A type b substituted modified hydroxyapatite supported nickel catalyst and application thereof in methane dry reforming reaction

Abstract

This invention provides a Ni-supported catalyst of B-type substituted modified hydroxyapatite and its application in the dry reforming reaction of methane. The B-type substituted modified hydroxyapatite has a hydroxyapatite crystal structure and a specific surface area greater than 70 m². 2 The catalyst, in nanosheet form, contains Ni uniformly dispersed on a sheet-like support with a particle size of 1.0–6.0 nm and a Ni mass percentage of 1–10 wt%. Type B substituted modified hydroxyapatite was prepared via co-precipitation, and the active component Ni was loaded onto it via impregnation to obtain the catalyst. Type B substituted modified hydroxyapatite possesses advantages such as large specific surface area, abundant basic sites, and stable properties. With Ni highly dispersed on the support, it is used in low-temperature methane-carbon dioxide dry reforming reactions. At 500–700 °C, the conversion rate approaches the equilibrium conversion rate. The catalyst exhibits excellent resistance to carbon deposition, high activity, high stability, and low carbon deposition, making it beneficial for industrial applications.

Description

Technical Field

[0001] This invention belongs to the field of methane dry reforming technology, and relates to a type B substituted modified hydroxyapatite supported Ni catalyst and its application in methane dry reforming reaction. Background Technology

[0002] Methane dry reforming (MDR) technology can simultaneously convert two major greenhouse gases, methane and carbon dioxide, into syngas (CO and H2), which can then be converted to high-value compounds via Fischer-Tropsch synthesis. Common Ni-based catalysts are inexpensive and possess high initial catalytic activity, making them promising catalysts for the industrialization of MDR reactions. However, the active metal Ni is prone to sintering during high-temperature reactions, leading to decreased catalyst stability. Although sintering problems are significantly reduced at lower temperatures (<700 °C), side reactions such as CO disproportionation and methane decomposition forming carbon deposits and causing deactivation are highly likely to occur in low-temperature MDR reactions, which is a bottleneck limiting its industrial application.

[0003] Hydroxyapatite (HAP) has attracted attention in catalysis, adsorption, and photoelectrochemistry in recent years due to its structural stability, acid-base controllability, and strong ion exchange capacity. HAP can be used as a catalyst for various reactions such as ethanol coupling, CO hydrogenation oxidation, toluene catalytic oxidation, and carbon dioxide methanation. Current reports show that HAP-supported Ni-based catalysts have high catalytic activity in high-temperature MDR reactions, but their stability is poor. Ni catalysts supported on Mg-partially hydroxyapatite exhibit stronger metal-support interactions, effectively suppressing Ni particle sintering and resulting in higher catalyst stability and activity [Chinese Patent, CN 116273090 A]. However, the anti-carbon deposition performance of HAP-supported Ni catalysts, especially below 700 °C, is rarely mentioned.

[0004] Stoichiometric HAP (Ca 10 (PO4)6(OH)2 possesses hexagonal lattice symmetry, and its acid-base properties and structural characteristics can be altered by incorporating different cations and anions, thereby changing its catalytic activity. Common ion substitutions include: alkaline earth metal ion substitution of cations and anion substitution. Substitution at the phosphate site is called B-type substitution, and common ions that can be B-type substituted include VO4+. 3- CO3 2- SiO3 2- SO4 2- BO3 3- etc., including VO4 3-Ion-substituted VAP supports have been shown to possess strong CO2 activation performance, and Ni / VAP catalysts exhibit strong metal-support interactions, resisting sintering in high-temperature MDR (800 °C) [Applied Catalysis A: General, 2023, 662, 119290.]. However, other types of anion-substituted HAPs have not yet been reported.

[0005] Based on the above background, it has been found that there is currently no publicly available method for the preparation of B-type substituted hydroxyapatite with main group oxyacid anions, especially a report on hydroxyapatite-supported Ni catalysts suitable for low-temperature methane dry reforming reactions. Summary of the Invention

[0006] The purpose of this invention is to provide a type B substituted modified hydroxyapatite supported Ni catalyst and its application in methane dry reforming reaction, so as to solve the carbon deposition problem in low-temperature methane dry reforming reaction and improve catalytic stability.

[0007] The technical solution of this invention is as follows: In a first aspect, the present invention provides a Ni catalyst supported on a type B substituted modified hydroxyapatite, wherein the type B substituted modified hydroxyapatite serves as a support, has a hydroxyapatite crystal structure, and has a specific surface area greater than 70 m². 2 / g, in the form of nanosheets, with Ni uniformly dispersed on the sheet-like support, the particle size being 1.0-6.0 nm, and the mass percentage of Ni in the catalyst being 1-10 wt%; the B-type substituted anion (introduced anion) includes main group oxyacid anions; the molar ratio of the main group element to phosphorus is 0.2-1.

[0008] The main group oxyacid anions include CO32-. 2- SiO3 2- SO4 2- or BO3 3- .

[0009] Preferably, the Ni particles have a size of 2.5-3.5 nm.

[0010] Preferably, the thickness of the nanosheet is 5-20 nm.

[0011] A second aspect of the present invention provides a method for co-precipitating the B-type substituted modified hydroxyapatite supported Ni catalyst, comprising the following steps: 1) Dissolve soluble calcium salts as a calcium source in deionized water to obtain a calcium ion solution; 2) Dissolve the phosphorus source and the anion source in deionized water to obtain an anion solution; then introduce the anion source into the solution. 3) Add the anionic solution dropwise to the calcium source and stir evenly in a water bath to obtain a suspension; 4) Use ammonia water as a precipitant, add it dropwise to the suspension to adjust the pH to alkaline, and continue to stir and age it under water bath conditions; 5) The precipitate is neutralized by filtration and washing, then dried to obtain a solid powder; 6) The obtained solid powder was calcined at high temperature to obtain type B substituted modified hydroxyapatite; 7) The obtained modified hydroxyapatite was impregnated in a nickel salt solution, and then dried and calcined to obtain a nickel-based modified hydroxyapatite catalyst.

[0012] Preferably, the soluble calcium salt includes at least one of calcium nitrate, calcium chloride, and calcium hydroxide; the phosphorus source includes at least one of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate; and the introduced anion source includes at least one of ammonium carbonate, ammonium bicarbonate, sodium silicate, sodium sulfate, and sodium tetraborate.

[0013] Preferably, the total concentration of cations and anions in the calcium ion solution in step 1) and the anion solution in step 2) (the sum of the concentrations of cations and anions in the calcium ion solution and the anion solution) is 1.0-1.8 mol / L. -1 .

[0014] Preferably, in step 3), the water bath temperature is 50~90 ℃.

[0015] Preferably, in step 4), ammonia is added to adjust the pH to 8-12, and the aging time is 2-24 h.

[0016] Preferably, in step 6), the roasting temperature is 400~600 ℃ and the time is 2~5 hours.

[0017] Preferably, in step 7), the nickel salt is at least one of nickel nitrate, nickel acetate, and nickel chloride.

[0018] Preferably, in step 7), the soaking time is 0.5 to 24 hours.

[0019] Preferably, the drying temperature in step 7) is 50~80℃.

[0020] Preferably, the calcination temperature in step 7) is 300~600 ℃ and the heat treatment time is 1~3 h.

[0021] A third aspect of the present invention provides the application of the type B substituted modified hydroxyapatite supported Ni catalyst in a low-temperature methane dry reforming reaction.

[0022] Preferably, the reaction temperature is 500~700 ℃.

[0023] Preferably, the catalyst is reduced in an H2 atmosphere before the reaction, and the feed gas is a mixture of CH4, CO2 and N2.

[0024] Preferably, the feed gas ratio is CH4:CO2 = 1:1, and the gas hourly space velocity is 12000~48000 mL·g. cat -1 ·h -1 The reaction pressure is 0.1 MPa.

[0025] Preferably, the reducing atmosphere is H2 / N2 or H2 / Ar, the H2 volume concentration is 10~30 vol%, the reduction time is 1~3 h, and the reduction temperature is 500~700 ℃.

[0026] The beneficial effects of this invention are: This invention uses group oxyacid ions to partially replace B-type substituted modified hydroxyapatite as a catalyst support. The modified hydroxyapatite support has a larger specific surface area and more weakly basic sites on the surface. The raw materials for this material are readily available, the preparation process is simple, and it is environmentally friendly.

[0027] The present invention proposes a method for preparing a type B substituted modified hydroxyapatite catalyst for low-temperature methane dry reforming reaction. The Ni species are highly dispersed on a thin-film support, which has the advantages of simple preparation method and strong versatility. The catalyst also has the advantages of high catalytic activity and strong stability at low temperature, which is beneficial for industrial production. Attached Figure Description

[0028] Figure 1 The XRD patterns are of the carriers obtained in Examples 1-5.

[0029] Figure 2 The XRD patterns of the carriers prepared in Comparative Examples 1 and 2 are shown.

[0030] Figure 3 The image shows the FT-IR spectrum of the carrier obtained in Example 2.

[0031] Figure 4 This is an SEM image of the carrier obtained in Example 2.

[0032] Figure 5 The images show TEM images of the catalyst prepared in Example 2 and particle size distribution of the surface-active metal Ni.

[0033] Figure 6 The graph shows the changes in CO2 conversion, CH4 conversion, and H2 / CO ratio with reaction time for the catalyst prepared in Example 2, as tested according to Application Example 2.

[0034] Figure 7 The image shows the TG of the catalyst prepared in Example 2 after 30 h of reaction. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the embodiments. It should be noted that the embodiments are based on the technical solution and provide detailed implementation methods and specific operation processes, but the present invention is not limited to these embodiments and application examples. Example 1:

[0036] (1) Preparation of CAP-1 vector Using 5.31 g Ca(NO3)2·4H2O dissolved in 50 mL of deionized water as the calcium source, 0.48 g (NH4)2CO3 as the carbon source, and 1.32 g NH4H2PO4 as the phosphorus source, with a molar ratio of 2:4 (CO3... 2- :PO4 3- = 1:2) Dissolved in 50 mL of deionized water to obtain an anionic solution. The anionic solution was added dropwise to Ca(NO3)2·4H2O solution and stirred evenly in an 80 ℃ water bath to obtain a suspension. 25 vol% ammonia water was added dropwise to the suspension to adjust the pH to 10~11. The suspension was then stirred and aged for 3 h in an 80 ℃ water bath. The resulting precipitate was filtered, washed until neutral, and dried overnight at 50 ℃. The dried sample was ground into powder and calcined in air at 500 ℃ for 3 h to obtain type B modified carbon hydroxyapatite support, denoted as CAP-1. Figure 1 The XRD pattern showed that carbon hydroxyapatite was successfully formed. Figure 3 The infrared spectrum of the sample from Example 2 shows obvious bulk carbonate characteristic peaks, indicating that carbonate successfully replaced phosphate, forming type B modified CAP. SEM image ( Figure 4 As can be seen, the CAP-1 carrier is a uniform nanosheet with a thickness of 10.0 nm. The specific surface area of ​​the CAP-1 sample is 152 m². 2 / g.

[0037] (2) Preparation of Ni / CAP-1 catalyst Metallic Ni was loaded onto a CAP-1 support using an equal-volume impregnation method at a loading of 1.25 wt%. The sample was impregnated at room temperature for 4 hours, then dried at 80 °C for 12 hours. Finally, the dried sample was calcined at 400 °C in air for 2 hours. The resulting sample was named Ni / CAP-1. Figure 5 The TEM image shows that Ni particles are highly dispersed on the carrier surface with a small size and an average particle size of 2.9 nm. Example 2:

[0038] (1) Preparation of CAP-2 carrier Using 5.60 g Ca(NO3)2·4H2O dissolved in 50 mL of deionized water as the calcium source, 0.24 g (NH4)2CO3 as the carbon source, and 1.65 g NH4H2PO4 as the phosphorus source, with a molar ratio of 1:5 (CO3... 2- :PO4 3- = 1:5) Dissolved in 50 mL of deionized water to obtain an anionic solution. The anionic solution was added dropwise to Ca(NO3)2·4H2O solution and stirred evenly in an 80 ℃ water bath to obtain a suspension. 25 vol% ammonia water was added dropwise to the suspension to adjust the pH to 10~11. The suspension was then stirred and aged for 3 h in an 80 ℃ water bath. The resulting precipitate was filtered, washed until neutral, and dried overnight at 50 ℃. The dried sample was ground into powder and calcined in air at 500 ℃ for 3 h to obtain type B modified carboapatite support, denoted as CAP-2. Figure 1 As shown, the XRD pattern indicates the successful formation of carbohydroxyapatite. The specific surface area of ​​the CAP-2 sample is 107 m². 2 / g, the sample is in the form of thin flakes.

[0039] (2) Preparation of Ni / CAP-2 catalyst Similar to Example 1, metallic Ni was loaded onto the CAP-2 support using the equal-volume impregnation method, with a loading amount of 1.25 wt%. Finally, the dried sample was calcined in air at 400 ℃ for 2 h, and the resulting sample was named Ni / CAP-2. The Ni particles were uniformly distributed on the support, with an average particle size of 3.1 nm. Example 3:

[0040] (1) Preparation of CAP-3 carrier Using 5.02 g Ca(NO3)2·4H2O dissolved in 50 mL of deionized water as the calcium source, 0.72 g (NH4)2CO3 as the carbon source, and 0.99 g NH4H2PO4 as the phosphorus source, with a molar ratio of 1:1 (CO3... 2- :PO4 3- = 1:1) Dissolved in 50 mL of deionized water to obtain an anionic solution. The anionic solution was added dropwise to Ca(NO3)2·4H2O solution and stirred evenly in an 80 ℃ water bath to obtain a suspension. 25 vol% ammonia water was added dropwise to the suspension to adjust the pH to 10~11. Stirring was continued in an 80 ℃ water bath for 3 h. The resulting precipitate was filtered, washed until neutral, and dried overnight at 50 ℃. The dried sample was ground into powder and calcined in air at 500 ℃ for 3 h to obtain type B modified carboapatite support, denoted as CAP-3. Figure 1 As shown, the XRD pattern indicates the successful formation of carbohydroxyapatite, and the specific surface area of ​​the CAP-3 sample is 101 m².2 / g, the sample appears as uniform small thin flakes.

[0041] (2) Preparation of Ni / CAP-3 catalyst Similar to Example 1, metallic Ni was loaded onto the CAP-3 support using an equal-volume impregnation method, with a loading amount of 1.25 wt%. Finally, the dried sample was calcined in air at 400 ℃ for 2 h, and the resulting sample was named Ni / CAP-3. Ni particles were uniformly distributed on the support surface, with an average particle size of 3.6 nm. Example 4:

[0042] (1) Preparation of SiAP support Using 5.31 g Ca(NO3)2·4H2O dissolved in 50 mL of deionized water as the calcium source, 0.61 g Na2SiO3 as the silicon source, and 1.32 g NH4H2PO4 as the phosphorus source, with a molar ratio of 2:4 (SiO3... 2- :PO4 3- = 1:2) Dissolved in 50 mL of deionized water to obtain an anionic solution. The anionic solution was added dropwise to Ca(NO3)2·4H2O solution and stirred evenly in an 80 ℃ water bath to obtain a suspension. 25 vol% ammonia water was added dropwise to the suspension to adjust the pH to 10~11. The suspension was then stirred and aged for 3 h in an 80 ℃ water bath. The resulting precipitate was filtered, washed until neutral, and dried overnight at 50 ℃. The dried sample was ground into powder and calcined in air at 500 ℃ for 3 h to obtain type B modified silanolapatite support, denoted as SiAP. Figure 1 As shown, the XRD pattern indicates that silanolapatite was successfully formed.

[0043] (2) Preparation of Ni / SiAP catalyst Similar to Example 1, metallic Ni was loaded onto the SiAP support using the equal-volume impregnation method, with a loading amount of 1.25 wt%. Finally, the dried sample was calcined in air at 400 ℃ for 2 h, and the resulting sample was named Ni / SiAP. Example 5:

[0044] (1) Preparation of SAP carrier Using 5.31 g Ca(NO3)2·4H2O dissolved in 50 mL of deionized water as the calcium source, 0.71 g Na2SO4 as the sulfur source, and 1.32 g NH4H2PO4 as the phosphorus source, with a molar ratio of 2:4 (SO4... 2- :PO4 3-= 1:2) Dissolved in 50 mL of deionized water to obtain an anionic solution. The anionic solution was added dropwise to Ca(NO3)2·4H2O solution and stirred evenly in an 80 ℃ water bath to obtain a suspension. 25 vol% ammonia water was added dropwise to the suspension to adjust the pH to 10~11. The suspension was then stirred and aged for 3 h in an 80 ℃ water bath. The resulting precipitate was filtered, washed until neutral, and dried overnight at 50 ℃. The dried sample was ground into powder and calcined in air at 500 ℃ for 3 h to obtain type B modified thiohydroxyapatite carrier, denoted as SAP. Figure 1 As shown, the XRD pattern indicates that thiohydroxyapatite was successfully formed.

[0045] (2) Preparation of Ni / SAP catalyst Similar to Example 1, metallic Ni was loaded onto the SAP support using the equal-volume impregnation method, with a loading amount of 1.25 wt%. Finally, the dried sample was calcined in air at 400 ℃ for 2 h, and the resulting sample was named Ni / SAP. Example 6:

[0046] (1) Preparation of BAP carrier Using 5.90 g Ca(NO3)2·4H2O dissolved in 50 mL of deionized water as the calcium source, 0.48 g Na2B4O7·10H2O as the boron source, and 1.32 g NH4H2PO4 as the phosphorus source, with a molar ratio of 2:4 (BO3... 3- :PO4 3- = 1:2) Dissolved in 50 mL of deionized water to obtain an anionic solution. The anionic solution was added dropwise to Ca(NO3)2·4H2O solution and stirred evenly in an 80 ℃ water bath to obtain a suspension. 25 vol% ammonia water was added dropwise to the suspension to adjust the pH to 10~11. The suspension was then stirred and aged for 3 h in an 80 ℃ water bath. The resulting precipitate was filtered, washed until neutral, and dried overnight at 50 ℃. The dried sample was ground into powder and calcined in air at 500 ℃ for 3 h to obtain type B modified boron hydroxyapatite support, denoted as BAP. Figure 1 As shown, the XRD pattern indicates that boron hydroxyapatite was successfully formed.

[0047] (2) Preparation of Ni / BAP catalyst Similar to Example 1, metallic Ni was loaded onto the BAP support using the equal-volume impregnation method, with a loading amount of 1.25 wt%. Finally, the dried sample was calcined in air at 400 ℃ for 2 h, and the resulting sample was named Ni / BAP.

[0048] Comparative Example 1: (1) Preparation of HAP vector 5.90 g of Ca(NO3)2·4H2O was dissolved in 50 mL of deionized water as the calcium source, and 1.98 g of NH4H2PO4 was dissolved in 50 mL of deionized water as the phosphorus source. NH4H2PO4 was added dropwise to the Ca(NO3)2·4H2O solution, and the mixture was stirred evenly in an 80 ℃ water bath to obtain a suspension. 25 vol% ammonia was added dropwise to the suspension to adjust the pH to 10-11, and the mixture was further aged in an 80 ℃ water bath with stirring for 3 h. The resulting precipitate was filtered, washed until neutral, and then dried overnight at 50 ℃. The dried sample was ground into powder and calcined at 500 ℃ in air for 3 h to obtain the hydroxyapatite support, denoted as HAP. Figure 2 As shown, the XRD pattern indicates the successful formation of a hydroxyapatite crystalline structure. HAP is a non-porous or macroporous material with a specific surface area of ​​46 m². 2 / g.

[0049] (2) Preparation of Ni / HAP catalyst Similar to Example 1, metallic Ni was loaded onto the HAP support using an equal-volume impregnation method, with a loading of 1.25 wt%. Finally, the dried sample was calcined in air at 400 °C for 2 h, and the resulting sample was named Ni / HAP. Obvious aggregated Ni particles (>10 nm) were observed on the catalyst, and the active sites were unevenly distributed. Comparative Example 2:

[0050] (1) Preparation of VAP carrier Using 5.90 g Ca(NO3)2·4H2O dissolved in 50 mL of deionized water as the calcium source, 0.46 g V2O5 as the vanadium source, and 1.32 g NH4H2PO4 as the phosphorus source, with a molar ratio of 2:4 (VO4... 3- :PO4 3- = 1:2) Dissolved in 50 mL of deionized water to obtain an anionic solution. The anionic solution was added dropwise to Ca(NO3)2·4H2O solution and stirred evenly in an 80 ℃ water bath to obtain a suspension. 25 vol% ammonia water was added dropwise to the suspension to adjust the pH to 10~11. The suspension was then stirred and aged for 3 h in an 80 ℃ water bath. The resulting precipitate was filtered, washed until neutral, and then dried overnight at 50 ℃. The dried sample was ground into powder and calcined in air at 500 ℃ for 3 h to obtain type B modified vanadium hydroxyapatite support, denoted as VAP. Figure 2 As shown, the XRD pattern indicates the successful formation of vanadium hydroxyapatite with a specific surface area of ​​27 m². 2 / g, VAP has extremely poor thermal stability and loses its hydroxyapatite structure after the reaction.

[0051] (2) Preparation of Ni / VAP catalyst Similar to Example 1, metallic Ni was loaded onto the VAP support using an equal-volume impregnation method, with a loading of 1.25 wt%. Finally, the dried sample was calcined in air at 400 ℃ for 2 h, and the resulting sample was named Ni / VAP. The Ni particles on the catalyst showed significant aggregation, with a wide particle size distribution (2-20 nm). Comparative Example 3:

[0052] Preparation of CAP-4 vector Using 4.72 g Ca(NO3)2·4H2O dissolved in 50 mL of deionized water as the calcium source, 0.96 g (NH4)2CO3 as the carbon source, and 0.66 g NH4H2PO4 as the phosphorus source, with a molar ratio of 4:2 (CO3... 2- :PO4 3- = 2) Dissolve in 50 mL of deionized water to obtain an anionic solution. Add the anionic solution dropwise to Ca(NO3)2·4H2O solution and stir evenly in an 80 ℃ water bath to obtain a suspension. Add 25 vol% ammonia water dropwise to the suspension to adjust the pH to 10-11, and continue stirring and aging in an 80 ℃ water bath for 3 hours. Filtering and washing do not yield a precipitate. Modified hydroxyapatite cannot be formed when the ratio of anion to phosphate is greater than 1. Comparative Example 4:

[0053] (1) Preparation of HAP-C vector Using the same raw materials as in Example 1, the phosphorus source, calcium source, and carbon source were dissolved in deionized water. First, the phosphorus source was added to the calcium source and stirred until homogeneous. Then, 25 vol% ammonia was added dropwise to adjust the pH to 10-11. Next, the carbon source was added to obtain a suspension. Subsequent steps were the same as in Example 1 to obtain the HAP-C carrier. Figure 2 As shown in the XRD pattern, a distinct CaCO3 phase was formed in the sample, but no carbohydroxyapatite was formed. This indicates that the introduction of anions requires mixing with a phosphorus source before being added to a calcium source to generate modified hydroxyapatite.

[0054] Application Example 1 The catalysts prepared in Examples 1-6 and Comparative Examples 1 and 2 were used to carry out a dry reforming reaction of methane in a fixed-bed reactor using methane and carbon dioxide as feedstocks. The reaction conditions were as follows: the catalyst was pressed into tablets to form a 40-60 mesh powder, and 100 mg was weighed and placed in a quartz tube with an inner diameter of 8 mm. The reaction was carried out at atmospheric pressure and at 600 °C under a 10H2 / N2 atmosphere for 60 min, followed by purging with N2 to room temperature. CH4 and CO2 were used as feed gases (molar ratio 1:1, no carrier gas), and the total volume hourly space velocity was 24000 mL·g. cat -1 ·h -1The pressure was at atmospheric pressure, the temperature was at 600 ℃, and the reaction time was 9 h. The results are shown in Table 1.

[0055] Table 1: Methane dry reforming conversion and deactivation rate with different catalysts

[0056] As shown in Table 1, the Ni / VAP catalyst exhibits extremely low MDR activity at low temperatures. In contrast, the B-type modified hydroxyapatite prepared by replacing phosphate ions with main group oxyacid ions has higher stability than Ni / HAP and is more suitable as a support for Ni-based catalysts applied to low-temperature MDR reactions. Among them, the Ni-based catalyst prepared by using CAP as a support has higher catalytic activity and stability.

[0057] Application Example 2 The stability of the catalyst prepared in Example 2 was tested under the reaction conditions described in Example 1 for 30 h. The results are as follows: Figure 6 As shown, the Ni / CAP catalyst maintained very high catalytic activity after 30 h of reaction, demonstrating high low-temperature MDR stability. The TG spectrum after the reaction (…) Figure 7 It can be seen that the carbon deposition on the catalyst is only 7.42% after 30 hours. This catalyst has good low-temperature carbon deposition resistance, corresponding to its high stability.

[0058] The above description is only a few embodiments of the present invention and is not intended to limit the present invention. Any modifications, substitutions or alterations made in accordance with the claims of the present invention are included within the protection scope of the present invention.

Claims

1. A type B substituted modified hydroxyapatite supported Ni catalyst, characterized in that: The B-type substituted modified hydroxyapatite serves as a carrier, possessing a hydroxyapatite crystal structure and a specific surface area greater than 70 m². 2 / g, in the form of nanosheets, with Ni uniformly dispersed on the sheet-like support, the particle size being 1.0-6.0 nm, and the mass percentage of Ni in the catalyst being 1-10 wt%; the B-type substituted anions include main group oxyacid anions; the molar ratio of the main group element to phosphorus is 0.2-1.

2. The catalyst according to claim 1, characterized in that: The main group oxyacid anions include CO32-. 2- SiO3 2- SO4 2- or BO3 3- .

3. The catalyst according to claim 1, characterized in that: The Ni particles have a size of 2.5-3.5 nm; and / or, The thickness of the nanosheets is 5-20 nm.

4. A method for co-precipitating the catalyst of claim 1, characterized in that: Includes the following steps: 1) Dissolve soluble calcium salts as a calcium source in deionized water to obtain a calcium ion solution; 2) Dissolve the phosphorus source and the introduced anion source in deionized water to obtain an anion solution; 3) Add the anionic solution dropwise to the calcium source and stir evenly in a water bath to obtain a suspension; 4) Use ammonia water as a precipitant, add it dropwise to the suspension to adjust the pH to alkaline, and continue to stir and age it under water bath conditions; 5) The precipitate is neutralized by filtration and washing, then dried to obtain a solid powder; 6) The obtained solid powder was calcined at high temperature to obtain type B substituted modified hydroxyapatite; 7) The obtained modified hydroxyapatite was impregnated in a nickel salt solution, and then dried and calcined to obtain a nickel-based modified hydroxyapatite catalyst.

5. The method as described in claim 4, characterized in that: The soluble calcium salt includes at least one of calcium nitrate, calcium chloride, and calcium hydroxide; the phosphorus source includes at least one of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate; the introduced anion source includes at least one of ammonium carbonate, ammonium bicarbonate, sodium silicate, sodium sulfate, and sodium tetraborate.

6. The method as described in claim 4, characterized in that: In step 3), the water bath temperature is 50~90 ℃.

7. The method as described in claim 4, characterized in that: In step 4), ammonia is added to adjust the pH to 8-12, and the aging time is 2-24 hours; and / or, In step 6), the roasting temperature is 400~600 ℃ and the time is 2~5 h.

8. The method as described in claim 4, characterized in that: In step 7), the soaking time is 0.5~24 h; and / or, In step 7), the calcination temperature is 300~600 ℃ and the heat treatment time is 1~3 h.

9. The application of the catalyst of claim 1 in a low-temperature dry reforming reaction of methane.

10. The application as described in claim 9, characterized in that: The reaction temperature is 500~700 ℃.

Images