Cu-SUZ-4 molecular sieve as well as preparation method and application thereof

Abstract

The invention discloses a Cu-SUZ-4 molecular sieve as well as a synthesis method and application thereof. In the prior art, a Cu-SUZ-4 molecular sieve needs to be prepared by adopting seed crystal assistance and step-by-step loading of a copper source, the invention provides a method for synthesizing the Cu-SUZ-4 molecular sieve by a one-step hydrothermal in-situ method of the copper source under a seed crystal-free condition, and the method comprises the following steps: mixing a silicon source, an aluminum source, a mineralizing agent, tetraethylammonium hydroxide, the copper source and water according to a set molar ratio to form gel; and carrying out hydrothermal crystallization to synthesize the Cu-SUZ-4 molecular sieve. The invention further discloses the Cu-SUZ-4 molecular sieve and application thereof in NH3-SCR reaction, the NOx removal efficiency of the catalyst in the temperature range of 250-450 DEG C exceeds 90 vol%, and the catalyst has high catalytic activity, sulfur resistance and hydrothermal stability and is suitable for the fields of diesel vehicle tail gas denitration and industrial waste gas purification.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of molecular sieves, and particularly relates to a method for synthesizing Cu-SUZ-4 molecular sieves by one-step hydrothermal in-situ doping of a copper source without seed assistance. Background Art

[0002] As one of the main air pollutants, nitrogen oxides (NOx) are important precursors of acid rain, photochemical smog and fine particulate matter (PM2.5), seriously threatening the ecological environment and human health. To effectively control NOx emissions, Selective Catalytic Reduction (SCR) technology has become the mainstream solution in the global industrial and mobile source denitrification fields due to its high efficiency and maturity. The core of the SCR technology is that through the action of a catalyst, within a specific temperature window, the reducing agent (such as ammonia or urea) selectively reacts with NOx in the flue gas to generate harmless nitrogen (N2) and water (H2O). The denitrification efficiency of this technology can reach more than 90%, and it is applicable to complex working conditions with high concentrations of NOx. It is currently the only large-scale denitrification method that can meet strict emission standards (such as National VI and Euro VI). Compared with technologies such as Selective Non-Catalytic Reduction (SNCR) and adsorption methods, the core advantages of SCR are: ① High efficiency: The catalyst significantly reduces the reaction activation energy, achieving high-efficiency denitrification in a wide temperature window from low temperature to high temperature (150 - 450 °C); ② Precision: By catalyst design, side reactions (such as SO2 oxidation) are selectively inhibited, reducing secondary pollution; ③ Adaptability: It can match various emission sources such as coal-fired power plants, boilers, and diesel vehicles, and has strong technical versatility.

[0003] The NH3-SCR technology usually uses V2O5-WO3 / TiO2 as a catalyst, but it has problems such as poor low-temperature activity, a narrow active temperature window range, and the toxicity of the active component V2O5, and has been gradually phased out in European and American countries. Molecular sieve-based SCR catalysts have advantages such as high catalytic activity, strong water and sulfur resistance, good thermal stability, and a wide reaction temperature range, and are considered to be the most promising SCR catalysts in terms of development research significance and practical application value.

[0004] The SUZ-4 molecular sieve belongs to the SZR type of silicoaluminate molecular sieve. Its crystal structure belongs to the orthorhombic system (space group Cmmm), and the unit cell parameters are: a≈18.8064 Å, b≈14.2298 Å, c≈7.4548 Å, α = β = γ = 90.00°. Its framework is formed by connecting [SiO4] and [AlO4] tetrahedra through oxygen bridges, constructing a three-dimensional cross-channel system: the main channel along the

[001] direction is a ten-membered ring with a pore size of 5.2 Å×4.1 Å, providing an efficient mass transfer channel; the secondary channels along the

[010] and

[110] directions are eight-membered rings with pore sizes of 4.8 Å×3.2 Å and 4.8 Å×3.0 Å respectively, enhancing the shape selectivity of the molecular sieve. This microporous structure endows the SUZ-4 molecular sieve with a high specific surface area (>400 m² / g), adjustable acidic sites, and excellent ion exchange ability. In addition, the flexible coordination characteristics of the Si-O-Al bonds in its framework provide a structural basis for the uniform doping of transition metals (such as Cu, Fe), enabling it to exhibit significant application potential in fields such as selective catalytic reduction of denitrification, conversion of light alkanes, and gas adsorption and separation.

[0005] In recent years, the following key progress has been reflected in the patented technologies related to the synthesis of metal-containing SUZ-4 molecular sieves: Patent CN116273148B synthesized potassium-type K-SUZ-4 molecular sieve by a one-step hydrothermal method, and then treated the K-SUZ-4 molecular sieve with an ammonium salt solution to obtain hydrogen-type H-SUZ-4 molecular sieve. Finally, a metal salt solution was used to treat the H-SUZ-4 molecular sieve to obtain a metal-containing heteroatom molecular sieve M-SUZ-4. This molecular sieve can simultaneously increase the Brønsted acid and the Lewis acid formed around the metal, effectively improving the catalytic performance of the SUZ-4 molecular sieve for dimethyl ether carbonylation. Patent CN109174172A proposed to synthesize a heteroatom-containing SUZ-4 molecular sieve by a one-step heating method using the dry gel method on the premise of adding SUZ-4 seeds. This catalyst has excellent low-temperature NH3-SCR catalytic performance, but the seeds need to be prepared in advance. Patent CN109289908A proposed that on the basis of the synthesis of the SUZ-4 molecular sieve, a phosphorus-nickel modified SUZ-4 molecular sieve was obtained by the equal-volume impregnation method using a phosphorus source and a nickel source, and then metal elements were loaded on this carrier by the impregnation method to obtain a metal-containing SUZ-4 molecular sieve. Patent US06645448B2 proposed that on the basis of the synthesis of the SUZ-4 molecular sieve, a metal-containing SUZ-4 molecular sieve was further obtained by the ion exchange method.

[0006] The innovation of the Cu-SUZ-4 molecular sieve disclosed in this patent lies in: directly synthesizing the target product by in-situ doping of copper source using a one-step hydrothermal method, without the assistance of seeds or stepwise treatment. Compared with the traditional stepwise method that requires prior synthesis of the SUZ-4 support followed by copper loading or copper exchange, and the synthesis method relying on seed assistance, the present invention simplifies the process flow, synchronously eliminates redundant steps such as seed preparation and copper ion exchange, significantly reduces equipment investment and energy consumption, shortens the production cycle, and provides an efficient and low-cost solution for the functional modification of molecular sieves and industrial production. Summary of the Invention

[0007] Aiming at the bottleneck problems such as strong seed dependence and complex stepwise operation in the traditional synthesis process of Cu-SUZ-4 molecular sieves, the present invention proposes a one-step hydrothermal in-situ copper doping technology to achieve the efficient synthesis of Cu-SUZ-4 through the synchronous construction of copper source and molecular sieve framework under the condition of no seed assistance.

[0008] The present invention adopts the following technical solutions:

[0009] Step 1: Drop water, aluminum source and mineralizer into a polytetrafluoroethylene inner liner.

[0010] Step 2: Slowly drop the template agent tetraethylammonium hydroxide into the solution in Step 1, stir evenly to form a mixed solution.

[0011] Step 3: Add a silicon source to the solution in Step 2 and stir evenly.

[0012] Step 4: Add a copper source to the solution in Step 3, stir evenly to form a mixed solution, and age.

[0013] Step 5: Place the polytetrafluoroethylene inner liner containing the above mixed solution in a stainless steel autoclave, seal it and then place it in a crystallization reactor for crystallization heating.

[0014] Step 6: After the crystallization is completed, cool the stainless steel autoclave to room temperature, wash the crystallization product with deionized water, separate the solid and liquid to obtain a solid product, and place it in an oven for drying to obtain a Cu-SUZ-4 molecular sieve precursor.

[0015] Step 7: Calcinate the Cu-SUZ-4 molecular sieve precursor in a heating furnace to obtain a Cu-SUZ-4 molecular sieve.

[0016] Step 8: Perform ammonium exchange on the Cu-SUZ-4 molecular sieve and further calcine it to obtain a hydrogen-type Cu-SUZ-4 molecular sieve.

[0017] Step 9: Press and granulate the molecular sieve obtained in Step 8, and evaluate its catalytic performance in the NH3-SCR reaction using a catalytic reaction test device.

[0018] Further, in step 1, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the copper source is calculated as Cu, the mineralizer is calculated as OH - calculated, tetraethylammonium hydroxide is calculated as TEA + calculated, and water is calculated as H2O. A gel is synthesized at a molar ratio of SiO2 / Al2O3 = 5 to 80, Cu / Al2O3 = 0 to 5, KOH / Al2O3 = 1 to 20, TEA + / Al2O3 = 1 to 10, and H2O / Al2O3 = 10 to 1000. Preferably, a gel is synthesized at a molar ratio of SiO2 / Al2O3 = 10 to 40, Cu / Al2O3 = 0.01 to 3, KOH / Al2O3 = 4 to 10, TEA + / Al2O3 = 1 to 5, and H2O / Al2O3 = 100 to 600.

[0019] Further, in step 1, the aluminum source is selected from at least one of the group consisting of aluminum powder, aluminum isopropoxide, aluminum hydroxide, alumina, pseudo-boehmite, coal gangue, aluminum sulfate, aluminum nitrate, and aluminum chloride; the mineralizer is selected from at least one of the group consisting of potassium hydroxide, sodium hydroxide, and lithium hydroxide; in step 3, the silicon source is selected from at least one of the group consisting of silicic acid, silica sol, sodium silicate, white carbon black, methyl orthosilicate, ethyl orthosilicate, coal gangue, clay, and water glass; in step 4, the copper source is selected from at least one of the group consisting of copper nitrate, copper sulfate, copper chloride, copper acetate, and copper oxide; in step 8, the ammonium source used in the ammonium exchange process is selected from at least one of the group consisting of ammonium chloride, ammonium nitrate, ammonium citrate, and ammonium tartrate.

[0020] Further, in step 5, the crystallization reactor is selected from at least one of the group consisting of a homogeneous reactor, an oven, and a stirred reaction kettle. The crystallization process of the mixture is dynamic crystallization or static crystallization by rotation / stirring, with a rotation speed of 10 to 40 rpm and a stirring speed of 30 to 200 rpm; the crystallization conditions of the mixture are crystallization for 1 to 12 days at 110 to 200 °C, preferably crystallization for 2 to 8 days at 130 to 180 °C, and more preferably crystallization for 4 to 6 days at 140 to 160 °C.

[0021] Further, in step 6, after the crystallization step is completed, the obtained solid-liquid mixture can be separated by any conventionally known separation method. As the separation method, for example, methods such as filtering, washing, and drying the obtained mixture can be cited. Here, the filtering, washing, and drying can be carried out in any manner conventionally known in the art. Specifically, for example, as the filtering, the obtained product mixture can be simply filtered by suction. As the washing, for example, washing with deionized water and / or ethanol can be cited. As the drying temperature, for example, 40-250 °C can be cited, preferably 60-120 °C. As the drying time, for example, 8-30 h can be cited, preferably 10-20 h. This drying can be carried out at normal pressure or under reduced pressure. In step 7, the calcination can be carried out in any manner conventionally known in the art. The heating furnace includes at least one of a muffle furnace or a tubular furnace. The calcination temperature is generally 450-700 °C, preferably 500-600 °C, and the calcination time is generally 3-10 h, preferably 4-6 h. The heating rate during the calcination process is 4-5 °C / min. Additionally, the calcination is generally carried out in an oxygen-containing atmosphere, such as an air or oxygen atmosphere.

[0022] Further, in step 8, the ammonium exchange of the Cu-SUZ-4 molecular sieve is to exchange the alkali metal cations such as Na + , K + in the molecular sieve into NH 4+ . The exchange is carried out at 20-60 °C for 0.5-4 h, and can be carried out once or multiple times. After the ammonium ion exchange, it is dried at 60-120 °C for 4-24 h, and then calcined. The calcination temperature is 500-600 °C, the calcination time is 1-12 h, and the calcination atmosphere is oxygen or air, to obtain a hydrogen-type Cu-SUZ-4 molecular sieve.

[0023] Further, in step 9, after the molecular sieve is tableted and formed, the granule size is selected to be 10-20 mesh. The catalytic reaction test device is selected from at least one of a fixed-bed reactor or a solar-driven thermal catalytic reactor. The reaction raw material gas composition is 500 ppm NH3, 500 ppm NO, 5% O2, and N2 as the balance carrier gas. The volumetric space velocity of the raw material gas is GHSV = 80,000 h -1 . A photoacoustic spectrometer is used to detect the concentrations of NO, N2O, NH3, and O2 before and after the reaction.

[0024] Compared with the prior art, the characteristics of the present invention are as follows: By directly introducing a copper source into the initial gel system, in-situ embedding of Cu² + is realized during the formation process of the molecular sieve, eliminating the metal ion exchange and loading steps and the seed preparation step in the traditional synthesis process of Cu-SUZ-4 molecular sieve, significantly shortening the process flow and reducing the production cost.

[0025] The Cu-SUZ-4 molecular sieve prepared by this method shows outstanding potential in the field of NH3-SCR environmental catalysis due to its high copper loading, excellent thermal stability (the specific surface area retention rate is >90% after calcination at 700 °C), and active site accessibility: the active temperature window ranges from 250 to 450 °C. Under low-temperature conditions (250 - 300 °C), NH3 and Cu² + form [Cu(NH3)2] + complex, which serves as a dynamic active site and promotes the reduction of NOx through local homogeneous reactions. This mechanism can significantly increase the reaction rate, and the low-temperature NOx conversion efficiency can reach over 90%. The pore structure of Cu-SUZ-4 allows the active sites to remain efficient within a wide temperature range, especially in the scenario of diesel vehicle exhaust treatment with alternating cold start and high-temperature regeneration. Description of the Drawings

[0026] Figure 1 It is a graph of the NOx conversion rate of the molecular sieve catalyzing the NH3-SCR reaction.

[0027] Figure 2 It is the X-ray diffraction pattern (XRD) of the molecular sieve obtained in Example 1.

[0028] Figure 3 It is the ammonia temperature-programmed desorption curve (NH3-TPD) of the molecular sieve obtained in Example 1.

[0029] Figure 4 It is the hydrogen temperature-programmed reduction curve (H2-TPR) of the molecular sieve obtained in Example 1.

[0030] Figure 5 It is the X-ray diffraction pattern (XRD) of the molecular sieve obtained in Example 2.

[0031] Figure 6 It is the X-ray diffraction pattern (XRD) of the molecular sieve obtained in Example 3.

[0032] Figure 7 It is the X-ray diffraction pattern (XRD) of the molecular sieve obtained in Example 4.

[0033] Figure 8 It is the ammonia temperature-programmed desorption curve (NH3-TPD) of the molecular sieve obtained in Example 5.

[0034] Figure 9 It is the hydrogen temperature-programmed reduction curve (H2-TPR) of the molecular sieve obtained in Example 5.

[0035] Figure 10 It is the X-ray diffraction pattern (XRD) of the molecular sieve obtained in Example 6. Detailed Embodiments

[0036] The following provides a detailed description of the specific embodiments of the present invention. It should be noted, however, that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the appended claims.

[0037] All publications, patent applications, patents, and other references mentioned in this specification are hereby incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0038] When this specification uses prefixes such as "known to those skilled in the art", "prior art", or their similar terms to introduce materials, substances, methods, steps, devices, or components, etc., the objects introduced by these prefixes cover those commonly used in the art at the time when this application is filed, but also include those that are not commonly used at present but will become recognized by the art as suitable for similar purposes.

[0039] In the context of this specification, except for the explicitly stated content, any matter or thing not mentioned directly applies to those known in the art without any modification. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the resulting technical solutions or technical concepts are regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider such combination to be obviously unreasonable.

[0040] In the context of this specification, for molecular sieves, before other substances (such as organic template molecules, etc.) filled in the pores during the synthesis of the molecular sieve, except for water and metal ions, in the pores are removed, it is called a "precursor".

[0041] In the context of this specification, including in the following examples and comparative examples, the X-ray diffraction pattern (XRD) of the molecular sieve is measured by a Panalytical X PERPRO type X-ray powder diffractometer, using a Cu-Kα ray source, Kα1 wavelength λ = 1.5405980 Å (angstrom), nickel filter, 2θ scanning range 2 - 50°, operating voltage 40 KV, current 40 mA, and scanning rate 10° / min.

[0042] In the context of this specification, including in the following examples and comparative examples, the elemental ratios of the molecular sieves were determined using a Varian 725-ES type inductively coupled plasma atomic emission spectrometer. The sample digestion method was as follows: The calcined molecular sieve sample was dissolved in a 5 wt.% hydrofluoric acid aqueous solution, sealed with a lid, and left standing until the solution became clear before being tested on the instrument.

[0043] In the context of this specification, including in the following examples and comparative examples, the acid amount and acid properties of the molecular sieves were determined using an Altamira AMI-3300 type ammonia temperature-programmed desorption (NH3-TPD) apparatus. Before testing, the sample needed to be activated in helium at 550 °C for 1 h. After the temperature dropped to 50 °C, ammonia was introduced until saturation adsorption occurred, then helium was introduced to purge for 1 h at 100 °C, and finally, the temperature was raised to 550 °C at a rate of 10 °C / min, and the working curve was recorded.

[0044] In the context of this specification, including in the following examples and comparative examples, the reduction properties of the catalyst were determined using an Altamira AMI-3300 type hydrogen temperature-programmed reduction (H2-TPR) instrument. The sample was pretreated at 300 °C for 1 h, cooled to room temperature, and then subjected to reduction testing by programming the temperature from room temperature to 900 °C at a heating rate of 7 °C / min in a H2 / Ar mixed gas (10%, volume fraction) with a flow rate of 40 ml / min.

[0045] In the context of this specification, including in the following examples and comparative examples, the coordination state of Cu atoms in the molecular sieve and the surface elemental composition of Si2p, Al2p, O1s, and Cu2p were determined by collecting X-ray photoelectron spectroscopy (XPS) using a Thermo ESCA LAB-250 type spectrometer, calibrated with C1s = 284.8 eV.

[0046] In the context of this specification, including in the following examples and comparative examples, the yield of the molecular sieve refers to the percentage of the mass of the calcined sample to the sum of the masses of SiO2 and Al2O3 contained in the raw materials.

[0047] The concentrations of NO, N2O, NH3, and O2 before and after the NH3-SCR reaction were detected using a photoacoustic spectrometer produced by Beijing Duketek Technology Co., Ltd.

[0048] The following further illustrates the present invention in detail using examples and comparative examples, but the present invention is not limited to these examples.

[0049] Example 1

[0050] Dissolve 0.5611 g of KOH and 0.4538 g of aluminum isopropoxide in 7 g of deionized water and stir for 30 minutes. Then add 1.70 g of tetraethylammonium hydroxide and stir for 15 minutes. Add 3.50 g of silica sol (HS-40), stir for 30 minutes, add 0.1073 g of copper nitrate trihydrate, and age at room temperature for 2 hours. The final gel ratio (molar ratio) is as follows:

[0051] SiO2 / Al2O3 = 21

[0052] K + / SiO2 = 0.43

[0053] TEA + / SiO2 = 0.12

[0054] Cu / Al2O3 = 0.40

[0055] H2O / SiO2 = 25

[0056] Load the above-aged mixture into a 100 mL stainless steel autoclave and crystallize at 150 °C and 20 rpm rotation for 4 days. After crystallization, centrifuge and wash until the pH value is nearly neutral (pH = 7 - 8), dry in an oven at 110 °C for 12 hours to obtain a molecular sieve precursor, and then calcine in air at 550 °C for 6 hours. After ammonium exchange calcination with ammonium chloride, the product Cu-SUZ-4 molecular sieve is obtained. The yield of the target molecular sieve is calculated to be 85%.

[0057] The XRD pattern of the sample is as Figure 2 shown, and the product is a pure-phase SZR-type Cu-SUZ-4 molecular sieve. The SiO2 / Al2O3 molar ratio of the Cu-SUZ-4 molecular sieve measured by inductively coupled plasma atomic emission spectrometer is 11.9, and the Cu / Al2O3 molar ratio is 0.32. The SiO2 / Al2O3 molar ratio on the surface of the Cu-SUZ-4 molecular sieve measured by X-ray photoelectron spectroscopy is 12.7, and the Cu / Al2O3 molar ratio is 0.25. The acid property results of the Cu-SUZ-4 molecular sieve measured by NH3-TPD temperature-programmed desorption device are as Figure 3 shown. The total acid amount of this molecular sieve is 1173 μmol / g, of which the weak acid amount is 137 μmol / g, the medium-strong acid amount is 626 μmol / g, and the strong acid amount is 410 μmol / g. The reduction performance of the Cu-SUZ-4 molecular sieve measured by H2-TPR temperature-programmed reduction device is as Figure 4 shown. It can be seen that this molecular sieve has two reduction peaks at 410 °C and 680 °C. The NOx conversion rate versus time curve obtained by SCR reaction testing of the Cu-SUZ-4 molecular sieve product is as Figure 1As shown by the Cu-SUZ-4-0.4 curve in, this molecular sieve has a relatively wide activity window, and the NOx conversion rate can reach over 90% between 280 and 450 °C.

[0058] Example 2

[0059] Dissolve 0.5611 g of KOH and 0.4538 g of aluminum isopropoxide in 7 deionized waters and stir for 30 minutes. Then add 3.40 g of tetraethylammonium hydroxide and stir for 15 minutes. Add 3.50 g of silica sol (HS-40), stir for 30 minutes, add 0.2146 g of copper nitrate trihydrate, and age at room temperature for 2 hours. The final gel ratio (molar ratio) is:

[0060] SiO2 / Al2O3 = 21

[0061] K + / SiO2 = 0.43

[0062] TEA + / SiO2 = 0.24

[0063] Cu / Al2O3 = 0.80

[0064] H2O / SiO2 = 25

[0065] Load the above-aged mixture into a 100 mL stainless steel autoclave and crystallize at 145 °C and 30 rpm rotation for 5 days. After crystallization, centrifuge and wash until the pH value is nearly neutral (pH = 7 - 8), dry in an oven at 100 °C for 14 hours to obtain a molecular sieve precursor, and then calcine in air at 600 °C for 5 hours. After ammonium exchange roasting with ammonium nitrate, the product Cu-SUZ-4 molecular sieve is obtained.

[0066] The XRD pattern of the sample is as Figure 5 shown, and the product is a pure-phase SZR-type Cu-SUZ-4 molecular sieve. The SiO2 / Al2O3 molar ratio of the Cu-SUZ-4 molecular sieve measured by inductively coupled plasma atomic emission spectrometer is 12.4, and the Cu / Al2O3 molar ratio is 0.32. The SiO2 / Al2O3 molar ratio on the surface of the Cu-SUZ-4 molecular sieve measured by X-ray photoelectron spectroscopy is 13.1, and the Cu / Al2O3 molar ratio is 0.52. The total acid amount of the Cu-SUZ-4 molecular sieve measured by NH3-TPD temperature-programmed desorption device is 1286 μmol / g. A reduction peak of the Cu-SUZ-4 molecular sieve appears at 380 °C measured by H2-TPR temperature-programmed reduction device. The Cu-SUZ-4 molecular sieve product is subjected to SCR reaction testing, and the curve of the NOx conversion rate changing with time is as Figure 1As shown in Cu-SUZ-4-0.8, this molecular sieve has a relatively wide activity window, and the NOx conversion rate can reach over 90% between 250 and 450 °C.

[0067] Example 3

[0068] Dissolve 0.5611 g of KOH and 0.4538 g of aluminum isopropoxide in 14 g of deionized water and stir for 12 minutes. Then add 1.70 g of tetraethylammonium hydroxide and stir for 10 minutes. Add 3.50 g of silica sol (AS-40), stir for 30 minutes, add 0.3219 g of copper nitrate trihydrate, and age at room temperature for 3 hours. The final gel ratio (molar ratio) is:

[0069] SiO2 / Al2O3 = 21

[0070] K + / SiO2 = 0.43

[0071] TEA + / SiO2 = 0.12

[0072] Cu / Al2O3 = 1.20

[0073] H2O / SiO2 = 50

[0074] Load the above-aged mixture into a 100 mL stainless steel autoclave and crystallize at 155 °C and 30 rpm rotation for 4.5 days. After crystallization, centrifuge and wash until the pH value is nearly neutral (pH = 7 - 8), dry in an oven at 90 °C for 10 hours to obtain the molecular sieve precursor, and then calcine in air at 550 °C for 6 hours. After ammonium exchange roasting with ammonium chloride, the product Cu-SUZ-4 molecular sieve is obtained.

[0075] The XRD pattern of the sample is as Figure 6 shown, and the product is a pure-phase SZR-type Cu-SUZ-4 molecular sieve. The SiO2 / Al2O3 molar ratio of the Cu-SUZ-4 molecular sieve measured by inductively coupled plasma atomic emission spectrometer is 13.3, and the Cu / Al2O3 molar ratio is 0.82. The SiO2 / Al2O3 molar ratio on the surface of the Cu-SUZ-4 molecular sieve measured by X-ray photoelectron spectroscopy is 15.3, and the Cu / Al2O3 molar ratio is 0.58. The total acid amount of the Cu-SUZ-4 molecular sieve measured by NH3-TPD temperature-programmed desorption device is 1355 μmol / g. A reduction peak of the Cu-SUZ-4 molecular sieve appears at 380 °C measured by H2-TPR temperature-programmed reduction device. The Cu-SUZ-4 molecular sieve product is subjected to SCR reaction test, and the curve of NOx conversion rate versus time obtained is as Figure 1As shown by the Cu-SUZ-4-1.2 curve in [reference], this molecular sieve has a relatively wide activity window, and the NOx conversion rate can reach over 90% between 280 and 440 °C.

[0076] Example 4

[0077] Dissolve 0.5611 g of KOH and 0.4538 g of aluminum isopropoxide in 6.3 g of deionized water and stir for 20 minutes. Then add 0.85 g of tetraethylammonium hydroxide and stir for 15 minutes. Add 3.50 g of silica sol (HS-40), stir for 20 minutes, add 0.4293 g of copper nitrate trihydrate, and age for 2.5 hours at room temperature. The final gel ratio (molar ratio) is as follows:

[0078] SiO2 / Al2O3 = 21

[0079] K + / SiO2 = 0.43

[0080] TEA + / SiO2 = 0.06

[0081] Cu / Al2O3 = 1.60

[0082] H2O / SiO2 = 18

[0083] Load the above-aged mixture into a 100 mL stainless steel autoclave and crystallize for 3 days at 145 °C and 40 rpm rotation. After crystallization, centrifuge and wash until the pH value is nearly neutral (pH = 7 - 8), dry in an oven at 80 °C for 18 hours to obtain a molecular sieve precursor, and then calcine in air at 600 °C for 6 hours. After ammonium exchange and calcination with ammonium chloride, the product Cu-SUZ-4 molecular sieve is obtained.

[0084] The XRD pattern of the sample is as Figure 7 shown, and the product is a pure-phase SZR-type Cu-SUZ-4 molecular sieve. The SiO2 / Al2O3 molar ratio of the Cu-SUZ-4 molecular sieve measured by inductively coupled plasma atomic emission spectrometer is 14.1, and the Cu / Al2O3 molar ratio is 1.37. The SiO2 / Al2O3 molar ratio on the surface of the Cu-SUZ-4 molecular sieve measured by X-ray photoelectron spectroscopy is 16.7, and the Cu / Al2O3 molar ratio is 0.73. The total acid amount of the Cu-SUZ-4 molecular sieve measured by NH3-TPD temperature-programmed desorption device is 1567 μmol / g. A reduction peak of the Cu-SUZ-4 molecular sieve appears at 380 °C measured by H2-TPR temperature-programmed reduction device.

[0085] Example 5

[0086] Dissolve 0.5611 g of KOH and 0.4538 g of aluminum isopropoxide in 7 g of deionized water and stir for 40 minutes. Then add 1.70 g of tetraethylammonium hydroxide and stir for 18 minutes. Add 3.50 g of silica sol (HS-40), stir for 30 minutes, add 0.5365 g of copper nitrate trihydrate, and age at room temperature for 3 hours. The final gel ratio (molar ratio) is as follows:

[0087] SiO2 / Al2O3 = 21

[0088] K + / SiO2 = 0.43

[0089] TEA + / SiO2 = 0.12

[0090] Cu / Al2O3 = 2.0

[0091] H2O / SiO2 = 25

[0092] Load the above-aged mixture into a 100 mL stainless steel autoclave and crystallize at 150 °C and 30 rpm rotation for 6 days. After crystallization, centrifuge and wash until the pH value is nearly neutral (pH = 7 - 8), dry in an oven at 110 °C for 12 hours to obtain a molecular sieve precursor, and then calcine in air at 550 °C for 6 hours. After ammonium exchange roasting with ammonium chloride, the product Cu-SUZ-4 molecular sieve is obtained.

[0093] From the XRD pattern of the sample, it can be seen that the product is a pure-phase SZR-type Cu-SUZ-4 molecular sieve. The SiO2 / Al2O3 molar ratio of the Cu-SUZ-4 molecular sieve measured by inductively coupled plasma atomic emission spectrometer is 14.8, and the Cu / Al2O3 molar ratio is 1.8. The SiO2 / Al2O3 molar ratio on the surface of the Cu-SUZ-4 molecular sieve measured by X-ray photoelectron spectroscopy is 15.6, and the Cu / Al2O3 molar ratio is 0.39. The acid property results of the Cu-SUZ-4 molecular sieve measured by NH3-TPD temperature-programmed desorption device are as Figure 8 shown. The total acid amount of this molecular sieve is 1988 μmol / g, of which the weak acid amount is 581 μmol / g, the medium-strong acid amount is 869 μmol / g, and the strong acid amount is 537 μmol / g. The reduction performance of the Cu-SUZ-4 molecular sieve measured by H2-TPR temperature-programmed reduction device is as Figure 9 shown. It can be seen that a reduction peak appears in this molecular sieve at 628 °C. Perform SCR reaction tests on the Cu-SUZ-4 molecular sieve product, and the curve of NOx conversion rate versus time obtained is as Figure 1 shown by the Cu-SUZ-4-2.0 curve in. This molecular sieve has a relatively wide activity window, and the NOx conversion rate can reach over 90% between 280 - 425 °C.

[0094] Example 6

[0095] Dissolve 0.5611 g of KOH and 0.4538 g of aluminum isopropoxide in 14 g of deionized water and stir for 30 minutes. Then add 1.70 g of tetraethylammonium hydroxide and stir for 15 minutes. Add 3.50 g of silica sol (HS-40), stir for 30 minutes, add 0.8584 g of copper nitrate trihydrate, and age at room temperature for 2 hours. The final gel composition (molar ratio) is as follows:

[0096] SiO2 / Al2O3 = 21

[0097] K + / SiO2 = 0.43

[0098] TEA + / SiO2 = 0.12

[0099] Cu / Al2O3 = 3.20

[0100] H2O / SiO2 = 50

[0101] Load the above-aged mixture into a 100 mL stainless steel autoclave and crystallize at 150 °C and 20 rpm rotation for 4 days. After crystallization, centrifuge and wash until the pH value is nearly neutral (pH = 7 - 8), dry in an oven at 120 °C for 8 hours to obtain a molecular sieve precursor, and then calcine in air at 550 °C for 6 hours.

[0102] The XRD pattern of the sample is as Figure 10 shown. Diffraction peaks of copper oxide appear at 2θ angles of 36.6° and 38.92°, indicating that the obtained product is a polymer of amorphous and copper oxide.

[0103] Example 7

[0104] Dissolve 0.5611 g of KOH and 0.5956 g of aluminum isopropoxide in 14 g of deionized water and stir for 20 minutes. Then add 1.70 g of tetraethylammonium hydroxide and stir for 15 minutes. Add 3.50 g of silica sol (HS-40), stir for 20 minutes, add 0.1073 g of copper nitrate trihydrate, and age at room temperature for 2 hours. The final gel composition (molar ratio) is as follows:

[0105] SiO2 / Al2O3 = 16

[0106] K + / SiO2 = 0.43

[0107] TEA + / SiO2 = 0.12

[0108] Cu / Al2O3 = 0.40

[0109] H2O / SiO2 = 50

[0110] The above-aged mixture was loaded into a 100 mL stainless steel autoclave and crystallized for 3 days under the conditions of 160 °C and 20 rpm rotation. After crystallization, it was centrifuged and washed until the pH value was nearly neutral (pH = 7 - 8), dried in an oven at 90 °C for 12 hours to obtain a molecular sieve precursor, and then calcined in air at 550 °C for 6 hours.

[0111] From the XRD pattern of the sample, the product was found to be a pure phase of SZR type Cu-SUZ-4 molecular sieve.

[0112] Example 8

[0113] 0.5611 g of KOH and 0.2647 g of aluminum isopropoxide were dissolved in 14 g of deionized water and stirred for 20 minutes. Then 1.70 g of tetraethylammonium hydroxide was added and stirred for 15 minutes. 3.50 g of silica sol (HS-40) was added and stirred for 20 minutes, and 0.1073 g of copper nitrate trihydrate was added. It was aged at room temperature for 2 hours, and the final gel ratio (molar ratio) was:

[0114] SiO2 / Al2O3 = 36

[0115] K + / SiO2 = 0.43

[0116] TEA + / SiO2 = 0.12

[0117] Cu / Al2O3 = 0.40

[0118] H2O / SiO2 = 50

[0119] The above-aged mixture was loaded into a 100 mL stainless steel autoclave and crystallized for 3 days under the conditions of 160 °C and 20 rpm rotation. After crystallization, it was centrifuged and washed until the pH value was nearly neutral (pH = 7 - 8), dried in an oven at 90 °C for 12 hours to obtain a molecular sieve precursor, and then calcined in air at 550 °C for 6 hours.

[0120] From the XRD pattern of the sample, the product was found to be a pure phase of SZR type Cu-SUZ-4 molecular sieve.

[0121] Example 9

[0122] Repeat Example 1, but using 1.4 g of fumed silica (SiO2) instead of silica sol as the silicon source. The final material ratio (molar ratio) was:

[0123] SiO2 / Al2O3 = 21

[0124] K + / SiO2 = 0.43

[0125] TEA + / SiO2 = 0.12

[0126] Cu / Al2O3 = 0.40

[0127] H2O / SiO2 = 25

[0128] The above-aged mixture was loaded into a 100 mL stainless steel autoclave and crystallized for 4 days under the conditions of 150 °C and 20 rpm rotation. After crystallization, it was centrifuged and washed until the pH value was nearly neutral (pH = 7 - 8), dried in an oven at 110 °C for 12 hours to obtain a molecular sieve precursor, and then calcined in air at 550 °C for 6 hours. The XRD pattern of the obtained sample was similar to that of Figure 2 the SZR type SUZ-4 molecular sieve.

[0129] Example 10

[0130] Same as Example 1, except that tetraethylenepentamine was added, and the final material ratio (molar ratio) was:

[0131] SiO2 / Al2O3 = 21

[0132] K + / SiO2 = 0.43

[0133] TEA + / SiO2 = 0.12

[0134] Cu / Al2O3 = 0.40

[0135] H2O / SiO2 = 25

[0136] Tetraethylenepentamine / SiO2 = 0.40

[0137] The above-aged mixture was loaded into a 100 mL stainless steel autoclave and crystallized for 4 days under the conditions of 150 °C and 20 rpm rotation. After crystallization, it was centrifuged and washed until the pH value was nearly neutral (pH = 7 - 8), dried in an oven at 110 °C for 12 hours to obtain a molecular sieve precursor, and then calcined in air at 550 °C for 6 hours. The XRD pattern of the obtained sample was similar to that of Figure 2 the SZR type SUZ-4 molecular sieve.

[0138] Comparative Example 1

[0139] Same as Example 1, except that the copper source was not added, and the final material ratio (molar ratio) was:

[0140] SiO2 / Al2O3 = 21

[0141] K + / SiO2 = 0.43

[0142] TEA + / SiO2 = 0.12

[0143] H2O / SiO2 = 25

[0144] The above-aged mixture was loaded into a 100 mL stainless steel autoclave and crystallized for 4 days under the conditions of 150 °C and 20 rpm rotation. After the crystallization was completed, it was centrifuged and washed until the pH value was nearly neutral (pH = 7 - 8), dried in an oven at 110 °C for 12 hours to obtain a molecular sieve precursor, and then calcined in air at 550 °C for 6 hours. After ammonium exchange roasting with ammonium chloride, the product SUZ-4 molecular sieve was obtained. The SUZ-4 molecular sieve product was subjected to SCR reaction testing, and the curve of NOx conversion rate versus time obtained was as shown by the SUZ-4 curve in Figure 1 . The catalytic performance of this molecular sieve is poor, and the highest NOx conversion rate only reaches 34%.

Claims

1. A preparation method of Cu-SUZ-4 molecular sieve, characterized in that, Seedless-assisted one-step hydrothermal in-situ doping of copper source; specifically including the following steps: Step 1, Drop water, aluminum source and mineralizer into the polytetrafluoroethylene inner liner; Step 2, Slowly drop the template agent tetraethylammonium hydroxide into the solution in Step 1, and stir evenly to form a mixed solution; Step 3, Add a silicon source to the solution in Step 2, and stir evenly; Step 4, Add a copper source to the solution in Step 3, stir evenly to form a mixed solution, and age; Step 5, Place the polytetrafluoroethylene inner liner containing the above mixed solution in a stainless steel autoclave, seal it and then place it in a crystallization reactor for crystallization heating; Step 6, After the crystallization is completed, cool the stainless steel autoclave to room temperature. Wash the crystallization product with deionized water and then perform solid-liquid separation to obtain a solid product. Place it in an oven for drying to obtain a Cu-SUZ-4 molecular sieve precursor; Step 7, Place the Cu-SUZ-4 molecular sieve precursor in a heating furnace for calcination to obtain a Cu-SUZ-4 molecular sieve; Step 8, Perform ammonium exchange on the Cu-SUZ-4 molecular sieve and further calcination treatment to obtain a hydrogen-type Cu-SUZ-4 molecular sieve; Step 9, Press and form the molecular sieve obtained in Step 8 and then granulate it. Use a catalytic reaction test device to evaluate its catalytic performance in the NH3-SCR reaction.

2. The preparation method of the Cu-SUZ-4 molecular sieve catalyst synthesized by the one-step hydrothermal in-situ doping of copper source without seed assistance according to claim 1, characterized in that: The silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the copper source is calculated as Cu, the mineralizer is calculated as OH - + + + / Al2O3 = 1 - 10, and H2O / Al2O3 = 10 - 1000 to synthesize a gel. Preferably, the gel is synthesized at a molar ratio of SiO2 / Al2O3 = 10 - 40, Cu / Al2O3 = 0.01 - 3, KOH / Al2O3 = 4 - 10, TEA​​​ 3. The preparation method of the Cu-SUZ-4 molecular sieve catalyst synthesized by one-step hydrothermal in-situ doping of copper source without seed assistance according to claim 1, wherein: In Step 1, the aluminum source is selected from at least one of the group consisting of aluminum powder, aluminum isopropoxide, aluminum hydroxide, alumina, pseudo-boehmite, coal gangue, aluminum sulfate, aluminum nitrate, and aluminum chloride; the mineralizer is selected from at least one of the group consisting of potassium hydroxide, sodium hydroxide, and lithium hydroxide; in Step 3, the silicon source is selected from at least one of the group consisting of silicic acid, silica sol, sodium silicate, white carbon black, methyl orthosilicate, ethyl orthosilicate, coal gangue, clay, and water glass; in Step 4, the copper source is selected from at least one of the group consisting of copper nitrate, copper sulfate, copper chloride, copper acetate, and copper oxide; the copper source is not limited to the copper source, and can also be at least one of the group consisting of iron source, zinc source, manganese source, magnesium source, nickel source, and cobalt source; in Step 8, the ammonium source used in the ammonium exchange process is at least one of the group consisting of ammonium chloride, ammonium nitrate, ammonium citrate, and ammonium tartrate.

4. The preparation method of the Cu-SUZ-4 molecular sieve catalyst synthesized by one-step hydrothermal in-situ doping of copper source without seed assistance according to claim 1, characterized in that: In Step 4, the aging conditions include: aging temperature 20~90°C, aging time 0 hours to 2 days; in Step 5, the crystallization reactor is selected from at least one of the group consisting of a homogeneous reactor, an oven, and a stirred autoclave. The crystallization process of the mixture is dynamic crystallization or static crystallization by rotation / stirring, the rotation speed is 10~40 rpm, and the stirring speed is 30~200 rpm; the crystallization conditions of the mixture are crystallization for 1~12 days at 110~200°C, preferably crystallization for 2~8 days at 130~180°C, more preferably crystallization for 4~6 days at 140~160°C.

5. The preparation method of the Cu-SUZ-4 molecular sieve catalyst synthesized by one-step hydrothermal in-situ doping of copper source without seed assistance according to claim 1, wherein: In Step 6, the solid-liquid separation method includes at least one of centrifugation or filtration; the drying temperature is 40~250°C, preferably 60~120°C, and the drying time is 8~30 h, preferably 10~20 h. This drying can be carried out under normal pressure or under reduced pressure.

6. The preparation method of the Cu-SUZ-4 molecular sieve catalyst synthesized by the seedless-assisted one-step hydrothermal in-situ doping copper source according to claim 1, wherein: In Step 7, the heating furnace is selected from at least one of a muffle furnace or a tube furnace; the roasting temperature is 450-700 °C, preferably 500-600 °C; the roasting time is 3-10 h, preferably 4-6 h, and the heating rate during the roasting process is 4-5 °C / min.

7. The preparation method of the Cu-SUZ-4 molecular sieve catalyst synthesized by one-step hydrothermal in-situ doping of copper source without seed assistance according to claim 1, wherein: In step 8, the ammonium exchange of the Cu-SUZ-4 molecular sieve is to exchange the Na + , K + and other alkali metal cations in the molecular sieve into NH 4+ . The exchange is carried out at 20~60 °C for 0.5~4 h, and can be carried out once or multiple times. After the ammonium ion exchange, it is dried at 60~120 °C for 4~24 h, and then calcined. The calcination temperature is 500~600 °C, the calcination time is 1~12 h, the calcination atmosphere is oxygen or air, and the hydrogen-form Cu-SUZ-4 molecular sieve is obtained after calcination.

8. The preparation method of the Cu-SUZ-4 molecular sieve catalyst synthesized by one-step hydrothermal in-situ doping of copper source without seed assistance according to claim 1, characterized in that: In step 9, the granule size after tableting the molecular sieve is selected to be 10-20 mesh; the catalytic reaction test device is selected from at least one of a fixed bed reactor or a solar-driven thermal catalytic reactor, and the reaction feed gas composition is 500 ppm NH3, 500 ppm NO, 5% O2, with N2 as the balance carrier gas, and the volumetric space velocity of the feed gas is GHSV = 80,000 h -1 , and a photoacoustic spectrometer is used to detect the concentrations of NO, N2O, NH3, and O2 before and after the reaction.

9. The preparation method of the Cu-SUZ-4 molecular sieve catalyst synthesized by one-step hydrothermal in-situ doping of copper source without seed assistance according to claim 1, characterized in that: The total acid amount of the molecular sieve is not less than 800 μmol / g, preferably 800-2000 μmol / g; the strong acid amount is not less than 200 μmol / g, preferably 200-700 μmol / g.

10. The preparation method of the Cu-SUZ-4 molecular sieve catalyst synthesized by one-step hydrothermal in-situ doping of copper source without seed assistance according to claim 1, wherein: The method obtains Cu-SUZ-4 molecular sieve by directly adding a copper source to the gel, without the subsequent copper ion exchange step and the seed-assisted method in the traditional process, simplifies the process flow, and reduces the production cost.

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