CN109250728B

CN109250728B - Cu-SAPO molecular sieve synthesis method, synthesized Cu-SAPO molecular sieve and application

Info

Publication number: CN109250728B
Application number: CN201710566426.7A
Authority: CN
Inventors: 杨淼; 孙丽婧; 田鹏; 刘中民; 曹毅; 向骁; 桑石云; 曹磊
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2017-07-12
Filing date: 2017-07-12
Publication date: 2022-02-18
Anticipated expiration: 2037-07-12
Also published as: CN109250728A; WO2019010812A1

Abstract

The invention relates to a method for synthesizing a Cu-SAPO molecular sieve, a product and application thereof. More particularly, the method comprises the step of taking the Cu-SAPO molecular sieve with high Cu content, which is synthesized by using a copper-amine complex as a template agent, as a Cu source and part of a silicon-phosphorus-aluminum source and seed crystals to synthesize the Cu-SAPO molecular sieve. The method can not only control the copper content in the SAPO molecular sieve in a wider range, but also effectively regulate the silicon content and the silicon atom distribution thereof, and has high product yield. The obtained Cu-SAPO molecular sieve catalyst shows excellent high-temperature hydrothermal stability and NO resistance_xThe catalytic selective reduction removal performance of (1).

Description

Cu-SAPO molecular sieve synthesis method, synthesized Cu-SAPO molecular sieve and application

Technical Field

The invention belongs to the field of chemistry and chemical engineering, relates to the field of molecular sieves and preparation methods thereof, and particularly relates to a method for synthesizing Cu-SAPO (copper-containing phosphorus-silicon-aluminum molecular sieve), a product obtained by the method and application thereof. The Cu-SAPO can be used as a catalyst in a nitrogen oxide purification process.

Background

United states Union carbide (UCC) was opened in 1984Sent out a series of PO₂ ⁺、AlO₂ ^-And SiO₂Novel silicoaluminophosphate molecular sieves (SAPO-n) whose tetrahedra form a three-dimensional open framework structure (USP 4,440,871). Si atoms enter a neutral aluminum phosphate framework structure in a substitution mode, so that the framework generates net negative charges to cause proton acidity, and the SAPO molecular sieve is endowed with catalytic performance. A Cu-SAPO-34 or Cu-SSZ-13 catalyst (SSZ-13 is a molecular sieve which has the same topological structure as the SAPO-34, and is different from the SAPO-34 in that the SSZ-13 is a silicon-aluminum molecular sieve and the SSZ-13 is a silicon-aluminum phosphate molecular sieve) prepared by taking the SAPO-34 as a carrier has high activity and excellent hydrothermal stability in the process of purifying nitrogen oxides by a diesel vehicle tail gas selective catalytic reduction (Urea-SCR) system. At present, most of copper ions in the SAPO molecular sieve catalyst are introduced by an ion exchange method, namely, the obtained molecular sieve is firstly roasted to remove a template agent, is exchanged with an ammonium nitrate solution to obtain an ammonia type sample, and then is mixed with a copper salt solution with a certain concentration and stirred for several hours, and then is filtered, washed, dried and roasted at a high temperature to obtain Cu-SAPO-34. Because SAPO molecular sieve has poor low-temperature hydrothermal stability, the molecular sieve framework is often subjected to partial hydrolysis in the ion exchange process, so that the specific surface area of the molecular sieve is reduced. Meanwhile, the ion exchange process is complicated, the utilization rate of copper ions in the copper salt solution is low in the exchange process, a large amount of purified water is consumed in the washing process and is converted into sewage, and the high-temperature roasting process consumes time and energy.

Compared with the ion exchange method, the one-step method for synthesizing the copper-containing molecular sieve has obvious advantages. CN 102259892A discloses a method for synthesizing a silicoaluminophosphate molecular sieve catalyst by using a metal-amine complex as a template agent, which avoids a complicated ion exchange process. However, the Cu-SAPO-34 synthesized in one step has poor high-temperature hydrothermal stability, and the industrial application of the Cu-SAPO-34 is limited. For example, Corma et al synthesizes Cu-SAPO-34 molecular sieve with copper-amine complex and diethylamine as template agent, the copper loading is controlled at 3.4-10.4%, and the crystal size is about 6-10 μm. Research shows that the activity of the low-copper-loading catalyst (copper content is 3.4%) synthesized by the method is obviously reduced after hydrothermal aging for 13h at 750 ℃, and for a Cu-SAPO-34 catalyst with medium (copper content is 6.0%) and high (10.4%) copper content, the framework structure is completely collapsed after hydrothermal aging for 13h at 750 ℃ (Applied catalysis B: Environmental,2012,127: 273). Besides the influence of Cu loading on the hydrothermal stability of the molecular sieve, the distribution of negative charges of the framework also influences the stability of copper ions outside the framework, thereby influencing the hydrothermal stability of a copper-loaded molecular sieve sample. For SAPO molecular sieves, the amount and distribution of negative framework charge is directly derived from the amount of silicon atom introduced and its distribution. For example, a single substitution of a P atom with a Si atom may form a Si (4Al) linkage, forming an acid center. When Si atoms replace adjacent P and Al atoms simultaneously, Si-rich regions and even silicon islands are formed, resulting in uneven distribution of negative charges in the framework, which is not favorable for the stable existence of copper ions. In order to further improve the hydrothermal stability of the synthesized Cu-SAPO-34 molecular sieve, a great deal of research efforts have been made to synthesize Cu-SAPO-34 by compounding various organic templates with copper-amine complexes in an attempt to modulate the copper content and the silicon amount and silicon atom distribution in the molecular sieve (J.catalysis 2014, 314, 73-82; Chemical Engineering Journal 2016, 294, 254-263; CN 104209141A; CN 103818927A). These works show that copper amine complexes as synthesis templates tend to create silicon islands in the framework of SAPO molecular sieves. However, if the amount of copper-amine complex templating agent and the amount of silicon source are reduced to avoid silicon island formation and to control the copper loading, the product yield and crystallinity will be affected.

Disclosure of Invention

In order to solve the problems, the Cu-SAPO with high copper content is obtained by using a copper-amine complex as a synthesis template, and then is directly used as a Cu source, a part of silicon-phosphorus-aluminum source and a seed crystal to synthesize the Cu-SAPO molecular sieve. The method avoids the competition of the copper-amine complex and other synthetic templates when the copper-amine complex and other templates are directly used as co-templates to synthesize the Cu-SAPO, better plays the guiding role of other organic templates in the synthesis, and effectively regulates and controls the crystal granularity, the Cu content, the silicon content and the distribution of the molecular sieve product, so that the obtained copper-containing molecular sieve has more excellent catalytic performance and hydrothermal stability.

In one aspect, the invention provides a method for synthesizing a Cu-SAPO molecular sieve, which is characterized by comprising the following steps:

(1) synthesizing a Cu-SAPO molecular sieve with high copper content using a template comprising a copper amine complex, with a Cu loading of 5-20 wt.%, preferably 5-15 wt.%;

(2) mixing an organic amine template agent R, water and optional silicon source, aluminum source and phosphorus source to prepare a crystallization liquid;

(3) and (3) mixing the Cu-SAPO molecular sieve with high copper content obtained in the step (1) as a raw material with the crystallization liquid prepared in the step (2) and carrying out hydrothermal crystallization to obtain a Cu-SAPO molecular sieve product.

Optionally, the Cu-SAPO molecular sieve raw material in step (1) is Cu-SAPO synthesized by using a copper-amine complex as a single template or as a mixed template together with an organic amine template R1 through hydrothermal crystallization from a silicon source, an aluminum source, a phosphorus source and water, wherein the silicon source may be one or more selected from ethyl orthosilicate, silica sol and white carbon black; the aluminum source can be one or more selected from aluminum isopropoxide, pseudo-boehmite, aluminum sol and aluminum hydroxide; the phosphorus source can be one or more selected from phosphoric acid, phosphorous acid and phosphorus pentoxide; the organic amine template R1 can be selected from one or more of triethylamine, diethylamine, morpholine, tetraethylammonium hydroxide, propylamine and piperazine.

Optionally, the molar ratio of the aluminum source, the phosphorus source, the silicon source, the copper-amine complex, the organic amine template R1 and the water used for synthesizing the Cu-SAPO molecular sieve raw material in the step (1) is Al₂O₃:P₂O₅:SiO₂:Cu:R1:H₂O＝1:0.8～1:0.3～1.0:0.1～0.8:0-3.5:40～80。

Alternatively, the copper amine complex in step (1) includes a copper-polyethylene polyamine complex, preferably a Cu-tetraethylenepentamine complex, a Cu-triethylene tetramine complex, a Cu-diethylenetriamine complex, and a Cu-pentaethylenehexamine complex.

Optionally, the synthesis of the Cu-SAPO molecular sieve with high copper content in step (1) is performed in the presence of SAPO seeds.

Optionally, the silicon source used in step (2) may be one or more selected from ethyl orthosilicate, silica sol and silica white; the aluminum source can be one or more selected from aluminum isopropoxide, pseudo-boehmite, aluminum sol and aluminum hydroxide; the phosphorus source can be one or more selected from phosphoric acid, phosphorous acid and phosphorus pentoxide; the organic amine template R can be one or a mixture of triethylamine, diethylamine, morpholine, tetraethylammonium hydroxide, propylamine and piperazine.

Optionally, the molar ratio of the aluminum source, the phosphorus source, the silicon source, the organic amine template R and the water used in the step (2) is Al₂O₃:P₂O₅:SiO₂:R:H₂O is 1:0.5 to 2:0.01 to 1.5:0.5 to 10:15 to 200, preferably Al₂O₃:P₂O₅:SiO₂:R:H₂O＝1:0.7～1.5:0.1～1.0:1～5:30～100。

Optionally, the feeding amount of the Cu-SAPO raw material with high copper content in the step (3) is 2-200 wt% of the total amount of the solid oxide substances in the crystallization liquid.

Optionally, the temperature for performing the hydrothermal crystallization in the step (3) is 140-. More preferably, the crystallization temperature is 150-.

Optionally, the Cu loading of the Cu-SAPO molecular sieve product prepared in step (3) is reduced by more than 10% compared to the copper content of the high copper content Cu-SAPO feedstock, preferably by 10-70% of the copper content of the high copper content Cu-SAPO feedstock.

Optionally, the Cu-SAPO molecular sieve comprises any one of a Cu-SAPO-34 molecular sieve, a Cu-SAPO-42 molecular sieve, and Cu-DNL-6 (RHO).

In another aspect, the present invention provides a Cu-SAPO-molecular sieve raw powder, preferably Cu-SAPO-34 molecular sieve raw powder, prepared by the above method, which is rhombohedral in shape, preferably having a particle size in the range of 1 to 2 μm.

In another aspect, the present invention also provides a method for the production of NO_xThe catalyst for the selective reduction desorption reaction is obtained by roasting the molecular sieve synthesized by the method in air at 500-800 ℃. The catalyst shows good catalytic performance especially in the catalytic removal reaction of nitrogen oxides. The activity of the catalyst is still maintained after the catalyst is treated by saturated steam at 800 ℃ for 16 hours.

In another aspect, the present invention provides a method for improving the high temperature hydrothermal stability of a Cu-SAPO molecular sieve, characterized in that the method comprises: a Cu-SAPO molecular sieve with high copper content synthesized by using a template comprising a copper amine complex is mixed with a crystallization liquid prepared by mixing an organic amine template R and water and optionally a silicon source, an aluminum source and a phosphorus source, and subjected to hydrothermal crystallization.

The invention can produce at least one of the following beneficial effects:

(1) the method realizes the high-yield synthesis of the Cu-SAPO with high hydrothermal stability and the high-efficiency utilization of a Cu source. The crystal granularity, Cu content and silicon content and distribution can be effectively regulated and controlled;

(2) the prepared molecular sieve can be used as a catalyst for catalytic removal reaction of nitrogen oxides and shows good catalytic performance. The catalytic performance of the catalyst is still improved or kept unchanged after the catalyst is treated by water vapor at 800 ℃ for 16 hours.

Drawings

FIG. 1 is an XRD pattern of the high copper content Cu-SAPO-34 synthesized in example 1.

FIG. 2 is a Scanning Electron Micrograph (SEM) of the high copper content Cu-SAPO-34 synthesized in example 1.

Figure 3 is the XRD pattern of the product of example 3.

FIG. 4 Scanning Electron Micrograph (SEM) of the product of example 5.

FIG. 5 is the solid of example 3²⁹And (4) a Si nuclear magnetic spectrum.

FIG. 6 is NH of examples 3, 5 and 8₃-SCR reaction evaluation results.

FIG. 7 is NH of samples before (example 5) and after (example 5-H) the high temperature hydrothermal treatment of the catalyst of example 5₃-SCR reaction evaluation result comparison.

Figure 8 is an XRD pattern of the sample of example 12.

Figure 9 is the XRD pattern of the sample of example 13.

FIG. 10 is a Scanning Electron Micrograph (SEM) of the product of example 14.

FIG. 11 is an SEM micrograph of a sample of comparative example 3.

FIG. 12 solids of comparative example 3 sample²⁹And (4) a Si nuclear magnetic spectrum.

Detailed Description

The invention is further illustrated by the following examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers. In the case where no specific description is given, the raw materials used in the present application are all purchased from commercial sources and used without any special treatment. The Cu-SAPO-34 molecular sieve raw material is high-copper-content Cu-SAPO-34 synthesized by using a copper amine complex as a single template or being synthesized in one step together with other organic amines as a mixed template, and the Cu load is 5-20 wt%. Synthetic methods reference is made to Applied Catalysis B, Environmental 127(2012)273-280, but is not limited thereto.

Without specific description, the test conditions of the present application are as follows:

the elemental composition was determined using a Philips Magix 2424X-ray fluorescence Analyzer (XRF).

X-ray powder diffraction phase analysis (XRD) an X' Pert PRO X-ray diffractometer from pananace (PANalytical) of the netherlands, Cu target, K α radiation source (λ ═ 0.15418nm), voltage 40KV, current 40mA were used.

The specific surface area and pore size distribution of the sample were measured using a physical adsorption apparatus model ASAP 2020, Micromeritics, usa. Before analysis, the sample is heated and pretreated for 6h at 350 ℃ in a vacuum manner, and the free volume of the sample tube is measured by taking He as a medium. When analyzing the sample, the physical adsorption and desorption measurements were carried out at a liquid nitrogen temperature (77K) using nitrogen as the adsorption gas. Determining the specific surface area of the material by adopting a BET formula; using relative pressure (P/P)₀) N at 0.99₂The total pore volume of the material was calculated. The micropore surface area and micropore volume were calculated by the t-plot method. When calculating, N₂The cross-sectional area of the molecule was taken to be 0.162nm²。

SEM topography analysis used Hitachi TM3000 model and Hitachi SU8020 model desktop scanning electron microscopes.

Of samplesThe solid-state nuclear magnetic experiments were carried out on a Bruker AvanceIII600(14.1Tesla) spectrometer.²⁹Si MAS NMR experiments were carried out using a 7mm dual resonance probe at a rotation speed of 6 kHz. The high-power proton decoupling program is adopted, the sampling frequency is 5000-6000, the pulse width of pi/4 is 2.5 mu s, the sampling delay is 10s, and the 4, 4-dimethyl-4-sodium propanesulfonate (DSS) is used as a chemical shift reference and is corrected to 0 ppm.

Example 1:

synthesis of copper-containing Cu-SAPO-34 samples as copper sources.

The mol ratio and crystallization conditions of the raw materials are shown in table 1, and the specific batching process is as follows:

adding pseudo-boehmite (65 wt%), water, phosphoric acid (85 wt%), silica sol (31 wt%), copper sulfate pentahydrate, Tetraethylenepentamine (TEPA), optional organic template agent R1 and SAPO-34 seed crystal into a 2L synthesis kettle in sequence, stirring uniformly, then sealing, heating to 140 ℃ and 200 ℃ under stirring, and crystallizing for 5-24 h. The solid product is centrifugally separated, the sample is washed to be neutral by deionized water, and after the sample is dried in air at 120 ℃, the Cu-SAPO-34 molecular sieve to be used (named as Cu-34-x, x ═ a, b, c and d) is obtained. The seed crystal is added in the synthesis process to reduce the granularity of the synthesized high-copper Cu-SAPO-34, so that the high-copper Cu-SAPO-34 can better participate in subsequent crystallization and plays a role of the seed crystal and a copper source, and the addition of the seed crystal is also beneficial to improving the product yield. The seed crystal is nano-scale SAPO-34 synthesized by the reference patent CN 104340986B. XRD of four high-copper Cu-SAPO-34 samples synthesized is shown in figure 1, SEM of the Cu-34-a sample is shown in figure 2, and the particle size is 300-500 nm.

TABLE 1 raw material molar ratio and crystallization conditions for Cu-SAPO-34 containing copper as copper source

^aThe feeding amount (wt%) of the seed crystal is (M)_{Seed crystal}/(M_P2O5+M_Al2O3+M_SiO2) 100%, product yield ═ M_{Raw powder of product}*85％/(M_P2O5+M_Al2O3+M_SiO2)*100％

Examples 2 to 9: preparation of Cu-SAPO-34 molecular sieve product with high hydrothermal stability

The molar ratio of the respective raw materials and the crystallization conditions are shown in Table 2. The specific batching process is as follows:

firstly, mixing and dissolving an aluminum source and water, and then sequentially adding an optional phosphorus source, a silicon source and a template agent R. To the above mixture was added a sample of Cu-SAPO-34 as prepared in example 1. After stirring uniformly at room temperature, the gel was transferred to a stainless steel reaction kettle. After the reaction kettle is placed in an oven, the temperature is raised to 160-200 ℃ for reaction for 0.5-72h, and the crystallization is finished. And centrifuging and washing the solid product, and drying in air at 120 ℃ to obtain the molecular sieve raw powder sample. XRD analysis of the sample shows typical CHA structure characteristic peak, and XRD diffraction pattern of example 3 is shown in figure 3. In addition, FIG. 4 shows an SEM photograph of the Cu-SAPO-34 molecular sieve prepared in example 5. It can be seen that the morphology of the resulting sample is rhombohedral with particle sizes ranging from 1 to 2 μm. Therefore, the granularity of the sample prepared by the synthesis method is smaller than the crystal granularity of the SAPO molecular sieve synthesized by the conventional hydrothermal method. This is directly related to the use of copper-containing Cu-SAPO-34 as a feedstock and seed. After the sample is roasted to remove the template agent, the specific surface area and the pore volume are measured, and the sample has high BET specific surface area of 560.7m²g^-1And a large pore volume of 0.29cm³g^-1Wherein the specific surface area and the volume of the micropores calculated according to the t-plot method are 542.5m respectively²g^-1And 0.25cm³g^-1. FIG. 5 shows the solid nuclear magnetic properties of the sample of example 7²⁹Si spectrogram, the result shows that the samples respectively have a single peak at 90ppm, and the single peak is assigned to the Si (4Al) coordination environment of the samples.

Example 10

The samples of examples 3, 5 and 8 were calcined at 650 ℃ for 2h, after removal of the templating agent, for NH₃Selective reduction removal of NO_xAnd (4) testing the catalytic performance of the reaction. The specific experimental procedures and conditions were as follows: after roasting, the sample is pressed into tablets and sieved, and 0.1g of 60 are weighedThe 80 mesh sample was mixed with 0.4g of quartz sand (60 to 80 mesh) and charged into a fixed bed reactor. Introducing nitrogen at 600 ℃ for activation for 40min, then cooling to 120 ℃ to start reaction, and heating to 550 ℃. The raw material gas for reaction is: NO: 500ppm, NH₃：500ppm，O₂：5％，H₂O：5％，N₂As an equilibrium gas, the gas flow rate was 300 mL/min. The reaction off-gas was analyzed by on-line FTIR using a Bruker model Tensor 27 instrument, and the results are shown in FIG. 6. It can be seen that the sample of example 3 has a lower copper content and is less active at temperatures below 200 c, and that the NO conversion increases progressively with increasing temperature, with 500 c still maintaining near 100% conversion. The copper content of the sample in example 5 is increased a little, so the low temperature reactivity is improved, the NO conversion rate is further increased along with the temperature increase, the conversion rate is close to 100% at 350 ℃, and the conversion rate is slightly reduced but still kept above 90% after the temperature is increased to 450-500 ℃. The sample of example 8 has a higher Cu content, and therefore, the low temperature activity is high, but the higher Cu content causes side reaction at high temperature, so that the NO conversion rate is reduced.

Example 11

Example 5 the sample was calcined at 650 deg.C for 2H, after removal of the templating agent, further hydrothermally treated at 800 deg.C for 16H, named sample 5-H and then NH-treated₃Selective reduction removal of NO_xAnd (4) testing the catalytic performance of the reaction. The test conditions were the same as in example 10, and the results are shown in FIG. 7. It can be seen that the SCR reactivity of the sample is well maintained after the high-temperature water treatment, which indicates that,

the Cu-SAPO-34 prepared by the method has excellent high-temperature hydrothermal stability, has the condition for practical application, and a sample with too high Cu content has poor high-temperature hydrothermal stability.

Example 12

The synthesis of copper-containing Cu-SAPO-42 samples as copper source was as follows:

pseudo-boehmite (65 wt%), water, phosphoric acid (85 wt%), silica sol (31 wt%), copper sulfate pentahydrate, Tetraethylenepentamine (TEPA), diethanolamine, trimethylamine were added to a 2L synthesis kettle in this order(33 wt%), hydrofluoric acid (40 wt%), and SAPO-42 seeds. Feeding ratio Al₂O₃:P₂O₅:SiO₂Cu-tetraethylenepentamine complex diethanolamine: trimethylamine (c): hydrofluoric acid H₂O is 1: 1: 1.0: 0.10: 3.0: 0.9: 0.5: 50, seed feeding 10 wt%. Stirring, sealing, heating to 180 deg.C under stirring, and crystallizing for 48 hr. And (3) centrifugally separating the solid product, washing the sample to be neutral by using deionized water, and drying the sample in air at 120 ℃ to obtain the Cu-SAPO-42 molecular sieve for standby, wherein the Cu-SAPO-42 molecular sieve is numbered and contains 9 wt% of copper. XRD of the synthesized Cu-SAPO-42 sample is shown in figure 8.

Examples 13 to 14

The molar ratio of the respective raw materials and the crystallization conditions are shown in Table 3. The specific batching process is as follows:

firstly, mixing and dissolving an aluminum source and water, and then sequentially adding an optional phosphorus source and a silicon source into the mixture. Diethanolamine, trimethylamine, and hydrofluoric acid. To the above mixture was added a sample of Cu-SAPO-42 as prepared in example 12. After stirring uniformly at room temperature, the gel was transferred to a stainless steel reaction kettle. And (4) after the reaction kettle is placed in an oven, heating to 200 ℃ for reaction for 48 hours, and finishing crystallization. And centrifuging and washing the solid product, and drying in air at 120 ℃ to obtain the molecular sieve raw powder sample. XRD analysis of the sample shows typical LTA structural characteristic peak, and XRD diffraction pattern of example 13 is shown in figure 9. In addition, FIG. 10 shows an SEM photograph of the Cu-SAPO-42 molecular sieve prepared in example 14.

TABLE 3 molar ratio of raw materials for synthesis, crystallization conditions and results of synthesis

Comparative examples 1 to 4:

the molar ratio of the respective raw materials and the crystallization conditions are shown in Table 3. The method comprises the following specific steps: to a 100mL synthesis kettle were added in sequence pseudo-boehmite (65 wt%), water, phosphoric acid (85 wt%), silica sol (31 wt%), copper sulfate pentahydrate, tetraethylenepentamine, and Diethylamine (DEA). The addition amount of the SAPO-34 crystal seeds is 5 wt% of the solid content of the reaction mixture, the mixture is stirred uniformly, then sealed, and the temperature is raised to 170 ℃ under stirring, and the crystallization is carried out for 3 days. The solid product was separated by centrifugation. Washing the sample with deionized water to neutrality, and drying in air at 120 ℃ to obtain the Cu-SAPO-34 molecular sieve sample.

TABLE 4 molar proportions of the starting materials and crystallization conditions

Yield of product (M)_Product(s)*85％/(M_P2O5+M_Al2O3+M_SiO2)*100％

FIG. 11 shows an SEM micrograph of comparative example 3 showing that the sample had a particle size of 5-10 microns. FIG. 12 shows comparative example 3²⁹Si NMR solid-state nuclear magnetic spectrum, it was found that, in addition to the Si (4Al) signal, the sample had a significant signal at 110ppm, which was attributed to Si (0 Al). Copper amine complex templating agents tend to cause silicon island formation. From the results of the four comparative examples, it can be seen that for the Cu-SAPO-34 molecular sieve synthesized by using the co-template of the copper amine complex and other organic amines, the copper content in the product can be reduced by reducing the dosage of the copper amine complex. However, the copper content of the synthesized product is also controlled by the silicon oxide feeding amount in the synthesis system. When the amount of silicon oxide is reduced, the reduction of copper content in the product is limited. The simultaneous reduction of the amounts of silica and copper amine complex fed also leads to a slow crystallization rate of the SAPO molecular sieve and a significant decrease of the yield (comparative example 4).

The present invention provides a solution to the above problems. Firstly, Cu-SAPO molecular sieve raw materials with high copper content are prepared in advance, the amount of copper amine complex added in the synthesis process is high, and the crystallization speed and the product yield are improved. Then, the prefabricated Cu-SAPO-34 raw material is used as a copper source, part of silicoaluminophosphate raw material and seed crystal to synthesize the Cu-SAPO-34. In the synthesis process, the problem of competition between the copper-amine complex and other organic amine templates is avoided, and the silicon content and the silicon atom distribution of the product are basically controlled by the selected organic amine templates. The Cu content can be regulated and controlled in a relatively wide range, and controllable synthesis of Cu-SAPO-34 is realized. The improvement of the silicon amount and the coordination environment in the Cu-SAPO molecular sieve provides possibility for improving the hydrothermal stability of the synthesized Cu-SAPO-34.

Comparative example 5

The samples obtained in the comparative examples 1 to 4 are roasted at the high temperature of 650 ℃ for 2h, after the template agent is removed, the samples are further hydrothermally treated at the high temperature of 800 ℃ for 16 h, XRD tests show that the diffraction peaks of the three samples belonging to the CHA crystal phase disappear, the samples have the diffraction peaks within the range of 20 to 25 ℃, a compact phase is formed, and the high-temperature hydrothermal stability of the samples is poor.

It should be noted that various modifications to these embodiments can be made by those skilled in the art without departing from the principles of the present invention, and these modifications should also be construed as being within the scope of the present invention.

Claims

1. A method for preparing a Cu-SAPO molecular sieve, comprising the steps of:

(1) synthesizing a Cu-SAPO molecular sieve with high copper content by using a template containing a copper amine complex in the presence of SAPO seed crystals, wherein the Cu loading is 5-20 wt%;

(2) mixing an organic amine template agent R, water, a silicon source, an aluminum source and a phosphorus source to prepare a crystallization liquid, wherein the organic amine template agent R is selected from one or a mixture of more of triethylamine, diethylamine, morpholine, tetraethylammonium hydroxide, propylamine and piperazine;

(3) mixing the Cu-SAPO molecular sieve with high copper content obtained in the step (1) as a raw material with the crystallization liquid prepared in the step (2) and carrying out hydrothermal crystallization to obtain a Cu-SAPO molecular sieve product,

wherein the molar ratio of the aluminum source, the phosphorus source, the silicon source, the organic amine template agent R and the water used in the step (2) is Al₂O₃:P₂O₅:SiO₂:R:H₂O＝1:0.5～2:0.01～1.5:0.5～10:15～200，

The feeding amount of the Cu-SAPO raw material with high copper content in the step (3) is 2-200 wt% of the total amount of solid oxides in the prepared crystallization liquid,

the temperature for performing the hydrothermal crystallization in the step (3) is 140 ℃ and 240 ℃, and the time is 0.5-72 hours.

2. The method as claimed in claim 1, wherein the Cu-SAPO molecular sieve with high copper content in step (1) is Cu-SAPO synthesized by hydrothermal crystallization from a silicon source, an aluminum source, a phosphorus source and water using a copper-amine complex as a single template or mixed with an organic amine template R1 as a co-template, wherein the organic amine template R1 is selected from one or more of triethylamine, diethylamine, morpholine, tetraethylammonium hydroxide, propylamine and piperazine.

3. The method of claim 1, wherein the copper amine complex in step (1) comprises a copper-polyethylene polyamine complex.

4. The method according to claim 1, wherein the copper amine complex is selected from the group consisting of Cu-tetraethylenepentamine complex, Cu-triethylenetetramine complex, Cu-diethylenetriamine complex, and Cu-pentaethylenehexamine complex.

5. The method according to claim 1, wherein the silicon source used in the step (2) is one or more selected from ethyl orthosilicate, silica sol and white carbon black; the aluminum source is one or more selected from aluminum isopropoxide, pseudo-boehmite, aluminum sol and aluminum hydroxide; the phosphorus source is one or more selected from phosphoric acid, phosphorous acid and phosphorus pentoxide.

6. The method according to claim 1, wherein the molar ratio of the aluminum source, the phosphorus source, the silicon source, the organic amine template R and the water used in the step (2) is Al₂O₃:P₂O₅:SiO₂:R:H₂O＝1:0.7～1.5:0.1～1.0:1～5:30～100。

7. The method as claimed in claim 1, wherein the crystallization temperature in the step (3) is 150-200 ℃.

8. The process of claim 1, wherein the Cu loading of the Cu-SAPO molecular sieve product prepared in step (3) is 10-70% of the copper content of the high copper content Cu-SAPO feedstock.

9. The method of any one of claims 1 to 8, wherein the Cu-SAPO molecular sieve comprises any one of Cu-SAPO-34 molecular sieve, Cu-SAPO-42 molecular sieve, Cu-DNL-6 (RHO).

10. A Cu-SAPO molecular sieve raw powder synthesized by the method of any one of claims 1 to 9.

11. The Cu-SAPO molecular sieve raw powder of claim 10, wherein the Cu-SAPO molecular sieve is a Cu-SAPO-34 molecular sieve, and wherein the Cu-SAPO-34 molecular sieve is rhombohedral.

12. The Cu-SAPO molecular sieve raw powder of claim 11, wherein the Cu-SAPO-34 molecular sieve has a particle size in the range of 1 to 2 μm.

13. For NO_xThe catalyst for selective reduction removal reaction is obtained by roasting the molecular sieve synthesized by the method according to any one of claims 1 to 10 in air at 500-800 ℃.

14. A method for improving the high temperature hydrothermal stability of a Cu-SAPO molecular sieve, comprising: mixing a Cu-SAPO molecular sieve with high copper content, which is synthesized by using a template comprising a copper-amine complex in the presence of SAPO seed crystals, with a crystallization liquid prepared by mixing an organic amine template R with water and a silicon source, an aluminum source and a phosphorus source, and performing hydrothermal crystallization,

wherein the organic amine template agent R is selected from one or a mixture of more of triethylamine, diethylamine, morpholine, tetraethylammonium hydroxide, propylamine and piperazine,

wherein the molar ratio of the aluminum source, the phosphorus source, the silicon source, the organic amine template agent R and the water used in the step of preparing the crystallization liquid is Al₂O₃:P₂O₅:SiO₂:R:H₂O is 1:0.5 to 2:0.01 to 1.5:0.5 to 10:15 to 200, and

wherein in the step of mixing the Cu-SAPO molecular sieve with high copper content and the crystallization liquid and carrying out hydrothermal crystallization, the feeding amount of the Cu-SAPO raw material with high copper content is 2-200 wt% of the total amount of solid oxides in the prepared crystallization liquid, the temperature for carrying out hydrothermal crystallization is 140-240 ℃, and the time is 0.5-72 hours.