Monolithic low-temperature manganese / cerium honeycomb denitration catalyst

Abstract

The application discloses a monolithic low-temperature manganese / cerium honeycomb denitration catalyst, which is prepared by using cerium dioxide (CeO2) and manganese oxide (MnO x ) as main active components, titanium dioxide (TiO2) as a paste material, adding a structure aid, and adopting an extrusion method. The catalyst is evaluated in terms of catalytic activity and SO2 poisoning resistance by simulating an actual industrial flue gas test environment. Experimental data show that the catalyst has excellent low-temperature denitration activity and SO2 poisoning resistance, and can remove nitrogen oxides in low-temperature flue gas in actual industrial applications. The catalyst has a simple preparation process, is easy to realize industrialized mass production, and uses environment-friendly materials for active components, thereby causing little environmental pollution.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of environmental protection technology and low-temperature denitration, and particularly relates to a monolithic low-temperature manganese / cerium honeycomb denitration catalyst. BACKGROUND

[0002] Nitrogen oxide (NO x ) as one of the main atmospheric pollutants, its emission not only seriously threatens human health, but also is the main reason for the formation of photochemical smog, aggravation of regional acid rain and ozone layer hole. Ammonia-selective catalytic reduction (NH3-SCR) is the most mature technology for controlling NO x emission at present and has been widely applied in various industries. The common SCR technology is roughly as follows: using a reducing agent (NH3, liquid ammonia, etc.) to selectively react with NO x under the action of a catalyst to generate non-toxic and non-polluting N2 and H2O products.

[0003] The catalyst is the core of the SCR technology, and a good catalyst can efficiently and selectively convert NO x into N2. The commercial vanadium-based denitration catalyst currently used is not suitable for low-temperature flue gas denitration in non-electricity industries because of its narrow active temperature window and easy poisoning by SO2, and the catalysts mainly used in China mainly operate at a medium-high temperature range (300℃-420℃), while the flue gas treatment temperature range required by large-scale non-power plants, cement kiln plants and other enterprises is mostly below 300℃. The low-temperature SCR catalysts at the present stage are easily affected by SO2, leading to catalyst deactivation.

[0004] In view of the actual needs of the low-temperature denitration industry such as cement kiln, glass plant, coking furnace, etc., it is of great significance for China to realize ultra-low emission of NO x to design and develop a catalyst with high-efficiency low-temperature denitration activity and SO2 poisoning resistance. The low-temperature denitration catalyst not only has better environmental applicability, but also can reduce the energy consumption in the process of NO x emission and save costs. Therefore, it is urgent to design and develop an excellent low-temperature denitration catalyst to meet the market demand of the low-temperature flue gas denitration industry and fill the gap in the field of low-temperature denitration catalysts in China. SUMMARY

[0005] The application provides a monolithic low-temperature manganese / cerium honeycomb denitration catalyst. MnO x and CeO2 are used as the main active components of the low-temperature manganese / cerium honeycomb denitration catalyst, and the denitration activity of the catalyst is associated with the process conditions for preparing the catalyst. Therefore, the manganese / cerium honeycomb denitration catalyst with low-temperature activity is prepared by optimizing the components of the catalyst and the forming process means.

[0006] The application achieves the technical solutions as follows:

[0007] A monolithic low-temperature manganese / cerium honeycomb denitration catalyst, which takes cerium dioxide (CeO2) and manganese oxide (MnO x ) as active components, takes titanium dioxide as a paste material, adds a structure aid, and is prepared by an extrusion method.

[0008] The preparation method of the monolithic low-temperature manganese / cerium honeycomb denitration catalyst specifically comprises the following process steps:

[0009] (1) In a pug mill, titanium dioxide (TiO2) powder and cerium oxide (CeO2) powder are added, and after mixing and stirring, a manganese salt solution and a structure aid are added, and stirring is continued to form a pug-shaped paste; wherein the molar ratio of the manganese salt, CeO2 and TiO2 is 1:2-6:5-20, preferably 1:2:9.

[0010] (2) The pug-shaped paste material is extruded and pugged, and the pugging process is repeated for several times to ensure that the pug is fully mixed during the pugging process.

[0011] (3) The pugged pug is covered with a plastic sealing film and is aged.

[0012] (4) The aged pug is placed in an extrusion molding machine for molding treatment, and then the molded honeycomb-shaped paste material is placed in an oven for drying.

[0013] (5) The dried honeycomb-shaped paste material is subjected to calcination treatment in an inert atmosphere environment, and a low-temperature manganese / cerium honeycomb denitration catalyst is obtained.

[0014] The preparation method of the monolithic low-temperature manganese / cerium honeycomb denitration catalyst of the application further comprises the following preferred schemes.

[0015] In the preferred scheme of the application, the manganese salt added in step (1) is at least one of manganese nitrate, manganese acetate, manganese carbonate, etc.

[0016] In the preferred scheme of the application, the structure aid in step (1) is at least one of methylol cellulose, polyethylene oxide, glass fiber, active clay, silicon powder, cobalt dioxide, silicon dioxide, etc. The addition of the structure aid can enable the pug to be well extruded and molded, and has good mechanical strength. The addition amount can be determined according to the state of the pug.

[0017] In the preferred scheme of the application, the aging in step (3) is specifically: the aging time is 2h-100h, the aging temperature is 10℃-80℃, and the humidity is 10%-80%.

[0018] In a preferred embodiment of the present invention, the drying in step (4) specifically involves a drying temperature of 30°C-100°C and a drying time of 1h-20h.

[0019] In a preferred embodiment of the present invention, the calcination process in step (5) specifically includes: a calcination temperature of 100℃-600℃, a heating rate of 1℃ / min-30℃ / min, a calcination time of 1h-50h, and the inert gas introduced being at least one of nitrogen (N2) and argon (Ar).

[0020] This invention also provides an integral low-temperature manganese / cerium honeycomb denitrification catalyst, wherein the catalyst comprises cerium dioxide (CeO2) and manganese oxide (MnO2). x The catalyst is prepared by the above method with titanium dioxide (TiO2) as the active ingredient and titanium dioxide (TiO2) as the paste material and structural additives added. The catalyst can be used as a catalyst for removing nitrogen oxides under low temperature conditions of 100-300℃.

[0021] Compared with existing technologies, the beneficial effects of the present invention are as follows:

[0022] This invention prepares a high-performance low-temperature denitrification catalyst using a simple process by adding active components cerium dioxide (CeO2) and manganese oxide (MnO2) to a paste material (TiO2). x By optimizing the proportions of active components, a low-temperature honeycomb denitrification catalyst suitable for temperatures ranging from 100℃ to 300℃ was prepared using an extrusion method. This was mainly achieved through the following aspects:

[0023] (1) CeO2 has a high efficiency in storing and releasing oxygen and unique redox properties, while MnO x It exhibits extremely excellent low-temperature SCR performance, achieved by controlling CeO2 and MnO. x The component ratio between CeO2 and TiO2 can make CeO2 and MnO x The advantages are simultaneously demonstrated, with the catalyst exhibiting good denitrification activity and resistance to SO2 poisoning.

[0024] (2) The use of CeO2 powder in the process of adding active components can effectively reduce the interaction between manganese ions and cerium ions during calcination, thereby overcoming the problems of reduced catalyst activity and poor anti-poisoning performance; the prepared integral honeycomb catalyst can achieve a dynamic balance between the formation and decomposition of ammonium sulfate on the catalyst surface, and can have an ultra-long-term anti-SO2 poisoning ability under actual working conditions.

[0025] (3) The method of preparing industrial monolithic honeycomb catalyst by extrusion effectively solves the problem that powder catalysts in the laboratory are difficult to apply industrially. This invention provides good guidance for the preparation of low-cost, high-performance catalysts.

[0026] (4) Extrusion molding has a relatively simple process compared to other methods, which can reduce the overall production cost of the honeycomb catalyst and the operation difficulty. In addition, the honeycomb catalyst has undergone a high-temperature calcination stage and is in a dense sintered state, has good mechanical strength, can be applied to the actual industrial production of flue gas pipelines, the internal chemical structure of the catalyst is stable, and the service life of the catalyst is greatly prolonged.

[0027] (5) The catalyst preparation process of the present application is simple, easy to realize industrialized mass production, and the materials used for the active components are all environmentally friendly materials, which has little environmental pollution. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Elemental distribution map of the low-temperature manganese / cerium honeycomb denitration catalyst prepared in Example 1.

[0029] Figure 2 Denitration performance data map of the low-temperature manganese / cerium honeycomb denitration catalyst prepared in Example 1 at different temperatures.

[0030] Figure 3 Actual picture of the low-temperature manganese / cerium honeycomb denitration catalyst prepared in Example 1.

[0031] Figure 4 Anti-SO2 performance data map of the low-temperature manganese / cerium honeycomb denitration catalyst prepared in Examples 1, 2 and Comparative Examples 1, 2. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0033] Example 1

[0034] An integral low-temperature manganese / cerium honeycomb denitrification catalyst is prepared by the following steps: (1) First, prepare 1L of manganese acetate solution with a concentration of 700g / L; (2) Weigh 1kg of industrial titanium dioxide, 480g of cerium oxide powder, 15g each of structural additives CMC and PEO, and 40g of glass fiber; (3) Pour the titanium dioxide and cerium oxide powder into a slurry mixer, mix thoroughly, and pour in 430ml of the manganese acetate solution prepared in step (1). During the mixing process, add the structural additives and 20ml of glycerol; (4) After the mixture is fully stirred, take out the mud-like paste material; (5) Put the mud-like paste material into a slurry mill for further extrusion and slurry processing; (6) Repeat the slurry processing in step (5) 5 times to ensure that the mud material is fully mixed during the slurry processing; (7) Cover the mud material with a plastic seal film and place it at room temperature for 24h of aging; (8) After the aging is completed, put the paste into an extrusion molding machine, and after extrusion, quickly place it in an oven at 60℃ for 8h of drying treatment. (9) The dried honeycomb catalyst is placed in a calcination furnace and calcined at 500°C for 6 hours under nitrogen atmosphere to obtain the integral low-temperature manganese / cerium honeycomb denitrification catalyst.

[0035] Figure 1 The elemental distribution diagram is shown for the monolithic low-temperature manganese / cerium honeycomb denitration catalyst prepared in Example 1 of the present invention. Figure 1 It can be seen that Mn and Ce are evenly distributed on the honeycomb structure.

[0036] The catalyst prepared in Example 1 was subjected to a modular low-temperature denitrification performance test in the laboratory stage, which specifically included the following steps:

[0037] (1) A modular catalyst, 5.5 cm long, 2 cm wide, and 2 cm high, was placed into a fixed tubular furnace reaction tube; (2) The reactor inlet contained 500 ppm NO, 500 ppm NH3, 5% O2, with the remainder being N2. The total gas flow rate was 2 L / min, and the reaction temperature was tested at 100℃-300℃. The denitrification performance of the catalyst prepared in Example 1 is as follows: Figure 2 As shown. By Figure 2 It can be seen that the manganese / cerium low-temperature honeycomb denitrification catalyst in this invention can achieve a denitrification efficiency of over 75% in flue gas at 150℃-250℃.

[0038] Example 2

[0039] The application relates to a monolithic low-temperature manganese / cerium honeycomb denitration catalyst, and a preparation method thereof.

[0040] Comparative example 1

[0041] The application relates to a monolithic low-temperature manganese / cerium honeycomb denitration catalyst, and a preparation method thereof.

[0042] Comparative example 2

[0043] The application discloses a monolithic low-temperature manganese / cerium honeycomb denitration catalyst, and a preparation method thereof. The preparation method comprises the following steps: (1) first, 500 ml of a cerium nitrate solution with a concentration of 900 g / L and 500 ml of a manganese acetate solution with a concentration of 700 g / L are prepared; (2) 1 kg of industrial titanium dioxide, 15 g of a structure aid CMC, 15 g of a structure aid PEO and 40 g of glass fiber are weighed; (3) the titanium dioxide is poured into a mud machine, and is fully stirred, and then the cerium nitrate solution prepared in the step (1) and the manganese acetate solution are poured into the mud machine, and 20 ml of glycerol is added in the mixing process; (4) after fully stirring, the mud-like paste material is taken out; (5) the mud-like paste material is put into a mud refining machine for further extrusion and mud refining; (6) the mud refining process in the step (7) is repeated for 5 times, so that the mud is fully mixed in the mud refining process; (7) the mud is wrapped with a plastic wrapping film, and is placed in a room temperature for aging for 24 hours; (8) after the aging is completed, the paste is put into an extrusion forming machine, and is rapidly placed in an oven for drying treatment at 60 DEG C for 8 hours after extrusion; (9) the honeycomb catalyst which has been dried is put into a calcination furnace, and is subjected to calcination treatment at 500 DEG C under a nitrogen atmosphere for 6 hours; and thus the monolithic low-temperature manganese / cerium honeycomb denitration catalyst is obtained.

[0044] The catalysts prepared in the examples 1 and 2 and the comparative examples 1 and 2 are subjected to the laboratory stage modular SO2 poisoning resistance low-temperature denitration performance test, and the test specifically comprises the following steps: (1) a module catalyst with a length of 5.5 cm, a width of 2 cm and a height of 2 cm is intercepted and is put into a fixed tube furnace reaction tube; (2) the reactor inlet contains 500 ppm of NO, 500 ppm of NH3, 200 ppm of SO2 and 5% of O2, and the rest is N2, the total gas flow is 2 L / min, the test reaction temperature is 200 DEG C, and the SO2 poisoning resistance performance of the catalyst is tested for 24 hours. The SO2 poisoning resistance performance of the catalysts prepared in the examples 1 and 2 and the comparative examples 1 and 2 is shown in the following table. Figure 4

[0045] The examples 1 and 2 both use cerium nitrate powder for catalyst preparation, the comparative examples 1 and 2 both use cerium salt solution for catalyst preparation, and the examples 1 and 2 and the comparative examples 1 and 2 respectively use the same active component proportioning. Figure 4 ​It can be seen that, no matter whether the catalyst is prepared by the method of cerium oxide powder or cerium salt solution, the anti-poisoning performance of the catalysts with different active component proportions can be compared, and it can be found that a specific active component proportion can make the catalyst have more stable and efficient catalytic efficiency in a high SO2 environment. Research has found that a specific active component proportion can better enable the generation and decomposition of ammonium sulfate salt on the surface of the catalyst to reach a dynamic balance, greatly extending the service life of the catalyst, and enabling the catalyst to have an ultra-long SO2 resistance capability. In addition, no matter which active component proportion is used for the catalyst, the catalyst prepared by the cerium oxide powder has much higher SO2 resistance performance than the catalyst prepared by the cerium salt solution, because the method of using cerium oxide powder can effectively avoid the interaction between manganese ions and cerium ions in the solution during calcination, thereby reducing the active component, reducing the activity of the catalyst, and reducing the problem of anti-poisoning performance.

[0046] The monolithic low-temperature manganese / cerium honeycomb denitration catalyst described in the application has excellent low-temperature denitration performance and excellent SO2 resistance performance in laboratory simulation performance evaluation. The monolithic low-temperature manganese / cerium honeycomb denitration catalyst described in the application not only has a simple preparation method, but also uses environmentally friendly materials for active components, has little environmental pollution, has good SO2 resistance, and fills the gap in the industrial application of domestic low-temperature manganese / cerium honeycomb denitration catalysts.

[0047] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modifications, equivalent replacements and improvements made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A method for producing a monolithic low-temperature manganese / cerium honeycomb De-NOx catalyst, characterized by, The catalyst is cerium dioxide CeO2 and manganese oxide MnO x The active ingredient is prepared by adding structural aids to titanium dioxide as a paste material and using an extrusion method. The preparation method comprises the following steps: (1) in the mud machine, add titanium dioxide TiO2 powder and cerium oxide CeO2 powder, after mixing and stirring, add manganese salt solution and structure aid, continue to stir into mud paste; wherein, the molar ratio of manganese salt, CeO2 and TiO2 is 1:2-6:5-20; (2) the mud paste material is extruded and kneaded, and the kneading process is repeated for several times, so as to ensure that the mud is fully mixed in the kneading process; (3) the kneaded mud is covered with plastic sealing film and aged; (4) the aged mud is put into an extrusion molding machine for molding treatment, and then the molded honeycomb paste material is placed in an oven for drying; (5) the dried honeycomb paste material is calcined in an inert atmosphere, and a low-temperature manganese / cerium honeycomb denitration catalyst is obtained; In step (1), the manganese salt is at least one of manganese nitrate, manganese acetate and manganese carbonate; The structure aid in step (1) is at least one of hydroxymethyl cellulose, polyethylene oxide, glass fiber, active clay, silicon powder and silicon dioxide.

2. The method of claim 1, wherein the method is characterized by: In step (3), the aging is specifically: the aging time is 2h-100h, the aging temperature is 10℃-80℃, and the humidity is 10%-80%.

3. The preparation method of the integral low-temperature manganese / cerium honeycomb denitration catalyst according to claim 1, characterized in that, In step (4), the drying is specifically: the drying temperature is 30℃-100℃, and the drying time is 1h-20h.

4. The method of claim 1, wherein the method is characterized by: In step (5), the calcination treatment is specifically: the calcination temperature is 200℃-600℃, the heating rate is 1℃ / min-30℃ / min, the calcination time is 1h-50h, and the inert atmosphere is at least one of nitrogen N2 and argon Ar.

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