Method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve and application of metal-modified MeSAPO-34 molecular sieve
By directly introducing metals into the SAPO-34 molecular sieve framework through a solvent-free in situ synthesis method, the safety and efficiency issues of the traditional hydrothermal synthesis method were solved, and efficient metal-modified MeSAPO-34 molecular sieves were obtained for the methanol to olefins reaction, thereby improving the activity and selectivity of the catalyst.
Patent Information
- Application Number
- CN202510809782.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-17
- Publication Date
- 2025-09-09
AI Technical Summary
Traditional hydrothermal synthesis of SAPO-34 molecular sieves has problems such as low template utilization, high synthesis cost, great safety hazards, insufficient catalyst activity and selectivity, and the metal introduction method is cumbersome and inefficient.
A solvent-free in-situ synthesis method is adopted to mix silicon source, phosphorus source, aluminum source and metal salt powder and then crystallize them in a high-pressure reactor, avoiding the use of water as a solvent. The metal is directly introduced into the molecular sieve framework to form a uniformly distributed metal-modified MeSAPO-34 molecular sieve.
A simple and green synthesis of metal-modified MeSAPO-34 molecular sieve was achieved, and the catalytic performance and life of the catalyst were improved, especially in the methanol to olefins reaction, which showed excellent ethylene and propylene yields.
Smart Images
Figure CN120607262A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of molecular sieve preparation, and in particular relates to a method and application of solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve. Background Art
[0002] Silicate phosphate aluminum molecular sieve (SAPO-n) developed by Union Carbide Corporation (UCC) is composed of three [SiO4 4- ],[PO4 + ],[AlO4 - Among the SAPO series, SAPO-34 has garnered widespread attention. Its structure, similar to chabazite, consists of three-dimensional, intersecting pores (0.38 nm × 0.38 nm) of intersecting octahedral rings and a large CHA cage (1.27 nm × 0.94 nm). It exhibits excellent hydrothermal and thermal stability, a high-temperature-resistant framework, and moderate acid strength, demonstrating excellent catalytic performance, particularly in the methanol-to-olefins (MTO) reaction.
[0003] Traditional hydrothermal synthesis of SAPO-34 molecular sieves faces several key challenges in practical applications, including low template utilization, high synthesis costs, excessive autogenous pressure in the reactor due to high-temperature heating, and low selectivity for light olefins, short catalytic life, and rapid deactivation of the catalyst in the MTO reaction. Compared to hydrothermal synthesis, the solvent-free synthesis method offers higher reaction efficiency and yield, is safe and simple to operate, and is an environmentally friendly synthesis method.
[0004] Although SAPO-34 performs well in the MTO reaction, traditional SAPO-34 zeolites have disadvantages such as uneven acid strength distribution, increased side reactions, rapid carbon deposition rate, short catalyst life, and difficulty in controlling the ethylene / propylene ratio. The introduction of metal elements can adjust the zeolite's acid strength and acid distribution, as well as the physicochemical properties such as the skeleton structure, promote the conversion of intermediate products, improve diffusion performance, regulate product distribution, and delay the catalyst's deactivation due to carbon deposition.
[0005] The most common methods for introducing metals into molecular sieves are hydrothermal and post-treatment methods. Although they can successfully introduce metals into the molecular sieve framework, they also have many drawbacks. The hydrothermal method uses a large amount of water as a solvent, which not only produces a large amount of wastewater and causes environmental pollution, but also the reactor is heated at high temperatures, resulting in excessive autogenous pressure, which can easily pose a safety hazard. The post-treatment method is cumbersome to operate, and when preparing mesoporous molecular sieves, the surface hydroxyl groups of the molecular sieve are reduced after high-temperature calcination, resulting in a relatively small amount of introduced metal, and most of it is concentrated on the surface of the matrix, resulting in low synthesis efficiency. In this patent, a solvent-free method is used to synthesize metal-modified MeSAPO-34 molecular sieves (Me is one of the metals Co, Ni, Mo, Fe, and Cu), and it is applied to the methanol to olefin reaction, avoiding the safety and pollution problems caused by the hydrothermal method. At the same time, a metal-modified MeSAPO-34 molecular sieve with well-dispersed active components is obtained, thereby improving the catalytic performance of the catalyst. Summary of the Invention
[0006] In view of the above-mentioned shortcomings of preparing molecular sieve catalysts in an aqueous environment, the purpose of the present invention is to provide a simple, anhydrous, and green method for in situ synthesis of metal-modified MeSAPO-34 molecular sieve catalysts and use them in the methanol to olefins reaction.
[0007] In order to achieve the above objectives, the present invention adopts the following technical solutions.
[0008] A method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieves comprises the following steps: Step 1: Grind and mix the silicon source, phosphorus source and aluminum source evenly; Step 2: Add the template and metal salt powder to the above mixture, grind and mix them evenly to obtain a precursor mixture; Step 3: The precursor mixture is placed in a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven for crystallization; Step 4: Wash, dry and calcine the crystallized solid product to obtain the solvent-free in-situ synthesized metal-modified MeSAPO-34 molecular sieve.
[0009] Furthermore, in step 1, the silicon source is one or a combination of tetraethyl orthosilicate (TEOS), propyl orthosilicate, white carbon black and acidic silica sol.
[0010] Furthermore, in step 1, the phosphorus source is one or a combination of phosphoric acid, ammonium dihydrogen phosphate, and polyphosphoric acid.
[0011] Furthermore, in step 1, the aluminum source is one or a combination of pseudo-boehmite, aluminum isopropoxide or aluminum isobutoxide.
[0012] Furthermore, in step 2, the template agent is one or a combination of morpholine (MOR), tetraethylammonium hydroxide (TEAOH), tetraethylammonium bromide (TEABr), and triethylamine (TEA).
[0013] Furthermore, in step 2, the metal salt is one of cobalt nitrate hexahydrate, nickel nitrate nonahydrate, ammonium molybdate, iron acetylacetonate and copper sulfate, and the mass fraction of metal Me is 0.1% to 5.0%.
[0014] Furthermore, in steps 1 and 2, the ratio of the silicon source, aluminum source, phosphorus source and template contained in the mixture is 0.3~1.5:1:0.2~2:1~10, wherein the aluminum source, phosphorus source and silicon source are calculated as Al2O3, P2O5 and SiO2, respectively.
[0015] Furthermore, in step 3, the crystallization temperature is 50-300° C., and the crystallization time is 5-50 h.
[0016] Furthermore, in step 4, the molecular sieve is calcined at a temperature of 500-700°C and a calcination time of 2-30 h.
[0017] Compared with the prior art, the present invention has the following beneficial effects.
[0018] The present invention provides a simple, anhydrous, and green method for synthesizing a metal-modified MeSAPO-34 molecular sieve catalyst. Compared to aqueous environments, the present invention employs a solvent-free method to add a metal precursor salt during the synthesis process. The metal precursor salt is thoroughly mixed with the molecular sieve synthesis raw materials through solid-state grinding. The molecular sieve raw materials naturally encapsulate the metal precursor during crystallization, preventing the agglomeration of metal components on the molecular sieve surface. This results in a well-dispersed molecular sieve confined metal catalyst. This facilitates the use of metal Me to regulate the physicochemical properties of the SAPO-34 molecular sieve, such as acid strength and acid distribution, as well as the skeleton structure, to obtain a methanol-to-olefins reaction catalyst with excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 X-ray diffraction pattern of SAPO-34 molecular sieve synthesized in Example 1
[0020] Figure 2 This is a scanning electron microscope image of the SAPO-34 molecular sieve synthesized in Example 1
[0021] Figure 3 EDS element distribution diagram of SAPO-34 molecular sieve synthesized in Example 1
[0022] Figure 4 Nitrogen adsorption / desorption isotherms and BJH pore size distribution curves of SAPO-34 molecular sieve synthesized in Example 1
[0023] Figure 5 Example 1 Synthesis of Ammonia Temperature-Programmed Desorption Curve of SAPO-34 Molecular Sieve DETAILED DESCRIPTION
[0024] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is described in detail below with reference to the accompanying drawings, but it should not be understood as limiting the scope of implementation of the present invention.
[0025] A method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieves comprises the following steps: Step 1: Grind and mix the silicon source, phosphorus source and aluminum source evenly; Step 2: Add the template and metal salt powder to the above mixture, grind and mix them evenly to obtain a precursor mixture; Step 3: The precursor mixture is placed in a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven for crystallization; Step 4: Wash, dry and calcine the crystallized solid product to obtain the solvent-free in-situ synthesized metal-modified MeSAPO-34 molecular sieve.
[0026] Furthermore, in step 1, the silicon source is one or a combination of tetraethyl orthosilicate (TEOS), propyl orthosilicate, white carbon black and acidic silica sol.
[0027] Furthermore, in step 1, the phosphorus source is one or a combination of phosphoric acid, ammonium dihydrogen phosphate, and polyphosphoric acid.
[0028] Furthermore, in step 1, the aluminum source is one or a combination of pseudo-boehmite, aluminum isopropoxide or aluminum isobutoxide.
[0029] Furthermore, in step 2, the template agent is one or a combination of morpholine (MOR), tetraethylammonium hydroxide (TEAOH), tetraethylammonium bromide (TEABr), and triethylamine (TEA).
[0030] Furthermore, in step 2, the metal salt is one of cobalt nitrate hexahydrate, nickel nitrate nonahydrate, ammonium molybdate, iron acetylacetonate and copper sulfate, and the mass fraction of metal Me is 0.1% to 5.0%.
[0031] Furthermore, in steps 1 and 2, the ratio of the silicon source, aluminum source, phosphorus source and template contained in the mixture is 0.3~1.5:1:0.2~2:1~10, wherein the aluminum source, phosphorus source and silicon source are calculated as Al2O3, P2O5 and SiO2, respectively.
[0032] Furthermore, in step 3, the crystallization temperature is 50-300° C., and the crystallization time is 5-50 h.
[0033] Furthermore, in step 4, the molecular sieve is calcined at a temperature of 500-700°C and a calcination time of 2-30 h.
[0034] Example 1 CoSAPO-34
[0035] 6.88 g of acidic silica sol, 8 g of pseudo-boehmite, and 6.52 g of ammonium dihydrogen phosphate were mixed and ground until uniform. 12.27 g of MOR and 8.10 g of TEAOH composite template were added dropwise. Cobalt nitrate hexahydrate solid powder (0.3% by mass) was added and further ground to obtain a precursor mixture. The precursor mixture was placed in a polytetrafluoroethylene-lined autoclave and crystallized in an oven at 200°C for 24 h. The solid product was then washed with deionized water to a pH of 7, dried in an oven at 80°C for 12 h, and calcined at 600°C (heating rate 3°C / min) for 5 h to obtain CoSAPO-34 molecular sieve.
[0036] Example 2 NiSAPO-34
[0037] The specific steps and synthesis conditions are similar to those in Example 1, except that the cobalt nitrate hexahydrate added in Example 1 is replaced by nickel nitrate nonahydrate, wherein the amount of metallic Ni added is 0.3% (mass fraction). The remaining components and synthesis conditions are the same as those in Example 1, and NiSAPO-34 molecular sieve is obtained.
[0038] Example 3 MoSAPO-34
[0039] The specific steps and synthesis conditions are similar to those in Example 1, except that the cobalt nitrate hexahydrate added in Example 1 is replaced by ammonium molybdate, wherein the amount of metal Mo added is 0.3% (mass fraction). The remaining components and synthesis conditions are the same as those in Example 1, and MoSAPO-34 molecular sieve is obtained.
[0040] Example 4 FeSAPO-34
[0041] The specific steps and synthesis conditions are similar to those in Example 1, except that the cobalt nitrate hexahydrate added in Example 1 is replaced by ferric acetylacetonate, wherein the amount of metallic Fe added is 1% (mass fraction). The remaining components and synthesis conditions are the same as those in Example 1, and FeSAPO-34 molecular sieve is obtained.
[0042] Example 5 CuSAPO-34
[0043] The specific steps and synthesis conditions are similar to those in Example 1, except that the cobalt nitrate hexahydrate added in Example 1 is replaced with copper sulfate, wherein the mass fraction of metallic Cu is 1%. The remaining components and synthesis conditions are the same as those in Example 1, to obtain CuSAPO-34 molecular sieve.
[0044] Comparative Example 1 SSAPO-34
[0045] Using a traditional hydrothermal synthesis method, pseudo-boehmite and deionized water were mixed uniformly under magnetic stirring. Phosphoric acid, triethylamine, and silica sol were added sequentially at hourly intervals while stirring to form a uniform silicoaluminophosphate solution. The initial gel composition was Al2O3:P2O5:SiO2:TEA:H2O = 1:1:0.4:3:100. The resulting mixed gel was transferred to a stainless steel high-pressure hydrothermal reactor lined with polytetrafluoroethylene and crystallized at 200°C for 24 hours. The SSAPO-34 molecular sieve was then filtered, washed, dried, and calcined to obtain the resulting product.
[0046] Comparative Example 2 GSAPO-34
[0047] SAPO-34 was synthesized using a solvent-free method. 6.88 g of acidic silica sol, 8 g of pseudo-boehmite, and 6.52 g of ammonium dihydrogen phosphate were mixed and ground evenly. A template consisting of 12.28 g of MOR and 8.10 g of TEAOH was added dropwise and further ground to obtain a precursor mixture. The precursor mixture was placed in an autoclave and crystallized at 200°C for 24 h. The GSAPO-34 molecular sieve was then washed, dried, and calcined to obtain the resulting product.
[0048] Comparative Examples 3-5
[0049] The sample GSAPO-34 molecular sieve of Comparative Example 2 was used as a carrier, and cobalt nitrate hexahydrate solution, nickel nitrate nonahydrate solution and ammonium molybdate solution were used as metal precursors, respectively. Metal Co, Ni or Mo with a mass fraction of 0.3% was loaded onto the GSAPO-34 molecular sieve by equal volume impregnation. The samples were allowed to stand at room temperature for 12 h, dried at 80 ° C for 6 h, and calcined at 550 ° C for 5 h. The GSAPO-34 molecular sieve samples modified with metal Co, Ni or Mo were named Co / SAPO-34, Ni / SAPO-34 and Mo / SAPO-34, respectively.
[0050] Comparative Examples 6-7
[0051] The GSAPO-34 molecular sieve sample of Comparative Example 2 was used as a carrier, and ferric sulfate solution and copper sulfate solution were used as metal precursors, respectively. Metal Fe or Cu with a mass fraction of 1% was loaded onto the GSAPO-34 molecular sieve by equal volume impregnation. The samples were allowed to stand at room temperature for 12 h, dried at 80 °C for 6 h, and calcined at 550 °C for 5 h. The molecular sieve samples modified with metal Fe or Cu were named Fe / SAPO-34 and Cu / SAPO-34, respectively.
[0052] Activity Evaluation: The metal-modified MeSAPO-34 molecular sieve synthesized by the solvent-free method in the example, the SAPO-34 molecular sieve synthesized by the hydrothermal synthesis method and the solvent-free method in the comparative example, and the metal-modified Me / SAPO-34 catalyst after medium-volume impregnation in the comparative example were pressed into 20-40 mesh tablets and loaded into reaction tubes with an inner diameter of 6 mm. The tablets were activated at 500°C under a 30 mL / min N2 atmosphere for 1 h.
[0053] The MTO reaction performance of the SAPO-34 catalysts prepared in the examples and comparative examples was evaluated using methanol as the raw material. The evaluation conditions were: a volume space velocity of 1.0 h -1 , the reaction temperature was 420°C, and the evaluation results are shown in Table 1.
[0054] Table 1 Evaluation results of MTO reaction performance on different SAPO-34 molecular sieves molecular sieves Conversion rate (%) Ethylene yield (%) Propylene yield (%) Diene yield (%) Lifespan (min) CoSAPO-34 99.9 47.0 41.3 88.3 420 NiSAPO-34 99.6 44.5 40.2 84.7 360 MoSAPO-34 99.5 44.9 39.6 84.5 360 FeSAPO-34 99.7 44.5 40.7 85.2 380 CuSAPO-34 99.5 44.7 38.8 83.5 380 SSAPO-34 99.2 41.3 37.4 78.7 260 GSAPO-34 99.3 43.3 38.4 81.7 320 Co / SAPO-34 99.5 43.5 39.6 83.1 350 Ni / SAPO-34 99.4 42.4 39.8 82.2 320 Mo / SAPO-34 99.3 42.8 38.9 81.7 320 Fe / SAPO-34 99.3 44.8 37.9 82.7 360 Cu / SAPO-34 99.3 43.7 38.5 82.2 320
[0055] The results in the table demonstrate that the solvent-free, in-situ synthesis of metal-modified MeSAPO-34 molecular sieves in Examples 1-5 exhibits excellent catalytic performance in methanol-to-olefins. Methanol conversion approaches 100%, diene yields reach as high as 88.3%, and catalyst life reaches up to 420 minutes. These examples demonstrate that metal-modified MeSAPO-34 molecular sieve catalysts can be prepared simply and with excellent catalytic performance using a solvent-free method.
[0056] The comparative experimental data show that the catalytic life of the SSAPO-34 molecular sieve synthesized by conventional hydrothermal method without metal modification and the GSAPO-34 molecular sieve synthesized by solvent-free method is short, and the diene yield is significantly lower than that of the metal-modified MeSAPO-34 molecular sieve catalyst. The catalytic performance of the Me / SAPO-34 catalyst synthesized by first synthesizing the GSAPO-34 molecular sieve by solvent-free method and then introducing the metal Me by equal volume impregnation is inferior to that of the metal-modified MeSAPO-34 molecular sieve synthesized directly by solvent-free in situ synthesis is inferior. The reason is that the active metal of the Me / SAPO-34 catalyst obtained by impregnation method is often distributed on the surface of the molecular sieve. After high-temperature calcination, the metal easily agglomerates and has poor dispersion, thereby affecting its catalytic performance.
[0057] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieves, characterized in that: The following steps are involved: Step 1: Grind and mix the silicon source, phosphorus source and aluminum source until uniform; Step 2: Add the template and metal salt powder to the above mixture, grind and mix them evenly to obtain a precursor mixture; Step 3: The precursor mixture is placed in a high-pressure reactor lined with polytetrafluoroethylene and placed in an oven for crystallization; Step 4: Wash, dry and calcine the crystallized solid product to obtain the solvent-free in-situ synthesized metal-modified MeSAPO-34 molecular sieve.
2. The method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve according to claim 1, characterized in that: In step 1, the silicon source is one or a combination of tetraethyl orthosilicate (TEOS), propyl orthosilicate, white carbon black and acidic silica sol.
3. The method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve according to claim 1, characterized in that: In step 1, the phosphorus source is one or a combination of phosphoric acid, ammonium dihydrogen phosphate, and polyphosphoric acid.
4. The method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve according to claim 1, characterized in that: In the step 1, the aluminum source is one or a combination of pseudo-boehmite, aluminum isopropoxide, aluminum isobutoxide, etc.
5. The method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve according to claim 1, characterized in that: In step 2, the template agent is one or a combination of morpholine (MOR), tetraethylammonium hydroxide (TEAOH), tetraethylammonium bromide (TEABr), and triethylamine (TEA).
6. The method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve according to claim 1, characterized in that: In the step 2, the metal salt is one of cobalt nitrate hexahydrate, nickel nitrate nonahydrate, ammonium molybdate, ferric acetylacetonate and copper sulfate, and the mass fraction of metal Me is 0.1% to 5.0%.
7. The method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve according to claim 1, characterized in that: In steps 1 and 2, the ratio of the silicon source, aluminum source, phosphorus source and template contained in the mixture is 0.3-1.5:1:0.2-2:1-10, wherein the aluminum source, phosphorus source and silicon source are calculated as Al2O3, P2O5 and SiO2 respectively.
8. The method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve according to claim 1, characterized in that: In step 3, the crystallization temperature is 50-300° C., and the crystallization time is 5-50 h.
9. The method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieve according to claim 1, characterized in that: In step 4, the molecular sieve is calcined at a temperature of 500-700° C. and for a time of 2-30 h.
10. Use of the method for solvent-free in-situ synthesis of metal-modified MeSAPO-34 molecular sieves according to any one of claims 1 to 9 in preparing MeSAPO-34 molecular sieves, characterized in that: The MeSAPO-34 molecular sieve is applied to the methanol to olefins reaction.