Bayer stone as well as preparation method and application thereof

Abstract

The invention relates to Bayer stone as well as a preparation method and application thereof, and belongs to the technical field of preparation of aluminum oxide or aluminum oxide precursor materials. The method comprises the following steps: mixing a Bayer stone seed crystal with an acidic aluminum source to obtain a first mixed solution; carrying out a neutralization reaction on the first mixed solution and sodium metaaluminate, and controlling the end point pH of the neutralization reaction to generate Alx (H2O) y (OH) mn < + > small clusters, so as to obtain a second mixed solution; and aging the second mixed solution at a set temperature, so that the Alx (H2O) y (OH) mn < + > small clusters are converted into a Bayer stone phase, and Bayer stone is obtained. The Bayer stone prepared by the invention meets the following indexes: the specific surface area is 325.3 m < 2 > / g to 382.3 m < 2 > / g, and the crystalline phase weight of the Bayer stone is 91.2 to 97.2 percent.

Description

Technical Field

[0001] The present application relates to the technical field of preparation of aluminum oxide or aluminum oxide precursor materials, and in particular to a Bayerite and a preparation method and application thereof. Background Art

[0002] Propane dehydrogenation is an important refining process for the production of propylene and hydrogen. At present, Co-based catalysts are commonly used as catalysts for propane dehydrogenation. However, the production route of preparing alumina by calcining pseudo-boehmite cannot meet the physical and chemical property requirements of Co-based catalysts for the carrier. This is mainly due to the fact that propane dehydrogenation requires the catalyst to have as few acid sites as possible, especially alumina carriers with low acid content. In order to meet this requirement, the catalyst carrier suitable for propane dehydrogenation needs to be calcined at above 800°C in advance to prepare an alumina carrier with low acidity and high stability as much as possible. Although increasing the calcination temperature can eliminate acidic sites, it also causes the destruction of the pore structure of the alumina carrier.

[0003] The formation of γ-alumina crystal phase is the main reason for the acidity of alumina carrier. Bayerite is prepared by directional preparation of alumina precursor with a specific crystal phase. The precursor will not be converted into γ-alumina crystal phase when calcined at low temperature, thereby obtaining an alumina carrier with low acid content. The carrier not only has low acid content, but also retains the pore structure of the carrier as much as possible. However, there is a lack of production technology for Bayerite products in both basic research and applied research, and the production process of some Bayerite is complicated, and the specific surface area of ​​the prepared Bayerite product is low, which makes it difficult to apply it to propane dehydrogenation catalytic reaction. Summary of the invention

[0004] The present application provides a bayerite and a preparation method and application thereof to solve the following technical problems: providing a new preparation method of bayerite.

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

[0006] Mixing the Bayerite seed crystals with an acidic aluminum source to obtain a first mixed solution;

[0007] The first mixed solution is subjected to a neutralization reaction with sodium aluminate, and the endpoint pH of the neutralization reaction is controlled to generate Alx(H2O)y(OH)mn+ small clusters to obtain a second mixed solution;

[0008] The second mixed solution is aged at a set temperature to transform the Alx(H2O)y(OH)mn+ small clusters into a Bayerite phase to obtain Bayerite.

[0009] Optionally, the endpoint pH of the neutralization reaction is 4.5 to 6.5.

[0010] Optionally, the temperature of the neutralization reaction is 75°C to 95°C.

[0011] Optionally, the set temperature is 25°C to 45°C.

[0012] Optionally, the weight of the bayerite seed crystals is 0.5% to 1.5% of the weight of alumina in the bayerite.

[0013] Optionally, the weight of aluminum oxide in the acidic aluminum source is 5 g / L to 30 g / L.

[0014] Optionally, the acidic aluminum source includes at least one of the following: aluminum sulfate, aluminum chloride, and aluminum nitrate.

[0015] Optionally, the Bayerite meets the following indicators: a specific surface area of ​​325.3 m 2 / g~382.3m 2 / g, the crystal phase weight of bayerite is 91.2% to 97.2%.

[0016] In a second aspect, the present application provides a bayerite, which is prepared by any method described in the first aspect.

[0017] In a third aspect, the present application provides a propane dehydrogenation catalyst, wherein the raw material of the propane dehydrogenation catalyst comprises the bayerite described in any one of the second aspects.

[0018] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0019] The preparation method of the bayerite provided in an embodiment of the present application comprises: mixing bayerite seed crystals with an acidic aluminum source to obtain a first mixed solution; neutralizing the first mixed solution with sodium aluminate, and controlling the endpoint pH of the neutralization reaction to generate small Alx(H2O)y(OH)mn+ clusters to obtain a second mixed solution; aging the second mixed solution at a set temperature to transform the small Alx(H2O)y(OH)mn+ clusters into a bayerite phase to obtain bayerite. The acidic aluminum source in the first mixed solution undergoes a neutralization reaction with sodium aluminate, and the endpoint pH of the neutralization reaction is controlled to generate as many Alx(H2O)y(OH)mn+ small clusters as possible; at a set temperature, the second mixed solution is aged, which is beneficial to the crystal phase transformation of the Alx(H2O)y(OH)mn+ small clusters to Bayerite, avoiding the formation of impurity crystals, and the Bayerite seeds can promote the transformation of the Alx(H2O)y(OH)mn+ small clusters to the Bayerite crystal phase, thereby obtaining Bayerite with a high Bayerite crystal phase content to the greatest extent, thereby making the specific surface area of ​​the Bayerite high. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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.

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0022] Figure 1 A schematic diagram of a process for preparing Bayerite provided in an embodiment of the present application;

[0023] Figure 2 The XRD diagrams of bayerite provided in Examples 1 to 5 of the present application are shown respectively. 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, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "include", "comprise", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "at least one" refers to one or more, and "multiple" 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, wherein a, b, c can be single or multiple, respectively. 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.

[0027] In a first aspect, the present application provides a method for preparing bayerite. Figure 1 A schematic diagram of a method for preparing Bayerite provided in an embodiment of the present application; see Figure 1 , the method comprising:

[0028] S1, mixing Bayerite seed crystals with an acidic aluminum source to obtain a first mixed solution;

[0029] In some embodiments, the weight of the bayerite seed crystals is 0.5% to 1.5% of the weight of the alumina of the bayerite.

[0030] In the embodiment of the present application, Bayerite is a hydrous aluminum oxide mineral with a chemical formula of Al(OH)3, usually in the form of white or slightly yellow crystals or powder. Bayerite has a layered structure, with layers connected by hydrogen bonds, has low hardness and chemical stability, is insoluble in water, but soluble in acid and alkali. Bayerite seeds are conducive to promoting the conversion of Alx(H2O)y(OH)mn+ small clusters (amorphous colloid particles) generated by subsequent neutralization reactions into Bayerite. The weight of Bayerite seeds can be 0.5% to 1.5% of the weight of the aluminum oxide of Bayerite, which is conducive to optimizing the utilization rate of Bayerite seeds on the basis of guiding the formation of Bayerite phase. Exemplarily, the weight of the Bayerite seeds can be 0.5%, 0.7%, 0.9%, 1%, 1.2%, 1.3%, 1.4%, 1.5%, etc. of the weight of the aluminum oxide of Bayerite.

[0031] In some embodiments, the weight of aluminum oxide in the acidic aluminum source is 5 g / L to 30 g / L.

[0032] In some embodiments, the acidic aluminum source includes at least one of the following: aluminum sulfate, aluminum chloride, and aluminum nitrate.

[0033] In the embodiment of the present application, the weight of alumina in the acidic aluminum source can be 5 g / L to 30 g / L, which can regulate the pH of the neutralization reaction system and is beneficial to increasing the generation rate of small Alx(H2O)y(OH)mn+ clusters. If the weight of alumina in the acidic aluminum source is higher than 30 g / L, it may cause the neutralization reaction system to be locally over-acidic or over-alkaline, thereby forming a pseudo-boehmite phase locally instead of small Alx(H2O)y(OH)mn+ clusters as the raw material for growing bayerite. It should be noted that if a pseudo-boehmite phase appears, the bayerite phase content of the subsequent bayerite product is reduced. When the bayerite product is calcined, the pseudo-boehmite therein will be transformed into a γ-alumina crystalline phase, which will increase the acidity of the alumina carrier and make it difficult to use it as a propane dehydrogenation catalyst. Therefore, it is necessary to avoid the formation of a pseudo-boehmite phase. Illustratively, the alumina weight of the acidic aluminum source can be 5 g / L, 8 g / L, 10 g / L, 13 g / L, 15 g / L, 18 g / L, 20 g / L, 23 g / L, 25 g / L, 28 g / L, 30 g / L, etc.

[0034] S2, neutralizing the first mixed solution with sodium aluminate, and controlling the endpoint pH of the neutralization reaction to generate Alx(H2O)y(OH)mn+ small clusters to obtain a second mixed solution;

[0035] In some embodiments, the endpoint pH of the neutralization reaction is 4.5-6.5.

[0036] Small clusters, also called ultrafine clusters, are part of the concept of nanomaterial scale. It is a relatively stable microscopic or submicroscopic aggregate composed of several or even thousands of atoms, molecules or ions through physical or chemical binding forces. The physical and chemical properties of small clusters will change with the number of atoms contained. Small clusters are usually regarded as a new material structure level between atoms, molecules and macroscopic solid substances. It is a transitional state in which various substances transform from atomic molecules to bulk substances, and can also be considered as the initial state of condensed matter. In an embodiment of the present application, the acidic aluminum source in the first mixed solution undergoes a neutralization reaction with sodium aluminate, and the endpoint pH of the neutralization reaction is controlled to generate as many Alx(H2O)y(OH)mn+ small clusters as possible. The endpoint pH of the neutralization reaction can be 4.5-6.5, and Alx(H2O)y(OH)mn+ small clusters are formed as much as possible, but these small clusters will not be converted into pseudo-boehmite colloids. Illustratively, the endpoint pH of the neutralization reaction can be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, etc.

[0037] In some embodiments, the neutralization reaction temperature is 75°C to 95°C.

[0038] In the embodiment of the present application, the temperature of the neutralization reaction can be 75°C to 95°C, which can increase the Al content in the neutralization reaction system. 3+ and AlO 2- activity, thereby regulating the generation rate of Alx(H2O)y(OH)mn+ small clusters; and it can also make the particle size of Alx(H2O)y(OH)mn+ small clusters uniform. If the temperature of the neutralization reaction is higher than 95°C, it may lead to the formation of pseudo-boehmite and other impurity phases; if the temperature of the neutralization reaction is lower than 75°C, it may lead to uneven particle size of Alx(H2O)y(OH)mn+ small clusters. Exemplarily, the temperature of the neutralization reaction can be 75°C, 78°C, 80°C, 83°C, 85°C, 87°C, 90°C, 93°C, 95°C, etc.

[0039] S3. At a set temperature, the second mixed solution is aged to transform the Alx(H2O)y(OH)mn+ small clusters into a Bayerite phase to obtain Bayerite.

[0040] In some embodiments, the set temperature is 25°C to 45°C.

[0041] In an embodiment of the present application, the second mixed solution is aged, and under the action of the above-mentioned Bayerite seed crystals, the small clusters of Alx(H2O)y(OH)mn+ are converted into Bayerite. The set temperature can be 25°C to 45°C, that is, the aging temperature can be 25°C to 45°C, which is conducive to the crystal phase transformation of the small clusters of Alx(H2O)y(OH)mn+ to Bayerite and avoids the formation of impurity crystals. Exemplarily, the set temperature can be 25°C, 27°C, 29°C, 31°C, 33°C, 35°C, 37°C, 39°C, 41°C, 43°C, 45°C, etc. In addition, the aging time can be 1h to 6h.

[0042] In some embodiments, the Bayerite meets the following indicators: a specific surface area of ​​325.3 m 2 / g~382.3m 2 / g, the crystal phase weight of bayerite is 91.2% to 97.2%.

[0043] In the embodiment of the present application, the above method can be used to obtain Bayerite with high specific surface area and high Bayerite crystal phase weight, which satisfies the specific surface area of ​​325.3m 2 / g~382.3m 2 / g, the crystal phase weight of bayerite is 91.2% to 97.2%.

[0044] The preparation method of Bayerite provided in this application has the following advantages:

[0045] 1. Mix the Bayerite seed crystals with the acidic aluminum source. The Bayerite seed crystals act as "seeds" here, providing the crystal nucleus basis for the subsequent formation of the Bayerite phase;

[0046] 2. The acidic aluminum source in the first mixed solution reacts with sodium aluminate to undergo a neutralization reaction. The endpoint pH of the neutralization reaction is controlled to generate as many small clusters as possible, laying the foundation for obtaining a high-content Bayerite crystal phase;

[0047] 3. The second mixed solution is aged at a set temperature, and the small clusters in the solution undergo a series of physical and chemical changes such as further polymerization and rearrangement, gradually forming a structure with the characteristics of the Bayerite crystal phase. The appropriate temperature can provide enough energy to promote these changes smoothly, while not causing the formation of impurities or destroying the Bayerite phase structure that has been formed due to excessive temperature;

[0048] 4. Bayerite seed crystals play an important inductive role in the entire aging process. Since the seed crystals themselves already have the crystal structure of Bayerite, they can provide a "template" for small clusters, making it easier for small clusters to arrange and grow according to the crystal structure characteristics of Bayerite, thereby more efficiently transforming to the Bayerite crystal phase, and ensuring that the Bayerite crystal phase content in the generated product is high to the greatest extent.

[0049] 5. When a high Bayerite crystal phase content is obtained, it means that the generated Bayerite crystal structure is relatively regular, complete and of high purity. Generally speaking, the stacking method between the particles and the internal pore structure of pure and well-crystallized Bayerite crystals are more conducive to showing a larger specific surface area.

[0050] In summary, this preparation method can, in principle, prepare a bayerite product with a high bayerite crystal phase content and a high specific surface area by controlling the conditions of each step and utilizing the inducing effect of the bayerite seed crystal. Each link cooperates with each other and is indispensable to ensure the preparation effect and quality.

[0051] In a second aspect, the present application provides a bayerite, which is prepared by any method described in the first aspect.

[0052] The Bayer stone is realized based on the preparation method of the Bayer stone mentioned above. The specific steps of the preparation method of the Bayer stone can refer to the above embodiment. Since the Bayer stone adopts part or all of the technical solutions of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be described one by one here.

[0053] In a third aspect, the present application provides a propane dehydrogenation catalyst, wherein the raw material of the propane dehydrogenation catalyst comprises the bayerite described in any one of the second aspects.

[0054] In the embodiment of the present application, Bayerite is prepared by directional preparation of an alumina precursor with a specific crystal phase. The precursor will not be converted into a γ-alumina crystal phase when calcined at a low temperature, thereby obtaining an alumina carrier with a low acid content. The carrier not only has a low acid content, but also retains the pore structure of the carrier as much as possible, so it is suitable as a raw material for a propane dehydrogenation catalyst. When the Bayerite is calcined and used as a carrier to load Co for propane dehydrogenation, the propane conversion rate is 24.5-27.2%, and the propylene selectivity is 91.6-93.7%. Among them, the cobalt loading is 5%.

[0055] The propane dehydrogenation catalyst is realized based on the above-mentioned Bayer stone. The specific preparation steps of the Bayer stone can refer to the above-mentioned embodiment. Since the propane dehydrogenation catalyst adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here one by one.

[0056] 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.

[0057] Example 1

[0058] A method for preparing bayerite, comprising:

[0059] Mixing Bayerite seed crystals with an acidic aluminum source to obtain a first mixed solution; wherein the acidic aluminum source is aluminum sulfate, and the weight of aluminum oxide in the aluminum sulfate is 10 g / L; and the weight of the Bayerite seed crystals is 1% of the weight of aluminum oxide in the Bayerite;

[0060] The first mixed solution is subjected to a neutralization reaction with sodium aluminate, and the endpoint pH of the neutralization reaction is controlled to generate Alx(H2O)y(OH)mn+ small clusters to obtain a second mixed solution; wherein the neutralization reaction temperature is 75°C, and the endpoint pH of the neutralization reaction is 4.5;

[0061] The second mixed solution is aged at a set temperature to transform the Alx(H2O)y(OH)mn+ small clusters into a Bayerite phase to obtain Bayerite; wherein the set temperature is 25°C and the aging time is 1 hour.

[0062] Bayerite (B-1): Specific surface area is 325.3m 2 / g, and the Bayerite crystal phase content is 91.2%.

[0063] Example 2

[0064] A method for preparing bayerite, comprising:

[0065] Mixing Bayerite seed crystals with an acidic aluminum source to obtain a first mixed solution; wherein the acidic aluminum source is aluminum sulfate, and the weight of aluminum oxide in the aluminum sulfate is 5 g / L; and the weight of the Bayerite seed crystals is 1.25% of the weight of aluminum oxide in the Bayerite;

[0066] The first mixed solution is subjected to a neutralization reaction with sodium aluminate, and the endpoint pH of the neutralization reaction is controlled to generate Alx(H2O)y(OH)mn+ small clusters to obtain a second mixed solution; wherein the neutralization reaction temperature is 80°C, and the endpoint pH of the neutralization reaction is 5.0.

[0067] The second mixed solution was aged at a set temperature to transform the Alx(H2O)y(OH)mn+ small clusters into a Bayerite phase to obtain Bayerite; wherein the set temperature was 35°C and the aging time was 3h.

[0068] Bayerite (B-2): Specific surface area is 343.5m 2 / g, and the Bayerite crystal phase content is 93.7%.

[0069] Example 3

[0070] A method for preparing bayerite, comprising:

[0071] Mixing Bayerite seed crystals with an acidic aluminum source to obtain a first mixed solution; wherein the acidic aluminum source is aluminum sulfate, and the weight of aluminum oxide in the aluminum sulfate is 15 g / L; and the weight of the Bayerite seed crystals is 1.5% of the weight of aluminum oxide in the Bayerite;

[0072] The first mixed solution is subjected to a neutralization reaction with sodium aluminate, and the endpoint pH of the neutralization reaction is controlled to generate Alx(H2O)y(OH)mn+ small clusters to obtain a second mixed solution; wherein the neutralization reaction temperature is 85°C, and the endpoint pH of the neutralization reaction is 5.5;

[0073] The second mixed solution was aged at a set temperature to transform the Alx(H2O)y(OH)mn+ small clusters into a Bayerite phase to obtain Bayerite; wherein the set temperature was 45°C and the aging time was 5 hours.

[0074] Bayerite (B-3): Specific surface area is 367.1m 2 / g, and the Bayerite crystal phase content is 95.6%.

[0075] Example 4

[0076] A method for preparing bayerite, comprising:

[0077] Mixing Bayerite seed crystals with an acidic aluminum source to obtain a first mixed solution; wherein the acidic aluminum source is aluminum sulfate, and the weight of aluminum oxide in the aluminum sulfate is 20 g / L; and the weight of the Bayerite seed crystals is 0.5% of the weight of aluminum oxide in the Bayerite;

[0078] The first mixed solution is subjected to a neutralization reaction with sodium aluminate, and the endpoint pH of the neutralization reaction is controlled to generate Alx(H2O)y(OH)mn+ small clusters to obtain a second mixed solution; wherein the neutralization reaction temperature is 90° C., and the endpoint pH of the neutralization reaction is 4.5;

[0079] The second mixed solution was aged at a set temperature to transform the Alx(H2O)y(OH)mn+ small clusters into a Bayerite phase to obtain Bayerite; wherein the set temperature was 35°C and the aging time was 4h.

[0080] Bayerite (B-4): Specific surface area is 371.9m 2 / g, and the Bayerite crystal phase content is 96.3%.

[0081] Example 5

[0082] A method for preparing bayerite, comprising:

[0083] Mixing Bayerite seed crystals with an acidic aluminum source to obtain a first mixed solution; wherein the acidic aluminum source is aluminum sulfate, and the weight of aluminum oxide in the aluminum sulfate is 30 g / L; and the weight of the Bayerite seed crystals is 0.5% of the weight of aluminum oxide in the Bayerite;

[0084] The first mixed solution is subjected to a neutralization reaction with sodium aluminate, and the endpoint pH of the neutralization reaction is controlled to generate Alx(H2O)y(OH)mn+ small clusters to obtain a second mixed solution; wherein the neutralization reaction temperature is 95°C, and the endpoint pH of the neutralization reaction is 6.5;

[0085] The second mixed solution was aged at a set temperature to transform the Alx(H2O)y(OH)mn+ small clusters into a Bayerite phase to obtain Bayerite; wherein the set temperature was 25°C and the aging time was 6 hours.

[0086] Bayerite (B-5): Specific surface area is 382.3m 2 / g, and the Bayerite crystal phase content is 97.2%.

[0087] Comparative Example 1

[0088] Based on the disclosure of Example 5, the difference between Comparative Example 1 and Example 5 is that the endpoint pH of the neutralization reaction is 7.

[0089] Bayerite (B-6): Specific surface area is 256.5m 2 / g, and the Bayerite crystal phase content is 51.7%.

[0090] Comparative Example 2

[0091] Based on the disclosure of Example 5, the difference between Comparative Example 1 and Example 5 is that the set temperature is 50°C.

[0092] Bayerite (B-7): Specific surface area is 301.5m 2 / g, and the Bayerite crystal phase content is 71.8%.

[0093] Through the analysis of Examples 1 to 5 and Comparative Examples 1 to 2, it can be found that the Bayerite prepared by the Bayerite preparation method provided in the present application has a high specific surface area and a high Bayerite crystal phase weight. However, the technical solutions of Comparative Examples 1 and 2 are not within the scope of the present application, which to some extent result in low Bayerite content and low specific surface area. Figure 2 XRD diagrams of a Bayerite provided in Examples 1 to 5 of the present application; see Figure 2 , indicating that Examples 1 to 5 all successfully prepared Bayerite, and all Bayerite samples had a Bayerite crystal phase, but there were differences in the crystallinity of different samples, which was specifically reflected in the Bayerite phase content of different samples.

[0094] Example 6

[0095] Bayerite (B-5) was used as a precursor and calcined at 600°C for 2 h to obtain a first alumina support;

[0096] Pseudo-boehmite provided by Chalco Shandong New Materials Co., Ltd. was selected as a precursor and calcined at 600°C for 2h to obtain a second alumina carrier;

[0097] The first alumina carrier and the second alumina carrier are impregnated, dried and calcined in sequence to obtain a first propane dehydrogenation catalyst and a second propane dehydrogenation catalyst, respectively; wherein, the cobalt loading amount is 5% based on the cobalt content in the catalyst when impregnated in an aqueous cobalt nitrate solution, the drying process parameters are: drying at 50°C for 12 hours, and the calcination process parameters are: calcination at 500°C for 3 hours.

[0098] The first propane dehydrogenation catalyst and the second propane dehydrogenation catalyst were respectively evaluated for activity according to the following methods:

[0099] Catalyst activation: 2 g of the catalyst was reduced at 400 °C for 1 h in a 40 ml / min H2 flow.

[0100] Catalyst activity evaluation: The catalyst was evaluated for propane dehydrogenation at 550°C in a reaction gas flow of 300 ml / min (propane / nitrogen=5 / 95).

[0101] The first propane dehydrogenation catalyst: propane conversion rate is 26.2%, propylene selectivity is 93.9%. The second propane dehydrogenation catalyst: propane conversion rate is 27.5%, propylene selectivity is 85.6%. Therefore, using Bayerite as a precursor is more advantageous.

[0102] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0103] (1) In the embodiment of the present application, sodium aluminate and aluminum sulfate solution undergo a neutralization reaction to gradually form small Alx(H2O)y(OH)mn+ clusters, and Bayerite seeds are used to control the directional growth of the small Alx(H2O)y(OH)mn+ clusters to prepare aluminum hydroxide having a Bayerite structure;

[0104] (2) The preparation method of Bayerite provided in the embodiments of the present application has the advantages of low synthesis cost, simple operation, synthesis using industrial raw materials, no use of any organic template, and suitability for industrial production.

[0105] 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 Bayerite, the method comprising: Mixing the Bayerite seed crystals with an acidic aluminum source to obtain a first mixed solution; The first mixed solution is subjected to a neutralization reaction with sodium aluminate, and the endpoint pH of the neutralization reaction is controlled to generate Alx(H2O)y(OH)mn+ small clusters to obtain a second mixed solution; The second mixed solution is aged at a set temperature to transform the Alx(H2O)y(OH)mn+ small clusters into a Bayerite phase to obtain Bayerite.

2. The method according to claim 1, characterized in that The endpoint pH of the neutralization reaction is 4.5 to 6.

5.

3. The method according to claim 1 or 2, characterized in that: The temperature of the neutralization reaction is 75°C to 95°C.

4. The method according to claim 1, characterized in that: The set temperature is 25°C to 45°C.

5. The method according to claim 1, characterized in that The weight of the Bayerite seed crystals is 0.5% to 1.5% of the weight of the aluminum oxide of the Bayerite.

6. The method according to claim 1, characterized in that The weight of aluminum oxide in the acidic aluminum source is 5 g / L to 30 g / L.

7. The method according to claim 1 or 6, characterized in that: The acidic aluminum source includes at least one of the following: aluminum sulfate, aluminum chloride, and aluminum nitrate.

8. The method according to claim 1, characterized in that The Bayerite meets the following indicators: specific surface area is 325.3m 2 / g~382.3m 2 / g, the crystal phase weight of bayerite is 91.2% to 97.2%.

9. Bayerite, which is prepared by the method according to any one of claims 1 to 8.

10. A propane dehydrogenation catalyst, wherein the raw material of the propane dehydrogenation catalyst comprises the Bayerite according to claim 9.

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