TWI891075B - A catalyst used in dry reforming of methane and preparation method thereof - Google Patents

Abstract

This invention provides a catalyst used in dry reforming of methane, which comprises an active component including Ni-MgO composite and a composite aluminum-phosphorus compound support that supports said active component and includes xAl ₂O ₃-AlPO ₄composite. x ranges from 0 to 4. Based on a total amount of said catalyst being 100wt%, a content range of Ni in said Ni-MgO composite is 5wt% to 30wt%, a content range of MgO in said Ni-MgO composite is 2wt% to 10wt%, and a content range of xAl ₂O ₃-AlPO ₄composite is 65wt% to 90wt%. This invention also provides a preparation method of a catalyst used in dry reforming of methane, which comprises a mixture with a pH value of 7 to 9 and containing an aluminum source compound and phosphoric acid is matured, filtered, dried and calcined in sequence to obtain a composite aluminum-phosphorus compound support including xAl ₂O ₃-AlPO ₄composite. Said composite aluminum-phosphorus compound support is impregnated with a solution in which a nickel source compound and a magnesium source compound are dissolved, and then dried, calcined and reduced in sequence to obtain a catalyst used in dry reforming of methane.

Description

Catalyst for methane dry reforming reaction and preparation method thereof

The present invention relates to a catalyst and a preparation method thereof, and in particular to a catalyst for methane dry reforming reaction and a preparation method thereof.

In recent years, research has begun to explore how to effectively utilize greenhouse gases (GHGs) such as methane and carbon dioxide (CO2) produced by burning natural gas or fossil fuels. Through methane dry reforming, methane and CO2 can be converted into synthesis gas (syngas), consisting of carbon monoxide and hydrogen. This synthesis gas can then be used to produce high-value-added hydrocarbon products such as methanol, acetic acid, dimethyl ether, hydroxyl alcohols, and long-chain hydrocarbons.

The methane dry reforming reaction is endothermic and requires high activation energy, necessitating high temperatures of 700°C to 900°C. To reduce the activation energy required, nickel catalysts are typically added to save energy and accelerate the reaction rate. Nickel catalysts comprise a nickel active component and an _Al2O3 substrate. However, the _Al2O3 substrate has small pores. Therefore, when the _methane dry reforming reaction is carried out at high temperatures of 700°C to 900°C, the diffusion of methane and carbon dioxide within the _{Al2O3 substrate} is easily hindered, resulting in poor mass transfer rates for methane and carbon dioxide. Consequently, the _nickel catalyst's effectiveness in accelerating the reaction rate is less than expected, and the conversion rates of methane and carbon dioxide are poor. Consequently, existing nickel catalysts exhibit poor catalytic activity.

Therefore, one object of the present invention is to provide a catalyst having high catalytic activity for methane dry reforming reaction.

Therefore, the catalyst for methane dry reforming reaction of the present invention comprises an active component and a composite aluminum-phosphorus compound carrier.

The active component includes a Ni-MgO composite. The composite aluminum-phosphorus compound carrier supports the active component and includes _{an xAl2O3-AlPO4 composite ,} where x ranges from 0 to 4. Based on 100 wt% of the total catalyst for methane dry reforming, the Ni content of the Ni-MgO composite ranges from 5 wt% to 30 wt%, the MgO content of the Ni-MgO composite ranges from 2 wt% to 10 wt%, and _{the xAl2O3-AlPO4 composite ranges} from 65 wt% to 90 wt%.

Another object of the present invention is to provide a method for preparing a catalyst for methane dry reforming reaction.

Therefore, the method for preparing a catalyst for methane dry reforming reaction of the present invention comprises: step (a), step (b), step (c), step (d), step (e), step (f), step (g), step (h) and step (i).

The step (a) is to dissolve an aluminum source compound and phosphoric acid in water to obtain a first mixture, wherein the molar ratio of aluminum in the aluminum source compound to phosphorus in the phosphoric acid ranges from 1 to 5.

The step (b) is to adjust the pH of the first mixture with an alkaline reagent to obtain a second mixture with a pH of 7 to 9.

The step (c) comprises aging the second mixture for 1 to 4 hours to obtain a third mixture containing a precipitate, and filtering the third mixture to obtain the precipitate.

The step (d) is to dry the precipitate at 50° C. to 150° C. for 2 to 6 hours to obtain a powdery solid.

The step (e) is to calcine the powdered solid at 300°C to 600°C for 2 hours to 6 hours to obtain a composite aluminum-phosphorus compound carrier including an xAl ₂ O ₃ -AlPO ₄ complex, where x ranges from 0 to 4.

The step (f) is to impregnate the composite aluminum-phosphorus compound support with an aqueous solution containing a nickel source compound and a magnesium source compound to obtain a first catalyst precursor.

The step (g) is to dry the first catalyst precursor at 60° C. to 150° C. for 2 to 6 hours to obtain a second catalyst precursor.

The step (h) is to calcinate the second catalyst precursor at 200° C. to 400° C. for 2 to 6 hours to obtain a third catalyst precursor.

The step (i) is to subject the third catalyst precursor to an oxidation-reduction reaction at 300° C. to 500° C. for 2 to 6 hours in a reaction atmosphere containing one of helium and nitrogen and hydrogen, thereby obtaining a catalyst for methane dry reforming reaction. The catalyst for methane dry reforming reaction comprises an active component and a composite aluminum-phosphorus compound carrier, wherein the composite aluminum-phosphorus compound carrier supports the active component, and the active component comprises a Ni-MgO composite. Based on the total amount of the catalyst for methane dry reforming reaction as 100wt%, the content of Ni in the Ni-MgO composite ranges from 5wt% to 30wt%, the content of MgO in the Ni-MgO composite ranges from 2wt% to 10wt%, and the xAl ₂ O ₃ -AlPO 4 is 0.05wt% and 0.1wt% respectively. ₄ The content of the complex ranges from 65wt% to 90wt%.

One benefit of the present invention is that the catalyst for methane dry reforming of the present invention exhibits high catalytic activity for methane and carbon dioxide at temperatures between ₇₀₀ °C _{and 900} ° _C , resulting in methane conversion rates exceeding 98% and carbon dioxide conversion rates exceeding 98%, due to the combination of the active component and the composite aluminum-phosphorus compound support, particularly the _xAl2O3 - _AlPO4 complex in the composite aluminum-phosphorus compound support, the Ni in the Ni-MgO complex, the MgO in the Ni-MgO complex, and the xAl2O3 _- AlPO4 complex in the catalyst for methane dry reforming.

Another benefit of the present invention is that the method for preparing a catalyst for methane dry reforming reaction of the present invention controls the pH of the second mixture between 7 and 9 through the combination of steps (a) to (i), particularly step (b). Therefore, the method for preparing a catalyst for methane dry reforming reaction can ensure that a composite aluminum-phosphorus compound matrix having a large number of pores with large pore diameters is obtained. Furthermore, the composite aluminum-phosphorus compound matrix can improve the dispersion of the active component in the composite aluminum-phosphorus compound matrix and increase the mass transfer rate of methane and carbon dioxide in the composite aluminum-phosphorus compound matrix, thereby endowing the catalyst for methane dry reforming reaction with excellent catalytic activity.

The catalyst for methane dry reforming of the present invention is suitable for catalyzing a methane dry reforming reaction in a gaseous composition comprising methane and carbon dioxide to promote the conversion of the methane and carbon dioxide into synthesis gas comprising carbon monoxide and hydrogen. The catalyst for methane dry reforming comprises an active component and a composite aluminum-phosphorus compound support.

The active component comprises a Ni-MgO composite. The composite aluminum-phosphorus compound carrier supports the active component. The composite aluminum-phosphorus compound carrier comprises an _xAl2O3 - _AlPO4 composite, where x ranges from 0 to _4. Based on 100 wt% of the total catalyst for methane dry reforming, the Ni content of the Ni-MgO composite ranges from 5 wt% to 30 wt%, the MgO content of the Ni-MgO composite ranges from 2 wt% to 10 wt%, and the _{xAl2O3 -AlPO4 composite} ranges from 65 wt% to 90 wt%.

Specifically, the Ni-MgO complex in the active component is formed by forging and redox-reducing raw materials containing a nickel source compound and a magnesium source compound, thereby converting the nickel source compound and the magnesium source compound in the raw materials into a complex composed of Ni and MgO. The nickel source compound is a compound capable of donating nickel ions, and the magnesium source compound is a compound capable of donating magnesium ions. The Ni-MgO complex exhibits high catalytic activity for the dry reforming of methane with carbon dioxide, imparting excellent catalytic stability to the catalyst used for this reaction. Furthermore, the Ni-MgO complex exhibits high selectivity for promoting the dry reforming of methane with carbon dioxide to produce high yields of carbon monoxide and hydrogen. In addition, the MgO in the Ni-MgO composite can also inhibit the carbon generated during the methane dry reforming reaction from being deposited on the Ni in the Ni-MgO composite.

The _xAl2O3 - _AlPO4 complex in the composite aluminum-phosphorus compound carrier is prepared by subjecting _a raw material comprising an aluminum source compound and phosphoric acid to aging, drying, and calcining to convert the aluminum source compound and phosphoric acid in the raw material into aluminum phosphate (i.e., x in the _xAl2O3 - _AlPO4 complex is 0), or into aluminum oxide and aluminum phosphate, thereby forming a complex composed of the aluminum oxide and aluminum phosphate (i.e., x in _{the xAl2O3-AlPO4 complex is in} the range of 1 to 4). The aluminum source compound is a compound capable of providing aluminum ions. x represents the molar number of _Al2O3 in the _{xAl2O3 - AlPO4} complex, based on 1 mol of _AlPO4 . In the present invention, by controlling x in the _xAl2O3 - _AlPO4 complex to be within a range of 0 to _{4 ,} the composite aluminum- _{phosphorus compound} support has a plurality of pores with a pore diameter range of greater than 2 _nm and less than 100 nm. This improves the dispersion of the active component in the composite aluminum-phosphorus compound support and increases the mass transfer rate of methane and carbon dioxide in the composite aluminum-phosphorus compound support, thereby imparting the catalyst for methane dry reforming with the advantage of increasing the reaction rate. In some embodiments of the present invention, in order to make the catalyst for methane dry reforming reaction have better catalytic activity, the range of x is 1 to 4. In some embodiments of the present invention, the range of x is 1 to 2. In one specific example of the present invention, the x is 1.

By controlling the Ni content of the Ni-MgO composite in the catalyst for methane dry reforming within a range of 5 wt% to 30 wt%, the catalyst for methane dry reforming can have high catalytic activity. Furthermore, controlling the Ni content of the Ni-MgO composite to below 30 wt% can prevent the Ni particles in the Ni-MgO composite from becoming too large, which would reduce the surface area of the Ni-MgO composite and lead to reduced catalytic activity. It also prevents the Ni particles from becoming too large, which would lead to clogging of the pores of the composite aluminum-phosphorus compound matrix. Furthermore, controlling the Ni content of the Ni-MgO composite to below 30 wt% can also avoid the problem of excessively high production costs of the catalyst for methane dry reforming. By controlling the MgO content of the Ni-MgO composite in the catalyst for methane dry reforming within a range of 2wt% to 10wt%, the catalyst can exhibit high catalytic activity. Furthermore, controlling the MgO content in the Ni-MgO composite to below 10wt% can prevent clogging of the pores of the composite aluminum- _phosphorus compound support, thereby facilitating the adsorption of carbon dioxide for the reaction. By controlling the _xAl2O3 - _AlPO4 composite content in the catalyst for methane dry reforming within a range of 65wt% to 90wt%, the catalyst can exhibit high catalytic activity.

In some embodiments of the present invention, to further control the particle size of the Ni particles in the Ni-MgO composite, thereby increasing the surface area of the Ni-MgO composite and thereby enhancing the catalytic activity of the catalyst for methane dry reforming, the Ni content in the Ni-MgO composite is set at 5% to 25% by weight, based on 100% by weight of the total catalyst for methane dry reforming. Furthermore, further controlling the Ni content in the Ni-MgO composite within a range of 5% to 25% by weight can further reduce the production cost of the catalyst for methane dry reforming.

The catalyst for the methane dry reforming reaction can be placed in a fixed-bed reactor and used to catalyze the methane dry reforming reaction of methane and carbon dioxide, wherein the reaction temperature of the methane dry reforming reaction ranges from 700°C to 900°C, the reaction pressure is 1 atm, and the molar ratio of carbon dioxide to methane ranges from 0.8 to 1.2.

The present invention also provides a method for preparing a catalyst for methane dry reforming reaction, comprising step (a), step (b), step (c), step (d), step (e), step (f), step (g), step (h), and step (i).

The step (a) is to dissolve an aluminum source compound and phosphoric acid in water to obtain a first mixture, wherein the molar ratio of aluminum in the aluminum source compound to phosphorus in the phosphoric acid ranges from 1 to 5.

The step (b) is to adjust the pH of the first mixture with an alkaline reagent to obtain a second mixture with a pH of 7 to 9.

The step (c) comprises aging the second mixture for 1 to 4 hours to obtain a third mixture containing a precipitate, and filtering the third mixture to obtain the precipitate.

The step (d) is to dry the precipitate at 50° C. to 150° C. for 2 to 6 hours to obtain a powdery solid.

The step (e) is to calcine the powdered solid at 300°C to 600°C for 2 hours to 6 hours to obtain a composite aluminum-phosphorus compound carrier including an xAl ₂ O ₃ -AlPO ₄ complex, where x ranges from 0 to 4.

The step (f) is to impregnate the composite aluminum-phosphorus compound support with an aqueous solution containing a nickel source compound and a magnesium source compound to obtain a first catalyst precursor.

The step (g) is to dry the first catalyst precursor at 60° C. to 150° C. for 2 to 6 hours to obtain a second catalyst precursor.

The step (h) is to calcinate the second catalyst precursor at 200° C. to 400° C. for 2 to 6 hours to obtain a third catalyst precursor.

The step (i) is to subject the third catalyst precursor to an oxidation-reduction reaction at 300° C. to 500° C. for 2 to 6 hours in a reaction atmosphere containing one of helium and nitrogen and hydrogen, thereby obtaining a catalyst for methane dry reforming reaction. The catalyst for methane dry reforming reaction comprises an active component and a composite aluminum-phosphorus compound carrier, wherein the composite aluminum-phosphorus compound carrier supports the active component, and the active component comprises a Ni-MgO composite. Based on the total amount of the catalyst for methane dry reforming reaction as 100wt%, the content of Ni in the Ni-MgO composite ranges from 5wt% to 30wt%, the content of MgO in the Ni-MgO composite ranges from 2wt% to 10wt%, and the xAl ₂ O ₃ -AlPO 4 is 0.05wt% and 0.1wt% respectively. ₄ The content of the complex ranges from 65wt% to 90wt%.

In step (a), the type of aluminum source compound is not particularly limited; any compound that is soluble in water and provides aluminum ions is suitable for use in the present invention. In some embodiments of the present invention, to prevent poisoning of the Ni in the Ni-MgO composite and reduced catalytic activity, the aluminum source compound does not contain sulfur. In some embodiments of the present invention, the aluminum source compound is selected from aluminum nitrate, etc. In the present invention, by controlling the molar ratio of aluminum in the aluminum source compound to phosphorus in the phosphoric acid within a range of 1 to 5, the composite aluminum-phosphorus compound matrix can have pores with a pore size range of greater than 2 nm and less than 100 nm.

In step (b), the type of alkaline reagent is not particularly limited; any reagent capable of adjusting the pH of the first mixture to a range of 7 to 9, thereby obtaining the second mixture, is suitable for use in the present invention. Examples of alkaline reagents include, but are not limited to, aqueous ammonia and urea. In some embodiments of the present invention, to obtain an impurity-free composite aluminum-phosphorus compound carrier after the powdered solid is forged, the alkaline reagent is aqueous ammonia at a concentration of 1M to 5M. In the present invention, controlling the pH of the second mixture above 7 facilitates the precipitation of aluminum phosphate in the second mixture and ensures that, when aluminum oxide is present, the aluminum phosphate can form an _xAl2O3 - _AlPO4 complex (x is 1 to ₄ ) with the aluminum oxide. Controlling the pH of the second mixture below 9 prevents the problem of the composite aluminum-phosphorus compound body's surface area being reduced due to the reduced pore size.

In step (c), the precipitate is an aluminum-phosphorus hydroxide. In the present invention, by controlling the aging time to 1 to 4 hours, the problem of the surface area of the composite aluminum-phosphorus compound carrier being reduced can be avoided.

In the step (d), by controlling the drying conditions to 50° C. to 150° C. for 2 to 6 hours, water adsorbed on the precipitate by physical adsorption can be effectively removed.

In step (e), controlling the calcination conditions between 300°C and 600°C for 2 to 6 hours facilitates the formation of the _xAl₂O₃ - _AlPO₄ complex, effectively removes impurities from the powdered solid derived from the aluminum source compound, and prevents a reduction in the surface area of the composite aluminum _- phosphorus compound. In some embodiments of the present invention, when the aluminum source compound is aluminum nitrate, the impurities derived from the aluminum source compound are nitrate ions. Specifically, when the forging temperature is less than 300°C, impurities originating from the aluminum source compound on the powdered solid cannot be removed; when the forging temperature is greater than 600°C, the surface area of the composite aluminum-phosphorus compound body will decrease; when the forging time is less than 2 hours, the incomplete phase transformation of aluminum oxide and aluminum phosphate will be detrimental to the formation of the _xAl2O3 - _AlPO4 complex; _and when the forging time is greater than 6 hours, the surface area of the composite aluminum-phosphorus compound body will decrease. In some embodiments of the present invention, the forging treatment in step (e) includes a first forging step and a second forging step after the first forging step. The first forging step is performed to remove water from the powdered solid, thereby facilitating the second forging step. The second forging step is performed to remove impurities from the powdered solid that originate from the aluminum source compound and to prevent changes in the surface area of the composite aluminum-phosphorus compound matrix.

In step (f), the types of the nickel source compound and the magnesium source compound are not particularly limited; any compound that is soluble in water and provides nickel ions, and any compound that is soluble in water and provides magnesium ions, are suitable for use in the present invention. In some embodiments of the present invention, to prevent Ni poisoning in the Ni-MgO composite and thus reducing catalytic activity, both the nickel source compound and the magnesium source compound are sulfur-free. In some embodiments of the present invention, the nickel source compound is selected from nickel nitrate, nickel acetate, and the like. In some embodiments of the present invention, the magnesium source compound is selected from magnesium nitrate, magnesium acetate, and the like.

In step (g), by controlling the drying conditions to 60° C. to 150° C. for 2 to 6 hours, water adsorbed on the first catalyst precursor by physical adsorption can be effectively removed.

In step (h), by controlling the calcination conditions at 200° C. to 400° C. for 2 to 6 hours, impurities from the nickel source compound and the magnesium source compound on the second catalyst precursor can be effectively removed, and the nickel from the nickel source compound and the magnesium from the magnesium source compound are converted to nickel oxide and magnesium oxide, respectively. In some embodiments of the present invention, when the nickel source compound is nickel nitrate and the magnesium source compound is magnesium nitrate, the impurities from the nickel source compound and the magnesium source compound are nitrate ions.

In step (i), by controlling the redox reaction conditions at 300° C. to 500° C. for 2 to 6 hours, nickel oxide and/or nickel ions present in the third catalyst precursor can be reduced to metallic nickel while preventing the metallic nickel from becoming too large in particle size. This allows the metallic nickel to react with magnesium oxide formed from magnesium ions to form the Ni-MgO composite.

The present invention will be further described with reference to the following embodiments. However, it should be understood that the embodiments are for illustration only and should not be construed as limiting the implementation of the present invention.

[Example 1] Catalyst for methane dry reforming reaction

Aluminum nitrate [Al(NO ₃ ) ₃ ] and phosphoric acid are dissolved in water to obtain a first mixture, wherein the molar ratio of aluminum in the aluminum nitrate to phosphorus in the phosphoric acid is 1. The pH of the first mixture is adjusted with 1M aqueous ammonia to obtain a second mixture having a pH of 8 to 9. The second mixture is then stirred and aged at 25°C for 2 hours to obtain a third mixture containing a precipitate of aluminum phosphate hydroxide, wherein the pH of the second mixture is maintained at 8 to 9 during the aging process. The third mixture is filtered to obtain the precipitate. The precipitate is then dried in an oven at 100°C for 2 hours to obtain a powdered solid. The powdered solid was placed in a forging furnace and subjected to a first forging step at 320°C for one hour and a second forging step at 550°C for one hour to obtain a composite aluminum-phosphorus compound support including an _xAl2O3 - _AlPO4 complex, wherein x in the _xAl2O3 - _AlPO4 complex is ₀ , i.e., _{the xAl2O3-AlPO4 complex is AlPO4 .}

The saturated water absorption of the composite aluminum-phosphorus compound support was measured, and 62.2 grams of nickel nitrate [Ni( _NO3 ) ₂ ] and 30.5 grams of magnesium nitrate [Mg( _NO3 ) ₂ ] were dissolved in deionized water equal to the saturated water absorption, yielding an aqueous solution containing the nickel nitrate and magnesium nitrate. The composite aluminum-phosphorus compound support was then added to the aqueous solution and impregnated with the aqueous solution, such that the dissolved nickel nitrate and magnesium nitrate in the aqueous solution were held within the pores of the composite aluminum-phosphorus compound support, thereby yielding a first catalyst precursor. The first catalyst precursor was placed in an oven and dried at 80°C for 3 hours. The dried first catalyst precursor was then ground into a powder to obtain a second catalyst precursor. The second catalyst precursor was then placed in a forging furnace and calcined at 400°C for 4 hours to obtain a third catalyst precursor. Finally, the third catalyst precursor was placed in a reaction atmosphere containing nitrogen and 10 vol% hydrogen and subjected to a redox reaction at 400° C. for 4 hours to obtain a catalyst for methane dry reforming reaction comprising an active component and a composite aluminum-phosphorus compound support. The active component included a Ni-MgO composite, the composite aluminum-phosphorus compound support included an xAl ₂ O ₃ -AlPO ₄ composite, and the catalyst for methane dry reforming reaction contained 20 wt% Ni, 5 wt% MgO, and 75 wt% xAl ₂ O ₃ -AlPO ₄ composite. The catalyst for methane dry reforming reaction can also be expressed as Ni-MgO/xAl ₂ O ₃ -AlPO ₄ catalyst.

[Examples 2 to 4] Catalyst for methane dry reforming reaction

Examples 2 to 4 were prepared in a manner similar to Example 1 to obtain catalysts for methane dry reforming, except that the molar ratio of aluminum in the aluminum nitrate to phosphorus in the phosphoric acid in the first mixture was varied. The molar ratios of aluminum in the aluminum nitrate to phosphorus in the phosphoric acid in Examples 2 to 4 were 2, 3, and 5, respectively, and x in _{the xAl2O3} - _AlPO4 complexes of Examples 2 to 4 was 0.5, 1, and 2, respectively, as shown in Table 1.

[Comparative Example 1] Ni/MgO Catalyst

Using MgO as a carrier and measuring its saturated water absorption, nickel nitrate [Ni( _NO₃ ) _₂ ] is dissolved in a volume of deionized water equal to the saturated water absorption to obtain an aqueous solution containing the nickel nitrate. MgO is then added to the aqueous solution and allowed to impregnate the aqueous solution, so that the dissolved nickel nitrate in the aqueous solution is carried within the pores of the MgO, thereby obtaining a first catalyst precursor. The first catalyst precursor is then dried in an oven at 80°C for 3 hours. The dried first catalyst precursor is then ground into a powder to obtain a second catalyst precursor. Next, the second catalyst precursor was placed in a forging furnace and calcined at 400°C for 4 hours to obtain a third catalyst precursor. Finally, the third catalyst precursor was placed in a reaction atmosphere containing nitrogen and 10 vol% hydrogen and subjected to a redox reaction at 400°C for 4 hours to obtain a catalyst comprising Ni as an active component and MgO as a carrier, i.e., a Ni/MgO catalyst.

[Comparative Example 2] Ni-MgO/Al ₂ O ₃ Catalyst

Using _Al2O3 as a carrier and measuring the saturated water absorption _of the _Al2O3 , nickel nitrate _[ Ni( _NO3 ) ₂ ] and magnesium nitrate [Mg( _NO3 ) ₂ ] are dissolved in deionized water at _a volume corresponding to the saturated water absorption, thereby obtaining an aqueous solution containing the nickel nitrate and magnesium _nitrate . _Al2O3 is then added to the aqueous solution and allowed to impregnate the _Al2O3 , so that the dissolved nickel nitrate and magnesium nitrate in the aqueous solution are carried in the pores of the _{Al2O3 ,} thereby obtaining a first catalyst precursor. The first catalyst precursor was placed in an oven and dried at 80°C for 3 hours. The dried first catalyst precursor was then ground into a powder to obtain a second catalyst precursor. The second catalyst precursor was then placed in a forging furnace and calcined at 400°C for 4 hours to obtain a third catalyst precursor. Finally, the third catalyst precursor was placed in a reaction atmosphere containing nitrogen and 10 vol% hydrogen and subjected to a redox reaction at 400°C for 4 hours to obtain a catalyst comprising a Ni-MgO composite as an _active component and _Al2O3 as a carrier, i.e., _a Ni-MgO/ _Al2O3 catalyst.

[Evaluation items]

X-ray Diffraction Analysis: The catalyst used in Example 1 for methane dry reforming is used as an example for illustration. Examples 2 to 4 were analyzed in the same manner. X-ray diffraction analysis of the catalyst used in Example 1 for methane dry reforming was performed using an X-ray diffraction instrument (Bruker, Model: D8 Advance). The scanning angle range was 10 degrees to 90 degrees 2θ, the scanning speed was 1 degree/min, the target material was a copper target, the operating voltage was 30 kV, and the operating current was 20 mA. The X-ray diffraction analysis results of the catalyst used in Examples 1 to 4 are shown in Figures 1 to 4.

Nitrogen Adsorption/Desorption Analysis: The following description uses the catalyst for methane dry reforming of Example 1 as an example. Examples 2 to 4 were analyzed in the same manner. The catalyst for methane dry reforming of Example 1 was analyzed using a nitrogen automatic adsorption instrument (Micromeritics, Model: ASAP 2020). Nitrogen was physically adsorbed onto the catalyst at 77 K (approximately -196°C). The catalyst was then heated at 573 K (approximately 300°C) for 24 hours to desorb nitrogen from the catalyst until the pressure within the nitrogen automatic adsorption instrument reached 2× ^10-5 Torr. The pore size distribution of the catalyst for methane dry reforming was then calculated using the BJH pore size distribution analysis method and the obtained nitrogen desorption curve. The adsorption isotherms and nitrogen desorption curves of the catalysts for methane dry reforming in Examples 1 to 4 are shown in Figures 5 to 8 . The pore size distribution results of the catalysts for methane dry reforming in Examples 1 to 4 are shown in Figures 9 and 10 .

Methane and Carbon Dioxide Conversion: The following description uses the catalyst for methane dry reforming in Example 1 as an example. Examples 2 to 4 and Comparative Examples 1 and 2 were analyzed in the same manner. The catalyst for methane dry reforming in Example 1 was placed in a fixed-bed reactor, and a gaseous component comprising methane, carbon dioxide, and argon was introduced into the fixed-bed reactor to conduct a methane dry reforming reaction, thereby obtaining a gaseous product comprising synthesis gas containing carbon monoxide and hydrogen. The operating pressure in the fixed-bed reactor was 1 atm, the temperature in the fixed-bed reactor was 700°C to 900°C, the spatial velocity of the reactant gas in the fixed-bed reactor was 60,000 mL ^{g⁻¹ h⁻¹} , and the volumetric proportions of methane, carbon dioxide, and argon in the reactant gas were 40 vol%, 40 vol%, and 20 vol%, respectively. The methane conversion rate and carbon dioxide conversion rate of the catalyst used in the methane dry reforming reaction to convert methane and carbon dioxide into synthesis gas were calculated using the following formulas. The results are shown in Table 2. Methane conversion rate (%) = (methane moles in the reaction gas - methane moles in the product gas) / methane moles in the reaction gas × 100% Carbon dioxide conversion rate (%) = (carbon dioxide moles in the reaction gas - carbon dioxide moles in the product gas) / carbon dioxide moles in the reaction gas × 100%

Table 1 Embodiment 1 2 3 4 Aluminum nitrate (g) 130.9 261.8 392.7 654.5 Phosphoric acid (g) 49.2 49.2 49.2 49.2 Molar ratio of aluminum in aluminum nitrate to phosphorus in phosphoric acid 1 2 3 5 Nickel nitrate (g) 62.2 62.2 62.2 62.2 Magnesium nitrate (g) 30.5 30.5 30.5 30.5 Catalyst for methane dry reforming reaction Ni(wt%) 20 20 20 20 MgO(wt%) 5 5 5 5 xAl ₂ O ₃ -AlPO ₄ (wt%) 75 75 75 75 x in xAl ₂ O ₃ -AlPO ₄ 0 0.5 1 2

Table 2 Embodiment Comparative example 1 2 3 4 1 2 Carbon dioxide conversion rate (%) 98 97 98 99 87 82 Methane conversion rate (%) 99 98 98 98 89 86

Referring to Table 2, the catalysts for the methane dry reforming reaction of Examples 1 to 4 can effectively convert methane and carbon dioxide into synthesis gas comprising carbon monoxide and _hydrogen , depending on the combination of the active component and the composite aluminum-phosphorus compound support, especially the _xAl2O3 - _AlPO4 complex in the composite aluminum-phosphorus compound support, the Ni in the Ni-MgO complex, the MgO in the Ni-MgO complex, and the _xAl2O3 - _{AlPO4 complex} in the catalyst for the methane dry reforming reaction. Furthermore, the catalysts for the methane dry reforming reaction of Examples 1 to 4 all have methane conversion rates exceeding 98% and carbon dioxide conversion rates exceeding 98%.

In contrast, in Comparative Examples 1 and 2, the catalyst of Comparative Example 1 uses Ni as the active component and MgO as the carrier, while the catalyst of Comparative Example 2 uses a Ni-MgO composite as the active component and _Al2O3 as the carrier _. Therefore, the methane conversion rate and carbon dioxide conversion rate obtained using the catalysts of Comparative Examples 1 and 2 are both less than 90%, indicating that the catalysts of Comparative Examples 1 and 2 are less effective in converting methane and carbon dioxide into synthesis gas containing carbon monoxide and hydrogen.

In summary, _the catalyst for methane dry reforming of the present invention, through the combination of the active component and the composite aluminum-phosphorus compound support, particularly the _xAl₂O₃ - _AlPO₄ complex in the composite aluminum-phosphorus compound support, and the Ni content of the Ni-MgO complex, the MgO content of the Ni-MgO complex, and the _xAl₂O₃ - _{AlPO₄ complex} in the catalyst for methane dry reforming, can effectively convert methane and carbon dioxide into synthesis gas comprising carbon monoxide and hydrogen at temperatures between 700°C and 900°C, with a methane conversion rate exceeding 98% and a carbon dioxide conversion rate exceeding 98%, thereby effectively achieving the objectives of the present invention.

On the other hand, the method for preparing a catalyst for methane dry reforming reaction of the present invention ensures that a composite aluminum-phosphorus compound matrix having a large number of macropores is obtained through the combination of steps (a) to (i), especially by controlling the pH of the second mixture in step (b). The composite aluminum-phosphorus compound matrix can also improve the dispersion of the active component in the composite aluminum-phosphorus compound matrix and the mass transfer rate of methane and carbon dioxide in the composite aluminum-phosphorus compound matrix, thereby endowing the catalyst for methane dry reforming reaction with excellent activity in catalyzing the conversion of methane and carbon dioxide into synthesis gas.

However, the above description is merely an example of the present invention and should not be used to limit the scope of the present invention. All simple equivalent changes and modifications made according to the scope of the patent application and the content of the patent specification of the present invention are still within the scope of the present patent.

Other features and benefits of the present invention will be more clearly illustrated in the accompanying drawings, in which: Figure 1 is an X-ray diffraction spectrum of the catalyst for methane dry reforming reaction according to Example 1; Figure 2 is an X-ray diffraction spectrum of the catalyst for methane dry reforming reaction according to Example 2; Figure 3 is an X-ray diffraction spectrum of the catalyst for methane dry reforming reaction according to Example 3; Figure 4 is an X-ray diffraction spectrum of the catalyst for methane dry reforming reaction according to Example 4; Figure 5 is an adsorption isotherm and nitrogen desorption curve of the catalyst for methane dry reforming reaction according to Example 1; Figure 6 shows the adsorption isotherm and nitrogen desorption curve of the catalyst used in the methane dry reforming reaction of Example 2; Figure 7 shows the adsorption isotherm and nitrogen desorption curve of the catalyst used in the methane dry reforming reaction of Example 3; Figure 8 shows the adsorption isotherm and nitrogen desorption curve of the catalyst used in the methane dry reforming reaction of Example 4; Figure 9 shows the pore size distribution of the catalyst used in the methane dry reforming reaction of Examples 1 and 2; and Figure 10 shows the pore size distribution of the catalyst used in the methane dry reforming reaction of Examples 3 and 4.

without.

Claims (2)

A method for preparing a catalyst for methane dry reforming reaction comprises: (a) dissolving an aluminum source compound and phosphoric acid in water to obtain a first mixture, wherein the molar ratio of aluminum in the aluminum source compound to phosphorus in the phosphoric acid ranges from 1 to 5; (b) adjusting the pH value of the first mixture with an alkaline reagent to obtain a second mixture with a pH value of 7 to 9; (c) subjecting the second mixture to a slurry of water. (d) subjecting the precipitate to a drying treatment at 50° C. to 150° C. for 2 hours to 6 hours to obtain a powdery solid; (e) subjecting the powdery solid to a calcination treatment at 300° C. to 600° C. for 2 hours to 6 hours to obtain a sintered product comprising xAl ₂ O ₃ -AlPO (f) impregnating the composite aluminum-phosphorus compound carrier with an aqueous solution containing a nickel source compound and a magnesium source compound to obtain a first catalyst precursor; (g) drying the first catalyst precursor at 60° C. to 150° C. for ₂ to 6 hours to obtain a second catalyst precursor; (h) calcining the second catalyst precursor at 200° C. to 400° C. for 2 to 6 hours to obtain a third catalyst precursor; and (i) calcining the third catalyst precursor at 300° C. in a reaction atmosphere containing one of helium and nitrogen and hydrogen. A catalyst for methane dry reforming is obtained by performing a redox reaction at a temperature of 100° C. to 500° C. for 2 to 6 hours. The catalyst comprises an active component and a composite aluminum-phosphorus compound carrier, wherein the composite aluminum-phosphorus compound carrier supports the active component, and the active component comprises a Ni-MgO composite. Based on 100wt% of the total amount of the catalyst for methane dry reforming, the Ni content of the Ni-MgO composite ranges from 5wt% to 30wt%, the MgO content of the Ni- _MgO composite ranges from 2wt% to 10wt%, and the _xAl2O3 - _AlPO4 composite ranges from 65wt% to 90wt%. The method for preparing a catalyst for methane dry reforming reaction as described in claim 1, wherein the alkaline reagent in step (b) is aqueous ammonia with a concentration of 1M to 5M.