CN109721088B - Aluminum hydroxide and preparation method thereof - Google Patents
Aluminum hydroxide and preparation method thereof Download PDFInfo
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Abstract
The invention discloses aluminum hydroxide and a preparation method thereof. The reaction system adopted by the preparation method of the aluminum hydroxide comprises N micro-reactors connected in series, the first micro-reactor adopts an impinging stream reactor, the acidic material and the alkaline material enter the first micro-reactor to perform parallel flow reaction, the obtained products sequentially enter the second micro-reactor to the N-1 micro-reactor, the pH value of the products is repeatedly swung, and when the products swing to the alkaline side, the reaction temperature is 20-30 ℃ lower than that of the first micro-reactor; and when the aluminum hydroxide swings to the acid side, the reaction temperature is 20-30 ℃ higher than that of the first microreactor, the obtained reaction product mixed liquid enters the Nth microreactor for aging reaction, and the aluminum hydroxide is obtained through post-treatment. The aluminum hydroxide prepared by the method has high crystallinity, uniform grain size distribution, elimination of amplification effect, uniform pore size distribution and large pore volume and specific surface area of the alumina obtained after roasting, and is very suitable for preparing mesoporous hydrogenation catalysts such as residual oil hydrodesulfurization, denitrification and the like.
Description
Technical Field
The invention relates to aluminum hydroxide and a preparation method thereof, in particular to aluminum hydroxide used for a residual oil hydrotreating catalyst carrier and a preparation method thereof.
Background
In recent years, microreactors have attracted tremendous academic and commercial interest to researchers in many fields. This interest has been generated by the following features of microtechnology including size reduction, productivity enhancement, scaling up of the system to any desired production capacity (i.e., "capacity expansion"), increased heat transfer and increased mass transfer. Certain work related to microreactors has been reviewed by Gavilididis et al in "Technology And Applications Of microbiological Reactors" Trans. IhemE, Vol.80, part A, pages 3-30 (2002, 1 month). The micro-reactor is a chemical reaction system with a unit reaction interface width of micron order, and is a micro-chemical technology which is started in the 90 s. Since the prediction and advantages of microreactors in the preparation of nanoparticles were reported in 2002 by deMello and co-workers, microchannel technology of microreactors and the like has become more and more popular in the preparation of nanocrystals. The microreactor has the following advantages: (1) the flow in the channel is laminar flow; (2) the specific surface area is large, the heat transfer capacity is strong, and the temperature control is easy; (3) short molecular diffusion distance and fast mass transfer.
Alumina is an important chemical substance and is widely applied to industries such as petroleum, chemical engineering, ceramics, building materials, military industry, national defense and the like. The traditional preparation method is to use bauxite as a raw material and prepare the bauxite through the steps of high-temperature roasting, alkali liquor leaching, acid neutralization, heating decomposition and the like. The most common inorganic method is to neutralize industrial aluminium hydroxide or aluminate as raw material with alkali and acid to aluminium hydroxide, dry and activate. The method is mostly operated intermittently by a reaction kettle, and the produced product has low purity and crystallinity, uneven particle size distribution and lower efficiency. Modern chemistry and chemical industry, especially fine ceramics, fine chemical industry and petrochemical industry, require alumina having higher purity and crystallinity, uniform particle size distribution, and particle size of several tens micrometers to several hundreds micrometers, and are expected to be capable of continuous production, which is an important research topic at present.
CN103043694A discloses a preparation method of hydrated alumina, which comprises the following processes: (1) adding bottom water into a neutralization kettle, heating to 50-95 ℃, and simultaneously adding an acidic aluminum salt aqueous solution to control the pH value to be 2-4, and stabilizing for a period of time; (2) continuously adding an acidic aluminum salt aqueous solution and an alkali metal aluminate (or alkaline precipitator) solution into a neutralization kettle at the same time, adjusting the pH value to 6-8, and stabilizing for a period of time; (3) introducing an alkali metal aluminate solution (or an alkaline precipitator solution), adjusting the pH value to 8.5-12, and stabilizing for a period of time; (4) introducing an acidic aluminum salt water solution, adjusting the pH value to 2-4, and stabilizing for a period of time; (5) introducing an alkaline aluminate solution or an alkaline precipitator aqueous solution, adjusting the pH value to 8.5-12, and stabilizing for a period of time; (6) repeating the steps (4) and (5) for 1-4 times; (7) after the cementing, the hydrated alumina is prepared by aging, filtering, washing and drying; the steps (1) to (3) are carried out under the action of ultrasonic waves, and the frequency of the ultrasonic waves is 10-80 kHZ. The hydrated alumina prepared by the method has the pore distribution of 10-20 nm of only 64-67 percent, the crystallinity of less than 90 percent, and the product has more dispersive pore distribution and low crystallinity.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides aluminum hydroxide and a preparation method thereof. The aluminum hydroxide has high purity, high crystallinity and uniform grain size distribution. The method for preparing the aluminum hydroxide has the advantages of simple process, short reaction time, high process continuity efficiency, elimination of amplification effect and suitability for industrial production.
The invention provides aluminum hydroxide, wherein the content of pseudo-boehmite is more than 95wt%, and the relative crystallization degree is not less than 95%; the grain size distribution of the aluminum hydroxide is as follows: the number of the crystal grains with the diameter less than or equal to 15 mu m accounts for 1 to 5 percent of the total number of the aluminum hydroxide crystal grains, the number of the crystal grains with the diameter more than 15 mu m and less than 25 mu m accounts for 85 to 90 percent of the total number of the aluminum hydroxide crystal grains, and the number of the crystal grains with the diameter more than or equal to 25 mu m accounts for 5 to 10 percent of the total number of the aluminum hydroxide crystal grains.
The invention provides an aluminum hydroxide which is converted into gamma-Al2O3The properties are then as follows: the specific surface area is 300-400 m2The pore volume is 1.1-1.3 mL/g, and the pore size distribution is as follows: diameter of hole<The pore volume occupied by the 10nm pores is 5-10% of the total pore volume, the pore volume occupied by the pores with the diameter of 10-20 nm accounts for 85-95% of the total pore volume, and the pore volume occupied by the pores with the diameter larger than 20nm accounts for 5-10% of the total pore volume.
In the present invention, aluminum hydroxide is converted to γ -Al2O3The roasting conditions were as follows: roasting at 450-650 ℃ for 2-8 h.
The invention provides a preparation method of aluminum hydroxide, wherein a reaction system adopted comprises N microreactors which are connected in series, a first microreactor, a second microreactor, … … and an N microreactor are respectively arranged along a material flow direction, the first microreactor adopts an impinging stream reactor, and the method comprises the following steps:
(1) respectively preparing an alkaline material and an acidic material;
(2) respectively introducing an alkaline material and an acidic material into a first microreactor to perform a neutralization precipitation reaction;
(3) the reaction product mixed liquid obtained in the step (2) sequentially enters a second micro-reactor to an N-1 micro-reactor, and the reaction system is repeatedly subjected to pH value swing;
(4) and (4) allowing the reaction product mixed solution obtained in the step (3) to enter an N micro reactor for aging reaction, allowing the effluent of the N micro reactor to enter a product collecting tank, and filtering, washing and drying to obtain the aluminum hydroxide.
In the method, N microreactors are connected in series, wherein N is an integer not less than 5, preferably 5-11, and more preferably 5-7.
In the method, when N microreactors are connected in series, the specific process of pH value swing in the step (3) is as follows:
the mixed solution of the reaction products obtained in the step (2) enters a second micro reactor, and simultaneously, an acid material is introduced into the second micro reactor, so that the reaction system swings to the acid side; and the reaction product mixed solution obtained by the second microreactor enters a third microreactor, and meanwhile, an alkaline material is introduced into the third microreactor, so that the reaction system swings … towards the alkaline side, the obtained reaction product mixed solution sequentially enters a fourth microreactor to an N-1 microreactor, and the reaction system repeatedly swings towards the acid side and towards the alkaline side.
In the preparation method of the aluminum hydroxide, the alkaline material and the acidic material are respectively prepared in the step (1), wherein the alkaline material and the acidic material can be the alkaline material and the acidic material used in the preparation of the aluminum hydroxide by the conventional neutralization method in the field, for example, the alkaline material can be the alkaline materialThe acidic material can adopt an acidic aluminum-containing compound, the alkaline material can adopt an alkaline aluminum-containing compound, the acidic material can adopt an acidic precipitator, the alkaline material can adopt an alkaline aluminum-containing compound, and the acidic material can adopt an acidic aluminum-containing compound. The alkaline precipitant can be one or more selected from sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, ammonia water, etc. The acidic precipitant can be one or more selected from hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, etc. The basic aluminum-containing compounds used can be metaaluminates, such as sodium metaaluminate and/or potassium metaaluminate. The acidic aluminum-containing compound used may be one or more of aluminum chloride, aluminum nitrate and aluminum sulfate. When the alkaline material adopts an alkaline aluminum-containing compound, the concentration is Al2O3The amount of the surfactant is 8 to 80g/100mL, preferably 30 to 50g/100 mL. When the acidic material adopts an acidic aluminum-containing compound, the concentration is Al2O3The amount of the surfactant is 8 to 80g/100mL, preferably 30 to 50g/100 mL. The weight concentration of the alkaline precipitant can be 5-25%, preferably 10-20%. The weight concentration of the acidic precipitator can be 5-25%, preferably 10-20%.
In the preparation method of the aluminum hydroxide, the alkaline material and the acidic material are introduced into the first microreactor in the step (2), and can be introduced in an atomization mode or a liquid mode.
In the preparation method of the aluminum hydroxide, the first micro reactor is an impinging stream micro reactor, two feed inlets of the impinging stream micro reactor are respectively connected with an alkaline material and an acidic material, the alkaline material and the acidic material enter the impinging stream micro reactor and are communicated through a jet orifice, the jet orifice of the alkaline material and the jet orifice of the acidic material impact at a certain angle, and the impact angle is 150-180 degrees.
In the preparation method of the aluminum hydroxide, the raw material tank and the first microreactor are heated by adopting oil bath, and the other microreactors are heated by adopting microwave radiation.
In the preparation method of the aluminum hydroxide, the precipitation reaction in the step (2) has the following reaction conditions: the reaction temperature is 50-150 ℃, preferably 50-120 ℃, and the pH value is 8.0-9.0. The diameter of an inner tube of the first micro-reactor is 10-20 mm, preferably 10-15 mm, and the residence time of materials is controlled to be 1-5 min, preferably 1-2 min.
In the step (2), the flow rate of the alkaline material is 10-50 mL/min, preferably 15-30 mL/min. The flow rate of the acidic material can be regulated and controlled according to the pH value required by the system.
In the method for producing aluminum hydroxide of the present invention, in the step (3), when the reaction system is oscillated to the alkali side, the reaction conditions are controlled as follows: the reaction temperature is 20-30 ℃ lower than that of the first microreactor, and the pH value is 10.0-11.0. The diameter of an inner pipe of the micro-reactor is 5-10 mm larger than that of the previous micro-reactor, and the optimal diameter is 8-10 mm. The residence time of the materials in the micro-reactor is controlled to be 8-15 min, preferably 10-15 min.
In the method for producing aluminum hydroxide of the present invention, in the step (3), when the reaction system is oscillated to the acid side, the reaction conditions are controlled as follows: the reaction temperature is 20-30 ℃ higher than that of the first microreactor, and the pH value is 3.0-5.0. The diameter of an inner tube of the micro-reactor is 1-10 mm larger than that of the previous micro-reactor, and preferably 2-3 mm. The residence time of the materials in the microreactor is controlled to be 2-5 min, and preferably 3-5 min.
In the preparation method of the aluminum hydroxide, the Nth micro-reactor in the step (4) carries out an aging process, and the aging conditions are controlled as follows: the aging temperature is 20-30 ℃ lower than that of the first microreactor, and the pH value is 8.0-9.0. Wherein, the pH value can be regulated and controlled by adopting the alkaline material or the acidic material prepared in the step (1) and also can be regulated and controlled by adopting other acidic or alkaline materials. The pipe diameter of the Nth micro-reactor is 5-10 mm larger than that of the Nth micro-reactor and is preferably 8-10 mm. The residence time in the Nth micro-reactor is 8-15 min, preferably 10-15 min.
In the preparation method of the aluminum hydroxide, in the step (4), the drying conditions are as follows: drying the mixture for 3 to 10 hours at a temperature of between 60 and 150 ℃.
Compared with the prior art, the aluminum hydroxide and the preparation method thereof provided by the invention have the following advantages:
1. the aluminum hydroxide of the invention has complete crystallization, high purity and high crystallinity, and the aluminum hydroxide crystal grains are uniformly and intensively distributed. Furthermore, when the catalyst is converted into gamma-alumina, the pore distribution is concentrated, the specific surface area and the pore volume are high, and the catalyst is particularly suitable for being used as a material for processing macromolecular raw materials or reactants, such as a carrier material of a residual oil hydrodesulfurization and denitrification catalyst.
2. The method for preparing the aluminum hydroxide utilizes the microreactor to lead the concentration of reactants to tend to be constant in the reaction process and combines the pH value swing, namely, the first micro reactor adopts an impinging stream reactor, firstly, aluminum hydroxide crystal nuclei with small crystal grains, high crystallinity and concentrated grain size distribution can be generated, then by controlling the condition of pH value swing, a high-temperature and rapid reaction mode is adopted when the subsequent acid side swings, on one hand, amorphous aluminum hydroxide is dissolved, on the other hand, the nucleation speed is promoted at high temperature, and form stable and uniform crystal nucleus, which is beneficial to the formation of monodisperse crystal, the alkali side swing adopts low temperature and slow reaction mode to inhibit the appearance of new crystal nucleus in the growth stage, but directly grows on the formed crystal nucleus and fully reacts, so that the free energy of the system is reduced to the maximum extent, and the formed crystal grains can stably exist in a monodisperse state. The method of the invention is beneficial to the complete crystallization, high purity and high crystallinity of the aluminum hydroxide through the repeated acid side swing and alkali side swing, and is also beneficial to the uniform and concentrated distribution and good stability of aluminum hydroxide crystal grains. In addition, the method is favorable for the uniform and orderly accumulation of aluminum hydroxide crystal grains, so that the generated aluminum oxide has concentrated pore distribution and higher specific surface area and pore volume.
3. According to the method for preparing the aluminum hydroxide, the second micro-reactor and the subsequent micro-reactors are heated by microwave radiation, so that the problems that ions of microfluid close to a tube wall are preferentially nucleated after the moment of mass transfer and heating, even the ions are bonded on the tube wall due to heterogeneous nucleation caused by the action of the tube wall, the mass transfer rate is reduced, and the crystallization degree, the particle size distribution, the dispersity and the yield of crystal grains are further influenced due to the agglomeration caused by high surface free energy of the crystal nucleus are solved.
4. Compared with the kettle type synthesis method, the method for preparing the aluminum hydroxide realizes the continuity of the reaction process, solves the problem of low production efficiency, has no amplification effect, and is very suitable for industrial production.
Drawings
FIG. 1 is a schematic flow diagram of the present invention for preparing aluminum hydroxide using 5 microreactors;
the device comprises a first micro reactor 1, a second micro reactor 2, a third micro reactor 3, a fourth micro reactor 4 and a fifth micro reactor 5.
Detailed Description
The aluminum hydroxide and the method for producing the same according to the present invention are described in more detail below by way of specific examples. The examples are merely illustrative of specific embodiments of the process of the present invention and do not limit the scope of the invention. In the present invention, wt% is a mass fraction.
In the invention, the content of the pseudo-boehmite in the aluminum hydroxide is measured by an X-ray diffraction method (XRD); the relative crystallinity is 100% of the crystallinity of commercial SB powder produced by Condea of DE, and the relative crystallinity is obtained by comparing the measured aluminum hydroxide with that; the particle size distribution was measured by a particle size distribution meter. The specific surface area, pore volume and pore size distribution of the alumina are measured by a low-temperature liquid nitrogen adsorption-desorption method.
The method of the present invention will be described in detail below with reference to FIG. 1, using 5 microreactors as an example. The preparation method of the aluminum hydroxide comprises the following steps: respectively introducing an alkaline material and an acidic material into a first microreactor 1 to perform a neutralization precipitation reaction, wherein the first microreactor 1 adopts an impinging stream microreactor; the product mixed liquid obtained by the first micro reactor 1 enters the second micro reactor 2, and simultaneously, the acid material is introduced into the second micro reactor 2, so that the reaction system swings to the acid side; the reaction product mixed solution obtained by the second microreactor 2 enters a third microreactor 3, and meanwhile, an alkaline material is introduced into the third microreactor 3, so that the reaction system swings to the alkaline side; the mixed solution of the reaction products obtained by the third micro-reactor 3 enters the fourth micro-reactor 4, so that the reaction system swings to the acid side; and the reaction product mixed solution obtained by the fourth micro reactor 4 enters a fifth micro reactor 5 for aging reaction, alkaline materials are added to adjust the pH value, the aged product enters a product collecting tank, and the product is filtered, washed and dried to obtain the aluminum hydroxide.
In the examples of the present invention and the comparative examples, the inner tube diameters of the respective microreactors were as follows: the diameter of the inner tube of the first microreactor is 12mm, the diameter of the inner tube of the second microreactor is 14 mm, the diameter of the inner tube of the third microreactor is 23mm, the diameter of the inner tube of the fourth microreactor is 25mm, and the diameter of the inner tube of the fifth microreactor is 34 mm.
Example 1
To be concentrated as Al2O3NaAlO in a volume of 30g/100mL2Solution and concentration of Al2O3Al in an amount of 50g/100mL2(SO4)3Adding the solution into each component tank, placing each raw material tank and the first impinging stream micro-reactor into an oil bath, heating to 90 deg.C, starting the booster pumps of the two component tanks, and adding NaAlO2Solution and Al2(SO4)3The solution enters a first impinging stream reactor through an atomizer to control NaAlO2The flow rate of the solution is 15mL/min, the pH value in the impinging stream reactor is adjusted to be 8.5, the neutralization and precipitation reaction is carried out, and the reaction mixed solution stays in the first impinging stream microreactor for 1min and then enters the second microreactor; heating the reaction temperature of the second micro-reactor to 110 ℃ by adopting microwave heating, starting a booster pump of the second micro-reactor, and adding Al2(SO4)3Injecting the solution into a second microreactor, controlling the pH value to be 3.0, and allowing the reaction mixed solution to stay in the second microreactor for 3min and then enter a third microreactor; raising the reaction temperature of the third micro-reactor to 60 ℃ by adopting microwave heating, starting a booster pump of the third micro-reactor and leading NaAlO to be added2Injecting the solution into a third microreactor, controlling the pH value to be 10.0, and allowing the reaction mixed solution to stay in the third microreactor for 10min and then enter a fourth microreactor; raising the reaction temperature of the fourth micro-reactor by 110 ℃ by adopting microwave heating, starting a booster pump of the fourth micro-reactor and adding Al2(SO4)3Injecting the solution into a fourth microreactor, controlling the pH value to be 3.0, and allowing the reaction mixed solution to stay in the fourth microreactor for 3min and then enter a fifth microreactor; heating the reaction temperature of the fifth micro-reactor to 60 ℃ by adopting microwave heating, starting a booster pump of the fifth micro-reactor and leading NaAlO to be added2Injecting the solution into a fifth micro-reactor, controlling the pH value to be 8.0 for an aging reaction, aging the reaction mixed solution in the fifth micro-reactor for 15min, then feeding the reaction mixed solution into a product collecting tank, filtering the product, and drying the product at 120 ℃ for 3h to obtain aluminum hydroxide A0The crystallinity and particle size distribution were determined as shown in Table 1, and the desired alumina A structure was obtained by calcining aluminum hydroxide at 600 ℃ for 3 hours as shown in Table 1.
Example 2
To be concentrated as Al2O3NaAlO in 50g/100mL2Solution and concentration of Al2O3Al in an amount of 50g/100mL2(SO4)3Adding the solution into each component tank, placing each raw material tank and the first impinging stream micro-reactor into an oil bath, heating to 80 deg.C, starting the booster pumps of the two component tanks, and adding NaAlO2Solution and Al2(SO4)3The solution enters a first impinging stream reactor through an atomizer to control NaAlO2The flow rate of the solution is 15mL/min, the pH value in the impinging stream reactor is adjusted to be 9.0, neutralization and precipitation reaction is carried out, and the reaction mixed solution stays in the first impinging stream micro-reactor for 1.5min and then enters the second micro-reactor; heating the reaction temperature of the second micro-reactor to 100 ℃ by adopting microwave heating, starting a booster pump of the second micro-reactor, and adding Al2(SO4)3Injecting the solution into a second microreactor, controlling the pH value to be 3.5, and allowing the reaction mixed solution to stay in the second microreactor for 5min and then enter a third microreactor; heating the third micro reactor by microwave to 60 deg.C, starting the booster pump of the third micro reactor, and introducing NaAlO2Injecting the solution into a third microreactor, controlling the pH value to be 10.5, and allowing the reaction mixed solution to stay in the third microreactor for 12min and then enter a fourth microreactor; heating the reaction temperature of the fourth micro-reactor to 110 ℃ by adopting microwave heating, and starting the fourth micro-reactorBooster pump of reactor for mixing Al2(SO4)3Injecting the solution into a fourth microreactor, controlling the pH value to be 3.5, and allowing the reaction mixed solution to stay in the fourth microreactor for 4min and then enter a fifth microreactor; heating the reaction temperature of the fifth micro-reactor to 55 ℃ by adopting microwave heating, starting a booster pump of the fifth micro-reactor and leading NaAlO to be added2Injecting the solution into a fifth micro-reactor, controlling the pH value to be 8.5 for an aging reaction, aging the reaction mixed solution in the fifth micro-reactor for 15min, then feeding the reaction mixed solution into a product collecting tank, filtering the product, and drying the product at 120 ℃ for 3h to obtain aluminum hydroxide B0The crystallinity and the particle size distribution are measured and shown in table 1, then the required alumina B is obtained after the aluminum hydroxide is roasted for 3h at 600 ℃, and the pore structure is measured and shown in table 1.
Example 3
To be concentrated as Al2O3NaAlO in the amount of 35g/100mL2Solution and concentration of Al2O3Al in an amount of 50g/100mL2(SO4)3Adding the solution into each component tank, placing each raw material tank and the first impinging stream microreactor into an oil bath, heating to 120 ℃, starting booster pumps of the two component tanks, and simultaneously adding NaAlO2Solution and Al2(SO4)3The solution enters a first impinging stream reactor through an atomizer to control NaAlO2The flow rate of the solution is 15mL/min, the pH value in the impinging stream reactor is adjusted to be 8.5, the neutralization and precipitation reaction is carried out, and the reaction mixed solution stays in the first impinging stream microreactor for 2min and then enters the second microreactor; heating the reaction temperature of the second micro-reactor to 140 ℃ by adopting microwave heating, starting a booster pump of the second micro-reactor, and adding Al2(SO4)3Injecting the solution into a second microreactor, controlling the pH value to be 4.0, and allowing the reaction mixed solution to stay in the second microreactor for 5min and then enter a third microreactor; heating the reaction temperature of the third micro-reactor to 100 ℃ by adopting microwave heating, starting a booster pump of the third micro-reactor and leading NaAlO to be added2Injecting the solution into a third microreactor, controlling the pH value to be 11.0, and allowing the reaction mixed solution to stay in the third microreactor for 10min and then enter a fourth microreactor;heating the reaction temperature of the fourth micro-reactor to 140 ℃ by adopting microwave heating, starting a booster pump of the fourth micro-reactor, and adding Al2(SO4)3Injecting the solution into a fourth microreactor, controlling the pH value to be 3.0, and allowing the reaction mixed solution to stay in the fourth microreactor for 3min and then enter a fifth microreactor; heating the reaction temperature of the fifth micro-reactor to 100 ℃ by adopting microwave heating, starting a booster pump of the fifth micro-reactor, and leading NaAlO to be added2Injecting the solution into a fifth micro-reactor, controlling the pH value to be 9.0 for an aging reaction, aging the reaction mixed solution in the fifth micro-reactor for 15min, then feeding the reaction mixed solution into a product collecting tank, filtering the product, and drying the product at 120 ℃ for 3h to obtain aluminum hydroxide C0The crystallinity and particle size distribution were measured and shown in Table 1, and then the desired alumina C was obtained by calcining aluminum hydroxide at 600 ℃ for 3 hours and the pore structure was measured and shown in Table 1.
Example 4
To be concentrated as Al2O3NaAlO in 50g/100mL2Solution and concentration of Al2O3Al in an amount of 30g/100mL2(SO4)3Adding the solution into each component tank, placing each raw material tank and the first impinging stream micro-reactor into an oil bath, heating to 85 deg.C, starting the booster pumps of the two component tanks, and adding NaAlO2Solution and Al2(SO4)3The solution enters a first impinging stream reactor through an atomizer to control NaAlO2The flow rate of the solution is 20mL/min, the pH value in the impinging stream reactor is adjusted to be 9.0, neutralization and precipitation reaction is carried out, and the reaction mixed solution stays in the first impinging stream microreactor for 1min and then enters the second microreactor; heating the reaction temperature of the second micro-reactor to 115 ℃ by adopting microwave heating, starting a booster pump of the second micro-reactor, and adding Al2(SO4)3Injecting the solution into a second microreactor, controlling the pH value to be 3.7, and allowing the reaction mixed solution to stay in the second microreactor for 3min and then enter a third microreactor; heating the reaction temperature of the third micro-reactor to 55 ℃ by adopting microwave heating, starting a booster pump of the third micro-reactor and leading NaAlO to be added2Injecting the solution into a third micro-reactor, controlling the pH value to be 10.7,the reaction mixed liquid stays in the third microreactor for 8min and then enters a fourth microreactor; heating the reaction temperature of the fourth micro-reactor to 115 ℃ by adopting microwave heating, starting a booster pump of the fourth micro-reactor, and adding Al2(SO4)3Injecting the solution into a fourth microreactor, controlling the pH value to be 3.8, and allowing the reaction mixed solution to stay in the fourth microreactor for 3min and then enter a fifth microreactor; heating the reaction temperature of the fifth micro-reactor to 65 ℃ by adopting microwave heating, starting a booster pump of the fifth micro-reactor, and leading NaAlO to be added2Injecting the solution into a fifth micro-reactor, controlling the pH value to be 8.9 for an aging reaction, aging the reaction mixed solution in the fifth micro-reactor for 13min, then feeding the reaction mixed solution into a product collecting tank, filtering the product, and drying the product at 120 ℃ for 3h to obtain aluminum hydroxide D0The crystallinity and particle size distribution were measured and shown in Table 1, and then the desired alumina D was obtained by calcining aluminum hydroxide at 600 ℃ for 3 hours and the pore structure was measured and shown in Table 1.
Comparative example 1
The comparative example was prepared using a conventional batch process.
The temperature of the reaction tank was heated to 120 ℃ and the stirring rate was adjusted to 200rad/min, and the concentration was adjusted to Al at a flow rate of 15mL/min2O3NaAlO in 50g/100mL2The solution is added into a reaction tank, and Al with concentration is added at the same time2O3Al in an amount of 40g/100mL2(SO4)3Adjusting pH of the solution to 8.5, stabilizing for 10min, and adding Al2O3Al in an amount of 40g/100mL2(SO4)3Adjusting pH of the solution to 3.0, stabilizing for 10min, and adding Al2O3NaAlO in a volume of 30g/100mL2Adjusting pH of the solution to 11.0, stabilizing for 10min, and adding Al2O3Al in an amount of 40g/100mL2(SO4)3Adjusting pH of the solution to 8.0, aging for 2 hr, filtering, and drying at 120 deg.C for 3 hr to obtain aluminum hydroxide E0The crystallinity and particle size distribution were measured and shown in Table 1, and then the desired alumina E was obtained by calcining aluminum hydroxide at 600 ℃ for 3 hours and the pore structure was measured and shown in Table 1.
Comparative example 2
The comparative example employs five microreactors in series, which are the same as those in example 4, and the specific process is as follows: to be concentrated as Al2O3NaAlO in 50g/100mL2Solution and concentration of Al2O3Al in an amount of 30g/100mL2(SO4)3Adding the solution into respective component tanks, heating each raw material tank and the first microreactor by adopting an oil bath, heating other reactors by adopting microwaves, starting booster pumps of the two component tanks, and simultaneously adding NaAlO2Solution and Al2(SO4)3The solution enters a first micro-reactor and NaAlO is controlled2The flow rate of the solution is 20mL/min, the pH value in the micro-reactor is adjusted to be 9.0, the reaction temperature is 120 ℃, neutralization and precipitation reaction is carried out, and the reaction mixed solution stays in the first micro-reactor for 1min and then enters the second micro-reactor; the reaction temperature of the second micro-reactor is 120 ℃, a booster pump of the second micro-reactor is started, and Al is added2(SO4)3Injecting the solution into a second microreactor, controlling the pH value to be 3.7, and allowing the reaction mixed solution to stay in the second microreactor for 3min and then enter a third microreactor; the reaction temperature of the third micro-reactor is 120 ℃, a booster pump of the third micro-reactor is started, and NaAlO is added2Injecting the solution into a third microreactor, controlling the pH value to be 10.7, and allowing the reaction mixed solution to stay in the third microreactor for 8min and then enter a fourth microreactor; the reaction temperature of the fourth micro-reactor is 120 ℃, a booster pump of the fourth micro-reactor is started, and Al is added2(SO4)3Injecting the solution into a fourth microreactor, controlling the pH value to be 3.8, and allowing the reaction mixed solution to stay in the fourth microreactor for 3min and then enter a fifth microreactor; the reaction temperature of the fifth micro-reactor is 120 ℃, a booster pump of the fifth micro-reactor is started, and NaAlO is added2Injecting the solution into a fifth micro-reactor, controlling the pH value to be 8.9 for an aging reaction, aging the reaction mixed solution in the fifth micro-reactor for 13min, then feeding the reaction mixed solution into a product collecting tank, filtering the product, and drying the product at 120 ℃ for 3h to obtain aluminum hydroxide F0The crystallinity and particle size distribution were determined as shown in Table 1, and then aluminum hydroxide was added at 600 deg.CAfter 3h of calcination, the desired alumina F was obtained and its pore structure was determined as shown in Table 1.
TABLE 1 Properties of aluminum hydroxide and alumina prepared in examples and comparative examples
| Aluminum hydroxide | A0 | B0 | C0 | D0 | E0 | F0 |
| Pseudo-boehmite content, wt% | 95 | 96 | 95 | 96 | 81 | 89 |
| Relative degree of crystallinity,% | 95 | 96 | 98 | 97 | 85 | 90 |
| Particle size distribution of% | ||||||
| ≤15μm | 2.5 | 3.0 | 2.7 | 1.5 | 46.6 | 29.2 |
| Greater than 15 μm and less than 25 μm | 88.9 | 89.2 | 89.5 | 89.9 | 50.2 | 65.4 |
| ≥25μm | 8.6 | 7.8 | 7.8 | 8.6 | 3.2 | 5.4 |
| Alumina oxide | A | B | C | D | E | F |
| Specific surface area, m2/g | 385 | 389 | 396 | 400 | 282 | 345 |
| Pore volume, mL/g | 1.25 | 1.27 | 1.24 | 1.23 | 0.85 | 0.93 |
| Several pore diameters, nm | 11.5 | 12.0 | 11.0 | 12.0 | 8.3 | 9.1 |
| Pore size distribution% | ||||||
| ＜10nm | 6.9 | 6.0 | 5.7 | 5.0 | 44.8 | 30.5 |
| 10～20nm | 85.2 | 86.2 | 87.9 | 88.6 | 50.3 | 64.3 |
| ＞20nm | 7.9 | 7.8 | 6.4 | 6.4 | 4.9 | 5.2 |
As can be seen from the data in Table 1, the particle size of the aluminum hydroxide prepared by the method is intensively distributed to be more than 15 μm and less than 25 μm, and the obtained aluminum oxide has high specific surface area, large pore volume and pore diameter, and the pore diameter is intensively distributed to be 10-20 nm, so that the method is very suitable for preparing mesoporous hydrogenation catalysts such as residual oil hydrodesulfurization, denitrification and the like.
Claims (21)
1. A preparation method of aluminum hydroxide is characterized by comprising the following steps: the adopted reaction system comprises N microreactors which are connected in series, and a first microreactor, a second microreactor, … … and an Nth microreactor are respectively arranged along the material flow direction, wherein the first microreactor adopts an impinging stream reactor, and the method comprises the following steps:
(1) respectively preparing an alkaline material and an acidic material;
(2) respectively introducing an alkaline material and an acidic material into a first microreactor to perform a neutralization precipitation reaction;
(3) the reaction product mixed liquid obtained in the step (2) sequentially enters a second micro-reactor to an N-1 micro-reactor, and the reaction system is repeatedly subjected to pH value swing;
(4) allowing the reaction product mixed solution obtained in the step (3) to enter an Nth micro reactor for aging reaction, allowing the effluent of the Nth micro reactor to enter a product collecting tank, and filtering, washing and drying to obtain aluminum hydroxide;
wherein in the step (3), when the reaction system swings to the alkali side, the reaction temperature is 20-30 ℃ lower than that of the first microreactor; when the reaction system swings to the acid side, the reaction temperature is 20-30 ℃ higher than that of the first microreactor.
2. The method of claim 1, wherein: n microreactors are connected in series, wherein N is an integer not less than 5.
3. The method of claim 2, wherein: n microreactors are connected in series, wherein N is 5-11.
4. The method of claim 2, wherein: n microreactors are connected in series, wherein N is 5-7.
5. The method of claim 1, wherein: the specific process of pH value swing in the step (3) is as follows:
the mixed solution of the reaction products obtained in the step (2) enters a second micro reactor, and simultaneously, an acid material is introduced into the second micro reactor, so that the reaction system swings to the acid side; and the reaction product mixed solution obtained by the second microreactor enters a third microreactor, and meanwhile, an alkaline material is introduced into the third microreactor, so that the reaction system swings … towards the alkaline side, the obtained reaction product mixed solution sequentially enters a fourth microreactor to an N-1 microreactor, and the reaction system repeatedly swings towards the acid side and towards the alkaline side.
6. The method of claim 1, wherein: respectively preparing an alkaline material and an acidic material in the step (1), and adopting at least one scheme as follows:
I. the alkaline material is an alkaline precipitator, and the acidic material is an acidic aluminum-containing compound;
II. The alkaline material is an alkaline aluminum-containing compound, and the acidic material is an acidic precipitator;
and III, the alkaline material is an alkaline aluminum-containing compound, and the acidic material is an acidic aluminum-containing compound.
7. The method of claim 6, wherein: the used alkaline precipitant is selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide and ammonia water, the used acidic precipitant is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid and oxalic acid, the used alkaline aluminum-containing compound adopts meta-aluminate, and the used acidic aluminum-containing compound adopts one or more of aluminum chloride, aluminum nitrate and aluminum sulfate; when the alkaline material is an alkaline aluminum-containing compound, the concentration is Al2O3Calculated as 8-80 g/100mL, and when the acidic material is an acidic aluminum-containing compound, the concentration is Al2O3The weight concentration of the alkaline precipitator is 8-80 g/100mL, the weight concentration of the alkaline precipitator is 5-25%, and the weight concentration of the acidic precipitator is 5-25%.
8. According toThe method of claim 7, wherein: when the alkaline material is an alkaline aluminum-containing compound, the concentration is Al2O3Calculated as 30-50 g/100mL, and when the acidic material is an acidic aluminum-containing compound, the concentration is Al2O3The weight concentration of the alkaline precipitator is 30-50 g/100mL, the weight concentration of the alkaline precipitator is 10-20%, and the weight concentration of the acidic precipitator is 10-20%.
9. The method of claim 1, wherein: the first micro-reactor is provided with two feed inlets which are respectively connected with an alkaline material and an acidic material, the alkaline material and the acidic material are communicated through a jet orifice after entering the first micro-reactor, the jet orifice of the alkaline material and the jet orifice of the acidic material are impacted at a certain angle, and the impact angle is 150-180 degrees.
10. The method of claim 1, wherein: the first micro reactor is heated by oil bath, and the other micro reactors are heated by microwave radiation.
11. The method of claim 1, wherein: the precipitation reaction in the step (2) has the following reaction conditions: the reaction temperature is 50-150 ℃, and the pH value is 8.0-9.0; the diameter of an inner tube of the first micro-reactor is 10-20 mm, and the residence time of materials is controlled to be 1-5 min.
12. The method of claim 11, wherein: the precipitation reaction in the step (2) has the following reaction conditions: the reaction temperature is 50-120 ℃; the diameter of an inner tube of the first micro-reactor is 10-15 mm, and the residence time of materials is controlled to be 1-2 min.
13. The production method according to claim 1 or 11, characterized in that: in the step (2), introducing an alkaline material and an acidic material into a first microreactor, and introducing the alkaline material and the acidic material in an atomization or liquid mode; the flow rate of the alkaline material is 10-50 mL/min.
14. The method of claim 13, wherein: the flow rate of the alkaline material is 15-30 mL/min.
15. The production method according to claim 1 or 11, characterized in that: in the step (3), when the reaction system is oscillated to the alkali side, the reaction conditions are controlled as follows: the reaction temperature is 20-30 ℃ lower than that of the first microreactor, and the pH value is 10.0-11.0; the diameter of an inner pipe of the micro reactor is 5-10 mm larger than that of the previous micro reactor, and the residence time of materials in the micro reactor is controlled to be 8-15 min;
in the step (3), when the reaction system is oscillated to the acid side, the reaction conditions are controlled as follows: the reaction temperature is 20-30 ℃ higher than that of the first microreactor, and the pH value is 3.0-5.0; the diameter of an inner pipe of the micro-reactor is 1-10 mm larger than that of the previous micro-reactor, and the residence time of materials in the micro-reactor is controlled to be 2-5 min.
16. The method of claim 15, wherein: in the step (3), when the reaction system swings to the alkali side, the diameter of an inner pipe of the micro-reactor is 8-10 mm larger than that of the previous micro-reactor, and the residence time of materials in the micro-reactor is controlled to be 10-15 min; in the step (3), when the reaction system swings to the acid side, the diameter of an inner pipe of the micro-reactor is 2-3 mm larger than that of the previous micro-reactor, and the residence time of materials in the micro-reactor is controlled to be 3-5 min.
17. The production method according to claim 1 or 11, characterized in that: in the step (4), the aging reaction conditions are as follows: the aging temperature is 20-30 ℃ lower than that of the first microreactor, the pH value is 8.0-9.0, and the pH value is regulated and controlled by preparing an alkaline material or an acidic material in the step (1) or regulating and controlling other acidic or alkaline substances; the pipe diameter of the Nth micro-reactor is 5-10 mm larger than that of the Nth-1 micro-reactor, and the residence time in the Nth micro-reactor is 8-15 min.
18. The method of claim 17, wherein: the pipe diameter of the Nth micro-reactor is 8-10 mm larger than that of the Nth-1 micro-reactor, and the residence time in the Nth micro-reactor is 10-15 min.
19. The method of claim 1, wherein: in the step (4), the drying conditions are as follows: drying the mixture for 3 to 10 hours at a temperature of between 60 and 150 ℃.
20. The method of claim 1, wherein: the content of pseudo-boehmite in the prepared aluminum hydroxide is more than 95wt%, and the relative crystallinity is not less than 95%; the grain size distribution of the aluminum hydroxide is as follows: the number of the crystal grains with the diameter less than or equal to 15 mu m accounts for 1 to 5 percent of the total number of the aluminum hydroxide crystal grains, the number of the crystal grains with the diameter more than 15 mu m and less than 25 mu m accounts for 85 to 90 percent of the total number of the aluminum hydroxide crystal grains, and the number of the crystal grains with the diameter more than or equal to 25 mu m accounts for 5 to 10 percent of the total number of the aluminum hydroxide crystal grains.
21. The method of claim 20, wherein: the aluminum hydroxide is converted into gamma-Al2O3The properties are then as follows: the specific surface area is 300-400 m2The pore volume is 1.1-1.3 mL/g, and the pore size distribution is as follows: diameter of hole<The pore volume occupied by the 10nm pores is 5-10% of the total pore volume, the pore volume occupied by the pores with the diameter of 10-20 nm accounts for 85-95% of the total pore volume, and the pore volume occupied by the pores with the diameter larger than 20nm accounts for 5-10% of the total pore volume.
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| CN112520768B (en) * | 2020-12-13 | 2023-04-18 | 中海油天津化工研究设计院有限公司 | Preparation method of rod-shaped high-purity pseudoboehmite |
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