Isomerization catalysts, methods for making and using the same

Abstract

The application relates to the technical field of catalysts, in particular to an isomerization catalyst and a preparation method and application thereof, the preparation method comprising the following steps: mixing a silicon source, an aluminum source, an alkali metal hydroxide, a template agent, ZSM-48 molecular sieve seeds and a solvent, sequentially performing aging treatment and crystallization treatment, and forming a crystallization product; mixing the crystallization product with an ammonium salt solution, performing ammonium exchange, and forming a catalyst precursor; and performing calcination treatment on the catalyst precursor in a rotating state, and forming the isomerization catalyst. The preparation method of the isomerization catalyst is low in production cost, the prepared isomerization catalyst is high in raw material conversion rate, excellent in isomerization selectivity, and suitable for continuous production operation of a fixed bed reactor.

Description

Technical Field

[0001] This application relates to the field of catalyst technology, and in particular to isomerization catalysts, their preparation methods, and applications. Background Technology

[0002] Isomerization of unsaturated fatty acids (such as oleic acid, linoleic acid, or linolenic acid) is a key technology for converting unsaturated fatty acids into branched isomers. The branched isomers prepared have important applications in biodiesel, lubricating oil, surfactants, and other fields.

[0003] The isomerization reaction of unsaturated fatty acids has been extensively studied. It has been reported that when traditional aluminosilicate molecular sieves are used as catalysts, the isomerization reaction mainly occurs at and near the sieve pores. Desorption of unsaturated fatty acids is hindered deep within the sieve channels, increasing the probability of product cracking and polymerization, and readily generating small-molecule hydrocarbons and trimers, leading to reduced selectivity and yield of the target product. To improve catalytic efficiency and reduce secondary cracking, bifunctional catalysts of aluminosilicate molecular sieves supported with noble metal components are generally used to improve isomerization selectivity. However, the cost of noble metals accounts for more than 60% of the total catalyst cost, which is 10-20 times that of non-noble metal catalysts, severely limiting the economic viability of the technology.

[0004] Meanwhile, since the above-mentioned bifunctional catalysts are prone to deactivation of metal active sites when using fixed-bed reactors, batch reactors are generally used. However, batch reactors are cumbersome to operate, time-consuming, have large quality fluctuations between different batches, and are difficult to separate after mixing with the product, resulting in low recovery rates. Summary of the Invention

[0005] Based on this, this application provides an isomerization catalyst, its preparation method and application. The preparation method of the isomerization catalyst has low production cost, high feed conversion rate, excellent isomerization selectivity, and is suitable for continuous production operation in a fixed-bed reactor.

[0006] In a first aspect, this application provides a method for preparing an isomerization catalyst, comprising the following steps:

[0007] A silicon source, an aluminum source, an alkali metal hydroxide, a template agent, ZSM-48 molecular sieve seed crystals and a solvent are mixed and then subjected to aging and crystallization treatments in sequence to form a crystallized product.

[0008] The crystallized product was mixed with an ammonium salt solution to undergo ammonium exchange, forming a catalyst precursor; and

[0009] The catalyst precursor is calcined under rotating conditions to form an isomerized catalyst.

[0010] The isomerization catalyst has a molar ratio of 1.0SiO2: (0.007-0.014)Al2O3: (0.06-0.08)M2O: (0.009-0.018)R1:(22-33.4)R2, where M is an alkali metal, R1 is a template agent, and R2 is a solvent; the mass ratio of silicon source to ZSM-48 molecular sieve seed crystals is 1:(0.03-0.1).

[0011] The crystallization temperature is 190℃-200℃, and the crystallization time is 18h-24h;

[0012] The calcination conditions include: sequentially subjecting the catalyst precursor to a first calcination, a second calcination, and a third calcination, with the first calcination temperature being 90℃-100℃, the second calcination temperature being 200℃-250℃, and the third calcination temperature being 530℃-600℃.

[0013] In some embodiments, the solvent content of the catalyst precursor is 75% or more; optionally, the solvent includes water.

[0014] In some implementations, at least one of the following conditions is met:

[0015] (1) The first calcination time is 1-2 hours;

[0016] (2) The second calcination time is 1-2 hours;

[0017] (3) The third calcination time is 1h-5h.

[0018] In some embodiments, the rotation conditions include: when the calcination temperature is less than 120°C, the rotation speed is 4 rpm-6 rpm; when the calcination temperature is greater than or equal to 120°C, the rotation speed is 14 rpm-16 rpm.

[0019] In some embodiments, the particle size D50 of the isomerization catalyst is 0.2 cm to 0.35 cm.

[0020] In some embodiments, the ammonium exchange step satisfies at least one of the following conditions:

[0021] (1) The ammonium salt in the ammonium salt solution includes one or more of ammonium chloride, ammonium sulfate and ammonium nitrate;

[0022] (2) The concentration of the ammonium salt solution is 0.5 mol / L-1 mol / L;

[0023] (3) The temperature for ammonium exchange is 75℃-85℃;

[0024] (4) The number of ammonium exchanges is 2-3 times, and the time for each ammonium exchange is 0.5h-1.5h independently;

[0025] (5) The solid-liquid ratio of the crystallization product to the ammonium salt solution is 0.1 g / mL - 0.2 g / mL;

[0026] (6) The solvent for ammonium salt solutions includes water.

[0027] In some implementations, at least one of the following conditions is met:

[0028] (1) The silicon source includes one or more of silicon dioxide and silica;

[0029] (2) The aluminum source includes one or more of sodium aluminate and aluminum sulfate;

[0030] (3) Alkali metal hydroxides include one or more of sodium hydroxide and potassium hydroxide, and M2O is one or more of Na2O and K2O;

[0031] (4) The template agent includes one or more of hexamethylammonium bromide, 1,6-hexanediamine and hexamethyldiammonium hydroxide.

[0032] Secondly, this application provides an isomerization catalyst, which is prepared using the above-described method for preparing isomerization catalysts.

[0033] Secondly, this application provides the application of the above-mentioned isomerization catalyst in the isomerization reaction of unsaturated fatty acids, wherein the unsaturated fatty acids include one or more of oleic acid, linoleic acid and linolenic acid.

[0034] In some embodiments, the unsaturated fatty acid isomerization reaction is carried out in a fixed-bed reactor at a reaction temperature of 260°C-280°C, a reaction pressure of 1.5 MPa-2.5 MPa, a carrier gas to unsaturated fatty acid volume ratio of (800-1200):1, and a liquid hourly space velocity of 0.15 h⁻¹. -1 -0.25h -1 .

[0035] Compared with traditional technologies, this application has at least the following beneficial effects:

[0036] 1. This application describes the preparation of an isomerization catalyst with a cruciform microstructure primary crystalline framework by controlling the synthesis formula and crystallization conditions. This framework is composed of interlocking rod-shaped nanocrystals. While retaining the inherent microporous structure of ZSM-48 molecular sieve, it introduces a large number of intercrystalline mesopores, forming a hierarchical porous structure with high specific surface area and excellent mass transfer performance. This hierarchical porous structure not only reduces the diffusion and mass transfer resistance of reactant and product molecules within the catalyst channels, allowing product molecules to rapidly desorb and leave the active sites, avoiding prolonged retention at acidic centers, but also inhibits secondary side reactions such as excessive cracking. Furthermore, this catalyst exhibits excellent feed conversion rate and isomerization selectivity without loading noble metal active components, significantly reducing production costs. It also avoids the problem of noble metal active sites being easily poisoned and deactivated during continuous reactions, and can operate efficiently and stably in a fixed-bed continuous flow reaction system, improving production efficiency and product quality consistency.

[0037] 2. The preparation method provided in this application only requires the addition of a small amount of template agent and does not introduce precious metal components, which significantly reduces the production difficulty and production cost.

[0038] 3. This application only performs calcination treatment after ammonium exchange, and adopts a three-stage programmed temperature rise calcination, which reduces the risk of violent combustion and ignition of the template agent and prevents local overheating from causing the collapse of the catalyst pore structure.

[0039] 4. This application achieves simultaneous removal of template agent, opening of micropores and intergranular mesopores, formation of acidic active centers, and rolling molding of catalyst particles by calcining the catalyst precursor in a rotating state, which simplifies the process and reduces energy consumption. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic flowchart of the preparation method of the isomerization catalyst in one embodiment of this application.

[0042] Figure 2 This is a schematic diagram of the reaction apparatus for the isomerization reaction in one embodiment of this application.

[0043] Figure 3 This is a SEM image of the isomerization catalyst prepared in Example 1 of this application.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1. Feeding unit; 11. First high-pressure constant flow pump; 12. Second high-pressure constant flow pump; 13. Gas mass flow controller; 14. Mixer; 2. Fixed bed reactor; 21. Protective bed; 22. Inert packing layer; 23. Catalytic reaction layer; 3. Product separation unit; 31. Cooler; 32. Gas-liquid separator; 33. Storage tank; 34. Back pressure valve regulator; 341. Back pressure pneumatic regulating valve; 342. First shut-off ball valve; 343. Second shut-off ball valve; 344. Bypass valve; 345. Pressure controller. Detailed Implementation

[0046] A detailed reference is now provided to embodiments of this application, one or more of which are described below. Each embodiment is provided for explanation and not for limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to this application without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0047] Therefore, this application is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of this application are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this application.

[0048] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0049] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0050] In this article, when referring to units of data ranges, if a unit is only followed by the right endpoint, it means that the units of the left and right endpoints are the same.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0052] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0053] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0054] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0055] like Figure 1 As shown, in a first aspect, this application provides a method for preparing an isomerization catalyst, comprising the following steps:

[0056] S10. Mix silicon source, aluminum source, alkali metal hydroxide, template agent, ZSM-48 molecular sieve seed crystal and solvent, and perform aging treatment and crystallization treatment in sequence to form crystallized product.

[0057] S20. The crystallized product is mixed with an ammonium salt solution to perform ammonium exchange and form a catalyst precursor.

[0058] S30. The catalyst precursor is calcined under rotation to form an isomerized catalyst.

[0059] The isomerization catalyst has a molar ratio of 1.0SiO2:(0.007-0.014)Al2O3:(0.06-0.08)M2O:(0.009-0.018)R1:(22-33.4)R2, where M is an alkali metal, R1 is a template agent, and R2 is a solvent. The mass ratio of silicon source to ZSM-48 molecular sieve seed crystals is 1:(0.03-0.1). The crystallization temperature is 190℃-200℃, and the crystallization time is 18h-24h. The calcination conditions include sequentially subjecting the catalyst precursor to a first calcination, a second calcination, and a third calcination. The first calcination temperature is 90℃-100℃, the second calcination temperature is 200℃-250℃, and the third calcination temperature is 530℃-600℃.

[0060] This application describes the preparation of an isomerization catalyst with a cruciform microstructure primary crystalline framework by controlling the synthesis formulation and crystallization conditions. This framework is composed of interlocking rod-shaped nanocrystals, and while retaining the inherent microporous structure of ZSM-48 molecular sieves, it introduces a large number of intergranular mesopores, forming a hierarchical porous structure with high specific surface area and excellent mass transfer performance. This hierarchical porous structure not only reduces the diffusion and mass transfer resistance of reactant and product molecules within the catalyst channels, allowing product molecules to rapidly desorb and leave the active sites, avoiding prolonged retention at acidic centers, but also inhibits secondary side reactions such as excessive cracking. Furthermore, this catalyst exhibits excellent feed conversion rate and isomerization selectivity without the need for loading noble metal active components, significantly reducing production costs. It also avoids the problem of noble metal active sites being easily poisoned and deactivated during continuous reactions, and can operate efficiently and stably in fixed-bed continuous flow reaction systems, improving production efficiency and product quality consistency.

[0061] The preparation method provided in this application only requires the addition of a small amount of template agent and does not introduce precious metal components, which significantly reduces the production difficulty and production cost.

[0062] Compared to the traditional process of calcining before and after ammonium exchange, this application only performs calcination after ammonium exchange, and adopts a three-stage programmed temperature rise calcination, which reduces the risk of violent combustion and ignition of the template agent and prevents local overheating from causing the collapse of the catalyst pore structure.

[0063] This application achieves simultaneous removal of template agent, opening of micropores and intergranular mesopores, formation of acidic active centers, and rolling molding of catalyst particles by calcining the catalyst precursor in a rotating state, thereby simplifying the process and reducing energy consumption.

[0064] In some embodiments, in S10, the aging conditions include: an aging temperature of room temperature (20°C-25°C) and an aging time of 20 min-40 min.

[0065] Optionally, in S10, the crystallization temperature is 190℃ or 200℃, or the crystallization temperature can be within any two of the above temperatures. The crystallization time is 18h, 20h, 22h, or 24h, or the crystallization time can be within any two of the above times. This application controls the crystallization conditions within the above range, regulates the relative rates of the "nucleation" and "growth" processes, increases the nucleation rate by increasing the crystallization temperature, suppresses end-face growth along the channel direction, preferentially grows on special crystal faces to obtain a cross-shaped crystal, and adjusts the crystallization time to obtain a regular, ordered, and highly crystalline crystal form.

[0066] In some embodiments, the crystallization process is followed by steps of cooling, separation, washing, and drying.

[0067] Optionally, the material can be washed with water until neutral and then dried at 90℃-110℃ to form a crystallized product. It is understood that the crystallized product prepared in this application is ZSM-48 molecular sieve raw powder.

[0068] In some embodiments, in S20, the ammonium salt in the ammonium salt solution includes one or more of ammonium chloride, ammonium sulfate, and ammonium nitrate.

[0069] In some embodiments, the concentration of the ammonium salt solution is 0.5 mol / L to 1 mol / L.

[0070] Optionally, the concentration of the ammonium salt solution can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L, or the concentration of the ammonium salt solution can be within any two of the above concentrations. This improves ion exchange efficiency and alkali metal removal rate.

[0071] In some embodiments, the ammonium exchange temperature is 75°C-85°C. Optionally, the ammonium exchange temperature is 75°C, 80°C, or 85°C, or it can be within any two of the above temperatures. By controlling the ammonium exchange temperature within the above range, the integrity of the crystal framework of the molecular sieve inside the catalyst is effectively protected. Further, the ammonium exchange temperature is 80°C-85°C.

[0072] In some embodiments, the ammonium exchange is performed 2-3 times, with each ammonium exchange lasting independently for 0.5-1.5 hours. This ensures the complete removal of alkali metal ions from the molecular sieve, laying the foundation for the formation of sufficient acidic active centers in subsequent calcination steps, while avoiding excessive time and number of exchanges that could lead to dealuminization.

[0073] In some embodiments, the solid-liquid ratio of the crystallized product to the ammonium salt solution is 0.1 g / mL to 0.2 g / mL.

[0074] In some embodiments, the solvent for the ammonium salt solution includes water.

[0075] In some embodiments, the alkali metal content in the catalyst precursor is less than 0.1 wt%.

[0076] In some embodiments, in S30, the first calcination time is 1-2 hours. Calcination at 90-100°C for this time removes moisture from the catalyst precursor, achieves low-temperature uniform preheating of the material, and initially forms mother pellets.

[0077] In some embodiments, in S30, the second calcination time is 1-2 hours. Calcination at 200-250°C for this time allows the template agent to decompose slowly and controllably, effectively preventing localized overheating from causing the collapse of the catalyst's pore structure.

[0078] In some embodiments, in S30, the third calcination time is 1-5 hours. Calcination at 530°C-570°C for this time removes residual template agent, opening the channels of micropores and intergranular mesopores; allowing NH4... + In-situ decomposition and conversion into H+ bound to skeletal oxygen + This forms acidic active centers and simultaneously stabilizes the crystal framework of the molecular sieve inside the catalyst.

[0079] In some embodiments, the heating rate of the calcination treatment is 2°C / min - 5°C / min.

[0080] In some embodiments, the solvent content of the catalyst precursor is 75% or higher. This facilitates the rolling and shaping of the material during calcination.

[0081] In some of these embodiments, the solvent includes water.

[0082] In some embodiments, the rotation conditions include: a rotation speed of 4-6 rpm when the calcination temperature is below 120°C, and a rotation speed of 14-16 rpm when the calcination temperature is above or equal to 120°C. When the calcination temperature is below 120°C, the material has a high solvent content and low strength, so low-speed rolling gently promotes the formation of mother pellets; when the temperature is above or equal to 120°C, the material has already been preliminarily shaped, so increasing the rotation speed enhances heat transfer, making the particles more uniformly heated and more uniform in size at high temperatures, and promoting the timely escape of template agent decomposition products and ammonia.

[0083] In some embodiments, the particle size D50 of the isomerization catalyst is 0.2 cm to 0.35 cm. This avoids excessive bed resistance due to excessively small particle size, while also avoiding excessive internal diffusion resistance of reactants due to excessively large particle size, thereby improving the catalytic efficiency of the isomerization reaction.

[0084] In some embodiments, the silicon source includes one or more of silicon dioxide and silica.

[0085] In some embodiments, the aluminum source includes one or more of sodium aluminate and aluminum sulfate.

[0086] In some embodiments, the alkali metal hydroxide includes one or more of sodium hydroxide and potassium hydroxide, and M2O is one or more of Na2O and K2O.

[0087] In some embodiments, the template agent includes hexamethylammonium bromide.

[0088] Secondly, this application provides an isomerization catalyst, which is prepared using the above-described method for preparing isomerization catalysts.

[0089] Thirdly, this application provides the application of the above-mentioned isomerization catalyst in the isomerization reaction of unsaturated fatty acids, wherein the unsaturated fatty acids include one or more of oleic acid, linoleic acid and linolenic acid.

[0090] In some embodiments, the unsaturated fatty acid isomerization reaction is carried out in a fixed-bed reactor 2 at a reaction temperature of 260°C-280°C, a reaction pressure of 1.5 MPa-2.5 MPa, a carrier gas to unsaturated fatty acid volume ratio of (800-1200):1, and a liquid hourly space velocity of 0.15 h⁻¹. -1 -0.25h -1 .

[0091] Optionally, the ratio of the number of moles of lithium in the lithium source to the number of moles of transition metal in the nickel-cobalt-manganese precursor is 1:1, 1.02:1, 1.04:1, 1.06:1, or 1.08:1. Alternatively, the ratio of the number of moles of lithium in the lithium source to the number of moles of transition metal in the nickel-cobalt-manganese precursor may also be within the range between any two of the above ratios.

[0092] In some of these implementations, such as Figure 2 As shown, the reaction apparatus for the isomerization reaction in this application includes a raw material pretreatment unit (not shown), a feeding unit 1, a reaction unit, and a product separation unit 3.

[0093] In some embodiments, the raw material pretreatment unit includes a heating tank, a dehydration tower, a filter (≤10μm), and an adsorption tower. The pretreatment process is as follows: the unsaturated fatty acid raw material is heated and melted by a heating tube, dehydrated in the dehydration tower until the moisture content is less than 0.1%, then filtered through the filter and enters the adsorption tower, where metal ions and colloids are removed.

[0094] In some embodiments, the feeding unit 1 includes a first high-pressure constant flow pump 11, a second high-pressure constant flow pump 12, a gas mass flow controller 13, and a mixer 14. The first high-pressure constant flow pump 11 is used to transport the pretreated unsaturated fatty acid raw material, the second high-pressure constant flow pump 12 is used to transport water, the gas mass flow controller 13 is used to transport nitrogen, and the unsaturated fatty acids and water are stirred and mixed evenly in the mixer 14 to prepare for the next process.

[0095] In some embodiments, the reaction unit includes a fixed-bed reactor. The fixed-bed reactor 2 includes a protective bed 21, a catalytic reaction layer 23, and an inert packing layer 22 disposed between the two. The protective bed 21 is packed with a demetallizing adsorbent, exemplarily including one or more of diatomaceous earth, activated alumina, activated carbon, and ceramic materials. The catalytic reaction layer 23 is packed with the aforementioned isomerization catalyst for carrying out the isomerization reaction. The inert packing layer 22 is packed with inert packing material, exemplarily including one or more of quartz sand, ceramic balls, and glass beads, to separate the protective bed 21 and the catalytic reaction layer 23.

[0096] In some embodiments, the volume ratio of the protective bed 21 to the catalyst reaction bed is 1:(2-5).

[0097] In some embodiments, the fixed-bed reactor 2 is made of 316L stainless steel, with an inner diameter of 12mm-50mm, a length-to-diameter ratio of (5-20):1, a design pressure of 10MPa, and a design temperature of 400℃.

[0098] In some embodiments, the fixed-bed reactor 2 is equipped with a segmented electric heater with a temperature control accuracy of ±1℃.

[0099] In some embodiments, the product separation unit 3 includes a cooler 31, a gas-liquid separator 32, a storage tank 33, and a back pressure valve regulator 34. The reaction products after the isomerization reaction are cooled by the cooler 31 and then enter the gas-liquid separator 32 to realize the gas-liquid reaction products. The liquid reaction products are transported to the storage tank 33 for collection. The pressure of the entire reaction system is regulated by the back pressure valve regulator 34.

[0100] In some embodiments, the back pressure regulator includes a back pressure pneumatic regulating valve 341, a first shut-off ball valve 342, a second shut-off ball valve 343, a bypass valve 344, and a pressure controller 345.

[0101] The following are specific embodiments. They are intended to provide a more detailed description of this application to help those skilled in the art and researchers better understand it. The technical conditions described do not constitute any limitation on this application. Any modifications made within the scope of the claims of this application are protected by the claims.

[0102] Unless otherwise stated, all raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. Experimental methods not specifying particular conditions in the examples were performed under conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0103] Example 1

[0104] This embodiment provides a method for preparing an isomerization catalyst, the preparation method is as follows:

[0105] 1) Preparation of crystallized product: Nano-sized silica (Wokai, 99.5%, 50±5nm), sodium aluminate, sodium hydroxide, hexamethylammonium bromide, ZSM-48 molecular sieve seed crystals, and deionized water were mixed and aged at 25℃ for 0.5h. The mixture was then transferred to a high-pressure reactor and crystallized at 190℃ for 18h with a stirring speed of 25rpm. After cooling, filtration, and washing until neutral, the mixture was dried at 90℃ for 3h to form the crystallized product (ZSM-48 molecular sieve raw powder with a relative crystallinity of 98%). The molar ratio of the isomerization catalyst raw materials met the following conditions: SiO2:Al2O3:Na2O:hexamethylammonium bromide:deionized water = 1:0.009:0.08:0.009:22.4. The mass ratio of silica to ZSM-48 molecular sieve seed crystals (ZSM-48 molecular sieve recovered from the isomerization reaction) was 1:0.07.

[0106] 2) Preparation of catalyst precursor: The above-mentioned crystallized product was mixed with ammonium chloride solution (1 mol / L, solvent: water), exchanged at 85℃ for 1 h, and the mixture was exchanged twice. The mixture was then washed with water until no chloride ions were found, thus forming the catalyst precursor. The solid-liquid ratio of the crystallized product to the ammonium salt solution was 0.1 g / mL.

[0107] 3) Preparation of the isomerization catalyst: The above-mentioned catalyst precursor was placed in a rotary kiln and calcined under air atmosphere in a stationary state with programmed temperature increase. The temperature was increased to 95℃ for 2 hours at a rate of 2℃ / min, followed by a second calcination at 200℃ for 1 hour, and then a third calcination at 550℃ for 2 hours, forming the isomerization catalyst with a particle size D50 of 0.35 cm. The rotational conditions included: a rotation speed of 6 rpm when the calcination temperature was below 120℃, and a rotation speed of 14 rpm when the calcination temperature was above or equal to 120℃.

[0108] The isomerized catalyst prepared in the examples was ground and dispersed, and then subjected to scanning electron microscopy (SEM) for testing. Figure 3 The image shows SEM images at different magnifications. A hierarchical porous molecular sieve with a cross-shaped morphology can be observed, exhibiting a cross-shaped structure with diameters of approximately 2.0 μm to 3.5 μm, composed of stacked rod-shaped nanocrystals. This unique morphology endows the molecular sieve with a larger specific surface area and a richer mesoporous structure, which is beneficial for the diffusion of macromolecular reactants and the desorption of products, demonstrating superior catalytic performance compared to traditional molecular sieves.

[0109] Example 2

[0110] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 to Al2O3 in step 1) is 1:0.0071.

[0111] Example 3

[0112] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 to Al2O3 in step 1) is 1:0.0077.

[0113] Example 4

[0114] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 to Al2O3 in step 1) is 1:0.0083.

[0115] Example 5

[0116] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 to Al2O3 in step 1) is 1:0.01.

[0117] Example 6

[0118] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 to Al2O3 in step 1) is 1:0.0111.

[0119] Example 7

[0120] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 to Na2O in step 1) is 1:0.06.

[0121] Example 8

[0122] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 and hexamethylammonium bromide in step 1) is 1:0.018.

[0123] Example 9

[0124] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the mass ratio of SiO2 to ZSM-48 molecular sieve seed crystals (initial ZSM-48 molecular sieve seed crystals) in step 1) is 1:0.03.

[0125] Example 10

[0126] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the mass ratio of SiO2 to ZSM-48 molecular sieve seed crystals (initial ZSM-48 molecular sieve seed crystals) in step 1) is 1:0.05.

[0127] Example 11

[0128] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the mass ratio of SiO2 to ZSM-48 molecular sieve seed crystals (recovered ZSM-48 molecular sieve seed crystals) in step 1) is 1:0.05.

[0129] Example 12

[0130] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the mass ratio of SiO2 to ZSM-48 molecular sieve seed crystals (recovered ZSM-48 molecular sieve seed crystals) in step 1) is 1:0.1.

[0131] Example 13

[0132] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 to deionized water in step 1) is 1:33.4.

[0133] Example 14

[0134] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the crystallization temperature in step 1) is 200℃.

[0135] Example 15

[0136] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the crystallization treatment time in step 1) is 21 hours.

[0137] Example 16

[0138] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the crystallization treatment time in step 1) is 24 hours.

[0139] Example 17

[0140] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the ammonium exchange is performed once in step 2).

[0141] Example 18

[0142] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the ammonium exchange is performed 3 times in step 2).

[0143] Example 19

[0144] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the concentration of the ammonium chloride solution in step 2) is 0.5 mol / L.

[0145] Example 20

[0146] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the concentration of the ammonium chloride solution in step 2) is 1.5 mol / L.

[0147] Example 21

[0148] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the ammonium exchange temperature in step 2) is 75°C.

[0149] Example 22

[0150] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the ammonium exchange temperature in step 2) is 95°C.

[0151] Example 23

[0152] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the temperature of the third calcination in step 3) is 530°C.

[0153] Example 24

[0154] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the temperature of the third calcination in step 3) is 600℃.

[0155] Example 25

[0156] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being: the third calcination for 1 hour in step 3).

[0157] Example 26

[0158] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being: the third calcination for 3 hours in step 3).

[0159] Example 27

[0160] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being: the third calcination for 4 hours in step 3).

[0161] Example 28

[0162] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being: the third calcination for 5 hours in step 3).

[0163] Comparative Example 1

[0164] The preparation methods of this comparative example and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 to Al2O3 in step 1) is 1:0.0143.

[0165] Comparative Example 2

[0166] The preparation methods of this comparative example and Example 1 are basically the same, except that the molar ratio of SiO2 to Na2O in step 1) is 1:0.045.

[0167] Comparative Example 3

[0168] The preparation methods of this comparative example and Example 1 are basically the same, except that the molar ratio of SiO2 and hexamethylammonium bromide in step 1) is 1:0.0056.

[0169] Comparative Example 4

[0170] The preparation methods of this comparative example and Example 1 are basically the same, except that the mass ratio of SiO2 to ZSM-48 molecular sieve seed crystals (initial ZSM-48 molecular sieve seed crystals) in step 1) is 1:0.01.

[0171] Comparative Example 5

[0172] The preparation methods of this comparative example and Example 1 are basically the same, except that the molar ratio of SiO2 to deionized water in step 1) is 1:20.

[0173] Comparative Example 6

[0174] The preparation methods of this comparative example and Example 1 are basically the same, the main difference being that the molar ratio of SiO2 to deionized water in step 1) is 1:46.7.

[0175] Comparative Example 7

[0176] The preparation methods of this comparative example and Example 1 are basically the same, except that the crystallization temperature in step 1) is 170°C.

[0177] Comparative Example 8

[0178] The preparation methods of this comparative example and Example 1 are basically the same, with the main difference being that the crystallization temperature in step 1) is 180°C.

[0179] Comparative Example 9

[0180] The preparation methods of this comparative example and Example 1 are basically the same, except that the crystallization treatment time in step 1) is 12 hours.

[0181] Comparative Example 10

[0182] The preparation methods of this comparative example and Example 1 are basically the same, except that the crystallization treatment time in step 1) is 15 hours.

[0183] Comparative Example 11

[0184] The preparation methods of this comparative example and Example 1 are basically the same, the main difference being that the temperature of the third calcination in step 3) is 500°C.

[0185] Comparative Example 12

[0186] The preparation methods of this comparative example and Example 1 are basically the same, the main difference being that in step 3), the temperature is increased to 550°C and calcined for 2 hours at a heating rate of 2°C / min.

[0187] Comparative Example 13

[0188] The preparation methods of this comparative example and Example 1 are basically the same, except that the catalyst is calcined in a non-rotating state in step 3).

[0189] Test case

[0190] (1) The relative crystallinity, total acid content, weak acid / medium strong acid ratio and catalyst preparation yield of the isomerization catalysts prepared in Examples 1-6 and Comparative Example 1 were tested. The test results are shown in Table 1 below.

[0191] Table 1

[0192]

[0193] Note: The silicon-to-aluminum ratio in Table 1 refers to the molar ratio of SiO2 to Al2O3.

[0194] (2) The relative crystallinity, specific surface area and catalyst preparation yield (%) of Examples 1, 7 and Comparative Example 2 were tested. The test results are shown in Table 2 below.

[0195] Table 2

[0196]

[0197] Note: The silicon-alkali ratio in Table 2 refers to the molar ratio of SiO2 to Na2O.

[0198] (3) The relative crystallinity, specific surface area and catalyst preparation yield (%) of the above Examples 1, 8 and Comparative Example 3 were tested. The test results are shown in Table 3 below.

[0199] Table 3

[0200]

[0201] (4) The relative crystallinity, specific surface area and catalyst preparation yield (%) of Examples 9-12 and Comparative Example 4 were tested, and the test results are shown in Table 4 below.

[0202] Table 4

[0203]

[0204] Note: The recovered seed crystals in Table 4 refer to the ZSM-48 molecular sieve recovered by isomerization reaction as seed crystals, and the initial seed crystals refer to the initial ZSM-48 molecular sieve as seed crystals.

[0205] (5) The relative crystallinity, specific surface area and catalyst preparation yield (%) of the above Examples 1, 13 and Comparative Examples 5-6 were tested. The test results are shown in Table 5 below.

[0206] Table 5

[0207]

[0208] Note: The silicon-to-water ratio in Table 5 above refers to the molar ratio of SiO2 to deionized water.

[0209] (6) The relative crystallinity, specific surface area and catalyst preparation yield (%) of the above Examples 1, 14 and Comparative Examples 7-8 were tested. The test results are shown in Table 6 below.

[0210] Table 6

[0211]

[0212] (7) The relative crystallinity, specific surface area and catalyst preparation yield (%) of the above Examples 1, 15-16 and Comparative Examples 9-10 were tested. The test results are shown in Table 7 below.

[0213] Table 7

[0214]

[0215] (8) The sodium content (wt%) and crystallinity retention rate (%) in the catalyst precursors of Examples 1 and 17-18 above were tested, and the test results are shown in Table 8 below.

[0216] Table 8

[0217]

[0218] (9) The sodium content (wt%) and crystallinity retention rate (%) in the catalyst precursors of Examples 1 and 19-20 above were tested, and the test results are shown in Table 9 below.

[0219] Table 9

[0220]

[0221] (10) The sodium content (wt%) and crystallinity retention rate (%) in the catalyst precursors of Examples 1 and 21-22 were tested. The test results are shown in Table 10 below.

[0222] Table 10

[0223]

[0224] (11) The template agent removal rate (%) and specific surface area (m²) of Examples 1, 23-24 and Comparative Example 11 were measured. 2 The test results for the ratio of strong acid (%) and the proportion of strong acid (%) are shown in Table 11 below.

[0225] Table 11

[0226]

[0227] (12) The template agent removal rate (%) and specific surface area (m²) of Examples 1 and 25-28 above were measured. 2 The test results for the ratio of strong acid (g / g) and the percentage of strong acid (%) are shown in Table 12 below.

[0228] Table 12

[0229]

[0230] (12) The isomerization reaction test was performed on the isomerization catalysts prepared in the above examples and comparative examples using an isomerization reaction apparatus. The fixed-bed reactor 2 in the reaction apparatus includes a protective bed 21, a catalytic reaction layer 23 and an inert packing layer 22 between the two. The protective bed 21 is filled with 5 mL of diatomaceous earth, the catalytic reaction layer 23 is filled with 10 mL of isomerization catalyst, and the inert packing layer 22 is filled with 5 mL of quartz sand. A first high-pressure constant flow pump 11 delivers oleic acid, melted at 90℃, to a mixer 14. A second high-pressure constant flow pump 12 delivers deionized water (3.6 wt% of the oleic acid mass) to the mixer 14. After mixing with the oleic acid in the mixer 14, the water is delivered to a fixed-bed reactor 2 at a rate of 2 mL / h (LHSV=0.2). Throughout the reaction, N2 is continuously introduced at a flow rate of 1.6 L / h (gas / liquid ratio 800:1), a constant pressure of 2.0 MPa, and a reaction temperature of 270℃. The continuous introduction of N2 helps to remove water and light components generated during the reaction, preventing their accumulation on the isomerization catalyst and thus catalyst deactivation. It also provides a positive pressure environment for the fixed-bed reactor 2. The oleic acid conversion rate (%) and isomerization selectivity (%) were tested, and the results are shown in Table 13.

[0231] Table 13

[0232]

[0233] As shown in Table 13, the isomerization catalyst provided in this application embodiment replaces the noble metal modification by changing the catalyst, and can achieve better oleic acid conversion rate and isomerization selectivity.

[0234] Based on Tables 1-13 and the comparison between Examples 1-6 and Comparative Example 1, it can be seen that when the molar ratio of SiO2 to Al2O3 is low, the prepared isomerization catalyst has an unstable structure, is prone to dealumination to form superacid sites, leading to an increase in side reactions and a decrease in isomerization selectivity.

[0235] According to the comparison of Examples 1 and 7 and Comparative Example 2, when the molar ratio of SiO2 to Na2O is greater than 1:0.006, the crystallinity of the prepared isomerization catalyst is insufficient, resulting in poor oleic acid conversion and isomerization selectivity.

[0236] According to the comparison of Examples 1 and 8 and Comparative Example 3, when the molar ratio of SiO2 to template agent is greater than 1:0.009, the crystallinity of the prepared isomerization catalyst is insufficient, resulting in poor oleic acid conversion and isomerization selectivity.

[0237] According to the comparison of Examples 1, 9-12 and Comparative Example 4, when the mass ratio of SiO2 to seed crystal is too large (1:0.01), no crystallization occurs; when the initial ZSM-48 molecular sieve is used as seed crystal, the mass ratio of SiO2 to seed crystal is controlled at 1:(0.003-0.005); when the recycled ZSM-48 molecular sieve is used as seed crystal, the mass ratio of SiO2 to seed crystal is controlled at 1:(0.005-0.01).

[0238] According to the comparison of Examples 1, 13 and Comparative Examples 5-6, when the molar ratio of SiO2 to deionized water is greater than 1:22.4, the water content is too low, and a non-flowing gel is formed during the aging process; when the molar ratio of SiO2 to deionized water is less than 1:33.4, the crystallinity of the prepared isomerization catalyst is insufficient, resulting in poor oleic acid conversion rate and isomerization selectivity.

[0239] According to the comparison of Examples 1, 14 and Comparative Examples 7-8, when the crystallization temperature is 170°C, the crystallization is incomplete, only 35%; when the crystallization temperature is 180°C, the specific surface area is insufficient, resulting in a decrease in oleic acid conversion rate.

[0240] Based on the comparison of Examples 1, 15-16 and Comparative Examples 9-10, it can be seen that the oleic acid conversion rate is low when the crystallization time is less than 18 hours.

[0241] According to the comparison between Examples 1 and Examples 17-18, the sodium content in the catalyst precursor after a single ammonium exchange is greater than 0.1 wt%, and the oleic acid conversion rate is low.

[0242] According to the comparison of Examples 1 and 19-20, it can be seen that using an ammonium salt solution with a concentration of 0.5 mol / L-1.5 mol / L for ammonium exchange reduces the sodium content of the catalyst precursor to below 0.1 wt%, and has good oleic acid conversion rate and isomerization selectivity.

[0243] According to the comparison of Examples 1 and 21-22, when the ammonium exchange temperature is controlled at 75℃-95℃ and the sodium content of the catalyst precursor is reduced to below 0.1wt%, it exhibits good oleic acid conversion rate and isomerization selectivity.

[0244] Based on the comparison of Examples 1, 23-24 and Comparative Example 11, it can be seen that when the third calcination temperature is below 530℃, the template agent removal rate is low, and the yield of isomerized oleic acid decreases to 52.7%. Among them, the yield of isomerized oleic acid is the product of oleic acid conversion rate and isomerization selectivity.

[0245] According to the comparison between Example 1 and Examples 25-28, when the third calcination time is more than 2 hours, the template agent is basically completely removed, and it has good oleic acid conversion rate and isomerization selectivity.

[0246] As can be seen from the comparison of Example 1 and Comparative Example 13, this application achieves the effect of calcining the catalyst precursor under rotating conditions. Otherwise, large agglomerates will occur, and the interior will appear gray, making it impossible to remove the template agent and expose the active center within 2 hours. After the rotational calcination treatment, it can be formed into isomerization catalyst particles with a particle size D50 of 0.2cm-0.35cm and a certain hardness, which effectively ensures that the isomerization catalyst has both good oleic acid conversion rate and isomerization selectivity in the isomerization reaction.

[0247] (13) After the isomerization reaction of the catalyst provided in Example 1 in (12) above was carried out for 150 h, a second isomerization reaction test was carried out, and the yield of isomerized oleic acid after 150 h was measured to be 75%.

[0248] (14) Equal masses of oleic acid and the isomerization catalyst prepared in Example 1 were ground into powder and mixed with deionized water in a reactor. Nitrogen gas was introduced to a pressure of 0.5 MPa, and the reaction was carried out under stirring for 5 hours. The results showed that the oleic acid conversion rate was 93.7%, the isomerization selectivity was 84.6%, and the yield of isomerized oleic acid was 79.3%.

[0249] After the isomerization catalyst was washed and dried after 5 hours of reaction, a second isomerization reaction test was conducted, and the yield of isomerized oleic acid was found to be 57.6%.

[0250] A comparison shows that the isomerization catalyst provided in this application embodiment exhibits comparable catalytic performance in the fixed-bed reactor 2 to that in the reaction vessel. The use of continuous fixed-bed operation overcomes the drawbacks of batch-to-batch fluctuations and difficulties in catalyst separation in batch reactors, resulting in good product consistency. Furthermore, due to the removal of metal ions and impurities by the protective bed 21 in the fixed-bed reactor 2, the isomerization catalyst remains deactivated even after continuous operation for over 150 hours.

[0251] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0252] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing an isomerization catalyst, characterized in that, Includes the following steps: A silicon source, an aluminum source, an alkali metal hydroxide, a template agent, ZSM-48 molecular sieve seed crystals and a solvent are mixed and then subjected to aging and crystallization treatments in sequence to form a crystallized product. The crystallized product is mixed with an ammonium salt solution to perform ammonium exchange, forming a catalyst precursor; as well as The catalyst precursor is calcined under rotation to form the isomerized catalyst. The isomerization catalyst has the following molar ratio: 1.0SiO2: (0.007-0.014)Al2O3: (0.06-0.08)M2O: (0.009-0.018)R1:(22-33.4)R2, where M is an alkali metal, R1 is a template agent, and R2 is a solvent; the mass ratio of the silicon source to the ZSM-48 molecular sieve seed crystals is 1:(0.03-0.1). The crystallization treatment temperature is 190℃-200℃, and the crystallization treatment time is 18h-24h; The calcination conditions include: subjecting the catalyst precursor to a first calcination, a second calcination, and a third calcination in sequence, with the first calcination temperature being 90℃-100℃, the second calcination temperature being 200℃-250℃, and the third calcination temperature being 530℃-600℃.

2. The method for preparing the isomerization catalyst according to claim 1, characterized in that, The solvent content of the catalyst precursor is above 75%; Optionally, the solvent includes water.

3. The method for preparing the isomerization catalyst according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The first calcination time is 1-2 hours; (2) The second calcination time is 1-2 hours; (3) The third calcination time is 1h-5h.

4. The method for preparing the isomerization catalyst according to any one of claims 1-3, characterized in that, The conditions for the rotation state include: when the calcination temperature is less than 120°C, the rotation speed is 4 rpm-6 rpm; when the calcination temperature is greater than or equal to 120°C, the rotation speed is 14 rpm-16 rpm.

5. The method for preparing the isomerization catalyst according to claim 4, characterized in that, The particle size D50 of the isomerization catalyst is 0.2 cm to 0.35 cm.

6. The method for preparing the isomerization catalyst according to any one of claims 1-3, characterized in that, The ammonium exchange procedure must satisfy at least one of the following conditions: (1) The ammonium salt in the ammonium salt solution includes one or more of ammonium chloride, ammonium sulfate and ammonium nitrate; (2) The concentration of the ammonium salt solution is 0.5 mol / L-1 mol / L; (3) The temperature for ammonium exchange is 75℃-85℃; (4) The number of ammonium exchanges is 2-3 times, and the time for each ammonium exchange is 0.5h-1.5h independently; (5) The solid-liquid ratio of the crystallized product to the ammonium salt solution is 0.1 g / mL to 0.2 g / mL; (6) The solvent of the ammonium salt solution includes water.

7. The method for preparing the isomerization catalyst according to any one of claims 1-3, characterized in that, At least one of the following conditions must be met: (1) The silicon source includes one or more of silicon dioxide and silica; (2) The aluminum source includes one or more of sodium aluminate and aluminum sulfate; (3) The alkali metal hydroxide includes one or more of sodium hydroxide and potassium hydroxide, and the M2O is one or more of Na2O and K2O; (4) The template agent includes one or more of hexamethylammonium bromide, 1,6-hexanediamine and hexamethyldiammonium hydroxide.

8. An isomerization catalyst, characterized in that, It was prepared using the method for preparing the isomerization catalyst according to any one of claims 1-7.

9. The application of the isomerization catalyst according to claim 8 in the isomerization reaction of unsaturated fatty acids, wherein the unsaturated fatty acids include one or more of oleic acid, linoleic acid and linolenic acid.

10. The application according to claim 9, characterized in that, The unsaturated fatty acid isomerization reaction is carried out in a fixed-bed reactor at a temperature of 260℃-280℃, a pressure of 1.5MPa-2.5MPa, a carrier gas to unsaturated fatty acid volume ratio of (800-1200):1, and a liquid hourly space velocity of 0.15 h⁻¹. -1 -0.25h -1 .

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