Preparation method and application of a metal oxide multi-core-silicoaluminate shell bifunctional catalyst

Abstract

The present invention belongs to the fields of environmental protection and catalysts, and discloses a bifunctional core-shell catalyst with a silicon-aluminum oxide-coated metal oxide multi-core and a preparation method and application thereof. The catalyst is prepared by assembling silicon-aluminum oxide nanoparticles on the surface of a carbon material containing rare earth metals and transition metals and then subjecting it to secondary growth and series of high-temperature calcination. The unique multi-core-silicon-aluminum shell structure of the catalyst is less prone to side reactions such as oxidative cracking and thermal cracking compared with traditional cracking-oxidation bifunctional catalysts, and is applicable to the oxygen-containing cracking purification of organic wastewater such as chemical waste liquid, tank washing water, landfill leachate, and kitchen waste wastewater.

Description

Technical Field

[0001] The present invention belongs to the fields of environmental protection and catalysts, and relates to a metal oxide multi-core-silicoaluminum shell bifunctional catalyst, in particular to a bifunctional catalyst suitable for the purification of wastewater by oxidative cracking in the presence of oxygen. The present invention also relates to the preparation method and application of the catalyst. Background Art

[0002] Most of the organic pollutants contained in industrial organic wastewater and domestic sewage are teratogenic, mutagenic, and carcinogenic substances. Some even undergo chemical reactions in the environment to transform into secondary pollutants with greater harm and stronger toxicity, causing great harm to the atmosphere, water bodies, ecosystems, and human life.

[0003] Patent CN111675358A proposes a method for treating chemical industrial organic wastewater by oxidative cracking reaction. Through the coupling of cracking and oxidation, macromolecular organic pollutants are converted into small molecules such as carbon dioxide and water that are harmless to the environment, realizing the low-temperature, high-efficiency, and short-process harmless treatment of chemical industrial organic wastewater. Regarding the oxidative cracking purification process of organic matter, patents CN107010709A and CN107099051A both propose a zeolite molecular sieve catalyst modified by different rare earth metal ions, patent CN111847483A proposes a copper oxide supported on Y-type molecular sieve catalyst, and CN115254108A discloses an amorphous silica-aluminum encapsulated metal oxide catalyst. However, in the above catalyst structures, the acidic sites from silica-aluminum oxides and the oxidation active sites from metal oxides are both distributed in the same space of the catalyst structure, causing the oxidation active sites to directly contact the organic pollutants, resulting in side reactions such as oxidative cracking and thermal cracking directly occurring on the catalyst surface, making it impossible for the organic pollutants to be completely converted into inorganic substances harmless to the environment such as CO2 and water.

[0004] If the catalyst is designed as a core-shell structure, the spatial positions of the acidic sites and the oxidation active sites in the catalyst can be separated, that is, the acidic sites are in the outer shell and the oxidation active sites are in the inner core. Theoretically, the above side reactions can be avoided, and the precise regulation of the cracking and oxidation reactions in the oxy-cracking reaction process can be realized. The literature [Nature Materials, 2022, 21(5): 572] introduced a mononuclear-shell catalyst with acidic zeolite as the shell and metal oxide as the core. However, the size of the metal oxide inner core is greater than 100 nanometers, resulting in fewer oxidation active sites per unit volume and reducing the oxidation reaction efficiency in oxy-cracking. The particle size of the active particles of common catalytic oxidation catalysts needs to be in the range of 0.1 to 50 nanometers. The literature [Carbon, 2006-03-01] introduced a multi-metal oxide core-shell catalyst formed by impregnating an amorphous carbon carrier formed by high-temperature carbonization of phenolic resin into a metal salt solution. Using carbon as the carrier during the preparation of this catalyst is beneficial to the formation of the internal structure of multi-core metal oxides. However, this catalyst has no acidic sites and cannot be used for oxy-cracking reactions. Moreover, the carbonaceous shell layer on the surface of the catalyst is extremely easy to decompose in an oxygen-rich high-temperature environment. Patent CN110252389B proposed a multi-core-shell catalyst with mesoporous acidic zeolite as the shell and elemental cobalt as the core. The size of the elemental cobalt inner core is less than 9 nanometers and the number is more than 2. Although the mesoporous acidic zeolite shell layer can achieve the cracking reaction of macromolecules in the oxy-cracking reaction, its mesoporous size is relatively large, and organic pollutants are likely to enter the pores and directly undergo a series of side reactions such as oxidative dehydrogenation and β-decomposition with elemental cobalt. To sum up, the current dual-functional catalysts with metal oxides as the core and silicon-aluminum oxides as the shell generally have defects such as large particle size of metal oxides leading to low catalytic reaction efficiency and large pore size of the shell layer leading to complex side reactions, which are not conducive to the progress of the oxy-cracking reaction. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-core metal oxide-silicon-aluminum shell dual-functional catalyst with high utilization rate of active sites, sufficient reaction, high catalytic reaction efficiency, etc., aiming at the defects of existing core-shell catalysts such as limited utilization rate of active sites and low catalytic reaction efficiency, as well as its preparation method and application.

[0006] The purpose of the present invention is to develop a multi-core metal oxide-silicon-aluminum shell dual-functional catalyst with high utilization rate of active sites and high catalytic reaction efficiency.

[0007] A preparation method of a multi-core metal oxide-silicon-aluminum shell dual-functional catalyst, the steps of which are as follows:

[0008] Step 1: Add a carbon carrier containing a metal element to a suspension of silicon-aluminum oxide nanoparticles and stir. The bridging oxygen in the silicon-aluminum oxide structure is deposited on the carbon carrier containing the metal element through metal ion coordination to form a complex;

[0009] Step 2: Immerse the above-mentioned composite in the secondary growth solution of acidic silicon-aluminum oxide for secondary growth;

[0010] Step 3: After secondary growth, a metal oxide multi-core - silicon-aluminum shell bifunctional catalyst can be obtained by high-temperature calcination.

[0011] In the above preparation method: the carbon support containing metal elements in Step 1 is a polyhedral carbon support formed by high-temperature carbonization of a metal complex, and the metal complex is one of the complexes containing Cu, Ce, Mn, Cr, Fe, Co, La, and Y;

[0012] Further preferably: the metal complex is selected from at least one of MOP-18, Cu-ITQ, HKUST-1, Ce-MOL, UIO-66-Ce, MOF-808-Ce, MOF-74-Mn, MIL-101-Cr, MIL-101-Fe, MIL-53-Fe, MOF-74-Co, copper acetate, manganese acetate, iron acetate, lanthanum acetate, and yttrium acetate.

[0013] In the above preparation method: the acidic silicon-aluminum oxide nanoparticles in Step 1 are one of ZSM-5 type nanocrystals, Y type nanocrystals, MOR type nanocrystals, Beta type nanocrystals, A type nanocrystals, and amorphous silicon-aluminum nanoparticles;

[0014] The mass ratio of the carbon support to the silicon-aluminum oxide nanoparticles is 1 - 30:1; preferably: the mass ratio of the carbon support to the silicon-aluminum oxide nanoparticles is 2 - 20:1; further preferably: the mass ratio of the carbon support to the silicon-aluminum oxide nanoparticles is 2 - 10:1.

[0015] In the above preparation method: the secondary growth solution in Step 2 is composed of a silicon source, an aluminum source, and a sodium source; the silicon source is one of sodium silicate, tetraethyl orthosilicate, silicic acid, and water glass; the aluminum source is one of aluminum isopropoxide, sodium metaaluminate, and sodium aluminate; the sodium source is one of sodium hydroxide, sodium metaaluminate, and sodium silicate; the mass ratio of the silicon source to the aluminum source is 1 - 8:1, and the mass ratio of the sodium source to the silicon source is 0.01 - 2:1;

[0016] Preferably: the mass ratio of the silicon source to the aluminum source is 3.24 - 4.82:1, and the mass ratio of the sodium source to the silicon source is 0.061 - 0.28:1.

[0017] In the above preparation method: the temperature of secondary growth in Step 2 is 80 - 120 °C, and the time is 3 - 12 h.

[0018] In the above preparation method: in Step 3: the high-temperature calcination temperature is 500 - 600 °C, the calcination time is 3 - 8 h; the number of metal oxide multi-cores is 10 - 50, and the size is 2 - 10 nanometers.

[0019] A metal oxide multi-core-silicon aluminum shell bifunctional catalyst is prepared by the above method.

[0020] In the technical solution of the present invention: the metal oxide multi-core-silicon aluminum shell bifunctional catalyst prepared by the above preparation method is used in catalytic degradation of organic wastewater.

[0021] In the above applications: COD concentration of organic wastewater is 500~300000mg / L;

[0022] The catalytic reaction temperature is 300-450°C, preferably: the catalytic reaction temperature is 380-420°C;

[0023] Airspeed: 0.5~4h -1 , preferably 1.5 to 3 hours -1 .

[0024] The beneficial effects of the present invention are embodied in:

[0025] The metal oxide multi-core-silicon-aluminum shell bifunctional catalyst created by the present invention can control the positions of acidic sites and oxidation sites in the catalyst to achieve precise regulation of catalytic activity; the multi-core metal oxide also improves the utilization rate of the catalyst's oxidation active sites, thereby improving the efficiency of the oxygen cracking reaction of organic pollutants.

[0026] The catalyst created by the present invention can achieve a COD removal rate of ≥99% in the process of purifying wastewater containing organic pollutants; the COD concentration of the purified effluent after oxygen cracking is less than 100 mg / L, and the ammonia nitrogen concentration is less than 25 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The scanning electron microscope image of the CeO2@Y material synthesized in Example 1 DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto:

[0029] Some of the original purchases include but are not limited to the following sources:

[0030] UIO-66-Ce (Shanghai Haohong Biopharmaceutical Technology Co., Ltd., UIO-66-Ce)

[0031] MIL-101-Fe (Shanghai Kaishu Chemical Technology Co., Ltd., MIL-101-Fe)

[0032] HKUST-1 (Xi'an Qiyue Biotechnology Co., Ltd., HKUST-1)

[0033] Example 1

[0034] Step 1: Take 100 mg of commercially available UIO-66-Ce (Shanghai Haohong Biomedical Technology Co., Ltd., UIO-66-Ce), MIL-101-Fe (Shanghai Kaishu Chemical Technology Co., Ltd., MIL-101-Fe), and HKUST-1 (Xi'an Qiyue Biotechnology Co., Ltd., HKUST-1) that have been carbonized at 400°C in a nitrogen atmosphere for 5 hours, add 200 mg of Y-type zeolite nanocrystal suspension (Nankai University Catalyst Factory, Si / Al mass ratio of 0.76, 10wt%), respectively, stir overnight, take out, wash, and dry to obtain a composite of Y-type zeolite nanocrystals loaded with different metal carbon carriers;

[0035] Step 2: The composites of Y-type zeolite nanocrystals loaded with different metal carbon carriers were placed in a secondary growth solution consisting of 0.56g sodium hydroxide, 0.67g aluminum sulfate, 2.84g sodium silicate, and 14.364g deionized water for secondary growth. The secondary growth conditions were heating at 80°C for 3h. After washing and drying, core-shell structured UIO-66-Ce@Y, MIL-101-Fe@Y, and HKUST-1@Y were obtained.

[0036] Step three: calcine UIO-66-Ce@Y, MIL-101-Fe@Y, and HKUST-1@Y at 550°C for 5h to obtain CuO@Y (the number of cores is 10, and the size is 10nm), CeO2@Y (the number of cores is 30, and the size is 4nm), and Fe2O3@Y (the number of cores is 50, and the size is 2nm) catalysts.

[0037] The acid contents of the prepared CuO@Y, CeO2@Y and Fe2O3@Y catalysts determined by ammonia-programmed temperature desorption method were 2.0, 4.0 and 3.1 mmol / g, respectively; the hydrogen consumption of the CuO@Y, CeO2@Y and Fe2O3@Y catalysts determined by hydrogen-programmed temperature reduction method were 7.5, 16.5 and 11.5 mmol / g, respectively.

[0038] 5 g of the above catalyst was loaded into a fluidized bed reactor and the reaction temperature was 400 ° C for 2 h. -1 Under the condition of air velocity, the landfill leachate with COD concentration of 8433mg / L was converted into CO2 and H2O. After 3 hours of reaction, it was found that CeO2@Y catalyst with UIO-66-Ce as carbon carrier had the best catalytic effect on landfill leachate, with effluent COD concentration of 9.3mg / L and COD removal rate of 99.9%.

[0039] Example 2

[0040] Step 1: Take 100 mg of commercially available UIO-66-Ce (Shanghai Haohong Biopharmaceutical Technology Co., Ltd., UIO-66-Ce), MOF-74-Mn (Shanghai Haohong Biopharmaceutical Technology Co., Ltd., MOF-74-Mn), and MOF-74-Co (Shanghai Haohong Biopharmaceutical Technology Co., Ltd., MOF-74-Co) that have undergone high-temperature carbonization at 400 °C in a nitrogen atmosphere for 5 h, and immerse them in 150 mg of an amorphous silica-alumina nanoparticle (Nankai University Catalyst Factory, 10 wt%) solution with a silica-alumina mass ratio of 0.3 respectively. After washing and drying, composites of amorphous silica-alumina nanoparticles supported on different metal carbon carriers can be obtained;

[0041] Steps 2 and 3: According to the same calcination and secondary growth treatments as in Example 1, catalysts of the CeO2@SiO2-Al2O3 (the number of nuclei is 30, the size is 4 nm), Co2O3@SiO2-Al2O3 (the number of nuclei is 20, the size is 25 nm), and Mn2O3@SiO2-Al2O3 (the number of nuclei is 35, the size is 20 nm) types can be obtained.

[0042] The acid amounts of the prepared catalysts of CeO2@SiO2-Al2O3, Co2O3@SiO2-Al2O3, and Mn2O3@SiO2-Al2O3 measured by ammonia-temperature programmed desorption method are 3.6, 2.8, and 3.1 mmol / g respectively; the hydrogen consumption amounts of the catalysts of CeO2@SiO2-Al2O3, Co2O3@SiO2-Al2O3, and Mn2O3@SiO2-Al2O3 measured by hydrogen-temperature programmed reduction method are 12.7, 11.3, and 10.6 mmol / g respectively.

[0043] Take 5 g of the above catalyst and load it into a fluidized bed reactor. At a reaction temperature of 380 °C and an hourly -1 space velocity, convert kitchen waste wastewater with a COD concentration of 4000 mg / L into CO2 and H2O. It is found that the CeO2@SiO2-Al2O3 catalyst with UIO-66-Ce as the carbon carrier has the best catalytic effect on kitchen waste wastewater, with an effluent COD concentration of 9.2 mg / L and a COD removal rate of 99.7%.

[0044] Example 3

[0045] Step 1: Take 100 mg of commercially available UIO-66-Ce (Shanghai Haohong Biopharmaceutical Technology Co., Ltd., UIO-66-Ce) that has undergone high-temperature carbonization at 400 °C under a nitrogen atmosphere for 5 h, and add it to 200 mg of Y-type (Nankai University Catalyst Factory, Si / Al mass ratio is 0.76, 10 wt%), 200 mg of MOR-type (Nankai University Catalyst Factory, Si / Al mass ratio is 7.6, 10 wt%), 200 mg of Beta-type (Nankai University Catalyst Factory, Si / Al mass ratio is 15.2, 10 wt%), 200 mg of A-type (Nankai University Catalyst Factory, Si / Al mass ratio is 1.52, 10 wt%), and 200 mg of ZSM-5 zeolite nanocrystal suspension (Nankai University Catalyst Factory, Si / Al mass ratio is 101.33, 10 wt%) respectively. After stirring overnight, take it out, wash, and dry to obtain the composite with different nanocrystals supported on the metal carbon carrier;

[0046] Steps 2 and 3: According to the same secondary growth and calcination conditions as in Example 1, multinuclear-shell CeO2@Y, CeO2@MOR, CeO2@Beta, CeO2@A, and CeO2@ZSM-5 catalysts with 30 nuclei and a size of 4 nm can be obtained.

[0047] The acid amounts of the prepared catalysts CeO2@Y, CeO2@MOR, CeO2@Beta, CeO2@A, and CeO2@ZSM-5 measured by ammonia-temperature programmed desorption method are 4.0, 3.2, 2.9, 3.3, and 2.8 mmol / g respectively; the hydrogen consumption amounts of the catalysts CeO2@Y, CeO2@MOR, CeO2@Beta, CeO2@A, and CeO2@ZSM-5 measured by hydrogen-temperature programmed reduction method are 16.5, 13.6, 9.4, 13.3, and 14.7 mmol / g respectively.

[0048] The performance test of the catalyst is carried out according to Example 4; the COD concentration of the selected food waste wastewater is 10,000 mg / L. It is found that the CeO2@Y catalyst loaded with Y-type nanocrystals has the best catalytic effect on food waste wastewater, the effluent COD concentration is 89.7 mg / L, and the COD removal rate is 99.1%.

[0049] Example 4

[0050] Step 1: Take 100 mg of commercially available UIO-66-Ce (Shanghai Haohong Biomedical Technology Co., Ltd., UIO-66-Ce) that has been carbonized at 400°C in a nitrogen atmosphere for 5 h, add 200 mg of Y-type zeolite nanocrystal suspension with silicon-aluminum mass ratios of 0.76, 4.6, and 5.4 (Nankai University Catalyst Plant, Si / Al mass ratio of 0.76, 10 wt%), stir overnight, take out, wash, and dry to obtain a metal-carbon carrier loaded with a Y-type zeolite nanocrystal composite with different silicon-aluminum ratios;

[0051] Steps 2 and 3: According to the same secondary growth and calcination conditions as in Example 1, multi-core-shell CeO2@Y-0.76, CeO2@Y-4.6, and CeO2@Y-5.4 with 30 cores and a size of 4 nm can be obtained.

[0052] The acid contents of the catalysts prepared by CeO2@Y-0.76, CeO2@Y-4.6 and CeO2@Y-5.4 were determined by ammonia-programmed temperature desorption method to be 4.0, 3.4 and 2.9 mmol / g, respectively; the hydrogen consumption of the catalysts prepared by CeO2@Y-0.76, CeO2@Y-4.6 and CeO2@Y-5.4 was determined by hydrogen-programmed temperature reduction method to be 16.5, 12.6 and 14.2 mmol / g, respectively.

[0053] The performance test of the catalyst was carried out according to Example 4, and it was found that the Y-type nanocrystalline CeO2@Y-1.5 catalyst with a silicon-aluminum mass ratio of 0.76 had the best effect on catalyzing kitchen waste wastewater, with an effluent COD concentration of 9.7 mg / L and a COD removal rate of 99.7%.

[0054] Example 5

[0055] Step 1: Take 100 mg of commercially available UIO-66-Ce (Shanghai Haohong Biomedical Technology Co., Ltd., UIO-66-Ce) that has been carbonized at 400°C for 5 h in a nitrogen atmosphere and soak it in 200 mg of amorphous silicon aluminum nanoparticles (Nankai University Catalyst Factory, 10 wt%) solution with silicon aluminum mass ratios of 0.3, 5, and 12, and then wash and dry the sample to obtain amorphous silicon aluminum nanoparticles with different contents loaded on the metal carbon carrier;

[0056] Steps 2 and 3: The bifunctional catalysts prepared by the same secondary growth as in Example 1 and calcination at 550°C in air atmosphere for 5 hours are CeO2@SiO2-Al2O3-0.3, CeO2@SiO2-Al2O3-5, and CeO2@SiO2-Al2O3-12, each with 30 nuclei and a size of 4 nm.

[0057] The acid amounts of the prepared catalysts CeO2@SiO2-Al2O3-0.3, CeO2@SiO2-Al2O3-5, and CeO2@SiO2-Al2O3-12 determined by ammonia-temperature programmed desorption method were 3.3, 3.7, and 3.0 mmol / g, respectively; the hydrogen consumption amounts of the catalysts CeO2@SiO2-Al2O3-0.3, CeO2@SiO2-Al2O3-5, and CeO2@SiO2-Al2O3-12 determined by hydrogen-temperature programmed reduction method were 11.5, 12.8, and 11.9 mmol / g, respectively.

[0058] The performance test of the catalyst was carried out according to Example 4, and it was found that the amorphous silica-alumina CeO2@SiO2-Al2O3-0.3 catalyst with a silica-alumina mass ratio of 0.3 had the best catalytic effect on kitchen waste wastewater, with the effluent COD concentration of 10.9 mg / L and the COD removal rate of 99.7%.

[0059] Example 6

[0060] Step 1: Using the Y-type zeolite nanocrystals prepared in Example 1, add 100 mg of commercially available UIO-66-Ce (Shanghai Haohong Biopharmaceutical Technology Co., Ltd., UIO-66-Ce) that has undergone high-temperature carbonization at 400 °C in a nitrogen atmosphere for 5 h to 200 mg of the above-mentioned synthesized Y-type zeolite nanocrystal suspension (Nankai University Catalyst Factory, Si / Al mass ratio of 0.76, 10 wt%). After stirring overnight, take it out, wash it, and dry it to obtain a composite of Y-type zeolite nanocrystals supported on a metal carbon carrier.

[0061] Steps 2 and 3: According to the same secondary growth conditions as in Example 1, and calcine at 500 °C for 5 h to obtain CeO2@Y-35 (the number of nuclei is 35, the size is 3 nm), calcine at 550 °C for 5 h to obtain CeO2@Y-30 (the number of nuclei is 30, the size is 4 nm), and calcine at 600 °C for 5 h to obtain CeO2@Y-25 (the number of nuclei is 30, the size is 8 nm) type catalysts.

[0062] The acid amounts of the prepared catalysts CeO2@Y-10, CeO2@Y-30, and CeO2@Y-50 determined by ammonia-temperature programmed desorption method were 2.8, 4.0, and 3.7 mmol / g, respectively; the hydrogen consumption amounts of the catalysts CeO2@Y-10, CeO2@Y-30, and CeO2@Y-50 determined by hydrogen-temperature programmed reduction method were 11.5, 16.5, and 12.7 mmol / g, respectively.

[0063] Take 5 g of the above catalyst and load it into a fluidized bed reactor at a reaction temperature of 450 °C for 4 h -1Under the condition of airspeed, the bilge water with a COD concentration of 7000 mg / L was converted into CO2 and H2O. It was found that the CeO2@Y-30 catalyst with a nuclear number of 30 had the best catalytic effect on bilge water, with an effluent COD concentration of 30.5 mg / L and a COD removal rate of 99.5%.

[0064] Example 7

[0065] Step 1: Using the Y-type zeolite nanocrystals prepared in Example 1, 100 mg of commercially available UIO-66-Ce (Shanghai Haohong Biopharmaceutical Technology Co., Ltd., UIO-66-Ce) that had been subjected to high-temperature carbonization at 400 °C for 5 h in a nitrogen atmosphere was added to 200 mg of the above-mentioned synthesized Y-type zeolite nanocrystal suspension (Nankai University Catalyst Factory, Si / Al mass ratio of 0.76, 10 wt%). After stirring overnight, it was taken out, washed, and dried to obtain a composite material of Y-type zeolite nanocrystals supported on a metal carbon carrier.

[0066] Step 2: The composite material of Y-type zeolite nanocrystals supported on a metal carbon carrier in Step 1 was placed in a secondary growth solution composed of 6.6 g of tetraethyl orthosilicate, 2.04 g of aluminum isopropoxide, 0.4 g of sodium hydroxide, and 67.5 g of deionized water, and the same secondary growth treatment as in Example 1 was carried out to obtain a core-shell structured UIO-66-Ce@Y-2 material.

[0067] Step 3: The material synthesized in Step 2 was calcined at 550 °C for 5 h to obtain a CeO2@Y-2 catalyst with a nuclear number of 30 and a size of 4 nm.

[0068] The acid amount of the prepared CeO2@Y-2 catalyst was measured by ammonia-temperature programmed desorption method to be 3.7 mmol / g in turn; the hydrogen consumption of the CeO2@Y-2 catalyst was measured by hydrogen-temperature programmed reduction method to be 14.9 mmol / g in turn.

[0069] The performance test of the catalyst was carried out according to Example 8, and the selected bilge water had a COD concentration of 10000 mg / L. It was found that the effluent COD concentration of the bilge water catalyzed by the CeO2@Y-2 catalyst was 80.3 mg / L, and the COD removal rate was 99.2%.

[0070] Example 8

[0071] Step 1: Using the Y-type zeolite nanocrystals prepared in Example 1, 100 mg of commercially available UIO-66-Ce (Shanghai Haohong Biopharmaceutical Technology Co., Ltd., UIO-66-Ce) that had been subjected to high-temperature carbonization at 400 °C for 5 h in a nitrogen atmosphere was added to 200 mg of the above-mentioned synthesized Y-type zeolite nanocrystal suspension (Nankai University Catalyst Factory, Si / Al mass ratio of 0.76, 10 wt%). After stirring overnight, it was taken out, washed, and dried.

[0072] Step 2: Put the material synthesized in Step 1 into the secondary growth solution composed of 3.95 g of silicic acid, 0.82 g of sodium metaaluminate, 1.1 g of sodium hydroxide, and 72 g of deionized water, and perform the same secondary growth treatment as in Example 1 to obtain the core-shell structured UIO-66-Ce@Y-3 material;

[0073] Step 3: Bake the material synthesized in Step 2 at 550 °C for 5 h to obtain a multi-core-shell CeO2@Y-3 type catalyst with 30 nuclei and a size of 4 nm.

[0074] The acid amounts of the prepared CeO2@Y-3 type catalysts measured by ammonia-temperature programmed desorption method are 2.8 mmol / g in sequence; the hydrogen consumption amounts of the CeO2@Y-3 type catalysts measured by hydrogen-temperature programmed reduction method are 13.7 mmol / g in sequence.

[0075] The performance test of the catalyst was carried out according to Example 8, and it was obtained that the effluent COD concentration of the CeO2@Y-3 type catalyst for catalytically treating bilge water was 90.3 mg / L, and the COD removal rate was 99.1%.

[0076] Comparative Example 1

[0077] Completely dissolve 800 mg of chromium nitrate in 20 mL of deionized water. After dissolution, add 7.5 g of kaolin and stir for 10 hours, then dry it at 80 °C, and then place it in a tubular furnace and heat-treat it from room temperature to 550 °C at a heating rate of 6 °C / min in an air atmosphere for 5 hours. The catalyst is named CeO2 / kaolin. Take 5 g of the above catalyst and load it into a fluidized bed reactor. Under the conditions of a reaction temperature of 300 °C, a reaction pressure of 0.15 MPa (gauge pressure), an oxygen addition amount of 5 mg / L in the bilge water concentration, and a space velocity of 0.5 h-1, convert the bilge water with a COD concentration of 7006 mg / L into CO2 and H2O. After reacting for 3 hours, the COD removal rate was obtained as 91.1%; the effluent COD concentration was as high as 667.8 mg / L, which did not meet the discharge standard; the long-term stability effect of the purification reaction was not good, and obvious catalyst deactivation occurred only after 20 h, and the catalytic efficiency was greatly reduced. -1 After reacting for 3 hours, the COD removal rate was obtained as 91.1%; the effluent COD concentration was as high as 667.8 mg / L, which did not meet the discharge standard; the long-term stability effect of the purification reaction was not good, and obvious catalyst deactivation occurred only after 20 h, and the catalytic efficiency was greatly reduced.

[0078] Comparative Example 2

[0079] Under the conditions of Example 1, 1.09 g of cerium nitrate hexahydrate was completely dissolved in 20 mL of deionized water. After dissolution, 7.5 g of kaolin was added and stirred for 10 hours, then placed at 80 °C, and subsequently placed in a tubular furnace and heated to 550 °C at a rate of 6 °C / min in an air atmosphere for heat treatment for 5 hours. The catalyst was named CeO2 / kaolin. 5 g of the above catalyst was loaded into a fluidized bed reactor, and at a reaction temperature of 450 °C, a reaction pressure of 0.25 MPa (gauge pressure), and an oxygen addition amount of 50 mg / L in the concentration of the tank washing water, the tank washing water was oxidized to CO2 and H2O under the condition of an airspeed of 4 h -1 Under the conditions of the space velocity, the tank washing water was oxidized to CO2 and H2O. After 3 hours of reaction, the removal rate of the COD concentration was 93.5%, and the effluent COD concentration was as high as 500.4 mg / L, but obvious catalyst deactivation occurred only after 38 h, and the catalytic efficiency was greatly reduced.

Claims

1. A preparation method of a metal oxide multi-core-silicoaluminate shell bifunctional catalyst, characterized in that, The steps of this method are as follows: Step 1: Add a carbon support containing a metal element into a suspension of silica-alumina oxide nanoparticles and stir. The bridging oxygen in the silica-alumina oxide structure is deposited on the carbon support containing the metal element through metal ion coordination to form a complex; among them, the carbon support containing the metal element is a polyhedral carbon support formed by high-temperature carbonization of a metal complex, and the metal complex is selected from at least one of MOP-18, Cu-ITQ, HKUST-1, Ce-MOL, UIO-66-Ce, MOF-808-Ce, MOF-74-Mn, MIL-101-Cr, MIL-101-Fe, MIL-53-Fe, MOF-74-Co; the acidic silica-alumina oxide nanoparticles are one of ZSM-5 type nanocrystals, Y type nanocrystals, MOR type nanocrystals, Beta type nanocrystals, A type nanocrystals, amorphous silica-alumina nanoparticles; Step 2: Immerse the above complex in a secondary growth solution of acidic silica-alumina oxide for secondary growth; the temperature of the secondary growth is 80 - 120 °C, and the time is 3 - 12 h; Step 3: After secondary growth, a metal oxide multi-core - silica-alumina shell bifunctional catalyst can be obtained by high-temperature calcination.

2. The preparation method of the metal oxide multi-core-silicoaluminate shell bifunctional catalyst according to claim 1, wherein: The mass ratio of the carbon support to the silica-alumina oxide nanoparticles is 1~30:

1.

3. The preparation method of the metal oxide multi-core-silicoaluminate shell bifunctional catalyst according to claim 2, characterized in that: The mass ratio of the carbon support to the silica-alumina oxide nanoparticles is 2~20:

1.

4. The preparation method of the metal oxide multi-core-silicoaluminate shell bifunctional catalyst according to claim 1, characterized in that: In Step 2, the secondary growth solution is composed of a silicon source, an aluminum source, and a sodium source; among them, the silicon source is one of sodium silicate, tetraethyl orthosilicate, silicic acid, and water glass; the aluminum source is one of aluminum isopropoxide, sodium metaaluminate, and sodium aluminate; the sodium source is one of sodium hydroxide, sodium metaaluminate, and sodium silicate; the mass ratio of the silicon source to the aluminum source is 1 - 8:1, and the mass ratio of the sodium source to the silicon source is 0.01 - 2:

1.

5. The preparation method of the metal oxide multi-core-silicoaluminate shell bifunctional catalyst according to claim 4, characterized in that: The mass ratio of the silicon source to the aluminum source is 3.24 - 4.82:1, and the mass ratio of the sodium source to the silicon source is 0.061 - 0.28:

1.

6. The preparation method of the metal oxide multi-core-silicoaluminate shell bifunctional catalyst according to claim 1, characterized in that: In Step 3: The high-temperature calcination temperature is 500 - 600 °C, and the calcination time is 3 - 8 h; the number of metal oxide multi-cores is 10 - 50, and the size is 2 - 10 nanometers.

7. A metal oxide multi-core-silicoaluminum shell bifunctional catalyst, characterized in that: The catalyst described above is prepared by the method described in any one of claims 1 - 6.

8. Application of the metal oxide multi-core - silica-alumina shell bifunctional catalyst prepared by the preparation method described in claim 1 in the catalytic degradation of organic wastewater.

9. The application according to claim 8, wherein: The COD concentration of the organic wastewater is 500~300000 mg / L; the reaction temperature is 300~450 °C; the space velocity is 0.5~4 h -1 .

10. The application according to claim 9, characterized in that, The catalytic reaction temperature is 380 - 420 °C; the space velocity is 1.5 - 3 h -1 .

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