition, the catalyst is rich in CO compared to other carbide catalysts₂Has good oxidation resistance in the reaction gas. In addition, the catalyst of the invention has simple production and lower cost, and is easy to realize industrialization.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. A high-load nickel-based carbide catalyst is characterized in that: it is a coated interstitial carbide alloy catalyst;

2. The high loading nickel-based carbide catalyst of claim 1, wherein: x is more than or equal to 0.25 and less than or equal to 0.8.

3. The high loading nickel-based carbide catalyst of claim 1, wherein: the Ni content is 40-60 wt%.

4. The high loading nickel-based carbide catalyst of claim 1, wherein: the M is at least one of Al, Zn, In, Ga, Mg and Ca;

5. A high loading nickel based carbide catalyst according to any of claims 1 to 4, wherein: the carrier fully or partially coats the interstitial carbide alloy.

6. A preparation method of a high-load nickel-based carbide catalyst is characterized by comprising the following steps: the method comprises the following steps:

7. The method of preparing the high loading nickel-based carbide catalyst of claim 6, wherein: the M is Al, the solvent is at least one of methanol solution, urea solution and ammonia water solution, and the organic ligand is at least one of 2-methylimidazole, ethylenediamine tetraacetic acid, 2-mercaptosuccinic acid and terephthalic acid.

8. The method of preparing the high loading nickel-based carbide catalyst of claim 6, wherein: the temperature of the hydrothermal reaction is 100-150 ℃, and the time is 12-36 h.

9. A method of preparing a high loading nickel-based carbide catalyst according to any of claims 6 to 8, wherein: the reduction temperature is 400-600 ℃, and the carbonization temperature is 450-650 ℃.

10. The application of the high-load nickel-based carbide catalyst is characterized in that: use of the high loading nickel-based carbide catalyst as claimed in any of claims 1 to 5 in dry reforming of methane.