CN112939014A - Method for synthesizing low-silicon ZSM-5 molecular sieve without template agent - Google Patents

Method for synthesizing low-silicon ZSM-5 molecular sieve without template agent Download PDF

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CN112939014A
CN112939014A CN202110283379.1A CN202110283379A CN112939014A CN 112939014 A CN112939014 A CN 112939014A CN 202110283379 A CN202110283379 A CN 202110283379A CN 112939014 A CN112939014 A CN 112939014A
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zeolite
mixture
zsm
template
silicon
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李牛
余永民
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Nankai University
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Nankai University
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
    • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
    • C01B39/36—Pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
    • C01B39/38—Type ZSM-5

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Abstract

The invention relates to a method for synthesizing low-silicon ZSM-5 without a template, which specifically comprises the steps of using high-activity ultrafine-particle silicic acid as a silicon source, using pseudo-boehmite, sodium metaaluminate and the like as an aluminum source, selecting a proper treatment mode, and synthesizing low-silicon ZSM-5 zeolite without the template in a hydrothermal environment at 170-190 ℃. The silicon source used needs to be milled to obtain particles with a small particle size, and the aluminum source needs to be easily dissolved. The method adopted by the invention uses high-activity silicic acid, has rich structural hydroxyl, is favorable for condensation with aluminum, does not need a template agent, does not cause pollution to the environment, is simple and convenient to operate, has low cost and wide application prospect.

Description

Method for synthesizing low-silicon ZSM-5 molecular sieve without template agent
Technical Field
The invention relates to a method for synthesizing a low-silicon ZSM-5 molecular sieve without a template, which specifically comprises the steps of using high-activity silicic acid containing abundant structural hydroxyl groups as a silicon source, using pseudo-boehmite, sodium metaaluminate and the like as an aluminum source, and synthesizing the low-silicon ZSM-5 molecular sieve without the template under certain treatment conditions and in a hydrothermal environment at 170-190 ℃.
Background
ZSM-5 is a zeolite with a unique structure, has three-dimensional crossed channels and ten-membered ring pore structures, and has good framework thermal stability, hydrothermal stability and acidity due to the special structure. ZSM-5 molecular sieve is widely applied to shape-selective catalysis in chemical industry. In recent years, the demand for low-silicon ZSM-5 is increasing, and the low-silicon ZSM-5 can be widely applied to the fields of aerospace material synthesis, radioactive material adsorption and the like. In general, the low-silicon ZSM-5 synthesis needs a large amount of organic template agent, but the cost is increased and the environmental pollution is also hidden. At present, the silica-alumina ratio of ZSM-5 synthesized by a template-free method can only reach about 27 at least, and if the silica-alumina ratio is required to be reduced continuously, further improvement needs to be carried out on the basis of the prior method.
The use of silica sols with smaller particle sizes has been found to be more advantageous for the synthesis of ZSM-5 zeolite, as the silicon source in the silica sol system has been investigated in Dai, f.y., deguchi.k., Suzuki, m., Takahashi, h., and Saito, y.chem.lett.1988, 86S;
the document shirakar V P, Clearfield a. zeolites, 1989, 9: 363 in 1989 systematically studied the collocation of silica sol and pseudo-boehmite, synthesizing ZSM-5 zeolite without template under different crystallization conditions, to obtain the conclusion that the synthesis range of ZSM-5 without template is much narrower than that under the condition with template, but the crystallization conditions and the treatment of the gel at the early stage are fixed, so that this range can be further expanded by some operations;
documents Kim S D, Noh S H, Seong K H, Kim W j. microporus mesoporus Mater, 2004, 72: 185 have been kinetically driven into the synthesis of template-free ZSM-5 using silica sol and NaAlO2ZSM-5 zeolite is synthesized under different silica-alumina ratios. And obtaining Na+Has structure-oriented effect on the generation of ZSM-5 in the template-free synthesis process, so when the silicon-aluminum ratio in the mother liquor is reduced, Na in the mother liquor can be adjusted2The content of 0 is used for promoting the synthesis of ZSM-5, which provides a theoretical basis for the template-free synthesis of the low-silicon ZSM-5;
in summary, it is considered that a silicon source with a small particle size and high activity is used, and the synthesis of the ZSM-5 zeolite with a low silica-alumina ratio is possible under the condition of low alkali-silica ratio by adopting a proper mode and without a template agent.
Disclosure of Invention
The invention discloses a method for synthesizing a low-silicon ZSM-5 molecular sieve without a template, which is characterized in that silicic acid containing rich structural hydroxyl, high activity and ultrafine particles is used as a silicon source to synthesize the low-silicon ZSM-5 zeolite without an organic template. The silicic acid used has abundant structural hydroxyl groups, and can effectively promote the condensation between silicon and aluminum in the synthesis process to form a zeolite structure. Simple process, no need of template agent, low cost and good application prospect.
The synthesis method of the template-free low-silicon ZSM-5 provided by the invention comprises the following steps:
1) mixing superfine particle silicic acid, water and part of NaOH, and stirring uniformly in a water bath at room temperature or 60 ℃ to obtain a mixture A; mixing an aluminum source with the other part of sodium hydroxide and water to obtain a uniform mixture B in a water bath at room temperature or 60 ℃, adding the mixture B into the mixture A, adding a proper amount of seed crystal (or not), and stirring for 0.5-24 hours at room temperature to form a uniform mixture;
2) and transferring the obtained mixture into a stainless steel kettle with a polytetrafluoroethylene lining, carrying out hydrothermal crystallization for 1-5 days at 170-190 ℃ under autogenous pressure, taking out, naturally cooling to room temperature, washing the obtained product to be neutral by using distilled water, separating and drying to finally obtain the target product.
Wherein the silicon source is SiO2Calculated by Al as the aluminum source2O3Calculated as Na, sodium hydroxide2Calculated by O, the molar ratio of the mixture is Na2O∶Al2O3∶SiO2∶H2O＝1～4∶1～1.2∶25～35∶500～2000；
The silicon source is high-activity ultrafine particle silicic acid;
the aluminum source is pseudo-boehmite and sodium metaaluminate;
the sodium hydroxide is a solution of 6.000-6.500 mol/L;
the crystallization conditions are 170-190 ℃ for 1-5 days.
The invention is characterized in that: the method does not use an organic template agent, uses high-activity silicic acid containing rich structural hydroxyl as a silicon source, can well condense with an aluminum source to generate a zeolite structure, and the product is ZSM-5 zeolite, wherein the silicon-aluminum ratio of the ZSM-5 zeolite is less than 25.
The invention is further described with reference to the following figures and examples.
Drawings
FIG. 1 is a powder X-ray diffraction pattern (XRD) of a low silicon ZSM-5 zeolite product of the invention.
Fig. 2 is an optical microscope picture of the product.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
The experimental methods in the examples, in which specific conditions are not specified, are generally performed under the conditions described in the manual and the conventional conditions, or under the conditions recommended by the manufacturer; the equipment, materials, reagents and the like used are commercially available unless otherwise specified.
Examples 1
2.730g of high-activity silicic acid is added into 10.00ml of distilled water, 0.30ml of 6.235mol/L sodium hydroxide solution is added, and the mixture is fully stirred in a water bath at the temperature of 60 ℃ to obtain turbid liquid A; dissolving 0.055g of aluminum foil (99 wt.%) in 6.235 mol/L0.66 ml of sodium hydroxide solution, adding 10.26ml of distilled water after the reaction is completed, and obtaining solution B; the solution B was poured into the turbid solution A and seeded with 0.05g of ZSM-5 zeolite and stirred for a further 1 hour to form a homogeneous mixture. Then, the mixture is transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining and is placed in a constant temperature oven at 170 ℃ for standing and crystallization for 24 hours. And finally, taking out the reaction kettle, rapidly cooling to room temperature by using cold water, taking out the product, washing to be neutral, separating, and drying (at the temperature of 60-80 ℃) to finally obtain the solid ZSM-5 zeolite product.
The solid product was analyzed by X-ray analysis to be ZSM-5 zeolite, as shown in figure 1, which is a powder X-ray diffraction pattern (XRD) of the product ZSM-5 zeolite of the present invention.
EXAMPLES example 2
2.459g of high-activity silicic acid is added into 2.00ml of distilled water and fully stirred at room temperature to obtain turbid liquid A; 0.137g of 74.25 percent pseudo-boehmite is dissolved in 1.28ml of sodium hydroxide solution with the concentration of 6.235mol/L, and 5.72ml of distilled water is added after the reaction is completed, so that the solution is called as solution B; the solution B was poured into the turbid solution A and stirring was continued for 1 hour to form a homogeneous mixture. Then, the mixture is transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining and is placed in a constant temperature oven at 190 ℃ for standing and crystallization for 72 hours. And finally, taking out the reaction kettle, rapidly cooling to room temperature by using cold water, taking out the product, washing to be neutral, separating, and drying (at the temperature of 60-80 ℃) to finally obtain the solid ZSM-5 zeolite product.
EXAMPLE 3
Mixing 1.963g of high-activity silicic acid with 10.00ml of distilled water, and stirring in a water bath at 60 ℃ for about 1 hour to obtain a uniform mixture A; 0.204g of 80 wt% NaAlO210.52ml of distilled water was added and stirred until a clear solution B was obtained. And pouring the solution B into the solution A, adding 0.08g of ZSM-5 seed crystal, mixing and aging for 0.5-24 hours to form a uniform mixture. Then, the mixture is transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining and is placed in a constant-temperature oven at 185 ℃ for standing and crystallizing for 34 hours. And finally, taking out the reaction kettle, rapidly cooling to room temperature by using cold water, taking out the product, washing to be neutral, separating, and drying (at the temperature of 60-80 ℃) to finally obtain the solid ZSM-5 zeolite product.
EXAMPLE 4
2.184g of high-activity silicic acid is added into 8.00ml of distilled water and fully stirred at room temperature to obtain turbid liquid A; dissolving 0.055g of aluminum foil (99 wt.%) in 0.73ml of sodium hydroxide solution with the concentration of 6.235mol/L, and adding 11.00ml of distilled water after the reaction is completed, so as to obtain solution B; the solution B was poured into the turbid solution A and stirring was continued for 1 hour to form a homogeneous mixture. Then, the mixture is transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining and is placed in a constant temperature oven at 173 ℃ for standing and crystallization for 120 hours. And finally, taking out the reaction kettle, rapidly cooling to room temperature by using cold water, taking out the product, washing to be neutral, separating, and drying (at the temperature of 60-80 ℃) to finally obtain the solid ZSM-5 zeolite product.
EXAMPLE 5
2.256g of high-activity silicic acid is mixed with 8.00ml of distilled water, 0.50ml of 6.209mol/L sodium hydroxide solution is added, and the mixture is stirred in a water bath at the temperature of 60 ℃ for 1 hour to form turbid liquid A; 0.137g of 74.25% pseudo-boehmite, 0.78ml of 6.209mol/L sodium hydroxide and 12.00ml of distilled water were mixed and stirred in a water bath at 60 ℃ for about 1 hour to form a solution B. Slowly adding the solution B into the solution A, and continuing stirring and aging for 3 hours. Transferring the mixture into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and standing and crystallizing for 40 hours in a constant-temperature oven at 176 ℃. And (3) taking out the reaction kettle, rapidly cooling to room temperature by using cold water, taking out the product, washing to be neutral, separating, drying (at the temperature of 60-80 ℃) and finally obtaining a solid ZSM-5 zeolite product.
EXAMPLE 6
Adding 2.086g of high-activity silicic acid into 10.00ml of distilled water, and heating the mixture in a water bath at 60 ℃ for 1 hour to obtain turbid liquid A; dissolving 0.055g of aluminum foil (99 wt.%) in 0.92ml of sodium hydroxide solution with the concentration of 6.235mol/L, and adding 10.00ml of distilled water after the reaction is completed, so as to obtain solution B; solution B was poured into solution A and stirring was continued for 1 hour to form a homogeneous mixture. Then, the mixture is transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining and is placed in a constant temperature oven at 175 ℃ for standing and crystallization for 48 hours. And finally, taking out the reaction kettle, rapidly cooling to room temperature by using cold water, taking out the product, washing to be neutral, separating, and drying (at the temperature of 60-80 ℃) to finally obtain the solid ZSM-5 zeolite product.
EXAMPLES example 7
2.383g of high-activity silicic acid is mixed with 5.00ml of distilled water, 1.00ml of 6.209mol/L sodium hydroxide solution is added, and the mixture is stirred in a water bath at the temperature of 60 ℃ for 1 hour to form turbid liquid A; 0.204g of 80 wt% NaAlO210.52ml of distilled water was added and stirred until a clear solution B was obtained. Slowly adding the solution B into the solution A, and continuing stirring and aging for 3 hours. Transferring the mixture into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and standing and crystallizing for 42 hours in a constant-temperature oven at 183 ℃. And (3) taking out the reaction kettle, rapidly cooling to room temperature by using cold water, taking out the product, washing to be neutral, separating, drying (at the temperature of 60-80 ℃) and finally obtaining a solid ZSM-5 zeolite product.

Claims (10)

1. A method for synthesizing low-silicon ZSM-5 zeolite without a template agent is characterized by comprising the following steps:
1) mixing high-activity silicic acid, water and part of NaOH, and uniformly stirring in a water bath at room temperature or 60 ℃ to obtain a mixture A; and mixing an aluminum source, sodium hydroxide and water, obtaining a uniform mixture B in a water bath at room temperature or 60 ℃, adding the mixture B into the mixture A, adding a proper amount of seed crystals or not adding the seed crystals, and stirring for 0.5-24 hours at room temperature to form a uniform mixture.
2) And transferring the obtained mixture into a stainless steel kettle with a polytetrafluoroethylene lining, carrying out hydrothermal crystallization for 1-5 days at 170-190 ℃ under autogenous pressure, taking out, naturally cooling to room temperature, washing the obtained product to be neutral by using distilled water, separating and drying to finally obtain the target product.
2. The mixture according to claim 1, wherein the molar ratio is in the range of Na2O∶Al2O3∶SiO2∶H2O＝1～4∶1～1.2∶25～35∶500～2000。
3. The template-free process for synthesizing a low-silicon ZSM-5 zeolite as claimed in claim 1 wherein the silicon source is a high activity, ultra-fine particulate silicic acid.
4. The template-free synthesis process of a low silicon ZSM-5 zeolite as claimed in claim 1, wherein the aluminum source is pseudoboehmite, sodium metaaluminate, etc.
5. The template-free method for synthesizing the low-silicon ZSM-5 zeolite according to claim 1, wherein the sodium hydroxide is a sodium hydroxide solution of 6.000 to 6.500 mol/L.
6. The template-free method for synthesizing the low-silicon ZSM-5 zeolite according to claim 1, wherein the drying temperature is 60 to 80 ℃.
7. A method for synthesizing low-silicon ZSM-5 zeolite without a template agent comprises the following actual steps: 2.730g of highly active silicic acid was added to 10.00ml of distilled water, and 0.30ml of 6.235mol/L sodium hydroxide solution was added thereto, and the mixture was stirred well in a water bath at 60 ℃ to obtain a suspension A.
8. A method for synthesizing low-silicon ZSM-5 zeolite without a template agent comprises the following practical steps: 0.055g of aluminum foil (99 wt.%) was dissolved in 6.235 mol/L0.66 ml of NaOH solution, and 10.26ml of distilled water was added after the reaction was completed, which was called solution B.
9. A method for synthesizing low-silicon ZSM-5 zeolite without a template agent comprises the following practical steps: the solution B was poured into the turbid solution A and seeded with 0.05g of ZSM-5 zeolite and stirred for a further 1 hour to form a homogeneous mixture.
10. A method for synthesizing low-silicon ZSM-5 zeolite without a template agent comprises the following practical steps: transferring the mixture into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and standing and crystallizing for 24 hours in a constant-temperature oven at 170 ℃.
CN202110283379.1A 2021-03-17 2021-03-17 Method for synthesizing low-silicon ZSM-5 molecular sieve without template agent Pending CN112939014A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5256391A (en) * 1992-09-11 1993-10-26 Mobil Oil Corporation Method for synthesizing microporous crystalline material
US6099820A (en) * 1999-08-17 2000-08-08 Chevron U.S.A. Inc. Method for making MTT zeolites without an organic template
CN110790283A (en) * 2019-12-10 2020-02-14 天津神能科技有限公司 Synthesis method of mordenite with high silicon-aluminum ratio
CN111547739A (en) * 2020-05-13 2020-08-18 西安交通大学 Preparation method of ZSM-5 zeolite molecular sieve with low silica-alumina ratio
CN112158857A (en) * 2020-09-30 2021-01-01 中汽研（天津）汽车工程研究院有限公司 CHA-OFF-ERI intergrowth structure molecular sieve, preparation method thereof, catalyst thereof and application of catalyst

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5256391A (en) * 1992-09-11 1993-10-26 Mobil Oil Corporation Method for synthesizing microporous crystalline material
US6099820A (en) * 1999-08-17 2000-08-08 Chevron U.S.A. Inc. Method for making MTT zeolites without an organic template
CN110790283A (en) * 2019-12-10 2020-02-14 天津神能科技有限公司 Synthesis method of mordenite with high silicon-aluminum ratio
CN111547739A (en) * 2020-05-13 2020-08-18 西安交通大学 Preparation method of ZSM-5 zeolite molecular sieve with low silica-alumina ratio
CN112158857A (en) * 2020-09-30 2021-01-01 中汽研（天津）汽车工程研究院有限公司 CHA-OFF-ERI intergrowth structure molecular sieve, preparation method thereof, catalyst thereof and application of catalyst

Non-Patent Citations (2)

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Title
KIM S D， ET AL.: "Compositional and kinetic study on the rapid crystallization of ZSM-5 in the absence of organic template under stirring", 《MICROPOROUS MESOPOROUS MATER》 *
裴东寒等: "无模板剂法合成ZSM-5分子筛的研究进展", 《应用化工》 *

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Application publication date: 20210611