A method for preparing X-type zeolite molecular sieves using red mud and electrolytic manganese slag
By using red mud and electrolytic manganese slag to prepare X-type zeolite molecular sieves, the problem of stockpiling electrolytic manganese slag and red mud was solved, the production cost was reduced and the crystallinity of zeolite molecular sieves was improved, realizing the resource utilization of waste and low-cost preparation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUIZHOU UNIV
- Filing Date
- 2024-06-26
- Publication Date
- 2026-07-31
AI Technical Summary
The stockpiling of electrolytic manganese slag and red mud leads to resource waste and environmental pollution. The high cost of existing zeolite molecular sieve preparation limits their widespread application.
X-type zeolite molecular sieves were prepared by using red mud and electrolytic manganese slag as raw materials and through calcination, magnetic separation, acid leaching and alkali dissolution. The process included aging and hydrothermal treatment steps, and the zeolite molecular sieves were synthesized by utilizing the alumina in the red mud and the silicon source in the electrolytic manganese slag.
It has achieved waste reduction and resource utilization, reduced the production cost of zeolite molecular sieves, improved crystallinity and purity, and broadened the application fields.
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Figure CN118771405B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of solid waste resource utilization technology, and in particular to a method for preparing X-type zeolite molecular sieves using red mud and electrolytic manganese slag. Background Technology
[0002] Electrolytic manganese slag is a waste residue generated during the electrolytic manganese industrial production process. It belongs to Class II general industrial solid waste and contains various pollutants. The annual production of electrolytic manganese slag is over 15 million tons, and based on historical production, the current stockpile of manganese slag exceeds 150 million tons. Electrolytic manganese slag not only removes some valuable components, resulting in resource waste, but also causes environmental pollution and safety hazards.
[0003] Red mud is an industrial solid waste discharged during the extraction of alumina in the aluminum industry. Because of its high iron oxide content and appearance resembling reddish soil, it is called red mud. Depending on the ore grade, production methods, and technological level, approximately 1.0 to 1.8 tons of red mud are discharged for every ton of alumina produced. Besides occupying a large amount of land during storage, the chemical components in red mud can easily infiltrate the soil, causing soil alkalization and groundwater pollution, resulting in environmental pollution.
[0004] Zeolite molecular sieves are porous aluminosilicate compounds with a tetrahedral structure. Due to their regular pore structure, strong acidity, and high hydrothermal stability, they are widely used in catalysis, adsorption, and ion exchange. X-type zeolite molecular sieves have a silica-to-alumina ratio between 1.0 and 1.5, relatively large micropore sizes, and abundant porosity.
[0005] Synthetic zeolites are typically produced using chemical raw materials such as alkalis, sodium aluminate, and sodium silicate. Due to their high cost, the widespread application of synthetic zeolites in various fields is limited, especially in environmental protection. Red mud has a high alumina content, while electrolytic manganese slag is rich in silica. Both have compositions similar to zeolite molecular sieves; therefore, they can be used to prepare zeolite molecular sieves. This would further reduce the production cost of synthetic zeolites and broaden the utilization pathways of red mud and electrolytic manganese slag.
[0006] Therefore, it is very important to realize the resource utilization of solid waste and to explore and develop zeolite molecular sieve materials with low manufacturing cost and low price. Summary of the Invention
[0007] The purpose of this invention is to provide a method for preparing X-type zeolite molecular sieves using red mud and electrolytic manganese slag, so as to solve the problems existing in the prior art and realize the reduction, harmlessness and resource utilization of waste.
[0008] To achieve the above objectives, the present invention provides the following solution:
[0009] One of the technical solutions of this invention is to provide a method for preparing X-type zeolite molecular sieves using red mud and electrolytic manganese slag, the steps of which include:
[0010] Red mud is pretreated by calcination and magnetic separation.
[0011] Pretreated electrolytic manganese slag is obtained by acid leaching and alkali dissolution of electrolytic manganese slag.
[0012] The pretreated red mud and pretreated electrolytic manganese slag are mixed with water, and then aged and hydrothermally heated to obtain the X-type zeolite molecular sieve.
[0013] Furthermore, the Al2O3 content in the red mud is 20–40 wt.%.
[0014] Furthermore, the SiO2 content in the electrolytic manganese slag is not less than 40 wt.%.
[0015] Furthermore, the calcination treatment step is as follows:
[0016] The red mud is mixed evenly with sodium carbonate and carbon powder, and then calcined and cooled under an inert atmosphere to complete the calcination treatment.
[0017] Preferably, the mass ratio of sodium carbonate to red mud is 0.4 to 1:1.
[0018] Preferably, the mass ratio of carbon powder to red mud is 1:5 to 10.
[0019] Preferably, the calcination temperature is 800–1100°C and the time is 0.5–2 hours.
[0020] Furthermore, the current for the magnetic separation process is 1 to 5 A.
[0021] Furthermore, the acid leaching treatment step is as follows:
[0022] After the electrolytic manganese slag is soaked in an acid solution, solid and liquid are separated to complete the acid leaching treatment.
[0023] Preferably, the acid solution is a sulfuric acid solution with a concentration of 5-10 wt.%.
[0024] Preferably, the liquid-to-solid ratio of the acid solution and the electrolytic manganese slag is 7 to 9:1.
[0025] Preferably, the immersion temperature is 90–110°C and the immersion time is 150–180 min.
[0026] Furthermore, the alkali dissolution treatment step is as follows:
[0027] The electrolytic manganese slag that has undergone acid leaching is mixed with sodium hydroxide, then calcined and cooled to complete the alkali dissolution treatment.
[0028] Preferably, the mass ratio of sodium hydroxide to acid-leached electrolytic manganese slag is 0.5 to 1.2:1.
[0029] Preferably, the calcination temperature is 600–900°C and the time is 1–3 hours.
[0030] Furthermore, the mass ratio of the pretreated red mud to the pretreated electrolytic manganese slag is 1:2 to 5.
[0031] Furthermore, the sum of the masses of the pretreated red mud and the pretreated electrolytic manganese slag has a solid-liquid ratio of 1:8 to 10 with water.
[0032] Furthermore, the aging temperature is 25–60°C, and the time is 9–12 hours.
[0033] Furthermore, the hydrothermal temperature is 80–100°C, and the time is 3–6 hours.
[0034] Furthermore, the inert atmosphere is a nitrogen atmosphere or a helium atmosphere.
[0035] The second technical solution of the present invention provides an X-type zeolite molecular sieve prepared by the above method.
[0036] The third technical solution of this invention: provides a method for improving the crystallinity of red mud-electrolytic manganese slag-based X-type zeolite molecular sieves, comprising the following steps:
[0037] Red mud is pretreated by calcination and magnetic separation.
[0038] Pretreated electrolytic manganese slag is obtained by acid leaching and alkali dissolution of electrolytic manganese slag.
[0039] The pretreated red mud and pretreated electrolytic manganese slag are mixed with water, and then aged and hydrothermally heated to obtain the X-type zeolite molecular sieve.
[0040] Furthermore, the Al2O3 content in the red mud is 20–40 wt.%.
[0041] Furthermore, the SiO2 content in the electrolytic manganese slag is not less than 40 wt.%.
[0042] Furthermore, the calcination treatment step is as follows:
[0043] The red mud is mixed evenly with sodium carbonate and carbon powder, and then calcined and cooled under an inert atmosphere to complete the calcination treatment.
[0044] Preferably, the mass ratio of sodium carbonate to red mud is 0.4 to 1:1.
[0045] Preferably, the mass ratio of carbon powder to red mud is 1:5 to 10.
[0046] Preferably, the calcination temperature is 800–1100°C and the time is 0.5–2 hours.
[0047] Furthermore, the current for the magnetic separation process is 1 to 5 A.
[0048] Furthermore, the acid leaching treatment step is as follows:
[0049] After the electrolytic manganese slag is soaked in an acid solution, solid and liquid are separated to complete the acid leaching treatment.
[0050] Preferably, the acid solution is a sulfuric acid solution with a concentration of 5-10 wt.%.
[0051] Preferably, the liquid-to-solid ratio of the acid solution and the electrolytic manganese slag is 7 to 9:1.
[0052] Preferably, the immersion temperature is 90–110°C and the immersion time is 150–180 min.
[0053] Furthermore, the alkali dissolution treatment step is as follows:
[0054] The electrolytic manganese slag that has undergone acid leaching is mixed with sodium hydroxide, then calcined and cooled to complete the alkali dissolution treatment.
[0055] Preferably, the mass ratio of sodium hydroxide to acid-leached electrolytic manganese slag is 0.5 to 1.2:1.
[0056] Preferably, the calcination temperature is 600–900°C and the time is 1–3 hours.
[0057] Furthermore, the mass ratio of the pretreated red mud to the pretreated electrolytic manganese slag is 1:2 to 5.
[0058] Furthermore, the sum of the masses of the pretreated red mud and the pretreated electrolytic manganese slag has a solid-liquid ratio of 1:8 to 10 with water.
[0059] Furthermore, the aging temperature is 25–60°C, and the time is 9–12 hours.
[0060] Furthermore, the hydrothermal temperature is 80–100°C, and the time is 3–6 hours.
[0061] Furthermore, the inert atmosphere is a nitrogen atmosphere or a helium atmosphere.
[0062] The present invention discloses the following technical effects:
[0063] This invention uses red mud and electrolytic manganese slag as the main raw materials to react, which alleviates the problem of hazardous solid waste accumulation, is of great significance for reducing environmental pollution, and realizes the reduction and utilization of waste treatment.
[0064] Compared to the traditional method of preparing zeolite molecular sieves using pure silicon-aluminum sources, such as sodium silicate and sodium aluminate, the reaction process of this invention is simple and the raw material is waste residue, which reduces the production cost of zeolite molecular sieves and improves the high-value utilization of red mud and electrolytic manganese slag.
[0065] This invention uses two types of solid waste as aluminum and silicon sources for zeolite molecular sieves, respectively. Red mud is reduced and calcined and magnetically separated to remove iron, and electrolytic manganese slag is acid-leached and alkali-fused. This reduces the adverse effects of excessive impurities in the solid waste on the growth and crystallization process of zeolite molecular sieves, so that the synthesized zeolite molecular sieves have a single crystal phase and high crystallinity. Attached Figure Description
[0066] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0067] Figure 1 The image shows the XRD pattern of the X-type zeolite molecular sieve prepared in Example 2.
[0068] Figure 2 The image shows the SEM pattern of the X-type zeolite molecular sieve prepared in Example 3.
[0069] Figure 3 The image shows the XRD pattern of the X-type zeolite molecular sieve prepared in Comparative Example 1.
[0070] Figure 4 The image shows the XRD pattern of the X-type zeolite molecular sieve prepared in Comparative Example 2.
[0071] Figure 5 The image shows the XRD pattern of the X-type zeolite molecular sieve prepared in Comparative Example 3. Detailed Implementation
[0072] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0073] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0074] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0075] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.
[0076] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0077] In the specific embodiments of the present invention, the Al2O3 content in the red mud is between 20 and 40 wt.%; the SiO2 content in the electrolytic manganese slag is not less than 40 wt.%; wherein, the red mud and electrolytic manganese slag are ball-milled, dried and sieved (80 mesh) (this is a conventional treatment and is not specifically limited).
[0078] Example 1
[0079] The preparation steps of X-type zeolite molecular sieve are as follows:
[0080] S1. Mix 10g of red mud with 5g of sodium carbonate and 2g of carbon powder, calcine at 1000℃ for 0.5h in a nitrogen atmosphere, cool to room temperature, grind, and then perform magnetic separation on the powder under a magnetic separation current of 2A to obtain pretreated red mud.
[0081] S2. Place 20g of electrolytic manganese slag into 180mL of 5wt.% sulfuric acid solution, leach at 90℃ for 150min, and filter to obtain filter residue.
[0082] S3. Mix 10g of the filter residue obtained in step S2 with 11g of sodium hydroxide evenly, calcine at 800℃ for 2h, cool to room temperature, and grind to obtain pretreated electrolytic manganese slag.
[0083] S4. Mix 4g of pretreated red mud, 10g of pretreated electrolytic manganese slag and 120mL of water, age at 60℃ for 12h, and then hydrothermally treat (crystallization reaction) at 100℃ for 4h to obtain X-type zeolite molecular sieve.
[0084] Example 2
[0085] The preparation steps of X-type zeolite molecular sieve are as follows:
[0086] S1. Mix 10g of red mud with 10g of sodium carbonate and 2g of carbon powder, calcine at 800℃ for 1h in a nitrogen atmosphere, cool to room temperature, grind, and then perform magnetic separation treatment on the powder under a magnetic separation current of 2A to obtain pretreated red mud.
[0087] S2. Place 20g of electrolytic manganese slag into 140mL of 10wt.% sulfuric acid solution, leach at 110℃ for 180min, and filter to obtain filter residue.
[0088] S3. Mix 10g of the filter residue obtained in step S2 with 12g of sodium hydroxide evenly, calcine at 800℃ for 2h, cool to room temperature, and grind to obtain pretreated electrolytic manganese slag.
[0089] S4. Mix 2g of pretreated red mud, 10g of pretreated electrolytic manganese slag and 100mL of water, age at 25℃ for 12h, and then hydrothermally treat (crystallization reaction) at 90℃ for 6h to obtain X-type zeolite molecular sieve.
[0090] Figure 1 The XRD pattern of the X-type zeolite molecular sieve prepared in Example 2 is shown below. Figure 1 It can be seen that the X-type zeolite molecular sieve prepared in Example 2 is exactly the same as the standard spectrum of X-type zeolite molecular sieve. There are no diffraction peaks of other heterocrystalline phases in the spectrum, and the peaks are sharp, indicating that the synthesized zeolite molecular sieve is a single crystalline phase with good crystallinity.
[0091] Example 3
[0092] The preparation steps of X-type zeolite molecular sieve are as follows:
[0093] S1. Mix 10g of red mud with 10g of sodium carbonate and 2g of carbon powder, calcine at 900℃ for 2h in a nitrogen atmosphere, cool to room temperature, grind, and then perform magnetic separation treatment on the powder under a magnetic separation current of 4A to obtain pretreated red mud.
[0094] S2. Place 20g of electrolytic manganese slag into 140mL of 5wt.% sulfuric acid solution, leach at 110℃ for 160min, and filter to obtain filter residue.
[0095] S3. Mix 10g of the filter residue obtained in step S2 with 11g of sodium hydroxide evenly, calcine at 750℃ for 3h, cool to room temperature, and grind to obtain pretreated electrolytic manganese slag.
[0096] S4. Mix 3g of pretreated red mud, 10g of pretreated electrolytic manganese slag and 120mL of water, age at 45℃ for 9h, and then hydrothermally treat (crystallization reaction) at 90℃ for 6h to obtain X-type zeolite molecular sieve.
[0097] Figure 2 The image shows the SEM pattern of the X-type zeolite molecular sieve prepared in Example 3. Figure 2 It can be seen that the X-type zeolite molecular sieve prepared in Example 3 has a typical octahedral zeolite morphology with clear outlines and distinct edges, indicating that it has a high degree of crystallinity.
[0098] Example 4
[0099] The preparation steps of X-type zeolite molecular sieve are as follows:
[0100] S1. Mix 10g of red mud with 8g of sodium carbonate and 2g of carbon powder, calcine at 900℃ for 2h in a nitrogen atmosphere, cool to room temperature, grind, and then perform magnetic separation treatment on the powder under a magnetic separation current of 5A to obtain pretreated red mud.
[0101] S2. Place 15g of electrolytic manganese slag into 100mL of 10wt.% sulfuric acid solution, leach at 110℃ for 180min, and filter to obtain filter residue.
[0102] S3. Mix 10g of the filter residue obtained in step S2 with 11g of sodium hydroxide evenly, calcine at 800℃ for 2h, cool to room temperature, and grind to obtain pretreated electrolytic manganese slag.
[0103] S4. Mix 5g of pretreated red mud, 10g of pretreated electrolytic manganese slag and 120mL of water, age at 25℃ for 9h, and then hydrothermally treat (crystallization reaction) at 110℃ for 4h to obtain X-type zeolite molecular sieve.
[0104] Comparative Example 1
[0105] The preparation steps of X-type zeolite molecular sieve are as follows:
[0106] S1. Mix 10g of red mud with 10g of sodium carbonate and 2g of carbon powder, calcine at 800℃ for 1h in a nitrogen atmosphere, cool to room temperature, grind, and then perform magnetic separation treatment on the powder under a magnetic separation current of 2A to obtain pretreated red mud.
[0107] S2. Place 20g of electrolytic manganese slag into 140mL of 10wt.% sulfuric acid solution, leach at 110℃ for 180min, and filter to obtain filter residue.
[0108] S3. Mix 10g of the filter residue obtained in step S2 with 12g of sodium hydroxide evenly, calcine at 800℃ for 2h, cool to room temperature, and grind to obtain pretreated electrolytic manganese slag.
[0109] S4. Mix 2g of pretreated red mud, 10g of pretreated electrolytic manganese slag and 100mL of water, age at 25℃ for 12h, and then hydrothermally treat (crystallization reaction) at 110℃ for 6h to obtain X-type zeolite molecular sieve.
[0110] Figure 3 The XRD pattern of the X-type zeolite molecular sieve prepared in Comparative Example 1 is shown below. Figure 3 As can be seen, when the hydrothermal treatment temperature is increased to 110℃, the characteristic peak of sodalite appears in the figure. This is due to the excessively high temperature causing the X-type zeolite molecular sieve to undergo crystal transformation.
[0111] Comparative Example 2
[0112] The preparation steps of X-type zeolite molecular sieve are as follows:
[0113] S1. Mix 10g of red mud with 10g of sodium carbonate and 2g of carbon powder, calcine at 800℃ for 1h in a nitrogen atmosphere, cool to room temperature, grind, and then perform magnetic separation treatment on the powder under a magnetic separation current of 2A to obtain pretreated red mud.
[0114] S2. Place 20g of electrolytic manganese slag into 140mL of 10wt.% sulfuric acid solution, leach at 110℃ for 180min, and filter to obtain filter residue.
[0115] S3. Mix 10g of the filter residue obtained in step S2 with 12g of sodium hydroxide evenly, calcine at 800℃ for 2h, cool to room temperature, and grind to obtain pretreated electrolytic manganese slag.
[0116] S4. Mix 10g of pretreated red mud, 10g of pretreated electrolytic manganese slag and 100mL of water, age at 25℃ for 12h, and then hydrothermally treat (crystallization reaction) at 90℃ for 6h to obtain X-type zeolite molecular sieve.
[0117] Figure 4 The XRD pattern of the X-type zeolite molecular sieve prepared in Comparative Example 2 is shown below. Figure 4 It can be seen that when the mass ratio of pretreated red mud to pretreated electrolytic manganese slag is 1, type A zeolite molecular sieve is generated. This is because the increased amount of pretreated red mud leads to an increased Al content in the mixture, resulting in the generation of type A zeolite molecular sieve with a low silica-to-alumina ratio.
[0118] Comparative Example 3
[0119] The preparation steps of X-type zeolite molecular sieve are as follows:
[0120] S1. Mix 10g of red mud with 10g of sodium carbonate and 2g of carbon powder, calcine at 800℃ for 1h in a nitrogen atmosphere, cool to room temperature, grind, and then perform magnetic separation treatment on the powder under a magnetic separation current of 2A to obtain pretreated red mud.
[0121] S2. Place 20g of electrolytic manganese slag into 140mL of 10wt.% sulfuric acid solution, leach at 110℃ for 180min, and filter to obtain filter residue.
[0122] S3. Mix 10g of the filter residue obtained in step S2 with 12g of sodium hydroxide evenly, calcine at 800℃ for 2h, cool to room temperature, and grind to obtain pretreated electrolytic manganese slag.
[0123] S4. Mix 2g of pretreated red mud, 10g of pretreated electrolytic manganese slag and 100mL of water, age at 25℃ for 12h, and then hydrothermally treat (crystallization reaction) at 90℃ for 12h to obtain X-type zeolite molecular sieve.
[0124] Figure 5 The XRD pattern of the X-type zeolite molecular sieve prepared in Comparative Example 3 is shown below. Figure 5 It can be seen that when the hydrothermal time is increased to 12 hours, sodalite begins to appear in the product, indicating that an excessively long hydrothermal time is not conducive to the synthesis of X-type zeolite molecular sieves.
[0125] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for preparing X-type zeolite molecular sieve using red mud and electrolytic manganese residue, characterized by the steps of include: Red mud is pretreated by calcination and magnetic separation. Pretreated electrolytic manganese slag is obtained by acid leaching and alkali dissolution of electrolytic manganese slag. The X-type zeolite molecular sieve is obtained by mixing the pretreated red mud and pretreated electrolytic manganese slag with water, followed by aging and hydrothermal treatment. The mass ratio of the pretreated red mud to the pretreated electrolytic manganese slag is 1:2~5; the solid-liquid ratio of the sum of the masses of the pretreated red mud and the pretreated electrolytic manganese slag to water is 1:8~10. The magnetic separation current is 1~5A; the aging temperature is 25~60℃ and the time is 9~12h; the hydrothermal temperature is 80~100℃ and the time is 3~6h. The calcination process is as follows: red mud is mixed evenly with sodium carbonate and carbon powder, calcined and cooled under an inert atmosphere to complete the calcination process; the mass ratio of sodium carbonate to red mud is 0.4~1:1; the mass ratio of carbon powder to red mud is 1:5~10; the calcination temperature is 800~1100℃ and the time is 0.5~2h. The acid leaching process is as follows: the electrolytic manganese slag is immersed in an acid solution, followed by solid-liquid separation to complete the acid leaching process; the acid solution is a sulfuric acid solution with a concentration of 5-10 wt.%; the liquid-solid ratio of the acid solution to the electrolytic manganese slag is 7-9:1; the acid leaching process is carried out at a temperature of 90-110℃ for 150-180 min. The alkaline dissolution treatment steps are as follows: the electrolytic manganese slag treated by acid leaching is mixed with sodium hydroxide, then calcined and cooled to complete the alkaline dissolution treatment; the mass ratio of sodium hydroxide to the electrolytic manganese slag treated by acid leaching is 0.5~1.2:1; the calcination temperature is 600~900℃ and the time is 1~3h.
2. The method according to claim 1, characterized in that, The red mud contains 20-40 wt.% Al2O3; the electrolytic manganese slag contains not less than 40 wt.% SiO2.
3. A method for improving the crystallinity of red mud-electrolytic manganese slag-based X-type zeolite molecular sieves, characterized in that, The method described in claim 1 includes the following steps: Red mud is pretreated by calcination and magnetic separation. Pretreated electrolytic manganese slag is obtained by acid leaching and alkali dissolution of electrolytic manganese slag. The pretreated red mud and pretreated electrolytic manganese slag are mixed with water, and then aged and hydrothermally heated to obtain the X-type zeolite molecular sieve.