Pseudo-boehmite and preparation method thereof

Abstract

The invention relates to pseudo-boehmite and a preparation method thereof, and belongs to the technical field of porous alumina preparation. The method comprises the following steps: carrying out neutralization reaction on aluminum sulfate and an alkali source to obtain pseudo-boehmite colloidal particle slurry; aging the pseudo-boehmite colloidal particle slurry to obtain aged slurry with a set pH value; carrying out solid-liquid separation on the aged slurry to obtain a solid-phase substance; and washing the solid-phase substance for multiple times by using an alkaline solution containing ammonium ions so as to remove sulfate radicals carried by the solid-phase substance, thereby obtaining the pseudo-boehmite. Through the synergistic effect of the aging slurry with the set pH value and the alkaline solution containing ammonium ions, the content of sulfate radicals in the pseudo-boehmite is specifically reduced.

Description

Technical Field

[0001] The present application relates to the technical field of porous alumina preparation, and in particular to pseudo-boehmite and a preparation method thereof. Background Art

[0002] For the catalyst carrier of hydrogenation reaction and the catalyst matrix of catalytic cracking reaction, alumina with a developed pore structure, especially a larger pore volume, is of great significance for promoting the mass transfer of macromolecules and improving the reaction performance.

[0003] At present, the aluminum sulfate-alkaline material neutralization method is often used to prepare porous alumina pseudo-boehmite. However, how to effectively remove sulfate in the product obtained by the neutralization method is an important problem that troubles basic research and production and life participants. The residual sulfate is to a certain extent not conducive to environmental safety, product indicators and catalytic performance. Therefore, how to effectively reduce the sulfate in the obtained product on the basis of having little impact on the pore structure of pseudo-boehmite is of great significance for the green preparation of pseudo-boehmite suitable for different catalytic reactions such as hydrogenation and dehydrogenation. Summary of the invention

[0004] The present application provides a pseudo-boehmite and a preparation method thereof to solve the following technical problem: how to reduce the sulfate content in the pseudo-boehmite.

[0005] In a first aspect, the present application provides a method for preparing pseudo-boehmite, the method comprising:

[0006] Aluminum sulfate and an alkali source are subjected to a neutralization reaction to obtain a pseudo-boehmite colloid particle slurry;

[0007] Aging the pseudo-boehmite colloid particle slurry to obtain an aged slurry with a set pH value;

[0008] Performing solid-liquid separation on the aged slurry to obtain a solid phase substance;

[0009] The solid phase material is washed multiple times with an alkaline solution containing ammonium ions to remove sulfate groups carried by the solid phase material, thereby obtaining pseudo-boehmite.

[0010] Optionally, the set pH value is 5.5-8.5.

[0011] Optionally, the alkaline solution containing ammonium ions includes at least one of the following: ammonium carbonate and ammonium bicarbonate.

[0012] Optionally, the mass concentration of the alkaline solution containing ammonium ions is 0.1% to 2%.

[0013] Optionally, the temperatures of the neutralization reaction, the aging and the washing are respectively 45° C. to 95° C.

[0014] Optionally, the number of washing times is ≥2.

[0015] Optionally, the volume of the alkaline solution containing ammonium ions is the same as the volume of the liquid phase of the aged slurry.

[0016] Optionally, the aluminum oxide content in the neutralization reaction system is 90 g / L to 110 g / L.

[0017] Optionally, the pseudo-boehmite meets the following indicators: the specific surface area of ​​alumina is 301.9 m 2 / g~380.0m 2 / g, the pore volume is 0.75ml / g~1.10ml / g, and the sulfate content is ≤2.0wt%.

[0018] In a second aspect, the present application provides a pseudo-boehmite, wherein the pseudo-boehmite is prepared by any method described in the first aspect.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0020] The preparation method of the pseudo-boehmite provided in an embodiment of the present application comprises: neutralizing aluminum sulfate and an alkali source to obtain a pseudo-boehmite colloid slurry; aging the pseudo-boehmite colloid slurry to obtain an aged slurry with a set pH value; performing solid-liquid separation on the aged slurry to obtain a solid phase substance; washing the solid phase substance multiple times with an alkaline solution containing ammonium ions to remove sulfate carried by the solid phase substance to obtain pseudo-boehmite. Aluminum sulfate and an alkali source are subjected to a neutralization reaction to obtain a pseudo-boehmite colloid particle slurry; the pseudo-boehmite colloid particle slurry is aged to obtain an aged slurry with a set pH value; the set pH value can regulate the charged properties (negative charge) of the pseudo-boehmite colloid particles on the basis of protecting the structure of the pseudo-boehmite pores, so that the pseudo-boehmite colloid particles and sulfate ions (positive charge) repel each other, thereby improving the subsequent washing effect; the aged slurry is subjected to solid-liquid separation to obtain a solid phase material; an alkaline solution containing ammonium ions can fully remove the sulfate carried by the solid phase material, and will not cause the formation of impurities in the pseudo-boehmite, the destruction of the pore structure, and the introduction of additional difficult-to-handle impurities, thereby reducing the sulfate content in the pseudo-boehmite. Therefore, the synergistic effect of the aged slurry with a set pH value and the alkaline solution containing ammonium ions specifically reduces the sulfate content in the pseudo-boehmite. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 A schematic flow chart of a method for preparing pseudo-boehmite provided in an embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0025] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0026] In the present application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "include", "comprise", etc. refer to "including but not limited to". In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple, respectively.

[0027] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0028] In a first aspect, the present application provides a method for preparing pseudo-boehmite. Figure 1 A schematic diagram of a preparation method of pseudo-boehmite provided in the embodiment of the present application; see Figure 1 , the method comprising:

[0029] S1, neutralizing aluminum sulfate and an alkali source to obtain a pseudo-boehmite colloid slurry;

[0030] In some embodiments, the content of aluminum oxide in the neutralization reaction system is 90 g / L to 110 g / L.

[0031] In the embodiment of the present application, the content of alumina in the system of the neutralization reaction is 90g / L to 110g / L. By regulating the content of alumina in the system of the neutralization reaction, the neutralization system can be prevented from being over-acidic or over-alkaline. Exemplarily, the content of alumina in the system of the neutralization reaction can be 90g / L, 92g / L, 94g / L, 96g / L, 98g / L, 100g / L, 102g / L, 104g / L, 106g / L, 108g / L, 110g / L, etc. In addition, the alkali source can be one of sodium aluminate, sodium hydroxide, and ammonia water. Generally speaking, the sodium aluminate-aluminum sulfate double aluminum method is commonly used to prepare pseudo-boehmite. Exemplarily, the alumina in the sodium aluminate and aluminum sulfate can be 45g / L to 55g / L, respectively. Pseudoboehmite, also known as pseudo-monohydrate soft boehmite, is an important inorganic chemical product. Crystal structure: Pseudoboehmite has a crystal structure similar to that of boehmite and belongs to the orthorhombic system. In its crystal structure, aluminum atoms and oxygen atoms interact through covalent bonds and hydrogen bonds to form a layered structure. It is usually a white or light yellow powder with a large specific surface area, a large pore volume, and a narrow pore size distribution. Chemical properties: Pseudoboehmite has a certain chemical stability, but it will react chemically in strong corrosive media such as strong acids and alkalis. It will undergo a series of changes such as dehydration during heating, and gradually transform into other aluminum oxide phases such as γ-alumina. This thermal stability and phase change characteristics are of great significance for its application in high-temperature reactions.

[0032] S2, aging the pseudo-boehmite colloid slurry to obtain an aged slurry with a set pH value;

[0033] In some embodiments, the set pH value is 5.5-8.5.

[0034] In the embodiment of the present application, the pseudo-boehmite colloid slurry is aged to obtain an aging solution with a set pH value. The set pH value of 5.5 to 8.5 can regulate the charged properties (negatively charged) of the pseudo-boehmite colloid particles on the basis of protecting the structure of the pseudo-boehmite pores, so that the pseudo-boehmite colloid particles and sulfate ions (positively charged) repel each other, thereby improving the subsequent washing effect. If the set pH value is higher than 8.5, it may lead to an increase in the content of gibbsite in the pseudo-boehmite colloid slurry and reduce the pore volume and specific surface area of ​​the product; if the set pH value is lower than 5.5, it may lead to a decrease in the crystallinity and grain size of the subsequent product, and the formed grains are not only positively charged but also very easy to wrap the mother liquor and inhibit the removal of sulfate; and the product has a worse pore structure, and the residual sulfate further reduces the pore volume and specific surface area of ​​the product. Exemplarily, the set pH value can be 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.8, 6.9, 7.0, 7.1, 7.2, 7.2, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, etc. The neutralization reaction and aging can be achieved in a one-pot process, so the ratio of the aluminum sulfate and the alkali source determines the set pH value.

[0035] S3, performing solid-liquid separation on the aged slurry to obtain a solid phase substance;

[0036] S4. Washing the solid phase material multiple times with an alkaline solution containing ammonium ions to remove sulfate ions carried by the solid phase material to obtain pseudo-boehmite.

[0037] In an embodiment of the present application, the solid phase obtained by solid-liquid separation of the aged slurry is washed multiple times with an alkaline solution containing ammonium ions, which can fully remove the sulfate carried by the solid phase without causing the formation of impurities in the pseudo-boehmite, destroying the pore structure, and introducing additional difficult-to-handle impurities, thereby reducing the sulfate content in the pseudo-boehmite.

[0038] In some embodiments, the alkaline solution containing ammonium ions includes at least one of the following: ammonium carbonate and ammonium bicarbonate.

[0039] In the embodiment of the present application, when the product is a porous alumina suitable for catalytic reaction rather than metallurgical grade alumina, it is difficult to meet the requirements by selecting a strong base or introducing an auxiliary agent for a new cation. On the other hand, although the pH (set pH value) of the aging endpoint can be used to regulate the pH of the aging endpoint in the process of the aluminum sulfate-sodium aluminate (alkaline material) neutralization method, however, when the obtained product is required to be pseudo-boehmite and have a developed pore structure, the regulation effect of neutralization-aging alone is poor. This is because increasing the pH by increasing the proportion of the alkali source can easily lead to an increase in the content of gibbsite, and the pore volume and specific surface area of ​​the product are reduced. Therefore, the sulfate of the product is removed in a targeted manner through the synergistic effect of an alkaline solution containing ammonium ions and a set pH value, and it will not cause the formation of miscellaneous crystals, the destruction of the pore structure, and the additional introduction of difficult-to-handle impurities. Therefore, an alkaline solution containing ammonium ions is selected, that is, the pH of the neutralization reaction endpoint and the pH of the washing system are coordinated to regulate the sulfate content in the macroporous pseudo-boehmite. At the same time, when considering the environmental health issues of ammonia nitrogen wastewater discharge and actual operation, when and only when an appropriate amount of ammonium carbonate or ammonium bicarbonate meets the requirements. The alkaline solution containing ammonium ions can be one or both of ammonium carbonate and ammonium bicarbonate. The alkaline solution containing ammonium ions is used as a washing liquid. In order to reduce the discharge of ammonia nitrogen wastewater as much as possible, the set pH value of the above-mentioned pseudo-boehmite colloid slurry and the synergistic effect of multiple washings with the alkaline solution containing ammonium ions are used to achieve the alkaline solution containing ammonium ions to fully remove sulfate carried by the solid phase material, so that the pseudo-boehmite is subsequently released as a small amount of ammonia and carbon dioxide in the process of preparing alumina through a roasting process, thereby not affecting the performance of alumina.

[0040] In some embodiments, the mass concentration of the alkaline solution containing ammonium ions is 0.1% to 2%.

[0041] In the embodiment of the present application, the mass concentration of the alkaline solution containing ammonium ions can be 0.1% to 2%, which can fully remove the sulfate carried by the solid phase and reduce the discharge of ammonia nitrogen wastewater. Exemplarily, the mass concentration of the alkaline solution containing ammonium ions can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, etc.

[0042] In some embodiments, the temperatures of the neutralization reaction, the aging, and the washing are respectively 45° C. to 95° C.

[0043] In the embodiment of the present application, the temperature of the neutralization reaction can be 45°C to 95°C, and uniform pseudo-boehmite colloid particles can be formed. Exemplarily, the temperature of the neutralization reaction can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc. The neutralization time can be 30min to 40min, and the endpoint pH of the neutralization reaction can be 8 to 9.

[0044] The aging temperature can be 45°C to 95°C, so that the particle size of the pseudo-boehmite colloid particles grows appropriately. For example, the aging temperature can be 45°C, 50°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc. The aging time can be 2h to 5h.

[0045] The washing temperature can be 45° C. to 95° C., which can improve the efficiency of removing sulfate radicals carried by the solid phase. Exemplarily, the washing temperature can be 45° C., 50° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., 95° C., etc.

[0046] In some embodiments, the number of washes is ≥2.

[0047] In some embodiments, the volume of the alkaline solution containing ammonium ions is the same as the volume of the liquid phase of the aged slurry.

[0048] In the embodiment of the present application, the number of washings is ≥2, and the washing temperature matches the number of washings to further promote the washing effect on sulfate, and the sulfate of the product is regulated according to the number of washings. Exemplarily, the number of washings can be 2, 3, 4, etc. The volume of the alkaline solution containing ammonium ions can be the same as the volume of the liquid phase of the aged slurry with a set pH value, which can reduce the waste of the alkaline solution containing ammonium ions and avoid the introduction of impurities, and the finished product is obtained by drying after multiple washings.

[0049] In some embodiments, the pseudo-boehmite meets the following indicators: the specific surface area of ​​alumina is 301.9 m 2 / g~380.0m 2 / g, the pore volume is 0.75ml / g~1.10ml / g, and the sulfate content is ≤2.0wt%.

[0050] In the examples of the present application, the pseudo-boehmite prepared by the above method can effectively reduce the sulfate in the obtained product on the basis of having little effect on the pore structure, meeting the index: 301.9m 2 / g~380.0m 2 / g, pore volume is 0.75ml / g~1.10ml / g, sulfate content is ≤2.0wt%

[0051] In summary, the preparation method of pseudo-boehmite provided in this application has the following advantages:

[0052] 1. Neutralization reaction steps

[0053] Reaction principle and product: Aluminum sulfate and an alkali source are used to neutralize to prepare pseudo-boehmite colloidal slurry. In this process, the two interact with each other to produce a chemical reaction. The acid-base neutralization causes the aluminum element to exist in the solution in a specific chemical form, and then gradually aggregates into pseudo-boehmite colloidal particles to form colloidal slurry. This is the starting link of the entire preparation process, laying the foundation for the subsequent generation of high-quality pseudo-boehmite.

[0054] 2. Aging Steps

[0055] Key influence of pH value: The pH value at the end of aging (setting pH value) plays many important roles. It can regulate the particle size of the pseudo-boehmite colloid slurry, and more importantly, it can not only play an active role in protecting the structure of the pseudo-boehmite pores to prevent the pore structure from being destroyed by chemical reactions or physical changes, but also regulate the charge properties of the pseudo-boehmite colloid particles to make them negatively charged. This change in charge property is of great significance, because sulfate ions are positively charged, and based on the principle of like charges repel each other, there is a repulsive effect between the colloid particles and the sulfate ions, which creates favorable conditions for more effective removal of sulfate ions in the subsequent washing process, thereby improving the washing effect and efficiency.

[0056] 3. Solid-liquid separation and washing steps

[0057] The significance of solid-liquid separation: The purpose of solid-liquid separation of aged slurry is to separate pseudo-boehmite from the solution containing other impurity ions in the form of solid phase to achieve preliminary purification. The quality of this step, such as whether the separation is thorough, will directly affect the workload of subsequent washing and the purity of the final pseudo-boehmite product.

[0058] Washing process and advantages: Using alkaline solution containing ammonium ions to wash the solid phase material multiple times is the key operation to remove sulfate impurities in the entire preparation method. Alkaline solution containing ammonium ions has unique chemical property advantages. On the one hand, it can react chemically with sulfate carried in the solid phase material, such as generating soluble sulfate, etc., thereby achieving the removal of sulfate; on the other hand, this solution will not have adverse effects on the pseudo-boehmite itself during the washing process, and will not induce the formation of impurity crystals, which means that no new impurity phases will be introduced, ensuring the purity and crystal quality of the pseudo-boehmite product, and at the same time will not destroy the pore structure of the pseudo-boehmite, maintaining its good physical properties, and will not introduce additional difficult-to-handle impurities, making the impurity control of the entire preparation process more accurate and effective, and ultimately significantly reducing the sulfate content in the pseudo-boehmite.

[0059] 4. Summary of synergy

[0060] The aged slurry with a set pH value and the alkaline solution containing ammonium ions have a close synergistic effect throughout the preparation process. The specific pH value of the aged slurry creates favorable conditions for subsequent washing, making it easier for sulfate ions to detach from the pseudo-boehmite particles; while the alkaline solution containing ammonium ions, with its appropriate chemical properties, actually removes these free sulfate ions. The two complement each other and specifically reduce the sulfate content in the pseudo-boehmite from multiple aspects such as chemistry and physics, and jointly ensure that the prepared pseudo-boehmite product has high quality and purity that meets the requirements of specific application scenarios.

[0061] In summary, the preparation method of pseudo-boehmite achieves efficient preparation of high-quality pseudo-boehmite and effective control of sulfate impurity content by rationally and orderly setting of each step and effectively controlling key factors, making full use of the synergistic effect between various links.

[0062] In a second aspect, the present application provides a pseudo-boehmite, wherein the pseudo-boehmite is prepared by any method described in the first aspect.

[0063] The pseudo-boehmite is realized based on the preparation method of the pseudo-boehmite mentioned above. The specific steps of the preparation method of the pseudo-boehmite can refer to the above embodiment. Since the pseudo-boehmite adopts part or all of the technical solutions of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment, which will not be described one by one here.

[0064] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for the unrecorded specific conditions in the following examples are usually measured according to national standards. If there is no corresponding national standard, then carry out according to general international standards, normal conditions or according to the conditions recommended by the manufacturer.

[0065] Example 1

[0066] A method for preparing pseudo-boehmite, comprising:

[0067] The sodium aluminate and aluminum sulfate are subjected to a neutralization reaction to obtain a pseudo-boehmite colloidal particle slurry; wherein the aluminum oxide content of the sodium aluminate is 45 g / L, the aluminum oxide content of the aluminum sulfate is 55 g / L, and the neutralization reaction temperature is 45°C;

[0068] Aging the pseudo-boehmite colloidal particle slurry to obtain an aged slurry with a set pH value; wherein the aging temperature is 45° C., the aging time is 2 h, and the set pH value is 8.5;

[0069] The aged slurry is subjected to solid-liquid separation to obtain a solid phase substance;

[0070] The solid phase material is washed multiple times with an alkaline solution containing ammonium ions to obtain pseudo-boehmite; the alkaline solution containing ammonium ions is an ammonium carbonate solution, and the mass concentration of the ammonium carbonate solution is 0.1%; the washing temperature is 45°C; the number of washings is 2 times; the volume of the alkaline solution containing ammonium ions is the same as the volume of the liquid phase of the aged slurry.

[0071] Pseudo-boehmite index: specific surface area is 301.9m 2 / g, pore volume is 0.75ml / g, sulfate content is 1.59wt%, and ammonium ion content in the washing liquid is 27mg / L.

[0072] Example 2

[0073] A method for preparing pseudo-boehmite, comprising:

[0074] The sodium aluminate and aluminum sulfate are subjected to a neutralization reaction to obtain a pseudo-boehmite colloidal particle slurry; wherein the aluminum oxide content of the sodium aluminate is 47 g / L, the aluminum oxide content of the aluminum sulfate is 52 g / L, and the neutralization reaction temperature is 55°C;

[0075] Aging the pseudo-boehmite colloid slurry to obtain an aged slurry with a set pH value; wherein the aging temperature is 55° C., the aging time is 2.5 h, and the set pH value is 7.5;

[0076] The aged slurry is subjected to solid-liquid separation to obtain a solid phase substance;

[0077] The solid phase material is washed multiple times with an alkaline solution containing ammonium ions to obtain pseudo-boehmite; the alkaline solution containing ammonium ions is an ammonium carbonate solution, and the mass concentration of the ammonium carbonate solution is 0.25%; the temperature of the neutralization reaction, aging and washing is 55°C respectively; the number of washings is 3 times; the volume of the alkaline solution containing ammonium ions is the same as the volume of the liquid phase of the aged slurry.

[0078] Pseudo-boehmite index: specific surface area is 333.6m 2 / g, pore volume is 1.03ml / g, sulfate content is 1.63wt%, and ammonium ion content in the washing liquid is 68mg / L.

[0079] Example 3

[0080] A method for preparing pseudo-boehmite, comprising:

[0081] The sodium aluminate and aluminum sulfate are subjected to a neutralization reaction to obtain a pseudo-boehmite colloidal particle slurry; wherein the aluminum oxide content of the sodium aluminate is 50 g / L, the aluminum oxide content of the aluminum sulfate is 50 g / L, and the neutralization reaction temperature is 65°C;

[0082] Aging the pseudo-boehmite colloid slurry to obtain an aged slurry with a set pH value; wherein the aging temperature is 65° C., the aging time is 3 h, and the set pH value is 6.5;

[0083] The aged slurry is subjected to solid-liquid separation to obtain a solid phase substance;

[0084] The solid phase material is washed multiple times with an alkaline solution containing ammonium ions to obtain pseudo-boehmite; the alkaline solution containing ammonium ions is an ammonium carbonate solution, and the mass concentration of the ammonium carbonate solution is 0.5%; the washing temperature is 65°C; the number of washings is 3 times; the volume of the alkaline solution containing ammonium ions is the same as the volume of the liquid phase of the aged slurry.

[0085] Pseudo-boehmite index: specific surface area is 346.8m 2 / g, pore volume is 1.10ml / g, sulfate content is 1.88wt%, and ammonium ion content in the washing liquid is 121mg / L.

[0086] Example 4

[0087] A method for preparing pseudo-boehmite, comprising:

[0088] The sodium aluminate and aluminum sulfate are subjected to a neutralization reaction to obtain a pseudo-boehmite colloidal particle slurry; wherein the aluminum oxide content of the sodium aluminate is 53 g / L, the aluminum oxide content of the aluminum sulfate is 48 g / L, and the neutralization reaction temperature is 75°C;

[0089] Aging the pseudo-boehmite colloidal particle slurry to obtain an aged slurry with a set pH value; wherein the aging temperature is 75° C., the aging time is 3.5 h, and the set pH value is 5.5;

[0090] The aged slurry is subjected to solid-liquid separation to obtain a solid phase substance;

[0091] The solid phase material is washed multiple times with an alkaline solution containing ammonium ions to obtain pseudo-boehmite; the alkaline solution containing ammonium ions is an ammonium carbonate solution, and the mass concentration of the ammonium carbonate solution is 1%; the washing temperature is 75°C; the washing times are 2 times; the volume of the alkaline solution containing ammonium ions is the same as the volume of the liquid phase of the aged slurry.

[0092] Pseudo-boehmite index: specific surface area is 329.5m 2 / g, pore volume is 0.83ml / g, sulfate content is 1.82wt%, and ammonium ion content in the washing liquid is 179mg / L.

[0093] Example 5

[0094] A method for preparing pseudo-boehmite, comprising:

[0095] The sodium aluminate and aluminum sulfate are subjected to a neutralization reaction to obtain a pseudo-boehmite colloidal particle slurry; wherein the aluminum oxide content of the sodium aluminate is 55 g / L, the aluminum oxide content of the aluminum sulfate is 45 g / L, and the neutralization reaction temperature is 85°C;

[0096] Aging the pseudo-boehmite colloid slurry to obtain an aged slurry with a set pH value; wherein the aging temperature is 85° C., the aging time is 4 hours, and the set pH value is 6.0;

[0097] The aged slurry is subjected to solid-liquid separation to obtain a solid phase substance;

[0098] The solid phase material is washed multiple times with an alkaline solution containing ammonium ions to obtain pseudo-boehmite; the alkaline solution containing ammonium ions is an ammonium carbonate solution, and the mass concentration of the ammonium carbonate solution is 1.5%; the washing temperature is 85°C; the washing times are 2 times; the volume of the alkaline solution containing ammonium ions can be the same as the volume of the liquid phase of the aged slurry.

[0099] Pseudo-boehmite index: specific surface area is 371.4m 2 / g, pore volume is 0.95ml / g, sulfate content is 1.51wt%, and ammonium ion content in the washing liquid is 226mg / L.

[0100] Example 6

[0101] A method for preparing pseudo-boehmite, comprising:

[0102] The sodium aluminate and aluminum sulfate are subjected to a neutralization reaction to obtain a pseudo-boehmite colloidal particle slurry; wherein the aluminum oxide content of the sodium aluminate is 55 g / L, the aluminum oxide content of the aluminum sulfate is 55 g / L, and the neutralization reaction temperature is 95°C;

[0103] Aging the pseudo-boehmite colloidal particle slurry to obtain an aged slurry with a set pH value; wherein the aging temperature is 95° C., the aging time is 5 h, and the set pH value is 8.0;

[0104] The aged slurry is subjected to solid-liquid separation to obtain a solid phase substance;

[0105] The solid phase material is washed multiple times with an alkaline solution containing ammonium ions to obtain pseudo-boehmite; the alkaline solution containing ammonium ions is an ammonium carbonate solution, and the mass concentration of the ammonium carbonate solution is 2%; the washing temperature is 95°C; the washing times are 2 times; the volume of the alkaline solution containing ammonium ions is the same as the volume of the liquid phase of the aged slurry.

[0106] Pseudo-boehmite index: specific surface area is 380.0m 2 / g, pore volume is 1.10ml / g, sulfate content is 1.63wt%, and ammonium ion content in the washing liquid is 253mg / L.

[0107] Comparative Example 1

[0108] A method for preparing pseudo-boehmite, comprising:

[0109] The sodium aluminate and aluminum sulfate are subjected to a neutralization reaction to obtain a pseudo-boehmite colloidal particle slurry; wherein the aluminum oxide content of the sodium aluminate is 45 g / L, the aluminum oxide content of the aluminum sulfate is 45 g / L, and the neutralization reaction temperature is 55° C.;

[0110] Aging the pseudo-boehmite colloid slurry to obtain an aged slurry with a set pH value; wherein the aging temperature is 55° C., the aging time is 4 hours, and the set pH value is 8.0;

[0111] The aged slurry is subjected to solid-liquid separation to obtain a solid phase substance;

[0112] The solid phase material was statically washed for several times (the filter cake was left to stand with washing water flowing continuously) to obtain pseudo-boehmite. The number of static washings was 3.

[0113] Pseudo-boehmite index: specific surface area is 238.1m 2 / g, the pore volume is 0.54 ml / g, and the sulfate content is 11.99 wt%.

[0114] Comparative Example 2

[0115] A method for preparing pseudo-boehmite, comprising:

[0116] The sodium aluminate and aluminum sulfate are subjected to a neutralization reaction to obtain a pseudo-boehmite colloidal particle slurry; wherein the aluminum oxide content of the sodium aluminate is 55 g / L, the aluminum oxide content of the aluminum sulfate is 55 g / L, and the neutralization reaction temperature is 95°C;

[0117] Aging the pseudo-boehmite colloidal particle slurry to obtain an aged slurry with a set pH value; wherein the aging temperature is 95° C., the aging time is 5 h, and the set pH value is 8.0;

[0118] The aged slurry is subjected to solid-liquid separation to obtain a solid phase substance;

[0119] The solid phase material is washed multiple times with an alkaline solution containing ammonium ions to obtain pseudo-boehmite; the alkaline solution containing ammonium ions is an ammonium carbonate solution, the mass concentration of the ammonium bicarbonate solution is 5%, and the washing times are 5 times.

[0120] Pseudo-boehmite index: specific surface area is 283.7m 2 / g, the pore volume is 0.76ml / g, the sulfate content is 1.5wt%, and the ammonium ion content in the washing liquid is 2770mg / L.

[0121] From Examples 1 to 6, it can be seen that the specific surface area of ​​alumina is 301.9 m 2 / g~380.0m 2 / g, pore volume is 0.75ml / g~1.10ml / g, sulfate content is ≤2.0wt%; ammonium ion content in washing liquid is 27mg / L~253mg / L, which can reduce the discharge pressure of ammonia nitrogen wastewater. The disadvantages of comparative example 1: the sulfate content of the material without alkaline auxiliary agent washing is significantly increased; the disadvantages of comparative example 2: the material without multiple solid-liquid separation-pulping process needs to be washed multiple times, and the ammonium content in the washing liquid is significantly exceeded.

[0122] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0123] (1) The present application is a method for preparing low-sulfate porous alumina suitable for catalytic reactions. The pseudo-boehmite meets the following indicators: the specific surface area of ​​alumina is 301.9 m 2 / g~380.0m 2 / g, pore volume is 0.75ml / g~1.10ml / g, sulfate content is ≤2.0wt%;

[0124] (2) The embodiment of the present application combines the synergistic effect of the end point pH after aging and the alkaline solution containing ammonium ions, removes sulfate while retaining the porous structure of porous alumina as much as possible, and at the same time, maximizes the utilization of the alkaline solution containing ammonium ions by coordinating the two pH values;

[0125] (3) While avoiding the problem of ammonia nitrogen wastewater discharge in actual production, the preparation method provided by the present invention has the advantages of being green and economical, simple to operate, using industrial raw materials, and being suitable for industrial production.

[0126] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing pseudo-boehmite, the method comprising: Aluminum sulfate and an alkali source are subjected to a neutralization reaction to obtain a pseudo-boehmite colloid particle slurry; Aging the pseudo-boehmite colloid particle slurry to obtain an aged slurry with a set pH value; Performing solid-liquid separation on the aged slurry to obtain a solid phase substance; The solid phase material is washed multiple times with an alkaline solution containing ammonium ions to remove sulfate groups carried by the solid phase material, thereby obtaining pseudo-boehmite.

2. The method according to claim 1, characterized in that The set pH value is 5.5-8.

5.

3. The method according to claim 1, characterized in that The alkaline solution containing ammonium ions includes at least one of the following: ammonium carbonate and ammonium bicarbonate.

4. The method according to claim 1 or 3, characterized in that: The mass concentration of the alkaline solution containing ammonium ions is 0.1% to 2%.

5. The method according to claim 1, characterized in that The temperatures of the neutralization reaction, the aging and the washing are 45° C. to 95° C. respectively.

6. The method according to claim 1, characterized in that The number of washings is ≥2.

7. The method according to claim 1, characterized in that The volume of the alkaline solution containing ammonium ions is the same as the volume of the liquid phase of the aged slurry.

8. The method according to claim 1, characterized in that The aluminum oxide content in the neutralization reaction system is 90 g / L to 110 g / L.

9. The method according to claim 1, characterized in that: The pseudo-boehmite meets the following indicators: the specific surface area of ​​alumina is 301.9 m 2 / g~380.0m 2 / g, the pore volume is 0.75ml / g~1.10ml / g, and the sulfate content is ≤2.0wt%.

10. Pseudo-boehmite, wherein the pseudo-boehmite is prepared by the method according to any one of claims 1 to 9.

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