CN113856678A - Oxidation catalyst and preparation method and application thereof - Google Patents

Abstract

The invention relates to an oxidation catalyst and a preparation method and application thereof, wherein the oxidation catalyst comprises a carrier and platinum metal and bismuth metal loaded on the carrier; the mass ratio of the platinum metal to the bismuth metal is (0.01-2) to 1. The oxidation catalyst provided by the invention has the advantages of low content of noble metal, low production cost, higher low-temperature catalytic activity and hydrothermal stability, capability of being secondarily processed into various shapes, and wide application in the fields of diesel engine tail gas treatment and the like.

Description

Oxidation catalyst and preparation method and application thereof

Technical Field

The invention relates to the field of catalysts, in particular to an oxidation catalyst and a preparation method and application thereof.

Background

Nitrogen Oxides (NO) in the context of an ever-increasing number of environmentally friendly and pollutant emission control initiatives_x) Emission levels of pollutants such as Particulate Matter (PM), carbon monoxide (CO), and Hydrocarbons (HCs)Are subject to severe restrictions. The diesel vehicle is one of the main sources of the pollutants, brings convenience to life and brings serious air pollution problems. The aftertreatment and purification technology of Diesel vehicles is an important technology for controlling exhaust pollution, and mainly includes Diesel catalytic oxidation (DOC), Diesel Particulate Filter (DPF), Selective Catalytic Reduction (SCR), and the like. Among them, the diesel catalytic oxidation technology is an important means for treating air pollutants at present.

The catalyst used in the DOC technology mainly functions to catalytically oxidize pollutants such as HCs, CO and PM, and reduce the emission of the pollutants. In addition, the DOC catalyst can oxidize part of NO into NO₂Conditions are provided for downstream DPF regeneration and SCR reactions. The DOC catalyst can be divided into a noble metal catalyst and a non-noble metal catalyst, wherein the carrier of the noble metal catalyst is usually modified alumina or cerium-zirconium solid solution, etc., the active component is metal such as Pt, Rh or Pd, etc., and the auxiliary agent is usually manganese, cerium or barium, etc. Generally, the noble metal Pt has stronger oxidation capability to NO and better sulfur resistance, and is the main active component of the noble metal catalyst. The non-noble metal catalyst mainly comprises metal oxide, spinel or perovskite. Although non-noble metal catalysts exhibit certain catalytic properties, their catalytic effect still does not meet the industrial requirements. Currently, the industry mainly uses precious metal catalysts, and with the stricter emission standards, the content of precious metals in the DOC catalyst is increased correspondingly, and the production cost is also increased remarkably.

CN111715222A discloses a preparation method of an oxidation type DOC catalyst for purifying diesel engine exhaust, which includes the processes of preparing inner layer slurry, preparing outer layer slurry and coating slurry, but the catalyst obtained by the method has high heavy metal content and complex preparation process.

CN103752338B discloses a preparation method of an oxidation catalyst for purifying diesel engine exhaust, which takes honeycomb ceramics or alloy as a substrate, takes titanium-silicon-aluminum composite oxide and a molecular sieve as coatings, takes Pt or/and Pd as active components, and leads the active components to be mixed with the honeycomb ceramics or alloyBy using different proportions of Pt and Pd to adjust NO₂Proportion in the tail gas. The catalyst obtained by the method is greatly influenced by the shape of the matrix, and the application range is limited.

Therefore, how to prepare DOC catalysts with low precious metal content, high catalytic activity and good hydrothermal stability is a current research hotspot.

Disclosure of Invention

In view of the above problems, the present invention aims to provide an oxidation catalyst, a preparation method and a use thereof, and compared with the prior art, the oxidation catalyst provided by the present invention has good low-temperature catalytic activity and hydrothermal stability, low precious metal content and low cost, and the preparation method of the oxidation catalyst provided by the present invention is simple and can be used for diesel engine exhaust gas treatment.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides an oxidation catalyst comprising a carrier and platinum metal and bismuth metal supported on the carrier; the mass ratio of the platinum metal to the bismuth metal is (0.01-2) to 1.

In the invention, bismuth metal is added in the preparation process of the platinum catalyst, so that excellent low-temperature catalytic activity is provided through the synergistic effect of the bismuth metal and the platinum metal, and under the same platinum addition amount, compared with a catalyst only added with the platinum metal, the oxidation catalyst provided by the invention has higher reaction activity and lower ignition temperature. On the basis, for the same pollutant treatment amount, the content of the platinum metal required to be added in the oxidation catalyst provided by the invention is greatly reduced compared with that of the traditional oxidation catalyst, and the effect of saving the cost can be achieved.

In the invention, when the mass ratio of the platinum metal to the bismuth metal is controlled to be (0.01-2):1, the platinum metal and the bismuth metal have better combined effect, and the obtained oxidation catalyst has higher catalytic activity and better catalytic effect.

In the present invention, the mass ratio of the platinum metal to the bismuth metal is controlled to (0.01-2):1, and may be, for example, 0.01:1, 0.02:1, 0.025:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.2:1, 0.5:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1 or 2:1, but not limited to the above-mentioned values, and other values not mentioned in the numerical range may be similarly applicable.

Preferably, the support comprises alumina.

Preferably, the alumina is in powder form.

In the invention, the powdery alumina carrier is further preferably adopted, so that the specific surface area is larger, the catalytic activity is improved, and the method is widely applied to the fields of diesel engine waste gas treatment and the like.

Preferably, the support has an average particle size of 1 to 100. mu.m, for example, 1 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, but is not limited to the values listed, and other values not listed in the numerical range are also applicable, and more preferably 60 to 70 μm.

Preferably, the platinum metal content of the oxidation catalyst is 0.01 to 4% by mass, for example, 0.01%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4% by mass, but not limited to the recited values, and other values not recited in the numerical range are also applicable, and more preferably 0.9 to 4% by mass.

Preferably, the bismuth metal content of the oxidation catalyst is 1 to 7% by mass, for example, 1%, 2%, 3%, 4%, 5%, 6% or 7% by mass, but not limited to the recited values, and other values not recited within the numerical range are also applicable, and more preferably 1 to 4% by mass.

In the invention, the bismuth metal and the platinum metal are synergistic to further improve the catalytic activity, and the mass percentage of the bismuth metal is preferably 1-4%, so that the bismuth metal can be uniformly loaded on the surface of a carrier, and the condition of reduced catalytic activity caused by nonuniform loading is avoided; but also can play a better role in concerted catalysis with platinum metal, and the catalytic activity is higher.

Preferably, the mass ratio of the platinum metal to the bismuth metal is (0.25-2): 1.

In the present invention, when the mass ratio of the platinum metal to the bismuth metal is preferably controlled to (0.25-2):1, higher catalytic activity and better catalytic effect can be achieved.

In a second aspect, the present invention provides a method for preparing an oxidation catalyst, comprising the steps of:

(1) mixing the bismuth salt solution and the carrier for the first time, and then sequentially carrying out rotary evaporation, drying and roasting to obtain a bismuth modified carrier;

(2) and (2) mixing and impregnating the bismuth modified carrier obtained in the step (1) and a platinum salt solution for the second time, and then drying and roasting the mixture in sequence to obtain the oxidation catalyst.

In the invention, bismuth metal is uniformly loaded on the surface of a carrier by mixing a bismuth salt solution and the carrier for one time, and then water in the obtained solid is removed by rotary evaporation; then drying and roasting are carried out in sequence to obtain a bismuth modified carrier; then mixing and impregnating the bismuth modified carrier and a platinum salt solution to load platinum metal on the surface of the bismuth modified carrier; and then, drying and roasting are sequentially carried out to obtain the oxidation catalyst, and bismuth metal and platinum metal can be uniformly loaded on the surface of the oxidation catalyst by adopting the operation method, so that the catalytic activity is favorably improved.

According to the method, bismuth is loaded firstly, and then platinum is loaded through impregnation, so that bismuth sites are formed on the surface of the carrier firstly, and platinum is loaded on the surface of the catalyst better through the introduction of the platinum.

Preferably, the bismuth salt solution of step (1) comprises Bi (NO)₃)₃And (3) solution.

Preferably, the molar concentration of bismuth metal in the bismuth salt solution is 0.02-0.06mol/L, and may be, for example, 0.02mol/L, 0.025mol/L, 0.03mol/L, 0.035mol/L, 0.04mol/L, 0.045mol/L, 0.05mol/L, 0.055mol/L or 0.06mol/L, but is not limited to the recited values, and other values within the range of values are equally applicable.

In the invention, when the molar concentration of bismuth metal in the bismuth salt solution is preferably controlled to be 0.02-0.06mol/L, the bismuth metal can be more fully and uniformly loaded on the surface of the carrier, thereby achieving higher catalytic activity and better catalytic effect.

Preferably, the platinum salt solution of step (1) comprises Pt (NO)₃)₂And (3) solution.

Preferably, the platinum metal is present in the platinum salt solution in a mass concentration of 0.001-0.1g/mL, such as 0.001g/mL, 0.002g/mL, 0.005g/mL, 0.008g/mL, 0.01g/mL, 0.02g/mL, 0.03g/mL, 0.04g/mL, 0.05g/mL, 0.06g/mL, 0.07g/mL, 0.08g/mL, 0.09g/mL, or 0.1g/mL, but not limited to the recited values, and any other values within the range are equally applicable.

In the invention, when the mass concentration of the platinum metal in the platinum salt solution is preferably controlled to be 0.001-0.1g/mL, the platinum metal can be uniformly loaded on the surface of the carrier, good catalytic activity is realized, the platinum metal is fully distributed on the surface of the carrier, the consumption of the platinum metal is reduced, and the production cost of the catalyst is saved.

Preferably, the primary mixing of the step (2) includes adding the bismuth salt solution and the carrier to the solvent and stirring.

Preferably, the solvent comprises deionized water.

Preferably, the mass ratio of bismuth metal to support in the bismuth salt solution is (1-7):100, and may be, for example, 1:100, 2:100, 3:100, 4:100, 5:100, 6:100 or 7:100, but is not limited to the recited values, and other values not recited within the range of values are equally applicable.

Preferably, the stirring time is 2 to 4 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4 hours, but not limited to the enumerated values, and other values not enumerated in the numerical range are also applicable, and further preferably 2.4 to 3.4 hours.

Preferably, the rotary evaporation temperature in step (1) is 60-80 ℃, for example, 60 ℃, 62 ℃, 64 ℃, 66 ℃, 68 ℃, 70 ℃, 72 ℃, 74 ℃, 76 ℃, 78 ℃ or 80 ℃, but not limited to the recited values, and other values not recited in the range of values are also applicable, and more preferably 66-74 ℃.

Preferably, the drying temperature in step (1) is 100-150 ℃, for example, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃ or 150 ℃, but not limited to the cited values, and other values not listed in the range of values are also applicable, and more preferably 115-130 ℃.

Preferably, the dry atmosphere in step (1) is air.

Preferably, the drying time in step (1) is 1 to 4 hours, such as 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4 hours, but not limited to the recited values, and other values not recited in the range of values are also applicable, and more preferably 3.6 to 4 hours.

Preferably, the temperature of the calcination in step (1) is 500-600 ℃, such as 500 ℃, 510 ℃, 520 ℃, 530 ℃, 540 ℃, 550 ℃, 560 ℃, 570 ℃, 580 ℃, 590 ℃ or 600 ℃, but not limited to the cited values, and other values not listed in the value range are also applicable, and further preferably 520-560 ℃.

Preferably, the calcination time in step (1) is 3 to 6 hours, such as 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours or 6 hours, but not limited to the enumerated values, and other values not enumerated within the numerical range are also applicable, and further preferably 4.8 to 5.4 hours.

Preferably, the mass ratio of platinum metal to bismuth-modified support in the platinum salt solution in step (2) is (0.01-4):100, and may be, for example, 0.01:100, 0.1:100, 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100 or 4:100, but is not limited to the enumerated values, and other unrecited values within the numerical range are equally applicable.

Preferably, the impregnation time is 2 to 4 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4 hours, but not limited to the enumerated values, and other values not enumerated within the numerical range are also applicable, and further preferably 2 to 2.4 hours.

Preferably, the drying temperature in step (2) is 100-150 ℃, for example, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃ or 150 ℃, but not limited to the cited values, and other values not listed in the range of values are also applicable, and more preferably 115-130 ℃.

Preferably, the dry atmosphere of step (a) is air.

Preferably, the drying time in step (2) is 2 to 4 hours, such as 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4 hours, but not limited to the enumerated values, and other unrecited values in the numerical range are also applicable, and further preferably 2.5 to 4 hours.

Preferably, the temperature of the calcination in step (2) is 500-600 ℃, such as 500 ℃, 510 ℃, 520 ℃, 530 ℃, 540 ℃, 550 ℃, 560 ℃, 570 ℃, 580 ℃, 590 ℃ or 600 ℃, but not limited to the cited values, and other values not listed in the value range are also applicable, and further preferably 520-560 ℃.

Preferably, the calcination time in step (2) is 1 to 4 hours, and may be, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4 hours, but not limited to the enumerated values, and other values not enumerated within the numerical range are also applicable, and further preferably 2.8 to 3.2 hours.

As a preferred embodiment of the second aspect of the present invention, the preparation method comprises the steps of:

(1) adding a bismuth salt solution with the molar concentration of 0.02-0.06mol/L and aluminum oxide into deionized water, stirring for 2-4h, wherein the mass ratio of bismuth metal to aluminum oxide in the bismuth salt solution is (1-7):100, then carrying out rotary evaporation at 60-80 ℃, drying a solid product obtained by rotary evaporation at 100-150 ℃ for 1-4h in an air atmosphere, and then roasting at 500-600 ℃ for 3-6h to obtain bismuth modified aluminum oxide;

(2) adding the bismuth modified alumina obtained in the step (1) into a platinum salt solution with the mass concentration of 0.001-0.1g/mL, mixing and soaking for 2-4h, wherein the mass ratio of platinum metal to bismuth modified alumina in the platinum salt solution is (0.01-4):100, drying the soaked solid product in an air atmosphere at 100-150 ℃ for 2-4h, and then roasting at 500-600 ℃ for 1-4h to obtain the oxidation catalyst.

In a third aspect, the invention also provides the use of the oxidation catalyst in the catalytic oxidation of diesel exhaust gas.

According to the oxidation catalyst provided by the invention, through the synergistic effect of the platinum metal and the bismuth metal, the introduction of Bi can improve the oxygen fluidity of the catalyst, improve the oxidation-reduction performance of the catalyst, further improve the catalytic activity of the catalyst, have excellent catalytic effect on CO, HCs and the like, can be used in the fields of diesel engine exhaust gas treatment and the like, can reduce the treatment cost compared with the traditional platinum catalyst, and can realize industrial popularization.

Compared with the prior art, the invention has the following beneficial effects:

(1) the oxidation catalyst provided by the invention has low heavy metal content and low production cost, can be secondarily processed into various shapes, and is widely applied to the fields of diesel engine tail gas treatment and the like.

(2) The oxidation catalyst provided by the invention catalyzes and oxidizes T of CO₅₀The temperature is lower than 170 ℃, T₉₀At a temperature below 175 ℃, T of catalytic oxidation propylene₅₀The temperature is lower than 170 ℃, T₉₀The temperature is lower than 180 ℃, and the catalyst has high low-temperature catalytic activity; after aging treatment, the T of CO is catalytically oxidized₅₀The temperature is lower than 190 ℃, T₉₀At a temperature below 210 ℃, T of catalytic oxidation propylene₅₀The temperature is lower than 220 ℃, T₉₀The temperature is lower than 250 ℃, and the hydrothermal stability is higher.

(3) The preparation method of the oxidation catalyst provided by the invention is simple to operate, can be used for large-scale production, and is beneficial to industrial popularization.

(4) The oxidation catalyst provided by the invention is used in the field of diesel engine tail gas treatment, and has excellent catalytic effect on CO, HCs and the like.

Drawings

FIG. 1 is a graph showing the results of XRD tests conducted on oxidation catalysts obtained in examples 1 to 3 of the present invention and comparative example 2;

FIG. 2 is a graph showing the results of CO catalytic activity tests conducted on the oxidation catalysts obtained in examples 1 to 3 of the present invention and comparative example 2;

FIG. 3 is a graph showing the results of the propylene catalytic activity test conducted on the oxidation catalysts obtained in examples 1 to 3 of the present invention and comparative example 2;

FIG. 4 is a graph showing the results of CO catalytic activity tests conducted on oxidation catalysts obtained in examples 1 to 3 of the present invention and comparative example 2 after aging treatment;

FIG. 5 is a graph showing the results of the aging treatment of the oxidation catalysts obtained in examples 1 to 3 of the present invention and comparative example 2, followed by the test of the catalytic activity of propylene.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

This example provides a method of preparing an oxidation catalyst, the method comprising the steps of:

(1) 1.7g of Bi (NO) is taken₃)₃·5H₂Adding O into 5mL of concentrated nitric acid (the mass fraction is 68 percent), adding deionized water to dilute to 100mL, preparing a 0.035mol/L bismuth salt solution, adding 6.9mL of the bismuth salt solution and 5g of aluminum oxide powder (the average particle size is 1 mu m) into 50mL of deionized water, stirring for 3h, wherein the mass ratio of bismuth metal to aluminum oxide powder in the bismuth salt solution is 1:100, then carrying out rotary evaporation at 70 ℃, drying a solid product obtained by the rotary evaporation at 110 ℃ for 4h in an air atmosphere, and then roasting at 550 ℃ for 5h to obtain bismuth modified aluminum oxide, which is marked as Bi (1) -Al₂O₃；

(2) 1g of Pt (NO) with the mass content of 18 percent is taken₃)₂Adding deionized water into the solution to dilute the solution to 18mL, preparing a platinum salt solution with the Pt mass concentration of 0.01g/mL, adding 5g of the bismuth modified alumina obtained in the step (1) into 5mL of the platinum salt solution, soaking the platinum salt solution for 2h at room temperature, drying the soaked solid product for 4h at 110 ℃ in an air atmosphere, and roasting the solid product for 3h at 550 ℃ to obtain the oxidation catalysisAgent, noted as Pt (1)/Bi (1) -Al₂O₃。

In the oxidation catalyst obtained in this example, the mass percentage content of Pt is 1%, the mass percentage content of Bi is 1%, and the mass ratio of Pt to Bi is 1: 1.

Example 2

This example provides a method of preparing an oxidation catalyst, the method comprising the steps of:

(1) 1.7g of Bi (NO) is taken₃)₃·5H₂Adding O into 5mL of concentrated nitric acid (mass fraction is 68%), adding deionized water to dilute to 100mL to prepare a 0.035mol/L bismuth salt solution, adding 13.8mL of the bismuth salt solution and 4.9g of aluminum oxide powder (average particle size is 50 microns) into 50mL of deionized water, stirring for 2h, wherein the mass ratio of bismuth metal to aluminum oxide powder in the bismuth salt solution is 2:100, then carrying out rotary evaporation at 60 ℃, drying a solid product obtained by the rotary evaporation at 150 ℃ for 1h in an air atmosphere, and then roasting at 600 ℃ for 3h to obtain bismuth modified aluminum oxide, which is marked as Bi (2) -Al₂O₃；

(2) Taking 1g of Pt with the mass content of 18% (NO)₃)₂Adding deionized water into the solution to dilute the solution to 18mL, preparing a platinum salt solution with the Pt mass concentration of 0.01g/mL, adding 5g of the bismuth modified alumina obtained in the step (1) into 5mL of the platinum salt solution, dipping the platinum salt solution for 3h at room temperature, drying the dipped solid product for 3h at 100 ℃ in an air atmosphere, and roasting the solid product for 1h at 600 ℃ to obtain an oxidation catalyst, namely Pt (1)/Bi (2) -Al₂O₃。

In the oxidation catalyst obtained in this example, the mass percentage content of Pt is 1%, the mass percentage content of Bi is 2%, and the mass ratio of Pt to Bi is 0.5: 1.

Example 3

This example provides a method of preparing an oxidation catalyst, the method comprising the steps of:

(1) 1.7g of Bi (NO) is taken₃)₃·5H₂Adding O into 5mL of concentrated nitric acid (the mass fraction is 68 percent), and adding deionized water for dilutionReleasing to 100mL, preparing to obtain 0.035mol/L bismuth salt solution, adding 27.6mL of the bismuth salt solution and 4.8g of alumina powder (average particle size is 100 mu m) into 50mL of deionized water, stirring for 4h, wherein the mass ratio of bismuth metal to the alumina powder in the bismuth salt solution is 4:100, then carrying out rotary evaporation at 60 ℃, drying a solid product obtained by the rotary evaporation at 100 ℃ for 4h in an air atmosphere, and then roasting at 500 ℃ for 6h to obtain bismuth modified alumina, which is recorded as Bi (4) -Al₂O₃；

(2) Taking 1g of Pt with the mass content of 18% (NO)₃)₂Adding deionized water into the solution to dilute the solution to 18mL, preparing a platinum salt solution with the Pt mass concentration of 0.01g/mL, adding 5g of the bismuth modified alumina obtained in the step (1) into 5mL of the platinum salt solution, dipping the platinum salt solution for 4h at room temperature, drying the dipped solid product for 4h at 150 ℃ in an air atmosphere, and roasting the solid product for 4h at 500 ℃ to obtain an oxidation catalyst, namely Pt (1)/Bi (4) -Al₂O₃。

In the oxidation catalyst obtained in this example, the mass percentage content of Pt is 1%, the mass percentage content of Bi is 4%, and the mass ratio of Pt to Bi is 0.25: 1.

Example 4

This example provides a method of preparing an oxidation catalyst, the method comprising the steps of:

(1) 1.7g of Bi (NO) are taken₃)₃·5H₂Adding O into 5mL of concentrated nitric acid (the concentration is 68% by mass), adding deionized water to dilute to 100mL, preparing 0.035mol/L bismuth salt solution, adding 13.8mL of the bismuth salt solution and 4.9g of aluminum oxide powder (the average particle size is 50 mu m) into 50mL of deionized water, stirring for 2h, wherein the mass ratio of bismuth metal to aluminum oxide powder in the bismuth salt solution is 2:100, then carrying out rotary evaporation at 60 ℃, drying the solid product obtained by rotary evaporation at 150 ℃ for 1h in air atmosphere, and then roasting at 600 ℃ for 3h to obtain bismuth modified aluminum oxide, wherein the mark is Bi (2) -Al₂O₃；

(2) 1g of Pt with the mass content of 36% (NO)₃)₂Solution, adding deionizationDiluting the solution to 18mL by water to prepare a platinum salt solution with the Pt mass concentration of 0.02g/mL, adding 5g of the bismuth modified alumina obtained in the step (1) into 5mL of the platinum salt solution, soaking the solution at room temperature for 3h, drying the soaked solid product at 100 ℃ in an air atmosphere for 3h, and then roasting the dried solid product at 600 ℃ for 1h to obtain an oxidation catalyst, namely Pt (2)/Bi (2) -Al₂O₃。

In the oxidation catalyst obtained in this example, the mass percentage content of Pt is 2%, the mass percentage content of Bi is 2%, and the mass ratio of Pt to Bi is 1: 1.

Example 5

This example provides a method for preparing an oxidation catalyst, which is only to add 5g of bismuth-modified alumina to 5mL of deionized water in step (2) and then to add 0.1mL of a platinum salt solution, as compared to example 2.

In the oxidation catalyst obtained in this example, the mass percentage content of Pt is 0.02%, the mass percentage content of Bi is 2%, and the mass ratio of Pt to Bi is 0.01: 1.

Example 6

This example provides a method for preparing an oxidation catalyst, which is only to add 5g of bismuth-modified alumina in step (2) to 1mL of a platinum salt solution, as compared with example 2.

In the oxidation catalyst obtained in this example, the mass percentage content of Pt is 0.2%, the mass percentage content of Bi is 2%, and the mass ratio of Pt to Bi is 0.1: 1.

Example 7

This example provides a method for preparing an oxidation catalyst, which is only to add 5g of bismuth-modified alumina in step (2) to 19mL of a platinum salt solution, as compared with example 2.

In the oxidation catalyst obtained in this example, the mass percentage content of Pt is 3.8%, the mass percentage content of Bi is 2%, and the mass ratio of Pt to Bi is 1.9: 1.

Example 8

This example provides a preparation method of an oxidation catalyst, which is only to take 1.1mL of bismuth salt solution and 5g of alumina powder in step (1) and add them into 50mL of deionized water for stirring, compared with example 2; in step (2), 5g of bismuth-modified alumina was added to 5mL of deionized water, followed by 0.4mL of platinum salt solution.

In the oxidation catalyst obtained in this example, the mass percentage content of Pt was 0.08%, the mass percentage content of Bi was 0.16%, and the mass ratio of Pt to Bi was 0.5: 1.

Example 9

This example provides a preparation method of an oxidation catalyst, which is only compared with example 2, in the step (1), 41.4mL of bismuth salt solution and 4.7g of alumina powder are added into 50mL of deionized water and stirred; in the step (2), 5g of bismuth-modified alumina was added to 15mL of a platinum salt solution.

In the oxidation catalyst obtained in this example, the mass percentage content of Pt is 3%, the mass percentage content of Bi is 6%, and the mass ratio of Pt to Bi is 0.5: 1.

Comparative example 1

This comparative example provides a method for preparing an oxidation catalyst, which is only in step (1) of adding 5g of bismuth-modified alumina to 25mL of a platinum salt solution, as compared with example 2.

In the oxidation catalyst obtained in the comparative example, the mass percentage of Pt is 5%, the mass percentage of Bi is 2%, and the mass ratio of Pt to Bi is 2.5: 1.

Comparative example 2

This comparative example provides a method of preparing an oxidation catalyst, which, in comparison with example 2, consists only in eliminating step (1) and in adding alumina powder directly to 25mL of platinum salt solution for the subsequent operation, to obtain an alumina-supported platinum catalyst, noted Pt/Al₂O₃Wherein the mass percentage of Pt is 5%.

Comparative example 3

This comparative example provides a preparation method of an oxidation catalyst, which is the same as example 2 except that the impregnation loading of platinum is completed by performing step (2) first and then the rotary evaporation loading of bismuth is completed by performing step (1) as compared with example 2.

Taking examples 1-3 and comparative example 2 as examples, XRD tests are carried out on the obtained oxidation catalysts, and the test results are shown in figure 1, and as can be seen from figure 1, the oxidation catalysts obtained in examples 1-3 do not show obvious species characteristic peaks of platinum and bismuth, which shows that the species dispersibility of bismuth metal and platinum metal is better by the preparation method of the invention.

The oxidation catalysts obtained in examples 1 to 9 and comparative examples 1 to 3 were subjected to CO and propylene catalytic activity tests under the following conditions: placing 75mg of newly prepared oxidation catalyst in a fixed bed reactor with an inner diameter of 5mm, continuously introducing reaction gas into the fixed bed reactor, and adding [ CO ] into the reaction gas]＝4000ppm，[C₃H₆]＝1000ppm，[O₂]＝10vol.％，N₂The space velocity is 240000 mL/g.h for balance gas^-1. In examples 1 to 3 and comparative example 2, the obtained oxidation catalysts were subjected to CO and propylene catalytic activity tests, and the results are shown in fig. 2 and 3, respectively.

The oxidation catalysts obtained in examples 1 to 9 and comparative examples 1 to 3 were subjected to aging treatment under the conditions: the catalyst is heated at 700 ℃ to [ H ]₂O]10 vol.% of H₂And (3) aging for 10 hours under the O/Air mixed atmosphere, wherein the gas flow is 125 mL/min. Among them, the aged catalysts obtained in examples 1 to 3 and comparative example 2 were respectively referred to as Pt (1)/Bi (1) -Al₂O₃-HTA、Pt(1)/Bi(2)-Al₂O₃-HTA、Pt(1)/Bi(4)-Al₂O₃HTA and Pt/Al₂O₃-HTA。

And (3) carrying out CO and propylene catalytic activity tests on the aged oxidation catalyst under the following test conditions: placing 75mg of newly prepared oxidation catalyst in a fixed bed reactor with an inner diameter of 5mm, continuously introducing reaction gas into the fixed bed reactor, and adding [ CO ] into the reaction gas]＝4000ppm，[C₃H₆]＝1000ppm，[O₂]＝10vol.％，N₂The space velocity is 240000 mL/g.h for balance gas^-1. Taking examples 1-3 and comparative example 2 as examples, the oxidation catalysts obtained therefrom were aged and tested for catalytic activity of CO and propylene, and the results are shown in fig. 4 and 5, respectively.

The results of the CO catalytic activity tests of the oxidation catalysts obtained in the above examples and comparative examples are shown in Table 1, and the results of the propylene catalytic activity tests are shown in Table 2.

TABLE 1

TABLE 2

In tables 1 and 2, "-" indicates that the catalytic activity test under the conditions was not performed.

From tables 1 and 2, the following points can be seen:

(1) it can be seen from a combination of examples 1-4 that the oxidation catalysts provided in examples 1-4 were tested for CO catalytic activity, T₅₀The temperature is lower than 170 ℃, T₉₀Temperature lower than 175 ℃ and T in the test of catalytic activity of propylene₅₀The temperature is lower than 170 ℃, T₉₀The temperature was less than 180 ℃, thus showing that the oxidation catalysts of examples 1-4 have high low-temperature catalytic activity.

After aging, the oxidation catalysts provided in examples 1-4 were tested for CO catalytic activity, T₅₀The temperature is lower than 190 ℃, T₉₀The temperature is lower than 210 ℃, and in the propylene catalytic activity test, T₅₀The temperature is lower than 220 ℃, T₉₀The temperature was less than 250 c, thus showing that the oxidation catalysts of examples 1-4 have higher hydrothermal stability.

(2) By combining examples 2, 5-7 and comparative example 1, it can be seen that the mass ratio of Pt to Bi in example 2 is 0.5:1 and the mass percentage of Pt is 1%, compared to the mass ratios of Pt to Bi in examples 5-7 and comparative example 1 of 0.01:1, 0.1:1, 1.9:1 and 2.5:1, respectively, the mass ratios of CO and propylene in examples 5, 6 and 1 are catalytic to CO and propylene in example 5, 6 and 1Chemical activity test of T₅₀The temperature is higher than that of the embodiment 2, and in the embodiment 7 and the comparative example 1, the addition amount of Pt is higher than that of the embodiment 2, and the mass percentage content of Pt is respectively 3.8% and 5%, so that the production cost of the catalyst is greatly increased, thereby showing that the invention can enable the catalyst to have good low-temperature catalytic activity and reduce the production cost by controlling the mass ratio of Pt and Bi and preferably controlling the mass ratio of Pt and Bi in a specific range.

(3) As can be seen from the combination of example 2 and examples 8 to 9, the mass% of Pt in example 2 was 1% and the mass% of Bi was 2%, as compared with the mass ratios of Pt to Bi in examples 8 and 9, in which the mass% of Pt was 0.08% and 3% and the mass% of Bi was 0.16% and 6%, respectively, and the T values in the catalytic activity tests of CO and propylene in examples 8 to 9 were 0.16% and 6%, respectively₅₀The temperature is higher than that of the embodiment 2, so that the invention needs to control the mixture ratio of the Bi and the Pt, and more preferably controls the mass percentage content of the Bi and the Pt to be in a specific range, so that the catalyst has good low-temperature catalytic activity.

(4) By combining example 2 and comparative example 2, it can be seen that comparative example 2 is compared with example 2 only in that the oxidation catalyst does not contain Bi metal, and the mass percent of Pt is 5%, and T of the CO and propylene catalytic activity test in comparative example 2₅₀And T₉₀Both temperatures are greater than T for the catalytic activity test on CO and propylene after aging of example 2₅₀And T₉₀The method is also larger than the embodiment 2, thereby showing that the low-temperature catalytic activity and the aging stability can be improved by adding the Bi metal to prepare the oxidation catalyst, the consumption of noble metal is reduced, and the production cost is saved.

(5) By combining example 2 and comparative example 3, it can be seen that comparative example 3 is compared with example 2 only in that impregnation loading of platinum is performed first and then loading of bismuth is performed, and T of the CO and propylene catalytic activity test in comparative example 3₅₀And T₉₀The temperatures were all greater than in example 2; t for CO and propylene catalytic Activity test in comparative example 3 after aging treatment₅₀And T₉₀The temperature is also higher than that of the example 2, thereby showing that the method of the invention can improve the catalysis by loading Bi firstly and then impregnating and loading PtLow temperature catalytic activity and aging stability of the catalyst.

In conclusion, the oxidation catalyst provided by the invention is low in production cost, has higher low-temperature catalytic activity and hydrothermal stability, is simple to operate and beneficial to industrial popularization, has a good catalytic oxidation effect on CO and propylene, and can be used in the field of diesel engine tail gas treatment.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims (10)

1. An oxidation catalyst, characterized in that the oxidation catalyst comprises a carrier and platinum metal and bismuth metal supported on the carrier;

the mass ratio of the platinum metal to the bismuth metal is (0.01-2) to 1.

2. The oxidation catalyst as set forth in claim 1 wherein the support comprises alumina;

preferably, the alumina is in powder form;

preferably, the support has an average particle size of 1 to 100 μm;

preferably, the mass percentage content of the platinum metal in the oxidation catalyst is 0.01-4%;

preferably, the mass percentage content of the bismuth metal in the oxidation catalyst is 1-7%;

preferably, the mass ratio of the platinum metal to the bismuth metal is (0.25-2): 1.

3. A method for preparing an oxidation catalyst according to claim 1 or 2, comprising the steps of:

(1) mixing the bismuth salt solution and the carrier for the first time, and then sequentially carrying out rotary evaporation, drying and roasting to obtain a bismuth modified carrier;

(2) and (2) mixing and impregnating the bismuth modified carrier obtained in the step (1) and a platinum salt solution for the second time, and then drying and roasting the mixture in sequence to obtain the oxidation catalyst.

4. The method according to claim 3, wherein the bismuth salt solution of step (1) comprises Bi (NO)₃)₃A solution;

preferably, the molar concentration of bismuth metal in the bismuth salt solution is 0.02-0.06 mol/L;

preferably, the platinum salt solution of step (1) comprises Pt (NO)₃)₂A solution;

preferably, the mass concentration of the platinum metal in the platinum salt solution is 0.001-0.1 g/mL.

5. The production method according to claim 3 or 4, wherein the primary mixing in the step (2) comprises adding the bismuth salt solution and the carrier to the solvent to stir;

preferably, the solvent comprises deionized water;

preferably, the mass ratio of the bismuth metal to the carrier in the bismuth salt solution is (1-7) to 100;

preferably, the stirring time is 2-4 h.

6. The method according to any one of claims 3 to 5, wherein the temperature of the rotary evaporation in the step (1) is 60 to 80 ℃;

preferably, the temperature for drying in step (1) is 100-150 ℃;

preferably, the dry atmosphere in step (1) is air;

preferably, the drying time of the step (1) is 1-4 h;

preferably, the roasting temperature in the step (1) is 500-600 ℃;

preferably, the roasting time of the step (1) is 3-6 h.

7. The production method according to any one of claims 3 to 6, wherein the mass ratio of the platinum metal to the bismuth-modified support in the platinum salt solution in step (2) is (0.01 to 4): 100;

preferably, the time of the impregnation is 2 to 4 hours.

8. The method according to any one of claims 3 to 7, wherein the drying temperature in step (2) is 100 ℃ to 150 ℃;

preferably, the dry atmosphere in step (2) is air;

preferably, the drying time of the step (2) is 2-4 h;

preferably, the roasting temperature in the step (2) is 500-600 ℃;

preferably, the roasting time of the step (2) is 1-4 h.

9. The method according to any one of claims 3 to 8, characterized in that it comprises the following steps:

(1) adding a bismuth salt solution with the molar concentration of 0.02-0.06mol/L and aluminum oxide into deionized water, stirring for 2-4h, wherein the mass ratio of bismuth metal to aluminum oxide in the bismuth salt solution is (1-7):100, then carrying out rotary evaporation at 60-80 ℃, drying a solid product obtained by rotary evaporation at 100-150 ℃ for 1-4h in an air atmosphere, and then roasting at 500-600 ℃ for 3-6h to obtain bismuth modified aluminum oxide;

(2) adding the bismuth modified alumina obtained in the step (1) into a platinum salt solution with the mass concentration of 0.001-0.1g/mL, mixing and soaking for 2-4h, wherein the mass ratio of platinum metal to bismuth modified alumina in the platinum salt solution is (0.01-4):100, drying the soaked solid product in an air atmosphere at 100-150 ℃ for 2-4h, and then roasting at 500-600 ℃ for 1-4h to obtain the oxidation catalyst.

10. Use of an oxidation catalyst according to claim 1 or 2 in the catalytic oxidation of diesel exhaust gases.

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