Aqueous phase dispersed aluminum hydroxide powder and its preparation system, preparation method and application

Abstract

The present invention discloses an aqueous phase dispersed aluminum hydroxide powder and a preparation system, preparation method and application thereof. The preparation system of the present invention includes a microreactor, an aging device, a hydrothermal device and a spray dryer, and integrates multiple process steps of microreaction precipitation, aging, hydrothermal and spray drying in a continuous reaction system. The present invention also provides a method for continuously preparing aqueous phase dispersed aluminum hydroxide powder using inorganic aluminum salt as a raw material by utilizing the preparation system under closed conditions. Through the continuous high-speed impact of the microreactor and the stable reaction environment provided by the continuous closed space, the particle size of the prepared aluminum hydroxide reaches the nanometer level, and it can maintain a self-dispersed state in an aqueous solution, and can be applied to multiple fields such as catalysts and ceramic coatings. The preparation system improves production efficiency and reduces energy consumption, and has significant economic benefits in large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the field of inorganic functional powder preparation, and in particular to a water-dispersed aluminum hydroxide powder and a preparation system, a preparation method and an application thereof. Background Art

[0002] Boehmite (γ-AlOOH) is a representative aluminum hydroxide that can be used as a precursor of aluminum oxide. Due to its large specific surface area, active functional groups, high surface charge, polymorphic properties, and different crystal structures and sizes, it is widely used in catalyst carriers, ceramic materials, coagulants, membranes, coatings, adsorbents, and optical materials. Nano aluminum hydroxide has a smooth surface. As a coating, it can improve the surface hardness and rigidity, is not easy to scratch, and can also adjust the thermal expansion coefficient of ceramics and improve its fracture toughness. Self-dispersed nano aluminum hydroxide has good adhesion and stable performance. It can be stably dispersed in water. It can be used as a flame retardant or synthesized with other powders to form a composite functional coating with excellent performance. The flaky nano aluminum hydroxide with small particle size and thickness, concentrated particle size distribution, and large diameter-thickness ratio is almost colorless and widely used in the field of cosmetics. At present, there are many preparation technologies, including precipitation method, hydrothermal method, alcohol aluminum method, gas phase method, etc. Among them, the precipitation method is widely used because of its simple operation, low cost and energy consumption. However, the performance of aluminum hydroxide products is greatly affected by preparation conditions such as concentration, pH, and temperature. The traditional precipitation method uses an intermittent reactor, the reaction environment is unstable, the prepared aluminum hydroxide has a large particle size and a wide distribution, and it is very difficult to use the precipitation method to prepare nano aluminum hydroxide powder with uniform particle size on an industrial scale. The traditional hydrothermal method uses an intermittent reactor, which has high equipment requirements, low safety, poor uniformity of powder particle size, and a large particle size. The alcohol aluminum method is also a common method for preparing aluminum hydroxide. It has low requirements for reaction temperature and high product purity, but its main disadvantage is that the reaction is limited by the concentration of reactants, the reaction time is too long, and the production efficiency is extremely low. Moreover, the alcohol aluminum method requires the preparation of alkoxy aluminum, which is very expensive. The gas phase method is expensive and there is no large-scale application example. Therefore, it is of great commercial value to develop an economical and environmentally friendly production technology for high-performance nano aluminum hydroxide powder.

[0003] Microreactors are microreactors with miniaturized structural characteristics. Different from the structure of traditional reactors, the channel size of microreactors generally reaches the micron level, with a large surface area to volume ratio. Microreactors have fast heat transfer effects and good micro-mixing effects, and can strictly control the heat or concentration gradient in the reactor channel, so that new methods with high yield and high chemical conversion can be realized. Microreactors can accurately control mixing time, reaction temperature and residence time, and have high repeatability. Under continuous flow, the reaction proceeds in a relatively stable state. Microreactors control the aggregation of nanoparticles by strengthening the mass transfer process in the microchannel, and construct anisotropic nanoparticles and microstructures from bottom to top to obtain particles with small particle size and narrow distribution. When the reactor size is further reduced to micron size, materials can be saved to optimize conditions. This study is helpful for the development of high-throughput microreactors and the industrialization of high-quality nano-alumina.

[0004] Chinese patent CN109721088 A discloses a method for preparing aluminum hydroxide using N microreactors connected in series. The aluminum hydroxide prepared by this method has a specific surface area of ​​300 to 400 m 2 / g, the pore volume is 1.1-1.3mL / g, and the pore size distribution is wide, which is suitable for use as a mesoporous hydrogenation catalyst for residue hydrodesulfurization and denitrogenation. The microreactor used in this invention is a single-channel T-type impinging flow microreactor with relatively low mixing efficiency and relatively small output. The subsequent microreactor N in series needs to repeatedly adjust the pH, which is cumbersome to operate and difficult to operate in practice, making it difficult to achieve industrial application. At present, in the field of preparation of aluminum hydroxide powder, microreaction technology has only remained in the stage of trace single-channel experiments, and there is no microreaction system that can be applied in the field of industrial production. Summary of the invention

[0005] In order to overcome the problem that aluminum hydroxide has a large particle size and a wide distribution under the existing preparation technology, the present invention provides a preparation system and a preparation method for aqueous phase dispersed aluminum hydroxide powder, and uses a high-throughput impinging flow microreactor to integrate multiple steps of micro-reaction precipitation, aging, hydrothermal, and spraying in a continuous reaction system. The continuous micro-reaction system has excellent mass transfer and heat transfer performance at a microscale, a stable reaction environment, and can achieve continuous synthesis of aluminum hydroxide, thereby improving the production efficiency of the product and reducing energy consumption. Through the continuous high-speed impact of the microreactor and the stable reaction environment provided by the continuous closed space, the prepared aluminum hydroxide particle size reaches the nanometer level, the particle size distribution is concentrated, the product morphology is uniform, and it is a lamellar structure, which improves the stability of the product. The 2-20wt% aluminum hydroxide aqueous solution of the present invention is translucent, and at room temperature and pH 7, the prepared aluminum hydroxide powder can maintain a self-dispersed state in the aqueous solution, and can be applied to naphtha reforming catalysts, ceramic coatings and other fields.

[0006] The invention proposes a preparation system of aqueous phase dispersed aluminum hydroxide powder, comprising a preparation system including a microreactor, a hydrothermal device and a spray dryer which are connected in sequence in a closed manner by pipelines, wherein the feed port of the microreactor is connected to a feed pump which controls the feed speed, so as to control the particle size and particle size distribution of the aluminum hydroxide by controlling the flow rate of the raw material feed pumped into the microreactor; the microreactor is an impinging flow microreactor for double-sided feeding, which is assembled together by stress extrusion in sequence from seven channel plates, namely a feed plate, a branch plate, a perforated plate, a mixing and discharging plate, a perforated plate, a branch plate and a feed plate, and the assembly body is sealed with a frame, wherein the seven channel plates are symmetrically arranged on both sides with the mixing and discharging plate as the center.

[0007] In the preparation system of the present invention, an aging device is preferably provided between the hydrothermal device and the micro-reaction device, and the aging device is preferably a split-flow heating tube composed of a plurality of pipes connected in parallel.

[0008] In the preparation system of the present invention, discharge valves are preferably provided at the inlet and outlet ports of the microreactor, aging device, hydrothermal device, and spray dryer.

[0009] In the preparation system of the present invention, the hydrothermal device is preferably a plurality of vertical tubular reactors capable of continuous hydrothermal heating.

[0010] The present invention further provides a method for preparing water-dispersed aluminum hydroxide powder using the above-mentioned preparation system, comprising the following steps:

[0011] 1) preparing one or more aluminum salt solutions of aluminum nitrate, aluminum sulfate, and aluminum chloride as the acid solution, wherein the aluminum oxide content is 3 to 20 g / 100 mL;

[0012] 2) preparing sodium aluminate solution as the alkaline solution, controlling the alumina content to 3-40 g / 100 mL and the caustic ratio to 1.3-1.8;

[0013] 3) pumping the acid solution and the alkaline solution into the microreactor at a feed rate of 80 to 160 L / h for reaction;

[0014] 4) The pH of the solution after the reaction is adjusted to 7.5-9.0 by adding ammonia water;

[0015] 5) Entering the aging device 8 for heating or directly entering the hydrothermal device for hydrothermal treatment;

[0016] 6) spray drying to obtain water-dispersed aluminum hydroxide powder.

[0017] In the above preparation method of the present invention, it is preferred that the heating temperature of the hydrothermal treatment is 100-260° C., the reaction pressure is 1.0-2.0 MPa, and the reaction time is 1-4 h.

[0018] The aqueous phase dispersed aluminum hydroxide powder prepared by the present invention has a Zeta potential greater than 65eV at room temperature and a pH value of 7, a particle size of 50 to 300nm, and a specific surface area of ​​80 to 220m 2 / g, pore volume 0.45~0.65cm 3 / g, with a pore size of 16 to 24 nm, and can maintain a self-dispersed state in an aqueous solution, wherein a 2 to 20 wt% aluminum hydroxide aqueous solution is translucent.

[0019] The present invention further provides water-dispersed aluminum hydroxide powder prepared by the above method.

[0020] The present invention also provides an application of the above-mentioned aqueous phase dispersed aluminum hydroxide powder in a naphtha reforming catalyst, wherein the aqueous phase dispersed aluminum hydroxide powder has a specific surface area of ​​160 to 220 m 2 / g, pore volume is 0.45~0.65cm 3 / g, pore size is 17~22nm.

[0021] The present invention further provides a naphtha reforming catalyst made from the aqueous phase dispersed aluminum hydroxide powder, the catalyst having a particle size of 1.6 to 1.8 mm, a bulk ratio of 0.55 to 0.65 g / mL, a strength of >40 N / particle, and a specific surface area of ​​160 to 220 m 2 / g, pore volume is 0.45~0.65cm 3 / g, the average pore size is 17-22nm, the aromatics yield is greater than 52%, and the octane number RON of reformed gasoline is greater than 92.

[0022] The present invention also provides an application of the above-mentioned aqueous phase dispersed aluminum hydroxide powder in a wear-resistant ceramic coating, which can improve the wear reduction and wear resistance in mechanical equipment parts and metal alloys such as steel. The aqueous phase dispersed aluminum hydroxide powder used has a particle size of 50 to 200 nm and a specific surface area of ​​80 to 160 m 2 / g, preferably 80-100m 2 / g, pore volume is 0.45~0.65cm 3 / g, preferably 0.45 to 0.55 cm 3 / g.

[0023] The present invention further provides a wear-resistant aluminum oxide ceramic coating made from the aqueous phase dispersed aluminum hydroxide powder, the coating has a hardness of 860-900 HV, a wear rate of 0.3-0.5%, a shear strength of 18-23 MPa, and a porosity of 1.0-1.5%.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The micro-reaction preparation system proposed in the present invention can control the particle size and particle size distribution of aluminum hydroxide by changing the flow rate of the raw material pumped into the micro-reactor, and the operation is flexible.

[0026] 2. The closed, continuous micro-reaction preparation system proposed by the present invention replaces the original intermittent reaction system, constructs a continuous reaction device for producing aluminum hydroxide, ensures that the product has a uniform reaction environment during the post-processing process, and ensures the stability of product quality. Compared with the traditional intermittent precipitation method, the particle size is more concentrated and the particle size distribution is narrower. Under the same reaction parameters, the product morphology is stable, which improves the quality of the product.

[0027] 3. The micro-reaction technology used in the present invention is a low-cost, green and environmentally friendly technical method. The proposed micro-reaction system and the continuous preparation method under closed conditions are new industrial preparation methods for high-throughput production of aluminum hydroxide. Compared with the traditional stirring tank precipitation preparation technology, the micro-reaction system has high production efficiency, low production cost, small footprint, and significant economic benefits.

[0028] 4. The aqueous phase dispersed aluminum hydroxide powder prepared by the micro-reaction preparation system and method of the present invention has a Zeta potential greater than 65 eV at room temperature and pH 7, and can maintain a self-dispersed state in an aqueous solution. The obtained 2-20 wt% aluminum hydroxide aqueous solution is translucent and can be used in naphtha reforming catalysts, ceramic coatings and other fields.

[0029] The above description is only an overview of the technical solution of the present invention. In order to clearly describe the technical means of the present invention, implement it according to the contents of the specification, and better understand the technical features and related advantages of the present invention, one or more preferred examples are given below and explained in detail with pictures and texts. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the preparation system of the water phase dispersed aluminum hydroxide powder of the present invention.

[0031] In the figure: 1 is an acid storage tank, 2 is an alkali storage tank, 3 is an acid feed pump, 4 is an alkali feed pump, 5 is a microreactor, 6 is an ammonia storage tank, 7 is an ammonia feed pump, 8 is an aging device, 9, 10, 11, 12 are hydrothermal devices, and 13 is a spray dryer.

[0032] Figure 2 It is a schematic diagram of the composition of the microreactor channel plate involved in the preparation system of the present invention.

[0033] In the figure: 51 and 51' are a pair of feed plates, 52 and 52' are a pair of branch plates, 53 and 53' are a pair of perforated plates, and 54 is a mixing discharge plate.

[0034] Figure 3The XRD diffraction pattern of aluminum hydroxide prepared in Example 1 is shown in FIG.

[0035] Figure 4 This is a transmission electron microscope image of the aluminum hydroxide prepared in Example 1.

[0036] Figure 5 This is a physical picture of the 10 wt % aluminum hydroxide aqueous solution prepared in Example 1. DETAILED DESCRIPTION

[0037] The technical solutions and beneficial effects of the present invention are further described below in conjunction with specific embodiments and the accompanying drawings.

[0038] As attached Figure 1 As shown, the preparation system of the aqueous phase dispersed aluminum hydroxide powder of the present invention comprises a microreactor 5, an aging device 8, a hydrothermal device (9-12), and a spray dryer 13, wherein the feed port of the microreactor 5 is connected to an acid feed pump 3 and an alkali feed pump 4 for controlling the feed speed, so as to control the particle size and particle size distribution of the aluminum hydroxide by controlling the flow rate of the raw material feed pump into the microreactor, and the acid feed pump 3 and the alkali feed pump 4 are respectively connected to the acid storage tank 1 and the alkali storage tank 2; the whole preparation system adopts a pipeline closed connection, and the connection sequence is that the outlet of the microreactor 5 is connected to the inlet of the aging device 8, the outlet of the aging device 8 is connected to the inlet of the hydrothermal device 9, the outlet of the microreactor 5 can also be directly connected to the inlet of the hydrothermal device 12, and the outlet of the hydrothermal device 12 is connected to the inlet of the spray dryer 13. Discharge valves are set at the inlet and outlet of the microreactor 5, the aging device 8, the hydrothermal device (9-12), and the spray dryer 13, which can be used to collect materials, facilitate the addition of water washing process to treat intermediate products, and can also be used to monitor and detect intermediate products. The inlet of the aging device 8 is also provided with an ammonia feed port for replenishing ammonia water, and the ammonia feed port is connected to the ammonia storage tank 6 through an ammonia feed pump 7. The heating temperature of the acid tank 1 and the alkali tank 2 is 20-260° C. The acid feed pump 3 and the alkali feed pump 4 have a head of 50-150 m and a flow rate of 80-320 L / h.

[0039] The preparation system uses a double-sided feeding impinging stream microreactor. The initial mixing of the acid solution and the alkaline solution is completed in the impinging stream microreactor. The reactor is composed of 7 channel plates, including a pair of feeding plates, a pair of branch plates, a pair of perforated plates and a mixed discharge plate. The mixed discharge plate is the center and the two sides are arranged symmetrically. To prevent leakage, the 7 channel plates are assembled together by stress extrusion, and the assembly body is sealed with a frame. Figure 2As shown, a total of 7 channel plates, namely, feed plate 51, branch plate 52, perforated plate 53, mixed discharge plate 54, perforated plate 53', branch plate 52' and feed plate 51', are assembled together by stress extrusion. The 7 channel plates are all made of 316L stainless steel and assembled together by mechanical stress extrusion. The corners are screwed and the assembly body is sealed with an iron frame. Feed pipes are welded at the inlet on the left side of feed plate 51 and the right side of feed plate 51'. The feed fluid at both ends is evenly divided into 16 identical parallel fluids, and the mixed discharge plate is discharged from the discharge hole after a violent collision. The mixed discharge plate is provided with a threaded pipe at the discharge port, and the other end of the discharge pipe is connected to a heating pipe. The heating temperature of the acid tank 1 and the alkali tank 2 is 20-260°C. The acid and alkali pumps have a lift of 50-150m and a flow rate of 180-320L / h. The feed pipeline of the microreactor is provided with a filter, a stop valve, a ball valve, a pressure regulating valve, a flow meter and a pressure gauge. The aging device 8 is a shunt heating pipe composed of multiple pipelines in parallel, and the heating temperature is 0 to 260°C. The hydrothermal device (9-12) is a plurality of vertical tubular reactors capable of continuous hydrothermal treatment. During the hydrothermal reaction, the heating temperature of the hydrothermal tubular reactor is 100 to 260°C, the reaction pressure is 1.0 to 2.0 MPa, and the reaction time is 1 to 4 hours. After the hydrothermal reaction, the spray dryer is used for spray drying.

[0040] The technical scheme of the preparation method of the present invention is further described below in conjunction with specific embodiments.

[0041] Example 1

[0042] Prepare an aluminum nitrate solution with an Al2O3 concentration of 5g / 100mL, load it into the acid storage tank 1, and heat it to 90°C. Prepare a sodium aluminate solution with an Al2O3 concentration of 25.8g / 100mL and a caustic ratio of 1.5, load it into the alkali storage tank 2, and heat it to 90°C. Simultaneously, start the acid feed pump 3 and the alkali feed pump 4, and both sides enter the microreactor 5 at the same rate of 120L / h. Load 25% ammonia water into the ammonia water storage tank 6, and pump it in at a rate of 17.5mL / min using the ammonia water feed pump 7. After mixing the reaction materials and ammonia water, directly enter 9, 10, 11, and 12 (using a vertical tubular reactor) for hydrothermal reaction. The hydrothermal temperature is 180°C, the pressure is 1.2Mpa, and the reaction time is 2h. After the hydrothermal reaction, the material enters 13 for spray drying and molding to obtain the final water-dispersed aluminum hydroxide powder. The obtained product XRD diffraction pattern is as follows Figure 3 As shown in the transmission electron microscopy image Figure 4 As shown in Figure 2, the BET analysis specific surface area of ​​the prepared aluminum hydroxide is 110 m 2 / g, pore volume is 0.52cm 3 / g, pore size 21.2nm, particle size D was analyzed by particle size analyzer 50The actual picture of 10wt% aluminum hydroxide aqueous dispersion solution is as follows Figure 5 As shown, the aluminum oxide ceramic coating for steel surface is prepared by thermal spraying technology, and its hardness is 872Hv, wear rate is 0.36%, shear strength is 20.5MPa, and porosity is 1.0%.

[0043] Example 2

[0044] Prepare an aluminum nitrate solution with an Al2O3 concentration of 10g / 100mL, load it into the acid storage tank 1, and heat it to 100°C. Prepare a sodium aluminate solution with an Al2O3 concentration of 30g / 100mL and a caustic ratio of 1.5, load it into the alkali storage tank 2, and heat it to 100°C. Simultaneously, start the acid feed pump 3 and the alkali feed pump 4, and both sides enter the microreactor 5 at the same rate of 80L / h. Load 25% ammonia water into the ammonia water storage tank 6 and pump it in with the ammonia water feed pump 7 at a rate of 21.8mL / min. After the reaction materials and ammonia water are mixed, they enter the aging device 8, the heating temperature is 100°C, and the reaction time is 1h. The heated and aged materials enter the hydrothermal devices 9, 10, 11, and 12 (using a vertical tubular reactor) for hydrothermal reaction, the hydrothermal temperature is 200-220°C, the pressure is 1.5Mpa, and the reaction time is 2h. After the hydrothermal reaction, the material enters the spray drying 13 to form the material to obtain the final water-dispersed aluminum hydroxide powder. The obtained aluminum hydroxide powder is analyzed by BET, and the specific surface area is 176m 2 / g, pore volume is 0.52cm 3 / g, pore size 17.6nm, particle size D was analyzed by particle size analyzer 50 The surface area of ​​γ-Al2O3 was 248 nm, and it was calcined at 650℃ for 4 hours. It was used as a naphtha reforming catalyst with a specific surface area of ​​170-210 m 2 / g, pore volume is 0.55~0.65cm 3 / g, with an average pore size of 17nm, which can maintain a higher aromatic yield (52%) and a higher reformed gasoline octane number (RON92).

[0045] Example 3

[0046] Prepare an aluminum nitrate solution with an Al2O3 concentration of 10g / 100mL, load it into the acid storage tank 1, and heat it to 100°C. Prepare a sodium aluminate solution with an Al2O3 concentration of 30g / 100mL and a caustic ratio of 1.5, load it into the alkali storage tank 2, and heat it to 100°C. Simultaneously, start the acid feed pump 3 and the alkali feed pump 4, and both sides enter the microreactor 5 at the same rate of 120L / h. Load 25% ammonia water into the ammonia water storage tank 6 and pump it in with the ammonia water feed pump 7 at a rate of 33.1mL / min. After the reaction materials and ammonia water are mixed, they enter the aging device 8, the heating temperature is 100°C, and the reaction time is 1h. The heated and aged materials enter 9, 10, 11, and 12 (using a vertical tubular reactor) for hydrothermal reaction, the hydrothermal temperature is 200-220°C, the pressure is 1.5Mpa, and the reaction time is 2h. After the hydrothermal reaction, the material enters the spray drying 13 molding discharge to obtain the final water-phase dispersed aluminum hydroxide powder. The aluminum hydroxide powder obtained has a specific surface area of ​​180m2 / g, a pore volume of 0.55cm3 / g, and a pore size of 17.5nm using BET analysis. The particle size D50 is 135nm using a particle size analyzer. After calcination at 650°C for 4h, γ-Al2O3 is obtained. It is prepared into a spherical naphtha reforming catalyst with a catalyst particle size of 1.6-1.8mm, a bulk ratio of 0.6-0.65g / mL, a strength of>40N / particle, a specific surface area of ​​180-220m2 / g, a pore volume of 0.55-0.65cm3 / g, and an average pore size of 18nm, which can maintain a higher aromatic yield (52%) and a higher reforming gasoline octane number (RON93).

Claims

1. A method for continuously preparing water-dispersible aluminum hydroxide powder using a preparation system for water-dispersible aluminum hydroxide powder, characterized in that: The following steps are involved: 1) Prepare one or more aluminum salt solutions of aluminum nitrate, aluminum sulfate, and aluminum chloride as the acid solution, wherein the aluminum oxide content is 3-20 g / 100 mL; 2) Prepare sodium aluminate solution as the alkaline solution, control the alumina content to 3-40 g / 100 mL, and the caustic ratio to 1.3-1.8; 3) Pumping the acid solution and the alkaline solution into the microreactor at a feed rate of 80-160 L / h for reaction; 4) The pH of the solution after the reaction is adjusted to 7.5-9.0 by adding a small amount of ammonia water; 5) After entering the aging device for heating or directly entering the hydrothermal device for hydrothermal treatment; 6) spray drying to obtain water-dispersed aluminum hydroxide powder; Among them, the preparation system includes a microreactor, a hydrothermal device, and a spray dryer which are connected in sequence in a closed manner by pipelines. The feed port of the microreactor is connected to a feed pump which controls the feed speed, so as to control the particle size and particle size distribution of aluminum hydroxide by controlling the flow rate of the raw material feed pump into the microreactor; the microreactor is an impact flow microreactor with double-sided feeding, which is assembled together by stress extrusion through 7 channel plates including a feed plate, a branch plate, a perforated plate, a mixing discharge plate, a perforated plate, a branch plate and a feed plate, and a frame is added outside the assembly body for edge sealing, wherein the 7 channel plates are symmetrically arranged on both sides with the mixing discharge plate as the center.

2. The method according to claim 1, characterized in that The heating temperature of the hydrothermal treatment in step 5) is 100-260°C, the reaction pressure is 1.0-2.0 MPa, and the reaction time is 1-4 h.

3. A method according to claim 1, characterized in that: The Zeta potential is greater than 65 eV at room temperature and pH 7. The particle size of the aqueous phase dispersed aluminum hydroxide powder is 50-300 nm, and the specific surface area is 80-220 m 2 / g, pore volume 0.45~0.65cm 3 / g, with a pore size of 16~24nm, it can maintain a self-dispersed state in an aqueous solution, and the obtained 2~20wt% aluminum hydroxide aqueous solution is translucent.

4. The method according to claim 1, characterized in that: An aging device is also arranged between the hydrothermal device and the micro-reaction device, and the aging device is a shunt heating pipe composed of a plurality of pipes connected in parallel.

5. The method according to claim 1, characterized in that Discharge valves are arranged at the inlet and outlet ports of the microreactor, aging device, hydrothermal device and spray dryer.

6. The method according to claim 1, characterized in that: The hydrothermal device is a plurality of vertical tubular reactors capable of continuous hydrothermal heating.

7. A method for preparing water-dispersed aluminum hydroxide powder according to any one of claims 1 to 6, characterized in that: The Zeta potential is greater than 65 eV at room temperature and pH 7. The particle size of the aqueous phase dispersed aluminum hydroxide powder is 50-300 nm, and the specific surface area is 80-220 m 2 / g, pore volume 0.45~0.65cm 3 / g, with a pore size of 16~24nm, it can maintain a self-dispersed state in an aqueous solution, and the obtained 2~20wt% aluminum hydroxide aqueous solution is translucent.

8. Use of the aqueous phase dispersed aluminum hydroxide powder according to claim 7 in a naphtha reforming catalyst, characterized in that: The specific surface area of ​​the aluminum hydroxide powder dispersed in water is 160~220m 2 / g, the pore volume is 0.45~0.65cm3 / g, and the pore diameter is 17~22nm.

9. A naphtha reforming catalyst, characterized in that: The invention comprises the aqueous phase dispersed aluminum hydroxide powder as claimed in claim 7, wherein the naphtha reforming catalyst has a particle size of 1.6-1.8 mm, a bulk ratio of 0.55-0.65 g / mL, a strength of >40 N / particle, and a specific surface area of ​​160-220 m 2 / g, pore volume is 0.45~0.65cm3 / g, average pore diameter is 17~22nm; aromatics yield is greater than 52%, and reforming gasoline octane number RON is greater than 92.

10. Use of the aqueous phase dispersed aluminum hydroxide powder as claimed in claim 7 in a wear-resistant ceramic coating, characterized in that: The particle size of the aluminum hydroxide powder dispersed in water is 50~200nm, and the specific surface area is 80~160m 2 / g, pore volume is 0.45~0.65cm 3 / g.

11. A wear-resistant alumina ceramic coating, characterized in that: The invention comprises the aqueous dispersed aluminum hydroxide powder as described in claim 7, wherein the wear-resistant aluminum oxide ceramic coating has a hardness of 860-900 HV, a wear rate of 0.3-0.5%, a shear strength of 18-23 MPa, and a porosity of 1.0-1.5%.

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