A method for preparing a SAPO molecular sieve having a RHO structure using a methanol to olefins catalyst

Abstract

The application discloses a method for preparing SAPO molecular sieve with RHO structure by using methanol-to-olefin catalyst. The method comprises the following steps: preparing an initial gel of raw material I containing methanol-to-olefin catalyst, organic amine R, water and cationic surfactant S, crystallizing, and roasting to obtain the SAPO molecular sieve with RHO structure; in the preparation process of the initial gel, raw material II containing at least the methanol-to-olefin catalyst and water in the raw material I is first aged to obtain a mixture, and then the mixture is mixed with the remaining components in the raw material I to prepare the initial gel. The method can reduce the pollution of methanol-to-olefin (MTO) waste catalyst to the environment, reduce the production cost of the catalyst, and has better economic benefits.

Description

Technical Field

[0001] This application relates to a method for preparing SAPO molecular sieves with RHO structure using a methanol-to-olefins catalyst, belonging to the field of chemical technology. Background Technology

[0002] Low-carbon olefins (ethylene and propylene) are the most important basic raw materials for the petrochemical industry. Currently, their industrial production mainly relies on petroleum routes. Given my country's resource endowment of "lacking oil and gas but rich in coal," the research and development of coal-based routes for synthesizing low-carbon olefins has become a current research hotspot. Among them, the technology of synthesizing low-carbon olefins (MTO) from coal, natural gas, etc. via methanol or dimethyl ether has attracted much attention.

[0003] MTO technology was commercialized as early as 2010. Currently, the commercially available catalyst for this technology is SAPO-34 molecular sieve with a CHA topology. SAPO-34 molecular sieve exhibits an ellipsoidal three-dimensional cage-like pore structure with eight-membered ring pores, where the diameter of the CHA cage is 0.94 nm, but its pore diameter is only 0.38 nm. The unique small-pore structure of SAPO-34 molecular sieve greatly restricts the formation of macromolecular products, but SAPO-34 is highly susceptible to deactivation due to coking.

[0004] Under conditions of high reaction temperature and high space velocity, the single-pass catalyst lifetime is relatively short. Furthermore, because industrial MTO plants utilize fluidized bed reactors, the MTO catalyst continuously circulates and regenerates between the reactor and regenerator under the influence of airflow. Catalyst particles in industrial fluidized bed plants undergo continuous and complex mechanical, thermal, and chemical processes, leading to catalyst wear and breakage. After multiple regenerations, this worn and broken catalyst becomes fine catalyst powder, resulting in a significant reduction in catalytic activity. When the activity drops to an unacceptable level, it becomes waste catalyst and cannot be reused in MTO industrial fluidized bed plants.

[0005] The carbon deposits in spent MTO industrial catalysts are mostly polycyclic aromatic hydrocarbons (PAHs). Simple landfill disposal will pollute soil and surface water resources, and the catalysts are expensive, so simple disposal will also result in economic losses. Therefore, recycling the aforementioned SAPO series spent catalysts can reduce environmental pollution and lower the cost of methanol-to-olefins (MTO), which is of great significance for the development of my country's coal chemical industry.

[0006] There are currently few reported methods for the resource utilization of industrial MTO waste catalysts.

[0007] Patent CN101157051A reports a method of using waste catalysts to be recycled as binders, mixing them with raw materials for preparing fresh microsphere catalysts in a certain proportion, and then spray drying and high-temperature calcination to obtain new microsphere catalysts.

[0008] Patent CN102389834B reports the calcination of catalyst micropowder produced during the MTO reaction to remove carbon deposits, and the separation of molecular sieves from binders, fillers, etc. by crushing method. The separated binders and matrix carriers are also used as binders in new catalysts.

[0009] Patent CN112708761A reports a method for recovering phosphorus and aluminum from spent MTO catalysts.

[0010] Patent CN109455747A reports a method for preparing alumina and phosphorus-containing fertilizers using MTO waste catalyst.

[0011] There are no reports on converting spent MTO catalysts into molecular sieve-type special functional materials. Summary of the Invention

[0012] According to one aspect of this application, a method is provided for preparing SAPO molecular sieve (DNL-6) with RHO structure using methanol-to-olefins (MTO) catalyst, which can reduce the environmental pollution caused by MTO waste catalyst and reduce the production cost of catalyst, thus having good economic benefits.

[0013] A method for preparing SAPO molecular sieves with RHO structure using a methanol-to-olefins catalyst, the method comprising the following steps:

[0014] Raw material I containing methanol-to-olefins catalyst, organic amine R, water, and cationic surfactant S was prepared into an initial gel, crystallized, and calcined to obtain the SAPO molecular sieve with the RHO structure.

[0015] In the preparation of the initial gel, raw material II, which contains at least the methanol-to-olefins catalyst in raw material I and water, is first aged to obtain a mixture, and then the mixture is mixed with the remaining components in raw material I to prepare the initial gel.

[0016] The molar ratios of the components in the initial gel satisfy the following:

[0017] Al2O3:SiO2 = 1.0:0.01-1.0;

[0018] Al2O3:P2O5 = 1.0:0.7-1.5;

[0019] Al2O3:R=1.0:0.5-10.0;

[0020] Al2O3:S = 1.0: 0.01-1.0;

[0021] Al2O3:H2O = 1.0:20.0-200.0;

[0022] The template agent R is selected from one or two of diethylamine, triethylamine, morpholine, diisopropylamine, tetraethylammonium hydroxide, diethanolamine, and triethanolamine.

[0023] Optionally, the methanol-to-olefins catalyst contains SAPO-34 molecular sieve, or the methanol-to-olefins catalyst contains SAPO-34 molecular sieve and a silica-alumina binder.

[0024] If the ratio of Al2O3, SiO2, and P2O5 in the methanol-to-olefins catalyst meets the above requirements, then no additional silicon, aluminum, or phosphorus source needs to be added. If any one or two of these components are insufficient, then additional silicon, aluminum, or phosphorus sources need to be added to supplement the missing components.

[0025] Optionally, Al2O3:SiO2 can be any one of the following values ​​or a range between any two values: 1.0:0.01, 1.0:0.2, 1.0:0.25, 1.0:0.3, 1.0:0.35, 1.0:0.4, 1.0:0.45, 1.0:0.5, 1.0:1.0, 1.0:0.6, 1.0:0.7, 1.0:0.8, 1.0:0.9, 1.0:1.0.

[0026] The Al2O3:P2O5 ratio can be any one of the following values ​​or a range between any two values: 1.0:0.7, 1.0:0.8, 1.0:0.85, 1.0:0.9, 1.0:0.95, 1.0:1.0, 1.0:1.05, 1.0:1.1, 1.0:1.15, 1.0:1.2, 1.0:1.3, 1.0:1.4, 1.0:1.5.

[0027] Al2O3:R can be any one of the following values ​​or a range between any two values: 1.0:0.5, 1.0:1, 1.0:2, 1.0:3, 1.0:4, 1.0:5, 1.0:6, 1.0:8, 1.0:10.

[0028] Al2O3:S can be any one of the following values ​​or a range between any two values: 1.0:0.01, 1.0:0.1, 1.0:0.15, 1.0:0.2, 1.0:0.3, 1.0:0.35, 1.0:0.4, 1.0:0.45, 1.0:0.5, 1.0:0.55, 1.0:0.7, 1.0:0.8, 1.0:1.0.

[0029] Al2O3:H2O can be any one of the following values ​​or a range between any two values: 1.0:20.0, 1.0:25.0, 1.0:30.0, 1.0:35.0, 1.0:40.0, 1.0:45.0, 1.0:50.0, 1.0:55.0, 1.0:60.0, 1.0:65.0, 1.0:70.0, 1.0:75.0, 1.0:80.0, 1.0:85.0, 1.0:90.0, 1.0:95.0, 1.0:100.0, 1.0:120.0, 1.0:140.0, 1.0:160.0, 1.0:180.0, 1.0:200.0.

[0030] Optionally, the methanol-to-olefins catalyst is selected from fresh catalysts or spent catalysts.

[0031] Optionally, the spent catalyst is subjected to calcination treatment.

[0032] Optionally, the molar ratio of the components in the methanol-to-olefins catalyst is:

[0033] Al2O3:SiO2 = 1:0.1~1.0;

[0034] Al2O3:P2O5 = 1:0.1~1.0.

[0035] Optionally, the molar ratio of the components in the methanol-to-olefins catalyst is:

[0036] Al2O3:SiO2=1:0.1, 1:0.5, 1:0.6, 1:0.877, 1:1.0;

[0037] Al2O3:P2O5=1:0.1, 1:0.296, 1:0.5, 1:0.8, 1:1.0.

[0038] Optionally, the dry basis amount of the methanol-to-olefins catalyst added is 10-80% of the total dry basis mass of inorganic matter in the initial gel.

[0039] Optionally, the dry basis amount of the MTO catalyst added is 10%, 18%, 20%, 23%, 25%, 28%, 30%, 32%, 35%, 37%, 41%, 46%, 50%, 60%, 65%, 70%, 75%, or 80% of the total dry basis mass of the inorganic matter in the initial gel.

[0040] Optionally, the cationic surfactant S is selected from at least one of dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.

[0041] Optionally, the raw material I may further include at least one of a silicon source, an aluminum source, and a phosphorus source.

[0042] Optionally, the silicon source is selected from at least one of tetraethyl orthosilicate, silica sol, silica gel, silica fume, and metakaolin.

[0043] Optionally, the aluminum source is selected from at least one of aluminum isopropoxide, boehmite, alumina, aluminum hydroxide, and sodium aluminate.

[0044] Optionally, the phosphorus source is at least one of orthophosphoric acid, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, organophosphorus compounds, and phosphorus oxides.

[0045] Optionally, the raw material I may also include SAPO molecular sieve seed crystals with an RHO structure.

[0046] Optionally, the SAPO molecular sieve seed crystals with the RHO structure are selected from either SAPO molecular sieve raw powder with the RHO structure containing a template agent or SAPO molecular sieve with the RHO structure that has been calcined to remove the template agent.

[0047] Optionally, preferably, the amount of SAPO molecular sieve seed crystals with RHO structure added does not exceed 5% of the total dry weight of inorganic matter in the initial gel.

[0048] Optionally, the amount of SAPO molecular sieve seed crystals with RHO structure added is 0.5 to 4% of the total dry mass of inorganic matter in the initial gel.

[0049] Optionally, the amount of SAPO molecular sieve seed crystals with RHO structure added is any one of 0.1%, 0.5%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5% of the total dry mass of inorganic matter in the initial gel, or a range between any two values.

[0050] Optionally, the raw material II may further include an organic amine R or a phosphorus source.

[0051] Optionally, the aging temperature is 10–100°C.

[0052] Optionally, the aging temperature is any one of 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 100°C or a range between any two of these values.

[0053] Optionally, the aging time is 6 to 24 hours.

[0054] Optionally, the aging time is any one of 6, 12, 16, 18, 20, 22, and 24 hours or a range between any two values.

[0055] Optionally, the crystallization temperature is 150–250°C.

[0056] Optionally, the crystallization temperature is any one of 150, 180, 200, 220, and 250°C, or a range between any two of these values.

[0057] Optionally, the crystallization time is 1 to 120 hours.

[0058] Optionally, the crystallization time is any one of 1, 10, 18, 24, 30, 36, 40, 48, 56, 70, 80, 90, 100, or 120 hours, or a range between any two values.

[0059] Optionally, the crystallization temperature is 180–220°C.

[0060] Optionally, the crystallization time is 3 to 48 hours.

[0061] Optionally, the method includes the following steps:

[0062] 1) Mix the methanol-to-olefins catalyst, organic amine R, and deionized water, and age the mixture to obtain a final product;

[0063] 2) Add aluminum source, phosphorus source, SAPO molecular sieve seed crystals with RHO structure and cationic surfactant S to the mixture, and stir to obtain the initial gel;

[0064] 3) The initial gel was crystallized and calcined to obtain SAPO molecular sieve with RHO structure.

[0065] Optionally, the method includes the following steps:

[0066] 1') Mix the methanol-to-olefins catalyst, phosphorus source, and deionized water, and age the mixture to obtain a mixture;

[0067] 2') Add an aluminum source, SAPO molecular sieve seed crystals with RHO structure, organic amine R and cationic surfactant S to the mixture, and stir to obtain an initial gel;

[0068] 3') The initial gel was crystallized and calcined to obtain SAPO molecular sieve with RHO structure.

[0069] According to another aspect of this application, a SAPO molecular sieve having an RHO structure prepared according to the method described above is provided.

[0070] According to another aspect of this application, SAPO molecular sieves with RHO structure prepared according to the method described above, or SAPO molecular sieves with RHO structure described above, are provided for use in the fields of catalysis or gas separation.

[0071] As one embodiment, this application discloses a method for preparing SAPO molecular sieve (DNL-6) with an RHO structure using a methanol-to-olefins (MTO) catalyst. This method uses the MTO catalyst as part of the silicon, aluminum, and phosphorus source in the synthesis raw materials, and then mixes it with silicon source, aluminum source, phosphorus source, organic amine R, cationic surfactant S, deionized water, and DNL-6 seed crystals. The mixture is then subjected to hydrothermal crystallization, centrifuged, washed, and dried to obtain the DNL-6 molecular sieve. This invention's method for preparing DNL-6 molecular sieve using an MTO catalyst solves the problem of large-scale MTO catalyst waste discharge while also achieving efficient and rapid utilization of the waste catalyst. The DNL-6 molecular sieve synthesized in this application is expected to have wide applications in the fields of catalysis and gas separation.

[0072] As one embodiment, this application provides a method for preparing DNL-6 molecular sieves using methanol-to-olefins (MTO) catalyst as a raw material. This method has the advantages of being simple and easy to scale up for industrial production. The DNL-6 molecular sieve prepared by this invention has broad application prospects in the fields of catalysis and gas separation.

[0073] As one embodiment, a method for preparing DNL-6 molecular sieves using methanol-to-olefins (MTO) catalyst as a raw material is provided, characterized in that the preparation process includes the following steps:

[0074] 1) Mix the MTO catalyst, organic amine R, and deionized water in a certain proportion, stir evenly, and continue aging for 6 to 24 hours;

[0075] 2) Add silicon source, aluminum source and phosphorus source to the mixture in step 1), and stir at room temperature until the mixture is homogeneous;

[0076] 3) Add DNL-6 molecular sieve seed crystals to the homogeneous mixture formed in step 2), stir until homogeneous, and obtain the desired initial gel;

[0077] The molar ratio of each component in the initial gel is SiO2:Al2O3:P2O5:R:S:H2O = 0-1.0:1.0:0.7-1.5:0.5-10.0:0.01-1.0:20.0-200.0;

[0078] The amount of seed crystals added is 0-5% of the total dry mass of inorganic matter in the initial gel;

[0079] 4) Transfer the gel obtained in step 3) into a high-pressure synthesis reactor and seal it. Perform hydrothermal crystallization at 150-250°C under autogenous pressure for 1-120 hours.

[0080] 5) After crystallization, the synthesis vessel was rapidly cooled to room temperature, the solid and liquid were separated, washed with deionized water, and dried to obtain DNL-6 molecular sieve.

[0081] As one embodiment, a method for preparing DNL-6 molecular sieves using methanol-to-olefins (MTO) catalyst as a raw material is provided, characterized in that the preparation process includes the following steps:

[0082] 1) Mix the MTO catalyst, phosphorus source, and deionized water in a certain proportion, stir evenly at room temperature, and continue aging for 6 to 24 hours.

[0083] 2) Add silicon source, aluminum source and organic amine R to the homogeneous mixture formed in step 1), and continue stirring at room temperature until the mixture is homogeneous;

[0084] 3) Add DNL-6 molecular sieve seed crystals to the mixture formed in step 2), and stir at room temperature until the mixture is homogeneous to obtain the desired initial gel;

[0085] The molar ratio of each component in the initial gel is SiO2:Al2O3:P2O5:R:S:H2O = 0-1.0:1.0:0.7-1.5:0.5-10.0:0.01-1.0:20.0-200.0;

[0086] The amount of seed crystals added is 0-5% of the total dry mass of inorganic matter in the initial gel;

[0087] 4) Transfer the gel obtained in step 3) into a high-pressure synthesis reactor and seal it. Perform hydrothermal crystallization at 150-250°C under autogenous pressure for 1-120 hours.

[0088] 5) After crystallization, the synthesis vessel was rapidly cooled to room temperature, the solid and liquid were separated, washed with deionized water, and dried to obtain DNL-6 molecular sieve.

[0089] When preparing DNL-6 molecular sieve using MTO catalyst, the aluminum source is one or a mixture of several of aluminum isopropoxide, boehmite, alumina, aluminum hydroxide, and sodium aluminate.

[0090] The silicon source is one or a mixture of several of tetraethyl orthosilicate, silica sol, silica gel, silica fume and metakaolin.

[0091] The phosphorus source is one or a mixture of several of orthophosphoric acid, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, organophosphorus compounds or phosphorus oxides;

[0092] The template agent R is selected from one or two of diethylamine (DEA), triethylamine (TEA), morpholine (MP), diisopropylamine (DiPA), tetraethylammonium hydroxide (TEAOH), diethanolamine (DELA), and triethanolamine (TELA);

[0093] The cationic surfactant S is selected from at least one of dodecyltrimethylammonium chloride (DTACl), dodecyltrimethylammonium bromide (DTABr), tetradecyltrimethylammonium chloride (TTACl), tetradecyltrimethylammonium bromide (TTABr), hexadecyltrimethylammonium chloride (CTACl), hexadecyltrimethylammonium bromide (CTABr), octadecyltrimethylammonium chloride (OTACl), and octadecyltrimethylammonium bromide (OTABr).

[0094] The method for preparing DNL-6 molecular sieve using MTO catalyst is characterized in that, in step 1), the dry basis amount of MTO catalyst added is 10-80% of the total dry basis mass of inorganic matter in the initial gel.

[0095] The method for preparing DNL-6 molecular sieve using MTO catalyst is characterized in that the amount of silicon-phosphorus-aluminum source added in step 2) depends on whether the amount of silicon-phosphorus-aluminum source added in the total feed gel ratio is met: that is, if the amount of MTO catalyst added does not meet the amount of silicon-phosphorus-aluminum source added in the gel ratio, then silicon-phosphorus-aluminum source needs to be added; if the amount of MTO catalyst added already meets the amount of silicon-phosphorus-aluminum source added in the gel ratio, then no additional silicon-phosphorus-aluminum source needs to be added.

[0096] When preparing DNL-6 molecular sieve using MTO catalyst, the DNL-6 molecular sieve seed crystals added in step 3) can be in the form of raw powder containing template agent, or they can be molecular sieves with template agent removed by calcination.

[0097] When preparing DNL-6 molecular sieve using MTO catalyst, the preferred addition amount of silicon is Al2O3:SiO2 = 1:0.1-0.6; the preferred addition amount of phosphorus is Al2O3:P2O5 = 1:0.8-1.2; the preferred addition amount of organic amine R is Al2O3:R = 1:1.0-4.0; the preferred addition amount of surfactant S is Al2O3:S = 1:0.05-0.5; the preferred addition amount of water is Al2O3:H2O = 1:30-100; the preferred amount of seed crystals is 0.5-4% of the total dry weight of inorganic matter in the initial gel; the preferred crystallization temperature is 180-220℃; and the preferred crystallization time is 3-48 hours.

[0098] When preparing DNL-6 molecular sieves using MTO catalyst, the MTO catalyst used can be a fresh catalyst or a spent MTO catalyst discharged from an industrial plant.

[0099] When preparing DNL-6 molecular sieves using MTO catalyst, the spent MTO catalyst used must be calcined at high temperature before use to remove any residual carbon that may be present.

[0100] As one implementation, this application provides the application of DNL-6 molecular sieves prepared according to any of the above methods in the field of catalysis.

[0101] As one implementation, this application provides the application of DNL-6 molecular sieves prepared according to any of the above methods in the field of gas separation.

[0102] The beneficial effects that this application may produce include at least the following:

[0103] 1) The method for preparing SAPO molecular sieves with RHO structure using methanol-to-olefins catalyst provided in this application can reduce the environmental pollution caused by MTO waste catalyst, and at the same time reduce the production cost of catalyst, thus having good economic benefits.

[0104] 2) The preparation method of SAPO molecular sieves with RHO structure using methanol-to-olefins catalyst provided in this application is simple and conducive to large-scale industrial production.

[0105] 3) The preparation method of SAPO molecular sieves with RHO structure using methanol-to-olefins catalyst provided in this application has the advantage of high yield.

[0106] 4) The preparation method of SAPO molecular sieve with RHO structure using methanol-to-olefins catalyst provided in this application has the advantages of short crystallization time and high crystallinity. Detailed Implementation

[0107] The present application is further illustrated below with reference to specific embodiments. The following descriptions are merely a few embodiments of the present application and are not intended to limit the present application in any way. Although the present application discloses preferred embodiments as follows, they are not intended to limit the present application. Any modifications or variations made by those skilled in the art without departing from the scope of the technical solution of the present application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

[0108] Unless otherwise specified, the raw materials used in the embodiments of this application are all purchased commercially and used directly without any special treatment.

[0109] The product analysis method in the embodiments of the present invention is as follows:

[0110] X-ray powder diffraction (XRD) phase analysis was performed using an X'Pert PRO X-ray diffractometer from PANalytical, Netherlands, with a Cu target, a Kα radiation source (λ = 0.15418 nm), a voltage of 40 kV, and a current of 40 mA.

[0111] In this application, both the spent MTO catalyst and the fresh MTO catalyst are composed of SAPO-34 molecular sieve and silica-alumina binder, and are provided by Shaanxi Yanchang Zhongmei Yulin Energy and Chemical Co., Ltd.; the composition of the spent MTO catalyst is: SiO2% = 26.4%, Al2O3% = 51.2%, P2O5% = 21.1%; that is, the molar ratio of Al2O3 to SiO2 is 1:0.877; the molar ratio of Al2O3 to P2O5 is 1:0.296; the composition of the fresh MTO catalyst is: SiO2% = 26.9%, Al2O3% = 50.8%, P2O5% = 20.0%.

[0112] MTO spent catalyst dry basis refers to SiO2, Al2O3 and P2O5 in MTO spent catalyst;

[0113] The inorganic dry basis in the initial gel refers to SiO2, Al2O3 and P2O5 in the initial gel [including MTO waste catalyst, seed crystals, and newly added raw materials (if any, including silicon-phosphorus-aluminum sources)].

[0114] Example 1: Sample 1 # Preparation

[0115] First, 5.68 g of spent MTO catalyst (its composition is shown in Table 1) was added to 86.64 g of deionized water, followed by 7.73 g of 80% H3PO4 solution. The mixture was stirred at 25°C for 12 hours. After thorough stirring, 8.86 g of aluminum isopropoxide (99%) and 0.61 g of DNL-6 seed crystals were added. Then, 11.08 g of DEA (99%) and 4 g of OTABr (98%) were added while stirring, and stirring continued until a homogeneous gel was formed, which was the initial gel. The gel was placed in a stainless steel reactor with a polytetrafluoroethylene liner and sealed. The mixture was heated to 200°C and crystallized for 48 hours. The resulting solid product was centrifuged, washed with deionized water until neutral, dried in air at 120°C, and finally calcined in a muffle furnace at 600°C for 5 hours to obtain 11.02 g of DNL-6 molecular sieve, designated as sample 1. # Sample 1 prepared # The types of raw materials, molar ratios, amount of MTO waste catalyst, amount of seed crystals, crystallization temperature, crystallization time, and yield in the initial gel are shown in Table 1.

[0116] Example 2: Sample 2 # Preparation

[0117] First, 5.11g of spent MTO catalyst was added to 76.17g of deionized water, followed by 15.33g of 99% TEA solution. The mixture was stirred at 20°C for 24 hours. After thorough mixing, 3.54g of 70% boehmite, 8.55g of 80% H3PO4 solution, 0.5g of DNL-6 seed crystals, and 1.78g of OTACl (98%) were added. Stirring continued until a homogeneous gel was formed, which was the initial gel. The gel was placed in a stainless steel reactor with a PTFE liner and sealed. The mixture was then heated to 200°C for 24 hours to crystallize. The resulting solid product was centrifuged, washed with deionized water until neutral, dried in air at 120°C, and finally calcined in a muffle furnace at 600°C for 5 hours to obtain 10.82g of DNL-6 molecular sieve, designated as sample 2. # Sample 2 prepared # The types of raw materials, molar ratios, amount of MTO waste catalyst, amount of seed crystals, crystallization temperature, crystallization time, and yield in the initial gel are shown in Table 1.

[0118] Example 3: Sample 3 # ~20 # Preparation

[0119] Sample 3 # ~11 # The specific adhesive preparation process was carried out according to Example 1; Sample 12 # ~20 # The specific rubber compounding process was carried out according to Example 2; the types of raw materials, molar ratios, amount of MTO waste catalyst added, amount of MTO waste catalyst used, amount of seed crystals, crystallization conditions, and product yield are shown in Table 1.

[0120] Example 4: Preparation of Sample S1

[0121] The specific ingredient preparation process is the same as that for sample 1 in Table 1. # The preparation method differs in that no seed crystals are added in the initial gel preparation step. The synthesis ratio is 0.5SiO2. a Al2O3 h 0.8P2O5 o The mixture of 100H2O, 3.0DEA, and 0.2OTABr was used to obtain the sample, which was denoted as sample S1.

[0122] Example 5: Preparation of Sample S2

[0123] The specific ingredient preparation process is the same as that for sample 8 in Table 1. # The preparation method differs from the previous one in that the spent MTO catalyst in the synthesis raw materials is replaced with fresh MTO catalyst. Otherwise, all other aspects are identical. The synthesis ratio is 0.2SiO2. aAl2O3 h 1.15P2O5 q The mixture of 30H2O, 2.0DEA, and 0.25DTACl was used to obtain the sample, which was denoted as sample S2.

[0124] Comparative Example 1: Preparation of Sample S3

[0125] The specific ingredient preparation process is the same as in Example 1, that is, sample 1 in Table 1. # The difference in preparation is that all raw materials are added at once during the ingredient preparation process, and there is no aging process; apart from this, all other processes (including the order of adding raw materials) are completely the same.

[0126] The specific preparation process is as follows: First, 5.68g of spent MTO catalyst was added to 86.64g of deionized water, followed by 7.73g of 80% H3PO4 solution. After stirring evenly, 8.86g of aluminum isopropoxide (99%) and 0.61g of DNL-6 seed crystals were added. While stirring, 11.08g of DEA (99%) and 4g of OTABr (98%) were added, and stirring continued until a uniform gel was formed. The gel was placed in a stainless steel reactor with a polytetrafluoroethylene liner and sealed. The temperature was raised to 200℃ for crystallization for 48 hours. The resulting solid product was centrifuged, washed with deionized water until neutral, dried in air at 120℃, and finally calcined in a muffle furnace at 600℃ for 5 hours to obtain sample S3.

[0127] Comparative Example 2: Preparation of Sample S4

[0128] The specific ingredient preparation process is the same as in Example 2, i.e., sample 2 in Table 1. # The difference in preparation is that all raw materials are added at once during the ingredient preparation process, and there is no aging process; apart from this, all other processes (including the order of adding raw materials) are completely the same.

[0129] The specific preparation process is as follows: First, 5.11g of spent MTO catalyst was added to 76.17g of deionized water, followed by 15.33g of 99% TEA. After stirring evenly, 3.54g of 70% boehmite, 8.55g of 80% H3PO4 solution, 0.5g of DNL-6 seed crystals, and 1.78g of OTACl (98%) were added, and stirring continued until a uniform gel was formed. The gel was placed in a stainless steel reactor with a polytetrafluoroethylene liner and sealed, and the temperature was raised to 200℃ for crystallization for 24h. The resulting solid product was centrifuged, washed with deionized water until neutral, dried in air at 120℃, and finally calcined in a muffle furnace at 600℃ for 5h to obtain sample S4.

[0130] Sample 1 # ~20# Characterization analysis of samples S1, S2, S3 and S4

[0131] Sample 1 was examined using X-ray diffraction. # ~20 # The phase composition of samples S1, S2, S3 and S4 was analyzed.

[0132] The results show that 1 # ~20 # The prepared samples were analyzed by XRD diffraction, and the results were consistent with the data in Table 2, indicating that the synthesized samples were all high-purity, high-crystallinity, and high-yield DNL-6 molecular sieves.

[0133] XRD diffraction analysis of sample S1 yielded results consistent with those in Table 2. Comparison with the XRD pattern of the standard RHO topology revealed that while the purity of sample S1 was maintained, its crystallinity was slightly reduced, and the yield decreased to 57%. This demonstrates that while the addition of seed crystals is not essential in the synthesis of DNL-6 molecular sieves using MTO waste catalyst according to this application, it can accelerate the crystallization rate of DNL-6 molecular sieves and improve the yield.

[0134] The XRD diffraction analysis results of sample S2 are consistent with those in Table 2; furthermore, the crystallinity and yield of the synthesized DNL-6 molecular sieve are both high. This indicates that the method of preparing DNL-6 molecular sieve using methanol-to-olefins (MTO) catalyst of the present invention is applicable to both spent MTO catalyst and fresh catalyst.

[0135] The XRD diffraction analysis results of samples S3 and S4 differ from the standard DNL-6 XRD diffraction pattern. In addition to the DNL-6 diffraction peaks, diffraction peaks also appeared at 2θ = 9.66, 16.13, and 20.67 in the XRD diffraction patterns of samples S3 and S4. This indicates that samples S3 and S4 are a mixture of DNL-6 and SAPO-34 molecular sieves. This also demonstrates that in the method of preparing DNL-6 molecular sieves using a methanol-to-olefins (MTO) catalyst of this invention, the aging process during the batching process is a necessary step to obtain pure-phase DNL-6 molecular sieves.

[0136]

[0137] Table 2. X-ray diffraction patterns of d-spacing and relative intensity

[0138]

[0139] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing pure-phase RHO-structured SAPO molecular sieves using a methanol-to-olefins catalyst, characterized in that, The method includes the following steps: 1) Mix the methanol-to-olefins catalyst, template agent R, and deionized water, and age the mixture to obtain a final product; 2) Add an aluminum source other than the methanol-to-olefins catalyst, a phosphorus source other than the methanol-to-olefins catalyst, seed crystals and cationic surfactant S to the mixture, and stir to obtain an initial gel; 3) The initial gel was crystallized and calcined to obtain SAPO molecular sieves with a pure phase RHO structure; Or the method may include the following steps: 1') Mix the methanol-to-olefins catalyst, phosphorus source, and deionized water, and age the mixture to obtain a mixture; 2') Add aluminum source, seed crystal, template agent R and cationic surfactant S (excluding methanol-to-olefins catalyst) to the mixture and stir to obtain initial gel; 3') The initial gel was crystallized and calcined to obtain SAPO molecular sieves with a pure phase RHO structure; The aging temperature is 10~100℃; The aging time is 6-24 hours; The methanol-to-olefins catalyst contains SAPO-34 molecular sieve, or the methanol-to-olefins catalyst contains SAPO-34 molecular sieve and a silica-alumina binder. The SAPO molecular sieve with the RHO structure is a DNL-6 molecular sieve. The seed crystal is a DNL-6 molecular sieve; The molar ratios of the components in the initial gel satisfy the following: Al2O3:SiO2 = 1.0 : 0.01~1.0; Al2O3:P2O5 = 1.0 : 0.7~1.5; Al2O3: R = 1.0 : 0.5~10.0; Al2O3: S = 1.0 : 0.01~1.0; Al2O3: H2O = 1.0: 20.0~200.0; The template agent R is selected from one or two of diethylamine, triethylamine, morpholine, diisopropylamine, tetraethylammonium hydroxide, diethanolamine, and triethanolamine.

2. The method according to claim 1, characterized in that, The methanol-to-olefins catalyst is selected from fresh catalyst or spent catalyst. The molar ratio of each component in the methanol-to-olefins catalyst is as follows: Al2O3:SiO2 = 1: 0.1~1.0; Al2O3:P2O5 = 1: 0.1~1.0; The dry basis addition amount of the methanol-to-olefins catalyst is 10-80% of the total dry basis mass of inorganic matter in the initial gel; The amount of seed crystals added shall not exceed 5% of the total dry mass of inorganic matter in the initial gel; The dry base of the methanol-to-olefins catalyst refers to SiO2, Al2O3 and P2O5 in the methanol-to-olefins catalyst. The inorganic dry basis in the initial gel refers to SiO2, Al2O3 and P2O5 in the initial gel.

3. The method according to claim 1, characterized in that, The amount of seed crystals added is 0.5 to 4% of the total dry mass of inorganic matter in the initial gel.

4. The method according to claim 1, characterized in that, The cationic surfactant S is selected from at least one of dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and octadecyltrimethylammonium bromide.

5. The method according to claim 1, characterized in that, The crystallization temperature is 150~250℃; The crystallization time is 1 to 120 hours.

6. The method according to claim 1, characterized in that, The crystallization temperature is 180~220℃; The crystallization time is 3 to 48 hours.

7. The SAPO molecular sieve with a pure phase RHO structure prepared by the method according to any one of claims 1 to 6.

8. The application of the SAPO molecular sieve with pure phase RHO structure prepared by the method according to any one of claims 1 to 6, or the SAPO molecular sieve with pure phase RHO structure according to claim 7, in the fields of catalysis or gas separation.

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