Halogen-modified hydroxyapatite nickel-loaded catalyst as well as preparation method and application thereof

Abstract

The invention discloses a halogen-modified hydroxyapatite nickel-loaded catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalyst preparation and reforming reaction. The catalyst comprises a halogen modified hydroxyapatite carrier MeHAP-Hal and an active metal Ni, wherein the mass percentage of the MeHAP-Hal is 90.0-99.5%; the invention relates to a halogen-modified hydroxyapatite carrier MeHAP-Hal material, which comprises the following components in percentage by mass: 0.5 to 10 percent of Ni, in the halogen-modified hydroxyapatite carrier MeHAP-Hal material,-OH is replaced by halogen Hal, Me is Ca or Ca + Sr, the atomic ratio of Me to P is controlled to be 1.67, the halogen Hal is F or a combination of F and Cl, the mass percent of F in the carrier is 0.3 to 2.8 percent, and the mass percent of Cl in the carrier is 1t. And 0.05%. The catalyst is high in activity, good in selectivity and low in cost, and when the catalyst is used for preparing synthesis gas through CH4-CO2 reforming, carbon deposition and deactivation of the catalyst can be effectively avoided under the reaction condition of lower than 700 DEG C.

Description

Technical Field

[0001] This invention relates to a halogen-modified hydroxyapatite-supported nickel catalyst, its preparation method, and its application, belonging to the field of catalyst preparation and reforming reaction technology. Background Technology

[0002] Natural gas, coalbed methane, shale gas, and biogas are primarily composed of methane (CH4), a colorless gas at room temperature and pressure with a high calorific value of 50.07 MJ / kg. Therefore, it can be used directly as fuel or chemically converted to produce high-value-added chemical products. The chemical utilization of CH4 can be divided into two methods: direct and indirect. Direct utilization refers to converting CH4 into the desired chemical product in one step, such as oxidation to methanol, oxidation to methanesulfonic acid, and anaerobic coupling. However, the CH bond energy in the CH4 molecule is as high as 415.5 kJ / mol, and its chemical properties are extremely stable at room temperature, making direct utilization difficult. Indirect utilization involves first converting CH4 into syngas through reforming, and then using the syngas to prepare chemical products. Given the widespread use of syngas in chemical production, the reforming reaction of CH4 has attracted considerable attention from researchers.

[0003] CH4 reforming methods include steam reforming (Wu Z. et al., Energ. Convers. Manage., 2021, 240, 114163), partial oxidation reforming (Nguyen TH, Appl. Catal. B: Environ., 2016, 199, 424-432), and dry carbon dioxide reforming (Wang J., ACS Catal., 2022, 12, 4382-4393). Steam reforming yields syngas with an H2 / CO ratio of approximately 3:1, making it an excellent industrial method for hydrogen production; however, the direct downstream utilization of this syngas is challenging. Partial oxidation yields syngas with an H2 / CO ratio of approximately 2, suitable for downstream Fischer-Tropsch synthesis and alcohol synthesis; however, this process requires high-purity O2 as a reactant, resulting in higher costs and a risk of explosion during the reaction. In comparison, the dry reforming (DRM) of CH4 has the following advantages: ① It uses two major greenhouse gases (CH4 and CO2) as reactants, which can convert inexpensive and readily available CO2 into high-value-added chemical products and create carbon sinks at the same time; ② The process can produce syngas with an H2 / CO ratio of about 1, which can be directly used for Fischer-Tropsch synthesis; ③ The dry reforming process is a strongly endothermic reaction, which can be used as a medium for energy storage.

[0004] For the CH4-CO2 dry reforming reaction, although noble metals can catalyze the reaction efficiently and have excellent anti-sintering and anti-coking properties, the cost of noble metal catalysts limits their industrial application. Currently, non-noble metals comparable to noble metals are mainly concentrated in metals such as Ni and Co, especially Ni-based catalysts, which have been the most studied and are most likely to be industrialized.

[0005] However, the dry reforming reaction of CH4 often requires temperatures above 700 °C to achieve effective conversion. Compared to noble metals, Ni-based catalysts have the following two problems: ① At high temperatures, Ni particles tend to flow and sinter on the support surface, leading to a decrease in catalyst activity; ② Carbon deposits easily form on the catalyst surface, especially the generated graphitic carbon, which is difficult to remove, thus causing catalyst deactivation. Over the years, researchers have devoted considerable effort to trying to solve these two problems, including improving Ni dispersion and preparing embedded structures (Zhang M. et al., Energ. Convers. Manage., 2020, 216,112950; Zhang XP et al., Fuel, 2015,147, 1, 243) to limit Ni particle growth and sintering, while simultaneously controlling the properties of the support and its interaction with the active component to inhibit carbon deposition.

[0006] Studies have shown that increasing the number of oxygen vacancies on the support surface (which is positively correlated with the adsorption of oxygen species) can activate CO2 molecules to some extent, enabling them to react with carbon species produced by methane cracking and achieve carbon removal. However, research has revealed that these oxygen vacancies can also promote methane cracking, especially at relatively low reaction temperatures (<700 °C), where the cracking capacity is far greater than the carbon removal capacity of CO2, leading to rapid carbon buildup and deactivation of the catalyst. Therefore, controlling the balance between the methane cracking rate and the CO2 carbon removal rate is key to solving the problem of catalyst deactivation due to carbon buildup. Previous literature has found that the reaction of -OH groups on the surface of hydroxyapatite with carbon species can effectively inhibit the formation of carbon on the catalyst surface, thereby delaying catalyst deactivation (O'Connor AM et al. Catal. Today 2006, 115, 191; Ferreira-Aparicio P. et al., J. Catal. 1999, 184, 202; Schuurman Y. et al., Catal. Today 1998, 46, 185). Meanwhile, the weakly basic sites on the catalyst surface exhibit inertness to CH4 cracking while simultaneously adsorbing and activating CO2. Furthermore, hydroxyapatite possesses good thermal stability and does not undergo pyrolysis in the CH4-CO2 reforming reaction (Sofronia A. M., Mater. Sci. Eng. C, 2014, 43, 153-163). Despite these studies demonstrating the advantages of -OH-rich apatite in the CH4-CO2 reforming reaction, these catalysts still exhibit some deactivation. Therefore, surface modification of hydroxyapatite, particularly enhancing its ability to adsorb and activate CO2, enabling its rapid participation in the carbon elimination reaction and achieving a carbon accumulation-elimination balance, is of great significance for addressing the current problem of carbon accumulation and deactivation in Ni-based catalysts.

[0007] Chinese patent CN113952970A discloses a hydroxyapatite-supported nickel catalyst, its preparation method, and its application in the CH4-CO2 reforming reaction. Although the catalyst reported in this method has shown significant advantages in the DRM reaction, and the conversion activity of CH4 and CO2 is significantly improved on the Ni catalyst prepared from hydroxyapatite, the catalyst still exhibits rapid carbon deposition and deactivation at low temperature (<700 °C). The main reason is that the carbon deposition and deactivation balance on the catalyst surface has not reached the optimal match.

[0008] In view of this, the present invention improves the preparation method of hydroxyapatite and introduces halogens to modify the surface of hydroxyapatite during the synthesis process, so as to achieve precise control of the distribution of surface hydroxyl groups (-OH) and chemical environment, enhance the rate of -OH participating in carbon elimination, better balance the carbon elimination rate under low temperature conditions, and thus improve the long-term stable operation of the catalyst at low temperature. Summary of the Invention

[0009] This invention aims to provide a halogen-modified alkaline earth metal hydroxyapatite-supported nickel catalyst and its preparation method. This catalyst exhibits high activity, good selectivity, and low cost, improves the catalyst's ability to adsorb and activate CO2, and effectively avoids catalyst deactivation due to carbon deposition under reaction conditions below 700 °C. This invention also provides the application of the catalyst in CH4-CO2 reforming to syngas.

[0010] Given the excellent performance of Ni-based catalysts supported on hydroxyapatite in the DRM reaction, this invention further improves the preparation method and introduces halogens to regulate the fine structure, morphology, and the number and properties of surface hydroxyl groups in hydroxyapatite. This promotes the efficient synergistic effect between the active metal component Ni and the support in the DRM reaction, improving catalytic performance at lower temperatures. Halogen-modified hydroxyapatite (Me 10 (OH)2(PO4)6-xF or Me 10 (OH)₂(PO₄)₆-xF+Cl, abbreviated as MeHAP-Hal, where Me = Ca or Ca+Sr) is used as the support. Hydroxypropyl-β-cyclodextrin (HP-β-CD) is added as a template agent during the synthesis process. Hydroxyapatite (Me) prepared using this method... 10 (OH)₂(PO₄)₆ (MeHAP) has well-developed pores and a large specific surface area, which is beneficial for improving the dispersion of Ni and the metal-support interaction. Furthermore, its surface is rich in uniformly distributed structural hydroxyl groups, exhibiting strong basicity and weak acidity. MeHAP also has advantages such as high thermal stability and good mechanical properties. The introduction of halogens effectively regulates the number, distribution, and chemical environment of structural hydroxyl groups, enabling the support to more effectively promote carbon removal under low-temperature conditions. These characteristics make it suitable as an environmentally friendly support for CH₄-CO₂ reforming reactions under low-temperature conditions.

[0011] This invention provides a halogen-modified hydroxyapatite-supported nickel catalyst, comprising a halogen-modified hydroxyapatite support (MeHAP-Hal) and an active metal Ni, wherein the mass percentages are: MeHAP-Hal: 90.0-99.5%; Ni: 0.5-10%. In the halogen-modified hydroxyapatite support MeHAP-Hal material, the halogen Hal replaces -OH, Me is Ca or Ca+Sr, the atomic ratio of Me to P is controlled at 1.67, and the halogen (Hal) is F or a combination of F and Cl, wherein the mass percentage of F in the support is 0.3-2.8%, and the mass percentage of Cl in the support is <0.05%.

[0012] This invention provides a method for preparing the above-mentioned halogen-modified hydroxyapatite-supported nickel catalyst, comprising the following steps: Step 1: Preparation of MeHAP-Hal support material: This can be prepared by in-situ substitution or ion exchange methods, which are explained below: The method for preparing MeHAP-Hal support material by in-situ substitution is as follows: equimolar amounts of Me(NO3)2 and hydroxypropyl-β-cyclodextrin are mixed to form solution A. NH4F or a mixture of NH4F and NH4Cl is added to (NH4)2HPO4 solution to prepare solution B. Then, solution B is added dropwise to solution A for hydrothermal reaction. After centrifugation, washing, drying, and calcination, MeHAP-xF support or MeHAP-xF+Cl support is obtained. The method for preparing MeHAP-Hal support material by ion exchange is as follows: Equimolar amounts of Me(NO3)2 and hydroxypropyl-β-cyclodextrin are prepared into solution A, and (NH4)2HPO4 solution is prepared into solution B. Solution B is then added dropwise to solution A, and the pH of the solution is adjusted to 10-11 with concentrated ammonia. Anhydrous ethanol is then added, and a hydrothermal reaction is carried out. The solution is then centrifuged, washed, dried, and calcined to obtain MeHAP. Finally, a prepared halogen solution is mixed with MeHAP and stirred to obtain the MeHAP-Hal support material. Step 2: Preparation of MeHAP-supported nickel-based catalyst (1) The catalyst was prepared by precipitation method, the specific steps of which were: weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in distilled water to prepare Ni 2+A solution with a concentration of 0.03–0.05 mol / L was heated to 45–65 °C in a water bath with stirring. Then, the MeHAP-Hal support prepared in the first step was added to the solution all at once, and stirring was continued for 4–8 h. The amounts of solution and support were calculated based on the desired Ni loading of the synthesized catalyst (the final Ni loading was 0.5–10 wt%). Subsequently, a saturated Na₂CO₃ solution was added dropwise to the suspension using a peristaltic pump until the pH reached 9–11. After stirring for another 4–8 h, the suspension was centrifuged and washed with distilled water to obtain a white sample. Finally, the sample was dried overnight at 110 °C and then calcined in a muffle furnace at 400–600 °C for 3–5 h to obtain the catalyst powder. (2) The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into 20-40 mesh particles to obtain the catalyst of the present invention, named nNi / MeHAP-Hal (n represents the loading of Ni (wt%)).

[0013] The preparation process of the carrier material is explained in detail below: (A) In-situ substitution preparation of MeHAP-Hal support material Preparation of MeHAP-xF: First, prepare a solution of Me(NO3)2 with a total concentration of 0.3-0.5 mol / L, and simultaneously add an equimolar amount of hydroxypropyl-β-cyclodextrin (HP-β-CD), named solution A; then prepare a solution of (NH4)2HPO4 with a concentration of 0.3-0.5 mol / L. In this step, the halogen is added in the form of NH4F, and the amount added is Me. 2+ The total molar amount is 4-20%, and it is named solution B. The stoichiometric ratio is n(Me). 2+ ) / n(PO4 3- Solution B was added dropwise to solution A in a constant temperature water bath at 45-65 °C with vigorous stirring, with a ratio of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 10-11 with concentrated ammonia, and stirring was continued for 4-8 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 100-150 °C for 12-24 h. After natural cooling, the resulting white precipitate was thoroughly washed by centrifugation with deionized water, dried at 110 °C for 12 h, and calcined at 600-800 °C for 2-4 h to obtain the MeHAP-xF support (x represents F). – (Percentage of the carrier mass).

[0014] Preparation of MeHAP-xF+Cl: Prepare a solution of Me(NO3)2 with a total concentration of 0.3-0.5 mol / L, and simultaneously add an equimolar amount of hydroxypropyl-β-cyclodextrin (HP-β-CD), named Solution A; subsequently prepare a solution of (NH4)2HPO4 with a concentration of 0.3-0.5 mol / L. In this step, halogens are added in the form of NH4F and NH4Cl, with the amount of NH4F added being Me. 2+ The total molar amount is 4-20%, and the amount of NH4Cl added is Me. 2+ 5% of the total molar mass, the resulting solution is named solution B. According to the stoichiometric ratio n(Me... 2+ ) / n(PO4 3- Solution B was added dropwise to solution A in a constant temperature water bath at 45-65 °C with vigorous stirring, with a ratio of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 10-11 with concentrated ammonia, and stirring was continued for 4-8 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 100-150 °C for 12-24 h. After natural cooling, the resulting white precipitate was thoroughly washed with deionized water by centrifugation, dried at 110 °C for 12 h, and calcined at 600-800 °C for 2-4 h to obtain the MeHAP-xF+Cl support (x represents F). – (Percentage of the carrier mass).

[0015] (B) Preparation of MeHAP-Hal support (ie-MeHAP-xF) materials by ion exchange Preparation of ie-MeHAP-xF: Prepare a solution of Me(NO3)2 with a total concentration of 0.3-0.5 mol / L, and simultaneously add an equimolar amount of hydroxypropyl-β-cyclodextrin (HP-β-CD), named Solution A; subsequently prepare a solution of (NH4)2HPO4 with a concentration of 0.3-0.5 mol / L, named Solution B. According to the stoichiometric ratio n(Me 2+ ) / n(PO4 3-Solution B was added dropwise to solution A in a constant temperature water bath at 45-65 °C with vigorous stirring, with a concentration of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 10-11 with concentrated ammonia, and stirring was continued for 4-8 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 100-150 °C for 12-24 h. After natural cooling, the resulting white precipitate was thoroughly washed with deionized water by centrifugation, dried at 110 °C for 12 h, and calcined at 600-800 °C for 2-4 h. Subsequently, a 0.2 mol / L NH4F solution (halogen solution) was prepared, and the two were mixed at a ratio of 100 mL halogen solution / 1 g MeHAP, and stirred continuously at 45-65 °C for 4-8 h. After natural cooling, the resulting white precipitate was vacuum filtered and thoroughly washed with distilled water, dried at 110 °C overnight, and thoroughly ground to obtain ie-MeHAP-F, where x represents the percentage of F in the carrier.

[0016] Preparation of ie-MeHAP-xF+Cl: First, prepare a solution of Me(NO3)2 with a total concentration of 0.3-0.5 mol / L, and simultaneously add an equimolar amount of hydroxypropyl-β-cyclodextrin (HP-β-CD), named solution A; then prepare a solution of (NH4)2HPO4 with a concentration of 0.3-0.5 mol / L, named solution B. According to the stoichiometric ratio n(Me 2+ ) / n(PO4 3- Solution B was added dropwise to solution A under constant temperature water bath at 45-65 °C with vigorous stirring, with a concentration of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 10-11 with concentrated ammonia, and stirring was continued for 4-8 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 100-150 °C for 12-24 h. After natural cooling, the resulting white precipitate was thoroughly washed with deionized water by centrifugation, dried at 110 °C for 12 h, and calcined at 600-800 °C for 2-4 h. Subsequently, a mixed solution of NH4F and NH4Cl was prepared, with the concentration of NH4F being 0.2 mol / L and the concentration of NH4Cl being 0.1 mol / L. The two were mixed at a ratio of 100 mL halogen solution / 1 g MeHAP and stirred continuously at 45-65 °C for 4-8 h. After natural cooling, the white precipitate was collected by vacuum filtration and thorough washing with distilled water. It was then dried at 110 °C overnight and thoroughly ground to obtain ie-MeHAP-xF+Cl, where x represents the percentage of F in the carrier.

[0017] In the above preparation of the MeHAP-Hal support, regardless of whether the halogen was introduced in situ or by ion exchange, the final Cl content in the support was trace (<0.05%). The main reason is that Cl... - The ionic radius is greater than that of -OH and F. - Therefore, it is difficult for F to undergo substitution with the -OH groups on the support surface, while F - The ionic size is smaller than -OH, making substitution easier, thus ultimately F - The replacement rate is relatively high.

[0018] This invention provides the application of the above-mentioned halogen-modified hydroxyapatite-supported nickel catalyst in the CH4-CO2 reforming to produce syngas.

[0019] The application of the catalyst of this invention includes the following steps: The catalyst is applied in the CH4-CO2 reforming reaction to produce syngas. The catalytic reaction is carried out in a fixed-bed reactor. The catalyst is first reduced at 600-700 °C for 1-3 h at 10 vol% H2 / Ar (H2:Ar volume ratio of 10:90). During the catalytic reaction, the molar ratio of CH4 to CO2 is 1:1, the volume fraction of CH4 is 10-50%, the volume fraction of CO2 is 10-50%, the volume fraction of Ar is 0-80% (Ar protection is optional), and the total volume hourly space velocity of the feed gas is 40,000-180,000 mL / (g). cat The reaction temperature is controlled at 600-750 °C and the reaction pressure is atmospheric pressure.

[0020] The beneficial effects of this invention are: (1) In the catalytic system of the present invention, various alkaline earth metal cationic hydroxyapatite materials with different halogen substitutions are used as catalyst supports, and hydroxypropyl-β-cyclodextrin is used as a template agent to expand the pores during the synthesis of the support. In the subsequent hydrothermal process, ethanol is added to improve the yield of the support.

[0021] (2) Hydroxypropyl-β-cyclodextrin (HP-β-CD) template agent was added during the synthesis of hydroxyapatite, which can prepare hydroxyapatite with well-developed pores and large specific surface area, which is beneficial to improve the dispersion of Ni and the interaction between metal and support; and the surface of the support is rich in uniformly distributed structural hydroxyl groups, exhibiting strong alkalinity, high thermal stability and good mechanical properties.

[0022] (3) The introduction of halogens can effectively regulate the number and distribution of -OH and change the chemical environment of -OH. This effectively improves the activity of the support for carbon elimination reaction, thereby more effectively balancing the carbon elimination rate in the reaction process and avoiding the deactivation of the catalyst due to carbon accumulation in the DRM reaction process.

[0023] (4) The material has good thermal stability, abundant and adjustable surface hydroxyl groups, and the components used in the material are all non-precious metals, with low raw material costs, simple synthesis process, and easy to achieve mass production. Attached Figure Description

[0024] Figure 1 The image shows a comparison of the FT-IR spectra of the in-situ substituted CaSrHAP-0.4F support material prepared in Example 1 and the unsubstituted CaHAP prepared in the comparative example. Detailed Implementation

[0025] To further illustrate the present invention, the following embodiments are provided; however, the rights of the present invention are not limited to these embodiments. Furthermore, the embodiments only provide some conditions for achieving the objectives of the present invention and do not imply that all of these conditions must be met to achieve the objectives of the present invention. Example 1 1. Preparation of Ni-supported catalysts from fluorine-substituted calcium strontium hydroxyapatite (CaSrHAP-1.02F) The specific steps are as follows: (1) Preparation of CaSrHAP-1.02F support material

[0026] First, prepare a solution with a concentration of 0.4 mol / L Ca(NO3)2 and 0.1 mol / L Sr(NO3)2 (Me in the solution). 2+ The total concentration is 0.5 mol / L), and an equimolar amount of HP-β-CD is added, named solution A; subsequently, a 0.3 mol / L (NH4)2HPO4 solution is prepared. In this step, the halogen is added in the form of NH4F, and the amount added is: Me 2+ 8% of the total molar mass, the resulting solution is named solution B. According to the stoichiometric ratio n(Me... 2+ ) / n(PO4 3- Solution B was added dropwise to solution A at a constant temperature of 45 °C with vigorous stirring, with a ratio of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 10 with concentrated ammonia, and stirring was continued for 8 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 150 °C for 24 h. After natural cooling, the resulting white precipitate was washed with deionized water by centrifugation, dried at 110 °C for 12 h, and calcined at 600 °C for 4 h to obtain the CaSrHAP-1.02 F support.

[0027] (2) Preparation of nickel-based catalyst supported on CaSrHAP-1.02F (A) The catalyst was prepared by a deposition-precipitation method, specifically by weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in an appropriate amount of distilled water to prepare Ni2+ A 0.03 mol / L solution was prepared, and 300 mL of this solution was heated to 45 °C in a water bath with stirring. Then, 10.0 g of the CaSrHAP-1.02F support prepared in the first step was weighed and added to the solution at once. The temperature was maintained and the mixture was stirred continuously for 4 h. Subsequently, a saturated Na2CO3 solution was added dropwise to the suspension using a peristaltic pump until the pH reached 9. After stirring for another 8 h, the suspension was centrifuged and washed thoroughly with distilled water. The resulting sample was dried overnight at 110 °C and then calcined in a muffle furnace at 400 °C for 5 h to obtain the catalyst powder. (B) The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst 5Ni / CaSrHAP-1.02F of the present invention.

[0028] 2. Catalytic performance test 0.4 g of the above catalyst was placed in a self-constructed fixed-bed reactor. Before the reaction, a 10 vol.% H2 / Ar mixture (flow rate: 30 mL / min) was introduced. -1 The catalyst was activated by reduction by heating to 600 °C within 150 min and maintaining the temperature for 3 h. After reduction, the reactor temperature was increased to 650 °C, and the inlet gas was switched to feed gas for the reaction. The feed gas composition (volume fraction) was a mixture of 20% CH4, 20% CO2, and 60% Ar. The reaction space velocity was controlled at 140,000 mL / (g). cat (·h). The reaction outlet gas is detected online using gas chromatography after passing through a cold trap.

[0029] Figure 1 The following is a comparison of FT-IR spectra of the in-situ substituted CaSrHAP-1.02F support material prepared in this embodiment and the unsubstituted CaHAP prepared in the comparative example. The FT-IR spectra show that F... – After the introduction of F, the characteristic spectral band A of -OH was significantly weakened, while the characteristic spectral band B appeared, indicating that the chemical environment of -OH was changed by F. – Effective regulation. Introducing Ni into this material simplifies the catalyst synthesis process. Under the catalytic action of this invention, the conversion rate of methane to CO2 during the reaction of CH4 and CO2 is 97.9%, and the conversion rate of CO2 is 99.4%. No significant deactivation was observed after 600 hours of catalyst operation. The catalyst exhibits good activity and stability. Example 2 1. Preparation of Ni-supported catalysts from fluorine-substituted calcium hydroxyapatite (CaHAP-0.78F) The specific steps are as follows: (1) Preparation of CaHAP-0.78F support

[0030] First, prepare a 0.5 mol / L Ca(NO3)2 solution and add an equimolar amount of HP-β-CD, naming this solution A. Then, prepare a 0.5 mol / L (NH4)2HPO4 solution. In this step, the halogen is added in the form of NH4F, with an addition amount of Me. 2+ 4% of the total molar mass, the resulting solution is named solution B. According to the stoichiometric ratio n(Me... 2+ ) / n(PO4 3- Solution B was added dropwise to solution A at a constant temperature of 65 °C with vigorous stirring, with a ratio of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 11 with concentrated ammonia, and stirring was continued for 8 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 100 °C for 12 h. After natural cooling, the resulting white precipitate was washed with deionized water by centrifugation, dried at 110 °C for 12 h, and calcined at 800 °C for 2 h to obtain the CaHAP-0.78F support.

[0031] (2) Preparation of nickel-based catalyst supported on CaHAP-0.78F (A) The catalyst was prepared by a deposition-precipitation method, specifically by weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in an appropriate amount of distilled water to prepare Ni 2+ A 0.05 mol / L solution was prepared, and 100 mL of this solution was heated to 65 °C in a water bath with stirring. Then, 14.4 g of the CaHAP-0.78F support prepared in the first step was weighed and added to the solution all at once. The temperature was maintained and stirring was continued for 4 h. Subsequently, a saturated Na2CO3 solution was added dropwise to the suspension using a peristaltic pump until the pH reached 10. After stirring for another 4 h, the suspension was centrifuged and thoroughly washed with distilled water. Finally, the obtained sample was dried at 110 °C overnight and then calcined in a muffle furnace at 600 °C for 4 h to obtain the catalyst powder. (B) The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst 2Ni / CaHAP-0.78F of the present invention.

[0032] 2. Catalytic performance test 0.4 g of the above catalyst was placed in a self-constructed fixed-bed reactor. Before the reaction, a 10 vol.% H2 / Ar mixture (flow rate: 30 mL / min) was introduced. -1The catalyst was activated by reduction by heating to 700 °C within 150 min and maintaining the temperature for 1 h. After reduction, the reactor temperature was kept constant at 700 °C, and the inlet gas was switched to feed gas for the reaction. The feed gas composition (volume fraction) was a mixture of 10% CH4, 10% CO2, and 80% Ar. The reaction space velocity was controlled at 180,000 mL / (g) cat (·h). The reaction outlet gas was detected online by gas chromatography after passing through a cold trap. The calculated conversion rates of methane and CO2 were 96.3% and 98.2%, respectively. No significant deactivation was observed after 400 h of catalyst operation. Example 3 1. Preparation of Ni-supported catalysts from fluorinated and chlorinated calcium hydroxyapatite (CaHAP-1.6F+Cl) The specific steps are as follows: (1) Preparation of CaHAP-1.6F+Cl support material

[0033] First, prepare a 0.3 mol / L Ca(NO3)2 solution and add an equimolar amount of HP-β-CD, naming this solution A. Then, prepare a 0.3 mol / L (NH4)2HPO4 solution. In this step, halogens are added in the form of NH4F and NH4Cl, with the amount of NH4F added being Me. 2+ 12% of the total molar amount, with NH4Cl added at a rate of Me. 2+ 5% of the total molar mass, the resulting solution is named solution B. According to the stoichiometric ratio n(Me... 2+ ) / n(PO4 3- Solution B was added dropwise to solution A at a constant temperature of 55 °C with vigorous stirring, with a ratio of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 11 with concentrated ammonia, and stirring was continued for 4 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 150 °C for 24 h. After natural cooling, the resulting white precipitate was washed by centrifugation with deionized water, dried at 110 °C for 12 h, and calcined at 700 °C for 3 h to obtain the CaHAP-1.6F+Cl support.

[0034] (2) Preparation of nickel-based catalyst supported on CaHAP-1.6F+Cl (A) The catalyst was prepared by a deposition-precipitation method, specifically by weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in an appropriate amount of distilled water to prepare Ni 2+A 0.04 mol / L solution was prepared, and 200 mL of this solution was heated to 65 °C in a water bath with stirring. Then, 15.2 g of the CaHAP-1.6F+Cl support prepared in the first step was weighed and added to the above solution in one go. The temperature was maintained and stirring was continued for 8 h. Subsequently, a saturated Na2CO3 solution was added dropwise to the above suspension using a peristaltic pump until the pH reached 11. After stirring for another 8 h, the suspension was centrifuged and thoroughly washed with distilled water. The final sample was dried at 110 °C overnight and then calcined in a muffle furnace at 600 °C for 3 h to obtain the catalyst powder. (B) The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst 3Ni / CaHAP-1.6F+Cl of the present invention.

[0035] 2. Catalytic performance test 0.4 g of the above catalyst was placed in a self-constructed fixed-bed reactor. Before the reaction, a 10 vol.% H2 / Ar mixture (flow rate: 30 mL / min) was introduced. -1 The catalyst was activated by reduction by raising the temperature to 700 °C within 150 min and maintaining it for 1 h. After reduction, the reactor temperature was raised to 750 °C and kept constant, and the inlet gas was switched to feed gas for the reaction. The feed gas composition (volume fraction) was a mixture of 25% CH4, 25% CO2, and 50% Ar, and the reaction space velocity was controlled at 80,000 mL / (g). cat (·h). The effluent gas from the reaction outlet was detected online by gas chromatography after passing through a cold trap. The calculated conversion rates of methane and CO2 were 97.1% and 98.5%, respectively. No significant deactivation was observed after 600 h of catalyst operation. Example 4 1. Preparation of Ni-supported catalysts from fluorinated and chlorinated calcium strontium hydroxyapatite (CaSrHAP-2.8F+Cl) The specific steps are as follows: (1) Preparation of CaSrHAP-2.8F+Cl support material

[0036] First, prepare a solution with a concentration of 0.2 mol / L Ca(NO3)2 and 0.1 mol / L Sr(NO3)2 (Me in the solution). 2+ The total concentration is 0.3 mol / L. An equimolar amount of HP-β-CD is added, and this solution is named Solution A. Subsequently, a 0.3 mol / L (NH4)2HPO4 solution is prepared. In this step, the halogen is added in the form of NH4F and NH4Cl, with the amount of NH4F added being Me. 2+ 20% of the total molar amount, with NH4Cl added at a rate of Me.2+ 5% of the total molar mass, the resulting solution is named solution B. According to the stoichiometric ratio n(Me... 2+ ) / n(PO4 3- Solution B was added dropwise to solution A at a constant temperature of 65 °C with vigorous stirring, with a ratio of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 11 with concentrated ammonia, and stirring was continued for 4 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 120 °C for 18 h. After natural cooling, the resulting white precipitate was washed by centrifugation with deionized water, dried at 110 °C for 12 h, and calcined at 600 °C for 4 h to obtain the CaSrHAP-2.8F+Cl support.

[0037] (2) Preparation of nickel-based catalyst supported on CaSrHAP-2.8F+Cl (A) The catalyst was prepared by a deposition-precipitation method, specifically by weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in an appropriate amount of distilled water to prepare Ni 2+ A 0.05 mol / L solution was prepared, and 500 mL of this solution was heated to 65 °C in a water bath with stirring. Then, 13.2 g of the CaSrHAP-2.8F+Cl support prepared in the first step was weighed and added to the above solution in one go. The temperature was maintained and the mixture was stirred continuously for 6 h. Subsequently, a saturated Na2CO3 solution was added dropwise to the above suspension using a peristaltic pump until the pH reached 11. After stirring for another 6 h, the suspension was centrifuged and thoroughly washed with distilled water. The resulting sample was dried overnight at 110 °C and then calcined in a muffle furnace at 600 °C for 4 h to obtain the catalyst powder. (B) The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst 10Ni / CaSrHAP-2.8F+Cl of the present invention.

[0038] 2. Catalytic performance test 0.4 g of the above catalyst was placed in a self-constructed fixed-bed reactor. Before the reaction, a 10 vol.% H2 / Ar mixture (flow rate: 30 mL / min) was introduced. -1 The catalyst was activated by reduction by heating to 700 °C within 150 min and maintaining the temperature for 1 h. After reduction, the reactor temperature was lowered to 600 °C, and the inlet gas was switched to a feed gas mixture (50% CH4, 50% CO2, volume fraction) for the reaction. The reaction space velocity was controlled at 40,000 mL / (g). cat(·h). The reaction outlet gas was detected online by gas chromatography after passing through a cold trap. The calculated conversion rates of methane and CO2 were 98.1% and 98.8%, respectively. No significant deactivation was observed after 600 h of catalyst operation. Example 5 1. Preparation of Ni-supported catalysts from fluorine-substituted calcium hydroxyapatite (CaHAP-1.3F) The specific steps are as follows: (1) Preparation of CaHAP-1.3F support material

[0039] First, prepare a 0.4 mol / L Ca(NO3)2 solution and add an equimolar amount of HP-β-CD, naming this solution A. Then, prepare a 0.3 mol / L (NH4)2HPO4 solution. In this step, the halogen is added in the form of NH4F, with an addition amount of Me. 2+ 10% of the total molar amount, the resulting solution is named solution B. According to the stoichiometric ratio n(Me... 2+ ) / n(PO4 3- Solution B was added dropwise to solution A at a constant temperature of 65 °C with vigorous stirring, with a ratio of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 11 with concentrated ammonia, and stirring was continued for 4 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 120 °C for 18 h. After natural cooling, the resulting white precipitate was washed by centrifugation with deionized water, dried at 110 °C for 12 h, and calcined at 700 °C for 4 h to obtain the CaHAP-1.3F support.

[0040] (2) Preparation of CaHAP-1.3F supported nickel-based catalyst (A) The catalyst was prepared by a deposition-precipitation method, specifically by weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in an appropriate amount of distilled water to prepare Ni 2+ A 0.05 mol / L solution was prepared, and 300 mL of this solution was heated to 50 °C in a water bath with stirring. Then, 10.6 g of the CaHAP-1.3F support prepared in the first step was weighed and added to the solution all at once. The temperature was maintained and the mixture was stirred continuously for 6 h. Subsequently, a saturated Na2CO3 solution was added dropwise to the suspension using a peristaltic pump until the pH reached 11. After stirring for another 4 h, the suspension was centrifuged and thoroughly washed with distilled water. The resulting sample was dried overnight at 110 °C and then calcined in a muffle furnace at 500 °C for 4 h to obtain the catalyst powder. (B) The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst 7.5Ni / CaHAP-1.3F of the present invention.

[0041] 2. Catalytic performance test 0.4 g of the above catalyst was placed in a self-constructed fixed-bed reactor. Before the reaction, a 10 vol.% H2 / Ar mixture (flow rate: 30 mL / min) was introduced. -1 The catalyst was activated by reduction by heating to 650 °C within 150 min and maintaining the temperature for 1 h. After reduction, the reactor temperature was maintained at 650 °C, and the inlet gas was switched to a feed gas mixture (50% CH4, 50% CO2, volume fraction) for the reaction. The reaction space velocity was controlled at 50,000 mL / (g). cat (·h). The effluent gas from the reaction outlet was detected online by gas chromatography after passing through a cold trap. The calculated conversion rates of methane and CO2 were 96.9% and 98.3%, respectively. No significant deactivation was observed after 400 h of catalyst operation. Example 6

[0042] 1. Preparation of Ni-supported catalysts from ion-exchange fluorine-substituted calcium hydroxyapatite (ie-CaHAP-0.54F) The specific steps are as follows: (1) Preparation of ie-CaHAP-0.54F carrier material First, prepare a 0.3 mol / L Ca(NO3)2 solution and simultaneously add an equimolar amount of hydroxypropyl-β-cyclodextrin (HP-β-CD), naming this solution A. Then, prepare a 0.5 mol / L (NH4)2HPO4 solution, naming this solution B. According to the stoichiometric ratio n(Me 2+ ) / n(PO4 3- = 5 / 3 (The amounts of solutions A and B used are based on Me) 2+ and PO4 3- (Concentration calculation ratio), under constant temperature water bath at 65 °C and vigorous stirring, solution B was added dropwise to solution A. After the addition was completed, the pH of the solution was adjusted to 11 with concentrated ammonia, and stirring was continued for 8 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 100 °C for 12 h. After natural cooling, the resulting white precipitate was thoroughly washed with deionized water by centrifugation, dried at 110 °C for 12 h, and calcined at 800 °C for 2 h. Subsequently, a 0.2 mol / L NH4F solution (halogen solution) was prepared, and the two were mixed at a ratio of 100 mL halogen solution / 1 g MeHAP, and stirred continuously at 45 °C for 8 h. After natural cooling, the resulting white precipitate was vacuum filtered and thoroughly washed with distilled water, dried at 110 °C overnight, and thoroughly ground to obtain ie-CaHAP-0.54F.

[0043] (2) Preparation of nickel-based catalyst supported on ie-CaHAP-0.54F (A) The catalyst was prepared by a deposition-precipitation method, specifically by weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in an appropriate amount of distilled water to prepare Ni 2+ A 0.03 mol / L solution was prepared, and 50 mL of this solution was heated to 65 °C in a water bath with stirring. Then, 17.5 g of the ie-CaHAP-0.54F support prepared in the first step was weighed and added to the above solution at once. The temperature was maintained and the mixture was stirred continuously for 4 h. Subsequently, a saturated Na2CO3 solution was added dropwise to the above suspension using a peristaltic pump until the pH reached 11. After stirring for another 8 h, the suspension was centrifuged and thoroughly washed with distilled water. The resulting sample was dried overnight at 110 °C and then calcined in a muffle furnace at 600 °C for 4 h to obtain the catalyst powder. (B) The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst 0.5Ni / ie-CaHAP-0.54F of the present invention.

[0044] 2. Catalytic performance test 0.4 g of the above catalyst was placed in a self-constructed fixed-bed reactor. Before the reaction, a 10 vol.% H2 / Ar mixture (flow rate: 30 mL / min) was introduced. -1 The catalyst was activated by reduction by heating to 600 °C within 150 min and maintaining the temperature for 3 h. After reduction, the reactor temperature was kept constant at 600 °C, and the inlet gas was switched to feed gas for the reaction. The feed gas composition (volume fraction) was a mixture of 10% CH4, 10% CO2, and 80% Ar. The reaction space velocity was controlled at 160,000 mL / (g) cat (·h). The effluent gas from the reaction outlet was detected online by gas chromatography after passing through a cold trap. The calculated conversion rates of methane and CO2 were 91.5% and 93.8%, respectively. No significant deactivation was observed after 800 h of catalyst operation. Example 7

[0045] 1. Preparation of Ni-supported catalysts from ion-exchange fluorine-substituted calcium strontium hydroxyapatite (ie-CaSrHAP-0.6F) The specific steps are as follows: (1) Preparation of ie-CaSrHAP-0.6F support material First, prepare a solution with a concentration of 0.3 mol / L Ca(NO3)2 and 0.2 mol / L Sr(NO3)2 (Me in the solution). 2+The total concentration was 0.5 mol / L. An equimolar amount of hydroxypropyl-β-cyclodextrin (HP-β-CD) was added, and this solution was named Solution A. Subsequently, a 0.3 mol / L (NH₄)₂HPO₄ solution was prepared and named Solution B. The stoichiometric ratio was n(Me). 2+ ) / n(PO4 3- =5 / 3 (The amounts of solutions A and B are based on Me) 2+ and PO4 3- (Concentration calculation ratio), under constant temperature water bath at 45 °C and vigorous stirring, solution B was added dropwise to solution A. After the addition was completed, the pH of the solution was adjusted to 10 with concentrated ammonia, and stirring was continued for 4 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 150 °C for 12 h. After natural cooling, the resulting white precipitate was thoroughly washed with deionized water by centrifugation, dried at 110 °C for 12 h, and calcined at 600 °C for 4 h. Subsequently, a 0.2 mol / L NH4F solution (halogen solution) was prepared, and the two were mixed at a ratio of 100 mL halogen solution / 1 g MeHAP, and stirred continuously at 65 °C for 8 h. After natural cooling, the resulting white precipitate was vacuum filtered and thoroughly washed with distilled water, dried at 110 °C overnight, and thoroughly ground to obtain ie-CaSrHAP-0.6F.

[0046] (2) Preparation of nickel-based catalyst supported on ie-CaSrHAP-0.6F (A) The catalyst was prepared by a deposition-precipitation method, specifically by weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in an appropriate amount of distilled water to prepare Ni 2+ A 0.05 mol / L solution was prepared, and 200 mL of this solution was heated to 55 °C in a water bath with stirring. Then, 14.1 g of the ie-CaSrHAP-0.6F support prepared in the first step was weighed and added to the solution all at once. The temperature was maintained and stirring was continued for 6 h. Subsequently, a saturated Na2CO3 solution was added dropwise to the suspension using a peristaltic pump until the pH reached 10. After stirring for another 6 h, the suspension was centrifuged and thoroughly washed with distilled water. Finally, the obtained sample was dried at 110 °C overnight and then calcined in a muffle furnace at 600 °C for 3 h to obtain the catalyst powder. (B) The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst 4Ni / ie-CaSrHAP-0.6F of the present invention.

[0047] 2. Catalytic performance test 0.4 g of the above catalyst was placed in a self-constructed fixed-bed reactor. Before the reaction, a 10 vol.% H2 / Ar mixture (flow rate: 30 mL / min) was introduced. -1 The catalyst was activated by reduction by heating to 700 °C within 150 min and maintaining the temperature for 2 h. After reduction, the reactor temperature was kept constant at 700 °C, and the inlet gas was switched to feed gas for the reaction. The feed gas composition (volume fraction) was a mixture of 25% CH4, 25% CO2, and 50% Ar. The reaction space velocity was controlled at 100,000 mL / (g) cat (·h). The effluent gas from the reaction outlet was detected online by gas chromatography after passing through a cold trap. The calculated conversion rates of methane and CO2 were 97.7% and 98.8%, respectively. No significant deactivation was observed after 400 h of catalyst operation. Example 8

[0048] 1. Preparation of Ni-supported catalysts from ion-exchange fluorine-chlorine-substituted calcium hydroxyapatite (ie-CaHAP-0.3F+Cl) The specific steps are as follows: (1) Preparation of ie-CaHAP-0.3F+Cl support material First, prepare a 0.5 mol / L Ca(NO3)2 solution and simultaneously add an equimolar amount of hydroxypropyl-β-cyclodextrin (HP-β-CD), naming this solution A. Then, prepare a 0.4 mol / L (NH4)2HPO4 solution, naming this solution B. According to the stoichiometric ratio n(Me 2+ ) / n(PO4 3- = 5 / 3 (The amounts of solutions A and B used are based on Me) 2+ and PO4 3- (Concentration calculation ratio), under constant temperature water bath at 45 °C and vigorous stirring, solution B was added dropwise to solution A. After the addition was completed, the pH of the solution was adjusted to 10 with concentrated ammonia, and stirring was continued for 6 h. Then, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 140 °C for 12 h. After natural cooling, the resulting white precipitate was thoroughly washed by centrifugation with deionized water, dried at 110 °C for 12 h, and calcined at 600 °C for 4 h. Subsequently, a mixed solution of 0.2 mol / L NH4F and 0.1 mol / L NH4Cl (halogen solution) was prepared, and the two were mixed at a ratio of 100 mL halogen solution / 1 g MeHAP, and stirred continuously at 45 °C for 4 h. After natural cooling, the resulting white precipitate was vacuum filtered and thoroughly washed with distilled water, dried at 110 °C overnight, and thoroughly ground to obtain ie-CaHAP-0.3F+Cl.

[0049] (2) Preparation of nickel-based catalyst supported on ie-CaHAP-0.3F+Cl (A) The catalyst was prepared by a deposition-precipitation method, specifically by weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in an appropriate amount of distilled water to prepare Ni 2+ A 0.04 mol / L solution was prepared, and 400 mL of this solution was heated to 55 °C in a water bath with stirring. Then, 10.80 g of the ie-CaHAP-0.3F+Cl support prepared in the first step was weighed and added to the above solution in one go. The temperature was maintained and stirring was continued for 8 h. Subsequently, a saturated Na2CO3 solution was added dropwise to the above suspension using a peristaltic pump until the pH reached 9. After stirring for another 6 h, the suspension was centrifuged and thoroughly washed with distilled water. Finally, the obtained sample was dried at 110 °C overnight and then calcined in a muffle furnace at 500 °C for 4 h to obtain the catalyst powder. (B) The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst 8Ni / ie-CaHAP-0.3F+Cl of the present invention.

[0050] 2. Catalytic performance test 0.4 g of the above catalyst was placed in a self-constructed fixed-bed reactor. Before the reaction, a 10 vol.% H2 / Ar mixture (flow rate: 30 mL / min) was introduced. -1 The catalyst was activated by reduction by heating to 650 °C within 150 min and maintaining the temperature for 2 h. After reduction, the reactor temperature was kept constant at 650 °C, and the inlet gas was switched to feed gas for the reaction. The feed gas composition (volume fraction) was a mixture of 40% CH4, 40% CO2, and 20% Ar. The reaction space velocity was controlled at 100,000 mL / (g) cat (·h). The effluent gas from the reaction outlet was detected online by gas chromatography after passing through a cold trap. The calculated conversion rates of methane and CO2 were 94.7% and 96.2%, respectively. No significant deactivation was observed after 600 h of catalyst operation. Example 9

[0051] 1. Preparation of Ni-supported catalysts from ion-exchange fluorine-chlorine substituted calcium strontium hydroxyapatite (ie-CaSrHAP-0.42F+Cl) The specific steps are as follows: (1) Preparation of ie-CaSrHAP-0.42F+Cl support material First, prepare a solution with a concentration of 0.3 mol / L Ca(NO3)2 and 0.1 mol / L Sr(NO3)2 (Me in the solution). 2+The total concentration was 0.4 mol / L. An equimolar amount of hydroxypropyl-β-cyclodextrin (HP-β-CD) was added, and this solution was named Solution A. Subsequently, a 0.4 mol / L (NH₄)₂HPO₄ solution was prepared and named Solution B. According to the stoichiometric ratio n(Me) 2+ ) / n(PO4 3- =5 / 3 (The amounts of solutions A and B are based on Me) 2+ and PO4 3- (Concentration calculation ratio), under constant temperature water bath at 65 °C and vigorous stirring, solution B was added dropwise to solution A. After the addition was completed, the pH of the solution was adjusted to 11 with concentrated ammonia, and stirring was continued for 4 h; then an equal volume of anhydrous ethanol was added to the resulting white suspension, transferred to a hydrothermal reactor, and hydrothermally heated at 100 °C for 24 h. After natural cooling, the resulting white precipitate was thoroughly washed with deionized water by centrifugation, dried at 110 °C for 12 h, and calcined at 700 °C for 3 h. Subsequently, a mixed solution of 0.2 mol / L NH4F and 0.1 mol / L NH4Cl (halogen solution) was prepared, and the two were mixed at a ratio of 100 mL halogen solution / 1 g MeHAP, and stirred continuously at 65 °C for 4 h. After natural cooling, the white precipitate was obtained by vacuum filtration and washing with distilled water; it was dried at 110 °C overnight and thoroughly ground to obtain ie-CaSrHAP-0.42F+Cl.

[0052] (2) Preparation of nickel-based catalyst supported on ie-CaSrHAP-0.42F (A). The catalyst was prepared by a deposition-precipitation method, specifically by weighing Ni(NO3)2·6H2O in stoichiometric proportions and dissolving it in an appropriate amount of distilled water to prepare Ni... 2+ A 0.05 mol / L solution was prepared, and 50 mL of this solution was heated to 55 °C in a water bath with stirring. Then, 14.5 g of the ie-CaSrHAP-0.42F+Cl support prepared in the first step was weighed and added to the above solution in one go. The temperature was maintained and the mixture was stirred continuously for 6 h. Subsequently, a saturated Na2CO3 solution was added dropwise to the above suspension using a peristaltic pump until the pH reached 10. After stirring for another 6 h, the suspension was centrifuged and thoroughly washed with distilled water. Finally, the obtained sample was dried at 110 °C overnight and then calcined in a muffle furnace at 600 °C for 3 h to obtain the catalyst powder. (B). The catalyst powder obtained in step (1) is pressed into tablets, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst 1Ni / ie-CaSrHAP-0.42F+Cl of the present invention.

[0053] 2. Catalytic performance test 0.4 g of the above catalyst was placed in a self-constructed fixed-bed reactor. Before the reaction, a 10 vol.% H2 / Ar mixture (flow rate: 30 mL / min) was introduced. -1 The catalyst was activated by reduction by heating to 600 °C within 150 min and maintaining the temperature for 2 h. After reduction, the reactor temperature was kept constant at 600 °C, and the inlet gas was switched to a feed gas mixture (50% CH4, 50% CO2, volume fraction) for the reaction. The reaction space velocity was controlled at 60,000 mL / (g). cat (·h). The reaction outlet gas was detected online by gas chromatography after passing through a cold trap. The calculated conversion rates of methane and CO2 were 92.8% and 94.0%, respectively. No significant deactivation was observed after 500 h of catalyst operation.

[0054] Comparative Example Preparation of Ni-supported catalysts from calcium hydroxyapatite (CaHAP) The specific steps are as follows: The preparation method, steps, and parameters of the CaHAP support are the same as those of the CaSrHAP-1.02F support in Example 1, except that Sr(NO3)2, HP-β-CD, and NH4F raw materials are not added during the preparation process. The specific steps are as follows: First, prepare a 0.4 mol / L Ca(NO3)2 solution (the solution contains Me). 2+ The total concentration was 0.5 mol / L, and this solution was named solution A; subsequently, a 0.3 mol / L (NH4)2HPO4 solution was prepared, and the resulting solution was named solution B. According to the stoichiometric ratio n(Me 2+ ) / n(PO4 3- Solution B was added dropwise to solution A at a constant temperature of 45 °C with vigorous stirring, with a ratio of 5 / 3. After the addition was complete, the pH of the solution was adjusted to 10 with concentrated ammonia, and stirring was continued for 8 h. Subsequently, an equal volume of anhydrous ethanol was added to the resulting white suspension, and the mixture was transferred to a hydrothermal reactor and hydrothermally heated at 150 °C for 24 h. After natural cooling, the resulting white precipitate was washed with deionized water by centrifugation, dried at 110 °C for 12 h, and calcined at 600 °C for 4 h to obtain the CaHAP support.

[0055] (2) Preparation of CaHAP-supported nickel-based catalysts The catalyst was prepared in exactly the same way as step (2) in Example 1, and a 5Ni / CaHAP catalyst was obtained.

[0056] The catalytic performance of the 5Ni / CaHAP catalyst prepared in the comparative example and the catalyst obtained in Example 1 were tested and compared as follows: The catalyst testing conditions and feed space velocity were exactly the same as those in Example 1.

[0057] Test results show that using the 5Ni / CaHAP catalyst in the comparative example, the conversion rate of methane in the methane-carbon dioxide reforming reaction is 87.4% and the conversion rate of CO2 is 90.5%. After running the catalyst for 300 h, the conversion rates of methane and carbon dioxide decreased slightly.

[0058] The evaluation results compared with those of Example 1 show that the initial activity of the catalyst prepared by F-modified hydroxyapatite is significantly lower than that of the modified catalyst, and the modified catalyst can maintain operation for a longer period of time without deactivation during the reaction.

[0059] Under the catalytic action of the catalyst of this invention, when CH4 and CO2 react, the highest conversion rate of CH4 and CO2 can reach 99% under optimized reaction conditions. The catalyst exhibits good activity and stability after 1000 h of operation, with a methane conversion rate decrease of < 5%, and the surface carbon content of the catalyst after the reaction is less than 2%.

Claims

1. A halogen-modified hydroxyapatite supported nickel catalyst, characterized in that: The halogen-modified hydroxyapatite carrier MeHAP-Hal and active metal Ni, the mass percentage of which is MeHAP-Hal: 90.0-99.5%; Ni: 0.5-10%, in the halogen-modified hydroxyapatite carrier MeHAP-Hal material, the halogen Hal replaces -OH, Me is Ca or Ca+Sr, the atomic ratio of Me to P is controlled at 1.67, and the halogen Hal is F or a combination of F and Cl, wherein the mass percentage of F in the carrier is 0.3%-2.8%, and the mass percentage of Cl in the carrier is <0.05%.

2. A process for the preparation of the halogen-modified hydroxyapatite supported nickel catalyst of claim 1, characterized in that The method comprises the following steps: Step 1: Preparation of the MeHAP-Hal carrier material: prepared by in-situ substitution or ion exchange, which are described as follows: The method for preparing the MeHAP-Hal carrier material by in-situ substitution is as follows: equal molar Me(NO3)2 and hydroxypropyl-β-cyclodextrin are mixed to prepare solution A, NH4F or a mixture of NH4F and NH4Cl is added to an (NH4)2HPO4 solution to prepare solution B, then solution B is added dropwise to solution A to perform a hydrothermal reaction, centrifugal washing, drying, and calcination to obtain the MeHAP-xF carrier or the MeHAP-xF+Cl carrier; The method for preparing the MeHAP-Hal carrier material by ion exchange is as follows: equal molar Me(NO3)2 and hydroxypropyl-β-cyclodextrin are mixed to prepare solution A, an (NH4)2HPO4 solution is prepared to prepare solution B, then solution B is added dropwise to solution A, concentrated ammonia water is used to adjust the pH of the solution to 10-11, then anhydrous ethanol is added, a hydrothermal reaction is performed, centrifugal washing, drying, and calcination are performed to obtain MeHAP, and then a prepared halogen solution is mixed with MeHAP to obtain the MeHAP-Hal carrier material; Step 2: Preparation of the MeHAP-supported nickel-based catalyst (1) The catalyst was prepared by deposition precipitation method, and the specific steps were as follows: Ni(NO3)2·6H2O was weighed according to the stoichiometric ratio, dissolved in distilled water to prepare a solution with a concentration of 0.03-0.05 mol / L, and the solution was heated to 45-65 °C in a water bath; then, the MeHAP-Hal carrier prepared in the first step was added to the above solution at one time, and the stirring was continued for 4-8 h, and the amount of the solution and the carrier was calculated based on the required Ni loading of the catalyst to be synthesized; then, a saturated Na2CO3 solution was added dropwise to the above suspension by peristaltic pump until the pH was 9-11; after continuing to stir for 4-8 h, the suspension was centrifuged and washed with distilled water to obtain a white sample; finally, the sample was dried at 110 °C overnight, and then calcined at 400-600 °C in a muffle furnace for 3-5 h to obtain the catalyst raw powder; 2+ concentration of 0.03-0.05 mol / L, and the solution was heated to 45-65 °C in a water bath; then, the MeHAP-Hal carrier prepared in the first step was added to the above solution at one time, and the stirring was continued for 4-8 h, and the amount of the solution and the carrier was calculated based on the required Ni loading of the catalyst to be synthesized; then, a saturated Na2CO3 solution was added dropwise to the above suspension by peristaltic pump until the pH was 9-11; after continuing to stir for 4-8 h, the suspension was centrifuged and washed with distilled water to obtain a white sample; finally, the sample was dried at 110 °C overnight, and then calcined at 400-600 °C in a muffle furnace for 3-5 h to obtain the catalyst raw powder; (2) The catalyst powder prepared in step (1) is pressed, crushed, and sieved into particles of 20-40 mesh to obtain the catalyst Ni / MeHAP-Hal.

3. The process for preparing a halogen-modified hydroxyapatite supported nickel catalyst according to claim 2, characterized in that: The steps for preparing the MeHAP-Hal carrier material by in-situ substitution are as follows: First, Me(NO3)2solution with total concentration of 0.3 - 0.5 mol / L was prepared, and equal molar amount of hydroxypropyl-β-cyclodextrin was added, named solution A; then, (NH4)2HPO4solution with concentration of 0.3 - 0.5 mol / L was prepared, in this step, halogen was added in the form of NH4F, and the amount of Me 2+ F was 4 - 20% of total molar amount, the obtained solution was named solution B; solution B was added into solution A drop by drop under the condition of constant temperature water bath of 45 - 65 °C and strong stirring, the pH of the solution was adjusted to 10 - 11 with concentrated ammonia water after the end of dropwise addition, and the stirring was continued for 4 - 8 h; then, equal volume of anhydrous ethanol was added into the obtained white suspension, and the obtained mixture was transferred into a hydrothermal reactor, and hydrothermal reaction was carried out at 100 - 150 °C for 12 - 24 h; after natural cooling, the obtained white precipitate was washed by centrifugation with deionized water, and the obtained white precipitate was dried at 110 °C for 12 h, and then calcined at 600 - 800 °C for 2 - 4 h, so that MeHAP-xF carrier was obtained, x represents the percentage of F in the carrier, and x is 0.78 - 2.

8. 2+ 3- F was 4 - 20% of total molar amount, the obtained solution was named solution B; solution B was added into solution A drop by drop under the condition of constant temperature water bath of 45 - 65 °C and strong stirring, the pH of the solution was adjusted to 10 - 11 with concentrated ammonia water after the end of dropwise addition, and the stirring was continued for 4 - 8 h; then, equal volume of anhydrous ethanol was added into the obtained white suspension, and the obtained mixture was transferred into a hydrothermal reactor, and hydrothermal reaction was carried out at 100 - 150 °C for 12 - 24 h; after natural cooling, the obtained white precipitate was washed by centrifugation with deionized water, and the obtained white precipitate was dried at 110 °C for 12 h, and then calcined at 600 - 800 °C for 2 - 4 h, so that MeHAP-xF carrier was obtained, x represents the percentage of F in the carrier, and x is 0.78 - 2.8.​ 4. The process for preparing a halogen-modified hydroxyapatite supported nickel catalyst according to claim 2, characterized in that: The steps for preparing the MeHAP-Hal carrier material by in-situ substitution are as follows: Me(NO3)2solution with total concentration of 0.3 - 0.5 mol / L, and add equal molar amount of hydroxypropyl-β-cyclodextrin, named solution A; then prepare (NH4)2HPO4solution with concentration of 0.3 - 0.5 mol / L, in this step, halogen is added in the form of NH4F and NH4Cl, the amount of NH4F added is Me 2+ 4 - 20% of total molar amount, the amount of NH4Cl added is Me 2+ 5% of total molar amount, the obtained solution is named solution B; according to the molar ratio of n(Me 2+ ) / n(PO4 3- ) = 5 / 3, solution B is added dropwise into solution A under the condition of constant temperature water bath at 45 - 65 °C and strong stirring; after the end of dropwise addition, the pH of the solution is adjusted to 10 - 11 with concentrated ammonia water, and the stirring is continued for 4 - 8 h; then equal volume of anhydrous ethanol is added into the obtained white suspension, which is transferred into a hydrothermal reaction kettle, and is hydrothermally treated at 100 - 150 °C for 12 - 24 h; after natural cooling, the obtained white precipitate is washed by centrifugation with deionized water, dried at 110 °C for 12 h, and calcined at 600 - 800 °C for 2 - 4 h, so that MeHAP-xF+Cl carrier is obtained, x represents the percentage of F in the carrier, and x is 0.78~2.

8.

5. The process for preparing a halogen-modified hydroxyapatite supported nickel catalyst according to claim 2, characterized in that: The steps for preparing the ie-MeHAP-xF material by ion exchange are as follows: Me(N03)2solution with total concentration of 0.3-0.5 mol / L, and then add equal molar amount of hydroxypropyl-β-cyclodextrin, named solution A; subsequently, prepare (NH4)2HPO4solution with concentration of 0.3-0.5 mol / L, named solution B; according to the molar ratio of n(Me 2+ ) / n(PO4 3- ) = 5 / 3, add solution B into solution A drop by drop under the condition of 45-65 °C constant temperature water bath and strong stirring; after the end of dropwise addition, adjust the pH of solution to 10-11 with concentrated ammonia water, and continue stirring for 4-8 h; subsequently, add equal volume of anhydrous ethanol into the obtained white suspension, and transfer into hydrothermal reactor, and hydrothermal reaction is carried out at 100-150 °C for 12-24 h; after natural cooling, the obtained white precipitate is washed by centrifugation with deionized water, dried at 110 °C for 12 h, and calcined at 600-800 °C for 2-4 h; subsequently, prepare NH4F halogen solution with concentration of 0.2 mol / L, and mix 100 mL halogen solution with 1 g MeHAP, and continue stirring at 45-65 °C for 4-8 h; after natural cooling, the obtained white precipitate is vacuum filtered and washed with distilled water, dried at 110 °C overnight, and ground thoroughly, to obtain ie-MeHAP-xF, wherein x represents the percentage of F in the carrier, and x is 0.3-0.

78.

6. The process for preparing a halogen-modified hydroxyapatite supported nickel catalyst according to claim 2, characterized in that: The steps for preparing the ie-MeHAP-xF+Cl material by ion exchange are as follows: First, Me(N03)2solution with total concentration of 0.3-0.5 mol / L was prepared, and equal molar amount of hydroxypropyl-β-cyclodextrin was added, named solution A; then (NH4)2HPO4solution with concentration of 0.3-0.5 mol / L was prepared, named solution B; according to the molar ratio of n(Me 2+ ) / n(PO4 3- ) = 5 / 3, solution B was added dropwise into solution A under the condition of 45-65 °C constant temperature water bath and strong stirring; after the end of dropwise addition, the pH of the solution was adjusted to 10-11 with concentrated ammonia water, and the stirring was continued for 4-8 h; then equal volume of anhydrous ethanol was added into the obtained white suspension, which was transferred into a hydrothermal reactor, and hydrothermal reaction was carried out at 100-150 °C for 12-24 h; after natural cooling, the obtained white precipitate was washed by centrifugation with deionized water, dried at 110 °C for 12 h, and calcined at 600-800 °C for 2-4 h; then a mixed solution of NH4F and NH4Cl was prepared, the concentration of NH4F was 0.2 mol / L, the concentration of NH4Cl was 0.1 mol / L, and the two were mixed according to the ratio of 100 mL halogen solution / 1 g MeHAP, and the stirring was continued at 45-65 °C for 4-8 h; after natural cooling, the white precipitate was collected by vacuum filtration and washed with distilled water, dried at 110 °C overnight, and ground thoroughly, to obtain ie-MeHAP-xF+Cl, x represents the percentage of F in the carrier, and x is 0.3-0.

78.

7. Use of the halogen-modified hydroxyapatite-supported nickel catalyst according to claim 1 in the reforming of CH4-CO2 to produce synthetic gas.

8. Use according to claim 7, characterized in that The catalyst is used in the reaction of CH4-CO2 reforming to obtain synthesis gas, the catalytic reaction is carried out in a fixed bed reactor, and the catalyst is first reduced at 600-700 °C for 1-3 h under 10 vol% H2 / Ar (H2: Ar volume ratio is 10:90). When the catalytic reaction is carried out, the molar ratio of raw materials CH4 to CO2 is 1:1, the volume fraction of CH4 is 10-50%, the volume fraction of CO2 is 10-50%, the volume fraction of Ar is 0-80%, the total volume space velocity of the raw gas is 40000-180000 mL / (g cat ·h), the reaction temperature is controlled at 600-750 °C, and the reaction pressure is normal pressure.

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