A reduced-state non-noble metal bifunctional catalyst, and a preparation method and application thereof

Abstract

This invention provides a reduced-state non-precious metal bifunctional catalyst, its preparation method, and its applications, relating to the fields of biofuel production and molecular sieve catalyst preparation. The reduced-state non-precious metal bifunctional catalyst comprises 20–40% Y molecular sieve, 10–20% ZSM-22 molecular sieve, 30–45% elemental nickel, and γ-Al₂O₃. The reduced-state non-precious metal bifunctional catalyst of this invention exhibits both isomerization and cracking properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biofuel production and molecular sieve catalyst preparation, in particular to a reduced non-noble metal bifunctional catalyst and a preparation method and application thereof. BACKGROUND

[0002] In order to cope with climate change and reduce greenhouse gas emissions, some countries have begun to develop and apply biofuels since the 1970s. In 1983, American scientist Graham Quick successfully used the methyl linoleate prepared by ester exchange reaction in the engine, and defined the fatty acid monoester obtained by ester exchange reaction of renewable oil and fat as biodiesel. Since then, a large amount of research work has been carried out around the synthesis method of fatty acid monoester, and the first generation of biofuel products represented by fatty acid methyl ester has been gradually formed. In recent years, some researchers at home and abroad have proposed a bio-diesel synthesis technology route based on catalytic hydrogenation process, forming a hydrocarbon-based biodiesel preparation technology.

[0003] According to the existing literature (Renew. Sustain. Energy Rev. 101 (2019) 568-589. ; Catal. Sci. Technol. 3 (2013) 70-80. ; Catalysts 9 (2019) 293. ; J. Catal. 282 (2011) 155-164.), hydrocarbon-based biodiesel is a product prepared by hydrogenation deoxygenation of bio-oil and its derivatives (fatty acid methyl ester, fatty acid), and the product is mainly n-alkanes of C 15 ~ C 18 alkanes. Because the cold flow property of n-alkanes is poor, an isomerization process is needed to improve the cold flow property of the product. Generally, in the presence of an isomerization catalyst, long-chain alkanes will undergo isomerization and cracking reactions at the same time. If the cracking reaction is too much, the yield of the product fuel oil will be reduced; if the isomerization is insufficient, the cold flow property requirement of the biofuel cannot be met. Therefore, in order to obtain as much valuable biofuel product (bio-jet fuel and low freezing point biodiesel) as possible, it is necessary to strictly control the process of hydroisomerization of bio-based long-chain alkanes, and the selectivity of isomerization and cracking is closely related to the performance of the catalyst. Alkane isomerization catalysts usually contain two types of active centers, metal centers and acid centers, which are used for the activation of C-H and C-C bonds, respectively, and belong to bifunctional catalysts. Because the acid centers on the surface of the catalyst can simultaneously catalyze the isomerization and cracking reactions of alkanes, moderate acid strength and acid amount are the key to balancing the isomerization and cracking reactions.

[0004] Patent CN200910188170.6 discloses a hydrodewaxing catalyst, its preparation method, and its application. This catalyst uses a molecular sieve support modified with metal additives and silicone oil. By sequentially depositing the additives and silicone oil, the acidity and pore shape of the inner and outer surfaces of the molecular sieve support are adjusted, thereby improving the isomerization rate of the raw material. However, the catalyst preparation process is complex, involving multiple impregnation and high-temperature calcination steps, resulting in a long preparation cycle. Furthermore, the addition of additives and silicone oil leads to a low active metal loading (1%–15%) and low reactivity; examples show that the isomerization reaction temperature reaches as high as 365℃, resulting in high energy consumption and a tendency for catalyst coking.

[0005] Patent CN201810935163.7 discloses a hydrocracking catalyst, its preparation method, and its application. The catalyst is prepared by impregnation and contains different types of phosphorus-containing molecular sieves and non-precious metal components. It exhibits excellent cracking performance in the hydrocracking reaction of Saudi vacuum residue. However, this catalyst cannot achieve co-production of biojet fuel and low-pour-point biodiesel and is not suitable for C2044. 15 ~C 18 Isomerization of bio-based long-chain alkanes. However, this catalyst requires sulfidation during use, making it unsuitable for processing near-sulfur-free bio-based feedstocks.

[0006] Patent CN201610412721.2 discloses an isomerization dewaxing method for producing bio-jet fuel and a catalyst used in the method. The catalyst is one or more mesoporous molecular sieves selected from ZSM-22, ZSM-23, ZSM-12, and SAPO-11 with silicon surface modification, and the active metal component is selected from noble metals Pt and / or Pd in ​​a content of 0.1wt% to 5wt%. Similarly, patent CN202010497292.X discloses a hydroisomerization catalyst, its preparation method, and its application. This catalyst uses ZSM-48 molecular sieve with a hollow spherical structure as a support, and the active metal component is selected from at least one of Group VIII noble metals, prepared by impregnation. Patents US11603501B2 and US20240034945A1 disclose catalyst preparation methods and their application in the production of bio-jet fuel. The catalysts used in these patents cannot simultaneously achieve isomerization and cracking, and all use noble metals as active components. Although precious metals have high activity at low temperatures, their catalysts are expensive and sensitive to impurities, making them highly susceptible to poisoning.

[0007] Patent CN202111280384.3 discloses a method for hydrodewaxing diesel fuel. The hydrodewaxing catalyst used is a non-precious metal catalyst supported on ZSM-5 molecular sieve treated with steam and other catalysts supported on molecular sieve supports, and is used in a staged loading manner. The invention shows that the preparation process of ZSM-5 molecular sieve support is complicated, energy-intensive, and easily generates acidic and alkaline waste liquids.

[0008] As is well known, petrochemical diesel and biodiesel differ significantly in composition. Petrochemical diesel contains a certain amount of cycloalkanes and aromatics, with a wide carbon number distribution; while biodiesel is almost entirely composed of n-chain alkanes, with carbon numbers concentrated between 15 and 18. Furthermore, existing petrochemical diesel aftertreatment catalysts have relatively singular functions. To ensure higher diesel yields, these catalysts tend to favor isomerization performance, making it difficult to achieve both isomerization and cracking simultaneously. The most common method is to use two reactors, one loaded with cracking catalyst and the other with isomerization catalyst, but this increases equipment investment. Therefore, conventional diesel isomerization depressant catalysts are not suitable for processing biodiesel, especially in processes aimed at producing biojet fuel and simultaneously low-pour-point biodiesel. In view of this, it is necessary to develop a non-precious metal bifunctional isomerization catalyst for the simultaneous production of biojet fuel and low-pour-point biodiesel. Summary of the Invention

[0009] To address the aforementioned issues, this application provides a reduced-state non-precious metal bifunctional catalyst. Non-precious active nickel metal nanoparticles are in situ embedded into the Y molecular sieve through a co-crystallization process. Nickel metal atoms induce the growth of the Y molecular sieve seed crystals and modify the surface of the molecular sieve particles, eliminating some acidic centers, thus forming a metal-Y molecular sieve catalyst with moderate cracking properties. This metal-Y molecular sieve catalyst is then mixed with ZSM-22 molecular sieve, which has isomerization properties, to form a bifunctional catalyst, which is then used in the production of oil-based biojet fuel and low-pour-point biodiesel.

[0010] The present invention provides a reduced non-precious metal bifunctional catalyst, which, by mass fraction, comprises 20-40% Y molecular sieve, 10-20% ZSM-22 molecular sieve, 30-45% elemental nickel and γ-Al2O3, wherein the total mass fraction of the raw materials Y molecular sieve, ZSM-22 molecular sieve, elemental nickel and γ-Al2O3 is 100%.

[0011] The preparation method of the reduced non-noble metal bifunctional catalyst includes the following steps:

[0012] S1: Prepare Y molecular sieve seed crystals;

[0013] S2: Nickel metal nanoparticles are in situ embedded into the Y molecular sieve seed crystals obtained in step S1 to obtain a metal-Y molecular sieve composite.

[0014] S3: The metal-Y molecular sieve composite prepared in step S2 is treated with an inorganic acid, and then filtered, washed with water, dried and calcined in sequence to obtain the metal-Y molecular sieve catalyst.

[0015] S4: Add ZSM-22 molecular sieve, aluminum hydroxide dry adhesive powder, dilute nitric acid solution and guar gum powder to the metal-Y molecular sieve catalyst obtained in step S3, and then mix, shape, dry, calcine and reduce to obtain a reduced non-precious metal bifunctional catalyst.

[0016] Optionally, in step S4, the mass ratio of the metal-Y molecular sieve catalyst, ZSM-22 molecular sieve, aluminum hydroxide dry adhesive powder, dilute nitric acid solution, and guar gum powder is (30-70):(5-20):(5-30):(2-4):(2-4). Alternatively, in step S4, the mass ratio of the metal-Y molecular sieve catalyst, ZSM-22 molecular sieve, aluminum hydroxide dry adhesive powder, dilute nitric acid solution, and guar gum powder is (30-50):(5-10):(10-20):(2-4):(2-4).

[0017] Optionally, the preparation method of Y molecular sieve seeds in step S1 includes the following steps:

[0018] A viscous liquid was obtained by dissolving silicon source, aluminum source and sodium hydroxide in deionized water, and then hydrothermally treating it at 30-80℃ to obtain Y molecular sieve seed crystals.

[0019] The chemical composition of the viscous liquid, calculated by the mass of oxides, is SiO2:Al2O3:Na2O:H2O = (20-40):(0.5-2):(20-40):(600-1000). Optionally, the chemical composition of the viscous liquid is SiO2:Al2O3:Na2O:H2O = (20-30):(0.5-1.5):(20-30):(600-800).

[0020] Furthermore, in step S1, Y molecular sieve seed crystals with specific structures are obtained, which promote the formation of subsequent Y molecular sieve structures and lay the foundation for the subsequent intercalation of active metals.

[0021] Optionally, the preparation method of the metal-Y molecular sieve complex in step S2 includes the following steps:

[0022] Y molecular sieve seed crystals were dispersed in deionized water, and a template agent was added. After dissolution, silicon source, aluminum source, nickel salt and sodium hydroxide were added. The reaction was carried out at 80℃-120℃. After filtration, washing and drying, a metal-Y molecular sieve composite with nickel metal nanoparticles embedded in situ into Y molecular sieve seed crystals was obtained.

[0023] The feed ratio of Y-zeolite seed crystals, silicon source, aluminum source, nickel salt, sodium hydroxide, and water, calculated by the mass of oxides, is (0.5–1.5):(1.5–2.5):(0.3–0.8):(4–6):(3.5–5):(300–400). Alternatively, the feed ratio of Y-zeolite seed crystals, silicon source, aluminum source, nickel salt, sodium hydroxide, and water, calculated by the mass of oxides, is (0.5–1.5):(2–2.5):(0.5–0.8):(5–6):(4–5):(300–350).

[0024] Furthermore, in step S2, nickel metal nanoparticles are in situ embedded in the molecular sieve through a co-hydrothermal process of nickel salt and Y molecular sieve seed crystals. On the one hand, the particle size of the molecular sieve is controlled, and on the other hand, the surface of the molecular sieve particles is modified to moderately reduce the number and intensity of acid centers, thereby obtaining a molecular sieve material with moderate cracking performance.

[0025] Optionally, the nickel salt may be one or more of the following: nitrate, sulfate, chloride, basic carbonate, and acetate.

[0026] Optionally, the template agent is one or more combinations of pyrrolidine, ethylenediamine, n-butylamine, di-n-propylamine, tetrapropylammonium bromide, tetrapropylammonium hydroxide, and hexadecyltrimethylammonium bromide (CTAB).

[0027] Optionally, the preparation method of the metal-Y molecular sieve catalyst in step S3 includes the following steps:

[0028] The metal-Y molecular sieve composite was treated with an inorganic acid solution at a temperature of 40-60℃. The treated material was then filtered, washed with water, dried, and calcined at 450-600℃ to obtain the metal-Y molecular sieve catalyst.

[0029] Furthermore, in step S3, removing the template agent through high-temperature treatment can improve the thermal and chemical stability of the molecular sieve.

[0030] Optionally, the properties of the metal-Y molecular sieve catalyst are as follows: BET specific surface area of ​​250–350 m². 2 The total pore volume is 0.3–0.45 cm³. 3 / g, SiO2:Al2O3 (molar ratio) = 5~10.

[0031] Optionally, the ZSM-22 molecular sieve has the following properties: a BET specific surface area of ​​180–220 m². 2 The total pore volume is 0.15–0.25 cm³. 3 / g, SiO2:Al2O3 molar ratio = 60~100.

[0032] Optionally, the inorganic acid is one or more of hydrochloric acid, phosphoric acid, acetic acid, and nitric acid; the concentration of the inorganic acid solution is 0.1–0.5 mol / L; preferably, the inorganic acid solution is a mixed acid solution of hydrochloric acid and phosphoric acid, wherein the mass ratio of hydrochloric acid to phosphoric acid is 1:1.

[0033] Optionally, the silicon source may be one or two of silica sol, sodium silicate, and kaolin.

[0034] Optionally, the aluminum source can be one or two of aluminum sulfate, aluminum nitrate, aluminum chloride, and sodium aluminate.

[0035] Another aspect of the present invention provides the application of a reduced non-precious metal bifunctional catalyst in the hydroisomerization / cracking reaction of bio-based long-chain alkanes. The bio-based long-chain alkanes are derived from the hydrodeoxygenation process of bio-oils and have a composition of a mixture of straight-chain alkanes of C15 to C18 with a sulfur content of <3 ppmw.

[0036] Furthermore, for C15-C18 n-alkane-based biodiesel, existing catalysts have relatively simple structures and uneven acid strength and quantity distribution, resulting in an inability to simultaneously achieve isomerization and cracking performance during hydroisomerization or cracking. This application utilizes nickel metal atoms to induce the growth of Y-zeolite seed crystals and modifies the surface of the zeolite particles to eliminate some acidic centers, forming a metal-Y-zeolite catalyst with moderate cracking performance. This catalyst is then mixed with ZSM-22 zeolite, which has isomerization properties, to create a bifunctional catalyst. When applied to C15-C18 n-alkane-based biodiesel, under moderate conditions (e.g., 260°C), the cracking rate is not less than 40%, and the isomerization rate is not less than 30%, simultaneously achieving both isomerization and cracking performance. Preferably, when the reaction temperature is increased (e.g., 300°C), the cracking rate is not less than 70%, and the isomerization rate is not less than 40%.

[0037] Optionally, the hydroisomerization reaction conditions are: reaction temperature 200–300℃, reaction pressure 3–8 MPa, and liquid hourly space velocity 0.2–3.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 400–800.

[0038] Optionally, the bio-oil is selected from waste oils and / or natural oils such as gutter oil, swill oil, acidified palm oil, soybean oil, rapeseed oil, palm oil, cottonseed oil, jatropha oil, peanut oil, tallow or lard.

[0039] Compared with the prior art, the present invention achieves at least one of the following beneficial effects:

[0040] (1) The reduced non-precious metal bifunctional catalyst of the present invention has both isomerization and cracking properties, and the selectivity of both can be adjusted by changing the molecular sieve content, thereby improving the flexibility of the entire production process. The ratio of biojet fuel and biodiesel can be flexibly adjusted according to market demand.

[0041] (2) The catalyst of this invention is a reduced catalyst, which does not require sulfidation before use and does not require sulfur replenishment during use. It will not affect the sulfur content of the product, nor will it generate sulfur-containing waste gas, thus avoiding environmental pollution. The catalyst prepared by this invention does not contain precious metals, and its production cost is much lower than that of precious metal catalysts. It is also more tolerant to raw materials.

[0042] (3) The catalyst prepared by the method of the present invention is unsupported, and the active metal content is 2 to 3 times that of conventional supported catalysts, exhibiting higher catalytic activity, and the reaction can be carried out at a lower temperature. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0044] Figure 1 The image shown is a transmission electron microscope (TEM) image of the metal-Y molecular sieve catalyst in Example 1 of the present invention;

[0045] Figure 2 A transmission electron microscope image of the Y molecular sieve in Comparative Example 1 of the present invention is shown;

[0046] Figure 3 The gas chromatogram of the liquid product obtained when the metal-Y molecular sieve catalyst of Example 4 of the present invention is applied to the hydroisomerization of hydrocarbon-based biodiesel is shown. Detailed Implementation

[0047] To more clearly illustrate the overall concept of the present invention, a detailed description will be provided below with reference to the accompanying drawings and examples.

[0048] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0049] Example 1

[0050] The reduced non-precious metal bifunctional catalyst, by mass fraction, consists of 40% Y molecular sieve, 20% ZSM-22 molecular sieve, 30% elemental nickel, and 10% γ-Al2O3.

[0051] The preparation method of reduced non-noble metal bifunctional catalysts includes the following steps:

[0052] S1: Dissolve sodium silicate, sodium aluminate and sodium hydroxide in deionized water to obtain a viscous liquid with a feed ratio of SiO2:Al2O3:Na2O:H2O = 30:1.5:30:800; then perform hydrothermal treatment at 60℃ for 2 days to obtain Y molecular sieve seed crystals.

[0053] S2: Disperse Y molecular sieve seed crystals in deionized water, add 2wt% CTAB, and after dissolution, add sodium silicate, sodium aluminate, nickel nitrate and sodium hydroxide. Crystallize at 100℃ for 36 hours. The product is filtered, washed with deionized water until neutral and dried to obtain metal-Y molecular sieve composite. The feed ratio of Y molecular sieve seed crystals, sodium silicate, sodium aluminate, nickel nitrate, sodium hydroxide and water is 0.5:2.5:0.8:4:3.5:300, calculated by the mass of oxides.

[0054] S3: The metal-Y molecular sieve composite was added to a mixed solution of 0.15 mol / L hydrochloric acid and phosphoric acid (mass ratio 1:1) and treated at 60℃ for 6 hours. The acid-treated composite was washed until neutral, then dried and calcined at 450℃ for 4 hours to obtain the metal-Y molecular sieve catalyst. The properties of the metal-Y molecular sieve catalyst are as follows: BET specific surface area is 250 m² / g. 2 The total pore volume is 0.3 cm³. 3 / g, SiO2:Al2O3 (molar ratio) = 5.

[0055] S4: Take 30g of metal-Y molecular sieve catalyst, 6g of ZSM-22 molecular sieve, 4g of aluminum hydroxide dry adhesive powder, 2g of dilute nitric acid solution, and 2g of guar gum powder. Then mix, shape, dry, calcine at 500℃ for 4 hours, and reduce at 500℃ for 4 hours to obtain an isomerization catalyst with a nickel content of 30wt%. The properties of ZSM-22 molecular sieve are as follows: BET specific surface area is 180m². 2 The total pore volume is 0.25 cm³. 3 / g, SiO2:Al2O3 molar ratio = 60.

[0056] Example 2

[0057] The reduced non-precious metal bifunctional catalyst, by mass fraction, consists of 30% Y molecular sieve, 20% ZSM-22 molecular sieve, 45% elemental nickel, and 5% γ-Al2O3.

[0058] The preparation method of reduced non-noble metal bifunctional catalysts includes the following steps:

[0059] S1: Dissolve sodium silicate, aluminum nitrate and sodium hydroxide in deionized water to obtain a viscous liquid with a feed ratio of SiO2:Al2O3:Na2O:H2O = 30:1.5:30:800; then perform hydrothermal treatment at 30℃ for 2 days to obtain Y molecular sieve seed crystals.

[0060] S2: Disperse Y molecular sieve seed crystals in deionized water, add 2wt% CTAB, and after dissolution, add sodium silicate, sodium aluminate, nickel sulfate and sodium hydroxide. Crystallize at 80℃ for 36 hours. The product is filtered, washed with deionized water until neutral and dried to obtain metal-Y molecular sieve composite. The feed ratio of Y molecular sieve seed crystals, sodium silicate, sodium aluminate, nickel sulfate, sodium hydroxide and water is 0.5:2.5:0.8:5:3.5:300, calculated by the mass of oxides.

[0061] S3: The metal-Y molecular sieve composite was added to a mixed solution of 0.15 mol / L hydrochloric acid and phosphoric acid (mass ratio 1:1) and treated at 40℃ for 6 hours. The acid-treated composite was washed until neutral, then dried and calcined at 500℃ for 4 hours to obtain the metal-Y molecular sieve catalyst. The properties of the metal-Y molecular sieve catalyst are as follows: BET specific surface area is 270 m² / g. 2 The total pore volume is 0.4 cm³. 3 / g, SiO2:Al2O3 (molar ratio) = 5.

[0062] S4: Take 30g of metal-Y molecular sieve catalyst, 15g of ZSM-22 molecular sieve, 5g of aluminum hydroxide dry adhesive powder, 2g of dilute nitric acid solution, and 2g of guar gum powder. Then mix, shape, dry, calcine at 500℃ for 4 hours, and reduce at 500℃ for 4 hours to obtain an isomerized catalyst with a nickel content of 45wt%. The properties of ZSM-22 molecular sieve are as follows: BET specific surface area is 180m². 2 The total pore volume is 0.25 cm³. 3 / g, SiO2:Al2O3 molar ratio = 60.

[0063] Example 3

[0064] The reduced non-precious metal bifunctional catalyst, by mass fraction, consists of 20% Y molecular sieve, 20% ZSM-22 molecular sieve, 30% elemental nickel, and 30% γ-Al2O3.

[0065] The preparation method of reduced non-noble metal bifunctional catalysts includes the following steps:

[0066] S1: Dissolve sodium silicate, aluminum nitrate and sodium hydroxide in deionized water to obtain a viscous liquid with a feed ratio of SiO2:Al2O3:Na2O:H2O = 30:1.5:30:800; then perform hydrothermal treatment at 80℃ for 2 days to obtain Y molecular sieve seed crystals.

[0067] S2: Disperse Y molecular sieve seed crystals in deionized water, add 2wt% CTAB, and after dissolution, add sodium silicate, sodium aluminate, nickel acetate and sodium hydroxide. Crystallize at 120℃ for 36 hours. The product is filtered, washed with deionized water until neutral and dried to obtain metal-Y molecular sieve composite. The feed ratio of Y molecular sieve seed crystals, sodium silicate, sodium aluminate, nickel acetate, sodium hydroxide and water is 0.5:2.5:0.8:4.6:3.5:300, calculated by the mass of oxides.

[0068] S3: The metal-Y molecular sieve composite was added to a mixed solution of 0.15 mol / L hydrochloric acid and phosphoric acid (mass ratio 1:1) and treated at 40℃ for 6 hours. The acid-treated composite was washed until neutral, then dried and calcined at 600℃ for 4 hours to obtain the metal-Y molecular sieve catalyst. The properties of the metal-Y molecular sieve catalyst are as follows: BET specific surface area is 300 m² / g. 2 The total pore volume is 0.35 cm³. 3 / g, SiO2:Al2O3 (molar ratio) = 5.

[0069] S4: Take 30g of metal-Y molecular sieve catalyst, 6g of ZSM-22 molecular sieve, 12g of aluminum hydroxide dry adhesive powder, 2g of dilute nitric acid solution, and 2g of guar gum powder. Then mix, shape, dry, calcine at 500℃ for 4 hours, and reduce at 500℃ for 4 hours to obtain an isomerization catalyst with a nickel content of 30wt%. The properties of ZSM-22 molecular sieve are as follows: BET specific surface area is 180m². 2 The total pore volume is 0.25 cm³. 3 / g, SiO2:Al2O3 molar ratio = 100.

[0070] Example 4

[0071] Based on Example 1, the main difference is that in step S2, the feeding ratio of Y molecular sieve seed crystals, sodium silicate, sodium aluminate, nickel nitrate, sodium hydroxide and water is 0.5:2:0.5:5:4.2:350;

[0072] In step S3: the properties of the metal-Y molecular sieve catalyst are as follows: BET specific surface area is 210 m². 2 The total pore volume is 0.26 cm³. 3 / g, SiO2:Al2O3 (molar ratio) = 4;

[0073] In step S4: 30g of metal-Y molecular sieve catalyst, 6g of ZSM-22 molecular sieve, 2g of aluminum hydroxide dry adhesive powder, 2g of dilute nitric acid solution, and 2g of guar gum powder were taken, then mixed, shaped, dried, calcined at 500℃ for 4 hours, and reduced at 500℃ for 4 hours to obtain an isomerized catalyst with a nickel content of 40wt%. The properties of the ZSM-22 molecular sieve are as follows: BET specific surface area is 200m². 2 The total pore volume is 0.2 cm³. 3 / g, SiO2:Al2O3 molar ratio = 80.

[0074] Example 5

[0075] Based on Example 1, the main difference is that in step S2, the feeding ratio of Y molecular sieve seed crystals, sodium silicate, sodium aluminate, nickel nitrate, sodium hydroxide and water is 0.5:2.5:0.8:6:5:350, calculated by the mass of oxides.

[0076] In step S3: the properties of the metal-Y molecular sieve catalyst are as follows: BET specific surface area is 180 m². 2 The total pore volume is 0.25 cm³. 3 / g, SiO2:Al2O3 (molar ratio) = 5;

[0077] In step S4: 30g of metal-Y molecular sieve catalyst, 6g of ZSM-22 molecular sieve, 2g of aluminum hydroxide dry adhesive powder, 2g of dilute nitric acid solution, and 2g of guar gum powder were taken, then mixed, shaped, dried, calcined at 500℃ for 4 hours, and reduced at 500℃ for 4 hours to obtain an isomerized catalyst with a nickel content of 45wt%. The properties of the ZSM-22 molecular sieve are as follows: BET specific surface area is 220m². 2 The total pore volume is 0.15 cm³. 3 / g, SiO2:Al2O3 molar ratio = 60.

[0078] Comparative Example 1

[0079] The catalyst preparation method includes the following steps:

[0080] S1: Dissolve sodium silicate, sodium aluminate and sodium hydroxide in deionized water to obtain a viscous liquid with a feed ratio of SiO2:Al2O3:Na2O:H2O = 30:1.5:30:800; then perform hydrothermal treatment at 60℃ for 2 days to obtain Y molecular sieve seed crystals.

[0081] S2: Disperse Y molecular sieve seed crystals in deionized water, add 2wt% CTAB, and after dissolution, continue to add sodium silicate, sodium aluminate, and sodium hydroxide. Calculated by the mass of oxides, the feed ratio is Y molecular sieve seed crystals: SiO2: Al2O3: Na2O: H2O = 0.5: 2.5: 0.8: 3.5: 300; then crystallize at 100℃ for 36 hours; after filtering the product, wash it with deionized water until neutral, and dry it to obtain Y molecular sieve.

[0082] S3: Y molecular sieve was treated in a mixed solution of 0.15 mol / L hydrochloric acid and phosphoric acid at 60°C for 6 hours; the acid-treated complex was washed until neutral, then dried and calcined at 450°C for 4 hours.

[0083] S4: Take 30g of Y molecular sieve powder, 15g of ZSM-22 molecular sieve, 10g of aluminum hydroxide dry adhesive powder, 2g of dilute nitric acid solution and 2g of guar gum powder, then mix, shape, dry and calcine at 500℃ for 4 hours to obtain a composite molecular sieve carrier;

[0084] S5: Prepare an aqueous solution of nickel nitrate, load nickel nitrate onto a support using an equal-volume impregnation method, and obtain an isomerization catalyst with a nickel loading of 30wt% after drying, calcination at 400℃ for 4 hours, and reduction at 400℃ for 4 hours.

[0085] Comparative Example 2

[0086] Based on Example 1, the main difference is that in step S4: 30g of metal-Y molecular sieve catalyst, 10.8g of aluminum hydroxide dry adhesive powder, 2g of dilute nitric acid solution and 2g of guar gum powder are taken, then mixed, shaped, dried, calcined at 500℃ for 4 hours, and reduced at 500℃ for 4 hours to obtain an isomerized catalyst with a nickel content of 30wt%.

[0087] Comparative Example 3

[0088] Based on Comparative Example 1, the main difference is that in step S4: 30g of Y molecular sieve powder, 10.8g of aluminum hydroxide dry adhesive powder, 2g of dilute nitric acid solution and 2g of guar gum powder are taken, then mixed, shaped, dried and calcined at 500℃ for 4 hours to obtain a composite molecular sieve carrier.

[0089] In step S5, an aqueous solution of chloroplatinic acid is prepared, and chloroplatinic acid is loaded onto the support using an equal-volume impregnation method. After drying, calcination at 400°C for 4 hours, and reduction at 400°C for 4 hours, an isomerization catalyst with a Pt loading of 0.5 wt% is obtained.

[0090] Experimental Example 1

[0091] The catalysts prepared in the examples and comparative examples were loaded into a high-pressure fixed-bed reactor and, after being sealed, treated at 200°C for 4 hours under a normal hydrogen atmosphere to remove adsorbed water and other gaseous impurities from the catalyst. Then, the hydrogen pressure in the reactor was increased to 4 MPa, and after the tail gas flow rate after the back pressure valve stabilized, the reactor temperature was programmed to 260°C. The isomerization reaction was then initiated with a volume hourly space velocity (VHSV) of 1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 800:1. The raw material used in the reaction is waste cooking oil that has undergone hydrodeoxygenation to obtain C20. 15 -C 18 A mixture of straight-chain alkanes, with a pour point of 17°C and a sulfur content of 2 ppmw. Performance tests were conducted, and the results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] Referring to Table 1, the bifunctional catalyst of this invention, when applied to the hydroisomerization of hydrocarbon-based biodiesel, achieves ideal results at relatively low reaction temperatures, with a liquid yield of not less than 95%, a pour point not higher than -20°C, a cracking rate of not less than 40%, and an isomerization rate of not less than 30%. Changes in metal content and addition method can significantly affect catalyst performance. With increasing nickel content, catalyst activity increases significantly; however, excessive nickel can affect the structure and content of the molecular sieve, thereby reducing the cracking rate and isomerization rate of the feedstock.

[0096] Compared with Example 1, the catalyst prepared by the conventional impregnation method has lower metal dispersion and excessive metal will cover a large number of acidic centers on the surface of the molecular sieve support, resulting in a decrease in catalyst activity, cracking and isomerization performance.

[0097] Compared with Example 1, Comparative Example 2 shows that using a single molecular sieve support affects the isomerization rate of the raw materials.

[0098] Compared to Comparative Example 3 and Example 1, the non-precious metal catalyst prepared in this invention exhibits a relatively higher feed conversion rate compared to precious metal catalysts. Although its cracking performance is lower, its product yield is higher. The non-precious metal bifunctional catalyst prepared in this invention can also achieve effects comparable to precious metal catalysts.

[0099] Experiment Example 2

[0100] The catalysts prepared in the examples and comparative examples were loaded into a high-pressure fixed-bed reactor and, after being sealed, treated at 200°C for 4 hours under a normal hydrogen atmosphere to remove adsorbed water and other gaseous impurities from the catalyst. Then, the hydrogen pressure in the reactor was increased to 4 MPa, and after the tail gas flow rate after the back pressure valve stabilized, the reactor temperature was programmed to 300°C. The isomerization reaction was then initiated with a volume hourly space velocity (VHSV) of 1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 800:1. The reactant used in the reaction is gutter oil that has undergone hydrodeoxygenation to obtain C2. 15 -C 18 A mixture of straight-chain alkanes, with a pour point of 15°C and a sulfur content of 2 ppmw. Performance tests were conducted, and the results are shown in Table 2.

[0101] Table 2

[0102]

[0103]

[0104] Referring to Table 2, when the bifunctional catalyst of this invention is applied to the hydroisomerization of hydrocarbon-based biodiesel, at higher reaction temperatures, the liquid yield is not less than 95%, the pour point is not higher than -20°C, the cracking rate is not less than 70%, and the isomerization rate is not less than 40%. Increasing the reaction temperature can improve the catalyst's reactivity and the cracking and isomerization rates of n-alkanes, but high temperatures will significantly reduce the product yield and generate more gas. Therefore, for the same catalyst, a moderate reaction temperature can yield more of the target product. The source of the straight-chain alkane feedstock has little effect on the reaction process.

[0105] refer to Figure 1 The image shows a transmission electron microscope (TEM) image of the metal-Y molecular sieve catalyst in Example 1 of this application. As can be seen from the image, in the composite catalyst prepared by in-situ embedding, the metal nanoparticles are uniformly dispersed inside the molecular sieve. The small particle size provides more metal active centers, which is beneficial to the activation of CH bonds in the raw material molecules.

[0106] refer to Figure 2 As shown, a transmission electron microscope (TEM) image of the Y molecular sieve in Comparative Example 1 of this application is displayed. It can be seen from the image that the molecular sieve is composed of blocky particles. Since it does not contain metal particles, its particle size is significantly larger than that of the metal-Y composite catalyst, which limits the exposure of active centers on the particle surface.

[0107] refer to Figure 3The figure shows a gas chromatogram of the liquid product obtained by using the metal-Y molecular sieve catalyst in Example 4 of this application. As can be seen from the figure, the product is composed of normal and isoalkanes with different carbon numbers, which are concentrated in the C8 to C16 jet fuel components. Combined with the pour point of the product in Table 2, it can be seen that the bifunctional catalyst prepared by this invention exhibits excellent cracking and isomerization performance, and is very suitable for the production of biojet fuel products.

[0108] The above description is merely an embodiment of the present invention and is not intended to limit the 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 principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. The application of a reduced-state non-precious metal bifunctional catalyst in the hydroisomerization / cracking reaction of bio-based long-chain alkanes, characterized in that, By mass fraction, the reduced non-precious metal bifunctional catalyst comprises 20-40% Y molecular sieve, 10-20% ZSM-22 molecular sieve, 30-45% elemental nickel and γ-Al2O3, with the total mass fraction of Y molecular sieve, ZSM-22 molecular sieve, elemental nickel and γ-Al2O3 being 100%. The preparation method of the reduced non-noble metal bifunctional catalyst includes the following steps: S1: Prepare Y molecular sieve seed crystals; S2: Nickel metal nanoparticles are in situ embedded into the Y molecular sieve seed crystals obtained in step S1 to obtain a metal-Y molecular sieve composite. S3: The metal-Y molecular sieve composite prepared in step S2 is treated with an inorganic acid, and then filtered, washed with water, dried and calcined in sequence to obtain the metal-Y molecular sieve catalyst. S4: Add ZSM-22 molecular sieve, aluminum hydroxide dry adhesive powder, dilute nitric acid solution and guar gum powder to the metal-Y molecular sieve catalyst obtained in step S3, then mix, shape, dry, calcine and reduce to obtain a reduced non-precious metal bifunctional catalyst. The preparation method of Y molecular sieve seeds in step S1 includes the following steps: A viscous liquid was obtained by dissolving silicon source, aluminum source and sodium hydroxide in deionized water, and then hydrothermally treating it at 30~80℃ to obtain Y molecular sieve seed crystals. The chemical composition of the viscous liquid, calculated by the mass of oxides, is SiO2:Al2O3:Na2O:H2O = (20~40):(0.5~2):(20~40):(600~1000). The preparation method of the metal-Y molecular sieve complex in step S2 includes the following steps: Y molecular sieve seed crystals were dispersed in deionized water, and a template agent was added. After dissolution, silicon source, aluminum source, nickel salt and sodium hydroxide were added. The reaction was carried out at 80℃-120℃. After filtration, washing and drying, a metal-Y molecular sieve composite with nickel metal nanoparticles embedded in situ into Y molecular sieve seed crystals was obtained. The feed ratio of Y molecular sieve seed crystals, silicon source, aluminum source, nickel salt, sodium hydroxide and water, calculated by oxide mass, is (0.5~1.5):(1.5~2.5):(0.3~0.8):(4~6):(3.5~5):(300~400). Bio-based long-chain alkanes are derived from the hydrodeoxygenation process of bio-oils and are composed of a mixture of straight-chain alkanes from C15 to C18 with a sulfur content of <3 ppmw.

2. The application of the reduced-state non-precious metal bifunctional catalyst according to claim 1 in the hydroisomerization / cracking reaction of bio-based long-chain alkanes, characterized in that, The preparation method of the metal-Y molecular sieve catalyst in step S3 includes the following steps: The metal-Y molecular sieve composite was treated with an inorganic acid solution at a temperature of 40-60℃. The treated material was then filtered, washed with water, dried, and calcined at 450-600℃ to obtain the metal-Y molecular sieve catalyst.

3. The application of the reduced-state non-precious metal bifunctional catalyst according to claim 1 in the hydroisomerization / cracking reaction of bio-based long-chain alkanes, characterized in that, The properties of the metal-Y molecular sieve catalyst are as follows: BET specific surface area is 250~350 m². 2 The total pore volume is 0.3~0.45cm. 3 / g, SiO2:Al2O3 molar ratio = 5~10.

4. The application of the reduced-state non-precious metal bifunctional catalyst according to claim 1 in the hydroisomerization / cracking reaction of bio-based long-chain alkanes, characterized in that, The properties of the ZSM-22 molecular sieve are as follows: BET specific surface area is 180~220m². 2 The total pore volume is 0.15~0.25cm³. 3 / g, SiO2:Al2O3 molar ratio = 60~100.

5. The application of the reduced-state non-precious metal bifunctional catalyst according to claim 1 in the hydroisomerization / cracking reaction of bio-based long-chain alkanes, characterized in that, The inorganic acid is one or more of hydrochloric acid, phosphoric acid, acetic acid, and nitric acid; the concentration of the inorganic acid solution is 0.1~0.5 mol / L.

6. The application of the reduced-state non-precious metal bifunctional catalyst according to claim 5 in the hydroisomerization / cracking reaction of bio-based long-chain alkanes, characterized in that, The inorganic acids are hydrochloric acid and phosphoric acid, and the inorganic acid solution is a mixed acid solution of hydrochloric acid and phosphoric acid, wherein the mass ratio of hydrochloric acid to phosphoric acid is 1:

1.

7. The application of the reduced-state non-precious metal bifunctional catalyst according to claim 1 in the hydroisomerization / cracking reaction of bio-based long-chain alkanes, characterized in that, The nickel salt is one or more of the following: nitrate, sulfate, chloride, basic carbonate, and acetate.

8. The application of the reduced-state non-precious metal bifunctional catalyst according to claim 1 in the hydroisomerization / cracking reaction of bio-based long-chain alkanes, characterized in that, The silicon source is one or two of silica sol, sodium silicate, and kaolin. And / or the aluminum source is one or two of aluminum sulfate, aluminum nitrate, aluminum chloride, and sodium aluminate.

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