A preparation method of low-temperature high-space-velocity VOC catalyst and catalyst

Abstract

The present invention discloses a preparation method and a catalyst for a low-temperature and high space velocity VOC catalyst, belonging to the field of industrial waste gas treatment. Volatile organic compounds (VOCs), as the main air pollutants, cause photochemical smog and endanger human health. The VOC catalysts in the prior art cannot meet the process conditions of catalytic combustion treatment at a high space velocity of 30,000 h⁻¹. The present invention develops a high space velocity VOCs noble metal catalyst that meets the industrial requirements for the catalytic combustion technology of complex VOCs, and its maximum space velocity meets 30,000 h⁻¹. The catalyst is a monolithic honeycomb catalyst composed of active components of a dual-effect synergistic dual-component noble metal precursor, a transition metal oxide, and a rare earth oxide, which enhances the oxygen vacancies on the carrier and the acidity of the Brønsted acid of the catalyst, and enhances the ability of the surface oxygen vacancy flow of the catalyst and the adsorption and oxidative dissociation of the surface functional groups of VOCs.

Description

Technical Field

[0001] The invention belongs to the field of industrial waste gas treatment, and specifically relates to a preparation method of a low-temperature high-space-velocity VOC catalyst and a catalyst. Background Art

[0002] Volatile organic compounds (VOCs) are one of the main air pollutants that can directly cause photochemical smog and aggravate haze pollution, endangering human health. The emission sources of VOCs mainly include petrochemicals, medicine, papermaking, transportation, textiles, coatings, printing, electronic component processing, solvent and cleaning product production, etc. Common VOCs waste gas treatment and disposal methods on the market usually include combustion, adsorption treatment, biological treatment and other methods. Combustion treatment converts VOCs into carbon dioxide and water through high-temperature combustion. Common combustion equipment includes incinerators, catalytic burners, etc. Conventional combustion scenarios include direct catalytic combustion, activated carbon adsorption and desorption + catalytic combustion CO, zeolite wheel adsorption and desorption + catalytic combustion CO and zeolite wheel adsorption and desorption + regenerative catalytic combustion RCO.

[0003] A catalyst for catalytic combustion of VOCs and its preparation method (patent number: CN110614101A) discloses a nano-coating material coated on a carrier, with a noble metal compounded with a transition metal as an active component, a compounded rare earth oxide as a catalyst promoter, and a solid solution made of an alkaline earth metal compound and a main group metal oxide as a carrier modifier; a VOC treatment catalyst (application number: 201880029094.1) discloses a scheme in which platinum is directly loaded on a cobalt·cerium composite oxide to obtain a VOC treatment catalyst, wherein platinum is prepared from a solution of platinum colloid protected by a dispersant, and the cobalt·cerium composite oxide is prepared from a compound of cobalt and cerium carbonate as a precursor by roasting at 300-500°C and then pulverizing;

[0004] With the simultaneous advancement of technology upgrades and green and low-carbon upgrades in the industry, VOCs catalysts with high air velocity and high activity have great advantages and potential in cost control and efficient catalytic oxidation of VOCs, so they can be adapted to air velocity of 30,000 h -1 The VOCs catalysts prepared by the above schemes cannot meet the requirements of 30000h -1 Process conditions for catalytic combustion treatment at high space velocity.

[0005] Therefore, in order to adapt to market demand, a high space velocity VOCs precious metal catalyst that can meet industrial needs is developed. Summary of the invention

[0006] In order to achieve the above-mentioned purpose, the present invention provides a preparation method and catalyst of a low-temperature high-space-velocity VOC catalyst, the purpose of which is to develop a high-space-velocity VOCs noble metal catalyst that meets the industrial needs for complex volatile organic compounds (VOCs) catalytic combustion technology, and its maximum space velocity meets 30000h -1 .

[0007] The technical solution adopted by the present invention is: by selecting rare earth metal oxides that can enhance the efficient mass transfer between VOCs gas and solid oxides and a rare earth metal La-modified gamma alumina carrier with high porosity, and modifying it to form a special composite oxide, the oxygen vacancies of the carrier and the acidity of the catalyst Brønsted acid are enhanced, the oxidation-reduction ability of oxygen vacancies on the catalyst surface is enhanced, and the ability of adsorption and oxidative dissociation of functional groups on the surface of VOCs substances is enhanced; in addition, through the dual-effect synergistic effect of the two-component noble metals, the low-temperature catalytic activity of the catalyst under high space velocity conditions is significantly improved.

[0008] A low-temperature high-space-velocity VOC catalyst proposed by the present invention is a coated monolithic VOCs noble metal high-space-velocity catalyst, which is a monolithic honeycomb catalyst composed of dual-effect synergistic dual-component noble metals, transition metals, and rare earth oxides as active components;

[0009] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0010] (1) The transition metal oxide precursor is loaded on La-Al by equal volume impregnation method. 2 O 3 and LaPr-CeZrO 2 Then drying and calcining to obtain a pre-treated catalyst A, and grinding the pre-treated catalyst A to a size of more than 300 meshes;

[0011] (2) Mix water, dispersant, noble metal precursor and pre-treated catalyst A, then add reducing agent to react for 4-6 hours, filter, wash, dry and calcine to obtain catalyst B;

[0012] (3) Catalyst B, γ-Al 2 O 3 The binder, lanthanum nitrate and barium nitrate are uniformly mixed in water to obtain a mixed solution, and then nitric acid and acetic acid are added to adjust the pH value of the mixed solution to 2-4, and then ball milling is performed to obtain a slurry, and the slurry is coated on a carrier by a vacuum coating method, and then dried and calcined to obtain a low-temperature high space velocity VOC catalyst.

[0013] In step (1), La-Al 2 O 3 The preparation process is as follows: La(NO 3 ) 2 6H2 O was loaded on Al by equal volume impregnation method 2 O 3 Then drying and calcining to obtain La-Al 2 O 3 ; the La(NO 3 ) 2 6H 2 O and Al 2 O 3 The mass ratio of La-Al is 1: (5-19); 2 O 3 For La 2 O 3 Modified Al 2 O 3 Modified composite oxides, La 2 O 3 Account for La 2 O 3 and Al 2 O 3 Total 2-7%;

[0014] In step (1), LaPr-CeZrO 2 The preparation process is as follows: nitric acid compounds of La, Pr, Ce and Zr elements are mixed and dissolved in water to obtain a mixed solution, and then the mixed solution is treated by ammonia coprecipitation method, aged overnight, and then filtered, washed, and finally dried and calcined to obtain the modified composite oxide LaPr-CeZrO 2 The concentration of the mixed solution is 1-2 mol / L; the nitrate compounds of La, Pr, Ce and Zr are La(NO 3 ) 2 6H 2 O、Pr(NO 3 ) 2 6H 2 O、Ce(NO 3 ) 2 6H 2 O and Zr(NO 3 ) 2 ·5H 2 O; La(NO 3 ) 2 6H 2 O、Pr(NO 3 ) 2 6H 2 O、Ce(NO 3 ) 2 6H 2 O and Zr(NO 3 ) 2 ·5H 2O is (1.2-4.3): (0.59-2.9): (47-61): (11-26); the LaPr-CeZrO 2 For La 2 O 3 and Pr 6 O 11 Modified Ce 60 Zr 30 O 2 The composite oxide, the La 2 O 3 and Pr 6 O 11 The mass ratio is (2-7): (1-5);

[0015] In step (1), La-Al 2 O 3 The specific surface area is greater than 190m 2 / g, pore volume greater than 50cm 3 / g; the LaPr-CeZrO 2 The specific surface area is greater than 70m 2 / g;

[0016] In step (1), La-Al 2 O 3 、LaPr-CeZrO 2 and a transition metal oxide precursor in a mass ratio of (10-40):(60-90):(0.1-2); the transition metal oxide precursor comprises ammonium molybdate or niobium nitrate;

[0017] In step (2), the dispersant and the noble metal precursor account for 0.1-0.3% and 0.45-1% of the total mass of the pretreated catalyst A and water, respectively; the mass ratio of water to catalyst A is (50-70):30;

[0018] The dispersant in step (2) includes PEG or PVA;

[0019] The noble metal precursor in step (2) includes a platinum source precursor and a palladium source precursor, wherein the platinum source precursor and the palladium source precursor are chloroplatinic acid solution and chloropalladic acid solution, respectively; the mass ratio of the Pt element to the Pd element in the chloroplatinic acid solution and the chloropalladic acid solution is Pt:Pd=(1-9):(1-3);

[0020] In step (2), the reducing agent is ascorbic acid, and the mass of the ascorbic acid is 1-10 times the molar mass of the noble metal precursor;

[0021] In step (3), the γ-Al 2 O 3The D50 is 10-20nm flake γ-Al 2 O 3 ;

[0022] The binder in step (3) comprises pseudo-boehmite or silica sol;

[0023] The catalyst B, γ-Al 2 O 3 The mass ratio of the binder, lanthanum nitrate and barium nitrate is (62.5-83.33): (5.67-28.5): (5-10): 2:2; the solid content of the mixed solution is 25-35%;

[0024] The volume ratio of the nitric acid to the acetic acid in step (3) is (1-3): (7-9);

[0025] The ball milling speed in step (3) is 300-400 r / min, and the ball milling time is 1-2 h; the d50 of the slurry is 4-15 um;

[0026] The carrier in step (3) comprises ceramic cordierite or porous metal, and the pore size of the carrier is 300-400 mesh;

[0027] The loading amount of the precious metal precursor in step (2) on the carrier in step (3) is 300-400 g / m based on the total mass of Pt and Pd. 3 ;

[0028] A low-temperature high-space-velocity VOC catalyst is prepared by the above preparation method.

[0029] The beneficial effects of the present invention are:

[0030] The present invention uses a gamma alumina carrier modified with rare earth oxides and high-porosity rare earth metal La that can enhance the efficient mass transfer between VOCs gas and carrier oxide, and modifies it with transition metal oxides to form a special composite oxide, thereby enhancing the carrier oxygen vacancies and the acidity of the catalyst Brønsted acid, reducing the formation energy of oxygen vacancies on the carrier surface, and strengthening the reaction kinetics between VOCs substances and catalyst active substances, thereby enhancing the ability of catalyst surface oxygen vacancies to flow and VOCs surface functional groups to adsorb and oxidatively dissociate. In addition, through the strong interaction between the dual-effect synergistic dual-component noble metal and the carrier, the low-temperature catalytic activity of the catalyst under high space velocity conditions is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The catalytic conversion curve of the catalyst prepared in Example 1 for different VOCs. DETAILED DESCRIPTION

[0032] In the scheme of the present invention, the chloropalladic acid comprises a tetrachloro compound or a hexachloro compound of chloropallatium, and a chloropalladic acid aqueous solution with a Pd mass content of 15%; the nitric acid is fuming nitric acid, and the mass concentration of the acetic acid is 99%.

[0033] Example 1

[0034] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0035] Weigh 95g Al 2 O 3 , 13.29 g La(NO 3 ) 2 6H 2 O was loaded by equal volume impregnation method, then dried at 110 °C for 2 h and calcined at 550 °C for 3 h to obtain a 5% La 2 O 3 Composite oxide La-Al 2 O 3 ;

[0036] Weigh 13.29 g La(NO 3 ) 2 6H 2 O, 16.96 g Pr(NO 3 ) 2 6H 2 O, 185.94 g Ce(NO 3 ) 2 6H 2 O and 141.19g Zr(NO 3 ) 2 ·5H 2 O, mixed and dissolved in water to form a solution with a mass concentration of 1%, excess ammonia water was added to the solution for precipitation by ammonia coprecipitation method, the solution containing the precipitate was aged overnight, filtered, washed with deionized water, and finally dried at 120℃ for 1h, and then calcined at 500℃ for 2h to obtain a 5% La 2 O 3 and 5%Pr 6 O 11 Modified Ce 60 Zr 30 O 2 Composite oxide LaPr-CeZrO 2 .

[0037] (1) Catalyst components contain La-Al 2 O 3 30g, LaPr-CeZrO 270g, ammonium molybdate 1.8g, loaded by equal volume impregnation method, dried at 100℃ for 2h, calcined at 500℃ for 2h to obtain pretreated catalyst A, and crushed and ground the pretreated catalyst A to more than 300 mesh;

[0038] (2) Add 233 g of deionized water, then add 2.1 g of dispersant PEG-400, 3.32 g of chloroplatinic acid and 0.37 g of chloropalladic acid solution, then add 100 g of pretreated catalyst A, and finally add 4.9 g of reducing agent L-ascorbic acid to react for 4 h, filter and wash with water, dry at 100 ° C for 1 h, and calcine at 500 ° C for 2 h to obtain catalyst B;

[0039] (3) Catalyst B and γ-Al 2 O 3 , 5% pseudo-boehmite, 2% lanthanum nitrate and 2% barium nitrate were evenly mixed in water, and the Ph was adjusted to 2 with a mixed solution of nitric acid and acetic acid in a volume ratio of 1:9 to form a mixed solution with a solid content of 30%, and the mixed solution was ball-milled at 300r / min for 1h to obtain a slurry; finally, a vacuum coater was used to coat the slurry on the inner pores of 300-mesh ceramic cordierite, dried at 110°C for 2h, and calcined at 600°C for 1h to obtain a low-temperature high-space-velocity VOC catalyst.

[0040] Example 2

[0041] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0042] Pretreatment catalyst A was prepared by replacing 1.8 g of ammonium molybdate in step (1) of Example 1 with 1.8 g of niobium nitrate. The other contents were the same as those in Example 1.

[0043] Comparative Example 1

[0044] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0045] The LaPr-CeZrO prepared in Example 1 2 Replaced with LaY-CeZrO 2 , that is, 16.96 g of Pr(NO 3 ) 2 6H 2 O is replaced by Y(NO 3 ) 3 6H 2 Preparation of LaY-CeZrO 2 ; Then in step (1), take 70g of LaY-CeZrO 2 Pretreated catalyst A was prepared; other contents were consistent with those in Example 1.

[0046] Comparative Example 2

[0047] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0048] The LaPr-CeZrO 2 The amount of was changed to 100 g to prepare pretreated catalyst A;

[0049] The other contents are consistent with those in Example 1.

[0050] Comparative Example 3

[0051] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0052] In step (1) of Example 1, La-Al 2 O 3 The amount of was changed to 100 g to prepare pretreated catalyst A;

[0053] The other contents are consistent with those in Example 1.

[0054] Comparative Example 4

[0055] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0056] In step (2) of Example 1, no dispersant PEG was added to prepare catalyst B; other contents were consistent with those in Example 1.

[0057] Comparative Example 5

[0058] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0059] In step (2) of Example 1, no reducing agent was added to prepare catalyst B; other contents were consistent with those in Example 1.

[0060] Comparative Example 6

[0061] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0062] No La-Al 2 O 3 , the La-Al in step (1) of Example 1 2 O 3 Replaced by γ-Al 2 O 3 , prepare pretreated catalyst A, and then prepare catalyst B according to the steps and contents in step (2) of Example 1; the other contents are consistent with those in Example 1.

[0063] Comparative Example 7

[0064] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0065] No La-Al 2 O 3 , the La-Al in step (1) of Example 1 2 O 3 Replaced by γ-Al 2 O 3 , a pretreated catalyst A is prepared, and then the 3.32 g of chloroplatinic acid and 0.37 g of chloropalladic acid solution added in step (2) of Example 1 are replaced with 3.69 g of chloroplatinic acid, and the contents of other steps remain unchanged to prepare catalyst B; the other contents are consistent with those in Example 1.

[0066] Comparative Example 8

[0067] A method for preparing a low-temperature high-space-velocity VOC catalyst comprises the following steps:

[0068] The 300-mesh ceramic cordierite in step (3) of Example 1 was changed to 200-mesh ceramic cordierite, and the other contents were consistent with those in Example 1.

[0069] Comparative Example 9

[0070] The 3.32 g of chloroplatinic acid and 0.37 g of chloropalladic acid solution in step (2) of Example 1 were replaced with 3.32 g of platinum nitrate and 0.37 g of palladium nitrate solution; the other contents were consistent with those in Example 1.

[0071] Test method: Cut the catalyst cylindrical honeycomb samples of Φ30×50 mm from Examples 1 and 2 and Comparative Examples 1 to 9, and test the space velocity at 30000 h -1 , test flow rate 17.7 L / min, toluene, ethyl acetate concentration 1000ppm, air atmosphere, volatile organic matter concentration detection by Fuli GC-9790PLUS gas chromatograph analysis detection (FID detector) after the catalyst before and after the concentration detection, the catalyst activity evaluation is shown in Table 1 and Figure 1 shown.

[0072] Table 1 Catalyst noble metal content and complete conversion temperature T99 of toluene catalytic oxidation

[0073] Sample name Toluene T99 / ℃ Ethyl acetate T99 / ℃ Example 1 200 270 Example 2 200 270 Comparative Example 1 210 280 Comparative Example 2 230 300 Comparative Example 3 260 320 Comparative Example 4 230 290 Comparative Example 5 260 320 Comparative Example 6 240 300 Comparative Example 7 260 320 Comparative Example 8 220 290 Comparative Example 9 240 290

[0074] As can be seen from Table 1, the activity of the catalysts prepared in Examples 1 and 2 is significantly better than that in Comparative Examples 1-9; the complete conversion temperature T99 of the catalytic oxidation of toluene in Example 1 is 200°C, which is 60°C lower than that in Comparative Example 7, and the complete conversion temperature T99 of the catalytic oxidation of ethyl acetate is 270°C, which is 50°C lower than that in Comparative Example 7. Through the above comparative tests, Example 1 has a higher conversion temperature T99 than Comparative Example 7 at 30000h. -1 The catalytic oxidation of toluene and ethyl acetate showed excellent low-temperature activity under high space velocity conditions.

[0075] The molybdenum additive and niobium additive used in Examples 1 and 2 increase the complete conversion temperature T99 of toluene and ethyl acetate to 30000h. -1 The complete conversion temperature T99 of toluene was reduced by 20°C at the same air velocity when the chloride noble metal precursor was used in Example 1 compared with the nitric acid noble metal precursor used in Comparative Example 9, indicating that selecting a suitable metal precursor is helpful to improve the low-temperature activity of the catalyst; the complete oxidation activity of the catalyst prepared in Example 1 for toluene and ethyl acetate is significantly better than that of Comparative Examples 1 to 5, indicating that by controlling the formula structure in the catalyst synthesis, and adding the dispersant and the reducing agent, and by finely controlling the size structure of the noble metal crystals in the catalyst synthesis step, the co-promotion effect formed can effectively improve the catalytic activity of the catalyst, so that the catalyst can be used at a high air velocity of 30000h -1 In the case of , still can achieve better low-temperature catalytic oxidation performance; in addition, through comparative examples 6 and 7, it is proved that the two-component precious metal is significantly better than the single-component precious metal for catalytic oxidation of VOCs, and through the fine control of the carrier modification and the precious metal loading form in the catalyst synthesis step, it is more conducive to the low-temperature performance of the catalyst at high space velocity; through Example 1 and Comparative Example 8, the complete conversion temperature T99 of toluene and ethyl acetate of the catalyst in Example 1 is reduced by 20°C at the same space velocity, proving that the use of a honeycomb catalyst carrier with a higher mesh number is conducive to the catalytic conversion of VOCs at high space velocity. The ability of the catalyst to catalytically convert VOCs at high space velocity is improved, and the honeycomb carrier with a higher mesh number is helpful to increase the specific surface area of ​​the coating per unit volume of the catalyst, and expose more catalysts in contact with VOCs substances, thereby improving the ability of the final formed honeycomb catalyst to capture VOCs gas, thereby enhancing the reaction kinetics of the catalyst during the reaction process, so that the catalyst still has relatively good low-temperature performance under high space velocity conditions.

[0076] Figure 1 Example 1 shows the results of different VOCs at high air velocity of 30000h -1The catalytic performance is excellent under the conditions of toluene complete conversion temperature of 200°C, ethyl acetate complete conversion temperature of 270°C, n-hexane complete conversion temperature of 280°C, styrene complete conversion temperature of 290°C, and common VOCs volatile organic compounds can be completely treated under high space velocity conditions within 300°C.

Claims

1. A method for preparing a low-temperature high-space-velocity VOC catalyst, characterized in that: The following steps are involved: (1) A transition metal oxide precursor is loaded on La-Al2O3 and LaPr-CeZrO2 by an equal volume impregnation method, and then dried and calcined to obtain a pretreated catalyst A, and the pretreated catalyst A is crushed and ground to a size of more than 300 mesh; the mass ratio of La-Al2O3, LaPr-CeZrO2 and the transition metal oxide precursor is (10-40): (60-90): (0.1-2); the transition metal oxide precursor includes ammonium molybdate or niobium nitrate; The LaPr-CeZrO2 is La2O3 and Pr6O 11 Modified Ce 60 Zr 30 Composite oxides of O2, La2O3 and Pr6O 11 The mass ratio is (2-7): (1-5); (2) Mix water, dispersant, noble metal precursor and pre-treated catalyst A, then add reducing agent to react for 4-6 hours, filter, wash, dry and calcine to obtain catalyst B; The noble metal precursor comprises a platinum source precursor and a palladium source precursor, wherein the platinum source precursor and the palladium source precursor are chloroplatinic acid solution and chloropalladic acid solution respectively, and the mass ratio of Pt element to Pd element in the chloroplatinic acid solution and the chloropalladic acid solution is Pt:Pd=(1-9):(1-3); (3) Catalyst B, γ-Al2O3, a binder, lanthanum nitrate and barium nitrate are mixed uniformly in water to obtain a mixed solution, and then nitric acid and acetic acid are added to adjust the pH value of the mixed solution to 2-4, and then ball milling is performed to obtain a slurry, and the slurry is coated on a carrier by a vacuum coating method, and then dried and calcined to obtain a low-temperature high space velocity VOC catalyst; The carrier comprises ceramic cordierite or porous metal, and the pore size of the carrier is 300-400 meshes.

2. The method for preparing a low-temperature high-space-velocity VOC catalyst according to claim 1, characterized in that: The preparation process of La-Al2O3 in step (1) is as follows: La(NO3)2·6H2O is loaded on Al2O3 by an equal volume impregnation method, and then dried and calcined to obtain La-Al2O3; the mass ratio of La(NO3)2·6H2O to Al2O3 is 1:(5-19); the La-Al2O3 is a modified composite oxide of La2O3 modified Al2O3, and the La2O3 accounts for 2-7% of the total amount of La2O3 and Al2O3.

3. The method for preparing a low-temperature high-space-velocity VOC catalyst according to claim 1, characterized in that: The preparation process of LaPr-CeZrO2 in step (1) is as follows: nitric acid compounds of La, Pr, Ce and Zr are mixed and dissolved in water to obtain a mixed solution with a concentration of 1-2 mol / L, and then the mixed solution is treated by ammonia coprecipitation method, aged overnight, filtered, washed, and finally dried and calcined to obtain a modified composite oxide LaPr-CeZrO2; The nitrate compounds of La, Pr, Ce and Zr elements are La(NO3)2·6H2O, Pr(NO3)2·6H2O, Ce(NO3)2·6H2O and Zr(NO3)2·5H2O respectively, and the molar ratios of La(NO3)2·6H2O, Pr(NO3)2·6H2O, Ce(NO3)2·6H2O and Zr(NO3)2·5H2O are (1.2-4.3):(0.59-2.9):(47-61):(11-26).

4. The method for preparing a low-temperature high-space-velocity VOC catalyst according to claim 1, characterized in that: The specific surface area of ​​La-Al2O3 in step (1) is greater than 190m 2 / g, pore volume greater than 50cm 3 / g; the specific surface area of ​​the LaPr-CeZrO2 is greater than 70m 2 / g.

5. The method for preparing a low-temperature high-space-velocity VOC catalyst according to claim 1, characterized in that: In step (2), the dispersant and the noble metal precursor account for 0.1-0.3% and 0.45-1% of the total mass of the pretreated catalyst A and water, respectively; the mass ratio of water to catalyst A is (50-70):30; the dispersant includes PEG or PVA; the reducing agent is ascorbic acid, and the mass of the ascorbic acid is 1-10 times the molar mass of the noble metal precursor.

6. The method for preparing a low-temperature high-space-velocity VOC catalyst according to claim 1, characterized in that: The γ-Al2O3 in step (3) is a flake γ-Al2O3 with a D50 of 10-20 nm; the binder comprises pseudo-boehmite or silica sol; the mass ratio of the catalyst B, γ-Al2O3, binder, lanthanum nitrate and barium nitrate is (62.5-83.33):(5.67-28.5):(5-10):2:2; the solid content of the mixed solution is 25-35%; and the volume ratio of nitric acid to acetic acid is (1-3):(7-9).

7. The method for preparing a low-temperature high-space-velocity VOC catalyst according to claim 1, characterized in that: The ball milling speed in step (3) is 300-400 r / min, and the ball milling time is 1-2 h; the d50 of the slurry is 4-15 um.

8. The method for preparing a low-temperature high-space-velocity VOC catalyst according to claim 1, characterized in that: The loading amount of the precious metal precursor in step (2) on the carrier in step (3) is 300-400 g / m based on the total mass of Pt and Pd. 3 .

9. The method for preparing a low-temperature high-space-velocity VOC catalyst according to any one of claims 1 to 3, characterized in that: The drying temperature of the drying and calcining is 80-120° C., the drying time is 1-2 hours, the calcining temperature is 450-600° C., and the calcining time is 1-5 hours.

10. A low-temperature, high-space-velocity VOC catalyst prepared according to the preparation method according to any one of claims 1 to 9.

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