A gasoline pre-hydrogenation tooth spherical alumina carrier and a preparation method thereof

Abstract

The present application belongs to the field of catalyst carrier, and particularly relates to a kind of gasoline prehydrogenation tooth spherical alumina carrier and its preparation method.The preparation method is as follows: (1) first kneading pseudo-boehmite powder and extrusion aid, then adding acidic aqueous solution to continue second kneading, to obtain mud material; (2) using five-tooth ball module to extrude, cutting the granules after extruding the mud material, to obtain granular material; (3) drying the granular material first, then calcining, to obtain the gasoline prehydrogenation tooth spherical alumina carrier.The carrier has a bulk density of 0.6-0.7 g / mL, 4-10 nm pores account for 65-75%, and >15 nm pores account for 10-20%, which can realize industrial continuous production and adapt to high-efficiency prehydrogenation catalyst.

Description

Technical Field

[0001] This invention belongs to the field of catalyst supports, specifically relating to a gasoline prehydrogenation toothed spherical alumina support and its preparation method. Background Technology

[0002] As a major consumer of refined oil products, my country is continuously tightening the limits on sulfur and olefin content in gasoline with the implementation of the China VI and even stricter fuel emission standards. The China VI b standard requires gasoline sulfur content to be no higher than 10 mg / kg and olefin content to be no more than 15%. In my country's refined oil product structure, fluidized bed catalytic cracking (FCC) gasoline accounts for more than 80% of the blending components of commercial gasoline. It is not only the main source of olefins in gasoline but also the source of more than 90% of sulfur. Therefore, deep desulfurization and olefin reduction of FCC gasoline are core aspects of clean gasoline production.

[0003] FCC gasoline contains a wide variety of sulfides. The light fractions below 100°C mainly consist of easily removed sulfides such as thiols and sulfides, while the heavy fractions above 100°C contain approximately 90% difficult-to-remove sulfides such as thiophenes and benzothiophenes. The efficient removal of these sulfides directly determines the overall desulfurization effect of the gasoline. While conventional hydrodesulfurization technology can effectively reduce sulfur content, it is accompanied by a large amount of olefin and aromatic hydrocarbon saturation reactions, causing a significant drop in the gasoline's octane number. Since octane number is a core indicator of gasoline's anti-knock properties, its loss directly affects gasoline performance. Therefore, "desulfurization while maintaining octane number" has become a key technical bottleneck in gasoline hydrotreating technology.

[0004] Gasoline pre-hydrogenation technology, with its selective hydrogenation characteristics, can specifically remove sulfides and some olefins. While reducing sulfur and olefin content, it maximizes the preservation of octane rating, improves gasoline stability, and reduces harmful emissions in exhaust gases, making it a mainstream technology for clean gasoline production. The core of this technology lies in a highly efficient supported catalyst. The catalyst support, as the medium for carrying and dispersing the active components, directly determines the catalyst's reactivity, selectivity, and lifespan.

[0005] From the perspective of the evolution of carrier morphology, it has successively gone through iterations from spherical, cylindrical, clover-shaped, and tetraclover-shaped to toothed spherical. Toothed spherical carriers, due to their unique toothed structure, have advantages over traditional carrier morphologies, including larger specific surface area, superior mass transfer channels, and higher mechanical strength. Pre-hydrogenation catalysts prepared based on them can achieve a 10-20℃ reduction in reaction temperature, a 15%-20% increase in processing load, and a catalyst lifetime extension of over 30%. However, the preparation of existing toothed spherical alumina carriers faces two major challenges: first, it is difficult to achieve continuous industrial production; mismatch between mold structure and extrusion parameters easily leads to uneven carrier morphology and poor batch stability; second, it is difficult to simultaneously achieve the desired pore structure and packing density. Most products either have insufficient proportion of effective mesopores (4-10nm), affecting the dispersion of active components, or have too low a proportion of pores (>15nm), restricting mass transfer efficiency. Simultaneously, the packing density deviates from the optimal industrial packing range of 0.6-0.7g / mL, resulting in low reactor space utilization. Therefore, developing a toothed spherical alumina carrier that can be continuously produced, has a reasonable pore structure, and meets the required packing density is of great significance for promoting the upgrading of gasoline pre-hydrogenation technology.

[0006] Therefore, based on this, the technical solution of the present invention is proposed. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a gasoline pre-hydrogenated toothed spherical alumina carrier and its preparation method, aiming to solve the problem of how to continuously produce toothed spherical carriers in industrial equipment while meeting the indicators of a bulk density of 0.6-0.7 g / mL, a pore size of 4-10 nm of 65-75%, and a pore size of >15 nm of 10-20%.

[0008] The purpose of this invention is to provide a method for preparing a gasoline pre-hydrogenated toothed spherical alumina support, the preparation method comprising the following steps:

[0009] (1) The pseudoboehmite powder and the extrusion aid are mixed for the first time, and then an acidic aqueous solution is added to continue the second mixing to obtain a mud-like material; wherein the pseudoboehmite powder has a colloidal index > 50% and a pore volume of 0.6-0.7 mL / g;

[0010] (2) The mud-like material is extruded and then granulated using a five-toothed ball module to obtain granular material;

[0011] (3) The particulate material is dried and then roasted to obtain the gasoline pre-hydrogenated toothed spherical alumina carrier.

[0012] Preferably, in step (1), the extrusion aid comprises guar gum powder, cellulose, and citric acid monohydrate; wherein:

[0013] The mass ratio of guar gum powder, cellulose and citric acid monohydrate is 30-50:10-30:10-20.

[0014] Preferably, in step (1), the acidic aqueous solution is an aqueous solution of nitric acid.

[0015] Preferably, in step (1), the first kneading time is 5-8 minutes, and the second kneading time is 20-40 minutes.

[0016] Preferably, in step (2), the five-tooth ball module has rectangular teeth with a tooth width of 1.2 mm.

[0017] Preferably, in step (2), during the extrusion molding process, the feeding frequency is 10-15Hz and the extrusion frequency is 5-15Hz; the pelletizing cutter has an arc-shaped blade, a cutter gap of 0.3mm, a blade gap of 4.0mm, and a depth of 2.1mm.

[0018] Preferably, in step (3), the drying temperature is 100-120℃ and the drying time is 2-4 hours;

[0019] The roasting temperature is 750-800℃, and the roasting time is 3-4 hours.

[0020] Based on the same technical concept, another aspect of the present invention is to provide a gasoline pre-hydrogenated toothed spherical alumina carrier obtained by the above preparation method.

[0021] Preferably, the packing density of the gasoline pre-hydrogenated toothed spherical alumina support is 0.6-0.7 g / mL, the proportion of 4-10 nm pores is 65-75%, and the proportion of >15 nm pores is 10-20%.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention comprehensively solves the technical pain points of existing gasoline prehydrogenation toothed spherical alumina supports, which are difficult to achieve continuous industrial production and cannot simultaneously achieve satisfactory pore structure and packing density. The prepared support can be adapted to the performance requirements of high-efficiency prehydrogenation catalysts, providing a high-quality support solution for clean gasoline production. The specific beneficial effects are as follows:

[0024] 1. Achieve continuous and stable industrial production

[0025] This invention achieves continuous molding of toothed spherical carriers on industrial equipment by precisely matching the parameters of the five-toothed ball module (rectangular teeth, tooth width 1.2mm), extrusion process parameters (feeding frequency 10-15Hz, extrusion frequency 5-15Hz), and pelletizing tool specifications (arc-shaped blade, cutter gap 0.3mm, etc.). This solves the problems of uneven carrier shape and large batch fluctuations in traditional processes, ensuring the consistency of carrier products.

[0026] 2. Balancing pore structure and packing density indicators

[0027] On the one hand, a special pseudoboehmite powder with a gel solubility index >50% and a pore volume of 0.6-0.7 mL / g is used, combined with a specific ratio of extrusion aid, to lay the foundation for the pore structure of the carrier. On the other hand, by using a 1.2 mm widened toothed ball mold and a 750-800℃ calcination process, the carrier's bulk density is kept stable within the optimal filling range of 0.6-0.7 g / mL, and a reasonable pore distribution is achieved with 65-75% of 4-10 nm pores and 10-20% of >15 nm pores, taking into account both the dispersibility of active components and the mass transfer efficiency of reactants.

[0028] 3. Improve the overall performance of the support and the compatibility with the catalyst.

[0029] The calcination temperature of 750-800℃ achieves complete sintering of the alumina support, which not only improves the mechanical strength of the support, but also forms a hierarchical pore structure through moderate pore collapse. The pre-hydrogenation catalyst prepared based on this support can effectively reduce the initial reaction temperature, improve desulfurization selectivity, and extend the catalyst service life, thus meeting the stringent process requirements of clean gasoline production. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a pore size distribution diagram of the gasoline pre-hydrogenated toothed spherical alumina carrier obtained in Example 1. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] Example 1

[0034] This embodiment provides a method for preparing a gasoline pre-hydrogenated toothed spherical alumina support, the preparation method comprising the following steps (detailed):

[0035] (1) Material pretreatment and weighing

[0036] Accurately weigh 1428g of boehmite powder (colloidal solubility index 55%, pore volume 0.65mL / g), 40g of guar gum powder, 20g of cellulose, 15g of citric acid monohydrate, 83g of 60% nitric acid, and 1043g of deionized water. Simultaneously, clean and dry the inner wall of the kneader to remove residual impurities. This ensures the purity of the raw materials and the accuracy of the proportions, preventing impurities from affecting the carrier's performance. Drying the kneader also prevents premature agglomeration of the materials.

[0037] (2) First dry mixing and kneading

[0038] Weigh out the pseudoboehmite powder and the composite extrusion aid (guar gum powder, cellulose, and citric acid monohydrate) and put them into a kneader. Set the kneader speed to 30 r / min and dry mix for 5 min. This allows the extrusion aid to be evenly dispersed in the pseudoboehmite powder. Guar gum powder can improve the plasticity of the material, cellulose can enhance the strength of the green body after molding, and citric acid monohydrate can assist in the subsequent sol-gel reaction. Dry mixing lays a uniform material foundation for subsequent wet mixing.

[0039] (3) Preparation of acidic aqueous solution and second wet kneading

[0040] Mix 83g of 60% nitric acid with 1043g of deionized water in a dedicated container to prepare a homogeneous nitric acid aqueous solution. Slowly and uniformly add this solution to the dry mixture in a kneader, adjust the kneader speed to 45 rpm, and continue kneading for 30 minutes until the material forms a homogeneous, particle-free, and resilient mud-like material. The nitric acid aqueous solution induces a gelation reaction in the boehmite powder, forming a colloidal system with suitable viscosity. Wet kneading ensures the material swells fully, guaranteeing smooth extrusion molding and the integrity of the preform.

[0041] (4) Adjustment of extrusion molding parameters

[0042] Install a five-tooth ball module (rectangular teeth, 1.2mm tooth width) with an outer diameter of Ф4.0mm in advance, and check that the module teeth are free from wear and blockage. Start the extrusion equipment, set the feeding frequency to 12Hz and the extrusion frequency to 10Hz, and test run the equipment to ensure that the extrusion pressure is stable in the range of 0.8-1.0MPa. Adjusting the parameters can avoid material blockage and uneven extrusion strip thickness during the extrusion process. The 1.2mm tooth width module provides a specific tooth structure for the carrier, ensuring the subsequent bulk density and pore structure indicators.

[0043] (5) Pelletizing

[0044] Wet-mixed, mud-like material is fed into the hopper of an extruder. The material is extruded through a five-toothed ball module to form a continuous toothed preform. An arc-shaped cutter (0.3mm cutter gap, 4.0mm blade clearance, 2.1mm blade depth) is used to granulate the extruded preform, resulting in uniformly sized particles. During granulation, the material conveying speed is controlled to match the cutter rotation speed to prevent preform breakage or adhesion. The arc-shaped blade ensures the integrity of the toothed spherical morphology of the particles, and the precise cutter gap parameters control the consistency of particle size, providing a uniform preform for subsequent drying and calcination.

[0045] (6) Drying treatment

[0046] Spread the pelleted material evenly on a tray (material thickness ≤ 2cm), place it in a forced-air drying oven, set the drying temperature to 120℃ and the drying time to 3 hours, and maintain an airflow of 2m³ / h inside the drying oven during the drying process. 3 / h, ensuring uniform heating of the material. Low-temperature drying at 120℃ can slowly remove free water from the material, avoiding cracking and deformation of the green body caused by high-temperature rapid drying, and ensuring the integrity of the carrier's morphology.

[0047] (7) Firing and shaping

[0048] The dried granular material was transferred to a muffle furnace and heated to 790°C at a rate of 5°C / min. After reaching the target temperature, it was calcined at a constant temperature for 3 hours. After calcination, the power to the muffle furnace was turned off, and the furnace was cooled to room temperature to obtain a gasoline-pre-hydrogenated toothed spherical alumina support. Calcination at 790°C allows the boehmite powder to undergo a crystal transformation, forming a γ-Al₂O₃ crystalline phase. Simultaneously, it achieves complete sintering of the support, improving its mechanical strength. Furthermore, the moderately high temperature promotes the collapse of some small pores, forming channels >15nm, thus optimizing the pore structure distribution.

[0049] Example 2

[0050] This embodiment provides a method for preparing a gasoline pre-hydrogenated toothed spherical alumina support, the preparation method comprising the following steps (briefly described):

[0051] (1) Take 1428g of pseudoboehmite powder with a gel solubility index of 51% and a pore volume of 0.6mL / g, and an extrusion aid composed of 30g of guar gum powder, 10g of cellulose and 10g of citric acid monohydrate, put them into a kneader and dry mix for 8min; add 66g of an acidic aqueous solution of 60% nitric acid and 1000g of water, and continue kneading for 20min to obtain mud-like material.

[0052] (2) A five-tooth ball module with an outer diameter of Ф4.0mm (rectangular teeth, tooth width 1.2mm) is used, and the feeding frequency is set to 10Hz and the extrusion frequency is set to 5Hz. A circular arc cutter with a cutter gap of 0.3mm, a blade gap of 4.0mm and a blade depth of 2.1mm is used to cut the material into granules.

[0053] (3) The particulate material is dried at 100°C for 4 hours and then calcined at 750°C for 4 hours to obtain the gasoline prehydrogenated toothed spherical alumina carrier.

[0054] Example 3

[0055] This embodiment provides a method for preparing a gasoline pre-hydrogenated toothed spherical alumina support, the preparation method comprising the following steps (briefly described):

[0056] (1) Take 1428g of pseudoboehmite powder with a gel solubility index of 57% and a pore volume of 0.7mL / g, and an extrusion aid composed of 50g of guar gum powder, 30g of cellulose and 20g of citric acid monohydrate, put them into a kneader and dry mix for 8min; add 100g of an acidic aqueous solution of 60% nitric acid and 1087g of water, and continue kneading for 40min to obtain mud-like material.

[0057] (2) A five-tooth ball module with an outer diameter of Ф4.0mm (rectangular teeth, tooth width 1.2mm) is used, and the feeding frequency and extrusion frequency are set to 15Hz. The ball is granulated with an arc-shaped cutter with a cutter gap of 0.3mm, a blade gap of 4.0mm, and a blade depth of 2.1mm to obtain granular material.

[0058] (3) The particulate material is dried at 120°C for 2 hours and then calcined at 800°C for 3 hours to obtain the gasoline pre-hydrogenated toothed spherical alumina carrier.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 1 is that the gel solubility index of the pseudoboehmite powder is 45%, while the other operations are the same as in Example 1.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that the tooth width of the five-tooth ball module is the normal value, i.e., 1.0 mm. Other operations are the same as in Example 1.

[0063] Comparative Example 3

[0064] The difference between this comparative example and Example 1 is that the calcination temperature is 700°C, while the other operations are the same as in Example 1.

[0065] Comparative Example 4

[0066] The difference between this comparative example and Example 1 is that the calcination temperature is 850°C, while the other operations are the same as in Example 1.

[0067] Verification Characterization Example 1

[0068] The gasoline pre-hydrogenated toothed spherical alumina supports obtained in Examples 1-3 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0069] Table 1

[0070]

[0071] Table 1 (continued)

[0072]

[0073] As shown in Table 1, Examples 1, 2, and 3 can all prepare a gasoline prehydrogenated toothed spherical alumina support with a bulk density of 0.6-0.7 g / mL, a pore size of 4-10 nm of 65-75%, and a pore size of >15 nm of 10-20%.

[0074] Furthermore:

[0075] (i) Compared with Example 1, the colloidal index of the pseudoboehmite powder in Comparative Example 1 is 45%, which is lower than 55% in Example 1. As a result, the two key indicators of "bulk density" and "4-10nm pore volume ratio" cannot meet the requirements. The reason may be that: a low colloidal index means poor dispersibility of the colloid, which leads to the particles not being packed tightly enough when the carrier is prepared, thereby reducing the bulk density of the carrier. The reduction in the bulk density of the carrier will lead to an increase in the proportion of >15nm pores, and thus a decrease in the proportion of 4-10nm pores.

[0076] (ii) Compared with Example 1, the tooth width of the five-tooth ball module in Comparative Example 2 is the normal value of 1.0 mm, which is smaller than 1.2 mm in Example 1. As a result, the two key indicators of "packing density" and "4-10 nm pore volume ratio" cannot meet the requirements. The reason may be that: reducing the tooth width reduces the mass of a single toothed spherical carrier of the same size, thereby reducing the packing density of the carrier. The reduction in the packing density of the carrier will lead to an increase in the proportion of >15 nm pores and a decrease in the proportion of 4-10 nm pores.

[0077] (iii) The difference between Comparative Example 3 and Example 1 is that the calcination temperature is 700°C, which is lower than 790°C in Example 1. As a result, the key indicator of ">15nm pore volume ratio" cannot meet the requirements. The reason may be that the lower the calcination temperature, the smaller the pore size is usually, which leads to an increase in the proportion of 4-10nm pores and a decrease in the proportion of >15nm pores.

[0078] (iv) The difference between Comparative Example 4 and Example 1 is that the calcination temperature is 850°C, which is higher than 790°C in Example 1. As a result, the key indicator of "4-10nm pore volume ratio" cannot meet the requirements. The reason may be that the higher the calcination temperature, the more grains grow and the more lightly sinter between particles, and the smaller pores merge into larger pores, resulting in a decrease in the proportion of 4-10nm pores.

[0079] Verification Characterization Example 2

[0080] The pore size of the gasoline pre-hydrogenated toothed spherical alumina support obtained in Example 1 was characterized, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the carrier obtained in Example 1 has a pore size distribution that fully meets the requirements of 65-75% of pores in the 4-10nm range and 10-20% of pores in the >15nm range.

[0081] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a gasoline pre-hydrogenated toothed spherical alumina carrier, characterized in that, The preparation method includes the following steps: (1) The pseudoboehmite powder and extrusion aid are mixed for the first time, and then an acidic aqueous solution is added for the second mixing to obtain a mud-like material; wherein: the pseudoboehmite powder has a colloidal index > 50% and a pore volume of 0.6-0.7 mL / g; (2) The mud-like material is extruded and then granulated to obtain granular material by using a five-tooth ball module; wherein the five-tooth ball module has rectangular teeth with a tooth width of 1.2 mm. (3) The particulate material is first dried and then calcined at 750-800℃ for 3-4 hours to obtain the gasoline pre-hydrogenated toothed spherical alumina carrier; wherein the gasoline pre-hydrogenated toothed spherical alumina carrier has a bulk density of 0.6-0.7 g / mL, a pore size of 4-10 nm of 65-75%, and a pore size of >15 nm of 10-20%.

2. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (1), the extrusion aid includes guar gum powder, cellulose, and citric acid monohydrate; wherein: The mass ratio of guar gum powder, cellulose and citric acid monohydrate is 30-50:10-30:10-20.

3. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (1), the acidic aqueous solution is an aqueous solution of nitric acid.

4. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (1), the first kneading time is 5-8 minutes, and the second kneading time is 20-40 minutes.

5. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (2), during the extrusion molding process, the feeding frequency is 10-15Hz and the extrusion frequency is 5-15Hz; the pelletizing cutter has an arc-shaped blade, a cutter gap of 0.3mm, a blade gap of 4.0mm, and a depth of 2.1mm.

6. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (3), the drying temperature is 100-120℃ and the drying time is 2-4h.

7. The gasoline prehydrogenated toothed spherical alumina support obtained by the preparation method according to any one of claims 1-6.

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