DE1032728B - Process for the production of spherical or lenticular active clay - Google Patents

Description

Process for the production of spherical or lenticular active clay In the production of spherical or lenticular catalysts or Kätälysatortträger active alumina is usually taken from a concentrated aluminum oxide hydrosol from which you can use a gel-forming agent. Hexamethylenetetramine, urea or. Like., below the gelling temperature and then mixed with water immiscible liquid at a temperature that accelerates gel formation lets drip in. The drops are not left a certain distance in the water miscible -liquid fall, being under the influence of -surface tension and gravity take on lenticular to spherical shape. One lets the balls resp. Lentils for some time. increased temperature in the water-immiscible liquid, until they are aged and solidified to such an extent that they undergo aftertreatment in water Withstand medium without disintegrating. This post-treatment is used for washing out of salts that are contained in the manufacture of alumina balls or lenses are, and is usually with ammonia-containing water in the cold or warm performed. The after-treatment is followed by careful drying Room temperature or moderately elevated temperature, whereupon the balls or lenses be calcined at temperatures from 300 to 600 ° C. The alumina balls produced in this way -hzw. -Lenses are usually very hard. They suffer in the course of their manufacture a considerable - volume contraction, which makes it brittle and hard as glass. Since the balls or lenses in the course; the strong shrinkage that they dry out at home suffer - they contain 70 to 80oio of water -, very easy to jump, arises from the production described a lot of waste.

The strong reduction in volume also has the consequence that the catalytic activity of the spheres or lenses produced in this way leaves something to be desired. It has been found that the described disadvantages resulting from the severe shrinkage of the moldings can be avoided if the aluminum oxide hydrosol is dried, finely ground aluminum hydroxide alone or in a mixture with finely ground, calcined, active one before the addition of the gel-forming agent Add alumina, mix the whole thing thoroughly and, after adding a gelling agent, shape it into gel balls or lenses in a known manner. Surprisingly, it has been shown that up to 90% of alumina hydrate can be added to the sol as a filler without the spheres or lenses produced from the mixture being impaired in their mechanical strength. Rather, the plasticity of the added, dry aluminum hydroxide reduces the brittleness of the finished spheres or lenses and achieves excellent pressure and abrasion resistance. The follow-up treatment is carried out in the same way as for. the known procedures; it includes aging of the gel at temperatures up to 100 ° C., optionally further aging in a basic medium, separation of the water-immiscible suspension liquid, washing of the gel with water or ammonia solution, drying and calcination. While the shrinkage of the alumina spheres or lenses produced by the known processes is up to 90% , in the process according to the invention it is only 30 to 80%, depending on the amount of alumina added. Another advantage of the process is that up to 90% of the alumina hydrate can now be used in the crystal form which is desired for the activity of catalysts consisting of alumina, ie in the form of boehmite, bayerite, hydrargillite, randolnlt or mixtures thereof . In contrast, in the known production of alumina gel from aluminum oxide hydrosol without the addition of the filler according to the invention, only boehmite is always produced, which after the thermal treatment, as is necessary in the production of spheres or lenses, is so well crystallized that it ages to trihydrates (bayerite , Hydrargillite, randomite) can no longer be achieved at all or only to a very limited extent.

The aluminum oxide hydrosol is essentially used for shaping while the main carrier of the catalytic activity is the admixed filler are.

The alumina hydrate to be admixed can by known methods for Production of active clay, e.g. B. by precipitation with ammoniacal solutions Aluminum salt solutions or with mineral acids from sodium aluminate or by hydrolysis of aluminum alcoholates.

Because alumina hydrates can be used as fillers, by far cheaper processes than the one used to manufacture the one previously used Alumina hydrosols are obtained from aluminum metal, offers the present Procedures also have a significant, economic advantage.

The catalytically active metals or metal oxides that the finished Is to contain catalyst can in a known manner either by impregnation of the shaped, calcined carrier with suitable salt solutions or by admixture corresponding metal salt solutions are introduced into the sol or the sol-alumina mixture will.

The spherical or lenticular manufactured according to the described process Alumina can be used wherever active alumina alone or as a carrier is used for other metal oxides or metals in static catalyst layers. The spherical or lens shape of the catalyst particles ensures a special one good space filling of the reaction vessels and low abrasion during loading with the catalytic converter or the emptying as well as during operation.

Examples 1. To 11 of a 1-mol. Aluminum chloride solution become 150 g aluminum powder added in portions. To complete the implementation will the reaction mixture is heated. The resulting hydrosol contains 26.5% A12 03 and 8.5% Cl. To 550 g of this sol, 425 g of alumina hydrate with a content of 67.2% A12 03 and 145 g obtained from the same alumina hydrate by annealing at 500 ° C, active clay and 120 cms of water are added and placed in a porcelain ball mill 16 Milled hours. The alumina hydrate is obtained by precipitating an aluminum chloride solution with a sodium aluminate solution, washing out the precipitate and drying 1.10 ° C and consists of 200 / a boehmite, 6001o bayerite, 15% hydrargillite and 5% Randomit. Shortly before the deformation, the ground mixture is using an intensive mixer 70 g of a 400 / own aqueous hexamethylenetetramine solution mixed in. The mixture thus obtained is drawn from a storage container through a dropper device a vertical tube filled with paraffin oil and heated externally with steam 1.8 m long and 20 mm wide. At the bottom of the tube, the gel balls or lenses formed from the drops in a kept at 95 ° C, collected with storage vessel filled with C51. The gel balls are used for 90 hours Maintained temperature of 95 ° C, treated with ammonia gas at 95 ° C for 2 hours, then separated from the oil and washed oil-free with carbon tetrachloride. Then they will Washed with ammonia-containing water at room temperature until free of chlorine are, 1 day in the air at room temperature, 4 hours at 45 ° C and 4 hours dried at 110 ° C, and finally 2 hours at 300 ° C and 5 hours at 500 ° C calcined. From 1420 cm3 of plastic gel balls, 695 cms are finished and sealed Catalyst obtained, which corresponds to a shrinkage of the gel by 51%. The finished Balls or lenses are characterized by great hardness and abrasion resistance.

2. To 600 g of an aluminum oxide hydrosol prepared as in Example 1 ' with a content of 23.6% A120 and 5.70 / a Cl are 770 g finely ground alumina hydrate added. The alumina dihydrate is by combining an Aliuminiumuhlori @ dlös, ung and a sodium aluminate solution, separation and washing out of the formed, precipitate and drying the same, produced at 105 ° C and According to the X-ray analysis, it consists of 35% boehmite and 65% bayerite. Zui dhem intimate mixture of sol and alumina hydrate are 125 cms of a 40 "/ own solution of Hexamethylenetetramdn added with cooling and, the suspension in the same In the same way as in Example 1, shaped into spheres and treated. The volume of fresh deformed spheres is 2150 cms, that of the completely calcined spheres is 900 cms, which corresponds to a shrinkage of 58%. The finished balls have diameters between 3.5 and 4.5 mm and have great hardness and abrasion resistance.

3. Balls are produced in the same way as in Example 2, only that instead of precipitated alumina hydrate, it is produced according to the Bayer process Hydrate, which consists entirely of hydrargilite (A12 0s - 3 H2 O), mixed with the sol will. The shrinkage is 55%. The bullets have one. Diameter of 3 up to 4 mm and are hard and. abrasion resistant.

It is known in the manufacture of alumina by equipping the Alumina hydrate from the aluminate liquor by the Bayer process leads to crystal formation to influence of alumina chydrate by adding finely ground to the finishing liquor Add alumina hydrate as a vaccine. In contrast, it is the case according to the invention Process for the replacement of a part of the for the manufacture of spherical or lenticular active alumina commonly used aluminum oxide hydrosol by finely ground Aluminum hydroxide on its own or in a mixture with calcined, active clay.

Claims (1)

PATENT CLAIM: Process for the production of spherical or lenticular, active clay by dropping in a mixture of an aluminum oxide hydrosol with, a yellowing agent in a heated, water-immiscible liquid, Aging, washing out, drying and calcining of the gel, characterized by that the aluminum = oxydhydrosol is dried before the addition of the gel-forming agent, finely ground aluminum hydroxide alone or in a mixture with finely ground, calcined active clay. Publications Considered: Journal of Ore Mining u. Metallhüttenwesen, Vol. VII, 1954, Issue 3, p. 3 (article by H. G i n s -berg).