nNi / Rh(x)-La 2 O 3 Preparation method and application of catalyst

Abstract

The present invention discloses a preparation method and application of an nNi / Rh(x)-La2O3 catalyst, belonging to the technical field of catalysts. The technical solution includes the following steps: 1) Preparation of La2O3 support particles: Sieving lanthanum nitrate, dropping nitric acid solution into lanthanum nitrate, drying and calcining after mixing; 2) Preparation of Rh(x)-La2O3: Adding La2O3 support particles and Rh(NO3)3·2H2O into water, stirring and reacting; drying and calcining to obtain the Rh(x)-La2O3 support; 3) Preparation of the nNi / Rh(x)-La2O3 catalyst: Dispersing the Rh(x)-La2O3 support in water, adding Ni(NO3)2·6H2O thereto, stirring, adjusting the pH, reacting, washing the precipitate, and drying; calcining to obtain the catalyst. The present invention has high catalytic activity and has good application prospects in the photocatalytic degradation of methyl acrylate.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a preparation method and application of an nNi / Rh(x)-La 2 O 3 catalyst. Background Art

[0002] Methyl acrylate (MA) is a colorless transparent liquid with a pungent odor and is readily soluble in organic solvents such as ethanol and ether. It is an important organic chemical raw material and is widely used in fields such as coatings, adhesives, and plastics. However, pollutants such as wastewater and waste gas may be generated during the production and use of methyl acrylate. Photocatalytic degradation is a technology that uses a photocatalyst to catalyze the decomposition of organic substances under light irradiation. After absorbing light energy, the photocatalyst can generate strongly oxidizing free radicals or electron-hole pairs, which can react with organic substances and decompose them into harmless small-molecule substances. The photocatalytic degradation technology has the advantages of high efficiency, environmental protection, and no secondary pollution, and has broad application prospects in fields such as wastewater treatment and air purification. Therefore, it is of great significance to study the photocatalytic degradation technology of methyl acrylate.

[0003] At present, certain research progress has been made in the photocatalytic degradation technology for methyl acrylate. In the existing technology, TiO 2 photocatalytic degradation: TiO 2 is a commonly used photocatalyst with excellent catalytic performance and stability. Research shows that under ultraviolet light irradiation, TiO 2 can catalyze the degradation of methyl acrylate and decompose it into CO 2 and H 2 O and other harmless substances. In addition, by modifying TiO 2 , such as doping metal ions or compositing with other semiconductor materials, its photocatalytic performance can be further improved. In addition to TiO 2 , some other photocatalysts have also been used for the degradation of methyl acrylate. For example, semiconductor materials such as ZnO and CdS. These photocatalysts can generate free radicals or electron-hole pairs under light irradiation, thereby catalyzing the decomposition of methyl acrylate. However, the catalysts in the existing technology often have the problem of low catalytic efficiency, and it is necessary to develop a new catalyst for photocatalytic degradation of methyl acrylate. Summary of the Invention

[0004] The present invention provides a preparation method and application of an nNi / Rh(x)-La 2 O 3 catalyst, and the nNi / Rh(x)-La 2 O 3The catalyst has high catalytic activity and has good application prospects in the photocatalytic degradation of methyl acrylate.

[0005] The technical solution of the present invention is as follows:

[0006] In the first aspect, a preparation method of nNi / Rh(x)-La 2 O 3 catalyst is disclosed, which includes the following steps:

[0007] 1) Preparation of La 2 O 3 support particles: Sieving lanthanum nitrate particles to 100 - 600 μm, dropping nitric acid solution into lanthanum nitrate, mixing, drying, and calcining to obtain La 2 O 3 support particles, and the particle size of La 2 O 3 support particles is 50 - 120 μm;

[0008] 2) Preparation of Rh(x)-La 2 O 3 : Using Rh(NO 3 ) 3 ·2H 2 O as a precursor, introducing Rh onto the surface of La 2 O 3 by the impregnation method to prepare Rh(x)-La 2 O 3 ; specifically: adding the La 2 O 3 support particles prepared in step 1) and Rh(NO 3 ) 3 ·2H 2 O into water, stirring at 50 - 60 °C for 5 - 8 h; drying the resulting viscous substance in an oven at 90 - 110 °C for 10 - 16 h to obtain a solid powder, and then transferring the solid powder to a tube furnace and calcining it in a helium atmosphere at 850 - 950 °C for 4 - 8 h to obtain the Rh(x)-La 2 O 3 support, where x = 2, 4, 6, 8, 10, and x represents the mass percentage of Rh in the support;

[0009] 3) Preparation of nNi / Rh(x)-La 2 O 3 catalyst: Loading Ni onto the Rh(x)-La 2 O 3 support by the deposition - precipitation method. First, activating the Rh(x)-La 2 O 3 support and then dispersing it in water, and adding Ni(NO3 ) 2 ·6H 2 O, stir for 40 - 60 min, adjust the pH to 9 - 12, react at 80 - 100 °C for 10 - 12 h, wash the precipitate and dry it; calcine in a tubular furnace under argon or helium conditions, the calcination temperature is 300 - 400 °C, the time is 3 - 5 h, then raise the temperature to 650 - 750 °C for secondary calcination for 3 - 4 h, and the obtained sample is the nNi / Rh(x)-La 2 O 3 catalyst, where n = 1, 5, 10, and n is the mass percentage of Ni in the support.

[0010] Preferably, in step 1), the drying temperature is 80 - 100 °C, the drying time is 4 - 8 h, the calcination temperature is 500 - 600 °C, and the calcination time is 5 - 8 h.

[0011] Preferably, in step 1), the concentration of the nitric acid solution is 0.08 - 0.12 mol / L, and the mass - volume ratio of lanthanum nitrate to the nitric acid solution in step 1) is (20 - 50) g:1 mL.

[0012] Preferably, in step 2), the mass - volume ratio of La 2 O 3 support particles, Rh(NO 3 ) 3 ·2H 2 O and water is 100 g:(6 - 65) g:(300 - 400) mL.

[0013] Preferably, in step 3), the mass - volume ratio of Rh(x)-La 2 O 3 support, Ni(NO 3 ) 2 ·6H 2 O and water is 100 g:(4 - 50) g:(300 - 400) mL.

[0014] Preferably, in step 3), the concentration of the dilute nitric acid used for activation is 0.08 - 0.12 mol / L. The specific activation method is: place the Rh(x)-La 2 O 3 support in a reaction vessel, dropwise add the dilute nitric acid solution, adjust the pH to 2 - 4, then stir at 80 - 120 °C for 8 - 12 h, then dry, the drying temperature is 100 - 150 °C, the drying time is 10 - 24 h, and finally calcine at 300 - 400 °C for 4 - 5 h.

[0015] Preferably, in step 3), Na 2 CO 3 or ammonia water is used to adjust the pH.

[0016] Preferably, in step 3), the drying is carried out at a temperature of 80-100 °C for 10-12 h.

[0017] In a second aspect, the application of the described catalyst in the photocatalytic degradation of methyl acrylate is disclosed, including the following steps:

[0018] A. Place the nNi / Rh(x)-La 2 O 3 catalyst in a photoreactor, and the set temperature of the photoreactor is 20-30 °C, and the pressure is 0.1-0.3 MPa;

[0019] B. Add a methyl acrylate solution to the photoreactor and stir for 90-110 min under dark conditions;

[0020] C. Under the irradiation of a xenon lamp, the irradiation power of the xenon lamp is 350 W, start the condensation device, maintain at 0 °C, carry out the degradation reaction for 5-7 h, and detect the reaction mixture solution with a gas chromatography-mass spectrometry instrument.

[0021] Nickel and rhodium are loaded on the surface of the La 2 O 3 support to form a Rh 2 O 3 and NiO metal oxide layer, improving the catalytic performance of the catalyst. Rh optimizes the strong interaction between the metal Ni and the support, thereby improving the catalytic performance. At the same time, the presence of Ni enhances the electron transfer between the La 2 O 3 support and Rh, thus promoting the degradation of methyl acrylate. Introducing Rh on the surface of La 2 O 3 generates the metal oxide Rh 2 O 3 which is the key to improving the catalytic activity. The addition of Rh effectively inhibits the sintering phenomenon of La 2 O 3 during the high-temperature calcination process, significantly increases the specific surface area of the catalyst, provides more mesoporous structures, and thus optimizes the dispersion of Ni. There is an electron transfer phenomenon between La 2 O 3 and the active component Ni, resulting in a strong interaction between Ni and the Rh(x)-La 2 O 3 support. This not only protects Ni from the influence of high-temperature sintering but also optimizes the bond energy between Rh and methyl acrylate during the catalytic reaction process, which is beneficial to the degradation of methyl acrylate, thus significantly improving the catalytic activity.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The nNi / Rh(x)-La prepared by the present invention 2 O 3 The catalyst exhibits excellent performance in the photocatalytic degradation of methyl acrylate, can effectively reduce the concentration of methyl acrylate, and reduce environmental pollution.

[0024] 2. The high specific surface area and suitable pore size distribution of La 2 O 3 of the present invention are beneficial to the uniform dispersion of Rh, thereby improving the catalytic activity. When Ni and Rh coexist in the catalyst, a synergistic catalytic effect can be produced. This synergistic effect can significantly improve the catalytic activity of the catalyst. Description of the Drawings

[0025] Figure 1 is the morphology diagram of the catalyst prepared in Example 1 of the present invention.

[0026] Figure 2 is the degradation curve of methyl acrylate over time in Example 1 and Comparative Example 1 of the present invention. Detailed Embodiments

[0027] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in conjunction with the embodiments of the present invention.

[0028] Example 1

[0029] The preparation method of the nNi / Rh(x)-La 2 O 3 catalyst includes the following steps:

[0030] 1) Preparation of La 2 O 3 support particles: Sieving lanthanum nitrate particles to 100 μm, adding 1 mL of 0.08 mol / L nitric acid solution to 20 g of lanthanum nitrate, drying at 80 °C for 8 h after mixing, and then calcining at 600 °C for 5 h to obtain La 2 O 3 support particles, and the particle size of La 2 O 3 support particles is 50 μm;

[0031] 2) Preparation of Rh(x)-La 2 O 3 : Mix 100 g of the La 2 O 3 support particles prepared in step 1) and 6 g of Rh(NO 3 ) 3 ·2H 2O is added to 300 mL of water and stirred at 50 °C for 8 h; the resulting viscous substance is dried in an oven at 90 °C for 16 h to obtain a solid powder, and then the solid powder is transferred to a tubular furnace and calcined in a helium atmosphere at 850 °C for 8 h to obtain Rh(x)-La 2 O 3 support, where x = 2 and x represents the mass percentage of Rh in the support;

[0032] 3) nNi / Rh(x)-La 2 O 3 Preparation of the catalyst: The Rh(x)-La 2 O 3 support is first activated. The specific activation method is as follows: 100 g of the Rh(x)-La 2 O 3 support is placed in a reaction vessel, 200 mL of deionized water is added, and a 0.08 mol / L dilute nitric acid solution is added dropwise. After adjusting the pH to 2, it is stirred at 80 °C for 12 h, then dried. The drying temperature is 100 °C and the drying time is 24 h. Finally, it is calcined at 300 °C for 5 h; 100 g of the activated Rh(x)-La 2 O 3 support is redispersed in 300 mL of water, 4 g of Ni(NO 3 ) 2 ·6H 2 O is added, stirred for 40 min, the pH is adjusted to 9 with ammonia water, reacted at 80 °C for 12 h, the precipitate is washed, and dried at 80 °C for 12 h; calcined in a tubular furnace under argon conditions, the calcination temperature is 300 °C and the time is 5 h, and then heated to 650 °C for secondary calcination for 4 h. The obtained sample is the nNi / Rh(x)-La 2 O 3 catalyst, where n = 1 and n is the mass percentage of Ni in the support. The morphology diagram of the prepared catalyst is as shown in Figure 1 shown.

[0033] Application of the described catalyst in photocatalytic degradation of methyl acrylate, including the following steps:

[0034] A. 20 mg of the nNi / Rh(x)-La 2 O 3 catalyst is placed in a photoreactor. The set temperature of the photoreactor is 20 °C and the pressure is 0.1 MPa;

[0035] B. A 20 mg / L methyl acrylate solution is added to the photoreactor and stirred in the dark for 90 min;

[0036] C. Under the irradiation of a xenon lamp with an irradiation power of 350 W, start the condensation device, maintain at 0 °C, carry out the degradation reaction for 6 h, and detect the reaction mixture solution with a gas chromatography-mass spectrometry instrument.

[0037] Example 2

[0038] The preparation method of the nNi / Rh(x)-La 2 O 3 catalyst includes the following steps:

[0039] 1) Preparation of La 2 O 3 support particles: Sieving lanthanum nitrate particles to 300 μm, adding 1 mL of 0.1 mol / L nitric acid solution to 30 g of lanthanum nitrate, drying at 90 °C for 6 h after mixing, and then calcining at 550 °C for 6 h to obtain La 2 O 3 support particles, and the particle size of La 2 O 3 support particles is 80 μm;

[0040] 2) Preparation of Rh(x)-La 2 O 3 : Adding 100 g of the La 2 O 3 support particles prepared in step 1) and 30 g of Rh(NO 3 ) 3 ·2H 2 O to 350 mL of water, stirring at 55 °C for 6 h; drying the resulting viscous substance in an oven at 100 °C for 12 h to obtain a solid powder, and then transferring the solid powder to a tubular furnace and calcining in a helium atmosphere at 900 °C for 6 h to obtain Rh(x)-La 2 O 3 support, where x = 6, and x represents the mass percentage of Rh in the support;

[0041] 3) Preparation of nNi / Rh(x)-La 2 O 3 catalyst: First, activate the Rh(x)-La 2 O 3 support. The specific activation method is as follows: Place 100 g of the Rh(x)-La 2 O 3 support in a reaction vessel, add 200 mL of deionized water, dropwise add 0.1 mol / L dilute nitric acid solution, adjust the pH to 3, stir at 100 °C for 10 h, then dry, the drying temperature is 120 °C, the drying time is 16 h, and finally calcine at 350 °C for 4 h; After activating 100 g of Rh(x)-La 2 O3 The carrier was redispersed in 350 mL of water, and 26 g of Ni(NO 3 ) 2 ·6H 2 O was added thereto, and the mixture was stirred for 50 min. The pH was adjusted to 10 with sodium carbonate, and the reaction was carried out at 90 °C for 11 h. The precipitate was washed and dried at 90 °C for 11 h; it was calcined in a tubular furnace under argon atmosphere, the calcination temperature was 350 °C, and the time was 4 h. Then it was heated to 700 °C for secondary calcination for 3.5 h. The obtained sample was the nNi / Rh(x)-La 2 O 3 catalyst, where n = 5, and n is the mass percentage of Ni in the carrier.

[0042] Application of the described catalyst in photocatalytic degradation of methyl acrylate, including the following steps:

[0043] A. 20 mg of the nNi / Rh(x)-La 2 O 3 catalyst was placed in a photoreactor, and the set temperature of the photoreactor was 25 °C and the pressure was 0.2 MPa;

[0044] B. A 20 mg / L methyl acrylate solution was added to the photoreactor and stirred for 100 min under dark conditions;

[0045] C. Under the irradiation of a xenon lamp with an irradiation power of 350 W, the condensation device was started and maintained at 0 °C, and the degradation reaction was carried out for 5 h. The reaction mixture solution was detected by gas chromatography-mass spectrometry.

[0046] Example 3

[0047] Preparation method of the described nNi / Rh(x)-La 2 O 3 catalyst, including the following steps:

[0048] 1) Preparation of La 2 O 3 support particles: Lanthanum nitrate particles were sieved to 600 μm, 1 mL of 0.12 mol / L nitric acid solution was added dropwise to 50 g of lanthanum nitrate. After mixing, it was dried at 100 °C for 4 h, and then calcined at 500 °C for 8 h to obtain La 2 O 3 support particles, and the particle size of La 2 O 3 support particles was 120 μm;

[0049] 2) Preparation of Rh(x)-La 2 O 3 : 100 g of the La 2 O 3Support particles and 65 g of Rh(NO 3 ) 3 ·2H 2 O were added to 400 mL of water and stirred at 60 °C for 5 h; the resulting viscous substance was dried in an oven at 110 °C for 10 h to obtain a solid powder, and then the solid powder was transferred to a tubular furnace and calcined in a helium atmosphere at 950 °C for 4 h to obtain Rh(x)-La 2 O 3 support, where x = 10 and x represents the mass percentage of Rh in the support;

[0050] 3) Preparation of the nNi / Rh(x)-La 2 O 3 catalyst: The Rh(x)-La 2 O 3 support was first activated. The specific activation method: 100 g of the Rh(x)-La 2 O 3 support was placed in a reaction vessel, 200 mL of deionized water was added, and a 0.12 mol / L dilute nitric acid solution was added dropwise. After adjusting the pH to 4, it was stirred at 120 °C for 8 h, then dried. The drying temperature was 150 °C and the drying time was 10 h. Finally, it was calcined at 400 °C for 4 h; 100 g of the activated Rh(x)-La 2 O 3 support was redispersed in 400 mL of water, 50 g of Ni(NO 3 ) 2 ·6H 2 O was added, stirred for 60 min, the pH was adjusted to 12 with ammonia water, reacted at 100 °C for 10 h, the precipitate was washed, and dried at 100 °C for 10 h; calcined in a tubular furnace under argon conditions, the calcination temperature was 400 °C and the time was 3 h, and then the temperature was raised to 750 °C for secondary calcination for 3 h. The obtained sample was the nNi / Rh(x)-La 2 O 3 catalyst, where n = 10 and n is the mass percentage of Ni in the support.

[0051] Application of the described catalyst in photocatalytic degradation of methyl acrylate, including the following steps:

[0052] A. 20 mg of the nNi / Rh(x)-La 2 O 3 catalyst was placed in a photoreactor. The set temperature of the photoreactor was 30 °C and the pressure was 0.2 MPa;

[0053] B. A 20 mg / L methyl acrylate solution was added to the photoreactor and stirred for 110 min under dark conditions;

[0054] C. Under the irradiation of a xenon lamp with an irradiation power of 350 W, start the condensation device, maintain at 0 °C, carry out the degradation reaction for 7 h, and detect the reaction mixture solution with a gas chromatography-mass spectrometry instrument.

[0055] Comparative Example 1

[0056] Different from Example 1, this comparative example does not include step 3), and Rh(x)-La 2 O 3 support is prepared.

[0057] Comparative Example 2

[0058] The preparation method of the described nNi / -La 2 O 3 catalyst includes the following steps:

[0059] 1) Preparation of La 2 O 3 support particles: Sieving lanthanum nitrate particles to 100 μm, adding 1 mL of 0.08 mol / L nitric acid solution to 20 g of lanthanum nitrate, drying at 80 °C for 8 h after mixing, and then calcining at 600 °C for 5 h to obtain La 2 O 3 support particles, and the particle size of La 2 O 3 support particles is 50 μm;

[0060] 2) Preparation of nNi / La 2 O 3 catalyst: Disperse 100 g of La 2 O 3 support in 300 mL of water, add 4 g of Ni(NO 3 ) 2 ·6H 2 O, stir for 40 min, adjust the pH to 9 with ammonia water, react at 80 °C for 12 h, wash the precipitate, and dry at 80 °C for 12 h; calcine in a tubular furnace under argon conditions, the calcination temperature is 300 °C, the time is 5 h, and then raise the temperature to 650 °C for secondary calcination for 4 h. The obtained sample is the nNi / La 2 O 3 catalyst, where n = 1, and n is the mass percentage of Ni in the support.

[0061] Comparative Example 3

[0062] Different from Example 1, in this comparative example, lanthanum nitrate particles are not sieved in step 1), and the remaining preparation methods and steps are the same as those in Example 1.

[0063] Comparative Example 4

[0064] Different from Example 1, step 1) of this comparative example is: La 2 O 3 Preparation of carrier particles: Screen lanthanum nitrate particles to 100 μm. Add 1 mL of 0.08 mol / L nitric acid solution to 20 g of lanthanum nitrate. After mixing, dry at 80 °C for 8 h, and then calcine at 650 °C for 8 h to obtain La 2 O 3 carrier particles, La 2 O 3 The particle size of the carrier particles is 40 μm; the remaining preparation methods and steps are the same as those in Example 1.

[0065] Comparative Example 5

[0066] Different from Example 3, in this comparative example, step 2) is: Preparation of Rh(x)-La 2 O 3 : Add 100 g of the La 2 O 3 carrier particles prepared in step 1) and 80 g of Rh(NO 3 ) 3 ·2H 2 O to 300 mL of water, and stir at 50 °C for 8 h; Dry the resulting viscous substance in an oven at 90 °C for 16 h to obtain a solid powder, and then transfer the solid powder to a tubular furnace and calcine it in a helium atmosphere at 850 °C for 8 h to obtain Rh(x)-La 2 O 3 carrier, where x = 12, and x represents the mass percentage of Rh in the carrier; the remaining preparation methods and steps are the same as those in Example 3.

[0067] Comparative Example 6

[0068] Different from Example 1, in step 3), the Rh(x)-La 2 O 3 carrier is not activated and is directly dispersed in water, and the remaining preparation methods and steps are the same as those in Example 1.

[0069] Comparative Example 7

[0070] The preparation method of the catalyst specifically includes the following steps:

[0071] 1) Preparation of La 2 O 3 carrier particles: Screen lanthanum nitrate particles to 100 μm. Add 1 mL of 0.08 mol / L nitric acid solution to 20 g of lanthanum nitrate. After mixing, dry at 80 °C for 8 h, and then calcine at 600 °C for 5 h to obtain La 2 O 3 carrier particles, La 2 O 3The particle size of the carrier particles is 50 μm;

[0072] 2) nNi-La 2 O 3 Preparation of the catalyst: Disperse 100 g of La 2 O 3 carrier in 300 mL of water, add 4 g of Ni(NO 3 ) 2 ·6H 2 O, stir for 40 min, adjust the pH to 9 with ammonia water, react at 80 °C for 12 h, wash the precipitate, and dry it; calcine in a tube furnace under argon atmosphere, the calcination temperature is 300 °C, the time is 5 h, and then raise the temperature to 650 °C for secondary calcination for 4 h. The obtained sample is the nNi-La 2 O 3 catalyst, where n = 1 and n is the mass percentage of Ni in the carrier.

[0073] 3) Preparation of Rh(x)-La 2 O 3 : First, activate the nNi-La 2 O 3 catalyst prepared in step 2). The specific activation method is as follows: Place 100 g of the nNi-La 2 O 3 carrier in a reaction vessel, add 200 mL of deionized water, dropwise add 0.08 mol / L dilute nitric acid solution, adjust the pH to 2, stir at 80 °C for 12 h, then dry, the drying temperature is 100 °C, the drying time is 24 h, and finally calcine at 300 °C for 5 h; Add 100 g of the activated nNi-La 2 O 3 and 6 g of Rh(NO 3 ) 3 ·2H 2 O to 300 mL of water, stir at 50 °C for 8 h; Dry the viscous substance produced in a 90 °C oven for 16 h to obtain a solid powder, then transfer the solid powder to a tube furnace and calcine it in a helium atmosphere at 850 °C for 8 h to obtain the Rh(x)-La 2 O 3 carrier, where x = 2 and x represents the mass percentage of Rh in the carrier.

[0074] Perform performance tests on the catalysts prepared in the examples and comparative examples, and the test results are shown in Table 1.

[0075] Table 1 Catalyst Performance Test Results

[0076]

[0077] As can be seen from Table 1, the catalyst prepared by the present invention has a relatively large average specific surface area and average pore diameter, and a relatively large crushing strength, which is more conducive to improving the catalytic performance.

[0078] The catalysts prepared in the above examples and comparative examples were used for photocatalytic degradation of methyl acrylate. The degradation methods in Comparative Examples 1-7 were the same as those in Example 1. The detection results are shown in Table 2. The degradation curves of methyl acrylate over time in Example 1 and Comparative Example 1 are as Figure 2 shown.

[0079]

[0080] η is the degradation rate of methyl acrylate, M 反应初 and M 反应后 are the concentration of methyl acrylate before the reaction and the concentration of methyl acrylate after the reaction, respectively.

[0081] Table 2 Detection results of photocatalytic degradation of methyl acrylate

[0082]

[0083] As can be seen from Table 2, when the catalyst prepared by the present invention is applied to the decomposition of methyl acrylate, the decomposition conversion rate is high. In Comparative Example 1, Ni is not included, and the degradation rate of methyl acrylate drops significantly. This is because in the nNi / Rh(x)-La 2 O 3 catalyst system, Ni and Rh play a synergistic catalytic role. When Ni is not included, the active centers provided by Ni in the catalyst system are missing, resulting in hindrance to the adsorption and activation processes of reactant molecules, making it difficult for the reaction to proceed effectively. Therefore, the degradation rate of methyl acrylate decreases significantly.

[0084] In Comparative Example 2, Rh is not included, and the degradation rate of methyl acrylate drops significantly. When Rh is not included, the number of active centers of the catalyst decreases, resulting in difficulty in efficiently carrying out the degradation reaction of methyl acrylate and a significant decrease in the degradation rate.

[0085] In Comparative Example 3, the non-screening of lanthanum nitrate particles leads to uneven particle size distribution. In the subsequent preparation of La 2 O 3 support particles and the process of loading active components, larger-sized lanthanum nitrate particles may not react sufficiently during calcination and other processes, resulting in an uneven and unstable structure of the La 2 O 3 support. At the same time, the uneven particle size of the support affects the loading and dispersion of the active components (Ni and Rh), making the active components unable to be evenly distributed on the surface of the support, thereby reducing the number of effective active sites.

[0086] In Comparative Example 4, La 2 O3 If the particle size is too small, the packing mode between the carrier particles will change, and the formed pore structure will be finer and more complex. Although a smaller particle size may increase the specific surface area, an overly small pore diameter will lead to an increase in the diffusion resistance of reactant molecules. In the reaction of photocatalytic degradation of methyl acrylate, it is difficult for reactant molecules to quickly enter the interior of the catalyst pores to contact the active sites, which limits the progress of the reaction. At the same time, an overly small particle size may also cause a decrease in the mechanical strength of the carrier, and it is prone to agglomeration and fragmentation during the reaction process, further affecting the stability and activity of the catalyst, and thus affecting the degradation rate of methyl acrylate.

[0087] In Comparative Example 5, the loading amount of Rh is too high, and Rh will agglomerate on the surface of the carrier to form larger particles. This will lead to a decrease in the dispersion of Rh and a reduction in the number of effective active sites. Excessive Rh may also block the pores of the carrier, reducing the average pore diameter and specific surface area of the catalyst, and hindering the diffusion and adsorption of reactant molecules. In addition, excessive Rh may interact with Ni, changing the electronic structure and surface properties of the catalyst, which has an adverse effect on the catalytic activity, resulting in a decrease in the degradation rate of methyl acrylate.

[0088] In Comparative Example 6, Rh(x)-La 2 O 3 The carrier is directly dispersed in water without activation. The purpose of activating the carrier is to improve the surface properties of the carrier and enhance its loading capacity and dispersion for the active component (Ni). Steps such as acid treatment, stirring, drying, and calcination during the activation process can remove impurities on the surface of the carrier, increase the surface active groups, and make the surface of the carrier more uniform and conducive to the attachment of the active component. When no activation treatment is carried out, the surface properties of the carrier are not conducive to the loading and dispersion of Ni, and Ni may not be evenly distributed on the surface of the carrier, resulting in uneven quantity and distribution of active sites, which will hinder the contact between reactant molecules and active sites, thereby reducing the catalytic performance of the catalyst and the degradation rate of methyl acrylate.

[0089] In Comparative Example 7, changing the loading order of Rh and Ni, loading Ni first and then Rh will result in that Rh cannot be well loaded on the Ni-La 2 O 3 surface, thus leading to a decrease in the degradation rate.

[0090] The catalyst prepared in Example 1 was subjected to a cyclic performance test. The specific catalytic method was the same as that in Example 1. After one catalytic reaction, it was necessary to restore the activity of the catalyst. Specifically: the catalyst after the catalytic reaction was first filtered and collected, washed with deionized water, dried at 100 °C for 11 h, and then placed in a tubular furnace for calcination for 8 h. The heating temperature was 650 °C. The degradation rates after 10 cycles are shown in Table 3.

[0091] Table 3 Degradation rate of cyclic performance test

[0092]

Claims

1. A method for preparing a nNi / Rh(x)-La2O3 catalyst, characterized in that: The following steps are involved: 1) Preparation of La2O3 carrier particles: sieving lanthanum nitrate particles to 100-600 μm, adding nitric acid solution to lanthanum nitrate, mixing, drying and calcining to obtain La2O3 carrier particles, the particle size of the La2O3 carrier particles is 50-120 μm; 2) Preparation of Rh(x)-La2O3: Rh(NO3)3·2H2O is used as a precursor, and Rh is introduced into the surface of La2O3 by an impregnation method to prepare Rh(x)-La2O3, specifically, the La2O3 carrier particles prepared in step 1) and Rh(NO3)·2H2O are added to water, and stirred at 50-60°C for 5-8h; the resulting viscous substance is dried in an oven at 90-110°C for 10-16h to obtain a solid powder, and then the solid powder is transferred to a tube furnace and calcined in a helium atmosphere at 850-950°C for 4-8h to obtain a Rh(x)-La2O3 carrier, wherein x=2, 4, 6, 8, 10, and x represents the mass percentage of Rh in the carrier; 3) Preparation of nNi / Rh(x)-La2O3 catalyst: Activate the Rh(x)-La2O3 carrier and then disperse it in water, add Ni(NO3)2·6H2O, stir for 40-60min, adjust the pH to 9-12, react at 80-100℃ for 10-12h, wash the precipitate and dry it; calcine in a tubular furnace under argon or helium conditions at a temperature of 300-400℃ for 3-5h, then heat to 650-750℃ for secondary calcination for 3-4h, and the obtained sample is the nNi / Rh(x)-La2O3 catalyst, wherein n=1, 5, 10, and n is the mass percentage of Ni in the carrier; in step 1), the drying temperature is 80-100℃, the drying time is 4-8h, the calcination temperature is 500-600℃, and the calcination time is 5-8h; The concentration of dilute nitric acid used for activation in step 3) is 0.08-0.12 mol / L. The specific activation method is: place the Rh(x)-La2O3 carrier in a reaction vessel, add dilute nitric acid solution, adjust the pH to 2-4, stir at 80-120°C for 8-12h, and then dry at 100-150°C for 10-24h, and finally calcine at 300-400°C for 4-5h.

2. The method for preparing the nNi / Rh(x)-La2O3 catalyst according to claim 1, characterized in that: The concentration of the nitric acid solution in step 1) is 0.08-0.12 mol / L, and the mass volume ratio of lanthanum nitrate and nitric acid solution in step 1) is (20-50) g:1 mL.

3. The method for preparing the nNi / Rh(x)-La2O3 catalyst according to claim 1, characterized in that: In step 2), the mass volume ratio of La2O3 carrier particles, Rh(NO3)3·2H2O and water is 100 g: (6-65) g: (300-400) mL.

4. The method for preparing the nNi / Rh(x)-La2O3 catalyst according to claim 1, characterized in that: In step 3), the mass volume ratio of Rh(x)-La2O3 carrier, Ni(NO3)2·6H2O and water is 100 g: (4-50) g: (300-400) mL.

5. The method for preparing the nNi / Rh(x)-La2O3 catalyst according to claim 1, characterized in that: In step 3), Na2CO3 or ammonia water is used to adjust the pH.

6. Use of the catalyst prepared by the preparation method according to any one of claims 1 to 5 in photocatalytic degradation of methyl acrylate, characterized in that: The following steps are involved: A. Place the nNi / Rh(x)-La2O3 catalyst in a photoreactor, the set temperature of the photoreactor is 20-30°C and the pressure is 0.1-0.3MPa; B. Add methyl acrylate solution to the photoreactor and stir for 90-110 min in dark conditions; C. Under the irradiation of a xenon lamp with an irradiation power of 350W, start the condensing device, maintain 0°C, and carry out the degradation reaction for 5-7 hours. Use a gas chromatography-mass spectrometer to detect the mixed solution after the reaction.

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