Method for preparing binder-free molecular sieve by adopting directional crystal transformation technology
Through countercurrent contact reaction in the reaction column through directional crystallization technology, the problems of instability and high crushing rate of clay minerals during the transformation process of molecular sieve particles are solved, and efficient adsorption performance and mechanical performance are improved.
Patent Information
- Application Number
- CN202411335864.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-24
- Publication Date
- 2024-12-20
AI Technical Summary
The prior art is difficult to simultaneously improve the adsorption performance of molecular sieves and reduce the particle crushing rate. The traditional stirring method can easily lead to instability of clay minerals during the transcrystallization process, affecting the adsorption selection performance and mechanical properties.
Directional transformation technology is adopted to achieve countercurrent contact of the molecular sieve containing clay minerals in the low-temperature induction zone and the high-temperature transformation zone through countercurrent contact reaction in the reaction column, controlling the temperature and time, realizing directional transformation of clay minerals and reducing heterogeneous crystals. Generate and improve mass transfer and diffusion efficiency.
The adsorption amount, strength and wear resistance of the binder-free molecular sieve are improved, the particle crushing and wear are reduced, and the adsorption selection performance is enhanced.
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Figure CN119160907A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing a binder-free molecular sieve by adopting a directional crystal rotation technology, and belongs to the technical field of preparing molecular sieve adsorption materials. Background Art
[0002] Molecular sieves, as commonly used adsorbents, desiccants and catalysts in industry, often contain about 20% kaolin clay minerals. The main function of kaolin is to bind zeolite powders of 1 to 10 μm together and form large particles with a diameter of 0.5 to 5 mm to reduce the bed resistance of the molecular sieve adsorption separation process. Kaolin can also bring negative effects. Because it does not have adsorption properties, the presence of kaolin reduces the adsorption capacity of molecular sieves and increases the diffusion resistance of gases in molecular sieve particles. Taking advantage of the similarity between kaolin and zeolite mineral compositions, kaolin can be converted into zeolite adsorption materials through hydrothermal chemical reactions, that is, the molecular sieve containing clay minerals is converted into a binder-free molecular sieve through crystallization, thereby improving the adsorption and mass transfer properties of the molecular sieve.
[0003] In order to improve the adsorption performance of molecular sieves, a large number of studies have been conducted on the preparation process of binder-free molecular sieves in the literature. Chinese patent document CN102513059A uses molecular sieve raw powder to mix with halloysite and attapulgite clay, granulates after adding additives, and then screens, calcines at high temperature after drying to obtain molecular sieves containing clay minerals, and then immerses the molecular sieve containing clay minerals in a sodium silicate mixed solution of sodium hydroxide and silicon dioxide for reaction, and then washes and dries the granular product for a second high temperature roasting to obtain a novel binder-free 13X molecular sieve product. Chinese patent document CN109485058A uses LSX molecular sieve powder and kaolin as raw materials, obtains a molecular sieve containing clay minerals after mixed molding, drying and roasting, and the molecular sieve containing clay minerals is subjected to saturated water absorption, sodium potassium mixed alkali solution treatment, sodium ion exchange, secondary drying and roasting and other processes to prepare binder-free LSX molecular sieves.
[0004] The clay minerals in the molecular sieve containing clay minerals have not undergone crystallization, which will lead to reduced adsorption performance of the molecular sieve and deviation in wear resistance. Therefore, the clay minerals can be converted into crystals with a structure similar to that of the molecular sieve through alkaline crystallization treatment to improve the performance of the molecular sieve. However, in actual application, the crystallization process of the molecular sieve particles is mostly carried out in a reaction tank, and the crystal transformation of the clay in the molecular sieve is achieved by continuous and slow stirring. The calcined molecular sieve particles, in which the binder kaolin mineral is very unstable in alkaline solution, can be converted into type A zeolite, type X zeolite and type P zeolite through different hydrothermal crystallization processes. The appearance of these impurities will affect the adsorption selectivity of the molecular sieve. The kaolin crystallization process must be precisely controlled to obtain the desired mineral phase. Traditional technologies have not systematically considered these aspects. In addition, due to the low strength of molecular sieve particles in the solution, too fast conversion stirring speed in the reaction tank can easily cause particle breakage and wear. Too slow stirring speed will affect the mass transfer and diffusion of the alkaline solution in the molecular sieve particles and reduce the conversion rate. Stirring speed that is too fast or too slow will affect the directional transformation of clay minerals into beneficial crystals related to adsorption, strength, abrasion and other properties. Summary of the invention
[0005] The purpose of the present invention is to provide a method for preparing a binderless molecular sieve using oriented crystal rotation technology, which can solve the problem that the current stirring method cannot prepare a binderless molecular sieve with low breakage rate and good adsorption performance.
[0006] In order to achieve the above objectives, the technical solution adopted by the method for preparing a binder-free molecular sieve using oriented crystal rotation technology of the present invention is:
[0007] A method for preparing a binder-free molecular sieve using a directional crystallization technology comprises the following steps: a molecular sieve containing clay minerals passes through a reaction column from top to bottom, and undergoes a countercurrent contact reaction with an alkali solution from bottom to top in the reaction column to achieve crystallization of the clay minerals; the countercurrent contact reaction comprises a low-temperature molecular sieve induction reaction containing clay minerals and a high-temperature crystallization reaction sequentially performed from top to bottom, the temperature of the low-temperature induction reaction is 45°C to 80°C, and the temperature of the high-temperature crystallization reaction is 80°C to 100°C.
[0008] The method for preparing a binder-free molecular sieve using directional crystallization technology of the present invention can realize directional crystallization of clay minerals and reduce impurity crystals by subjecting a molecular sieve containing clay minerals to countercurrent contact reaction with an alkali solution, and can also improve the mass transfer and diffusion efficiency between clay minerals and alkali solution, improve the crystallization efficiency of clay minerals, and avoid the molecular sieve particles from being broken and worn during the crystallization process, effectively improving the adsorption capacity, strength and wear resistance of the binder-free molecular sieve. When the molecular sieve containing clay minerals is a 4A molecular sieve, a 13X molecular sieve or a low-silicon molecular sieve containing kaolin, in the low-temperature induction zone, the calcined kaolin amorphous phase undergoes structural reorganization under the action of the zeolite matrix to form a specific A-type, X-type or low-silicon zeolite mineral crystal nucleus; in the high-temperature crystallization zone, the zeolite crystal nucleus converted from kaolin grows up at a higher temperature to form a stable A-type, X-type or low-silicon zeolite mineral phase.
[0009] Preferably, the temperature of the low temperature induction reaction is 60°C to 80°C.
[0010] Preferably, the molecular sieve containing clay minerals is a 4A molecular sieve containing kaolin, and the low-temperature induction reaction time is 1 to 6 hours; the molecular sieve containing clay minerals is a low-silicon molecular sieve containing kaolin or a 13X molecular sieve, and the low-temperature induction reaction time is 10 to 15 hours.
[0011] Preferably, the molecular sieve containing clay minerals is a 4A molecular sieve, a 13X molecular sieve or a low-silicon molecular sieve containing kaolin, and the kaolin content is 5-40%.
[0012] Preferably, the kaolin content is 10-20%.
[0013] Preferably, the molecular sieve containing clay minerals is a 4A molecular sieve containing kaolin, the alkali solution is composed of sodium hydroxide and water, and the concentration of sodium hydroxide is 30-120 g / L calculated as Na2O; the molecular sieve containing clay minerals is a low-silicon molecular sieve containing kaolin, the alkali solution is composed of sodium hydroxide, potassium hydroxide and water, the concentration of sodium hydroxide is 70-90 g / L calculated as Na2O, and the concentration of potassium hydroxide is 50-60 g / L calculated as K2O; the molecular sieve containing clay minerals is a 13X molecular sieve containing kaolin, the alkali solution is composed of sodium hydroxide, sodium silicate and water, the concentration of sodium hydroxide is 30-120 g / L calculated as Na2O, and the concentration of sodium silicate is 50-80 g / L calculated as SiO2.
[0014] Preferably, the molecular sieve containing clay mineral is prepared by mixing molecular sieve raw powder and clay mineral through granulation, screening, drying and calcining.
[0015] Preferably, the high temperature crystal transformation reaction time is 1 to 4 hours.
[0016] Preferably, the method for preparing a binder-free molecular sieve using directional crystallization technology further comprises the following steps: countercurrently contacting the crystallized molecular sieve with water to wash the crystallized molecular sieve, and then drying and calcining the washed molecular sieve to obtain a binder-free molecular sieve.
[0017] In the present invention, the molecular sieve containing clay minerals can be added continuously or intermittently, but it is necessary to ensure that the temperature and time of the countercurrent contact reaction between the molecular sieve containing clay minerals and the alkali solution meet the requirements.
[0018] In the present invention, the alkali solution flowing out of the reaction column can be recycled after the alkali concentration is adjusted. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a schematic flow chart of a method for preparing a binder-free molecular sieve using oriented crystallization technology according to Example 1 of the present invention. DETAILED DESCRIPTION
[0020] The method of preparing a binderless molecular sieve using directional crystallization technology of the present invention is a pioneering invention. The experimental results of the present invention show that the binderless molecular sieve prepared by the method of the present invention has better adsorption performance than the binderless molecular sieve prepared by the conventional stirring method. The fundamental reason is that when the binderless molecular sieve is prepared by the method of the present invention, the clay mineral in the molecular sieve containing clay minerals can be directional transformed into crystals that are beneficial to the strength, adsorption and abrasion of the molecular sieve during the countercurrent contact reaction with the alkali solution, thereby achieving directional crystallization.
[0021] The method for preparing a binderless molecular sieve using directional crystallization technology of the present invention comprises the following steps: subjecting a molecular sieve containing clay minerals to countercurrent contact reaction with an alkali solution to realize crystallization of the clay minerals, and during the countercurrent contact reaction, the molecular sieve containing clay minerals passes through a low-temperature induction zone and a high-temperature crystallization zone in sequence; the temperature of the low-temperature induction zone is 45°C to 80°C, and the temperature of the high-temperature crystallization zone is 80°C to 100°C. The method for preparing a binderless molecular sieve using directional crystallization technology of the present invention realizes directional crystallization of clay minerals with zeolite as the matrix by subjecting a molecular sieve containing clay minerals to countercurrent contact reaction with an alkali solution, controlling key parameters (including temperature, concentration, time, etc.) of the hydrothermal chemical reaction process, and the technology can also improve the mass transfer and diffusion efficiency between clay minerals and alkali solution, improve the crystallization efficiency of clay minerals, and at the same time avoid the molecular sieve particles from being broken and worn during the crystallization process, effectively improving the adsorption capacity, strength and wear resistance of the binderless molecular sieve. The present invention utilizes the countercurrent contact reaction between molecular sieve particles and an alkaline solution to complete the directional alkalization and crystallization process of clay minerals in the molecular sieve particles. The binder-free 4A molecular sieve, low-silicon molecular sieve or 13X molecular sieve prepared by the present invention has an adsorption performance that is 10-20% higher than that of traditional products, the particles do not break or peel, and the abrasion rate is reduced by more than 50%.
[0022] In some preferred embodiments, the countercurrent contact reaction is carried out in a tubular reactor, and the diameter of the tubular reactor is 0.1 to 3 m, more preferably 0.2 to 1 m. When the diameter of the tubular reactor is less than 0.5 m, an external water circulation interlayer is provided for temperature adjustment; when the diameter of the tubular reactor is 0.5 to 3 m, a coil heat exchanger is provided internally to adjust the temperature of the material in the reactor. When the tubular reactor is arranged in a vertical direction, the upper part of the tubular reactor is a low-temperature induction zone, and the lower part is a high-temperature crystallization zone. During the crystallization process, the alkalizing solution flows into the reactor from the lower part, and the molecular sieve particles with kaolin minerals as a binder enter from the upper part of the reactor, pass through the low-temperature induction zone and the high-temperature crystallization zone in turn, and are washed after flowing out of the reactor.
[0023] In some preferred embodiments, washing is achieved by contacting the molecular sieve after crystallization with water in countercurrent.
[0024] In some preferred embodiments, washing is performed in a tubular reactor. During the washing process in the tubular reactor, clean water flows into the reactor from the bottom, and the crystallized molecular sieve is added to the scrubber from the top, and a directional crystallized binder-free molecular sieve product can be obtained at the bottom of the tubular reactor. The washing process should control the appropriate washing water flow rate, molecular sieve particle discharge speed and washing water temperature to ensure that the alkaline solution remaining in the molecular sieve alkalization process is washed clean.
[0025] In some preferred embodiments, the residence time of the molecular sieve after crystallization in the tubular reactor is 2 to 4 hours.
[0026] In some preferred embodiments, the washing temperature is 60-90°C, more preferably 80-90°C.
[0027] In some preferred embodiments, the molecular sieve containing clay minerals is 4A molecular sieve or 13X molecular sieve, and the length of the low temperature induction zone is 3 to 6 m; the molecular sieve containing clay minerals is a low silicon molecular sieve, and the length of the low temperature induction zone is 8 to 10 m. The residence time of the molecular sieve in the reactor is adjusted according to the molecular sieve discharge speed.
[0028] In some preferred embodiments, the length of the high temperature crystallization zone is 5 to 8 m.
[0029] In some preferred embodiments, the washed molecular sieve is dried and calcined to obtain a binder-free molecular sieve product.
[0030] The traditional molecular sieve crystallization process uses a reaction tank to carry out alkalization crystallization of molecular sieve particles. During the conversion process, the interaction between the alkaline solution and the molecular sieve particles is insufficient, which affects the clay conversion efficiency and the adsorption performance of the product. In addition, accompanied by mechanical stirring or air flow stirring, it is easy to cause the molecular sieve particles to break and the surface to wear, affecting the mechanical properties of the product. The molecular sieve products produced using the traditional alkalization crystallization process often have reduced application effects in the aerospace, pharmaceutical and gas separation industries due to mechanical strength, wear resistance and dust output. The present invention uses a tubular reactor to carry out directional crystallization of molecular sieve particles, which has the following advantages compared with the traditional process:
[0031] 1) Use tubular reactors to achieve directional crystallization of clay minerals in molecular sieve particles and improve the adsorption performance of molecular sieves. The molecular sieve particles slowly move downward in the reactor, and undergo low-temperature induction and high-temperature crystallization processes under the action of alkaline solution. The clay is transformed into the same mineral structure as the molecular sieve matrix zeolite under strict hydrothermal environmental conditions with the zeolite matrix as the guiding agent, without generating other miscellaneous crystalline minerals.
[0032] 2) The molecular sieve particles and the alkaline crystallization solution in the reactor move in opposite directions, and the solid particles and solution components are fully in contact, which enhances the mass transfer efficiency of the alkaline crystallization process and effectively improves the directional crystallization effect of the molecular sieve particles.
[0033] 3) During the alkalization and crystallization process, the molecular sieve moves slowly downward freely due to gravity, and the alkalization solution moves from bottom to top under pressure. The molecular sieve particles do not need to withstand traditional mechanical stirring and air stirring forces. The converted molecular sieve particles will not be broken, and can ensure excellent wear resistance and low dust output.
[0034] In the present invention, 60-95% of 4A zeolite raw powder and 5-40% of clay mineral are mixed and granulated, and then sieved, dried and calcined to obtain 0.5-5mm 4A molecular sieve particles; low silicon molecular sieve raw powder or 13X molecular sieve raw powder can also be used to prepare low silicon molecular sieve particles or 13X molecular sieve particles according to the same method.
[0035] The technical solution of the present invention is further described below in conjunction with specific embodiments.
[0036] Example 1
[0037] The method of preparing the binder-free molecular sieve by using the directional crystallization technology of this embodiment is as follows: Figure 1 As shown, it specifically includes the following steps: 1000kg of molecular sieve containing clay minerals (4A molecular sieve with kaolin as binder, kaolin content of 10%, molecular sieve particle size of 1.6-2.5mm) is continuously added to the reaction column from the feeding port at the upper end of the reaction column at a feeding rate of 1.2kg / min (the diameter of the reaction column is 0.3m and the effective height is 8.5m. The reaction column is divided into a low-temperature induction zone and a high-temperature crystallization zone from top to bottom. The length of the low-temperature induction zone is 6.5m, and the length of the high-temperature crystallization zone is 2m. Two jackets A and B are set outside the reaction column. Water at different temperatures is introduced into the jacket to control the temperature of the upper and lower zones of the reaction column, such as Figure 1 As shown in the figure, alkali solution (the alkali solution is sodium hydroxide solution, and the concentration is 60g / L in terms of Na2O) is pumped into the liquid inlet at the lower end of the reaction column at the same time. The temperature of the alkali solution is 98°C and the pumping speed is 4.2kg / min. After the molecular sieve containing clay minerals is added to the reaction column, it moves from top to bottom under the action of gravity, and the alkali solution moves from bottom to top under the action of the pump pressure. The molecular sieve containing clay minerals and the alkali solution are in countercurrent contact in the reaction column to achieve alkalization and crystallization of the clay minerals. During the countercurrent contact, the molecular sieve containing clay minerals passes through the low-temperature induction zone and the high-temperature crystallization zone respectively. The residence time in the low-temperature induction zone is 4h, and the residence time in the high-temperature crystallization zone is 2h. The temperature of the low-temperature induction zone is 60-80°C, and the temperature of the high-temperature crystallization zone is 80-100°C. Since a jacket is provided on the outside of the reaction column, the temperature of the low-temperature induction zone and the high-temperature crystallization zone is controlled in the jacket. The uppermost temperature of the low-temperature induction zone is 60°C, the lowermost temperature is 80°C, and the temperature of the low-temperature induction zone gradually increases from top to bottom; the uppermost temperature of the high-temperature induction zone is 80°C, the lowermost temperature is 100°C, and the temperature of the high-temperature induction zone gradually increases from top to bottom.
[0038] Every 10 minutes, 12kg of alkalized molecular sieve product is discharged from the bottom of the reaction column, and 12kg of molecular sieve is added from the top of the reaction column. The discharged molecular sieve is transported to the washing column for washing with water, and the water flow rate is 3L / min. 12kg of product is discharged from the bottom of the washing column every minute. According to the experiment, after accumulative discharge of 500kg, the conversion washing process reaches a stable state. Take the discharged product with stable process, dry and activate it, and test the strength, wear, dust, breakage rate and static water absorption of the product.
[0039] In this embodiment, the molecular sieve containing clay minerals is prepared by the following method: 90% of 4A zeolite raw powder and 10% of clay mineral (kaolin) are mixed and granulated, and then sieved, dried (drying temperature is 120°C), and calcined (calcination temperature is 600°C, time is 2h) to obtain 4A molecular sieve particles of 1.6 to 2.5 mm.
[0040] Example 2
[0041] The method for preparing a binder-free molecular sieve using directional crystallization technology in this embodiment specifically comprises the following steps: 1000 kg of molecular sieve containing clay minerals (a low-silicon molecular sieve with kaolin as a binder, a kaolin content of 10%, and a molecular sieve particle size of 1.6-2.5 mm) is continuously added to a reaction column (the reaction column has a diameter of 0.3 m and an effective height of 12 m, and the reaction column is divided into a low-temperature induction zone and a high-temperature crystallization zone from top to bottom, the low-temperature induction zone is 10 m long, and the high-temperature crystallization zone is 2 m long, and two jackets A and B are arranged on the outside of the reaction column, and water at different temperatures is introduced into the jackets to control the temperatures of the upper and lower zones of the reaction column) at a feeding rate of 0.75 kg / min, and alkali solution (the alkali solution is composed of hydroxide) is pumped into the liquid inlet at the lower end of the reaction column. The reaction column is composed of sodium, potassium hydroxide and water, the concentration of sodium hydroxide is 80g / L in terms of Na2O, and the concentration of potassium hydroxide is 55g / L in terms of K2O), the temperature of the alkali solution is 98°C, the pumping speed is 3.6kg / min, the molecular sieve containing clay minerals is added to the reaction column and moves from top to bottom under the action of gravity, the alkali solution moves from bottom to top under the action of pump pressure, the molecular sieve containing clay minerals and the alkali solution are in countercurrent contact in the reaction column to achieve alkalization and crystallization of the clay minerals, during the countercurrent contact, the molecular sieve containing clay minerals passes through the low-temperature induction zone and the high-temperature crystallization zone respectively, the residence time in the low-temperature induction zone is 10h, the residence time in the high-temperature crystallization zone is 2h, the temperature of the low-temperature induction zone is 60-80°C, and the temperature of the high-temperature crystallization zone is 80-100°C. Since a jacket is provided on the outside of the reaction column, water for controlling the low-temperature induction zone and the high-temperature crystallization zone is introduced into the jacket. The uppermost temperature of the low-temperature induction zone is 60°C, the lowermost temperature is 80°C, and the temperature of the low-temperature induction zone gradually increases from top to bottom; the uppermost temperature of the high-temperature induction zone is 80°C, the lowermost temperature is 100°C, and the temperature of the high-temperature induction zone gradually increases from top to bottom.
[0042] Every 10 minutes, 7.5 kg of alkalized molecular sieve product is discharged from the bottom of the reaction column, and 7.5 kg of molecular sieve is added from the top of the reaction column. The discharged molecular sieve is transported to the washing column for washing with water, and the water flow rate is 3L / min. Every 10 minutes, 7.5 kg of product is discharged from the bottom of the washing column. According to the test, after 600 kg of cumulative discharge, the conversion washing process reaches a stable state. The product discharged in the stable state is taken, and the strength, abrasion, dust, breakage rate and static water absorption of the product are tested after drying and activation.
[0043] In this embodiment, the molecular sieve containing clay minerals is prepared by the following method: 90% of the low-silicon molecular sieve raw powder and 10% of the clay mineral (kaolin) are mixed and granulated, and the mixture is screened, dried (drying temperature is 150°C, time is 2h), and calcined (calcination temperature is 600°C, time is 2h) to obtain a low-silicon molecular sieve of 1.6 to 2.5 mm.
[0044] In other embodiments, the molecular sieve containing clay minerals is a 4A molecular sieve with kaolin as a binder, the kaolin content is 5-40%, the alkali solution is a sodium hydroxide solution, the concentration is 30-120 g / L in terms of Na2O, the time for low-temperature induction reaction is 1-6 hours, and the time for high-temperature crystallization reaction is 1-4 hours.
[0045] In other embodiments, the molecular sieve containing clay minerals is a low-silicon molecular sieve with kaolin as a binder, the kaolin content is 5-40%, the alkali solution is composed of sodium hydroxide, potassium hydroxide and water, the concentration of sodium hydroxide is 70-90 g / L in terms of Na2O, the concentration of potassium hydroxide is 50-60 g / L in terms of K2O, the time for low-temperature induction reaction is 10-15 h, and the time for high-temperature crystallization reaction is 1-4 h.
[0046] In other embodiments, the molecular sieve containing clay minerals is a 13X molecular sieve with kaolin as a binder, the kaolin content is 5-40%, the alkali solution is composed of sodium hydroxide, sodium silicate and water, the concentration of sodium hydroxide is 30-120 g / L in terms of Na2O, the concentration of sodium silicate is 50-80 g / L in terms of SiO2, the time for low-temperature induction reaction is 10-15 h, the time for high-temperature crystallization reaction is 1-4 h, and the ratio of the mass flow rates of the molecular sieve containing clay minerals and the alkali solution is 1:(4-6).
[0047] Comparative Example 1
[0048] The method for preparing a binder-free molecular sieve using directional crystallization technology in this comparative example specifically comprises the following steps: 3600 L of alkali solution (the same as that used in Example 1) was added to the reactor, and its temperature was raised to 70°C. 500 kg of 4A molecular sieve (the same as the molecular sieve containing clay minerals used in Example 1) with kaolin as a binder was taken and added to the reactor. The materials in the reactor were then aged at low temperature for 4 h (the temperature of low temperature aging was 70°C). Intermittent stirring was adopted during the low temperature aging process, stirring once every 30 minutes, and each stirring was 2 minutes. The materials in the reactor were then heated to 98°C and stirred continuously at a low speed for 120 minutes to perform high temperature crystallization. After the high temperature crystallization was completed, the sample was taken out and washed with distilled water until the pH value of the washing liquid was 11. The washed sample was activated and dried, and the strength, abrasion, dust, breakage rate and adsorption amount of the product were tested.
[0049] Comparative Example 2
[0050] The method for preparing a binder-free molecular sieve using directional crystallization technology in this comparative example specifically comprises the following steps: 3 850L of alkali solution (the same as that used in Example 2) was added to the reactor, and its temperature was raised to 60°C. 550kg of low-silicon molecular sieve with kaolin as a binder (the same as the molecular sieve containing clay minerals used in Example 2) was taken and added to the reactor. The materials in the reactor were then aged at low temperature for 12h (the temperature of low temperature aging was 65°C). Intermittent stirring was adopted during the low temperature aging process, stirring once every 30min, and each stirring was 2min. The materials in the reactor were then heated to 98°C and stirred continuously at a low speed for 120min to carry out high temperature crystallization. After the high temperature crystallization, the samples were taken out and washed with distilled water until the pH value of the washing liquid was 11. The washed samples were activated and dried, and the strength, abrasion, dust, breakage rate and adsorption amount of the products were tested.
[0051] The strength, abrasion, dust, breakage rate and adsorption amount of the molecular sieve samples obtained in Example 1-2 and Comparative Example 1-2 are shown in Table 1-2. In Table 1, the strength, abrasion and static water adsorption of the samples were measured with reference to the national standard "3A molecular sieve" GB / T 10504-2017.
[0052] Sample breakage rate detection: Observe the integrity of the particles with the naked eye. If the spherical particles are peeled, the particles are considered broken. Take 100 samples, observe the number of molecular sieve particles with peeled shells, and calculate the sample breakage rate.
[0053] Dust detection: Take 5g of activated molecular sieve sample, add it to 100ml of water, let it stand for 10 minutes, gently shake the mixture, and use a turbidity meter to detect the turbidity of the mixture, which is the sample dust.
[0054] Table 1 Properties of molecular sieves prepared in Example 1 and Comparative Example 1
[0055]
[0056] Table 2 Performance of molecular sieves prepared in Example 2 and Comparative Example 2
[0057]
[0058] It can be seen from Table 1-2 that, compared with the binderless molecular sieve prepared by the conventional stirring method, the binderless molecular sieve prepared by the present invention has higher strength, better adsorption performance and wear resistance, and significantly reduced dust content.
Claims
1. A method for preparing a binder-free molecular sieve using oriented crystallization technology, characterized in that: The following steps are involved: The molecular sieve containing clay minerals passes through a reaction column from top to bottom, and undergoes a countercurrent contact reaction with an alkali solution from bottom to top in the reaction column to achieve crystallization of the clay minerals; the countercurrent contact reaction includes a low-temperature induction reaction and a high-temperature crystallization reaction sequentially performed from top to bottom, the temperature of the low-temperature induction reaction is 45°C to 80°C, and the temperature of the high-temperature crystallization reaction is 80°C to 100°C.
2. The method for preparing a binder-free molecular sieve using oriented crystallization technology according to claim 1, characterized in that: The temperature of the low temperature induction reaction is 60°C to 80°C.
3. The method for preparing a binder-free molecular sieve using oriented crystallization technology according to claim 1 or 2, characterized in that: The molecular sieve containing clay minerals is a 4A molecular sieve containing kaolin, and the time for low-temperature induction reaction is 1 to 6 hours; the molecular sieve containing clay minerals is a low-silicon molecular sieve containing kaolin or a 13X molecular sieve, and the time for low-temperature induction reaction is 10 to 15 hours.
4. The method for preparing a binder-free molecular sieve using oriented crystallization technology according to claim 1, characterized in that: The molecular sieve containing clay minerals is a 4A molecular sieve, a 13X molecular sieve or a low-silicon molecular sieve containing kaolin, and the kaolin content is 5-40%.
5. The method for preparing a binder-free molecular sieve using oriented crystallization technology according to claim 4, characterized in that: The kaolin content is 10-20%.
6. The method for preparing a binder-free molecular sieve using oriented crystallization technology according to claim 4, characterized in that: The molecular sieve containing clay minerals is a 4A molecular sieve containing kaolin, the alkali solution is composed of sodium hydroxide and water, and the concentration of sodium hydroxide is 30-120 g / L calculated as Na2O; the molecular sieve containing clay minerals is a low-silicon molecular sieve containing kaolin, the alkali solution is composed of sodium hydroxide, potassium hydroxide and water, the concentration of sodium hydroxide is 70-90 g / L calculated as Na2O, and the concentration of potassium hydroxide is 50-60 g / L calculated as K2O; the molecular sieve containing clay minerals is a 13X molecular sieve containing kaolin, the alkali solution is composed of sodium hydroxide, sodium silicate and water, the concentration of sodium hydroxide is 30-120 g / L calculated as Na2O, and the concentration of sodium silicate is 50-80 g / L calculated as SiO2.
7. The method for preparing a binder-free molecular sieve using oriented crystallization technology according to claim 1, 4, 5 or 6, characterized in that: The molecular sieve containing clay mineral is prepared by mixing molecular sieve raw powder and clay mineral through granulation, screening, drying and roasting.
8. The method for preparing a binder-free molecular sieve using oriented crystallization technology according to claim 1, characterized in that: The time of high temperature crystallization reaction is 1 to 4 hours.
9. The method for preparing a binder-free molecular sieve using oriented crystallization technology according to claim 1, characterized in that: The method for preparing a binder-free molecular sieve using directional crystallization technology also includes the following steps: contacting the crystallized molecular sieve with water in countercurrent flow to wash the crystallized molecular sieve, and then drying and calcining the washed molecular sieve to obtain a binder-free molecular sieve.