A method for treating a shaped catalyst of saPO-34 molecular sieve

Abstract

The application provides a treatment method of a SAPO-34 molecular sieve shaped catalyst. First, the shaped catalyst to be treated is subjected to acid treatment in an acid solution with a pH value of 2-4, then is mixed with a template agent and a phosphorus-containing aqueous solution, and is subjected to crystallization treatment at a temperature of not less than 120 DEG C, and finally is dried and calcined to obtain the shaped catalyst. The treatment method can effectively remove the carrier, the binder and other substances which block the micropore channels of the molecular sieve during the shaping process of the SAPO-34 molecular sieve catalyst, and meanwhile, the original micro morphology is maintained. When the treated catalyst is used in a catalytic methanol-to-olefin reaction, excellent catalytic activity can be achieved, the selectivity of dienes (ethylene+propylene) is significantly improved, and the service life of the catalyst is obviously prolonged.

Description

Technical Field

[0001] This invention relates to the field of industrial catalysts, and more specifically to a method for processing SAPO-34 molecular sieve shaped catalysts. Background Technology

[0002] Methanol-to-olefins (MTO) reactions typically use solid acid catalysts, i.e., MTO catalysts. A common catalyst is the SAPO-34 molecular sieve containing the active species. The unique CHA cage structure of SAPO-34 molecular sieve provides the site for the methanol conversion reaction. Furthermore, because the pore size of the eight-membered rings entering and exiting the cage is 0.38 nm, close to the molecular dynamic diameter of ethylene and propylene, it exhibits high selectivity for ethylene and propylene. However, to improve the wear resistance of MTO catalysts and the dispersion of the active molecular sieve, clay supports and binders are often added during catalyst preparation. Catalyst microspheres are obtained through mixing, molding, and spray drying. During the mixing process, the binder or clay support can partially block the micropores of the molecular sieve, thereby easily reducing the catalytic effect.

[0003] Chinese patent CN 102319583A provides a method for removing residual silica sol from SAPO-34 molecular sieve products, comprising the following steps: (1) dissolving and / or dispersing the solid SAPO-34 molecular sieve product in water or a mixed solvent of organic solvent and water for 1-10 hours to obtain a slurry; (2) performing solid-liquid separation on the slurry; and (3) drying the solid sample obtained in step (2) at 105-120°C for 8-24 hours to obtain pure SAPO-34 molecular sieve powder. This patent addresses the purification of molecular sieves, but the potential for blockage of the micropores by the carrier and binder during the MTO catalyst molding process remains unresolved.

[0004] Chinese patent CN 112062138A discloses a methanol-to-olefins catalyst, its preparation method, and its application. The preparation method includes: dispersing an aluminum source in water, adding a phosphorus source, a silicon source, and an organic template agent, and stirring until a uniform initial gel mixture is formed; placing the initial gel in a reactor and raising it to a set temperature for crystallization; after the crystallization reaction, distilling and recovering the organic template agent; then adding a binder and kaolin to the molecular sieve slurry and mixing uniformly; spraying the mixture into pellets after gel milling; placing the pelletized catalyst and the organic template agent in a solid-phase reactor and raising it to a set temperature for a secondary crystallization reaction; and separating the organic template agent after the reaction to obtain the final product. In this patent's preparation method, the molecular sieve synthesis mother liquor does not need to be separated. After direct mixing and spraying with kaolin and a binder, the insufficiently crystallized silicon, aluminum, and phosphorus sources in the mother liquor are converted into molecular sieve crystals during the solid-phase crystallization process, improving the catalyst's methanol conversion activity and significantly reducing mother liquor emissions. However, this patent cannot ensure that all unreacted raw materials are crystallized into crystals. The residual part will block the micropores of the original molecular sieve. In addition, during the secondary crystallization process, the ratio of local silicon source, aluminum source and phosphorus source cannot be precisely controlled to the optimal range, and there is a possibility of crystallization into impurities or mixed crystals. Even if a directional molecular sieve is generated, it is difficult to ensure the stability of physicochemical properties.

[0005] It is evident that existing technologies rarely address the problem of MTO catalysts clogging the micropores of molecular sieves during the molding process, or fail to provide effective solutions. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, one object of the present invention is to provide a method for processing SAPO-34 molecular sieve molding catalyst. This method can effectively solve the problem of micropore blockage in molecular sieves during catalyst molding, thereby significantly increasing the micropore volume of the catalyst, thereby improving the catalytic effect and extending the service life of the catalyst.

[0007] Another object of the present invention is to provide a SAPO-34 molecular sieve molding catalyst and its uses.

[0008] Another object of the present invention is to provide a method for producing olefins from methanol.

[0009] The first aspect of this invention provides a method for processing SAPO-34 molecular sieve shaped catalysts, comprising the following steps:

[0010] S1: The shaped catalyst to be treated is acid-treated in an acidic solution with a pH of 2 to 4;

[0011] S2: The shaped catalyst treated in step S1 is mixed with a template agent and a phosphorus-containing aqueous solution, and then crystallized at a temperature not lower than 120°C; and

[0012] S3: Dry and calcine the shaped catalyst after step S2.

[0013] The processing method provided by this invention first uses an acid solution to wash away the molding reagents, such as carriers and binders, that are clogging the pores. Then, a template agent and phosphorus species are added for in-situ crystallization, thereby filling the defects caused by the acid treatment and maintaining the integrity and stability of the molecular sieve framework. The crystallization temperature is set to not less than 120°C, which can ensure that the dissolution rate of the molecular sieve framework is lower than the crystallization rate during the crystallization process, thereby achieving the goal of maintaining the original morphology of the molecular sieve.

[0014] After the aforementioned treatment process, the reagents clogging the pores can be effectively removed, and the microstructure of the molecular sieve remains essentially unchanged (e.g., Figure 1 and Figure 2 (As shown). Compared to untreated catalysts, the micropore volume of catalysts treated by the method of the present invention can be increased by more than 20%, and when used to catalyze the reaction of methanol to olefins, the catalytic effect can be significantly improved and the service life can be significantly extended.

[0015] In the processing method provided by the present invention, the SAPO-34 molecular sieve molding catalyst can be any type commonly used in the art. For example, it can be prepared by spray molding of SAPO-34 molecular sieve, support and binder. The spray molding process can also be a common process in the art.

[0016] In the processing method provided by this invention, the support used for the SAPO-34 molecular sieve molding catalyst can be any type commonly used in the art, such as one or more of kaolin, perlite, and bentonite. The binder can also be any type commonly used in the art, such as one or two of silica sol and alumina sol. In some preferred embodiments, the mass ratio of the SAPO-34 molecular sieve, support, and binder can be 2–5:1.5–4:2–5. In some more preferred embodiments, the mass ratio of the SAPO-34 molecular sieve, support, and binder can be 3.5–4.5:2–3:3–4, for example, 4:2.5:3.5.

[0017] In the processing method provided by this invention, in step S1, the acid solution can be an aqueous solution of an inorganic acid and / or an organic acid commonly used in the art. In some preferred embodiments, the acid solution can be an aqueous solution formed from one or more of phosphoric acid, nitric acid, hydrochloric acid, oxalic acid, citric acid, tartaric acid, and ethylenediaminetetraacetic acid. In some preferred embodiments, the pH value of the acid solution can be further set to 2-3.

[0018] In the processing method provided by this invention, in step S1, the mass ratio of the molding catalyst to the acid solution to be treated can be 1:5 to 50, for example, about 1:5, about 1:10, about 1:15, about 1:20, about 1:25, about 1:30, about 1:35, about 1:40, about 1:45, about 1:50, or any combination of mass ratios within this range. In some preferred embodiments, the mass ratio of the molding catalyst to the acid solution to be treated can be 1:10 to 30.

[0019] In the processing method provided by this invention, in step S1, the acid treatment temperature can be 30–80°C, and the treatment time can be 1–10 hours. In some preferred embodiments, the acid treatment temperature can be 50–70°C, and the treatment time can be 1–3 hours.

[0020] In the processing method provided by the present invention, step S1 further includes: after the acid treatment is completed, separating the solid, washing it, and drying it. In some preferred embodiments, drying can be carried out at 100-120°C for 1-10 hours.

[0021] In the processing method provided by this invention, in step S2, the mass ratio of the molding catalyst, template agent, and phosphorus-containing aqueous solution after step S1 can be 1:5 to 20:1 to 5, and the mass ratio of the template agent to the phosphorus-containing aqueous solution is greater than 2. By controlling the proportion of the template agent, the crystallization rate can be further ensured to be greater than the dissolution rate during the crystallization process, thereby ensuring the improvement of micropore volume. In some preferred embodiments, the mass ratio of the molding catalyst, template agent, and phosphorus-containing aqueous solution after step S1 can be 1:8 to 12:3 to 5, and the mass ratio of the template agent to the phosphorus-containing aqueous solution is greater than 3.

[0022] In the processing method provided by the present invention, the template agent can be one or more of the organic amine template agents commonly used in the art, such as triethylamine, diethylamine, morpholine, tetraethylammonium hydroxide, di-n-propylamine, and diisopropylamine.

[0023] In the processing method provided by this invention, the phosphorus-containing aqueous solution can be an aqueous solution formed from one or more of phosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate. The mass ratio of P2O5 to H2O, calculated as P2O5, can be 1 to 4:1, for example, approximately 1:1, approximately 1.5:1, approximately 2:1, approximately 2.5:1, approximately 3:1, approximately 3.5:1, approximately 4:1, or any combination of these mass ratios. By controlling the mass ratio of P2O5 to H2O, the proportion of water is minimized, thereby avoiding excessive dissolution of the molecular sieve framework during crystallization.

[0024] In the processing method provided by this invention, in step S2, the crystallization treatment temperature can be 120–150°C, and the treatment time can be 1–48 hours. In some preferred embodiments, the crystallization treatment temperature can be 120–140°C, and the treatment time can be 5–24 hours.

[0025] In the processing method provided by this invention, the crystallization process in step S2 can be a dynamic process, that is, the material inside the crystallization device (such as a high-pressure crystallization kettle commonly used in the art) is in a dynamic mixing process, thereby improving the mass transfer and heat transfer efficiency of the material. The dynamic processing method can be any method commonly used in the art, such as connecting an online stirring device for stirring, or placing it in a rotating device to drive rotation.

[0026] In the processing method provided by the present invention, step S2 further includes: after the crystallization process is completed, separating the solid and washing it.

[0027] In the processing method provided by this invention, in step S3, the drying temperature can be 100–130°C, the drying time can be 2–16 h, the calcination temperature can be 500–700°C, and the calcination time can be 2–6 h. In some preferred embodiments, the drying temperature can be 110–120°C, and the drying time can be 4–10 h. In other preferred embodiments, the calcination temperature can be 500–600°C, and the calcination time can be 3–5 h.

[0028] In the processing method provided by the present invention, the desired material can be obtained through a separation step. The separation equipment or method can be common in the art, including but not limited to natural sedimentation, (atmospheric pressure or vacuum) filtration, centrifugation and other common equipment.

[0029] In the processing method provided by the present invention, the washing step refers to washing the material with distilled water or deionized water until the surface of the material is close to or neutral. The number of washing times can be adjusted according to the actual situation, for example, it can be 2 to 5 times, and usually it can be 3 times.

[0030] In the processing method provided by this invention, room temperature refers to 25±5℃.

[0031] A second aspect of the present invention provides a SAPO-34 molecular sieve molding catalyst, which is obtained by processing according to any one of the above technical solutions.

[0032] A third aspect of the present invention provides the use of the SAPO-34 molecular sieve molding catalyst described in any of the above technical solutions as a methanol-to-olefins catalyst (i.e., MTO catalyst).

[0033] A fourth aspect of the present invention provides a method for methanol-to-olefins, which uses the SAPO-34 molecular sieve molding catalyst described in any of the above technical solutions as a catalyst.

[0034] Apart from the catalyst, the methanol-to-olefins method provided by this invention can be a process commonly used in the art.

[0035] The technical solution provided by this invention has the following advantages:

[0036] (1) The processing method of the present invention can effectively remove the carrier, binder and other substances that block the micropores of the molecular sieve during the forming process of SAPO-34 molecular sieve catalyst, while maintaining the original micromorphology and not damaging or changing other physicochemical properties of the catalyst.

[0037] (2) When the catalyst treated by the method of the present invention is used to catalyze the methanol-to-olefins reaction, it can achieve excellent catalytic activity, significantly improve the selectivity of dienes (ethylene + propylene), and significantly extend the catalyst life.

[0038] (3) The processing method of the present invention is simple, highly operable, and does not require expensive raw materials or reagents, thus having good industrial applicability. Attached Figure Description

[0039] Figure 1 Scanning electron microscope image of catalyst D1 prepared for the preparation example.

[0040] Figure 2 This is a scanning electron microscope image of catalyst S1 prepared in Example 1. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0042] Unless otherwise specified, all raw materials or reagents used in this invention are commercially available products, and all percentages used are mass percentages unless otherwise specified.

[0043] Preparation Example

[0044] Using boehmite (70% Al2O3) as the aluminum source, phosphoric acid (85% H3PO4) as the phosphorus source, silica sol (30% SiO2) as the silicon source, and triethylamine as the organic template agent, an initial mixed gel was prepared according to the molar ratio of aluminum source: phosphorus source: silicon source: organic template agent: water = 1:1:0.3:3.5:50. After being evenly dispersed, the gel was transferred to a high-pressure reactor and crystallized at 200℃ for 24 hours. After cooling, separation, washing with deionized water, and drying, SAPO-34 molecular sieve was obtained.

[0045] Molecular sieves, alumina sol (21% Al2O3), and kaolin (85% dry basis) were mixed uniformly at a dry basis weight percentage of 40%:25%:35%. The mixture was then spray-molded after gel milling to obtain methanol-to-olefins catalyst D1. The pore structure determined by BET analysis is shown in Table 1, and the scanning electron microscope images are shown below. Figure 1 .

[0046] Example 1

[0047] A citric acid solution with a concentration of 1.9 g / L was prepared, and the pH of the solution was measured to be 2.6 at 20℃. 20 g of methanol-to-olefins catalyst D1 was mixed with 400 g of the citric acid solution (solid-liquid mass ratio 1:20), and the mixture was stirred at 60℃ for 2 h. After filtration, the filter cake was washed three times with deionized water and dried at 120℃ for 6 h. The dried filter cake was then mixed with triethylamine and phosphoric acid aqueous solution (where the mass ratio of P2O5 to water was 1:1) at a mass ratio of 1:10:3. The mixture was transferred to a high-pressure crystallization reactor, heated to 120℃, and dynamically treated for 6 h. After cooling, the mixture was filtered, and the filter cake was washed three times with deionized water, dried at 120℃ for 6 h, and calcined at 550℃ for 4 h to obtain the improved methanol-to-olefins catalyst S1. The pore structure determined by BET is shown in Table 1, and the scanning electron microscope images are shown in [Table 1]. Figure 2 .

[0048] pass Figure 1 and Figure 2 The comparison shows that the morphology of the catalyst before and after the process of Example 1 did not change significantly.

[0049] Example 2

[0050] The difference from Example 1 is that citric acid was replaced with phosphoric acid, the phosphoric acid concentration was 0.49 g / L, and the pH of the solution was measured at 20°C to be 2.4. All other steps were the same as in Example 1. The improved methanol-to-olefins catalyst obtained was denoted as S2. The BET pore structure is shown in Table 1.

[0051] Example 3

[0052] The difference from Example 1 is that triethylamine is replaced with diethylamine, and the rest of the steps are the same as in Example 1. The improved methanol-to-olefins catalyst obtained is denoted as S3, and the pore structure determined by BET is shown in Table 1.

[0053] Example 4

[0054] The difference from Example 1 is that the mass ratio of the dried filter cake to triethylamine and phosphoric acid aqueous solution is 1:10:5. All other steps are the same as in Example 1. The improved methanol-to-olefins catalyst obtained is denoted as S4. The pore structure determined by BET is shown in Table 1.

[0055] Example 5

[0056] The difference from Example 1 is that the mass ratio of P2O5 to water in the phosphoric acid aqueous solution used is 3:1. All other steps are the same as in Example 1. The improved methanol-to-olefins catalyst obtained is denoted as S5. The pore structure determined by BET is shown in Table 1.

[0057] Example 6

[0058] The difference from Example 1 is that the phosphoric acid aqueous solution is replaced with an ammonium phosphate aqueous solution, wherein the mass ratio of P2O5 to water is 2:1. The remaining steps are the same as in Example 1. The improved methanol-to-olefins catalyst obtained is denoted as S6. The pore structure determined by BET is shown in Table 1.

[0059] Example 7

[0060] The difference from Example 1 is that the temperature in the high-pressure crystallization reactor was raised to 140°C and dynamically treated for 20 hours. All other steps were the same as in Example 1. The improved methanol-to-olefins catalyst obtained was designated as S7. The pore structure determined by BET is shown in Table 1.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that the mixture of dried filter cake and triethylamine and phosphoric acid aqueous solution was transferred to a high-pressure crystallization reactor, heated to 100°C, and dynamically treated for 6 hours. The remaining steps were the same as in Example 1. The methanol-to-olefins catalyst obtained was denoted as D2. The pore structure determined by BET is shown in Table 1.

[0063] Comparative Example 2

[0064] The difference from Example 1 is that the mass ratio of the dried filter cake to triethylamine and phosphoric acid aqueous solution is 1:2:10. All other steps are the same as in Example 1. The methanol-to-olefins catalyst obtained is denoted as D3. The pore structure determined by BET is shown in Table 1.

[0065] Comparative Example 3

[0066] The difference from Example 1 is that: the citric acid solution was mixed with catalyst D1 for acid treatment, and after steps such as filtration, washing and drying, it was no longer crystallized in situ. The dried filter cake was directly calcined at 550°C for 4 hours. The methanol-to-olefins catalyst obtained was denoted as D4. The pore structure determined by BET is shown in Table 1.

[0067] Table 1 Pore structure properties of each catalyst

[0068]

[0069] As shown in Table 1, when the crystallization temperature is low (Comparative Example 1), the dissolution rate is greater than the crystallization rate, resulting in the dissolution of the molecular sieve framework. The micropore volume of catalyst D2 is even lower than before treatment. Similarly, when a large amount of phosphoric acid aqueous solution is used (Comparative Example 2), excessive dissolution also leads to a decrease in the micropore volume of catalyst D3. Furthermore, if only acid treatment is performed without repairing the molecular sieve framework (Comparative Example 3), even after removing the reagents clogging the micropores, the micropore volume is not improved. This is because the molecular sieve framework is damaged during the acid treatment process.

[0070] The treatment process in Examples 1-7 of the present invention can improve the pore structure properties of molecular sieves. Compared with the untreated catalyst D1, all properties have changed significantly, especially the increase in micropore volume, which is very beneficial to the improvement of catalytic performance.

[0071] Catalyst performance evaluation of test examples

[0072] Catalyst performance was evaluated using a fixed fluidized bed reactor with an 80% methanol-water solution as feed, a reaction temperature of 480℃, and a space velocity of 1.5 h⁻¹. -1 The catalyst loading amount is 10g.

[0073] Specific steps: The catalyst is loaded into a stainless steel reaction tube, heated to 500℃ for 1 hour, cooled to 480℃, and methanol-water solution is introduced. Online sampling is used, and the product is separated by condensation. The gas phase components are analyzed by a gas chromatograph (Agilent, model 7890A). The chromatogram is equipped with an HP-PLOT Al2O3 / KCl column (50m×0.53mm×15μm) (for separating C1-C6 hydrocarbons), an HP-PLOT Q column (30m×320μm×20μm) (for separating alcohols and ethers), a Hayesep Q column and an X molecular sieve column (for separating permanent gases such as CO, CO2, H2, and N2), two FID detectors, and one TCD detector.

[0074] Methanol conversion rate (X) and product selectivity (Si), expressed in terms of the number of carbon atoms and based on carbon-based selectivity, are calculated using the following equations:

[0075]

[0076] Wherein, X - methanol conversion rate; S - product selectivity; i - species entering the reactor; o - species exiting the reactor; CxHy - olefin (x - number of carbon atoms in hydrocarbon species, y - number of hydrogen atoms in hydrocarbon species); m - number of carbon atoms in the corresponding substance CxHy; n - number of moles of the corresponding substance; MeOH - methanol; DME - dimethyl ether.

[0077] When the methanol conversion rate in the tested component is less than 99%, it is considered that the catalyst is deactivated. The catalyst lifetime is the time during which the methanol conversion rate is above 99%. The test results are shown in Table 2.

[0078] Table 2 Results of methanol conversion reaction lifetime and product selectivity tests

[0079]

[0080]

[0081] As can be seen from the results in Table 2, the change in the pore structure of the catalyst can lead to the change in catalytic performance. Compared with the untreated catalyst D1, the catalysts obtained in Examples 1-7 of the present invention can achieve significantly better catalytic activity, higher diene selectivity, and significantly longer service life.

[0082] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art.

[0083] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is only defined by the claims.

Claims

1. A method for processing SAPO-34 molecular sieve shaped catalyst, characterized in that, Includes the following steps: S1: The SAPO-34 molecular sieve shaped catalyst to be treated is subjected to acid treatment in an acidic solution with a pH value of 2 to 4. The SAPO-34 molecular sieve shaped catalyst is prepared by spray molding of SAPO-34 molecular sieve, support and binder. S2: The molding catalyst treated in step S1 is mixed with a template agent and a phosphorus-containing aqueous solution, and crystallized at a temperature not lower than 120°C. The mass ratio of the molding catalyst treated in step S1, the template agent, and the phosphorus-containing aqueous solution is 1:5 to 20:1 to 5, and the mass ratio of the template agent to the phosphorus-containing aqueous solution is greater than 2. The phosphorus-containing aqueous solution is an aqueous solution formed from one or more of phosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate, wherein, based on P2O5, the mass ratio of P2O5 to H2O is 1 to 4:1; and S3: Dry and calcine the shaped catalyst after step S2.

2. The processing method according to claim 1, characterized in that, The carrier is one or more of kaolin, perlite, and bentonite, and the binder is silica sol and / or alumina sol.

3. The processing method according to claim 2, characterized in that, The mass ratio of the SAPO-34 molecular sieve, carrier, and binder is 2-5: 1.5-4: 2-5.

4. The processing method according to claim 1, characterized in that, In step S1, the acid solution is an aqueous solution formed from one or more of phosphoric acid, nitric acid, hydrochloric acid, oxalic acid, citric acid, tartaric acid, and ethylenediaminetetraacetic acid; and / or The mass ratio of the catalyst to be treated to the acid solution is 1:5 to 50.

5. The processing method according to claim 4, characterized in that, The mass ratio of the SAPO-34 molecular sieve catalyst to the acid solution is 1:10-30.

6. The processing method according to claim 1, characterized in that, In step S1, the acid treatment temperature is 30–80°C, and the treatment time is 1–10 h; and / or After the acid treatment is completed, the solid is separated, washed, and dried.

7. The processing method according to claim 1, characterized in that, The template agent is one or more of triethylamine, diethylamine, morpholine, tetraethylammonium hydroxide, di-n-propylamine, and diisopropylamine.

8. The processing method according to claim 1, characterized in that, In step S2, the crystallization treatment is carried out at a temperature of 120–150°C for a duration of 1–48 h; and / or After the crystallization process is completed, the solid is separated and washed.

9. The processing method according to any one of claims 1-8, characterized in that, In step S3, the drying temperature is 100-130℃, the drying time is 2-16 h, the calcination temperature is 500-700℃, and the calcination time is 2-6 h.

10. A SAPO-34 molecular sieve molding catalyst, obtained by the treatment method according to any one of claims 1-9.

11. Use of the SAPO-34 molecular sieve molding catalyst of claim 10 as a methanol-to-olefins catalyst.

12. A method for producing olefins from methanol, characterized in that, The SAPO-34 molecular sieve molding catalyst as described in claim 10 is used as the catalyst.

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