A monolithic SCR denitration catalyst based on extrusion type direct writing 3D printing and a preparation method thereof

Abstract

The present application relates to the field of catalysts, in particular to a kind of based on extrusion type direct writing 3D printing monolithic SCR denitration catalyst and its preparation method, the method will titanium dioxide, binder, reinforcing agent and pore-forming agent be mixed uniformly, then ammonium metavanadate, ammonium heptamolybdate, niobium oxalate, cerium nitrate, zirconium nitrate, peptizing agent and deionized water are mixed and stirred, continue to stir after adding auxiliary agent, two are mixed, adjust rheological property, make it form printable slurry with shear thinning characteristics and yield stress, after defoaming, using extrusion type direct writing 3D printing layer-by-layer deposition forming, and calcining, obtain the catalyst.The present application can directly construct three-dimensional interconnected pore network structure without special mould, the mechanical strength of the obtained catalyst reaches 82~97N / cm, the bulk density is 0.7~0.89g / cm 3 Outlet NO concentration ≤10ppm under 180℃~450℃, high space velocity, with good catalytic performance, thermal stability and anti-poisoning capacity.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more specifically to an integral SCR denitrification catalyst based on extrusion direct-write 3D printing and its preparation method. Background Technology

[0002] Increased energy consumption in transportation and industrial production leads to higher nitrogen oxide (NOx) emissions. X NOx emissions have become a significant factor affecting air quality and environmental health. Nitrogen oxides are not only precursors to acid rain but also have a serious impact on ozone formation and air pollution. X The main sources of NOx emissions are vehicle exhaust, industrial boilers, thermal power plants, and other combustion processes. Therefore, reducing NOx emissions has become an important issue in environmental protection and energy utilization.

[0003] Traditional NO X Treatment methods include wet denitrification, selective catalytic reduction (SCR), and selective non-catalytic reduction (SNCR). Among these, SCR denitrification technology has become one of the most widely used denitrification technologies in industry due to its high efficiency, stability, and wide applicability. However, despite its significant NOx removal efficiency, SCR denitrification technology still faces some challenges, such as insufficient catalyst mechanical strength, high bulk density, and inadequate high-temperature stability and poisoning resistance. These factors limit its application in more demanding industrial environments. Furthermore, the support molding of existing monolithic SCR denitrification catalysts is mostly achieved through extrusion or molding, and the channel structure is limited by the mold, making it difficult to achieve gradient pores, variable cross-section channels, or complex three-dimensional structures.

[0004] Patent CN115845833B discloses a method for preparing and applying an Nb-Ce-W / TiO2 denitration catalyst for SCR degradation. Using TiO2 as a support and Nb as the main active component, with Ce and W introduced as promoters, the catalyst is prepared through precursor dissolution, impregnation, water bath evaporation, drying, and calcination. This method demonstrates that the Nb, Ce, and W multi-metal system can broaden the SCR reaction temperature window and improve NO conversion performance through synergistic effects. However, it is difficult to simultaneously achieve synergistic optimization of complex channel construction, mechanical strength, and low bulk density.

[0005] CN114749216B discloses a 3D-printed monolithic catalyst porous structure and its biomimetic preparation method. The structure is designed using fluid simulation, then sliced ​​and fabricated using a direct-write molding process to create a monolithic catalyst porous structure with biomimetic channels. This method demonstrates that direct-write 3D printing is beneficial for constructing complex channels and enhancing the heat and mass transfer performance of monolithic catalysts. However, the core of this patent lies in the biomimetic porous structure design of the monolithic catalyst, not in the active component system of the NH3-SCR denitrification catalyst under operating conditions of 180℃~450℃. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, the present invention aims to provide a method for preparing a monolithic SCR denitrification catalyst based on extrusion direct-write 3D printing. The catalyst is a multi-metal oxide SCR catalyst operating at temperatures ranging from 180℃ to 450℃. After subsequent calcination at 550℃ to 600℃, the formed body needs to form a stable inorganic oxide framework and maintain unobstructed heat and mass transfer channels. The prepared catalyst exhibits higher mechanical strength, a more suitable bulk density, and a lower NO outlet concentration, while also improving catalytic performance. The catalyst of this invention can significantly improve NOx removal efficiency under actual operating conditions of 180℃ to 450℃.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing an SCR denitration catalyst based on extrusion direct-write 3D printing includes the following steps: Titanium dioxide, binder, reinforcing agent, pore-forming agent, ammonium metavanadate, ammonium heptamolybdate, niobium oxalate, water-soluble zirconium salt, water-soluble cerium salt, adhesive solvent, water and additives are mixed to form a printable paste.

[0008] The adjuvant is an alcohol amine adjuvant, which is a water-soluble organic amine compound containing at least one hydroxyl group and at least one amino group.

[0009] The mass ratio of ammonium metavanadate, ammonium heptamolybdate, niobium oxalate, water-soluble cerium salt, water-soluble zirconium salt, and colloidal solvent is 1:0.6-0.8:0.3-0.4:3.2-5.0:0.3-0.4:2.6-3.2.

[0010] After degassing, the printable slurry is deposited layer by layer using extrusion direct writing 3D printing to obtain a catalyst semi-finished product.

[0011] The catalyst semi-finished product was calcined to obtain an SCR denitration catalyst based on extrusion direct-write 3D printing.

[0012] The printable paste exhibits shear thinning characteristics at 25°C, and its thinning time is within 1 second. -1 The apparent viscosity at the shear rate is 5 × 10⁻⁶. 2Pa·s ~5×10 4 Pa·s, in 100 s -1 The apparent viscosity at the shear rate is 10 Pa·s ~ 1×10⁻⁶. 3 Pa·s; the slurry yield stress is 150 Pa~800 Pa; in the shear recovery test, the viscosity recovery rate of the slurry is not less than 70% within 60 s~180 s after high shear.

[0013] In a preferred embodiment of the present invention, the amine additive is any one or more of monoethanolamine, diethanolamine, triethanolamine and N-methylethanolamine, used for precursor complexation dispersion and adjustment of slurry printability.

[0014] In a preferred embodiment of the present invention, the mass of the adhesive is 7% to 15% of the mass of titanium dioxide, the mass of the reinforcing agent is 7.5% to 16% of the mass of titanium dioxide, and the mass of the pore-forming agent is 3% to 5.5% of the mass of titanium dioxide.

[0015] In a preferred embodiment of the present invention, the mass of the adhesive is 12% of the mass of titanium dioxide, the mass of the reinforcing agent is 8% of the mass of titanium dioxide, and the mass of the pore-forming agent is 4% of the mass of titanium dioxide.

[0016] In a preferred embodiment of the present invention, the adhesive is one or more of aluminum stearate, attapulgite, and kaolin; the reinforcing agent is one or more of hydroxyethyl cellulose, alkali-free glass fiber, and methyl cellulose; and the pore-forming agent is one or more of carbon black, cellulose, and lignin.

[0017] In a preferred embodiment of the present invention, the water-soluble zirconium salt is any one or more of zirconium nitrate, zirconium oxynitrate, zirconium oxynitrate, zirconium acetate, and zirconium oxychloride; the water-soluble cerium salt is selected from any one or more of cerium nitrate, cerium ammonium nitrate, cerium acetate, and cerium sulfate; the colloidal solvent is citric acid, oxalic acid, sulfuric acid, or nitric acid; the mass ratio of the mixed powder to the mixed material is 1.5~1.8:1; and the amount of additive added is 0.5%~2.5% of the mass of titanium dioxide.

[0018] In a preferred embodiment of the present invention, the mixing method is any one of stirring, kneading or ball milling; the printing parameters for extrusion direct-write 3D printing layer-by-layer deposition are: nozzle inner diameter of 0.2mm~1.5mm, layer height of 0.1mm~0.8mm, printing speed of 5mm / s~80mm / s, fill rate of 20%~100%, and printing pressure of 0.1MPa~0.8MPa.

[0019] In a preferred embodiment of the present invention, the mixing temperature is 20℃~30℃, the mixing time is 10 min~60 min, the degassing pressure is -0.08 MPa~-0.095 MPa, and the degassing time is 5 min~30 min.

[0020] In a preferred embodiment of the present invention, the heating rate of calcination is 5-15℃ / min, the calcination temperature is 550℃~600℃, and the calcination time is 2h~3h.

[0021] Another objective of this invention is to produce an SCR denitrification catalyst based on extrusion direct-write 3D printing using the aforementioned preparation method.

[0022] The catalyst has a permeable integral structure with an outer contour that is a polyhedron, a polygonal column, a short column, or a near-spherical shape. The interior is a three-dimensional interconnected network of channels formed by interlaced filament bundles or support rods. The unit structure can be any one or more of the following: grid unit, honeycomb unit, straight channel unit, regular tetrahedron unit, or biomimetic curved channel unit.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. The preparation method of this invention incorporates alkanolamine additives, which complex and disperse the precursors of the metal active components (ammonium metavanadate, ammonium heptamolybdate, niobium oxalate, water-soluble zirconium salt, and water-soluble cerium salt, etc.), improving the dispersion uniformity of each active component in the slurry and preventing the agglomeration of active species after calcination, thereby increasing the density of active sites on the catalyst surface. Vanadium (V) and cerium (Ce), as the main active components, maintain high catalytic activity in a wide temperature range of 180℃ to 450℃, ensuring that the NO outlet concentration is not greater than 10%. ppm; By adding appropriate amounts of water-soluble zirconium salt, water-soluble cerium salt, and ammonium heptamolybdate, the activity, thermal stability, and anti-poisoning ability of the main active components vanadium and cerium on the catalyst surface can be effectively improved, affecting their active site density and high-temperature resistance, as well as their long-term effective use, thereby optimizing the catalyst's catalytic ability; Furthermore, the preparation method is simple, requiring no special mold, and can be directly deposited layer by layer using high-solids-content printable slurry, eliminating the dependence on molds in traditional extrusion or compression molding, enabling the rapid construction of complex three-dimensional structures, and facilitating customized design according to different flue gas conditions.

[0024] 2. The denitrification catalyst prepared by the method of this invention has high mechanical strength, reaching 82 N / cm to 97 N / cm, is not easily pulverized, has a long service life, and is suitable for practical industrial applications; the catalyst has a low bulk density of 0.7 g / cm³. 3 ~0.89g / cm 3 At temperatures of 180℃~450℃ and NO concentrations of 400ppm~2000ppm, for 60,000 hours...-1 ~80000h -1 Under high air velocity conditions, the NO concentration in the outlet flue gas can be guaranteed to be no more than 10 ppm.

[0025] 3. This invention uses extrusion-based direct-write 3D printing, which can quickly construct integral structures such as honeycomb, mesh, tetrahedron or biomimetic interconnected channels without the need for special molds, making it easy to customize designs according to different flue gas conditions. Compared with traditional extrusion or compression molding, it is beneficial to reduce pressure drop, improve heat and mass transfer, and take into account both high mechanical strength and low bulk density. Attached Figure Description

[0026] Figure 1 This is a representative three-dimensional structural diagram of the monolithic SCR denitrification catalyst in Example 1.

[0027] Figure 2 This is a representative three-dimensional structural diagram of the monolithic SCR denitrification catalyst in Example 2. Detailed Implementation

[0028] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0030] Example 1 A method for preparing an SCR denitration catalyst based on extrusion direct-write 3D printing includes the following steps: (1) Mix 3000g of titanium dioxide, 420g of binder, 260g of reinforcing agent and 150g of pore-forming agent evenly to obtain a mixed powder; the binder is attapulgite and aluminum stearate (mass ratio of 2:1), the reinforcing agent is hydroxyethyl cellulose and alkali-free glass fiber (mass ratio of 1:1), and the pore-forming agent is lignin and cellulose (mass ratio of 1:1).

[0031] (2) Mix 91g ammonium metavanadate, 236g cerium nitrate, 24.6g ethanolamine, 37.5g ammonium heptamolybdate, 26.6g niobium oxalate, 28.4g zirconium nitrate, 95g adhesive solvent and 1762g water evenly to obtain a mixture: the adhesive solvent is sulfuric acid (chemically pure).

[0032] (3) Mix the mixture in (2) with the powder in step one evenly, add an appropriate amount of deionized water to adjust to obtain a printable slurry, and after degassing, use extrusion direct writing 3D printing to form the slurry; the printing parameters can be selected within the following range: nozzle inner diameter 0.8mm, layer height 0.65mm, printing speed 20mm / s, filling rate 60%, printing pressure 0.3MPa; to obtain a catalyst semi-finished product with a polyhedral, polygonal columnar, short columnar or near-spherical shape, and an internal permeable three-dimensional interconnected channel network composed of interlaced filament bundles / support rods.

[0033] (4) After drying the catalyst semi-finished product described in (3), calcinate it at 570°C for 3 hours, and after cooling, obtain an integral finished catalyst with a polyhedral, polygonal columnar, short columnar, or near-spherical shape and an internal permeable three-dimensional interconnected pore network. Its three-dimensional structure is shown in the figure below. Figure 1 As shown.

[0034] Example 2 A method for preparing an SCR denitration catalyst based on extrusion direct-write 3D printing includes the following steps: (1) Mix 3000g of titanium dioxide, 630g of binder, 310g of reinforcing agent and 180g of pore-forming agent evenly to obtain a mixed powder; the binder is attapulgite and aluminum stearate (mass ratio 1:2), the reinforcing agent is methylcellulose and hydroxyethylcellulose (mass ratio 1:1), and the pore-forming agent is lignin and carbon black (mass ratio 1:1).

[0035] (2) Mix 79g ammonium metavanadate, 256g cerium nitrate, 48.3g ammonium heptamolybdate, 51.3g ethanolamine, 28.1g niobium oxalate, 27.6g zirconium nitrate, 210g adhesive solvent and 1780g water evenly to obtain a mixture: the adhesive solvent is oxalic acid (chemically pure). (3) Mix the mixture in (2) with the powder in step one evenly, add an appropriate amount of deionized water to adjust to obtain a printable slurry, and after degassing, use extrusion direct writing 3D printing to form the slurry; the printing parameters can be selected within the following range: nozzle inner diameter 1.0 mm, layer height 0.85 mm, printing speed 40 mm / s, filling rate 75%, printing pressure 0.5 MPa; to obtain a catalyst semi-finished product with a polyhedral, polygonal columnar, short columnar or near-spherical shape, and an internal permeable three-dimensional interconnected channel network composed of interlaced filament bundles / support rods.

[0036] (4) After drying the catalyst semi-finished product described in (3), calcinate it at 600℃ for 3 hours, and after cooling, obtain an integral finished catalyst with a polyhedral, polygonal columnar, short columnar, or near-spherical shape and an internal permeable three-dimensional interconnected pore network. Its three-dimensional structure is shown in the figure. Figure 2 As shown.

[0037] Example 3 A method for preparing an SCR denitration catalyst based on extrusion direct-write 3D printing includes the following steps: (1) Step 1: Mix 3000g of titanium dioxide, 570g of binder, 360g of reinforcing agent and 150g of pore-forming agent evenly to obtain a mixed powder; the binder is attapulgite and aluminum stearate (mass ratio 3:1), the reinforcing agent is hydroxyethyl cellulose, methyl cellulose and alkali-free glass fiber (mass ratio 1:1:1), and the pore-forming agent is lignin, cellulose and carbon black (mass ratio 1:1:1); (2) Step 2: Mix 71g ammonium metavanadate, 355g cerium nitrate, 52.1g ammonium heptamolybdate, 52.4g ethanolamine, 27.6g niobium oxalate, 28.1g zirconium nitrate, 220g adhesive solvent, and 1770g water evenly to obtain a mixture. The adhesive solvent is nitric acid (chemically pure). (3) Step 3: Mix the mixture in Step 2 with the powder in Step 1 evenly, add an appropriate amount of deionized water to adjust and obtain a printable slurry, and then degas it and use extrusion direct writing 3D printing to form it; the printing parameters can be selected within the following range: nozzle inner diameter 1.2mm, layer height 1.1mm, printing speed 80mm / s, filling rate 90%, printing pressure 0.6MPa; to obtain a catalyst semi-finished product with a polyhedral, polygonal columnar, short columnar or near-spherical shape, and an internal permeable three-dimensional interconnected channel network composed of interlaced filament bundles / support rods.

[0038] Step 4: After drying the catalyst semi-finished product described in Step 3, calcine it at 600℃ for 2 hours. After cooling, a monolithic finished catalyst with a polyhedral, polygonal columnar, short columnar, or near-spherical shape and an internal permeable three-dimensional interconnected pore network is obtained. Its three-dimensional structure is shown in the diagram below. Figure 2 As shown.

[0039] Comparative Example 1 The traditional extrusion molding process includes the following steps: (1) Mix 3000g of titanium dioxide, 360g of binder, 95g of reinforcing agent and 150g of pore-forming agent evenly to obtain a mixed powder; the binder is aluminum stearate, the reinforcing agent is alkali-free glass fiber and the pore-forming agent is carbon black.

[0040] (2) Mix 96g ammonium metavanadate, 210g cerium nitrate, 76.2g ammonium heptamolybdate, 25.3g niobium oxalate, 75g adhesive solvent and 1700g water evenly to obtain a mixture: the adhesive solvent is citric acid (chemically pure).

[0041] (3) Mix the mixture in (2) with the powder in step one evenly, adjust it to a plastic wet material suitable for traditional extrusion molding, and then use traditional extrusion molding to obtain a cylindrical catalyst semi-finished product through a die. The catalyst can be stacked into a multi-cylinder clover or four-leaf clover shape.

[0042] (4) After drying the catalyst semi-finished product obtained by extrusion molding in (3), it is calcined at 550°C for 2 hours and cooled to obtain a cylindrical catalyst with a diameter of 0.9 mm and a length of 10 mm.

[0043] Comparative Example 2 The traditional extrusion molding process includes the following steps: (1) Mix 3000g of titanium dioxide, 560g of binder, 300g of reinforcing agent and 75g of pore-forming agent evenly to obtain a mixed powder; the binder is attapulgite, the reinforcing agent is methylcellulose and the pore-forming agent is lignin.

[0044] (2) Mix 98g ammonium metavanadate, 180g cerium nitrate, 142.2g ammonium heptamolybdate, 23.3g ethanolamine, 51.3g niobium oxalate, 95g adhesive solvent and 1740g water evenly to obtain a mixture: the adhesive solvent is citric acid (chemically pure).

[0045] (3) Mix the mixture in (2) with the powder in step one evenly, adjust it to a plastic wet material suitable for traditional extrusion molding, and then use traditional extrusion molding to obtain a cylindrical catalyst semi-finished product through a die. The catalyst can be stacked into a multi-cylinder clover or four-leaf clover shape.

[0046] (4) After drying the catalyst semi-finished product obtained by extrusion molding in (3), it is calcined at 560°C for 3 hours and cooled to obtain a cylindrical catalyst with a diameter of 0.9 mm and a length of 10 mm.

[0047] Results Analysis The catalyst prepared in Example 1 of this invention has a mechanical strength of 94 N / cm, is not easily pulverized, has a long service life, and a bulk density of 0.83 g / cm³. 3 .

[0048] The catalytic performance of the monolithic finished catalyst prepared in this example was evaluated according to the evaluation method described in Example 1, and the evaluation results are shown in Table 1.

[0049] Table 1. Outlet NO concentration of the catalytic reaction at different temperatures and with different inlet NO concentrations.

[0050] As shown in Table 1, within the temperature range of 180℃ to 450℃, the NO outlet concentration is generally between 8 ppm and 10 ppm. At 180℃, the NO outlet concentration reaches 10 ppm; at 400℃ and 450℃, within the range of 400 ppm to 2000 ppm for the NO inlet concentration, the NO outlet concentration remains around 9 ppm.

[0051] The catalyst prepared in Example 2 of this invention has a mechanical strength of 95 N / cm, is not easily pulverized, has a long service life, and while improving the mechanical strength of the catalyst, its bulk density is controlled at 0.7~0.89 g / cm³. 3 .

[0052] The catalytic performance of the monolithic finished catalyst prepared in this example was evaluated according to the evaluation method described in Example 1, and the evaluation results are shown in Table 2.

[0053] Table 2. Outlet NO concentration of the catalytic reaction at different temperatures and inlet NO concentrations.

[0054] As shown in Table 2, the NO outlet concentration is generally between 7 ppm and 9 ppm within the temperature range of 180℃ to 450℃. At 180℃, the NO outlet concentration is 8 ppm; at 400℃, the NO inlet concentration is between 400 ppm and 2000 ppm, while the NO outlet concentration remains around 8 ppm.

[0055] The catalyst prepared in Example 3 of this invention has a mechanical strength of 97 N / cm, is not easily pulverized, has a long service life, and a bulk density of 0.89 g / cm³. 3 .

[0056] The catalytic performance of the monolithic finished catalyst prepared in Example 3 was evaluated according to the evaluation method described in Example 1, and the evaluation results are shown in Table 3.

[0057] Table 3. Outlet NO concentration of the catalytic reaction at different temperatures and inlet NO concentrations.

[0058] As can be seen from Table 3, within the temperature range of 180℃ to 450℃, the NO outlet concentration is generally between 7ppm and 8ppm. At 180℃, the NO outlet concentration is 8ppm; within the temperature range of 350℃ to 450℃, the NO inlet concentration is between 400ppm and 2000ppm, while the NO outlet concentration remains around 7ppm.

[0059] The catalyst prepared in Comparative Example 1 of this invention has a mechanical strength of 82 N / cm, is not easily pulverized, has a long service life, and a bulk density of 0.74 g / cm³. 3 .

[0060] The catalytic performance of the cylindrical catalyst prepared in Comparative Example 1 was evaluated. The evaluation method was as follows: 10 ml of catalyst was loaded into a tubular reactor. N2 and air were introduced into the reactor, and it was heated. After the temperature reached 180℃, NO, NH3, and water vapor were introduced. After stabilizing for about 1 hour, the NO concentration at the reactor outlet and inlet was measured. After measurement, the flow meter temperature parameter was adjusted, and after stabilization, the next temperature measurement point (230℃, 290℃, 350℃, 400℃, and 450℃) was measured. After measurement, NO, NH3, water vapor, and air were shut off, and the pipeline was purged with N2 for about half an hour before the entire system was shut down. The measurement conditions were: space velocity 60000h~80000h, temperature 180℃~450℃, NO volume concentration 400ppm~2000ppm, NH3 / NO (molar ratio) = 1.0, water vapor volume ratio 5%, O2 concentration 10%, and equilibrium gas N2. The evaluation results are shown in Table 4.

[0061] Table 4. Outlet NO concentration of the catalytic reaction at different temperatures and with different inlet NO concentrations.

[0062] As shown in Table 4, within the temperature range of 180℃ to 450℃, the NO outlet concentration is generally between 8 ppm and 10 ppm. At 180℃, the NO outlet concentration reaches 10 ppm; at 400℃, the NO inlet concentration is in the range of 400 ppm to 2000 ppm, while the NO outlet concentration remains around 9 ppm.

[0063] The catalyst prepared in this embodiment has a mechanical strength of 85 N / cm, is not easily pulverized, has a long service life, and a bulk density of 0.76 g / cm³. 3 .

[0064] The catalytic performance of the cylindrical catalyst prepared in this example was evaluated according to the evaluation method described in Example 1, and the evaluation results are shown in Table 5.

[0065] Table 5. Outlet NO concentration of the catalytic reaction at different temperatures and with different inlet NO concentrations.

[0066] As shown in Table 2, the NO outlet concentration remained between 8 ppm and 10 ppm within the temperature range of 180℃ to 450℃. At 180℃, the NO outlet concentration reached 10 ppm; at 400℃, the NO outlet concentration remained around 10 ppm within the range of 400 ppm to 2000 ppm at the NO inlet concentration. Compared to Example 1, the mechanical strength of the catalyst increased from 82 N / cm to 85 N / cm after adding the ethanolamine additive under conventional extrusion molding conditions, indicating that the ethanolamine additive has a promoting effect on the catalyst molding performance and SCR denitrification performance.

[0067] Comparative Examples 1 and 2 show that under traditional extrusion molding conditions, the mechanical strength of the catalyst increased from 82 N / cm to 85 N / cm after the addition of alkanolamine auxiliaries. This indicates that alkanolamine auxiliaries have a certain promoting effect on the dispersion and molding performance of the precursor. However, traditional extrusion molding still has difficulty forming complex three-dimensional interconnected pore structures.

[0068] As can be seen from the comparison between Example 1 and Comparative Examples 1 and 2, the mechanical strength of the catalyst increased to 94 N / cm after using extrusion direct writing 3D printing. This indicates that the structural integrity and anti-pulverization ability of the monolithic catalyst can be significantly improved by rheological control of printable slurry and layer-by-layer deposition molding.

[0069] A comparison of Examples 2 and 3 with Example 1 shows that after introducing zirconium nitrate and optimizing the ratio of vanadium, cerium, molybdenum, niobium, zirconium multimetal components and colloidal solvent, the mechanical strength of the catalyst is further improved to 95 N / cm~97 N / cm, and the NO outlet concentration is reduced from 8 ppm~10 ppm to 7 ppm~9 ppm. In the preferred embodiment, the NO outlet concentration is stable at 7 ppm~8 ppm in the range of 180℃~450℃.

[0070] In summary, this invention employs a combined technical approach of "alkanolamine-based auxiliary agent complexation and dispersion + slurry rheology regulation + extrusion direct-write 3D printing molding + multi-metal oxide synergistic active component" to enable the catalyst to possess high mechanical strength, customizable three-dimensional interconnected channels, low NO outlet concentration, and excellent wide-temperature SCR denitrification performance. Compared with traditional extrusion-molded catalysts, this invention does not require a dedicated extrusion die and can customize honeycomb, mesh, tetrahedral, or biomimetic curved channel structures according to flue gas conditions, which is beneficial for improving heat and mass transfer, reducing the risk of local blockage, and increasing the effective utilization rate of the catalyst. It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0071] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing an SCR denitration catalyst based on extrusion direct-write 3D printing, characterized in that, Includes the following steps: Titanium dioxide, binder, reinforcing agent, pore-forming agent, ammonium metavanadate, ammonium heptamolybdate, niobium oxalate, water-soluble zirconium salt, water-soluble cerium salt, adhesive solvent, water and additives are mixed to form a printable paste; The adjuvant is an alcohol amine adjuvant, a water-soluble organic amine compound containing at least one hydroxyl group and at least one amino group; The mass ratio of ammonium metavanadate, ammonium heptamolybdate, niobium oxalate, water-soluble cerium salt, water-soluble zirconium salt, and colloidal solvent is 1:0.6-0.8:0.3-0.4:3.2-5.0:0.3-0.4:2.6-3.2; After degassing, the printable slurry is deposited layer by layer using extrusion direct-write 3D printing to obtain a catalyst semi-finished product. The catalyst semi-finished product was calcined to obtain an SCR denitrification catalyst based on extrusion direct-write 3D printing.

2. The preparation method of the SCR denitration catalyst based on extrusion direct-write 3D printing according to claim 1, characterized in that, The amine adjuvant is any one or more of monoethanolamine, diethanolamine, triethanolamine, and N-methylethanolamine.

3. The preparation method of the SCR denitration catalyst based on extrusion direct-write 3D printing according to claim 1, characterized in that, The mass of the binder is 7% to 15% of the mass of titanium dioxide, the mass of the reinforcing agent is 7.5% to 16% of the mass of titanium dioxide, and the mass of the pore-forming agent is 3% to 5.5% of the mass of titanium dioxide.

4. The preparation method of the SCR denitration catalyst based on extrusion direct-write 3D printing according to claim 1, characterized in that, The adhesive is one or more of aluminum stearate, attapulgite, and kaolin; the reinforcing agent is one or more of hydroxyethyl cellulose, alkali-free glass fiber, and methyl cellulose; and the pore-forming agent is one or more of carbon black, cellulose, and lignin.

5. The method for preparing the SCR denitration catalyst based on extrusion direct-write 3D printing according to claim 1, characterized in that, The water-soluble zirconium salt is any one or more of zirconium nitrate, zirconium oxynitrate, zirconium oxynitrate, zirconium acetate, and zirconium oxychloride; the water-soluble cerium salt is selected from any one or more of cerium nitrate, cerium ammonium nitrate, cerium acetate, and cerium sulfate; the adhesive solvent is citric acid, oxalic acid, sulfuric acid, or nitric acid; the total solids content of the printable slurry is 65 wt% to 75 wt%; the amount of additives added is 0.5% to 2.5% of the mass of titanium dioxide.

6. The method for preparing the SCR denitration catalyst based on extrusion direct-write 3D printing according to claim 1, characterized in that, The mixing method can be any one of stirring, kneading or ball milling; the printing parameters for extrusion direct-write 3D printing layer-by-layer deposition are: nozzle inner diameter 0.2mm~1.5mm, layer height 0.1mm~0.8mm, printing speed 5mm / s~80mm / s, fill rate 20%~100%, and printing pressure 0.1MPa~0.8MPa.

7. The method for preparing the SCR denitration catalyst based on extrusion direct-write 3D printing according to claim 6, characterized in that, The degassing pressure is -0.08 MPa to -0.095 MPa, and the degassing time is 5 min to 30 min.

8. The method for preparing the SCR denitration catalyst based on extrusion direct-write 3D printing according to claim 1, characterized in that, The heating rate for calcination is 5℃ / min-15℃ / min, the calcination temperature is 550℃~600℃, and the calcination time is 2h~3h.

9. An SCR denitrification catalyst prepared by the preparation method according to any one of claims 1-8 based on extrusion direct-write 3D printing.

10. The SCR denitrification catalyst based on extrusion direct-write 3D printing according to claim 9, characterized in that, The catalyst has a permeable integral structure with an outer contour that is a polyhedron, a polygonal column, a short column, or a near-spherical shape. The interior is a three-dimensional interconnected network of channels formed by interlaced filament bundles or support rods. The unit structure can be any one or more of the following: grid unit, honeycomb unit, straight channel unit, regular tetrahedron unit, or biomimetic curved channel unit.

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