FR2668762A1 - ALUMINUM OXIDE SPHERES AND PREPARATION METHOD, IN PARTICULAR FOR USE AS ABSORBENTS IN CHROMATOGRAPHY OR AS CATALYSTS. - Google Patents

Abstract

a) Aluminum oxide balls and method of preparation. b) The aluminum oxide balls are characterized by: - a specific surface of 150 to 300 m2 / g - an apparent density of 0.3 to 0.85 g / ml - a pore volume of 0.4 to 0 , 7 ml / g - a breaking strength of 5 to 150 N - a diameter of 0.05 to 5 mm - a tight particle size distribution with a relative standard difference of less than 5%, - a spherical shape with a ratio of diameters between maximum diameter and minimum diameter less than 1.05 for 75% of the balls and less than 1.10 for at least 99% of the balls and their manufacturing process is characterized in that the droplets of oxide hydrosol are produced of aluminum by means of a plate of vibrating injectors and they are presolidified after obtaining the spherical shape by blowing laterally with ammonia gas and then received in an ammoniacal solution.

Description

"Aluminum oxide spheres and process for preparing

  particularly to be used as absorbents in chroma-

  The invention relates to spheres of aluminum oxide for use as absorbents, in the form of

  graphy or as catalysts, or as vehicles for

  talyseurs. For use in a fixed bed, the sphere shape of the catalyst offers the possibility of obtaining a

  very regular wrapping of the catalyst in the

  In addition, spherical shaped supports

  have a weak tendency to form

  desirable In a bed of catalyst moving (moving bed) the good ability to flow

  round particles are also advantageous.

  A known method of making spheres

  of aluminum is described in the process of US Pat.

  2,620,314, wherein aluminum chips, aluminum trichloride and water are prepared from

  hydrosol, which is mixed with a solution of hexamethy-

  The small spheres of gel are allowed to mature in the hot oil for at least 10 hours,

  then washed, dried and calcined.

  Other known methods based on this principle

  Aluminum oxide hydrosol stabilization pipe in hot oil filled form columns are described in US 2,774,773, US

  3,096,295, US 3,600,129, US 3,714,091, US 3,887,492,

  US 3,919,117, US 3,943,070, US 3,972,990, US

  3,979,334, US 4,250,058, DE 2,742,709, DE 2,942,768 and

DE 2 943 599.

  US Pat. No. 4,116,882 discloses a method, in which an aluminum oxide filter cake,

  which is obtained by hydrolysis from alkoxides of

  luminium, is peptized with the aid of an extended acid and the resulting suspension is added dropwise to a column, in which the upper phase is

  consists of naphtha and the lower phase of a solution

  10% ammonia solution. To reduce the voltage

  between the hydrocarbon phase and the aqueous phase, an agent is added to the ammoniacal solution.

  Nonionic surfactant The gel balls are ame-

  matured in aqueous ammonia, dried

and calcined.

  DE-OS 28 12 875 discloses a

  in which a slurry is first formed from a microcrystalline product,

  intermediate form between the boehmite and the pseudo-

boehmite with addition of an acid.

  This is then poured drop by drop

  in a column of ammonia / hydrocarbon and

  the obtained are dried and calcined.

  have a specific surface area of 90 to 120 m 2 / g and a

  apparent density of 0.42 to 0.51 g / cm 3.

  German patent 32 12 249 discloses a

  yielded to produce aluminum oxide in the form of balls, in which a stable hydrosol is obtained

  by dispersion of a mixture of boehmite and pseudo-

  boehmite in an aqueous acid in the presence of urea This soil is finally shaped by pouring it drop to

  drop in a column of ammoniacal / hydro-

  Here again, the surfactant is added to the ammoniacal solution. Then, it is possible to influence certain essential properties of the balls, such as porosity, apparent density and breaking strength by soil additions.

  in the form of hydrocarbons and emulsifiers

requested.

  DE-OS 33 46 044 discloses a

  assigned to produce aluminum oxide-based

  minium, in which by dissolving boehmite in a

  aqueous acid with addition of an aluminum oxide ob-

  held by annealing from the boehmite, we get

  firstly an aqueous suspension or dispersion Cel-

  it is then mixed with an organic phase and an emulsifier and the emulsion obtained (of the "oil in water" type) is shaped in a known manner in a two-phase column.

  pore volumes and apparent density between

  limits from the proportions by weight of hydro-

  carbide introduced and calcined aluminum oxide into

floor.

  U.S. Patent 3,558,508 discloses a method for preparing aluminum oxide balls, wherein

  an acidic dispersion of aluminum hydroxide is

  troduced in a column and is added drop to

  drop of a mixture of mineral oil and tetrachloro-

  The CC 14 oil mixture is saturated with ammonia gas, resulting in solidification

  drops of soil during their descent into the co-

umn.

  DE-OS 32 42 293 describes a procedure for

  Preparation dice balls from 0.01 to 2 mm diameter

  For this, small drops of soil are obtained

  spraying of an acid aluminum oxide sol

  with a gas or an inert liquid The droplets can be put for coagulation in a column

  of the type "aqueous ammonia solution / hydro carbide

  In US Pat. No. 4,198,318 there is disclosed a process in which aluminum oxide particles of essentially spherical structure are obtained by

  dropwise addition of low viscosity hydrosols

  directly in an aqueous ammonia

  The acidic hydrosol is added dropwise from a

  drop height of 0.5 to 2 cm in the ammonia phase

  In order to facilitate the immersion of the droplets in the coagulation medium, the ammoniacal solution is mixed with a nonionic surfactant.

  process, in which the use of hy-

  as the medium providing the form, it is obviously of great importance to optimize the drop path in any case very short and to maintain it, because the shape of the small balls of gel can

  be adjusted only by the drop height.

  However, significant flows are not

  achieved with these different processes, because each

  jector can only create a maximum of 5 drops per

  second In addition, with falling heights so cour-

  There is always the danger of clogging

  as a result of rising ammonia vapors.

  German patent 24 59 445 discloses a

  assigned to the preparation of fuel particles,

  between them, spherical, by conversion

  of a liquid jet flowing from one or more

  tors, set in oscillatory motion, coming from

  lutions containing thorium and / or uranium, in a quantity of 3000 drops per minute, in which the drops first run through a drop pathway free of ammonia gas before immersion in the ammoniacal solution, which path is dimensioned so that the drops just receive their spherical structure and immediately after they run through a drop section traversed by ammonia gas to stabilize their spherical structure, the ammonia gas

  being directed in this section so that

  in addition to a current of ammonia gas in the opposite direction

  to that of the drops, a horizontal crossflow component of the ammonia gas through the spaces between the drops, and this drop section is

  dimensioned so that the spherical drops dur-

  enough before they are immersed in the

ammonia solution.

  The objective of the invention is therefore to prepare

  molded aluminum oxide

  optimal spherical configuration and a granular spectrum

  tight lometry combined with proper porosity and high tensile strength as well as

low friction loss.

  The object of the invention comprises balls of aluminum oxide having a surface area of 150 to 300 m 2 / g. A bulk density of 0.3 to 0.85 g / ml. A pore volume of 0.4 to 0.7 ml / g A breaking strength of 5 to 150 N A diameter of 0.05 to 5 mm

  A narrow particle size distribution with a

  relative standard persion less than 5%.

  A spherical shape with a diametral ratio between the maximum diameter and the minimum of less than 1.05 for% of the balls and less than 1.10 for at least 99%

balls.

  Another object of the invention is a method

  to prepare balls of aluminum oxide, in the-

  which produces an acidic aluminum oxide sol or

  an acid suspension of aluminum oxide, they are

  turns into droplets; these are coagulated in ammonia and then the small spheres of gel are allowed to mature, washed, dried and calcined.

  process is characterized in that the droplets are

  aluminum oxide hydrosol carriers by means of a

  plate of injectors set in vibration and they are

  lidifies after obtaining the spherical shape by

  side with ammonia gas and

  then in an ammoniacal solution.

  Other features of the invention are that:

  the aluminum oxide sol or suspension

  during the production of the drops a viscosity in the range from 10 to

  500 m Pa S at room temperature.

  on the surface of the ammoniacal solution, in which the small balls of gel are united, there is a layer of foam a few centimeters thick. For the process according to the invention, indicated aluminum oxide sols or aluminum oxide suspensions can be prepared in accordance with the state of the art.

  of the art for example from aluminum hydrates

  such as boehmite, ultra-fine pseudo-boehmite, hydrargylite or bayerite etc., by dispersion

  in concentrated acid, for example, nitric acid

  In addition, it is possible in a known manner, from aluminum metal by the action of an acid

  extended, for example HC 1, to obtain aluminum soils

  nium or suspensions, which can be processed by

the process according to the invention.

  The observation of a narrow range of visco-

  site is important for the process according to the invention.

  With a high viscosity of the soil / suspension, the disintegration of the liquid jet into drops is hampered,

  which leads to a broad particle size spectrum.

  On the other hand, soils / suspensions of too low viscosity can not be obtained in spheres

  of aluminum oxide in magnitudes of several millimeters

  because, in this case, products are created in

  In a preferred embodiment of the invention, the sol of lentils or oblong globules

  aluminum oxide or the suspension of aluminum oxide

  may include during the production of

  A viscosity in the range of 10 to 500 m Pa.s, preferably 50 to 200 m Pa S at room temperature. Adjustment of the viscosity range is

  for example with the concentration of aluminum oxide

  the acid concentration, the temperature or the

ripening conditions.

  A mass product such as aluminum oxide balls can be produced economically only in large quantities. This is why we use the known method of producing drops by vibration.

  by the German patent 24 59 445 to increase

  flow, a plate of injectors is used.

  to several equal injectors instead of

  jector to a known constituent This injector plate

  is connected, like the injector, to a ground supply tank / suspension by a hose

  or a rigid pipe and a rheometer

  setting of the same flow conditions to each injector

  of the injector plate, conditions obtained previously

  with a single-component injector, we obtain

  then surprisingly holds for each injector the same homogeneous disintegration of the jets of liquid into uniform drops, provided, however, that the

  soil viscosity / suspension is included in the

indicated age.

  Another condition must be fulfilled,

  see that the resistance to the flow of each injector of the injector plate is of the same magnitude.

  gives the same form of injector, the same length of

  laceration and same diameter of injector.

  It has been shown that with precise manufacture it is possible to use injector plates or

  Moreover, if the mechanical coupling of the

  vibratory system is adapted to the larger mass.

  For low viscosity liquids, it is even possible to use

  successfully complete a 101-series injector plate

  The vibration frequency of the plate

  injectors can reach from 300 to 1500 Hz,

  from 50 to 1200 Hz, especially 500 Hz.

  By using injector plates, the method offers the possibility of preparing balls

  of aluminum oxide with high flow rates without

  ge regarding the reproducibility of the granulometry

and the spherical shape.

  The method according to the invention has the advantage that, as opposed to the state of the art, the use of organic liquids can be completely omitted as a medium intended to give the form or as a coagulation agent. charge

  exhaust air and waste water with sub-

  organic stanzas as well as expensive reprocessing.

  The collection of soil droplets or sus-

  pension derived from aluminum oxide hydrate

  an aqueous ammonia solution which may have a concentration

  from 5 to 10% by weight,

  larger fall arrestors, as occurs using the formation of vibration drops, not spherical gel particles, but

snowflakes.

  But, according to the invention, these drops can be transformed into small spheres of gel, by

  pre-solidifying with ammonia gas before immersing

  in the aqueous solution. The inversion of the electric charge of the soil then occurring on the surface of the drops is sufficient for

  stabilize the spherical shape, so that the

  can be collected in the bath of

  pity like balls of gel The condition for this is that the drops are not too big because

otherwise they burst.

  The use of injector plates at 10

  injectors or more makes it difficult to contact the

  with ammonia gas, it is particularly

  to bind because a lot of air is driven from the top into the ammonia gas, that the drops partly

  can not solidify at all.

  According to the invention, the drops of each

  jector of the injector plate are blown off

  with ammonia gas adequately

  a determined fall course Thanks to this we ob-

  maintains accurate, stable and punctual drops solidification and thus prevents in the

  still liquid drops, turbulence

  these uncontrolled, which lead to a granular spectrum

  broad metric because of the meeting of drops.

  By side-blowing the soil / suspension droplets with ammonia, a rapid presolidification is obtained, thanks to which the

  drop in the gas phase can be decreased.

  Surprisingly, it is possible for

  prepare small balls of final diameter

greater than one millimeter.

  Another improvement in the shape of the balls of the gel particles can be obtained by creating a layer of foam a few centimeters high on the ammoniacal solution by addition of a surfactant and by light sparging of air or air containing water. Ammonia Using a glass frit to create very fine gas bubbles, one can realize

  a layer of foam 10 to 20 mm thick

  continually re-emerging, which leads surprisingly

  to another improvement in shape of the gel spheres especially from the large drops of soil With this, spherical gel particles of

  3.5 mm in diameter and more, can be obtained.

  This embodiment according to the invention of a layer of foam by addition of a surfactant to the ammonia solution and air sparging using a thin-pore frit, makes possible the broadening of the

  granulometric range of the small balls of A 1203 f a-

  Brittle up to 5 mm in diameter Dodecyl sulphate has proved particularly effective in the form of its sodium salt, which is dissolved for example at

0.2% by volume in ammonia.

  The small gel balls produced for example in ammonia can be made to mature. Then the small particles are extracted and possibly washed, for example with water or an extended ammoniacal solution.

  Particle drying is carried out at times

  temperatures between 20 and 3000 C during

  from about 5 to 24 h possibly in several

  steps and at given water vapor pressures.

  Then, as a general rule, a shrinkage occurs whereby the balls can lose up to 70% of their volume. The activation which follows is carried out by annealing of 500 to 8000 C. With the process according to the invention, can it prepare balls of aluminum oxide with a diameter of between 50 x 10-6 m and 5 mm, preferably between 3 and 5 mm Thanks to a previous possible evaluation of the grain sizes, one can avoid tests of long optimization and in the preparation one only creates a very small fraction of downgraded grains

  upper and lower downgraded.

  An essential advantage of oxide particles

  of aluminum according to the invention, is their spherical

  This has an advantageous influence on the flow behavior and also on

  properties for packaging Optimum sphericity

  the balls, characterized by the lack of deformation

  tions, bulges and notches, as well as ex-

  growth, guarantees a breaking strength of

  and a favorable abrasion behavior, for example

  example for use in a moving bed.

Example 1

  0 kg of aluminum oxide hydrosol are prepared by introducing 1250 g of aluminum oxide hydrate (pseudo-broehmite, 75% A 1203, specific surface area according to BET 258 m 2 / g) at room temperature. with intensive stirring in a solution of 69.0 g of nitric acid (65%) and 3681 g of water and with stirring.

then for another 15 minutes.

  The soil, which had a concentration of A 1203 of 221 g / l, a density of 1.18 Kg / l and a viscosity of 90 m Pa S at room temperature, is then transferred to a closed feed container, where

  is maintained in low agitation with the aid of

  awarded at 0.3 bar, the soil is sent from the food container

  a flexible pipe and a rheometer to a vibrating nozzle plate with 10 injectors

  arranged in a 350 x 10-6 m diameter ring, at the

  Thousands of thin soil jets flow quickly

  constant and form uniform drops by following

  of the periodic vibration established The form of the 10

  injectors is the same and corresponds to that of

* Known monobloc jets The difference in diameter is between all injectors less than 10 x 10-6 m After a fall course of 5 cm in length

  air, the drops are blown off

  ral of ammonia gas in a container of precipitation

  and are then captured in an ammoniacal solution.

  Then the liquid drops turn into small

balls of gel of A 1203-

  The blowing of the drops is done separately for each injector from small narrow tubes

  of diameter 10 mm at distances of about 1 cm.

  The drop path in the ammonia gas is 5 cm in length The ground flow reaches 140 ml / mm and the periodic vibration 1200 Hz Thus is produced at each injector per second 1200 small drops of 0.7 mm in diameter This corresponds to a

  amount of 1.8 Kg of A 1203 per hour.

  The small balls of gel are left for

  about 1 hour in an aqueous ammonia solution

  niacal (10%) and then they are dried for 2 hours at C. For activation, the dried particles are

  annealed for 4 hours at 650 C.

  For comparison, instead of the injector plate with 10 compartments, a standard monobloc injector of the same shape and diameter as the injectors of the injector plate is used. With normally equal process parameters, a reduced flow is produced. its tenth, or 14 ml / mm, drops or balls of gel of the same size as

  using the injector plate.

  After the drying and activating

  the final diameter of the aluminum oxide balls is the same size as the balls prepared with

the plates of 10 injectors.

  The physical properties of the finished aluminum oxide balls are gathered, like those of the following examples, in Table I.

Example 2

  The aluminum oxide hydrosol is produced, as for Example 1 and introduced into the feed tank at a pressure of 0.34 bar, the soil is transformed as in Example 1, using a vibrating injector plate with 10 injectors, diameter 760

x 10-6 m in drops.

  The installed vibration frequency is

  at 500 Hz and the flow rate is set at 450 ml / mm, it is

  me then to each injector per minute 30 000 drops of diameter 1.4 mm The flow reaches thus 6.0 Kg of A 1203 / h After transformation of the drops into balls of gel with ammonia, it follows the treatment

  according to the description of Example 1.

  Example 3 The aluminum oxide hydrosol is, as

  described in Example 1, produced and poured into the

  see power supply Using an injection plate

  10 seater with diameter injectors 1,72

  mm, the hydrosol is converted into drops with a

  frequency of 50 Hz and a flow rate of 460 ml / mm as

  Example 1 and is converted to gel balls by reacting with

  The flow rate is also 6.1 kg of A 1203 / h. In order to improve the spherical shape of the gel particles which directly after their

  hardening a diameter of 3.0 mm, the super-

  of the aqueous ammonia solution is reduced

  by the addition of the doddy sulfate surfactant

  Sodium cyclic at a concentration of 0.2% By a light bubbling of air through a glass frit in the ammonia solution thus relaxed, a layer of foam approximately 10 mm high is created, which is constantly renewed. and acts by improving the shape of the drops precured by the reaction with the ammonia gas. The small balls of gel are collected in the ammoniacal solution and then are treated

as in Example 1.

Example 4

  An aluminum oxide hydrosol, prepared

  as in Example 1, is converted into drops and

  verti in balls of gel by reaction with ammonia

  The injectors of the 10 compartment plate have a diameter of 2.40 mm At a frequency of 50 Hz a flow rate of 860 ml / mm is adjusted, which corresponds to

  a flow rate of 11.4 kg of A 1203 / h The solution is

  due to a 0.2% by volume sodium dodecyl sulphate By a light air sparge through a glass frit, a layer of foam 10 to 20 mm high is created. This way, we also create

  for these large gel particles 3.8 mm in diameter

  be a good spherical shape After having

  appeared in the ammonia solution, the small

  balls of gel are treated again as in the example

ple 1.

TABLE 1

  Physical properties of oxide balls

Example

  Specific Surface Total Pore Volume Resistance to Breakdown Bulk Density (m 2 / g) (ml / g) (N) (g / l) 0.46 nb 0.47 aluminum 0.45 0.47 Diameter Average Diameter ( Mm) 394 772 1685 2077 Standard difference (pm) 11 14 40 22

(%) 2.8 1.8 2.4 1.1

  Spherical shape Average value of 1,015 1,012 1,039 1, 039 d max / d min Balls with d max / dmnin (%) 99 99 99 99

<1.09

  Flow rate (kg Al 203 / h) 1.8 6.0 6.1 11.4 The quantities indicated are determined by the following methods: Specific surface Volume porous Resistance to break Absorption N 2 Micro and mesopors: absorption-N 2 Macropores printing process-Hg total pore volume by calculation from pores

micro, meso and macro.

  with a device from the company Pharmatest (PTB 301)

from at least 50

separate res.

  Diameter Use of two optical processes

  1) Manual measurement with the stereomicroscope.

  Using an eyepiece-micrometer calibrated at a magnification of 50 to 100 times, we measure 50 balls statistically, ie each particle is measured "once" and in fact, as it is

precisely located.

  The determination of the ratio dmai / dmin diameters is also done by manual measurement For this, we obtain visually a choice of the largest

  and smaller diameters possibly in

  particles with small tweezers or

similar treasure.

  2) Automatic device for determining the diameter.

  2.1 PSA device "Particle size analyzer".

  The isolated balls fall freely

  to an optical system from the projected surface

the diameter is calculated.

  Number of particles measured: 1000 2.2 PDA device - "Particle diameter analyzer" The measuring operation is done as indicated in paragraph 2 1, each particle being recycled 50 times and measured from the 50 measurements determined

dmû and dmin-

Number of particles measured: 200

Claims (4)

R E V E N D I C A T IO N S   1) aluminum oxide balls having a specific surface area of 150 to 300 m 2 / g, an apparent density of 0.3 to 0.85 g / ml and a pore volume of 0.4 to 0.7 ml / g; breaking strength 5 to 150 N a diameter of 0.05 to 5 mm   a narrow particle size distribution with a diffe-   relative standard deviation less than 5%, a spherical shape with a diameter ratio between maximum diameter and minimum diameter of less than 1.05 for 75% of balls and less than 1.10 for less 99% of the balls.   2) Process for the preparation of aluminum oxide balls according to claim 1, wherein   prepares an acidic sol of aluminum oxide or a sus-   aluminum oxide acid and they are converted into drops, they are coagulated in an aqueous ammonia solution, and then the small balls of gel formed are left to mature, washed and   calcined, characterized in that the droplets are   hydrosol aluminum oxide by means of a   plate of injectors set in vibration and they are   lidifie after obtaining the spherical form in-souf-   side with ammonia gas and   then in an ammoniacal solution.   3) Process for the preparation of aluminum oxide balls according to claim 2, characterized in that the aluminum oxide sol or the suspension   of aluminum oxide during the production of   a viscosity in the range of 10 to 500 m Pa.s at room temperature.   4) Process for the preparation of aluminum oxide balls according to claim 2, characterized in that on the surface of the ammoniacal solution, in which the small balls of gel are united, there is a layer of foam of a few centimeters thick.