DE2255463A1 - METHOD FOR PRODUCING AN ALUMINUM OXIDE WITH LOW DENSITY, HIGH POROSITY AND LARGE SPECIFIC SURFACE - Google Patents

Description

y H. /? ^^ - y November 13, 1972

Continental "Oil Company P.O. Box 1267 Ponca City, Oklahoma - 4601, USA

Method of making a low density aluminum oxide., ^ ^ OhgX ^ P ^ lo ^ si ^ ö.tj-ind g] specific surface

The invention relates to a method for producing Alumina with low density, high porosity and large specific surface from aqueous alumina slurries or alumina cake.

There are numerous processes for making alumina known, "for example the aqueous hydrolysis of aluminum alcoholates, the alum process and the sodium aluminate process. The alumina made in this way is used in a wide variety of areas, for example as a catalyst or catalyst carrier. In most of these application areas, the suitability depends of the respective aluminum oxide directly depends on its pore volume, its specific surface and its density.

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In general, the aluminum oxides are the better, the lighter they are and the lower their bulk density, the greater their specific surface and the greater their porosity. The aluminum oxides produced by the known processes have bulk material densities of greater than approx. 561 kg / m, pore volumes of less than approx. 1.0 cm / g and specific surfaces of less than approx. 275 m / g. Although some processes can also be used to produce lighter aluminum oxides with a larger pore volume, the pores of such aluminum oxides can for the most part be described as macropores with a pore diameter of greater than 10,000 Å. Aluminum oxides with such macropores are practically worthless for catalytic purposes.

In the articles by KISTLER, Journal of Physical Chemistry, 36 (1932), 52, and by JOHNSON and MOOI, Journal of Catalysis, 22 (1963), 342-354, are theoretical considerations for Formation of alumina aerogels and the manufacture of low density alumina aerogels by treatment with methanol included. It becomes an alumina with a pore volume of approximately 0.4 cm / g described. In the articles mentioned, however, no solvents other than methanol are mentioned, besides there is no indication in these articles that larger pore volumes are caused by the use of other organic solvents or even solvent vapor e achieved v / ground.

From German patents 1 230 410, 1 191 353 and 1 170 3ÖÖ processes are known after aqueous hydrolysis of aluminum alcoholates !! and then filtering the alcoholic ones from the aluminum oxide filter cake To remove reaction products. This happens

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by treating the aluminum oxide filter case with organic solvents. The ones mentioned in the However, methods disclosed in patents relate to exclusively the removal of the organic impurities from the filter cake and do not disclose any Teaching about the production of aluminum oxides with low density. In the German patent specification 1 191 353, the use of hydrocarbons and alcohols with low molecular weight as a solvent. Low molecular weight alcohols include also the substances suitable in the context of the present process.

In US Pat. No. 3,394,990 (WEINGrARTNER) a method described for the hydrolysis of aluminum alcoholates, in which the aluminum oxide filter cake is washed with butanol will. In the description, however, there is no indication that via vision with butanol is easier Aluminum could lead. The focus in the procedural, Leadership is also in this patent on the removal of the organic reaction products, and not converted starting products from the aluminum oxide filter cake directed.

Also refer to the US PS for the sake of completeness 3,577,353 (WHITE), which also falls within this area, albeit more distantly.

Another method of making im catalytic The range of aluminum oxides that can be used starts with a mixture of organic solvents and aqueous solvents Aluminum oxide slurries, which are then used for Preparation of the end product is dried. This process is also based on the use of liquid organic materials

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Solvent and does not see the use of solvent fumes for drying the aqueous aluminum slurries and for making the desired ones Aluminum oxide products.

As the above summary shows, great efforts have already been made to facilitate " Aluminum oxides with high porosity and a large specific surface for use in the catalytic area to manufacture. But it is precisely the large number of attempts that have been made shows how unsatisfactory all of them are these methods were previously with regard to the products obtained.

It is accordingly the object of the invention to provide a process for the production of aluminum oxides with opposite the prior art significantly improved properties with regard to catalytic in particular To create areas of application, in particular for the production of aluminum oxides with a bulk density of less than 560 kg / m, a pore volume of greater than about 1.0 cnr / g, the pore diameter should be in the range from 0 to 10,000 Å, and with a specific surface area greater than 275 m / g.

To achieve this object the invention proposes that an aqueous alumina slurry or an aqueous alumina cake with an Al ₂ 0 ^ content of up to about 32 Ge \ f .-% with acetone steam or the vapors of an alcohol having '1 to 8 Treated carbon atoms and that an aluminum oxide with a pore volume of approx. 1.0-2.75 cnr / g, a bulk density of approx. 120 - 400 kg / nr ⁵ and a specific surface area of approx. 260 - 400 m ² / g can get.

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As already mentioned, alumina is found in the catalyst area a wide field of application, but it should not be left unmentioned that aluminum oxide is also one of the main refractory materials in practice is. So can that produced by the method according to the invention Aluminum oxide is not only used as a catalyst material for chemical reactions or as a catalyst carrier but also as a lining, for example in reaction vessels or muffle furnaces, in turn not infrequently the catalytic effectiveness of the aluminum oxide produced according to the process of the invention can also be used at the same time In these applications, however, it will be desirable and necessary to use specifically acting catalysts, such as For example, metal ions, finely divided metals or other cations to add to the aluminum oxide. Such Process for the production of "modified" aluminum oxides by adding the catalyst substances to the aluminum oxide for example in US patent application 138 835 (HIRTZ et> al.) described in 1971 »After that, the catalytically active. Substances before the aqueous aluminum oxide or during the treatment with the organic solvent added or the finished aluminum oxide is immersed in solutions of the catalytically active substance covered with this. In addition, a number of other processes for the production of such modified ones are available to the person skilled in the art Common aluminum oxides,

Especially for catalytic applications Aluminum oxides have so far also been produced by a wide variety of processes, for example by the aqueous Hydrolysis of aluminum alcohols, precipitation of aluminum from alums or the sodium aluminate process * Although all aluminum oxides obtained in this way can be used in the catalytic sector

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may be, they have not yet been able to achieve the desired qualities as they have been through the process can be made available according to the invention. A quite usable aluminum oxide can be used on the other hand produce when you combine an aqueous aluminum oxide slurry with organic solvents produces a solvent-water-aluminum oxide mixture and dries it. The alumina thus obtained has certain similarities with the aluminum oxide produced according to the invention. In contrast, however, is the procedure According to the ruling, an essential in this respect better than by using it from solution sin .; '. leldärapf en not only from the water the aqueous aluminum oxide slurries are removed, but also products are obtained at the same time, which are of the highest quality in catalytic terms. In addition, when carrying out the procedure in accordance with the invention obviates the need to adjust the composition of the liquid phase so that it corresponds to the composition of an azeotropic mixture. Furthermore, when carrying out the procedure According to the invention, the process-technically difficult handling of the mixtures of solvent, water and Avoided aluminum oxide.

The aqueous alumina slurries suitable for carrying out the process according to the invention contain up to approx. 32 wt .-% aluminum oxide, calculated as AIpC ,, with this aluminum oxide following its manufacture has not been pre-dried. As a manufacturing process for the aqueous alumina starting product For example, there is the hydrolysis of aluminum alcoholates, alums or alkali metal aluminates in question.

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When the term "alumina slurry" is used in the context of this specification, so are meant thereby AlpO ^ water phases, which both the more or less liquid consistency of Aufsehlämmungen in the narrower sense, can have, as well as ", in particular in the case of higher AlpCU concentrations, increasingly pasty can be, up to the consistency of moist FiIterschlämme or; Filter cake. Even where these forms of consistency are not expressly included in the description are mentioned, they are, "as I said, with under the term To understand alumina slurry "

It should also be noted at this point that a number of dispersible aluminum oxides, if these are redispersed and treated according to the method according to the invention, have an improvement in their properties, which are desirable from a catalytic point of view, but this improvement in properties is by no means sufficient to to achieve those properties which can be achieved with non-predried aluminum oxides, as used according to the invention. On the other hand has been ensured, however, that dilute aqueous Aluminiumoxidaufschlämmungen z ALPO-drying or similar methods, to about 32 wt .-% prior to use in the process according to the invention can be concentrated, without any _v such a concentration detrimental to the Parameters of the final product. Only at concentrations of dilute aqueous starting aluminum oxide suspensions above approx. 32% by weight AlpO, was a quality loss of the end products observed. Preferably, suspensions with approx. 12 to approx. 22% by weight Al ₂ O ^ used .: -

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An embodiment of the invention is shown in the drawing and described in more detail below. The figure shows the flow diagram of an exemplary embodiment of a plant as it is used to carry out the method according to FIG can serve the invention.

A mixture of manufactured according to the ZIEGLER process Aluminum alcoholates with 1 to approx. 30 carbon atoms in each alcohol group is via the supply line 10 in given the reactor 1. In addition, the reactor 1 is charged with water via the feed line 12. The reaction products, i.e., the alcohols and an aqueous alumina slurry are discharged via outlet lines 14 or 16 removed. From the settling tank 3, the reactor 1 is fed via line 24 with a butanol-water mixture applied, this water at the required total amount of water with which the reactor 1 must be charged is taken into account. The withdrawn from the reactor 1 via the outlet line 16 aqueous Alumina slurry is fed to mixer 2 and mixed there with a butanol-water stream which is supplied to the mixer 2 via the supply line 18 from the settling tank is fed. The aqueous alumina slurry mixed with the solvent is passed through the line transferred from the mixer 2 into the settling tank 3, where the aluminum oxide settles. The butanol-water phase is, as already described above, fed from the settling tank 3 via the line 24 to the reactor 1. The aluminum oxide-water phase is transferred from the settling tank 3 via the outlet line 22 into the mixer 4 and there mixed with a butanol applied via the feed line 26. The alumina-water mixture mixed with the butanol is transferred to the settling tank 5, where the aqueous aluminum oxide sediments again. About the

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Outlet line 18, the butanol-water mixture is drawn off from the settling tank 5 and fed to the mixer 2. The water-aluminum oxide phase is removed from the settling tank 5 via the outlet line 30 and placed on the filter. On the filter 6, the aluminum oxide-water phase is separated into an aqueous aluminum oxide suspension with about 16% by weight of AlpO ^ and water. The filtrate, water with butanol fractions, is fed via line 34 to the butanol recovery. The aqueous alumina. slurry, the filter residue “is fed to the drying device 7 via the line 32. From the solvent reservoir 8, the solvent is via the. Line "given 36 to the heater 9 The abgegebene- from the heater solvent vapor is _'Ρ supplied naehgeschalteten heater 10 in which the drying device 7 fed through line 40 superheated followed by further heating of the vapors' via line 38 to a solvent vapors are generated. The superheated solvent vapors are brought into contact with the aqueous aluminum oxide slurry in the drying device 7, a dried aluminum oxide being obtained which is removed via the discharge line 42. The water-containing solvent vapor escapes from the drying device 7 via the discharge line 44 and becomes the Solvent recovery 11 is supplied. In the solvent recovery 11, the solvent vapor is condensed and fractionated, the water being drawn off via the line 48 and the solvent being fed back to the storage container 8 via the line 46.

In the embodiment described above, the do not represent a restriction of the process according to the invention was to run the process to prepare the starting aqueous alumina slurry

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by hydrolysis of aluminum alcoholates !! described, however, under the conditions set out above, any other alumina slurry can in principle also be used can be used.

The aluminum oxide produced by the process according to the invention has, above all, properties which are extremely desirable for materials that can be used catalytically. Typical properties of the products obtained in this way are as follows: bulk density of approx. 120 to 400 kg / m 2, specific surface area of approx. 260 to approx. 400 m ^ / g and a pore volume of approx. 1.0 to approx. 2.75 cm / g. Before ^ -, in each case, the process is carried out in such a way that the aluminum oxides produced have a bulk density of approx. 144 to approx. 240 kg / m, a pore volume of approx. 1.5 to approx. 2.75 cm / g and a specific Have a surface of approx. 300 to approx. 400 m / g. Such aluminum oxides are particularly suitable for catalytic applications. Another desirable property found in the aluminum oxides produced in this way is that a large proportion, usually more than 50 %, of the total pore volume is accounted for by pores with a diameter of less than 1000 Å. The typical mean pore diameter is in the order of magnitude of approx. 80 to approx. 250 2.

For the sake of clarity, it should be emphasized at this point that the term "aluminum oxide" used in the context of this description refers to a solid appearing dry, which in addition to AlpO, water, for example in the form of free adsorption water or water of hydration or crystal water or traces of other impurities, may contain.

Furthermore, according to the method according to the invention

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8ADOWGtNAL

2255483

produced alumina, if it was obtained from alumina slurries obtained by hydrolysis of 'aluminum alcoholates, in that the produced alumina, if it is dried only to the extent that its AlpO ₇ content is over 85% by weight , can be extruded flawlessly with the acceptance of only a slight deterioration in properties. A corresponding extrusion process is the subject of a US patent application and is described in more detail there. It has not yet been possible to find any satisfactory explanation for this unusual and completely surprising property.

In the practical implementation of the process, an aqueous aluminum slurry, which is up to approx. 32% by weight AlpO ^ r, in contact with solvent vapors brought with the vapors of acetone or organic alcohols with 1 to about 8 carbon atoms. Examples of such alcohols are methanol, ethanol, propanol, Butanol, isobutanol, sea-butanols tert-butanol, i-propanol, Hexanol, heptanol or octanol. The bringing into contact can take place in any manner known per se, as is customary in chemical reaction engineering for the treatment of slurries with vapors. In other words, for example, the vapors can spread over thin layers of the alumina slurry or ascending through the 'alumina slurry' be passed through. In principle, all are the procedures suitable, which lead to an intimate contact of the aluminum oxide slurry with the solvent vapor. To this Way, the aqueous alumina slurry can be up to; to any desired AlpO ^ content with the help of the solvent vapor it dried v / ground, usually it is there however, preferable 'no further than an AXx Q ■ * .- * ■.

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Dry content of approx. 75 Ge \ f .-%. A more extensive drying is sometimes only more difficult to achieve and easily leads to the formation of carbon deposits on the aluminum oxide produced. The expression "carbon deposits" is intended to include organic decomposition products of all kinds. Also becomes a drying about 75 percent -.,% AIoO- his approach to pull an external heat source is usually because the heat transfer in this method is not very high v / herself especially as noticeable if to further evaporation and drying The necessary heat should be made available exclusively from the solvent vapor.

The solvent vapor used can have any temperature above the boiling point of the solvent at the respective process pressure. It is preferable, however, that the solvent vapor itself has been preheated again in order to avoid noticeable condensation of the solvent in the aluminum oxide slurry. This heating can in and of itself take place at any temperature, as long as it is ensured that the decomposition temperature of the particular solvent used is not reached and no undesired by-products are formed. At atmospheric pressure, the preferred operating conditions are in the temperature range up to approx. 260 ^° C.

Excellent results have been obtained from the solvents listed above, particularly when using ethanol and butanol vapors. The use of these two solvents is also extremely recommendable for the reason that in many of those processes with which aluminum oxide is produced _f butanol and ethanol are already in the material streams of the

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Proceedings are conducted.

While the alumina slurry, as described, can be dried to an alumina containing up to 70 to 75% by weight. AIPO ^ contains, a preferred embodiment of the method is to dry the alumina just enough so that it contains about 50 wt .-% AI2Q3 j said alumina then subsequently dried with superheated steam to the respectively desired degree of drying. The steam can in and of itself be heated to any temperature, as long as it is ensured that it is superheated, ie that it no longer carries any free water with it. The use of superheated steam offers various advantages; on the surface of the aluminum oxide bed, the use of water vapor is much more economical than the use of additional solvent vapor and "the downstream devices for recycling the solvents are not burdened to the same extent as when using solvent vapor alone.

The above essentially and principally described Methods can be understood by those skilled in the art without the scope of the invention to leave, can be modified in many ways in detail. Some other embodiments are "below described in more detail.

Aluminum alcoholates which were produced by the ZIEGLER process were subjected to aqueous hydrolysis and filtered. The aluminum oxide filter cake, which was used as the starting product for the further experiments, contained, converted, approx. 1-515% by weight AlpQ- * »approx. 8 % by weight butanol and approx. 76.5% by weight water.

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example 1

This alumina was transferred to a container designed to contain the solvent vapors could be passed over the aluminum oxide filter cake .. The solvent was placed in a closed vessel, the evaporation line with the aluminum oxide container was connected. The device was placed in an oven with the solvent evaporated and over the alumina stroked. A number of different solvents were tested in this experiment. Both the experimental conditions and the properties of the aluminum oxides obtained in each case are summarized in Table I.

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TäoelleJC

Solvent Control · Acetone Methanol Ethanol Butanol Propanol Hexanol

·. _{ _ _l _ __ _i try ' ■ ,, ■' ·,

■. Filter cake (g) 100 solvent (g) 'oven temperature ( ⁰ C) 149

100 100 100 100 too 100 600 300 500 150 269 357 149 149 149 149 177. 204

Properties

des Prodü'k'tes -90 0.30 . 0.58 1.04 1.41 .6.55 15.0 15.2 VTI • ¹ carbon (weight 708.0 573.4 520.6 344.4 206 _? 6th 259.5. 240.3 I. T o cht well - ⁰ A 79.4 79.0 79.1 79.0 76.0 64.2 63.9 ■ Al _o 0 _T ~ content (weight * 223.4 ■ 281.1 310.0 ■ 320.9 ³ 329.0 360.6 373.8 specific ρ,
Surface (m year) 0.55 ■ 0.90 0.95 1.40 2.10 1.90 2.15 Pore volume
(em ^ / g)

1. Organic residues, given as% by weight C

2. After calcining at 482 ^° C. for 3 h

3. After steam treatment as in example 2

From Table I it can be clearly seen that treating the aqueous aluminum oxide filter cake with the Steaming organic solvents leads to a reduction in the bulk density and an increase in the specific surface area and to an increase in the pore volume and thus to the production of a high quality from a catalytic point of view Alumina leads.

The values for the AlpCU content are apparently lower in the experiments with butanol, propanol and hexanol than in the other experiments, but they actually correspond to the other values and are higher than the stated values indicate, which is due to the higher ones Carbon content of these samples is due. After correcting the Alr, O, content on a carbon-free reference basis, the following values result: for butanol 81.5 wt .- ^ Al ₂ O ₃ ,
Hexanol 75.5% by weight

, 5 wt .- ^ Al ₂ O ₃ , for propanol 75.5 wt .- ^ Al ₂ O, and for

Example 2

The alumina produced according to Example 1 using Butanoldämpfen was subsequently treated / O, kg alumina minutes kg at 149 ⁰ C with steam in an amount of 0.227 35th The carbon content could

can be reduced from 6.55 to about 3.85 while the Schüttet

good density was 203.4 kg / irr.

Example 3

111 g of aluminum oxide filter cake were used in the example 1 described device treated with 220 g of butanol darupf at 149 ° C. for 3 hours. The aluminum oxide thus obtained was ■ onclosing.1 for about 90 minutes with superheated steam in a quantity of 0.5 g per 1 g of aluminum oxide at 149 ° C

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treated. After steam treatment, the aluminum oxide had an Al ^ O ^ content of 73 * 2 % by weight _3, a specific surface area of 320 m / g, a bulk density of 182.6 kg / m, a pore volume of 2.25 cm- / g and a carbon content of 1.81% by weight . compared to a carbon content of 3.86% by weight before the steam treatment. The pore volume showed the following distribution:

Pore diameter Ä Cumulative pore volume

cm3 / g

0-35 A 0.0750

40 0.0750

50 0.1366

65 0.2159

80 O, .4173

100 0.7586

120 ■ '. 0.8746

150 x 0.9732

. 200 1.0746

250 1.1409

350 1.2289

-500 1.3186

800 1.4145

1000 1.4937

2000 1.6408

5000 1.9229

10000 ■ 2.2541

Example 4

50 g of alumina filter cake were treated with 158 g'Äthanoldarapf for 4 hours in an apparatus as described in Example 1 at 121 ⁰ C. The aluminum oxide obtained had an Al _o 0, content of 79% by weight, a specific surface area of 322.9 m / g, a pore volume of 1.29 cm / g, a bulk density of 346.0 kg / mm and a Carbon content of 0.91% by weight. The product obtained has not undergone any steam treatment

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subject. It became the following pore volume distribution found:

Pore diameter X cumulative pore volume

(cm3 / g)

0-35 X 0.1046

40 0.1066

50 0.1685

65 0.5440

80 0.7057

100 0.7896

120 0.8236

150 0.8895

200 0.9294

250 0.9574

350 0.9713

500 0.9913

800 1.0253

1000 1.0532

2000 1.0931

5000 1.1750

10000 1.2909

As the results of Examples 3 and 4 show, will obtain the desired pore volume both with the application and with the omission of the steam treatment. As Examples 2 and 3 show that the steam treatment has the main effect that the residual carbon content can be effectively reduced without affecting the essential and desirable properties of the obtained aluminum oxide are adversely affected. From Table I it can be seen that when using of the higher alcohols, aluminum oxides with a higher residual carbon content can easily be obtained. These higher residual carbon However, as shown in Examples 2 and 4, contents can be achieved by subsequent treatment with over- ' hitztera water vapor can be reduced.

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Claims (9)

Claims 1. A process for producing alumina having a low density, high porosity and a large specific surface from aqueous Aluminiumoxidäufschlämmungen or cakes, characterized in ₅ that an aqueous alumina slurry or an aqueous alumina cake with an ALPO ^ content of up to about wt. -% treated with acetone vapor or the vapors of an alcohol with 1 'to 8 carbon atoms and that one such an aluminum oxide with a pore volume of approx. 1.0 to 2.75 cm / g, a bulk density of approx. 120 to 400 kg / m · ⁵ and a specific surface area of approx. »2βΟ up to 400 m / g can be obtained. 2. The method of claim 1, characterized in ₅ that the aqueous Aluminiumoxidausgangsprcdukt with such an amount of organic solvent vapor treated so that the alumina obtained at least about 50 wt .-% of Al ₀ OZ and that the alumina thus obtained subsequently to the action of exposed to superheated steam. 3. A method according to any one of claims 1 or 2, characterized in that the aqueous alumina slurry about 12 to 22 wt -.% Al ₉ O _x contains. 4. The method according to any one of claims 1 to 3, characterized characterized in that the aqueous aluminum oxide starting product with methanol, ethanol, propanol, butanol-isobutanol-j se c. -But a no I-, tert-butanol-yi-P ^ opanol ™, -s, heptanol or octanol vapors treated-. . 098 3 2/08 2 5. The method according to any one of claims 1 to 3, characterized in that the aqueous aluminum oxide starting product treated with ethanol or butanol vapors. 6. alumina obtained by one of the processes according to any one of claims 1 to 5, characterized by a Pore volume of approx. 1.5 to 2.75 cnr / g, a bulk density of approx. 144 to 24o kg / m and a specific 2 surface of approx. 300 to 400 m / g. 7. The method according to claim 1, characterized in that one with an aqueous Alumiriiurnoxidaufschläruinung with a ΑΙρΟ, content of approx. 12 to 22 wt. 56 and Butanol vapor works and thus an aluminum oxide with a pore volume of approx. 1.5 to 2.75 cnr / g> a bulk density of approx. 144 to 240 kg / ra and a specific surface area of approx. 300 to 400 m / g. 8. The method according to claim 7, characterized in that the aluminum oxide thus obtained is ^{treated with superheated steam of approx. 121 to 193 °} C. for approx. 10 min. 9. The method according to claim 1, characterized in that one works with an aqueous aluminum oxide slurry with an Al ^ O ^ content of approx. 12 to 22 Ge \ f. ~% And ethanol vapor and thereby an aluminum oxide with a pore volume of approx , 5 to 2.75 cm / g, a bulk density of approx. 144 to 240 kg / W and a specific surface area of approx. 300 to 400 m / g. 309832/0823