DE534905C - Process for the production of hard, strongly adsorbent gels of low apparent density - Google Patents

Description

Process for the production of hard, strongly adsorbent gels of low apparent density The invention relates to a method for producing hard, strongly adsorbent gels of low apparent density due to their hardness are very resistant to mechanical stress and, for example, at the transport through an adsorption chamber by means of an air stream or a Snail experience no change in their context. The procedure persists in that hydrogels prepared in a known manner in the presence of water or Steam-saturated gases are heated to moderate temperatures. It was found, that in general by moderate heating with a slow increase in temperature under an excellent end product is obtained under the specified conditions.

The procedure is carried out as follows: First, one creates a hydrosol which can be converted into a strongly adsorbent end product, e.g. B. by decomposing a silicate by means of an acid with vigorous stirring, whereby the precipitation of silica should be avoided. The quantity and Concentration ratio Se chosen so that the acidity of the sol is 0.1 to o, g N lies. If the same volumes were used, ten percent by weight hydrochloric acid would be used correspond to a silicate solution of specific gravity I, I to I, 3. The ordinary Commercial waterglass contains 9 01o Na2 0 to about 29 to 30 01o SiO2. At an acid concentration below 0.1 N, the formation of precipitates by cooling the ingredients before Bringing together or prevented during mixing.

The mixture of the reaction components solidifies after some time Formation of the hydrogel into a gelatinous mass. The hydrogel is optionally disassembled into pieces, suitably washed with warm water of about o and then according to the invention treated with heating so that a highly active end product of less apparent density arises. So far one has only proceeded in such a way that the hydrogel broken into pieces after its formation, washed out, and then immediately was dehydrated to a water content of 5 to 15%.

The thermal treatment of the hydrogel can be done in several ways take place: Example I By bringing some into a closed pipe, if necessary crushed hydrogel a gas saturated with water vapor, e.g. Air, the initial temperature of which is gradually increased from about 100 to 80 to 95 " C is increased.

However, the temperature can also, so that the desired effect occurs, possibly rise to 1665 ". The temperature gradually becomes approximately within half an hour to 5 hours to the specified maximum point. Man then goes up to the temperature of the circulating gas stream in about 15 minutes Return to starting temperature 1 hour or more. You can also use the gas circulation after the maximum temperature has been reached, interrupt and gradually open the pipe up to Let room temperature cool down. During this treatment phase is always make sure that the heating medium is saturated with water vapor.

Example 2 The hydrogel is in an autoclave with the addition of a brought in enough water to cover it. The autoclave will then slow down heated to 100-1650 ° C. At 1000 C the internal pressure is equal to the atmospheric, at 165 "C the internal pressure is about 6.8 atm.

When the maximum temperature of I65 "C is reached, the heat supply turned off and the autoclave gradually allowed to cool to room temperature. The whole treatment lasts about 1 to 5 hours, with the increase in temperature covers a greater period of time than or cooling process.

It was found that a hydrogel, which for example 5 hours in a completely closed autoclave heated to 150 ° 0 and heated in 1 hour was cooled to 1000, converted into an end product of much lower density leaves as such, which is brought to this temperature in one hour and in 5 Minutes was cooled to 100 °. You get an even better product if the Temperature rise phase a little over 5 hours and the cooling stage a little over an hour is extended. The length of time the hydrogel is on the If the maximum temperature is maintained, the final product does not appear to be significantly affected So much water is to be brought into the autoclave with the hydrogel that the the maximum temperature reached in each case, in addition to the steam, was always a sufficient quantity Water is present so that the water required for steam formation is not in larger Amount is withdrawn from the gel.

A long cylinder, which is closed at one end, serves as the autoclave and on the other with a flange for loading and unloading the goods is. In the container is a worm gear serving as a treatment space for the hydrogel located some distance from the inner surface of the cylinder. Of the After inserting hydrogel and water, the cylinder is fitted with a flange provided end tightly closed.

Example 3 The hydrogel is poured into a steam vent Introduced into the autoclave and covered with water at a sufficient height.

The autoclave is gradually brought to 1000 C in about 1 to 2 hours heated to atmospheric pressure. During this preheating, the water content of the Hydrogel not diminished.

When the temperature has risen to 100 ° C, the make-up water evaporates in the autoclave at the same time as the larger portion. the hydrogel water; at a Moisture content of the hydrogel from 5 to 15% of the dry weight of the gel the heat supply is turned off and the autoclave to cool to room temperature left to itself.

Thanks to the special design of the autoclave, you can do both Treatment stages, namely the heating of the hydrogel provided according to the invention without dehydration, and the dehydration of the hydrogel successively in a container make.

Example 4 The hydrogel is placed in a container with a cover brought in sufficient amount of water. The container will gradually increase in 1 to 2 hours or heated above that the water temperature rises to about 80 to 95 "C.

Then the supply of heat is interrupted and the hydrogel is used to cool down left to itself. One achieves with a slow increase in temperature and more gradually Cooling down the best results. The cooling time is expediently 15 minutes to I or 2 hours.

If you do the treatment in a dryer, it will Hydrogel in this spread on perforated surfaces and bounded by a Amount of air, the temperature of which gradually rises to 1650 C., repeated in the circulating current flows through. Since only a limited amount of air is introduced into the circulating flow, there is no significant drainage of the gel.

Instead of the treatment in a continuous temperature change To make the amount of circulating air, you can also insert the hydrogel one after the other Bring in steam-saturated air currents at different temperatures, for example be heated to 65, 105 and 1500 C. Finally can one that Change the circulation process so that the individual circulating currents are not at constant Temperature must be maintained, but a gradual increase up to the specified Experience maximum limit. The cooling takes place afterwards, as indicated above.

After the thermal treatment, the hydrogel is dried. to For this purpose, an air flow of 75 to 1200 is first passed over the gel and increased gradually the temperature to 300 to 4000. The end product contains 5 to 15 0 / o Water, and the apparent density measured after activation is about 870 " at 0.5 or below this value.

Activation is the treatment of the dried gel, through which this is enabled to adsorb gases, vapors, etc. Man activated for example by heating for three hours in a stream of air at 3I5 "C.

The washing operation is done prior to heating as indicated or after the heat treatment with water, which is appropriately warmed up a little or weakly is acidified. Sometimes washing out of the hydrogel or end product even becomes not be required.

Example 5 Alumina hydrogel is placed in a closed tube and pour a sufficient amount of water over it to cover it.

The tube is then heated to a higher temperature, e.g. B. I25 "C, heated, the pressure being 2.3 to 2.7 atm. amounts to. After four hours of heating, the pretreatment stopped and the tube allowed to cool to room temperature.

Example 6 Alumina hydrogel is treated as indicated in Example 5, however, the temperature of the thermal pretreatment is 165 ° C. at one pressure from about 6.8 to 7.1 atm.

The properties of the final gel are determined by several factors determined by the maximum temperature, the duration of the temperature increase and cooling, the amount of water applied.

Finally, the degree of purity of the hydrogel also determines the properties of the end product, in the sense that when completely cleaned, an adsorbent of lower density is obtained. If the material is not in the form of the hydrogel was washed before or after the heat treatment, the Density of the finally dried gel can be reduced by washing out. If so desired the cleaning process can also be carried out in several of these stages.

With regard to the variability of certain adsorbents After activation it is appropriate to adjust the density of the adsorbent after activation to eat. Since in technology it is activated at a maximum of 870 ", one can assume that a gel that, when repeatedly heated to this temperature, the absorption capacity has not changed to any significant extent, suitable for technical use is.

So far, hydrogels have been dried in this way; that this at slower Temperature increase to 75 to 1200 and then to 300 to 400 "C gradually were heated.

In contrast, the present procedure differs in that that the hydrogels are thermally pretreated before the actual drying, as explained in the description. This makes it possible to obtain a dried End product of lower apparent density to obtain a hydrogel according to the invention heated to a certain temperature for a certain time before drying after drying gives an end product with a certain apparent density. When a hydrogel e.g. B. has been pretreated at 80 "C for a long time, the apparent Density of the final dried product about 0.522. This is true for a dried one Gel, which was activated by heating to 3I5 "in a stream of air, and a grain size from 1.168 to 2.362 mm.

If the same hydrogel is pretreated at I250 C for the same time after activation at 315 "C, the dried end product has an apparent appearance Density of about 0.46 with a grain size of 1.168 to 2.362 mm.

Gels that have an apparent density of 0.5 or less are suitable is particularly suitable for the adsorption of vapors from vapor-saturated air mixtures and for the adsorption of dissolved substances. A known after the previously described Process prepared hydrogel washed with 15 "C water for 40 hours provides a final product with an apparent density of about 0.7; such gels are suitable is only suitable for the adsorption of vapors from air mixtures with a low vapor content.

The following table shows the dependence of the apparent density of the gel is expressed by the temperature of the pretreatment of the hydrogel.

The method described can also be applied to the hydrogels of tungsten oxide, aluminum oxide, titanium oxide, etc. or to mixed hydrogels, Temperature of the apparent activation grain size Chemical thermal density of the temperature of the dried composition Pre-treatment of dried dried gels of the hydrogel of hydrogel of hydrogel gels gels mm SiO2 ............... - 1.33 870 ° C 0.048 to 0.074 SiO2 ............... 125 ° C 0.60 870 ° C 0.048 - 0.074 SiO2 ............... 165 ° C 0.58 870 ° C 0.048 - 0.074 Al2O3 .................. - 32 870 ° C 0.048 o74 Al2O3 .............. 125 ° C 1.147 870 ° C 0.048 - 0.074 Al2O3 .............. 165 ° C 1.065 870 ° C 0.048 - 0.074

Claims (6)

PATENT CLAIMS: I. Process for the production of hard, strongly adsorbing Gels of low apparent density, characterized in that one on any Ways made hydrogel, e.g. B. Silicic acid hydrogel, in a water vapor saturated Gas or steam atmosphere, if necessary in the presence of water, is heated, the water content of the hydrogel is practically not reduced, and that the Wash out before or after the heat treatment or after drying and Activation takes place in one step or in several stages of the process. 2. The method according to claim 1, characterized in that the hydrogel heated to the maximum temperature in about 15 minutes to 5 hours and then in allowed to cool for about 15 minutes to 2 hours. 3. The method according to claim I and 2, characterized in that a Gas or steam flow saturated with water vapor with a slow increase in temperature and decrease is passed through the hydrogel. 4. The method according to claim I to 3, characterized in that a A limited amount of gas or steam is repeatedly passed over the hydrogel in a circulating current will. 5. The method according to claim 1 to 4, characterized by the use several circulating currents, which are kept at a constant temperature or a slow one Experience temperature increase. 6. The method according to claim I and 5, characterized by a maximum temperature from about 80 to 1650.