CN1803618A - Process for preparing mesopored alumina - Google Patents

Abstract

The invention relates to a preparation method for alumina. Wherein, with aluminum sol as precursor, adding surfactant and high polymer or hydroxyl acid as structure guide agent, adding base to regulate system pH value within 8-11; hydrothermal composing at 80-100Deg, separating, clearing with water, drying, and baking at 500Deg; or drying directly the mixture at 30-100Deg, then baking at 500Deg to obtain the product. The experiments show: the product has connected worm-shaped pore structure with wall frame formed by crystal phase gamma-Al2O3 as well as high specific surface area and controllable pore size distribution, is simple and low cost and stable, and spreads its larger-scale application.

Description

A kind of preparation method of mesoporous aluminas

Technical field

The present invention relates to the preparation of mesoporous aluminas, to be that a kind of high-specific surface area, large pore volume, pore size distribution are concentrated specifically controlled, skeleton is by crystalline phase γ-Al ₂O ₃The preparation method of the mesoporous aluminas of forming.

Background technology

Aluminum oxide has various good physics, chemical property, is widely applied in the numerous areas such as Industrial Catalysis, absorption, ion-exchange.As support applications the time, because the carbon distribution that produces in the reaction process will stop up the duct of aluminum oxide gradually, thereby suppressed the mass transfer of reactant and product, finally cause the inactivation of catalyzer.Known to carrier, the contribution of micropore contrast table area is big more, pore size distribution is wide more, and the deactivation rate of catalyzer is just fast more.As seen, the pore passage structure of aluminum oxide has material impact to activity of such catalysts, selectivity and life-span.And its pore passage structure of aluminum oxide of traditional method preparation is uncontrollable body phase hole, and this is restricted its application.Therefore, preparation has high-specific surface area, large pore volume, the concentrated controlled mesoporous aluminas of pore size distribution, has considerable economic worth and realistic meaning.

The preparation method of mesoporous aluminas is mainly sol-gel method and surfactant templates method at present.Sol-gel method at first prepares the regular and uniform colloidal sol of micelle shape, by meticulous thermal treatment micelle is piled up regularly then, and the space between the micelle constitutes the mesopore duct.Therefore, this mesopore essence is the body phase hole that unordered accumulation produces between particle, and the specific surface area of product and pore volume are all less, and also exist a large amount of micropores except that mesopore.The mesoporous aluminas specific surface area that the aluminium colloidal sol of homogeneous grain diameter is obtained after vacuum-drying, roasting as Yao etc. is less than 266m ²/ g, pore volume is no more than 0.13cm ³/ g, the aperture mainly is distributed in 0.8～3.8nm (CN 1323740A).On the other hand, seek out the colloidal sol that homogeneous grain diameter distributes, it is very harsh to make each process, and the precipitation process of presoma, one-tenth adhesive tape part, drying condition etc. all have material impact to the pore structure of product.Therefore, directly be difficult to obtain high-quality mesoporous aluminas by sol-gel method.

The supramolecule that the surfactant templates method has utilized surfactant molecule to form comes controlled oxidation aluminium mesopore duct as stay in place form formation.Can be by changing the raw material ratio of synthetic system, or add the variation that other organic additive is controlled pore passage structure, also can be by changing the modulation of realizations such as synthesis condition such as synthesis temperature, crystallization condition, washing methods, template removal path to pore structure parameter.But present this method is a precursor with poisonous, inflammable, expensive aluminium-alcohol salt mainly, carry out in mutually at alcohol, and preparation cycle is long, complicated operating process industrialization (Chem.Commun., 1998,1185 of having limited preparation; Microp.Mesop.Mater., 2002,52,169; Microp.Mesop.Mater., 2001,44,203).In addition, most its skeletons of mesoporous aluminas of having reported are amorphous, do not have special crystalline phase of transition state of alumina and surface properties, and very sensitive to water, in air, will lose central hole structure (Chem.Mater., 1996 behind the placement some months under the room temperature, 8,1451).These make unbodied mesoporous aluminas be very restricted in the application as aspects such as sorbent material, catalyzer and support of the catalyst.

Summary of the invention

The object of the present invention is to provide a kind of preparation method of mesoporous aluminas.

The preparation method of mesoporous aluminas provided by the invention, its skeleton is by crystalline phase γ-Al ₂O ₃Form, main preparation process is:

With the boehmite sol is precursor, add tensio-active agent and mix under room temperature, add urea or ammoniacal liquor and make the final pH value of system be 8-11,80-100 ℃ of following hydro-thermal synthesized 12-24 hour, separate, the washing back is in 30-100 ℃ of drying, 450-550 ℃ roasting 2-4 hour.Wherein:

Mol ratio in the Al in the boehmite sol and tensio-active agent is 1: 0.04-0.25;

Tensio-active agent is a kind of in hexadecyl trimethyl ammonium bromide, polyethylene oxide-poly(propylene oxide)-polyethylene oxide or the tween.

Perhaps be precursor, add tensio-active agent, high molecular polymer or alcohol acid and make structure directing agent with the boehmite sol, directly in 30-100 ℃ of drying, 450-550 ℃ roasting 2-4 hour.Wherein:

Mol ratio in the Al in the boehmite sol and structure directing agent is 1: 0.005-1;

Tensio-active agent is a kind of in hexadecyl trimethyl ammonium bromide, two (2-ethylhexyl) sulfosuccinate sodium, polyethylene oxide-poly(propylene oxide)-polyethylene oxide or the tween;

High molecular polymer is Macrogol 2000, polyethylene glycol 6000 or Macrogol 2000 0;

Alcohol acid is a kind of in citric acid, tartrate, oxysuccinic acid or the lactic acid.

The present invention replaced with aluminium colloidal sol cheap, stable, high dispersive cost an arm and a leg, poisonous, inflammable aluminium-alcohol salt is as the aluminium source, avoided the use of a large amount of organic solvents, and adopt cheap tensio-active agent, high molecular polymer or alcohol acid as structure directing agent, realized effective regulation and control to aluminum oxide duct structure.Product not only has the mesopore duct of pore size distribution high concentration, and skeleton is by the γ-Al of crystalline state ₂O ₃Form, possessed special surface properties and the superior body phase character of mesopore material of transition state of alumina simultaneously, therefore, have very big application potential in fields such as Industrial Catalysis, absorption, ion-exchanges.Simultaneously, technology of the present invention is simple, control is convenient, cheap, the environmental friendliness of raw material, for the high-quality mesoporous aluminas of industrialized mass provides possibility.

Description of drawings

Fig. 1 is the XRD figure of the mesoporous aluminas that obtains with the different templates agent.Wherein:

The A representative is the mesoporous aluminas that template prepares under alkaline condition with the hexadecyl trimethyl ammonium bromide;

The B representative is the directly mesoporous aluminas of preparation of template with polyethylene oxide-poly(propylene oxide)-polyethylene oxide;

The C representative is the mesoporous aluminas of template preparation with the Macrogol 2000;

The D representative is the mesoporous aluminas of template preparation with the citric acid;

" ● " represents γ-Al ₂O ₃Characteristic peak.

Embodiment

Example one prepares boehmite sol with commerce with the boehmite powder.

Get 13.67g boehmite powder (Al ₂O ₃Mass content is 74.6%) be dispersed in the 200ml water, 80 ℃ of nitric acid 14ml that add down 1M keep temperature to continue to stir 6 hours, are stablized, the 1M boehmite sol of high dispersive.

Example two is template alkaline condition preparation mesoporous aluminas down with the tensio-active agent.

Under 30 ℃, 3.64g hexadecyl trimethyl ammonium bromide (CTAB), 3.6g urea (or ammoniacal liquor of 60ml 2M) are joined in the boehmite sol of 40ml 1M, the dissolving back continues to stir 12 hours fully, change 100 ℃ of hydrothermal treatment consists 24 hours over to, go out the pH=9.0 of mixture behind the still, through separate, washing, 30 ℃ dry down after in 500 ℃ of roastings 3 hours.The skeleton of XRD analysis proof product is by γ-Al ₂O ₃Form (seeing accompanying drawing 1).Other is that the preparation condition of template and the main physico-chemical property of product see Table 1 with polyethylene oxide-poly(propylene oxide)-polyethylene oxide (P123), tween (Tween-80).

Table 1 is the pore structure character that template obtains mesoporous aluminas with the tensio-active agent

Template	The Al/Surf./Urea mol ratio	Hydrothermal temperature ℃	Drying temperature ℃	Specific surface area m 2/g	Pore volume cm 3/g	Aperture nm
							CTAB P123 Tween-80	1∶0.25∶1.5 1∶0.05∶1.0 1∶0.04∶1.0	100 100 100	30 75 100	335.6 294.6 355.1	0.66 0.56 0.87	6.1 5.8 7.5

Example three is that template directly prepares mesoporous aluminas with the tensio-active agent.

Under 35 ℃, 5.80g P123 is dissolved in the boehmite sol of 20ml 1M, continuously stirring was directly dried in 75 ℃ of vacuum drying ovens after 12 hours, 500 ℃ of roastings 3 hours.The skeleton of XRD analysis proof product is by γ-Al ₂O ₃Form (seeing accompanying drawing).Other is that the preparation condition of template and the main physico-chemical property of product see Table 2 with CTAB, two (2-ethylhexyl) sulfosuccinate sodium (AOT), Tween-80.

Table 2 is the pore structure character that template obtains mesoporous aluminas with the tensio-active agent

Template	Al/Surf. mol ratio	Drying temperature ℃	Specific surface area m 2/g	Pore volume cm 3/g	Aperture nm
						P123 CTAB AOT Tween-80	1∶0.02 1∶0.25 1∶0.02 1∶0.08	75 30 100 100	323.0 305.0 350.8 333.9	1.19 0.48 0.50 0.74	9.6 4.8 4.5 8.0

Example four is that template prepares mesoporous aluminas with the high molecular polymer.

The 0.8g Macrogol 2000 is added in the boehmite sol of 20ml 1M, directly in 100 ℃ of oven dry, 500 ℃ of roastings obtained mesoporous aluminas in 3 hours after 3 hours in stirring under the room temperature.The skeleton of XRD analysis proof product is by γ-Al ₂O ₃Form (seeing accompanying drawing).The physico-chemical property of product sees Table 3.

Table 3 is the pore structure character that template obtains mesoporous aluminas with the polyoxyethylene glycol

PEG	The Al/PEG mol ratio	Specific surface area m 2/g	Pore volume cm 3/g	Aperture nm
					PEG2000 PEG6000 PEG20000	1∶0.02 1∶0.02 1∶0.005	343.7 344.6 354.0	0.70 0.88 1.30	6.0 7.9 11.7

Example five is that template prepares mesoporous aluminas with alcohol acid (citric acid, oxysuccinic acid, tartrate, lactic acid).

The preparation method is with example four.The main physico-chemical property of preparation condition and product sees Table 4.The skeleton of XRD analysis proof product is by γ-Al ₂O ₃Form (seeing accompanying drawing).

Table 4 is the pore structure character that template obtains mesoporous aluminas with the alcohol acid

Alcohol acid	Al/ alcohol acid mol ratio	Specific surface area m 2/g	Pore volume cm 3/g	Aperture nm
					Citrate malate acid tartrate lactic acid	1∶1 1∶1 1∶1 1∶1	320.6 314.1 290.5 374.2	0.43 0.45 0.42 0.42	4.1 4.4 4.5 4.0

Comparative example

According to the preparation method of Yao, excessive ammonia progressively is added drop-wise in the aluminum nitrate solution of 25ml 0.96M, make pH＞9.2 of final system.The precipitation repetitive scrubbing that obtains is about 7.4 until the pH of system value, put into the ultrasonic water bath effect immediately 10 minutes behind the nitric acid of adding 6ml 0.94M.The aluminium colloidal sol that obtains is dried 450 ℃ of roastings 3 hours under the room temperature in vacuum drying oven.The main physico-chemical property of product is: specific surface area 265.72m ²/ g, pore volume 0.08cm ³/ g, aperture 1.4～2nm.

Claims (4)

1, a kind of preparation method of mesoporous aluminas, its skeleton is by crystalline phase γ-Al ₂O ₃Form, main preparation process is:

With the boehmite sol is precursor, adds tensio-active agent and makes structure directing agent and mix under room temperature, add alkali and make the final pH value of system be 8-11, synthetic 12-24 hour of 80-100 ℃ of following hydro-thermal, after separating in 30-100 ℃ of drying, 450-550 ℃ roasting 2-4 hour; Wherein:

Mol ratio in the Al in the boehmite sol and tensio-active agent is 1: 0.04-0.25;

Tensio-active agent is a kind of in hexadecyl trimethyl ammonium bromide, polyethylene oxide-poly(propylene oxide)-polyethylene oxide or the tween.

2, the preparation method of claim 1 is characterized in that, is precursor with the boehmite sol, add tensio-active agent, high molecular polymer or alcohol acid and mix as structure directing agent, 30-100 ℃ of drying, 450-550 ℃ roasting 2-4 hour; Wherein:

Mol ratio in the Al in the boehmite sol and structure directing agent is 1: 0.005-1;

Tensio-active agent is a kind of in hexadecyl trimethyl ammonium bromide, two (2-ethylhexyl) sulfosuccinate sodium, polyethylene oxide-poly(propylene oxide)-polyethylene oxide or the tween;

High molecular polymer is a polyoxyethylene glycol;

Alcohol acid is a kind of in citric acid, tartrate, oxysuccinic acid or the lactic acid.

3, the preparation method of claim 1 is characterized in that, employed alkali is urea or ammoniacal liquor.

4, the preparation method of claim 2 is characterized in that, polyoxyethylene glycol is Macrogol 2000, polyethylene glycol 6000 or Macrogol 2000 0.