A low-cost, high-silicon, hierarchically porous loess-based SSZ-13 molecular sieve and its preparation method and application

Abstract

The present invention provides a low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve and its preparation method and application. Specifically, the process includes: using loess as raw material, after activation treatment, only adding a silicon source, a template agent, and water for preparation; after aging, crystallization, and ion exchange, calcining to obtain a multi-level porous high-silicon molecular sieve SSZ-13 with coexisting micropores and mesopores; the prepared high-silicon multi-level porous molecular sieve SSZ-13 has a spindle-aggregated honeycomb structure and a specific surface area of ​​425.3 to 486.19 m 2 / g, pore size distribution range is 0.4925~51.4956nm, pore volume distribution range is 0.0833~0.1810cm 3 / g, with an average particle size of 4.814 to 5.589 μm. The microstructure of the loess-based molecular sieve SSZ-13 obtained by the present invention has a multi-level pore structure with micropores and mesopores. Using it as a catalyst can significantly improve the effect of the methanol to olefins reaction, especially improve the selectivity of propylene. In addition, the loess-based molecular sieve SSZ-13 itself has a high silicon-aluminum ratio and contains a small amount of Fe 3+ ions, and their composition can also greatly improve the anti-carbon deposition performance and catalytic activity of molecular sieve SSZ-13 in methanol to propylene.

Description

Technical Field

[0001] The invention belongs to the technical field of loess-based molecular sieve synthesis, and particularly relates to a high-silicon multi-level pore loess-based SSZ-13 molecular sieve and a preparation method and application thereof. Background Art

[0002] Molecular sieve, also known as zeolite, is a porous crystalline material of aluminosilicate or aluminophosphate with an inorganic skeleton. The general chemical formula is (M′2M)O·Al2O3·xSiO2·yH2O, where M′ and M are monovalent or divalent cations, such as K + 、Na + and Ca 2+ 、Ba 2+ Due to its unique internal pore structure, molecular sieves have excellent catalytic, ion exchange, selective adsorption, anti-fouling and other properties, and are widely used in industrial processes such as adsorption separation, washing, catalysis and high-tech materials.

[0003] Molecular sieve SSZ-13 is an important industrial catalyst. It is a microporous rhombohedral zeolite with a cubic structure. Its synthesis methods primarily include hydrothermal, solid-phase grinding, dry gel transformation, crystallization, and ultrasound, microwave, or seed-assisted synthesis. Currently, the hydrothermal method is still the most widely used for the synthesis of molecular sieve SSZ-13. It uses N,N,N-trimethyl-1-adamantanammonium hydroxide as a template and a silicon and aluminum source as a chemical framework. However, the expensive template and cost of SSZ-13 have limited its use. Furthermore, when used in methanol-to-olefins or propylene reactions, molecular sieve SSZ-13 exhibits disadvantages such as poor carbon deposition resistance and low propylene selectivity, limiting its industrial application.

[0004] Prior research on molecular sieve SSZ-13 includes: Patent 201910955427.X, which discloses a method for preparing an olefin catalyst. This method uses a chemical reagent method to synthesize molecular sieve SSZ-13. Its catalytic performance in the methanol-to-olefins reaction was evaluated using a fixed bed. The results showed that the mass selectivity of ethylene and propylene in the cracked gas was only approximately 35% and 46% respectively. Moreover, its high specific surface area resulted in poor resistance to carbon deposition. Furthermore, this method uses a chemical reagent method to synthesize molecular sieve SSZ-13, which is costly, and the gas selectivity of ethylene and propylene in the catalytic reaction is not very high. Patent 201710161214.0 discloses a multi-level pore SSZ-13 molecular sieve catalyst, its synthesis method, and applications. This method uses long-chain silane as an auxiliary agent for the crystallization synthesis reaction, adjusts the molar ratio of alkali source, silicon source, aluminum source, template, long-chain silane and water, and adopts a segmented dynamic / static crystallization method to obtain a high-crystallinity multi-level pore SSZ-13 molecular sieve with orderly microporous-mesoporous distribution. However, this method uses a chemical reagent method to synthesize the porous molecular sieve SSZ-13, which has a high synthesis cost. At the same time, it is also necessary to add organic polymer materials as auxiliary agents, which will pollute the environment and increase the synthesis cost. 202110698018.3 discloses a method for synthesizing SSZ-13 molecular sieves using diatomaceous earth as a silicon source. Because diatomaceous earth contains Fe elements, it can be directly introduced into the SSZ-13 molecular sieve during the crystallization process, so that the molecular sieve SSZ-13 has good high-temperature catalytic activity. However, the diatomaceous earth raw material used in this method, as a mineral, has limited reserves and cannot be produced on a large scale in the northwest.

[0005] In summary, the existing methods for synthesizing molecular sieve SSZ-13 all suffer from high synthesis costs, impracticality for large-scale production, and environmental pollution. Furthermore, these issues can affect the performance of molecular sieve SSZ-13 in the methanol-to-olefins reaction, such as poor carbon deposition resistance and low ethylene and propylene yields.

[0006] Therefore, obtaining an SSZ-13 molecular sieve with excellent catalytic performance in the methanol to olefins reaction using a cheap and green synthesis method is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0007] The object of the present invention is to provide a low-cost, high-silicon, multi-level pore loess-based SSZ-13 molecular sieve. The present invention uses loess produced in Northwest China as raw material, and through purification, acidification, alkalization, and medium- and low-temperature hydrothermal crystallization processes, it can replace the chemical reagent raw material of the existing molecular sieve SSZ-13. After controlling the aging time and reaction time, and then undergoing ion exchange and calcination, a low-cost high-silicon multi-level pore molecular sieve SSZ-13 can be obtained. The scheme of the present invention only requires loess components and does not require the addition of an aluminum source. It has the advantages of simple steps, mild conditions, low cost, and environmental friendliness. The preparation method is simple and easy, and the raw material source is extensive and sufficient. It is particularly suitable for large-scale industrial production and preparation, and can truly realize the resource utilization of loess and alleviate the problems of soil erosion and ecological fragility in the Loess Plateau.

[0008] To achieve the above-mentioned object, the present invention provides a low-cost high-silicon multi-level porous loess-based SSZ-13 molecular sieve. The loess is used as raw material. After activation treatment, only a silicon source, a template and water need to be added for preparation. After aging, crystallization and ion exchange, the high-silicon multi-level porous loess-based molecular sieve SSZ-13 with coexisting micropores and mesopores is obtained by calcination. The high-silicon multi-level porous molecular sieve SSZ-13 has a spindle-aggregated honeycomb structure and a specific surface area of ​​425.3 to 486.19 m 2 / g, pore size distribution range is 0.4925~51.4956nm, pore volume distribution range is 0.0833~0.1810cm 3 / g, and the average particle size is 4.814~5.589μm.

[0009] To achieve the above object, the present invention provides a method for preparing a low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve, which specifically comprises the following steps:

[0010] S1 purification: Using loess from the northwest as raw material, purified loess is obtained through washing and drying;

[0011] S2 acidification: adding an acidifying agent to the product of the previous step to carry out an acidification reaction to obtain acidified loess;

[0012] S3 alkalization: mixing the product of the previous step with an alkalizing agent, calcining, and obtaining alkalized loess;

[0013] S4 crystallization: adding a silicon source, a template and water to the product of the previous step to make the molar ratio of the raw materials in the system be SiO2:Al2O3:template:Na2O:H2O=220:1:6:24:2060 to obtain a prepared slurry; aging the prepared slurry at room temperature, and then performing a crystallization reaction under certain conditions to obtain an unactivated loess-based SSZ-13 molecular sieve;

[0014] S5 activated loess-based SSZ-13 molecular sieve: unactivated loess-based molecular sieve SSZ-13 is mixed with NH4Cl solution to carry out ion exchange reaction, filtered, the filter cake is collected, washed and calcined to obtain active high-silicon multi-level pore loess-based molecular sieve SSZ-13.

[0015] In a preferred embodiment, in the S1 purification step, the molar ratio of silicon to aluminum in the loess is SiO2:Al2O3=(6.1-8.5):1.

[0016] In a preferred embodiment, in the S1 purification step, the water washing and drying conditions can be any method known to those skilled in the art, as long as impurities can be removed. Preferably, washing with deionized water and then filtering with a 200-mesh sieve is repeated 3-5 times, and then drying at 100-120°C for 1-5 hours.

[0017] In a preferred embodiment, in the S2 acidification step, the acidulant includes one or more of HCl, H2SO4, and HNO3; the mass concentration of the acidulant is 10-30%, preferably, the mass concentration of the acidulant is 15%-25%.

[0018] In a preferred embodiment, in the acidification step S2, the solid-liquid ratio of the acidifier to the purified loess is 1:(3-6), preferably, the solid-liquid ratio of the acidifier to the purified loess is 1:4.

[0019] In a preferred embodiment, in the acidification step S2, the acidification reaction conditions are: stirring the reaction at 70-90°C for 1-10 hours, preferably, stirring the reaction at 80-85°C for 4-8 hours.

[0020] In a preferred embodiment, in the acidification step S2, after the acidification reaction is completed, the step further includes washing with deionized water, filtering, and drying the filter residue to obtain acidified loess.

[0021] The present invention performs an acidification treatment on loess. The purpose is that loess has a relatively complex silicate structure, and its chemical composition contains impurities such as Fe2O3, CaO, MgO, and TiO2 in addition to SiO2 and Al2O3. Therefore, the acid-treated loess can remove most of the impurities such as CaO, MgO, and TiO2, thereby increasing the whiteness of the loess-based molecular sieve SSZ-13 product. To modify the molecular sieve SSZ-13, the acidification step requires controlling the acidification time and temperature to retain a portion of Fe ions in the catalyst, thereby improving the performance of the subsequent catalyst. At the same time, to prepare the high-silicon molecular sieve SSZ-13, excess Al2O3 must be dissolved with acid. Acidification not only destroys the crystal structure of the loess layer, but also removes most of the aluminum in the loess. However, since some aluminum atoms are encapsulated within the silicate crystal structure and cannot be completely dissolved, a silicon source must be added in the subsequent crystallization step to increase the silicon-to-aluminum ratio in the crystallization raw material.

[0022] In a preferred embodiment, in the alkalization step S3, the alkalizing agent is one or more of NaOH, KOH, and LiOH; preferably, the alkalizing agent is solid powdered NaOH.

[0023] In a preferred embodiment, in the alkalization step S3, the mass ratio of the alkalizer to the acidified loess is (0.5-2):1; preferably, the mass ratio of the alkalizer to the acidified loess is (1-1.5):1.

[0024] In a preferred embodiment, in the alkalization step S3, the calcination conditions are: calcination at 350-450° C. for 1-5 h; preferably, the calcination conditions are: calcination at 400° C. for 2-4 h.

[0025] In the present invention, the alkalizing agent is added for activation treatment, which can completely destroy the silicate crystal structure in the loess, so that the silicon oxide crystals are dissolved from the loess and become amorphous active silica sol.

[0026] In a preferred embodiment, in the crystallization step S4, the template is N,N,N-trimethyl-1-adamantyl ammonium hydroxide (R).

[0027] In a preferred embodiment, in the S4 crystallization step, the pH of the slurry is prepared to be 13-14.

[0028] In a preferred embodiment, in the S4 crystallization step, in order to ensure the pore size distribution (micropore-mesopore) of the multi-level pore molecular sieve SSZ-13, the aging time is 4 to 18 hours; preferably, the aging time is 6 to 12 hours.

[0029] The purpose of room temperature aging in the present invention is that aging can increase the number of crystal nuclei in the slurry system and reduce the crystallization reaction time. At the same time, by controlling the aging time within a certain time range, the loess is more likely to form a multi-level porous molecular sieve SSZ-13. However, if the aging time is too long, it is easy to form a cubic microporous molecular sieve SSZ-13, and the mesoporous molecular sieve SSZ-13 cannot be obtained. Therefore, setting the aforementioned aging time range and controlling the number of crystal nuclei not only shortens the formation time of the molecular sieve SSZ-13 and improves the yield, but also makes it easier to form a multi-level porous molecular sieve SSZ-13.

[0030] In a preferred embodiment, in the S4 crystallization step, to ensure the formation of (microporous-mesoporous) hierarchical molecular sieve SSZ-13, the crystallization reaction temperature is 150-170°C and the crystallization time is 36-72 hours. Preferably, the crystallization reaction apparatus is a closed reactor; more preferably, the crystallization reaction temperature is 160-165°C and the crystallization reaction time is 48-60 hours.

[0031] In a preferred embodiment, in the S4 crystallization step, in order to shorten the crystallization time and improve the crystallization effect, molecular sieve SSZ-13 seed crystals can be added to the prepared slurry. Preferably, the amount of the molecular sieve SSZ-13 seed crystals added is 1 to 5% of the mass of the prepared slurry; preferably, the amount of the molecular sieve SSZ-13 seed crystals added is 2% to 3% of the mass of the prepared slurry.

[0032] In a preferred embodiment, after the S4 crystallization step is completed, filtration is further included, the filter cake is collected, washed to a pH of 9, and dried. The washing can be performed using conventional operations known to those skilled in the art, such as washing the product 1 to 2 times with acidic water having a pH of 2 to 4; then washing the product 2 to 5 times with deionized water until the pH is about 9; preferably, ultrasonic treatment can be performed during washing to obtain a high-quality molecular sieve SSZ-13 product with a clean surface. The drying can be performed using any equipment and method known to those skilled in the art, preferably, drying at 80 to 120°C for 2 to 8 hours.

[0033] In a preferred embodiment, in the step of activating the loess-based SSZ-13 molecular sieve in S5, the molar ratio of the amount of NH4Cl added to the alkalizer in S3 is 1:(1-3), preferably, the molar ratio of the amount of NH4Cl added to the alkalizer in S3 is 1:2.

[0034] In a preferred embodiment, in the S5 activation loess-based SSZ-13 molecular sieve step, the ion exchange reaction conditions are: reaction at 70-80°C for 1-3 hours; preferably, the ion exchange reaction conditions are: reaction at 75°C for 2 hours; more preferably, in order to improve the ion exchange effect, two ion exchanges can be carried out under exactly the same treatment conditions.

[0035] In a preferred embodiment, in the S5 activation loess-based SSZ-13 molecular sieve step, the filter cake is calcined at 500-600°C for 1-8 hours; preferably, the filter cake is calcined at 550°C for 3-6 hours.

[0036] Another object of the present invention is to provide an application of a low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve, specifically including: the application of the loess-based SSZ-13 molecular sieve in the fields of fine chemicals, environmental protection, petrochemicals, coal chemicals, and automobile exhaust treatment.

[0037] In the technical solution provided by the present invention, based on the raw materials and the scheme design, the amount of template agent used is small, and there is no need to add an additional aluminum source. It is only necessary to supplement the silicon source and increase the silicon-aluminum ratio in the ratio to 220. The prepared molecular sieve presents a honeycomb structure with spindle aggregation, and the microscopic morphology shows a multi-level pore feature of micropores and mesopores. Compared with the molecular sieve SSZ-13 conventionally prepared in the prior art, the molecular sieve obtained by the present invention has a larger pore size, a smaller specific surface area, and presents a distinct honeycomb structure with spindle aggregation. It is precisely this optimization of microscopic morphology that makes it more conducive to the generation of larger molecular propylene gas products when used as a catalyst for the methanol to olefins reaction. At the same time, the larger pore size of the loess-based molecular sieve SSZ-13 prepared by the present invention gives it better anti-carbon deposition performance, which provides conditions and directions for the large-scale development and use of the molecular sieve SSZ-13.

[0038] In a preferred embodiment, the loess-based SSZ-13 molecular sieve is used in methanol to produce light olefins and remove NO from automobile exhaust. X And as a catalyst in gas separation and adsorption processes.

[0039] In a preferred embodiment, the loess-based SSZ-13 molecular sieve is used as a catalyst for methanol to olefins to obtain light olefins with high selectivity, which specifically includes the following steps:

[0040] The high-silicon multi-level porous loess-based SSZ-13 molecular sieve is tableted, crushed, and sieved, and 0.5 to 2 g is loaded into a fluidized bed reactor. Nitrogen is introduced as a carrier gas, and then methanol is introduced. The reaction is carried out at a certain temperature to obtain light olefin products.

[0041] In a preferred embodiment, the loess-based SSZ-13 molecular sieve is tableted, crushed, and then passed through a 50-mesh sieve.

[0042] In a preferred embodiment, the nitrogen flow rate is 30-100 mL / min.

[0043] In a preferred embodiment, the reaction temperature is 400-480°C, the mass concentration of methanol is: alcohol-water ratio (1-9): 1, and the mass space velocity is 2-8h -1 Preferably, the reaction temperature is 450°C, the methanol concentration is 7:3, and the mass space velocity is 5h -1 hour.

[0044] In a preferred embodiment, the loess-based SSZ-13 molecular sieve is used as a catalyst for methanol to olefins, and the selectivity of propylene reaches above 56%, and the selectivity of ethylene reaches above 47%.

[0045] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0046] 1. The present invention uses loess as raw material, and after activation and crystallization, loess-based molecular sieve SSZ-13 can be simply and quickly prepared. From the perspective of raw materials, loess is widely available, easy to obtain, and has huge reserves, which can greatly reduce the cost of raw material procurement; from the perspective of process, the present invention has high safety and low energy consumption, which can reduce the cost of the production process; in addition, the acidifiers and alkalizers used in the production process can be recycled, which not only reduces waste liquid discharge, but also further reduces costs. In summary, the loess-based SSZ-13 molecular sieve provided by the present invention is low in cost, easy to prepare, has a large price advantage, and can be produced on a large scale industrially.

[0047] 2. The technical solution provided by this invention, by controlling the raw material ratio and crystallization reaction conditions, can produce a high-silica, hierarchically porous loess-based molecular sieve SSZ-13 without the addition of additives or an aluminum source. The formulation used is streamlined, and the preparation process is simple and safe.

[0048] 3. From the product point of view, the microscopic morphology of the loess-based molecular sieve SSZ-13 obtained by the present invention presents a honeycomb structure with spindle aggregation, and its pore size has a multi-level pore with both micropores and mesopores. Using it as a catalyst can significantly improve the effect of methanol to olefins reaction, especially improve the selectivity of propylene with a larger molecular structure. On the other hand, the molecular sieve SSZ-13 itself has a high silicon-aluminum ratio and contains a small amount of Fe 3+ ions, and their modification can also greatly improve the anti-carbon deposition performance and catalytic activity of molecular sieve SSZ-13 in methanol to olefins. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] These and / or other aspects and advantages of the present invention will become more apparent and more readily understood from the following detailed description of embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0050] Figure 1XRD patterns of the high-silicon multi-level porous loess-based molecular sieve SSZ-13 and the standard SSZ-13 molecular sieve prepared in Example 1;

[0051] Figure 2 This is an SEM image of the high-silicon multi-level porous loess-based molecular sieve SSZ-13 prepared in Example 1;

[0052] Figure 3 This is the pore size distribution diagram of the high-silicon multi-level pore loess-based molecular sieve SSZ-13 prepared in Example 1;

[0053] Figure 4 This is the N2 adsorption diagram of the high-silicon multi-level porous loess-based molecular sieve SSZ-13 prepared in Example 1. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that the protection scope of the present invention is not limited to the specific embodiments.

[0055] The present invention provides a low-cost, high-silicon, multi-level-porous loess-based SSZ-13 molecular sieve, its preparation method, and application. This approach addresses the high cost, impracticality for large-scale production, and environmental pollution issues inherent in existing SSZ-13 molecular sieve synthesis methods. Furthermore, the present invention effectively addresses the technical issue of the poor performance of existing SSZ-13 molecular sieves in methanol-to-olefins reactions.

[0056] The technical solution in the present invention is to solve the above problems, and the overall idea is as follows:

[0057] Unless otherwise specified, the technical means used in the present invention are conventional means well known to those skilled in the art. The various raw materials, reagents, instruments, and equipment used in the present invention can be purchased commercially or prepared by existing methods. Unless otherwise specified, all reagents used in the present invention are of analytical grade. Unless otherwise specified, room temperature in the present invention is 25°C.

[0058] In the present invention, parts by weight may be weight units known in the art such as μg, mg, g, kg, etc., or multiples thereof, such as 1 / 10, 1 / 100, 10 times, 100 times, etc.

[0059] The loess used in the examples herein was sourced from northwestern China, specifically from Qingyang City, Gansu Province. Compared to other soils and raw materials, loess offers advantages such as abundant resources and freedom from raw material restrictions. However, it has a complex crystal structure and numerous components, which can affect the synthesis and performance of the molecular sieve. Chemical composition analysis of the loess is shown in Table 1.

[0060] Table 1: Content of each component of loess

[0061]

[0062] Example 1

[0063] Purification: Wash the loess raw material with deionized water, filter it through a 200-mesh sieve, repeat this process five times, and then dry it at 120°C for 3 hours to obtain purified loess.

[0064] Acidification: prepare a dilute sulfuric acid solution with a mass concentration of 20%, add 80g of purified loess, maintain a solid-liquid ratio of 1:4, acidify at 85°C for 5h, filter, wash to neutrality, and dry at 120°C to obtain acidified loess.

[0065] Alkalization: Take 20g of acidified loess and 22g of sodium hydroxide solid and mix them evenly. Calcine at 400℃ for 2h, calcine twice, cool to room temperature to obtain alkaline loess, and set aside.

[0066] Crystallization: Take 21g of alkalized loess (including 10g loess and 11g sodium hydroxide), in a molar ratio of SiO2:Al2O3:template:Na2O:H2O=220:1:6:24:2060, add 52.83g of template (N,N,N-trimethyl-1-adamantyl ammonium hydroxide, 24wt%), 313.95g of silica sol (40wt% SiO2), 1.3g of seed crystals, 142.287g of deionized water, stir evenly, at this time pH=13 or so, age at room temperature for 8h, then move into a high-pressure reactor, place in an oven at 165°C for 48h, after the reaction is completed, rinse with acidic solution, rinse with deionized water, wash to pH=9 or so, filter, and dry at about 120°C for 6h to obtain unactivated loess-based SSZ-13 molecular sieve.

[0067] Activation of loess-based SSZ-13 molecular sieve: Prepare an approximately 10% NH4Cl solution with 7.35g of NH4Cl and 80g of deionized water. Add all the unactivated loess-based molecular sieve SSZ-13 and stir. Perform an ion exchange reaction at 75°C for 2 hours. After completion, filter and wash, and repeat the ion exchange twice to obtain a filter cake of loess-based molecular sieve SSZ-13. Grind the filter cake into powder and calcine at 550°C for 4 hours to obtain the activated high-silicon hierarchical pore loess-based molecular sieve SSZ-13.

[0068] (1) The characterization and analysis results of the SSZ-13 molecular sieve prepared in Example 1 of the present invention are as follows:

[0069] 1. X-ray diffraction analysis

[0070] X-ray diffraction analysis (XRD) is mainly aimed at analyzing crystalline substances in minerals. By analyzing the diffraction peaks of the XRD pattern, the components of the crystalline substances in the minerals and the content of each component can be obtained. The present invention performs X-ray diffraction scanning with a 2θ range of 10-80 degrees on the standard SSZ-13 molecular sieve and the loess-based SSZ-13 molecular sieve prepared in Example 1 of the present invention. The results are as follows: Figure 1 shown.

[0071] By comparison, from Figure 1 It can be seen that the characteristic peak positions of loess-based SSZ-13 molecular sieve and standard SSZ-13 molecular sieve are basically the same, indicating that the technical solution of the present invention successfully prepared SSZ-13 molecular sieve using loess as raw material.

[0072] 2. Microscopic Analysis

[0073] Microscopic analysis mainly used scanning electron microscopy (SEM) to observe the morphology of the material. The results are as follows Figure 2 As shown, the average particle size was measured to be 5.132 μm.

[0074] As can be seen from the figure, the loess-based SSZ-13 molecular sieve prepared and synthesized by the present invention exhibits a honeycomb-like structure composed of spindles.

[0075] 3. BET specific surface area test

[0076] The specific surface area of ​​the prepared loess-based SSZ-13 molecular sieve was analyzed and detected using a BET specific surface area analyzer. It was found that the specific surface area of ​​the loess-based SSZ-13 molecular sieve prepared by the present invention was 425.3 m 2 / g, compared with the general SSZ-13 molecular sieve, it has a smaller specific surface area and a larger pore size. The pore size distribution diagram is shown in Figure 3 The pore size distribution is 0.5178~51.4956nm, and the pore volume distribution range is 0.0926~0.1391cm 3 / g; its N2 adsorption diagram is shown in Figure 4 It can be seen that the molecular sieve has a multi-level pore characteristic of micropores and mesopores.

[0077] From the above analysis, it can be seen that the loess-based SSZ-13 molecular sieve prepared in the present invention has a multi-level pore characteristic of micropores and mesopores, and has high anti-carbon deposition performance and propylene selectivity.

[0078] (2) Testing the catalytic effect of the SSZ-13 molecular sieve prepared in Example 1 of the present invention

[0079] The catalytic performance of high-silicon hierarchical pore loess-based SSZ-13 molecular sieve in methanol to light olefins was evaluated using a fluidized bed, specifically including the following steps:

[0080] The high-silicon multi-level porous loess-based SSZ-13 molecular sieve was tableted, crushed, and sieved. 1 g was taken and loaded into a fluidized bed reactor. Nitrogen was introduced as a carrier gas at a nitrogen flow rate of 50 mL / min. Methanol was then introduced with a methanol mass concentration of 7:3 and a methanol-water ratio of 5:3. The reaction temperature was 450°C and the methanol mass space velocity was 5 h -1 The gases were collected and analyzed qualitatively and quantitatively by gas chromatography.

[0081] The results showed that the mass selectivities of ethylene and propylene in the cracking gas were 42.53% and 56.32% respectively.

[0082] Example 2

[0083] Purification: Wash the loess raw material with deionized water, filter it through a 200-mesh sieve, repeat this process five times, and then dry it at 120°C for 3 hours to obtain purified loess.

[0084] Acidification: prepare a dilute sulfuric acid solution with a mass concentration of 20%, add 80g of purified loess, maintain a solid-liquid ratio of 1:4, acidify at 85°C for 5h, filter, wash to neutrality, and dry at 120°C to obtain acidified loess.

[0085] Alkalization: Take 20g of acidified loess and 22g of sodium hydroxide solid and mix them evenly. Calcine at 400℃ for 4h, calcine twice, cool to room temperature to obtain alkalized loess, and set aside.

[0086] Crystallization: Take 21g of alkalized loess (including 10g loess and 11g sodium hydroxide), in a molar ratio of SiO2:Al2O3:template:Na2O:H2O=220:1:6:24:2060, add 52.83g of template (N,N,N-trimethyl-1-adamantyl ammonium hydroxide, 24wt%), 313.95g of silica sol (40wt% SiO2), 142.287g of deionized water, stir evenly, at this time pH=13 or so, age at room temperature for 12h, then move into a high-pressure reactor, place in an oven at 160°C for 60h, after the reaction is completed, rinse with acidic solution, rinse with deionized water, wash to pH=9 or so, filter, and dry at about 120°C for 6h to obtain unactivated loess-based SSZ-13 molecular sieve.

[0087] Activate loess-based SSZ-13 molecular sieve: Prepare an approximately 10% NH4Cl solution with 7.35g of NH4Cl and 80g of deionized water. Add all the unactivated loess-based molecular sieve SSZ-13 and stir. Perform an ion exchange reaction at 80°C for 2 hours. After the reaction is complete, filter and wash, and repeat the ion exchange twice to obtain a filter cake of loess-based molecular sieve SSZ-13. Grind the filter cake into powder and calcine at 550°C for 4 hours to obtain the activated loess-based molecular sieve SSZ-13.

[0088] Characterization analysis: Microscopic analysis revealed that the prepared loess-based molecular sieve had a honeycomb structure with spindle aggregation and a multi-level pore size with micropores and mesopores. The specific test data were: the specific surface area was 456.4 m 2 / g, the pore size distribution range is 0.5055~50.3277nm, and the pore volume distribution range is 0.0893~0.1320cm 3 / g, and the average particle size is 5.089μm.

[0089] The catalytic performance of high-silicon multi-level pore loess-based SSZ-13 molecular sieve in methanol to light olefins was evaluated under the same conditions as in Example 1. The results showed that the mass selectivities of ethylene and propylene in the cracked gas were 44.87% and 52.65%, respectively.

[0090] Example 3

[0091] Purification: Wash the loess raw material with deionized water, filter it through a 200-mesh sieve, repeat this process five times, and then dry it at 120°C for 2 hours to obtain purified loess.

[0092] Acidification: Prepare a mixed acid solution with a mass concentration of 25% by volume of dilute hydrochloric acid and dilute nitric acid in a volume ratio of 1:1, add 80 g of the above-mentioned purified loess, maintain a solid-liquid ratio of 1:4, acidify at 80°C for 6 h, filter, wash to neutrality, and dry at 120°C to obtain acidified loess.

[0093] Alkalization: Take 40g of acidified loess and 40g of sodium hydroxide solid and mix them evenly. Calcined at 450℃ for 4h, cooled to room temperature to obtain alkaline loess, set aside.

[0094] Crystallization: Take 10g of alkalized loess (including 5g loess and 5g sodium hydroxide), add 26.42g of template (N,N,N-trimethyl-1-adamantyl ammonium hydroxide, 24wt%), 156.98g of silica sol (40wt% SiO2), and 71.144g of deionized water according to the ratio of SiO2:Al2O3:template:Na2O:H2O=220:1:6:24:2060, stir evenly, at this time pH=13 or so, age at room temperature for 8h, then move into a high-pressure reactor, place in an oven at 160°C for reaction for 72h, after the reaction is completed, rinse with acidic solution, rinse with deionized water, wash to pH=9 or so, filter, and dry at about 120°C for 6h to obtain unactivated loess-based SSZ-13 molecular sieve.

[0095] Activate loess-based SSZ-13 molecular sieve: Prepare an approximately 10% NH4Cl solution with 3.675g of NH4Cl and 40g of deionized water. Add all the unactivated loess-based molecular sieve SSZ-13 and stir. Perform an ion exchange reaction at 80°C for 2 hours. After the reaction, filter and wash, and repeat the ion exchange twice to obtain a filter cake of loess-based molecular sieve SSZ-13. Grind the filter cake into powder and calcine at 550°C for 4 hours to obtain the activated loess-based molecular sieve SSZ-13.

[0096] Characterization analysis: Microscopic analysis revealed that the prepared loess-based molecular sieve had a honeycomb structure with spindle aggregation and a multi-level pore structure with micropores and mesopores. The specific test data were: the specific surface area was 463.2 m 2 / g, the pore size distribution range is 0.5011~48.1835nm, and the pore volume distribution range is 0.0833~0.1181cm 3 / g, and the average particle size is 4.814μm.

[0097] Under the same conditions as in Example 1, the catalytic performance of high-silicon multi-level porous loess-based SSZ-13 molecular sieve in methanol to light olefins was evaluated. The results showed that the mass selectivities of ethylene and propylene in the cracked gas were 47.63% and 50.47% respectively.

[0098] Example 4

[0099] Purification: Wash the loess raw material with deionized water, filter it through a 200-mesh sieve, repeat 3-5 times, and then dry it at 120°C for 3 hours to obtain purified loess;

[0100] Acidification: Prepare a mixed acid solution with a mass concentration of 25% by volume of dilute hydrochloric acid and dilute nitric acid in a volume ratio of 1:1, add 80 g of the above-mentioned purified loess, maintain a solid-liquid ratio of 1:4, acidify at 80°C for 6 hours, filter, wash to neutrality, and dry at 120°C to obtain acidified loess.

[0101] Alkalization: Take 40g of acidified loess and 40g of sodium hydroxide solid and mix them evenly. Calcined at 450℃ for 3h, cooled to room temperature and set aside.

[0102] Crystallization: Take 10g of alkalized loess (including 5g loess and 5g sodium hydroxide), add 26.42g of template (N,N,N-trimethyl-1-adamantyl ammonium hydroxide, 24wt%), 156.98g of silica sol (40wt% SiO2), 71.144g of deionized water, and 0.7g of seed crystals according to the ratio of SiO2:Al2O3:template:Na2O:H2O=220:1:6:24:2060, stir evenly, at this time pH=13 or so, age at room temperature for 8h, then move into a high-pressure reactor, place in an oven at 165°C for 60h, after the reaction is completed, rinse with acidic solution, rinse with deionized water, wash to pH=9 or so, filter, and dry at about 120°C for 6h to obtain unactivated loess-based SSZ-13 molecular sieve.

[0103] Activate loess-based SSZ-13 molecular sieve: Prepare an approximately 10% NH4Cl solution with 3.675g of NH4Cl and 40g of deionized water. Add all the unactivated loess-based molecular sieve SSZ-13 and stir. Perform an ion exchange reaction at 80°C for 2 hours. After the reaction, filter and wash, and repeat the ion exchange twice to obtain a filter cake of loess-based molecular sieve SSZ-13. Grind the filter cake into powder and calcine at 550°C for 6 hours to obtain the activated loess-based molecular sieve SSZ-13.

[0104] Characterization analysis: Microscopic analysis revealed that the prepared loess-based molecular sieve had a spindle-aggregated honeycomb structure, with a multi-level pore size with micropores and mesopores coexisting. The specific test data were: a specific surface area of ​​451.43 m 2 / g, pore size distribution range is 0.5255~51.3277nm, pore volume distribution range is 0.0893~0.1320cm 3 / g, and the average particle size is 5.589μm.

[0105] The catalytic performance of high-silica multi-level porous loess-based SSZ-13 molecular sieve in methanol to light olefins was evaluated under the same conditions as in Example 1. The results showed that the selectivities of ethylene and propylene in the cracked gas were 45.78% and 52.55% respectively.

[0106] Example 5

[0107] Purification: Wash the loess raw material with deionized water, filter it through a 200-mesh sieve, repeat 3-5 times, and then dry it at 120°C for 2 hours to obtain purified loess;

[0108] Acidification: Prepare a dilute hydrochloric acid solution with a mass concentration of 25%, add 40g of the above-mentioned purified loess, maintain a solid-liquid ratio of 1:4, acidify at 90°C for 5h, filter, wash to neutrality, and dry at 120°C to obtain acidified loess.

[0109] Dry alkalization: Take 30g of acidified loess and 30g of sodium hydroxide solid and mix them evenly. Calcined at 450℃ for 4h, cooled to room temperature and set aside.

[0110] Crystallization: Take 10g of alkalized loess (including 5g loess and 5g sodium hydroxide), add 26.42g of template (N,N,N-trimethyl-1-adamantyl ammonium hydroxide, 24wt%), 156.98g of silica sol (40wt% SiO2), and 71.144g of deionized water according to the ratio of SiO2:Al2O3:template:Na2O:H2O=220:1:6:24:2060, stir evenly, at this time pH=13 or so, age at room temperature for 12h, then move into a high-pressure reactor, place in an oven at 160°C for reaction for 72h, after the reaction is completed, rinse with acidic solution, rinse with deionized water, wash to pH=9 or so, filter, and dry at about 120°C for 6h to obtain unactivated loess-based SSZ-13 molecular sieve.

[0111] Activate loess-based SSZ-13 molecular sieve: Prepare an approximately 10% NH4Cl solution with 3.675g of NH4Cl and 40g of deionized water. Add all the unactivated loess-based molecular sieve SSZ-13 and stir. Perform an ion exchange reaction at 75°C for 2 hours. After the reaction, filter and wash, and repeat the ion exchange twice to obtain a filter cake of loess-based molecular sieve SSZ-13. Grind the filter cake into powder and calcine at 550°C for 4 hours to obtain the activated loess-based molecular sieve SSZ-13.

[0112] Characterization analysis: Microscopic analysis revealed that the prepared loess-based molecular sieve had a spindle-aggregated honeycomb structure, with a multi-level pore size with micropores and mesopores coexisting. The specific test data were: the specific surface area was 486.19 m 2 / g, pore size distribution range is 0.4925~49.4356nm, pore volume distribution range is 0.0881~0.1810cm 3 / g, and the average particle size is 5.289μm.

[0113] Under the same conditions as in Example 1, the catalytic performance of high-silicon multi-level porous loess-based SSZ-13 molecular sieve in the production of light olefins from methanol was evaluated. The results showed that the mass selectivities of ethylene and propylene in the cracked gas were 44.56% and 49.61% respectively.

[0114] In summary, Examples 1 and 4 of the present application are preparation schemes with the addition of seed crystals, and Examples 2, 3, and 5 are preparation schemes without the addition of seed crystals. It can be seen that the obtained high-silicon multi-level pore loess-based SSZ-13 molecular sieves all have a honeycomb structure with spindle aggregation, and have a larger pore size and a smaller specific surface area. When used as a catalyst for the production of light olefins, it has a high selectivity for both ethylene and propylene in the cracking gas.

[0115] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve, characterized in that: Using loess as raw material, after activation treatment, only silicon source, template and water need to be added for preparation. After aging, crystallization and ion exchange, calcination is performed to obtain multi-level pore high-silica loess-based molecular sieve SSZ-13 with coexistence of micropores and mesopores. The high-silicon multi-level pore molecular sieve SSZ-13 has a spindle-aggregated honeycomb structure and a specific surface area of ​​425.3 to 486.19 m 2 / g, pore size distribution range is 0.4925~51.4956nm, pore volume distribution range is 0.0833~0.1810cm 3 / g, and the average particle size is 4.814~5.589μm.

2. The method for preparing the low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve according to claim 1, characterized in that: The following steps are involved: S1 purification: Using loess from the northwest as raw material, purified loess is obtained through washing and drying; S2 acidification: adding an acidifying agent to the product of the previous step to carry out an acidification reaction to obtain acidified loess; S3 alkalization: mixing the product of the previous step with an alkalizing agent, calcining, and obtaining alkalized loess; S4 crystallization: adding a silicon source, a template and water to the product of the previous step to make the molar ratio of the raw materials in the system be SiO2:Al2O3:template:Na2O:H2O=220:1:6:24:2060 to obtain a prepared slurry; aging the prepared slurry at room temperature, and then performing a crystallization reaction under certain conditions to obtain an unactivated loess-based SSZ-13 molecular sieve; S5 activated loess-based SSZ-13 molecular sieve: unactivated loess-based molecular sieve SSZ-13 is mixed with NH4Cl solution to carry out ion exchange reaction, filtered, the filter cake is collected, washed and calcined to obtain active high-silicon multi-level pore loess-based molecular sieve SSZ-13.

3. The method for preparing the low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve according to claim 2, characterized in that: In the S1 purification step, the molar ratio of silicon to aluminum in the loess is SiO2:Al2O3=(6.1-8.5):

1.

4. The method for preparing the low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve according to claim 2, characterized in that: In the alkalization step S3, the calcination conditions are: calcination at 350-450° C. for 1-5 hours.

5. The method for preparing the low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve according to claim 2, characterized in that: In the S4 crystallization step, the template is N,N,N-trimethyl-1-adamantyl ammonium hydroxide; the aging time is 4 to 18 hours; the crystallization reaction temperature is 150 to 170° C., and the crystallization time is 36 to 72 hours.

6. The method for preparing the low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve according to claim 5, characterized in that: In the crystallization step S4, molecular sieve SSZ-13 seed crystals are added to the prepared slurry, and the amount of the seed crystals added is 2-5% of the mass of the prepared slurry.

7. The method for preparing the low-cost, high-silicon, multi-level porous loess-based SSZ-13 molecular sieve according to claim 2, characterized in that: In the step of activating the loess-based SSZ-13 molecular sieve in S5, the molar ratio of the amount of NH4Cl added to the alkalizing agent in S3 is 1:(1-3).

8. Use of the low-cost, high-silicon, multi-level-pore loess-based SSZ-13 molecular sieve prepared according to claim 2 or any one of claims 3 to 7, characterized in that: The loess-based SSZ-13 molecular sieve is used in the fields of fine chemicals, environmental protection, petrochemicals, coal chemical industry, and automobile exhaust treatment.

9. The use according to claim 8, characterized in that The loess-based SSZ-13 molecular sieve is used as a catalyst for methanol to olefins to obtain light olefins with high selectivity, which specifically includes the following steps: The high-silicon multi-level porous loess-based SSZ-13 molecular sieve is tableted, crushed, and sieved, and 0.5 to 2 g is loaded into a fluidized bed reactor. Nitrogen is introduced as a carrier gas, and then methanol is introduced. The reaction is carried out at a certain temperature to obtain light olefin products.

10. The use according to claim 9, characterized in that When the loess-based SSZ-13 molecular sieve is used as a catalyst for methanol to olefins, the selectivity of propylene reaches more than 56%, and the selectivity of ethylene reaches more than 47%.

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