Macroporous pseudo-boehmite and production method thereof

Abstract

The invention discloses macroporous pseudo-boehmite and a production method thereof, and belongs to the technical field of pseudo-boehmite production. The production method of the macroporous pseudo-boehmite provided by the invention comprises the following steps: diluting a clinker dissolution crude solution in a sintering method aluminum oxide process, standing, and filtering to obtain a sodium aluminate solution with the Al2O3 concentration of 60-80g / L; adding a pore-enlarging agent into the sodium aluminate solution, introducing CO2 to carry out carbonization reaction, and then sequentially carrying out aging, washing and drying steps to obtain macroporous pseudo-boehmite; and the washed washing liquid is returned to the sintering method alumina process. According to the production method, a large amount of red mud can be digested, high-quality macroporous pseudo-boehmite can be prepared under the condition of high alumina concentration, and the energy consumption is low; the pore volume of the obtained macroporous pseudo-boehmite is more than 0.95 cm < 3 > / g, and the whiteness is high; meanwhile, the whole production process is green and environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of pseudo-boehmite production, in particular to macroporous pseudo-boehmite and a production method thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance the understanding of the overall background of the invention and should not be necessarily regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Macroporous pseudo-boehmite has the characteristics of high crystal purity, strong adhesion, good peptization performance, large pore volume, etc. It is widely used as a catalyst, catalyst carrier and binder in the petrochemical industry and other industries, as well as a raw material for the production of other high-end fine alumina products. The product has high added value.

[0004] At present, there are two main methods for producing pseudo-boehmite: neutralization method and carbonization method. The raw materials used in the production of macroporous pseudo-boehmite by neutralization method are mainly aluminum salts and aluminates. This method can only be used to produce small batches of pseudo-boehmite, and some materials in the process cannot be recycled. At the same time, it will also cause SO4 in the system to 2- The content increases, washing becomes more difficult, and during the high-temperature roasting process of the carrier, sulfate decomposes into sulfur trioxide, which causes serious corrosion to the equipment and does not meet environmental protection requirements. The carbonization method for preparing pseudo-boehmite is green and environmentally friendly, and the prepared pseudo-boehmite has no corrosive impurities.

[0005] At present, the main raw materials used in the production of macroporous pseudo-boehmite by carbonization are aluminum hydroxide and sodium hydroxide, which will increase the cost to a certain extent. The process is relatively complicated, and the slurry concentration in the preparation process is low (20-50g / L). If the concentration is too high, it will cause uneven neutralization reaction, thereby aggravating the hydrolysis of NaAlO2, and more gibbsite (miscellaneous crystals) will be generated in the product, making the pore volume and pore size of the product smaller, thereby causing the product quality to decline; and low slurry concentration will lead to increased energy consumption; at the same time, when aluminum hydroxide and sodium hydroxide are used as the main raw materials, it is difficult to form a closed loop in the production system, and pollutants are discharged, which does not meet the current requirements of green development.

[0006] In the prior art, there is a method of producing pseudo-boehmite using washing liquid to reduce washing liquid discharge and new water consumption. For example, the patent with authorization announcement number CN111592022B (authorization announcement date: 2023.05.12) discloses a method for producing pseudo-boehmite, which uses the secondary washing liquid in the washing process of pseudo-boehmite to dilute and prepare the sodium aluminate solution to obtain a sodium aluminate solution that meets the preset indicators, and uses this as a raw material for subsequent carbonization to produce pseudo-boehmite. The patent requires that the concentration of alumina in the sodium aluminate solution be diluted and adjusted to 40-45g / L, which is still below 50g / L; in addition, the pseudo-boehmite produced using the washing liquid has a yellowish appearance, low whiteness, and poor quality, and it is impossible to produce high-quality pseudo-boehmite from a high-concentration sodium aluminate solution.

[0007] Therefore, how to produce high-quality pseudo-boehmite from high-concentration sodium aluminate solution using a "green" process is an urgent problem to be solved. Summary of the invention

[0008] In view of this, the present invention provides a macroporous pseudo-boehmite and a production method thereof, which can realize the preparation of high-quality macroporous pseudo-boehmite at a higher alumina raw material concentration, and the wastewater generated in the production can be returned to the alumina production process to achieve no waste liquid discharge.

[0009] In a first aspect, the present invention provides a method for producing macroporous pseudo-boehmite, comprising the following steps:

[0010] The crude liquid from the clinker dissolution in the sintering process for producing alumina is diluted, allowed to stand and filtered to obtain a sodium aluminate solution with an Al2O3 concentration of 60 to 80 g / L; a pore-enlarging agent is added to the sodium aluminate solution, and CO2 is introduced to carry out a carbonization reaction, and then the solution is subjected to aging, washing and drying steps in sequence to obtain macroporous pseudo-boehmite; the washed liquid is returned to the sintering process for producing alumina.

[0011] Preferably, the parameters of the clinker dissolution crude solution in the sintering alumina process are as follows: caustic ratio a k It is 1.0~1.5, the concentration of Al2O3 is 70~90g / L, and the concentration of SiO2 is 1.0~2.5g / L.

[0012] Preferably, the pore expanding agent is selected from urea or ethanol.

[0013] Preferably, the added amount of the pore expanding agent is 0.5-2 wt % of the mass of the sodium aluminate solution.

[0014] Preferably, in the step of adding the pore expanding agent, the temperature of the sodium aluminate solution is controlled to be 30-50° C., and the pore expanding agent is added under stirring conditions.

[0015] Preferably, the volume fraction of CO2 is 30-35%, and the carbonization reaction time is 15-20 minutes.

[0016] Preferably, the aging temperature is 60-90° C., and the aging time is 0.5-2 h.

[0017] Preferably, the washing step comprises: beating and washing the aged slurry with water at 85 to 95°C.

[0018] Preferably, the drying step is: first drying at 85-100° C. for 0.5-2 h, and then drying at 105-110° C. for 2-4 h.

[0019] In a second aspect, the present invention provides a macroporous pseudo-boehmite obtained by the above production method.

[0020] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0021] The invention uses the raw material of the clinker dissolution crude liquid in the sintering alumina process, can digest a large amount of red mud, and can realize the preparation of high-quality macroporous pseudo-boehmite at a higher alumina concentration (60-80g / L), with low energy consumption; the obtained macroporous pseudo-boehmite has a pore volume of 0.95cm 3 / g or more, with high whiteness; at the same time, the washing waste liquid generated by the present invention is directly returned to the sintering alumina process, and will not cause waste liquid discharge, and the entire production process is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 Schematic diagram of the production process of macroporous pseudo-boehmite in Example 1 of the present invention;

[0024] Figure 2 is a SEM picture of the macroporous pseudo-boehmite of Example 1 of the present invention at a magnification of 100k;

[0025] Figure 3 This is a SEM picture of the macroporous pseudo-boehmite of Example 1 of the present invention at a magnification of 5k;

[0026] Figure 4 is a macroscopic photograph of the macroporous pseudo-boehmite of Example 1 of the present invention;

[0027] Figure 5This is a SEM picture of the macroporous pseudo-boehmite of Example 3 of the present invention. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0029] The present invention provides a method for producing macroporous pseudo-boehmite, comprising the following steps:

[0030] The crude liquid dissolved from the clinker in the sintering alumina process is diluted, allowed to stand and filtered to obtain a sodium aluminate solution with an Al2O3 concentration of 60 to 80 g / L; a pore-enlarging agent is added to the sodium aluminate solution, and CO2 is introduced to carry out a carbonization reaction, and then the solution is subjected to aging, washing and drying steps in sequence to obtain macroporous pseudo-boehmite; the washed liquid is returned to the sintering alumina process.

[0031] The present invention uses the crude liquid leached from the clinker in the sintering alumina process as the raw material source of alumina. The clinker in the sintering alumina process has been calcined at a high temperature of 1100-1200°C. The Al2O3 content in the crude liquid finally obtained is low, which meets the requirements of the pseudo-boehmite production process. Only a small amount of water needs to be added for preparation, which can save a lot of water, and the generated washing liquid can be returned to the alumina production process, and the production process can achieve a closed loop; in addition, a small amount of impurity SiO2 in the crude liquid can increase the pore volume and increase the catalytic activity of the product. At the same time, the above-mentioned crude liquid leached from the clinker has stable performance and can prepare high-quality macroporous pseudo-boehmite. The method can consume a large amount of red mud and promote the high added value utilization of industrial waste red mud.

[0032] In the present invention, the parameters of the clinker dissolution crude solution in the sintering alumina process are as follows: caustic ratio a k It is 1.0~1.5, the concentration of Al2O3 is 70~90g / L, and the concentration of SiO2 is 1.0~2.5g / L.

[0033] The present invention uses soft water to dilute the crude liquor dissolved from the clinker in the sintering alumina process, and the standing time is 20 to 30 hours.

[0034] The pore-enlarging agent of the present invention is selected from urea or ethanol. After urea is added, it can gradually decompose and generate gas at high temperature, which plays a role of expanding the pores. After ethanol is added, the characteristic of forming an azeotrope with water is utilized to replace water in the material to the maximum extent, reduce the generation of agglomeration phenomenon, and effectively improve the performance of pseudo-boehmite. The amount of the pore-enlarging agent added is 0.5-2wt% of the mass of the sodium aluminate solution. Too much urea added will reduce the relative crystallinity of the pseudo-boehmite, and too much ethanol added will affect the peptization solubility of the pseudo-boehmite.

[0035] In the present invention, in the step of adding the pore-enlarging agent, the temperature of the sodium aluminate solution is controlled to be 30-50° C., and the pore-enlarging agent is added under stirring conditions to increase the contact between the solutions and accelerate the reaction.

[0036] In the present invention, the volume fraction of CO2 is 30-35%, and the carbonization reaction time is 15-20 minutes. The temperature during the carbonization process is controlled within 57°C. When the temperature is low, the product is mainly pseudo-boehmite. If the carbonization temperature is too high, the hydrolysis reaction rate of NaAlO2 is accelerated, and the gibbsite content gradually increases, which will affect the structure and performance of the pseudo-boehmite; when the temperature is too low, the CO2 absorption rate is too low, resulting in a longer reaction time, so the temperature of the carbonization process is further preferably 35-45°C. The decomposition rate of alumina is 90-97%.

[0037] In the present invention, the aging temperature is 60-90° C., and the aging time is 0.5-2 hours. The present invention does not impose any special restrictions on the aging process, and the aging method commonly used in the art can be used.

[0038] After the aging step, the present invention performs solid-liquid separation on the aging liquid obtained after the aging step, and then repeatedly washes and filters the filter cake after solid-liquid separation with hot water at 85 to 95° C. until the pH of the filtrate reaches 7; the hot water after washing is returned to the sintering alumina process as washing water.

[0039] The drying steps of the present invention are: first drying at 85-100° C. for 0.5-2 hours, and then drying at 105-110° C. for 2-4 hours. Drying at a relatively low temperature first is to ensure that the peptization rate of the pseudo-boehmite does not change significantly, and the particle size does not decrease significantly. Drying at 105-110° C. is mainly to dry out the moisture in the product.

[0040] The present invention also provides macroporous pseudo-boehmite obtained by the above production method; the pore volume of the macroporous pseudo-boehmite is 1.0 cm 3 / g or more, and whiteness is above 95%.

[0041] The technical solution of the present invention is further described below in conjunction with specific embodiments. In the following embodiments, the composition parameters of the raw liquor of clinker dissolution in the sintering alumina process are as follows: caustic ratio a k is 1.2, Al2O3 concentration is 85g / L, and SiO2 is 1.5g / L.

[0042] Example 1

[0043] This embodiment provides a method for producing macroporous pseudo-boehmite. The preparation process diagram is shown in FIG. Figure 1 shown.

[0044] (1) After the crude liquid from the clinker dissolution in the sintering alumina process is cooled by heat exchange with cold water using a plate heat exchanger, it is diluted with soft water (hardness ≤ 10, alkalinity ≤ 300 μmol / L) sent from a power plant to a concentration of 65 g / L Al2O3 and 1.15 g / L SiO2, and allowed to stand in a sedimentation tank for 24 hours, and then the precipitate is filtered out by a bag filter to obtain a high-purity sodium aluminate solution;

[0045] (2) Carbonization: Add 1 wt% ethanol to the high-purity sodium aluminate solution in step (1), control the temperature to 40°C, stir and mix, and then pump it into a carbonization tank. Pass the solution at one end of the carbonization tank and pass CO2 gas at the other end (control the volume fraction of CO2 to 35%) to make the end point pH about 11. Complete the decomposition into gel within 20 minutes to obtain a carbonized slurry;

[0046] (3) Aging: The carbonized slurry in step (2) is pumped into an aging tank, and the temperature is raised by hot water and fresh steam from a plate heat exchanger, and the temperature is kept constant at 85° C. and stirred for 1 hour; and an aging liquid that has passed the aging test is obtained;

[0047] (4) Washing: The aged liquid that has passed the aging test in step (3) is passed through a plate and frame filter press for solid-liquid separation, and the filter cake is then repeatedly washed and filtered with hot water at 90° C. until the pH of the filtrate reaches about 7. The hot water after washing is returned to the alumina process as washing water.

[0048] (5) Drying: The filter cake in step (4) is placed in a rotary flash dryer for drying, first at 90° C. for 1 h, and then at 105° C. for 3 h, to obtain a macroporous pseudo-boehmite product.

[0049] The scanning electron microscope (SEM) image of the macroporous pseudo-boehmite obtained in this example is as follows: Figure 2 and Figure 3 As shown in the macroscopic photograph Figure 4 shown.

[0050] Example 2

[0051] This embodiment provides a method for producing macroporous pseudo-boehmite.

[0052] (1) After the crude liquid from the clinker dissolution in the sintering alumina process is cooled by heat exchange with cold water using a plate heat exchanger, it is diluted with soft water (hardness ≤ 10, alkalinity ≤ 300 μmol / L) sent from a power plant to a concentration of 70 g / L Al2O3 and 1.2 g / L SiO2, and allowed to stand in a sedimentation tank for 24 hours. The precipitate is then filtered out using a bag filter to obtain a high-purity sodium aluminate solution;

[0053] (2) Carbonization: Add 1 wt% urea to the high-purity sodium aluminate solution in step (1), control the temperature to 40°C, stir and mix, and then pump into a carbonization tank. Pass the solution at one end of the carbonization tank and pass CO2 gas at the other end (control the volume fraction of CO2 to 35%) to make the end point pH about 11. Complete the decomposition into gel within 15 minutes to obtain a carbonized slurry;

[0054] (3) Aging: The carbonized slurry in step (2) is pumped into an aging tank, and the temperature is raised by hot water and fresh steam from a plate heat exchanger, and the temperature is kept constant at 85° C. and stirred for 1 hour; and an aging liquid that has passed the aging test is obtained;

[0055] (4) Washing: The aged liquid that has passed the aging test in step (3) is passed through a plate and frame filter press for solid-liquid separation, and the filter cake is then repeatedly washed and filtered with hot water at 90° C. until the pH of the filtrate reaches about 7. The hot water after washing is returned to the alumina process as washing water.

[0056] (5) Drying: The filter cake in step (4) is placed in a rotary flash dryer for drying, first at 90° C. for 1 h, and then at 105° C. for 3 h, to obtain a macroporous pseudo-boehmite product.

[0057] Example 3

[0058] This embodiment provides a method for producing macroporous pseudo-boehmite.

[0059] (1) After the crude liquid from the clinker dissolution in the sintering alumina process is cooled by heat exchange with cold water using a plate heat exchanger, it is diluted with soft water (hardness ≤ 10, alkalinity ≤ 300 μmol / L) sent from a power plant to a concentration of 78 g / L Al2O3 and 1.4 g / L SiO2, and allowed to stand in a sedimentation tank for 24 hours. The precipitate is then filtered out using a bag filter to obtain a high-purity sodium aluminate solution;

[0060] (2) Carbonization: Add 1 wt% ethanol to the high-purity sodium aluminate solution in step (1), control the temperature to 40°C, stir and mix, and then pump it into a carbonization tank. Pass the solution at one end of the carbonization tank and pass CO2 gas at the other end (control the volume fraction of CO2 to 30%) to make the end point pH about 11. Complete the decomposition into gel within 20 minutes to obtain a carbonized slurry;

[0061] (3) Aging: The carbonized slurry in step (2) is pumped into an aging tank, and the temperature is raised by hot water and fresh steam from a plate heat exchanger, and the temperature is kept constant at 85° C. and stirred for 1 hour; and an aging liquid that has passed the aging test is obtained;

[0062] (4) Washing: The aged liquid that has passed the aging test in step (3) is passed through a plate and frame filter press for solid-liquid separation, and the filter cake is then repeatedly washed and filtered with hot water at 90° C. until the pH of the filtrate reaches about 7. The hot water after washing is returned to the alumina process as washing water.

[0063] (5) Drying: The filter cake in step (4) is placed in a rotary flash dryer for drying, first at 90° C. for 1 h, and then at 105° C. for 3 h, to obtain a macroporous pseudo-boehmite product.

[0064] The scanning electron microscope (SEM) image of the macroporous pseudo-boehmite obtained in this example is as follows: Figure 5 shown.

[0065] Comparative Example 1

[0066] Compared with Example 1, the high-purity sodium aluminate solution in this comparative example is obtained by reacting sodium hydroxide and aluminum hydroxide, and the Al2O3 concentration is 65 g / L. Steps (2) to (4) are the same as those in Example 1.

[0067] Comparative Example 2

[0068] Compared with Example 2, the high-purity sodium aluminate solution in this comparative example is obtained by reacting sodium hydroxide and aluminum hydroxide, the Al2O3 concentration is 70 g / L, and steps (2) to (4) are the same as those in Example 2.

[0069] The properties of the pseudo-boehmite obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were measured. The pore volume and specific surface area were measured using a NOVA 4000e specific surface area and pore size distribution instrument. The whiteness was measured using a whiteness meter. The test results are shown in Table 1.

[0070] Table 1 Pseudo-boehmite performance data of Examples 1 to 3 and Comparative Examples 1 to 2

[0071]

[0072] It can be seen from Table 1 that the pseudo-boehmite product obtained in the embodiment has a higher pore volume than the pseudo-boehmite product in the comparative example, and the pore volume reaches 0.95 cm 3 / g or more, and the specific surface area is larger, exceeding 350m 2 / g.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing macroporous pseudo-boehmite, characterized in that: The steps include: The crude liquid dissolved from the clinker in the sintering alumina process is diluted, allowed to stand and filtered to obtain a sodium aluminate solution with an Al2O3 concentration of 60 to 80 g / L; a pore-enlarging agent is added to the sodium aluminate solution, and CO2 is introduced to carry out a carbonization reaction, and then the solution is subjected to aging, washing and drying steps in sequence to obtain macroporous pseudo-boehmite; the washed liquid is returned to the sintering alumina process.

2. The production method according to claim 1, characterized in that The parameters of the raw liquor dissolved from the clinker in the sintering alumina process are as follows: caustic ratio a k It is 1.0~1.5, the concentration of Al2O3 is 70~90g / L, and the concentration of SiO2 is 1.0~2.5g / L.

3. The production method according to claim 1, characterized in that The pore expanding agent is selected from urea or ethanol.

4. The production method according to claim 3, characterized in that The amount of the pore-enlarging agent added is 0.5-2 wt % of the mass of the sodium aluminate solution.

5. The production method according to claim 1, characterized in that In the step of adding the pore-enlarging agent, the temperature of the sodium aluminate solution is controlled to be 30-50° C., and the pore-enlarging agent is added under stirring conditions.

6. The production method according to claim 1, characterized in that The volume fraction of CO2 is 30-35%, and the carbonization reaction time is 15-20 minutes.

7. The production method according to claim 1, characterized in that The aging temperature is 60-90° C., and the aging time is 0.5-2 h.

8. The production method according to claim 1, characterized in that The washing step comprises: performing solid-liquid separation on the aged liquid obtained after the aging step, and then repeatedly washing and filtering the filter cake after the solid-liquid separation with hot water at 85 to 95° C. until the pH of the filtrate reaches 7.

9. The production method according to claim 1, characterized in that The drying step is: first drying at 85-100° C. for 0.5-2 h, and then drying at 105-110° C. for 2-4 h.

10. A macroporous pseudo-boehmite obtained by the production method according to any one of claims 1 to 9.

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