CN117142503B - Composite active alumina powder and preparation method thereof - Google Patents

Composite active alumina powder and preparation method thereof Download PDF

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CN117142503B
CN117142503B CN202311091699.2A CN202311091699A CN117142503B CN 117142503 B CN117142503 B CN 117142503B CN 202311091699 A CN202311091699 A CN 202311091699A CN 117142503 B CN117142503 B CN 117142503B
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alumina powder
polyethylene glycol
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aqueous solution
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CN117142503A (en
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李涛
王绍华
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Shandong Aowei New Material Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
    • C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/14—Pore volume
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • C01P2006/17—Pore diameter distribution

Abstract

The application provides a composite active alumina powder and a preparation method thereof, wherein the method comprises the following steps: s10: dissolving soluble aluminum salt in a template agent aqueous solution to obtain a composite aluminum salt aqueous solution; the template agent is a star-shaped multi-arm branched polymer, the number of arms in the star-shaped multi-arm branched polymer is not less than 3, and the arms are independently represented as polyethylene glycol chain segments; s20: dropwise adding ammonia water into the composite aluminum salt aqueous solution until the pH value of the solution is 8-9, and aging to obtain aluminum hydroxide colloid; s30: and calcining and crushing the composite aluminum hydroxide colloid to obtain the composite active alumina powder. The composite active alumina powder prepared by the method forms pore canals which diverge from the center to the periphery, and all pore canals are mutually communicated to obtain the composite active alumina powder with better pore size distribution.

Description

Composite active alumina powder and preparation method thereof
Technical Field
The application relates to the technical field of catalyst carriers, in particular to composite active alumina powder and a preparation method thereof.
Background
Activated alumina (gamma-Al) 2 O 3 ) Is a porous and highly dispersed solid material, has the characteristics of large surface area, good adsorption performance, good surface acidity and good thermal stability, and can be used as a catalyst and a catalyst carrier for various chemical reactions.
The catalyst carrier needs to have a larger specific surface area, and the large specific surface area is beneficial to the adhesion and dispersion of the catalyst active substances, so that the catalyst activity is improved. Therefore, the active alumina powder is characterized as a main index of the catalyst carrier, and has pore volume and specific surface area. When these two parameters are high, the activity is generally considered to be high. The activity of the active alumina powder is guaranteed and improved by the high importance of the activity of the active alumina powder at present, and the preparation of raw materials, the proportion of the raw materials during molding, the selection of auxiliary agents, the molding process, the drying and the activation are strictly controlled.
Since the activity and selectivity of the catalyst are directly related to the carrier, the selectivity of the catalyst using activated alumina powder as the carrier is often also referred to as the problem of selectivity of the catalyst using activated alumina powder as the carrier, and the selectivity and pore size distribution of the catalyst are directly related to the pore size distribution of the carrier. Thus, the activated alumina powder as a carrier also needs to have a reasonable pore size distribution.
The macropores in the activated alumina powder are usually channels for participating in the catalytic reaction of the reactant entering the catalyst, and have a small Kong Caishi catalytic reaction occurrence point with rich specific surface area, meanwhile, the concentration of the reactant in the macropores is relatively uniform, the reactant is easy for the contact reaction on the surface of the catalyst, and the molecules of the reacted product can quickly migrate from the macropores to the macropores and then diffuse from the surface of the macropores to the medium. Thus, in order to obtain a catalyst having good activity and conversion, it is necessary to obtain activated alumina powder having a good pore size distribution.
Patent CN112794351a discloses a preparation method of macroporous active alumina powder, which comprises the following steps: 1) Mixing aluminum hydroxide powder and sodium hydroxide solution, pressurizing to 0.1-0.4 MPa, heating to 110-140 ℃, and reacting for 2-6 h to obtain sodium metaaluminate solution; 2) Adding the sodium metaaluminate solution obtained in the step 1) and the aluminum sulfate solution into a stirring reaction kettle in parallel, heating to 30-60 ℃, starting to react, adding the sodium metaaluminate solution, controlling the pH of the reaction solution to 8.5-9.5, continuing to react until the reaction is finished, heating to 70-90 ℃, standing and ageing; 3) Washing, drying and crushing the product obtained in the step 2) to obtain the product. The macroporous activated alumina powder is prepared by the method, but the problem is that the particle size distribution of the activated alumina powder prepared by the method is uncontrollable.
Patent CN115318267a discloses a preparation method of small-pore alumina powder, which comprises the following steps: a1, preparing an alumina precursor, A2, preparing core-shell alumina precursor-silica, A3, wrapping the core-shell alumina precursor-silica by polydopamine, and A4, calcining at high temperature, and crushing to obtain double-layer core-shell activated alumina-silica-carbonized polydopamine powder, namely the small-pore activated alumina powder. The patent prepares the small-pore active alumina powder with good thermal stability, high dispersion, high specific surface area and uniform crystal particle size distribution by the method. However, there is a problem in that the particle size distribution of the activated alumina powder prepared by this method is not controllable.
At present, when activated alumina powder is used as a catalyst carrier, the main focus is on expanding the specific surface area and pore volume of the activated alumina powder so as to improve the activity of the catalyst. It has now been found that the pore size distribution of the catalyst support is related to the activity and selectivity of the catalyst.
The prior art has little research on pore diameter control in activated alumina powder, and mainly prepares activated alumina powder with relatively large pore diameter or small pore diameter. In general, in order to increase the specific surface area and pore volume of the activated alumina powder, the aluminum hydroxide colloid is directly calcined, and water vapor produced during dehydration of aluminum hydroxide forms a high gas pressure in the crystal, thereby producing pores with wide distribution and obtaining activated alumina powder with smaller pore diameter. In order to obtain the active alumina powder with larger pore diameter, a plurality of pore expanding agents such as polyethylene glycol, fiber, carbon black and the like are added into the aluminum hydroxide colloid, and gas is generated in the calcination process to expand the pore diameter. However, the active alumina powder obtained by the above method has a narrow pore size distribution, which is disadvantageous for the use of the active alumina powder as a catalyst carrier.
Based on this, it is desirable to provide a method for preparing composite activated alumina powder having a better pore size distribution.
Disclosure of Invention
The application provides a composite active alumina powder and a preparation method thereof, which aim to prepare aluminum hydroxide colloid in situ by using a specific template agent, and prepare the composite active alumina powder with better pore size distribution by further calcining.
In a first aspect, the present application provides a method for preparing composite activated alumina powder, comprising the steps of:
s10: dissolving soluble aluminum salt in a template agent aqueous solution to obtain a composite aluminum salt aqueous solution; the template agent is a star-shaped multi-arm branched polymer, the number of arms in the star-shaped multi-arm branched polymer is not less than 3, and the arms are independently represented as polyethylene glycol chain segments;
s20: dropwise adding ammonia water into the composite aluminum salt aqueous solution until the pH value of the solution is 8-9, and aging to obtain aluminum hydroxide colloid;
s30: and calcining and crushing the composite aluminum hydroxide colloid to obtain the composite active alumina powder.
According to the application, in step S10, the soluble aluminum salt is directly dissolved in the aqueous solution of the template agent, wherein the template agent is a star-shaped multi-arm branched polymer, the number of arms in the star-shaped multi-arm branched polymer is not less than 3, the arms are independently represented as polyethylene glycol chain segments, the polyethylene glycol chain segments contain more ether bonds, the surface of the oxygen atoms contains more lone pair electrons, meanwhile, the polyethylene glycol chain segments have better flexibility, and aluminum ions can promote the extension of the polyethylene glycol chain segments and are dispersed around the star-shaped multi-arm branched polymer.
In step S20, ammonia water is added dropwise into the aqueous solution of the compound aluminum salt, so that aluminum hydroxide can be generated on the star-shaped multi-arm branched polymer in situ, and the compound aluminum hydroxide colloid compounded by the star-shaped multi-arm branched polymer and the compound aluminum hydroxide colloid can be formed through aging. In the composite aluminum hydroxide colloid, the star-shaped multi-arm branched polymer is embedded in the aluminum hydroxide colloid.
In step S30, the composite aluminum hydroxide colloid is calcined, wherein aluminum hydroxide is dehydrated to form a small-aperture pore canal, and the star-shaped multi-arm branched polymer embedded in the aluminum hydroxide colloid is decomposed to form a pore canal similar to the structure of the star-shaped multi-arm branched polymer in the interior of the active alumina, the pore canal diverges from the center to the periphery, and meanwhile, the aperture of the surface of the active alumina can be enlarged by gas generated by decomposition, so that the composite active alumina with better aperture distribution is obtained by cooperation of the three materials. In addition, because of the special structure of the template star-shaped multi-arm branched polymer, the inside of the activated alumina is communicated with each other, which is favorable for the diffusion and transmission of reactants, so that the composite activated alumina powder prepared by the method is more suitable for being used as a catalyst carrier.
It can be understood that the star-shaped multi-arm branched polymer is used as a template agent, compared with common chain polyethylene glycol or fiber, the proportion of the medium-aperture pore canal can be effectively improved, and the specific surface area and the pore volume of the activated alumina can be considered while better aperture distribution can be obtained; on the other hand, the pore channels formed by the chain template agent are mutually independent, which is unfavorable for the diffusion and transmission of reactants. In addition, a polymer having a complicated structure and a certain degree of crosslinking may cause excessive pore size due to the influence on the formation of aluminum hydroxide colloid.
According to the method, the star-shaped multi-arm branched polymer is used as a template agent, and the compound aluminum hydroxide colloid is obtained in situ by dropwise adding ammonia water into an aluminum salt aqueous solution, and because of the unique structure of the star-shaped multi-arm branched polymer which diverges from the center to the periphery, pore channels which diverge from the center to the periphery can be formed in the compound active alumina powder after calcination, and all pore channels are mutually communicated, so that the compound active alumina powder with better pore size distribution is obtained, the diffusion transfer in the compound active alumina powder which is a reaction substrate is facilitated, and the compound active alumina powder is more suitable to be used as a catalyst carrier.
In some embodiments, in step S10, the soluble aluminum salt may include at least one of aluminum chloride, aluminum nitrate, and aluminum sulfate.
In some embodiments, in step S10, the mass fraction of the template in the aqueous solution of the template is 0.1% to 2%. The proper mass fraction is beneficial to controlling the pore diameter in the composite active alumina powder.
In some embodiments, in step S10, the concentration of the soluble aluminum salt in the complex aluminum salt aqueous solution is 0.5-2 g/mL.
In some embodiments, in step S10, the method for preparing the star-shaped multi-arm branched polymer comprises the steps of:
m1: dissolving methoxy polyethylene glycol with weight average molecular weight of 500-1500 and succinic anhydride in toluene for reaction to obtain single-end carboxylated polyethylene glycol;
m2: dissolving single-end carboxylated polyethylene glycol and thionyl chloride in toluene for reaction to obtain single-end acyl chlorinated polyethylene glycol;
m3: and mixing single-end acyl chloride polyethylene glycol with polyhydroxy compound with hydroxyl number not less than 3, and heating to react to obtain the star-shaped multi-arm branched polymer.
In some embodiments, a preparation method of a star-shaped multi-arm branched polymer is specifically provided, wherein hydroxyl groups of methoxy polyethylene glycol end groups with weight average molecular weight of 500-1500 are carboxylated, then the carboxylated hydroxyl groups are reacted with thionyl chloride to carry out acyl chlorination on the end groups, and finally single-end acyl chlorinated polyethylene glycol and polyhydroxy compounds are mixed and heated to react, so that the star-shaped multi-arm branched polymer is obtained. The weight average molecular weight of the methoxy polyethylene glycol is 500-1500, which is favorable for obtaining the composite active alumina powder with better pore size distribution.
It will be appreciated that in the above preparation method, the product may be isolated after the reaction in each step by using operations including, but not limited to, drying, filtering, extracting, rotary steaming, etc.
In some embodiments, in step M1, the amount ratio of polyethylene glycol, succinic anhydride, and toluene is 20g: 5-15 g: 100-150 mL, and the reaction condition is that the reaction is carried out for 5-12 h at 60-80 ℃.
In some embodiments, in step M2, the amount ratio of single-ended carboxylated polyethylene glycol, thionyl chloride, and toluene is 10g: 10-25 mL: 50-100 mL, and the reaction condition is that the reaction is carried out for 20-30 h at 70-90 ℃.
In some embodiments, in step M3, the mass ratio of single end acyl chlorinated polyethylene glycol to polyhydroxy compound is 1:0.05 to 0.5, and the heating reaction condition is that the reaction is carried out for 5 to 10 hours at the temperature of 80 to 100 ℃. The appropriate mass ratio can be selected according to the kind of the polyol.
In some embodiments, in step M3, the polyhydroxy compound comprises at least one of glycerol, pentaerythritol, xylitol, D-sorbitol, β -cyclodextrin.
In some of the above embodiments, a few polyhydroxy compounds are specifically exemplified, and it is understood that the star-shaped multi-arm branched polymer is prepared by the above method, and the more the number of hydroxyl groups in the polyhydroxy compound, the more the number of arms of the star-shaped multi-arm branched polymer correspondingly prepared. Different polyhydroxy compounds are selected to obtain the composite active alumina powder with different particle size distribution.
In some embodiments, the polyhydroxy compound may be a β -cyclodextrin. Experiments show that when the hydroxyl compound is beta-cyclodextrin, the obtained composite active alumina powder has higher specific surface and pore volume, and the possible reason is that on one hand, the beta-cyclodextrin has more polyhydroxy than common polyol, so that the obtained star-shaped multi-arm branched polymer has more arms and more pore channels which are mutually communicated, and on the other hand, the beta-cyclodextrin has better stability than grafted polyethylene glycol chain segments, the polyethylene glycol chain segments are decomposed firstly in the calcination process, and the beta-cyclodextrin is decomposed again under the action of secondary reaming, so that the specific surface and pore volume of the composite active alumina powder are further improved, and the composite active alumina powder is more favorable for serving as a catalyst carrier.
In some embodiments, in step S20, S20 specifically includes: and (3) dropwise adding ammonia water into the aluminum salt aqueous solution until the pH value of the solution is 8-9, aging for 2-5 h, and filtering and washing to obtain the composite aluminum hydroxide colloid. The washing after aging is mainly to remove anions introduced by the soluble aluminum salt.
In some embodiments, in step S30, the calcination conditions are elevated to 700-800 ℃ at a rate of 3-5 ℃/min and incubated for 3-8 hours. The formation of composite activated alumina powder with better pore size distribution can be ensured by proper temperature rising rate.
In a second aspect, the present application provides a composite activated alumina powder prepared according to the method of any one of the embodiments of the first aspect.
According to the application, the composite active alumina powder is prepared by the method according to any embodiment of the first aspect, so that the composite active alumina powder has the beneficial effects of the first aspect.
Detailed Description
Each example or embodiment in this specification is described in a progressive manner, each example focusing on differences from other examples.
In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Example 1
Preparation of star-shaped multi-arm branched polymer:
m1: dissolving 20g of methoxy polyethylene glycol with weight average molecular weight of 1000 and 7.5g of succinic anhydride in 150mL of toluene, heating at 70 ℃ for reaction for 6 hours, adding chloroform for extraction, drying, removing chloroform by rotary evaporation, dissolving in diethyl ether, and drying to obtain single-end carboxylated polyethylene glycol;
m2: dissolving 10g of single-end carboxylated polyethylene glycol and 15.5mL of thionyl chloride in 50mL of toluene, heating at 80 ℃ for reaction for 24 hours, and performing rotary evaporation and drying to obtain single-end acyl chlorinated polyethylene glycol;
m3: 10g of single-end acyl chloride polyethylene glycol and 1g of glycerol are mixed, heated at 90 ℃ for reaction for 8 hours, dissolved in water, stood for 2 hours, added with methylene dichloride for extraction, dried by anhydrous sodium sulfate, and the methylene dichloride is removed by rotary evaporation to obtain the star-shaped multi-arm branched polymer.
Preparation of composite active alumina powder:
s10: 200g of aluminum chloride is heated and dissolved in 200mL of 1wt% of the aqueous solution of the star-shaped multi-arm branched polymer at 60 ℃ to obtain a composite aluminum salt aqueous solution;
s20: dropwise adding 7mg/mL ammonia water into the composite aluminum salt water solution until the pH value of the solution is 8, aging for 3 hours, filtering, washing until silver nitrate is added into the filtrate without precipitation, and obtaining composite aluminum hydroxide colloid;
s30: and (3) placing the composite aluminum hydroxide colloid in a heating furnace, heating to 750 ℃ at a speed of 3 ℃/min, preserving heat for 5 hours, calcining, cooling and crushing to obtain the composite active alumina powder.
Example 2
Preparation of star-shaped multi-arm branched polymer:
m1: dissolving 20g of methoxy polyethylene glycol with weight average molecular weight of 1000 and 7.5g of succinic anhydride in 150mL of toluene, heating at 70 ℃ for reaction for 6 hours, adding chloroform for extraction, drying, removing chloroform by rotary evaporation, dissolving in diethyl ether, and drying to obtain single-end carboxylated polyethylene glycol;
m2: dissolving 10g of single-end carboxylated polyethylene glycol and 15.5mL of thionyl chloride in 50mL of toluene, heating at 80 ℃ for reaction for 24 hours, and performing rotary evaporation and drying to obtain single-end acyl chlorinated polyethylene glycol;
m3: 10g of single-end acyl chloride polyethylene glycol and 1g of pentaerythritol are mixed, heated at 90 ℃ for reaction for 8 hours, dissolved in water, kept stand for 2 hours, added with methylene dichloride for extraction, dried by anhydrous sodium sulfate, and the methylene dichloride is removed by rotary evaporation to obtain the star-shaped multi-arm branched polymer.
Preparation of composite active alumina powder:
s10: 200g of aluminum chloride is heated and dissolved in 200mL of 1wt% of the aqueous solution of the star-shaped multi-arm branched polymer at 60 ℃ to obtain a composite aluminum salt aqueous solution;
s20: dropwise adding 7mg/mL ammonia water into the composite aluminum salt water solution until the pH value of the solution is 8, aging for 3 hours, filtering, washing until silver nitrate is added into the filtrate without precipitation, and obtaining composite aluminum hydroxide colloid;
s30: and (3) placing the composite aluminum hydroxide colloid in a heating furnace, heating to 750 ℃ at a speed of 3 ℃/min, preserving heat for 5 hours, calcining, cooling and crushing to obtain the composite active alumina powder.
Example 3
Preparation of star-shaped multi-arm branched polymer:
m1: dissolving 20g of methoxy polyethylene glycol with weight average molecular weight of 1000 and 7.5g of succinic anhydride in 150mL of toluene, heating at 70 ℃ for reaction for 6 hours, adding chloroform for extraction, drying, removing chloroform by rotary evaporation, dissolving in diethyl ether, and drying to obtain single-end carboxylated polyethylene glycol;
m2: dissolving 10g of single-end carboxylated polyethylene glycol and 15.5mL of thionyl chloride in 50mL of toluene, heating at 80 ℃ for reaction for 24 hours, and performing rotary evaporation and drying to obtain single-end acyl chlorinated polyethylene glycol;
m3: 10g of single-end acyl chloride polyethylene glycol and 1g D-sorbitol are mixed, heated at 90 ℃ for reaction for 8 hours, dissolved in water, stood for 2 hours, added with methylene dichloride for extraction, dried by anhydrous sodium sulfate, and the methylene dichloride is removed by rotary evaporation to obtain the star-shaped multi-arm branched polymer.
Preparation of composite active alumina powder:
s10: 200g of aluminum chloride is heated and dissolved in 200mL of 1wt% of the aqueous solution of the star-shaped multi-arm branched polymer at 60 ℃ to obtain a composite aluminum salt aqueous solution;
s20: dropwise adding 7mg/mL ammonia water into the composite aluminum salt water solution until the pH value of the solution is 8, aging for 3 hours, filtering, washing until silver nitrate is added into the filtrate without precipitation, and obtaining composite aluminum hydroxide colloid;
s30: and (3) placing the composite aluminum hydroxide colloid in a heating furnace, heating to 750 ℃ at a speed of 3 ℃/min, preserving heat for 5 hours, calcining, cooling and crushing to obtain the composite active alumina powder.
Example 4
Preparation of star-shaped multi-arm branched polymer:
m1: dissolving 20g of methoxy polyethylene glycol with weight average molecular weight of 1000 and 7.5g of succinic anhydride in 150mL of toluene, heating at 70 ℃ for reaction for 6 hours, adding chloroform for extraction, drying, removing chloroform by rotary evaporation, dissolving in diethyl ether, and drying to obtain single-end carboxylated polyethylene glycol;
m2: dissolving 10g of single-end carboxylated polyethylene glycol and 15.5mL of thionyl chloride in 50mL of toluene, heating at 80 ℃ for reaction for 24 hours, and performing rotary evaporation and drying to obtain single-end acyl chlorinated polyethylene glycol;
m3: 10g of single-end acyl chloride polyethylene glycol and 2g of beta-cyclodextrin are mixed, heated at 90 ℃ for reaction for 8 hours, dissolved in water, stood for 2 hours, added with methylene dichloride for extraction, dried by anhydrous sodium sulfate, and the methylene dichloride is removed by rotary evaporation to obtain the star-shaped multi-arm branched polymer.
Preparation of composite active alumina powder:
s10: 200g of aluminum chloride is heated and dissolved in 200mL of 1wt% of the aqueous solution of the star-shaped multi-arm branched polymer at 60 ℃ to obtain a composite aluminum salt aqueous solution;
s20: dropwise adding 7mg/mL ammonia water into the composite aluminum salt water solution until the pH value of the solution is 8, aging for 3 hours, filtering, washing until silver nitrate is added into the filtrate without precipitation, and obtaining composite aluminum hydroxide colloid;
s30: and (3) placing the composite aluminum hydroxide colloid in a heating furnace, heating to 750 ℃ at a speed of 3 ℃/min, preserving heat for 5 hours, calcining, cooling and crushing to obtain the composite active alumina powder.
Comparative example 1
Preparation of composite active alumina powder:
s10: 200g of aluminum chloride is heated and dissolved in 200mL of 1wt% methoxy polyethylene glycol aqueous solution with weight average molecular weight of 1000 at 60 ℃ to obtain composite aluminum salt aqueous solution;
s20: dropwise adding 7mg/mL ammonia water into the composite aluminum salt water solution until the pH value of the solution is 8, aging for 3 hours, filtering, washing until silver nitrate is added into the filtrate without precipitation, and obtaining composite aluminum hydroxide colloid;
s30: and (3) placing the composite aluminum hydroxide colloid in a heating furnace, heating to 750 ℃ at a speed of 3 ℃/min, preserving heat for 5 hours, calcining, cooling and crushing to obtain the composite active alumina powder.
Comparative example 2
The star multi-arm branched polymer was prepared as in example 1.
Preparation of composite active alumina powder:
s10: 200g of aluminum chloride is heated and dissolved in water at 60 ℃ to obtain an aluminum salt aqueous solution;
s20: dropwise adding 7mg/mL ammonia water into the composite aluminum salt water solution until the pH value of the solution is=8, adding 2g of the star-shaped multi-arm branched polymer, performing ultrasonic dissolution, aging for 3 hours, filtering, washing until silver nitrate is added into the filtrate without precipitation, and obtaining composite aluminum hydroxide colloid;
s30: and (3) placing the composite aluminum hydroxide colloid in a heating furnace, heating to 750 ℃ at a speed of 3 ℃/min, preserving heat for 5 hours, calcining, cooling and crushing to obtain the composite active alumina powder.
The composite activated alumina powder obtained in the above examples and comparative examples was subjected to nitrogen adsorption process by a nitrogen physical adsorption instrument (ASAP 2010 type of Micromeritics Co., U.S.A.), and the specific surface area, pore volume, pore size and distribution were measured. The results are shown in Table 1.
TABLE 1
According to the results shown in Table 1, the composite activated alumina powder obtained in the embodiment of the present application has a higher specific surface area and pore volume than those of the comparative example, and at the same time, the pore size distribution is more concentrated in 20-50 nm, the proportion of pores with diameters larger than 50nm is reduced, and the composite activated alumina powder can have a larger specific surface area and pore volume while having large pore channels, so that the composite activated alumina powder is more suitable for being used as a carrier of a catalyst. The single-chain polyethylene glycol used in comparative example 1, as a template agent, was not effective in increasing the specific surface area and pore volume of the composite activated alumina powder, nor in increasing the proportion of pore diameters of 20 to 50 nm; in comparative example 2, although a star-shaped multi-arm branched polymer was used, the addition after the preparation of aluminum hydroxide colloid resulted in failure to function similarly to that in example 1, and the specific surface area, pore volume and pore size distribution of the composite activated alumina powder were poor.
The results of comparative examples 1 to 4 revealed that, as the number of arms in the star-shaped multi-arm branched polymer increases, the specific surface area and pore volume of the composite activated alumina powder tend to increase, and the proportion of pore diameters of 20 to 50nm increases relatively, wherein example 4 is better than examples 1 to 3, the proportion of pore diameters of 20 to 50nm is the largest, the proportion of pore diameters of less than 20nm decreases relatively, and the specific surface area and pore volume are the best, probably because the secondary pore-enlarging effect of beta-cyclodextrin can enlarge the pore diameters of 2 part of pore channels in addition to the increase in the number of arms.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims (5)

1. A process for preparing a composite activated alumina powder comprising the steps of:
s10: dissolving soluble aluminum salt in a template agent aqueous solution to obtain a composite aluminum salt aqueous solution; the template agent is a star-shaped multi-arm branched polymer, the number of arms in the star-shaped multi-arm branched polymer is not less than 3, and the arms are independently represented as polyethylene glycol chain segments;
the preparation method of the star-shaped multi-arm branched polymer comprises the following steps:
m1: dissolving methoxy polyethylene glycol and succinic anhydride with weight average molecular weight of 500-1500 in toluene, and reacting at 60-80 ℃ for 5-12 h to obtain single-end carboxylated polyethylene glycol; wherein the dosage ratio of the methoxy polyethylene glycol, the succinic anhydride and the toluene is 20g: 5-15 g: 100-150 mL;
m2: dissolving the single-end carboxylated polyethylene glycol and thionyl chloride in toluene, and reacting for 20-30 hours at 70-90 ℃ to obtain single-end acyl chlorinated polyethylene glycol; wherein the dosage ratio of the single-end carboxylated polyethylene glycol to the thionyl chloride to the toluene is 10g: 10-25 mL: 50-100 mL;
m3: mixing the single-end acyl chloride polyethylene glycol with a polyhydroxy compound with the hydroxyl number not less than 3, and reacting for 5-10 hours at 80-100 ℃ to obtain a star-shaped multi-arm branched polymer; the mass ratio of the single-end acyl chloride polyethylene glycol to the polyhydroxy compound is 1: 0.05-0.5 of polyhydroxy compound comprising at least one of glycerol, pentaerythritol, xylitol, D-sorbitol and beta-cyclodextrin;
s20: dropwise adding ammonia water into the composite aluminum salt aqueous solution until the pH value of the solution is 8-9, and aging to obtain composite aluminum hydroxide colloid;
s30: and calcining and crushing the aluminum hydroxide colloid to obtain the composite active alumina powder.
2. The method according to claim 1, wherein in the step S10, the mass fraction of the template in the aqueous solution of the template is 0.1% -2%.
3. The method according to claim 1, wherein in the step S10, the concentration of the soluble aluminum salt in the aqueous solution of the composite aluminum salt is 0.5-2 g/mL.
4. The method according to claim 1, wherein in the step S30, the calcination condition is to raise the temperature to 700-800 ℃ at a rate of 3-5 ℃/min and keep the temperature for 3-8 hours.
5. A composite activated alumina powder prepared by the method of any one of claims 1 to 4.
CN202311091699.2A 2023-08-28 2023-08-28 Composite active alumina powder and preparation method thereof Active CN117142503B (en)

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