CN108097301A - One kind is used for NH3Composite catalyst of-SCR reactions and its preparation method and application - Google Patents

Abstract

The invention provides a composite catalyst for NH ₃ -SCR reaction and its preparation method and application. The composite catalyst uses molecular sieve as a carrier, and uses transition metal loaded on the molecular sieve through ion exchange as an active component. The method of the invention comprises: firstly mixing the molecular sieve with the transition metal salt solution to carry out ion exchange reaction, and then through solid-liquid separation and roasting to obtain the AEI molecular sieve catalyst. The raw materials used in the present invention are non-toxic and harmless, and the preparation method is simple and easy. The prepared catalyst has the characteristics of high catalytic activity, low N ₂ O generation, wide operating temperature window, and can adapt to high space velocity reaction conditions. Catalytic purification of mobile source exhaust and stationary source flue gas nitrogen oxides represented by vehicle exhaust.

Description

A kind of composite catalyst for NH3-SCR reaction and its preparation method and application

technical field

The invention belongs to the field of environmental pollution control, and relates to a composite catalyst for NH ₃ -SCR reaction and its preparation method and application, especially to an AEI molecular sieve catalyst for NH ₃ -SCR reaction and its preparation method and mobile The use of catalytic purification of nitrogen oxides in source tail gas and/or stationary source flue gas.

Background technique

Nitrogen oxide (NOx) is an important pollutant in air pollution. It can cause major environmental problems such as acid rain, smog, and photochemical smog. It not only has a major hazard to the ecological environment, but also endangers human health. Therefore, NOx removal is a The top priority of environmental protection today. At present, the selective catalytic reduction of NOx (NH ₃ -SCR) using NH ₃ as a reducing agent has been widely used in stationary source flue gas due to its high conversion rate of NOx, no secondary pollution of N ₂ generated, and low reaction temperature. Denitrification and diesel vehicle exhaust purification.

High-efficiency NH ₃ -SCR catalyst is the core of this technology. At present, the V ₂ O ₅ -WO ₃ (MoO ₃ )/TiO ₂ system has the characteristics of high catalytic activity and good resistance to SO ₂ poisoning, and has been widely used in the NH ₃ -SCR reaction. However, there are still many problems in this system, such as: narrow operating window, low _N2 selectivity at high temperature, and biological toxicity of active component V. However, the non-toxic and harmless non-V catalysts currently researched and developed, such as oxide catalysts Ce-W, Fe-Ti, Cu-based or Fe-based molecular sieve catalysts based on ZSM-5 and beta molecular sieves, all have varying degrees of temperature There are problems such as narrow operating window, poor hydrothermal stability and poor HC poisoning ability.

In recent years, small-pore molecular sieve catalysts represented by the CHA configuration have both high catalytic activity and high hydrothermal stability, have attracted widespread attention, and have been applied to the purification of NOx from diesel vehicle exhaust. For example, CN101065321A and CN105314648A all disclose CHA configuration molecular sieve catalysts for NH ₃ -SCR. However, the current molecular sieve catalysts with CHA as the configuration are expensive, and the hydrothermal stability still needs to be further improved.

Therefore, it is a huge challenge to develop catalysts with high catalytic activity, wide temperature operating window, low price and high hydrothermal stability.

Contents of the invention

The purpose of the present invention is to provide a composite catalyst for NH ₃ -SCR reaction and its preparation in order to overcome the problems of narrow temperature operating window, poor hydrothermal stability and poor HC poisoning ability in existing NH ₃ -SCR molecular sieve catalysts The method and application, especially an AEI molecular sieve catalyst for NH ₃ -SCR reaction, its preparation method and the application of catalytic purification of nitrogen oxides in mobile source tail gas and/or stationary source flue gas.

To achieve the above object, the present invention adopts the following technical solutions:

In the first aspect, the present invention provides a composite catalyst. The composite catalyst uses molecular sieve as a carrier and transition metal loaded on the molecular sieve through ion exchange as an active component.

The following are preferred technical solutions of the present invention, but not as limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

Preferably, the specific surface area of the composite catalyst is 350m ² /g-800m ² /g, such as 350m ² /g, 500m ² /g, 600m ² /g, 700m ² /g or 800m ² /g, etc., but not Not limited to the listed values, other unlisted values within the range of values are also applicable.

As a preferred technical solution of the composite catalyst of the present invention, the molecular sieve is an AEI molecular sieve.

In this preferred technical solution, the composite catalyst is an AEI molecular sieve catalyst with aluminum-rich AEI molecular sieve as the carrier and transition metal as the active component, which is a catalyst that can be used for NH ₃ -SCR to achieve high-efficiency catalysis. Among them, the structure of AEI molecular sieve is similar to that of CHA, both have a three-dimensional eight-membered ring (0.38nm×0.38nm) channel structure, which are arranged in a staggered manner and connected by six-membered rings and four-membered rings. The difference is that the double six-membered rings in the AEI structure are mirror-symmetrically distributed, while the double six-membered rings are distributed in parallel in the CHA structure. The specific structure of AEI molecular sieve determines that it has a good application prospect in the field of NH ₃ -SCR.

Preferably, the AEI molecular sieve is an aluminum-rich AEI molecular sieve, and the silicon-aluminum ratio Si/Al of the aluminum-rich AEI is 15-2, such as 15, 13, 10, 8, 6, 4 or 2, etc., but not Not limited to the numerical values listed, other unlisted numerical values within this numerical range are also applicable, preferably 12-5.

Preferably, the transition metal is any one or a combination of at least two of copper, iron, cerium or manganese. Typical but non-limiting examples of the combination include: a combination of copper and iron, a combination of iron and cerium, A combination of copper and cerium, a combination of copper, iron and cerium, a combination of copper and manganese, a combination of iron and manganese, a combination of copper, iron and manganese, etc., preferably copper and/or iron. When the at least two transition metals mentioned in the present invention are combined, there is no limitation on the mixing ratio of various transition metals, and it can be in any ratio.

Preferably, the active component accounts for 1% to 10% of the total mass of the composite catalyst, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% etc., but not limited to the listed values, other unlisted values within the range of values are also applicable, preferably 2% to 5%.

In the present invention, the loading capacity of the active components on the composite catalyst can be adjusted by adjusting the concentration of the transition metal salt solution and/or the number of ion exchange reactions.

In a second aspect, the present invention provides a method for preparing the composite catalyst as described in the first aspect, said method comprising the following steps:

(1) The molecular sieve is mixed with the salt solution of the transition metal for ion exchange to obtain a mixed solution;

(2) solid-liquid separation is carried out to the mixed solution obtained in step (1), to obtain a solid mixture;

(3) Calcining the solid mixture obtained in step (2) to obtain a composite catalyst.

In the method of the present invention, the ion exchange reaction in step (1) can be carried out multiple times, which is adjusted according to the required load.

In the method of the present invention, by adjusting the number of ion exchange reactions and/or the concentration of the transition metal salt solution in step (1), the loading capacity of the active components on the composite catalyst can be regulated.

As a preferred technical solution of the method of the present invention, the transition metal salt solution in step (1) is any one or a combination of at least two of copper salts, iron salts, cerium salts or manganese salts. Typical but non-limiting examples of such combinations are: combinations of copper salts and iron salts, combinations of iron salts and cerium salts, combinations of copper salts and cerium salts, combinations of copper salts, iron salts and cerium salts, copper salts and manganese The combination of salt, the combination of iron salt and manganese salt, the combination of copper salt, iron salt and manganese salt, etc., is preferably a salt solution of copper salt and/or iron salt.

Preferably, the transition metal salt solution in step (1) is any one or a combination of at least two of transition metal sulfate solution, transition metal nitrate solution or transition metal acetate solution. Typical but non-limiting examples of such combinations are: a combination of a transition metal sulfate solution and a transition metal nitrate solution, a combination of a transition metal nitrate solution and a transition metal acetate solution, a transition metal sulfate solution , a combination of a transition metal nitrate solution and a transition metal acetate solution, etc.

Preferably, the concentration of the transition metal salt solution in step (1) is 0.01 mol/L～1.0 mol/L, preferably, the concentration of the transition metal salt solution in step (1) is 0.01 mol/L～1.0 mol/L, such as 0.01mol/L, 0.05mol/L, 0.1mol/L, 0.2mol/L, 0.5mol/L, 0.7mol/L or 1.0mol/L, etc., but not limited to the listed values, Other unrecited values within this value range are also applicable. It is adjusted according to the required load.

In the present invention, the concentration of the transition metal salt solution is one of the factors affecting the AEI molecular sieve catalyst. Compared with molecular sieves (such as AEI molecular sieves), the concentration of transition metal salt solution is too high or too low will eventually affect the catalytic performance of the catalyst. Take AEI molecular sieve as an example: for a certain quality of AEI molecular sieve, if the concentration of the transition metal salt solution is too low (less than 0.01mol/L), the loading of active components on the AEI molecular sieve will be too small, and the catalyst will be reduced. The medium and low temperature catalytic activity; and the concentration of transition metal salt solution is too high (higher than 1.0mol/L), the metal ions loaded on the molecular sieve will be too high, and agglomeration will occur during the roasting process, resulting in AEI molecular sieve catalyst under high temperature conditions lower catalytic performance.

Preferably, the molecular sieve in step (1) is an AEI molecular sieve, preferably an aluminum-rich AEI molecular sieve, and the silicon-aluminum ratio Si/Al of the aluminum-rich AEI is 15-2, preferably 12-5.

Preferably, the ratio of the mass of the molecular sieve in step (1) to the volume of the transition metal salt solution is 1g:(20mL～200mL), such as 1g:50mL, 1g:70mL, 1g:100mL, 1g:130mL, 1g: 150mL, 1g:170mL or 1g:200mL, etc., but not limited to the listed values, other unlisted values within this range are also applicable, preferably 1g:(50mL～100mL).

Preferably, the reaction temperature of the ion exchange reaction in step (1) is 20°C to 80°C, such as 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, etc., but not limited to For the listed values, other unlisted values within the range of values are also applicable. In the present invention, the temperature condition of the ion exchange reaction is one of the factors affecting the performance of the AEI molecular sieve catalyst. Compared with the AEI molecular sieve, the excessively high temperature of the ion exchange (higher than 80° C.) will lead to the accumulation of transition metal ions, and in the roasting process Medium agglomeration reduces the catalytic performance of AEI molecular sieve catalysts under high temperature conditions. If the ion exchange temperature is too low (below 20°C), the loading of active components on the AEI molecular sieve catalyst will be too small, which will reduce the medium and low temperature activity of the catalyst.

Preferably, the ion exchange reaction in step (1) is carried out under stirring conditions.

Preferably, the reaction time of the ion exchange reaction in step (1) is 5h to 24h, such as 5h, 8h, 12h, 14h, 16h, 18h, 20h, 22h, or 24h, etc., but not limited to the listed values, Other unrecited values within this value range are also applicable.

Preferably, the method of solid-liquid separation in step (2) includes, but is not limited to, any one or a combination of at least two of suction filtration, filtration or centrifugation.

As a preferred technical solution of the method of the present invention, the method further includes performing step (2)' after step (2) solid-liquid separation and before step (3) roasting: washing and drying the solid mixture.

Preferably, in step (2)', the drying temperature is 80°C to 105°C, such as 80°C, 83°C, 85°C, 87°C, 90°C, 93°C, 95°C, 97°C, 100°C or 105°C °C, etc., but not limited to the listed values, other unlisted values within this range of values are also applicable, preferably 100 °C.

Preferably, in step (2)', the drying time is 12h to 36h, such as 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h or 36h, etc., but not only Limited to the numerical value listed, other unlisted numerical values within this numerical range are also applicable, preferably 12h.

As a preferred technical solution of the method of the present invention, the temperature of the roasting in step (3) is 450°C to 650°C, such as 450°C, 470°C, 500°C, 530°C, 550°C, 570°C, 600°C, 630°C °C or 650 °C, etc., but not limited to the listed values, and other unlisted values within this range are also applicable.

In the present invention, the calcination temperature is also one of the factors affecting the AEI molecular sieve catalyst. Compared with molecular sieves (such as AEI molecular sieves), too low or too high a calcination temperature will affect the catalyst performance of the catalyst. Take AEI molecular sieve as an example: if the calcination temperature is too low (less than 450°C), sulfate, nitrate or acetate will remain on the surface of the catalyst and cover the active sites, thereby reducing the catalytic performance of the AEI molecular sieve catalyst. If the calcination temperature is too high (higher than 650°C), the metal ions loaded on the molecular sieve will migrate and agglomerate on the AEI molecular sieve during the calcination process, and further oxidation will occur. At the same time, the configuration of the AEI molecular sieve will be destroyed, which will easily cause The deactivation of the catalyst reduces the catalytic performance of the AEI molecular sieve catalyst.

Preferably, the calcination time in step (3) is 3h to 8h, such as 3h, 4h, 5h, 6h, 7h or 8h, etc., but it is not limited to the listed values, and other unlisted values within this range are also applicable .

As a further preferred technical solution of the method of the present invention, the method comprises the following steps:

(1) Mix the AEI molecular sieve with the transition metal salt solution with a concentration of 0.01mol/L～1.0mol/L according to the mass-to-volume ratio of 1g:(20mL～200mL), and carry out ionization under stirring at 20℃～80℃. Exchange reaction, reaction 5h ~ 24h, to obtain a mixed solution;

(2) Suction filtering the mixed solution obtained in step (1) to obtain a solid mixture;

(3) Wash the solid mixture obtained in step (2), dry at 80°C-105°C for 12h-36h, and then roast at 450°C-650°C for 3h-8h to obtain the AEI molecular sieve catalyst.

In a third aspect, the present invention provides the use of the composite catalyst as described in the first aspect, the composite catalyst is used in the field of catalytic purification of nitrogen oxides, preferably the carrier in the composite catalyst is AEI molecular sieve to achieve better catalytic effect .

Preferably, the composite catalyst is used for NH ₃ -SCR reaction.

Preferably, the composite catalyst is used for catalytic purification of nitrogen oxides in tail gas from mobile sources and/or flue gas from stationary sources.

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

(1) The composite catalyst of the present invention (such as AEI molecular sieve catalyst) has a wide temperature operating window, and can maintain a nitrogen oxide removal rate of more than 80% in the range of 200°C to 650°C.

(2) The composite catalyst of the present invention (such as AEI molecular sieve catalyst) has a high specific surface area and multiple active sites, and compared with other types of molecular sieve catalysts, it has stronger thermal stability and water resistance, and excellent N _generation selective,

(3) The composite catalyst of the present invention adopts non-toxic and harmless components, which will not cause harm to human health and ecological environment, and the preparation method is simple and feasible.

(4) The composite catalyst of the present invention, especially the AEI molecular sieve catalyst, is especially suitable for the purification of motor vehicle exhaust and the low-temperature denitrification of flue gas from stationary sources.

Description of drawings

Fig. 1 is the catalytic activity figure of catalyst described in the example 1 of the present invention;

Fig. 2 is the _N2O generation figure of catalyst described in the example 1 of the present invention;

Fig. 3 is the catalytic activity figure of catalyst described in the example 2 of the present invention;

Figure 4 is a graph of _N2O formation for the catalyst described in Example 2 of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation methods.

The specific embodiment part of the present invention provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction and its preparation method and application. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and ion-exchange transition metal as an active component.

In the present invention, the "ion-exchange transition metal" refers to a transition metal supported on a molecular sieve through ion exchange.

Its preparation method comprises the following steps:

(1) AEI molecular sieve is mixed with transition metal salt solution to carry out ion exchange reaction to obtain a mixed solution;

(2) The mixed solution obtained in step (1) is subjected to solid-liquid separation to obtain a solid mixture;

(3) Calcining the solid mixture obtained in step (2) to obtain an AEI molecular sieve catalyst.

The following are typical but non-limiting embodiments of the present invention:

Example 1:

This embodiment provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction and its preparation method and application. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and ion-exchange metal copper as an active component.

Its preparation method is:

(1) Prepare 0.1mol/L copper sulfate solution, mix aluminum-rich AEI molecular sieve with copper sulfate solution, wherein the mass ratio of AEI molecular sieve to copper sulfate solution is 1g:80mL, stir at 25°C for 12h for ionization exchange reaction to obtain a mixed solution;

(2) The mixed solution obtained in step (1) is suction filtered and washed 3 times to obtain a filter cake;

(3) Put the filter cake obtained in step (2) into an oven and dry it at 100° C. for 12 h, then bake it at 550° C. for 5 h in a muffle furnace to obtain a powdered Cu-AEI catalyst with AEI configuration. The obtained catalyst is pressed into tablets, crushed, sieved, and 20-40 meshes are taken for later use.

The obtained Cu-AEI catalyst is used for NH ₃ -SCR reaction, wherein the composition of the reaction mixture is: [NO]=[NH ₃ ]=500ppm, [O ₂ ]=5%, [H ₂ O]=5%, N ₂ is used as the balance gas, the total gas flow rate is 500mL/min, and the reaction temperature is between 150°C and 550°C.

The amount of catalyst used is 25mg, 50mg and 100mg respectively, the corresponding space velocities are 800,000h ^-1 , 400,000h ^-1 and 200,000h ^-1 respectively, and the corresponding condition numbers are A, B and C respectively. NO and NH ₃ and the by-products N ₂ O and NO ₂ were measured using an infrared gas cell.

The catalytic activity of the obtained catalyst was carried out on a fixed reaction bed, and the composition of the reaction gas was measured until the reaction was carried out to a steady state. In the three test cases of A, B and C, the catalytic activity of the catalyst was shown in Figure 1. The N ₂ O The amount generated is shown in Figure 2.

It can be seen from Fig. 1 that the catalyst has excellent catalytic activity of nitrogen oxides. In the case of conditions B and C, the conversion rate of nitrogen oxides of the catalyst is above 80% in the temperature range of 200°C to 550°C. Even in the very severe condition A, the catalyst can maintain a nitrogen oxide conversion rate of more than 80% in the temperature range of 225°C to 550°C.

It can be seen from Figure 2 that in the temperature range of 150°C to 550°C, the amount of N ₂ O produced in the three cases is all below 10ppm, which has excellent N ₂ selectivity. The above shows that the catalyst has very excellent NH ₃ -SCR catalytic performance.

Example 2:

This embodiment provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction and its preparation method and application. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and metal copper as an active component.

Its preparation method is with reference to the preparation method in Example 1, difference is: the copper nitrate solution of preparation 0.3mol/L in the step (1), and the quality of AEI molecular sieve and the volume ratio of copper nitrate solution are 1g:50mL, at 50 Stirring at ℃ for 8h for ion exchange reaction.

The obtained Cu-AEI catalyst was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1. In the three test cases of A, B and C, the catalytic activity of the catalyst is shown in Figure 3, and the amount of N ₂ O produced is shown in Figure 4.

It can be seen from Figure 3 and Figure 4 that the catalyst in this example can maintain a NO conversion rate of more than 80% under the three conditions of A, B and C in the temperature range of 225 ° C to 550 ° C, and the N ₂ O produced at the same time The contents are all below 10ppm, with excellent _N2 selectivity.

Example 3:

This embodiment provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction and its preparation method and application. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and metal iron as an active component.

Its preparation method is with reference to the preparation method in Example 1, difference is: the ferric nitrate solution of preparation 0.1mol/L in the step (1), and the quality of AEI molecular sieve and the volume ratio of ferric nitrate solution are 1g:100mL, at 35 Stirring at ℃ for 24h for ion exchange reaction.

The obtained Fe-AEI catalyst was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1.

Under the condition C of the Fe-AEI catalyst prepared in this embodiment, the conversion rate of nitrogen oxides of the catalyst is more than 60% in the temperature range of 250°C to 450°C; , the amount of N ₂ O produced in the three cases is all below 15ppm, and has very excellent NH ₃ -SCR catalytic performance.

Example 4:

This example provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction and its preparation method and application. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and supports metal copper and cerium as active components.

Its preparation method is with reference to the preparation method in Example 1, difference is: in the step (1), prepare the copper nitrate and cerium nitrate mixed solution of 0.1mol/L and 0.1mol/L, and the quality of AEI molecular sieve and the volume of mixed solution The ratio is 1g:150mL, and the ion exchange reaction is carried out by stirring at 25°C for 30h.

The obtained Cu/Ce-AEI catalyst was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1.

The obtained Cu/Ce-AEI catalyst was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1.

In the case of the Cu/Ce-AEI catalyst prepared in this example, under condition C, the conversion rate of nitrogen oxides of the catalyst is above 80% in the temperature range of 200°C to 500°C; Within the range, the N ₂ O production in the three cases is below 10ppm, which has very excellent NH ₃ -SCR catalytic performance.

Example 5:

This embodiment provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction and its preparation method and application. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and metal copper as an active component.

Its preparation method refers to the preparation method in Example 1, the difference is that in step (3), the calcination temperature is 650°C, and the calcination time is 6h.

The obtained Cu-AEI catalyst was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1.

The obtained Cu-AEI catalyst is used for NH ₃ -SCR reaction. Under condition C, the conversion rate of nitrogen oxides of the catalyst is above 80% in the temperature range of 200°C to 550°C; In the temperature range, the amount of N ₂ O generated in the three cases is below 10ppm, which has very excellent NH ₃ -SCR catalytic performance.

Comparative example 1:

This comparative example provides a CHA configuration molecular sieve catalyst for NH ₃ -SCR reaction, which is obtained from commercial sources.

It was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1.

Under the condition C of the catalyst, the nitrogen oxide conversion rate of the catalyst is only 80% in the high temperature range of 450° C. to 550° C., and the performance is worse than that of the AEI catalyst described in this application.

Comparative example 2:

This comparative example provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and metal copper as an active component.

Its preparation method refers to the preparation method in Example 1, the difference is: the concentration of the copper sulfate solution in step (1) is 1.2mol/L, that is, the concentration of the copper sulfate solution is too high.

The obtained Cu-AEI catalyst was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1.

Under condition C of the catalyst, in the high temperature range of 400°C to 550°C, the highest conversion rate of nitrogen oxides of the catalyst is only 80%, and the content of N ₂ O generated in the three cases is more than 10ppm. It can be seen that due to If there are too many active components, agglomeration occurs, which reduces the high temperature selectivity of the catalyst.

Comparative example 3:

This comparative example provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and metal copper as an active component.

Its preparation method refers to the preparation method in Example 1, the difference is: the concentration of the copper sulfate solution in step (1) is 0.005mol/L, that is, the concentration of the copper sulfate solution is too low.

The obtained Cu-AEI catalyst was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1.

In the case of catalyst condition C, the highest conversion rate of nitrogen oxides of the catalyst is only 76% within the temperature range of 150°C to 350°C; it can be seen that the low-temperature activity is significantly reduced due to too few active components.

Comparative example 4:

This comparative example provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and metal copper as an active component.

Its preparation method refers to the preparation method in Example 1, with the difference that: the calcination temperature in step (3) is 400° C., that is, the calcination temperature is relatively low.

The obtained Cu-AEI catalyst was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1.

In the case of catalyst condition C, within the temperature range of 150° C. to 550° C., the highest conversion rate of nitrogen oxides of the catalyst is only 85%, which shows that the catalytic performance is obviously reduced.

Comparative example 5:

This comparative example provides an AEI molecular sieve catalyst for NH ₃ -SCR reaction. The AEI molecular sieve catalyst uses AEI molecular sieve as a carrier and metal copper as an active component.

Its preparation method refers to the preparation method in Example 1, with the difference that: the calcination temperature in step (3) is 750° C., that is, the calcination temperature is relatively high.

The obtained Cu-AEI catalyst was used for NH ₃ -SCR reaction, the reaction conditions were the same as those in Example 1, and the catalytic activity testing method was the same as in Example 1.

In the case of catalyst condition C, the highest conversion rate of nitrogen oxides of the catalyst is only 75% in the temperature range of 400°C to 550°C; in the temperature range of 350°C to 500°C, the N ₂ O The generation amount of 15ppm is more than 15ppm, it can be seen that the calcination at too high temperature makes the surface active components of the catalyst agglomerate, and then reduces the _N2 selectivity.

Based on the above examples and comparative examples, it can be seen that the AEI molecular sieve catalyst of the present invention has a wide temperature operating window, which can maintain a high removal rate of nitrogen oxides in the range of 200 ° C to 550 ° C, and nitrogen oxides The material removal rate can reach more than 80%; at the same time, the AEI molecular sieve catalyst of the present invention has high specific surface area and multiple active sites, and has stronger thermal stability and water resistance compared with other types of molecular sieve catalysts, and excellent N ₂ Generate selectivity.

The applicant declares that the present invention illustrates the detailed methods of the present invention through the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed methods, that is, it does not mean that the present invention must rely on the above-mentioned detailed methods to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

Claims (10)

1. A composite catalyst, characterized in that, the composite catalyst is a carrier with molecular sieve, and the transition metal loaded on the molecular sieve by ion exchange is an active component. 2 . The composite catalyst according to claim 1 , characterized in that, the specific surface area of the composite catalyst is 350 m ² /g˜800 m ² /g. 3. composite catalyst according to claim 1 and 2, is characterized in that, described molecular sieve is AEI molecular sieve; Preferably, the AEI molecular sieve is an aluminum-rich AEI molecular sieve, and the silicon-aluminum ratio Si/Al of the aluminum-rich AEI is 15-2, preferably 12-5. 4. according to the composite catalyst described in any one of claim 1-3, it is characterized in that, described transition metal is any one or the combination of at least two in copper, iron, cerium or manganese, is preferably copper and/or or iron; Preferably, the active component accounts for 1%-10% of the total mass of the composite catalyst, preferably 2%-5%. 5. as the preparation method of the composite catalyst described in any one of claim 1-4, it is characterized in that, described method is ion exchange method, specifically comprises the following steps: (1) The molecular sieve is mixed with the salt solution of the transition metal for ion exchange to obtain a mixed solution; (2) solid-liquid separation is carried out to the mixed solution obtained in step (1), to obtain a solid mixture; (3) Calcining the solid mixture obtained in step (2) to obtain a composite catalyst. 6. The method according to claim 5, characterized in that the salt solution of the transition metal in step (1) is any one or at least two salts of copper salt, iron salt, cerium salt or manganese salt A solution, preferably a salt solution of a copper salt and/or an iron salt; Preferably, the transition metal salt solution in step (1) is: any one or a combination of at least two of transition metal sulfate solution, transition metal nitrate solution or transition metal acetate solution; Preferably, the concentration of the transition metal salt solution in step (1) is 0.01mol/L～1.0mol/L; Preferably, the molecular sieve in step (1) is an AEI molecular sieve, preferably an aluminum-rich AEI molecular sieve, and the silicon-aluminum ratio Si/Al of the aluminum-rich AEI is 15-2, preferably 12-5; Preferably, the ratio of the mass of the molecular sieve in step (1) to the volume of the transition metal salt solution is 1g:(20mL-200mL), preferably 1g:(50mL-100mL); Preferably, the reaction temperature condition of the ion exchange reaction in step (1) is 20°C to 80°C; Preferably, the ion exchange reaction described in step (1) is carried out under stirring conditions; Preferably, the reaction time of the ion exchange reaction in step (1) is 5h-24h. 7. The method according to claim 5 or 6, wherein the method of solid-liquid separation in step (2) is any one or a combination of at least two of suction filtration, filtration or centrifugation; Preferably, the method further includes performing step (2)' after step (2) solid-liquid separation and before step (3) roasting: washing and drying the solid mixture; Preferably, in step (2)', the drying temperature is 80°C to 105°C, preferably 100°C; Preferably, in step (2)', the drying time is 12h to 36h, preferably 12h. 8. The method according to any one of claims 5-7, characterized in that the roasting temperature in step (3) is 450°C to 650°C; Preferably, the calcination time in step (3) is 3h-8h. 9. The method according to any one of claims 5-8, characterized in that the method comprises the following steps: (1) Mix the AEI molecular sieve with the transition metal salt solution with a concentration of 0.01mol/L～1.0mol/L according to the mass to volume ratio of 1g:(20mL～200mL), and carry out ionization under stirring at 20℃～80℃. Exchange reaction, reaction 5h ~ 24h, to obtain a mixed solution; (2) Suction filtering the mixed solution obtained in step (1) to obtain a solid mixture; (3) Washing the solid mixture obtained in step (2), drying at 80°C to 105°C for 12h to 36h, and then roasting at 450°C to 650°C for 3h to 8h to obtain the AEI molecular sieve catalyst. 10. the purposes of the composite catalyst as described in any one of claim 1-4, it is characterized in that, described composite catalyst is used for nitrogen oxide catalytic purification field; Preferably, the composite catalyst is used for NH ₃ -SCR reaction; Preferably, the composite catalyst is used for catalytic purification of nitrogen oxides in tail gas from mobile sources and/or flue gas from stationary sources.