A cerium-doped zinc-zirconium solid solution catalyst, a preparation method and application thereof

Abstract

The application provides a cerium-doped zinc-zirconium solid solution catalyst and a preparation method and application thereof. a Zn b Zr c O x , wherein 0<=a<=4, 1<=b<=4, c=4, x represents an oxygen vacancy in the catalyst; the catalyst has a first diffraction peak with 2theta of 28.46 o ~30.48 o , a second diffraction peak with 2theta of 47.50 o ~50.81 o , a third diffraction peak with 2theta of 56.27 o ~60.43 o , and a fourth diffraction peak with 2theta of 32.98 o ~35.42 o , and the intensity ratio of the first diffraction peak, the second diffraction peak, the third diffraction peak and the fourth diffraction peak is (2.2~3.1):(1.1~1.4):(0.9~1.2):1. The cerium-doped zinc-zirconium solid solution catalyst provided by the application can catalyze carbon dioxide and phenol to synthesize diphenyl carbonate, and has a high phenol conversion rate, an optimal diphenyl carbonate selectivity and a high catalyst service life.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, and more particularly to a cerium-doped zinc-zirconium solid solution catalyst, its preparation method, and its application. Background Technology

[0002] The cerium-doped zinc-zirconium solid solution catalyst provided by this invention belongs to the petrochemical field and can be used as a catalyst to catalyze the reaction of carbon dioxide and phenol to synthesize diphenyl carbonate. Diphenyl carbonate is mainly used in the production of polycarbonate, and is also widely used in solvents, plasticizers, pharmaceuticals, pesticides and other fields.

[0003] Currently, the traditional large-scale production processes for diphenyl carbonate mainly include the phosgene method, the oxidative carbonylation method, and the transesterification method. Among these synthetic routes, the phosgene method uses toxic phosgene as a raw material, posing a threat to the environment and the health of operators. This route also requires large amounts of NaOH to neutralize the generated inorganic acids, producing large quantities of waste salts and wastewater. For the oxidative carbonylation process, the synthesis requires the use of palladium as a catalyst, along with the addition of various co-catalysts (anhydrous copper acetate, tetrabutylammonium bromide, and hydroquinone, etc.), while the precious metal Pd... 2+ The reduction and aggregation of molecules lead to catalyst deactivation, making catalyst recycling difficult. Transesterification uses readily available, non-toxic raw materials, and produces only methanol as a byproduct. However, dimethyl carbonate is both a raw material and a product in transesterification, and the reaction equilibrium constant is relatively small. Limitations in chemical equilibrium and chemical activity mean that transesterification is currently still in the laboratory research stage.

[0004] To address the shortcomings of the aforementioned preparation methods, utilizing carbon dioxide as a C1 substrate to catalyze the formation of C-O bonds has been a challenging task in organic synthesis and catalysis research. The direct catalytic synthesis of diphenyl carbonate from carbon dioxide and phenol not only avoids the drawbacks of the above-mentioned production routes but also achieves comprehensive utilization of carbon dioxide resources, making it considered an ideal route for diphenyl carbonate production. The synthesis of diphenyl carbonate from carbon dioxide and phenol aligns with the current requirements of green chemistry development; therefore, developing a suitable reaction system for this catalytic reaction will undoubtedly accelerate the process of diphenyl carbonate production from the experimental development stage to industrial production.

[0005] Currently, a series of catalysts have been reported, including metal Lewis acid catalysts (such as ZnCl2, CoCl2, AlBr3) (Li ZH, Qin ZF, Zhu HQ, Wang JG, Chem. Lett., 2006, 35, 784-785; FanG Z, Wang ZG, Zou B, Wang M, Fuel Proc. Tech., 2011, 92, 1052-1055; Wang SL, Jiang N, Peng JL, Yang P, Cui CX, Niu HY, Zhang QY, Wang JJ, ACSSustain. Chem. Eng., 2022, 10, 12689-12697) and metal-hydrochloric acid complexes (Fan GZ, Wang M, Duan ZX, Wan MH, Fang T, Aust. J. Chem, 2012, 65). 1667-1673), supported catalysts (such as MCl) X / SiMCM-41, Fe3O4@SiO2−ZnBr2, Zn / SiO2−TiO2) (Su KM, Li ZH, Cheng BW, RenY L, Catal. Commun., 2008, 9, 1666-1670; Su K, Li Z, Cheng B, Ren Y, Yu L,Wang F, Kinet. Catal., 2010, 51, 359-363; Wang M, Duan ZX, Fang T, Wang MH,Fan GZ, Adv. Mat. Res., 2011, 391-392, 1235-1238; GZ Fan, SS Luo, Q Wu, TFang, JF Li, GS Song, RSC Adv., 2015, 5, 56478-56485; Wang M, Duan ZX, FangT, Wang MH, Fan GZ, (Adv. Mat. Res., 2011, 391-392, 1235-1238). Compared to catalysts such as ZnCl2, which are dissolved in the reaction system and are difficult to separate, recover, and reuse, supported catalysts have advantages such as easy product separation and simple recovery, which can simplify the process and reduce energy consumption. Current Zn-based catalysts are mainly supported, modified with K2CO3, triethylamine, etc., as promoters to improve catalytic performance. However, they suffer from low conversion, poor selectivity, low stability, and easy deactivation. Supporting Lewis metal acids on supports also presents problems such as easy loss of active components and low stability.

[0006] Therefore, developing a catalyst with both high conversion rate and high stability for the preparation of diphenyl carbonate has become a research direction in this field. Summary of the Invention

[0007] This invention provides a cerium-doped zinc-zirconium solid solution catalyst that can catalyze the synthesis of diphenyl carbonate from carbon dioxide and phenol, exhibiting high phenol conversion, superior diphenyl carbonate selectivity, and long catalyst lifetime.

[0008] This invention provides a method for preparing the above-mentioned catalyst, achieving the technical effect of simple and easy preparation process.

[0009] This invention provides a method for preparing diphenyl carbonate, achieving high conversion rate and selectivity.

[0010] This invention provides a cerium-doped zinc-zirconium solid solution catalyst, wherein the chemical formula of the catalyst is Ce. a Znb Zr c O x Where 0≤a≤4, 1≤b≤4, and c=4;

[0011] The catalyst has a 2θ of 28.46. o ~30.48 o The first diffraction peak, 2θ is 47.50. o ~50.81 o The second diffraction peak, 2θ is 56.27. o ~60.43 o The third diffraction peak, and 2θ at 32.98. o ~35.42 o The fourth diffraction peak, and the intensity ratio of the first diffraction peak, the second diffraction peak, the third diffraction peak and the fourth diffraction peak is (2.2~3.1):(1.1~1.4):(0.9~1.2):1.

[0012] The cerium-doped zinc-zirconium solid solution catalyst described above is prepared by a method comprising the following process:

[0013] The pH of an aqueous solution containing Ce, Zn, and Zr elements was adjusted to be greater than or equal to 10. The resulting mixed system was subjected to aging treatment and solid-liquid separation treatment in sequence. The resulting solid product was then calcined to obtain the catalyst.

[0014] This invention also provides a method for preparing a cerium-doped zinc-zirconium solid solution catalyst, which can be used to prepare any of the above-mentioned cerium-doped zinc-zirconium solid solution catalysts. The method includes the following steps:

[0015] The pH of an aqueous solution containing Ce, Zn, and Zr elements was adjusted to be greater than or equal to 10. The resulting mixed system was subjected to aging treatment and solid-liquid separation treatment in sequence. The resulting solid product was then calcined to obtain the catalyst.

[0016] In the preparation method of the cerium-doped zinc-zirconium solid solution catalyst described above, the molar ratio of Ce / (Zn+Zr) is 0.125~0.8; and / or,

[0017] The concentration of total metal elements in the aqueous solution is 0.150~0.225 mol / L.

[0018] In the preparation method of the cerium-doped zinc-zirconium solid solution catalyst as described above, the pH value of the aqueous solution containing Ce, Zn and Zr elements is adjusted to 10-11.

[0019] In the preparation method of the cerium-doped zinc-zirconium solid solution catalyst described above, the aging treatment temperature is 70~90℃ and the treatment time is 2~4h.

[0020] The preparation method of the cerium-doped zinc-zirconium solid solution catalyst as described above, wherein the calcination treatment temperature is 500~600℃, the treatment time is 2~4h, and the heating rate is 1~3℃ / h.

[0021] The preparation method of the cerium-doped zinc-zirconium solid solution catalyst as described above further includes drying the solid product before calcination, wherein the drying temperature is 100~120℃ and the drying time is 6~10h.

[0022] The present invention also provides a method for preparing diphenyl carbonate, wherein the method uses any of the above-mentioned cerium-doped zinc zirconium solid solution catalysts to catalyze the reaction of carbon dioxide and phenol to obtain diphenyl carbonate.

[0023] The method for preparing diphenyl carbonate as described above, wherein the reaction temperature is 90~130℃, the reaction pressure is 1~5MPa, and the reaction time is 4~8h.

[0024] The cerium-doped zinc-zirconium solid solution catalyst of the present invention improves the electronic structure of the catalyst by doping cerium into the zinc-zirconium solid solution, thereby effectively increasing the strong acid sites in the catalyst, resulting in a higher phenol conversion rate, better diphenyl carbonate selectivity, and a longer service life. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced one by one below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 X-ray diffraction patterns of catalysts A1-A7 and catalyst B1;

[0027] Figure 2 Raman plots for catalysts A1 and B1;

[0028] Figure 3 EPR diagrams for catalysts A1 and B1;

[0029] Figure 4 The Py-IR spectra of catalysts A1 and B1 are shown.

[0030] Figure 5 The NH3-TPD diagrams for catalysts A1 and B1 are shown.

[0031] Figure 6 The graph shows the phenol conversion rates of catalysts A1-A7 and catalyst B1 under different reaction pressures.

[0032] Figure 7 The selectivity of diphenyl carbonate for catalysts A1-A7 and catalyst B1 under different reaction pressures is shown in the diagram.

[0033] Figure 8 The graph shows the yield of diphenyl carbonate for catalysts A1-A7 and catalyst B1 under different reaction pressures. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0035] The cerium-doped zinc-zirconium solid solution catalyst provided by this invention can be used as a catalyst to catalyze the reaction of carbon dioxide and phenol to synthesize diphenyl carbonate.

[0036] Currently, catalysts used for the synthesis of diphenyl carbonate suffer from problems such as low conversion rate, poor selectivity, low stability, and easy deactivation. The inventors doped cerium into a zinc-zirconium solid solution to obtain the above-mentioned catalyst, which improved the electronic structure of the catalyst and effectively increased the strong acid sites in the catalyst, giving the catalyst a higher phenol conversion rate, better diphenyl carbonate selectivity, and a longer service life.

[0037] Based on this, the first aspect of the present invention provides a cerium-doped zinc-zirconium solid solution catalyst, the chemical formula of which is Ce. a Zn b Zr c O x Where 1≤a≤4, 1≤b≤4, c=4, x represents the presence of oxygen vacancies in the catalyst, 1≤x≤2, and the exact value cannot be precisely determined using existing techniques; furthermore, the catalyst has a 2θ of 28.46. o ~30.48 o The first diffraction peak, 2θ is 47.50. o ~50.81 o The second diffraction peak, 2θ is 56.27. o ~60.43 o The third diffraction peak, and 2θ at 32.98.o ~35.42 o The fourth diffraction peak, and the intensity ratio of the first diffraction peak, the second diffraction peak, the third diffraction peak, and the fourth diffraction peak is (2.2~3.1): (1.1~1.4): (0.9~1.2): 1.

[0038] The inventors have discovered that the cerium-doped zinc-zirconium solid solution catalyst provided by this invention exhibits high conversion rate and selectivity while being less prone to deactivation. Based on the above phenomena, the inventors speculate that the reasons may be as follows: First, cerium doping improves the electronic structure of the catalyst, increasing the oxygen vacancy concentration while effectively enhancing the number of strong acid sites in the catalyst; second, the XRD characteristics indicate the presence of uniformly dispersed Zn / Ce-Ov-Zr sites in the catalyst. These sites can promote the synergistic effect between Zn, Ce, and Zr, which is beneficial to CO2 conversion and diphenyl carbonate selectivity. Therefore, the cerium-doped zinc-zirconium solid solution catalyst provided by this invention exhibits high conversion rate and selectivity while being less prone to deactivation.

[0039] This invention improves the electronic structure of the catalyst by doping cerium into the zinc-zirconium solid solution, thereby effectively increasing the strong acid sites in the catalyst and giving it higher phenol conversion, better diphenyl carbonate selectivity, and longer service life.

[0040] In detail, the catalyst provided by the first aspect of the present invention can also be prepared by a method including the following process: adjusting the pH value of an aqueous solution including Ce, Zn and Zr elements to greater than or equal to 10, subjecting the resulting mixed system to aging treatment and solid-liquid separation treatment in sequence, and calcining the obtained solid product to obtain the catalyst provided by the first aspect of the present invention.

[0041] The aqueous solution containing Ce, Zn, and Zr elements refers to a solution that uses water as a solvent and simultaneously contains cerium, zinc, and zirconium elements. It is understood that to achieve a high concentration of these three elements in the aqueous solution, soluble salts of these three elements can be dissolved in water to obtain an aqueous solution containing cerium, zinc, and zirconium metal sources. This invention does not limit the specific selection of the soluble salts of these three elements. Specifically, nitrates, sulfates, or halides of cerium, zinc, and zirconium can be used as cerium, zinc, and zirconium metal sources, respectively. In a preferred embodiment, nitrates and sulfates of cerium, zinc, and zirconium are used as cerium, zinc, and zirconium metal sources, respectively.

[0042] When the pH of an aqueous solution containing cerium, zinc, and zirconium metal sources is adjusted to a value greater than or equal to 10, the cerium, zinc, and zirconium elements in the aqueous solution are converted into hydroxide precipitates and separated from the liquid phase system.

[0043] This invention does not limit the method of adjusting the pH of the aqueous solution to a value greater than or equal to 10; conventional methods in the art can be used. Specifically, this can be achieved by adding an alkaline substance to the aqueous solution. This invention does not limit the specific selection of the alkaline substance; at least one of alkali metal hydroxides, alkali metal carbonates, and ammonia can be used. In a preferred embodiment, the alkaline substance is ammonia. Adjusting the pH of the aqueous solution using ammonia achieves complete precipitation of the hydroxide by controlling the hydrolysis rate of the precipitant. If sodium hydroxide or sodium carbonate is used for pH adjustment, incomplete precipitation or agglomeration may occur, affecting the preparation of the cerium-doped zinc-zirconium solid solution catalyst.

[0044] After cerium, zinc, and zirconium elements in aqueous solution are converted into hydroxide precipitates, the mixed system, including the solid-phase hydroxide precipitate and the liquid-phase solution, can be subjected to aging treatment. The aging treatment involves continuous stirring of the mixed system, ending when stirring ceases. This treatment improves the specific surface area and pore size of the catalyst by altering the phase composition of the catalyst precursor, thereby enhancing catalytic performance.

[0045] The mixed system obtained after aging treatment is subjected to solid-liquid separation to obtain an aged solid substance. This solid substance is then calcined to obtain the catalyst provided by this invention. During calcination, phase transitions and redox reactions occur, forming a catalyst with the aforementioned characteristics. This invention does not limit the specific processing conditions of the calcination reaction; any treatment that yields the catalyst provided in the first aspect of this invention is acceptable.

[0046] The second aspect of the present invention provides a method for preparing a cerium-doped zinc-zirconium solid solution catalyst, the method comprising the following steps: adjusting the pH value of an aqueous solution containing Ce, Zn and Zr elements to greater than or equal to 10, subjecting the resulting mixed system to aging treatment and solid-liquid separation treatment in sequence, and calcining the obtained solid product to obtain the catalyst.

[0047] The meanings of aqueous solutions, aging treatment, solid-liquid separation treatment and calcination treatment, including Ce, Zn and Zr elements, are the same as those mentioned above and will not be repeated here.

[0048] The method for preparing cerium-doped zinc-zirconium solid solution catalyst provided by this invention uses simple and readily available reagents to obtain a catalyst with high conversion rate and selectivity that is not easily deactivated. It has the advantages of simple process flow, mild conditions, and low cost, and is suitable for mass production.

[0049] To further improve the selectivity of the catalyst for diphenyl carbonate, the molar ratio of Ce / (Zn+Zr) in the aqueous solution containing Ce, Zn, and Zr can be set to 0.125–0.8, that is, the ratio of Ce concentration to the sum of Zn and Zr concentrations is 0.125–0.8. Suitable element concentration ratios can yield catalysts with appropriate molar ratios, which further enhance the electronic structure and moderately strong acid sites, thereby increasing the phenol conversion, diphenyl carbonate selectivity, and lifetime of the catalyst. In a preferred embodiment, the molar ratio of Ce / (Zn+Zr) can be controlled to 0.2–0.4.

[0050] To achieve uniform dispersion of Ce and Zn elements in ZrO2, the total metal element concentration in the aqueous solution containing Ce, Zn, and Zr can be set at 0.150–0.225 mol / L. If the total metal element concentration is below this range, the number of active sites in the prepared catalyst will decrease; if the concentration is above this range, phase separation will easily occur in the aqueous solution. Controlling the total metal concentration within the above range achieves the technical advantage of a uniformly dispersed Zn / Ce-Ov-Zr structure.

[0051] To further increase the phenol conversion rate, diphenyl carbonate selectivity, and service life of the prepared catalyst, the pH of the aqueous solution containing cerium, zinc, and zirconium can be adjusted to 10-11 during the catalyst preparation process. Controlling the pH within this range ensures complete formation of hydroxide precipitates of the three metal elements, improving the yield of the preparation method. It also reduces the degree of redissolution of zinc hydroxide due to the formation of zincates at excessively high pH, ​​allowing more zinc to enter the solid phase as hydroxide. This results in a catalyst with a suitable metal element ratio, leading to better application performance.

[0052] Further research by the inventors revealed that when the aging treatment temperature was controlled at 70–90°C and the treatment time at 2–4 hours, the resulting catalyst exhibited better phenol conversion, diphenyl carbonate selectivity, and service life. Based on these findings, the inventors speculate that the reason for this improvement may be that suitable treatment temperature and time can achieve performance optimization and stability enhancement through thermodynamic and kinetic principles.

[0053] Further research by the inventors revealed that when the calcination temperature was controlled at 500–600°C, the treatment time at 2–4 h, and the heating rate at 1–3°C / h, the resulting catalyst exhibited better phenol conversion, diphenyl carbonate selectivity, and lifespan. Based on these observations, the inventors speculate that the optimal treatment temperature, time, and rate can be achieved through phase transformation and redox mechanisms. In a preferred embodiment, the calcination temperature was 550°C, the treatment time was 3 h, and the heating rate was 2°C / h.

[0054] To achieve the effect of removing moisture, the inventors discovered that before calcining the solid product, a drying treatment is also included. The drying treatment temperature is 100~120℃ and the treatment time is 6~10h.

[0055] A third aspect of this invention provides a method for preparing diphenyl carbonate, wherein the method uses a cerium-doped zinc-zirconium solid solution catalyst provided in the first aspect of this invention to catalyze the reaction of carbon dioxide and phenol to obtain diphenyl carbonate. Because the catalyst provided in the first aspect of this invention has a high phenol conversion rate, superior diphenyl carbonate selectivity, and a long service life, the method for preparing diphenyl carbonate provided in the third aspect of this invention has the characteristics of high phenol conversion rate and superior diphenyl carbonate selectivity.

[0056] Further research by the inventors revealed that when using the cerium-doped zinc-zirconium solid solution catalyst provided in the first aspect of this invention to catalyze the reaction of carbon dioxide and phenol, controlling the reaction temperature to be 90~130℃, the reaction pressure to be 1~5MPa, and the reaction time to be 4~8h can yield a higher yield of diphenyl carbonate.

[0057] The present invention will be further described below through specific embodiments.

[0058] Examples 1-7 illustrate the preparation of cerium-doped zinc-zirconium solid solution catalysts with different cerium contents:

[0059] Example 1

[0060] Weigh 5 mmol of cerium nitrate hexahydrate, 5 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.15 mol / L. After stirring in an 80°C water bath for 0.5 h, slowly add 25 wt% ammonia solution to the precursor solution, adjusting the pH of the aqueous solution to 11. After the addition is complete, age the solution in an 80°C water bath for 2 h. The resulting product has the molecular formula CeZnZr4O. x The catalyst A1 has a Ce / (Zn+Zr) molar ratio of 1:5.

[0061] Example 2

[0062] Weigh 10 mmol of cerium nitrate hexahydrate, 5 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.175 mol / L. Other preparation steps are the same as in Example 1, yielding a solution with the molecular formula Ce₂ZnZr₄O. x The catalyst A2 has a Ce / (Zn+Zr) molar ratio of 2:5.

[0063] Example 3

[0064] Weigh 15 mmol of cerium nitrate hexahydrate, 5 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.20 mol / L. Other preparation steps are the same as in Example 1. The molecular formula is Ce3ZnZr4O. x The catalyst A3 has a Ce / (Zn+Zr) molar ratio of 3:5.

[0065] Example 4

[0066] Weigh 20 mmol of cerium nitrate hexahydrate, 5 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.225 mol / L. Other preparation steps are the same as in Example 1, yielding a solution with the molecular formula Ce₄ZnZr₄O. x The catalyst A4 has a Ce / (Zn+Zr) molar ratio of 4:5.

[0067] Example 5

[0068] Weigh 5 mmol of cerium nitrate hexahydrate, 10 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.175 mol / L. Other preparation steps are the same as in Example 1, yielding a solution with the molecular formula CeZn2Zr4O. x The catalyst A5 has a Ce / (Zn+Zr) molar ratio of 1:6.

[0069] Example 6

[0070] Weigh 5 mmol of cerium nitrate hexahydrate, 15 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.20 mol / L. Other preparation steps are the same as in Example 1, yielding a solution with the molecular formula CeZn3Zr4O. xThe catalyst A6 has a Ce / (Zn+Zr) molar ratio of 1:7.

[0071] Example 7

[0072] Weigh 5 mmol of cerium nitrate hexahydrate, 20 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.225 mol / L. Other preparation steps are the same as in Example 1, yielding a solution with the molecular formula CeZn4Zr4O. x The catalyst A7 has a Ce / (Zn+Zr) molar ratio of 1:8.

[0073] Comparative Example 1

[0074] Weigh 5 mmol of zinc nitrate hexahydrate and 25 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.15 mol / L. Other preparation steps are the same as in Example 1, yielding a solution with the molecular formula ZnZr5O. x Catalyst B1, wherein the molar ratio of Zn / Zr is 1:5.

[0075] Test case

[0076] Catalyst evaluation

[0077] The catalyst samples obtained in Examples 1-7 and the comparative examples were characterized using X-ray diffraction. The results are shown in the figure. Figure 1 Typically, catalyst A1 obtained in Example 1 is used as an example for comparison with a comparative catalyst, such as... Figure 1 XRD results show that catalysts B1 and A1-A7 prepared in this invention exhibit characteristic diffraction peaks of tetragonal ZrO2, while catalysts A1-A3 and A5-A6 form solid solution structures. In the case of excessive doping, A4 and A7 show characteristic diffraction peaks of CeO2 and ZnO. Compared with the standard XRD card (JCPDS 88-1007) for t-ZrO2, the characteristic peaks of catalyst B1 shift to higher angles. This is because the atomic radius of Zn is smaller than that of Zr. When Zn atoms partially replace Zr atoms in t-ZrO2, lattice contraction occurs, resulting in a shift of the characteristic peaks to higher angles in the XRD spectrum. Conversely, when Ce, which has a larger atomic radius than Zr, is doped, the XRD spectra of catalysts A1-A4 shift to lower angles compared to catalyst B1. This characterization result demonstrates that this invention successfully prepared a cerium-doped zinc-zirconium solid solution catalyst.

[0078] Raman spectroscopy was performed on catalysts A1 and B1, with values ​​of 149, 269, 312, 465, and 643 cm⁻¹. -1The Raman spectral band at this location belongs to the tetragonal phase of ZrO2, as shown in the Raman analysis results. Figure 2 As shown. After adding Zn to catalyst B1, at ~312 cm⁻¹ -1 The band shifts towards higher wavenumbers, and the Zr-O bond length in catalyst B1 shortens. However, when Ce with a larger atomic radius is doped, the Zr-O bond length in the resulting catalyst A1 increases, further indicating that catalysts A1 and B1 exist as solid solutions. In the Raman plot, oxygen vacancies are observed in the 550–620 cm⁻¹ region. -1 The broadband region, compared to catalyst B1, shows that cerium doping further increases the number of oxygen vacancies in the solid solution, which contribute to the activation of reactants during the reaction.

[0079] To further analyze the relative concentration of oxygen vacancies, EPR measurements were performed on catalysts A1 and B1. Unpaired electrons were captured in the EPR measurements, and the results are as follows: Figure 3 As shown, the signal intensity near g=2.003 is positively correlated with the oxygen vacancy content. The order of oxygen vacancy concentration changes is ZnCeZrO. X >ZnZrO X This is consistent with the Raman results and further proves that the introduction of Ce increases the number of oxygen vacancies in the solid solution.

[0080] To investigate the effect of catalyst acidity on the DPC reaction performance, Py-IR tests were performed on catalysts A1 and B1. The results are shown in [Figure 1]. Figure 4 Py-IR can be used to identify the acidity type of a catalyst. 1446 cm⁻¹ -1 1540cm -1 and 1491cm -1 The peaks at these locations are attributed to Lewis-coordinated pyridine (L), Brønsted-coordinated pyridine (B), and Lewis+Brønsted-coordinated pyridine (L+B), respectively. Figure 4 It can be seen that ZnCeZrO X The Lewis acid sites of (A1) are greater than those of ZnZrO. X (B1) is much stronger. This indicates that in the preparation of ZnCeZrO X At the same time, the addition of Ce not only increases the concentration of oxygen vacancies in the material, but also promotes electron rearrangement and interaction, thereby improving the material's electron accepting ability and Lewis acidity.

[0081] To further analyze the effect of Lewis acid strength on DPC selectivity, NH3-TPD studies were conducted on catalysts A1 and B1. The results are shown below. Figure 5 .Depend on Figure 5It can be seen that catalyst B1 is dominated by weak acid sites, while catalyst A1 contains both weak acid sites and medium-strong acid sites. The medium-strong acid sites are conducive to the synthesis of the target product. This indicates that cerium doping effectively increases the acid sites of the catalyst while improving the electronic structure of the catalyst, thereby improving the yield and selectivity of the target product.

[0082] Experimental Example 1

[0083] The catalytic performance of catalysts A1-A7 and catalyst B1 (as a comparative example) prepared in Examples 1-7 for the synthesis of diphenyl carbonate from carbon dioxide and phenol was tested. The specific operation was as follows: A 100 mL high-pressure micro reactor was used. Catalysts A1-A7 were added to the reactor as catalysts. 20 mmol of phenol, 0.2 g of catalysts A1-A7 and 10 mL of CCl4 were added to the reactor. After sealing, carbon dioxide was introduced into the reactor to replace the air inside. The reactor was heated to 120 °C. After that, carbon dioxide was introduced into the reactor to increase the pressure inside the reactor to the reaction pressure. The gas inlet valve was then closed. The reaction was continued to be stirred for 6 h and then stopped. The reaction was then cooled to room temperature. The catalyst was separated by centrifugation. The reaction solution was qualitatively and quantitatively analyzed by gas chromatography using the internal standard method.

[0084] Quantitative analysis of the product was performed using the internal standard method. Biphenyl was used as the internal standard. A series of diphenyl carbonate standard solutions of varying concentrations were accurately prepared, and the internal standard was added quantitatively. Quantitative analysis was performed by comparing the ratio of the response values ​​(peak area or peak height) of the standard solution and the internal standard during the response period, along with the amount of internal standard added. The conversion rate of phenol was calculated using equation a, and the selectivity and yield of the target product, diphenyl carbonate, were calculated using equations b and c, respectively. The calculation formulas are as follows:

[0085] a. Conversion rate (C)

[0086] C (%) = n (phenol conversion) / n (initial phenol) × 100

[0087] b. Selectivity (S)

[0088] S (%) = 2n(diphenyl carbonate) / n(phenol conversion) × 100

[0089] c. Yield (Y)

[0090] Y (%) = C (%) × S (%)

[0091] Where n is the amount of substance.

[0092] Table 1 - Catalytic performance evaluation results of Examples 1-7 and comparative examples

[0093]

[0094] The following conclusions can be drawn from Table 1:

[0095] 1) The catalytic performance of catalysts A1-A7 with different cerium contents under different pressures was compared. The test results are shown in […]. Figures 6 to 8 .Depend on Figures 6 to 8 It was found that, compared with catalyst B1 (which does not contain Ce), the catalytic performance of catalysts A1-A7 in the synthesis of diphenyl carbonate from phenol and carbon dioxide was significantly improved when cerium-doped zinc-zirconium solid solution was used, exhibiting good phenol conversion and high selectivity and yield for the target product diphenyl carbonate. Catalyst A1 showed good activity for diphenyl carbonate under a pressure of 4 MPa. However, the selectivity for diphenyl carbonate decreased with further increasing the Ce doping content.

[0096] 2) According to the comparison of catalysts A1-A4 in Table 1, the selectivity and yield of the target product diphenyl carbonate show a gradual decreasing trend with increasing cerium content. According to the comparison of catalysts A1, A5-A7, the selectivity and yield of the target product diphenyl carbonate show a gradual decreasing trend with increasing zinc content, indicating that catalyst A1 has the best catalytic performance.

[0097] Examples 8-10 illustrate the preparation of cerium-doped zinc-zirconium solid solution catalysts with different metal precursors:

[0098] Example 8

[0099] Weigh 5 mmol of cerium nitrate hexahydrate, 5 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium chloride, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.15 mol / L. Other preparation steps are the same as in Example 1, yielding a solution with the molecular formula CeZnZr4O. x The catalyst A8 has a Ce / (Zn+Zr) molar ratio of 1:5.

[0100] Example 9

[0101] Weigh 5 mmol of cerium nitrate hexahydrate, 5 mmol of zinc sulfate heptahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.15 mol / L. Other preparation steps are the same as in Example 1, yielding a solution with the molecular formula CeZnZr4O. x The catalyst A9 has a Ce / (Zn+Zr) molar ratio of 1:5.

[0102] Example 10

[0103] Weigh 5 mmol of cerium chloride, 5 mmol of zinc sulfate heptahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.15 mol / L. Other preparation steps are the same as in Example 1, yielding a solution with the molecular formula CeZnZr4O. x The catalyst A10 has a Ce / (Zn+Zr) molar ratio of 1:5.

[0104] Experimental Example 2

[0105] The catalysts A8-A10 obtained in Examples 8-10 were used to synthesize diphenyl carbonate from carbon dioxide and phenol. The catalyst evaluation procedure was the same as that in Experimental Example 1.

[0106] Table 2 - Evaluation results of catalytic performance of different metal salt precursors

[0107]

[0108] Table 2 shows that catalysts prepared from different metal salt precursors exhibit significantly different catalytic activities for the synthesis of diphenyl carbonate from carbon dioxide and phenol. Among the remaining catalysts A1, A8-A10 in Table 2, the catalysts prepared using cerium nitrate hexahydrate, zinc cerium nitrate hexahydrate, and zirconium oxynitrate hydrate as precursors show the highest activity for the synthesis of diphenyl carbonate from carbon dioxide and phenol. This is because catalyst A1 uses a metal precursor that does not contain Cl... - The compound, therefore, has no Cl on the catalyst. - The presence of residues and the high surface cleanliness of the catalyst during its use are another reason for its high activity.

[0109] Examples 11-14 illustrate the preparation of cerium-doped zinc-zirconium solid solution catalysts at different aging temperatures and times:

[0110] Example 11

[0111] Weigh 5 mmol of cerium nitrate hexahydrate, 5 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.15 mol / L. After stirring in a 70°C water bath for 0.5 h, slowly add 25 wt% ammonia solution to the precursor solution and adjust the pH of the aqueous solution to 11. After the addition is complete, maintain the solution at 70°C in a water bath for 2 h of aging. Other preparation steps are the same as in Example 1, yielding a product with the molecular formula CeZnZr4O. x The catalyst A11 has a Ce / (Zn+Zr) molar ratio of 1:5.

[0112] Example 12

[0113] Weigh 5 mmol of cerium nitrate hexahydrate, 5 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.15 mol / L. After stirring in an 80°C water bath for 0.5 h, slowly add 25 wt% ammonia solution to the precursor solution and adjust the pH of the aqueous solution to 11. After the addition is complete, age the solution in a 90°C water bath for 2 h. Other preparation steps are the same as in Example 1, yielding a product with the molecular formula CeZnZr4O. x The catalyst A12 has a Ce / (Zn+Zr) molar ratio of 1:5.

[0114] Example 13

[0115] This embodiment provides a CeZnZrO X The preparation method of -13 includes the following steps:

[0116] Weigh 5 mmol of cerium nitrate hexahydrate, 5 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.15 mol / L. After stirring in an 80°C water bath for 0.5 h, slowly add 25 wt% ammonia solution to the precursor solution and adjust the pH of the aqueous solution to 11. After the addition is complete, maintain the solution in an 80°C water bath for 3 h of aging. Other preparation steps are the same as in Example 1, yielding a product with the molecular formula CeZnZr4O. x The catalyst A13 has a Ce / (Zn+Zr) molar ratio of 1:5.

[0117] Example 14

[0118] This embodiment provides a method for preparing CeZnZrO2-14, including the following steps:

[0119] Weigh 5 mmol of cerium nitrate hexahydrate, 5 mmol of zinc nitrate hexahydrate, and 20 mmol of zirconium oxynitrate hydrate, dissolve them in 200 mL of deionized water, and stir until homogeneous to form a mixed solution with a metal ion concentration of 0.15 mol / L. After stirring in an 80°C water bath for 0.5 h, slowly add 25 wt% ammonia solution to the precursor solution and adjust the pH of the aqueous solution to 11. After the addition is complete, age the solution in an 80°C water bath for 4 h. Other preparation steps are the same as in Example 1, yielding a product with the molecular formula CeZnZr4O. x The catalyst A14 has a Ce / (Zn+Zr) molar ratio of 1:5.

[0120] Example 15

[0121] This embodiment is basically the same as Example 1, except that the aging time is 1 hour. The resulting product has the molecular formula CeZnZr4O. x Catalyst A15.

[0122] Example 16

[0123] This embodiment is basically the same as Example 1, except that the aging temperature is 50℃. The resulting product has the molecular formula CeZnZr4O. x Catalyst A16.

[0124] Experimental Example 3

[0125] The catalysts obtained in Examples 11-14 were used to synthesize diphenyl carbonate from carbon dioxide and phenol, and the catalyst evaluation steps were the same as in Example 1.

[0126] Table 3 - Effects of different aging temperatures and times on catalytic performance

[0127]

[0128] Table 3 shows that the selectivity and yield of diphenyl carbonate initially increase and then decrease with aging temperature, with the catalyst prepared at aging temperature of 80℃ exhibiting better catalytic activity. The effect of aging time on catalytic activity was investigated in catalysts A1, A13, and A14, with the catalyst prepared at an aging time of 2 h showing better activity.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cerium-doped zinc-zirconium solid solution catalyst, characterized in that, The chemical formula of the catalyst is Ce. a Zn b Zr c O x Where 1≤a≤3, 1≤b≤3, and c=4; The catalyst has a 2θ of 28.

46. o ~30.48 o The first diffraction peak, 2θ is 47.

50. o ~50.81 o The second diffraction peak, 2θ is 56.

27. o ~60.43 o The third diffraction peak, and 2θ at 32.

98. o ~35.42 o The fourth diffraction peak, and the intensity ratio of the first diffraction peak, the second diffraction peak, the third diffraction peak and the fourth diffraction peak is (2.2~3.1):(1.1~1.4):(0.9~1.2):

1.

2. The catalyst according to claim 1, characterized in that, The catalyst is prepared by a method comprising the following process: The pH of an aqueous solution containing Ce, Zn, and Zr elements was adjusted to be greater than or equal to 10. The resulting mixed system was subjected to aging treatment and solid-liquid separation treatment in sequence. The resulting solid product was then calcined to obtain the catalyst.

3. A method for preparing the cerium-doped zinc-zirconium solid solution catalyst according to claim 1 or 2, characterized in that, Includes the following steps: The pH of an aqueous solution containing Ce, Zn, and Zr elements was adjusted to be greater than or equal to 10. The resulting mixed system was subjected to aging treatment and solid-liquid separation treatment in sequence. The resulting solid product was then calcined to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that, The molar ratio of Ce / (Zn+Zr) is 0.125~0.8; and / or, The concentration of total metal elements in the aqueous solution is 0.150~0.225 mol / L.

5. The preparation method according to claim 3 or 4, characterized in that, The pH of the aqueous solution containing Ce, Zn, and Zr elements is adjusted to 10-11.

6. The preparation method according to any one of claims 3-5, characterized in that, The aging treatment is carried out at a temperature of 70~90℃ for 2~4 hours.

7. The preparation method according to any one of claims 3-6, characterized in that, The calcination treatment is carried out at a temperature of 500~600℃, for a duration of 2~4h, and at a heating rate of 1~3℃ / h.

8. The preparation method according to any one of claims 3-7, characterized in that, Before calcining the solid product, the solid product is further subjected to a drying treatment at a temperature of 100-120°C for 6-10 hours.

9. A method for preparing diphenyl carbonate, characterized in that, The catalyst described in claim 1 or 2 is used to catalyze the reaction of carbon dioxide and phenol to obtain diphenyl carbonate.

10. The method for preparing diphenyl carbonate according to claim 9, characterized in that, The reaction temperature is 90~130℃, the reaction pressure is 1~5MPa, and the reaction time is 4~8h.

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