Articles with water absorption function and preparation method and application thereof

Abstract

The present application relates to the field of waste catalyst recycling, and discloses a product with water absorption function, a preparation method and application thereof. The method is used for removing P element by treating waste phosphorus-aluminum molecular sieve catalyst, adding raw materials after the residue is treated by alkali fusion, stirring, and then preparing the water absorbent through crystallization and other processes. The present application can effectively recycle the waste phosphorus-aluminum molecular sieve catalyst, prepare the water absorbent reaching the first-grade product, effectively utilize the waste catalyst, change waste into treasure, be environment-friendly, and obtain considerable benefits, and can be used in harmless and resourceful industrial production of waste phosphorus-aluminum molecular sieve catalyst.

Description

Technical Field

[0001] This invention relates to the field of waste catalyst utilization, specifically to products with water-absorbing function made from waste phosphorus-aluminum molecular sieve catalysts, their preparation methods, and applications. Background Technology

[0002] With the dwindling supply of petroleum resources, the development of natural gas-based, coal-based, and bio-based routes for the synthesis of low-carbon olefins has become a hot topic. Among these, the methanol-to-olefins (MTO) technology, using coal and natural gas as raw materials, has attracted significant attention. During the reaction, the shape selectivity of the SAPO molecular sieve, with its acidity and small pore diameter, ensures high selectivity in converting methanol to ethylene and propylene. However, the presence of the "cage" structure in the SAPO molecular sieve and the inherent acidic catalytic properties also lead to rapid catalyst deactivation due to coking. Under high reaction temperatures and high space velocities, the single-pass lifetime is short, and the catalyst is completely discarded when its activity cannot meet the reaction requirements. Furthermore, the catalyst is expensive. If these waste catalyst powders could be reused, it would solve the environmental problems caused by discarded catalyst powders, turning waste into treasure; on the other hand, it would also reduce catalyst costs, thereby lowering the cost of the methanol-to-olefins process.

[0003] The phosphorus content (calculated as P2O5) in the waste MTO catalyst is 10-15% by weight, and 84-89% by weight is aluminum and silicon. Direct disposal of waste also wastes beneficial resources. Moreover, environmental protection policies are becoming increasingly strict, and simple disposal methods such as landfill are restricted.

[0004] CN106938849A describes the reuse of waste silica-alumina molecular sieves as raw materials for ZSM-5 molecular sieve preparation. CN105271331A describes the reuse of waste silica-alumina molecular sieves, but only Al is used to prepare boehmite; the reuse of silicon is not addressed, and the product's added value is low. CN105585405A and CN105582885A describe the direct recovery of waste phosphorus-alumina molecular sieve catalysts, which are then mixed with high specific surface area materials to prepare adsorbents. Valuable elements P, Al, and Si are not further separated to prepare high-value-added products. CN209306962U describes a production system for preparing alumina and phosphorus-containing multi-element fertilizers using spent MTO catalysts, mainly focusing on the process methods of the production system, but without mentioning the reuse of silicon. Therefore, how to achieve high-value-added reuse of waste phosphorus-alumina molecular sieve catalysts requires further research. Summary of the Invention

[0005] The purpose of this invention is to make up for the deficiencies of existing technologies and provide a method for preparing desiccant using waste phosphorus-aluminum molecular sieve catalysts, so as to alleviate environmental pressure and enable the waste catalysts to be utilized in a diversified and multi-path high-value-added manner.

[0006] The inventors of this invention have discovered that by using pretreated waste MTO catalyst as raw material, leaching out the phosphorus element, and separately utilizing it for resource recovery, while reusing the remaining silica-alumina solid slag, a product with certain value can be prepared. This not only alleviates environmental pressure but also enables the waste catalyst to achieve diversified and multi-path high-value-added utilization. Therefore, to achieve the above objectives, this invention provides a method for preparing a product with water-absorbing function, characterized in that the method includes:

[0007] (1) Remove phosphorus from the waste phosphorus-aluminum molecular sieve catalyst to obtain the residue after phosphorus removal;

[0008] (2) The residue obtained in step (1) is subjected to alkali fusion treatment;

[0009] (3) Mix the product obtained in step (2) with water, and then age, crystallize, dry and calcine the mixture in sequence, wherein the molar ratio of Si to Al in the mixture is greater than or equal to 1.

[0010] The present invention also provides an article obtained by the above method and its application in water absorption.

[0011] Through the above technical solution, the method of this invention can effectively utilize waste catalysts that cannot be regenerated after industrial operation, and is an environmentally friendly recycling method. Furthermore, the obtained molecular sieve product, after drying and calcination, can be used as an adsorbent for specific components, meeting the standards of first-class commercial desiccant, and is highly practical. The method of this invention is particularly suitable for the reuse of waste MTO catalysts, providing technical support for the resource utilization of such solid waste. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] In this invention, unless otherwise stated, the term "removal" does not mean the absolute removal of a substance / element, but rather the reduction of the content of a substance / element to a lower level known to those skilled in the art. "Pressure" refers to gauge pressure.

[0014] This invention provides a method for preparing a product with water-absorbing function, characterized in that the method includes:

[0015] (1) Remove phosphorus from the waste phosphorus-aluminum molecular sieve catalyst to obtain the residue after phosphorus removal;

[0016] (2) The residue obtained in step (1) is subjected to alkali fusion treatment;

[0017] (3) Mix the product obtained in step (2) with water, and then age, crystallize, dry and calcine the mixture in sequence. The molar ratio of Si to Al in the mixture is greater than or equal to 1, preferably 1-5 (such as 1, 1.1, 1.2, 1.5, 2, 3, 4, 5 or any value between the above values).

[0018] In a preferred embodiment of the present invention, in step (1), the phosphorus content in the residue after phosphorus removal is <2% by weight, that is, the conditions for removing phosphorus from the waste phosphorus-aluminum molecular sieve catalyst make the phosphorus content in the residue <2% by weight.

[0019] Phosphorus can be removed from waste phosphorus-aluminum molecular sieve catalysts using methods commonly used in the art. However, more preferably, in step (1), the method for removing phosphorus includes: reacting the waste phosphorus-aluminum molecular sieve catalyst with an inorganic acid solution, followed by solid-liquid separation. The solid phase obtained from the solid-liquid separation is used as the residue after phosphorus removal in step (2). Optionally, the liquid phase obtained from the solid-liquid separation is used to recover phosphorus. Phosphorus is an extremely limited, almost non-renewable and irreplaceable resource, and the world faces a shortage of phosphorus resources. The step of recovering phosphorus in step (1) has important strategic significance in the long term. Furthermore, the combination of phosphorus removal and phosphorus recovery and reuse takes into account both economic and social benefits. In addition, the presence of phosphorus will affect the performance of desiccant products prepared from waste catalysts. Therefore, the implementation of step (1) can ensure the desiccant performance of the resulting product. The liquid phase obtained from the solid-liquid separation is used to recover phosphorus. Conventional methods can be used to recover phosphorus from the liquid phase, which will not be elaborated here.

[0020] More preferably, the amount of inorganic acid solution used is 10-60 mol per kilogram of waste phosphorus-aluminum molecular sieve catalyst.

[0021] More preferably, the concentration of the inorganic acid solution is 1-3 mol / L. The amount of inorganic acid solution used is preferably sufficient to cover the waste aluminum phosphate molecular sieve catalyst; preferably, the amount of inorganic acid solution used, calculated as inorganic acid, is 20-30 mol per kilogram of waste aluminum phosphate molecular sieve catalyst. Using a specific (concentration, amount, and type) inorganic acid solution in the manner described above can further improve the water absorption of the resulting product.

[0022] The inorganic acid in the inorganic acid solution can be a strong acid commonly used in the art. More preferably, the inorganic acid in the inorganic acid solution is at least one of nitric acid, sulfuric acid, and hydrochloric acid.

[0023] More preferably, the contact conditions include a temperature of 50-90℃ (e.g., 55℃, 60℃, 70℃, 80℃, 85℃, 90℃, or any value between these values). More preferably, the contact conditions also include a time of 0.5-2 hours.

[0024] In step (2) of this invention, the use of high-temperature alkali fusion to treat the residue can improve the leaching and utilization rate of silicon and aluminum, and can avoid the drawbacks of using a large amount of water in hydrothermal synthesis, thus reducing wastewater generation. The amount of alkali used in the alkali fusion treatment is preferably 0.4-0.7g per gram of residue.

[0025] In step (2) of the present invention, the alkaline substance used in the alkali fusion treatment can be at least one of alkali metal hydroxide, alkali metal carbonate and alkali metal bicarbonate, preferably at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate and potassium bicarbonate.

[0026] In step (2) of this invention, the conditions for the alkali fusion treatment preferably include: a temperature of 400-900℃ (e.g., 405℃, 410℃, 420℃, 450℃, 500℃, 600℃, 700℃, 800℃, 900℃, or any value between the above values). The conditions for the alkali fusion treatment also preferably include: a time of 3-8 hours (e.g., 3.2 hours, 3.5 hours, 4 hours, 5 hours, 6 hours, 7 hours, or any value between the above values). This invention can achieve superior results even when performing alkali fusion treatment under relatively low temperature and short time conditions.

[0027] In step (3) of the present invention, the mixture may further contain an aluminum source and / or a silicon source (introduced from the outside). The amount of aluminum source and / or silicon source (introduced from the outside) is such that the molar ratio of Si to Al in the mixture is preferably 1-5 (e.g., 1, 1.1, 1.2, 1.5, 2, 3, 4, 5 or any value between the above values). Controlling the molar ratio of Si to Al in the mixture within the above range can further improve the water absorption of the resulting product. Those skilled in the art will understand that, in the above preferred embodiment, if the molar ratio of Si to Al in the product obtained in step (1) already falls within the above range, it may be possible to obtain the effect of further improving the water absorption of the resulting product without adding additional aluminum source and / or silicon source. If the molar ratio of Si to Al in the product obtained in step (1) does not fall within the above range, it can be adjusted to fall within the above range by adding additional aluminum source and / or additional silicon source, thereby obtaining the effect of further improving the water absorption of the resulting product. The molar ratio of Si to Al in the mixture can be obtained by testing the molar ratio of Si to Al in the residue in step (1).

[0028] The aluminum source can be a common substance in the art that can provide aluminum. Preferably, the aluminum source is selected from at least one of aluminum salts, aluminates, aluminum oxides, aluminum hydroxide, and aluminum alkoxides. More preferably, the aluminum source is selected from at least one of sodium aluminate, boehmite, pseudoboehmite, aluminum hydroxide, and aluminum isopropoxide.

[0029] The silicon source can be a common material in the art that can provide silicon. Preferably, the silicon source is selected from at least one of silicon oxides, silicates, and silicic acid. More preferably, the silicon source is selected from at least one of silica sol, sodium silicate, silicic acid, and silica.

[0030] In step (3) of the present invention, the amount of water used may be 3-10g relative to each gram of product obtained in step (2).

[0031] In step (3) of the present invention, the method may further include standing aging before crystallization, wherein the standing aging time is preferably 0-72h (e.g., 5h, 10h, 20h, 23h, 25h, 30h, 50h, 60h, 70h or any value between the above values).

[0032] In step (3) of the present invention, the crystallization temperature is preferably 70-110°C. The crystallization time is preferably 12-72 hours.

[0033] In step (3) of the present invention, the roasting temperature is preferably 300-600℃ (such as 400℃, 410℃, 420℃, 440℃, 445℃, 450℃, 455℃, 460℃, 500℃, 600℃ or any value between the above). The roasting time is preferably 4-6 hours.

[0034] In this invention, the waste phosphorus-aluminum molecular sieve catalyst refers to a phosphorus-, silicon-, and aluminum-containing catalyst whose catalytic activity has decreased to less than 60% of its unused value. Generally, the phosphorus content in the waste phosphorus-aluminum molecular sieve catalyst is 5-20% by weight, calculated as P2O5. The aluminum content in the waste phosphorus-aluminum molecular sieve catalyst can be 60-70% by weight, calculated as Al2O3. The silicon content in the waste phosphorus-aluminum molecular sieve catalyst can be 10-25% by weight, calculated as SiO2. The waste phosphorus-aluminum molecular sieve catalyst is preferably a spent methanol-to-olefins catalyst, more preferably a non-renewable spent methanol-to-olefins catalyst, especially a spent methanol-to-olefins catalyst that cannot be regenerated and reused (e.g., through carbonization).

[0035] This invention also provides an article prepared by the above method and its application in water absorption. Although this invention mainly describes the application of the article in water absorption, the article is not limited to water absorption; it has a molecular sieve structure and therefore can also be used in other adsorption and separation fields (such as air separation for oxygen production, separation of normal and isomeric alkanes, etc.).

[0036] The present invention will be described in detail below through examples. In the following examples, the waste catalyst is a waste phosphorus aluminum molecular sieve catalyst (the dry basis composition after removing organic matter is: Al2O3 69.36 wt%, SiO2 18.21 wt%, P2O5 11.65 wt%); room temperature refers to "around 25°C"; the drying temperature is 80°C and the time is 24 hours.

[0037] Example 1

[0038] (1) Add 50g of waste catalyst to 1000mL of 1mol / L nitric acid solution, stir and react at 90℃ for 1h, filter, wash, dry, and X-ray fluorescence spectrometry (XRF) analysis to determine that the phosphorus content in the product of this step is 0.326% by weight, and the molar ratio of Si to Al is about 1.01;

[0039] (2) Sodium hydroxide is ground and mixed with the product obtained in step (1) at a weight ratio of 0.6, and treated at 400°C for 3 hours. After cooling, the material is crushed and ground for later use.

[0040] (3) Add 10g of the product obtained in step (2) to 40g of deionized water, stir and mix for 30min, let stand at room temperature for 24h, crystallize at 80℃ for 24h, filter, wash, dry, and calcine at 450℃ for 4h to obtain the water absorbent product. According to the standard of "Method for Determination of Static Water Adsorption of Molecular Sieves" (GB / T 6287-1986), the static water adsorption capacity of the water absorbent is measured to be 25.47%, which meets the standard of first-class commercial water absorbent.

[0041] Example 2

[0042] The absorbent product was prepared according to the method described in Example 1, except that:

[0043] The volume of nitric acid solution used in step (1) was 1500 mL. XRF analysis showed that the phosphorus content in the product of this step was 0.132% by weight, and the Si / Al molar ratio was approximately 2.1.

[0044] After crystallization, the product is filtered, washed, dried, and calcined to obtain the desiccant product. The static water adsorption capacity of the desiccant is 25.98% according to the test.

[0045] Example 3

[0046] The absorbent product was prepared according to the method described in Example 1, except that:

[0047] The volume of nitric acid solution used in step (1) was 1250 mL. XRF analysis showed that the phosphorus content in the product of this step was 0.249% by weight, and the Si / Al molar ratio was approximately 1.57.

[0048] After crystallization, the product is filtered, washed, dried, and calcined to obtain the desiccant product. The static water adsorption capacity of the desiccant is 25.69% as tested.

[0049] Example 4

[0050] The absorbent product was prepared according to the method described in Example 1, except that:

[0051] The concentration and volume of the nitric acid solution used in step (1) were 2 mol / L and 500 mL, respectively. XRF analysis showed that the phosphorus content in the product of this step was 0.332% by weight, and the Si / Al molar ratio was approximately 1.

[0052] After crystallization, the product is filtered, washed, dried, and calcined to obtain the water absorbent. The static water adsorption capacity of the water absorbent is 25.42%.

[0053] Example 5

[0054] The absorbent product was prepared according to the method described in Example 1, except that:

[0055] The concentration and volume of the nitric acid solution used in step (1) were 3 mol / L and 500 mL, respectively. XRF analysis showed that the phosphorus content in the product of this step was 0.108 wt%, and the Si / Al molar ratio was approximately 2.02.

[0056] After crystallization, the product is filtered, washed, dried, and calcined to obtain the desiccant product. The static water adsorption capacity of the desiccant is 26.12%.

[0057] Example 6

[0058] The absorbent product was prepared according to the method described in Example 1, except that:

[0059] In step (2), sodium hydroxide is ground and mixed with the product obtained in step (1) at a weight ratio of 1:1.

[0060] After crystallization, the product is filtered, washed, dried, and calcined to obtain the desiccant product. The static water adsorption capacity of the desiccant is 22.358% as tested.

[0061] Example 7

[0062] The absorbent product was prepared according to the method described in Example 1, except that:

[0063] The volume of nitric acid solution used in step (1) was 0.5 mol / L, 500 mL. XRF analysis showed that the phosphorus content in the product of this step was 1.856% by weight, and the Si / Al molar ratio was approximately 0.35.

[0064] In step (3), sodium silicate is dissolved in 40g of water to replenish the silicon source until the Si / Al molar ratio is approximately 1.

[0065] After crystallization, the product is filtered, washed, dried, and calcined to obtain the water absorbent. The static water adsorption capacity of the water absorbent is 24.520%.

[0066] Comparative Example 1

[0067] The absorbent product was prepared according to the method described in Example 1, except that:

[0068] The concentration and volume of the nitric acid solution used in step (1) were 3 mol / L and 250 mL, respectively. XRF analysis showed that the phosphorus content in the product of this step was 0.398 wt%, and the Si / Al molar ratio was approximately 0.79.

[0069] After crystallization, the product is filtered, washed, dried, and calcined to obtain the desiccant product. The static water adsorption capacity of the desiccant is 5.47% as tested.

[0070] Comparative Example 2

[0071] The absorbent product was prepared according to the method described in Example 1, except that:

[0072] The volume of nitric acid solution used in step (1) was 500 mL. XRF analysis showed that the phosphorus content in the product of this step was 0.536 wt%, and the Si / Al molar ratio was approximately 0.55.

[0073] After crystallization, the product is filtered, washed, dried, and calcined to obtain the desiccant product. The static water adsorption capacity of the desiccant is 3.25% according to the test.

[0074] Comparative Example 3

[0075] The absorbent product was prepared according to the method described in Example 1, except that:

[0076] In step (2), 1.8g of sodium hydroxide is added to 40g of water and dissolved completely;

[0077] In step (3), 10g of the material obtained in step (1) is added to the sodium hydroxide solution prepared in step (2).

[0078] After stirring and mixing for 30 minutes, the product was crystallized, filtered, washed, dried, and calcined to obtain the water absorbent product. The static water adsorption capacity of the water absorbent was tested to be 20.17%.

[0079] Comparing Example 1 and Example 6, it can be seen that controlling the amount of alkali used in the alkali fusion treatment within a preferred range can yield a desiccant with a higher static water adsorption capacity. Comparing Example 1 and Comparative Examples 1-2, it can be seen that controlling the molar ratio of Si to Al in the mixture of step (3) within a suitable range is necessary to obtain a desiccant with a higher static water adsorption capacity.

[0080] In addition, using waste phosphorus-aluminum molecular sieve catalysts to prepare water-absorbing agents not only reduces the treatment cost of waste catalysts but also creates certain economic benefits. The cost and benefit accounting table is shown in Table 1. From Table 1, it can be seen that the minimum economic benefit of reusing waste phosphorus-aluminum molecular sieve catalysts using the method of the present invention is RMB 5,850 per ton of water-absorbing agent. In addition, on the one hand, it reduces the environmental pressure on enterprises and is environmentally friendly; on the other hand, the P and Al elements in the acid leaching solution described in step (1) of the embodiment can also be further utilized as resources.

[0081] Table 1

[0082]

[0083] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing an article having a water absorbing function, characterized by, The method comprises: (1) removing phosphorus elements from the waste phosphorus-aluminum molecular sieve catalyst to obtain a residue after removing phosphorus elements; (2) performing alkali fusion treatment on the residue obtained in step (1); (3) mixing the product obtained in step (2) with water, and sequentially performing crystallization, drying and calcination on the obtained mixture, wherein the molar ratio of Si to Al in the mixture is greater than or equal to 1; The conditions of the alkali fusion treatment include: a temperature of 400-500°C and a time of 3-8 h; In step (1), the content of phosphorus elements in the residue after removing phosphorus elements is <2% by weight; In step (2), the amount of alkali used in the alkali fusion treatment is 0.4-0.7 g per gram of residue.

2. The method of claim 1, wherein, In step (1), the method for removing phosphorus elements comprises: contacting the waste phosphorus-aluminum molecular sieve catalyst with an inorganic acid solution to react, and then performing solid-liquid separation, wherein the solid phase obtained by the solid-liquid separation is used as the residue after removing phosphorus in step (2), and optionally, the liquid phase obtained by the solid-liquid separation is used for recovering phosphorus.

3. The method of claim 2, wherein, The amount of inorganic acid solution is 10-60 mol per kilogram of waste phosphorus-aluminum molecular sieve catalyst, calculated as inorganic acid; And / or, the concentration of the inorganic acid solution is 1-3 mol / L; And / or, the inorganic acid in the inorganic acid solution is at least one of nitric acid, sulfuric acid and hydrochloric acid; And / or, the contacting conditions include: a temperature of 50-90°C and a time of 0.5-2 h.

4. The method of claim 1, wherein, The alkaline substance used in the alkali fusion treatment is at least one of alkali metal hydroxides, alkali metal carbonates and alkali metal bicarbonates.

5. The method of claim 1 or 4, wherein, In step (2), the alkaline substance used in the alkali fusion treatment is selected from at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate and potassium bicarbonate.

6. The method of claim 1, wherein, In step (3), the mixture further contains an aluminum source and / or a silicon source.

7. The method of claim 6, wherein, The amount of the aluminum source and / or the silicon source is such that the molar ratio of Si to Al in the mixture is 1-5; And / or, the aluminum source is at least one of aluminum salts, aluminates, oxides of aluminum, aluminum hydroxide and aluminum alkoxides; And / or, the silicon source is at least one of oxides of silicon, silicates and silicic acid.

8. The method of claim 6, wherein, The aluminum source is at least one of sodium aluminate, boehmite, pseudoboehmite, aluminum hydroxide and aluminum isopropylate; And / or, the silicon source is at least one of silica sol, sodium silicate, silicic acid and white carbon black.

9. The method of claim 1, wherein, In step (3), the amount of water is 3-10 g per gram of the product obtained in step (2); And / or, the temperature of the crystallization is 70-110°C, and the time of the crystallization is 12-72 h; And / or, the temperature of the calcination is 300-600°C, and the time of the calcination is 4-6 h.

10. A product obtained by the method according to any one of claims 1-9.

11. Use of a product obtained by the method according to any one of claims 1-9 in water absorption.

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