Bimodal pore distribution alumina pellets, method of making and catalytic reforming catalyst

Abstract

The present application relates to a kind of bimodal pore distribution alumina small ball, preparation method and catalytic reforming catalyst, the bimodal pore distribution alumina small ball has two most probable pore diameter, the pore diameter of two most probable pore diameter is in 2-100nm;The pore diameter of first most probable pore diameter is in 2-15nm, the pore diameter of second most probable pore diameter is in 15-100nm;Bimodal pore distribution alumina small ball contains group IVA metal;The content of Si element in bimodal pore distribution alumina small ball is less than 100ppm, the content of Fe element is less than 200ppm, the content of Na element is less than 50ppm, based on the mass of bimodal pore distribution alumina small ball.The bimodal pore distribution alumina small ball prepared by the preparation method of the present application has higher purity and mechanical strength, pore size distribution can be adjusted in a larger range, presents obvious most probable pore diameter bimodal at pore diameter 2-15nm and 15-100nm, high specific surface area, large pore volume, high crush strength, low impurity element content.

Description

Technical Field

[0001] This invention relates to the field of alumina support technology, specifically to alumina microspheres with a bimodal pore distribution, a preparation method thereof, and a catalytic reforming catalyst. Background Technology

[0002] Alumina, due to its high specific surface area, narrow particle size distribution, good adsorption properties, thermal stability, and surface acidity, is widely used as a support, adsorbent, and hydrogenation catalyst in petrochemical processes. As a support, the pore structure of alumina significantly influences catalyst activity, selectivity, and lifetime. For example, in the preparation of heavy oil hydrodemetallization catalysts, alumina with a bimodal pore structure is typically used as the support, possessing both micropores providing catalytic activity and macropores facilitating the rapid migration of metal compound molecules. The micropores are determined by the precursor properties of the alumina support, while the macropores are often created by adding various pore-expanding agents. Macropores provide ample contact space between reactants and the catalyst's active sites, facilitating the formation of intermediate products and the rapid escape of reaction products, thus increasing the reaction rate. Simultaneously, they can accumulate carbon residue to some extent, extending catalyst lifetime.

[0003] Chinese patent CN1044337C describes a method for preparing a catalyst support for heavy oil hydrodemetallization. Two types of aluminum hydroxide powder with different properties are added to carbon black and a surfactant, extruded into strips, and calcined in an oxygen-containing stream to produce an alumina product. The pore diameter is [not specified]. The holes account for more than 50% of the total hole volume and the hole diameter is greater than The pores account for 5% to 30% of the total pore volume.

[0004] For continuous reforming moving bed catalytic processes, in order to achieve continuous catalyst delivery and meet other industrial design requirements, and to reduce catalyst mechanical wear, the alumina support must be made into spherical spheres with a diameter of 1.4 to 2.0 mm, while its crushing strength is not less than 39 N / particle.

[0005] The earliest known method for preparing spherical alumina using hot oil column molding of aluminum sol is US Patent 2620314. This method involves reacting metallic aluminum with hydrochloric acid solution to prepare aluminum sol. The sol is then mixed with hexamethylenetetramine solution and molded in a hot oil column apparatus. After pressure aging in an oil bath, washing with water, drying, calcining, and steam pore-expanding treatment, spherical alumina is obtained. This method requires many steps, each of which takes a long time. The alumina prepared by this process has a diffuse distribution of micropores, with a high proportion of micropores smaller than 8 nanometers. At the same time, its hydrothermal stability is relatively low.

[0006] Chinese patent CN105502447B describes a method for preparing alumina microspheres by hot oil column molding. The method involves mixing boehmite powder obtained by alkoxyaluminum hydrolysis, a first gelling agent, and water to form an alumina suspension. An acid solution is then added to the suspension to obtain an alumina slurry. A second gelling agent is added to the alumina slurry and mixed thoroughly. The mixture is then dropped into a hot oil column to form microspheres. The microspheres are collected directly at the bottom of the hot oil column. The collected microspheres are then washed, dried, and calcined. The resulting alumina microspheres exhibit a unimodal pore distribution, with a pore volume less than 0.5 mL / g and a specific surface area less than 170 m². 2 / g.

[0007] Chinese patent CN 1120971B describes a method for preparing a bimodal porous alumina support. The method involves uniformly mixing boehmite dry powders prepared by two or more different raw material routes, followed by sol-gelation, oil-ammonia column molding, drying, and calcination to obtain alumina microspheres. The macropores are provided by boehmite prepared via the sodium aluminate route, while the micropores are provided by a combination of boehmite prepared via the sodium aluminate and aluminum chloride routes. By adjusting the proportions of the mixture, the strength of the alumina support can be significantly altered, and the ratio of macropores to micropores can be adjusted within a wide range. However, the alumina microspheres prepared by this method have a relatively high impurity content, making them unsuitable for loading noble metal active components and prone to catalyst poisoning.

[0008] How to prepare alumina microspheres with obvious bimodal pore distribution in pore diameters of 2-15 nm and 15-100 nm and low impurity element content is a technical problem that urgently needs to be solved. Summary of the Invention

[0009] This invention provides alumina microspheres with a bimodal pore distribution, a preparation method, and a catalytic reforming catalyst, to obtain alumina microspheres exhibiting a distinct bimodal pore distribution at pore diameters of 2-15 nm and 15-100 nm and low impurity element content, thereby obtaining a catalyst with excellent catalytic performance.

[0010] In a first aspect, the present invention relates to a bimodal pore-distributed alumina microsphere having two most probable pore diameters, both of which have a diameter of 2-100 nm; the first most probable pore diameter has a diameter of 2-15 nm, and the second most probable pore diameter has a diameter of 15-100 nm; the bimodal pore-distributed alumina microsphere contains a Group IVA metal; the content of Si in the bimodal pore-distributed alumina microsphere is less than 100 ppm, the content of Fe is less than 200 ppm, and the content of Na is less than 50 ppm, based on the mass of the bimodal pore-distributed alumina microsphere.

[0011] Optionally, the specific surface area of ​​the bimodal pore-distributed alumina microspheres is 170-250 m².2 / g, with a pore volume of 0.70-1.0 mL / g; preferably, the specific surface area of ​​the bimodal pore distribution alumina microspheres is 180-220 m² / g. 2 / g, with a pore volume of 0.75-0.90mL / g.

[0012] Optionally, the Group IVA metal is germanium or tin; the content of the Group IVA metal is 0.1-1.0%, based on the mass of the bimodal pore distribution alumina microspheres.

[0013] Secondly, the present invention relates to a method for preparing the above-mentioned bimodal pore distribution alumina microspheres, comprising: mixing aluminum sol with a Group IVA metal precursor and a directing agent, then mixing it with a gelling agent and dripping it into a hot oil column to form a microsphere, wherein the directing agent is polyethylene glycol.

[0014] Optionally, the weight ratio of the directing agent to the dry alumina in the aluminum sol is (1.0-15):100; preferably, the weight ratio of the directing agent to the dry alumina in the aluminum sol is (1.0-10):100.

[0015] Optionally, the polyethylene glycol is selected from one of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, polyethylene glycol 2000 and polyethylene glycol 4000.

[0016] Optionally, the gelling agent is selected from urea and / or hexamethylenetetramine, and the weight ratio of the gelling agent to the dry alumina in the aluminum sol is (50-96):100; preferably, the weight ratio of the gelling agent to the dry alumina in the aluminum sol is (55-75):100.

[0017] Optionally, the solid content of the aluminum sol, calculated as alumina, is 10-30% by mass; preferably, the solid content of the aluminum sol, calculated as alumina, is 15-25% by mass.

[0018] Optionally, the aluminum sol is prepared by reflux reaction of metallic aluminum with hydrochloric acid solution or aluminum chloride solution; when the aluminum sol is prepared by reflux reaction of metallic aluminum with hydrochloric acid solution, the mass ratio of metallic aluminum to hydrochloric acid solution is 1:(2-5), the concentration of hydrochloric acid solution is 10-30% by mass%, the temperature of reflux reaction is 60-200℃, and the time is 4-100 hours.

[0019] Optionally, the oil phase material of the hot oil column is selected from at least one of medical lubricating oil, liquid paraffin oil, and white oil, and the temperature of the oil phase material is 80-120℃ and the thickness is 100-600 cm; preferably, the oil phase material of the hot oil column is liquid paraffin oil, and the liquid paraffin oil is a C44-type liquid with a distillation range of 250-500℃. 16 ~C20 The oil phase material is a n-alkanes; preferably, the oil phase material has a temperature of 90-105℃ and a thickness of 200-500 cm.

[0020] Optionally, the preparation method further includes collecting the shaped alumina microspheres, aging, washing, drying, and calcining.

[0021] Optionally, the aging conditions include: being carried out under sealed conditions at a temperature of 100-200℃ for 4-96 hours; the drying temperature at 60-150℃ for 0.5-24 hours; and the calcination temperature at 500-1000℃ for 0.5-24 hours. Preferably, the aging temperature is 110-180℃ for 6-72 hours; the drying temperature is 90-140℃ for 4-12 hours; and the calcination temperature is 550-750℃ for 2-8 hours.

[0022] Optionally, the Group IVA metal precursor is selected from chloride, nitrate or carbonate salts of germanium or tin; the amount of the Group IVA metal precursor is 0.1-1.0% based on the mass of the Group IVA metal and the dry-basis alumina in the alumina sol.

[0023] In another aspect, the present invention relates to a catalytic reforming catalyst comprising alumina microspheres and an active component supported on the alumina microspheres, wherein the alumina microspheres are the bimodal pore distribution alumina microspheres described above, or are prepared by the above preparation method, and the active component comprises 0.1-1.0% by mass of platinum and 0.5-2.0% by mass of halogen, based on the mass of the alumina microspheres.

[0024] Beneficial effects:

[0025] The alumina microspheres prepared by the method of this invention exhibit high purity and mechanical strength, with pore size distribution that can be adjusted over a wide range. They show distinct bimodal pore size distributions at 2-15 nm and 15-100 nm, high specific surface area, large pore volume, high crushing strength (above 50 N / particle), and low impurity element content. The catalytic reforming catalyst prepared based on the alumina microsphere support of this invention can significantly improve the yield of light aromatic hydrocarbons (benzene, toluene, xylene) and reduce C9 phosphate density in catalytic reforming reactions. + The above components have high yield and strong resistance to carbon buildup. Attached Figure Description

[0026] Figure 1 This is a pore size distribution diagram of the alumina microspheres prepared in Examples 1-5 of the present invention (the horizontal axis represents the pore diameter, and the unit is...). The ordinate represents the differential aperture distribution dV / dlogD, in cm. 3 ·g-1 ·nm -1 ).

[0027] Figure 2 This is a pore size distribution diagram of the alumina microspheres prepared in Examples 6-8 of the present invention (the horizontal axis represents the pore diameter, and the unit is...). The ordinate represents the differential aperture distribution dV / dlogD, in cm. 3 ·g -1 ·nm -1 ). Detailed Implementation

[0028] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0029] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0030] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0031] In a first aspect, the present invention provides a bimodal pore-distributed alumina microsphere having two most probable pore diameters, both of which are in the range of 2-100 nm; the first most probable pore diameter is in the range of 2-15 nm, and the second most probable pore diameter is in the range of 15-100 nm; the bimodal pore-distributed alumina microsphere contains a Group IVA metal; the content of Si in the bimodal pore-distributed alumina microsphere is less than 100 ppm, the content of Fe is less than 200 ppm, and the content of Na is less than 50 ppm, based on the mass of the bimodal pore-distributed alumina microsphere.

[0032] In a preferred embodiment, the first most probable pore diameter of the bimodal pore-distributed alumina microspheres is 8-15 nm, and the second most probable pore diameter is 15-30 nm.

[0033] It should be noted that the bimodal pore distribution alumina microspheres of the present invention not only have two most probable pore sizes at 2-15 nm and 15-100 nm, but also have low impurity element contents. Furthermore, in a preferred embodiment, the Si element content is less than 50 ppm, the Fe element content is less than 70 ppm, and the Na element content is less than 20 ppm, based on the mass of the bimodal pore distribution alumina microspheres.

[0034] According to one embodiment of the present invention, the specific surface area of ​​the bimodal pore-distributed alumina microspheres is 170-250 m². 2 / g, with a pore volume of 0.70-1.0 mL / g; preferably, the specific surface area of ​​the bimodal pore distribution alumina microspheres is 180-220 m² / g. 2 / g, with a pore volume of 0.75-0.90mL / g.

[0035] It should be noted that the bimodal pore distribution alumina microspheres of the present invention, as described above, have advantages such as high specific surface area and large pore volume, and exhibit a bimodal pore size distribution at 2-15nm and 15-100nm, with low impurity content. Therefore, they can exhibit better adsorption or loading performance when performing subsequent catalyst adsorption or loading, thereby improving the performance of the catalyst.

[0036] As a preferred embodiment, the bimodal pore distribution alumina microspheres of the present invention, as described above, have advantages such as high specific surface area and large pore volume, and exhibit a bimodal pore size distribution at 5-15nm and 15-25nm.

[0037] According to one embodiment of the present invention, the Group IVA metal is germanium or tin. Tin is preferred. The content of the Group IVA metal is 0.1-1.0%, based on the mass of the bimodal pore distribution alumina microspheres.

[0038] It should be noted that the content of the Group IVA metals can refer to the content of Group IVA metals such as Sn; the content of the Group IVA metals being 0.1-1.0% can also be based on the mass of dry alumina in the alumina sol used to prepare the bimodal porous alumina microspheres. This is because, after calcination, the directing agent and gelling agent have decomposed or volatilized at high temperatures, and the alumina in the alumina sol and the Group IVA metals in the added Group IVA metal precursors are all present in the generated bimodal porous alumina microspheres. The added Group IVA metal precursors are very small compared to the mass of dry alumina in the alumina sol.

[0039] Secondly, the present invention provides a method for preparing the above-mentioned bimodal pore distribution alumina microspheres, comprising: mixing aluminum sol with a Group IVA metal precursor and a directing agent, then mixing it with a gelling agent and dripping it into a hot oil column to form a microsphere, wherein the directing agent is polyethylene glycol.

[0040] It should be noted that in the preparation method of this invention, aluminum sol is first mixed with a Group IVA metal precursor and polyethylene glycol, and stirred for a certain time, such as 0.5-2 hours, to obtain a first mixture. Then, a gelling agent is added to the first mixture, and stirred for a certain time, such as 0.5-2 hours, to obtain another mixture. The resulting mixture is dropped into a column of hot oil to form a microsphere. The droplet shrinks into a spherical shape due to surface tension. The resulting alumina microspheres exhibit two most probable pore sizes in the range of 2-100 nm, with the first most probable pore size having a diameter of 2-15 nm and the second most probable pore size having a diameter of 15-100 nm, exhibiting a bimodal pore distribution within the above two pore size ranges. In addition, the bimodal pore distribution alumina microspheres prepared by the preparation method of this invention also have high specific surface area, large pore volume, and high crushing strength.

[0041] In the preparation method of the present invention, aluminum sol is first mixed with Group IVA metal precursor and polyethylene glycol. Polyethylene glycol can coat the outside of alumina particles, so that the alumina particles and Group IVA metal precursor in the aluminum sol form particles coated with polyethylene glycol. Then, a gelling agent is added and mixed, and the mixture is formed by hot oil column molding. The final alumina microspheres exhibit a bimodal pore size distribution at 2-15nm and 15-100nm.

[0042] According to one embodiment of the present invention, the weight ratio of the directing agent to the dry alumina in the alumina sol is (1.0-15):100. As a preferred embodiment, the weight ratio of the directing agent to the dry alumina in the alumina sol is (1.0-10):100. In the preparation method of the present invention, parameters or characteristics such as the pore size distribution of the obtained alumina microspheres can be changed by altering certain control conditions during the preparation process.

[0043] According to one embodiment of the present invention, the polyethylene glycol is selected from polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, polyethylene glycol 2000 and polyethylene glycol 4000.

[0044] According to one embodiment of the present invention, the gelling agent is selected from urea and / or hexamethylenetetramine, and the weight ratio of the gelling agent to the dry alumina in the aluminum sol is (50-96):100; preferably, the weight ratio of the gelling agent to the dry alumina in the aluminum sol is (55-75):100.

[0045] It should be noted that, in the process of preparing alumina microspheres by the oil column method, adding the above-mentioned gelling agent according to the above dosage is beneficial to the better agglomeration or gelation of alumina in the alumina sol into alumina microspheres, which helps the alumina microspheres to form a bimodal pore size distribution and exhibit a large specific surface area and large pore volume.

[0046] According to another embodiment of the present invention, the solid content of the aluminum sol, calculated as alumina, is 10-30% by mass; preferably, the solid content of the aluminum sol, calculated as alumina, is 15-25% by mass.

[0047] It should be noted that in the process of preparing alumina microspheres, while controlling the selection and dosage of the aforementioned directing agents and gelling agents, the solid content in the alumina sol and the preparation process of the alumina sol also have a certain influence or effect on parameters such as pore size distribution, pore volume and specific surface area of ​​the prepared alumina microspheres.

[0048] According to one embodiment of the present invention, the aluminum sol is prepared by reflux reaction of metallic aluminum with hydrochloric acid solution or aluminum chloride solution; when the aluminum sol is prepared by reflux reaction of metallic aluminum with hydrochloric acid solution, the mass ratio of metallic aluminum to hydrochloric acid solution is 1:(2-5), the concentration of hydrochloric acid solution is 10-30% by mass%, the temperature of reflux reaction is 60-200°C, and the time is 4-100 hours.

[0049] It should be noted that the aluminum can be aluminum ingots, aluminum sheets, aluminum wires, or aluminum powder. In a preferred embodiment, the reflux reaction temperature is 90-180°C, and the time is 12-72 hours. The aluminum to chlorine mass ratio in the aluminum sol obtained by the reflux reaction can be (1.0-1.4):1.

[0050] According to one embodiment of the present invention, the oil phase material of the hot oil column is selected from at least one of medical lubricating oil, liquid paraffin oil, and white oil, and the temperature of the oil phase material is 80-120°C and the thickness is 100-600 cm; preferably, the oil phase material of the hot oil column is liquid paraffin oil, and the liquid paraffin oil is a C44-type oil with a distillation range of 250-500°C. 16 ~C 20 The oil phase material is a n-alkanes; preferably, the oil phase material has a temperature of 90-105℃ and a thickness of 200-500 cm.

[0051] It should be noted that, in the process of forming alumina microspheres from hot oil column, by selecting the oil phase material of the hot oil column and controlling the above conditions, the mixture of aluminum sol, guiding agent and gelling agent can be better formed into alumina microspheres with bimodal pore size distribution, and a large specific surface area and pore volume can be obtained.

[0052] According to one embodiment of the present invention, the preparation method further includes collecting the shaped alumina microspheres, aging, washing, drying and calcining.

[0053] According to one embodiment of the present invention, the aging conditions include: being carried out under sealed conditions at a temperature of 100-200°C for 4-96 hours; the drying temperature being 60-150°C for 0.5-24 hours; and the calcination temperature being 500-1000°C for 0.5-24 hours. Preferably, the aging temperature is 110-180°C for 6-72 hours; the drying temperature is 90-140°C for 4-12 hours; and the calcination temperature is 550-750°C for 2-8 hours.

[0054] It should be noted that in the preparation method of the present invention, by controlling the steps after molding as described above, the final bimodal pore distribution alumina can obtain better mechanical strength.

[0055] According to one embodiment of the present invention, the Group IVA metal precursor is selected from chloride, nitrate, or carbonate salts of germanium or tin; the amount of the Group IVA metal precursor, based on the mass of the Group IVA metal and the dry-basis alumina in the alumina sol, is 0.1-1.0%. Preferably, the Group IVA metal precursor is tin chloride.

[0056] On the other hand, the present invention also provides a catalytic reforming catalyst, comprising alumina microspheres and an active component supported on the alumina microspheres, wherein the alumina microspheres are the bimodal pore distribution alumina microspheres described above, or are prepared by the above preparation method, and the active component comprises 0.1-1.0% by mass of platinum and 0.5-2.0% by mass of halogen, based on the mass of the alumina microspheres.

[0057] The present invention is further described in detail below through examples. In the following examples and comparative examples, the crushing strength of the alumina microspheres was determined using a ZQJ intelligent particle strength testing machine manufactured by Dalian Equipment Diagnostic Instrument Factory, with an application speed of 5 N / s and a range of 250 N. The specific surface area and pore volume of the alumina microspheres were determined using a low-temperature nitrogen adsorption method on a Micromeritics ASAP2400 instrument. The specific surface area was calculated using the BET method, and the pore volume was calculated when the relative pressure P / P0 was 0.99, where P is the measurement pressure and P0 is the saturated vapor pressure of N2 at the adsorption temperature. The pore size distribution of the sample was calculated using a desorption curve. The diameter of the alumina microspheres was measured using a vernier caliper. A certain mass of alumina microspheres was weighed using an electronic balance, and their compacted volume was measured using a graduated cylinder. The quotient of the two measurements yielded the bulk density of the alumina microspheres. The amount of coke deposited on the catalyst was measured using an EMIA-820V infrared sulfur and carbon analyzer from HORIBA Corporation of Japan.

[0058] The liquid yield was defined as the ratio of the mass of liquid product collected per unit reaction time to the mass of the feed. The aromatic content of the liquid product was detected by an Agilent gas chromatograph with a G7890 flame ionization detector. The relative content of each component was calculated using the area normalization method. The aromatic yield was the product of the liquid yield and the aromatic content. The contents of silicon, iron, and sodium in the alumina spheres were determined by ICP.

[0059] Example 1

[0060] (1) Preparation of aluminum sol

[0061] Take 115g of aluminum sheet and mix it with 420g of 20% hydrochloric acid solution. Reflux the mixture at 120℃ for 24h. After cooling and filtration, aluminum sol is obtained with a solid content of 21.7% by mass based on alumina and an aluminum / chlorine mass ratio of 1.15.

[0062] (2) Hot oil column forming

[0063] The oil phase of the hot oil column is liquid paraffin oil, the oil phase temperature is 100℃, and the oil phase thickness is 200cm. Take 500g of the aluminum sol obtained in step (1), add 0.59g of SnCl2·2H2O and 5.8g of polyethylene glycol PEG200, stir and dissolve for 0.5h, then add 220g of 30% by mass hexamethylenetetramine solution and stir for 0.5h, then drop it into the hot oil column to form. Take out the hot oil column formed into small balls at the bottom of the device, then seal them in a high pressure autoclave for static aging treatment at 140℃ for 6h, wash with water, dry at 120℃ for 6h, and calcine at 650℃ for 4h to obtain finished alumina small balls. The particle diameter (ball diameter), crushing strength, specific surface area, pore volume, most probable pore size and Si, Fe and Na content are shown in Table 1. The pore size distribution curve is shown in Table 1. Figure 1 .

[0064] Example 2

[0065] Take 500g of the aluminum sol obtained in step 1 of Example 1, add 0.59g of SnCl2·2H2O and 4.6g of polyethylene glycol PEG400, stir and dissolve for 0.5h, then add 230g of 30% by mass hexamethylenetetramine solution and stir for 0.5h. Perform hot oil column molding according to the method in step 1 of Example 1, then perform aging treatment at 140℃ for 6h, water washing, drying at 120℃ for 2h, and calcination at 650℃ for 4h to obtain alumina microspheres. The particle diameter, crushing strength, specific surface area, pore volume, most probable pore size and Si, Fe and Na contents are shown in Table 1. The pore size distribution curve is shown in Table 1. Figure 1 .

[0066] Example 3

[0067] Take 500g of the aluminum sol obtained in step 1 of Example 1, add 0.59g of SnCl2·2H2O and 3.2g of polyethylene glycol PEG600, stir and dissolve for 0.5h, then add 240g of 30% by mass hexamethylenetetramine solution and stir for 0.5h. Perform hot oil column molding according to the method in step 1 of Example 1 (2), and then perform aging treatment at 140℃ for 6h, water washing, drying at 120℃ for 2h, and calcination at 650℃ for 4h to obtain alumina microspheres. The particle diameter, crushing strength, specific surface area, pore volume, most probable pore size and Si, Fe and Na contents are shown in Table 1. The pore size distribution curve is shown in Table 1. Figure 1 .

[0068] Example 4

[0069] Take 500g of the aluminum sol obtained in step 1 of Example 1, add 0.59g of SnCl2·2H2O and 2.8g of polyethylene glycol PEG1000, stir and dissolve for 0.5h, then add 220g of 30% by mass hexamethylenetetramine solution and stir for 0.5h. Perform hot oil column molding according to the method in step 1 of Example 1, then perform aging treatment at 140℃ for 6h, water washing, drying at 120℃ for 2h, and calcination at 650℃ for 4h to obtain alumina microspheres. The particle diameter, crushing strength, specific surface area, pore volume, most probable pore size and Si, Fe and Na contents are shown in Table 1. The pore size distribution curve is shown in Table 1. Figure 1 .

[0070] Example 5

[0071] Take 500g of the aluminum sol obtained in step 1 of Example 1, add 0.59g of SnCl2·2H2O and 2.0g of polyethylene glycol PEG2000, stir and dissolve for 0.5h, then add 225g of 30% by mass hexamethylenetetramine solution and stir for 0.5h. Perform hot oil column molding according to the method in step 1 of Example 1, then perform aging treatment at 140℃ for 6h, water washing, drying at 120℃ for 2h, and calcination at 650℃ for 4h to obtain alumina microspheres. The particle diameter, crushing strength, specific surface area, pore volume, most probable pore size and Si, Fe and Na contents are shown in Table 1. The pore size distribution curve is shown in Table 1. Figure 1 .

[0072] Table 1 shows that the alumina microspheres obtained in Examples 1-5 have a particle size of 1.65 mm, a bulk density of 0.55-0.56 g / mL, a crushing strength of over 50 N / particle, and Si and Fe element contents below 100 ppm, and Na content below 20 ppm. Figure 1 It can be seen that by changing the molecular weight of polyethylene glycol and using a similar oil column molding process, the resulting alumina microspheres exhibit a distinct bimodal distribution at pore diameters of 2-15 nm and 15-100 nm.

[0073] Example 6

[0074] (1) Preparation of aluminum sol

[0075] Take 115g of aluminum sheet and mix it with 450g of 20% hydrochloric acid solution. Reflux at 120℃ for 24h. After cooling and filtration, aluminum sol is obtained with a solid content of 20.8% by mass based on alumina and an aluminum / chlorine mass ratio of 1.05.

[0076] (2) Hot oil column forming

[0077] Take 500g of the aluminum sol obtained in step 6(1) of Example 6, add 0.59g of SnCl2·2H2O and 2.0g of polyethylene glycol PEG2000, stir and dissolve for 0.5h, then add 220g of 30% by mass hexamethylenetetramine solution and stir for 0.5h. Perform hot oil column molding according to the method in step 1(2) of Example 6, then perform aging treatment at 160℃ for 6h, water washing, drying at 120℃ for 2h, and calcination at 650℃ for 4h to obtain alumina microspheres. The particle diameter, crushing strength, specific surface area, pore volume, most probable pore size and Si, Fe and Na contents are shown in Table 1. The pore size distribution curve is shown in Table 1. Figure 2 .

[0078] Example 7

[0079] Take 500g of the aluminum sol obtained in step 6(1) of Example 6, add 0.59g of SnCl2·2H2O and 2.0g of polyethylene glycol PEG2000, stir and dissolve for 0.5h, then add 220g of 30% by mass hexamethylenetetramine solution and stir for 0.5h. Perform hot oil column molding according to the method in step 1(2) of Example 6, then perform aging treatment at 170℃ for 6h, water washing, drying at 120℃ for 2h, and calcination at 650℃ for 4h to obtain alumina microspheres. The particle diameter, crushing strength, specific surface area, pore volume, most probable pore size and Si, Fe and Na contents are shown in Table 1. The pore size distribution curve is shown in Table 1. Figure 2 .

[0080] Example 8

[0081] Take 500g of the aluminum sol obtained in step 1 of Example 1, add 0.59g of SnCl2·2H2O and 2.0g of polyethylene glycol PEG2000, stir and dissolve for 0.5h, then add 220g of 30% by mass hexamethylenetetramine solution and stir for 0.5h. Perform hot oil column molding according to the method in step 1 of Example 1, then perform aging treatment at 180℃ for 6h, water washing, drying at 120℃ for 2h, and calcination at 650℃ for 4h to obtain alumina microspheres. The particle diameter, crushing strength, specific surface area, pore volume, most probable pore size and Si, Fe and Na contents are shown in Table 1. The pore size distribution curve is shown in Table 1. Figure 2 .

[0082] Depend on Figure 2 As can be seen, in Examples 6-8, using the same polyethylene glycol but different oil bath aging temperatures, the resulting alumina microspheres exhibited a distinct bimodal distribution at pore diameters of 2-15 nm and 15-100 nm. As the aging temperature increased, the most probable pore size of the resulting alumina microspheres at pore diameters of 2-15 nm increased, while the most probable pore size at pore diameters of 15-100 nm remained unchanged (Table 1).

[0083] Comparative Example 1

[0084] Alumina sol was prepared according to the method of Example 1, except that no directing agent was added to the aluminum sol. 500g of the aluminum sol obtained in step (1) was taken, and 0.59g of SnCl2·2H2O and 220g of 30% by mass hexamethylenetetramine solution were added and mixed and stirred for 0.5h. Then, it was dropped into a hot oil column to form small balls. The small balls formed by the hot oil column were taken out from the bottom of the device and then sealed in a high pressure vessel for static aging treatment at 140℃ for 6h. After washing with water, drying at 120℃ for 6h, and calcining at 650℃ for 4h, the finished alumina small balls were obtained. The particle diameter, crushing strength, specific surface area, pore volume, most probable pore size and Si, Fe and Na contents are shown in Table 1.

[0085] Test Implementation Examples

[0086] (1) Preparation of reforming catalyst

[0087] Take 9 portions of 22.3 mL of chloroplatinic acid aqueous solution with a platinum concentration of 6.5 mg / mL, add 20 mL of hydrochloric acid solution with a concentration of 100 mg / mL and 80 mL of deionized water respectively, then add 50 g of the finished alumina microspheres prepared in Examples 1-8 and Comparative Example 1 respectively, stir and impregnate for 1 h, and let stand for 12 h. Filter out the filtrate, dry the impregnated alumina microspheres at 120 °C for 12 h, then treat with air at 520 °C for 6 h under a gas / agent volume ratio of 500, followed by hydrogen reduction for 6 h to obtain a reduced catalytic reforming catalyst, wherein the platinum content based on alumina is 0.29% by mass.

[0088] (2) Catalytic reforming reaction

[0089] Using hydrotreated straight-run naphtha as feedstock, the specific properties of which are shown in Table 2, the prepared catalyst was evaluated for catalytic reforming under the following conditions: temperature 500℃, reaction pressure 0.7 MPa, hydrogen / hydrocarbon volume ratio 1000, and liquid hourly space velocity (LISH) 1.8 h⁻¹. -1 The total reaction time was 140 hours, and the reaction results are shown in Table 3.

[0090] Table 1

[0091]

[0092] Table 2

[0093]

[0094] Table 3

[0095]

[0096]

[0097] In the description of this application, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this application. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0098] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0099] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A type of alumina microsphere with a bimodal pore distribution, characterized in that, The bimodal pore distribution alumina microspheres have two most probable pore sizes, both of which are between 2 and 100 nm in diameter; the first most probable pore size has a diameter between 2 and 15 nm, and the second most probable pore size has a diameter between 15 and 100 nm; the bimodal pore distribution alumina microspheres contain Group IVA metals; the Si content in the bimodal pore distribution alumina microspheres is less than 50 ppm, the Fe content is less than 70 ppm, and the Na content is less than 20 ppm, based on the mass of the bimodal pore distribution alumina microspheres; The bimodal pore distribution alumina microspheres were prepared by the following method: Aluminum sol is mixed with a Group IVA metal precursor and a directing agent, then mixed with a gelling agent and dripped into a hot oil column to form alumina microspheres. The microspheres are collected, aged, washed, dried and calcined to obtain alumina microspheres with a bimodal pore distribution. The directing agent is polyethylene glycol, which is selected from polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, polyethylene glycol 2000 and polyethylene glycol 4000.

2. The alumina microspheres with bimodal pore distribution according to claim 1, characterized in that, The specific surface area of ​​the bimodal pore-distributed alumina microspheres is 170-250 m². 2 / g, with a pore volume of 0.70-1.0mL / g.

3. The alumina microspheres with bimodal pore distribution according to claim 2, characterized in that, The specific surface area of ​​the bimodal pore-distributed alumina microspheres is 180-220 m². 2 / g, with a pore volume of 0.75-0.90mL / g.

4. The bimodal pore distribution alumina microspheres according to any one of claims 1-3, characterized in that, The IVA metal is germanium or tin; the content of the IVA metal is 0.1-1.0%, based on the mass of the bimodal pore distribution alumina microspheres.

5. A method for preparing bimodal pore distribution alumina microspheres according to any one of claims 1-4, characterized in that, include: Aluminum sol was mixed with a Group IVA metal precursor and a directing agent, then mixed with a gelling agent and dripped into a hot oil column to form alumina microspheres. The microspheres were collected, aged, washed, dried and calcined to obtain alumina microspheres with a bimodal pore distribution. The directing agent was polyethylene glycol.

6. The preparation method according to claim 5, characterized in that, The weight ratio of the directing agent to the dry alumina in the aluminate sol is (1.0-15):

100.

7. The preparation method according to claim 6, characterized in that, The weight ratio of the directing agent to the dry alumina in the alumina sol is (1.0-10):

100.

8. The preparation method according to any one of claims 5-7, characterized in that, The polyethylene glycol is selected from one of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, polyethylene glycol 2000 and polyethylene glycol 4000.

9. The preparation method according to claim 8, characterized in that, The gelling agent is selected from urea and / or hexamethylenetetramine, and the weight ratio of the gelling agent to the dry alumina in the aluminum sol is (50-96):

100.

10. The preparation method according to claim 9, characterized in that, The weight ratio of the gelling agent to the dry alumina in the aluminum sol is (55-75):

100.

11. The preparation method according to claim 9 or 10, characterized in that, The solid content of the alumina sol is 10-30% by mass, calculated as alumina.

12. The preparation method according to claim 11, characterized in that, The solid content of the alumina sol is 15-25% by mass, calculated as alumina.

13. The preparation method according to claim 12, characterized in that, The aluminum sol is prepared by reflux reaction of metallic aluminum with hydrochloric acid solution or aluminum chloride solution. When the aluminum sol is prepared by reflux reaction of metallic aluminum and hydrochloric acid solution, the mass ratio of metallic aluminum to hydrochloric acid solution is 1:(2-5), the concentration of hydrochloric acid solution is 10-30% by mass, the temperature of reflux reaction is 60-200℃, and the time is 4-100 hours.

14. The preparation method according to claim 13, characterized in that, The oil phase material of the hot oil column is selected from at least one of medical lubricating oil, liquid paraffin oil and white oil, and the temperature of the oil phase material is 80-120℃ and the thickness is 100-600 cm.

15. The preparation method according to claim 14, characterized in that, The oil phase material in the hot oil column is liquid paraffin oil, which is a C400 oil with a distillation range of 250~500℃. 16 ~C 20 n-alkanes.

16. The preparation method according to claim 14, characterized in that, The oil phase material has a temperature of 90-105℃ and a thickness of 200-500 cm.

17. The preparation method according to claim 16, characterized in that, The aging conditions include: being carried out under sealed conditions at a temperature of 100-200℃ for 4-96 hours; the drying temperature being 60-150℃ for 0.5-24 hours; and the calcination temperature being 500-1000℃ for 0.5-24 hours.

18. The preparation method according to claim 17, characterized in that, The aging temperature is 110-180℃ and the time is 6-72 hours; the drying temperature is 90-140℃ and the time is 4-12 hours; the calcination temperature is 550-750℃ and the time is 2-8 hours.

19. The preparation method according to claim 17 or 18, characterized in that, The Group IVA metal precursor is selected from chloride, nitrate or carbonate salts of germanium or tin; the amount of the Group IVA metal precursor is 0.1-1.0% based on the mass of dry alumina in the aluminum sol.

20. A catalytic reforming catalyst, characterized in that, The alumina microspheres include alumina microspheres and an active component loaded on the alumina microspheres. The alumina microspheres are bimodal pore distribution alumina microspheres as described in any one of claims 1-4, or are prepared by the preparation method described in any one of claims 5-19. The active component includes 0.1-1.0% by mass of platinum and 0.5-2.0% by mass of halogen, based on the mass of the alumina microspheres.

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