Methods for surface crystallization of spent FCC catalyst microspheres and catalysts

Abstract

This invention relates to the field of catalyst preparation, and discloses a method for surface crystallization of spent FCC catalyst microspheres and the catalyst prepared therefrom. The method includes the following steps: 1) mixing the spent FCC catalyst with a sodium source, a silicon source, and a directing agent in the presence of water to obtain a crystallization slurry; 2) crystallizing the crystallization slurry obtained in step 1). The processing method described in this invention is simple and efficient. While avoiding the influence of heavy metal components in the spent FCC catalyst, it can re-prepare the spent FCC catalyst into an FCC catalyst with high crystallinity and strong catalytic activity.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation, specifically to a method for surface crystallization of waste FCC catalyst microspheres and the catalyst prepared therefrom. Background Technology

[0002] Catalytic cracking (FCC) catalysts are among the most widely used catalysts in petroleum processing. With continuous recycling, the crystallinity of the catalyst gradually decreases, and metal elements from the crude oil continuously deposit on the catalyst surface, causing metal poisoning. This leads to a significant reduction in the catalyst's catalytic cracking activity and selectivity. Therefore, catalytic cracking production plants need to periodically discharge large quantities of catalysts with high metal content and reduced activity and selectivity, thus forming spent FCC catalysts.

[0003] The generation of spent FCC catalysts is enormous, and currently, most are disposed of through landfill. However, because spent FCC catalysts contain a large amount of metal elements, landfilling them pollutes the soil and groundwater. Furthermore, spent FCC catalysts contain significant amounts of silicon and aluminum, and landfilling them also results in a serious waste of resources.

[0004] In recent years, researchers have been dedicated to studying how to reuse spent FCC catalysts. Existing research generally focuses on two methods for recycling spent FCC catalysts: one is to recover valuable metals, such as vanadium and nickel, from the spent FCC catalyst through methods like acid washing; the other is to pulverize the spent catalyst and reuse its silicon and aluminum components through methods such as crushing and alkali fusion.

[0005] However, while the above methods can recover useful components from spent FCC catalysts to some extent, the low content of valuable metals in spent FCC catalysts makes recovery difficult, and the consumption of acids, alkalis, and energy is significant. Furthermore, they generate large amounts of waste liquid and residue, causing further environmental pollution. The recovery of components such as silicon and aluminum involves complex processes and high economic costs, which is detrimental to improving production efficiency and profitability.

[0006] Therefore, there is an urgent need for a simple, low-cost, and effective method for treating waste FCC molecular sieves. Summary of the Invention

[0007] The purpose of this invention is to overcome the difficulties in treating waste FCC molecular sieves in the existing technology, and to provide a method for surface crystallization of waste FCC catalyst microspheres and the catalyst prepared therefrom. This treatment method is simple and efficient. While avoiding the influence of heavy metal components in the waste FCC catalyst, it can re-prepare the waste FCC catalyst into an FCC catalyst with high crystallinity and strong catalytic activity.

[0008] The inventors of this invention, considering that spent FCC catalysts retain usable molecular sieve structures, high levels of metakaolinite, and some amorphous alumina and silica, have been dedicated to developing a method that minimizes catalyst loss and maximizes efficiency by fully utilizing the amorphous silica-alumina source without damaging the molecular sieve structure of the spent FCC catalyst. Ultimately, they discovered that surface crystallization can be performed on the microsphere structure of spent FCC catalysts, thus completing this invention.

[0009] Therefore, the first aspect of the present invention provides a method for surface crystallization of waste FCC catalyst microspheres, the method comprising the following steps:

[0010] 1) In the presence of water, waste FCC catalyst is mixed with sodium source, silicon source and directing agent to obtain crystallization slurry;

[0011] 2) Crystallize the crystallized slurry obtained in step 1).

[0012] The total proportion of the crystallization slurry, in molar ratio, is Na2O:Al2O3:SiO2:H2O = 1.8-3.7:1:7-10:300-400.

[0013] Preferably, the total proportion of the crystallization slurry, in molar ratio, is Na2O:Al2O3:SiO2:H2O = 2-3:1:8.5-10:340-360.

[0014] Preferably, the molar ratio of the directing agent is Na2O:Al2O3:SiO2:H2O = 13-18:1:13-18:160-380.

[0015] More preferably, the molar ratio of the directing agent is Na2O:Al2O3:SiO2:H2O = 15-17:1:15-17:180-250.

[0016] Preferably, based on the total amount of the crystallized slurry, the amount of the directing agent is 1-10% by weight, calculated as Al2O3.

[0017] More preferably, the amount of the directing agent is 5-10% by weight, calculated as Al2O3.

[0018] Preferably, in step 1), the weight ratio of the waste FCC catalyst to the water is 1:5-20.

[0019] More preferably, in step 1), the weight ratio of the waste FCC catalyst to the water is 1:8-12.

[0020] Preferably, the sodium source is sodium hydroxide and / or sodium silicate; more preferably, the sodium source is sodium hydroxide.

[0021] Preferably, the silicon source is one or more of silica sol, silicon dioxide, and water glass; more preferably, the silicon source is silica sol.

[0022] Preferably, the crystallization conditions include: a crystallization temperature of 90-120℃ and a crystallization time of 12-72h; more preferably, the crystallization conditions include: a crystallization temperature of 100-120℃ and a crystallization time of 24-48h.

[0023] Preferably, the method further includes the steps of washing and drying the crystallized product.

[0024] Preferably, the drying temperature is 100-110℃ and the drying time is 6-48h.

[0025] A second aspect of the present invention provides a catalyst prepared by the method described in the first aspect of the present invention.

[0026] Through the above technical solution, while retaining the original structure of the waste FCC catalyst, the waste FCC catalyst can be re-crystallized, thereby regrowing molecular sieves on the surface of the waste FCC catalyst microspheres. The molecular sieves are Y-type molecular sieves, thus obtaining new FCC catalysts simply and effectively.

[0027] In addition, by crystallizing on the surface of the original waste FCC catalyst, the heavy metal elements accumulated on the surface of the waste FCC catalyst are encapsulated inside, eliminating the need for complex treatment methods to remove the heavy metal elements and avoiding the impact of heavy metal elements on the catalyst's catalytic performance.

[0028] This method is very simple to operate and low in cost, and can efficiently and environmentally renew spent FCC catalysts. In addition, the FCC catalyst prepared in this way has excellent catalytic performance. Attached Figure Description

[0029] Figure 1 These are SEM images of catalyst C1 prepared in Example 1 of this invention and spent FCC catalyst;

[0030] Figure 2 These are the XRD patterns of catalysts C1 and C2 and spent FCC catalyst prepared in Examples 1 and 2 of this invention. Detailed Implementation

[0031] 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.

[0032] The first aspect of this invention provides a method for surface crystallization of waste FCC catalyst microspheres, wherein the method includes the following steps:

[0033] 1) In the presence of water, waste FCC catalyst is mixed with sodium source, silicon source and directing agent to obtain crystallization slurry;

[0034] 2) Crystallize the crystallized slurry obtained in step 1).

[0035] The total ratio of the crystallization slurry is Na2O:Al2O3:SiO2:H2O = 1.8-3.7:1:7-10:300-400.

[0036] The inventors of this invention have discovered that by controlling the total proportion of the crystallization slurry within the above-mentioned range, it is possible to ensure that a catalyst with performance close to that of a new FCC catalyst can still be prepared using waste FCC catalyst.

[0037] In this invention, the spent FCC catalyst can be any spent FCC catalyst produced after catalytic cracking reaction in various heavy oil fixed-bed reactors in the art, without any particular limitation.

[0038] According to the method provided by the present invention, since the surface of the spent FCC catalyst has an alumina structure, it can be used as a substrate to crystallize the surface of the spent FCC catalyst microspheres through the action of a directing agent. By crystallizing the surface of the spent FCC catalyst microspheres, new molecular sieves are grown on their surface, thereby encapsulating the heavy metals that accumulate on their surface and affect catalytic performance while obtaining a new FCC catalyst, maximizing the reduction of its catalytic effect.

[0039] Unlike existing technologies, the waste FCC catalysts from the aforementioned sources do not undergo grinding or other crushing steps and can be directly used for surface crystallization in this invention. Preferably, waste FCC catalysts with intact particles are selected for surface crystallization.

[0040] Furthermore, in actual production, wear and tear inevitably occurs during the loading, unloading, and use of the catalyst. This wear and tear does not affect its use as the waste FCC catalyst of this invention. However, considering the superior effect of obtaining catalytic products, it is preferable to select a waste FCC catalyst with a particle size of 20 μm or more; more preferably, a waste FCC catalyst with a particle size of 40 μm or more; and preferably 100 μm or less, more preferably 90 μm or less, more preferably 80 μm or less, more preferably 60 μm or less, and even more preferably 55 μm or less.

[0041] According to the method for surface crystallization of waste FCC catalyst microspheres of the present invention, firstly, in the presence of water, the waste FCC catalyst is mixed with a sodium source, a silicon source and a directing agent to obtain a crystallization slurry, and then the crystallization slurry is crystallized.

[0042] According to the present invention, for ease of operation, preferably, water is first mixed with waste FCC catalyst to obtain a mixture of water and waste FCC catalyst, and then the above-mentioned sodium source, silicon source and directing agent are added to the mixture to obtain a crystallization slurry.

[0043] In this invention, when mixing water with waste FCC catalyst, the amount of water added can be determined based on the weight of the waste FCC catalyst. For example, the weight ratio of waste FCC catalyst to water can be 1:5-20; preferably, the weight ratio of waste FCC catalyst to water is 1:8-12. By first adding water within the above range, the waste FCC catalyst can be fully dispersed in the mixture, which is beneficial to the subsequent steps. Furthermore, the mixing of waste FCC catalyst and water can wash away dust and other impurities from the surface of the waste FCC catalyst, improving the effect of subsequent surface crystallization and the quality of the final catalyst.

[0044] Furthermore, in this invention, preferably, the method further includes a step of cleaning the spent FCC catalyst before use. Cleaning removes dust and impurities from the surface and pores of the spent FCC catalyst accumulated over long-term use, making it more conducive to the subsequent crystallization step.

[0045] In this invention, the cleaning can be carried out using various conventional cleaning methods in the art, as long as the above-mentioned cleaning purpose can be achieved. For example, the waste FCC molecular sieve can be soaked in 5-10 times its volume of water for 10-60 minutes, and then drained.

[0046] In this invention, the addition of the sodium source, silicon source, and directing agent is not particularly limited and can be done in the conventional order used in molecular sieve crystallization. Preferably, the sodium source is added first, followed by the silicon source, and finally the directing agent. Of course, stirring can also be performed during and after the addition of these components to ensure more thorough and uniform mixing.

[0047] According to the present invention, a crystallization slurry is obtained by mixing a waste FCC catalyst with a sodium source, a silicon source, and a directing agent in the presence of water, such that the total ratio of the crystallization slurry is Na₂O:Al₂O₃:SiO₂:H₂O = 1.8-3.7:1:7-10:300-400. Preferably, the total ratio of the crystallization slurry, in molar ratio, is Na₂O:Al₂O₃:SiO₂:H₂O = 2-3:1:8.5-10:340-360. This ensures that the crystallization slurry meets the crystallization conditions, and a molecular sieve meeting the requirements can be prepared through crystallization.

[0048] In this invention, the sodium source can be any conventional sodium source used in the art for the crystallization synthesis of molecular sieves, such as sodium hydroxide and / or sodium silicate, without particular limitation. Preferably, the sodium source is sodium hydroxide. By selecting sodium hydroxide, while providing sodium, it can also act as an alkali in the above-mentioned water and aqueous solution of waste FCC catalyst, removing some water-insoluble impurities from the surface and pores of the waste FCC molecular sieve, further improving the effect of subsequent surface crystallization and the quality of the final catalyst.

[0049] In this invention, the silicon source can be any silicon source conventionally used in the art for the crystallization synthesis of Y-type molecular sieves, such as one or more of silica sol and silica water glass. Preferably, the silicon source is silica sol. By selecting silica sol as the silicon source, the crystallinity and purity of the generated Y-type molecular sieve can be better controlled.

[0050] In this invention, the directing agent can be any of the conventional directing agents used in the crystallization synthesis of Y-type molecular sieves, and its preparation method can also employ conventional directing agent preparation methods in the art. For example, a mixture of silicon source, aluminum source, sodium source, and water can be obtained, and the mixture can be aged at 20-40°C for 10-48 hours. Here, the silicon source can be, for example, one or more of silica sol, silica, and water glass; the aluminum source can be sodium aluminate and / or aluminum sulfate; and the sodium source can be, for example, sodium hydroxide and / or sodium silicate.

[0051] According to the present invention, the molar ratio of the directing agent is Na₂O:Al₂O₃:SiO₂:H₂O = 13-18:1:13-18:160-380; preferably, the molar ratio of the directing agent is Na₂O:Al₂O₃:SiO₂:H₂O = 15-17:1:15-17:180-250. By controlling the ratio of the directing agent within the above range, the subsequent crystallization process can be better achieved.

[0052] In this invention, the amount of the directing agent can be the same as that used in conventional crystallization synthesis of Y-type molecular sieves in the art. For example, based on the total amount of the crystallization slurry, the amount of the directing agent, calculated as Al2O3, is 1-10% by weight; preferably, the amount of the directing agent, calculated as Al2O3, is 5-10% by weight.

[0053] According to the present invention, the crystallization conditions can be any of the conditions for crystallizing and synthesizing Y-type molecular sieves in the art, without any particular limitation. For example, the crystallization conditions may include: a crystallization temperature of 90-120°C and a crystallization time of 12-72h; preferably, the crystallization conditions include: a crystallization temperature of 100-120°C and a crystallization time of 24-48h.

[0054] Furthermore, in this invention, the crystallization can be static crystallization or dynamic crystallization. To ensure a more uniform molecular sieve, dynamic crystallization is preferred. Dynamic crystallization refers to crystallization in which the crystallization slurry is kept in a non-static state during the crystallization process. Dynamic crystallization can be carried out in various devices commonly used in the art for dynamic crystallization, such as a homogeneous reactor. The conditions for dynamic crystallization include a rotational speed of 0.5-20 RPM, preferably 0.5-10 RPM.

[0055] In this invention, the method may further include steps such as washing and drying the crystallized product. The washing and drying can be carried out using various methods conventional in the art for washing and drying the crystallized molecular sieve, without any particular limitations. For example, deionized water can be used for washing, and drying can be carried out at 100-110°C for 6-48 hours, etc., which will not be elaborated here.

[0056] A second aspect of the present invention provides a catalyst prepared by the method described in the first aspect of the present invention.

[0057] According to the present invention, the catalyst is an FCC catalyst, and a crystallized Y-type molecular sieve is formed on its surface. Preferably, the molecular sieve is a Y-type molecular sieve.

[0058] The present invention will be described in detail below through embodiments, but the present invention is not limited to the following embodiments.

[0059] In the following examples, the spent FCC catalyst used was provided by Beijing Yanshan Branch of China Petroleum & Chemical Corporation. Its particle size was about 40-50 μm, and the content of Al2O3 in the spent molecular sieve was 49.8% by weight and the content of SiO2 was 39.4% by weight.

[0060] In the following examples, the Al2O3 and SiO2 contents in waste FCC were determined by XRF fluorescence spectrometry (XRF fluorescence spectrometer purchased from Rikagu Corporation, Japan).

[0061] In the following examples, the crystal form of the molecular sieve was determined by XRD diffractometer (XRD diffractometer was purchased from Rikagu Corporation, Japan, model Smart SE).

[0062] In the following examples, the SEM images of the catalyst were obtained by scanning electron microscopy (the scanning electron microscope was purchased from FEI GmbH, Netherlands, model Quanta 200).

[0063] Preparation Example 1: Preparation of Directing Agent

[0064] A mixture of water glass, sodium aluminate, sodium hydroxide, and deionized water was prepared by mixing them in a molar ratio of Na2O:Al2O3:SiO2:H2O = 17:1:17:209. The mixture was then aged at 35°C for 24 hours to obtain the directing agent.

[0065] Example 1

[0066] 1) Mix 31.6g of deionized water with 3g of waste FCC catalyst and stir until homogeneous to obtain the first mixture;

[0067] 2) Add 9.6g of NaOH to the first mixture and stir for 5 minutes to obtain the second mixture;

[0068] 3) Add 21.6g of silica sol (purchased from Dezhou Jinghuo Technology Glass Co., Ltd., with SiO2 content of 30% by weight, the same below) to the second mixture and stir for 10 minutes to obtain the third mixture;

[0069] 4) Add 6.8g of directing agent to the third mixture and stir for 1 hour to obtain a crystallized slurry. The total proportion of the crystallized slurry is Na2O:Al2O3:SiO2:H2O = 2.9:1:8.8:345, based on the molar ratio.

[0070] 5) Add the crystallized slurry obtained in step 4) to the homogeneous reactor and crystallize at 120°C for 24 hours. The rotation speed of the homogeneous reactor is 5 RPM.

[0071] 6) The crystallized product was washed with 5 times the amount of deionized water and dried at 100°C for 24 hours to obtain catalyst C1.

[0072] Figure 1 These are SEM images of catalyst C1 and spent FCC catalyst, where a1 and a2 are SEM images of spent FCC catalyst, and b1 and b2 are SEM images of crystallized catalyst C1.

[0073] Depend on Figure 1 It can be seen that new molecular sieves have grown on the surface of the original waste FCC catalyst and are uniformly encapsulated.

[0074] Figure 2 The XRD patterns are of catalyst C1, catalyst C2 prepared in Example 2 below, and waste FCC catalyst (for easy comparison, the XRD patterns of the three catalysts are placed in the same sub-figure corresponding to the horizontal axis).

[0075] Depend on Figure 2 It can be seen that the waste FCC catalyst microsphere surface crystallization method of the present invention can grow a large number of molecular sieves on the surface of waste FCC, and they are Y molecular sieves.

[0076] Example 2

[0077] 1) Mix 33g of deionized water with 2.8g of waste FCC catalyst and stir until homogeneous to obtain the first mixture;

[0078] 2) Add 8.3g of NaOH to the first mixture and stir for 5 minutes to obtain the second mixture;

[0079] 3) Add 22.3g of silica sol to the second mixture and stir for 10 minutes to obtain the third mixture;

[0080] 4) Add 6.3g of directing agent to the third mixture and stir for 1 hour to obtain a crystallized slurry. The total proportion of the crystallized slurry is Na2O:Al2O3:SiO2:H2O = 2:1:9.6:360 in molar ratio.

[0081] 5) Add the crystallized slurry obtained in step 4) to the homogeneous reactor and crystallize at 110°C for 48 hours. The rotation speed of the homogeneous reactor is 10 RPM.

[0082] 6) The crystallized product was washed with 5 times the amount of deionized water and dried at 110℃ for 24h to obtain catalyst C2.

[0083] Example 3

[0084] 1) Mix 37g of deionized water with 4.3g of waste FCC catalyst and stir until homogeneous to obtain the first mixture;

[0085] 2) Add 10.5g of NaOH to the first mixture and stir for 5 minutes to obtain the second mixture;

[0086] 3) Add 24.8g of silica sol to the second mixture and stir for 10 minutes to obtain the third mixture;

[0087] 4) Add 7.0g of directing agent to the third mixture and stir for 1h to obtain a crystallized slurry. The total proportion of the crystallized slurry is Na2O:Al2O3:SiO2:H2O = 2.2:1:9.8:355, based on the molar ratio.

[0088] 5) Add the crystallized slurry obtained in step 4) to the homogeneous reactor and crystallize at 100°C for 36 hours. The rotation speed of the homogeneous reactor is 7 RPM.

[0089] 6) The crystallized product was washed with 5 times the amount of deionized water and dried at 105℃ for 30h to obtain catalyst C3.

[0090] Test Example 1: Crystallinity Test

[0091] The crystallinity of the spent FCC catalyst C, the new FCC catalyst C0 before the corresponding spent FCC catalyst was used (FCC catalyst C0 was provided by China Petroleum & Chemical Corporation Beijing Yanshan Branch), and the catalysts C1, C2 and C3 prepared in the embodiments of the present invention were tested, and the results are shown in Table 1.

[0092] Table 1

[0093] Catalyst number C C0 C1 C2 C3 Crystallinity (%) 45.3 89.9 88.3 90.2 90.6

[0094] As can be seen from the results in Table 1, the crystallinity of catalysts C1-C3 prepared using the embodiments of the present invention can be restored to a level similar to that of the new FCC catalyst, proving that it has the same catalytic performance as the new FCC catalyst.

[0095] 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 crystallizing the surface of spent FCC catalyst microspheres, characterized by, The method comprises the following steps: 1) mixing the waste FCC catalyst with a sodium source, a silicon source and a directing agent in the presence of water to obtain a crystallization slurry; 2) crystallizing the crystallization slurry obtained in step 1), wherein the total proportion of the crystallization slurry is Na2O:Al2O3:SiO2:H2O=2-2.2:1:9.6-9.8:355-360 in terms of molar ratio, the proportion of the directing agent is Na2O:Al2O3:SiO2:H2O=15-17:1:15-17:180-250 in terms of molar ratio, the crystallization conditions comprise a crystallization temperature of 100-120℃ and a crystallization time of 24-48h.

2. The method of claim 1, wherein, The amount of the directing agent is 1-10% by weight in terms of Al2O3 based on the total amount of the crystallization slurry.

3. The method of claim 2, wherein, The amount of the directing agent is 5-10% by weight in terms of Al2O3 based on the total amount of the crystallization slurry.

4. The method of claim 1, wherein, In step 1), the weight ratio of the waste FCC catalyst to the water is 1:5-20.

5. The method of claim 4, wherein, In step 1), the weight ratio of the waste FCC catalyst to the water is 1:8-12.

6. The method of claim 1, wherein, The sodium source is sodium hydroxide and / or sodium silicate.

7. The method of claim 6, wherein, The sodium source is sodium hydroxide.

8. The method of claim 1, wherein, The silicon source is one or more of silica sol, silicon dioxide and water glass.

9. The method of claim 8, wherein, The silicon source is silica sol.

10. The method of claim 1, wherein, The method further comprises the steps of washing and drying the product after crystallization; The drying temperature is 100-110℃ and the drying time is 6-48h.

11. The catalyst prepared by the method of any one of claims 1-10.

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