CN116078393B - Transition metal supported high-entropy oxide low-temperature methane dry reforming catalyst and preparation method and application thereof - Google Patents

Abstract

The invention provides a transition metal supported high-entropy oxide low-temperature methane dry reforming catalyst, and a preparation method and application thereof. The catalyst prepared by the invention has strong catalytic cracking effect on methane at a lower temperature (600 ℃), enhances the adsorption and dissociation of CO ₂, ensures that carbon deposition is not easy to generate on the catalyst, simultaneously inhibits the migration of transition metal by virtue of the entropy stability of the high-entropy oxide carrier, effectively prolongs the service life of the catalyst and maintains high catalytic activity. The adopted raw materials are cheap and easy to obtain, the preparation method is simple, the requirements on equipment are low, and the method is suitable for large-scale production.

Description

A transition metal-supported high entropy oxide low-temperature methane dry reforming catalyst and its preparation method and application

Technical Field

The invention belongs to the field of catalytic materials, and particularly relates to a transition metal-supported high-entropy oxide low-temperature methane dry reforming catalyst and a preparation method and application thereof.

Background Art

Dry reforming of methane (DRM) is considered to be a very promising reaction. It can produce synthesis gas using CH ₄ produced by sewage treatment plants, landfills, and agricultural waste fermentation, and CO ₂ produced by fuel combustion as raw materials. It can effectively treat the two major greenhouse gases while producing industrial raw materials.

Transition metals are often used to make DRM catalysts because of their low price, abundant reserves, and strong catalytic ability. However, there are problems with transition metal catalysts. First, they are prone to produce a large amount of carbon deposits during the DRM process, which leads to the clogging or even deactivation of the catalyst active sites. Second, they are prone to agglomeration, resulting in a decrease in catalytic ability.

Single-phase oxides containing five or more metal elements are usually classified as high-entropy oxides. The entropy stability of high-entropy oxides helps these catalysts maintain stable catalytic performance for a long time in high-temperature reactions, so they have great potential. However, existing high-entropy oxide catalysts are mainly used in the field of electrocatalysis, are overly stable in DRM, and have very limited catalytic performance.

It can be seen that both the commonly used transition metal catalysts and the potential high-entropy oxide catalysts need to be further improved for DRM.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings and deficiencies of the existing DRM transition metal catalysts, such as poor stability, short life, poor selectivity of high entropy oxide catalysts, and unsatisfactory catalytic effect, and to provide a dissolution transition metal-supported high entropy oxide catalyst for low-temperature methane dry reforming. The dissolution transition metal-supported high entropy oxide catalyst prepared by the method combines the advantages of strong catalytic ability of transition metal catalysts and high stability of high entropy oxide catalysts, and has the advantages of maintaining high selectivity and high catalytic ability for a long time.

Another object of the present invention is to provide a method for preparing the above catalyst.

Another object of the present invention is to provide application of the above catalyst.

The purpose of the present invention is achieved through the following technical solutions:

A method for preparing a transition metal-supported high entropy oxide low-temperature methane dry reforming catalyst comprises the following steps:

(1) preparing a metal salt solution;

(2) preparing an alkaline solution;

(3) adding the alkaline solution to the metal salt solution, filtering and drying to obtain a precipitate;

(4) Calcine the precipitate obtained in step (3), and then reduce it in a reducing atmosphere to obtain a transition metal-supported high entropy oxide low-temperature methane dry reforming catalyst.

The metal salt in step (1) is a metal salt of a transition metal or a non-transition metal.

The metal salts described in step (1) are metal salts of at least 6 different metals.

The transition metal salt includes at least one of nitrate, acetate or chloride of manganese, iron, nickel, cobalt and copper.

The non-transition metal salt includes at least one of nitrates or acetates of magnesium, yttrium, zirconium, lanthanum, cerium and erbium.

The metal salts are nickel nitrate hexahydrate, magnesium nitrate hexahydrate, yttrium acetate hydrate, zirconium nitrate pentahydrate, cerium nitrate hexahydrate and erbium nitrate hexahydrate.

The specific steps of the preparation described in step (1) are: dissolving the metal salt in water and stirring to obtain a metal salt solution.

The specific steps of the preparation described in step (2) are: dissolving the alkali in water and stirring to obtain an alkaline solution.

The alkali in step (2) is at least one of sodium carbonate, potassium carbonate, sodium hydroxide or potassium hydroxide.

The specific steps of adding in step (3) are: adding the alkaline solution dropwise into the precursor salt solution within 2 hours and stirring, and then continuing to stir for 2 hours.

The filtration in step (3) is suction filtration.

The drying in step (3) is performed by using an air drying oven.

The calcination in step (4) is performed at 700-1000°C for 0.5-2h; preferably at 900°C for 1h.

The reducing atmosphere in step (4) is H ₂ /N ₂ at a rate of 100 mL/min, and the ratio of H ₂ :N ₂ is 10:90.

The reduction in step (4) is carried out at 700-1000° C. for 0.5-2 h, preferably at 900° C. for 1 h.

The transition metal-supported high entropy oxide low-temperature methane dry reforming catalyst prepared by the above preparation method.

Application of the above transition metal supported high entropy oxide low temperature methane dry reforming catalyst in catalytic methane dry reforming.

The reaction temperature of the catalytic methane dry reforming is 550-650°C, preferably 600°C.

Compared with the prior art, the present invention has the following advantages and effects:

The catalyst prepared by the present invention has a strong catalytic cracking effect on methane at a relatively low temperature (600°C), and enhances the adsorption and dissociation of _CO2 , so that carbon deposition is not easy to be generated on the catalyst. At the same time, the entropy stability of the high entropy oxide carrier inhibits the migration of transition metals, effectively prolongs the life of the catalyst and maintains high catalytic activity. The raw materials used are cheap and easy to obtain, the preparation method is simple, the equipment requirements are low, and it is suitable for large-scale production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an XRD diagram of Ni/(CeZrMgYEr)O _2-x prepared in Example 1.

FIG. 2 is a TEM image of Ni/(CeZrMgYEr)O _2-x prepared in Example 1.

FIG. 3 is an EDX image of Ni/(CeZrMgYEr)O _2-x prepared in Example 1

FIG. 4 is an XPS graph of Ni/(CeZrMgYEr)O _2-x prepared in Example 1.

FIG. 5 is a CO ₂ -TPD graph of the dissolved transition metal-supported high entropy oxide catalyst prepared by the present invention.

FIG6 is a graph showing the conversion rate of the catalytic activity test of the dissolved transition metal-supported high entropy oxide catalyst prepared by the present invention.

FIG. 7 is a graph showing the H ₂ /CO result of the catalytic activity test of the dissolved transition metal-supported high entropy oxide catalyst prepared by the present invention.

FIG8 is a graph showing the results of a continuous 50 h catalytic activity test of Ni/(CeZrMgYEr)O _2-x prepared in Example 1.

FIG9 is a graph showing the TG analysis results of Ni/(CeZrMgYEr)O _2-x prepared in Example 1 after continuous 50 h catalytic activity testing.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

If no specific experimental conditions are specified in the following embodiments, conventional experimental conditions or experimental conditions recommended by the reagent company are generally followed. Materials and reagents used, unless otherwise specified, are all reagents and materials obtained from commercial sources.

Example 1 Preparation of Ni/(CeZrMgYEr)O _2-x

(1) Dissolve 1.45 g of nickel nitrate hexahydrate, 0.51 g of magnesium nitrate hexahydrate, 0.53 g of yttrium acetate hydrate, 0.86 g of zirconium nitrate pentahydrate, 0.87 g of cerium nitrate hexahydrate, and 0.92 g of erbium nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Dissolve 2.1 g of anhydrous potassium carbonate in 100 ml of deionized water and stir for 30 min to form an alkaline solution.

(3) Add the alkaline solution dropwise to the precursor salt solution within 2 hours, stir, and gradually form a stable suspension. After all the alkaline solution is dripped into the precursor salt solution and stirred for 2 hours, continue stirring for 2 hours. Then use a circulating water vacuum pump to filter, wash the filter residue with 100 ml of deionized water three times, and then put it into a 105°C forced air drying oven to dry for 12 hours to obtain a precipitate;

(4) The precipitate obtained in step (3) was placed in a muffle furnace and calcined at 900°C for 1 hour. 10% _H2 / _N2 ( _H2 : _N2 is 10:90) was introduced into the tube furnace at a rate of 100 ml/min to maintain the reducing atmosphere of the heating tube. The tube furnace was maintained at 900°C. 1 g of the precipitate calcined in step (3) was taken and placed in the tube furnace for reduction for 1 hour to obtain a transition metal-supported high entropy oxide low-temperature methane dry reforming catalyst Ni/(CeZrMgYEr)O2 _-x . The obtained catalyst was then subjected to XRD/TEM/EDX/XPS characterization tests, and the results are shown in Figures 1 to 4.

Example 2 Preparation of Fe/(CeZrMgYEr)O _2-x

(1) Dissolve 2.02 g of nickel nitrate nonahydrate, 0.51 g of magnesium nitrate hexahydrate, 0.53 g of yttrium acetate hydrate, 0.86 g of zirconium nitrate pentahydrate, 0.87 g of cerium nitrate hexahydrate, and 0.92 g of erbium nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Fe/(CeZrMgYEr)O _2-x was prepared by referring to the method of steps (2) to (4) of Example 1.

Example 3 Preparation of Co/(CeZrMgYEr)O _2-x

(1) Dissolve 1.46 g of cobalt nitrate hexahydrate, 0.51 g of magnesium nitrate hexahydrate, 0.53 g of yttrium acetate hydrate, 0.86 g of zirconium nitrate pentahydrate, 0.87 g of cerium nitrate hexahydrate, and 0.92 g of erbium nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Co/(CeZrMgYEr)O _2-x was prepared by referring to the method of steps (2) to (4) of Example 1.

Example 4 Ni/(CeZrMgYLa)O _2-x

(1) Dissolve 1.45 g of nickel nitrate hexahydrate, 0.51 g of magnesium nitrate hexahydrate, 0.53 g of yttrium acetate hydrate, 0.86 g of zirconium nitrate pentahydrate, 0.87 g of cerium nitrate hexahydrate, and 0.87 g of lanthanum nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Ni/(CeZrMgYLa)O _2-x was prepared by referring to the method of steps (2) to (4) of Example 1.

Example 5 Preparation of Ni/(Ce _0.1 Zr _0.4 Mg _0.2 Y _0.2 Er _0.1 )O _2-x

(1) Dissolve 1.45 g of nickel nitrate hexahydrate, 0.26 g of magnesium nitrate hexahydrate, 0.27 g of yttrium acetate hydrate, 0.86 g of zirconium nitrate pentahydrate, 0.22 g of cerium nitrate hexahydrate, and 0.46 g of erbium nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Ni/(Ce _0.1 Zr _0.4 Mg _0.2 Y _0.2 Er _0.1 )O _2-x was prepared by referring to steps (2) to (4) of Example 1.

Example 6 Preparation of Ni/(Ce _0.25 Zr _0.25 Mg _0.2 Y _0.2 Er _0.1 )O _2-x

(1) Dissolve 1.45 g of nickel nitrate hexahydrate, 0.26 g of magnesium nitrate hexahydrate, 0.27 g of yttrium acetate hydrate, 0.54 g of zirconium nitrate pentahydrate, 0.54 g of cerium nitrate hexahydrate, and 0.46 g of erbium nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Ni/(Ce _0.25 Zr _0.25 Mg _0.2 Y _0.2 Er _0.1 )O _2-x was prepared by referring to steps (2) to (4) of Example 1.

Example 7 Preparation of Ni/(Ce _0.4 Zr _0.1 Mg _0.2 Y _0.2 Er _0.1 )O _2-x

(1) Dissolve 1.45 g of nickel nitrate hexahydrate, 0.26 g of magnesium nitrate hexahydrate, 0.27 g of yttrium acetate hydrate, 0.21 g of zirconium nitrate pentahydrate, 0.87 g of cerium nitrate hexahydrate, and 0.46 g of erbium nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Ni/(Ce _0.4 Zr _0.1 Mg _0.2 Y _0.2 Er _0.1 )O _2-x was prepared by referring to steps (2) to (4) of Example 1.

Example 8 Preparation of Ni/(Ce _0.25 Zr _0.25 Mg _0.3 Y _0.1 Er _0.1 )O _2-x

(1) Dissolve 1.45 g of nickel nitrate hexahydrate, 0.77 g of magnesium nitrate hexahydrate, 0.27 g of yttrium acetate hydrate, 0.54 g of zirconium nitrate pentahydrate, 0.54 g of cerium nitrate hexahydrate, and 0.46 g of erbium nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Ni/(Ce _0.25 Zr _0.25 Mg _0.3 Y _0.1 Er _0.1 )O _2-x was prepared by referring to steps (2) to (4) of Example 1.

Example 9 Preparation of Ni/(Ce _0.25 Zr _0.25 Mg _0.1 Y _0.3 Er _0.1 )O _2-x

(1) Dissolve 1.45 g of nickel nitrate hexahydrate, 0.26 g of magnesium nitrate hexahydrate, 0.80 g of yttrium acetate hydrate, 0.54 g of zirconium nitrate pentahydrate, 0.54 g of cerium nitrate hexahydrate, and 0.46 g of erbium nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Ni/(Ce _0.25 Zr _0.25 Mg _0.1 Y _0.3 Er _0.1 )O _2-x was prepared by referring to steps (2) to (4) of Example 1.

Example 10 Preparation of Ni/(Ce _0.25 Zr _0.25 Mg _0.1 Y _0.1 Er _0.3 )O _2-x

(1) Dissolve 1.45 g of nickel nitrate hexahydrate, 0.26 g of magnesium nitrate hexahydrate, 0.27 g of yttrium acetate hydrate, 0.54 g of zirconium nitrate pentahydrate, 0.54 g of cerium nitrate hexahydrate, and 1.38 g of erbium nitrate hexahydrate in 100 ml of deionized water and stir for 30 minutes to form a precursor salt solution.

(2) Ni/(Ce _0.25 Zr _0.25 Mg _0.1 Y _0.1 Er _0.3 )O _2-x was prepared by referring to steps (2) to (4) of Example 1.

Example 11 Study on CO ₂ adsorption characteristics of transition metal supported high entropy oxides

CO ₂ temperature programmed desorption (CO ₂ -TPD) experiments were performed on Example 1 and Examples 8 to 10 on an AutoChem1 II 2920 device. About 50 mg of fresh sample was placed in a U-shaped quartz tube, pretreated for 30 min at 300°C and an argon flow rate of 20 mL·min ^-1 , and then cooled to 50°C. The gas was then switched to 10% CO ₂ /N ₂ (50 mL·min-1) to adsorb CO ₂ for 1 h. After purging for 1 h under an argon flow (50 mL·min ^- 1), the sample was heated to 800°C (10°C·min ^-1 ). The desorbed CO ₂ was recorded using a thermal conductivity detector (TCD). The experimental results are recorded as shown in Figure 5. Among them, the CO ₂ adsorption amount of Example 1 is much higher than that of other examples, proving that Example 1 has excellent CO ₂ adsorption capacity.

Example 12 Study on the catalytic activity of transition metal supported high entropy oxides

0.6 g of the catalyst prepared in Example 1 was added to a straight quartz tube (length 350 mm, inner diameter = 12 mm) and fixed in the middle of the tube with quartz wool. The raw gas (36% CH ₄ , 21% CO ₂ , 7% O ₂ , balanced with N ₂ ) was passed through the catalyst at a total flow rate of 140 mL·min ^-1 . The quartz tube was placed in a tube furnace at a constant temperature of 600°C for reaction. The generated gas was collected 1 hour after the start of the reaction, and the collection time was 2 minutes each time, and the concentration of the gas product in the reactor effluent was analyzed by GC (Agilent).

The CH ₄ and CO ₂ conversion rates and H ₂ /CO values of the samples were calculated, and the calculation results were statistically analyzed, as shown in FIG6 .

The CH ₄ conversion rate was calculated according to the following formula:

Wherein, C _CH4 is the CH ₄ conversion rate, N _CH4,in is the CH ₄ input amount, and N _{CH4,out is} the CH ₄ remaining amount after the reaction detected in the gas phase.

The _CO2 conversion rate is calculated according to the following formula:

Among them, C _CO2 is the CO ₂ conversion rate, N _CO2,in is the CO ₂ input amount, and N _{CO2,out is} the CO ₂ remaining amount after the reaction detected in the gas phase.

The H ₂ /CO value is calculated according to the following formula:

Wherein, _{NH2,OUT is} the amount _{of H2} produced after the reaction detected in the gas phase, and _{NCO,OUT is} the amount of CO produced after the reaction detected in the gas phase.

The catalysts prepared in Examples 2 to 10 were subjected to the same test.

The experimental results are shown in Figures 6 and 7. The conversion rates of CH ₄ and CO ₂ in Example 1 are the highest compared with those in other examples. The reason why the conversion rate of CO ₂ is lower than that of CH ₄ is that O ₂ and CO ₂ in the atmosphere are in a competitive relationship in the reaction, and the conversion of O ₂ replaces part of the conversion of CO _2. In addition, the H ₂ /CO in Example 1 is closest to 1 compared with those in other examples, indicating that almost no side reactions occur. The above proves that Example 1 has excellent catalytic performance.

Example 13 Study on the Cycling Effect of Transition Metal Supported High Entropy Oxides

The setting of the cycle experiment was consistent with the catalytic activity experiment of Example 12. The gas production began to be collected 1 hour after the start of the reaction, and then collected once every 1 hour for 50 consecutive times. The experimental results are statistically shown in Figure 8.

As shown in Figure 8, the _CH4 conversion rate was relatively stable in the first 28 hours, above 50%, and the highest conversion rate reached 54.5%. Then it slowly decreased and dropped to the lowest value at the 50th hour, but still had a conversion rate of 40.4%. The _CO2 conversion rate was relatively stable, almost maintained between 10% and 15% within 50 hours. The _CH4 conversion rate and _CO2 conversion rate remained at a relatively stable level in 50 hours, proving that Example 1 has a high stability. In addition, there are fewer side reactions in the early stage of the reaction, and the products are mainly _H2 and CO, so the _H2 /CO value is close to 1.00.

As shown in FIG. 9 , after 50 hours of continuous reaction, only 5.52 wt % of carbon deposits were generated in Example 1, indicating that Example 1 can effectively inhibit the generation of carbon deposits in the reaction.

The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims (3)

1. A transition metal supported high entropy oxide low temperature methane dry reforming catalyst, characterized in that: It is composed of one of the following: Ni/(CeZrMgYEr)O _2-x ， Fe/(CeZrMgYEr)O _2-x ， Co/(CeZrMgYEr)O _2-x ， Ni/(CeZrMgYLa)O _2-x ， Ni/(Ce _0.1 Zr _0.4 Mg _0.2 Y _0.2 Er _0.1 )O _2-x , Ni/(Ce _0.25 Zr _0.25 Mg _0.2 Y _0.2 Er _0.1 )O _2-x , Ni/(Ce _0.4 Zr _0.1 Mg _0.2 Y _0.2 Er _0.1 )O _2-x , Ni/(Ce _0.25 Zr _0.25 Mg _0.3 Y _0.1 Er _0.1 )O _2-x , Ni/(Ce _0.25 Zr _0.25 Mg _0.1 Y _0.3 Er _0.1 )O _2-x , Ni/(Ce _0.25 Zr _0.25 Mg _0.1 Y _0.1 Er _0.3 )O _2-x . 2. The method for preparing the transition metal supported high entropy oxide low temperature methane dry reforming catalyst according to claim 1, characterized in that it comprises the following steps: (1) Preparation of metal salt solution; (2) preparing alkaline solution; (3) adding the alkaline solution to the metal salt solution, filtering and drying to obtain a precipitate; (4) calcining the precipitate obtained in step (3), and then reducing it in a reducing atmosphere to obtain a transition metal-supported high entropy oxide low-temperature methane dry reforming catalyst; The catalyst is Ni/(CeZrMgYEr)O _2-x , Fe/(CeZrMgYEr)O _2-x , Co/(CeZrMgYEr)O _2-x , Ni/(Ce _0.1 Zr _0.4 Mg _0.2 Y _0.2 Er _0.1 )O _2-x , Ni/(Ce _0.25 Zr _0.25 Mg _0.2 Y _0.2 Er _0.1 )O _2-x , Ni/(Ce _0.4 Zr _0.1 Mg _0.2 Y _0.2 Er _0.1 )O _2-x , Ni/(Ce _0.25 Zr _0.25 Mg _0.3 Y _0.1 Er _0.1 )O _2-x ，Ni/(Ce _0.25 Zr _0.25 Mg _0.1 Y _0.3 Er _0.1 )O _2-x , Ni/(Ce _0.25 Zr _0.25 Mg _0.1 Y _0.1 Er _0.3 )O _2-x , the metal salt is a nitrate of cerium, zirconium, magnesium, yttrium or erbium or acetate, and one of the nitrates of nickel, iron, or cobalt; When the catalyst is Ni/(CeZrMgYLa)O _2-x , the metal salt is nitrate or acetate of cerium, zirconium, magnesium, yttrium and lanthanum, and nickel nitrate; The alkaline solution in step (2) is at least one of an aqueous solution of sodium carbonate, potassium carbonate, sodium hydroxide or potassium hydroxide; The specific steps of the preparation described in step (1) are: Dissolving a metal salt in water and stirring to obtain a metal salt solution; The specific steps of adding in step (3) are: The alkaline solution was added dropwise to the metal salt solution within 2 h with stirring, and then continued to stir for 2 h; The filtration in step (3) is suction filtration; The drying in step (3) is performed by using an air drying oven; The calcination in step (4) is performed at 700-1000°C for 0.5-2 h; The reducing atmosphere in step (4) is H ₂ /N ₂ at a rate of 100 mL/min, and the ratio of H ₂ :N ₂ is 10:90; The reduction in step (4) is carried out at 700-1000° C. for 0.5-2 h. 3. Use of the transition metal-supported high entropy oxide low-temperature methane dry reforming catalyst according to claim 1 in catalytic methane dry reforming.