DD221160A1 - PROCESS FOR PREPARING LOW CRYSTALLINE SOLIDS POWDERS - Google Patents

Abstract

The invention relates to a process for the preparation of low-crystalline solid powders by thermal shock treatment of suitable starting materials. The object and the object of the invention are to develop a technologically, economically and economically favorable method for the thermal activation of solid powders. According to the invention this is achieved by the fact that pulverulent solid particles during the continuous transport using a Traegergasstroms in a heated pipe or Rohrbuendelreaktor are shock-heated by radiation energy and thereby thermally activated and / or partially destructured. The invention can be used, for example, to produce virtually roentgenamorphic aluminum oxides, Al.sub.2O.sub.3 SiO.sub.2 solids that are almost roentgenamorphic, or solid metal powders containing heavy metals.

Description

Field of application of Erfln Jutiy

The invention relates to a process for the preparation of low-crystalline solid powders, which are characterized by a particularly high reactivity due to the presence of lattice defects and defects. Such low crystalline solid powders can ζ. B. are advantageously used for the preparation of catalysts.

Characteristic of the known technical solutions

For the production of low-crystalline solid powders, the thermal shock treatment is preferably used, since longer treatment times lead to the healing of the lattice defects and defects, whereby the reactivity of these products is greatly reduced.

The principle of shock-like heating for the production of low-crystalline products is exploited primarily in the field of the production of highly active aluminum oxides by dehydration of Aluminiumaquoxiden. The aluminum oxides obtained in this way are usually used after appropriate processing as catalyst components or desiccant. A preferred embodiment of the shock-like heating is the metering of the solid into hot gas streams of (DE-AS 1028106, DE-AS 1008722, GB-PS 1081098, DE-AS 2227804, GB-PS 801462, DE-OS 2059946, DE-OS 2411846 , US-PS 3790495, DE-AS 2500548). The disadvantage of such methods is that the precipitators are exposed to a very high thermal load by the hot gas streams. In addition, such processes run energetically extremely unfavorable, since the heating of the gases, a multiple of the amount of energy is needed, which is consumed for the reaction.

Furthermore, fluidized bed apparatuses for thermal shock treatment are proposed in numerous patents (DE-AS 1592140, DE-OS 2805906, SU-PS 517564). To ensure a stable operation of fluidized bed apparatus, a narrow grain fraction must be used, creating a number of technological problems. The behavior of fluidized bed reactors, which is similar to a continuous stirred tank, has a very unfavorable effect on the properties of the thermally activated products due to the large residence time spectrum and leads to their heterogeneous composition. In the patents US-PS 3222129, FR-PS 7909875, FR-PS 1488218, FR-PS 1364940, DE-AS 1034162, DE-AS 2923064, DE-AS 3045190 the reaction of the starting material in the combustion zone of a flame is recommended. When working on this principle reactors in addition to a poorly controllable temperature influence also leads to large residence time differences in the hot combustion zone. Also in this solution variant, a multiple of the energy compared to the amount required for the course of the reaction is applied in order to achieve a stable flame formation. Furthermore, one obtains uncontrollable hydrothermal conditions in the reaction space.

Further, the patents DE-AS 1176619, SU-PS 528733 and SU-PS 477113 describe methods of thermal activation of solids in which the residence times are greater than those typical of shock heating but involve much shorter time periods than needed to produce well crystallized products become. Therefore, in this case, hydrothermal conditions can not be avoided, as a result, a healing of crystal lattice defects takes place, so that the reactivity of the resulting products is insufficient.

The disadvantages of the known technical solutions thus consist in the fact that it is difficult to set defined and reproducible reaction conditions for the entire process sequence. On the other hand, the proposed solutions are very difficult to implement technically and energy consuming.

Object of the invention

The aim of the invention is to develop an energetically favorable and therefore economical process for the preparation of low crystallized solid powders. The process should be technologically easy to implement and allow the setting of defined reaction conditions.

Explanation of the essence of the invention

The invention is based on the object to develop a suitable method for the production of low-crystalline solid powders by thermal shock treatment. The object is achieved in that powdery solid particles during the continuous transport by means of a carrier gas stream in a heated tube or tube reactor by radiation energy shock-like heated while thermally activated and / or partially destructed. As the carrier gas inert or reactive with the solid gases can be used.

The advantages of the solution according to the invention are that due to a continuous transport of the solid through the reactor space hydrothermal conditions are largely avoided, whereby the conversion of the starting material defines and runs reproducibly to a low-crystalline reaction product. Therefore, for example, almost X-ray amorphous alumina transition forms can advantageously be prepared by the process according to the invention. Furthermore, for example, the preparation of X-ray amorphous Al ₂ O ₃ SiO ₂ solids and heavy metal-containing solid powder is possible from suitable starting materials.

By applying the radiation principle for heat transfer to the solid, the amount of energy used is optimally utilized in comparison to other methods. The inventive method is characterized in that it is technically feasible in a simple manner, in contrast to the previously known solutions.

exemplary

The invention is described in more detail below by means of the following exemplary embodiments:

-2- 255798

BeispieM

According to the invention, a pulverulent hydrargillite having a water content of 2.97 mol / mol Al ₂ O ₃ and a specific surface area of 5.5 m ² × g ^{-1 is} continuously transported through a heated tubular reactor by means of a stream of nitrogen. The temperature distribution has a nearly constant course over the length of the reactor. By means of the thermal energy radiated from the tube wall and directly absorbed by the hydrargillite particles, they are almost completely thermally decomposed during transport through the reactor space. This produces an almost X-ray amorphous Abbaüprodukt whose residual water content of 1.51 mol / mol Al ₂ O ₃ and a specific Qberflächengröße of 234m ² .g ^-1 aufweint; This product can be advantageously further processed to catalyst carriers,

According to the invention, a homogenized mixture of solids from Hydrargilfit having a specific surface area of 5j5m * ·· g ^"1 and silica gel (specific surface area 420 m ² · g" is ¹ in a molar ratio of SiO _2: Al ₂ O ₃ = 1: 5 continuously by means of a Lüftstromes by The solid particles are thereby converted completely to almost X-ray amorphous Al ₂ O ₃ -SiO ₂ solids.After suitable further processing, catalysts with excellent properties are formed.

example

A homogenized solid mixture of hydrargillite and silica gel in a molar ratio 1: 5 and nickel carbonate (3.5% Ni / molAl ₂ O ₃ ) and molybdenum oxide (14% Mo0 ₃ / molAI ₂ 0 ₃ ) is thermally activated according to the invention.

The degradation product has a firing residue of 97.5% and a specific surface area of 235 m ² / g. 500 g of this material were plasticized in a kneader with the addition of 2% concentrated HNO ₃ 30 min and then deformed by means of a screw extruder into extrudates with a diameter of 1.8 mm. These were predried and then calcined.

This catalyst was used to desulfurize a hydrocarbon fraction. The sulfur content was of 2.2%

lowered to 0.08% :,

The test result shows that the degree of desulfurization meets the requirements of a modern desulphurisation process. ,

Claims (2)

-1-255 798 5 Invention claims: 1. A process for the preparation of low-crystalline solid powders by thermal shock treatment, characterized in that powdery solid particles are shock-heated during the continuous transport by means of a carrier gas stream in a heated tube or tube reactor by radiation energy while thermally activated and / or partially destructured. 2. The method according to item 1, characterized dsdursh that is used as a carrier gas is inert with respect to the reaction inert gas or a reaction mstdem the solid.