A mechanochemical preparation method for strongly basic hydroxyapatite and its application in ethanol coupling reaction.

Abstract

This invention provides a mechanochemical preparation method for strongly basic hydroxyapatite and its application in ethanol coupling reactions. The preparation method includes drying or calcining a calcium-phosphorus source and a supplementary calcium source for pretreatment, mixing the pretreated calcium-phosphorus source and the supplementary calcium source, ball milling, and calcining to obtain strongly basic hydroxyapatite. The calcium-phosphorus ratio added is 1.50–1.75 in molar ratio. This invention only requires the calcium-phosphorus source and the supplementary calcium source, without the need for additives. The preparation method is simple, generates no waste, and the synthesized powder is a pure hexagonal hydroxyapatite phase. It solves the defects of liquid-phase methods for modifying surface properties, such as the introduction of other substances, cumbersome steps, and difficulty in controlling the purity of the product crystal phase. In addition, the hydroxyapatite prepared by this invention has controllable surface properties, high alkali content, large specific surface area, and stable properties. When used in the ethanol coupling reaction to prepare higher alcohols, the selectivity for higher alcohols is 80–98% under normal pressure conditions, and the catalyst performance is reproducible, which is beneficial for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalysis technology, specifically relating to a mechanochemical preparation method of strongly basic hydroxyapatite and its application in ethanol coupling reactions. Background Technology

[0002] Ethanol resources produced through biomass fermentation and coal-based fuels are abundant. Catalytically converting ethanol into high-value-added products holds promise as a new route for producing fine chemicals. Higher alcohols are important raw materials for fine chemicals and can be used as surfactants and plasticizers. Furthermore, higher alcohols have a flammability similar to gasoline and, as alcohol-based fuels, offer a higher air-fuel ratio and lower water solubility than ethanol, making them ideal biofuels and petroleum additives for the future.

[0003] Solid catalysts with Lewis acid-base sites, such as hydroxyapatite, magnesium aluminum oxides, and supported metal oxides, are often used for the catalytic coupling of ethanol to higher alcohols. Due to the easily modulated surface acidity and basicity of hydroxyapatite, especially its strong-base-weak-acid properties, it exhibits higher selectivity for higher alcohols in the coupling process.

[0004] The properties of hydroxyapatite are closely related to its preparation method, with liquid-phase and solid-phase methods being common approaches. Existing research indicates that the number and types of acid-base active sites on the surface of hydroxyapatite affect its catalytic performance. Currently, both domestically and internationally, the surface properties of hydroxyapatite are generally controlled using soluble calcium and phosphorus sources via liquid-phase methods, with the addition of modifiers, surfactants, or pH adjusters to prepare hydroxyapatite powder.

[0005] Takashi et al. prepared hydroxyapatite with different calcium-to-phosphorus ratios by controlling the solution pH during precipitation synthesis. The ratio of acid-base sites on the catalyst varied with the calcium-to-phosphorus ratio, and the selectivity of the product butanol was closely related to the acid-base properties. When the calcium-to-phosphorus ratio was 1.67, the base content was 20 μmol g. -1 The selectivity of butanol is about 70% [T. Tsuchida et al. Journal of Catalysis 259 (2008) 183–189].

[0006] Shuhei Ogo et al. prepared a series of apatite samples with different strontium-to-phosphorus ratios via hydrothermal synthesis. The catalyst with the highest alkali content (37.6 μmol g) was observed when the strontium-to-phosphorus ratio was 1.70. -1 Its optimal ethanol conversion rate is 11%, and the selectivity for higher alcohols is 94.2% [S. Ogo et al. Journal of Catalysis 296(2012)24–30].

[0007] Invention patent CN107555405B discloses a liquid-phase preparation method for calcium phosphate nanopowder with controllable aspect ratio and calcium-to-phosphorus ratio. The method involves mixing a phosphorus source and a calcium source, and controlling the aspect ratio and calcium-to-phosphorus ratio of the product by adding a pH adjuster to the reactants or controlling the ratio of phosphorus and calcium sources. However, the powder prepared by this method is mostly a mixed phase of β-tricalcium phosphate and hydroxyapatite, with only a pure hydroxyapatite phase at a calcium-to-phosphorus ratio of 1.67.

[0008] Liquid-phase synthesis is time-consuming, requires precise control of synthesis conditions, and generates significant amounts of waste liquid and gas. Furthermore, controlling the surface properties of hydroxyapatite using liquid-phase methods not only introduces other substances into the system, affecting catalytic activity, but also increases production costs, making the process cumbersome and economically unfeasible. In contrast, solid-phase synthesis is simpler, effectively reduces waste generation, offers better reproducibility, and the properties of the synthesized powder are not strongly influenced by processing parameters, making it suitable for large-scale production. Moreover, the energy accumulation during the mechanochemical synthesis process in solid-phase methods leads to the formation of new surface and crystal defects and morphological changes in the catalyst, thereby creating new catalytic sites and increasing catalytic activity.

[0009] The literature [MVChaikina, et al.Ceramics International 45(2019)16927–16933] reports a solid-phase synthesis method for hydroxyapatite. The article focuses on the formation kinetics of hydroxyapatite during ball milling of a mixture of calcium phosphate and calcium oxide or calcium hydroxide, but does not mention the changes in the acidity and alkalinity of the hydroxyapatite surface.

[0010] Based on the above background, it has been found that preparing strongly basic hydroxyapatite is beneficial for improving the selectivity of higher alcohols in ethanol coupling reactions. However, there is currently no existing technology that discloses a mechanochemical method for preparing strongly basic hydroxyapatite, especially a method for preparing hydroxyapatite catalysts suitable for ethanol coupling reactions. Summary of the Invention

[0011] In view of the aforementioned existing technical situation, this invention proposes a mechanochemical preparation method for strongly basic hydroxyapatite and its application in ethanol coupling reactions. Through extensive experiments and in-depth research, the inventors of this invention discovered that by pretreating the calcium-phosphorus source and supplementary calcium source, the amount of bound water generated alongside the formation of hydroxyapatite during mechanochemical preparation can be clearly determined, which affects the specific surface area and surface acidity / alkalinity of the sample. With increasing bound water content, the specific surface area of ​​the sample gradually increases, while the surface alkalinity shows a trend of first increasing and then decreasing. Excessive bound water formation has a negative effect on the hydroxyapatite structure. This is because the removal of bound water during the subsequent calcination process alters the pore structure, and the presence of water causes the formation of new hydroxyl groups on the sample surface, changing the surface alkalinity. Furthermore, this invention achieves control over the surface alkalinity and calcium-phosphorus ratio of hydroxyapatite by changing the ratio of calcium to phosphorus sources and regulating the proportion of different group combinations, especially the binding state of surface oxygen.

[0012] The aforementioned "generation of hydroxyapatite accompanied by the generation of bound water" refers to the process in which, during the preparation of hydroxyapatite, calcium and phosphorus sources and supplementary calcium sources undergo thermodynamic reorganization of calcium, phosphorus, hydrogen, and oxygen atoms under the thermodynamic driving force of mechanical ball milling to produce hydroxyapatite, with the remaining hydrogen and oxygen atoms generated in the form of bound water along with the hydroxyapatite.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A mechanochemical method for preparing strongly basic hydroxyapatite, wherein the method involves mixing and reacting a calcium-phosphorus source with a supplementary calcium source to prepare hydroxyapatite powder, including pretreatment of the calcium-phosphorus source and the supplementary calcium source by drying or calcination, mixing the pretreated calcium-phosphorus source and the supplementary calcium source, ball milling in a ball mill, and calcining to obtain strongly basic hydroxyapatite; the added (Ca) is in a molar ratio of... 2+ ):(PO4 3- () = 1.50~1.75; the calcium and phosphorus source is one or more of tricalcium phosphate, dicalcium phosphate, anhydrous dicalcium phosphate, and dicalcium phosphate monohydrate; the supplementary calcium source is one or two of calcium oxide and calcium hydroxide.

[0015] This invention regulates the amount of bound water generated alongside hydroxyapatite formation by controlling the hydrogen content in the calcium-phosphorus source or by supplementing the calcium source, thereby altering the specific surface area and surface alkalinity of the hydroxyapatite sample. The prepared samples have a specific surface area of ​​1-130 m². 2 g -1 The alkali content is 4-50 μmol g. -1(CO2-TPD measurement); By controlling the ratio of calcium to phosphorus sources in the raw materials, the composition and ratio of different functional groups can be adjusted, thereby controlling the alkalinity of the sample surface and the calcium-to-phosphorus ratio. The alkalinity content of the prepared samples is 3-60 μmol g. -1 The calcium-to-phosphorus ratio is 1.50–1.75. The hydroxyapatite powder has a hexagonal crystal phase.

[0016] Preferably, the calcium and phosphorus source is one or more of calcium hydrogen phosphate, anhydrous calcium dihydrogen phosphate, and calcium dihydrogen phosphate monohydrate.

[0017] Preferably, during pretreatment, the drying temperature is 50-180℃ and the drying time is 1-6h; the calcination temperature is 200-800℃ and the calcination time is 1-6h.

[0018] Preferably, the calcium and phosphorus source is tricalcium phosphate. In addition to the drying or calcination pretreatment, the tricalcium phosphate is also subjected to water absorption treatment. The water absorption method is immersion or spraying, and the water absorption amount is 0.5-65%. The hydrogen content of the raw material is further controlled.

[0019] Preferably, (Ca) 2+ ):(PO4 3- =1.61 to 1.75.

[0020] Preferably, the calcium phosphorus source and the supplementary calcium source are mixed by physical mixing; more specifically, the mixing method is stirring or grinding.

[0021] Preferably, the mixing reaction process is a mechanochemical reaction, and the ball mill is selected from planetary ball mills, vibratory ball mills, stirred ball mills, or drum ball mills.

[0022] Preferably, the ball milling time is 3 to 60 minutes.

[0023] Preferably, the ball milling speed is 400-800 rpm.

[0024] Preferably, the calcination temperature of the ball-milled sample is 350–600°C, and further, the calcination time is 1–5 hours.

[0025] Preferably, the roasting atmosphere is air, nitrogen, or argon.

[0026] Preferably, the amount of bound water generated along with the formation of hydroxyapatite is 0-18 mol (based on the formation of 1 mol of hydroxyapatite), and further, the amount of bound water generated along with the formation of hydroxyapatite is 5-15 mol.

[0027] The present invention also provides the application of the strongly basic hydroxyapatite in the catalytic coupling of ethanol to prepare higher alcohols.

[0028] Preferably, the ethanol coupling reaction is carried out in a fixed-bed reactor at atmospheric pressure, a reaction temperature of 200–350°C, and a mass hourly space velocity of 0.98–20 h⁻¹. -1 Specifically, mass hourly space velocity (MSV) refers to the ratio of the mass flow rate of ethanol to the amount of catalyst (strongly basic hydroxyapatite) loaded.

[0029] The ethanol conversion rate reaches over 55%, and the total selectivity of higher alcohols reaches over 97%.

[0030] The beneficial effects of this invention are as follows: Compared with the prior art, this invention utilizes the thermodynamic driving force of mechanical ball milling to provide a method for preparing strongly basic hydroxyapatite by controlling the hydrogen content or the ratio of phosphorus and calcium sources in the raw materials before the reaction. This invention only requires the provision of calcium and phosphorus sources, eliminating the need for additives. The preparation method is simple, generates no waste, and the synthesized powder is a pure hexagonal hydroxyapatite phase without other impurities. The catalyst can be stably and repeatedly prepared. This invention solves the defects of existing liquid-phase methods for modifying surface properties, such as the introduction of other substances, cumbersome steps, and difficulty in controlling the purity of the product's crystal phase. Furthermore, the hydroxyapatite prepared by this invention has controllable surface properties, high alkali content, large specific surface area, and stable properties. When used in the coupling reaction of ethanol to prepare higher alcohols, the selectivity of higher alcohols is in the range of 80-98% under normal pressure conditions. The yield of higher alcohols is superior to catalysts reported in the current literature, and the catalyst performance is reproducible, which is beneficial for its application in industrial production. Attached Figure Description

[0031] Figure 1 The XRD patterns of the catalysts prepared in Examples 1-5 are shown below.

[0032] Figure 2 The XRD patterns of the catalysts prepared in Examples 6-11 are shown below.

[0033] Figure 3 The XRD patterns of the catalysts prepared in Comparative Examples 1 and 2 are shown.

[0034] Figure 4 The XRD patterns of the catalysts prepared in comparative examples 3-4 are shown. Detailed Implementation

[0035] The present invention will be described in detail below through some specific embodiments and comparative examples, but the present invention is not limited to these embodiments.

[0036] Example 1

[0037] Weigh out 2.3621g of tricalcium phosphate and 0.1887g of calcium hydroxide as calcium and phosphorus sources, respectively. 2+ ):n(PO4 3-The ratio of tricalcium phosphate to calcium hydroxide was 1.67:1, resulting in 0 bound water per mol of hydroxyapatite. Tricalcium phosphate and calcium hydroxide powders were dried separately at 120℃ for 2 hours, then mixed and ball-milled at 800 rpm for 30 minutes in a planetary ball mill. The resulting powder sample was placed in a muffle furnace and calcined at 400℃ for 2 hours to obtain the hydroxyapatite catalyst (e.g., Figure 1 As shown), the specific surface area is 1.2 m². 2 g -1 The alkali content is 4.8 μmol g. -1 .

[0038] Example 2

[0039] Weigh out 1.8705g of dicalcium phosphate and 0.6792g of calcium hydroxide as calcium and phosphorus sources, respectively. 2+ ):n(PO4 3- The ratio of 1.67:1 resulted in the formation of 6 mol of bound water accompanying the production of 1 mol of hydroxyapatite. Calcium hydrogen phosphate and calcium hydroxide powders were dried separately at 120℃ for 2 hours. After mixing, the samples were ball-milled at 800 rpm for 30 minutes. The resulting powder samples were then calcined in a muffle furnace at 400℃ for 2 hours to obtain the hydroxyapatite catalyst (e.g., ...). Figure 1 As shown in the figure, the specific surface area is 64.4 m². 2 g -1 The alkali content is 10.7 μmol g. -1 .

[0040] Example 3

[0041] Weigh out 1.6678 g of anhydrous calcium dihydrogen phosphate and 0.9324 g of calcium oxide as calcium and phosphorus sources, respectively. 2+ ):n(PO4 3- The ratio of 1.67:1 resulted in the formation of 5 mol of bound water accompanying the production of 1 mol of hydroxyapatite. Anhydrous calcium dihydrogen phosphate was dried at 120℃ for 2 h, and calcium oxide was calcined at 600℃ for 2 h. After mixing, the samples were ball-milled at 800 rpm for 30 min in a planetary ball mill. The resulting powder was then placed in a muffle furnace and calcined at 400℃ for 2 h to obtain the hydroxyapatite catalyst (e.g., ...). Figure 1 As shown in the figure, the specific surface area is 63.2 m². 2 g -1 The alkali content is 10.5 μmol g. -1 .

[0042] Example 4

[0043] Weigh out 1.5588g of anhydrous calcium dihydrogen phosphate and 1.1518g of calcium hydroxide as calcium and phosphorus sources, respectively. 2+ ):n(PO43- The ratio of 1.67:1 resulted in the formation of 12 mol of bound water accompanying the production of 1 mol of hydroxyapatite. Anhydrous calcium dihydrogen phosphate and calcium hydroxide powders were dried separately at 120℃ for 2 hours. After mixing, the samples were ball-milled at 800 rpm for 30 minutes in a planetary ball mill. The resulting powder sample was then placed in a muffle furnace and calcined at 400℃ for 2 hours to obtain the hydroxyapatite catalyst (e.g., ...). Figure 1 As shown in the figure, the specific surface area is 99.2 m². 2 g -1 The alkali content is 40.3 μmol g. -1 .

[0044] Example 5

[0045] Weigh out 1.5720g of calcium dihydrogen phosphate monohydrate and 1.0780g of calcium hydroxide as calcium and phosphorus sources, respectively. 2+ ):n(PO4 3- The ratio of 1.67:1 resulted in the formation of 15 mol of bound water accompanying the production of 1 mol of hydroxyapatite. Calcium dihydrogen phosphate monohydrate was dried at 50℃ for 1 h, and calcium hydroxide powder was dried at 120℃ for 2 h. The samples were then mixed and ball-milled at 800 rpm for 30 min in a planetary ball mill. The resulting powder was then calcined at 400℃ for 2 h in a muffle furnace to obtain the hydroxyapatite catalyst (e.g., ...). Figure 1 As shown), the specific surface area is 110.3 m². 2 g -1 The alkali content is 25.7 μmol g. -1 .

[0046] Example 6

[0047] This embodiment uses the same calcium and phosphorus sources as in Example 4, but changes the amounts of calcium and phosphorus sources added. Specifically, 1.6188g of calcium dihydrogen phosphate and 1.2812g of calcium hydroxide are weighed out, n(Ca 2+ ):n(PO4 3- The ratio of anhydrous calcium dihydrogen phosphate to calcium hydroxide powder was 1.75:1. Anhydrous calcium dihydrogen phosphate and calcium hydroxide powders were dried separately at 120℃ for 2 hours. After mixing, the samples were ball-milled at 800 rpm for 30 minutes in a planetary ball mill. The resulting powder sample was then placed in a muffle furnace and calcined at 400℃ for 2 hours to obtain a hydroxyapatite catalyst (e.g., Figure 2 As shown in the figure, the specific surface area is 117.6 m². 2 g -1 The alkali content is 12.5 μmol g. -1 .

[0048] Example 7

[0049] This embodiment uses the same calcium and phosphorus sources as in Example 4, but changes the amounts of calcium and phosphorus sources added. Specifically, 1.5681g of calcium dihydrogen phosphate and 1.1819g of calcium hydroxide are weighed out, n(Ca 2+ ):n(PO4 3- The ratio of anhydrous calcium dihydrogen phosphate to calcium hydroxide powder was 1.69:1. Anhydrous calcium dihydrogen phosphate and calcium hydroxide powders were dried separately at 120℃ for 2 hours. After mixing, the samples were ball-milled at 800 rpm for 30 minutes in a planetary ball mill. The resulting powder sample was then placed in a muffle furnace and calcined at 400℃ for 2 hours to obtain a hydroxyapatite catalyst (e.g., Figure 2 As shown), the specific surface area is 119.5 m². 2 g -1 The alkali content is 25.4 μmol g. -1 .

[0050] Example 8

[0051] This embodiment uses the same calcium and phosphorus sources as in Example 4, but changes the amounts of calcium and phosphorus sources added. Specifically, 1.7331 g of calcium dihydrogen phosphate and 1.2469 g of calcium hydroxide are weighed out, n(Ca 2+ ):n(PO4 3- The ratio of anhydrous calcium dihydrogen phosphate to calcium hydroxide powder was 1.64:1. Anhydrous calcium dihydrogen phosphate and calcium hydroxide powders were dried separately at 120℃ for 2 hours. After mixing, the samples were ball-milled at 800 rpm for 30 minutes in a planetary ball mill. The resulting powder sample was then placed in a muffle furnace and calcined at 400℃ for 2 hours to obtain a hydroxyapatite catalyst (e.g., Figure 2 As shown), the specific surface area is 115.0 m². 2 g -1 The alkali content is 56.1 μmol g. -1 .

[0052] Example 9

[0053] This embodiment uses the same calcium and phosphorus sources as in Example 4, but changes the amounts of calcium and phosphorus sources added. Specifically, 1.4265g of calcium dihydrogen phosphate and 1.0035g of calcium hydroxide are weighed out, n(Ca 2+ ):n(PO4 3- The ratio of anhydrous calcium dihydrogen phosphate to calcium hydroxide powder was 1.61:1. Anhydrous calcium dihydrogen phosphate and calcium hydroxide powders were dried separately at 120℃ for 2 hours. After mixing, the samples were ball-milled at 800 rpm for 30 minutes in a planetary ball mill. The resulting powder sample was then placed in a muffle furnace and calcined at 400℃ for 2 hours to obtain a hydroxyapatite catalyst (e.g., Figure 2 As shown in the figure, the specific surface area is 113.8 m². 2 g -1 The alkali content is 29.8 μmol g. -1 .

[0054] Example 10

[0055] This embodiment uses the same calcium and phosphorus sources as in Example 4, but changes the amounts of calcium and phosphorus sources added. Specifically, 1.8982 g of calcium dihydrogen phosphate and 1.2018 g of calcium hydroxide are weighed out, n(Ca 2+ ):n(PO4 3- The ratio of anhydrous calcium dihydrogen phosphate to calcium hydroxide powder was 1.50:1. Anhydrous calcium dihydrogen phosphate and calcium hydroxide powders were dried separately at 120℃ for 2 hours. After mixing, the samples were ball-milled at 800 rpm for 30 minutes in a planetary ball mill. The resulting powder sample was then placed in a muffle furnace and calcined at 400℃ for 2 hours to obtain a hydroxyapatite catalyst (e.g., Figure 2 As shown in the figure, the specific surface area is 98.9 m². 2 g -1 The alkali content is 2.94 μmol g. -1 .

[0056] Example 11

[0057] This embodiment uses the same calcium and phosphorus sources as in Example 1, weighing 2.3621g of tricalcium phosphate and 0.1887g of calcium hydroxide as the calcium and phosphorus sources, respectively. 2+ ):n(PO4 3- The ratio of tricalcium phosphate to calcium hydroxide powder was 1.67:1. After drying tricalcium phosphate at 120℃ for 2 hours, 0.8% water was absorbed by impregnation. The calcium hydroxide powder was then dried at 120℃ for 2 hours, resulting in the formation of 1 mol of hydroxyapatite with 6 mol of bound water. The sample was stirred and mixed, then ball-milled at 800 rpm for 30 minutes in a planetary ball mill. The resulting powder sample was then placed in a muffle furnace and calcined at 400℃ for 2 hours to obtain the hydroxyapatite catalyst (e.g., ...). Figure 2 As shown in the figure, the specific surface area is 46.3 m². 2 g -1 The alkali content is 7.5 μmol g. -1 .

[0058] Comparative Example 1 (not the present invention)

[0059] This comparative example used the same calcium and phosphorus sources as Example 4. 1.7255 g of calcium dihydrogen phosphate and 1.2745 g of calcium hydroxide were mixed evenly in a mortar and then calcined in a muffle furnace at 600°C for 2 hours. No hydroxyapatite was formed in the calcined sample. The results indicate that simple mixing and heating cannot form hydroxyapatite (e.g., ...). Figure 3 As shown in the figure, mechanical force can induce some chemical reactions that are difficult or impossible to carry out using thermal energy.

[0060] Comparative Example 2 (not the present invention)

[0061] This comparative example uses the same calcium and phosphorus sources as Example 4, but the amounts of calcium and phosphorus sources are changed. Specifically, 1.8633 g of calcium dihydrogen phosphate and 0.8268 g of calcium hydroxide are weighed out, n(Ca 2+ ):n(PO4 3- The ratio of anhydrous calcium dihydrogen phosphate to calcium hydroxide powder was 1.20:1. Anhydrous calcium dihydrogen phosphate and calcium hydroxide powders were dried at 120℃ for 2 hours. The samples were then ball-milled in a planetary ball mill for 30 minutes. The resulting powder samples were placed in a muffle furnace and calcined at 400℃ for 2 hours. Hydroxyapatite (e.g.) did not form. Figure 3 (As shown). The results indicate that hydroxyapatite will not form if the ratio of calcium to phosphorus sources exceeds a certain range.

[0062] Comparative Example 3 (not the present invention)

[0063] This comparative example uses the same calcium and phosphorus sources as Example 4, weighing out 1.5588 g of anhydrous calcium dihydrogen phosphate and 1.1518 g of calcium hydroxide, n(Ca 2+ ):n(PO4 3- The ratio of calcium to phosphorus sources was 1.67:1. No drying pretreatment was performed on the calcium and phosphorus sources. After mixing, the samples were ball-milled at 800 rpm for 30 min in a planetary ball mill and calcined at 400℃ for 2 h to obtain the hydroxyapatite catalyst (e.g., ...). Figure 4 As shown in the figure, the specific surface area is 97.6 m². 2 g -1 The alkali content is 30.4 μmol g. -1 The alkali content was lower than that of the hydroxyapatite sample prepared by drying pretreatment of calcium and phosphorus sources in Example 4. The results indicate that drying or calcining pretreatment of calcium and phosphorus sources can significantly increase the alkali content of hydroxyapatite.

[0064] Comparative Example 4 (not the present invention)

[0065] This comparative example uses the same calcium and phosphorus sources as Example 1, weighing out 2.3621 g of tricalcium phosphate and 0.1887 g of calcium hydroxide, n(Ca 2+ ):n(PO4 3- The ratio of calcium to phosphorus sources was 1.67:1. No drying pretreatment was performed on the calcium and phosphorus sources. After mixing, the samples were ball-milled at 800 rpm for 30 min in a planetary ball mill and calcined at 400℃ for 2 h to obtain the hydroxyapatite catalyst (e.g., ...). Figure 4 As shown), the specific surface area is 1.0 m². 2 g -1 The alkali content is 3.7 μmol g. -1 Similarly, the alkali content was lower than that of the hydroxyapatite sample prepared by drying pretreatment of calcium and phosphorus sources in Example 1.

[0066] Application Example 1

[0067] The catalysts prepared in Examples 1-11 and Comparative Examples 3-4 were used to carry out an ethanol coupling reaction in a fixed-bed reactor using ethanol as a raw material. The reaction conditions were as follows: 100 mg of catalyst was packed into a fixed-bed reactor with an inner diameter of 8 mm; the reaction was carried out at atmospheric pressure and a temperature of 325 °C; ethanol was introduced into the reactor by nitrogen bubbling, with an ethanol partial pressure of 6 kPa and a mass hourly space velocity of 1.96 h⁻¹. -1 After the reaction stabilized, the reactants and products (ethanol, butanol, and higher alcohols) were analyzed by online chromatography. The conversion rate of ethanol and the selectivity of the products were calculated using the normalization method. The results are shown in Table 1.

[0068] Table 1. Ethanol conversion and product selectivity for different catalysts

[0069]

[0070]

[0071] For some catalysts with ethanol conversion ≤2%, product selectivity is not listed in Table 1.

[0072] As shown in Table 1, at normal pressure and 325℃, the mass hourly space velocity (MHV) is 1.96 h⁻¹. -1 Under these conditions, the total selectivity of higher alcohols in the product is in the range of 80-97%.

[0073] Based on the alkali content of the hydroxyapatite catalyst, it can be noted that the ethanol conversion performance is positively correlated with the alkali content of the catalyst; the higher the alkali content, the higher the ethanol conversion rate.

[0074] Application Example 2

[0075] The catalyst prepared in Example 4 was used to investigate the effect of different mass hourly space velocities (MHSVs) on the coupling performance of ethanol. The reaction conditions were as follows: different masses of catalyst were packed in a fixed-bed reactor with an inner diameter of 8 mm; the reaction was carried out at atmospheric pressure and a temperature of 325 °C; ethanol was introduced into the reactor by nitrogen bubbling, with an ethanol partial pressure of 6 kPa and a MHSV ranging from 0.98 to 13 h⁻¹. -1 After being held at the reaction temperature for 30 min, the reactants and products (ethanol, butanol, and higher alcohols) were analyzed by online chromatography. The conversion rate of ethanol and the selectivity of the products were calculated using the normalization method. The results are shown in Table 2.

[0076] Table 2. Effects of different mass space velocities on ethanol coupling performance.

[0077]

[0078] The above description is only a few embodiments of the present invention and is not intended to limit the present invention. Any modifications, substitutions and alterations made in accordance with the claims of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for mechanochemical preparation of strong alkaline hydroxyapatite, characterized by: The strong alkaline hydroxyapatite is obtained by drying or calcining pretreatment of calcium and phosphorus sources respectively, mixing the pretreated calcium and phosphorus sources, ball milling in a ball mill, and calcining. 2+ ) : (PO4 3- ) =1.61~1.75; the calcium and phosphorus source is one or more of calcium hydrogen phosphate, anhydrous calcium dihydrogen phosphate and calcium dihydrogen phosphate monohydrate; the calcium supplement source is one or both of calcium oxide and calcium hydroxide; the amount of combined water generated along with the generation of 1 mol of hydroxyapatite is 5~15 mol.

2. A mechanochemical method of preparation of strong alkaline hydroxyapatite according to claim 1, characterized in that: The drying temperature is 50-180 ℃, and the drying time is 1-6 h; the calcination temperature is 200-800 ℃, and the calcination time is 1-6 h.

3. A mechanochemical method of preparation of strong alkaline hydroxyapatite according to claim 1, characterized in that: The ball milling time is 3-60 min, and the ball milling rotation speed is 400-800 rpm.

4. A mechanochemical method of preparation of strong alkaline hydroxyapatite according to claim 1, characterized in that: The calcination temperature of the sample after ball milling is 350-600 ℃, the calcination time is 1-5 h, and the calcination atmosphere is air, nitrogen or argon.

5. Use of the strong base hydroxyapatite of claim 1 in catalyzing the coupling of ethanol to produce higher alcohols.

6. Use of a strong alkaline hydroxyapatite according to claim 5 for catalyzing the coupling of ethanol to produce higher alcohols, characterized in that: The ethanol coupling reaction was carried out in a fixed bed reactor at atmospheric pressure, a reaction temperature of 200-350 ℃, a mass space velocity of 0.98-20 h -1 The following was carried out.

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