CN109250729B

CN109250729B - Cu-SAPO-34 molecular sieve synthesis method, synthesized molecular sieve and application

Info

Publication number: CN109250729B
Application number: CN201710566782.9A
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: 2022-02-25
Anticipated expiration: 2037-07-12
Also published as: WO2019010815A1; CN109250729A

Abstract

The invention relates to a method for synthesizing a Cu-SAPO-34 molecular sieve, a product and application thereof. More particularly, the method comprises the step of taking the Cu-SSZ-13 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-aluminum source and seed crystals to synthesize the Cu-SAPO-34 molecular sieve. The method can not only control the copper loading in the SAPO-34 molecular sieve within a certain wide range, but also effectively control the silicon atom content and the distribution thereof in the molecular sieve, and has high product yield. The obtained Cu-SAPO-34 molecular sieve catalyst shows excellent hydrothermal stability and selective reduction for removing NO_xCatalytic performance of the reaction.

Description

Cu-SAPO-34 molecular sieve synthesis method, synthesized molecular sieve and application

Technical Field

The invention belongs to the field of chemical engineering, relates to a molecular sieve and a preparation method thereof, and particularly relates to a method for synthesizing Cu-SAPO-34, a product obtained by the method and application thereof. The Cu-SAPO-34 can be used as a catalyst for a nitrogen oxide elimination process.

Background

Nitrogen oxides (NOx), one of the major atmospheric pollutants, can cause many environmental problems such as acid rain, photochemical smog, and the like, and pose serious hazards to human health. Mobile source automobile exhaust emissions and stationary source plant exhaust emissions are the major sources of NOx. By NH₃Selective catalytic reduction of NOx, NH, for a reductant₃SCR technology can convert it into harmless nitrogen, playing a very important role in the catalytic removal of NOx. The key core of the method is the development of an SCR catalyst. The traditional denitration catalyst is mainly a V-Ti-W system, but with the wide adoption of a lean burn technology in the engine technology, the emission temperature of lean burn tail gas is reduced, and the catalyst of the V-Ti-W system is narrowerThe temperature application range is not satisfactory, and the potential for environmental pollution limits its application. In 1986, Iwamoto et al reported Cu for the first time²⁺Exchanged ZSM-5 with direct decomposition of NO to N₂And O₂But subsequent studies have found that direct decomposition of NO is difficult to be applied directly due to low efficiency. Cu-ZSM-5 was not used in the SCR reaction until the early 90 s of the last century. In the subsequent studies, molecular sieve catalytic systems are becoming the focus of research. In recent years, Cu-based small pore molecular sieve catalysts with CHA structure, Cu-SSZ-13 and Cu-SAPO-34(SSZ-13 is a molecular sieve with the same topology as SAPO-34, except that the former is a silicoaluminophosphate molecular sieve and the latter is a silicoaluminophosphate molecular sieve), have been used due to their high low temperature catalytic activity and N₂Selectivity, excellent hydrothermal stability and anti-poisoning ability are of great concern.

Typically, copper ion loading in molecular sieve catalysts is achieved by ion exchange. In order to ensure the introduced copper amount and the high dispersion degree thereof, a multi-step ion exchange process is often required, and partial hydrolysis of the SAPO molecular sieve framework in the ion exchange process often occurs to reduce the specific surface area and the stability of the molecular sieve. Meanwhile, 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. CN102259892A 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, but the Cu-SAPO-34 synthesized in one step has poor high-temperature hydrothermal stability and limits the industrial application thereof. 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 synthesized by the method is obviously reduced after hydrothermal aging for 13h at 750 ℃, and for Cu-SAPO-34 catalyst with medium and high 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 result in Si (4A1) 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 dosage of the copper amine complex template and the silicon source in the system is reduced simultaneously in order to control the copper loading and avoid the formation of silicon islands, the product yield and the crystallinity are influenced.

Disclosure of Invention

In order to solve the problems, the Cu-SSZ-13 with high copper content is firstly synthesized by using a copper-amine complex as a template, and is used as a Cu source, a part of a silicon-aluminum source and a seed crystal to synthesize the Cu-SAPO-34 molecular sieve. The copper amine complex wrapped in the Cu-SSZ-13 hole cage can avoid competition with other organic amine templates, and better plays a guiding role of the organic amine template in synthesis. Particularly, the method can realize effective regulation and control of the crystal granularity, the Cu content and the silicon content and distribution of the product, thereby obtaining more excellent catalytic performance and hydrothermal stability.

In one aspect, the present invention provides a method for preparing a Cu-SAPO-34 molecular sieve, comprising the steps of:

(1) synthesizing a copper-containing silicon-aluminum molecular sieve Cu-SSZ-13 molecular sieve by using a template containing a copper amine complex;

(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-SSZ-13 molecular sieve obtained in the step (1) as a raw material with the crystallization liquid prepared in the step (2) and performing hydrothermal crystallization to obtain a Cu-SAPO-34 molecular sieve product.

Optionally, the Cu content of the Cu-SSZ-13 molecular sieve in the step (1) is 5-15 wt%.

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

Optionally, the silicon source used in the step (2) is selected from one or more of 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 selected from one or more of phosphoric acid, phosphorous acid and phosphorus pentoxide; the organic amine template agent R is selected from one or a mixture of 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 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 amount of the Cu-SSZ-13 raw material added in the step (3) is 5-80 wt% of the total mass of the solid oxides in the prepared 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-SAPO-34 molecular sieve product prepared in step (3) has a copper loading of 0.5 to 8 wt%.

In another aspect, the invention provides a Cu-SAPO-34 molecular sieve raw powder, which is synthesized by the above method.

In another aspect, the present invention provides a method for the production of NO_xThe catalyst for selective reduction and desorption reaction is obtained by roasting the molecular sieve synthesized by the method in air at the temperature of 550-800 ℃. The catalyst is particularly applicable to catalytic removal reaction of nitrogen oxides, and shows good catalytic performance. The activity of the catalyst is still well maintained after the treatment of 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-34 molecular sieve, characterized in that the method comprises: a copper-containing silicoaluminophosphate molecular sieve Cu-SSZ-13 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-34 with high hydrothermal stability and the high-efficiency utilization of a Cu source, and the crystal granularity, the Cu content, the silicon content and the distribution of the Cu-SAPO-34 molecular sieve 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 well maintained after the catalyst is treated by water vapor at 800 ℃ for 16 hours.

Drawings

FIG. 1 is an XRD pattern of the high copper Cu-SSZ-13 synthesized in example 1.

FIG. 2 is a Scanning Electron Micrograph (SEM) of the high copper Cu-SSZ-13 synthesized in example 1.

Figure 3 is the XRD pattern of the product of example 2.

FIG. 4 Scanning Electron Micrograph (SEM) of the product of example 3.

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

FIG. 6 shows NH of examples 3, 5 and 7₃-SCR reaction evaluation results.

FIG. 7 is NH before (example 3) and after (example 3H) the high temperature hydrothermal treatment of the catalyst of example 3₃-SCR reaction evaluation result comparison.

FIG. 8 is an SEM micrograph of a sample of comparative example 3.

FIG. 9 is a solid of the sample of comparative example 3²⁹And (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.

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.

Solid-state nuclear magnetic experiments of the samples were performed on a Bruker avance iii600(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 Cu-SSZ-13 sample as copper source. The synthesis method can be referred to chem.Commun.2011,47, 9789-9791. The molar ratio of the respective raw materials and the crystallization conditions are shown in Table 1. The specific batching process is as follows:

to a 2L synthesis kettle was added in sequence a quantity of sodium aluminate (65 wt%), water, copper sulfate pentahydrate, Tetraethylenepentamine (TEPA), sodium hydroxide, silica sol (31 wt%) and optionally seed crystals. The raw material mixture is stirred evenly and then sealed, and the temperature is raised to 140 ℃ and 180 ℃ under stirring for rotating crystallization for 5-24 h. The solid product was centrifuged, the sample was washed to neutrality with deionized water, and after drying in air at 120 ℃, a sample of Cu-SSZ-13 molecular sieve to be used (named Cu-13-x, x ═ a, b, c, d) was obtained. The seed crystal is added to reduce the grain size of the synthesized high-copper Cu-SSZ-13, so that the seed crystal can better participate in subsequent crystallization and can play a role of the seed crystal and the copper source. The addition of seed crystals is also beneficial to improving the product yield. The seed crystal can be conventional SSZ-13 or Cu-SSZ-13 synthesized by chem.Commun.2011,47,9789-9791, and can also be conventional SAPO-34 molecular sieve or nanoscale SAPO-34 molecular sieve synthesized by the reference CN 104340986B. XRD of the synthesized high-copper Cu-SSZ-13 samples Cu-13-a and Cu-13-b is shown in figure 1, SEM of the sample Cu-13-a is shown in figure 2, and the particle size is 300-500 nm.

TABLE 1 raw material molar ratio, crystallization conditions and synthesis results of Cu-SSZ-13 as copper source

^aSeed crystal charging amount (wt%) (M)_{Seed crystal}/(M_Al2O3+M_SiO2) 100%) is producedYield of product (M)_{Raw powder of product}/(M_CuO+M_Al2O3+M_SiO2)*100％

Examples 2 to 8: 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:

an optional aluminum source is mixed with water to be dissolved, and then an optional phosphorus source, a silicon source and a template R are sequentially added into the mixture. To the above mixture was added a sample of the Cu-SSZ-13 molecular sieve 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 140 ℃ and 240 ℃ for reaction for 0.5 to 72 hours, 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 2 is shown in figure 3. In addition, FIG. 4 shows an SEM photograph of the Cu-SAPO-34 molecular sieve prepared in example 3. 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 Cu-SSZ-13 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 570.3m²g^-1And a large pore volume of 0.28cm³g^-1Wherein the specific surface area and the volume of each micropore calculated according to the t-plot method are 548.5m²g^-1And 0.26cm³g^-1. FIG. 5 shows the solid nuclear magnetic properties of the sample of example 3²⁹Si spectrogram, the result shows that the samples respectively have a single peak at 91ppm, and the single peak is assigned to the Si (4Al) coordination environment of the samples.

Example 9

The samples obtained in examples 3, 5 and 7 were calcined at 650 ℃ for 2 hours, and the mold was removedAfter plating, 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 the calcination, the sample was pressed into a sheet and sieved, and 0.1g of a 60 to 80 mesh sample was weighed and mixed with 0.4g of quartz sand (60 to 80 mesh), and the mixture was 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 samples of example 3 have low NO conversion rate in the low temperature range, 89% NO conversion rate in the high temperature range of 250 ℃, and higher NO conversion rate in the whole temperature range, and the samples of example 5 and example 7 have higher Cu content, so that the low temperature range reaction activity is further improved. However, due to the increase of the copper content, side reactions occur in the high-temperature section, so that the NO conversion rate is reduced to within 10 percent after 400 ℃.

Example 10

The sample of example 3 was calcined at 650 ℃ for 2h, after removal of the template, further hydrothermally treated at 800 ℃ for 16 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 after the high-temperature hydrothermal treatment, the reactivity of the sample is well maintained, and even the low-temperature section is improved. Therefore, the Cu-SAPO-34 prepared by the method has excellent high-temperature hydrothermal stability.

Comparative examples 1 to 4:

a certain amount of pseudo-boehmite (65 wt%), water, phosphoric acid (85 wt%), silica sol (31 wt%), copper sulfate pentahydrate, tetraethylenepentamine and diethylamine were sequentially added to a 100mL synthesis kettle. And adding 5 wt% of the solid content of the reaction mixture into the SAPO-34 seed crystals, uniformly stirring, sealing, heating to 170 ℃ under stirring, and crystallizing for 3 d. 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 for standby.

TABLE 3 molar proportions of the starting materials and crystallization conditions

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

FIG. 8 shows an SEM micrograph of comparative example 3 showing that the sample had a particle size of 5-10 microns. FIG. 9 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 method provided by the invention ingeniously solves the problems. First, a small-grain Cu-SSZ-13 molecular sieve with high copper content is prepared. Then, the Cu-SAPO-34 is synthesized by taking the Cu-SAPO-34 as a copper source, a part of a silicon-aluminum source and seed crystals. In the synthesis process, the copper-amine complex wrapped in the Cu-SSZ-13 hole cage can avoid competition with other organic amine templates, better plays the guiding role of the organic amine template in synthesis, and can regulate and control the Cu content in a range which is relatively low and meets the requirement of catalytic performance. The economic utilization of Cu atoms is realized. Meanwhile, the silicon atom distribution is mainly controlled by the selected organic amine template, so that the possibility of improving the hydrothermal stability of the synthesized Cu-SAPO-34 is provided. In addition, the distribution and coordination environment of silicon atoms in the SAPO molecular sieve are greatly influenced by an organic amine template, so that the method can flexibly adjust the type of the organic amine and 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 a high temperature of 650 ℃ for 2h, after the template agent is removed, the three samples are subjected to hydrothermal treatment at a high temperature of 800 ℃ for 16 h, diffraction peaks of CHA crystal phases of the three samples disappear, the samples have diffraction peaks within a range of 20 to 25 ℃ to form a compact phase, and the synthetic samples provided by the patent have better high-temperature hydrothermal stability.

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-34 molecular sieve, comprising the steps of:

(1) synthesizing a copper-containing silicon-aluminum molecular sieve Cu-SSZ-13 by using a template containing a copper amine complex;

(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-SSZ-13 molecular sieve 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-34 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 adding amount of the Cu-SSZ-13 raw material in the step (3) is 5 to 80 weight percent of the total mass 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 of claim 1, wherein the Cu-SSZ-13 molecular sieve in step (1) has a Cu content of 5 to 15 wt%.

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

4. The method of claim 3, wherein the copper amine complex comprises 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 method of claim 1, wherein the Cu-SAPO-34 molecular sieve product prepared in step (3) has a Cu content of 0.5 to 8 wt.%.

9. A Cu-SAPO-34 molecular sieve raw powder synthesized by the method according to any one of claims 1 to 8.

10. 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 8 in air at 550-800 ℃.

11. A method for improving the high temperature hydrothermal stability of a Cu-SAPO-34 molecular sieve, comprising: mixing a copper-containing silicoaluminophosphate molecular sieve Cu-SSZ-13 synthesized by using a template agent containing a copper amine complex with a crystallization liquid prepared by mixing an organic amine template agent R and water with 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-SSZ-13 with the crystallization liquid and carrying out hydrothermal crystallization, the adding amount of the Cu-SSZ-13 raw material is 5-80 wt% of the total mass of the solid oxides in the prepared crystallization liquid, and the temperature for carrying out the hydrothermal crystallization is 140 ℃ and 240 ℃ for 0.5-72 hours.