SSZ-39 molecular sieve and its preparation method and DeNOx reaction catalyst

Abstract

The present invention provides a SSZ-39 molecular sieve and a preparation method thereof and a DeNOx reaction catalyst. The preparation method comprises mixing the components in the SSZ-39 molecular sieve raw material, aging, and obtaining a gel; stirring the gel, crystallizing, filtering, washing, and roasting to obtain the SSZ-39 molecular sieve; the SSZ-39 molecular sieve raw material comprises a silicon source, an alkali source, an organic template, an aluminum source, and water, and the SSZ-39 molecular sieve raw material contains heteroatoms; the heteroatoms are present in the aluminum source. The present invention also provides the SSZ-39 molecular sieve obtained by the above-mentioned preparation method, and a DeNOx reaction catalyst comprising the molecular sieve. Compared with conventional SSZ-39 molecular sieves, the SSZ-39 molecular sieve provided by the present invention has a smaller particle size, a higher specific surface area, and a higher catalytic activity.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieve synthesis, and in particular to an SSZ-39 molecular sieve and a preparation method thereof, and a DeNOx reaction catalyst. Background Art

[0002] SSZ-39 molecular sieve is a molecular sieve with AEI topological structure. It is composed of AlO4 and SiO4 tetrahedrons connected end to end through oxygen atoms to form a double six-membered ring secondary structure unit (SBU). The two adjacent layers of double six-membered rings are rotated 180° around the z-axis and arranged in a cross distribution. The double six-membered rings are connected by four-membered rings to form an aei cage (asymmetric pear-shaped cage) with an eight-membered ring structure and a three-dimensional pore structure. The pore size is Due to the characteristics of SSZ-39 molecular sieve, such as orderly pore structure, high specific surface area, good hydrothermal stability, more surface proton acidic centers and excellent cation exchangeability, it has shown excellent performance in industrial catalytic processes such as NH3-selective catalytic reduction reaction (NH3-SCR) and methanol to olefins catalytic reaction (MTO) in recent years.

[0003] The crystal size of SSZ-39 molecular sieve synthesized by conventional hydrothermal synthesis is generally large, usually 1-3 microns. Zeolite crystal size will have a great impact on the reaction. Compared with zeolites of conventional size, the specific surface area of ​​small crystal zeolites has changed significantly, especially the increase of external specific surface area, because when the crystal size is reduced, a large amount of unexposed surfaces in the bulk phase are exposed as surfaces, thereby greatly improving its external specific surface area. The prior art is less researched on small crystal SSZ-39 zeolites, but more researches on other zeolites, such as zeolites such as MFI and FAU, with the increase of crystal size, its external specific surface area decreases exponentially, and when the crystal size is reduced, a large amount of atoms in the bulk phase will become surface atoms, thereby exposing more active centers, and small crystal size can reduce the diffusion restriction of reactants and products, and its large specific surface area can provide good dispersibility for raw materials, thereby avoiding excessive reaction of raw materials. There is less research on the crystal size of SSZ-39 zeolite now, so it is necessary to propose a method for reducing SSZ-39 zeolite. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide an SSZ-39 molecular sieve and its preparation method and DeNOx reaction catalyst. Compared with conventional SSZ-39 molecular sieve, the SSZ-39 molecular sieve provided by the present invention has a smaller particle size, a higher specific surface area and a higher catalytic activity.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a method for preparing SSZ-39 molecular sieve, which comprises: mixing SSZ-39 molecular sieve raw materials, aging to obtain gel; stirring the gel, crystallizing, filtering, washing, and calcining to obtain SSZ-39 molecular sieve; wherein the SSZ-39 molecular sieve raw materials contain heteroatoms; the heteroatoms exist in an aluminum source; the heteroatoms include one or a combination of two or more of Mg, Zr, Cr, Mn, Zn and Ti.

[0006] In the above preparation method, the catalytic activity of SSZ-39 molecular sieve can be effectively improved by introducing heteroatoms into the SSZ-39 molecular sieve raw material. Specifically:

[0007] On the one hand, the introduction of heteroatoms prolongs the crystallization induction period of molecular sieves and shortens the crystal growth time, thereby reducing the particle size of molecular sieves: the presence of heteroatoms in the raw materials can promote the early nucleation of molecular sieves during crystallization. The crystal nuclei formed by early nucleation are smaller, the number of crystal nuclei in the same space increases, and the crystal nuclei particle size is smaller, resulting in early crystal agglomeration, thereby obtaining molecular sieves with small crystal agglomeration particles, making the final molecular sieve particle size smaller. The reduction of molecular sieve particle size is conducive to the improvement of catalytic activity;

[0008] On the other hand, the heteroatoms introduced in the present invention have DeNOx reaction catalytic performance, and after the SSZ-39 molecular sieve is loaded with Cu, the heteroatoms can increase the DeNOx reaction efficiency of the SSZ-39 molecular sieve, especially promote the DeNOx reaction catalytic performance of the catalyst under low temperature (exhaust gas treatment temperature ≤300°C) conditions.

[0009] In the above preparation method, the aluminum source in the SSZ-39 molecular sieve raw material may include a first aluminum source and / or a second aluminum source, and both the first aluminum source and the second aluminum source contain heteroatoms. Specifically, the first aluminum source is an aluminum source post-treated with a heteroatom compound, and the second aluminum source is an aluminum source synthesized using a heteroatom compound as a raw material (that is, a heteroatom compound is added during the synthesis process to obtain the second aluminum source).

[0010] In a specific embodiment of the present invention, when the aluminum source includes a first aluminum source and a second aluminum source, the mass ratio of the first aluminum source to the second aluminum source can be controlled to be (0.5-10):1, preferably 1-5:1.

[0011] In a specific embodiment of the present invention, the crystallization process and catalytic activity of the SSZ-39 molecular sieve can be improved by controlling the amount of heteroatoms added in the raw material. The present invention has found that if the amount of heteroatoms added is too high, the heteroatoms will not be able to enter the molecular sieve framework, but will form a large number of metal oxide aggregates, and excessive heteroatoms will affect the growth of SSZ-39 molecular sieve crystals, resulting in a large number of miscellaneous crystals, thereby adversely affecting the specific surface area and activity of the molecular sieve. In some specific embodiments, the mass content of the heteroatoms in the aluminum source containing heteroatoms can be controlled to be 0.1%-0.8% in terms of heteroatom oxides.

[0012] Furthermore, when the aluminum source includes a first aluminum source and / or a second aluminum source (ie, an aluminum source containing heteroatoms), the aluminum source may further include a third aluminum source, and the third aluminum source does not contain heteroatoms.

[0013] In a specific embodiment of the present invention, the mass ratio of the first aluminum source and / or the second aluminum source (aluminum source containing heteroatoms) to the third aluminum source (aluminum source without heteroatoms) can be controlled to be 1:(0-1) (i.e., less than or equal to 1:1). Specifically, when the aluminum source is the first aluminum source and the third aluminum source, the mass ratio of the first aluminum source to the third aluminum source is less than or equal to 1:1; when the aluminum source is the second aluminum source and the third aluminum source, the mass ratio of the second aluminum source to the third aluminum source is less than or equal to 1:1; when the aluminum source includes the first aluminum source, the second aluminum source and the third aluminum source, the ratio of the sum of the masses of the first aluminum source and the second aluminum source to the mass of the third aluminum source is less than or equal to 1:1.

[0014] In the above preparation method, preferably, the first aluminum source includes one or a combination of two or more of the following molecular sieves post-treated with heteroatom compounds: FAU molecular sieve, MFI molecular sieve, Beta molecular sieve, USY molecular sieve.

[0015] In the above preparation method, preferably, the post-treatment method includes one or a combination of two or more of ion exchange, impregnation, liquid phase deposition and liquid phase precipitation. In a specific embodiment, the treatment effect of the ion exchange is generally better than that of impregnation, liquid phase deposition and liquid phase precipitation.

[0016] In the above preparation method, preferably, the second aluminum source comprises one or a combination of two or more of the following molecular sieves whose synthetic raw materials contain heteroatom compounds: FAU molecular sieve, MFI molecular sieve, Beta molecular sieve, USY molecular sieve.

[0017] In the above preparation method, preferably, the third aluminum source includes one or more combinations of aluminum-containing minerals, aluminum salts, aluminum hydroxides, and aluminum oxides. In some specific embodiments, the aluminum-containing mineral includes boehmite, the aluminum hydroxide includes aluminum hydroxide, the aluminum salt includes one or more combinations of sodium aluminate, pseudo-boehmite, and aluminum isopropoxide, and the aluminum oxide includes aluminum oxide, and the aluminum oxide preferably includes aluminum sol. That is, the third aluminum source includes one or more combinations of boehmite, aluminum hydroxide, sodium aluminate, pseudo-boehmite, aluminum isopropoxide, and aluminum oxide.

[0018] In the present invention, the heteroatom compound (the heteroatom compound used for post-treatment of the first aluminum source, the heteroatom compound used for preparing the second aluminum source) may include one or a combination of two or more of an inorganic acid salt of a heteroatom, an organic coordination metal containing a heteroatom, an oxide of a heteroatom, and a hydroxide of a heteroatom. In some specific embodiments, the heteroatom compound may include an inorganic acid salt of a heteroatom and / or an oxide of a heteroatom. Specifically, the inorganic acid salt of a heteroatom may include one or a combination of two or more of a sulfate of a heteroatom, a nitrate of a heteroatom, and a hydrochloride of a heteroatom.

[0019] In the above preparation method, the SSZ-39 molecular sieve raw materials may specifically include a silicon source, an alkali source, an organic template, an aluminum source and water, and heteroatoms exist in the aluminum source.

[0020] In the above preparation method, preferably, the silicon source includes one or a combination of two or more of silicon dioxide, silicate, orthosilicate, water glass, silicon powder, kaolin, bentonite. Wherein, the silicon dioxide can be added in the form of silica sol. The silicon source is preferably silica sol and / or silicate. The water glass can be solid water glass, liquid water glass, etc.

[0021] In the above preparation method, preferably, the organic template includes one or more combinations of compounds that can provide one or more combinations of the following ions: N,N-diethyl-2,6-dimethylpiperidinium ion, 3,5-dimethyl-N,N-dimethylpiperidinium ion, N,N-diethyl-2-ethylpiperidinium ion, N-ethyl-N-propyl-2,6-dimethylpiperidinium ion, N-methyl-N-ethyl-2,6-dimethylpiperidinium ion, N-methyl-N-ethyl-2-ethylpiperidinium ion, 2,5-dimethyl-N,N-diethylpyrrole ion, 2,6-dimethyl-N,N-dimethylpiperidinium ion, 2-ethyl-N,N-dimethylpiperidinium ion, 2,2,6,6-tetramethyl-N-methyl-N-ethylpiperidinium ion, 2,2,6,6-tetramethyl-N,N-dimethylpiperidinium ion, N,N-dimethyl-N,N-bicyclononane ion. Further, the organic template preferably includes one or a combination of two or more of N,N-diethyl-2,6-dimethylpiperidinium hydroxide, 3,5-dimethyl-N,N-dimethylpiperidinium hydroxide and N,N-dimethyl-N,N-bicyclononane. Further, the organic template is preferably a compound capable of providing 3,5-dimethyl-N,N-dimethylpiperidinium ions.

[0022] In the above preparation method, preferably, the chemical composition of the SSZ-39 molecular sieve raw material satisfies the following molar ratio range: A / SiO2=0.001-0.5, A is the molar number of the heteroatom element. It can be further controlled to A / SiO2=0.02-0.2.

[0023] In a specific embodiment of the present invention, the chemical composition of the SSZ-39 molecular sieve raw material can further satisfy the following molar ratio range: SiO2 / Al2O3=5-200, OH - / SiO2 is less than or equal to 2, H2O / SiO2=2-80, R / SiO2 is less than or equal to 0.5; wherein R is the molar number of the organic template. Preferably, the chemical composition of the SSZ-39 molecular sieve raw material satisfies the following molar ratio range: SiO2 / Al2O3=5-30, OH - / SiO2 is less than or equal to 0.5, H2O / SiO2=5-40, R / SiO2 is less than or equal to 0.2.

[0024] In a specific embodiment of the present invention, the SSZ-39 molecular sieve raw material can be in the following composition form:

[0025] Form 1: comprising a silicon source, an alkali source, an organic template, a first aluminum source, and water, wherein the first aluminum source is a molecular sieve post-treated with a heteroatom compound, and the type of the molecular sieve preferably comprises one or a combination of two or more of FAU molecular sieve, MFI molecular sieve, Beta molecular sieve, and USY molecular sieve;

[0026] Form 2: including a silicon source, an alkali source, an organic template, a second aluminum source, a third aluminum source, and water, wherein the second aluminum source is a molecular sieve containing heteroatoms in the synthesis raw material, and the type of molecular sieve preferably includes one or a combination of two or more of FAU molecular sieve, MFI molecular sieve, Beta molecular sieve, and USY molecular sieve, and the third aluminum source does not contain heteroatoms, and the third aluminum source includes one or a combination of two or more of aluminum-containing minerals, aluminum salts, aluminum hydroxides, and aluminum oxides;

[0027] Form 3: including silicon source, alkali source, organic template, second aluminum source, and water;

[0028] Form 4: including a silicon source, an alkali source, an organic template, a first aluminum source, a third aluminum source, and water;

[0029] Form 5: including a silicon source, an alkali source, an organic template, a first aluminum source, a second aluminum source, and water;

[0030] Form 6: includes a silicon source, an alkali source, an organic template, a first aluminum source, a second aluminum source, a third aluminum source, and water.

[0031] In the above forms, the chemical composition of the SSZ-39 molecular sieve raw material meets the following molar ratio range:

[0032] SiO2 / Al2O3=5-200, preferably SiO2 / Al2O3=5-30,

[0033] OH - / SiO2 is less than or equal to 2, preferably OH - / SiO2 is less than or equal to 0.5,

[0034] H2O / SiO2=2-80, preferably H2O / SiO2=5-40,

[0035] R / SiO2 is less than or equal to 0.5, preferably R / SiO2 is less than or equal to 0.2, R is the molar number of the organic template,

[0036] A / SiO2=0.001-0.5, preferably A / SiO2=0.02-0.2, where A is the molar number of the heteroatom element.

[0037] In a specific embodiment of the present invention, compared with adding heteroatoms separately to the SSZ-39 molecular sieve raw material in the form of heteroatom compounds, the use of an aluminum source containing heteroatoms can introduce heteroatoms into the aluminum source in advance and the resulting molecular sieve has a large surface area. The heteroatoms are better dispersed uniformly inside the molecular sieve after gelation and are not easy to lose and aggregate, thereby improving the activity of the molecular sieve after the SSZ-39 molecular sieve is loaded with copper; and by adding an appropriate amount of aluminum source with a high degree of heteroatom dispersion as a raw material for preparing the SSZ-39 molecular sieve, the crystallization process of the molecular sieve can also be improved. An appropriate amount of heteroatoms enters the molecular sieve framework to promote the rapid and stable formation of SSZ-39 molecular sieve crystals and can improve the catalytic performance of the SSZ-39 molecular sieve, but the more heteroatoms, the better. Excessive heteroatoms will break the crystallization balance and lead to the appearance of impure crystals, which is not conducive to obtaining a pure phase SSZ-39 molecular sieve.

[0038] In a specific embodiment of the present invention, the aging temperature is generally controlled to be room temperature to 100° C., and the aging time is generally controlled to be 0.1 h to 100 h. The aging time can be further controlled to be 1 h to 2 h.

[0039] In a specific embodiment of the present invention, the stirring time is generally controlled to be 0-10 hours, and can be further controlled to be 0.5-20 hours. In some specific embodiments, the stirring can be performed in a rotating manner.

[0040] In a specific embodiment of the present invention, the crystallization temperature is generally controlled to be 120° C.-210° C., and the crystallization time is generally controlled to be 38 h-150 h. The crystallization time can be further controlled to be 50 h-130 h.

[0041] In a specific embodiment of the present invention, the calcination temperature is generally controlled to be 500-800° C., such as 550° C., and the calcination time is generally controlled to be 2-8 h, such as 4 h.

[0042] In a specific embodiment of the present invention, the preparation method of the SSZ-39 molecular sieve comprises:

[0043] 1. Mix the components (silicon source, aluminum source, alkali source, organic template and water) in the SSZ-39 molecular sieve raw material, age at room temperature to 100° C. for 0.1 h to 100 h (preferably 1 h to 2 h) to obtain a gel, the chemical composition of which satisfies the following molar ratio range:

[0044] SiO2 / Al2O3=5-200 (preferably SiO2 / Al2O3=5-30);

[0045] OH - / SiO2 is less than or equal to 2 (preferably OH - / SiO2 is less than or equal to 0.5);

[0046] H2O / SiO2=2-80 (preferably H2O / SiO2=5-40);

[0047] R / SiO2 is less than or equal to 0.5 (preferably R / SiO2 is less than or equal to 0.2), where R is the molar number of the organic template;

[0048] A / SiO2=0.001-0.5 (preferably A / SiO2=0.02-0.2), A is the molar number of the heteroatom element.

[0049] 2. Stir the gel and crystallize it at 120° C.-210° C. for 38 h-150 h (preferably 50 h-130 h), filter, wash and calcine the crystallized product to obtain SSZ-39 molecular sieve.

[0050] The present invention also provides a SSZ-39 molecular sieve, which is obtained by the above preparation method.

[0051] In a specific embodiment of the present invention, the mass content of heteroatom oxides in the SSZ-39 molecular sieve is generally 0.1%-2%, for example, 0.1%-1%, 0.1%-0.8%.

[0052] In a specific embodiment of the present invention, compared to conventional SSZ-39 molecular sieves, the SSZ-39 molecular sieve provided by the present invention has a smaller particle size, a larger specific surface area, and more surface atoms and exposed active centers. In addition, the SSZ-39 molecular sieve with a small particle size can shorten the diffusion length of reactants and products in the molecular sieve, reduce the diffusion restrictions of reactants and products, and increase the diffusion rate. At the same time, the larger specific surface area can provide good dispersibility for the raw material, thereby avoiding excessive reaction of the raw material, thereby improving the catalytic activity of the SSZ-39 molecular sieve. In addition, when preparing a DeNOx reaction catalyst, the use of a molecular sieve with a small particle size can provide more catalytic reaction gaps and surface areas in the same coating area, and can achieve a better coating effect, so the molecular sieve particle size reduction can also promote the catalytic activity of the DeNOx reaction.

[0053] In a specific embodiment of the present invention, the particle size of the SSZ-39 molecular sieve is 0.1 μm-10 μm, which can be further controlled to be 0.1 μm-4 μm, and further controlled to be 0.1 μm-1 μm.

[0054] In a specific embodiment of the present invention, the specific surface area of ​​the SSZ-39 molecular sieve is 720 m 2 ·g -1 -780m 2 ·g -1, further reaching 730-780m 2 ·g -1 ;

[0055] In a specific embodiment of the present invention, the relative crystallinity of the SSZ-39 molecular sieve is 85%-100%.

[0056] The present invention also provides a DeNOx reaction catalyst, which includes the above-mentioned SSZ-39 molecular sieve. The SSZ-39 molecular sieve provided by the present invention has a high DeNOx reaction catalytic activity, and the conversion rate in the DeNOx reaction at 150°C can reach more than 60%, the conversion rate in the DeNOx reaction at 350°C can reach more than 95%, and the conversion rate in the DeNOx reaction at 550°C can reach more than 94%.

[0057] The beneficial effects of the present invention are:

[0058] Compared with the existing SSZ-39 molecular sieve, the SSZ-39 molecular sieve provided by the present invention has a smaller particle size, a larger specific surface area, and a significantly improved catalytic activity, especially a low-temperature catalytic activity. The SSZ-39 molecular sieve of the present invention is used to catalyze the DeNOx reaction, and a conversion rate of more than 60% can be obtained at a temperature of 150°C, and a conversion rate of more than 94% can be obtained at a temperature of 350-550°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is the SEM image of the SSZ-39 molecular sieve of Example 1.

[0060] Figure 2 This is the SEM image of the SSZ-39 molecular sieve of Example 2.

[0061] Figure 3 This is the SEM image of the SSZ-39 molecular sieve of Example 3.

[0062] Figure 4 This is the SEM image of the SSZ-39 molecular sieve of Example 4.

[0063] Figure 5 This is the SEM image of the SSZ-39 molecular sieve of Comparative Example 1.

[0064] Figure 6 This is the SEM image of the SSZ-39 molecular sieve of Comparative Example 2.

[0065] Figure 7 This is the SEM image of the SSZ-39 molecular sieve of Comparative Example 3.

[0066] Figure 8 The XRD diagrams of the SSZ-39 molecular sieves of Examples 1 to 4 and Comparative Examples 1 to 2 are shown.

[0067] Fig. 9 This is the XRD diagram of the molecular sieve of Comparative Example 3. DETAILED DESCRIPTION

[0068] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0069] In the following examples and comparative examples, the content of heteroatom oxides in the molecular sieves was determined by XRF.

[0070] Relative crystallinity refers to XRD crystallinity. The commercial SSZ-39 molecular sieve (SSZ-39 molecular sieve from China Catalyst Company, particle size 2μm-3.5μm) is used as the standard sample, and its crystallinity is calculated as 100%. The calculation method of the relative crystallinity of the synthetic sample is: crystallinity (%) = XRD diffraction peak area of ​​synthetic sample / XRD diffraction peak area of ​​standard sample × 100%; the 2θ range of the XRD diffraction peak is 5-35°.

[0071] Example 1

[0072] This embodiment provides a SSZ-39 molecular sieve, the preparation method of which includes:

[0073] 1. Perform ion exchange on NaY molecular sieve and magnesium chloride to obtain magnesium-exchanged NaY molecular sieve;

[0074] 2. Sodium hydroxide, pure water, silica sol with a silica concentration of 40 wt%, an aqueous solution of 25 wt% 3,5-dimethyl-N,N-dimethylpiperidine hydroxide (as an organic template) and magnesium-exchanged NaY molecular sieves were fully mixed to obtain a raw material composition having the following molar ratio, and aged at room temperature for 1 h to obtain a gel:

[0075] SiO2 / Al2O3=70,

[0076] R / SiO2=0.2, R is an organic template,

[0077] Mg / SiO2=0.08,

[0078] OH - / SiO2=0.5,

[0079] H2O / SiO2=20.

[0080] 3. Place the gel in an autoclave, stir at room temperature for 5 hours, and heat to 180°C for crystallization for 50 hours. Cool the crystallized product to below 40°C, filter, wash, dry the solid sample, and calcine at 550°C for 4 hours to obtain SSZ-39 molecular sieve.

[0081] Figure 1 This is the SEM image of the SSZ-39 molecular sieve of this example.

[0082] The particle size of the SSZ-39 molecular sieve obtained in this example is 0.5-1 μm, the relative crystallinity is 93%, and the specific surface area is 735 m 2 / g. The content of MgO in SSZ-39 molecular sieve is 0.6wt%.

[0083] Example 2

[0084] This embodiment provides a SSZ-39 molecular sieve, the preparation method of which includes:

[0085] 1. USY molecular sieve and chromium nitrate are liquid-phase deposited under the action of urea, and calcined at 550°C for 4 hours to obtain USY molecular sieve containing chromium (CrIII); in the liquid-phase deposition process, urea is used as a precipitant to promote the precipitation of metal on the surface of the molecular sieve;

[0086] 2. Sodium hydroxide, pure water, silica sol with a silicon dioxide concentration of 40 wt%, 3,5-dimethyl-N,N-dimethylpiperidine hydroxide (as an organic template) with a concentration of 25 wt%, and chromium-containing USY molecular sieve are fully mixed to obtain a raw material composition with the following molar ratio, and aged at room temperature for 1 hour to obtain a gel:

[0087] SiO2 / Al2O3=50,

[0088] R / SiO2=0.2,

[0089] Cr / SiO2=0.09,

[0090] OH - / SiO2=0.63,

[0091] H2O / SiO2=20.

[0092] 3. Place the gel in an autoclave, stir at room temperature for 0.5 h, and heat to 160°C for crystallization for 60 h. Cool the crystallized product to below 40°C, filter, wash, dry the solid sample, and calcine at 550°C for 4 h to obtain SSZ-39 molecular sieve.

[0093] Figure 2 This is the SEM image of the SSZ-39 molecular sieve of this example.

[0094] The particle size of the SSZ-39 molecular sieve obtained in this example is 0.4-0.8 μm, the relative crystallinity is 91%, and the specific surface area is 726 m 2 / g. The content of Cr2O3 in SSZ-39 molecular sieve is 0.8wt%.

[0095] Example 3

[0096] This embodiment provides a SSZ-39 molecular sieve, the preparation method of which includes:

[0097] 1. In the process of NaY molecular sieve synthesis, a certain amount of titanium sulfate (Ti IV) is introduced to hydrothermally synthesize Ti-containing NaY molecular sieve, and then ion exchange and hydrothermal calcination are performed to prepare TiUSY molecular sieve. The specific synthesis method is as follows:

[0098] 1) Sodium hydroxide, pure water, water glass, a gel directing agent and a certain amount of titanium sulfate are fully mixed to obtain a raw material composition having the following molar ratio, and aged at room temperature for 5 hours to obtain a gel:

[0099] SiO2 / Al2O3=9,

[0100] TiO2 / SiO2=0.05,

[0101] OH - / SiO2=0.5,

[0102] H2O / SiO2=20.

[0103] 2) The gel was placed in an autoclave, heated to 100° C. and crystallized for 40 hours. The crystallized product was cooled to below 40° C., filtered, washed, and the solid sample was dried to obtain a Ti-NaY molecular sieve.

[0104] 3) Ti-NaY molecular sieve and ammonium sulfate are treated by ion exchange and hydrothermal calcination to obtain TiUSY molecular sieve.

[0105] 2. Sodium hydroxide, pure water, silica sol with a silicon dioxide concentration of 40 wt%, 3,5-dimethyl-N,N-dimethylpiperidine hydroxide (as an organic template) with a concentration of 25 wt%, and TiUSY molecular sieve were fully mixed to obtain a raw material composition with the following molar ratio, and aged at room temperature for 1 hour to obtain a gel:

[0106] SiO2 / Al2O3=45,

[0107] R / SiO2=0.2,

[0108] Ti / SiO2=0.03,

[0109] OH - / SiO2=0.5,

[0110] H2O / SiO2=20.

[0111] 3. Place the gel in an autoclave, stir at room temperature for 0.5 h, and heat to 170°C for crystallization for 40 h. Cool the crystallized product to below 40°C, filter, wash, dry the solid sample, and calcine at 550°C for 4 h to obtain SSZ-39 molecular sieve.

[0112] Figure 3 This is the SEM image of the SSZ-39 molecular sieve of this example.

[0113] The particle size of the SSZ-39 molecular sieve obtained in this example is 0.3-0.7 μm, the relative crystallinity is 89%, and the specific surface area is 740 m 2 / g. The content of TiO2 in SSZ-39 molecular sieve is 0.1wt%.

[0114] Example 4

[0115] This embodiment provides a SSZ-39 molecular sieve, the preparation method of which includes:

[0116] 1. Liquid phase deposition of USY molecular sieve and manganese (II) nitrate solution under the action of sodium hydroxide, drying, and calcination at 500°C for 2h to obtain manganese-containing USY molecular sieve. In the liquid phase deposition process, sodium hydroxide acts as a precipitant to promote metal precipitation on the surface of the molecular sieve, and divalent manganese ions can be converted into tetravalent manganese ions;

[0117] 2. Sodium hydroxide, pure water, silica sol with a silicon dioxide concentration of 40 wt%, 3,5-dimethyl-N,N-dimethylpiperidine hydroxide (as an organic template) with a concentration of 25 wt%, and manganese-containing USY molecular sieve are fully mixed to obtain a raw material composition with the following molar ratio, and aged at room temperature for 1 hour to obtain a gel:

[0118] SiO2 / Al2O3=60,

[0119] R / SiO2=0.2,

[0120] Mn / SiO2=0.04,

[0121] OH - / SiO2=0.7,

[0122] H2O / SiO2=20.

[0123] 3. Place the gel in an autoclave, stir at room temperature for 0.5 h, heat to 160°C for crystallization for 50 h. Cool the crystallized product to below 40°C, filter, wash, dry the solid sample, and calcine at 550°C for 4 h to obtain SSZ-39 molecular sieve.

[0124] Figure 4The SEM image of the SSZ-39 molecular sieve of this embodiment is shown in Figure 2. According to the measurement, the particle size of the SSZ-39 molecular sieve obtained in this embodiment is 0.3 μm-0.7 μm.

[0125] The relative crystallinity of the SSZ-39 molecular sieve obtained in this example is 93%, and the specific surface area is 750 m 2 / g. The content of Mn metal oxide in SSZ-39 molecular sieve is 0.3wt%.

[0126] Comparative Example 1

[0127] This comparative example provides a SSZ-39 molecular sieve, the preparation method of which comprises:

[0128] 1. Sodium hydroxide, pure water, silica sol with a silicon dioxide concentration of 40 wt%, an aqueous solution of 3,5-dimethyl-N,N-dimethylpiperidine hydroxide (as an organic template) with a concentration of 25 wt%, and USY molecular sieves are fully mixed to obtain a raw material composition with the following molar ratio, and aged at room temperature for 1 hour to obtain a gel:

[0129] SiO2 / Al2O3=45,

[0130] R / SiO2=0.2,

[0131] OH - / SiO2=0.5,

[0132] H2O / SiO2=20.

[0133] 2. Place the gel in an autoclave, stir at room temperature for 0.5 h, and heat to 160°C for crystallization for 50 h. Cool the crystallized product to below 40°C, filter, wash, dry the solid sample, and calcine at 550°C for 4 h to obtain SSZ-39 molecular sieve.

[0134] Figure 5 The SEM image of the SSZ-39 molecular sieve of this comparative example. After measurement, the particle size of the SSZ-39 molecular sieve obtained in this comparative example is 2μm-3.5μm. Compared with Examples 1 to 4, the raw material composition used in this comparative example does not contain heteroatoms. It can be seen from the particle size comparison that compared with the molecular sieve without introducing heteroatoms in the raw material, the SSZ-39 molecular sieve of the embodiment of the present invention can obtain molecular sieve particles with smaller particle size by introducing heteroatoms in the raw material molecular sieve.

[0135] The SSZ-39 molecular sieve obtained in this comparative example has a crystallinity of 90% and a specific surface area of ​​745 m 2 ·g -1 .

[0136] Comparative Example 2

[0137] This comparative example provides a SSZ-39 molecular sieve, the preparation method of which comprises:

[0138] 1. Sodium hydroxide, pure water, silica sol with a silicon dioxide concentration of 40wt%, 3,5-dimethyl-N,N-dimethylpiperidine hydroxide (as an organic template) with a concentration of 25wt%, manganese nitrate and USY molecular sieve are fully mixed to obtain a raw material composition with the following molar ratio, and aged at room temperature for 1h to obtain a gel:

[0139] SiO2 / Al2O3=60,

[0140] R / SiO2=0.2,

[0141] Mn / SiO2=0.04,

[0142] OH - / SiO2=0.5,

[0143] H2O / SiO2=20.

[0144] 2. Place the gel in an autoclave, stir at room temperature for 0.5 h, and heat to 180°C for crystallization for 60 h. Cool the crystallized product to below 40°C, filter, wash, dry the solid sample, and calcine at 550°C for 4 h to obtain SSZ-39 molecular sieve.

[0145] Figure 6 This is the SEM image of the SSZ-39 molecular sieve of this comparative example.

[0146] The particle size of the SSZ-39 molecular sieve obtained in this comparative example is 0.4-0.8 μm, the crystallinity is 80%, and the specific surface area is 690 m 2 / g. The content of manganese oxide in SSZ-39 molecular sieve is 0.12wt%.

[0147] Compared with the above implementation, this comparative example uses an aluminum source without heteroatoms, and directly uses heteroatom compounds as raw materials for preparing SSZ-39 molecular sieves. Compared with the SSZ-39 molecular sieves prepared in the examples, the SSZ-39 molecular sieves prepared in this comparative example have low specific surface area and crystallinity, and low catalytic activity.

[0148] Comparative Example 3

[0149] This comparative example provides a SSZ-39 molecular sieve, the preparation method of which comprises:

[0150] 1. Mix USY molecular sieve and manganese nitrate solution in liquid phase under the action of urea, dry and roast to obtain manganese-containing USY molecular sieve.

[0151] 2. Sodium hydroxide, pure water, silica sol with a silicon dioxide concentration of 40 wt%, 3,5-dimethyl-N,N-dimethylpiperidine hydroxide (as an organic template) with a concentration of 25 wt%, and manganese-containing USY molecular sieve are fully mixed to obtain a raw material composition with the following molar ratio, and aged at room temperature for 1 hour to obtain a gel:

[0152] SiO2 / Al2O3=60,

[0153] R / SiO2=0.2,

[0154] Mn / SiO2=0.6

[0155] OH - / SiO2=0.7,

[0156] H2O / SiO2=20.

[0157] 3. Place the gel in an autoclave, stir at room temperature for 0.5 h, heat to 160°C for crystallization for 50 h. Cool the crystallized product to below 40°C, filter, wash, dry the solid sample, and calcine at 550°C for 4 h to obtain SSZ-39 molecular sieve.

[0158] Figure 7 This is the SEM image of the SSZ-39 molecular sieve of this comparative example, and it was found that the SSZ-39 molecular sieve could not be synthesized.

[0159] Figure 8 The XRD diagrams of the product samples of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in FIG. Figure 8 It can be seen that the products of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 are all SSZ-39 molecular sieves. The product of Comparative Example 3 was subjected to XRD scanning, and the results are as follows: Fig. 9 As shown, it can be seen that the product of Comparative Example 3 does not belong to SSZ-39 molecular sieve.

[0160] Test Example 1

[0161] This test example provides the NH3-SCR reaction performance test results of SSZ-39 molecular sieve samples prepared in Examples 1 to 4 and Comparative Examples 1 to 2 and commercial SSZ-39 molecular sieve products. The specific test method includes:

[0162] (1) Molecular sieve ammonium exchange: The SSZ-39 molecular sieve prepared in Examples 1 to 4 and Comparative Examples 1 to 2 is used as the molecular sieve to be tested, and the mixture is mixed in a ratio of ammonium nitrate: molecular sieve to be tested: water (mass ratio) = 1:1:10, and the pH is adjusted to 8-8.5 with aqueous ammonia, and the mixture is exchanged at 90°C for 1 hour under stirring, filtered, washed, dried, and calcined at 550°C for 4 hours. The above process is repeated 3 times until the Na2O content in the molecular sieve is less than 0.1%.

[0163] (2) Molecular sieve copper loading: Dissolve copper acetate equivalent to 5% of the CuO loading of the molecular sieve to be tested in 50 times the amount of water, add the ammonium-exchanged molecular sieve under stirring, adjust the pH to 8-8.5 with ammonia water, filter, wash, dry, and calcine at 550°C for 4 hours to obtain a Cu-SSZ-39 composite molecular sieve.

[0164] (3) The Cu-SSZ-39 composite molecular sieve was pressed into tablets, crushed, sieved, and hydrothermally aged at 650°C in a 10% H2O+90% nitrogen atmosphere for 100 h. Then, 0.5 g of a 40-60 mesh sample was taken for NH3-SCR reaction. The composition of the reaction mixture was: 1000 ppm NO, 1100 ppm NH3, 10 Vol% O2, 10 Vol% H2O, N2 as the balance gas, and the volumetric space velocity was 120,000 h -1 The reaction temperature is 150℃-600℃, and the NOx concentration in the exhaust gas is detected online using an MKS infrared gas analyzer.

[0165] Table 1 shows the conversion rate of nitrogen oxides in the reaction mixture at different temperatures (150-350°C).

[0166] Among them, NO x The conversion rate is defined as:

[0167]

[0168] Among them, [NO] in is the concentration of NO in the reaction gas mixture, [NO] out is the concentration of NO in the exhaust gas, [NO2] out is the concentration of NO2 in the exhaust gas, [N2O] out is the concentration of N2O in the exhaust gas.

[0169] Table 1

[0170] 150℃ 350℃ 550℃ Example 1 66 97 97 Example 2 68 98 97 Example 3 63 96 95 Example 4 65 97 98 Comparative Example 1 52 95 93 Comparative Example 2 55 94 85 Commercial Zeolite 51 92 90

[0171] The commercial zeolite is SSZ-39 molecular sieve purchased from China Catalyst Company, with a particle size of 2 μm-3.5 μm.

[0172] From the data in Table 1, it can be seen that the Cu-SSZ-39 molecular sieve prepared in the embodiment of the present invention has a better DeNOx activity than the conventional SSZ-39 molecular sieve at different temperatures within the temperature range of 150-550°C, and in particular, the molecular sieve provided by the present invention has a significant advantage in activity at low temperatures (such as 150°C) compared to commercial zeolites. This structure shows that the small-grain SSZ-39 synthesized by the preparation method provided by the present invention has a good application in DeNOx.

[0173] At the same time, by comparing the performance of Comparative Example 2 with Examples 1 to 4, it can be seen that, compared with adding heteroatom compounds in the SSZ-39 raw material mixing stage, pre-introducing heteroatoms into the aluminum source can improve the uniformity of the dispersion of heteroatoms in the SSZ-39 molecular sieve, thereby improving the catalytic activity of the SSZ-39 molecular sieve, especially significantly improving the catalytic activity of the SSZ-39 molecular sieve at around 150°C and 550°C.

Claims

1. A method for preparing SSZ-39 molecular sieve, wherein: The preparation method comprises: The SSZ-39 molecular sieve raw materials are mixed and aged to obtain a gel; the gel is stirred, crystallized, filtered, washed, and calcined to obtain the SSZ-39 molecular sieve; Wherein, the SSZ-39 molecular sieve raw material contains heteroatoms; the heteroatoms exist in the aluminum source; The heteroatom includes one or a combination of two or more of Mg, Zr, Cr, Mn, Zn and Ti; The mass content of heteroatom oxide in the SSZ-39 molecular sieve is 0.1%-2%; The chemical composition of the SSZ-39 molecular sieve raw material satisfies the following molar ratio range: A / SiO2=0.001-0.5, where A is the molar number of the heteroatom element.

2. The preparation method according to claim 1, wherein The aluminum source includes a first aluminum source and / or a second aluminum source, The first aluminum source is an aluminum source that has been post-treated with a heteroatom compound, and the second aluminum source is an aluminum source synthesized using the heteroatom compound as a raw material.

3. The preparation method according to claim 2, wherein The aluminum source further includes a third aluminum source, and the third aluminum source does not contain heteroatoms.

4. The preparation method according to claim 3, wherein The mass ratio of the first aluminum source and / or the second aluminum source to the third aluminum source is 1:(0-1).

5. The preparation method according to claim 2, wherein: The first aluminum source includes one or a combination of two or more of the following molecular sieves that have been post-treated with heteroatom compounds: FAU molecular sieve, MFI molecular sieve, Beta molecular sieve, and USY molecular sieve.

6. The preparation method according to claim 2, wherein: The second aluminum source includes one or a combination of two or more of the following molecular sieves whose synthetic raw materials contain heteroatom compounds: FAU molecular sieve, MFI molecular sieve, Beta molecular sieve, and USY molecular sieve.

7. The preparation method according to claim 2, wherein: In the first aluminum source, the post-treatment method includes one or a combination of two or more of ion exchange, impregnation, liquid phase deposition and liquid phase precipitation.

8. The preparation method according to any one of claims 1 to 6, wherein: The heteroatom compound includes one or a combination of two or more of a heteroatom inorganic acid salt, a heteroatom-containing organic coordination metal, a heteroatom oxide, and a heteroatom hydroxide.

9. The preparation method according to claim 8, wherein: The heteroatom compound includes an inorganic acid salt of a heteroatom and / or an oxide of a heteroatom.

10. The preparation method according to claim 8, wherein: The inorganic acid salt of the heteroatom includes one or a combination of two or more of the heteroatom sulfate, heteroatom nitrate and heteroatom hydrochloride.

11. The preparation method according to claim 3, wherein: The third aluminum source includes one or a combination of two or more of aluminum-containing minerals, aluminum salts, aluminum hydroxides, and aluminum oxides.

12. The preparation method according to claim 11, wherein The aluminum-containing mineral includes boehmite; The aluminum hydroxide includes aluminum hydroxide; The aluminum salt includes one or a combination of two or more of sodium metaaluminate, pseudo-boehmite, and aluminum isopropoxide; The aluminum oxide includes aluminum oxide.

13. The preparation method according to claim 12, wherein: The aluminum oxide includes aluminum sol.

14. The preparation method according to claim 1, wherein: The SSZ-39 molecular sieve raw materials include a silicon source, an alkali source, an organic template, an aluminum source and water.

15. The preparation method according to claim 14, wherein: The silicon source includes one or a combination of two or more of silicon dioxide, silicate, orthosilicate, water glass, silica powder, kaolin, and bentonite.

16. The preparation method according to claim 15, wherein: The silicon dioxide includes silica sol.

17. The preparation method according to claim 15, wherein: The silicon source is silica sol and / or silicate.

18. The preparation method according to claim 14, wherein: The organic template includes one or more combinations of compounds that can provide one or more combinations of the following ions: N,N-diethyl-2,6-dimethylpiperidinium ion, 3,5-dimethyl-N,N-dimethylpiperidinium ion, N,N-diethyl-2-ethylpiperidinium ion, N-ethyl-N-propyl-2,6-dimethylpiperidinium ion, N-methyl-N-ethyl-2,6-dimethylpiperidinium ion, N-methyl-N-ethyl-2-ethylpiperidinium ion, 2,5-dimethyl-N,N-diethylpyrrole ion, 2,6-dimethyl-N,N-dimethylpiperidinium ion, 2-ethyl-N,N-dimethylpiperidinium ion, 2,2,6,6-tetramethyl-N-methyl-N-ethylpiperidinium ion, 2,2,6,6-tetramethyl-N,N-dimethylpiperidinium ion, N,N-dimethyl-N,N-bicyclononane ion.

19. The preparation method according to claim 18, wherein: The organic template comprises one or a combination of two or more of N,N-diethyl-2,6-dimethylpiperidine hydroxide, 3,5-dimethyl-N,N-dimethylpiperidine hydroxide and N,N-dimethyl-N,N-bicyclononane.

20. The preparation method according to claim 1, wherein: The chemical composition of the SSZ-39 molecular sieve raw material satisfies the following molar ratio range: A / SiO2=0.02-0.2, where A is the molar number of the heteroatom element.

21. The preparation method according to claim 1, wherein: The chemical composition of the SSZ-39 molecular sieve raw material satisfies the following molar ratio range: SiO2 / Al2O3=5-200, OH - / SiO2 is less than or equal to 2, H2O / SiO2=2-80, R / SiO2 is less than or equal to 0.5; wherein R is the molar number of the organic template.

22. The preparation method according to claim 21, wherein The chemical composition of the SSZ-39 molecular sieve raw material meets the following molar ratio range: SiO2 / Al2O3=5-30, OH - / SiO2 is less than or equal to 0.5, H2O / SiO2=5-40, R / SiO2 is less than or equal to 0.

2.

23. The preparation method according to claim 1, wherein The aging temperature is from room temperature to 100° C., and the aging time is from 0.1 h to 100 h; the crystallization temperature is from 120° C. to 210° C., and the crystallization time is from 38 h to 150 h.

24. The preparation method according to claim 23, wherein: The aging time is 1h-2h.

25. The preparation method according to claim 23, wherein: The crystallization time is 50h-130h.

26. The preparation method according to claim 23, wherein The calcination temperature is 500-800° C., and the calcination time is 2-8 hours.

27. An SSZ-39 molecular sieve obtained by the preparation method according to any one of claims 1 to 26.

28. The SSZ-39 molecular sieve according to claim 27, wherein The mass content of heteroatom oxides in the SSZ-39 molecular sieve is 0.1%-1%.

29. The SSZ-39 molecular sieve according to claim 27, wherein The particle size of the SSZ-39 molecular sieve is 0.1 μm-10 μm.

30. The SSZ-39 molecular sieve according to claim 29, wherein The particle size of the SSZ-39 molecular sieve is 0.1 μm-4 μm.

31. The SSZ-39 molecular sieve according to claim 29, wherein The particle size of the SSZ-39 molecular sieve is 0.1 μm-1 μm.

32. The SSZ-39 molecular sieve according to claim 27, wherein The specific surface area of ​​the SSZ-39 molecular sieve is 720 m 2 ·g -1 -780m 2 ·g -1 .

33. The SSZ-39 molecular sieve according to claim 32, wherein The specific surface area of ​​the SSZ-39 molecular sieve is 730 m 2 ·g -1 -780m 2 ·g -1 .

34. The SSZ-39 molecular sieve according to claim 27, wherein The relative crystallinity of the SSZ-39 molecular sieve is 85%-100%.

35. A DeNOx reaction catalyst comprising the SSZ-39 molecular sieve according to any one of claims 27 to 34.

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