Process for the preparation of an alumina support and alumina support

Abstract

The application discloses a preparation method of an alumina carrier and the prepared alumina carrier, and the preparation method comprises the following steps: (1) mixing raw materials to obtain a plastic body, wherein the raw materials comprise hydrated alumina P1 containing pseudo-boehmite, an extrusion aid, a peptizing agent and water; (2) shaping, drying and calcining the plastic body; and the calcining comprises oxygen-free calcining and oxygen-containing calcining. Compared with the prior art, the alumina carrier prepared by the method has a bimodal pore structure, a higher pore concentration, a reduced proportion of small pore volume in total pore volume, and a significantly reduced proportion of pore volume of pores below 4 nm and 10 nm in total pore volume, and is very suitable for being used as a carrier of a residual oil hydrogenation catalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalytic materials, and particularly relates to a preparation method of an alumina carrier and an alumina carrier prepared by the method. BACKGROUND

[0002] Efficient clean conversion of residual oil is the core of crude oil utilization. Among the many routes of residual oil utilization, fixed bed residual oil hydrogenation process can remove metal, sulfur, nitrogen and other impurities in residual oil, realize heavy oil lightening, and is the most widely used residual oil processing process at present. At present, one of the main problems of fixed bed residual oil hydrogenation is the deposition of Fe, Ca, Ni, V and other metals in the catalyst, which blocks the pores of the catalyst, causes the pressure drop of the reactor bed to rise and the catalyst to deactivate rapidly, limits the processing of poor quality feedstock, and affects the operation cycle of the device. One of the effective ways to solve this problem is to improve the pore structure of the hydrogenation catalyst carrier, so that the catalyst has a bimodal pore structure, in which the large pores are used to provide diffusion channels for macromolecules, and the medium pores are used for catalytic reaction. At the same time, the proportion of pores with a pore size of less than 10 nm in the carrier should be reduced. The existence of these pores is not conducive to the diffusion of residual oil and other macromolecules, and on the other hand, the micropore effect will cause a large amount of impregnated metal to be adsorbed in the small pores, reducing the utilization rate of active metal.

[0003] CN106914279A discloses an alumina carrier and a preparation method thereof. Hydrated alumina is mixed with a non-acidic binder and a composite pore expander, and then molded, dried and pre-baked. The pre-baked material is then treated with an acidic solution with gradually increasing concentration to obtain a bimodal pore alumina carrier with a specific surface area of 80-300m 2 / g, and the pore volume corresponding to the pores with a pore diameter of more than 500nm accounts for 5%-30% of the total pore volume, and the pore volume corresponding to the pores with a pore diameter of more than 1000nm accounts for 5%-15% of the total pore volume.

[0004] CN106582515A discloses a carbon-coated alumina carrier with a bimodal pore structure and a preparation method thereof. Hydrated alumina is first mixed with aluminum ammonium carbonate, and then kneaded with a carbon precursor to form a plastic body. After molding, the carbon-coated alumina carrier with a bimodal pore structure is obtained by calcining in an oxygen-free atmosphere. The pores with a pore diameter of 5-20nm account for 45.6%-67.8% of the total pore volume, and the pores with a pore diameter of 20-60nm account for 2.2%-37.4% of the total pore volume.

[0005] A series of alumina carriers with specific pore distribution have been prepared in the prior art, but there is little research on alumina carriers and preparation methods for reducing the proportion of small pore volume, such as pores below 4nm or pores below 10nm relative to the total pore volume. It should be noted that the information disclosed in the foregoing background section is only used to strengthen the understanding of the background of the present application, so it can include information that does not constitute prior art known to those skilled in the art. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a method for preparing an alumina carrier, and provides an alumina carrier prepared by the method of the present application. Specifically, the present application includes the following contents:

[0007] The present application provides a method for preparing an alumina carrier, comprising the following steps: (1) mixing raw materials to obtain a plastic body, the raw materials comprising pseudoboehmite-containing hydrated alumina P1, a extrusion aid, a peptizing agent and water; (2) shaping, drying and calcining the above-mentioned plastic body; characterized in that the calcining comprises oxygen-free calcining and oxygen-containing calcining, the conditions of the oxygen-free calcining comprising: the calcining atmosphere is a gas atmosphere containing no oxidizing gas, the temperature is 450-1200℃, and the time is 1-10h; the conditions of the oxygen-containing calcining comprising: the calcining atmosphere is a gas atmosphere containing oxidizing gas, the temperature is 350-900℃, and the time is 1-10h.

[0008] The present application also provides an alumina carrier prepared by the above-mentioned method.

[0009] Compared with the prior art, the proportion of the pore volume of the small pores of the alumina carrier obtained by the present application to the total pore volume is significantly reduced, especially the proportion of the pore volume of the pores with a diameter of 4nm and 10nm and below to the total pore volume is significantly reduced. DETAILED DESCRIPTION

[0010] First of all, it should be pointed out that the endpoints of the ranges and any values disclosed in the present specification are not limited to the exact range or value, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0011] The method for preparing alumina provided by the application mainly comprises two steps: (1) mixing raw materials to prepare a plastic body; and (2) shaping, drying and calcining the plastic body, wherein the calcining comprises oxygen-free calcining and oxygen-containing calcining. The oxygen-free calcining conditions comprise: a calcining atmosphere free of oxidizing gas, a temperature of 450-1000°C, preferably 500-900°C, 600-800°C, a time of 1-10h, preferably 2-8h; and the oxygen-containing calcining conditions comprise: a calcining atmosphere containing oxidizing gas, a temperature of 350-900°C, preferably 450-850°C, 500-750°C, etc., a time of 1-10h, preferably 2-8h.

[0012] The raw materials for preparing the plastic body comprise hydrated alumina P1 containing pseudo-boehmite, a extrusion aid, a peptizing agent and water. Under the premise that the final carrier meets the requirements of the application, the pseudo-boehmite P1 in the raw materials has no special requirements and can be any pseudo-boehmite prepared by prior art, or a mixture of pseudo-boehmite and any hydrated alumina selected from one or more of monohydrate alumina, trihydrate alumina and amorphous hydrated alumina. In the application, the pore volume, specific surface area and most probable pore diameter of the hydrated alumina containing pseudo-boehmite are obtained by a nitrogen physical adsorption-desorption instrument after calcining the hydrated alumina containing pseudo-boehmite P1 at 600°C for 4h. Preferably, the pore volume of P1 is 0.9-1.4ml / g, the specific surface area is 100-450m 2 / gram, and the most probable pore diameter is 8-30nm; preferably, the pore volume of the hydrated alumina containing pseudo-boehmite P1 is 0.95-1.35ml / g, the specific surface area is 200-350m 2 / gram, and the most probable pore diameter is 10-25nm. Characterized by X-ray diffraction, the content of pseudo-boehmite in the hydrated alumina containing pseudo-boehmite P1 is not less than 50%, preferably 50%-95%, and further preferably not less than 60%-90%; the content of bayerite is not higher than 20%, preferably 2%-20%; and the balance is amorphous alumina.

[0013] According to the method provided by the present application, the mixing and the forming described in the present application can be carried out by conventional methods, for example, one method or a combination of several methods among spray drying, rolling, tabletting and extrusion forming, and various easily operated formed products such as microspheres, spheres, honeycombs, bird nests, tablets or strips (three-leaf clover, butterfly, cylinder, etc.) can be prepared according to different requirements. In the forming, for example, in the extrusion forming, in order to ensure the smooth progress of the forming, water, extrusion aids and / or adhesives, with or without pore-expanding agents, can be added to the mixture, and then extrusion forming is carried out, followed by drying and calcination. In the present application, the types and amounts of the extrusion aids and the solvents are known to those skilled in the art, for example, the common extrusion aids can be selected from one or more of sesbania gum, methyl cellulose, starch, polyvinyl alcohol and polyethylene glycol, and the solvents can be inorganic acids and / or organic acids, the inorganic acids can be nitric acid, boric acid, phosphoric acid, etc., the organic acids can be ordinary carboxylic acids, amino carboxylic acids, hydroxyl carboxylic acids, etc., and the pore-expanding agents can be one or more of starch, synthetic cellulose, polyhydric alcohol and surfactant.

[0014] The drying of the plastic body is carried out by conventional means and conditions in the art, and generally, the drying conditions can be at a temperature of 100-250℃ for 2-10 hours.

[0015] The present inventors have found that, in the calcination process, under the protection of an inert atmosphere, the carbon-containing precursor is deoxidized, and the organic carbon skeleton after carbonization forms a C-O bond with the oxygen on the pseudoboehmite surface, so that specific sintering occurs between the pseudoboehmite particles in the subsequent air calcination process, ensuring that the pore volume is increased, the pore size is increased, the pore concentration is improved, and the proportion of small-pore pores that are not conducive to the diffusion and reaction of macromolecules is significantly reduced, especially the proportion of pores with a pore size of less than 4 nm or less than 10 nm. Through the combined treatment of oxygen-free calcination and aerobic calcination, the proportion of pores with a pore diameter of less than 4 nm and 10 nm in the total pore volume is significantly reduced.

[0016] In the present application, the oxygen-free calcination in step (2) refers to the absence of oxidizing gas in the calcination atmosphere, and preferably an inert atmosphere, such as one or more of nitrogen, helium and argon; the aerobic calcination refers to the presence of oxidizing gas in the calcination atmosphere, and the most common is oxygen, and preferably a mixture of oxygen and other gases, such as air, or air diluted with nitrogen, or a mixture of oxygen and air, etc. Generally, the volume content of the oxidizing gas can be 5% to 50% by volume, and preferably air.

[0017] In order to achieve better effect of reducing the proportion of small pores, the heating rate of the aerobic roasting and the anaerobic roasting is preferably 50-600℃ / h. Meanwhile, the aerobic roasting and the anaerobic roasting can be performed for several times according to the need, preferably alternately, and the last one is the aerobic roasting.

[0018] The inventors of the present application further found that adding the pseudo-boehmite-containing hydrated alumina P2 to the material before molding can adjust the water-powder ratio of the molding material to a greater extent, reduce the extrusion pressure in the molding process, and thus reduce the loss of the pore volume of the carrier and the change of the pore structure in the molding process, especially beneficial to the formation of large pores in the molding process of the carrier, and further reduce the content of small pores. Therefore, the present application preferably further comprises the step of adding and mixing the pseudo-boehmite-containing hydrated alumina P2 before the molding of the plastic body in the step (2), and the weight ratio of the P1 and P2 is 70-97:3-30 on a dry basis; preferably the weight ratio of the P1 and P2 is 80-95:5-20. The pseudo-boehmite-containing powder P2 can be any pseudo-boehmite powder or a mixture of several pseudo-boehmite powders, and can be P1 or a modified P1. When P2 is a modified P1, the method for modifying P1 to P2 includes the following methods: (1) roasting the pseudo-boehmite-containing hydrated alumina P1 to obtain the powder P2; (2) molding and drying the pseudo-boehmite-containing hydrated alumina P1, and then grinding and sieving all or part of it to obtain the powder P2, wherein the drying conditions include a temperature of 100-350℃ and a time of 1-10 hours; (3) drying the molding material obtained in (2) and then roasting it at a temperature of 500-1000℃ for 1-10 hours, and then grinding and sieving all or part of it to obtain the powder P2; (4) mixing one or more of the modified materials obtained in (1), (2) and (3) to obtain P2. Further preferably, the P2 is a modified P1 with a particle size of 100-400 mesh.

[0019] According to the preparation method provided by the present application, any substance that can improve the performance of the carrier provided by the present application and the catalyst prepared from the obtained carrier can be introduced during the preparation process, such as various additives, and one or more of the more representative F, P, B additives, which can be introduced as one of the raw materials of the plastic body in step (1) or added together with P2 before molding. The additive is one or more of a boron-containing compound, a phosphorus-containing compound and a fluorine-containing compound, and the amount of the additive is 0.5-10% by weight of P1 on a dry basis, preferably 0.5-5% by weight. The boron-containing compound is preferably one or more of boric acid, boron oxide and borate, and the phosphorus-containing compound is preferably phosphoric acid, phosphorous acid, phosphate, etc.

[0020] In another aspect, the present application also provides an alumina support prepared by any of the above methods. Preferably, the alumina support provided by the present application has a pore volume of 0.9-1.6 ml / g and a specific surface area of 100-400 m 2 / gram, as characterized by mercury porosimetry. The support is a bimodal pore alumina support, which exhibits a bimodal pore distribution with pores having a diameter of 5-20 nm and pores having a diameter of 100-500 nm. The pore volume of the pores having a diameter of 5-20 nm accounts for 50-80% of the total pore volume, and the pore volume of the pores having a diameter of 100-500 nm accounts for 19-40% of the total pore volume. Preferably, the pore volume of the pores having a diameter of 10 nm or less accounts for no more than 20% of the total pore volume, and more preferably no more than 17%, as characterized by mercury porosimetry. More preferably, the pore volume of the pores having a diameter of 4 nm or less accounts for no more than 5.5% of the total pore volume, and more preferably no more than 5%.

[0021] As can be seen from the above technical solutions, the present application significantly reduces the proportion of small pores in the alumina support that are not conducive to the diffusion and reaction of macromolecules, especially the proportion of pores having a diameter of 4 nm or less and the proportion of pores having a diameter of 10 nm or less. Meanwhile, the pore diameter is increased and the pore concentration is improved under the condition of an increased pore volume. In addition, the alumina support provided by the present application has a typical bimodal pore distribution, with the pore diameter being concentrated in the range of 5-20 nm and 100-500 nm. The pore structure of the support is conducive to the diffusion of macromolecules such as residual oil and the dispersion of active metals, and is particularly suitable for use as a support for preparing catalysts for heavy oil processing, such as hydrogenation protectors and deasphalting and demetallization hydrogenation treatment catalysts, and has a good application prospect.

[0022] The present application will be described in detail below with reference to the examples, but the scope of the present application is not limited thereto. The reagents used in the examples are all of chemical purity, unless otherwise specified.

[0023] The pseudoboehmite used in the following examples is as follows:

[0024] P1-1: Dry gel powder produced by Yantai Henghui Chemical Co., Ltd. (pore volume: 1.1 ml / g, specific surface area: 260 m 2 / gram, most accessible pore diameter: 12 nm. Dry basis: 71%, of which the content of pseudoboehmite is 67%, the content of gibbsite is 5% by weight, and the balance is amorphous alumina.

[0025] P1-2: Dry gel powder produced by Changling Catalyst Branch (pore volume: 1.2 ml / g, specific surface area: 280 m 2 / gram, most accessible pore diameter: 15.8 nm. Dry basis: 73%, of which the content of pseudoboehmite is 68%, the content of gibbsite is 5% by weight, and the balance is amorphous alumina.

[0026] P2A: Take P1-1 dry glue powder to form, and then dry at 120°C, grind, sieve, select 100-400 mesh powder from it, get the modified P2A of P1-1.

[0027] P2B: Take P1-2 dry glue powder to form, and then dry at 120°C, dry the formed material at 600°C for 3 hours, then grind and sieve the calcined sample, select 100-400 mesh powder from it, get the modified P2B of P1-2.

[0028] Example 1:

[0029] Take 950 grams of P1-1, mix evenly with 20g sesbania powder and 20g hydroxymethyl cellulose, then add 1200ml of water solution containing 10ml of nitric acid, knead into a plastic body, then add 50g of P1-1 powder, mix evenly, then extrude into butterfly-shaped strip with outer diameter φ1.6mm on double screw extruder. Dry the wet strip at 120°C for 4 hours, get the dry strip, calcine the dry strip at 750°C for 4 hours in nitrogen atmosphere, then calcine at 750°C for 4 hours in air atmosphere, get the carrier Z1.

[0030] Example 2: Take 800 grams of P1-2, mix evenly with 20g sesbania powder and 20g hydroxymethyl cellulose, then add 1350ml of water solution containing 20g of citric acid and 20g of boric acid, knead into a plastic body, then add 200g of P1-2 powder, mix evenly, then extrude into butterfly-shaped strip with outer diameter φ1.6mm on double screw extruder. Dry the wet strip at 120°C for 4 hours, get the dry strip, calcine the dry strip at 600°C for 4 hours in nitrogen atmosphere, then calcine at 600°C for 4 hours in air atmosphere, get the carrier Z2.

[0031] Example 3: Take 900 grams of P1-2, mix evenly with 20g sesbania powder and 20g hydroxymethyl cellulose, then add 1350ml of water solution containing 10g of acetic acid and 20g of boric acid, knead into a plastic body, then add 100g of modified P2A of P1, mix evenly, then extrude into butterfly-shaped strip with outer diameter φ1.6mm on double screw extruder. Dry the wet strip at 120°C for 4 hours, get the dry strip, calcine the dry strip at 800°C for 3 hours in nitrogen atmosphere, then calcine at 500°C for 5 hours in air atmosphere, get the carrier Z3.

[0032] Example 4: 750 g of P1-2 was weighed, mixed uniformly with 20 g of sesbania powder and 20 g of hydroxymethyl cellulose, then 1350 ml of an aqueous solution containing 20 g of oxalic acid and 20 g of boric acid was added, and kneaded into a plastic body, then 250 g of P1 modified product P2B powder was added, mixed uniformly, and then extruded into a butterfly-shaped strip with an outer diameter of φ 1.6 mm on a double screw extruder. The wet strip was dried at 120°C for 4 hours to obtain a dry strip, which was calcined at 650°C for 5 hours in a nitrogen atmosphere, and then calcined at 600°C for 3 hours in an air atmosphere to obtain a carrier Z4.

[0033] Example 5: 1000 g of P1-1 was weighed, mixed uniformly with 20 g of sesbania powder and 20 g of hydroxymethyl cellulose, then 1200 ml of an aqueous solution containing 10 ml of nitric acid was added, and kneaded into a plastic body, and then extruded into a butterfly-shaped strip with an outer diameter of φ 1.6 mm on a double screw extruder. The wet strip was dried at 120°C for 4 hours to obtain a dry strip, which was calcined at 750°C for 4 hours in a nitrogen atmosphere, and then calcined at 750°C for 4 hours in an air atmosphere to obtain a carrier Z5.

[0034] Comparative Example 1: 1000 g of P1-1 was weighed, mixed uniformly with 20 g of sesbania powder and 20 g of hydroxymethyl cellulose, then 1200 ml of an aqueous solution containing 10 ml of nitric acid was added, and kneaded into a plastic body, and then extruded into a butterfly-shaped strip with an outer diameter of φ 1.6 mm on a double screw extruder. The wet strip was dried at 120°C for 4 hours to obtain a dry strip, which was calcined at 750°C for 4 hours in an air atmosphere to obtain a carrier DZ1.

[0035] Comparative Example 2: 1000 g of P1-1 was weighed, mixed uniformly with 20 g of sesbania powder and 20 g of hydroxymethyl cellulose, then 1200 ml of an aqueous solution containing 10 ml of nitric acid was added, and kneaded into a plastic body, and then extruded into a butterfly-shaped strip with an outer diameter of φ 1.6 mm on a double screw extruder. The wet strip was dried at 120°C for 4 hours to obtain a dry strip, which was calcined at 750°C for 8 hours in an air atmosphere to obtain a carrier DZ2.

[0036] Comparative Example 3: 1000 g of P1-1 was weighed, mixed uniformly with 20 g of sesbania powder and 20 g of hydroxymethyl cellulose, then 1200 ml of an aqueous solution containing 10 ml of nitric acid was added, and kneaded into a plastic body, and then extruded into a butterfly-shaped strip with an outer diameter of φ 1.6 mm on a double screw extruder. The wet strip was dried at 120°C for 4 hours to obtain a dry strip, which was calcined at 750°C for 4 hours in a nitrogen atmosphere to obtain a carrier DZ3.

[0037] Comparative Example 4: 1000 g of P1-1 was mixed with 20 g of sesbania powder and 20 g of hydroxymethyl cellulose, and then 1200 ml of a water solution containing 10 ml of nitric acid was added to knead into a plastic body, which was extruded into a butterfly-shaped strip with an outer diameter of φ1.6 mm on a double-screw extruder. The wet strip was dried at 120°C for 4 hours to obtain a dry strip, which was calcined at 750°C for 8 hours in a nitrogen atmosphere to obtain a carrier DZ4.

[0038] As can be seen from the characterization data, the pore volume of the alumina carrier prepared by the method of the present application is 0.9-1.6 ml / g, the specific surface area is 100-400 m 2 / gram, characterized by mercury porosimetry, the carrier exhibits a bimodal pore distribution with a diameter of 5-20 nm and a diameter of 100-500 nm, the pore volume of the pores with a diameter of 5-20 nm accounts for 50-80% of the total pore volume, the pore volume of the pores with a diameter of 100-500 nm accounts for 19-40% of the total pore volume; the proportion of pores below 4 nm accounts for less than 5.5% of the total pore volume, and the pore volume of pores with a diameter of 10 nm or less accounts for no more than 20% of the total pore volume. Compared with the prior art, the pore volume and pore diameter are increased, the pore concentration is improved, the proportion of small pores is reduced, and in particular, the proportion of pores with a diameter of 4 nm or less and pores with a diameter of 10 nm or less is significantly reduced, which is very suitable for use as a catalyst carrier, especially for preparing a hydrogen protective agent and a demetalization and deasphalting catalyst carrier for heavy oil processing.

[0039] Table 1

[0040]

Claims

1. A method for preparing an alumina carrier, comprising the following steps: (1) mixing raw materials to obtain a plastic body, the raw materials including hydrated alumina P1 containing boehmite, an extrusion aid, a binder, and water; (2) molding, drying, and calcining the above-mentioned plastic body; characterized in that, The roasting includes anaerobic roasting and aerobic roasting. The conditions for anaerobic roasting are as follows: the roasting atmosphere is a gaseous atmosphere without oxidizing gases, the temperature is 450-1200℃, and the time is 2-10h. The conditions for aerobic roasting are as follows: the roasting atmosphere is a gaseous atmosphere containing oxidizing gases, the temperature is 300-900℃, and the time is 2-10h. Before the plastic body is formed in step (2), the step of adding and mixing hydrated alumina P2 containing boehmite is also included. On a dry basis, the mass ratio of P1 to P2 is 70-97:3-30. P2 is a modified product of P1, modified by drying or calcination, or P2 is a mixture of the dried and calcined products of P1.

2. The method according to claim 1, wherein, The P1 pore volume is 0.9~1.4 ml / g, and the specific surface area is 100~450 m. 2 / gram, with a maximum pore diameter of 8~30nm.

3. The method according to claim 1, wherein, The P1 contains 50-95% boehmite by weight, 2-20% gibbsite by weight, and the remainder is amorphous alumina.

4. The preparation method according to claim 1, wherein, The raw materials used to prepare the plastic body in step (1) also contain additives, which are one or more of boron-containing compounds, phosphorus-containing compounds and fluorine-containing compounds. The amount of additives added is 0.5-10% of the weight of P1 on a dry basis.

5. The preparation method according to claim 4, wherein, The amount of the additive added is 0.5-5% by weight of P1 on a dry basis.

6. The method according to claim 1, wherein, The drying conditions described in step (2) include: a temperature of 100~250℃ and a time of 2~10 hours.

7. The method according to claim 1, wherein, The gas atmosphere that does not contain oxidizing gases contains one or more of nitrogen and inert gases; the oxidizing gas is a mixture of oxygen and nitrogen, with an oxygen volume content of 5-50%.

8. The method according to claim 1, wherein, The anaerobic roasting conditions include a temperature of 500-900℃ and a time of 2-8h; the aerobic roasting conditions include a temperature of 450-850℃ and a time of 2-8h.

9. The method according to claim 1, wherein, First, perform anaerobic roasting, then perform aerobic roasting.

10. An alumina support prepared by the method according to any one of claims 1-9.

11. The carrier according to claim 10, wherein, The carrier has a pore volume of 0.9-1.6 ml / g and a specific surface area of ​​100-400 m². 2 The carrier, characterized by mercury porosimetry, exhibits a bimodal pore distribution with diameters of 5-20 nm and 100-500 nm. The pore volume of pores with diameters of 5-20 nm accounts for 50-80% of the total pore volume, while the pore volume of pores with diameters of 100-500 nm accounts for 19-40% of the total pore volume.

12. The carrier according to claim 11, wherein, Characterized by mercury porosimetry, the pore volume of pores with a diameter of less than 10 nm does not exceed 20% of the total pore volume.

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