Synthetic molecular sieve and preparation method thereof

Abstract

The synthetic molecular sieve comprises 40-60 parts of a silicon source, 15-25 parts of an aluminum source, 5-10 parts of a sodium source, 10-20 parts of water glass, 0.1-2 parts of a catalyst, 5-15 parts of a template agent and 30-70 parts of deionized water, the silicon source is silicic acid or silica gel, the aluminum source is aluminum hydroxide or aluminum salt, the sodium source is sodium hydroxide or sodium nitrate, and the water glass is a sodium silicate solution. The catalyst is sodium hydroxide or potassium hydroxide, the template agent is hexadecyl trimethyl ammonium bromide, the synthesized molecular sieve has high purity and good crystallinity by accurately controlling the raw material ratio and optimizing the preparation conditions, and the high purity means that the impurity content in the molecular sieve is low, so that the interference of impurities on the performance of the molecular sieve can be effectively avoided; the molecular sieve prepared by the method has high selectivity and efficiency in applications such as adsorption and separation, good crystallinity ensures that the molecular sieve has a regular microporous structure and a large specific surface area, the large specific surface area provides more adsorption sites, and the adsorption performance of the molecular sieve is further enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieves, and in particular relates to a synthetic molecular sieve and a preparation method thereof. Background Art

[0002] As a material with uniform microporous structure, molecular sieve is widely used in many fields such as petrochemical industry, gas separation, environmental purification, etc. due to its unique screening performance, large specific surface area and good adsorption selectivity.

[0003] Currently, the preparation process of molecular sieves often has problems such as complex procedures, high energy consumption, unsatisfactory product purity and crystallinity, which limit the further improvement of the performance of molecular sieves and the economic benefits of large-scale industrial production. For example, some preparation methods have strict requirements on the ratio of raw materials, and slight deviations will lead to defects in the crystal structure of the molecular sieve; and some synthesis processes require long-term high temperature and high pressure, which increases equipment costs and operational risks, resulting in low production efficiency and increased production cycle and cost. Summary of the invention

[0004] The object of the present invention is to provide a synthetic molecular sieve and a preparation method thereof to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a synthetic molecular sieve, comprising, by weight:

[0006] 40-60 parts of silicon source, 15-25 parts of aluminum source, 5-10 parts of sodium source, 10-20 parts of water glass, 0.1-2 parts of catalyst, 5-15 parts of template, and 30-70 parts of deionized water.

[0007] Preferably, the composition comprises, by weight: 55 parts of the silicon source, 22 parts of the aluminum source, 8 parts of the sodium source, 15 parts of water glass, 1 part of the catalyst, 10 parts of the template, and 50 parts of deionized water.

[0008] Preferably, the silicon source is silicic acid or silica gel, which is used to provide the silicon element of the molecular sieve, the aluminum source is aluminum hydroxide or aluminum salt, which is used to provide the aluminum element of the molecular sieve, and the sodium source is sodium hydroxide or sodium nitrate, which is used to provide the sodium element of the molecular sieve.

[0009] Preferably, the water glass is a sodium silicate solution for adjusting the pore size and strength of the molecular sieve, the catalyst is sodium hydroxide or potassium hydroxide for accelerating the synthesis process of the molecular sieve, and the template agent is hexadecyltrimethylammonium bromide.

[0010] A method for preparing a synthetic molecular sieve comprises the following steps:

[0011] S1. Mix the silicon source, aluminum source, sodium source, water glass, catalyst, template and deionized water in proportion, add appropriate amount of deionized water, and stir evenly at room temperature until a uniform and transparent sol is formed;

[0012] S2, transferring the sol into a stainless steel reactor lined with polytetrafluoroethylene, sealing it and placing it in a constant temperature oven to perform a crystallization reaction to promote crystal nucleation and growth;

[0013] S3, after the crystallization is completed, the reactor is cooled naturally to room temperature, the product is taken out and centrifuged several times, and the separated finished product is then vacuum dried;

[0014] S4. Finally, the product is calcined in air atmosphere to burn off the template to obtain a synthetic molecular sieve product with a pure porous structure.

[0015] Preferably, in step S1, stirring is performed in a stirrer at a stirring speed of 300-500 rpm at room temperature for 2-4 hours until a uniform transparent sol is formed, ensuring that each component is fully dispersed, hydrolyzed and initially polymerized, and a pH meter is used to monitor in real time during the stirring process to maintain the stability of the pH value of the transparent sol.

[0016] Preferably, in step S2, crystallization is started at a crystallization temperature of 120-180° C. and the crystallization time is 12-36 hours, and the autogenous pressure in the reactor is maintained between 0.5-1.5 MPa during the crystallization to promote crystal nucleation and growth.

[0017] Preferably, in step S3, the crystallized product is centrifuged multiple times by a centrifuge, and the centrifugal speed of the centrifuge is 8000-10000 rpm, each centrifugation time is 10-15 minutes, and the crystallized product is washed with deionized water until the pH value of the washing liquid is 7, so as to remove residual alkali solution and unreacted raw materials in the crystallized product.

[0018] Preferably, in step S4, the crystallized product after centrifugation is dried in a vacuum drying oven at a drying temperature of 80-120° C. for a drying time of 6-12 hours.

[0019] Preferably, in step S4, after drying, the crystallized product is calcined in a tube furnace under air atmosphere, and the calcination temperature is 400-600° C., and the calcination time is 4-8 hours to burn off the template.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) By precisely controlling the raw material ratio and optimizing the preparation conditions, the synthesized molecular sieve has high purity and good crystallinity. High purity means that the impurity content in the molecular sieve is low, which can effectively avoid the interference of impurities on its performance, making it show higher selectivity and efficiency in applications such as adsorption and separation. Good crystallinity ensures that the molecular sieve has a regular microporous structure and a large specific surface area. The regular microporous structure enables the molecular sieve to accurately screen molecules of different sizes, and the large specific surface area provides more adsorption sites, further enhancing its adsorption performance.

[0022] (2) The waste generated during the preparation process is relatively small, mainly some washing liquid and waste gas. Through reasonable treatment measures, such as neutralization of the washing liquid and purification of the waste gas, the impact of the preparation of molecular sieves on the environment can be minimized.

[0023] (3) The preparation method abandons complex equipment and extreme process conditions, the reaction temperature is 30-50°C lower than the traditional one, the crystallization time is shortened by 8-12 hours, the energy consumption and equipment loss are reduced, and the raw material utilization rate is 85%, which reduces waste emissions, conforms to the concept of green chemical production, and the cost is lower than the conventional one, which is conducive to large-scale industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the preparation method of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides Figure 1 A synthetic molecular sieve shown, by weight, comprises:

[0027] 40-60 parts of silicon source, 15-25 parts of aluminum source, 5-10 parts of sodium source, 10-20 parts of water glass, 0.1-2 parts of catalyst, 5-15 parts of template, and 30-70 parts of deionized water.

[0028] The composition comprises, by weight: 55 parts of the silicon source, 22 parts of the aluminum source, 8 parts of the sodium source, 15 parts of water glass, 1 part of the catalyst, 10 parts of the template, and 50 parts of deionized water.

[0029] The silicon source is silicic acid or silica gel, which is used to provide the silicon element of the molecular sieve; the aluminum source is aluminum hydroxide or aluminum salt, which is used to provide the aluminum element of the molecular sieve; and the sodium source is sodium hydroxide or sodium nitrate, which is used to provide the sodium element of the molecular sieve.

[0030] The water glass is a sodium silicate solution, which is used to adjust the pore size and strength of the molecular sieve; the catalyst is sodium hydroxide or potassium hydroxide, which is used to accelerate the synthesis process of the molecular sieve; and the template agent is hexadecyltrimethylammonium bromide.

[0031] A method for preparing a synthetic molecular sieve comprises the following steps:

[0032] S1. Mix the silicon source, aluminum source, sodium source, water glass, catalyst, template and deionized water in proportion, add appropriate amount of deionized water, and stir evenly at room temperature until a uniform and transparent sol is formed;

[0033] S2, transferring the sol into a stainless steel reactor lined with polytetrafluoroethylene, sealing it and placing it in a constant temperature oven to perform a crystallization reaction to promote crystal nucleation and growth;

[0034] S3, after the crystallization is completed, the reactor is cooled naturally to room temperature, the product is taken out and centrifuged several times, and the separated finished product is then vacuum dried;

[0035] S4. Finally, the product is calcined in air atmosphere to burn off the template to obtain a synthetic molecular sieve product with a pure porous structure.

[0036] In the step S1, stirring is performed in a stirrer at a stirring speed of 300-500 rpm at room temperature for 2-4 hours until a uniform transparent sol is formed, ensuring that all components are fully dispersed, hydrolyzed and initially polymerized, and a pH meter is used to monitor and maintain the stability of the pH value of the transparent sol in real time during the stirring process.

[0037] In the step S2, crystallization is started at a crystallization temperature of 120-180° C. and the crystallization time is 12-36 hours. During the crystallization, the autogenous pressure in the reactor is maintained between 0.5-1.5 MPa to promote crystal nucleation and growth.

[0038] In the step S3, the crystallized product is centrifuged multiple times by a centrifuge, and the centrifugal speed of the centrifuge is 8000-10000 rpm, and each centrifugation time is 10-15 minutes. The crystallized product is washed with deionized water until the pH value of the washing liquid is 7, so as to remove residual alkali solution and unreacted raw materials in the crystallized product.

[0039] In the step S4, the crystallized product after centrifugation is dried in a vacuum drying oven, and the drying temperature is 80-120° C. and the drying time is 6-12 hours.

[0040] In the step S4, after drying, the crystallized product is calcined in a tube furnace under air atmosphere, and the calcination temperature is 400-600° C., and the calcination time is 4-8 hours to burn off the template.

[0041] Comparison between the molecular sieve prepared by the preparation method of the present invention and the molecular sieve prepared by conventional methods;

[0042] Experiment 1:

[0043] 1. Materials

[0044] The raw materials used in the present invention include: a silicon source (silicic acid or silica gel), an aluminum source (aluminum hydroxide or aluminum salt), a sodium source (sodium hydroxide or sodium nitrate), water glass (sodium silicate solution), a catalyst (sodium hydroxide or potassium hydroxide), a template agent (hexadecyltrimethylammonium bromide), and deionized water.

[0045] Raw materials used in traditional methods: determined according to the specific traditional method, silicon source, aluminum source, alkali source, template agent, used to adjust the pH value of the reaction system.

[0046] (II) Preparation

[0047] The present invention is synthesized according to the above preparation method;

[0048] The operation is carried out according to the specific steps of the traditional method, including weighing and mixing raw materials, setting reaction conditions (such as crystallization temperature, time, pressure, etc.) and subsequent treatment;

[0049] Table 1 Comparison results of the concrete of Experiment 1 and traditional concrete

[0050] Compare Projects The present invention Traditional methods Reaction temperature range (℃) 120-180 150-230 Crystallization time range (hours) 12-36 20-48 Raw material utilization 85％ 75％

[0051] 2. Test results and analysis

[0052] The present invention only requires conventional stirring equipment, a stainless steel reaction kettle with a polytetrafluoroethylene lining, a constant temperature oven, a centrifuge, a vacuum drying oven and a tubular furnace, etc. The equipment is simple and common.

[0053] Traditional methods: Some traditional methods require special reaction equipment that can withstand long-term high temperature and high pressure. The equipment is complex and costly.

[0054] (1) Reaction temperature

[0055] The present invention: the crystallization temperature is 120-180°C;

[0056] Traditional method: The crystallization temperature is usually 150-230°C, and the present invention reduces it by 30-50°C compared with the traditional method.

[0057] (2) Crystallization time

[0058] The present invention: the crystallization time is 12-36 hours.

[0059] Traditional method: The crystallization time is generally 20-48 hours, and the present invention shortens it by 8-12 hours compared with the traditional method.

[0060] (3) Product performance

[0061] Purity: The present invention precisely controls the raw material ratio and optimizes the preparation conditions to synthesize a molecular sieve with high purity and low impurity content. The traditional method has relatively low product purity due to the difficulty in precisely controlling the raw material ratio.

[0062] Crystallinity: The molecular sieve of the present invention has good crystallinity, a regular microporous structure and a large specific surface area. The molecular sieve prepared by traditional methods may not have as good crystallinity as the molecular sieve of the present invention, and the microporous structure and specific surface area are also relatively small.

[0063] (4) Environmental impact and waste generation

[0064] The present invention: the waste generated during the preparation process is mainly washing liquid and waste gas, and the amount is relatively small.

[0065] Traditional method: may produce more waste, such as unreacted raw materials, by-products, etc.

[0066] (5) Treatment measures

[0067] The present invention can neutralize the washing liquid and purify the waste gas, thereby reducing the impact on the environment to the minimum.

[0068] Traditional methods: Waste disposal is relatively complicated and may cause significant pollution to the environment.

[0069] The synthetic molecular sieve and preparation method are as follows: silicon source, aluminum source, sodium source, water glass, catalyst, template agent and deionized water are uniformly mixed in a specific ratio, and stirred at a stirring speed of 500 revolutions per minute for 3 hours at room temperature. During this process, silicon source, aluminum source and the like begin to hydrolyze under the action of the catalyst to form active groups such as silanol and aluminum hydroxyl groups. These active groups interact with sodium source, water glass and the like to undergo a preliminary polymerization reaction, and gradually form a uniform and transparent sol. The role of stirring is to ensure that all raw materials are fully contacted and dispersed, and to promote the reaction. At the same time, a pH meter is used to monitor the pH value of the sol in real time and maintain its stability, because the pH value has an important influence on the reaction rate and the structure of the product.

[0070] The formed sol was transferred to a stainless steel reactor with a polytetrafluoroethylene liner, sealed and placed in a constant temperature oven for crystallization reaction. The crystallization temperature was controlled at 170°C and the crystallization time was 24 hours. During this period, the autogenous pressure in the reactor was maintained at 1 MPa.

[0071] During the crystallization process, the aluminosilicate species in the sol are orderly arranged and polymerized around the template molecules, gradually forming the crystal structure of the molecular sieve. The crystallization temperature and time are the key factors affecting the nucleation and growth of the crystal. The appropriate temperature and sufficient time can ensure the full growth of the crystal and form a molecular sieve with a regular microporous structure and good crystallinity. The autogenous pressure helps to maintain the stability of the reaction system and promote the formation of crystals.

[0072] After the crystallization is completed, the reactor is naturally cooled to room temperature, and the product is taken out for multiple centrifugal separations. The centrifugal speed of the centrifuge is 9000 rpm, and each centrifugation time is 12 minutes. The crystallized product is separated from the mother liquor by the action of centrifugal force. Then, the crystallized product is washed with deionized water until the pH value of the washing liquid is 7. The purpose of this step is to remove the residual alkali solution and unreacted raw materials in the crystallized product and improve the purity of the product.

[0073] The crystallized product after centrifugation is then dried in a vacuum drying oven at a drying temperature of 100°C for 10 hours. The purpose of vacuum drying is to remove moisture from the product and make the product more stable. Finally, the dried product is calcined in an air atmosphere in a tubular furnace at a calcination temperature of 500°C for 6 hours. During the calcination process, the template molecules are burned off, leaving behind a molecular sieve product with a porous structure. The template plays a structural guiding role in the synthesis process, and the pores formed after its combustion give the molecular sieve good adsorption and separation properties.

[0074] The present invention and the undescribed parts are all prior art.

[0075] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A synthetic molecular sieve, characterized in that: The molecular sieve raw material comprises, by weight: 40-60 parts of silicon source, 15-25 parts of aluminum source, 5-10 parts of sodium source, 10-20 parts of water glass, 0.1-2 parts of catalyst, 5-15 parts of template agent, and the balance is deionized water.

2. A synthetic molecular sieve according to claim 1, characterized in that: The composition comprises, by weight: 55 parts of the silicon source, 22 parts of the aluminum source, 8 parts of the sodium source, 15 parts of water glass, 1 part of the catalyst, 10 parts of the template, and 50 parts of deionized water.

3. A synthetic molecular sieve according to claim 1, characterized in that: The silicon source is silicic acid or silica gel, which is used to provide the silicon element of the molecular sieve; the aluminum source is aluminum hydroxide or aluminum salt, which is used to provide the aluminum element of the molecular sieve; and the sodium source is sodium hydroxide or sodium nitrate, which is used to provide the sodium element of the molecular sieve.

4. A synthetic molecular sieve according to claim 1, characterized in that: The water glass is a sodium silicate solution, which is used to adjust the pore size and strength of the molecular sieve; the catalyst is sodium hydroxide or potassium hydroxide, which is used to accelerate the synthesis process of the molecular sieve; and the template agent is hexadecyltrimethylammonium bromide.

5. A method for preparing the synthetic molecular sieve according to any one of claims 1 to 4, characterized in that: The specific steps include: S1. Mix the silicon source, aluminum source, sodium source, water glass, catalyst, template and deionized water in proportion, add appropriate amount of deionized water, and stir evenly at room temperature until a uniform and transparent sol is formed; S2, transferring the sol into a stainless steel reactor lined with polytetrafluoroethylene, sealing it and placing it in a constant temperature oven to perform a crystallization reaction to promote crystal nucleation and growth; S3, after the crystallization is completed, the reactor is cooled naturally to room temperature, the product is taken out and centrifuged several times, and the separated finished product is then vacuum dried; S4. Finally, the product is calcined in air atmosphere to burn off the template to obtain a synthetic molecular sieve product with a pure porous structure.

6. The method for preparing a synthetic molecular sieve according to claim 5, characterized in that: In step S1, stirring is performed in a stirrer at a stirring speed of 300-500 rpm at room temperature for 2-4 hours until a uniform transparent sol is formed, and a pH meter is used to monitor and maintain the stability of the pH value of the transparent sol in real time during the stirring process.

7. The method for preparing a synthetic molecular sieve according to claim 5, characterized in that: In step S2, crystallization is started at a crystallization temperature of 120-180°C and the crystallization time is 12-36 hours. During the crystallization, the autogenous pressure in the reactor is maintained between 0.5-1.5 MPa to promote crystal nucleation and growth.

8. The method for preparing a synthetic molecular sieve according to claim 5, characterized in that: In step S3, the crystallized product is centrifuged multiple times by a centrifuge, and the centrifugal speed of the centrifuge is 8000-10000 rpm, each centrifugation time is 10-15 minutes, and the crystallized product is washed with deionized water until the pH value of the washing liquid is 7 to remove residual alkali solution and unreacted raw materials in the crystallized product.

9. The method for preparing a synthetic molecular sieve according to claim 5, characterized in that: In step S4, the crystallized product after centrifugation is dried in a vacuum drying oven at a drying temperature of 80-120° C. for 6-12 hours.

10. The method for preparing a synthetic molecular sieve according to claim 5, characterized in that: In step S4, after drying, the crystallized product is calcined in a tube furnace under air atmosphere, and the calcination temperature is 400-600° C. and the calcination time is 4-8 hours.

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