CN107376990B - Preparation method of SCR catalyst with loose and porous structure - Google Patents

Preparation method of SCR catalyst with loose and porous structure Download PDF

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CN107376990B
CN107376990B CN201710503094.8A CN201710503094A CN107376990B CN 107376990 B CN107376990 B CN 107376990B CN 201710503094 A CN201710503094 A CN 201710503094A CN 107376990 B CN107376990 B CN 107376990B
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molecular sieve
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catalyst
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CN107376990A (en
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于力娜
崔龙
张克金
张斌
潘艳春
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FAW Group Corp
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    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/78—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
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    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/48—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing arsenic, antimony, bismuth, vanadium, niobium tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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Abstract

The invention relates to a preparation method of a loose porous SCR catalyst, wherein the prepared loose porous SCR catalyst has the NOX conversion rate of over 70 percent at the temperature of 150-500 ℃, the NOX conversion rate of 78 percent at the temperature of 150 ℃ and 98 percent at the temperature of 200 ℃, shows a wider temperature window, excellent low-temperature performance and better sulfur resistance effect, can effectively solve the problem of low NOX activity of a vehicle in a low-speed running state for a long time and in a cold start or stop state in winter, and has stronger practical application value. In addition, the invention simplifies the preparation process, has easily controlled synthesis conditions and is easy for industrial application.

Description

Preparation method of SCR catalyst with loose and porous structure
Technical Field
The invention relates to a preparation method of a loose and porous SCR catalyst, belongs to the technical field of automobile emission, and particularly belongs to the field of preparation of SCR denitration catalysts.
Background
In order to meet emission regulations, the Urea-SCR technology has become the first technical route for reducing NOx of medium and heavy diesel engine enterprises, is more and more accepted by people and becomes the main research direction for the NOx after-treatment of diesel engine tail gas. The core of the Urea-SCR technology is a catalyst, and the current Urea-SCR catalysts include metal oxide catalysts, noble metal catalysts and zeolite molecular sieve catalysts. Wherein the noble metalThe catalyst is too costly and tends to form sulfates with the sulfides in the exhaust gas resulting in catalyst deactivation. The vanadium-based catalyst is widely used at home at present and has the advantages of rich application experience, mature technology and the like, but the vanadium-based catalyst has a narrow temperature window, and the vanadium-based catalyst can be decomposed at high temperature to generate V2O5Belongs to high-toxicity substances, has great harm to human health and environment, so that the vanadium catalyst is only a temporary transition technology and cannot meet the requirements of stricter emission standards, and the developed countries in Europe, America, Japan and the like definitely forbid the use of the vanadium catalyst.
Transition metal supported molecular sieve catalysts have received much attention in recent years because of their higher thermal stability and wider temperature window than vanadium-based catalysts. For example, the patent application No. CN 103599813A discloses a molecular sieve based catalyst for low-temperature SCR denitration and a preparation method thereof, wherein the molecular sieve based catalyst comprises a Cu modified molecular sieve carrier and one or more oxides selected from Ce, Zr and Mn. The catalyst has a nitrogen oxide removal effect of 62-100% within a temperature range of 100-250 ℃, and has good sulfur resistance; application number CN 102029178A discloses a copper-based molecular sieve catalyst and a preparation method thereof, firstly preparing a mixed solution of copper acetate and ammonium ceric nitrate, then adding a molecular sieve carrier ZSM-5 into the mixed solution, stirring, and finally drying and roasting to obtain the copper-based molecular sieve catalyst, wherein the molecular formula of the obtained copper-based molecular sieve catalyst is represented as Cu-Ce-ZSM-5, and the copper-based molecular sieve catalyst comprises the following components: copper accounts for 3-12% of the total weight of the catalyst, cerium accounts for 5-8% of the total weight of the catalyst, ZSM-5 accounts for 80-92% of the total weight of the catalyst, the catalyst has high efficiency on NH3-SCR reaction at 200-500 ℃, has good water resistance and sulfur resistance, can meet the requirements of stricter emission regulations, and achieves the purposes of reducing cost and improving use safety; the application number CN 103008002A discloses a preparation method and application of a Fe and Cu composite molecular sieve catalyst, Fe or Cu is used as an active component, a ZSM-5, SSZ-13, SAPO-34, MOR or Beta molecular sieve is used as a catalyst carrier, the catalyst is prepared by adopting an ion exchange method, then the Fe molecular sieve catalyst and the Cu molecular sieve catalyst prepared by mechanical series connection are adopted, the working temperature window of the molecular sieve catalyst is widened, and the purification efficiency of nitrogen oxide reaches more than 95% within the range of 200-500 ℃.
Although the prepared Cu-based, Fe-based or Cu-Fe-based modified molecular sieve catalyst improves the NOx activity to different degrees, widens the temperature window and has certain hydrothermal stability, in practical application, the following findings are found: (1) the ion exchange method has complicated procedures and cannot realize industrial mass production; (2) the catalyst with the temperature of 200-500 ℃ prepared can be used when the exhaust temperature is higher than 200 ℃, but the catalyst is under low-temperature working conditions such as cold start in winter, low idling, stop and go, and the like, and the NOx activity is very low and even zero; (3) for the catalyst with better low-temperature NOx, the activity of the NOx at the high-temperature section at 300-500 ℃ is lower.
Disclosure of Invention
In view of the above-mentioned shortcomings in the prior art, an object of the present invention is to provide a method for preparing a loose porous SCR catalyst, in which a modified molecular sieve catalyst is used as an inner layer active center, a transition metal element treated by an activator is loaded on the surface of the inner layer active center through an outer layer transition introduction agent, the inner and outer layer active metal components form a synergistic effect between the inner and outer layers through a chemical reaction during calcination, and the outer layer transition introduction agent is completely volatilized during calcination, so as to finally form a flexible loose porous structure on the surface of the inner layer structure. The loose and porous SCR catalyst prepared by the invention has NO in the range of 150-500 DEG CXThe conversion rate is up to more than 70%, the conversion rate is up to 78% at 150 ℃ and 98% at 200 ℃, a wider temperature window, excellent low-temperature performance and a better sulfur resistance effect are shown, the problem of low NOx activity of the vehicle in a low-speed running state for a long time and in a cold start or stop-and-go state in winter can be effectively solved, and the method has a stronger practical application value. In addition, the invention simplifies the preparation process, has easily controlled synthesis conditions and is easy for industrial application.
The technical scheme of the invention is realized as follows: the preparation method of the loose porous SCR catalyst is characterized by comprising the following specific steps: (1) dissolving one or more of 12.5-15.6 parts of copper salt and 1.6-3.7 parts of metal auxiliary agent in deionized water, stirring for dissolving, adding 34-47.6 parts of molecular sieve carrier, mixing and stirring for 2-4 h; (2) adding 1.5-1.9 parts of ammonium carbamate, and stirring at 45-60 ℃ for 1-3 hours to obtain a mixed solution; (3) drying, calcining at high temperature and grinding the mixed solution to obtain metal modified molecular sieve powder; (4) dissolving 10.8-16.2 parts of transition metal acetate in deionized water to prepare a solution, adding 0.5-0.9 part of an activating agent, 12.5-15.6 parts of an outer layer transfer introduction agent and 1.5-2.6 parts of a surface dispersing agent, and strongly stirring at 45-105 ℃ for 2-5 hours; (5) adding 33.3-43.2 parts of the metal modified molecular sieve powder obtained in the step (3), and strongly stirring at 60-115 ℃ for 3-6 hours to obtain a paste; (6) and drying and crushing the paste in an oven at 85-120 ℃, calcining at 450-520 ℃ for 4-6 h, and grinding to obtain the SCR catalyst with the flexible porous double-layer structure.
The metal auxiliary agent is one or more of La, Ti, Cr, Mn and Ce.
The transition acetate is one or more of Co, Zr, Cr, Mn and Ce metals.
The activating agent is one or more of ammonium formate, ammonium carbamate, ammonium oxalate, formamide, ammonium carbonate, ammonium bicarbonate and urea.
The outer layer transfer introduction agent is CMC (mass fraction of 1%), and the surface dispersing agent is one or a combination of ethanol and propanol.
The invention has the advantages that the loose and porous SCR catalyst is in the range of 150-500 ℃, and NO is generatedXThe conversion rate is up to more than 70%, the conversion rate is up to 78% at 150 ℃ and 98% at 200 ℃, a wider temperature window, excellent low-temperature performance and better sulfur resistance effect are shown, the problem of low NOx activity of the vehicle in a low-speed running state for a long time and in a cold start or stop-and-go state in winter can be effectively solved, and the high-conversion-rate sulfur-resistant material has a high practical application value; in addition, the preparation process is simplified, the synthesis condition is easy to control, and the method is easy for industrial application.
Drawings
FIG. 1 is a transmission TEM image of a catalyst prepared in example 1;
FIG. 2 is a NOx conversion test curve for example 1 and comparative example 1;
FIG. 3 is a test curve of NOx conversion after 24h of presulfiding treatment in example 1.
Detailed Description
In the following description of specific examples, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details.
Example 1
(1) Dissolving 900g of copper nitrate and 100g of cerium nitrate in 2200g of deionized water, stirring for dissolving, adding 3000g of beta40 molecular sieve carrier, mixing and stirring for 2 hours; (2) adding 100g of ammonia carbamate, and stirring for 3 hours at 45 ℃ to obtain a mixed solution; (3) drying the mixed solution at 105 ℃, calcining the mixed solution at 450 ℃ for 5 hours, and grinding the calcined mixed solution to obtain metal modified molecular sieve powder; (4) dissolving 900g of manganese acetate in 2900g of deionized water to prepare a solution, adding 56g of ammonium formate, 1000g of CMC with the mass fraction of 1% and 150g of absolute ethyl alcohol, and strongly stirring for 5 hours at 45 ℃; (5) adding 3000g of the metal modified molecular sieve powder obtained in the step (3), and strongly stirring at 60 ℃ for 6h to obtain a paste; (6) and drying and crushing the paste in an oven at 85 ℃, calcining for 6h at 450 ℃, and grinding to obtain the loose and porous SCR catalyst.
Fig. 1 is a TEM image of the catalyst prepared in example 1, and it can be seen that the outer layer pores are relatively abundant and are relatively uniformly distributed.
The SCR conversion rate test of the catalyst powder prepared in example 1 at different temperatures is carried out by adopting a micro-reverse fixed bed gas-solid phase reaction device to simulate tail gas, and the test conditions are that the NO concentration is 1000 ppm and O is2: 5% (volume fraction), NH3：1000 ppm、H2O: 8 percent (volume fraction), nitrogen as balance gas and airspeed of 150000h-1The test results are shown in FIG. 2, and the catalyst has NO at 150 ℃XThe conversion rate is up to 78%, the conversion rate at 200 ℃ is up to 98%, excellent low-temperature performance is shown, and the NOx conversion rate of the catalyst at 150-450 ℃ is up to more than 75%.
The catalyst prepared in example 1 was presulfided at 200 ℃ in fresh catalyst for a period of time24h, gas composition O2 8 vol %，SO2 200ppm，N2The results of the equilibrium gas test are shown in fig. 3, and it can be seen from the graph that compared with the fresh sample prepared in example 1, except that the conversion rate of NOx at 450-.
Comparative example 1
(1) Dissolving 900g of copper nitrate and 100g of cerium nitrate in deionized water, stirring for dissolving, adding 3000g of beta40 molecular sieve carrier, mixing and stirring for 2 hours; (2) adding 100g of ammonia carbamate, and stirring for 3 hours at 45 ℃ to obtain a mixed solution; (3) and drying the mixed solution at 105 ℃, calcining the mixed solution at 450 ℃ for 5 hours, and grinding the calcined mixed solution to obtain the metal modified molecular sieve powder. Comparative example 1 was tested at a concentration of NO of 1000 ppm, O2: 5% (volume fraction), NH 3: 1000 ppm, H2O: 5 percent (volume fraction), nitrogen as balance gas and space velocity set to 150000h-1The results of the tests are shown in fig. 2, NOX conversion at 150 ℃ is 62%, conversion at 200 ℃ is as high as 78%, and the temperature window is significantly shifted to higher temperatures compared to example 1, indicating that the low temperature performance of the catalyst of comparative example 1 is not as good as that of the catalyst prepared in example 1.
Example 2
(1) 1005g of copper nitrate and 200g of lanthanum nitrate are dissolved in 3000g of deionized water, stirred and dissolved, 3000g of Sapo34 molecular sieve carrier is added, and the mixture is mixed and stirred for 4 hours; (2) adding 118g of ammonium carbamate, and stirring for 2 hours at 60 ℃ to obtain a mixed solution; (3) drying the mixed solution at 105 ℃, calcining the mixed solution at 450 ℃ for 5 hours, and grinding the calcined mixed solution to obtain metal modified molecular sieve powder; (4) dissolving 830g of zirconium acetate in 2100g of deionized water to prepare a solution, adding 35g of formamide, 825g of CMC with the mass fraction of 1.0% and 150g of propanol, and strongly stirring for 3 hours at 105 ℃; (5) adding 3000g of the metal modified molecular sieve powder obtained in the step (3), and strongly stirring at 105 ℃ for 5 hours to obtain a paste; (6) drying and crushing the paste in an oven at 105 ℃, calcining for 5h at 500 ℃, and grinding to obtain the loose and porous SCR catalyst.
Example 3
(1) Dissolving 1200g of copper nitrate and 300g of cerium nitrate in 3500g of deionized water, stirring for dissolving, adding 3000g of ZSM5 molecular sieve carrier, mixing and stirring for 4 hours; (2) adding 145g of ammonium carbamate, and stirring for 1h at 60 ℃ to obtain a mixed solution; (3) drying the mixed solution at 105 ℃, calcining at 450 ℃, and grinding to obtain metal modified molecular sieve powder; (4) 1005g of cerium acetate is dissolved in 2900g of deionized water to prepare a solution, 76g of ammonium oxalate, 1000g of CMC with the mass fraction of 1.0 percent and 160g of absolute ethyl alcohol are added, and strong stirring is carried out for 2 hours at 85 ℃; (5) adding 3000g of the metal modified molecular sieve powder obtained in step (3), and strongly stirring at 105 ℃ for 3h to obtain a paste; (6) drying and crushing the paste in a 120 ℃ oven, calcining for 5h at 450 ℃, and grinding to obtain the loose and porous SCR catalyst.
Example 4
(1) Dissolving 1350g of copper nitrate and 250g of manganese nitrate in deionized water, stirring for dissolving, adding 3000g of SSZ13 molecular sieve carrier, mixing and stirring for 3 hours; (2) adding 160g of ammonium carbamate, and stirring for 2 hours at 45 ℃ to obtain a mixed solution; (3) drying the mixed solution at 115 ℃, calcining at 500 ℃ and grinding to obtain metal modified molecular sieve powder; (4) dissolving 950g of chromium acetate in 2800g of deionized water to prepare a solution, adding 56g of ammonium carbamate, 920g of CMC with the mass fraction of 1% and 120g of absolute ethyl alcohol, and strongly stirring for 3 hours at 60 ℃; (5) adding 3000g of the metal modified molecular sieve powder obtained in the step (3), and strongly stirring at 85 ℃ for 4h to obtain a paste; (6) drying and crushing the paste in a 105 ℃ oven, calcining for 4h at 520 ℃, and grinding to obtain the loose and porous SCR catalyst.
Example 5
(1) Dissolving 1000g of copper nitrate and 130g of titanium nitrate in deionized water, stirring for dissolving, adding 3000g of beta25 molecular sieve carrier, mixing and stirring for 4 hours; (2) adding 138g of ammonium carbamate, and stirring for 2 hours at 50 ℃ to obtain a mixed solution; (3) drying the mixed solution at 105 ℃, calcining at 500 ℃ and grinding to obtain metal modified molecular sieve powder; (4) dissolving 1200g of manganese acetate in 3200g of deionized water to prepare a solution, adding 56g of ammonium carbonate, 1350g of CMC with the mass fraction of 1% and 215g of absolute ethyl alcohol, and strongly stirring at 70 ℃ for 5 hours to obtain a paste; (5) adding 3000g of the metal modified molecular sieve powder obtained in step (3), and strongly stirring at 115 ℃ for 3h to obtain a paste; (6) drying and crushing the paste in an oven at 115 ℃, calcining for 5h at 500 ℃, and grinding to obtain the loose and porous SCR catalyst.
Example 6
(1) Dissolving 1350g of copper nitrate and 300g of chromium nitrate in deionized water, stirring for dissolving, adding 3000g of ZSM5 molecular sieve carrier, and mixing and stirring for 4 hours; (2) adding 165g of ammonium carbamate, and stirring for 2 hours at 60 ℃ to obtain a mixed solution; (3) drying the mixed solution at 105 ℃, calcining at 500 ℃ and grinding to obtain metal modified molecular sieve powder; (4) dissolving 1430g of cobalt acetate in 3000g of deionized water to prepare a solution, adding 72g of ammonium bicarbonate, 1150g of CMC with the mass fraction of 1.0% and 200g of absolute ethyl alcohol, and strongly stirring for 2 hours at 85 ℃; (5) adding 3000g of the metal modified molecular sieve powder obtained in step (3), and strongly stirring at 115 ℃ for 3h to obtain a paste; (6) drying and crushing the paste in an oven at 115 ℃, calcining for 4h at 520 ℃, and grinding to obtain the loose and porous SCR catalyst.
Example 7
(1) Dissolving 900g of copper nitrate and 180g of lanthanum nitrate in 3200g of deionized water, stirring for dissolving, adding 3000g of Sapo34 molecular sieve carrier, mixing and stirring for 3 hours; (2) adding 110g of ammonium carbamate, and stirring for 3 hours at 60 ℃ to obtain a mixed solution; (3) drying the mixed solution at 115 ℃, calcining at 500 ℃ and grinding to obtain metal modified molecular sieve powder; (4) dissolving 800g of cerium acetate in 2500g of deionized water to prepare a solution, adding 60g of urea, 900g of CMC with the mass fraction of 1.0% and 160g of absolute ethyl alcohol, and strongly stirring for 2 hours at 120 ℃; (5) adding 3000g of the metal modified molecular sieve powder obtained in step (3), and strongly stirring at 115 ℃ for 3h to obtain a paste; (6) drying and crushing the paste in an oven at 115 ℃, calcining for 5h at 480 ℃, and grinding to obtain the loose and porous SCR catalyst.

Claims (1)

1. The preparation method of the loose porous SCR catalyst is characterized by comprising the following specific steps: (1) dissolving one or more of 12.5-15.6 parts of copper salt and 1.6-3.7 parts of metal auxiliary agent in deionized water, stirring for dissolving, adding 34-47.6 parts of molecular sieve carrier, mixing and stirring for 2-4 h; (2) adding 1.5-1.9 parts of ammonium carbamate, and stirring at 45-60 ℃ for 1-3 hours to obtain a mixed solution; (3) drying, calcining at high temperature and grinding the mixed solution to obtain metal modified molecular sieve powder; (4) dissolving 10.8-16.2 parts of transition metal acetate in deionized water to prepare a solution, adding 0.5-0.9 part of an activating agent, 12.5-15.6 parts of an outer layer transfer introduction agent and 1.5-2.6 parts of a surface dispersing agent, and strongly stirring at 45-105 ℃ for 2-5 hours; (5) adding 33.3-43.2 parts of the metal modified molecular sieve powder obtained in the step (3), and strongly stirring at 60-115 ℃ for 3-6 hours to obtain a paste; (6) drying and crushing the paste in an oven at 85-120 ℃, calcining at 450-520 ℃ for 4-6 h, and grinding to obtain the SCR catalyst with the flexible porous double-layer structure; the metal auxiliary agent is one or more of La, Ti, Cr, Mn and Ce, and the transition metal acetate is one or more of Co, Zr, Cr, Mn and Ce; the activating agent is one or more of ammonium formate, ammonium carbamate, ammonium oxalate, formamide, ammonium carbonate, ammonium bicarbonate and urea, and the outer-layer transfer introduction agent is CMC with the mass fraction of 1%; the surface dispersing agent is one or a combination of ethanol and propanol.
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