A preparation method of modified alumina

Abstract

An embodiment of the present invention discloses a preparation method of modified alumina, which relates to the technical field of inorganic catalytic materials. The preparation method includes the following steps: Step 1: Prepare a rare earth modifier solution containing a dispersant and a sodium aluminate solution containing a pore expander for standby; Step 2: Prepare a Me(OH) x slurry by coprecipitation method; Step 3: Age the prepared Me(OH) x slurry at 50°C to 90°C for 24 h to 240 h to obtain a wet Me(OH) x filter cake; Step 4: Hydrothermally react the wet Me(OH) x filter cake with an aqueous alkali solution in an autoclave to obtain a dry Me(OH) x powder; Step 5: Calcinate the dry Me(OH) x powder to obtain modified alumina. The preparation method of the present invention has the advantages of short process flow, simple process, low construction cost, low production cost, excellent physical and chemical properties of the product, etc., and can greatly improve the high-temperature thermal stability of the automotive exhaust catalytic purifier and the service life of the catalyst.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of inorganic catalytic materials, and particularly to a preparation method of modified alumina. Background Art

[0002] With the development of the automotive industry, automotive exhaust has caused extremely serious harm to the human living environment and is one of the main pollutants of global air pollution today. The main pollutants emitted by automobiles include hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO), and particulate matter (PM), etc. Catalytic purification of automotive exhaust is one of the effective means to control automotive exhaust emissions today. By the end of 2014, the number of motor vehicles in China reached 264 million, including 154 million automobiles. Since the end of 2016, China has fully implemented the National V emission standards for gasoline and diesel vehicles. After the implementation of the National V standards, a new catalyst market with a capacity of up to 15 million liters will emerge. China produces more than 70 million engines annually, and the number of automobiles in China exceeds 190 million. Calculated based on a catalyst life of 80,000 kilometers or 5 years, the exhaust purification catalysts of more than 20 million automobiles will reach the end of their service life and need to be replaced every year. Industry insiders estimate that the annual market demand for exhaust purification catalysts is as high as tens of billions to hundreds of billions of yuan.

[0003] Activated alumina has porosity, a high specific surface area, and good adsorption properties. It is the most widely used variety in the field of catalyst carriers and is also widely used in the catalytic purification of automotive exhaust. At present, the main method for producing modified alumina is the impregnation method, that is, impregnating activated alumina with a modifier. This process is restricted by the product indexes of activated alumina, and the specific surface area, pore volume, and pore diameter of the produced modified alumina do not meet the requirements of catalyst carriers. Methods such as deposition precipitation method, co-current precipitation method, and alcohol-aluminum method are restricted by the control of the technological process and cannot be well applied in production practice. Summary of the Invention

[0004] Therefore, the embodiments of the present invention provide a preparation method of modified alumina to solve the problems in the prior art that the prepared modified alumina does not meet the requirements of catalyst carriers and has poor application effects.

[0005] To achieve the above object, the embodiments of the present invention provide the following technical solutions:

[0006] According to the first aspect of the embodiments of the present invention, a preparation method of modified alumina, the preparation method includes the following steps:

[0007] Step 1: Dissolve a dispersant and a rare earth modifier in water to prepare a modifier solution for standby; add a pore-expanding agent wetted with absolute ethanol to a sodium aluminate solution with a concentration of 75 - 120 g / L to prepare a sodium aluminate solution containing the pore-expanding agent for standby;

[0008] Step 2: Using the co-precipitation method, under the protection of carbon dioxide gas, a modifier solution is dropped into a sodium aluminate solution containing a pore-forming agent to prepare Me(OH) x slurry;

[0009] Step 3: The prepared Me(OH) x slurry is aged at 50°C to 90°C for 24h to 240h. After aging, it is filtered and washed to obtain wet Me(OH) x filter cake;

[0010] Step 4: The wet Me(OH) x filter cake and an aqueous alkali solution with a concentration of 5g / l to 50g / l are placed in an autoclave for hydrothermal reaction; the mixed solution obtained after the hydrothermal reaction is filtered, washed, and dried to obtain dry Me(OH) x powder;

[0011] Step 5: The dry Me(OH) x powder is calcined at 730°C for 2h to obtain modified alumina.

[0012] Further, in Step 1, the dispersant is one of polyvinyl alcohol, sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, polyacrylamide, citric acid, and Tween 80, and is added in an amount of 1% to 10% of the mass of alumina.

[0013] Further, in Step 1, the rare earth modifier is a mixture of lanthanum nitrate, cerium nitrate, and zirconium nitrate, and the total amount of the rare earth modifier is 5% to 40% of the mass of alumina in terms of oxide.

[0014] Further, in Step 1, the pore-forming agent is one or two of acetylene black, activated carbon powder, and graphite powder, and is added in an amount of 1% to 20% of the mass of alumina.

[0015] Further, in Step 2, the process parameters of the co-precipitation method are: the precipitation temperature is 25°C to 80°C, the industrial CO 2 flow rate is 1L / min to 100L / min, the end point pH value is 9 to 9.5, and the titration rate of the modifier solution is 0.1L / h to 50L / h.

[0016] Further, in Step 4, the weight ratio of the wet Me(OH) x filter cake to the aqueous alkali solution with a concentration of 5g / l to 50g / l is 1:1 - 20:1.

[0017] Further, in Step 4, the aqueous alkali solution is an aqueous ammonium bicarbonate solution or an aqueous ammonia solution.

[0018] Further, in Step 4, the conditions for the hydrothermal reaction are: the reaction temperature is 100°C - 160°C, and the reaction time is 1 - 10 h.

[0019] The embodiments of the present invention have the following advantages:

[0020] The embodiments of the present invention provide a preparation method for modified alumina with a large specific surface area and large pore volume. This preparation method uses sodium aluminate solution and rare earth modifiers as raw materials, and prepares γ-alumina with an Na 2 O content of less than 0.1%, having a large specific surface area and large pore volume through processes such as carbonation co-precipitation, aging, hydrothermal treatment, and calcination. The present invention has the advantages of a short process flow, simple process, low construction cost, low production cost, wide raw material sources, low requirements for raw material components, and excellent physical and chemical properties of the product, and can greatly improve the high-temperature thermal stability and catalyst service life of automotive exhaust catalytic purifiers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained based on the provided drawings.

[0022] The structures, ratios, sizes, etc. shown in this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limited conditions for the implementation of the present invention. Therefore, they do not have technical essential significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the efficacy and purpose that the present invention can achieve, should still fall within the scope covered by the technical content disclosed in the present invention.

[0023] Figure 1 It is a process flow chart of a preparation method for modified alumina provided in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following specific embodiments illustrate the embodiments of the present invention. Those familiar with this technology can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope protected by the present invention.

[0025] Embodiment 1

[0026] A preparation method for modified alumina, the process flow of which is asFigure 1 As shown, the preparation method includes the following steps:

[0027] Step 1: Dissolve the dispersant and rare earth modifier in water to prepare 1 L of modifier solution for standby; among them, the rare earth modifier is a mixture of lanthanum nitrate, cerium nitrate and zirconium nitrate, and the rare earth modifier accounts for 20% of alumina in terms of oxide, and the ratio of each oxide is: CeO 2 45%, ZrO 2 40%, La 2 O 3 15%; the dispersant is sodium dodecylbenzenesulfonate, which is added according to 2% of the mass of alumina;

[0028] Add the pore former wetted with absolute ethanol to the sodium aluminate solution with a concentration of 75 g / L to prepare 1 L of sodium aluminate solution containing the pore former for standby; among them, the pore former is acetylene black, which is added according to 5% of the mass of alumina, and the acetylene black is wetted with 20 ml of absolute ethanol.

[0029] Step 2: Adopt the co-precipitation method. Under the protection of carbon dioxide gas, drop the modifier solution into the sodium aluminate solution containing the pore former to prepare Me(OH) x slurry; the process parameters of the co-precipitation method are: the precipitation temperature is 48 °C, the flow rate of industrial CO 2 is 1.5 L / min, the final pH value is 9.0, and the titration rate of the modifier solution is 0.5 L / h.

[0030] Step 3: Age the prepared Me(OH) x slurry at 75 °C for 68 h. After aging, filter and wash four times to obtain wet Me(OH) x filter cake;

[0031] Step 4: Place the wet Me(OH) x filter cake and the ammonia water solution with a concentration of 15 g / l in an autoclave and carry out hydrothermal reaction at 120 °C for 2 h; filter and wash the mixed liquid obtained after the hydrothermal reaction twice, take the filter cake and place it in a drying oven at 80 °C to dry to obtain dry Me(OH) x powder; among them, the weight ratio of the wet Me(OH) x filter cake to the ammonia water solution with a concentration of 15 g / l is 2:1.

[0032] Step 5: Calcinate the dry Me(OH) x powder at 730 °C for 2 h to obtain modified alumina.

[0033] Through XRD test and analysis, it is obtained that the modified alumina is γ-phase alumina.

[0034] The specific surface area of the obtained modified alumina is 352 m 2 / g, with a pore volume of 0.8 ml / g and its Na 2 O content being 0.084%.

[0035] Example 2

[0036] A preparation method of modified alumina, whose technological process is the same as that of Example 1. The preparation method includes the following steps:

[0037] Step 1: Dissolve the dispersant and rare earth modifier in water to prepare 1 L of modifier solution for standby; among them, the rare earth modifier is a mixture of lanthanum nitrate, cerium nitrate and zirconium nitrate. The rare earth modifier accounts for 40% of alumina calculated as oxides, and the ratio of each oxide is: CeO 2 60%, ZrO 2 30%, La 2 O 3 10%; the dispersant is polyvinyl alcohol, which is added according to 5% of the mass of alumina;

[0038] Add the pore-expanding agent wetted with absolute ethanol to the sodium aluminate solution with a concentration of 120 g / L to prepare 1 L of sodium aluminate solution containing the pore-expanding agent for standby; among them, the pore-expanding agent is a mixture of acetylene black and activated carbon powder in a mass ratio of 1:1, and the total amount of the mixture is added according to 20% of the mass of alumina. The mixed pore-expanding agent is wetted with 50 ml of absolute ethanol.

[0039] Step 2: Adopt the co-precipitation method. Under the protection of carbon dioxide gas, add the modifier solution dropwise to the sodium aluminate solution containing the pore-expanding agent to prepare Me(OH) x slurry; the technological parameters of the co-precipitation method are: the precipitation temperature is 75 °C, the flow rate of industrial CO 2 is 2 L / min, the final pH value is 9.5, and the titration speed of the modifier solution is 1 L / h.

[0040] Step 3: Age the prepared Me(OH) x slurry at 85 °C for 120 h. After aging, filter and wash it four times to obtain wet Me(OH) x filter cake;

[0041] Step 4: Place the wet Me(OH) x filter cake and the ammonium bicarbonate aqueous solution with a concentration of 50 g / l in a pressure kettle and carry out hydrothermal reaction at 150 °C for 6 h; after the hydrothermal reaction is completed, filter and wash the obtained mixed solution twice, take the filter cake and place it in a drying oven to dry at 80 °C to obtain dry Me(OH) x powder; among them, the weight ratio of the wet Me(OH) x filter cake to the ammonium bicarbonate aqueous solution with a concentration of 15 g / l is 5:1.

[0042] Step 5: Place the dry Me(OH) xThe powder is calcined at 730 °C for 2 h to obtain modified alumina.

[0043] Through XRD test and analysis, it is obtained that the modified alumina is γ-phase alumina.

[0044] The specific surface area of the obtained modified alumina is 407 m 2 / g, the pore volume is 1.1 ml / g, and its Na 2 O content is 0.023%.

[0045] Example 3

[0046] A preparation method of modified alumina, the process flow of which is the same as that of Example 1. The preparation method includes the following steps:

[0047] Step 1: Dissolve the dispersant and rare earth modifier in water to prepare 20 L of modifier solution for standby; among them, the rare earth modifier is a mixture of lanthanum nitrate, cerium nitrate and zirconium nitrate. The rare earth modifier accounts for 25% of alumina in terms of oxide, and the ratio of each oxide is: CeO 2 30%, ZrO 2 60%, La 2 O 3 10%; the dispersant is polyvinylpyrrolidone, which is added according to 5% of the mass of alumina;

[0048] Add the pore-expanding agent wetted with absolute ethanol to the sodium aluminate solution with a concentration of 75 g / L to prepare 10 L of sodium aluminate solution containing the pore-expanding agent for standby; among them, the pore-expanding agent is a mixture of acetylene black and graphite powder in a mass ratio of 1:1, and the total amount of the mixture is added according to 20% of the mass of alumina. The mixed pore-expanding agent is wetted with 50 ml of absolute ethanol.

[0049] Step 2: Adopt the co-precipitation method. Under the protection of carbon dioxide gas, add the modifier solution dropwise to the sodium aluminate solution containing the pore-expanding agent to prepare Me(OH) x slurry; the process parameters of the co-precipitation method are: the precipitation temperature is 55 °C, the flow rate of industrial CO 2 is 25 L / min, the end point pH value is 9.5, and the titration rate of the modifier solution is 20 L / h.

[0050] Step 3: Age the prepared Me(OH) x slurry at 60 °C for 200 h. After aging, filter and wash it four times to obtain wet Me(OH) x filter cake;

[0051] Step 4: The wet Me(OH) xThe filter cake and the ammonia water solution with a concentration of 20 g / l are placed in an autoclave and subjected to hydrothermal reaction at 160 °C for 2 h; after the hydrothermal reaction is completed, the obtained mixed solution is filtered and washed twice, and the filter cake is placed in a drying oven and dried at 80 °C to obtain dry Me(OH) x powder; where the wet Me(OH) x The weight ratio of the filter cake to the ammonia water solution with a concentration of 20 g / l is 10:1.

[0052] Step five: Calcinate the dry Me(OH) x powder at 730 °C for 2 h to obtain modified alumina.

[0053] Through XRD test and analysis, it is obtained that the modified alumina is γ-phase alumina.

[0054] The specific surface area of the obtained modified alumina is 422 m 2 / g, the pore volume is 1.0 ml / g, and its Na 2 O content is 0.022%.

[0055] Example 4

[0056] A preparation method of modified alumina includes the following steps:

[0057] Step one: Dissolve the dispersant and the rare earth modifier in water to prepare 20 L of modifier solution for standby; among them, the rare earth modifier is a mixture of lanthanum nitrate, cerium nitrate and zirconium nitrate, and the rare earth modifier accounts for 5% of alumina in terms of oxide, and the ratio of each oxide is: CeO 2 30%, ZrO 2 60%, La 2 O 3 10%; the dispersant is polyacrylamide, which is added according to 1% of the alumina mass;

[0058] Add the pore-expanding agent wetted with absolute ethanol to the sodium aluminate solution with a concentration of 120 g / L to prepare 10 L of sodium aluminate solution containing the pore-expanding agent for standby; among them, the pore-expanding agent is a mixture of acetylene black and graphite powder in a mass ratio of 1:1, and the total amount of the mixture is added according to 1% of the alumina mass, and the mixed pore-expanding agent is wetted with 50 ml of absolute ethanol.

[0059] Step two: Adopt the co-precipitation method, under the protection of carbon dioxide gas, drop the modifier solution into the sodium aluminate solution containing the pore-expanding agent to prepare Me(OH) x slurry; the process parameters of the co-precipitation method are: the precipitation temperature is 25 °C, the industrial CO 2 flow rate is 1 L / min, the end point pH value is 9.5, and the titration rate of the modifier solution is 50 L / h.

[0060] Step three: Place the prepared Me(OH)x The slurry was aged at 50 °C for 24 h, and after the aging was completed, it was filtered and washed four times to obtain wet Me(OH) x filter cake;

[0061] Step Four: Place the wet Me(OH) x filter cake and an aqueous alkali solution with a concentration of 5 g / l in an autoclave and carry out a hydrothermal reaction at 100 °C for 1 h; after the hydrothermal reaction is completed, the obtained mixture is filtered and washed twice, and the filter cake is placed in an oven and dried at 80 °C to obtain dry Me(OH) x powder; where the wet Me(OH) x filter cake and the aqueous alkali solution with a concentration of 5 g / l have a weight ratio of 20:1.

[0062] Step Five: Calcinate the dry Me(OH) x powder at 730 °C for 2 h to obtain modified alumina.

[0063] Through XRD test and analysis, it is obtained that the modified alumina is γ-phase alumina.

[0064] The specific surface area of the obtained modified alumina is 301 m 2 / g, the pore volume is 0.68 ml / g, and its Na 2 O content is 0.025%.

[0065] Example 5

[0066] A preparation method of modified alumina includes the following steps:

[0067] Step One: Dissolve a dispersant and a rare earth modifier in water to prepare 20 L of a modifier solution for standby; among them, the rare earth modifier is a mixture of lanthanum nitrate, cerium nitrate and zirconium nitrate, and the rare earth modifier accounts for 34% of alumina in terms of oxides, and the ratio of each oxide is: CeO 2 30%, ZrO 2 60%, La 2 O 3 10%; the dispersant is Tween 80, and it is added according to 10% of the mass of alumina;

[0068] Add the pore-expanding agent wetted with absolute ethanol to a sodium aluminate solution with a concentration of 75 g / L to prepare 10 L of a sodium aluminate solution containing the pore-expanding agent for standby; among them, the pore-expanding agent is a mixture of acetylene black and graphite powder in a mass ratio of 1:1, and the total amount of the mixture is added according to 10% of the mass of alumina, and the mixed pore-expanding agent is wetted with 50 ml of absolute ethanol.

[0069] Step Two: Adopt the co-precipitation method, under the protection of carbon dioxide gas, drop the modifier solution into the sodium aluminate solution containing the pore-expanding agent to prepare Me(OH) xSlurry; The process parameters of the coprecipitation method are as follows: the precipitation temperature is 80 °C, the industrial CO 2 flow rate is 100 L / min, the final pH value is 9.5, and the titration rate of the modifier solution is 0.1 L / h.

[0070] Step three: Age the prepared Me(OH) x slurry at 90 °C for 240 h. After aging, filter and wash it four times to obtain wet Me(OH) x filter cake;

[0071] Step four: Place the wet Me(OH) x filter cake and the alkaline aqueous solution with a concentration of 50 g / l in an autoclave and carry out hydrothermal reaction at 100 °C for 10 h; After the hydrothermal reaction is completed, filter and wash the obtained mixture twice, take the filter cake and place it in an oven to dry at 80 °C to obtain dry Me(OH) x powder; The weight ratio of the wet Me(OH) x filter cake to the alkaline aqueous solution with a concentration of 50 g / l is 20:1.

[0072] Step five: Calcinate the dry Me(OH) x powder at 730 °C for 2 h to obtain modified alumina.

[0073] Through XRD test and analysis, it is obtained that the modified alumina is γ-phase alumina.

[0074] The specific surface area of the obtained modified alumina is 451 m 2 / g, the pore volume is 1.2 ml / g, and its Na 2 O content is 0.019%.

[0075] Example 6

[0076] A preparation method of modified alumina includes the following steps:

[0077] Step one: Dissolve the dispersant and rare earth modifier in water to prepare 20 L of modifier solution for standby; Among them, the rare earth modifier is a mixture of lanthanum nitrate, cerium nitrate and zirconium nitrate. The rare earth modifier accounts for 34% of alumina in terms of oxide, and the ratio of each oxide is: CeO 2 30%, ZrO 2 60%, La 2 O 3 10%; The dispersant is polyacrylamide, which is added according to 10% of the mass of alumina;

[0078] The pore-expanding agent wetted with absolute ethanol was added to the sodium aluminate solution with a concentration of 100 g / L to prepare 10 L of sodium aluminate solution containing the pore-expanding agent for standby; the pore-expanding agent was composed of acetylene black and graphite powder mixed in a mass ratio of 1:1, and the total amount of the mixture was added at 10% of the mass of alumina. The mixed pore-expanding agent was wetted with 50 ml of absolute ethanol.

[0079] Step 2: Using the co-precipitation method, under the protection of carbon dioxide gas, a modifier solution was dropped into the sodium aluminate solution containing the pore-expanding agent to prepare Me(OH) x slurry; the process parameters of the co-precipitation method were: the precipitation temperature was 80 °C, the industrial CO 2 flow rate was 100 L / min, the final pH value was 9.5, and the titration rate of the modifier solution was 0.1 L / h.

[0080] Step 3: The prepared Me(OH) x slurry was aged at 90 °C for 240 h. After aging, it was filtered and washed four times to obtain wet Me(OH) x filter cake;

[0081] Step 4: The wet Me(OH) x filter cake and the alkaline aqueous solution with a concentration of 50 g / l were placed in an autoclave and hydrothermally reacted at 100 °C for 10 h; the mixed solution obtained after the hydrothermal reaction was filtered and washed twice, and the filter cake was placed in a drying oven and dried at 80 °C to obtain dry Me(OH) x powder; the weight ratio of the wet Me(OH) x filter cake to the alkaline aqueous solution with a concentration of 50 g / l was 20:1.

[0082] Step 5: The dry Me(OH) x powder was calcined at 730 °C for 2 h to obtain modified alumina.

[0083] Through XRD test and analysis, it was found that the modified alumina was γ-phase alumina.

[0084] The specific surface area of the obtained modified alumina was 403 m 2 / g, the pore volume was 0.9 ml / g, and its Na 2 O content was 0.020%.

[0085] Comparative Example

[0086] A preparation method of modified alumina includes the following steps:

[0087] Step 1: The rare earth modifier was dissolved in water to prepare 20 L of modifier solution for standby; among them, the rare earth modifier was a mixture of lanthanum nitrate, cerium nitrate and zirconium nitrate. The rare earth modifier accounted for 34% of alumina in terms of oxides. The ratio of each oxide was: CeO 230%, ZrO 2 60%, La 2 O 3 10%;

[0088] Step 2: Using the co-precipitation method, under the protection of carbon dioxide gas, add the modifier solution dropwise to the sodium aluminate solution to prepare a Me(OH) x slurry; the process parameters of the co-precipitation method are: the precipitation temperature is 80 °C, the industrial CO 2 flow rate is 100 L / min, the final pH value is 9.5, and the titration rate of the modifier solution is 0.1 L / h.

[0089] Step 3: Age the prepared Me(OH) x slurry at 90 °C for 240 h. After aging, filter and wash four times to obtain a wet Me(OH) x filter cake;

[0090] Step 4: Place the wet Me(OH) x filter cake and the alkaline aqueous solution with a concentration of 50 g / l in an autoclave and carry out a hydrothermal reaction at 100 °C for 10 h; after the hydrothermal reaction is completed, filter and wash the obtained mixture twice, take the filter cake and place it in a drying oven to dry at 80 °C to obtain dry Me(OH) x powder; the weight ratio of the wet Me(OH) x filter cake to the alkaline aqueous solution with a concentration of 50 g / l is 20:1.

[0091] Step 5: Calcinate the dry Me(OH) x powder at 730 °C for 2 h to obtain modified alumina.

[0092] The specific surface area of the obtained modified alumina is 277 m 2 / g, the pore volume is 0.63 ml / g, and its Na 2 O content is 0.024%.

[0093] It can be seen from the above experimental results that the modified alumina prepared by using the preparation method of a modified alumina of the present invention has the advantages of low impurity Na content, large specific surface area, and large pore volume; through the comparison results of Example 6 and the comparative example, it can be seen that in the preparation process, the modifier solution added with a dispersant and the sodium aluminate solution added with a pore expander are used as raw materials, and the modified alumina prepared through processes such as carbonation co-precipitation, aging, hydrothermal treatment, and calcination has a lower sodium content, a larger specific surface area, and a larger pore volume.

[0094] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made thereto based on the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A preparation method of modified alumina, characterized in that, the preparation method comprises the following steps: Step 1: Dissolve a dispersant and a rare earth modifier in water to prepare a modifier solution for standby; Add an expanded pore agent wetted with absolute ethanol to a sodium aluminate solution with a concentration of 75 - 120 g / L to prepare a sodium aluminate solution containing the expanded pore agent for standby; Step 2: Using the co-precipitation method, under the protection of carbon dioxide gas, a modifier solution is dropped into the sodium aluminate solution containing a pore-expanding agent to prepare a Me(OH) x slurry; Step 3: Aging the prepared Me(OH) x slurry at 50°C to 90°C for 24 h to 240 h. After aging, filter and wash to obtain wet Me(OH) x filter cake; Step 4: Place the wet Me(OH) x filter cake and an aqueous alkali solution with a concentration of 5 g / l to 50 g / l in an autoclave for hydrothermal reaction; filter, wash, and dry the mixed solution obtained after the hydrothermal reaction to obtain dry Me(OH) x powder; Step Five: Calcinate dry Me(OH) x powder at 730 °C for 2 h to obtain modified alumina; In Step 1, the expanded pore agent is one or two of acetylene black, activated carbon powder and graphite powder, and is added in an amount of 1% - 20% of the mass of alumina; In Step 2, the process parameters of the coprecipitation method are as follows: the precipitation temperature is 25°C to 80°C, the industrial CO 2 flow rate is 1 L / min to 100 L / min, the final pH value is 9 to 9.5, and the titration rate of the modifier solution is 0.1 L / h to 50 L / h: In Step 4, wet Me(OH) x The weight ratio of the filter cake to the aqueous alkali solution with a concentration of 5 g / l to 50 g / l is 1:1 - 20:1; In Step 4, the alkaline aqueous solution is an ammonium bicarbonate aqueous solution or an ammonia aqueous solution; In Step 4, the conditions of the hydrothermal reaction are: the reaction temperature is 100°C - 160°C, and the reaction time is 1 - 10 h; In Step 1, the dispersant is one of polyvinyl alcohol, sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, polyacrylamide, citric acid, and Tween 80, and is added in an amount of 1% - 10% of the mass of alumina; In Step 1, the rare earth modifier is a mixture of lanthanum nitrate, cerium nitrate and zirconium nitrate, and the total amount of the rare earth modifier is 5% - 40% of the mass of alumina in terms of oxide.

Images