DE4114924A1 - Alumina support prodn. with active component by sol-gel method - and use esp. for regenerative absorption of sulphur di:oxide, oxygen or hydrogen sulphide - Google Patents

Abstract

Prodn. of a support contg. Al2O3 with an active component and/or precursor for this is carried out by the sol/gel technique by (a) producing a sol from AlCl3 or material forming Al2O3, (b) supplying the sol to the top of a column filled with a water-immiscible solvent (I) in the upper pt. and an alkaline aq. soln. (II) contg. the active component (III) or precursor in soln. and/or complexed form in the lower pt., so that particles with the required texture are formed in the lower pt., (c) sepg. the particles from the liq., and (d) drying and calcining the particles. Also claimed is a new sorbent (IV) consisting of the claimed support produced by a sol/gel technique with a Ca and/or Mn aluminate or Cu on the surface. USE/ADVANTAGE - (IV) is claimed for regenerative absorption of gaseous components, (esp. SO2), using (III) based on a Ca cpd., O2, using (III) based on Cu, or H2S using (III) based on a Mn cpd. (III) is dispersed very homogeneously over the particles, which are strong and have good pore distribution.

Description

The invention relates to a method for Production of a support material containing aluminum oxide on a sorbent consisting of a sol / gel technique carrier material obtained and on a method for regenerative absorption of gaseous components.

In the technique of heterogeneous catalysis as well as Absorption of gaseous components with the help of solid Absorbents there is a great need for materials which has a good homogeneous distribution of the active component and / or the precursor therefor. It was in the Past proposed a variety of methods the active component is homogeneously distributed on carrier materials to apply. A well known method is the impregnation of the Carrier material with a solution (a complex) of the active Component and / or a precursor therefor. By the The base material becomes the starch and the pore structure (Texture), with the active component on the Deposits surface of the carrier material.

 However, this method can solve the problem reveal that the distribution is far from optimal, e.g. B. in that the active material is very poor across the grain is distributed or that it is in the form of large crystals over the whole grain is distributed.

A frequently used carrier material is γ-Al₂O₃, Alumina. A good way to get particles of it is the so-called sol / gel technique, in which one more or less spherical or teardrop-shaped particles are obtained by a sol of AlOOH through an oil layer in an alkaline Water layer drips. This way you get very strong, uniform, more or less spherical particles  uniform porosity. Such a method is u. a. in the European patent specification 90.994.

It is an object of the invention using a sol / gel technique a method of manufacturing a substrate create on which an active material and / or a precursor it is applied which material is very good and homogeneous is distributed over the particles.

The invention therefore relates to a method for Production of a support material containing aluminum oxide with an active component applied thereon and / or Precursors for this, using a sol / gel technique, comprising making a sol from alumina or an alumina forming material, which sol above in a column is inserted, the upper part of which with a Water immiscible liquid is filled and its lower part with an alkaline aqueous solution, which also the active component or a precursor to it in dissolved and / or complexed form, is filled, wherein in lower part in the presence of the active component and / or the Precursor for this, particles of the carrier material with the desired texture are formed, separating the particles of the liquid, the drying and the calcining of the Particles.

Surprisingly, it has been shown that with the inventive method a carrier material with a active material or precursor therefor applied thereon is obtained with a very homogeneous distribution of the active Material or precursor to it while the particles are on are particularly strong and have a good pore distribution have.

The essence of the invention is that the active Material or the precursor for it present in the liquid with which the gelation of the sol particles is accomplished is so that during the phase in which the particles are formed the active material or the precursor for it is recorded or in the drops of the carrier material is adsorbed. During the gelling phase, the  Initial texture of the particles formed, from which during the Drying / calcining the final texture is created so that then at the same time the active component in the particles is built in. This method has the advantage that the Particles after drying and calcining none closer They need to be loaded so that texture changes no longer occur.

As already stated, the sol / gel method exists from dropping an alumina sol or a Alumina containing material by two Layers of liquid, the top of which is lighter than and with water is immiscible, while the lower one is made from an alkaline aqueous solution of the active component, one Precursors for this and / or a complex of these substances.

The temperature at which the inventive method is not critical. Preferably one turns Room temperature, i.e. H. a temperature between 15 and 35 ° C.

When carrying out the method according to the invention one first makes a sol from an aluminum oxide and / or an alumina-containing material. This sol there a pH of 1 to 5, preferably by adding a sufficient amount of a monovalent inorganic acid. A suitable amount of acid is 0.15 to 0.3 mol / l H⁺ educated. The solids content of the sol, calculated as Al₂O₃, is preferably between 5 and 30% by weight, very particularly this is a maximum of 25% by weight. The latter upper limit for the Solids content is due to the manageability of the sol prefers. A preferred lower limit of the solids content is 18% by weight in connection with the strength of the preserving particles.

It is possible and sometimes desired to go to the sol to give other additives to the properties of the Optimally adjust particles. Suitable additives are u. a. Urea and combustible substances. The addition of Urea is used for a quick increase in viscosity to avoid and therefore adjust the texture of the particles, where a suitable urea content is at most 1.5 mol / l is. The purpose of adding burnable substances is  Creation of a suitable enlarged pore structure that can be obtained by burning these substances out.

The upper layer is immiscible with water in principle from a liquid hydrocarbon or a Mixture of liquid hydrocarbons. The Surface tension at the interface Hydrocarbon / water should not be too high. It has namely shown that too high a surface tension performs problems with passing the interface the balls arise. The surface tension can if desired, by applying an amount of anionogenic surfactant, e.g. B. a Fatty alcohol sulfonate such as TEEPOL can be reduced.

Examples of suitable liquid hydrocarbons are known from the literature, such as petroleum ether, diesel oil, kerosene, Boiling point petrol u. the like

The thickness of the layer of liquid Hydrocarbons are not critical and can be caused by some simple experiments can be determined. Since the layer in essentially serves to form the drop and To stabilize to some extent, a dwelling time is sufficient Layer of at least 0.5 s. Generally the dwell time lie between 0.5 and 3 s, with an optimum of approximately 1 s.

The alkaline water layer generally contains a base such as NH₃ or a hydroxide of the metal, the one Forms part of the active component. Preferably one turns NH₃ to that in an amount of generally a maximum of 3.0 mol / l is present. The amount thereof is preferably 0.8 to 1.6 mol / l. In addition, according to the invention is in the water layer the active component or a precursor to it in solution available, possibly in a complex form.

The residence time of the particles in the aqueous phase is generally sufficient to gel the particles so that these are strong enough and also contain the active material. Suitable residence times are between 5 and 60 minutes, preferably between 10 and 20 minutes. By adjusting the  The desired dwell time can be obtained. All in particular, it is possible to apply by Counterflow techniques to set a desired dwell time.

The type of active component that is on the Carrier material is applied, can vary widely. It is possible to assign a material as an active material use that can serve as a sorbent or as a catalyst. In almost all cases, however, the active material should be contain a metal component. Suitable metal components based u. a. on one or more metals selected from the group consisting of manganese, cobalt, nickel, copper, Calcium, strontium, barium, magnesium, zinc, tin, lead, Lanthanum, iron, molybdenum, silver, gold, palladium, platinum, Rhodium, rhenium, vanadium, chromium and tungsten.

According to a preferred embodiment of the invention to make a sorbent with an active component Base of calcium, manganese, copper or the alloys CuCoZn and CuNiZn, the whole and / or after application especially during calcining, in whole or in part the carrier material can react. The so obtained Surprisingly, materials are particularly good regenerable. When using calcium in the active Component you can get a sorbent for SO₂, while Manganese compounds are suitable for absorbing H₂S. A Sorbent, which contains copper material as an active component, is suitable for removing oxygen from gas mixtures.

One particularly makes a sorbent that a calcium compound based during and / or after Apply completely or partially with the carrier material responds. Calcium aluminate is formed. The The surprising advantage of such a sorbent is that it is it is possible to absorb SO₂ regeneratively from gas flows. It it has been shown that a sorbent thus obtained absorbs well and regenerate even at relatively low temperatures is. Because of this low temperature you have little Problems with unwanted sintering and / or formation  unwanted compounds like CaS. This way you get therefore an optimally applicable sorbent.

The active material is in the case of a absorbent material preferably at most as monomolecular layer on the substrate. Higher Loads have no practical advantages, because in one in such a case no reaction with the carrier material occurs can and the absorbent material as single crystallites may be present in the pores. These crystallites can probably react too difficult to regenerate compounds.

According to another embodiment of the invention one uses a catalytically active as active material Material. You can u. a. on metal catalysts think that get by reducing a precursor to it will. The catalysts thus obtained have the advantage that it is possible to structure the catalyst much more accurately adapt the kinetics of the reaction while at the same time very homogeneous distribution of the active component over the Surface is obtained. This enables optimal Matching the catalyst to the one to be catalyzed Reaction.

The active component can be as metal or as Metal connection must be present. It is also possible, Apply combinations of metals, these metals can be wholly or partially alloyed with one another.

After gelling, the particles become aqueous Phase separated and dried. This should preferably Drying should be done fairly carefully, otherwise the particles can tear. According to a preferred embodiment, the Particles first with a lower alcohol such as methanol or Treated ethanol and then dried with heating.

After drying, the material is heated calcined at a temperature of at least 450 ° C. The If desired, material can be further processed experienced, e.g. B. a reduction or oxidation.

The invention also relates to a sorbent, consisting of one obtained according to a sol / gel technique  Backing material with a calcium and / or Manganese aluminate is applied. Such a material is new and has surprisingly good properties for removing or SO₂ and H₂S from gas mixtures. Due to the good regenerability can also be a longer use of the invention Sorbents are made.

The invention also relates to a method for regenerative absorption of gaseous components, whereby one a sorbent according to the invention or using the sorbent obtained according to the invention uses. A Preferred process involves absorbing SO₂ with the help a carrier material with an active applied thereon Component based on a calcium compound, which material is obtained using a sol / gel technique.

Another preferred method involves absorbing of O₂ with the help of a carrier material with one on it applied active component based on copper, which Material is obtained using a sol / gel technique.

A third preferred method involves absorbing of H₂S with the help of a carrier material with one on it applied active component based on a Manganese compound, which material using a Sol / gel technology is preserved.

The invention will now be illustrated by a few examples explained without being limited to this.

example 1

To an aqueous solution of 0.195 mol HNO₃ / l and 0.75 mol Urea / l was 0.5 g / l pseudoboehmite (ALOOH.1, 4 H₂O, PURAL SB-70, CONDEA Chemie GmbH, Germany) in 60 min. given and with an agitator at a speed of 200 to 250 rpm. dispersed. After the material had been dispersed, stirring was continued for 15 minutes continued.

The sol thus obtained was in a dropping column introduced in which there is a calcium-containing, ammoniacal Solution was in water. This solution contained 1.1 mol / l Calcium nitrate and 0.85 mol / l ammonia. The solution was over  the column recirculates. The calcium remained in the solution the complexing effect of ammonia.

The top of the drip column was one stationary layer of boiling point petrol (40-60 ° C, altitude about 20 cm; Room temperature). Just under the Interface with the aqueous solution was arranged an outlet through which the aqueous solution is withdrawn from the drip column has been.

The sol was placed in this drip column from above dropped in. The drops, which have a diameter of about 5 mm owned, formed almost perfect spheres and gelled there kind of while going through the top layer fell down. This kept the particles intact, in shape of gel particles when they subsequently cross the interface happened. Due to the action of the anionogenic surfactant that was present in the system the particles simply passed the boundary layers.

The particles continued to fall through the calcium-containing ammoniacal solution in which they continue to gel and were simultaneously impregnated with calcium. Depending on the Calcium concentration in the solution was greater, which contained final porous particles were more calcium and these Particles stronger.

The calcium-containing extracted from the top of the drip column Solution was fed back down so that the particles slowly fell in countercurrent. There was one down in the drip column Constriction provided, creating such a strong flow of Solution was obtained that the falling particles in the first Instance could not fall further and a bed gelled Particle emerged. By gelling and by osmotic Water disappeared from the particles effect simultaneously Calcium absorbed so that their density increased. In one At a certain moment the particles became so heavy that they could probably continue to fall. The pumping speed The solution was regulated so that the average Particle dwell time in the dropping column approx. 15 min. amounted to.  

After passing the constriction, the gelled particles in a downward stream of calcium-containing ammoniacal solution. This solution was Sieved where the particles separated from the solution were. The separated particles were washed twice during 15 Seconds immersed in ethanol to remove the excess water to remove. The particles treated in this way were kept for 20 Hours at 80 ° C under increased water vapor tension dried. The dried particles became thereby calcined that their temperature around 1 ° C / min. to 80 ° C increased and then the particles on this for 10 hours Temperature held.

The particles obtained had one average diameter of 3.0 mm with a Breaking strength of 150 N (average of 25 particles), a BET surface area of 93 m² / g, a pore volume of 0.28 ml / g and a calcium content of 14.3% by weight.

The particles were tested for their properties as sorbents for SO₂ tested at 850 ° C using a gas, consisting of from 20 vol .-% O₂, 0.5 vol .-% SO₂ and the rest N₂, using the so-called SRO test, which is described in the article by A.E. Duisterwinkel, E.B.M. Doesburg and G. Hakvoort, Thermochimica Acta 141 (1989), 51-59.

After 2.5 hours the weight of the sample resulted the reaction of a calcium oxide with SO₂ / O₂ to calcium sulfate 8 wt .-% increased. Regeneration of this sample at 850 ° C with a gas consisting of 10 vol.% H₂ and 90 vol.% N₂ gave 90% Calcium oxide.

Using a conventional sorbent for SO₂ / O₂, consisting of impregnated α-alumina particles with a Pore volume of 0.36 ml / g, 10 wt .-% calcium oxide, a BET surface of 10 m² / g and a breaking strength of 140 N, you get a weight gain of 14 wt .-% during one 2.5 hours treatment and only 60% formation Calcium oxide during regeneration.  

Example 2

Using those described in Example 1 Methods were applied using different Acid concentrations in the sol produced some sorbents. In The table below shows which results were achieved with it.

table

This table shows the meaning of the Acid concentration for the possibility of simultaneously To increase pore volume and breaking strength. At the same time results from the fact that a maximum achievable Drip speed strongly due to the acid concentration being affected.

The influence on the pore volume and the Breaking strength is not entirely explainable, but is in the Practice is of course particularly important.

Because the average pore radii in the different products do not differ greatly from each other differ, the reaction parameters hardly change.  

Example 3

Using the method of claim 1 a sorbent is produced for the regenerative removal of H₂S. Deviating from example 1 was instead of one calcium-containing solution, a solution of 159 g of manganese (II) acetate, 170 g sodium EDTA in 565 ml water and 35 ml 25% by weight Ammonia in the drip column. The solution was N₂ blown to oxidize the manganese (II) through oxygen avoid. After leaving the column, the particles became dried quickly and then heated up 1 ° C / min. Calcined to 600 ° C, followed by heating to 600 ° C for 10 hours.

The particles had a manganese content of 4% by weight, a BET surface area of 195 m² / g and a pore volume (measured with N₂ desorption) of 0.35 ml / g. This product was reduced at 600 ° C with hydrogen and then at exposed to a gas at this temperature, consisting of 1% by volume H₂S, 10 vol .-% H₂ and 89 vol .-% N₂. After the treatment was over approximately 80% of the manganese converted to manganese sulfide. This was at 600 ° C with steam in about 10 vol .-% H₂ and continues to regenerate nitrogen. Then the Treatment with H₂S repeated. In this second cycle and in The following cycles showed that the sorbent per Cycle intake of sulfur was constant, although significantly lower than in the first cycle (30%).

The means known to date for absorbing H₂S also show a clear difference between the first and the second cycle. However, these products also show in the following cycles a decrease, so that the product according to of the present invention is much better.

Example 4

To make a catalyst for the Methanol decomposition was 51.0 g zinc nitrate · 6 H₂O in water dissolved and added to 100 ml of 25 wt .-% ammonia. The mixture was shaken until the zinc nitrate was completely dissolved. Then solutions of 62.1 g of copper nitrate · 3 H₂O and 49.9 g of nickel nitrate · 6 H₂O in water slowly to the zinc-containing  Solution given. This solution was supplemented up to 500 ml what resulted in a total cation concentration of 0.6 mol / l.

The solution thus obtained was made up to that in Example 1 described way instead of the calcium-containing ammoniacal Solution applied.

The way described in Example 1 obtained gelled and simultaneously impregnated particles were in air once at room temperature dried, dried for 3 hours at 80 ° C and then by warming up at a warm-up rate of 1 ° C / min. calcined to 400 ° C. The particles were kept for 3 hours kept at this temperature and then cooled.

In this way, particularly strong spherical ones Catalyst particles obtained in a fluidized bed reactor were used. The average breaking strength of the Particle was 70 N and the pore volume was 0.30 ml / g. In the Application of this catalyst to decompose methanol resulted himself that his activity despite the low content active substance was good and that this activity increased Temperature was constantly increasing, in contrast to that usual catalysts that have an optimum activity in the Own temperature.

At a reaction temperature of 350 ° C, 3.8 g Methanol decomposed per hour per gram (CuO + NiO).

Example 5

For the preparation of a catalyst for dimethyl ether 46.7 g of zinc nitrate · 6 H₂O was dissolved in water and 100 ml Given 25 wt .-% ammonia, which was shaken until the Zinc nitrate was completely dissolved. Solutions from 56.9 g copper nitrate · 3 H₂O and 45.7 g cobalt nitrate · x H₂O in water added to the zinc-containing solution. This solution was up to 500 ml supplemented so that the total cation concentration Was 0.55 mol / l. In the manner described in Example 4 catalyst particles were produced.

The gelled and impregnated particles were dried in air at room temperature for 24 hours, then dried for 3 hours at 80 ° C and through  Warm-up at a warm-up rate of 0.5 ° C / min. on Calcined at 464 ° C. The particles were on this for 3 hours Temperature, whereupon they were cooled. There were particularly strong spherical catalyst particles receive. The average breaking strength of the particles was 125 N and the pore volume was 0.45 ml / g. The material was a good catalyst for the production of Dimethyl ether.

Claims (24)

1. Process for producing an alumina containing carrier material with an applied thereon active component and / or precursor for it, using a sol / gel technique comprising making a sol from Aluminum chloride or an aluminum oxide forming material, which sol is placed in the top of a column, the top one Part filled with a water-immiscible liquid is and the lower part with an alkaline aqueous Solution that is also the active component or a precursor contains in a dissolved and / or complex form is, in the lower part in the presence of the active component and / or the precursor therefor particles with the desired Are formed, separating the particles from the texture Liquid, drying and calcining the particles. 2. The method according to claim 1, characterized in that the alkaline aqueous solution is a complexing agent for the aluminum component and / or the precursor, preferably NH₃, in an amount of preferably not more than 3 mol / l, contains in particular from 0.8 to 1.6 mol / l. 3. The method according to claim 1 or 2, characterized characterized that the active component or the precursor for that is a metal connection. 4. The method according to claim 3, characterized in that the active component on one or more metals based, selected from the group consisting of manganese, cobalt, Nickel, copper, calcium, strontium, barium, magnesium, zinc, Tin, lead, lanthanum, iron, molybdenum, silver, gold, palladium, Platinum, rhodium, rhenium, vanadium, chromium and tungsten. 5. The method according to claim 4, characterized in that a sorbent with an active component based on Calcium, manganese and / or copper produces.   6. The method according to claim 5, characterized in that one as an active component and / or precursor for it Calcium compound used during and / or after Application to the carrier material in whole or in part with the Carrier material reacts. 7. The method according to claim 5 or 6, characterized characterized in that the active component as a maximum monomolecular layer is present on the carrier material. 8. The method according to claims 1 to 4, characterized characterized in that a catalyst with an active Component based on a metal and a metal compound produces, comprising at least one of the metal components Metals selected from the group consisting of manganese, cobalt, Nickel, copper, calcium, strontium, barium, magnesium, zinc, Tin, lead, lanthanum, iron, molybdenum, silver, gold, palladium, Platinum, rhodium, rhenium, vanadium, chromium and tungsten. 9. The method according to claim 8, characterized in that a metal composition comprising CuCoZn or CuNiZn applies. 10. The method according to claims 1 to 9, characterized characterized in that a sol with a pH of 1 to 5, preferably 2.5 to 3.5. 11. The method according to claims 1 to 10, characterized characterized in that a sol with a solids content of 5 to 30 wt .-%, calculated as Al₂O₃, produces. 12. The method according to claim 10, characterized in that that a sol with a solids content of at most 25 wt .-% produces. 13. The method according to claim 12, characterized in that that a sol with a solids content of at least 28 wt .-% produces. 14. The method according to claims 1 to 13, characterized characterized in that the sol is one or more monovalent inorganic acids and possibly other Contains additives. 15. The method according to claim 14, characterized in that the sol contains urea and / or burnable substances.   16. The method according to claim 15, characterized in that the sol contains 0 to 1.5 mol / l urea. 17. The method according to any one of claims 1 to 16, characterized characterized in that the water immiscible liquid contains a surfactant. 18. The method according to claim 17, characterized in that that the residence time of the sol in the water phase is at least 5 minutes. is. 19. The method according to claims 1 to 18, characterized characterized in that the particles after the separation of the liquid is treated with a lower alkanol. 20. Sorbent, consisting of a sol / gel technique obtained carrier material, on the surface of which Calcium and / or manganese aluminate or copper is applied. 21. Process for the regenerative absorption of gaseous Components, characterized in that a sorbent after Claim 20 and / or obtained using the method according to one or more of claims 1 to 19 applies. 22. The method according to claim 21, characterized in that SO₂ with the help of a carrier material with one on it applied active component based on a Calcium compound absorbed. 23. The method according to claim 21, characterized in that that one O₂ with the help of a carrier material with one on it applied active component based on a copper absorbed. 24. The method according to claim 21, characterized in that that one H₂S with the help of a carrier material with one on it applied active component based on a Manganese compound absorbed.