A self-forming attapulgite-based zeolite foam material of type A, and a preparation method and application thereof

Abstract

The application discloses a self-forming A-type molecular sieve foam material taking attapulgite as raw material and a preparation method and application thereof, and belongs to the field of green synthesis of molecular sieve foam materials. The steps are as follows: 1) grinding and sieving attapulgite to obtain attapulgite powder, and then calcining the attapulgite powder at 950-1000 DEG C for 2-4 hours to prepare activated attapulgite powder as a solid-phase raw material; 2) mixing the solid-phase raw material with an alkaline activator according to a mass ratio of 0.82-1.13:1, fully stirring and uniformly mixing, adding a seed crystal inducer, then adding a foaming agent, uniformly stirring, pouring into a mold, sealing, crystallizing, and obtaining the self-forming A-type molecular sieve foam material. The application only uses natural mineral attapulgite, does not add any chemical reagent as a silicon-aluminum source, obtains the self-forming A-type molecular sieve foam without a binder, and can effectively avoid problems such as pore blockage, dilution of effective molecular sieve sites and limitation of guest molecule transmission when used as an adsorbent.

Description

Technical Field

[0001] This invention belongs to the field of green synthesis of molecular sieve foam materials, specifically a self-forming type A molecular sieve foam material using attapulgite as raw material, its preparation method, and its application. Background Technology

[0002] Type A molecular sieves (LTA structure, typical chemical formula Na) 12 [Al 12 Si 12 O 48 With a theoretical SiO2 / Al2O3 molar ratio of 2, it has the lowest SiO2 / Al2O3 ratio among molecular sieves. It has abundant Si-O-Al structures, is rich in exchangeable Na ions, and has excellent ion exchange performance due to its rich OH functional groups on the surface. Its pore size is 0.41 nm, which can adsorb any molecule smaller than 0.41 nm. It has excellent adsorption performance and thermal stability, and has wide applications in petroleum processing, chemical production, environmental protection and other fields.

[0003] Traditional methods for preparing type A molecular sieves typically involve hydrothermal reactions using high-cost chemical raw materials based on the silicon-to-aluminum ratio. This process is complex, generates alkaline wastewater, poses significant environmental hazards, and is prohibitively expensive. To address these issues, researchers both domestically and internationally have been synthesizing molecular sieves using natural mineral raw materials as silicon and aluminum sources to reduce costs. For example, calcined kaolin can be used as the silicon and aluminum source, with chemical reagents added to adjust the silicon source and prepare type A molecular sieves. However, hydrothermally synthesized type A molecular sieves are in powder form and cannot be used directly. They require binders to form shaped molecular sieve bodies, which suffers from the disadvantage of binders clogging pores and reducing the effective molecular sieve content. Furthermore, using a carrier framework to create molecular sieves of specific shapes can lead to crystal detachment due to the difference in expansion coefficients between the molecular sieve grains and the carrier material.

[0004] Pitotite is a mineral widely distributed globally, with large-scale pits found in Hubei Province, my country. Existing research and data indicate that pitotite possesses excellent physicochemical properties, multiple applications, and broad development prospects. However, in reality, research findings on pitotite remain largely undeveloped, and the utilization rate of its mines is low, with no high-value-added products currently available. Natural pitotite is a 1:1 regularly layered silicate mineral with water-absorbing and swelling properties. Its SiO2 / Al2O3 molar ratio is similar to that of type A molecular sieves, suggesting that pitotite is highly suitable for synthesizing type A molecular sieves. However, there are many difficulties in synthesizing type A molecular sieves using natural mineral attapulgite as a raw material. These difficulties mainly stem from two aspects: First, conventional methods for synthesizing molecular sieves using activated attapulgite (as discussed in the study of type A molecular sieve synthesis and physicochemical properties using attapulgite, Lu Shumu et al.) employ alkaline hydrothermal synthesis, producing powdered molecular sieves. A binder is then added for further molding, resulting in a long reaction process, wasting significant water resources and causing alkaline pollution. Second, the SiO2 / Al2O3 molar ratio of natural attapulgite is generally between 2.5 and 2.7, while research reports indicate that the suitable SiO2 / Al2O3 molar ratio for type A molecular sieve synthesis is between 1.4 and 2.4. Therefore, the synthesis of type A molecular sieves using attapulgite as a raw material typically requires the addition of a chemical reagent, such as sodium aluminate, to adjust the system composition to suit the synthesis of type A molecular sieves.

[0005] Therefore, improving the development and utilization of attapulgite, increasing its added value, and ensuring the activity of molecular sieves are urgent priorities. Summary of the Invention

[0006] To address the aforementioned issues of reduced activity in molecular sieves supported by binders / carriers, high synthesis costs due to the use of silica-alumina sources for chemical reagents, low utilization of attapulgite, and low added value of existing products, this invention aims to provide a self-forming type A molecular sieve foam material made from attapulgite, its preparation method, and its application. Utilizing only the natural mineral attapulgite without adding any chemical reagents as silica-alumina sources, a self-forming type A molecular sieve foam without binders is obtained. When used as an adsorbent, it effectively avoids problems such as pore blockage, dilution of effective sites in the molecular sieve, and limited transport of guest molecules.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material is provided, comprising the following steps:

[0009] 1) Grind and sieve attapulgite to obtain attapulgite powder, and then calcine it at 950-1000℃ for 2-4 hours to prepare activated attapulgite powder as a solid phase raw material;

[0010] 2) Mix the solid raw material obtained in step 1) with the alkaline activator at a mass ratio of 0.82 to 1.13:1 and stir thoroughly. Add the seed crystal inducer, followed by the foaming agent. Stir thoroughly, pour into a mold, seal, and crystallize to obtain the self-formed type A molecular sieve foam material. The alkaline activator is a sodium hydroxide solution with a concentration of 6.14 to 10.74 mol / L. The mass of the seed crystal inducer added is 1 to 5 wt% of the solid raw material.

[0011] According to the above scheme, in step 1), the sample is passed through a 100-mesh sieve.

[0012] According to the above scheme, in step 1), the molar ratio of SiO2 / Al2O3 in the solid raw material is 2.5-2.7.

[0013] According to the above scheme, in step 2), the seed inducer is type A molecular sieve crystals.

[0014] According to the above scheme, in step 2), the foaming agent is hydrogen peroxide. Preferably, the concentration of hydrogen peroxide is 20-35 wt%.

[0015] According to the above scheme, in step 2), the foaming agent added is 1 to 6 wt% of the solid raw material.

[0016] According to the above scheme, in step 2), sodium hydroxide and water are mixed in a mass ratio of 0.246 to 0.430:1 to prepare a sodium hydroxide solution of 6.14 to 10.74 mol / L.

[0017] According to the above scheme, in step 2), crystallization is carried out in the range of 70-100℃ for 12-48 hours.

[0018] A self-forming type A molecular sieve foam material prepared by the above preparation method is provided.

[0019] According to the above scheme, the self-forming type A molecular sieve foam material is a three-dimensional self-forming foam structure with a compressive strength of 1.58 to 2.18 MPa.

[0020] This invention provides an application of the aforementioned self-forming type A molecular sieve foam material as an adsorbent.

[0021] This invention provides a method for preparing self-forming type A molecular sieve foam material. Using natural attapulgite as raw material, the calcined and activated natural attapulgite serves as the aluminosilicate source for the synthesis of type A molecular sieves. By adding an appropriate ratio and concentration of alkali activator, a quasi-solid-phase reaction system is formed. This system dissolves associated minerals (such as kaolinite, illite, pyrophyllite, etc.) in the natural attapulgite and the newly formed aluminosilicate-containing minerals after activation, obtaining a suitable activated aluminosilicate component. Seed crystals are then added to gradually induce the dissolved aluminosilicate component to form type A molecular sieves, allowing them to be successfully generated in the quasi-solid-phase reaction system. Excess unreacted silicon exists in the system in an amorphous form (such as geopolymer), serving as a carrier and binder for the type A molecular sieve. Combined with a foaming agent, a three-dimensional self-forming foam structure is finally formed. No additional binder is required, effectively avoiding problems such as pore blockage, dilution of effective sites in the molecular sieve, and limited transport of guest molecules.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention provides a method for preparing a self-forming type A molecular sieve foam material. It utilizes activated natural attapulgite as the silicon-aluminum source for the synthesis of type A molecular sieves without the need for additional adjustment of the silicon-aluminum ratio. By adding appropriate alkali activators, seed crystals, and foaming agents, type A molecular sieves are successfully formed in a quasi-solid phase system, ultimately yielding a three-dimensional self-forming foam structure. This invention directly obtains a three-dimensional self-forming type A molecular sieve foam material without the need for additional binders. When used as an adsorbent, it effectively avoids problems such as pore blockage, dilution of effective sites on the molecular sieve, and limited transport of guest molecules. Furthermore, the resulting foam exhibits high compressive strength, facilitating its recycling as an adsorbent and demonstrating significant application potential.

[0024] 2. The preparation method of this invention is simple and mild, and it directly uses attapulgite as a raw material without the need to add additional chemical reagents as a silicon-aluminum source, which is conducive to the development and utilization of attapulgite and reduces the cost of molecular sieve synthesis. At the same time, it can obtain self-formed type A molecular sieve foam material without the need to add additional carriers and binders, which can be used directly as an adsorbent. The product has high added value and effectively avoids the high cost and reprocessing disadvantages caused by using carriers or binders for molding, and has prospects for industrial application. Attached Figure Description

[0025] Figure 1 These are photographs of the self-forming type A molecular sieve foam materials prepared under different formulation conditions in Examples 1-6.

[0026] Figure 2 XRD diffraction pattern of rettosite raw material (a) and XRD diffraction patterns of self-forming type A molecular sieve foam prepared under different ratio conditions in Examples 1-8 (b).

[0027] Figure 3 SEM images of self-forming type A molecular sieve foams prepared under different formulation conditions in Examples 1-6.

[0028] Figure 4 XRD patterns of self-forming foams prepared for comparative examples 1-3. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, and to enable those skilled in the art to better understand the process solutions of this invention, specific embodiments are as follows:

[0030] Example 1

[0031] A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material is provided, comprising the following steps:

[0032] (1) Mineral raw material preparation: Natural palygorskite was ground through a 100-mesh sieve to obtain palygorskite powder. The palygorskite powder was then calcined at 950℃ for 2 hours to prepare activated palygorskite powder. XRF testing showed that the palygorskite powder contained 49% SiO2 and 32% Al2O3, with a SiO2 / Al2O3 molar ratio of 2.6. This raw material is the solid-phase raw material for preparing self-forming type A molecular sieve foam.

[0033] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (11.0g) and water (25.5g) were mixed at a mass ratio of 0.430:1, stirred evenly and cooled to room temperature to obtain the basic activator of molecular sieve synthesis with a concentration of 10.74mol / L.

[0034] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (36.5g) are mixed at a mass ratio of 0.82:1 and stirred thoroughly. 0.6g of type A molecular sieve seed inducing agent is added, followed by 1.2g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture is poured into a mold and sealed. The mold is then placed in an electric heating drying oven and crystallized at 70℃ for 48h to obtain self-forming type A molecular sieve foam material with a compressive strength of 2.08MPa.

[0035] Example 2

[0036] A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material is provided, comprising the following steps:

[0037] (1) Mineral raw material preparation: Natural palygorskite was ground through a 100-mesh sieve to obtain palygorskite powder. The palygorskite powder was then calcined at 950℃ for 4 hours to prepare activated palygorskite powder. XRF testing showed that the palygorskite powder contained 49% SiO2 and 32% Al2O3, with a SiO2 / Al2O3 molar ratio of 2.6. This raw material is the solid-phase raw material for preparing self-forming type A molecular sieve foam.

[0038] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (7.8g) and water (22.5g) were mixed at a mass ratio of 0.348:1, stirred evenly and cooled to room temperature to obtain the basic activator of molecular sieve synthesis with a concentration of 8.70mol / L.

[0039] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (30.2g) are mixed at a mass ratio of 0.99:1 and stirred thoroughly. 0.3g of type A molecular sieve seed inducing agent is added, followed by 1.8g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture is poured into a mold and sealed. The mold is then placed in an electric heating drying oven and crystallized at 80℃ for 24h to obtain self-forming type A molecular sieve foam material with a compressive strength of 1.95MPa.

[0040] Example 3

[0041] A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material is provided, comprising the following steps:

[0042] (1) Mineral raw material preparation: Natural palygorskite was ground through a 100-mesh sieve to obtain palygorskite powder. The palygorskite was then calcined at 1000℃ for 2 hours to prepare activated palygorskite. XRF testing showed that the palygorskite powder contained 49% SiO2, 32% Al2O3, and a SiO2 / Al2O3 molar ratio of 2.6. This raw material is the material for preparing self-forming type A molecular sieve foam.

[0043] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (7.8g) and water (19.5g) were mixed at a mass ratio of 0.401:1, stirred evenly and cooled to room temperature to obtain the basic activator of molecular sieve synthesis with a concentration of 10.03mol / L.

[0044] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (27.3g) are mixed at a mass ratio of 1.10:1 and stirred thoroughly. 0.9g of type A molecular sieve crystal seed inducer is added, followed by 0.3g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture is poured into a mold and sealed. The mold is then placed in an electric heating drying oven and crystallized at 90℃ for 24h to obtain the self-forming type A molecular sieve foam material with a compressive strength of 1.69MPa.

[0045] Example 4

[0046] A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material is provided, comprising the following steps:

[0047] (1) Mineral raw material preparation: Natural palygorskite was ground through a 100-mesh sieve to obtain palygorskite powder. The palygorskite was then calcined at 1000℃ for 3 hours to prepare activated palygorskite. XRF testing showed that the palygorskite powder contained 49% SiO2, 32% Al2O3, and a SiO2 / Al2O3 molar ratio of 2.6. This raw material is the material for preparing self-forming type A molecular sieve foam.

[0048] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (6.3g) and water (25.5g) were mixed at a mass ratio of 0.246:1, stirred evenly and cooled to room temperature to obtain the basic activator synthesized from molecular sieves with a concentration of 6.14mol / L.

[0049] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (31.8g) are mixed at a mass ratio of 0.94:1 and stirred thoroughly. 1.5g of type A molecular sieve seed inducing agent is added, followed by 1.8g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture is poured into a mold and sealed. The mold is then placed in an electric heating drying oven and crystallized at 90℃ for 18h to obtain self-forming type A molecular sieve foam material with a compressive strength of 1.57MPa.

[0050] Example 5

[0051] A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material is provided, comprising the following steps:

[0052] (1) Mineral raw material preparation: Natural palygorskite was ground through a 100-mesh sieve to obtain palygorskite powder. The palygorskite was then calcined at 1000℃ for 4 hours to prepare activated palygorskite. XRF testing showed that the palygorskite powder contained 49% SiO2 and 32% Al2O3, with a SiO2 / Al2O3 molar ratio of 2.6. This raw material is the material for preparing self-forming type A molecular sieve foam.

[0053] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (7.8g) and water (22.5g) were mixed at a mass ratio of 0.348:1 to obtain the basic activator for molecular sieve synthesis with a concentration of 8.70mol / L.

[0054] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (26.6g) are mixed at a mass ratio of 1.13:1 and stirred thoroughly. 1.2g of type A molecular sieve seed inducing agent is added, followed by 1.5g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture is poured into a mold and sealed. The mold is then placed in an electric heating drying oven and crystallized at 100℃ for 12h to obtain self-forming type A molecular sieve foam material with a compressive strength of 1.62MPa.

[0055] Example 6

[0056] A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material is provided, comprising the following steps:

[0057] (1) Mineral raw material preparation: Natural palygorskite was ground through a 100-mesh sieve to obtain palygorskite powder. The palygorskite was then calcined at 1000℃ for 2 hours to prepare activated palygorskite. XRF testing showed that the palygorskite powder contained 49% SiO2, 32% Al2O3, and a SiO2 / Al2O3 molar ratio of 2.6. This raw material is the material for preparing self-forming type A molecular sieve foam.

[0058] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (7.8g) and water (25.5g) were mixed at a mass ratio of 0.307:1, stirred evenly and cooled to room temperature to obtain the basic activator synthesized from molecular sieves with a concentration of 7.67mol / L.

[0059] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (33.3g) are mixed at a mass ratio of 0.90:1 and stirred thoroughly. 0.9g of type A molecular sieve seed inducing agent is added, followed by 0.6g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture is poured into a mold and sealed. The mold is then placed in an electric heating drying oven and crystallized at 80℃ for 24h to obtain self-forming type A molecular sieve foam material with a compressive strength of 1.58MPa.

[0060] Example 7

[0061] A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material is provided, comprising the following steps:

[0062] (1) Mineral raw material preparation: Natural palygorskite was ground through a 100-mesh sieve to obtain palygorskite powder. The palygorskite was then calcined at 1000℃ for 2 hours to prepare activated palygorskite. XRF testing showed that the palygorskite powder contained 49.7% SiO2 and 33.3% Al2O3, with a SiO2 / Al2O3 molar ratio of 2.54. This raw material is the material for preparing self-forming type A molecular sieve foam.

[0063] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (7.8g) and water (22.5g) were mixed at a mass ratio of 0.348:1 to obtain the basic activator for molecular sieve synthesis with a concentration of 8.70mol / L.

[0064] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (26.6g) are mixed at a mass ratio of 1.13:1 and stirred thoroughly. 1.2g of type A molecular sieve seed inducing agent is added, followed by 1.5g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture is poured into a mold and sealed. The mold is then placed in an electric heating drying oven and crystallized at 100℃ for 12h to obtain self-forming type A molecular sieve foam material with a compressive strength of 1.67MPa.

[0065] Example 8

[0066] A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material is provided, comprising the following steps:

[0067] (1) Mineral raw material preparation: Natural palygorskite was ground through a 100-mesh sieve to obtain palygorskite powder. The palygorskite was then calcined at 1000℃ for 2 hours to prepare activated palygorskite. XRF testing showed that the palygorskite powder contained 45.2% SiO2, 29.1% Al2O3, and a SiO2 / Al2O3 molar ratio of 2.64. This raw material is the material for preparing self-forming type A molecular sieve foam.

[0068] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (7.8g) and water (22.5g) were mixed at a mass ratio of 0.348:1 to obtain the basic activator for molecular sieve synthesis with a concentration of 8.70mol / L.

[0069] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (26.6g) are mixed at a mass ratio of 1.13:1 and stirred thoroughly. 1.2g of type A molecular sieve seed inducing agent is added, followed by 1.5g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture is poured into a mold and sealed. The mold is then placed in an electric heating drying oven and crystallized at 100℃ for 12h to obtain self-forming type A molecular sieve foam material with a compressive strength of 1.63MPa.

[0070] Comparative Example 1

[0071] Based on Example 1, the calcination temperature of retardant was changed. The specific steps are as follows:

[0072] (1) Preparation of mineral raw materials: Natural palygorskite was ground through a 100-mesh sieve to obtain palygorskite powder. The palygorskite powder was calcined at 550℃ for 2 hours to prepare activated palygorskite powder. XRF testing showed that the palygorskite powder contained 49% SiO2 and 32% Al2O3, with a SiO2 / Al2O3 molar ratio of 2.6. This raw material is the solid phase raw material for preparing self-forming type A molecular sieve foam.

[0073] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (11.0g) and water (25.5g) were mixed at a mass ratio of 0.430:1, stirred evenly and cooled to room temperature to obtain the basic activator of molecular sieve synthesis with a concentration of 10.74mol / L.

[0074] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (36.5g) were mixed at a mass ratio of 0.82:1 and stirred thoroughly. 0.6g of type A molecular sieve seed inducing agent was added, followed by 1.2g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture was poured into a mold and sealed. The mold was then placed in an electric heating drying oven and crystallized at 70℃ for 48h. The product was mainly sodalite and could not form type A molecular sieve.

[0075] Comparative Example 2

[0076] Based on Example 5, without adding a seed crystal inducer, the specific steps are as follows:

[0077] (1) Preparation of mineral raw materials: Natural attapulgite was ground through a 100-mesh sieve to obtain attapulgite powder. The attapulgite was then calcined at 1000℃ for 4 hours to prepare activated attapulgite. XRF testing showed that the attapulgite powder contained 49% SiO2 and 32% Al2O3, with a SiO2 / Al2O3 molar ratio of 2.6. This raw material is the material for preparing self-forming type A molecular sieve foam.

[0078] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (7.8g) and water (22.5g) were mixed at a mass ratio of 0.348:1 to obtain the basic activator for molecular sieve synthesis with a concentration of 8.70mol / L.

[0079] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (26.6g) were mixed at a mass ratio of 1.13:1 and stirred thoroughly. Then, 1.5g of 30wt% hydrogen peroxide foaming agent was added, stirred thoroughly, poured into a mold and sealed. The mold was then placed in an electric heating drying oven and crystallized at 100℃ for 12h. The main products were mullite and sodalite, which could not form type A molecular sieve.

[0080] Comparative Example 3

[0081] Based on Example 6, the SiO2 / Al2O3 molar ratio was adjusted. The specific steps are as follows:

[0082] (1) Mineral raw material preparation: Natural attapulgite was ground through a 100-mesh sieve to obtain attapulgite powder. The attapulgite was then calcined at 1000℃ for 2 hours to prepare activated attapulgite. XRF testing showed that the attapulgite powder contained 49% SiO2 and 32% Al2O3. Sodium aluminate (aluminum source) was added to the activated attapulgite, resulting in a SiO2 / Al2O3 molar ratio of 2.4. This raw material is used to prepare self-forming type A molecular sieve foam.

[0083] (2) Preparation of sodium hydroxide solution: Sodium hydroxide (7.8g) and water (25.5g) were mixed at a mass ratio of 0.307:1, stirred evenly and cooled to room temperature to obtain the basic activator synthesized from molecular sieves with a concentration of 7.67mol / L.

[0084] (3) Preparation of self-forming type A molecular sieve foam material: The solid raw material (30g) and alkaline activator (33.3g) were mixed at a mass ratio of 0.90:1 and stirred thoroughly. 0.9g of type A molecular sieve crystal seed inducing agent was added, followed by 0.6g of 30wt% hydrogen peroxide foaming agent. After stirring thoroughly, the mixture was poured into a mold and sealed. The mold was then placed in an electric heating drying oven and crystallized at 80℃ for 24h. The main products were calcium nepheline and sodalite, which could not form type A molecular sieve.

[0085] Figure 1 The images show actual photographs of the self-forming type A molecular sieve foam materials prepared in Examples 1-6. The figures show that the diameter of the self-forming type A molecular sieve foam material is approximately 4 cm, consistent with the specifications of the mold used, and the material shows no dimensional shrinkage.

[0086] Figure 2 XRD diffraction pattern of rettosite raw material (a) and XRD diffraction pattern of self-forming type A molecular sieve foam prepared in Examples 1-8 (b). Figure 2 The a-type mineral used contains not only attapulgite but also associated elements such as illite, pyrophyllite, quartz, and kaolinite. Figure 2 b shows that the prepared product is mainly type A molecular sieve.

[0087] Figure 3 The images show SEM images of the self-forming type A molecular sieve foams prepared in Examples 1-6. The images show that the prepared type A molecular sieves are uniformly distributed granular (quasi-cubic) particles, which is a typical morphology of type A molecular sieves.

[0088] Figure 4 The figures show the XRD diffraction patterns of the foams prepared in Comparative Examples 1-3. The figures show that the product of Comparative Example 1 is sodalite, the product of Comparative Example 2 is mainly a mixture of mullite and sodalite, and the product of Comparative Example 3 is a mixture of nepheline and sodalite; none of these yielded type A molecular sieves. From Comparative Examples 1-3, it can be concluded that:

[0089] This invention provides three comparative examples. By simply changing the calcination temperature, not adding a seed inducer, or adding an aluminum source to adjust the raw material composition, no type A molecular sieve was formed. Comparative Example 1, changing the calcination temperature of attapulgite, failed to form a type A molecular sieve because the calcination temperature of attapulgite was too low, resulting in a low content of active silica-alumina components, thus preventing the formation of type A molecular sieves. Comparative Examples 2 and 3 show that the molar ratio of seed crystals and silica-alumina significantly affects the formation of type A molecular sieves. The addition of a seed inducer provides a large number of active sites for the formation of molecular sieve nuclei, promoting the smooth formation of type A molecular sieves in the quasi-solid phase system. A suitable silica-alumina molar ratio is a prerequisite for the nucleation of type A molecular sieves. In this invention, natural attapulgite, after activation by calcination at a suitable temperature, was dissolved with an appropriate concentration and ratio of alkali activator to obtain a suitable silica-alumina ratio, eliminating the need for additional chemical reagents to adjust the silica-alumina ratio.

[0090] This invention uses attapulgite as raw material, which is activated by calcination at a suitable temperature, and then dissolved with an appropriate alkali activator to form a quasi-solid phase reaction system, obtaining a suitable activated silica-alumina component. Then, a seed crystal inducer is used to gradually induce the dissolved silica-alumina component to form a type A molecular sieve, realizing the smooth generation of type A molecular sieve in the quasi-solid phase system. A small amount of unreacted silica-alumina exists in the system in an amorphous form (such as geopolymer), becoming a high-strength type A molecular sieve carrier and binder. With the help of a foaming agent, a three-dimensional self-forming foam structure is finally formed. When used as an adsorbent, it can effectively avoid problems such as pore blockage, dilution of effective sites of molecular sieve, and limited transport of guest molecules.

[0091] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. All technical scopes disclosed in the present invention are covered within the scope of protection of the present invention.

Claims

1. A method for preparing a self-forming type A molecular sieve foam material using attapulgite as raw material, characterized in that, Includes the following steps: 1) The attapulgite is ground and sieved to obtain attapulgite powder, and then calcined at 950~1000℃ for 2~4 h to prepare activated attapulgite powder as a solid raw material; wherein the molar ratio of SiO2 / Al2O3 in the solid raw material is 2.5-2.7; 2) Mix the solid raw material obtained in step 1) with the alkaline activator at a mass ratio of 0.82~1.13:1 and stir thoroughly. Add the seed crystal inducer, followed by the foaming agent. Stir thoroughly, pour into a mold, seal, and crystallize to obtain the self-formed type A molecular sieve foam material. Wherein: the alkaline activator is a sodium hydroxide solution with a concentration of 6.14~10.74 mol / L; the seed crystal inducer is added at a mass of 1~5 wt% of the solid raw material; the seed crystal inducer is type A molecular sieve crystals.

2. The preparation method according to claim 1, characterized in that, In step 1), the sample is passed through a 100-mesh sieve.

3. The preparation method according to claim 1, characterized in that, In step 2), the foaming agent is hydrogen peroxide.

4. The preparation method according to claim 1, characterized in that, In step 2), the foaming agent is added at a mass of 1-6 wt% of the solid raw material.

5. The preparation method according to claim 1, characterized in that, In step 2), crystallization is carried out at 70-100 °C for 12-48 h.

6. A self-forming type A molecular sieve foam material prepared by the preparation method according to any one of claims 1-5.

7. The self-forming type A molecular sieve foam material according to claim 6, characterized in that, The self-forming type A molecular sieve foam material has a three-dimensional self-forming foam structure and a compressive strength of 1.58~2.18 MPa.

8. The application of the self-forming type A molecular sieve foam material of claim 6 as an adsorbent.

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