阅读说明：本技术 一种球形氧化铝及其制备方法 (Spherical alumina and preparation method thereof ) 是由 吴春正 陈凤娇 刘青 王强 刘伟 周峰 于 2020-04-03 设计创作，主要内容包括：本发明公开了一种球形氧化铝及其制备方法,所述方法包括,将低钠拟薄水铝石、大孔拟薄水铝石和水混合并进行一次搅拌,获得拟薄水铝石悬浊液；所述低钠拟薄水铝石和所述大孔拟薄水铝石的质量比为1:0.2～10；将所述拟薄水铝石悬浊液和酸液混合并进行二次搅拌,获得铝溶胶；将所述铝溶胶和脲混合并进行三次搅拌,后进行油氨柱成型、老化、干燥和焙烧,获得球形氧化铝。本发明球形氧化铝表面光滑、圆球度高、孔体积大且均匀、孔径可调、比表面较大,机械强度高；本方法原料来源广、成本低、制备工艺简单；有利于实现工业化生产。(The invention discloses a spherical alumina and a preparation method thereof, wherein the method comprises the steps of mixing low-sodium pseudo-boehmite, macroporous pseudo-boehmite and water, and stirring for one time to obtain a pseudo-boehmite suspension; the mass ratio of the low-sodium pseudo-boehmite to the large-pore pseudo-boehmite is 1: 0.2-10; mixing the pseudo-boehmite suspension and acid liquor, and stirring for the second time to obtain alumina sol; and mixing the aluminum sol and urea, stirring for three times, and then carrying out oil ammonia column molding, aging, drying and roasting to obtain the spherical alumina. The spherical alumina has smooth surface, high sphericity, large and uniform pore volume, adjustable pore diameter, larger specific surface and high mechanical strength; the method has the advantages of wide raw material source, low cost and simple preparation process; is favorable for realizing industrialized production.)

1. A method for preparing spherical alumina is characterized by comprising the following steps,

mixing low-sodium pseudo-boehmite, macroporous pseudo-boehmite and water, and stirring for the first time to obtain a pseudo-boehmite suspension; the mass ratio of the low-sodium pseudo-boehmite to the large-pore pseudo-boehmite is 1: 0.2-10;

mixing the pseudo-boehmite suspension and acid liquor, and stirring for the second time to obtain alumina sol;

and mixing the aluminum sol and urea, stirring for three times, and then carrying out oil ammonia column molding, aging, drying and roasting to obtain the spherical alumina.

2. The method of claim 1, wherein the low-sodium pseudoboehmite contains Na₂The mass fraction of O is less than 0.04 percent, and the pore volume of the macroporous pseudo-boehmite is 0.8-1.5 ml/g.

3. The method for preparing spherical alumina according to claim 1, wherein the primary stirring rate is 300 to 700r/min, the secondary stirring rate is 500 to 800r/min, and the secondary stirring time is 20 to 120 min; the third stirring speed is 600-1000 r/min, and the third stirring time is 10-50 min.

4. The method for preparing spherical alumina according to claim 1, wherein the mass fraction of alumina in the pseudoboehmite suspension is 10-30%.

5. The method for preparing spherical alumina according to claim 1, wherein the acid solution is one of nitric acid, formic acid, acetic acid and perchloric acid, the mass concentration of the acid solution is 5 to 30%, and the ratio of the added mass of the acid solution to the sum of the masses of the low-sodium pseudo-boehmite and the large-pore pseudo-boehmite is 0.06 to 0.1.

6. The method for preparing spherical alumina according to claim 1, wherein the ratio of the mass of the urea added to the sum of the mass of the low-sodium pseudoboehmite and the mass of the large-pore pseudoboehmite is 0.1 to 0.4.

7. The preparation method of the spherical alumina according to claim 1, wherein in the oil ammonia column forming process, a dispersed dripper is adopted to drip the mixture of the aluminum sol and the urea into the oil ammonia column for forming, the oil ammonia column comprises an oil phase and an ammonia water phase, the oil is hydraulic oil, transformer oil or kerosene, the height of the oil phase is 5-60 cm, the height ratio of the oil phase to the ammonia water phase is 12: 1-5, and the mass concentration of the ammonia water in the ammonia water is 5-20%.

8. The method for preparing spherical alumina according to claim 1, wherein the aging time is 2-12 hours, the drying temperature is 90-110 ℃, and the drying time is 2-5 hours.

9. The method for preparing spherical alumina according to claim 1, wherein the roasting temperature is 550-650 ℃, and the roasting time is 2-12 h.

10. The spherical alumina is characterized by being prepared by the preparation method of the spherical alumina as claimed in any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of alumina preparation, and particularly relates to spherical alumina and a preparation method thereof.

Background

The aluminum oxide has 8 crystal forms, respectivelyα, gamma, η, theta, rho, kappa and chi-Al₂O₃Among them, α -alumina is the most stable, when the heating temperature exceeds 1200 ℃, other seven crystal forms of alumina can be converted into α -alumina, gamma, η, theta and chi-Al₂O₃It is also called active alumina because of its porosity, adsorptivity, catalytic property, etc. The active alumina is used as catalyst carrier, and the shape of the alumina is strip, sphere and sheet. Pore structure parameters such as pore volume, specific surface area and pore size distribution of the catalyst carrier are important factors influencing the activity of the catalyst carrier, and the catalyst carrier with good performance has proper specific surface area and pore structure and higher mechanical strength.

Spherical alumina is widely used in moving beds and fixed beds due to its high sphericity, smooth surface, high mechanical strength, etc. At present, the spherical alumina is usually prepared by adopting an oil ammonia column forming process, but the strength of the spherical alumina prepared by the oil ammonia column forming process can not meet the requirement.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides spherical alumina and a preparation method thereof, which aim to solve the problem that the strength of the spherical alumina prepared by the oil ammonia column forming process in the prior art is insufficient.

The invention realizes the purpose through the following technical scheme:

in one aspect, the present invention provides a method for preparing spherical alumina, the method comprising,

mixing low-sodium pseudo-boehmite, macroporous pseudo-boehmite and water, and stirring for the first time to obtain a pseudo-boehmite suspension; the mass ratio of the low-sodium pseudo-boehmite to the large-pore pseudo-boehmite is 1: 0.2-10;

mixing the pseudo-boehmite suspension and acid liquor, and stirring for the second time to obtain alumina sol;

and mixing the aluminum sol and urea, stirring for three times, and then carrying out oil ammonia column molding, aging, drying and roasting to obtain the spherical alumina.

Further, it is characterized byNa in the low-sodium pseudo-boehmite₂The mass fraction of O is less than 0.04 percent, and the pore volume of the macroporous pseudo-boehmite is 0.8-1.5 ml/g.

Further, the primary stirring speed is 300-700 r/min, the secondary stirring speed is 500-800 r/min, and the secondary stirring time is 20-120 min; the third stirring speed is 600-1000 r/min, and the third stirring time is 10-50 min.

Furthermore, the mass fraction of alumina in the pseudo-boehmite suspension is 10-30%.

Further, the acid solution is one of nitric acid, formic acid, acetic acid and perchloric acid, the mass concentration of the acid solution is 5-30%, and the ratio of the added mass of the acid solution to the sum of the mass of the low-sodium pseudoboehmite and the mass of the macroporous pseudoboehmite is 0.06-0.1.

Further, the ratio of the added mass of the urea to the sum of the mass of the low-sodium pseudoboehmite and the mass of the large-pore pseudoboehmite is 0.1 to 0.4.

Further, in the oil-ammonia column forming process, a mixture obtained after stirring the aluminum sol and the urea is dripped into the oil-ammonia column by adopting a dispersing dripper for forming, wherein the oil-ammonia column comprises an oil phase and an ammonia water phase, the oil is hydraulic oil, transformer oil or kerosene, the height of the oil phase is 5-60 cm, the height ratio of the oil phase to the ammonia water phase is 12: 1-5, and the mass concentration of the ammonia water in the ammonia water is 5-20%.

Further, the aging time is 2-12 hours, the drying temperature is 90-110 ℃, and the drying time is 2-5 hours.

Further, the roasting temperature is 550-650 ℃, and the roasting time is 2-12 hours.

In a second aspect, the invention also provides spherical alumina prepared by the preparation method of the spherical alumina.

The beneficial effects of the invention at least comprise:

the invention provides a spherical alumina and a preparation method thereof, wherein the method comprises the steps of mixing low-sodium pseudo-boehmite, macroporous pseudo-boehmite and water, and stirring for one time to obtain a pseudo-boehmite suspension; the mass ratio of the low-sodium pseudo-boehmite to the large-pore pseudo-boehmite is 1: 0.2-10; mixing the pseudo-boehmite suspension and acid liquor, and stirring for the second time to obtain alumina sol; and mixing the aluminum sol and urea, stirring for three times, and carrying out oil ammonia column forming, aging, drying and roasting to obtain the spherical alumina. The low-sodium pseudo-boehmite plays a role in bonding and is mixed with the macroporous pseudo-boehmite with good dispersibility according to a certain mass ratio to prepare the alumina sol, the alumina sol is gelatinized in an alkaline environment, is aged, solidified and formed, the inside of the alumina sol is formed by the twisting among colloid particles, and the spherical alumina has higher strength.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a process step diagram of a preparation method of spherical alumina according to an embodiment of the present invention.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In order to solve the technical problems, the technical scheme in the embodiment of the invention has the following general idea:

in one aspect, the embodiments of the present invention provide a method for preparing spherical alumina, the method including,

s1, mixing the low-sodium pseudo-boehmite, the macroporous pseudo-boehmite and water, and stirring for the first time to obtain a pseudo-boehmite suspension; the mass ratio of the low-sodium pseudo-boehmite to the large-pore pseudo-boehmite is 1: 0.2-10;

the preparation of the pseudo-boehmite suspension is prepared for preparing the alumina sol in the next step, and the pseudo-boehmite suspension can better react with the acid liquor after the acid liquor is dripped to prepare the alumina sol.

Further, Na in the low-sodium pseudoboehmite₂The mass fraction of O is less than 0.04 percent, and the pore volume of the macroporous pseudo-boehmite is 0.8-1.5 ml/g. The low-sodium pseudo-boehmite adopted by the invention has good peptization, and can be used as a binder after being dissolved in acid; whereas the large pore pseudo-boehmite provides the predominant pore volume of the spherical alumina. The invention can select common low-sodium pseudoboehmite produced by Zhongai Shandong limited company and macroporous pseudoboehmite produced by Shandong practical industry in Shandong, and can also select any other low-sodium pseudoboehmite and macroporous pseudoboehmite which meet the requirements.

Further, the primary stirring speed is 300-700 r/min,

under the condition of primary stirring, the pseudoboehmite suspension is formed in an accelerating way.

Furthermore, the mass fraction of alumina in the pseudo-boehmite suspension is 10-30%.

The mass fraction of alumina in the pseudo-boehmite suspension is controlled to be 10-30%, when the mass fraction of the alumina is lower than 10%, the prepared wet ball has low strength, the small ball is easy to deform or break in the aging and drying processes, and the yield is low; in the pseudo-boehmite suspension, the larger the mass fraction of alumina is, the poorer the fluidity of the alumina sol prepared after acid dissolution is, which is not favorable for later-stage molding, so that the mass fraction of alumina in the pseudo-boehmite suspension is limited to 10-30%.

S2, mixing the pseudo-boehmite suspension and acid liquor, and stirring for the second time to obtain alumina sol;

mixing the pseudo-boehmite suspension and the acid solution, and continuously stirring; the pseudo-boehmite particles react with acid in the stirring process and are acidolyzed into smaller colloidal particles, and after a period of reaction time, the pseudo-boehmite particles are completely acidolyzed to finally obtain the alumina sol.

Further, the secondary stirring speed is 500-800 r/min, and the secondary stirring time is 20-120 min;

further, the acid solution is one of nitric acid, formic acid, acetic acid and perchloric acid, the mass concentration of the acid solution is 5-30%, and the ratio of the added mass of the acid solution to the sum of the mass of the low-sodium pseudoboehmite and the mass of the macroporous pseudoboehmite is 0.06-0.1.

The acid solution is used for reacting with the pseudo-boehmite suspension to prepare alumina sol; when the concentration of the acid liquor is too high, the gelation effect is easy to occur, small lumps are generated, and the preparation of the aluminum sol with certain fluidity is difficult.

And S3, mixing the aluminum sol and urea, stirring for three times, and then carrying out oil ammonia column molding, aging, drying and roasting to obtain the spherical alumina.

Further, the ratio of the added mass of the urea to the sum of the mass of the low-sodium pseudoboehmite and the mass of the large-pore pseudoboehmite is 0.1 to 0.4; the third stirring speed is 500-800 r/min, and the third stirring time is 10-50 min.

The stability of the aluminum sol can be improved by adding urea, the addition amount of urea cannot be too high, otherwise, the viscosity of the aluminum sol is greatly reduced, the aluminum sol is not beneficial to forming, the addition amount of urea cannot be too small, and otherwise, the effect of stabilizing the aluminum sol cannot be achieved. The urea is added and matched with the stirring for three times, so that the aluminum sol and the urea can be quickly more uniform.

Further, in the oil-ammonia column forming process, a mixture obtained after stirring the aluminum sol and the urea is dripped into the oil-ammonia column by adopting a dispersing dripper for forming, wherein the oil-ammonia column comprises an oil phase and an ammonia water phase, the oil is hydraulic oil, transformer oil or kerosene, the height of the oil phase is 5-60 cm, the height ratio of the oil phase to the ammonia water phase is 12: 1-3, and the mass concentration of the ammonia water in the ammonia water is 5-20%.

Due to the existence of oil-water interfacial tension, the sol drops quickly shrink into a regular sphere in the oil phase; under the action of gravity, the sol balls in the oil phase enter the alkaline ammonia water phase to react quickly to form gel balls, and then the gel balls are aged and solidified. The height of the oil phase is high enough to make the sol drop have enough time to shrink to form a more regular sphere; the ammonia water phase has proper height, so that the sol drops can be fully solidified and aged in the falling process, and the sol balls are prevented from being deformed by contacting with the bottom before being fully aged. The solubility of ammonia is too low to be beneficial to the aging of the sol-gel spheres, and the aging time of the sol-gel spheres is increased or the sol-gel spheres cannot be completely aged.

Further, the aging time is 2-12 h.

The aging aims to ensure that the sol balls fully react with ammonia water to be solidified and formed; if the aging time is too short, the colloidal particles in the sol ball are not sufficiently stranded, and the sol ball is easy to deform or break in the drying process. If the aging time is too long, the surface of the sol pellet is easy to peel, so that the pellet is deformed.

Further, the drying temperature is 90-110 ℃, and the drying time is 2-5 hours.

Taking out the aged sol balls from ammonia water, drying the sol balls to remove water, wherein the water content of the sol balls is high; if the drying temperature is too low, the required drying time is too long, and the adhesion phenomenon is easy to occur after the sol pellets are dried; if the drying temperature is too high, the sol pellets are dehydrated too quickly and are easy to break.

Further, the roasting temperature is 550-650 ℃, and the roasting time is 2-12 hours.

Roasting the dried pellets, wherein if the roasting temperature is too low or the roasting time is too short, colloidal particles in the pellets cannot be converted into gamma-phase alumina or cannot be completely converted into gamma-phase alumina; if the roasting temperature is too high, colloidal particles in the small spheres are converted into gamma-phase alumina, and then are converted into alumina in other phase states, so that the pore volume of the prepared spherical alumina is reduced.

On the other hand, the invention provides spherical alumina which is prepared by the preparation method of the high-strength spherical alumina.

In the present application, "primary stirring", "secondary stirring" and "tertiary stirring" are merely terms, and "primary", "secondary" and "tertiary" do not indicate the order or the order of the steps.

The invention takes common low-sodium pseudo-boehmite and macroporous pseudo-boehmite as raw materials, the raw materials are mixed according to a certain mass proportion, a proper amount of water is added, a stirrer is used for stirring for a period of time until the powder is completely dispersed in the water, pseudo-boehmite suspension is formed, no pore-expanding agent or surfactant is added, and spherical alumina with smooth surface, high sphericity, large and uniform pore volume, adjustable pore diameter, larger specific surface and high mechanical strength is prepared by adopting an oil ammonia column forming process. The prior art mostly adopts imported pseudoboehmite (SB) with high price abroad as a raw material, and the application adopts low-sodium pseudoboehmite and macroporous pseudoboehmite with low price and wide source as raw materials, so the application has low cost and simple preparation process and is beneficial to realizing industrial production.

The technical solution of the present application will be further described with reference to specific examples.