A fischer-tropsch wax isomerization cracking catalyst, its preparation method and application

Abstract

The application provides a Fischer-Tropsch wax isomerization cracking catalyst, a preparation method and application thereof. The preparation method comprises the following steps: S1, mixing a smectite initial gel with an isomerization molecular sieve, and then performing crystallization treatment to obtain an intermediate product; then performing ion exchange treatment on the intermediate product, and then performing calcination to obtain a smectite / isomerization molecular sieve material without sodium; S2, mixing the smectite / isomerization molecular sieve material without sodium with an alumina source, and then performing molding to obtain a smectite / isomerization molecular sieve carrier; and S3, loading the smectite / isomerization molecular sieve carrier with a noble metal to obtain the Fischer-Tropsch wax isomerization cracking catalyst. The application can solve the problem that in the prior art, heavy wax fractions lack a good processing method for hydrogenation conversion into oil products.

Description

Technical Field

[0001] This invention relates to the field of Fischer-Tropsch wax processing technology, and more specifically, to a Fischer-Tropsch wax isomerization cracking catalyst, its preparation method, and its application. Background Technology

[0002] Coal indirect liquefaction technology converts syngas into Fischer-Tropsch wax products through the Fischer-Tropsch synthesis process. The refined Fischer-Tropsch wax obtained through further processing is characterized by a high content of saturated chain hydrocarbons (>99%), making it very suitable for producing high viscosity-temperature index base oil products. However, the high melting point (80–90°C) and wide distillation range (350–700°C) of refined Fischer-Tropsch wax also increase the difficulty of producing Fischer-Tropsch base oils. To address these issues, the art typically employs an isomerization process, cutting the full-fraction refined wax into light, narrow-fraction Fischer-Tropsch wax (350–550°C) as feedstock. This lowers the melting point of the feedstock to 60–70°C, reducing the difficulty of isomerization processing.

[0003] CN104560136B discloses a method for isomerization hydrocracking of Fischer-Tropsch synthetic waxes, describing an amorphous silica-alumina supported Fischer-Tropsch wax isomerization cracking catalyst, using Fischer-Tropsch waxes with a distillation range of 200–530°C as feedstock, with the aim of obtaining higher diesel product yields. However, the reaction temperature in this patent is stringent, and the target feedstock has a short carbon number, making it impossible to demonstrate its effectiveness on heavy wax fractions with a distillation range of 500–700°C.

[0004] CN109420522A discloses a method for preparing a hydroisomerization-cracking catalyst, describing a method for preparing a Fischer-Tropsch wax isomerization cracking catalyst with a ZSM-22 / ZSM-23 composite support, using Fischer-Tropsch wax with a distillation range of 260–610℃ as raw material, which features a low naphtha product ratio and a low product pour point. However, the target raw material of this patent has a short carbon number, and it also cannot prove its effectiveness on heavy wax fractions with a distillation range of 500–700℃.

[0005] CN101230290B provides a method for producing solvent oils, lubricating base oils, and heavy waxes from Fischer-Tropsch synthetic waxes. The method involves separating refined Fischer-Tropsch waxes into light wax fractions with a final boiling point below 380–550°C and heavy wax fractions with an initial boiling point above 380–550°C. The light wax fraction is isomerized to prepare base oils, and the heavy wax fraction is refined to produce wax products.

[0006] Currently, there are no reports on effective hydrotreating methods for converting heavy wax fractions into oil products.

[0007] The problem with the commonly used isomerization processing and fractionation cutting routes is that the melting point of the remaining heavy Fischer-Tropsch wax (550-700℃) is above 100℃, making it more difficult to process into oil products.

[0008] Therefore, it is necessary to provide a catalyst that can efficiently convert heavy Fischer-Tropsch wax (550-700℃) into products such as diesel and base oil. Summary of the Invention

[0009] The main objective of this invention is to provide a Fischer-Tropsch wax isomerization cracking catalyst, its preparation method, and its application, in order to solve the problem that there is a lack of good hydrogenation methods for converting heavy wax fractions into oil products in the prior art.

[0010] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a Fischer-Tropsch wax isomerization catalyst is provided, comprising: S1, mixing an initial saponite gel with an isomerized molecular sieve and then performing a crystallization treatment to obtain an intermediate product; then subjecting the intermediate product to ion exchange treatment and calcining to obtain a sodium-free saponite / isomerized molecular sieve material; S2, mixing the sodium-free saponite / molecular sieve material with an alumina source and then molding it to obtain a saponite / isomerized molecular sieve support; S3, loading a noble metal onto the saponite / isomerized molecular sieve support to obtain a Fischer-Tropsch wax isomerization catalyst.

[0011] Furthermore, in the sodium-free saponite / isomeric molecular sieve material, the weight percentage of saponite is 10-90%; preferably 20-40%.

[0012] Furthermore, based on dry weight, the alumina source in the saponite / isomeric molecular sieve support comprises 10–90% by weight, preferably 50–70%; more preferably, the alumina source is boehmite.

[0013] Furthermore, the Si / Al ratio in the soapstone framework is 7–50, preferably 20–30.

[0014] Furthermore, the weight percentage of the precious metal in the Fischer-Tropsch wax isomerization catalyst is 0.2-0.6%, preferably 0.5%; more preferably, the precious metal is Pt.

[0015] Furthermore, the crystallization treatment temperature is 200–300°C and the time is 12–48 h; preferably, the calcination temperature is 400–600°C and the time is 2–10 h.

[0016] Furthermore, the isomeric molecular sieve is one or more of ZSM-22, ZSM-23, and ZSM-48.

[0017] Furthermore, the ion exchange treatment is carried out using ammonium salts, preferably ammonium chloride and / or ammonium nitrate; more preferably, the weight ratio of ammonium salt to intermediate product is (0.01 to 0.1):1.

[0018] To achieve the above objectives, according to one aspect of the present invention, a Fischer-Tropsch wax isomerization cracking catalyst prepared according to the above preparation method is provided.

[0019] According to another aspect of the present invention, the application of the above-mentioned Fischer-Tropsch wax isomerization cracking catalyst in the process of preparing lubricating oil base oil by heavy Fischer-Tropsch wax isomerization cracking is provided, wherein the heavy Fischer-Tropsch wax has a distillation range of 500-700°C and a melting point of >100°C.

[0020] Using the technical solution of this invention, a Fischer-Tropsch wax isomerization cracking catalyst was prepared. This Fischer-Tropsch wax isomerization cracking catalyst combines saponite and molecular sieves, and is suitable for catalyzing the isomerization and cracking of Fischer-Tropsch wax, especially heavy Fischer-Tropsch wax feedstock, to produce high-quality lubricating oil base products.

[0021] Soapstone is a silicate material with a lamellar structure containing silica-alumina structures. Although the lamellar structure of soapstone itself does not have pores, adjustable-size pores can be formed between the lamellars by intercalation of cationic columnar materials. The preparation of initial soapstone gel is well known to those skilled in the art; exemplarily, it can be prepared by referring to the method disclosed in patent CN106607101B.

[0022] Existing technologies include a variety of isomeric molecular sieves. However, current isomeric molecular sieve catalysts also have limitations. Their small pore diameter typically hinders hydrocarbon molecule diffusion. Although isomeric molecular sieves possess strong isomerization capabilities, they generally suffer from low liquid yields and a high naphtha proportion in cracking products. Particularly for heavy Fischer-Tropsch waxes with a distillation range of 500–700°C, using isomeric molecular sieves alone fails to yield light base oil products (distillation range 350–500°C), and the degree of isomerization in the feed fraction is also low, resulting in high pour points for heavy oil products.

[0023] Unlike existing technologies, the saponite / isomeric molecular sieve catalyst composite Fischer-Tropsch wax isomerization cracking catalyst of this invention achieves a suitable morphology by controlling the composite growth mode through a designed preparation method. This Fischer-Tropsch wax isomerization cracking catalyst efficiently combines the cracking function of saponite and the isomerization function of molecular sieves. For the isomerization cracking of heavy Fischer-Tropsch wax with a distillation range of 500–700°C, it can produce as little naphtha, diesel, and other byproducts as possible, while producing more qualified light base oil products with a distillation range of 350–500°C, with a small amount of heavy oil with a low pour point of 500–700°C remaining. This heavy oil can be used as a blending component for bright base oils or processed into gear lubricants, etc. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0025] To address the problems in the prior art as described above, according to one aspect of the present invention, a method for preparing a Fischer-Tropsch wax isomerization catalyst is provided, comprising: S1, mixing an initial saponite gel with an isomerized molecular sieve and then performing a crystallization treatment to obtain an intermediate product; then subjecting the intermediate product to ion exchange treatment and calcining to obtain a sodium-free saponite / isomerized molecular sieve material; S2, mixing the sodium-free saponite / molecular sieve material with an alumina source and then molding it to obtain a saponite / isomerized molecular sieve support; S3, loading a noble metal onto the saponite / isomerized molecular sieve support to obtain a Fischer-Tropsch wax isomerization catalyst.

[0026] The Fischer-Tropsch wax isomerization cracking catalyst of the present invention combines saponite and molecular sieve, and is suitable for catalyzing the isomerization and cracking of Fischer-Tropsch wax, especially heavy Fischer-Tropsch wax feedstock, to produce high-quality lubricating oil base oil products.

[0027] Soapstone is a silicate material with a lamellar structure containing silica-alumina structures. Although the lamellar structure of soapstone itself does not have pores, adjustable-size pores can be formed between the lamellars by intercalation of cationic columnar materials. The preparation of initial soapstone gel is well known to those skilled in the art; exemplarily, it can be prepared by referring to the method disclosed in patent CN106607101B.

[0028] Existing technologies include a variety of isomeric molecular sieves. However, current isomeric molecular sieve catalysts also have limitations. Their small pore diameter typically hinders hydrocarbon molecule diffusion. Although isomeric molecular sieves possess strong isomerization capabilities, they generally suffer from low liquid yields and a high naphtha proportion in cracking products. Particularly for heavy Fischer-Tropsch waxes with a distillation range of 500–700°C, using isomeric molecular sieves alone fails to yield light base oil products (distillation range 350–500°C), and the degree of isomerization in the feed fraction is also low, resulting in high pour points for heavy oil products.

[0029] Unlike existing technologies, the saponite / isomeric molecular sieve catalyst composite Fischer-Tropsch wax isomerization cracking catalyst of this invention achieves a suitable morphology by controlling the composite growth mode through a designed preparation method. This Fischer-Tropsch wax isomerization cracking catalyst efficiently combines the cracking function of saponite and the isomerization function of molecular sieves. For the isomerization cracking of heavy Fischer-Tropsch wax with a distillation range of 500–700°C, it can produce as little naphtha, diesel, and other byproducts as possible, while producing more qualified light base oil products with a distillation range of 350–500°C, with a small amount of heavy oil with a low pour point of 500–700°C remaining. This heavy oil can be used as a blending component for bright base oils or processed into gear lubricants, etc.

[0030] This invention uses a heterogeneous molecular sieve as a core to grow saponite on its surface. In addition to providing the growth core, the heterogeneous molecular sieve also provides a portion of the silicon source for saponite growth.

[0031] In the saponite / isomeric molecular sieve composite Fischer-Tropsch wax isomerization cracking catalyst of the present invention, saponite and isomerization molecular sieve work synergistically. Saponite typically has a lamellar structure; the composite structure of the saponite molecular sieve in this invention facilitates closer proximity between the cracking acidic sites and the isomerization acidic sites. The isomerization function weakens the cracking function, thereby reducing the formation of cracking dry gas products and increasing liquid yield. The lamellar saponite structure grown on the surface of the isomerization molecular sieve facilitates the diffusion of isomerization products, reduces the cracking of heavy oil products, and can improve the yield of low-pour-point heavy oil.

[0032] The catalyst of this invention has significant improvements over the prior art. On the one hand, it reduces the generation of cracked dry gas, resulting in a higher product liquid yield and better economic benefits. On the other hand, it increases the yield of low-pour-point heavy oil products, which can be used to process heavy lubricating oil products such as bright oil and gear oil.

[0033] In the preparation method of the invention, ion exchange is necessary because if the catalyst of the present invention contains Na, the acidic sites of the catalyst cannot be released, and thus it does not have catalytic activity.

[0034] In practice, the method for molding sodium-free soapstone / molecular sieve materials by mixing them with an alumina source can be as follows: Under the action of nitric acid solution, the composite material is mixed with boehmite and kneaded into a dough-like consistency, then extruded using an extruder. After molding, calcination is required, and the calcination process can be conventional in the field. Those skilled in the art can also select other suitable molding processes based on published literature; the process conditions are well known to those skilled in the art and will not be elaborated upon here.

[0035] In a preferred embodiment, the weight percentage of soapstone in the sodium-free saponite / isomeric molecular sieve material is 10-90%, preferably 20-40%. After the calcination treatment in step S1 of this invention, the resulting sodium-free soapstone / molecular sieve material is a composite of soapstone and isomeric molecular sieve. In actual operation, those skilled in the art can calculate the amount of raw materials added based on this weight content, and finally complete the preparation of the Fischer-Tropsch wax isomeric cracking catalyst of this invention. The preferred soapstone weight ratio is more conducive to its catalytic cracking function without causing too much Fischer-Tropsch wax to be cracked.

[0036] To better reduce the formation of cracked dry gas products, in a preferred embodiment, the weight percentage of alumina source in the saponite / isomeric molecular sieve support is 10-90%, preferably 50-70%, based on dry weight; more preferably, the alumina source is boehmite. The above-mentioned preferred alumina source ratio is more advantageous in balancing catalyst activity and product selectivity. If the amount used exceeds the preferred range of this invention, the catalyst activity will decrease; if it is less than the preferred range, the proportion of cracked dry gas products will increase, leading to a decrease in liquid yield.

[0037] To improve the yield of light base oil products and lower the pour point of heavy oils, in a preferred embodiment, the Si / Al ratio in the soapstone skeleton is 7–50, preferably 20–30. The Si / Al ratio is a key parameter in this invention. The inventors have found that controlling the Si / Al ratio within the above-mentioned range is more conducive to obtaining light base oil and heavy oil products with low pour points. If the Si / Al ratio is greater than the preferred range of this invention, the pour point of the heavy oil product will increase; if it is less than the preferred range, the yield of light base oil will decrease. In practical operation, the Si / Al ratio can be controlled by adjusting the proportion of raw materials used to prepare the initial soapstone gel. By controlling the Si / Al ratio of the soapstone material, soapstone and heterogeneous molecular sieves can be more tightly integrated and grown together.

[0038] In a preferred embodiment, the weight percentage of the noble metal in the Fischer-Tropsch wax isomerization cracking catalyst is 0.2-0.6%, preferably 0.5%; more preferably, the noble metal is Pt. Such a loading is more conducive to improving the catalytic activity of the Fischer-Tropsch wax isomerization cracking catalyst.

[0039] In a preferred embodiment, the crystallization treatment is carried out at a temperature of 200–300°C for 12–48 hours; preferably, the calcination temperature is 400–600°C for 2–10 hours. These preferred treatment conditions are more conducive to the growth of soapstone on the surface of heterogeneous molecular sieves.

[0040] In a preferred embodiment, the isomeric molecular sieve is one or more of ZSM-22, ZSM-23, and ZSM-48. Those skilled in the art can choose to purchase suitable isomeric molecular sieves, or prepare them themselves based on publicly available literature. The methods are well known to those skilled in the art and will not be described in detail here. The aforementioned preferred isomeric molecular sieves are more suitable for implementing the preparation method of the present invention to obtain a Fischer-Tropsch wax isomeric cracking catalyst with suitable performance.

[0041] To better construct channels with suitable pore sizes for ion exchange, in a preferred embodiment, the ion exchange treatment is carried out using ammonium salts, preferably ammonium chloride and / or ammonium nitrate; more preferably, the weight ratio of ammonium salt to intermediate product is 1 to 10%.

[0042] According to another aspect of the present invention, a Fischer-Tropsch wax isomerization cracking catalyst prepared by the above-described preparation method is provided. It is suitable as a catalyst for the isomerization cracking of heavy dewaxed oils and can yield high-quality lubricating oil base oil products.

[0043] According to another aspect of the present invention, the application of the above-mentioned Fischer-Tropsch wax isomerization cracking catalyst in the process of preparing lubricating oil base oil by heavy Fischer-Tropsch wax isomerization cracking is provided, wherein the heavy Fischer-Tropsch wax has a distillation range of 500-700°C and a melting point of >100°C.

[0044] The application of this invention does not impose additional requirements on the conditions of isomerization cracking. Exemplarily, the conditions in the isomerization cracking reaction can be: hydrogen partial pressure 1–10 MPa, hydrogen-to-oil ratio 300–1200:1, and space velocity 0.1–5.0 h⁻¹. -1 Temperature 300–350℃; preferably hydrogen partial pressure 3–7 MPa, hydrogen-to-oil ratio 500–800:1, and space velocity 0.5–2.0 h⁻¹. -1 The temperature is 320–340℃. The specific process for implementing the isomerization cracking reaction is well known to those skilled in the art and will not be described in detail here.

[0045] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0046] In the following embodiments, unless otherwise specified, the composition of the heavy Fischer-Tropsch wax used is shown in Table 1, where the values ​​in the left and right columns represent the percentage of distillate mass and their corresponding distillation temperatures, respectively.

[0047] Table 1

[0048]

[0049]

[0050] The preparation method of the Fischer-Tropsch wax isomerization cracking catalyst is as follows:

[0051] 1. Preparation of initial soapstone gel: Weigh 99.5g sodium metasilicate nonahydrate, 4.8g sodium hydroxide, and 82.68g sodium carbonate and dissolve them in 500g water to prepare an alkaline solution. Then, dissolve 60.9g magnesium chloride hexahydrate and 2.8g aluminum chloride hexahydrate in 50g water to prepare a salt solution. Slowly add the salt solution dropwise to the above alkaline solution at 60℃ to obtain the initial soapstone gel. Continue aging for 30 minutes and set aside for later use.

[0052] 2. Take 30g of the heterogeneous molecular sieve sample and add it to the initial saponite gel, and continue stirring for 30min. Then place it in a 1L high-pressure crystallization reactor and crystallize at 300℃ for 48h. Wash the obtained product with deionized water until neutral to obtain an intermediate product. Perform ion exchange treatment on the intermediate product with ammonium chloride (10% by weight of the intermediate product) and calcine at 600℃ for 10h to obtain sodium-free saponite / heterogeneous molecular sieve material.

[0053] 3. Mix sodium-free soapstone / isomorphic molecular sieve material and pseudoboehmite, add nitric acid solution and knead in a kneader.

[0054] 4. Impregnate Pt using the conventional equal-volume impregnation method.

[0055] The specific amounts of each component in Examples 1-8 and Comparative Examples 1-2 are shown in Table 2.

[0056] Table 2

[0057]

[0058] The product performance of the Fischer-Tropsch wax isomerization cracking catalysts obtained in Examples 1-8 and Comparative Examples 1-2 applied to heavy Fischer-Tropsch wax isomerization cracking is shown in Table 3.

[0059] The conditions for isomerization cracking were: hydrogen partial pressure 3.5 MPa, hydrogen-to-oil ratio 500:1, and space velocity 1.0 h⁻¹. -1 Temperature 345℃.

[0060] Table 3

[0061]

[0062] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0063] As shown in Comparative Examples 1 and 2, neither soapstone nor isomerized molecular sieves alone can achieve a good base oil yield at 330–550°C. In the embodiments of this invention, Examples 1 and 2, performed within the preferred scope of this invention, are superior to Examples 3–8, which are outside the preferred scope. Examples 1 and 2 of this invention yield the highest base oil yield at 330–550°C and have the lowest pour point, indicating that the catalyst of this invention effectively improves the yield of qualified base oil. Furthermore, the low pour point of the heavy oil produced facilitates further processing and utilization.

[0064] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a Fischer-Tropsch wax isomerization cracking catalyst for the preparation of lubricating oil base oil by heavy Fischer-Tropsch wax isomerization cracking, characterized in that, include: S1, the initial saponite gel is mixed with the heterogeneous molecular sieve and then crystallized to obtain an intermediate product; then the intermediate product is subjected to ion exchange treatment and then calcined to obtain a sodium-free saponite / heterogeneous molecular sieve material. S2, The sodium-free soapstone / molecular sieve material is mixed with an alumina source and then molded to obtain a soapstone / isomeric molecular sieve carrier; S3, loading noble metals onto the saponite / isomeric molecular sieve support to obtain the Fischer-Tropsch wax isomerization cracking catalyst; In the sodium-free saponite / isomeric molecular sieve material, the weight percentage of saponite is 10-90%; The Si / Al ratio in the framework of the soapstone is 7~50; The heavy Fischer-Tropsch wax has a distillation range of 500~700℃ and a melting point of >100℃; The heterogeneous molecular sieve is one or more of ZSM-22, ZSM-23, and ZSM-48.

2. The preparation method according to claim 1, characterized in that, In the sodium-free soapstone / isomeric molecular sieve material, the weight percentage of soapstone is 20-40%.

3. The preparation method according to claim 1, characterized in that, On a dry weight basis, the alumina source in the soapstone / isomeric molecular sieve support comprises 10-90% by weight.

4. The preparation method according to claim 3, characterized in that, On a dry weight basis, the alumina source accounts for 50-70% of the total weight of the soapstone / isomeric molecular sieve support.

5. The preparation method according to claim 3, characterized in that, The alumina source is boehmite.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The Si / Al ratio in the framework of the soapstone is 20-30.

7. The preparation method according to any one of claims 1 to 5, characterized in that, The precious metal accounts for 0.2-0.6% by weight in the Fischer-Tropsch wax isomerization catalyst.

8. The preparation method according to claim 7, characterized in that, The precious metal accounts for 0.5% by weight in the Fischer-Tropsch wax isomerization catalyst.

9. The preparation method according to claim 7, characterized in that, The precious metal is Pt.

10. The preparation method according to any one of claims 1 to 5, characterized in that, The crystallization treatment is performed at a temperature of 200-300℃ for 12-48 hours.

11. The preparation method according to claim 10, characterized in that, The roasting temperature is 400~600℃ and the time is 2~10h.

12. The preparation method according to any one of claims 1 to 5, characterized in that, The ion exchange treatment is carried out using ammonium salts.

13. The preparation method according to claim 12, characterized in that, The ammonium salt is ammonium chloride and / or ammonium nitrate.

14. The preparation method according to claim 12, characterized in that, The weight ratio of the ammonium salt to the intermediate product is (0.01~0.1):

1.

15. A Fischer-Tropsch wax isomerization cracking catalyst prepared by the preparation method according to any one of claims 1 to 14.

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