Hydrodesulfurization method in the presence of catalysts on mesoporous-macroporous matrices

Abstract

A method for hydrodesulfurizing a sulfur-containing olefinic gasoline fraction is disclosed, wherein the gasoline fraction, hydrogen, and a catalyst are contacted, the catalyst comprising a Group VIB metal, a Group VIII metal, and a mesoporous-macroporous alumina matrix with a bimodal mesoporous distribution, wherein: - the volume of mesopores having a diameter greater than or equal to 2 nm and less than 18 nm is equivalent to 10-30% by volume of the total pore volume of the matrix; - the volume of mesopores having a diameter greater than or equal to 18 nm and less than 50 nm is equivalent to 30-50% by volume of the total pore volume of the matrix; - the volume of macropores having a diameter greater than or equal to 50 nm and less than 8000 nm is equivalent to 30-50% by volume of the total pore volume of the matrix.

Description

Technical Field

[0001] This invention relates to the field of hydrotreating gasoline fractions, particularly gasoline fractions produced by self-fluidized bed catalytic cracking units. More specifically, this invention relates to the use of catalysts in a method for hydrodesulfurizing sulfur-containing olefinic gasoline fractions (e.g., gasoline produced by autocatalytic cracking), for which it is desirable to reduce the content of sulfur-containing compounds without hydrogenating olefins and aromatic compounds. Existing technology

[0002] Currently, both petroleum refining and petrochemicals are facing new restrictions. This is because all countries are gradually adopting strict sulfur specifications, aiming to achieve, for example, 10 ppm by weight sulfur in gasoline sold in Europe and Japan. The issue of reducing sulfur content is essentially focused on gasoline obtained through cracking, whether the cracking is catalytic cracking (FCC, fluid catalytic cracking) or non-catalytic cracking (coking, viscous cracking, steam cracking), which is a major precursor of sulfur in the gasoline pool.

[0003] One solution well known to those skilled in the art for reducing sulfur content involves hydrotreating (or hydrodesulfurizing) hydrocarbon fractions (particularly catalytic cracking gasoline) in the presence of hydrogen and a heterogeneous catalyst. However, this approach exhibits a major drawback: a very significant reduction in octane number, if the catalyst used lacks sufficient selectivity. This reduction in octane number is particularly related to the hydrotreating of olefins present in this type of gasoline (which occurs simultaneously with hydrodesulfurization). Therefore, unlike other hydrotreating methods, hydrodesulfurization of gasoline must address the contradictory dual constraints of providing deep hydrodesulfurization of gasoline and limiting the hydrogenation of unsaturated compounds present.

[0004] One approach to addressing these dual problems is to employ a hydrodesulfurization catalyst that is both active in hydrodesulfurization and highly selective for hydrodesulfurization relative to olefin hydrogenation.

[0005] Therefore, in the prior art, document US 2009 / 321320 is known, which discloses a hydrodesulfurization catalyst comprising an active metal phase containing cobalt / molybdenum and a support based on high-temperature alumina (i.e., alumina calcined at a temperature greater than 800°C), said support containing less than 50% by weight of γ-alumina, η-alumina, and χ-alumina, and having a 40-200 μm 2 The catalyst has a specific surface area of ​​ / g. It is obtained by dry impregnation with an aqueous solution containing cobalt, molybdenum, and at least one organic compound as an additive.

[0006] Document EP 1892039 describes a selective hydrodesulfurization catalyst comprising at least one support, at least one Group VIII element, at least one Group VIB element, and phosphorus, wherein the support may consist substantially of at least one transition alumina, that is, the support contains at least 51% by weight of transition alumina, and the support may have a molecular weight of less than 135 μm. 2 Specific surface area per g.

[0007] Furthermore, it is known from existing technology that the pore distribution of the catalyst support can have a beneficial effect on catalytic performance, especially in the case of multi-peak pores.

[0008] Document CN109894122 discloses a method for hydrodesulfurization of catalytic cracking (FCC) gasoline in the presence of a catalyst, wherein the catalyst comprises a cobalt- and molybdenum-based active phase, an alkaline dopant, and a mesoporous-macroporous alumina support with a specific surface area of ​​260-290 m². 2 The total pore volume is 0.8-2.2 ml / g, with a pore size of 10-200 nm. Pores with a diameter of 10-50 nm account for 10%-50% of the total pore volume, and pores with a diameter of 50-200 nm account for 50%-90% of the total pore volume. The carriers used include both mesopores and macropores with unimodal distributions.

[0009] Document CN109420504 discloses a method for hydrodesulfurization of catalytic cracking (FCC) gasoline in the presence of a catalyst. The catalyst comprises a cobalt- and molybdenum-based active phase and a mesoporous-macroporous alumina support, wherein pores with diameters of 60-200 nm account for 1%-80% of the total pore volume of the support, and pores with diameters of 5-50 nm account for 20%-70% of the total pore volume. The support used includes both mesoporous and macroporous unimodal distributions.

[0010] Document US 6,589,908 discloses a method for preparing a catalyst support that is not macroporous and has a bimodal pore structure in the mesopores, such that the bimodal pores are separated by 1-20 nm.

[0011] Therefore, refiners still have a strong interest in hydrodesulfurization catalysts, especially for gasoline fractions, which have improved catalytic performance, particularly in terms of catalytic activity and / or selectivity in hydrodesulfurization. Thus, once such catalysts are used, low-sulfur gasoline with no significant drop in octane number can be produced.

[0012] In this context, one object of the present invention is to provide a method for hydrodesulfurizing sulfur-containing olefinic gasoline fractions in the presence of a supported catalyst, wherein the method performs at least as well as, or even better than, methods known in the prior art in terms of activity and selectivity.

[0013] Invention Theme

[0014] This invention relates to a method for hydrodesulfurizing a sulfur-containing olefinic gasoline fraction, wherein the gasoline fraction, hydrogen, and a catalyst are contacted, and the hydrodesulfurization method is carried out at a temperature of 200°C-400°C, a total pressure of 1-3 MPa, and for 1-10 hours. -1 The reaction is carried out at a space velocity of 100-600 Nl / l and a hydrogen / gasoline fraction volume ratio, wherein the space velocity is defined as the volumetric flow rate of the feedstock divided by the volume of the catalyst, and the catalyst comprises at least one Group VIB metal, at least one Group VIII metal, and macroporous and mesoporous alumina supports with a bimodal mesoporous distribution, wherein:

[0015] - The volume of the mesopores with a diameter greater than or equal to 2 nm and less than 18 nm is equivalent to 10%-30% of the total pore volume of the carrier;

[0016] - The volume of the mesopores with a diameter greater than or equal to 18 nm and less than 50 nm is equivalent to 30%-50% of the total pore volume of the carrier;

[0017] - The volume of macropores with a diameter greater than or equal to 50 nm and less than 8000 nm is equivalent to 30%-50% of the total pore volume of the carrier.

[0018] The applicant unexpectedly discovered that using catalysts based on at least one Group VIB metal and at least one Group VIII metal supported on a mesoporous-macroporous support (the support having bimodal mesoporous pores and a combination of high-medium pore volumes and a given macroporous volume) can improve the catalytic performance of the method in terms of both catalytic activity and selectivity. This results in better feedstock conversion under the same operating conditions as in the prior art. Specifically, without being constrained by any scientific theory, the use of such catalysts in gasoline hydrodesulfurization processes improves the internal diffusion of reactants and products through the presence of mesoporous groups of different sizes. Furthermore, the presence of macroporous combinations is particularly desirable when the feedstock contains a large amount of reactive olefins (unsaturated compounds), especially dienes (as is the case with gasoline, which can lead to gum formation and thus block the catalyst pores in the absence of macropores). Therefore, optimizing the pore size range of the catalyst constitutes a decisive factor regarding the performance of gasoline hydrodesulfurization processes.

[0019] According to one or more embodiments, the carrier has a size of 50-210m.2 Specific surface area per g.

[0020] According to one or more embodiments, the carrier has a total pore volume of 0.7-1.3 ml / g.

[0021] According to one or more embodiments, the volume of the mesopore having a diameter greater than or equal to 2 nm and less than 18 nm is equivalent to 15%-25% of the total pore volume of the carrier.

[0022] According to one or more embodiments, the volume of the mesopores having a diameter greater than or equal to 18 nm and less than 50 nm is equivalent to 35%-45% of the total pore volume of the carrier.

[0023] According to one or more embodiments, the volume of macropores with a diameter greater than or equal to 50 nm and less than 8000 nm is equivalent to 35%-50% of the total pore volume of the carrier.

[0024] According to one or more embodiments, the content of Group VIB metals in the catalyst, expressed in oxide form, is 1% to 30% by weight relative to the total weight of the catalyst.

[0025] According to one or more embodiments, the content of Group VIII metals in the catalyst, expressed in oxide form, is 0.5% to 10% by weight relative to the total weight of the catalyst.

[0026] According to one or more embodiments, the Group VIII metal is cobalt.

[0027] According to one or more embodiments, the Group VIB metal is molybdenum.

[0028] According to one or more embodiments, the catalyst further comprises phosphorus, with a phosphorus content of 0.1% to 10% by weight, expressed in P2O5, relative to the total weight of the catalyst.

[0029] According to one or more embodiments, the pore distribution of mesopores with a diameter greater than or equal to 2 nm and less than 18 nm is concentrated in the numerical range of 10.5-14.5 nm.

[0030] According to one or more embodiments, the pore distribution of mesopores with a diameter greater than or equal to 18 nm and less than 50 nm is concentrated in the numerical range of 22-28 nm.

[0031] According to one or more embodiments, the gasoline is catalytic cracking gasoline.

[0032] According to one or more embodiments, the carrier is in the form of beads with a diameter of 2-4 mm.

[0033] According to one or more embodiments, the carrier in bead form is obtained by the following steps:

[0034] s1) Aluminum hydroxide or aluminum oxyhydroxide is dehydrated at a temperature of 400℃-1200℃, preferably 600℃-900℃, for 0.1 seconds to 5 seconds, preferably 0.1 seconds to 4 seconds, to obtain aluminum oxide powder;

[0035] s2) The alumina powder obtained in step s1) is formed into beads;

[0036] s3) Heat-treat the alumina beads obtained in step s2) at a temperature of 200°C or higher;

[0037] s4) The alumina beads obtained at the end of step s3) are subjected to hydrothermal treatment by immersion in water or aqueous solution and then staying in an autoclave at a temperature of 100℃-300℃.

[0038] s5) Calcine the alumina beads obtained at the end of step s4) at a temperature of 500℃-820℃. Invention Details

[0040] 1. Definition

[0041] In the following text, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, published by CRC Press, edited by DRLide, 81st edition, 2000-2001). For example, Group VIII according to the CAS classification corresponds to the metals in columns 8, 9, and 10 according to the new IUPAC classification.

[0042] BET surface area was measured by nitrogen physical adsorption according to standard ASTM D3663-03 (the method described in "Adsorption by Powders & Porous Solids: Principles, Methodology and Applications" by Rouquerol F., Rouquerol J. and Singh K., Academic Press, 1999).

[0043] In this specification, in accordance with IUPAC convention, "micropore" should be understood as a pore with a diameter of less than 2 nm, i.e., 0.002 μm; "mesopore" should be understood as a pore with a diameter of greater than 2 nm, i.e., 0.002 μm and less than 50 nm, i.e., 0.05 μm; and "macropore" should be understood as a pore with a diameter of greater than or equal to 50 nm, i.e., 0.05 μm.

[0044] In the following description of the invention, the “total pore volume” of alumina or catalyst should be understood as the volume measured by mercury intrusion porosimetry under a maximum pressure of 4000 bar (400 MPa), a surface tension of 484 dynes / cm, and a contact angle of 140°, according to standard ASTM D4284-83. Following the recommendation on pages 1050-1055 of the publication “Techniques de l′ingénieur, traité analyze et caractérisation” [Techniques of the Engineer, Analysis and Characterization Treatise] by Jean Charpin and Bernard Rasneur, the wetting angle is taken as 140°.

[0045] For better accuracy, the total pore volume values ​​given below in ml / g are equivalent to the total mercury volume in ml / g measured on the sample (total pore volume measured by mercury porosimetry) minus the mercury volume in ml / g measured on the same sample at a pressure equivalent to 30 psi (approximately 0.2 MPa).

[0046] According to standard ASTM D4284-83, the volume of macropores and mesopores is measured by mercury intrusion porosimetry under a maximum pressure of 4000 bar (400 MPa), using a surface tension of 484 dynes / cm and a contact angle of 140°.

[0047] When the value is equal to or higher than a certain value, mercury fills all interparticle voids. This value is set at 0.2 MPa, and it is considered that above this value, mercury penetrates into the pores of the sample.

[0048] The macropore volume of the catalyst is defined as the cumulative volume of mercury introduced under pressure of 0.2 MPa-30 MPa, which is equivalent to the volume contained in pores with an apparent diameter greater than 50 nm.

[0049] The mesopore volume of the catalyst is defined as the cumulative volume of mercury introduced under a pressure of 30 MPa-400 MPa, equivalent to the volume contained in a pore with an apparent diameter of 2-50 nm.

[0050] When the incremental pore volume measured by mercury porosimetry is plotted as a function of pore diameter, the pore size modes correspond to the inflection points of the function.

[0051] The content of metal elements (Group VIII metals and Group VIB metals) and phosphorus content were measured by X-ray fluorescence method.

[0052] 2. Description

[0053] catalyst

[0054] The catalyst used in the context of the hydrodesulfurization method according to the invention comprises an active phase containing at least one Group VIB metal, at least one Group VIII metal, and optionally phosphorus, preferably composed thereof.

[0055] The Group VIB metals present in the active phase of the catalyst are preferably selected from molybdenum and tungsten, more preferably molybdenum. The Group VIII metals present in the active phase of the catalyst are preferably selected from cobalt, nickel, and mixtures of the two elements, more preferably cobalt.

[0056] The total content of the Group VIII metal relative to the total weight of the catalyst is typically 0.5 wt% to 10 wt% (expressed as oxides of the Group VIII metal), preferably 1 wt% to 10 wt%, more preferably 1 wt% to 7 wt%, very preferably 1 wt% to 6 wt%, and even more preferably 1.5 wt% to 5 wt% relative to the total weight of the catalyst. When the metal is cobalt or nickel, the metal content is expressed as CoO or NiO, respectively.

[0057] The content of the Group VIB metal relative to the total weight of the catalyst is typically 1%-30% by weight (expressed as an oxide of the Group VIB metal), preferably 3%-20% by weight, more preferably 5%-18% by weight, and very preferably 7%-14% by weight relative to the total weight of the catalyst. When the metal is molybdenum or tungsten, the metal content is expressed as MoO3 or WO3, respectively.

[0058] When phosphorus is present in the catalyst, the phosphorus content is 0.1% to 10% by weight of P2O5 relative to the total weight of the catalyst, preferably 0.5% to 5% by weight of P2O5 relative to the total weight of the catalyst, and even more preferably 1% to 3% by weight of P2O5 relative to the total weight of the catalyst.

[0059] The catalyst typically has a concentration of 50-200 mg / m³. 2 / g, preferably 60-170m 2 / g, preferably 70-130m 2Specific surface area per g.

[0060] The pore volume of the catalyst is typically 0.5 ml / g-1.3 ml / g, preferably 0.6 ml / g-1.1 ml / g.

[0061] Alumina carrier

[0062] In the context of the hydrodesulfurization method according to the present invention, the alumina support for the catalyst is a macroporous-mesoporous alumina support comprising a bimodal mesoporous distribution, wherein:

[0063] - The volume of the mesopores with a diameter greater than or equal to 2 nm and less than 18 nm is equivalent to 10%-30% of the total pore volume of the carrier;

[0064] - The volume of the mesopores with a diameter greater than or equal to 18 nm and less than 50 nm is equivalent to 30%-50% of the total pore volume of the carrier;

[0065] - The volume of macropores with a diameter greater than or equal to 50 nm and less than 8000 nm is equivalent to 30%-50% of the total pore volume of the carrier.

[0066] Preferably, the volume of the mesopores in the carrier having a diameter greater than or equal to 2 nm and less than 18 nm is equivalent to 15%-25% of the total pore volume of the carrier.

[0067] Preferably, the volume of the mesopores in the carrier having a diameter greater than or equal to 18 nm and less than 50 nm is equivalent to 35%-45% of the total pore volume of the carrier.

[0068] Preferably, the volume of the macropores in the carrier having a diameter greater than or equal to 50 nm and less than 8000 nm is equivalent to 35%-50% of the total pore volume of the carrier.

[0069] In one embodiment of the invention, the pore distribution of the mesopores having a diameter greater than or equal to 2 nm and less than 18 nm is concentrated in the numerical range of 10.5-14.5 nm, preferably 12-13 nm.

[0070] In one embodiment of the invention, the pore distribution of the mesopores having a diameter greater than or equal to 18 nm and less than 50 nm is concentrated in the numerical range of 22-28 nm, preferably 23-27 nm.

[0071] The carrier typically has a diameter of 50-210m. 2 / g, preferably 70-180m 2 / g, or even more preferably 70-160m 2Specific surface area per g.

[0072] The pore volume of the carrier is typically 0.7 ml / g-1.3 ml / g, preferably 0.8 ml / g-1.2 ml / g.

[0073] Advantageously, the carrier is in the form of beads having a diameter of 0.8-10 mm, preferably 1-5 mm, more preferably 2-4 mm.

[0074] Methods for preparing carriers

[0075] The alumina support for the catalyst used in the context of the hydrodesulfurization method according to the present invention can be synthesized by any method known to those skilled in the art.

[0076] According to a preferred embodiment, the alumina support used according to the present invention is in the form of beads. According to this preferred embodiment, the preparation of the support includes the following steps:

[0077] s1) Aluminum hydroxide or aluminum hydroxide is dehydrated at a temperature of 400℃-1200℃, preferably 600℃-900℃, for 0.1 seconds to 5 seconds, preferably 0.1 seconds to 4 seconds, to obtain aluminum oxide powder;

[0078] s2) The alumina powder obtained in step s1) is formed into beads;

[0079] s3) Heat-treat the beads obtained in step s2) at a temperature of 200°C or higher;

[0080] s4) The alumina beads obtained at the end of step s3) are subjected to hydrothermal treatment by impregnation with water or an aqueous solution, preferably an acidic aqueous solution, and then kept in an autoclave at a temperature of 100°C-300°C, preferably 150°C-250°C.

[0081] s5) Calcine the alumina beads obtained at the end of step s4) at a temperature of 500℃-820℃.

[0082] Steps s1 through s5 are described in detail below.

[0083] Step s1)

[0084] According to step s1), aluminum hydroxide or aluminum hydroxyaluminate is dehydrated at a temperature of 400°C-1200°C, preferably 600°C-900°C, for 0.1 seconds to 5 seconds, preferably 0.1 seconds to 4 seconds, to obtain alumina powder. Aluminum hydroxide can be selected from hydrargillite, gibbsite, or gibbsite. Aluminum hydroxyaluminate can be selected from boehmite or diaspore. Preferably, step s1) is performed using gibbsite.

[0085] Typically, step s1) is carried out in the presence of a hot air stream, such as dry or humid air, which can quickly remove and entrain evaporated water.

[0086] Typically, activated alumina powder obtained by dehydrating aluminum hydroxide or aluminum hydroxide is ground to a particle size of 10-200 μm.

[0087] Typically, the activated alumina powder obtained after dehydration of aluminum hydroxide or aluminum hydroxide is washed with water or an acidic aqueous solution. When performing the washing step with an acidic aqueous solution, any inorganic or organic acid can be used. For inorganic acids, nitric acid, hydrochloric acid, perchloric acid, or sulfuric acid are preferred, and for organic acids, carboxylic acids (formic acid, acetic acid, or malonic acid), sulfonic acids (p-toluenesulfonic acid), or sulfate esters (dodecyl sulfate) are preferred.

[0088] Step s2)

[0089] According to step s2), the alumina powder obtained at the end of step s1) is shaped.

[0090] The alumina powder is shaped to obtain beads; this is called granulation and is typically carried out using rotary techniques, such as rotary granulators or rotary drums. This type of method yields beads with controlled diameter and pore distribution, which are usually formed during the agglomeration step.

[0091] Pores can be formed in various ways, such as by selecting the particle size distribution of the alumina powder or by agglomerating several alumina powders with different particle size distributions. Another method is to mix one or more compounds with the alumina powder before or during the agglomeration step; these compounds are called pore-forming compounds. Heating causes these compounds to dissolve, thereby forming pores in the beads. Pore-forming compounds used include, for example, wood flour, charcoal, activated carbon, carbon black, sulfur, tar, plastics or plastic emulsions such as polyvinyl chloride, polyvinyl alcohol, naphthalene, etc. The amount of pore-forming compound added is 500-1100 kg / m³ to obtain the initial green filling density. 3 The preferred strength is 700-950 kg / m³.3 The required volume of beads with a diameter of 0.8-10 mm, preferably 1-5 mm, or even more preferably 2-4 mm, is determined by the desired size. Beads can be selected using a sieving method based on the required particle size.

[0092] Step s3)

[0093] According to step s3), the alumina powder obtained at the end of step s2) and formed into beads is heat-treated at a temperature of 200°C or higher, preferably 200°C-1200°C, preferably 300°C-900°C, and most preferably 400°C-750°C, for a duration typically 1-24 hours, preferably 1-6 hours. The beads obtained in this intermediate step have a particle size of 50-420 μm. 2 / g, preferably 60-350m 2 / g, or even better, 80-300m 2 Specific surface area per g.

[0094] Step s4)

[0095] According to step s4), the alumina beads obtained at the end of step s3) are subjected to hydrothermal treatment by immersion in water or an aqueous solution, preferably an acidic aqueous solution, and then kept in an autoclave at a temperature of 100℃-300℃, preferably 150℃-250℃.

[0096] Hydrothermal treatment is typically carried out at temperatures between 100°C and 300°C, preferably between 150°C and 250°C, for a duration exceeding 45 minutes, preferably 1-24 hours, and very preferably 1.5-12 hours. The hydrothermal treatment is usually performed using an acidic aqueous solution containing one or more inorganic and / or organic acids, preferably nitric acid, hydrochloric acid, perchloric acid, sulfuric acid, or a weak acid, wherein the solution of the weak acid has a pH less than 4, such as acetic acid or formic acid. Typically, the acidic aqueous solution also contains one or more compounds capable of releasing anions that can bind with aluminum ions, preferably compounds containing nitrate ions (e.g., aluminum nitrate), chloride ions, sulfate ions, perchlorate ions, chloroacetic acid ions, trichloroacetic acid ions, bromoacetic acid ions, or dibromoacetic acid ions, and anions having the general formula R-COO- (e.g., formate and acetate ions).

[0097] Step s5)

[0098] According to step s5), the alumina beads obtained at the end of step s4) are calcined at a temperature of 500℃-820℃, preferably 550℃-750℃, typically for 1-24 hours, preferably 1-6 hours. At the end of this step, the obtained alumina beads have a particle size of 50-210 μm. 2 / g, preferably 70-180m 2 / g, or even more preferably 70-160m 2 Specific surface area per g.

[0099] Methods for preparing catalysts

[0100] The catalyst used in the context of the hydrodesulfurization method according to the invention can be prepared by any technique known to those skilled in the art, in particular by impregnating a selected support with Group VIII and Group VIB elements, optionally phosphorus.

[0101] According to a first embodiment, the Group VIB metal component, the Group VIII metal component, and the phosphorus component are deposited on the support through one or more co-impregnation stages; that is, the Group VIB metal component, the Group VIII metal component, and the phosphorus component are simultaneously introduced into the support. The one or more co-impregnation steps are preferably carried out by dry impregnation or impregnation in an excess solution. When the first embodiment includes several co-impregnation steps, each co-impregnation step is preferably followed by an intermediate drying step at a temperature typically below 200°C, advantageously 50-180°C, preferably 60-150°C, and very preferably 75-140°C.

[0102] According to a preferred embodiment of co-impregnation, the impregnation solution is preferably an aqueous solution. Preferably, when the aqueous impregnation solution contains cobalt, molybdenum, and phosphorus, the aqueous impregnation solution is prepared under pH conditions that promote the formation of heteropolyanions in the solution. For example, such an aqueous solution has a pH of 1-5.

[0103] According to a second embodiment, a catalyst precursor is prepared by sequentially depositing a Group VIB metal component, a Group VIII metal component, and optionally phosphorus on the support in any order. The deposition can be carried out using methods well known to those skilled in the art, such as dry impregnation, over-impregnation, or deposition-precipitation. In this second embodiment, the deposition of the Group VIB metal component, the Group VIII metal component, and optionally phosphorus can be carried out by several impregnations, with an intermediate drying step between two consecutive impregnations, typically at a temperature below 200°C, advantageously 50-180°C, preferably 60-150°C, and very preferably 75-140°C.

[0104] Regardless of the deposition method used for metals and phosphorus, the solvent selected to participate in the composition of the impregnation solution is to dissolve the metal precursor of the active phase, such as water or an organic solvent (e.g., alcohol).

[0105] For example, sources of molybdenum can include oxides and hydroxides, molybdic acid and its salts, especially ammonium salts, such as ammonium molybdate and ammonium heptamolybdate, and phosphomolybdic acid (H3PMo). 12 O40 ) and its salts, and optionally silicomolybdic acid (H4SiMo) 12 O 40 Molybdenum can also be derived from any heteropoly compound, such as Keggin type, vacant Keggin type, substituted Keggin type, Dawson type, Anderson type, or Strandberg type. Preferably, molybdenum trioxide and Keggin type, vacant Keggin type, substituted Keggin type, and Strandberg type heteropoly compounds are used.

[0106] The tungsten precursors that can be used are well known to those skilled in the art. For example, among the sources of tungsten, oxides and hydroxides, tungstates and their salts, especially ammonium salts, such as ammonium tungstate, ammonium metatungstate, phosphotungstic acid and their salts, and optionally silicotungstic acid (H4SiW) can be used. 12 O 40 ) and its salts. The source of tungsten can also be any heteropoly compound, such as Keggin type, absent Keggin type, substituted Keggin type, or Dawson type. Oxides and ammonium salts, such as ammonium metatungstate, or Keggin type, absent Keggin type, or substituted Keggin type heteropoly anions, are preferred.

[0107] The cobalt precursors that can be used are advantageously selected from, for example, oxides, hydroxides, basic carbonates, carbonates, and nitrates. Cobalt hydroxide and cobalt carbonate are preferred.

[0108] The nickel precursors that can be used are advantageously selected from, for example, oxides, hydroxides, basic carbonates, carbonates, and nitrates. Nickel hydroxide and basic nickel carbonate are preferred.

[0109] Phosphorus can be advantageously introduced into the catalyst in various ways during the various steps of catalyst preparation. Phosphorus can be introduced during the forming of the alumina support, or preferably after forming. Phosphorus can be advantageously introduced alone or as a mixture with at least one of Group VIB and Group VIII metals. Phosphorus is preferably introduced as a mixture with Group VIB and Group VIII metal precursors, by dry impregnation of the alumina support with a solution containing the metal precursor and the phosphorus precursor, either completely or partially, onto the formed alumina support. A preferred source of phosphorus is orthophosphoric acid (H3PO4), but its salts (e.g., ammonium phosphate) and esters or mixtures thereof are also suitable. Phosphorus can also be introduced simultaneously with one or more Group VIB elements in heteropolyanionic forms, such as Keggin type, absent Keggin type, substituted Keggin type, or Strandberg type.

[0110] At the end of one or more steps involving contacting Group VIB and Group VIII metals, as well as phosphorus, with the support, the catalyst precursor is subjected to a drying step using any technique known to those skilled in the art. This is advantageously carried out under atmospheric or reduced pressure. Preferably, this step is carried out under atmospheric pressure. The step is carried out at a temperature below 200°C, preferably 50°C-180°C, more preferably 60°C-150°C, and very preferably 75°C-140°C.

[0111] The drying step is advantageously carried out in a crossflow bed using hot air or any other hot gas. Preferably, when drying is carried out in a crossflow bed, the gas used is air or an inert gas, such as argon or nitrogen. Very preferably, drying is carried out in a crossflow bed in the presence of air.

[0112] Preferably, the drying step lasts for 30 minutes to 24 hours, more preferably 1 hour to 12 hours.

[0113] At the end of the drying step, a dried catalyst is obtained, which can be used as a hydrotreating catalyst after the activation stage (sulfidation step).

[0114] According to one alternative, the dried catalyst can undergo a subsequent calcination stage, for example, in air at a temperature greater than or equal to 200°C. Calcination is typically carried out at a temperature less than or equal to 600°C, preferably 200°C-600°C, and particularly preferably 250°C-500°C. The calcination time is typically 0.5 hours to 16 hours, preferably 1 hour to 5 hours. It is usually carried out in air. Calcination can convert Group VIB and Group VIII metal precursors into oxides.

[0115] Prior to its use as a hydrotreating catalyst, the dried or optionally calcined catalyst is advantageously subjected to a sulfidation step (activation stage). This activation stage is carried out by methods well known to those skilled in the art, advantageously in the presence of hydrogen and hydrogen sulfide under a sulfur-reducing atmosphere. Hydrogen sulfide can be used directly or generated by a sulfiding agent (e.g., dimethyl disulfide).

[0116] Method of hydrogenating desulfurization of gasoline

[0117] The hydrotreating method involves contacting a sulfur-containing olefin gasoline fraction with the above-mentioned catalyst and hydrogen under the following conditions:

[0118] Temperature range: -200-400℃, preferably 230-330℃;

[0119] -1-3MPa, preferably 1.5-2.5MPa total pressure;

[0120] -1-10h -1 , preferably 2-6h -1The definition of is the volumetric flow rate of the feedstock divided by the volumetric space velocity (HSV) of the catalyst.

[0121] A hydrogen / gasoline feedstock volume ratio of -100-600 Nl / l, preferably 200-400 Nl / l.

[0122] Therefore, the method according to the invention can process any type of sulfur-containing olefinic gasoline fraction, for example, fractions from self-coking, viscosity-reducing cracking, steam cracking, or catalytic cracking (FCC, fluidized bed catalytic cracking) units. Such gasoline may optionally contain a substantial portion derived from other production methods, such as atmospheric distillation (gasoline produced by straight distillation or straight-run gasoline) or self-conversion methods (coking or steam cracking gasoline). The feedstock preferably consists of gasoline fractions from self-catalytic cracking units.

[0123] The feedstock is advantageously a gasoline fraction containing sulfur compounds and olefins, with a boiling point of 30°C to less than 250°C, preferably 35°C-240°C, and more preferably 40°C-220°C.

[0124] The sulfur content of gasoline fractions produced by catalytic cracking (FCC) depends on the sulfur content of the feedstock processed by FCC, whether the FCC feedstock is pretreated, and the fraction's final boiling point. Typically, the overall sulfur content of gasoline fractions, especially those produced by FCC, is greater than 100 ppm by weight, and in most cases greater than 500 ppm by weight. For gasoline with a final boiling point greater than 200°C, the sulfur content is usually greater than 1000 ppm by weight; in some cases, it can even reach values ​​in the range of 4000-5000 ppm by weight.

[0125] In addition, gasoline produced by the self-catalytic cracking (FCC) unit contains, on average, 0.5 wt% to 5 wt% dienes, 20 wt% to 50 wt% olefins, and 10 wt% to 0.5 wt% sulfur, including typically less than 300 ppm thiols. Thiols are generally concentrated in the lighter fractions of gasoline, more specifically, in fractions with boiling points below 120°C.

[0126] It should be noted that sulfur-containing compounds present in gasoline can also include heterocyclic sulfur-containing compounds, such as thiophene, alkylthiophene, or benzothiophene. Unlike thiols, these heterocyclic compounds cannot be removed by extraction. Therefore, these sulfur-containing compounds are removed by hydrogenation, which results in their conversion into hydrocarbons and H2S.

[0127] Preferably, the gasoline processed by the method according to the invention is heavy gasoline (or heavy cracked naphtha, HCN) produced from a distillation step aimed at separating a wide-range cracked naphtha (or full-range cracked naphtha, FRCN) of gasoline produced by a cracking process into light gasoline (light cracked naphtha, LCN) and heavy gasoline HCN. The fractionation points of the light and heavy gasoline are determined to limit the sulfur content of the light gasoline and make it usable in a gasoline pool, preferably without requiring additional post-treatment. Advantageously, a selective hydrogenation step is performed on the wide-range FRCN prior to the distillation step. Example

[0128] Example 1: Catalyst A (according to the present invention)

[0129] The support S1 for catalyst A is made of gibbsite ( The alumina powder was obtained by dehydration with Merck (a type of carbon black). The temperature was set to 800°C, and the contact time between the material to be dehydrated and the dry air stream was 1 second. The obtained alumina powder was ground to a particle size of 10-200 μm and then washed three times with distilled water at twice the volume of the powder used. In the presence of carbon black, the alumina powder is shaped using a disc granulator (GRELBEXP30) equipped with a conical cylindrical disc at a 30° angle and a rotation speed of 40 rpm, thereby obtaining beads with a diameter mainly of 2-4 mm after sieving the solids. The amount of carbon black is adjusted to obtain 800 kg / m³. 3 The original filling density of the target material. The beads were heat-treated in air at 720°C to give them a density of 200 μm. 2 The specific surface area was measured in g. The beads were then subjected to hydrothermal treatment by impregnating the pore volume with an aqueous nitric acid solution (0.1N, Merck). This hydrothermal treatment was carried out at 200°C in a rotary basket autoclave for 6.5 hours. The resulting beads were then subjected to a final calcination treatment in air at 650°C for 2 hours. The carrier S1 has a specific surface area of ​​141 μm. 2 The specific surface area per g, the total pore volume of 0.97 ml / g, and the following pore distribution obtained by mercury intrusion porosimetry:

[0130] - The mesopore volume with a diameter greater than or equal to 2 nm and less than 18 nm is 0.15 ml / g, which is equivalent to 15% of the total pore volume, and its pore distribution is concentrated at 13 nm;

[0131] - The mesopore volume with a diameter greater than or equal to 18 nm and less than 50 nm is 0.43 ml / g, which is equivalent to 44% of the total pore volume, and its pore distribution is concentrated at 26 nm;

[0132] - The volume of macropores with a diameter greater than or equal to 50 nm and less than 8000 nm is 0.39 ml / g, which is equivalent to 40% of the total pore volume.

[0133] The water absorption volume of support S1 is 0.95 ml / g. An impregnation solution was prepared by heating a solution of 1.15 g of molybdenum oxide (MoO3 > 99.5%, Merck), 0.28 g of cobalt hydroxide (95% Co(OH)2, Merck), and 0.26 g of phosphoric acid (85 wt% H3PO4 in water, Merck) in 9.3 ml of distilled water at 90 °C for 3 hours. After dry impregnation of 10 g of the support and aging in a moisture-saturated atmosphere for 12 hours, the solid was dried at 120 °C for 12 hours. Subsequently, the solid was calcined in air at 450 °C for 2 hours. The obtained catalyst A, relative to the total weight of the catalyst, contains 1.9 wt% CoO, 10 wt% MoO3, and 1.4 wt% P2O5. The total pore volume of catalyst A is 0.88 ml / g, and the specific surface area is 118 m². 2 / g.

[0134] Example 2: Catalyst B (according to the present invention)

[0135] By using 1.35g of ammonium heptamolybdate ((NH4)6Mo7O) 24 Catalyst B was obtained by dry impregnation of alumina support S1 with an aqueous solution of 1.38 g of cobalt nitrate (Co(NO3)2·6H2O, 99.98%, Merck) in 9.4 ml of distilled water. After dry impregnation of 10 g of the support and aging in a moisture-saturated atmosphere for 12 hours, the solid was dried at 120 °C for 12 hours. Subsequently, the solid was calcined in air at 450 °C for 2 hours. The obtained catalyst B contained 3.1 wt% CoO and 9.6 wt% MoO3 relative to the total weight of the catalyst. The total pore volume of catalyst B was 0.89 ml / g, and the specific surface area was 124 m². 2 / g.

[0136] Example 3: Catalyst C (macroporous and unimodal macroporous and mesoporous catalysts) not based on the present invention

[0137] The support S2 for catalyst C is gibbsite ( The activated alumina powder was obtained by dehydration (Merck) to obtain activated alumina powder. The temperature was set to 800°C, and the contact time between the material to be dehydrated and the dry air stream was 1 second. The obtained activated alumina powder was ground to a particle size of 10-200 μm, and then washed three times with distilled water at a volume equal to twice the volume of the powder used. The activated alumina powder was shaped using a disc granulator (GRELBEX P30) equipped with a conical cylindrical disc at a 30° angle and a rotation speed of 40 rpm, thereby (after sieving the solids) obtaining a particle size primarily of 2-4 mm and a weight of 780 kg / m³. 3 The beads were prepared with the original filling density of the target material. The beads were then heat-treated in air at 700°C to achieve a density of 250 μm. 2 The specific surface area was measured in g. The beads were then subjected to hydrothermal treatment by impregnating the pore volume with an aqueous nitric acid solution (0.1N, Merck). This hydrothermal treatment was carried out at 200°C in a rotary basket autoclave for 6.5 hours. The resulting beads were then subjected to a final calcination treatment in air at 950°C for 2 hours. The carrier S2 has a specific surface area of ​​71 m². 2 The specific surface area per g, the total pore volume of 0.56 ml / g, and the following pore distribution obtained by mercury porosimetry:

[0138] - The mesopore volume with a diameter greater than or equal to 10 nm and less than 50 nm is 0.35 ml / g, which is equivalent to 63% of the total pore volume, and its pore distribution is concentrated at 20 nm;

[0139] - The macropore volume with a diameter greater than or equal to 50 nm and less than 8000 nm is 0.21 ml / g, which is equivalent to 38% of the total pore volume.

[0140] The water absorption volume of support S2 is 0.54 ml / g. An impregnation solution was prepared by heating a solution of 1.15 g of molybdenum oxide (MoO3 > 99.5%, Merck), 0.28 g of cobalt hydroxide (95% Co(OH)2, Merck), and 0.26 g of phosphoric acid (85 wt% H3PO4 in water, Merck) in 5.2 ml of distilled water at 90 °C for 3 hours. After dry impregnation of 10 g of the support and aging in a moisture-saturated atmosphere for 12 hours, the solid was dried at 120 °C for 12 hours. Subsequently, the solid was calcined in air at 450 °C for 2 hours. The obtained catalyst C, relative to the total weight of the catalyst, contains 1.9 wt% CoO, 10 wt% MoO3, and 1.4 wt% P2O5. The total pore volume of catalyst C is 0.47 ml / g, and the specific surface area is 62 m². 2 / g.

[0141] Example 4: Catalyst D (macroporous catalyst) not based on the present invention

[0142] Commercial carriers S3 (SA52124) are available in bead form with a diameter of 2-4 mm. NorPro). Carrier S3 has 8m 2 The specific surface area per g, the total pore volume of 0.33 ml / g, and the following pore distribution obtained by mercury porosimetry:

[0143] - The macropore volume with a diameter greater than or equal to 50 nm and less than 8000 nm is 0.33 ml / g, which is equivalent to 100% of the total pore volume.

[0144] The water absorption volume of support S3 is 0.37 ml / g. An impregnation solution was prepared by heating a solution of 1.15 g of molybdenum oxide (MoO3 > 99.5%, Merck), 0.28 g of cobalt hydroxide (95% Co(OH)2, Merck), and 0.26 g of phosphoric acid (85 wt% H3PO4 in water, Merck) in 3.5 ml of distilled water at 90 °C for 3 hours. After dry impregnation of 10 g of the support and aging in a moisture-saturated atmosphere for 12 hours, the solid was dried at 120 °C for 12 hours. At the end of both impregnation steps, the solid was subsequently calcined in air at 450 °C for 2 hours. The obtained catalyst D, relative to the total weight of the catalyst, contains 1.9 wt% CoO, 10 wt% MoO3, and 1.4 wt% P2O5. The total pore volume of catalyst D is 0.21 ml / g, and the specific surface area is 5 m². 2 / g.

[0145] Example 5: Catalyst E (single-peak mesoporous catalyst) not according to the present invention

[0146] Commercial carrier S4 (SA 6578, NorPro) is available in extrusion form with a diameter of 5 mm. Carrier S4 has a diameter of 175 m. 2 The specific surface area per g, the total pore volume of 0.82 ml / g, and the following pore distribution obtained by mercury porosimetry:

[0147] - The volume of mesopores with a diameter greater than or equal to 2 nm and less than or equal to 20 nm is 0.82 ml / g, which is equivalent to 100% of the total pore volume, and the pore distribution is concentrated at 13 nm.

[0148] The water absorption volume of support S4 is 0.54 ml / g. An impregnation solution was prepared by heating a solution of 1.15 g of molybdenum oxide (MoO3 > 99.5%, Merck), 0.28 g of cobalt hydroxide (95% Co(OH)2, Merck), and 0.26 g of phosphoric acid (85 wt% H3PO4 in water, Merck) in 7.9 ml of distilled water at 90 °C for 3 hours. After dry impregnation of 10 g of the support and aging in a moisture-saturated atmosphere for 12 hours, the solid was dried at 120 °C for 12 hours. Subsequently, the solid was calcined in air at 450 °C for 2 hours. The obtained catalyst E, relative to the total weight of the catalyst, contains 1.9 wt% CoO, 10 wt% MoO3, and 1.4 wt% P2O5. The total pore volume of catalyst E is 0.74 ml / g, and the specific surface area is 136 m². 2 / g.

[0149] Example 6: Catalyst F (macroporous and unimodal small-mesoporous catalyst) not based on the present invention

[0150] Commercial carrier S5 (SA 6176, NorPro) is available in extruded form with a diameter of 1.6 mm. Carrier S5 has a diameter of 250 m. 2 The specific surface area per g, the total pore volume of 1.05 ml / g, and the following pore distribution obtained by mercury porosimetry:

[0151] - The volume of mesopores with a diameter greater than or equal to 2 nm and less than or equal to 20 nm is 0.68 ml / g, which is equivalent to 65% of the total pore volume, and the pore distribution is concentrated at 7 nm;

[0152] - The macropore volume with a diameter greater than or equal to 50 nm and less than 8000 nm is 0.37 ml / g, which is equivalent to 35% of the total pore volume.

[0153] The water absorption volume of the support S5 was 1.02 ml / g. An impregnation solution was prepared by heating a solution of 1.15 g of molybdenum oxide (MoO3 > 99.5%, Merck), 0.28 g of cobalt hydroxide (95% Co(OH)2, Merck), and 0.26 g of phosphoric acid (85 wt% H3PO4 in water, Merck) in 10.0 ml of distilled water at 90 °C for 3 hours. After dry impregnation of 10 g of the support and aging in a moisture-saturated atmosphere for 12 hours, the solid was dried at 120 °C for 12 hours. Subsequently, the solid was calcined in air at 450 °C for 2 hours. The obtained catalyst F, relative to the total weight of the catalyst, contained 1.9 wt% CoO, 10 wt% MoO3, and 1.4 wt% P2O5. The total pore volume of catalyst F was 0.87 ml / g, and the specific surface area was 211 m². 2 / g.

[0154] Example 7: Evaluation of the performance of the catalyst used in the hydrodesulfurization reactor

[0155] In this embodiment, the performance of catalysts A to F in the hydrodesulfurization of catalytic cracked gasoline was evaluated.

[0156] The catalytic performance of various catalysts was evaluated using a model feedstock representing catalytic cracking (FCC) gasoline containing 10 wt% 2,3-dimethylbut-2-ene and 0.33 wt% 3-methylthiophene (i.e., the feedstock contains 1000 wt% sulfur). Heptane was used as the solvent.

[0157] The hydrodesulfurization (HDS) reaction was carried out in a fixed crossflow reactor in the presence of 4 ml of catalyst, at a total pressure of 1.5 MPa and a temperature of 210 °C, with a flow rate of HSV = 6 h. -1 (HSV = feed volume flow rate / catalyst volume) and an H2 / feed volume ratio of 300 N1 / l were used. Before the HDS reaction, the catalyst was in-situ sulfided for 2 hours at 350 °C, atmospheric pressure, and a hydrogen stream containing 15 mol% H2S.

[0158] Each catalyst was placed sequentially in the reactor. Samples were taken at different time intervals and analyzed by gas chromatography to observe the disappearance of reactants and the formation of products.

[0159] The catalytic performance of the catalysts was evaluated in terms of catalytic activity and selectivity. Hydrodesulfurization (HDS) activity was represented by the rate constant (kHDS) of the HDS reaction of 3-methylthiophene, normalized by the introduced catalyst volume, and assumed first-order kinetics with respect to sulfur-containing compounds. Olefin hydrogenation (HydO) activity was represented by the rate constant of the hydrogenation reaction of 2,3-dimethylbut-2-ene, normalized by the introduced catalyst volume, and assumed first-order kinetics with respect to olefins.

[0160] The selectivity of the catalyst is represented by the normalized ratio of the rate constant, kHDS / kHydO. The kHDS / kHydO ratio increases with increasing catalyst selectivity. The obtained values ​​are normalized using catalyst A as a reference (relative HDS activity and relative selectivity equal to 100). Therefore, the performance criteria are relative HDS activity and relative selectivity.

[0161] Table 1

[0162]

[0163] Therefore, it can be seen that the catalyst according to the invention has better performance in terms of activity and selectivity, thus emphasizing the importance of the pore size of the catalyst support for performance in gasoline hydrodesulfurization methods. This improvement in catalyst selectivity is particularly advantageous in the case of hydrodesulfurization methods for olefin-containing gasoline, for which the aim is to limit octane number loss due to olefin hydrogenation as much as possible.

Claims

1. A method for hydrodesulfurizing a sulfur-containing olefinic gasoline fraction, wherein the gasoline fraction, hydrogen, and a catalyst are contacted, and the hydrodesulfurization method is carried out at a temperature of 200°C-400°C, a total pressure of 1-3 MPa, and for 1-10 hours. -1 The reaction was carried out at a space velocity of 100-600 Nl / l and a hydrogen / gasoline fraction volume ratio, wherein the space velocity was defined as the volumetric flow rate of the feedstock divided by the volume of the catalyst, and the catalyst comprised at least one Group VIB metal, at least one Group VIII metal, and a mesoporous-macroporous alumina support with a bimodal mesoporous distribution, wherein: - The volume of the mesopores with a diameter greater than or equal to 2 nm and less than 18 nm is equivalent to 10-30% of the total pore volume of the carrier. - The volume of the mesopores with a diameter greater than or equal to 18 nm and less than 50 nm is equivalent to 30-50% of the total pore volume of the carrier. - The volume of macropores with a diameter greater than or equal to 50 nm and less than 8000 nm is equivalent to 30-50% of the total pore volume of the carrier.

2. The method of claim 1, wherein the carrier has a density of 50-210m. 2 Specific surface area per g.

3. The method of claim 1, wherein the carrier has a total pore volume of 0.7-1.3 ml / g.

4. The method according to any one of claims 1-3, wherein the volume of the mesopore having a diameter greater than or equal to 2 nm and less than 18 nm is equivalent to 15%-25% of the total pore volume of the carrier.

5. The method according to any one of claims 1-3, wherein the volume of the mesopore having a diameter greater than or equal to 18 nm and less than 50 nm is equivalent to 35%-45% of the total pore volume of the carrier.

6. The method of any one of claims 1-3, wherein the volume of the macropores having a diameter greater than or equal to 50 nm and less than 8000 nm is equivalent to 35%-50% of the total pore volume of the carrier.

7. The method according to any one of claims 1-3, wherein the content of a Group VIB metal in the catalyst, expressed in oxide form, is 1%-30% by weight relative to the total weight of the catalyst.

8. The method according to any one of claims 1-3, wherein the content of Group VIII metals in the catalyst, expressed in oxide form, is 0.5%-10% by weight relative to the total weight of the catalyst.

9. The method of claim 8, wherein the Group VIII metal is cobalt.

10. The method of claim 7, wherein the Group VIB metal is molybdenum.

11. The method of any one of claims 1-3, wherein the catalyst further comprises phosphorus, and the phosphorus content, expressed in the form of P2O5, is 0.1%-10% by weight relative to the total weight of the catalyst.

12. The method of any one of claims 1-3, wherein the pore distribution of the mesopores having a diameter greater than or equal to 2 nm and less than 18 nm is concentrated in the numerical range of 10.5-14.5 nm.

13. The method of any one of claims 1-3, wherein the pore distribution of the mesopores having a diameter greater than or equal to 18 nm and less than 50 nm is concentrated in the numerical range of 22-28 nm.

14. The method according to any one of claims 1-3, wherein the gasoline is catalytic cracked gasoline.

15. The method according to any one of claims 1-3, wherein the carrier is in the form of beads with a diameter of 2-4 mm.

16. The method of claim 15, wherein the carrier is obtained according to the following steps: s1) Dehydrate aluminum hydroxide or aluminum hydroxide at a temperature of 400℃-1200℃ for 0.1 seconds to 5 seconds to obtain aluminum oxide powder; s2) The alumina powder obtained in step s1) is formed into beads; s3) Heat-treat the alumina beads obtained in step s2) at a temperature of 200°C or higher; s4) The alumina beads obtained at the end of step s3) are subjected to hydrothermal treatment by immersion in water or aqueous solution and then staying in an autoclave at a temperature of 100℃-300℃. s5) Calcine the alumina beads obtained at the end of step s4) at a temperature of 500℃-820℃.

17. The method of claim 16, wherein step s1) comprises dehydrating aluminum hydroxide or aluminum hydroxide at a temperature of 600°C-900°C for 0.1 seconds to 4 seconds to obtain aluminum oxide powder.

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