H-type FER molecular sieve, preparation method and application thereof

Abstract

The application relates to the field of catalyst technology, in particular to an H-type FER molecular sieve and a preparation method and application thereof. In the preparation method of the H-type FER molecular sieve, the template agent has a precise guiding effect on the FER crystal type, can effectively inhibit the generation of impurities, and the prepared H-type FER molecular sieve has high crystallinity, single crystal phase and regular morphology, and the channel structure is unobstructed, thereby providing good conditions for the diffusion of reactants and products. The H-type FER molecular sieve prepared by the application is suitable for a methanol SCR denitration system, does not use an ammonia reducing agent, avoids the problems of catalyst deactivation and equipment blockage caused by the deposition of sulfur ammonium salt from the source, can be widely applied to the removal of nitrogen oxides under complex working conditions containing sulfur such as motor vehicle exhaust, coal-fired boilers and heavy oil combustion flue gas, and has good environmental protection benefits and industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to an H-type FER molecular sieve, its preparation method, and its application. Background Technology

[0002] With the continuous increase in industrial production and the number of motor vehicles, nitrogen oxides... Nitrogen oxides (NOx) have become one of the major air pollutants. They are highly irritating and corrosive, causing harm to human health. Furthermore, they readily react with other harmful components in the atmosphere, leading to environmental problems such as acid rain and photochemical smog. Selective catalytic reduction (SCR) is currently the most mainstream technology for removing NOx, with ammonia or urea as the reducing agent for NH3. With its advantages of high denitrification efficiency and wide range of applications, SCR technology has been widely used in the fields of industrial flue gas and motor vehicle exhaust purification.

[0003] However, in the treatment of waste gas generated from the combustion of high-sulfur fuels such as coal and heavy oil, sulfur oxides present in the system can further generate sulfur trioxide under catalyst and oxygen-enriched conditions. Sulfur trioxide readily reacts with ammonia-based reducing agents to form ammonium sulfate, ammonium bisulfate, and other ammonium sulfate deposits. These substances are highly adhesive and corrosive, adhering to the catalyst surface and clogging catalyst pores, leading to a rapid decline in catalyst activity or even deactivation. They also corrode flues, reactors, and other equipment, increasing the difficulty of system operation and maintenance and posing safety risks. Although existing technologies improve sulfur resistance by modifying catalyst components and optimizing carrier structure, the use of ammonia-based reducing agents cannot fundamentally solve the series of problems caused by ammonium sulfate deposits.

[0004] Furthermore, ammonia-based reducing agents pose safety hazards during storage, transportation, and use. Urea solutions are prone to crystallization at low temperatures, causing pipeline blockage and affecting the stable operation of the denitrification system. In contrast, lower alcohol reducing agents such as methanol and ethanol are widely available, safe to store and transport, and less likely to react with sulfur oxides to form ammonium sulfate precipitates. Alcohols used as reducing agents... SCR denitrification technology can avoid catalyst deactivation and equipment failure caused by ammonium sulfate from the source, and has become an important development direction in the field of denitrification.

[0005] FER-type molecular sieves, due to their unique cross-channel structure, suitable acidic sites, and good stability, are suitable for mixing with alcohols. SCR is an ideal catalytic material for the reaction. However, existing H-type FER molecular sieve preparation technology has obvious defects: traditional template agents have poor directivity and are prone to generating impurities, resulting in low crystallinity and insufficient crystal phase purity of the molecular sieve; the silicon-aluminum ratio control range is narrow, and it is difficult to match the strength and number of acidic sites with alcohols. SCR catalytic requirements; the prepared molecular sieves have poor low-temperature activity and NO XThe conversion efficiency is low, and it is prone to aging and deactivation under high temperature and humidity conditions, failing to meet the requirements for efficient and long-lasting denitrification under complex conditions of motor vehicle exhaust and industrial flue gas. Therefore, it is necessary to develop an H-type FER molecular sieve with pure crystal phase, tunable acidity, high catalytic activity, and excellent hydrothermal stability, and its preparation method, to promote the denitrification of alcohols. The industrial application of SCR denitrification technology is of great significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for the selective reduction of NO using alcohols. x H-type FER molecular sieves, their preparation methods, and applications.

[0007] To achieve this objective, the present invention employs the following technical solution: a method for preparing H-type FER molecular sieves, the preparation method comprising the following steps: (1) A mixture of inorganic alkali, aluminum source, silicon source, template agent and water was subjected to hydrothermal reaction, followed by filtration, washing, drying and calcination to obtain Na-type FER molecular sieve; (2) Exchange the Na-type FER molecular sieve obtained in the previous step with the ammonium salt solution to prepare NH4-type FER molecular sieve, and then calcine the NH4-type FER molecular sieve to obtain H-type FER molecular sieve; In step (1), the structural formula of the template agent is shown in (1). ,in, n is selected from the natural number 1 or 2; a, b, c, and d are each independently selected from the natural number 0, 1, 2, 3, or 4.

[0008] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, the template agent is selected from A-1, A-2, A-3, A-4, A-5 or A-6. , Preferably, the template agent is selected from A-6. .

[0009] As a preferred embodiment of the preparation method of H-type FER molecular sieve of the present invention, in step (1), the inorganic base refers to an inorganic compound with alkalinity, specifically including water-soluble base, the aluminum source includes at least one of sodium aluminate, sodium tetrahydroxyaluminate, potassium aluminate, boehmite, boehmite, alumina, bauxite and alunite, and the silicon source includes at least one of silica sol, fumed silica and tetraethyl orthosilicate.

[0010] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, the water-soluble alkali includes sodium hydroxide and / or potassium hydroxide, the aluminum source is sodium aluminate, and the silicon source is silica sol.

[0011] As a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, the silica sol refers to a colloidal solution formed by uniformly dispersing nano-sized silica particles in water, wherein the mass concentration of silica particles in the colloidal solution is 25%~45%.

[0012] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, in step (1), the molar ratio of silicon element in the silicon source to aluminum element in the aluminum source is 5~50:1.

[0013] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, in step (1), the molar ratio of the alkali metal element in the inorganic base to the silicon element in the silicon source is (0.1~1):1.

[0014] In a preferred embodiment of the preparation method of H-type FER molecular sieve of the present invention, in step (1), the water is deionized water, and the mass ratio of the water to the amount of silicon dioxide in the silicon source is (10~100):1.

[0015] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, in step (1), the ratio of the amount of the template agent to the amount of silicon in the silicon source is 0.05~2:1.

[0016] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, in step (1), the molar ratio of silicon element in the silicon source to aluminum element in the aluminum source is 5:1, 7:1, 10:1, 12:1, 15:1, 17:1, 18:1, 20:1, 23:1, 25:1, 28:1, 30:1, 32:1, 35:1, 40:1, 42:1, 45:1, 48:1 or 50:1.

[0017] More preferably, in step (1), the molar ratio of silicon in the silicon source to aluminum in the aluminum source is 15 to 35:1, which can be 35:1, 40:1, 42:1, 45:1, 48:1 or 50:1.

[0018] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, in step (1), the molar ratio of the alkali metal element in the inorganic base to the silicon element in the silicon source is 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1.

[0019] More preferably, in step (1), the molar ratio of the alkali metal element in the inorganic base to the silicon element in the silicon source is 0.2~0.5:1, which can be 0.2:1, 0.3:1, 0.4:1, or 0.5:1.

[0020] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, in step (1), the mass ratio of the water to the amount of silicon dioxide in the silicon source is 10:1, 16:1, 20:1, 25:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1 or 100:1.

[0021] More preferably, in step (1), the mass ratio of the water to the amount of silicon dioxide in the silicon source is 15 to 50:1, which can be 16:1, 20:1, 25:1, 30:1, 40:1, or 50:1.

[0022] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, in step (1), the ratio of the amount of the template agent to the amount of silicon in the silicon source is 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.4:1, 0.5:1, 0.8:1, 1:1, 1.3:1, 1.5:1 or 1.8:1, 2:1.

[0023] More preferably, in step (1), the ratio of the amount of the template agent to the amount of silicon in the silicon source is 0.1 to 0.5:1, which can be 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.4:1, or 0.5:1.

[0024] In a preferred embodiment of the preparation method of H-type FER molecular sieve of the present invention, in step (2), the calcination temperature is 400~800℃ and the calcination time is 4~6h.

[0025] Preferably, in step (2), the calcination temperature is 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃; and the calcination time is 4h, 5h or 6h.

[0026] More preferably, in step (2), the calcination temperature is 450~650℃.

[0027] In a preferred embodiment of the preparation method of the H-type FER molecular sieve of the present invention, in step (2), the calcined product is washed until the washing liquid is neutral, and then dried at 120~180℃ for 8~24h. The calcined product contains residual alkali metal ions (Na+). + ) and other soluble impurities.

[0028] On the other hand, the present invention provides an H-type FER molecular sieve, which is prepared by the above-described preparation method of the present invention. The beneficial effects of this invention are as follows: (1) The template agent used in this invention has a precise guiding effect on the FER crystal form, which can effectively inhibit the formation of impurity crystals. The prepared H-type FER molecular sieve has high crystallinity, single crystal phase, regular morphology, and smooth pore structure, which provides good conditions for the diffusion of reactants and products.

[0029] (2) The present invention can flexibly adjust the molar ratio of silicon and aluminum elements within a wide range of 5 to 50:1, so as to achieve precise control of the number, intensity and distribution of acidic sites, and make the molecular sieve acidic and alcoholic. SCR denitrification reaction is highly compatible, significantly enhancing its activation ability for alcohol reducing agents and NO. x Reduction selectivity.

[0030] (3) The H-type FER molecular sieve prepared in this invention in methanol The SCR system exhibits excellent catalytic activity, with NO showing good performance at a low temperature of 200℃. x Conversion rate can reach over 66%, NO in the medium-high temperature range of 300~350℃ x The conversion rate can reach up to 97.8%, which is much higher than that of FER molecular sieves prepared by traditional template agents. The low-temperature activity and denitrification efficiency across the entire temperature range are significantly improved.

[0031] (4) The H-type FER molecular sieve prepared by this invention has excellent hydrothermal stability. After aging at 700℃, 15% water vapor for 8 hours, it still maintains extremely high catalytic activity. NO at 300℃ and 350℃ x The conversion rate can still reach over 90%, and the activity of some samples only decreases slightly after aging. It has outstanding anti-aging and anti-hydrothermal deactivation capabilities and can adapt to complex and harsh exhaust gas conditions.

[0032] (5) The preparation process of this invention is simple, the reaction conditions are mild, and the raw materials are readily available. It uses conventional industrial-grade silicon source, aluminum source and inorganic base, without the need for special equipment and harsh reaction conditions. The process has good repeatability and low production cost, making it suitable for industrial scale-up production.

[0033] (6) The H-type FER molecular sieve prepared in this invention is suitable for methanol. The SCR denitrification system does not use ammonia-based reducing agents, thus avoiding catalyst deactivation and equipment blockage caused by ammonium sulfate deposition from the source. It can be widely used for nitrogen oxide removal in complex sulfur-containing conditions such as motor vehicle exhaust, coal-fired boilers, and heavy oil combustion flue gas, and has good environmental benefits and industrial application prospects. Attached Figure Description

[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is the XRD pattern of the H-type FER molecular sieve sample prepared in Example 1.

[0035] Figure 2 This is the XRD pattern of the H-type FER molecular sieve sample prepared in Comparative Example 1.

[0036] Figure 3 This is a scanning electron microscope image of the H-type FER molecular sieve sample prepared in Example 1. Detailed Implementation

[0037] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0038] Example 1: This example illustrates the preparation method of the H-type FER molecular sieve described in this invention, comprising the following steps: (1) In a three-necked flask, add 1g of sodium hydroxide and 10g of deionized water, stir to dissolve, then add 2g of sodium aluminate, 10g of silica sol (SiO2 content 40%), 1.3g of template agent A-1, and 100ml of water, stir evenly, then pour the material into a high-pressure reactor, seal and heat to 160℃, hydrothermal reaction for 24h, take out the material, let it stand, filter, wash the filter cake with deionized water until neutral, remove water from the washed filter cake and dry it, then place it in a muffle furnace and calcine at 650℃ for 5h, then wash it with water until neutral, and dry it at 150℃ for 12h to obtain Na-type FER molecular sieve.

[0039] (2) Dissolve 1.5g of ammonium chloride in 20ml of aqueous solution, add 3g of the Na-type FER molecular sieve obtained above, keep at 60℃ for 6 hours, filter, wash with pure water until neutral, dry to obtain NH4-type FER molecular sieve, and then calcine the obtained NH4-type FER molecular sieve at 550℃ for 3h to obtain H-type FER molecular sieve, denoted as P1.

[0040] The XRD pattern of the H-type FER molecular sieve prepared in this embodiment is as follows: Figure 1 As shown, the scanning electron microscope image is as follows: Figure 3 As shown.

[0041] Example 2: This example is the preparation method of the H-type FER molecular sieve of the present invention. The preparation method is the same as that in Example 1, except that 1.3g template agent A-1 is replaced with 1.6g template agent A-2 in step (1); the rest of the steps are the same as in Example 1. Then, the H-type FER molecular sieve is prepared and is denoted as P2.

[0042] Example 3: This example is the preparation method of the H-type FER molecular sieve of the present invention. The preparation method is the same as that in Example 1, except that 1.3g template agent A-1 is replaced with 1.2g template agent A-3 in step (1); the rest of the steps are the same as in Example 1. Then, the H-type FER molecular sieve is prepared and is denoted as P3.

[0043] Example 4: This example is the preparation method of the H-type FER molecular sieve of the present invention. The preparation method is the same as that in Example 1, except that 1.3g template agent A-1 is replaced with 1.0g template agent A-6 in step (1); the rest of the steps are the same as in Example 1. Then, the H-type FER molecular sieve is prepared and is denoted as P4.

[0044] Example 4-1: This example is the preparation method of the H-type FER molecular sieve of the present invention. It refers to the preparation method in Example 1, except that in step (1), 1.3g template agent A-1 is replaced with 1.0g template agent A-1 and 0.3g template agent A-6; the rest of the steps are the same as in Example 1. Then, the H-type FER molecular sieve is prepared and is denoted as P4-1.

[0045] Example 4-2: This example is the preparation method of the H-type FER molecular sieve of the present invention. It refers to the preparation method in Example 1, except that in step (1), 1.3g template agent A-1 is replaced with 0.3g template agent A-1 and 1.0g template agent A-6; the other steps are the same as in Example 1. Then, the H-type FER molecular sieve is prepared and is denoted as P4-2.

[0046] Comparative Example 1: This comparative example is a method for preparing an H-type FER molecular sieve. The preparation method is the same as in Example 1, except that in step (1), 1.3g of template agent A-1 is replaced with 1.9g of pyrrolidine. The remaining steps are the same as in Example 1. After that, an H-type FER molecular sieve is prepared and is denoted as PD1.

[0047] The XRD pattern of the H-type FER molecular sieve prepared in this comparative example is shown below. Figure 2 As shown.

[0048] Comparative Example 2: This comparative example is a method for preparing an H-type FER molecular sieve. The preparation method is the same as in Example 1, except that in step (1), 1.3g of template agent A-1 is replaced with 2.2g of cyclohexylamine. The remaining steps are the same as in Example 1. After that, an H-type FER molecular sieve is prepared and is denoted as PD2.

[0049] Performance testing: Experimental Example 1: Catalytic performance testing was conducted using the H-type FER molecular sieves prepared in Examples 1-4 and Comparative Examples 1-2. Using a Synthetic Catalyst Activity Tester (SCAT) apparatus, the H-type FER molecular sieve of this invention was tested as a catalyst for detecting NO in automotive exhaust. x NO removal agent X Conversion rate.

[0050] The specific test conditions are as follows: 1500 ppm NO, 2500 ppm methanol, 12% O2, 6% H2O, and balance N2; and a space velocity of 40,000 rpm, with conversion temperatures of 200℃, 250℃, 300℃, and 350℃ respectively. X The conversion rate test results are shown in Table 1 below.

[0051] Table 1: NO X Conversion rate test results The results in Table 1 show that, at the same temperature, the H-type FER molecular sieves prepared in Examples 1-4 showed a good effect on NO. X The conversion rate was significantly higher than that of the H-type FER molecular sieves prepared in Comparative Examples 1-2. However, for the same H-type FER molecular sieve, at temperatures of 200℃, 250℃, 300℃, and 350℃, the NO conversion rate decreased with increasing temperature. X Conversion rate increased.

[0052] Furthermore, in the preparation process of H-type FER molecular sieve P4 in Example 4, the template agent was A-6, and the prepared P4 had the best performance.

[0053] Experiment Example 2: Aging Resistance Test The H-type FER molecular sieves P4, P4-1, and P4-2 prepared in Examples 4, 4-1, and 4-2 of this invention were aged at high temperature and humidity. The aging conditions were set as follows: 700℃, 15% water vapor, and aging time of 8 hours. The H-type FER molecular sieves P4, P4-1, and P4-2 prepared in Examples 4 / 4-1 / 4-2 of this invention were tested using a Synthetic Catalyst Activity Tester (SCAT) device, respectively, as a test for NO₂ in automotive exhaust. X NO removal agent X Conversion rate.

[0054] The specific test conditions were as follows: 1000 ppm NO, 2000 ppm methanol, 8% O2, 5% H2O, and balance N2; and a space velocity of 40,000 rpm. The conversion temperatures were 300℃ and 350℃, respectively. X The conversion rate test results are shown in Table 2 below.

[0055] Table 2: NO X Conversion rate test results Table 2 shows that the H-type FER molecular sieve prepared by this invention exhibits excellent hydrothermal stability. After aging at 700℃ and 15% water vapor for 8 hours under high temperature and humidity, it still maintains extremely high catalytic activity, and NO at 300℃ and 350℃... X The conversion rate can still reach over 90%, and the activity of some samples only decreases slightly after aging. It has outstanding anti-aging and anti-hydrothermal deactivation capabilities and can adapt to complex and harsh exhaust gas conditions.

[0056] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing H-type FER molecular sieves, characterized in that, The preparation method includes the following steps: (1) A mixture of inorganic alkali, aluminum source, silicon source, template agent and water was subjected to hydrothermal reaction, followed by filtration, washing, drying and calcination to obtain Na-type FER molecular sieve; (2) Exchange the Na-type FER molecular sieve obtained in the previous step with the ammonium salt solution to prepare NH4-type FER molecular sieve, and then calcine the NH4-type FER molecular sieve to obtain H-type FER molecular sieve; In step (1), the template agent is A-6, and the structural formula of A-6 is shown below: ； In step (1), the molar ratio of silicon in the silicon source to aluminum in the aluminum source is 5~50:

1. The molar ratio of the alkali metal element in the inorganic base to the silicon element in the silicon source is (0.1~1):1; The water is deionized water, and the mass ratio of the water to the amount of silicon dioxide in the silicon source is (10~100):

1. The ratio of the amount of the template agent to the amount of silicon in the silicon source is 0.05 to 2:

1.

2. The method for preparing H-type FER molecular sieve as described in claim 1, characterized in that, In step (1), the inorganic base includes a water-soluble base, the aluminum source includes at least one of sodium aluminate, sodium tetrahydroxyaluminate, potassium aluminate, boehmite, boehmite, alumina, bauxite and alunite, and the silicon source includes at least one of silica sol, fumed silica and tetraethyl orthosilicate.

3. The method for preparing H-type FER molecular sieve as described in claim 2, characterized in that, The water-soluble alkali includes sodium hydroxide and / or potassium hydroxide, the aluminum source is sodium aluminate, and the silicon source is silica sol; the silica sol refers to a colloidal solution formed by uniformly dispersing nano-sized silica particles in water, and the mass concentration of silica particles in the colloidal solution is 25%~45%.

4. The method for preparing H-type FER molecular sieve as described in claim 1, characterized in that, The molar ratio of silicon in the silicon source to aluminum in the aluminum source is 5:1, 7:1, 10:1, 12:1, 15:1, 17:1, 18:1, 20:1, 23:1, 25:1, 28:1, 30:1, 32:1, 35:1, 40:1, 42:1, 45:1, 48:1 or 50:1; The molar ratio of the alkali metal element in the inorganic base to the silicon element in the silicon source is 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1; The mass ratio of the water to the amount of silicon dioxide in the silicon source is 10:1, 16:1, 20:1, 25:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1 or 100:

1. The ratio of the amount of the template agent to the amount of silicon in the silicon source is 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.4:1, 0.5:1, 0.8:1, 1:1, 1.3:1, 1.5:1, or 1.8:1, 2:

1.

5. The method for preparing H-type FER molecular sieve as described in claim 1, characterized in that, In step (2), the calcination temperature is 400~800℃ and the calcination time is 4~6h; the calcined product is washed until the washing liquid is neutral, and then dried at 120~180℃ for 8~24h.

6. An H-type FER molecular sieve, characterized in that, The H-type FER molecular sieve is prepared using the preparation method of the H-type FER molecular sieve according to any one of claims 1-5.

7. The application of the H-type FER molecular sieve as described in claim 6 in the removal of nitrogen oxides from automobile exhaust.

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