Method for preparing high-purity macroporous pseudo-boehmite by steam hydrolysis method

Abstract

The invention provides a method for preparing high-purity macroporous pseudo-boehmite, which comprises the following steps: putting organic aluminum alkoxide into a quartz tube of a tube furnace, then introducing mixed steam of water and an organic solvent into the quartz tube, enabling the organic aluminum alkoxide to be in contact with the mixed steam, and carrying out hydrolysis reaction to generate amorphous pseudo-boehmite, and carrying out aging treatment on the obtained amorphous pseudo-boehmite through a solvent / hydrothermal method to finally obtain the macroporous pseudo-boehmite with high purity and good crystallinity. The macroporous pseudo-boehmite prepared by the method has the advantages of simple and easy-to-control process flow, high product purity, easy recovery of hydrolysate and the like, and is suitable for industrial popularization and application.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of catalytic materials, and particularly relates to a method for preparing high-purity macroporous pseudoboehmite. Background Art

[0002] Among many catalyst carriers, alumina has an adjustable pore structure, a large specific surface area, excellent loading capacity and high mechanical strength, and is one of the most widely used catalyst carriers. For catalytic reactions, the properties of the catalyst carrier largely determine the activity and selectivity of the catalyst. Catalyst carriers with a large pore volume have the following advantages. First, they can accelerate the diffusion rate of guest molecules in the pores, increasing the catalytic reaction activity. Second, they can improve the carbon tolerance of the catalyst and slow down the deactivation rate of the catalyst. Third, they are beneficial to improving the dispersion degree of the active components of the catalyst in the carrier. In addition, the purity of the catalyst carrier is also crucial. If the impurity content is too high, it often leads to a decrease in catalyst activity and an increase in side reactions.

[0003] Pseudoboehmite can be converted into alumina after high-temperature calcination, and its properties largely determine the properties of alumina. Therefore, the key to obtaining high-purity macroporous alumina lies in pseudoboehmite. Pseudoboehmite (AlOOH·nH2O) is a type of alumina hydrate with a relatively special structure and an uncertain number of crystal waters, also known as pseudo-boehmite, boehmite-like, etc., and has advantages such as a high specific surface area, a large porosity, and good peptization performance. However, currently, domestic pseudoboehmite often has disadvantages such as low purity and small porosity. The production technology of high-quality macroporous pseudoboehmite has not been completely broken through and almost completely relies on imports. Therefore, it is of great significance to develop a preparation technology for high-purity macroporous pseudoboehmite.

[0004] Patent CN 110963514A discloses a method for preparing macroporous modified pseudoboehmite. It uses the acidification co-current method to prepare a solution of one or more of sulfates, meta-aluminates, and nitrates. Under the conditions of appropriate pH, temperature, stirring speed, and a certain amount of pore-expanding stabilizer, the obtained solution is reacted with an alkaline solution and a modifying agent to form a gel, and the product is aged, solid-liquid separated, washed, spray-dried, etc. to obtain macroporous modified pseudoboehmite powder. The modified pseudoboehmite prepared by this invention has a specific surface area of 30 - 400 m 2 / g, a macropore volume of 0.85 - 1.1 cm 3 / g, and the proportion of macropores with a pore diameter concentrated in the range of 5 - 15 nm is greater than 85%.

[0005] Patent CN 106348327A provides a method for preparing super macroporous pseudo-boehmite. First, fast-detaching powder is put into an aqueous solution containing ammonium carbonate and an auxiliary agent and stirred to make it fully hydrated and combined with a template agent. Then, the filter cake is obtained by filtration. After the filter cake is dried, ammonium carbonate and the auxiliary agent are removed by heating to obtain super macroporous pseudo-boehmite. The super macroporous pseudo-boehmite prepared by this invention has a pore volume ≥ 1.5 ml / g and a specific surface area ≥ 400 m 2 / g.

[0006] Although the above patent has prepared macroporous pseudo-boehmite, however, it all uses the inorganic method to synthesize pseudo-boehmite. The raw materials used contain impurities, which will lead to a relatively low purity of pseudo-boehmite and it is difficult to be used as a catalyst carrier in reactions with high requirements for the purity of the catalyst. And when using a template agent for pore expansion, since the template agent usually needs to be removed by calcination and cannot be recycled, the production cost of pseudo-boehmite is relatively high. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing high-purity macroporous pseudo-boehmite. This method has a simple and easy-to-control process and the hydrolysis solution is easy to recycle. The prepared pseudo-boehmite has a large pore volume, high purity and high crystallinity.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions: A method for preparing high-purity macroporous pseudo-boehmite, which comprises the following steps: (1) Loading organoaluminum alkoxide into a quartz tube and placing it in a tube furnace; (2) Heating organic solvent and water respectively to evaporate them to form steam, mixing them and then introducing them into the tube furnace to make the mixed steam contact with the organoaluminum alkoxide in the tube; (3) Heating the tube furnace to completely hydrolyze the organoaluminum alkoxide in full contact with the mixed steam to obtain amorphous pseudo-boehmite; (4) Continuing to introduce the mixed steam of organic solvent and water and raising the temperature to age the obtained amorphous pseudo-boehmite to obtain macroporous pseudo-boehmite; (5) Filtering and drying the sample after the aging treatment in step (4) to obtain the high-purity macroporous pseudo-boehmite.

[0009] Further, the organoaluminum alkoxide in step (1) includes one or more of aluminum isopropoxide, aluminum sec-butoxide, aluminum n-butoxide, aluminum n-pentoxide.

[0010] Further, the organic solvent in step (2) is one of low-boiling non-alcoholic organic solvents, specifically including n-pentane, methyl tert-butyl ether, methyl acetate, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, methyl ethyl ketone, 1,2-dichloroethane, etc.

[0011] Further, in step (2), the heating temperatures of the organic solvent and water are 40~140 °C and 100~150 °C, respectively.

[0012] Further, in step (2), the organic solvent vapor and water vapor are mixed in a volume ratio of 1:4~3:1.

[0013] Further, in step (3), the temperature of the hydrolysis reaction is 100~140 °C, and the time is 1~4 h.

[0014] Further, in step (4), the temperature of the aging is 100~180 °C, and the time is 4~64 h.

[0015] Further, in step (5), the temperature of the drying is 100~180 °C, and the time is 6~36 h.

[0016] The obtained high-purity macroporous pseudoboehmite has a purity of over 99%, a specific surface area of 188~420 m 2 / g, a pore volume of 1.21~1.88 cm 3 / g, and an average pore diameter of 11.9~28.4 nm.

[0017] In the present invention, organoaluminum alkoxide is used as the aluminum source, and hydrolysis reaction is carried out by means of steam hydrolysis. Then, the hydrolysis product is aged by the solvent / hydrothermal method to obtain high-purity macroporous pseudoboehmite. In this process, by controlling the heating temperature of water, the generation rate of water vapor is controlled, and water molecules are dispersed to the greatest extent, so as to slow down the hydrolysis rate of aluminum alkoxide, enabling sufficient time for the growth of pseudoboehmite crystals. The crystals grow and tend to be complete, thus achieving the effect of pore expansion. Moreover, during the aging treatment of pseudoboehmite, the functional groups of the added non-alcohol organic solvent replace some non-bridging hydroxyl groups on the surface of pseudoboehmite colloidal particles, which can reduce the formation of hydrogen bonds, play a certain steric hindrance role, and further reduce or eliminate the generation of hard agglomeration, further playing a role in pore expansion. At the same time, the use of low-boiling solvents facilitates the recovery and reuse of solvents, with high economic benefits.

[0018] Compared with the prior art, the advantages of the present invention are as follows: The process flow of the present invention is simple and easy to control. By regulating the heating temperatures of water and solvent, the reaction rate can be controlled. The prepared pseudoboehmite has a large pore volume, high purity, and high crystallinity. Moreover, the hydrolysis solution is easy to collect, convenient for recycling, and has high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the device for preparing high-purity macroporous pseudoboehmite by the steam hydrolysis method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] A preparation method of high-purity macroporous pseudo-boehmite, the specific steps are as follows: (1) As Figure 1 , load the organoaluminum alkoxide into a quartz tube and place it in a tube furnace. (2) Load the organic solvent and water into flasks respectively, heat them to 40~140 °C and 100~150 °C through an oil bath, evaporate the organic solvent and water to form vapors, and then mix the organic solvent vapor and water vapor in a volume ratio of 1:4~3:1 and introduce them into the tube furnace. (3) Heat the tube furnace to 100~140 °C, make the organoaluminum alkoxide fully contact with the mixed vapor for 1~4 h, and completely hydrolyze the organoaluminum alkoxide to obtain amorphous pseudo-boehmite. (4) Continue to introduce the mixed vapor of the organic solvent and water, and raise the temperature of the tube furnace to 100~180 °C, and age the obtained amorphous pseudo-boehmite for 4~64 h to obtain macroporous pseudo-boehmite. (5) Filter the sample after the aging treatment in step (4) and dry it at 100~180 °C for 6~36 h to obtain high-purity macroporous pseudo-boehmite.

[0021] Among them, the organoaluminum alkoxide includes one or more of aluminum isopropoxide, aluminum sec-butoxide, aluminum n-butoxide, and aluminum n-pentoxide. The organic solvent is one of low-boiling non-alcoholic organic solvents, specifically including n-pentane, methyl tert-butyl ether, methyl acetate, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, methyl ethyl ketone, 1,2-dichloroethane, etc.

[0022] For the convenience of understanding the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise specified, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0024] Example 1: Place 1 mol of aluminum isopropoxide in a quartz tube in a tube furnace. Set the heating temperature of n-pentane to 40 °C and the heating temperature of water to 130 °C, and then introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 1:4 to fully contact with the aluminum isopropoxide. Then heat the tube furnace to 100 °C and hydrolyze the aluminum isopropoxide for 2 h. After hydrolysis, continue to introduce the mixed vapor of the organic solvent and water into the tube furnace, and heat the tube furnace to 140 °C and age for 24 h. The sample after the aging treatment is filtered and dried at 140 °C for 8 h to obtain high-purity macroporous pseudo-boehmite.

[0025] Example 2: Place 1 mol of aluminum sec-butoxide in a quartz tube within a tube furnace. Set the heating temperature of methyl tert-butyl ether to 80 °C and the heating temperature of water to 120 °C. Then, introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 1:2 to come into full contact with the aluminum sec-butoxide. Next, heat the tube furnace to 105 °C and hydrolyze the aluminum sec-butoxide for 2 h. After hydrolysis is completed, continue to introduce the mixed vapor of the organic solvent and water into the tube furnace and heat the tube furnace to 100 °C for aging for 64 h. The sample after aging treatment is filtered and dried at 100 °C for 24 h to obtain high-purity macroporous pseudo-boehmite.

[0026] Example 3: Place 1 mol of aluminum n-butoxide in a quartz tube within a tube furnace. Set the heating temperature of 1,2-dichloroethane to 100 °C and the heating temperature of water to 100 °C. Then, introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 2:1 to come into full contact with the aluminum n-butoxide. Next, heat the tube furnace to 140 °C and hydrolyze the aluminum n-butoxide for 3 h. After hydrolysis is completed, continue to introduce the mixed vapor of the organic solvent and water into the tube furnace and heat the tube furnace to 110 °C for aging for 12 h. The sample after aging treatment is filtered and dried at 110 °C for 6 h to obtain high-purity macroporous pseudo-boehmite.

[0027] Example 4: Place 1 mol of aluminum n-pentoxide in a quartz tube within a tube furnace. Set the heating temperature of methyl acetate to 90 °C and the heating temperature of water to 150 °C. Then, introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 1:3 to come into full contact with the aluminum n-pentoxide. Next, heat the tube furnace to 110 °C and hydrolyze the aluminum n-pentoxide for 1 h. After hydrolysis is completed, continue to introduce the mixed vapor of the organic solvent and water into the tube furnace and heat the tube furnace to 180 °C for aging for 4 h. The sample after aging treatment is filtered and dried at 180 °C for 6 h to obtain high-purity macroporous pseudo-boehmite.

[0028] Example 5: Place 1 mol of aluminum isopropoxide in a quartz tube within a tube furnace. Set the heating temperature of ethylene glycol dimethyl ether to 140 °C and the heating temperature of water to 110 °C. Then, introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 3:1 to come into full contact with the aluminum isopropoxide. Next, heat the tube furnace to 120 °C and hydrolyze the aluminum isopropoxide for 2.5 h. After hydrolysis is completed, continue to introduce the mixed vapor of the organic solvent and water into the tube furnace and heat the tube furnace to 110 °C for aging for 48 h. The sample after aging treatment is filtered and dried at 110 °C for 36 h to obtain high-purity macroporous pseudo-boehmite.

[0029] Example 6: Place 1 mol of aluminum sec-butoxide in a quartz tube in a tube furnace. Set the heating temperature of 2-methyltetrahydrofuran to 120 °C and the heating temperature of water to 105 °C. Then, introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 1:4 to fully contact with the aluminum sec-butoxide. Next, heat the tube furnace to 130 °C to hydrolyze the aluminum sec-butoxide for 3.5 h. After hydrolysis is completed, continue to introduce the mixed vapor of organic solvent and water into the tube furnace, and heat the tube furnace to 120 °C for aging for 18 h. The sample after aging treatment is filtered and dried at 120 °C for 12 h to obtain high-purity macroporous pseudoboehmite.

[0030] Example 7: Place 1 mol of aluminum n-butoxide in a quartz tube in a tube furnace. Set the heating temperature of methyl ethyl ketone to 100 °C and the heating temperature of water to 140 °C. Then, introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 1:3 to fully contact with the aluminum n-butoxide. Next, heat the tube furnace to 128 °C to hydrolyze the aluminum n-butoxide for 4 h. After hydrolysis is completed, continue to introduce the mixed vapor of organic solvent and water into the tube furnace, and heat the tube furnace to 100 °C for aging for 24 h. The sample after aging treatment is filtered and dried at 100 °C for 8 h to obtain high-purity macroporous pseudoboehmite.

[0031] Example 8: Place 1 mol of aluminum sec-butoxide in a quartz tube in a tube furnace. Set the heating temperature of methyl acetate to 90 °C and the heating temperature of water to 110 °C. Then, introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 1:2 to fully contact with the aluminum sec-butoxide. Next, heat the tube furnace to 105 °C to hydrolyze the aluminum sec-butoxide for 2 h. After hydrolysis is completed, continue to introduce the mixed vapor of organic solvent and water into the tube furnace, and heat the tube furnace to 130 °C for aging for 16 h. The sample after aging treatment is filtered and dried at 130 °C for 10 h to obtain high-purity macroporous pseudoboehmite.

[0032] Example 9: Place 1 mol of aluminum isopropoxide in a quartz tube inside a tube furnace. Set the heating temperature of 1,2-dichloroethane to 110 °C and the heating temperature of water to 110 °C. Then, introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 1:4 to fully contact with the aluminum isopropoxide. Next, heat the tube furnace to 100 °C to hydrolyze the aluminum isopropoxide for 3 h. After hydrolysis is completed, continue to introduce the mixed vapor of organic solvent and water into the tube furnace and heat the tube furnace to 140 °C for aging for 24 h. The sample after aging treatment is filtered and dried at 120 °C for 12 h to obtain high-purity macroporous pseudo-boehmite.

[0033] Example 10: Place 1 mol of aluminum isopropoxide in a quartz tube inside a tube furnace. Set the heating temperature of methyl tert-butyl ether to 60 °C and the heating temperature of water to 120 °C. Then, introduce the formed organic solvent vapor and water vapor into the tube furnace in a volume ratio of 2:1 to fully contact with the aluminum isopropoxide. Next, heat the tube furnace to 140 °C to hydrolyze the aluminum isopropoxide for 4 h. After hydrolysis is completed, continue to introduce the mixed vapor of organic solvent and water into the tube furnace and heat the tube furnace to 120 °C for aging for 8 h. The sample after aging treatment is filtered and dried at 120 °C for 16 h to obtain high-purity macroporous pseudo-boehmite.

[0034] Comparative Example 1: Mix 1 mol of aluminum sec-butoxide with 8 mol of isopropanol and heat to 105 °C. When the aluminum sec-butoxide is completely dissolved by stirring, add 8 mol of deionized water through a peristaltic pump (the water addition rate is 3 rpm) and carry out hydrolysis reaction for 2 h. Transfer the sample after the reaction to a reaction kettle and age at 130 °C for 16 h. The sample after aging treatment is filtered and dried at 130 °C for 10 h to obtain pseudo-boehmite.

[0035] Comparative Example 2: Mix 1 mol of aluminum sec-butoxide with 8 mol of methyl acetate and heat to 105 °C. When the aluminum sec-butoxide is completely dissolved by stirring, add 8 mol of deionized water through a peristaltic pump (the water addition rate is 3 rpm). Carry out hydrolysis reaction for 2 h. Transfer the sample after the reaction to a reaction kettle and age at 130 °C for 16 h. The sample after aging treatment is filtered and dried at 130 °C for 10 h to obtain pseudo-boehmite.

[0036] Comparative Example 3: Place 1 mol of aluminum sec-butoxide in a quartz tube in a tubular furnace. Set the heating temperature of isopropyl alcohol to 90 °C and the heating temperature of water to 110 °C. Then, introduce the formed organic solvent vapor and water vapor into the tubular furnace in a volume ratio of 1:2 to fully contact with aluminum sec-butoxide. Next, heat the tubular furnace to 105 °C and hydrolyze aluminum sec-butoxide for 2 h. After hydrolysis is completed, continue to introduce the mixed vapor of organic solvent and water into the tubular furnace and heat the tubular furnace to 130 °C for aging for 16 h. The sample after aging treatment is filtered and dried at 130 °C for 10 h to obtain pseudo-boehmite.

[0037] Comparative Example 4 Place 1 mol of aluminum sec-butoxide in a quartz tube in a tubular furnace. Set the heating temperature of water to 110 °C. Then, introduce the formed water vapor into the tubular furnace to fully contact with aluminum sec-butoxide. Next, heat the tubular furnace to 105 °C and hydrolyze aluminum sec-butoxide for 2 h. Transfer the sample after the reaction to a reaction kettle and age it at 130 °C for 16 h. The sample after aging treatment is filtered and dried at 130 °C for 10 h to obtain pseudo-boehmite.

[0038] The performance data of the pseudo-boehmite prepared in the examples and comparative examples are shown in Table 1.

[0039] Table 1 Performance data of the pseudo-boehmite prepared in the examples and comparative examples

[0040] It can be seen from the comparison with the data of the comparative examples in Table 1 that the use of non-alcohol organic solvents combined with steam hydrolysis method has an obvious pore-expanding effect on pseudo-boehmite, and the pseudo-boehmite prepared in Example 8 has the best pore structure properties.

[0041] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A method for preparing high-purity macroporous pseudo-boehmite, characterized in that, It includes the following steps: (1) Load the organoaluminum alkoxide into a quartz tube and place it in a tube furnace; (2) Heat the organic solvent and water separately to evaporate them into vapors, mix the vapors and introduce them into the tube furnace so that the mixed vapors contact the organoaluminum alkoxide in the tube; (3) Heat the tube furnace to completely hydrolyze the organoaluminum alkoxide in full contact with the mixed vapors to obtain amorphous pseudo-boehmite; (4) Continuously introduce the mixed vapors of the organic solvent and water, and raise the temperature to age the obtained amorphous pseudo-boehmite to obtain macroporous pseudo-boehmite; (5) Filter and dry the sample after the aging treatment in step (4) to obtain the high-purity macroporous pseudo-boehmite.

2. The preparation method of high-purity macroporous pseudo-boehmite according to claim 1, characterized in that, The organoaluminum alkoxide described in step (1) includes one or more of aluminum isopropoxide, aluminum sec-butoxide, aluminum n-butoxide, and aluminum n-pentoxide.

3. The preparation method of high-purity macroporous pseudo-boehmite according to claim 1, characterized in that, The organic solvent described in step (2) is one of low-boiling non-alcoholic organic solvents.

4. The preparation method of high-purity macroporous pseudo-boehmite according to claim 1, characterized in that, In step (2), the organic solvent vapor and water vapor are mixed in a volume ratio of 1:4 to 3:

1.

5. The preparation method of the high-purity macroporous pseudo-boehmite according to claim 1, characterized in that, In step (3), the temperature of the hydrolysis reaction is 100-140 °C and the time is 1-4 h.

6. The preparation method of high-purity macroporous pseudo-boehmite according to claim 1, characterized in that, In step (4), the temperature of the aging is 100-180 °C and the time is 4-64 h.

7. The preparation method of high-purity macroporous pseudo-boehmite according to claim 1, characterized in that, In step (5), the temperature of the drying is 100-180 °C and the time is 6-36 h.

8. The preparation and synthesis method of high-purity macroporous pseudo-boehmite according to claim 1, characterized in that, The purity of the obtained high-purity macroporous pseudo-boehmite reaches over 99%, the specific surface area is 188 - 420 m 2 / g, the pore volume is 1.21 - 1.88 cm 3 / g, and the average pore diameter is 11.9 - 28.4 nm.

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