Preparation of nickel-indium catalyst with carbon-nitrogen modified hydroxyapatite as carrier and its application in preparation of 1,4-cyclohexanedimethanol

Abstract

The application discloses a kind of carbon-nitrogen modified hydroxyapatite as carrier preparation and its application in 1,4-cyclohexane dimethyl alcohol preparation nickel-indium catalyst. The carbon-nitrogen layer modification strategy is applied to hydroxyapatite in the present application, which greatly improves the dispersion and particle size distribution of nickel-indium alloy nanoparticles on the surface of hydroxyapatite, further improves the catalyst activity. In addition, the present application introduces indium into the nickel-based catalyst to form nickel-indium alloy. Indium will transfer electrons to nickel, further enhancing the hydrogenation deoxidation ability of nickel to ester. The catalyst of the present application realizes the efficient conversion of PET and its derivatives to CHDM under relatively mild conditions, and CHDM can be obtained with excellent yield and selectivity.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis, specifically relating to the preparation of a nickel-indium catalyst supported on carbon-nitrogen modified hydroxyapatite and its application in the preparation of 1,4-cyclohexanediethanol. Background Technology

[0002] The large amount of waste plastics that cannot degrade rapidly in nature poses a significant challenge to the global environment. Among these plastics, polyethylene terephthalate (PET) is the most widely used polyester (A. Stubbins.; KLLaw.; SE Munoz. Plastics in the Earth system. Science 373 (2021) 51-55). Its resistance to degradation leads to the accumulation of large amounts of PET waste. Therefore, PET recycling has become a focus of attention. Generally, PET recycling methods are divided into mechanical recycling and chemical recycling. Due to surface contamination, the presence of additives in the plastic production process, and repeated heating during recycling, the quality of plastics recycled by this method inevitably declines after multiple cycles. In contrast, the advantage of chemical recycling is that the recycled polymer can maintain the exact same properties as virgin PET, thus allowing it to be reused for the highest grade of applications. This is especially important when dealing with heavily polluted waste PET that is unsuitable for mechanical recycling. Currently, various chemical strategies have been developed to recycle PET waste, such as hydrolysis, methanololysis, glycolysis, and hydrogenolysis. Through these strategies, PET can be depolymerized into small molecule compounds, including terephthalic acid (TPA), dimethyl terephthalate (DMT), bis(2-hydroxyethyl) terephthalate (BHET), and p-xylene (PX), which can be directly or repolymerized into PET after oxidation.

[0003] However, considering the large number of oxygen-containing groups in the PET structure, selectively converting PET into high-value-added oxygen-containing molecules is highly desirable. Upstream recycling of waste PET into 1,4-cyclohexanediethanol (CHDM) through depolymerization and hydrogenation would be a more promising strategy. CHDM is a valuable and widely used linking monomer that can be directly used in the polymer industry to manufacture various high-quality, non-toxic resins and fibers, such as polyethylene terephthalate-1,4-cyclohexanedimethyl terephthalate (PETG) and poly(1,4-cyclohexanedimethyl terephthalate) (PCT).

[0004] Currently, there are two main recycling methods: two-step recycling and one-step recycling.

[0005] Two-step recovery: Cao et al. used a graphene oxide-supported Pd catalyst to convert PET into the intermediate PECHD, which was then hydrogenated with a CuZn catalyst to obtain CHDM (Angew. Chem. Int. Ed. 63 (2024) e202408561); Wang et al. used a Pd-modified Ni / CeO2 catalyst to convert PET into DMCD with high selectivity in a one-pot process, including PET methanolization and subsequent benzene ring hydrogenation, followed by the use of a Cu-based catalyst to obtain DMCD in 83.8% yield (Chem. Eng. J. 500 (2024) 157249); Xie et al. used a homogeneous [Ru] catalytic reaction, which allowed PET to depolymerize and directly convert into PXG at only 80 °C. Although the reaction conditions are relatively mild, the use of soluble complex catalysts, stoichiometric bases, and slow reaction rates have limited its further application (Angew. Chem. Int. Ed. 62 (2023) e202312564). Liu et al. achieved the hydrolysis of PET and the hydrogenation of the hydrolysis product CHDA in the aqueous phase. At 200 °C and 3 MPa hydrogen, PET was converted to CHDA on a Pd / C catalyst with a conversion rate of 100% and a selectivity of 84.5%. Subsequently, CHDA was hydrogenated to CHDM on a Ru-Sn / C catalyst with a yield of 88.9% (Sci. China Chem. (2025)); Patent CN115301248B reported a route to obtain 1,4-cyclohexanedicarboxylic acid from 1,4-cyclohexanedicarboxylic acid via esterification and hydrogenation; other researchers have developed a three-step tandem route to obtain value-added CHDM from PET using a base metal nickel-based catalyst and an environmentally friendly Cu-based catalyst, including first methanol hydrolysis of PET to obtain DMT, then hydrogenation of DMT on a NiLa-40wt% catalyst to form the intermediate DMCD, and then... 0.5 Further hydrogenolysis of DMCD on the catalyst yields CHDM with a total yield of 90.2%, but the need to change solvents and catalysts midway limits its large-scale application (Polym. Degrad. Stabil. 79 (2003) 529-533). CN119504354A reports a three-step method for the efficient degradation of PET waste plastics to prepare 1,4-cyclohexanedimethyl methanol. The first step involves the alcoholysis degradation of PET waste plastics to dimethyl terephthalate; the second step involves the hydrogenation of dimethyl terephthalate to prepare dimethyl 1,4-cyclohexanedimethyl methanol using a supported Ru-based catalyst; and the third step involves the preparation of 1,4-cyclohexanedimethyl methanol from dimethyl 1,4-cyclohexanedimethyl methanol using a Cu-based catalyst.

[0006] One-step recovery: A one-step conversion typically involves converting DMT, a product of PET depolymerization, into CHDM in a single pot. The first method developed by Thomas's team was Ru... 10 The Pt2 / SiO2 catalyst can convert DMT to CHDM at 100℃ and 2MPa hydrogen for 4 hours, but the conversion rate (23.3%) and selectivity (52.3%) are relatively low (Angew. Chem. Int. Ed. 40 (2001) 4638–4642). The introduction of a third component, tin, slightly improved the catalytic performance, achieving a conversion rate of 63.9% and a CHDM selectivity of 71.2% (Angew. Chem. Int. Ed. 45 (2006) 4782-4785). Recently, the Ru4Pt2Sn8 / Al2O3 catalyst has shown even better performance, achieving a conversion rate of 98.2% and a selectivity of 75.1% (Ind. Eng. Chem. Res. 53 (2013) 619–625). However, the reaction process is quite demanding: the reaction system must first be pressurized to 6 MPa hydrogen and heated to 180°C for 2 hours, then adjusted to 260°C / 8.5 MPa and maintained for 8 hours. In contrast, the physically mixed 5Pd / CMK-3 and Cu-600 catalysts can achieve complete DMT conversion at 250°C and 5 MPa hydrogen for 3 hours, with a CHDM selectivity of 82.3% (Applied Catalysis A, General 632 (2022) 118510). The physically mixed Pd / C and CuMn-3 can also achieve good yields through a one-pot two-step process (Applied Catalysis B: Environment and Energy 377 (2025) 125466). CN120571586A uses non-precious metals nickel (Ni) and copper (Cu) as active components and silica as a support to obtain CHDM from DMT in a one-pot two-step process with a yield of 93.1%; CN1806913A uses RuMnSn catalysis to hydrogenate DMT to CHDM with a conversion of 98.25% and a yield of 98.05%; CN113248346A reports a one-pot catalytic hydrogenation reaction to prepare CHDM by mixing a supported palladium-based catalyst and a copper-based catalyst prepared by co-precipitation with dimethyl terephthalate in a 1,4-dioxane solvent, achieving a DMT conversion of 100% and a CHDM yield of 91%.

[0007] In summary, the two-step conversion requires the design of two catalysts for the reduction of benzene rings and ester groups respectively, necessitates catalyst or solution replacement, and the separation and purification of the target product at each step increases recycling costs. While the one-step method can directly obtain CHDM from DMT, the involvement of precious metals is unavoidable, leading to higher costs, regardless of whether it's a single catalyst (Ru5PtSn / SiO2, Ru4Pt2Sn8 / Al2O3, etc.) or a physically mixed combination of two (Pd / C and Cu-600, Pd / C and CuMn-3). Therefore, designing a highly active catalyst composed of base metals capable of reducing benzene rings and ester groups to achieve a one-pot upgrade of PET to CHDM for recycling, thereby reducing waste plastic recycling costs, is highly significant. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a method for preparing a nickel-indium catalyst with carbon-nitrogen modified hydroxyapatite as a support and its application in the preparation of 1,4-cyclohexanediethanol.

[0009] The present invention provides a method for preparing a nickel-indium catalyst supported on carbon and nitrogen-modified hydroxyapatite, comprising the following steps:

[0010] Step 1: Mix hydroxyapatite with an aqueous solution of lysine to obtain a suspension, heat and stir, then rotary evaporate to obtain the carrier precursor;

[0011] Step 2: The obtained support precursor was calcined at 500℃ for 2 hours under a nitrogen atmosphere to obtain carbon and nitrogen modified hydroxyapatite support;

[0012] Step 3: Using the excess impregnation method, the carbon-nitrogen modified hydroxyapatite support obtained in Step 2 is impregnated in an aqueous solution of metal salt, and the catalyst precursor is obtained by rotary evaporation.

[0013] Step 4: The catalyst precursor obtained in Step 3 is placed in a tube furnace and calcined under hydrogen or a hydrogen-nitrogen mixture to obtain the catalyst, abbreviated as Ni. x In y / HAP / CN z x and y represent the mass percentages (by mass of metal elements) of the loaded Ni and In, respectively, ranging from 0 to 10. z represents the mass fraction of carbon and nitrogen modified on the hydroxyapatite, ranging from 0 to 0.33. For example, Ni5In5 / HAP / CN 0.1 This indicates that 5 wt% metallic Ni and 5 wt% metallic In were loaded onto a HAP support modified with 10% carbon and nitrogen.

[0014] In step 1, the mass ratio of lysine to hydroxyapatite is (0-0.67):2, such as 0:2, 0.2:2, 0.5:2, 0.67:2, preferably (0.2-0.5):2, and more preferably 0.2:2.

[0015] In step 3, the metal salt is nickel nitrate hexahydrate and indium nitrate hydrate. The mass ratio of nickel to indium is 0-10:10-0, for example, 0:10, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1, 10:0. For the hydrogenation of DMT to DMCD, a ratio of 10:0 is preferred; for the hydrogenation of DMCD to CHDM, a ratio of 5:5 is preferred. The total loading of indium and nickel in the catalyst precursor is 2%-10%, preferably 10%.

[0016] In step 4, a hydrogen-nitrogen mixture is preferred, wherein the volume percentage of hydrogen in the hydrogen-nitrogen mixture is 10%.

[0017] In step 4, the calcination temperature is 400℃-600℃, preferably 500℃, and the calcination time is 2 hours.

[0018] The present invention relates to the application of a nickel-indium catalyst supported on carbon-nitrogen modified hydroxyapatite in the hydrodeoxygenation of PET or its derivatives to prepare CHDM.

[0019] The PET or its derivatives include one or more of PET, DMT, and DMCD.

[0020] Specifically, the steps include the following:

[0021] PET or its derivatives, the catalyst, and the mixed solvent were added to a high-pressure autoclave reactor. The air in the reactor was replaced with hydrogen and maintained at about 1 MPa. The reactor was purged and vented 5 times, and then the temperature was increased. After the reaction was completed, the mixture was diluted with dioxane, and the CHDM yield was detected by GC.

[0022] The mixed solvent is 5 mL of a mixture of dioxane and methanol (v / v=9:1).

[0023] The catalyst includes Ni / HAP / CN. z and Ni x In y / HAP / CN z .

[0024] The reaction route is shown below:

[0025]

[0026] PET first depolymerizes into DMT under the promoting effect of Lewis acidity of the catalyst, and then in Ni / HAP / CNz Catalytic conversion of saturated benzene rings to DMCD, and finally to Ni bimetallic catalyst. x In y / HAP / CN z Catalytic hydrogenation and deoxygenation to the final product CHDM.

[0027] In the hydrogenation of dimethyl terephthalate (DMT) to dimethyl 1,4-cyclohexanedicarboxylate (DMCD), the catalyst used is Ni / HAP / CN. 0.1 The catalyst dosage ranges from 0 to 1 molar equivalent of DMT, preferably 0.2 molar equivalent. The reaction temperature is 100-180℃, preferably 100℃.

[0028] In the reaction of DMCD hydrodeoxygenation to CHDM, the catalyst used is Ni5In5 / HAP / CN. 0.1 The catalyst dosage ranges from 0 to 1 molar equivalent of DMCD, preferably 1 molar equivalent. The preferred reaction temperature is 180°C.

[0029] As can be seen from the above reaction route, the reaction from PET to CHDM requires three steps, but the present invention can be prepared directly in a one-pot method without changing equipment or adding raw materials and catalysts.

[0030] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0031] 1. This invention prepares a series of inexpensive and highly active nickel or nickel-indium catalysts supported on carbon and nitrogen-modified hydroxyapatite, which achieve efficient conversion of PET and its derivatives to CHDM under relatively mild conditions, and can obtain CHDM with excellent yield and selectivity.

[0032] 2. This invention applies a carbon-nitrogen layer modification strategy to hydroxyapatite, which greatly improves the dispersion and particle size distribution of nickel-indium alloy nanoparticles on the surface of hydroxyapatite, making the particle size very small, only about 4 nm, thereby further improving the catalyst activity.

[0033] 3. This invention applies a carbon-nitrogen layer modification strategy to hydroxyapatite, which enhances the interaction between the metal and the carrier, making the metal nanoparticles more firmly anchored on it and reducing the possibility of leaching of the metal nanoparticles during the reaction process.

[0034] 4. This invention applies a carbon-nitrogen layer modification strategy to hydroxyapatite. The carbon-nitrogen layer can donate electrons to the metal center, which further enhances the ability of metal nanoparticles to activate hydrogen and improves the reactivity.

[0035] 5. In this invention, indium is introduced into a nickel-based catalyst to form a nickel-indium alloy. Indium will transfer electrons to nickel, further enhancing the ability of nickel to hydrogenate and deoxygenate esters. Attached Figure Description

[0036] Figure 1 High-angle annular dark-field transmission electron microscopy (HAADF-STEM) images of Ni5In5 catalysts with different supports: Ni5In5 / HAP (Figure a), Ni5In5 / HAP / CN 0.1 (Figure b), Ni5In5 / HAP / CN 0.25 (Figure c), Ni5In5 / HAP / CN 0.33 (d figure), Ni5In5 / CN (e figure).

[0037] Figure 2 These are particle size distribution diagrams of Ni5In5 catalysts with different supports: Ni5In5 / HAP (Figure a), Ni5In5 / HAP / CN 0.1 (Figure b), Ni5In5 / HAP / CN 0.25 (Figure c), Ni5In5 / HAP / CN 0.33 (d) Ni5In5 / CN (e) and particle size comparison (f). From Figure 1 , Figure 2 It can be seen that with CN modification, the particle size of the metal nanoparticles on the support decreases from 9 nm in HAP to HAP / CN. 0.33 The nanoparticles are about 4nm in size, and CN modification also makes the metal nanoparticles more uniformly dispersed.

[0038] Figure 3 XRD patterns of Ni5In5 catalysts with different supports. Figure 3 As can be seen, the full width at half maximum (FWHM) of the Ni / In alloy peak at around 42° narrows with the increase of CN modification, which indicates the dispersing effect of CN modification on metal nanoparticles.

[0039] Figure 4 XRD patterns of catalysts with different metal ratios. Figure 4 As can be seen from this, excluding In / HAP / CN 0.1 Because the catalyst particles are relatively large, an In peak appears in the XRD pattern. For the other catalysts, due to the better dispersion of the metal, only the peak of the support HAP can be seen in the XRD pattern.

[0040] Figure 5 Ni5In5 / HAP / CN 0.1 Catalyst EDS-Mapping Plot. From Figure 5 As can be seen, Ni and In are distributed relatively evenly, and carbon and nitrogen have been successfully modified on the HAP support. Detailed Implementation

[0041] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0042] Example 1: Synthesis of a nickel-indium catalyst supported on carbon and nitrogen-modified hydroxyapatite

[0043] HAP / CN 0.1 Preparation of the support: 2 g of hydroxyapatite was poured into a 250 mL round-bottom flask, followed by 100 mL of water. The temperature of the magnetically stirred oil bath was set to 45 °C and the rotation speed to 500 rpm. Then, using a constant-pressure dropping funnel, an aqueous solution containing 0.2 g of lysine was slowly added dropwise to the stirred solution at a rate of one drop per second. The mixture was stirred overnight for approximately 24 h. The solution was then subjected to rotary evaporation and vacuum drying to obtain a nitrogen-carbon modified hydroxyapatite support precursor. Finally, the obtained precursor was calcined at 400 °C under a nitrogen inert atmosphere to obtain carbon-nitrogen modified hydroxyapatite.

[0044] Ni7In3 / HAP / CN 0.1 Catalyst preparation: With a total nickel-indium mass fraction of 10%, 800 mg of support was uniformly dispersed in a round-bottom flask containing 100 mL of methanol. The temperature of the magnetically stirred oil bath was set to 45 °C and 500 rpm. The calculated amounts of indium nitrate hydrate and nickel nitrate hexahydrate were dissolved in 20 mL of methanol and sonicated for 5 minutes to ensure complete dissolution. This solution was then added dropwise to the uniformly dispersed support methanol solution at a rate of one drop per second using a constant-pressure dropping funnel, allowing for thorough impregnation for 24 h. Subsequently, rotary evaporation and vacuum drying were performed to obtain the impregnated catalyst precursor. Finally, the obtained precursor was calcined at 500 °C under a 10% (v / v) hydrogen-nitrogen atmosphere for 2 h to obtain carbon-nitrogen modified hydroxyapatite as the supported nickel-indium catalyst.

[0045] Example 2-11:

[0046] The operation process is similar to that in Example 1, except that while ensuring the total nickel-indium loading is 10wt%, the nickel-indium mass ratio is changed, with the ratio range being 0:10, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 8:2, 9:1, and 10:0.

[0047] Example 12:

[0048] The operation process is similar to that in Example 1, except that hydroxyapatite is used directly as a carrier.

[0049] Examples 13-14:

[0050] The operation process is similar to that in Example 2, except that the mass of lysine is different, ranging from 0.5g to 0.67g.

[0051] Example 15:

[0052] Two g of lysine was directly placed in a tube furnace and calcined at 400°C under a nitrogen inert atmosphere to obtain a carbon-nitrogen support. The operation process was similar to that in Example 1, except that carbon and nitrogen were used directly as the support.

[0053] Example 16:

[0054] 0.1 g DMT, 0.2 eq. (based on the molar amount of DMT) of Ni / HAP catalyst and 5 mL of dioxane / methanol (v / v=9 / 1) mixed solvent were placed in a high-pressure reactor. The air in the reactor was replaced with hydrogen and maintained at about 1 MPa. The reactor was purged and vented 5 times. Then the temperature was raised to 100 °C. After the reaction was completed, the mixture was diluted with dioxane and the DMCD yield was detected by gas chromatography.

[0055] Examples 17-19:

[0056] The operation process is similar to that in Example 16, except that the catalyst is replaced with Ni / HAP / CN. 0.1 Ni / HAP / CN 0.25 Ni / HAP / CN 0.33 .

[0057]

[0058]

[0059] In the hydrogenation reaction of DMT to DMCD, a series of Ni / HAP / CN modified with different CN ratios were used. z Catalysts were found to be modified with a small amount of CN, i.e., Ni / HAP / CN. 0.1 The catalyst with the best catalytic effect is Ni / HAP / CN, and further modification will decrease the yield. Therefore, the best catalyst for this step is Ni / HAP / CN. 0.1 .

[0060] Example 20:

[0061] 20 mg DMCD and 1 eq. (based on the number of moles of DMCD) of Ni7In3 / HAP / CN were added. 0.1The catalyst and 5 mL of dioxane / methanol (v / v=9 / 1) mixed solvent were placed in a high-pressure reactor. The air in the reactor was replaced with hydrogen and maintained at about 1 MPa. The reactor was purged and vented 5 times. Then the temperature was raised to 100 °C. After the reaction was completed, the mixture was diluted with dioxane. The yield of CHDM was detected by gas chromatography.

[0062] Examples 21-24:

[0063] The operation process is similar to that in Example 20, except that the catalyst is replaced with Ni7In3 / HAP or Ni7In3HAP / CN. 0.25 Ni7In3 / HAP / CN 0.33 、Ni7In3 / CN.

[0064]

[0065]

[0066] In the reaction of DMCD to CHDM, Ni7In3 catalysts with different supports were used, and it was found that HAP / CN 0.1 The carrier showed the best catalytic effect, therefore HAP / CN was subsequently used. 0.1 The metal ratio is selected for the carrier.

[0067] Examples 25-34:

[0068] The operation process is similar to that of Example 20, except that the catalyst is replaced with Ni / HAP / CN. 0.1 Ni9In1HAP / CN 0.1 Ni8In2 / HAP / CN 0.1 Ni6In4HAP / CN 0.1 Ni5In5 / HAP / CN 0.1 Ni4In6HAP / CN 0.1 Ni3In7 / HAP / CN 0.1 Ni2In8HAP / CN 0.1 Ni1In9 / HAP / CN 0.1 In / HAP / CN 0.1 .

[0069]

[0070] In the reaction of DMCD to CHDM, Ni / In catalysts with different metal ratios were used, and Ni5In5 was found to be the most effective. Therefore, for the reaction of DMCD hydrogenation to CHDM, the optimal catalyst is Ni5In5 / HAP / CN. 0.1 .

[0071] Example 35:

[0072] 0.1 mmol DMT (19.4 mg), 0.2 eq. (based on the molar amount of DMT) of Ni / HAP catalyst (12 mg), and 1 eq. Ni5In5 / HAP / CN were added. 0.1 (86 mg) and 5 mL of dioxane / methanol (v / v=9 / 1) mixed solvent were placed in a high-pressure reactor. The air in the reactor was replaced with hydrogen and maintained at about 1 MPa. The reactor was purged and vented 5 times. Then the temperature was raised to 180 °C. After the reaction was completed, the mixture was diluted with dioxane. The yield of CHDM was detected by gas chromatography.

[0073]

[0074] Example 36:

[0075] The mixture consisted of 0.1 mmol PET (19.2 mg), 0.2 eq. (based on the number of moles of repeating structural units in PET) of Ni / HAP catalyst (12 mg), and 1 eq. of Ni5In5 / HAP / CN. 0.1 (86 mg) and 5 mL of dioxane / methanol (v / v=9 / 1) mixed solvent were placed in a high-pressure reactor. The temperature was first raised to 180 °C to depolymerize PET into DMT with methanol. After cooling, the air in the reactor was replaced with hydrogen and maintained at about 1 MPa. The gas was purged and vented 5 times. Then the temperature was raised to 180 °C. After the reaction was completed, the mixture was diluted with dioxane. The yield of CHDM was detected by gas chromatography.

[0076] .

Claims

1. A method for preparing a nickel-indium catalyst using carbon-nitrogen modified hydroxyapatite as a support, characterized in that... Includes the following steps: Step 1: Mix hydroxyapatite with an aqueous solution of lysine to obtain a suspension, heat and stir, then rotary evaporate to obtain the carrier precursor; Step 2: The obtained support precursor was calcined at 500℃ for 2 hours under a nitrogen atmosphere to obtain carbon and nitrogen modified hydroxyapatite support; Step 3: Using the excess impregnation method, the carbon-nitrogen modified hydroxyapatite support obtained in Step 2 is impregnated in an aqueous solution of metal salt, and the catalyst precursor is obtained by rotary evaporation. Step 4: The catalyst precursor obtained in Step 3 is placed in a tube furnace and calcined under hydrogen or a hydrogen-nitrogen mixture to obtain the catalyst, abbreviated as Ni. x In y / HAP / CN z .

2. The preparation method according to claim 1, characterized in that: In step 1, the mass ratio of lysine to hydroxyapatite is (0-0.67):

2.

3. The preparation method according to claim 2, characterized in that: The mass ratio of lysine to hydroxyapatite is (0.2-0.5):

2.

4. The preparation method according to claim 1, characterized in that: In step 3, the metal salt is nickel nitrate hexahydrate and indium nitrate hydrate; the mass ratio of nickel to indium is 0-10:10-0.

5. The preparation method according to claim 4, characterized in that: The total loading of nickel and indium in the catalyst precursor is 2%-10%.

6. The preparation method according to claim 1, characterized in that: In step 4, the calcination temperature is 400℃-600℃ and the calcination time is 2 hours.

7. The application of a nickel-indium catalyst supported on carbon-nitrogen modified hydroxyapatite prepared by any one of the preparation methods of claims 1-6 in the hydrodeoxygenation of PET or its derivatives to prepare CHDM, characterized in that: The PET or its derivatives include one or more of PET, DMT, and DMCD.

8. The application according to claim 7, characterized in that: PET or its derivatives, the catalyst, and the mixed solvent are added to a high-pressure autoclave reactor, the air inside the reactor is replaced with hydrogen, and then the temperature is raised to start the reaction.

9. The application according to claim 8, characterized in that: The mixed solvent is composed of dioxane and methanol.

10. The application according to claim 8, characterized in that: The catalyst includes Ni / HAP / CN. z and Ni x In y / HAP / CN z .

Images