Mesopore-micropore composite hydroisomerization catalyst and preparation method thereof

Abstract

The present application belongs to the technical field of hydroisomerization catalysts, and particularly relates to a mesopore-micropore composite hydroisomerization catalyst and a preparation method thereof, comprising the following steps: (1) contacting molecular sieve, a binder, a thickening agent, nitric acid and water, and wet mixing and beating under the conditions of heating and stirring until uniform to obtain a wet mixed slurry, wherein the heating temperature is 30-100 DEG C; (2) the obtained wet mixed slurry is further subjected to extrusion, drying and calcination to obtain a catalyst carrier containing mesopores-micropores; (3) the obtained catalyst carrier is immersed in an impregnation liquid to obtain a hydroisomerization catalyst; in step (1), the ratio of nitric acid to dry basis is 0.5-10 wt%, and the ratio of the thickening agent to dry basis is 0.01-5.0 wt%. The method has fewer processes, and effectively avoids phase separation, so that the formed mesopores are more uniformly distributed, and the catalytic effect and the selectivity of isomerization products are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of hydroisomerization catalysts, and particularly relates to a mesoporous-microporous composite hydroisomerization catalyst and its preparation method. Background Technology

[0002] In this field, the conventional production process of hydroisomerization catalysts includes: dry mixing (mixing molecular sieves and binders such as alumina to obtain a dry material), kneading (mixing the dry material with dilute nitric acid solution) to prepare a wet material, extrusion forming (preparing support strips), drying, calcination, impregnation, drying again, and recalcination. Among these, the dry mixing step, the kneading step, and the extrusion step have the greatest impact on the performance of the final product.

[0003] In existing technologies, the process of "uniformly mixing alumina powder, organic alkali-modified ZSM-48 molecular sieve powder, etc." employs a dry-mixing method. However, this method yields poor mixing results and cannot guarantee uniform mixing between the alumina powder and other binders and the organic alkali-modified ZSM-48 molecular sieve powder. For example,

[0004] Patent document CN 102085488A discloses a method for preparing a hydroisomer catalyst with MFI micropores and MCM mesopores. The method involves synthesizing a mesoporous-microporous material under hydrothermal conditions using alkali-treated low-crystallinity MFI molecular sieves, a template agent, an aluminum source, and a silicon source. This material is then mixed with alumina using conventional methods, soluble in acid, and extruded and impregnated to prepare the catalyst. While this method produces catalysts with both mesopores and micropores, the uneven distribution of acidic centers leads to poor matching between the acidic and hydrogenation centers after subsequent loading, resulting in suboptimal catalytic performance.

[0005] Patent document CN105800635A discloses a method for preparing ZSM-48 molecular sieves with a hierarchical mesoporous-microporous structure. During the molecular sieve synthesis process, starch is added to regulate the synthesis pathway of ZSM-48 molecular sieves, resulting in a hierarchical ZSM-48 molecular sieve. Because starch is rich in hydroxyl groups, it forms a sponge-like structure at aging temperatures. Simultaneously, the hydroxyl groups interact with the silica-alumina structure, ultimately forming a mesoporous-microporous hierarchical composite structure. After calcination to remove the starch, a mesoporous channel structure is produced. The ZSM-48 molecular sieve synthesized by this method has a microporous structure with abundant mesopores within and between crystal grains, exhibiting a large confined specific surface area and mesopore volume. Although this mesoporous-microporous composite molecular sieve can reduce the diffusion resistance of reactants or products in isomerization reactions, the use of conventional dry mixing methods when mixing it with alumina makes it difficult to achieve uniform dispersion of hydrogenation centers. This affects the subsequent matching of hydrogenation centers, and the acid center distribution is also uneven, making it difficult to achieve the desired catalytic effect.

[0006] In other words, the existing problems in the preparation of hydroisomer catalysts are that, in the conventional method, the uniform distribution of binders such as molecular sieves and alumina cannot be controlled during the kneading and molding process. As a result, the acidic centers and hydrogenation centers cannot be well matched after molding and impregnation, which ultimately affects the catalytic effect.

[0007] Therefore, how to improve and effectively control the uniform distribution of binders such as molecular sieves and alumina has become a worthy research direction. Summary of the Invention

[0008] The purpose of this invention is to address the problems existing in the preparation of hydroisomerization catalysts in the prior art by providing a mesoporous-microporous composite hydroisomerization catalyst and its preparation method. By adding a thickener, the molecular sieve and binder can be mixed in a suspension, which effectively avoids phase separation and makes the resulting mesoporous distribution more uniform, thereby improving the catalytic effect and the selectivity of isomer products.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] In the first aspect, a method for preparing a mesoporous-microporous composite hydroisomer catalyst is provided, comprising the following steps:

[0011] (1) Molecular sieve, binder, thickener, nitric acid and water are brought into contact and mixed into a wet paste under heating and stirring conditions until homogeneous. The heating temperature is 30-100℃ (e.g., 40℃, 50℃, 60℃, 80℃, 90℃), and the stirring time is optionally 10-120min (e.g., 20min, 40min, 60min, 80min, 100min) to obtain a wet paste.

[0012] (2) The wet slurry obtained above is then extruded, dried and calcined to obtain a catalyst support containing mesoporous-microporous structures.

[0013] (3) The catalyst support obtained above is then immersed in the impregnation solution to obtain the hydroisomerization catalyst.

[0014] The proportions of each component used in step (1) of preparing the catalyst support are as follows, based on a total dry weight of 100 wt%:

[0015] The dry base comprises a molecular sieve and a binder, wherein;

[0016] The molecular sieve content is 10-90 wt% (e.g., 15 wt%, 20 wt%, 40 wt%, 60 wt%, 80 wt%, 85 wt%).

[0017] The binder content is 10-90 wt% (e.g., 15 wt%, 20 wt%, 40 wt%, 60 wt%, 80 wt%, 85 wt%);

[0018] The ratio of nitric acid to dry basis is 0.5-10 wt% (e.g., 0.6 wt%, 1.0 wt%, 2.0 wt%, 4.0 wt%, 8.0 wt%), preferably 1.0-5.0 wt%.

[0019] The ratio of thickener to dry base is 0.01-5.0 wt% (e.g., 0.02 wt%, 0.04 wt%, 0.08 wt%, 0.1 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, 4.0 wt%), preferably 0.5-3.0 wt%.

[0020] According to the preparation method provided by the present invention, in some embodiments, the molecular sieve is selected from one or more of ZSM series molecular sieves, SSZ series molecular sieves and SAPO series molecular sieves, preferably ZSM series molecular sieves;

[0021] The ZSM series molecular sieves are preferably selected from ZSM-48 molecular sieve, ZSM-22 molecular sieve, ZSM-35 molecular sieve or ZSM-53 molecular sieve, and more preferably ZSM-48 molecular sieve.

[0022] The preferred SSZ series molecular sieve is SSZ-32 molecular sieve.

[0023] The SAPO series molecular sieve is preferably SAPO-11 molecular sieve.

[0024] In some embodiments, the binder is selected from one or more of boehmite, alumina, and aluminosilicate.

[0025] In some embodiments, the thickener is selected from one or more of natural thickeners, cellulosic thickeners, and synthetic polymeric thickeners;

[0026] The natural thickener is preferably selected from starch, xanthan gum, gelatin, guar gum, natural rubber, or agar;

[0027] The cellulose-based thickener is preferably selected from methylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, or sodium carboxymethylcellulose;

[0028] The synthetic polymeric thickener is preferably selected from polyurethane thickeners, sodium polyacrylate, polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyethylene oxide, carbomer resin, polyacrylic acid or polyacrylate copolymer emulsions.

[0029] According to the preparation method provided by the present invention, in some embodiments, in step (1), the ratio of water to dry basis is 200-1000 wt%; by controlling the amount of water and thickener added, it can be ensured that the molecular sieve and the binder are uniformly mixed in the suspension, thus avoiding phase separation.

[0030] During the wet mixing process, heating and stirring are stopped when the water-to-dry-base ratio is controlled to 50-150 wt%, thus obtaining the wet-mixed slurry. Furthermore, by controlling the heating temperature and stirring time, uniform mixing of the molecular sieve and binder in the suspension can be further ensured.

[0031] In some implementations, the drying process conditions in step (2) include: a drying temperature of 40-120°C (e.g., 60°C, 90°C, 115°C), preferably 80-110°C, and a drying time of 2-8h (e.g., 2.5h, 4h, 7h), preferably 3-6h.

[0032] In some implementations, the roasting process conditions in step (2) include: a roasting temperature of 400-750℃ (e.g., 500℃, 550℃, 650℃, 700℃), preferably 450-600℃; and a roasting time of 2-5h (e.g., 2.5h, 3h, 4h).

[0033] In this article, the extrusion process for preparing the catalyst support is a conventional operation, and the equipment used in the drying and calcination processes is well known to those skilled in the art, and will not be described in detail here.

[0034] Before drying and calcination, the extruded catalyst support can be shaped. In some embodiments, the extruded catalyst support is shaped using a cylindrical or clover-shaped perforated plate.

[0035] In some embodiments, step (3) uses a solution containing a hydrogenation precursor as an impregnation liquid to impregnate the catalyst support; the impregnation method is preferably pore saturation impregnation.

[0036] In some embodiments, the solution containing the hydrogenated precursor contains a hydrogenated element, which is a Group VIII noble metal, or a Group VIB metal and / or a Group VIII non-noble metal.

[0037] Preferably, the Group VIII noble metal element is palladium and / or platinum;

[0038] Preferably, the group VIB metal element is selected from one or more of tungsten, molybdenum, and chromium;

[0039] Preferably, the Group VIII non-precious metal element is nickel and / or cobalt.

[0040] In some embodiments, the loading of the Group VIII noble metal element is less than or equal to 10 wt% (e.g., 0.01 wt%, 0.5 wt%, 1 wt%, 4 wt%, 8 wt%), preferably 0.1-5 wt%, and more preferably 0.2-2 wt%, based on the weight of the catalyst.

[0041] In some embodiments, the loading of the Group VIB metal element, based on the weight of the catalyst, is 1-35 wt% (e.g., 2 wt%, 6 wt%, 10 wt%, 14 wt%, 18 wt%, 20 wt%, 24 wt%, 28 wt%, 32 wt%), preferably 5-30 wt%; and the loading of the Group VIII non-noble metal element is 1-25 wt% (e.g., 3 wt%, 5 wt%, 8 wt%, 10 wt%, 16 wt%, 20 wt%, 24 wt%), preferably 2-15 wt%.

[0042] In some embodiments, the catalyst support described in step (3) is impregnated and then calcined; the calcination conditions include: a calcination temperature of 400-700℃ (e.g., 500℃, 600℃, 650℃), preferably 450-550℃; and a calcination time of 1-12h (e.g., 3h, 6h, 8h), preferably 2-4h.

[0043] In a second aspect, a mesoporous-microporous composite hydroisomer catalyst prepared by the method described above is provided.

[0044] The mesoporous-microporous composite hydroisomerization catalyst described herein contains a certain distribution of mesopores, and the catalyst structure exhibits a hierarchical pore distribution. The pore volume, specific surface area, and pore size distribution of the mesopores and micropores can be characterized and determined using BET (Boolean Emission Test). For example, the St of this catalyst... BET 270-400m 2 / g, S ext 95-300m 2 / g, S micro 100-170m 2 / g;V total It is 0.2-0.4cm 3 / g, V micro It is 0.02-0.1cm 3 / g, V ext It is 0.15-0.25cm 3 / g.

[0045] This invention employs a wet mixing method during the mixing of molecular sieve powder, thickener, and binder powder, presenting the mixture as a suspension. This effectively avoids phase separation between the molecular sieve and binders such as alumina, ensuring more thorough dispersion of the various binders. Because phase separation between the molecular sieve and binder is avoided, the slurry, after calcination, exhibits a more uniform distribution of micropores in the molecular sieve and mesopores formed after calcination. This results in better matching between micropores and mesopores, as well as between acidic and hydrogenation centers, formed in the catalyst after impregnation, leading to better catalytic performance as a hydroisomerization catalyst for treating large molecular weight alkanes such as Fischer-Tropsch waxes.

[0046] Compared with the traditional dry-mixing extrusion forming method, the method of the present invention greatly simplifies the operation, eliminates the dry mixing and kneading steps, shortens the process, and saves time and operating costs.

[0047] Furthermore, the role of the thickener in catalyst support preparation is to ensure uniform dispersion of the molecular sieve and alumina support (in the powder mixing process, adding even a small amount of acid and water during kneading and extrusion will not result in uniform dispersion of the molecular sieve), rather than simply acting as an extrusion aid. The ability to uniformly disperse the molecular sieve in alumina during preparation is crucial and affects catalyst performance. By mixing the molecular sieve and binder powders with the thickener in a slurry manner, phase separation between the molecular sieve and binder is effectively avoided. This results in a more uniform mixture and, after calcination to remove the binder, allows the support to develop numerous mesopores. Impregnating this mesoporous support allows for the preparation of mesoporous-microporous composite catalysts, which can reduce secondary cracking during the hydroisomerization of large molecular feedstocks such as Fischer-Tropsch waxes and improve the selectivity of isomer products.

[0048] The catalyst prepared using this invention is more conducive to the diffusion of reactant and product molecules. On the other hand, due to the more uniform distribution of acidic centers, the closer distance and better matching between hydrogenation active centers and acidic active centers, its isomer selectivity is higher.

[0049] Compared with the existing technologies, the beneficial effects of the technical solution of the present invention are as follows:

[0050] (1) Compared with the traditional extrusion molding method, the steps are simplified, the dry mixing and kneading steps are eliminated, the process is shortened, and time and operating costs are saved.

[0051] (2) Due to the introduction of thickener, not only can the molecular sieve and binder be fully dispersed, but also a large number of mesopores are introduced into the carrier after calcination, reducing secondary cracking; it also makes the acid centers uniformly distributed, and the acid centers and hydrogenation centers are better matched after impregnation.

[0052] (3) The prepared catalyst eliminates the problem of low utilization of acid sites caused by uneven mixing of molecular sieve and binder; the presence of mesopores is more conducive to the diffusion of macromolecules, which can reduce the occurrence of secondary cracking and improve the selectivity of isomers. Detailed Implementation

[0053] To provide a detailed understanding of the technical features and content of this invention, preferred embodiments will be described in more detail below. While preferred embodiments of the invention are described in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0054] <Source of Raw Materials>

[0055] ZSM-48 molecular sieve, SSZ-32 molecular sieve, and SAPO-11 molecular sieve were all purchased commercially.

[0056] Boehmite, commercially available, model SB;

[0057] Starch, methylcellulose, agar, hydroxyethylcellulose, and polyacrylamide were all commercially purchased and were all Inokai brand reagents.

[0058] Example 1

[0059] (1) ZSM-48 molecular sieve (Si / Al2=150), boehmite, starch, nitric acid (in the form of dilute nitric acid solution), and water are mixed in a mixing device under electric stirring and heating until homogeneous; the dry basis includes molecular sieve and binder, and the proportions of each raw material are as follows, based on a total weight of 100wt% of the dry basis:

[0060] The content of ZSM-48 molecular sieve is 65wt%, and the content of Al2O3 is 35wt%.

[0061] The ratio of nitric acid to dry basis is 2.0 wt%, the ratio of starch to dry basis is 0.5 wt%, and the ratio of water to dry basis is 500%.

[0062] Electric stirring was carried out at 60°C to obtain a viscous homogeneous system. When the ratio of water to dry base reached 60 wt%, heating and stirring were stopped to obtain a wet slurry.

[0063] (2) After the obtained wet slurry is cooled at room temperature, it is directly extruded. A cylindrical perforated plate with a diameter of 1.5 mm is selected for extrusion to obtain a shaped catalyst support. The catalyst support is dried at 80°C for 2 hours and then calcined at 550°C for 2 hours.

[0064] (3) Select tetraammonium platinum nitrate as platinum source to prepare impregnation solution, and impregnate the obtained catalyst support in the impregnation solution according to the same volume; based on the weight of the catalyst, the loading percentage of Pt in the catalyst is 0.35% during the impregnation process.

[0065] Then, the catalyst was dried at 40°C for 4 hours, dried at 80°C for 2 hours, and calcined at 500°C for 2 hours to obtain the hydroisomerization catalyst.

[0066] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0067] Example 2

[0068] (1) ZSM-48 molecular sieve (Si / Al2=150), boehmite, methylcellulose, nitric acid (in the form of dilute nitric acid solution), and water are mixed in a mixing device under electric stirring and heating until homogeneous; the dry basis includes the molecular sieve and binder, and the proportions of each raw material are as follows, based on a total weight of 100wt% of the dry basis:

[0069] The content of ZSM-48 molecular sieve is 70wt%, and the content of Al2O3 is 30wt%.

[0070] The ratio of nitric acid to dry basis is 2.5 wt%, the ratio of methylcellulose to dry basis is 1.5 wt%, and the ratio of water to dry basis is 600 wt%.

[0071] Electric stirring was carried out at 80°C to obtain a viscous homogeneous system. When the ratio of water to dry base reached 65wt%, heating and stirring were stopped to obtain a wet slurry.

[0072] (2) After the obtained wet slurry is cooled at room temperature, it is directly extruded. A 1.5 mm clover-shaped perforated plate is selected for extrusion to obtain a shaped catalyst support. The catalyst support is dried at 60°C for 2 hours and then calcined at 550°C for 2 hours.

[0073] (3) Chloroplatinic acid was selected as the platinum source to prepare the impregnation solution, and the obtained catalyst support was impregnated in the impregnation solution in equal volumes; based on the weight of the catalyst, the loading percentage of Pt in the catalyst was 0.35% during the impregnation process.

[0074] Then, the catalyst was dried at 40°C for 4 hours, dried at 80°C for 2 hours, and calcined at 500°C for 2 hours to obtain the hydroisomerization catalyst.

[0075] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0076] Example 3

[0077] (1) ZSM-48 molecular sieve (Si / Al2=180), boehmite, agar, nitric acid (in the form of dilute nitric acid solution), and water were mixed in a mixing device under electric stirring and heated until homogeneous; the dry basis includes the molecular sieve and binder, and the proportions of each raw material are as follows, based on a total weight of 100wt% of the dry basis:

[0078] The content of ZSM-48 molecular sieve is 90wt%, and the content of Al2O3 is 10wt%.

[0079] The ratio of nitric acid to dry basis is 3.0 wt%, the ratio of agar to dry basis is 3.0 wt%, and the ratio of water to dry basis is 1000 wt%.

[0080] Electric stirring was carried out at 30°C to obtain a viscous homogeneous system. When the ratio of water to dry basis reached 85wt%, heating and stirring were stopped to obtain a wet slurry.

[0081] (2) After the obtained wet slurry is cooled at room temperature, it is directly extruded. A cylindrical perforated plate with a diameter of 2.0 mm is selected for extrusion to obtain a shaped catalyst support. The catalyst support is dried at 120°C for 2 hours and then calcined at 550°C for 2 hours.

[0082] (3) Select dichlorotetraammineplatinum as the platinum source to prepare an impregnation solution, and impregnate the obtained catalyst support in the impregnation solution according to the same volume; based on the weight of the catalyst, the loading percentage of Pt in the catalyst is 0.55% during the impregnation process.

[0083] Then, the catalyst was dried at 40°C for 4 hours, dried at 80°C for 2 hours, and calcined at 500°C for 2 hours to obtain the hydroisomerization catalyst.

[0084] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0085] Example 4

[0086] (1) ZSM-48 molecular sieve (Si / Al2=240), boehmite, hydroxyethyl cellulose, nitric acid (in the form of dilute nitric acid solution), and water are mixed in a mixing device under electric stirring and heating until homogeneous; the dry basis includes the molecular sieve and binder, and the proportions of each raw material are as follows, based on a total weight of 100wt% of the dry basis:

[0087] The content of ZSM-48 molecular sieve is 80wt%, and the content of Al2O3 is 20wt%.

[0088] The ratio of nitric acid to dry basis is 1.0 wt%, the ratio of hydroxyethyl cellulose to dry basis is 5 wt%, and the ratio of water to dry basis is 500%.

[0089] Electric stirring was carried out at 50°C to obtain a viscous homogeneous system. When the ratio of water to dry base reached 130 wt%, heating and stirring were stopped to obtain a wet slurry.

[0090] (2) After the obtained wet slurry is cooled at room temperature, it is directly extruded. A cylindrical perforated plate with a diameter of 2.0 mm is selected for extrusion to obtain a shaped catalyst support. The catalyst support is dried at 80°C for 2 hours and then calcined at 550°C for 2 hours.

[0091] (3) Select dichlorotetraammineplatinum as the platinum source to prepare the impregnation solution, and impregnate the obtained catalyst support in the impregnation solution according to the same volume; based on the weight of the catalyst, the loading percentage of Pt in the catalyst is 0.35% during the impregnation process.

[0092] Then, the catalyst was dried at 40°C for 4 hours, dried at 80°C for 2 hours, and calcined at 500°C for 2 hours to obtain the hydroisomerization catalyst.

[0093] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0094] Example 5

[0095] (1) ZSM-48 molecular sieve (Si / Al2=300), pseudo-hydraulic diatomite, polyacrylamide, nitric acid (in the form of dilute nitric acid solution), and water are mixed in a mixing device under electric stirring and heating until homogeneous; the dry basis includes molecular sieve and binder, and the proportions of each raw material are as follows, based on a total weight of 100wt% of the dry basis:

[0096] The content of ZSM-48 molecular sieve is 90wt%, and the content of Al2O3 is 10wt%.

[0097] The ratio of nitric acid to dry basis is 1.0 wt%, the ratio of polyacrylamide to dry basis is 5 wt%, and the ratio of water to dry basis is 500%.

[0098] Electric stirring was carried out at 50°C to obtain a viscous homogeneous system. When the ratio of water to dry base reached 150 wt%, heating and stirring were stopped to obtain a wet slurry.

[0099] (2) After the obtained wet slurry is cooled at room temperature, it is directly extruded. A cylindrical 2.0 mm perforated plate is selected for extrusion to obtain a shaped catalyst support. The support is dried at 80°C for 2 hours and then calcined at 550°C for 2 hours.

[0100] (3) Nickel nitrate and ammonium metatungstate are selected to prepare an impregnation solution, and the obtained catalyst support is impregnated in the impregnation solution in equal volumes; based on the weight of the catalyst, the loading percentage of NiO in the catalyst is 6.0% and the loading mass fraction of WO3 is 20% during the impregnation process.

[0101] Then, it was dried at 80°C for 4 hours and calcined at 500°C for 2 hours to obtain the hydroisomerization catalyst.

[0102] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0103] Example 6

[0104] The hydroisomerization catalyst was prepared according to the method in Example 1, except that the molecular sieve used was SSZ-32 (Si / Al2 = 40).

[0105] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0106] Example 7

[0107] The hydroisomerization catalyst was prepared according to the method in Example 1, except that the molecular sieve used was SAPO-11 (Si / Al2 = 1:6).

[0108] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0109] Comparative Example 1

[0110] The catalyst was prepared according to the method of Example 1, except that the thickener starch was not added in step (1) to obtain the hydroisomer catalyst.

[0111] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0112] Comparative Example 2

[0113] (1) Add ZSM-48 molecular sieve (Si / Al2=150), starch, nitric acid (in the form of dilute nitric acid solution) and water to a mixing device according to the ratio and mix at room temperature to obtain a viscous system; then add pseudoboehmite dry powder directly to the obtained viscous system until the ratio of water to dry basis is 60wt% and then stop adding pseudoboehmite.

[0114] The dry basis includes molecular sieves and binders. Based on a total weight of 100 wt% of the dry basis, the proportions of each raw material are as follows:

[0115] The content of ZSM-48 molecular sieve is 65wt%, and the content of Al2O3 is 35wt%.

[0116] The ratio of nitric acid to dry basis is 2.0 wt%, the ratio of starch to dry basis is 0.5 wt%, and the initial ratio of water to dry basis is 500%.

[0117] Steps (2) to (3) are the same as in Example 1, and a hydroisomerization catalyst is obtained.

[0118] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0119] Comparative Example 3

[0120] (1) Mix ZSM-48 molecular sieve (Si / Al2=150) and pseudoboehmite dry powder in a kneader at 100 rpm for 20 min.

[0121] (2) Add nitric acid (in the form of dilute nitric acid solution) dropwise to the dry-mixed mixture containing molecular sieve and pseudoboehmite dry powder to perform gelation. The gelation process takes 15 minutes and the kneader speed is 200 rpm to obtain wet mixed slurry.

[0122] The aforementioned dry basis includes molecular sieves and binders. Based on a total weight of 100 wt% of the dry basis, the proportions of each raw material are as follows:

[0123] The content of ZSM-48 molecular sieve is 65wt%, and the content of Al2O3 is 35wt%.

[0124] The ratio of nitric acid to dry basis is 2.0 wt%, and the ratio of water to dry basis is 60%.

[0125] (3) The obtained wet slurry is extruded in a kneader and a cylindrical perforated plate with a diameter of 1.5 mm to obtain a shaped catalyst support. The catalyst support is dried at 80°C for 2 hours and then calcined at 550°C for 2 hours.

[0126] (4) Select tetraammonium platinum nitrate as platinum source to prepare impregnation solution, and impregnate the obtained catalyst support in the impregnation solution according to the same volume; based on the weight of the catalyst support, the loading percentage of Pt in the catalyst is 0.35% during the impregnation process.

[0127] Then, the catalyst was dried at 40°C for 4 hours, dried at 80°C for 2 hours, and calcined at 500°C for 2 hours to obtain the hydroisomerization catalyst.

[0128] The specific surface area of ​​the obtained hydroisomerization catalyst was measured (results are shown in Table 1), and the hydroisomerization performance was evaluated using hexadecane as a model compound (results are shown in Table 2).

[0129] <Testing Methods>

[0130] 1) BET test of catalyst: The catalyst was tested using a 3Flex three-station multi-purpose gas adsorption instrument manufactured by Micromeritics, USA. The N2 adsorption / desorption method was used, and the test temperature was -196℃. Before the test, the samples were pretreated to remove surface moisture and impurities (vacuum heat treatment at 300℃ for 4 hours).

[0131] 2) Evaluation conditions for hydroisomerization performance: The prepared hydroisomerization catalyst was placed in a fixed bed, with n-hexadecane as the model compound, a hydrogen-to-oil ratio of 500, and a mass hourly space velocity of 2.32 h⁻¹. -1 The overall conversion and isohexadecane selectivity of the hydroisomers were evaluated under normal pressure, and the methods used to calculate them are as follows:

[0132] Total conversion rate = (mass percentage of n-hexadecane before reaction - mass percentage of n-hexadecane after reaction) / mass percentage of n-hexadecane before reaction * 100%;

[0133] Isohexadecane selectivity = mass percentage of isohexadecane after reaction / (mass percentage of n-hexadecane before reaction - mass percentage of n-hexadecane after reaction).

[0134] Table 1. BET test results of hydroisomerization catalysts

[0135]

[0136] As can be seen from the data in Table 1, controlling the type and amount range of thickeners in the raw materials used to prepare the catalyst can effectively adjust the dispersibility of molecular sieves and binders, thereby improving the mesoporous structure and the combined structure and distribution of mesoporous-microporous structures in the obtained catalyst.

[0137] Table 2 Evaluation of Hydroisomerization Performance

[0138]

[0139] Fischer-Tropsch waxes are mainly composed of straight-chain alkanes with different carbon numbers and a small amount of isoalkanes. For straight-chain alkanes with higher carbon numbers, the pore size of ten-membered ring molecular sieves such as ZSM-48 and ZSM-5 is relatively small (0.53*0.57nm). They mainly use the orifice mechanism or lock-and-key mechanism to achieve isomerization reactions. The isomers are mainly monomethyl or polymethyl products with low branching and large molecular size. It is difficult for the isomers to diffuse and remove quickly, and some will crack, resulting in low isomerization yields.

[0140] As shown in Table 2, the catalyst of this invention exhibits superior activity (reflected by changes in reaction temperature) and product selectivity at the same conversion rate. This indicates that the mesoporous-microporous composite catalyst with a uniform pore structure distribution prepared in this invention, due to the presence of more mesopores, is more conducive to the timely diffusion of branched products, preventing further cracking, resulting in better catalytic effect and increased yield of isomers.

[0141] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the spirit of the invention.

Claims

1. A process for preparing a meso-microporous composite hydroisomerization catalyst, characterized by, Includes the following steps: (1) Molecular sieve, binder, thickener, nitric acid and water are brought into contact and mixed wet under heating and stirring conditions until uniform. The heating temperature is 30-100℃ to obtain wet mixed slurry. (2) The wet slurry obtained above is then extruded, dried and calcined to obtain a catalyst support containing mesoporous-microporous structures. (3) The catalyst support obtained above is then immersed in the impregnation solution to obtain the hydroisomerization catalyst. The proportions of each component used in step (1) of preparing the catalyst support are as follows, based on a total dry weight of 100 wt%: The dry base comprises a molecular sieve and a binder, wherein; The molecular sieve content is 10-90 wt%. The binder content is 10-90 wt%; The ratio of nitric acid to dry basis is 0.5-10 wt%. The ratio of thickener to dry basis is 0.01-5.0 wt%. The binder is selected from one or more of boehmite, alumina and aluminosilicate; The thickener is selected from one or more of natural thickeners, cellulose thickeners, and synthetic polymer thickeners; The natural thickener is selected from starch, xanthan gum, gelatin, guar gum, natural rubber, or agar; The cellulose-based thickener is selected from methylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, or sodium carboxymethylcellulose; The synthetic polymer thickener is selected from polyurethane thickener, sodium polyacrylate, polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyethylene oxide, carbomer resin, polyacrylic acid or polyacrylate copolymer emulsion.

2. The production method according to claim 1, characterized by, The proportions of each component used in the catalyst support process are calculated based on a total dry weight of 100 wt%. The dry base comprises a molecular sieve and a binder, wherein; The molecular sieve content is 10-90 wt%. The binder content is 10-90 wt%; The ratio of nitric acid to dry basis is 1.0-5.0 wt%. The ratio of thickener to dry base is 0.5-3.0 wt%.

3. The production method according to claim 1, characterized by, The molecular sieve is selected from one or more of the ZSM series molecular sieves, SSZ series molecular sieves, and SAPO series molecular sieves.

4. The method of claim 1, wherein, The molecular sieve is a ZSM series molecular sieve.

5. The preparation method according to claim 3, characterized in that, The ZSM series molecular sieves are derived from ZSM-48 molecular sieve, ZSM-22 molecular sieve, ZSM-35 molecular sieve or ZSM-53 molecular sieve; The SSZ series molecular sieve is SSZ-32 molecular sieve; The SAPO series molecular sieve is SAPO-11 molecular sieve.

6. The preparation method according to claim 3, characterized in that, The ZSM series molecular sieve is ZSM-48 molecular sieve.

7. The preparation method according to claim 1, characterized in that, In step (1), the ratio of water to dry basis is 200-1000 wt%. During the wet mixing process, heating and stirring are stopped when the ratio of water to dry basis is controlled to 50-150 wt%, thus obtaining the wet mixed slurry.

8. The method of claim 1, wherein, The drying process conditions in step (2) include: a drying temperature of 40-120℃ and a drying time of 2-8 hours; and / or The roasting process conditions in step (2) include: roasting temperature of 400-750℃; roasting time of 2-5h.

9. The method of claim 1, wherein, The drying process conditions in step (2) include: drying temperature of 80-110℃ and drying time of 3-6h.

10. The method of claim 1, wherein, The roasting process conditions in step (2) include: roasting temperature of 450-600℃; roasting time of 2-5h.

11. The method of claim 1, wherein, Step (3) The catalyst support is impregnated with a solution containing a hydrogenation component precursor.

12. The method of claim 11, wherein, The impregnation method is pore saturation impregnation.

13. The preparation method according to claim 11, characterized in that, The solution containing the hydrogenated precursor contains a hydrogenated element, which is a Group VIII noble metal element, or a Group VIB metal element and / or a Group VIII non-noble metal element.

14. The method of claim 13, wherein, The Group VIII noble metal element is palladium and / or platinum; The group VIB metal elements are selected from one or more of tungsten, molybdenum, and chromium; The group VIII non-precious metal elements are nickel and / or cobalt; Based on the weight of the catalyst, the loading of the Group VIII noble metal element is less than or equal to 10 wt%; or Based on the weight of the catalyst, the loading of the group VIB metal element is 1-35 wt%; the loading of the group VIII non-precious metal element is 1-25 wt%.

15. The preparation method according to claim 14, characterized in that, Based on the weight of the catalyst, the loading of the Group VIII noble metal element is 0.1-5 wt%; or Based on the weight of the catalyst, the loading of the group VIB metal element is 5-30 wt%; the loading of the group VIII non-precious metal element is 2-15 wt%.

16. The method of claim 14, wherein, Based on the weight of the catalyst, the loading of the Group VIII noble metal element is 0.2-2 wt%.

17. The method of claim 1, wherein, The catalyst support described in step (3) is impregnated and then calcined; the calcination conditions include: calcination temperature of 400-700℃; calcination time of 1-12h.

18. The method of claim 17, wherein, The catalyst support described in step (3) is impregnated and then calcined; the calcination conditions include: calcination temperature of 450-550℃; calcination time of 2-4h.

19. The mesoporous-microporous composite hydroisomer catalyst prepared by any one of claims 1-18.

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