Pseudo-boehmite and method for producing the same

Abstract

The present application belongs to the field of pseudo-boehmite, and discloses a pseudo-boehmite and a preparation method thereof. The content of sodium oxide in the pseudo-boehmite is less than 0.1 wt%, the R value of the pseudo-boehmite satisfies 1.3<=R<=1.6, wherein R=D(130) / D(020), and / or the pore volume of the pseudo-boehmite is 0.65-0.9 mL / g, and the specific surface area of the pseudo-boehmite is >=400 m 2 / g. The preparation method comprises the following steps: first, preparing aluminum stone by carbonization method, aging, then destroying the double electric layer structure of the aluminum stone colloidal particles, and ion exchange. The pseudo-boehmite has low sodium oxide content and high pore volume, and can be used in the field of special catalysts or electronic ceramics. The preparation method can obtain low-sodium pseudo-boehmite under low water consumption, and keeps the structure of the aluminum stone from being destroyed by washing.

Description

Technical Field

[0001] This invention relates to the field of boehmite, specifically to a macroporous, low-sodium boehmite and its preparation method. Background Technology

[0002] The carbonization method for preparing boehmite is currently the lowest-cost industrial production method for boehmite. It involves the neutralization reaction of sodium aluminate solution with CO2 to generate hydrated alumina, followed by aging, washing, and drying to obtain the boehmite product. The raw materials are inexpensive, the process is simple, and it allows for the resource utilization of CO2, aligning with the contemporary requirements of carbon reduction. However, due to its unique material properties, the boehmite has an extremely fine particle size, reaching or approaching colloidal particle size, making sodium removal extremely difficult and requiring significant water consumption. Currently, the washing water consumption for ordinary boehmite (sodium oxide content ≤0.3%) is 30-35 t / t; the water consumption for producing low-sodium boehmite (sodium oxide content ≤0.1%) is as high as 100 t / t or more. Compared to ordinary boehmite, low-sodium boehmite is approximately 1.5-2 times more expensive and is a core carrier for the production of high-end petroleum catalysts. If the water consumption in the production of low-sodium boehmite can be reduced, water resources can be saved, wastewater treatment costs can be reduced, and economic benefits can be significantly improved.

[0003] CN109179461A discloses a method and apparatus for preparing low-sodium boehmite. This method involves adding a weakly acidic water purifier during the washing process, which can significantly reduce the sodium ion content in the product without increasing the amount of hot water used for washing (or with very little additional hot water). This method is suitable for easily washable boehmite; however, for difficult-to-wash boehmite, such as boehmite prepared by carbonization, washing still requires a higher water consumption. Furthermore, it does not address how to further reduce water consumption, nor does it address how to obtain boehmite with a higher pore volume and / or specific surface area.

[0004] There is a need for a method to prepare low-sodium boehmite by efficiently removing sodium under low water consumption conditions. This method can maintain the structure of the boehmite and give it a high pore volume and / or surface area. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the problems of difficulty in removing sodium oxide from boehmite and large water consumption in the preparation of low-sodium boehmite. The present invention provides a boehmite and its preparation method, which uses less water and can make the sodium oxide content in the boehmite lower, and can prepare boehmite with a higher specific surface area and / or larger pore volume.

[0006] The inventors of this invention discovered that using alkaline substances and water makes it difficult to reduce sodium content with low water consumption, and direct ion exchange washing is ineffective. Through analysis of the reasons why pseudoboehmite is difficult to remove sodium by water washing, the inventors found that pseudoboehmite has extremely fine grains and exists in the slurry as a colloidal double-layer structure, with the double-layer structure consisting entirely of hydrated ion clusters, which also contain a large amount of Na+. + Alkaline substances and water have no effect on disrupting the electric double layer structure, making it difficult to reduce sodium content with low water consumption. Therefore, the inventors of this invention have creatively proposed a highly efficient sodium removal method that first disrupts the electric double layer structure and then performs ion exchange.

[0007] Therefore, the first aspect of the present invention provides a method for preparing boehmite (hereinafter referred to as boehmite), comprising: neutralizing a sodium aluminate solution with CO2, aging to obtain aged boehmite, filtering to obtain a first filter cake, and washing; wherein, the washing includes:

[0008] First washing: The colloidal double layer structure in the first filter cake is destroyed by the first acidic washing aid (hereinafter referred to as the first washing aid), and the second filter cake is obtained by selective filtration, thus obtaining the product of the first washing.

[0009] Second wash: The product from the first wash is washed by contacting it with a second acidic washing aid (hereinafter referred to as the second washing aid), followed by filtration.

[0010] A second aspect of the present invention provides a pseudoboehmite, wherein the pseudoboehmite contains less than 0.1 wt% sodium oxide and has a high pore volume and / or a high specific surface area.

[0011] A third aspect of the present invention provides a pseudoboehmite, wherein the sodium oxide content in the pseudoboehmite is less than 0.1 wt%, and the pseudoboehmite has an R value satisfying 1.3 ≤ R ≤ 1.6. Wherein R = D(130) / D(020), where D(130) represents the grain size of the crystal plane represented by the 130 peak in the XRD pattern of the pseudoboehmite grain, and D(020) represents the grain size of the crystal plane represented by the 020 peak in the XRD pattern of the pseudoboehmite grain. The 130 peak refers to a peak with 2θ of 34-43° in the XRD pattern, and the 020 peak refers to a peak with 2θ of 10-15° in the XRD pattern.

[0012] The fourth aspect of the present invention provides a method for preparing the pseudoboehmite and the pseudoboehmite obtained therefrom.

[0013] The fifth aspect of this invention provides the application of the pseudoboehmite described in the second, third, or fourth aspects in the fields of catalysts, adsorbents, and electronic ceramics.

[0014] The method for preparing boehmite provided by this invention has at least one of the following beneficial technical effects, and preferably has multiple or all of them:

[0015] (1) The method for preparing boehmite provided by the present invention first destroys the double electric layer of the colloid after the aging reaction of preparing boehmite, and then washes the aging product by ion exchange, which effectively reduces the sodium oxide content in the obtained boehmite and consumes less water for washing.

[0016] (2) The boehmite washing method described in this invention involves adding an acidic washing aid in the first stage of washing to disrupt the colloidal double-layer structure, thereby weakening the interaction between alumina particles and Na. + The interaction between the two; the addition of acid washing aids in the second washing stage reduces the sodium content through ion exchange, which can stably obtain low-sodium boehmite and avoid large fluctuations in sodium oxide content in the product.

[0017] (3) The boehmite washing method described in this invention does not damage the structure of boehmite, has little impact on the surface area, and unexpectedly can increase the grain size and improve the pore volume.

[0018] (4) The method for preparing boehmite provided by the present invention, preferably, involves adjusting the gelation reaction conditions and aging conditions to adjust the growth rate of the crystal grains on the crystal plane represented by the 130 peak and the 020 peak, thereby obtaining boehmite with high specific surface area and large pore volume, while the CO2 capture rate is not less than 50%.

[0019] (5) The method for preparing boehmite provided by the present invention, in a preferred case, can obtain low-sodium boehmite with a ratio of 1.3≤R≤1.6.

[0020] The pseudoboehmite provided by this invention has a low sodium oxide content, high pore volume, high specific surface area and / or a large R value.

[0021] The pseudoboehmite provided by this invention can efficiently adsorb impurities in liquids and gases in the field of adsorbents; as a functional carrier, it can be widely used in the field of catalysts, such as catalytic cracking catalysts, hydrogenation catalysts, reforming catalysts, and automotive exhaust purification catalysts; in the ceramics industry, its low sodium content is beneficial to improving the electrical insulation of electronic ceramics; in addition, its low sodium content and good pore structure have the potential to play a role in the field of fine chemicals. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the pseudoboehmite reaction system.

[0023] Explanation of reference numerals in the attached figures

[0024] 1-Sodium aluminate inlet; 2-Reaction chamber; 3-CO2 gas inlet.

[0025] 4- Conical air chamber; 5- Porous baffle; 6- Air inlet (only one shown for illustration).

[0026] 7-Detection port 8-Exhaust port 9-Discharge port

[0027] 10-Cladle Detailed Implementation

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, 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.

[0029] According to the present invention, the washing includes a first wash (or first stage wash) and a second wash (or second stage wash). In the first wash, an acidic washing aid is used to disrupt the colloidal double-layer structure, weakening the interaction between alumina particles and Na. + The interaction between them. In the second wash, an acidic detergent is used to replace sodium ions through ion exchange to reduce the sodium oxide content.

[0030] According to a preferred embodiment of the present invention, the first and second washing processes are performed by agitation washing. The agitation rate is not particularly limited. The acidic detergent additives (including a first acidic detergent additive and a second acidic detergent additive) can be added separately in each agitation washing cycle, or they can be added step-by-step in a single agitation washing cycle. Specifically, mixing the solid to be washed (e.g., the first filter cake), water, and the acidic detergent additive, followed by filtration, constitutes a single agitation washing cycle.

[0031] In this invention, when performing multiple stirring and washing, the stirring and washing product is subjected to solid-liquid separation after the first stirring and washing, and the filter cake is pulped before the next stirring and washing.

[0032] In this invention, when the washing process involves adding acidic washing aids in a stepwise manner with a single stirring wash, the washing aids are added twice (e.g., the first washing aid and the second washing aid are added sequentially) after the filtered aged product (i.e., the first filter cake) is slurried with water, and no solid-liquid separation is performed between the two additions.

[0033] In one embodiment, the first washing includes: forming a mixture of a first filter cake, water, and a first acidic washing agent with a pH value preferably 7-7.8, filtering (to obtain a second filter cake) or not filtering, to obtain the product of the first washing. The first washing disrupts the double-layer structure of the colloids in the first filter cake.

[0034] Preferably, the pH value of the first washing slurry is 7-7.5.

[0035] In one embodiment, the second washing involves mixing a second filter cake, water, and a second washing aid to obtain a washing slurry, wherein the pH value of the washing slurry is preferably 5-6.5, more preferably 5-6, followed by filtration; or, the second washing aid is added to a mixture of the first filter cake after the colloidal double layer structure has been disrupted, water, and the first washing aid (i.e., the product of the first washing that has disrupted the colloidal double layer structure in the first filter cake but has not been filtered), wherein the pH value of the resulting mixture is optionally 5-6.5, followed by filtration.

[0036] In this invention, the pH value mentioned above is the pH value of the washing slurry at the corresponding washing temperature.

[0037] According to the present invention, preferably, the conditions for the first and second washing each include: the washing temperature is independently 70-90°C, preferably 75-80°C. High temperatures will increase energy consumption.

[0038] In this invention, the washing time is not particularly limited, and those skilled in the art can adjust the washing time adaptively according to the washing conditions. Optionally, the total washing time (including the first washing time and the second washing time) is 30-40 minutes. Extending the washing time will reduce production efficiency. Optionally, the first washing time is 15-20 minutes; the second washing time is 15-20 minutes.

[0039] In one embodiment, the washing process includes: forming a mixture with a pH of 7-7.8 from a first filter cake, water, and a first acidic washing aid, and stirring for, for example, 15-20 minutes; adding a second acidic washing aid to adjust the pH of the resulting mixture to 5-6.5, for example, 5-6, and stirring for, for example, 15-20 minutes, followed by filtration.

[0040] In one embodiment, the washing process includes: forming a mixture with a pH of 7-7.8 by first filter cake, water, and first acidic detergent, stirring for 15-20 minutes, and filtering to obtain a filter cake referred to as a second filter cake; mixing the second filter cake, water, and second acidic detergent to obtain a washing slurry with a pH of 5-6.5, for example 5-6, stirring for 15-20 minutes, and filtering.

[0041] In this invention, the washing method and the amount of acidic washing aid added are not particularly limited. The mixture obtained by filtering the first filter cake from the aged product and mixing it with water and acidic washing aid only needs to meet the pH value limits of the washing slurry in each stage. Optionally, when the first washing and filtration are followed by the second washing, the ratio of water volume for the first washing and the second washing is 0.8-1.2:1, such as 1:1. The first washing stage can be partially or entirely performed using the filtrate from the second washing stage. In one embodiment, the first washing stage uses entirely the filtrate obtained from the second washing filtration, or uses the filtrate obtained from the second washing filtration and fresh water. Optionally, the ratio of water volume (referring to fresh water, i.e., water that has not been washed) for the first washing and the second washing stage is 0-1.2:1. Optionally, the total weight ratio of water volume (newly added washing water or fresh water) for the first washing and the second washing stage to the weight of boehmite (calculated as alumina) is 20-36:1.

[0042] In this invention, the washing water consumption refers to the amount of water consumed in washing the aged products.

[0043] According to the present invention, preferably, the acidic detergent additive is an acid and / or a salt of a strong acid and a weak base.

[0044] According to the present invention, the type of acid is not particularly limited, and is a conventional organic acid and / or inorganic acid in the art. The organic acid is selected from at least one of formic acid, acetic acid, oxalic acid, and citric acid. The inorganic acid is selected from at least one of sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid. Preferably, the acid is selected from at least one of acetic acid, oxalic acid, citric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid.

[0045] According to the present invention, the type of strong acid-weak base salt is not particularly limited, and is a conventional strong acid-weak base salt in the art. Preferably, the strong acid-weak base salt is selected from at least one of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium dihydrogen phosphate, and aluminum chloride.

[0046] In this invention, during the segmented stirring and washing process, the types of acidic detergent additives added twice—namely, the first acidic detergent additive and the second acidic detergent additive—can be the same or different. Optionally, the two acidic detergent additives added do not react with each other.

[0047] According to the present invention, preferably, the method further includes: after the second washing, washing the second washing product, such as the filter cake obtained from the second washing filtration, with water to obtain a third washing product. The washing method is not particularly limited; any conventional washing method in the art can be used. In the present invention, washing the second washing product with water after the second washing can effectively reduce other elements introduced by the acidic washing aid, meeting the higher quality requirements for boehmite in certain applications, and further reducing the sodium oxide content in the boehmite.

[0048] According to the present invention, preferably, the method further includes: drying the washing product to obtain pseudoboehmite. The drying method and conditions are not particularly limited as long as the purpose of the present invention is achieved. In some embodiments, the drying conditions include: a drying temperature of 60-120°C, preferably 70-100°C, and / or a drying time of 2-6 hours, preferably 2-4 hours.

[0049] The present invention provides a method for preparing pseudoboehmite, wherein, in one embodiment, the method for preparing aged pseudoboehmite includes the following steps:

[0050] (S1) The CO2 gas source is reacted with sodium aluminate solution to form a gel. The gelation reaction is stopped when the pH of the solution is 8-10.

[0051] (S2) The product from step (S1) is aged to obtain aged pseudoboehmite.

[0052] Optionally, the reaction temperature of the gelation reaction is 50-80℃; the ratio of the mass concentration of the sodium aluminate solution to the volume concentration of CO2 in the CO2 gas source is ≤2.

[0053] In this invention, the method for preparing the pseudo-boehmite involves controlling the gelation reaction temperature, aging conditions, and the ratio of reactants to achieve directional grain growth. Without adding additional growth regulators, the growth rate of the grains on the 020 and 130 crystal planes is adjusted. Based on this, primary particles directionally aggregate to form larger, elongated secondary particles, resulting in lightweight boehmite with high specific surface area and large pore volume.

[0054] According to the present invention, preferably, the apparent gas velocity of the CO2 gas source is 0.6-12 cm / s, for example, 0.6 cm / s, 1.2 cm / s, 1.5 cm / s, 1.8 cm / s, 2 cm / s, 2.1 cm / s, 2.4 cm / s, 3 cm / s, 4 cm / s, 5 cm / s, 6 cm / s, 7 cm / s, 8 cm / s, 9 cm / s, 10 cm / s, 12 cm / s, or any range between the two. For example, for a reactor with a diameter of 10 cm and a height-to-diameter ratio of 3-10, the apparent gas velocity is 1.2-2.5 cm / s. In the present invention, those skilled in the art can adapt the apparent gas velocity of the CO2 gas source to the reactor diameter.

[0055] In this invention, the term "apparent gas velocity" refers to the ratio of gas flow rate to the cross-sectional area of ​​the column reactor.

[0056] According to the present invention, preferably, the volume concentration of CO2 in the CO2 gas source is not greater than 20%, and more preferably 5-20%.

[0057] In this invention, the volume of a gas refers to its volume under standard conditions.

[0058] According to the present invention, optionally, the CO2 gas source is obtained by adjusting high-concentration CO2 gas; wherein, high-concentration CO2 gas refers to gas in which the volume concentration of CO2 is greater than 20%.

[0059] According to the present invention, in some embodiments, the CO2 gas source is derived from industrial flue gas. The industrial flue gas mainly contains N2 and CO2, and may contain small amounts of SO2. x NO x The industrial flue gas contains components such as oxygen, oxygen, and very little dust. Examples of industrial flue gas include FCC regeneration flue gas, thermal power plant flue gas, steel plant flue gas, flue gas generated by boilers, flue gas generated by combustion furnaces, and flue gas generated by calcining furnaces. Preferably, the industrial flue gas is washed industrial flue gas. Specifically, the industrial flue gas is washed by a flue gas scrubbing tower. The washing method is a conventional method in the art, which will not be described in detail in this invention.

[0060] In this invention, CO2 from industrial flue gas is used to prepare pseudoboehmite, which reduces CO2 emissions and the cost of pseudoboehmite preparation, thus achieving resource utilization of CO2. Typically, the CO2 concentration in industrial flue gas is below 20% by volume, a concentration lower than that required for carbonization using existing technologies. Using the preparation method of this invention, high-purity, lightweight pseudoboehmite can be prepared under low CO2 concentration conditions, while maintaining a CO2 capture rate of at least 50%.

[0061] According to the present invention, preferably, the mass concentration of the sodium aluminate solution, calculated as Al2O3, is 5-40 g / L, for example, 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, or any range between the two, preferably 10-40 g / L. In the present invention, sodium aluminate solution refers to a solution formed by mixing sodium aluminate with water.

[0062] According to the present invention, preferably, the ratio of the mass concentration of the sodium aluminate solution to the volume concentration of CO2 in the CO2 gas source is ≤2, more preferably 0.5-2. In the present invention, a reaction system satisfying the above-mentioned limitations can reduce side reactions and decrease the content of boehmite impurities under this preparation method.

[0063] According to the present invention, the conditions for the gelation reaction include a reaction temperature of 50-80°C, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or any range between the two, preferably 60-75°C. In the present invention, carrying out the gelation reaction under the above conditions helps to regulate the growth rate of grains on the 020 and 130 crystal planes, achieving directional growth of pseudoboehmite grains and obtaining pseudoboehmite with high specific surface area and high pore volume. The above temperature can be achieved by a hot sodium aluminate solution, a hot CO2 gas source, or by the reaction system itself.

[0064] According to the present invention, in some embodiments, the conditions for the gelation reaction include: the endpoint of the gelation reaction is a pH value of 8-10. It is understood that when the gelation reaction reaches its endpoint, the introduction of the CO2 gas source can be stopped. In the present invention, the pH value of the gelation reaction solution should not be too low, as a low pH value easily leads to the formation of gibbsite, which is difficult to remove in subsequent processes; the pH value of the gelation reaction solution should not be too high, as this easily leads to the formation of gibbsite impurities.

[0065] In this invention, the pH value of the gelation reaction solution is the pH value of the solution at the gelation reaction temperature. At a higher gelation reaction temperature, the degree of water ionization increases, and the pH value of the gelation reaction solution is lower than the pH value of the solution at room temperature.

[0066] According to the present invention, the aging conditions are not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the aging conditions include: a temperature of 60-100°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or any range between the two, preferably 80-100°C; and an aging time of 30-240 minutes, such as 30 minutes, 45 minutes, 60 minutes, 75 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes, 210 minutes, 240 minutes, or any range between the two, preferably 60-180 minutes.

[0067] According to the present invention, preferably, the gelation of the preparation method is carried out in a boehmite reaction system, the reaction system comprising: a column reactor for contacting sodium aluminate solution with a CO2 gas source to carry out the gelation reaction;

[0068] The height-to-diameter ratio of the reactor is ≥3;

[0069] The reactor is equipped with at least one porous baffle.

[0070] In this invention, the pseudo-boehmite reaction system has a simple structure and a small footprint. The porous baffle can break up bubbles, reduce bubble size, increase the gas-liquid phase contact area, and enhance mass transfer. On the other hand, the porous baffle can effectively prolong the residence time of CO2 gas in the liquid phase under high gas velocity conditions, increase gas content, and effectively improve CO2 capture rate.

[0071] According to the present invention, the air inlets are uniformly distributed on the porous partition, and the number of air inlets on each porous partition is not particularly limited. Those skilled in the art can calculate and determine the number based on the diameter of the column reactor, the aperture of the air inlets, and the spacing between the air inlets. Preferably, the number of air inlets is ≥2.

[0072] According to the present invention, preferably, the geometric center distance between any two adjacent air inlets is not less than 2.5 times their maximum diameter. The maximum diameter refers to the diameter of the larger of the two adjacent air inlets. The geometric center distance refers to the straight-line distance between the geometric centers of the corresponding air inlets. Preferably, the geometric center distance between any two adjacent air inlets is not greater than 5 times their maximum diameter.

[0073] In this invention, preferably, the diameter of each air inlet hole of the porous partition is independently 3-10 mm, for example, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or any range between the two, preferably 5-8 mm. In this invention, by setting the air inlets according to the above-mentioned preferred method, the CO2 gas source can break up bubbles, reduce bubble size, increase the gas-liquid phase contact area, and enhance mass transfer when passing through the porous partition.

[0074] In this invention, preferably, the column reactor is a multi-section column reactor. Using a multi-section column reactor can reduce the footprint of the equipment and lower production investment.

[0075] In this invention, preferably, the bottom of the reactor is further provided with an air inlet and a conical gas chamber. The air inlet is connected to the conical gas chamber, whose cross-section gradually increases upwards, and the top of the conical gas chamber is connected to the reaction chamber of the reactor. Using the above embodiment, the CO2 gas source can be fully contacted with the sodium aluminate solution, resulting in a more thorough gelation reaction.

[0076] In this invention, the cone angle of the conical air chamber is not particularly limited, as long as it achieves the purpose of this invention. Preferably, the cone angle of the conical air chamber is 50-70°.

[0077] In this invention, the height-to-diameter ratio of the column reactor is not particularly limited, and those skilled in the art can adjust it adaptably according to the number of porous baffles. Preferably, the height-to-diameter ratio of the column reactor is 4-10. In this invention, the height-to-diameter ratio refers to the ratio of the height of the column reactor to its diameter, and the reactor diameter refers to the diameter of the cross-section of the column reactor, which has a uniform cross-section. The reactor diameter is not particularly limited, and those skilled in the art can adjust it adaptably according to the reactant feed rate and the capacity of the column reactor.

[0078] According to the present invention, preferably, the porous baffle is circular. Preferably, the porous baffle is arranged perpendicular to the CO2 gas source inlet direction, the circular porous baffle is connected to the inner wall of the reactor, and the number of porous baffles is 2-5. In the present invention, the porous baffle can prolong the residence time of the CO2 gas source in the liquid phase under high gas velocity conditions, thereby improving the gas holdup and CO2 capture rate.

[0079] In this invention, preferably, the spacing between any two adjacent porous baffles satisfies the following condition: 2 times the reactor diameter ≤ spacing between porous baffles ≤ 3 times the reactor diameter. Controlling the spacing between any two adjacent porous baffles to meet the above range in this invention can improve the CO2 capture rate while ensuring uniform reaction.

[0080] In this invention, the porous baffle closest to the air inlet is located at the top of the conical air chamber where it connects to the reaction chamber. Other baffle locations are not particularly limited, as long as the spacing is sufficient.

[0081] In this invention, the column reactor is provided with a sodium aluminate inlet that communicates with the reaction chamber for adding sodium aluminate solution into the column reactor; wherein, the position of the sodium aluminate inlet on the column reactor is not particularly limited, as long as it allows the sodium aluminate solution to be added.

[0082] According to the present invention, in some embodiments, the column reactor is provided with a detection port communicating with the reaction chamber for monitoring the reaction temperature and reaction progress of the reaction system; wherein, as those skilled in the art will understand, during the gelation reaction, the reaction progress can be reflected by the pH value of the reaction system, that is, the detection port can detect the pH value.

[0083] In this invention, "reaction system" refers to the system in which the reaction takes place in the reaction chamber of the column reactor of the reaction system described in this invention, which is the gelation reaction in this invention.

[0084] According to the present invention, in some embodiments, the column reactor has an outlet communicating with the reaction chamber for removing the final reactant material obtained from the reaction system.

[0085] According to the present invention, in some embodiments, the column reactor is provided with an exhaust port communicating with the reaction chamber for the series connection of multiple reaction systems and / or the discharge of unreacted gaseous materials. When using the reaction system described in the present invention to prepare boehmite, some CO2 gas source may not be completely reacted. This embodiment can further improve the utilization rate of CO2 gas source.

[0086] According to the present invention, it is understood that when multiple reaction systems are used in series, the exhaust port of the previous reaction system is connected to the CO2 gas source inlet assembly of the next reaction system.

[0087] According to the present invention, there may still be some unreacted CO2 gas in the reaction system, which can be discharged from the exhaust port. In order to further improve the utilization rate of CO2 gas, in some embodiments, the preparation method further includes introducing the unreacted CO2 gas source discharged from the exhaust port into the corresponding reaction system through the CO2 gas source inlet assembly of the next reaction system to continue to contact with the sodium aluminate solution in the column reactor of the next reaction system for gelation reaction.

[0088] According to a preferred embodiment of the present invention, the preparation of the pseudoboehmite is carried out in... Figure 1 The reaction is carried out in the aforementioned system. Sodium aluminate solution is added to reaction chamber 2 through sodium aluminate inlet 1. CO2 gas enters reaction chamber 2 sequentially through CO2 gas inlet 3 and conical gas chamber 4. The CO2 gas breaks up air bubbles through inlet holes 6 on porous partition 5, reacting with the sodium aluminate solution to form a gel. The pH and temperature of the solution in reaction chamber 2 are monitored through detection port 7. When the pH reaches 8-10, the CO2 gas supply is stopped. Unreacted CO2 gas is discharged through exhaust port 8. The reacted slurry is transferred to an aging tank through outlet 9 for aging. The aged slurry is filtered, washed with an acidic detergent, and dried to obtain pseudoboehmite dry powder. The aging and washing apparatus is not shown in the diagram. The reaction temperature can be reached and maintained by heating through jacket 10.

[0089] In this invention, pseudoboehmite prepared by the above preparation method has a high CO2 capture rate of ≥50%.

[0090] In this invention, the CO2 capture rate is calculated using the following formula;

[0091]

[0092] The present invention provides a method for preparing pseudoboehmite, wherein, in one specific embodiment, the method includes the following steps:

[0093] (1) A CO2 gas source is subjected to a gelation reaction with a sodium aluminate solution. The gelation reaction is stopped when the pH value of the solution is 8-10, for example, 8.3-9.8. Optionally, the reaction temperature of the gelation reaction is 50℃-80℃. The ratio of the mass concentration of the sodium aluminate solution to the volume concentration of CO2 in the CO2 gas source is ≤2.

[0094] (2) The product of step (1) is aged to obtain pseudoboehmite, which is called aged pseudoboehmite; filtration;

[0095] (3) The aging product obtained after filtration, water and acidic detergent are mixed and subjected to staged acid washing to obtain low-sodium pseudoboehmite; preferably, the staged acid washing includes a first stage washing and a second stage washing; preferably, the conditions of the staged acid washing include: the pH value of the first stage washing slurry is 7-7.8, preferably 7-7.5; the pH value of the second stage washing slurry is 5-6.5, preferably 5-6.

[0096] In one embodiment, the present invention provides a pseudoboehmite, wherein the sodium oxide content in the pseudoboehmite is less than 0.1 wt%. The pseudoboehmite has a high pore volume and / or specific surface area. Optionally, the pore volume of the pseudoboehmite is 0.65-0.9 mL / g. Optionally, the specific surface area of ​​the pseudoboehmite is ≥400 m². 2 / g. Preferably, the R value of the pseudoboehmite provided by the present invention satisfies 1.3≤R≤1.6, where R=D(130) / D(020), where D(130) represents the grain size of the crystal plane represented by the 130 peak in the XRD pattern of the pseudoboehmite grain, and D(020) represents the grain size of the crystal plane represented by the 020 peak in the XRD pattern of the pseudoboehmite grain. The 130 peak refers to the peak with 2θ of 34-43° in the XRD pattern, and the 020 peak refers to the peak with 2θ of 10-15° in the XRD pattern.

[0097] In one embodiment, the present invention provides a pseudoboehmite, wherein the sodium oxide content in the pseudoboehmite is less than 0.1 wt%, and the R value of the pseudoboehmite satisfies 1.3 ≤ R ≤ 1.6, where R = D(130) / D(020), where D(130) represents the grain size of the crystal plane represented by the 130 peak in the XRD pattern of the pseudoboehmite grains, and D(020) represents the grain size of the crystal plane represented by the 020 peak in the XRD pattern of the pseudoboehmite grains. The 130 peak refers to the peak with 2θ of 34-43° in the XRD pattern, and the 020 peak refers to the peak with 2θ of 10-15° in the XRD pattern. The pore volume of the pseudoboehmite is 0.65-0.9 mL / g, and the specific surface area of ​​the pseudoboehmite is ≥400 m². 2 / g. This pseudoboehmite has a specific grain size, high specific surface area and large pore volume, and low sodium oxide content.

[0098] According to any of the above-described technical solutions of the present invention, the pseudoboehmite preferably has an R value that satisfies 1.3 ≤ R ≤ 1.6, for example, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, or any range between the two, for example, 1.4 ≤ R ≤ 1.6. In the present invention, the pseudoboehmite satisfying the above-described preferred R value range has a higher specific surface area and a larger pore volume.

[0099] In this invention, the grain size of the pseudoboehmite was determined by X-ray powder diffraction (XRD) using the RIPP 145-90 and RIPP 146-90 standard methods (see *Petrochemical Analysis Methods* (RIPP Test Methods), edited by Yang Cuiding et al., Science Press, 1990). The grain size calculation formula is as follows: (where D is the grain size, K = 1.075, λ is the wavelength of the Kα1 spectrum of the anodic radiation, β1 is the half width at half maximum of the corrected diffraction peak, and θ is the Bragg diffraction angle of the diffraction peak). The grain size of (020) is calculated as D(020) with the parameter of 2θ as the peak size of 10-15°, and the grain size of (130) is calculated as D(130) with the parameter of 2θ as the peak size of 34-43°. R = D(130) / D(020) is calculated.

[0100] In this invention, the range of values ​​for D(130) and D(020) is not particularly limited. Preferably, D(130) is 4-5 nm and D(020) is 2.5-3.5 nm.

[0101] In this invention, the pseudoboehmite described in any of the above technical solutions is preferably of high purity, and the content of alumina trihydrate impurity phase in the pseudoboehmite is less than 1 wt%, preferably free of alumina trihydrate impurity phase. The content of alumina trihydrate impurity phase in the pseudoboehmite is determined according to RIPP138-90.

[0102] According to the present invention, preferably, the pore volume of the pseudoboehmite described in any of the above technical solutions is 0.65-0.9 mL / g, for example 0.65 mL / g, 0.7 mL / g, 0.75 mL / g, 0.8 mL / g, 0.85 mL / g, 0.9 mL / g, or any range between the two.

[0103] According to the present invention, preferably, the specific surface area of ​​the pseudoboehmite described in any of the above technical solutions is 400-460 m². 2 / g, for example 400m 2 / g、405m2 / g、410m 2 / g、415m 2 / g、420m 2 / g、425m 2 / g、430m 2 / g、435m 2 / g、440m 2 / g、445m 2 / g、450m 2 / g、455m 2 / g、460m 2 / g, or any range in between.

[0104] In this invention, the specific surface area and pore volume of the pseudoboehmite were determined by the BET method using a Micromeritics ASAP 2405N V1.01 automated adsorption instrument, employing the low-temperature static nitrogen adsorption capacity method. The sample was at a surface area of ​​1.33 × 10⁻⁶. -2 The sample was degassed under vacuum at 300℃ for 4 hours using N2 as the adsorption medium, and the adsorption-desorption isotherm was measured at 77.4K. The specific surface area (SBET) of the sample was calculated according to the BET formula, and the volume of N2 adsorbed by the sample at a relative pressure p / p0 = 0.98 was measured and converted into liquid nitrogen volume, i.e., pore volume.

[0105] According to the present invention, the sodium oxide content in the pseudoboehmite is less than 0.1 wt%, preferably less than 0.07 wt%. The sodium oxide content in the pseudoboehmite is determined by X-ray fluorescence spectroscopy (XRF).

[0106] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available.

[0107] The test methods for the grain size, specific surface area, and pore volume of boehmite, the test methods for the content of trihydrate impurities and sodium oxide, and the calculation methods for CO2 capture rate are described in the aforementioned specification and will not be repeated here.

[0108] Example 1

[0109] like Figure 1 As shown, the reactor used in the embodiment has a height-to-diameter ratio of 5, a volume of 4.15L (including the conical air chamber), a cone angle of 60° in the conical air chamber, a reactor diameter of 10cm, and is equipped with 3 porous baffles. The distance between two adjacent porous baffles is twice the reactor diameter. Each porous baffle is equipped with 19 air inlets, each with a diameter of 6mm. The geometric center distance between any two adjacent air inlets is 17.5mm.

[0110] (1) A sodium aluminate solution with a mass concentration of 10 g / L (calculated as Al2O3) is added to the reaction chamber 2 through the sodium aluminate inlet 1. Hot water is introduced into the jacket to raise the solution temperature to 60°C. A CO2 gas source (CO2 volume concentration of 5%, the remainder being nitrogen) enters the reaction chamber 2 through the CO2 gas source inlet 3 and the conical gas chamber 4 in sequence. The apparent gas velocity of the CO2 gas source is 1.6 cm / s. The CO2 gas source breaks the bubbles through the gas inlet 6 on the porous partition 5 and reacts with the sodium aluminate solution to form a gel. The pH of the solution in the reaction chamber 2 is monitored through the detection port 7. The temperature of the reaction system is maintained through the jacket 10. When the pH reaches 9.8, the introduction of the CO2 gas source is stopped, and the post-reaction slurry is obtained.

[0111] (2) Unreacted CO2 gas is discharged through exhaust port 8. The slurry after reaction is transferred to the aging tank through discharge port 9 for aging. The aging temperature is controlled at 80℃ and the aging time is 120 minutes.

[0112] (3) After aging, the slurry obtained from aging is filtered, and 75°C deionized water at 14 times the mass of alumina in the sodium aluminate solution is added to the filter cake for pulping. At the same time, phosphoric acid is added to make the pH of the first washing slurry = 7.8, and the mixture is stirred for 15 min. After filtration, 75°C deionized water at 14 times the mass of alumina in the sodium aluminate solution is added to the filter cake for pulping. At the same time, phosphoric acid is added to make the pH of the second washing slurry = 6.5, and the mixture is stirred for 15 min. After filtration, the filter cake is dried at 100°C for 3 hours to obtain boehmite A1, the properties of which are shown in Table 1.

[0113] Example 2

[0114] (1) Adopt Figure 1 In the reaction system, a sodium aluminate solution with a concentration of 15 g / L (based on Al2O3) is added to the reaction chamber 2 through the sodium aluminate inlet 1. Hot water is introduced into the jacket to raise the solution temperature to 80°C. A CO2 gas source (CO2 volume concentration of 10%, with the remainder being nitrogen) enters the reaction chamber 2 sequentially through the CO2 gas source inlet 3 and the conical gas chamber 4. The apparent gas velocity of the CO2 gas source is 2.2 cm / s. The CO2 gas source breaks up the bubbles through the air inlet 6 on the porous partition 5 and reacts with the sodium aluminate solution to form a gel. The pH of the solution in the reaction chamber 2 is monitored through the detection port 7. The temperature of the reaction system is maintained by the jacket 10. When the pH reaches 9.2, the introduction of the CO2 gas source is stopped, and the reacted slurry is obtained.

[0115] (2) Unreacted CO2 gas is discharged through exhaust port 8. The slurry after reaction is transferred to the aging tank through discharge port 9 for aging. The aging temperature is controlled at 90℃ and the aging time is 180 minutes.

[0116] (3) After aging, the slurry obtained from aging is filtered, and 80°C deionized water at 14 times the mass of alumina in the sodium aluminate solution is added to the filter cake for pulping. At the same time, aluminum chloride is added to make the pH of the first washing slurry = 7.2, and the mixture is stirred for 15 min. After filtration, 80°C deionized water at 14 times the mass of alumina in the sodium aluminate solution is added to the filter cake for pulping. At the same time, hydrochloric acid is added to make the pH of the second washing slurry = 6, and the mixture is stirred for 15 min. After filtration, the filter cake is dried at 100°C for 3 hours to obtain boehmite A2, the properties of which are shown in Table 1.

[0117] Example 3

[0118] (1) Adopt Figure 1 In the reaction system, a sodium aluminate solution with a mass concentration of 30 g / L (based on Al2O3) is added to the reaction chamber 2 through the sodium aluminate inlet 1. Hot water is introduced into the jacket to raise the solution temperature to 65°C. A CO2 gas source (CO2 volume concentration of 15%, with the remainder being nitrogen) enters the reaction chamber 2 sequentially through the CO2 gas source inlet 3 and the conical gas chamber 4. The apparent gas velocity of the CO2 gas source is 2 cm / s. The CO2 gas source breaks up the bubbles through the air inlet 6 on the porous partition 5 and reacts with the sodium aluminate solution to form a gel. The pH of the solution in the reaction chamber 2 is monitored through the detection port 7. The temperature of the reaction system is maintained by the jacket 10. When the pH reaches 8.7, the introduction of the CO2 gas source is stopped, and the reacted slurry is obtained.

[0119] (2) Unreacted CO2 gas is discharged through exhaust port 8. The slurry after reaction is transferred to aging tank through discharge port 9 for aging. The aging temperature is controlled at 90℃ and the aging time is 120 minutes.

[0120] (3) After aging, the slurry obtained from aging is filtered, and 80°C deionized water at 14 times the mass of alumina in the sodium aluminate solution is added to the filter cake for slurrying. At the same time, ammonium sulfate is added to make the pH of the first washing slurry = 7.5, and the mixture is stirred for 15 min. After filtration, 80°C deionized water at 14 times the mass of alumina in the sodium aluminate solution is added to the filter cake for slurrying. At the same time, sulfuric acid is added to make the pH of the second washing slurry = 5.5, and the mixture is stirred for 15 min. After filtration, the filter cake is dried at 100°C for 3 hours to obtain boehmite powder A3, the physicochemical properties of which are shown in Table 1.

[0121] Example 4

[0122] (1) Adopt Figure 1In the reaction system, a sodium aluminate solution with a mass concentration of 35 g / L (based on Al2O3) is added to the reaction chamber 2 through the sodium aluminate inlet 1. Hot water is introduced into the jacket to raise the solution temperature to 75°C. A CO2 gas source (CO2 volume concentration of 20%, with the remainder being nitrogen) enters the reaction chamber 2 sequentially through the CO2 gas source inlet 3 and the conical gas chamber 4. The apparent gas velocity of the CO2 gas source is 1.8 cm / s. The CO2 gas source breaks up the bubbles through the air inlet 6 on the porous partition 5 and reacts with the sodium aluminate solution to form a gel. The pH of the solution in the reaction chamber 2 is monitored through the detection port 7. The temperature of the reaction system is maintained by the jacket 10. When the pH reaches 8.3, the introduction of the CO2 gas source is stopped, and the reacted slurry is obtained.

[0123] (2) Unreacted CO2 gas is discharged through exhaust port 8. The slurry after reaction is transferred to the aging tank through discharge port 9 for aging. The aging temperature is controlled at 100℃ and the aging time is 120 minutes.

[0124] (3) After aging, the slurry obtained during aging is filtered, and 75°C deionized water at 14 times the mass of alumina in the sodium aluminate solution is added to the filter cake for slurrying. Formic acid is added at the same time to make the pH of the first washing slurry = 7.8, and the mixture is stirred for 15 min. After filtration, 75°C deionized water at 14 times the mass of alumina in the sodium aluminate solution is added to the filter cake for slurrying. Formic acid is added at the same time to make the pH of the second washing slurry = 5, and the mixture is stirred for 15 min. After filtration, the filter cake is dried at 100°C for 3 min to obtain pseudoboehmite powder A4, the physicochemical properties of which are shown in Table 1.

[0125] Example 5

[0126] Boehmite was prepared according to the method in Example 3, except that after aging in step (3), the slurry was filtered, and 14 times the mass of alumina in the sodium aluminate solution was added to the filter cake at 80°C for slurrying. At the same time, ammonium sulfate was added to make the pH of the first washing slurry = 7.5, and the mixture was stirred for 10 min. Sulfuric acid was added to the slurry to make the pH of the second washing slurry = 5.5, and the mixture was stirred for 10 min. After filtration, 14 times the mass of alumina in the sodium aluminate solution was added to the filter cake at 80°C for slurrying, and the mixture was stirred for 10 min. After filtration, the filter cake was dried at 100°C for 3 hours to obtain boehmite A5, the physicochemical properties of which are shown in Table 1.

[0127] Example 6

[0128] Boehmite was prepared according to the method in Example 3, except that a water wash was added after two acid washes. The amount of deionized water added was 8 times the mass of alumina in the sodium aluminate solution used in the feed, and the temperature was 80°C. Boehmite A6 was obtained, and its physicochemical properties are shown in Table 1.

[0129] Example 7

[0130] The pseudoboehmite was prepared according to the method of Example 3, except that (3) after aging, the slurry was filtered, and 35 times the mass of alumina in the sodium aluminate solution was added to the filter cake and stirred for 10 min; filtered, 35 times the mass of alumina in the sodium aluminate solution was added to the filter cake and stirred for 10 min; filtered, 35 times the mass of alumina in the sodium aluminate solution was added to the filter cake and stirred for 10 min; filtered, 35 times the mass of alumina in the sodium aluminate solution was added to the filter cake and stirred for 10 min; filtered, and dried at 100°C for 3 hours to obtain pseudoboehmite A7, the properties of which are shown in Table 1.

[0131] Example 8

[0132] Boehmite was prepared according to the method in Example 3, with the following differences: ① During the first acid wash of this batch, the deionized water added was the filtrate obtained after the second acid wash and filtration of the previous batch. ② During the second acid wash of this batch, 20 times the mass of alumina in the sodium aluminate solution was added to the filter cake at 80°C for pulping. The washing aids and pH were kept unchanged. This further conserved water resources and achieved the recycling of wash water. Boehmite A8 was obtained, and its properties are shown in Table 1.

[0133] Comparative Example 1

[0134] Boehmite was prepared according to the method of Example 3, except that no acidic detergent was added during either washing, and the amount of water used for washing was the same as in Example 3. Boehmite D1 was obtained, and its properties are shown in Table 1.

[0135] Comparative Example 2

[0136] Boehmite was prepared according to the method in Example 3, except that no acidic washing aid was added during the first wash, and the pH of the first wash slurry was 9.0. Boehmite D2 was obtained, and its properties are shown in Table 1.

[0137] Comparative Example 3

[0138] Boehmite was prepared according to the method in Example 3, except that no acidic washing aid was added during the second wash, and the pH of the second wash slurry was 7.8. Boehmite D3 was obtained, and its properties are shown in Table 1.

[0139] Comparative Example 4

[0140] The aged pseudoboehmite prepared by the methods in steps (1) and (2) of Example 1 was filtered to obtain a filter cake. Then, according to CN109179461A, phosphoric acid was added in the first and second washes at a certain weight ratio. The scheme and results are shown in Table 2.

[0141] Table 1

[0142]

[0143] Table 2

[0144] Comparative Example 4 Experiment No. 1 2 3 First washing phosphoric acid addition amount, g phosphoric acid / Kg boehmite 2 10 6 First washing pH value 9.9 9.3 8.9 Second washing phosphoric acid addition amount, g phosphoric acid / Kg boehmite 2 20 12 Second washing pH value 9.6 7.7 8.0 First wash water / Second wash water, by weight ratio 1 1 0 (The filtrate from the second wash is used in the first wash) Washing water consumption, L / Kg of boehmite 28 28 28 <![CDATA[Na₂O in the product, wt%]]> 1.02 0.54 0.49 Pore ​​volume, mL / g 0.73 0.74 0.74 <![CDATA[specific surface area, m 2 / g]]> 438.36 443.13 446.72

[0145] Note: The washing water consumption in Tables 1 and 2 is the amount of water used to produce 1 kg of pseudoboehmite (calculated as alumina).

[0146] As can be seen from the results in Table 1, the pseudoboehmite prepared by the method of the present invention through segmented acid washing has a lower sodium oxide content and has a certain effect on increasing the pore volume of the product.

[0147] As can be seen from Tables 1 and 2, the method of the present invention can achieve better sodium removal effect with lower or the same amount of washing water, without damaging the structure of the aluminum stone.

[0148] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing low-sodium pseudoboehmite, comprising, The sodium aluminate solution is neutralized with CO2, aged, filtered to obtain a first filter cake, and washed; wherein the washing method includes: First washing: The colloidal double layer structure in the first filter cake is destroyed by the first acidic washing aid, and the second filter cake is obtained by filtration; for example, the first filter cake, water and the first acidic washing aid are mixed to form a solution with a pH of 7-7.8, and then filtered. Second washing: Contact the product of the first washing with a second acidic washing aid and filter; for example: mix the second filter cake, water and the second acidic washing aid to obtain a washing slurry, wherein the pH value of the washing slurry is 5-6.5, and filter; or add the second washing aid to a mixture of the first filter cake, water and the first washing aid that disrupts the colloidal double layer structure, wherein the pH value of the resulting mixture is optionally 5-6.5, and filter.

2. The method for preparing low-sodium pseudoboehmite according to claim 1, characterized in that, The pH value of the mixture formed by the first filter cake, water and the first acidic washing aid is preferably 7-7.5, and the temperature of the first washing is, for example, 70-90°C, preferably 75-80°C; The pH value of the washing slurry obtained by mixing the second filter cake, water, and the second washing aid is preferably 5-6. The temperature for the second washing is 70-90℃, preferably 75-80℃; Optionally, the total washing time is 30-40 minutes; optionally, the first washing takes 15-20 minutes, and the second washing takes 15-20 minutes.

3. The method for preparing low-sodium pseudoboehmite according to claim 1, characterized in that, The first acidic detergent additive and the second acidic detergent additive are each an acid and / or a salt of a strong acid and a weak base; The acid is an organic acid and / or an inorganic acid, wherein the organic acid may be selected from one or more of formic acid, acetic acid, oxalic acid, and citric acid, and the inorganic acid may be selected from one or more of sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid; preferably, the acid is selected from at least one of acetic acid, oxalic acid, citric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid. Preferably, the strong acid-weak base salt can be selected from at least one of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium dihydrogen phosphate, and aluminum chloride; Optionally, the ratio of water used in the first wash to the second wash can be 0 to 1.2:1, for example, 1:1; optionally, the first wash can be performed partially or entirely using the filtrate from the second wash. Optionally, the total water volume for the first and second washes is in a weight ratio of 20-36:1 to the boehmite content in alumina.

4. A method for preparing low-sodium pseudoboehmite, characterized in that, Includes the following steps: (1) The CO2 gas source is reacted with sodium aluminate solution to form a gel, and the gel reaction is stopped when the pH value of the solution is 8-10. Optionally, the reaction temperature of the gelation reaction is 50℃-80℃, for example, the reaction temperature is 60-75℃; the ratio of the mass concentration of the sodium aluminate solution to the volume concentration of CO2 in the CO2 gas source is ≤2, preferably 0.5-2; Preferably, the volume concentration of CO2 in the CO2 gas source is not greater than 20%, and more preferably 5-20%. Preferably, the mass concentration of the sodium aluminate solution, calculated as Al2O3, is 5-40 g / L, and more preferably 10-40 g / L. (2) Aging the reaction product obtained in step (1); Preferably, the aging conditions include: a temperature of 60-100℃, for example, 80-100℃, and an aging time of 30-240 minutes, for example, 60-180 minutes; (3) Filter and wash the aging product from step (2), wherein the washing results in a sodium oxide content of no more than 0.1% by weight in the obtained boehmite.

5. The method for preparing low-sodium pseudoboehmite according to claim 4, characterized in that, The apparent gas velocity of the CO2 gas source is 0.6-12 cm / s; Preferably, the low-concentration CO2 gas is obtained by blending high-concentration CO2 gas and / or comes from industrial flue gas.

6. The method for preparing low-sodium pseudoboehmite according to claim 4, characterized in that, The gelation reaction between CO2 gas source and sodium aluminate solution was carried out in a column reactor; The height-to-diameter ratio of the column reactor is ≥3; the interior of the column reactor is provided with at least one porous baffle. The porous partition is also provided with at least one air inlet hole; the diameter of each air inlet hole of the porous partition is 3-10mm.

7. The method for preparing low-sodium boehmite according to claim 6, wherein, The column reactor is a multi-section column reactor; Preferably, the bottom of the column reactor is further provided with an air inlet and a conical air chamber; preferably, the cone angle of the conical air chamber is 50-70°; preferably, the height-to-diameter ratio of the column reactor is 4-10; preferably, the porous baffle is circular; preferably, the number of porous baffles is 2-5. Preferably, the spacing between any two adjacent porous baffles satisfies the following condition: 2 times the reactor diameter ≤ spacing between porous baffles ≤ 3 times the reactor diameter.

8. The method for preparing low-sodium boehmite according to claim 7, wherein, The number of air inlets is ≥2; Preferably, the diameter of each air inlet hole in the porous partition is 5-8 mm. Preferably, the distance between the geometric centers of any two adjacent air inlets is not less than 2.5 times their maximum diameter.

9. The method for preparing low-sodium boehmite according to claim 4, wherein, The washing method is the washing method described in any one of claims 1 to 3.

10. A pseudoboehmite, characterized in that, The pseudoboehmite has less than 0.1% sodium oxide by mass and has a high pore volume and / or a high specific surface area.

11. A pseudoboehmite, characterized in that, The sodium oxide content of the pseudoboehmite is less than 0.1% by mass, and the R value of the pseudoboehmite satisfies 1.3 ≤ R ≤ 1.6, where R = D(130) / D(020), where D(130) represents the grain size of the crystal plane represented by the 130 peak in the XRD pattern of the pseudoboehmite grain, and D(020) represents the grain size of the crystal plane represented by the 020 peak in the XRD pattern of the pseudoboehmite grain. The 130 peak refers to the peak with 2θ of 34-43° in the XRD pattern, and the 020 peak refers to the peak with 2θ of 10-15° in the XRD pattern.

12. The pseudoboehmite according to claim 10 or 11, characterized in that, The R value of the pseudoboehmite satisfies 1.4≤R≤1.

6.

13. The low-sodium pseudoboehmite according to any one of claims 10-12, characterized in that, The pore volume of the pseudoboehmite is 0.65-0.9 mL / g, and the specific surface area of ​​the pseudoboehmite is optionally ≥400 m². 2 / g for example 400-460m 2 / g such as 410-460m 2 / g, wherein the content of alumina trihydrate heterocrystalline phase in the pseudoboehmite is less than 1wt%; preferably, D(130) is 4-5nm and D(020) is 2.5-3.5nm.

14. The use of boehmite according to any one of claims 10-13 in the fields of catalysts, adsorbents, or electronic ceramics.

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