High-silicon CHA structure molecular sieve as well as preparation method and application thereof

Abstract

The invention provides a high-silicon CHA structure molecular sieve as well as a preparation method and application thereof, and the high-silicon CHA structure molecular sieve is prepared by mixing a silicon source, an alkali source, a template agent, a seed crystal and water to prepare crystallized gel, crystallizing the crystallized gel under a hydrothermal condition, and washing, filtering, drying and roasting in sequence, wherein the silicon source is metered by SiO2, the alkali source is metered by M2O, the template agent is metered by cation R < + >, the molar ratio of the components in the crystallized gel is M2O / SiO2 = 0.03-0.15, the molar ratio of R < + > / SiO2 = 0.05-0.20, the molar ratio of H2O / SiO2 = 15-120, and M is alkali metal; the ratio of the dry basis mass of the seed crystal to the dry basis mass of the silicon source is 0.01-0.25; the seed crystal is obtained by carrying out hydrothermal treatment and acid pickling treatment on a molecular sieve precursor with a CHA structure. The high-silicon CHA structure molecular sieve has the characteristics of wide silica-alumina ratio range, high upper limit, high crystallinity and the like.

Description

Technical Field

[0001] The invention relates to a high-silicon CHA structure molecular sieve and a preparation method and application thereof, belonging to the technical field of molecular sieve material synthesis in chemistry and chemical engineering. Background Art

[0002] The framework of SSZ-13 molecular sieve with chabazite (CHA) structure is composed of AlO4 and SiO4 tetrahedrons connected by oxygen atoms to form an ellipsoidal cage with an eight-membered ring structure. and three-dimensional cross-channel structure The specific surface area of ​​SSZ-13 molecular sieve can exceed 600m 2 / g, good thermal stability, many exchangeable cations and surface proton acidic centers, which make it show excellent characteristics in catalytic reactions and gas separations, and it is widely used as an adsorbent or catalyst carrier, such as in the fields of methanol to olefins, automobile exhaust nitrogen oxide removal, CO2 adsorption separation, etc. In recent years, with the continuous deepening of research on molecular sieve materials, great progress has been made in the synthesis and application of SSZ-13 molecular sieves. Due to the lack of aluminum centers, the enhanced skeleton stability, improved hydrophobic properties, and reduced acidic center content of high-silicon or even pure-silicon SSZ-13 molecular sieves provide more powerful conditions for their application in the fields of VOCs adsorption in water-containing atmospheres and as inactive porous carriers, but there are few reports on the synthesis methods of this type of SSZ-13.

[0003] At present, the synthesis of SSZ-13 molecular sieve mainly adopts hydrothermal synthesis method. Various template agents such as N,N,N-trimethyladamantanammonium (TMAda+), benzyltrimethylamine (BTMA+), N-alkyl-1,4-diazabicyclooctane cation, N,N-dimethylpiperidine, choline chloride, etc. can be directly used to synthesize SSZ-13 molecular sieve. In addition, Xiao Fengshou et al. (Chin. J. Catal., 2012, 33:92-105) used in-situ synthesis method to synthesize copper amine complex (Cu 2+ -tetraethylenepentamine, Cu-TEPA) as a template to synthesize Cu-SSZ-13. In addition, researchers have found that SSZ-13 molecular sieves can be prepared by intercrystalline conversion, that is, a starting molecular sieve with a different structure is crystallized into SSZ-13 molecular sieve. This method has the advantages of short crystallization time and reduced template dosage. At present, the starting molecular sieves that can be used mainly include GIS (P type), FAU, LEV, LTL and other structural molecular sieves. Using TMAda+ or BTMA+ structural directing agents, CHA structure SSZ-13 molecular sieves can be synthesized. Adding SSZ-13 molecular sieves or SAPO-34 molecular sieves with CHA structure as seeds during the synthesis process can also effectively shorten the nucleation stage, thereby shortening the overall crystallization time.

[0004] Above, whether it is the method of direct synthesis with a template agent or the intercrystalline conversion method, the silicon-aluminum ratio of the SSZ-13 molecular sieve obtained is low, generally not exceeding 400. In the process of direct synthesis with a template agent, when the silicon-aluminum ratio in the crystallized gel exceeds 200, the difficulty of nucleation increases sharply, and it is easier to produce miscellaneous crystals in an alkaline environment and at a higher crystallization temperature. In this process, adding seed crystals can not only shorten the crystallization time, but also widen the silicon-aluminum ratio range of the synthesizable molecular sieve to a certain extent (not exceeding 400). In the process of intercrystalline conversion synthesis, since the silicon-aluminum ratio of the product is directly related to the silicon-aluminum ratio of the starting molecular sieve, and the silicon-aluminum ratio of the starting molecular sieve is relatively low, it is also difficult to synthesize a high-silicon SSZ-13 molecular sieve, generally not exceeding 100.

[0005] CN107758691A discloses a method for synthesizing high-silicon CHA-type SSZ-13 molecular sieves by topological reconstruction using crystal seeds and LTL-type L zeolite, including: weighing water, alkali source, template agent, adding solid silicon source, L zeolite, and crystal seeds for crystallization reaction, obtaining a crystallization reaction product after the reaction is completed, cooling and washing to neutrality, drying to obtain molecular sieve raw powder, and then roasting the molecular sieve raw powder in air at 550°C for a certain time to obtain the final product SSZ-13 molecular sieve. This prior art uses LTL-type L zeolite with a low silicon-aluminum ratio to directly reconstruct the synthesis of high-silicon CHA-type SSZ-13 molecular sieves, without the need for dealuminization pretreatment of the starting L zeolite. By adjusting the amount of L zeolite added, the silicon-aluminum ratio of the synthesized product SSZ-13 molecular sieve can be adjusted in a wide range, and the solid phase yield is improved, which can reduce production costs and is conducive to industrial production.

[0006] CN108579449A discloses a method for preparing a high-silicon SSZ-13 molecular sieve membrane. The molecular sieve membrane includes a crystal membrane layer with selective separation and a support body, and the crystal membrane layer is coated on the surface of the support body; the selective separation crystal membrane layer is composed of SSZ-13 molecular sieve; the support body is Al2O3, mullite or stainless steel. The SSZ-13 molecular sieve membrane is quickly prepared by adding crystal nuclei and heating in an oil bath. The membrane layer prepared by this method is dense, and compared with the traditional heating method, it greatly shortens the membrane synthesis time while ensuring the separation performance of the membrane. At the same time, the structure directing agent is removed in an ozone atmosphere, which effectively avoids the generation of crystal defects during the demolding process. The SSZ-13 molecular sieve membrane prepared by this method has good separation performance for CO2 / CH4 and N2 / CH4 mixed gases, and can be used for natural gas purification.

[0007] It can be found that the addition of seed crystals is beneficial to the synthesis of high-silicon SSZ-13 molecular sieve, but the additional aluminum component introduced by the seed crystals and the insufficient induced nucleation activity of the seed crystals in the high-silicon crystallized gel are the main reasons why this method is difficult to obtain SSZ-13 molecular sieves with a higher silicon-aluminum ratio.

[0008] Therefore, providing a new type of high-silicon CHA structure molecular sieve and its preparation method and application has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0009] In order to solve the above-mentioned shortcomings and deficiencies, an object of the present invention is to provide a high-silicon CHA structure molecular sieve.

[0010] Another object of the present invention is to provide a method for preparing the above-mentioned high-silicon CHA structure molecular sieve.

[0011] Another object of the present invention is to provide the use of the high-silicon CHA structure molecular sieve as an adsorbent or catalyst carrier.

[0012] In order to achieve the above objectives, on the one hand, the present invention provides a high-silicon CHA structure molecular sieve, wherein the high-silicon CHA structure molecular sieve is prepared by first mixing a silicon source, an alkali source, a template, a seed crystal, and water to obtain a crystallized gel, and then crystallizing the crystallized gel under hydrothermal conditions, followed by washing, filtering, drying, and calcining in sequence;

[0013] Among them, the silicon source is calculated as SiO2, the alkali source is calculated as M2O, and the template agent is calculated as the cation R + The molar ratio of each component in the crystallized gel is: M2O / SiO2=0.03-0.15, R + / SiO2=0.05-0.20, H2O / SiO2=15-120, wherein M is an alkali metal;

[0014] Seed dry basis mass / silicon source dry basis mass = 0.01-0.25;

[0015] The seed crystal is obtained by subjecting a molecular sieve precursor having a CHA structure to hydrothermal treatment and acid washing.

[0016] As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, wherein the molecular sieve precursor with a CHA structure is a SSZ-13 molecular sieve or a high-silicon CHA structure molecular sieve, which can be a natural mineral, a homemade or commercially available product, or a silicate or contain other metal elements. For example, when the molecular sieve precursor with a CHA structure is a high-silicon CHA structure molecular sieve, the high-silicon CHA structure molecular sieve can be a high-silicon CHA structure molecular sieve provided / prepared by the present invention, that is, the high-silicon CHA structure molecular sieve provided / prepared by the present invention can be reused as a molecular sieve precursor with a CHA structure, and after hydrothermal treatment and acid washing, it can be used as a seed for preparing a high-silicon CHA structure molecular sieve. In addition, the SSZ-13 molecular sieve or the high-silicon CHA structure molecular sieve can be an H-type molecular sieve or a Na-type molecular sieve, etc. If it is an H-type molecular sieve, it does not contain other metal cations, and if it is a Na-type molecular sieve, it contains Na + ions, and possibly K + , Ca + wait.

[0017] As an embodiment of the high-silicon CHA structure molecular sieve described above, the SiO2 / Al2O3 molar ratio of the molecular sieve precursor with the CHA structure is greater than or equal to 30, and the grain size is 50nm-1.5μm.

[0018] In the present invention, the temperature, water vapor content, time, etc. of the hydrothermal treatment depend on the silicon-aluminum ratio and grain size of the molecular sieve precursor with a CHA structure. As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, the conditions of the hydrothermal treatment include: temperature 600-1200°C, water vapor content 5-100v%, time 0.5-24h, preferably 0.5-15h, more preferably 0.5-10h. The water vapor content is calculated based on the total volume of water vapor and other gases (such as nitrogen or air, etc.) entering the hydrothermal aging device used for the hydrothermal treatment.

[0019] In the present invention, the pH value, temperature, time, etc. of the pickling treatment depend on the silicon-aluminum ratio of the molecular sieve precursor with a CHA structure and the target silicon-aluminum ratio of the seed crystal. As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, the conditions of the pickling treatment include: a pH value of 1.0-6.0 of the acidic aqueous solution, a temperature of 20-90°C, a time of 0.5-24h, preferably 0.5-12h, and more preferably 0.5-5h. In addition, since the silicon-aluminum ratio of the seed crystal directly affects the silicon-aluminum ratio of the final product, and the silicon-aluminum ratio of the seed crystal is related to the silicon-aluminum ratio of the molecular sieve precursor with a CHA structure. Therefore, in order to achieve the required silicon-aluminum ratio, in some embodiments of the present invention, the number of pickling treatments can be 1 time or more.

[0020] As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, the acidic aqueous solution used in the acid washing treatment includes an inorganic acid and / or an organic acid.

[0021] As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, the acidic aqueous solution includes one or a combination of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, hydrofluoric acid, hydrocyanic acid, carbonic acid, formic acid, acetic acid, citric acid, oxalic acid, tartaric acid, ascorbic acid, malic acid and salicylic acid.

[0022] As an embodiment of the high silicon CHA structure molecular sieve described above in the present invention, the template includes at least one of a compound containing N,N,N-trimethyl-1-adamantyl ammonium ion or a compound containing tetraethyl ammonium ion. The present invention does not make specific requirements on the anions in the template (organic ammonium salt as shown above), and can be reasonably selected according to the actual needs of the on-site operation. In some embodiments of the present invention, the anions in the template can be, for example, halogen anions, sulfate anions, hydroxides, etc.

[0023] As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, the template includes at least one of N,N,N-trimethyl-1-adamantyl ammonium hydroxide, N,N,N-trimethyl-1-adamantyl ammonium bromide, N,N,N-trimethyl-1-adamantyl ammonium iodide, tetraethylammonium hydroxide, tetraethylammonium bromide and tetraethylammonium chloride.

[0024] As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, the silicon source includes at least one of coarse-pore silica gel, silica sol, white carbon black, water glass and the like.

[0025] As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, the alkali source includes at least one of sodium hydroxide, potassium hydroxide and the like.

[0026] As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, the crystallization temperature is 150-185° C., and the crystallization time is 12-120 h, preferably 12-96 h.

[0027] As an embodiment of the high silicon CHA structure molecular sieve described above, the calcination temperature is 500-650°C. The calcination time can be reasonably adjusted according to the actual operation needs on site, as long as the target high silicon CHA structure molecular sieve finished product can be obtained. For example, in some embodiments of the present invention, the calcination time can be 1-100h, preferably 1-10h.

[0028] As an embodiment of the high-silicon CHA structure molecular sieve described above in the present invention, the silicon-to-aluminum ratio of the high-silicon CHA structure molecular sieve can be adjusted from 200 to pure silicon.

[0029] On the other hand, the present invention also provides a method for preparing the high-silicon CHA structure molecular sieve described above, wherein the preparation method comprises:

[0030] Step 1: subjecting a molecular sieve precursor having a CHA structure to a hydrothermal treatment and an acid washing treatment in sequence, and then filtering, washing, drying and calcining the product obtained after the acid washing treatment in sequence to obtain a seed crystal;

[0031] Step 2: Mixing a silicon source, an alkali source, a template, a seed crystal, and water to obtain a crystallized gel;

[0032] Step 3: crystallizing the crystallized gel under hydrothermal conditions, and then washing, filtering, drying and calcining the crystallized product in sequence to obtain the high-silicon CHA structure molecular sieve.

[0033] The preparation method of the high-silicon CHA structure molecular sieve provided by the present invention adopts a cheap silicon source, and can synthesize the high-silicon CHA structure molecular sieve which is difficult to obtain by conventional synthesis methods in one step under the induction of a small amount of seed crystals and a template agent.

[0034] The present invention does not make specific requirements on the filtering, washing, drying and roasting performed in the process of preparing the seed crystals in step 1 and the washing, filtering, drying, etc. performed in the process of preparing the high-silicon CHA structure molecular sieve in step 3. The operating steps involved and the process parameters used can be reasonably adjusted according to actual operation needs.

[0035] In another aspect, the present invention also provides the use of the high-silicon CHA structure molecular sieve as an adsorbent or catalyst carrier.

[0036] Compared with the prior art, the beneficial technical effects that can be achieved by the present invention include:

[0037] (1) The present invention firstly performs a hydrothermal treatment on a molecular sieve precursor having a CHA structure. Under a high temperature and water vapor environment, the molecular sieve precursor having a CHA structure begins to gradually undergo a dealumination reaction and a crystal structure collapse. The microcrystalline crystal structure can be retained by controlling the temperature and the water vapor content. The precursor after the hydrothermal treatment is then subjected to an acid wash treatment to wash off the aluminum component separated from the crystal framework, thereby obtaining a high-activity, high-silicon microcrystalline CHA structure seed. Under the joint induction of the seed and the template, a high-silicon CHA structure molecular sieve can be directly synthesized without additionally introducing an aluminum source, and even a CHA structure molecular sieve close to pure silicon can be synthesized, that is, the silicon-to-aluminum ratio of the product can be regulated from 200 to pure silicon, and the silicon-to-aluminum ratio (oxide molar ratio) has a wide range and a high upper limit. At the same time, the synthesized high-silicon CHA structure molecular sieve has a very high degree of crystallinity and has a very broad application prospect in the fields of small molecule VOCs adsorption in water-containing atmospheres and as an inactive porous carrier.

[0038] (2) Since the seed crystals used in the present invention have high activity, the amount of organic template used can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 This is the XRD spectrum of the molecular sieve precursor with CHA structure used in the embodiment of the present invention.

[0041] Figure 2 This is a SEM image of the molecular sieve precursor with a CHA structure used in the examples of the present invention.

[0042] Figure 3 This is the XRD spectrum of the high-silicon CHA structure molecular sieve prepared in Example 1 of the present invention.

[0043] Figure 4 This is a SEM image of the high-silicon CHA structure molecular sieve prepared in Example 1 of the present invention.

[0044] Figure 5 This is the XRD spectrum of the high-silicon CHA structure molecular sieve prepared in Example 2 of the present invention.

[0045] Figure 6 This is a SEM image of the high-silicon CHA structure molecular sieve prepared in Example 2 of the present invention.

[0046] Figure 7This is the XRD spectrum of the high-silicon CHA structure molecular sieve prepared in Example 3 of the present invention.

[0047] Figure 8 This is a SEM image of the high-silicon CHA structure molecular sieve prepared in Example 3 of the present invention.

[0048] Fig. 9 This is the XRD spectrum of the high-silicon CHA structure molecular sieve prepared in Example 4 of the present invention.

[0049] Fig.10 This is a SEM image of the high-silicon CHA structure molecular sieve prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0050] It should be noted that the term "comprises" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0051] "Scope" disclosed in the present invention is given in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, for a specific parameter, a range of 60-120 and 80-110 is listed, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​listed are 3, 4 and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0052] In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in the present invention, and "0-5" is just an abbreviation of these numerical combinations.

[0053] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0054] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0055] In the present invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0056] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the attached table, drawings and examples. The following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0057] The raw materials used in the examples include:

[0058] Silicon source: macroporous silica gel (purity 99%), silica sol (30 wt % aqueous solution), white carbon black (purity 99%).

[0059] Aluminum source: sodium aluminate (Al2O3 content 41wt%).

[0060] Template: N,N,N-trimethyl-1-adamantyl ammonium hydroxide (25wt% aqueous solution), N,N,N-trimethyl-1-adamantyl ammonium bromide (purity 99%), N,N,N-trimethyl-1-adamantyl ammonium iodide (purity 99%), tetraethylammonium hydroxide (35wt% aqueous solution), tetraethylammonium bromide (purity 99%).

[0061] Alkali source: sodium hydroxide (purity 99%), potassium hydroxide (purity 99%).

[0062] Seed 1-3: Molecular sieve precursor with CHA structure, which can be prepared by the following method:

[0063] The silica sol, sodium aluminate, sodium hydroxide, N,N,N-trimethyl-1-adamantyl ammonium hydroxide and deionized water were fully mixed, and the molar ratio of the mixed materials (silicon source is calculated as SiO2, aluminum source is calculated as Al2O3, alkali source is calculated as M2O, template agent is calculated as cationic R + =SiO2 / Al2O3=40, M2O / SiO2=0.05, R + / SiO2=0.1, H2O / SiO2=24, crystallization reaction was carried out under hydrothermal conditions, the conditions of crystallization reaction were: 170℃, time 48h; the crystallized product was filtered, washed, dried, and calcined at 550℃ for 4h to obtain a molecular sieve precursor (SSZ-13 molecular sieve) with CHA structure, and its XRD spectrum and SEM picture are shown in Fig. Figure 1 and Figure 2 As shown, from Figure 1 It can be seen from the figure that the product has typical CHA structural characteristic peaks. Figure 2 It can be seen that the product is cubic crystals; in addition, the silicon-aluminum ratio of the product is 35.7, and the grain size is 0.8-1.2μm; the precursor is hydrothermally treated at a temperature of 600℃ and a water vapor content of 20v% for 0.5h, and then pickled in an oxalic acid solution at pH=4.5 and a temperature of 60℃ for 1h. The product after pickling is filtered, washed, dried, and calcined at 550℃ for 4h to obtain seed crystal 1, and the silicon-aluminum ratio of seed crystal 1 is 43.1, which is set aside.

[0064] The precursor prepared above was hydrothermally treated at a temperature of 650°C and a water vapor content of 30v% for 1h, and then pickled in a citric acid solution at pH = 5.5 and a temperature of 30°C for 1h. The product obtained after the pickling treatment was filtered, washed, dried, and calcined at 550°C for 4h to obtain seed crystal 2. The silicon-aluminum ratio of seed crystal 2 was 78.3, and it was kept for later use.

[0065] The precursor prepared as above was hydrothermally treated at a temperature of 700°C and a water vapor content of 50v% for 3h, and then pickled in an acetic acid solution with a pH of 3.5 and a temperature of 45°C for 2h. The product obtained after the pickling treatment was filtered, washed, dried, and calcined at 550°C for 4h to obtain seed crystal 3. The silicon-aluminum ratio of seed crystal 3 was 110.5, and it was kept for later use.

[0066] The precursor prepared as above was hydrothermally treated at a temperature of 1200°C and a water vapor content of 100v% for 0.5h, and then pickled in a hydrochloric acid solution at pH=2.0 and a temperature of 85°C for 0.5h. The product obtained after the pickling treatment was filtered, washed, dried, and calcined at 550°C for 4h to obtain seed crystal 4. The silicon-aluminum ratio of seed crystal 4 was 130.7 and was set aside.

[0067] It should be noted that the raw materials, ratios, reaction conditions, etc. used in the preparation of the molecular sieve precursor with a CHA structure of the present invention are not limited to the above process, and purchased molecular sieves can also be used as precursors to prepare seed crystals.

[0068] Others: Deionized water.

[0069] Example 1

[0070] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0071] Dissolve 1.5g of sodium hydroxide and 27g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 6.0g of seed crystal 1 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying and calcining at 550℃ for 4h, a high-silicon CHA structure molecular sieve product is obtained.

[0072] The XRD spectrum of the high silicon CHA structure molecular sieve product prepared in this example is shown in Figure 3 As shown, from Figure 3 It can be seen that the product has typical CHA structural characteristic peaks, and the SEM image is shown in Figure 4 As shown, from Figure 4 In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this embodiment is 110% (the comparative sample is a molecular sieve precursor with a CHA structure synthesized in the process of preparing seed crystal 1, the same below), and the silicon-aluminum ratio of the product is 204.8 (XRF test method, the same below).

[0073] Example 2

[0074] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0075] Dissolve 1.5g of sodium hydroxide and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 3.0g of seed crystal 1 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying and calcining at 550℃ for 4h, a high-silicon CHA structure molecular sieve product is obtained.

[0076] The XRD spectrum of the high silicon CHA structure molecular sieve product prepared in this example is shown in Figure 5As shown, from Figure 5 It can be seen that the product has typical CHA structural characteristic peaks, and the SEM image is shown in Figure 6 As shown, from Figure 6 It can be seen that the product is a cubic crystal. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this embodiment is 107%, and the silicon-aluminum ratio of the product is 378.6.

[0077] Example 3

[0078] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0079] Dissolve 1.5g of sodium hydroxide and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 4.8g of seed crystal 2 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying and calcining at 550℃ for 4h, a high-silicon CHA structure molecular sieve product is obtained.

[0080] The XRD spectrum of the high silicon CHA structure molecular sieve product prepared in this example is shown in Figure 7 As shown, from Figure 7 It can be seen that the product has typical CHA structural characteristic peaks, and the SEM image is shown in Figure 8 As shown, from Figure 8 It can be seen that the product is a cubic crystal. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this embodiment is 112%, and the silicon-aluminum ratio of the product is 383.2.

[0081] Example 4

[0082] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0083] Dissolve 1.5g of sodium hydroxide and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 2.4g of seed crystal 2 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying and calcining at 550℃ for 4h, a high-silicon CHA structure molecular sieve product is obtained.

[0084] The XRD spectrum of the high silicon CHA structure molecular sieve product prepared in this example is shown in Fig. 9 As shown, from Fig. 9It can be seen that the product has typical CHA structural characteristic peaks, and the SEM image is shown in Fig.10 As shown, from Fig.10 It can be seen that the product is a cubic crystal. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this embodiment is 103%, and the silicon-aluminum ratio of the product is 598.7.

[0085] Example 5

[0086] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0087] Dissolve 1.5g of sodium hydroxide and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 3.6g of seed crystal 3 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying and calcining at 550℃ for 4h, a high-silicon CHA structure molecular sieve product is obtained.

[0088] According to the characterization results in Examples 1 to 4, it can be reasonably expected that the high-silicon CHA structure molecular sieve product prepared in this example also has typical CHA structure characteristic peaks and is cubic crystal. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this example is 111%, and the silicon-aluminum ratio of the product is 791.2.

[0089] Example 6

[0090] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0091] Dissolve 1.5g of sodium hydroxide and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 1.8g of seed crystal 3 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying and calcining at 550℃ for 4h, a high-silicon CHA structure molecular sieve product is obtained.

[0092] According to the characterization results in Examples 1 to 4, it can be reasonably expected that the high-silicon CHA structure molecular sieve product prepared in this example also has typical CHA structure characteristic peaks and is cubic crystals. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this example is 95%, and the silicon-aluminum ratio of the product is 1356.0.

[0093] Example 7

[0094] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0095] The high-silicon CHA structure molecular sieve product obtained in Example 1 was hydrothermally treated at a temperature of 750°C and a water vapor content of 50v% for 5h, and then pickled in an oxalic acid solution at pH = 5.0 and a temperature of 70°C for 3h. The pickled product was filtered, washed, dried, and calcined at 550°C for 4h to obtain seed crystal 5. The silicon-aluminum ratio of seed crystal 5 was 257.9, which was set aside.

[0096] Dissolve 1.5g of sodium hydroxide and 42.2g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 4.8g of seed crystal 5 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170°C for 48h. After filtering, washing, drying and calcining the product, a high-silicon CHA structure molecular sieve product is obtained.

[0097] According to the characterization results in Examples 1 to 4, it can be reasonably expected that the high-silicon CHA structure molecular sieve product prepared in this example also has typical CHA structure characteristic peaks and is cubic crystals. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this example is 126%, and the silicon-aluminum ratio of the product is 1084.6.

[0098] Example 8

[0099] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0100] The high-silicon CHA structure molecular sieve product obtained in Example 3 was hydrothermally treated at a temperature of 750°C and a water vapor content of 50v% for 5h, and then pickled in an oxalic acid solution at pH = 5.0 and a temperature of 70°C for 3h. The product obtained after pickling was filtered, washed, dried, and calcined at 550°C for 4h to obtain seed crystal 6. The silicon-aluminum ratio of seed crystal 6 was 420.6, which was kept for later use.

[0101] Dissolve 1.65g of sodium hydroxide and 50.6g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 4.8g of seed crystal 6 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 173°C for 48h. After filtering, washing, drying and calcining the product, a high-silicon CHA structure molecular sieve product is obtained.

[0102] According to the characterization results in Examples 1 to 4, it can be reasonably expected that the high-silicon CHA structure molecular sieve product prepared in this example also has typical CHA structure characteristic peaks and is cubic crystals. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this example is 113%, and the silicon-aluminum ratio of the product is 1784.6.

[0103] Example 9

[0104] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0105] The high-silicon CHA structure molecular sieve product obtained in Example 5 was hydrothermally treated at a temperature of 800°C and a water vapor content of 70v% for 10 hours, and then pickled in an oxalic acid solution at pH = 5.0 and a temperature of 70°C for 3 hours. The product after pickling was filtered, washed, dried, and calcined at 550°C for 4 hours to obtain seed crystal 7. The silicon-aluminum ratio of seed crystal 7 was 810.9, which was set aside.

[0106] Dissolve 1.85g of sodium hydroxide and 67.5g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 4.8g of seed crystal 7 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 175℃ for 48h. After filtering, washing, drying and calcining at 550℃ for 4h, a high-silicon CHA structure molecular sieve product is obtained.

[0107] According to the characterization results in Examples 1 to 4, it can be reasonably expected that the high-silicon CHA structure molecular sieve product prepared in this example also has typical CHA structure characteristic peaks and is in the form of cubic crystals. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this example is 99%, and the silicon-aluminum ratio of the product is positive infinity (no aluminum content is detected).

[0108] Example 10

[0109] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0110] 1.5g of sodium hydroxide, 3g of N,N,N-trimethyl-1-adamantyl ammonium bromide (molecular weight 274) and 7.9g of tetraethylammonium hydroxide (molecular weight 147.258) were added to 106g of water and stirred until the solution was clear. 80g of silica sol was slowly added under continuous stirring and stirred for more than 1h. 2.4g of seed crystal 2 was added under continuous stirring and stirred for 3h to obtain a crystallized gel. The crystallized gel was transferred to a high-pressure reactor and crystallized at 170°C for 48h. After the product was filtered, washed, dried and calcined at 550°C for 4h, a high-silicon CHA structure molecular sieve product was obtained.

[0111] According to the characterization results in Examples 1 to 4, it can be reasonably expected that the high-silicon CHA structure molecular sieve product prepared in this example also has typical CHA structure characteristic peaks and is cubic crystal. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this example is 97%, and the silicon-aluminum ratio of the product is 397.1.

[0112] Embodiment 11

[0113] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0114] Dissolve 2.1g potassium hydroxide, 3.2g N,N,N-trimethyl-1-adamantyl ammonium iodide (molecular weight 321) and 3g tetraethylammonium bromide (molecular weight 210.155) in 112g water and stir until the solution is clear. Slowly add 80g silica sol under continuous stirring and stir for more than 1h. Add 2.4g seed 2 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170°C for 48h. After filtering, washing, drying and calcining at 600°C for 3h, a high-silicon CHA structure molecular sieve product is obtained.

[0115] According to the characterization results in Examples 1 to 4, it can be reasonably expected that the high-silicon CHA structure molecular sieve product prepared in this example also has typical CHA structure characteristic peaks and is cubic crystal. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this example is 93%, and the silicon-aluminum ratio of the product is 412.4.

[0116] Example 12

[0117] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0118] Dissolve 1.5g of sodium hydroxide and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 146g of water and stir until the solution is clear. Slowly add 24g of coarse-pore silica gel under continuous stirring and stir for more than 1h. Add 6.0g of seed crystal 4 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 150°C for 96h. After filtering, washing, drying and calcining at 500°C for 10h, a high-silicon CHA structure molecular sieve product is obtained.

[0119] According to the characterization results in Examples 1 to 4, it can be reasonably expected that the high-silicon CHA structure molecular sieve product prepared in this example also has typical CHA structure characteristic peaks and is cubic crystal. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this example is 88%, and the silicon-aluminum ratio of the product is 435.2.

[0120] Example 13

[0121] This embodiment provides a high-silicon CHA structure molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0122] Dissolve 1.5g of sodium hydroxide and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 146g of water and stir until the solution is clear. Slowly add 24g of white carbon black under continuous stirring and stir for more than 1h. Add 6.0g of seed crystal 4 under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 185℃ for 15h. After filtering, washing, drying and calcining at 650℃ for 2h, a high-silicon CHA structure molecular sieve product is obtained.

[0123] According to the characterization results in Examples 1 to 4, it can be reasonably expected that the high-silicon CHA structure molecular sieve product prepared in this example also has typical CHA structure characteristic peaks and is cubic crystal. In addition, the relative crystallinity of the high-silicon CHA structure molecular sieve product prepared in this example is 109%, and the silicon-aluminum ratio of the product is 411.9.

[0124] Comparative Example 1

[0125] This comparative example provides a molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0126] Dissolve 1.4g of sodium hydroxide, 0.5g of sodium aluminate (the effective content of alumina in sodium aluminate is 41%), and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying, and calcining at 550℃ for 4h, the molecular sieve product is obtained.

[0127] The molecular sieve product obtained in this comparative example has a relative crystallinity of 15%, and contains a large amount of amorphous products.

[0128] Comparative Example 2

[0129] This comparative example provides a molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0130] Dissolve 1.5g of sodium hydroxide, 0.25g of sodium aluminate (the effective content of alumina in sodium aluminate is 41%), and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying, and calcining at 550℃ for 4h, the molecular sieve product is obtained.

[0131] The relative crystallinity of the products obtained in this comparative example is 0%, and they are all amorphous products.

[0132] Comparative Example 3

[0133] This comparative example provides a molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0134] Dissolve 1.4g of sodium hydroxide, 0.5g of sodium aluminate (the effective content of alumina in sodium aluminate is 41%), and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 2.4g of the molecular sieve precursor with CHA structure obtained when preparing seed crystal 1 as a seed crystal under continuous stirring, stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170°C for 48h. After filtering, washing, drying, and calcining at 550°C for 4h, the molecular sieve product is obtained.

[0135] The relative crystallinity of the molecular sieve product obtained in this comparative example is 98%, and the silicon-aluminum ratio of the product is 173.2. It can be found that when the silicon-aluminum ratio of the feed is 200, the molecular sieve precursor also has a strong structural induction effect.

[0136] Comparative Example 4

[0137] This comparative example provides a molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0138] Dissolve 1.5g of sodium hydroxide and 33.76g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 2.4g of the molecular sieve precursor with CHA structure obtained when preparing seed crystal 1 as a seed crystal under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170°C for 48h. After filtering, washing, drying and calcining at 550°C for 4h, the molecular sieve product is obtained.

[0139] The relative crystallinity of the molecular sieve product obtained in this comparative example is 22%, and the product contains a large amount of sodium hydroxydimethoxysilane impurity crystals. Compared with Example 4, it can be shown that the untreated molecular sieve precursor has insufficient structural effect in the high-silicon crystallized gel, and the seed treated by the method of the present invention shows a strong structural induction effect, which can well solve the synthesis problem of ultra-high silicon and pure silicon CHA structure molecular sieves.

[0140] Comparative Example 5

[0141] This comparative example provides a molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0142] The molecular sieve precursor with CHA structure obtained when preparing seed crystal 1 was pickled in an oxalic acid solution with pH = 4.5 and temperature of 60°C for 1 hour. The pickled product was filtered, washed, dried, and calcined at 550°C for 4 hours to obtain pickled seed crystals. The silicon-aluminum ratio of the pickled seed crystals was 37.9.

[0143] Dissolve 1.5g of sodium hydroxide and 27g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 6.0g of acid-washed seed crystals under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying and calcining at 550℃ for 4h, the molecular sieve product is obtained.

[0144] The relative crystallinity of the molecular sieve product obtained in this comparative example is 37% (including amorphous products). Compared with Example 1, it is explained that the molecular sieve precursor with CHA structure is directly pickled without hydrothermal treatment. Although the aluminum center on the surface of the molecular sieve precursor can be eluted, the improvement of the silicon-aluminum ratio of the seed crystal is not obvious. In addition, without hydrothermal treatment, the structural collapse of the micron-sized precursor cannot be achieved to obtain microcrystalline seeds. The structural induction effect of larger molecular sieves is weak. It is difficult to obtain a high-crystallinity product when applied to the synthesis process of high-silicon CHA structure molecular sieves.

[0145] Comparative Example 6

[0146] This comparative example provides a molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0147] The molecular sieve precursor with CHA structure obtained when preparing seed crystal 1 was alkali-washed in a sodium hydroxide solution with a pH of 13.5 and a temperature of 60°C for 1 hour. The product after alkali washing was filtered, washed, dried, and calcined at 550°C for 4 hours to obtain alkali-washed seed crystals. The silicon-aluminum ratio of the alkali-washed seed crystals was 29.2, and the mass of the treated seed crystals was 73% of the precursor.

[0148] Dissolve 1.5g of sodium hydroxide and 27g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide in 90g of water and stir until the solution is clear. Slowly add 80g of silica sol under continuous stirring and stir for more than 1h. Add 6.0g of alkali-washed seed crystals under continuous stirring and stir for 3h to obtain a crystallized gel. Transfer the crystallized gel to a high-pressure reactor and crystallize at 170℃ for 48h. After filtering, washing, drying and calcining at 550℃ for 4h, the molecular sieve product is obtained.

[0149] The relative crystallinity of the molecular sieve product obtained in this comparative example is 53% (including amorphous products). Compared with Example 1, it is shown that alkali washing is beneficial for further reducing the seed size to improve the structure induction performance, and the silicon aluminum content of the seed after alkali washing is reduced compared with the precursor, which is equivalent to an increase in the aluminum content in the crystallization system, and the difficulty of crystallization is also reduced to a certain extent. Therefore, the relative crystallinity of the product is improved compared with Comparative Examples 4 and 5. However, this is not conducive to the synthesis of high-silicon products, and alkali washing will elute the silicon center on the surface of the precursor, resulting in a large mass loss, and the atomic economy is poor.

[0150] The raw material information involved in Examples 1 to 13 of the present invention and Comparative Examples 1 to 6 and the parameter information of the obtained products are shown in Table 1 below.

[0151] Table 1

[0152]

[0153]

[0154] It can be seen from Table 1 above that the silicon-to-aluminum ratio of the high-silicon CHA structure molecular sieves prepared in Examples 1 to 13 of the present invention can be regulated from 200 to pure silicon, and the relative crystallinity of these high-silicon CHA structure molecular sieves is also relatively high, all above 88%.

[0155] In Comparative Example 1, the feed silicon-aluminum ratio is 200, the relative crystallinity of the molecular sieve product is 15%, and it contains a large amount of amorphous products. In Comparative Example 2, the feed silicon-aluminum ratio is increased to 400, and the relative crystallinity of the obtained product is 0%, both of which are amorphous products. This indicates that as the feed silicon-aluminum ratio in the crystallized gel exceeds 200, it is difficult to synthesize the SSZ-13 molecular sieve product using only an organic template.

[0156] In Comparative Example 3, a molecular sieve precursor having a CHA structure was added as a seed crystal when preparing the molecular sieve, and the relative crystallinity of the obtained molecular sieve product was 98%, and the silicon-aluminum ratio of the product was 173.2. It can be found that when the silicon-aluminum ratio of the feed is 200, the molecular sieve precursor having a CHA structure also has a strong structural induction effect, but the silicon-aluminum ratio of the obtained molecular sieve product is relatively low, only 173.2.

[0157] In Comparative Example 4, ordinary SSZ-13 molecular sieve was added as a seed crystal when preparing the molecular sieve, and the relative crystallinity of the obtained molecular sieve product was 22%, and the product contained a large amount of sodium hyaluronate impurity crystals. Compared with Example 4, it can be explained that the untreated molecular sieve precursor, i.e., ordinary SSZ-13 molecular sieve and organic template agent, have insufficient structural guidance effect in high silicon crystallization gel, especially in the nucleation stage, resulting in excessively high silicon-aluminum ratio gel in high temperature and alkaline environment, preferentially generating impurity crystals such as sodium hyaluronate, while the seed crystal treated by the method of the present invention exhibits a very strong structural induction effect, which can well solve the synthesis problem of ultra-high silicon and pure silicon CHA structure molecular sieve.

[0158] In Comparative Example 5, pickling seed crystals were added during the preparation of the molecular sieve, and the relative crystallinity of the obtained molecular sieve product was 37% (including amorphous products). Compared with Example 1, it is shown that the molecular sieve precursor with a CHA structure is directly pickled without hydrothermal treatment. Although the aluminum center on the surface of the molecular sieve precursor can be eluted, the improvement of the seed silicon-aluminum ratio of the precursor is not obvious. In addition, without hydrothermal treatment, the structural collapse of the micron-sized precursor cannot be achieved to obtain microcrystalline seed crystals. The structural induction effect of larger molecular sieves is weak, and it is difficult to obtain a high-crystallinity product when applied to the synthesis process of high-silicon CHA structure molecular sieves.

[0159] In Comparative Example 6, alkali-washed seed crystals were added during the preparation of the molecular sieve, and the relative crystallinity of the obtained molecular sieve product was 53% (including amorphous products). Compared with Example 1, it is shown that alkali washing is beneficial for further reducing the seed size to improve the structural induction performance, and the silicon-aluminum ratio of the seed crystals after alkali washing is reduced compared with the precursor, which is equivalent to an increase in the aluminum content in the crystallization system, and the difficulty of crystallization is also reduced to a certain extent. Therefore, the relative crystallinity of the product is improved compared with Comparative Examples 4 and 5. However, this is not conducive to the synthesis of high-silicon products, and alkali washing will elute the silicon center on the surface of the precursor, resulting in a large mass loss, and the atomic economy is poor.

[0160] In summary, compared with the prior art, the embodiments of the present invention can achieve the following beneficial technical effects:

[0161] (1) In the embodiment of the present invention, a molecular sieve precursor having a CHA structure is first subjected to a hydrothermal treatment. Under a high temperature and water vapor environment, the molecular sieve precursor having a CHA structure begins to gradually undergo a dealumination reaction and a crystal structure collapse. The microcrystalline crystal structure can be retained by controlling the temperature and the water vapor content. The precursor after the hydrothermal treatment is then subjected to an acid wash treatment to wash off the aluminum component that has separated from the crystal framework, thereby obtaining a highly active, high-silicon microcrystalline CHA structure seed. Under the joint induction of the seed and the template, a high-silicon CHA structure molecular sieve can be directly synthesized without additionally introducing an aluminum source, and even a CHA structure molecular sieve close to pure silicon can be synthesized, that is, the silicon-to-aluminum ratio of the product can be regulated from 200 to pure silicon, and the silicon-to-aluminum ratio (oxide molar ratio) has a wide range and a high upper limit. At the same time, the synthesized high-silicon CHA structure molecular sieve has a very high degree of crystallinity and has a very broad application prospect in the fields of small molecule VOCs adsorption in aqueous atmospheres and as an inactive porous carrier.

[0162] (2) Since the seed crystals used in the embodiments of the present invention have high activity, the amount of organic template used can be reduced.

[0163] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the protection scope of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other and with each other, and with each other.

Claims

1. A high-silicon CHA structure molecular sieve, characterized in that: The high-silicon CHA structure molecular sieve is prepared by first mixing a silicon source, an alkali source, a template agent, a seed crystal, and water to obtain a crystallized gel, then crystallizing the crystallized gel under hydrothermal conditions, and then washing, filtering, drying, and calcining in sequence; Among them, the silicon source is calculated as SiO2, the alkali source is calculated as M2O, and the template agent is calculated as the cation R + The molar ratio of each component in the crystallized gel is: M2O / SiO2=0.03-0.15, R + / SiO2=0.05-0.20, H2O / SiO2=15-120, wherein M is an alkali metal; Seed dry basis mass / silicon source dry basis mass = 0.01-0.25; The seed crystal is obtained by subjecting a molecular sieve precursor having a CHA structure to hydrothermal treatment and acid washing.

2. The high-silicon CHA structure molecular sieve according to claim 1, characterized in that: The molecular sieve precursor with a CHA structure is a SSZ-13 molecular sieve or a high-silicon CHA structure molecular sieve.

3. The high-silicon CHA structure molecular sieve according to claim 1 or 2, characterized in that: The SiO2 / Al2O3 molar ratio of the molecular sieve precursor with CHA structure is greater than or equal to 30, and the grain size is 50nm-1.5μm.

4. The high-silicon CHA structure molecular sieve according to any one of claims 1 to 3, characterized in that: The conditions of the hydrothermal treatment include: temperature 600-1200° C., water vapor content 5-100 v%, and time 0.5-24 h.

5. The high-silicon CHA structure molecular sieve according to any one of claims 1 to 3, characterized in that: The conditions of the pickling treatment include: pH value of the acidic aqueous solution is 1.0-6.0, temperature is 20-90° C., and time is 0.5-24 hours.

6. The high-silicon CHA structure molecular sieve according to claim 5, characterized in that: The acidic aqueous solution used in the pickling treatment includes an inorganic acid and / or an organic acid.

7. The high-silicon CHA structure molecular sieve according to claim 6, characterized in that: The acidic aqueous solution includes one or a combination of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, hydrofluoric acid, hydrocyanic acid, carbonic acid, formic acid, acetic acid, citric acid, oxalic acid, tartaric acid, ascorbic acid, malic acid and salicylic acid.

8. The high-silicon CHA structure molecular sieve according to claim 1, characterized in that: The template agent includes at least one of a compound containing N,N,N-trimethyl-1-adamantyl ammonium ion or a compound containing tetraethyl ammonium ion.

9. The high-silicon CHA structure molecular sieve according to claim 8, characterized in that: The template agent includes at least one of N,N,N-trimethyl-1-adamantyl ammonium hydroxide, N,N,N-trimethyl-1-adamantyl ammonium bromide, N,N,N-trimethyl-1-adamantyl ammonium iodide, tetraethylammonium hydroxide, tetraethylammonium bromide and tetraethylammonium chloride.

10. The high-silicon CHA structure molecular sieve according to claim 1, characterized in that: The silicon source includes at least one of macroporous silica gel, silica sol, white carbon black and water glass.

11. The high-silicon CHA structure molecular sieve according to claim 1, characterized in that: The alkali source includes at least one of sodium hydroxide and potassium hydroxide.

12. The high-silicon CHA structure molecular sieve according to claim 1, characterized in that: The crystallization temperature is 150-185° C. and the crystallization time is 12-120 hours.

13. The high-silicon CHA structure molecular sieve according to claim 1 or 12, characterized in that: The calcination temperature is 500-650°C.

14. The method for preparing a high-silicon CHA structure molecular sieve according to any one of claims 1 to 13, characterized in that: The preparation method comprises: Step 1: subjecting a molecular sieve precursor having a CHA structure to a hydrothermal treatment and an acid washing treatment in sequence, and then filtering, washing, drying and calcining the product obtained after the acid washing treatment in sequence to obtain a seed crystal; Step 2: Mixing a silicon source, an alkali source, a template, a seed crystal, and water to obtain a crystallized gel; Step 3: crystallizing the crystallized gel under hydrothermal conditions, and then washing, filtering, drying and calcining the crystallized product in sequence to obtain the high-silicon CHA structure molecular sieve.

15. Use of the high-silicon CHA structure molecular sieve according to any one of claims 1 to 13 as an adsorbent or catalyst carrier.

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