DD258909A3 - PROCESS FOR SHORT-TERM THERMOCHECK TREATMENT OF INORGANIC SOLIDS MIXTURES - Google Patents

Abstract

The object of the invention is a cost-effective, material-saving and environmentally friendly process for short-term thermal shock treatment of mechanically dispersed or activated solid mixtures based on hydrargillite in admixture with optionally SiO.sub.2 or SiO.sub.2-containing substances and / or metal oxides or metal compounds, preferably of these the IV. and / or VI. and / or VIII. Subgroup of the Periodic Table, to develop. This is achieved according to the invention in that a heated tubular reactor is used in which the ground or mechanically activated pulverulent solid mixture (a particle size of 0.1 to 45 m) in a gas stream of a linear flow rate of 5 to 20 ms 1 continuously transported through a tubular reactor and briefly thermally shocked within 0.1 to 10 s. The novel process is used for the preparation of catalyst components or catalyst intermediates.

Description

Field of application of the invention

The invention relates to a process for the brief thermal shock treatment of inorganic mixtures of substances, such as hydrargillite or hydrargillite-containing solid mixtures which optionally S1O2 or SiCV-containing substances and / or metal oxides or metal compounds, preferably those of the IV. And / or Vl. and / or VIII. Subgroup of the Periodic Table of the Elements, and are suitable as catalyst components or intermediates of the catalyst preparation.

Characteristic of the known technical solutions

It is known that alumina-based catalysts containing S1O2 and / or metallic active components can generally be prepared by very labor-intensive and material-intensive solution precipitation processes with numerous technological stages. In some cases, the compounds containing S1O2 and / or heavy metals are already added during the precipitation of highly dispersed aluminum-oxide gels and further processed together to form the catalyst.

Another method for producing such catalysts, which is also very frequently used, involves the sole precipitation of the Al 2 O 3 and Al 2 O 3 -SiO 2 components independently of the metallic additive, as well as their packaging and subsequent thermal treatment. The metallic active component is introduced in such catalyst variants only during the preparation or soaked in the finished calcined Al ₂ O ₃ or Al ₂ O ₃ -SiO ₂ -forming and further treated accordingly thermally.

The disadvantage of both methods is that a very large consumption of chemicals for the digestion of the hydrargillite or the precipitation of Aluminiumaquoxidgele itself or together with other catalyst components is required.

In addition, arise in such a solubilization-precipitation process, large amounts of by-products whose processing is cost-inefficient, and represent a large wastewater pollution.

Furthermore, various processes or principle solutions from the patent literature are known, based on which predominantly surface-rich aluminum oxides are obtained from partially dehydrated products, which in turn were obtained by short-term thermal activation of aluminum-containing solids.

A preferred embodiment of the short-term thermal heating of Aluminiumaquoxiden is to supply the solid particles to a hot gas stream (DT-OS 2059946.2411846). A disadvantage in such a method proves that the discharge or separation of the reactors are exposed by the hot gas of a very high thermal load. A decisive disadvantage is, in particular, that such a process control is difficult to control reproducible, resulting in fluctuating product qualities.

The patents (SU-PS 477113, 517564, US-PS 4166100) proposed by the principle of the fluidized bed reactors for the shock-like heating of aluminum trihydroxides. The use of a very narrow grain fraction of the starting material to create a stable fluidized bed over the entire reactor and the very close to the principle of the continuous stirred tank behavior (wide dispersion of the residence time of the solid particles) also cause an uneven and fluctuating composition of discharged from the reactor activated

Products. '

The documents (US-PS 3222129, DD-PS 62821, FR-PS 7909875.1 488218.1 364940, DE-AS 1 280231.1 592140) describe the thermal decomposition of the substance used in a combustion zone by direct contact of the solid powder with the Flame. When using such constructed reactors there are large temperature gradients over the length of the reactor and thus to a little controllable influence of the temperature on the solid particles whose residence time in the hot Brerinzone is subject to very large fluctuations. In such a procedure, it comes to uncontrolled hydrothermal conditions in the solid grain during the thermal treatment. A major disadvantage of this method is the unavoidable overheating of the solid particles in the reaction zone, which always leads to very difficult to control product heterogeneities. Partly well-crystallized Al ₂ O ₃ transition forms (usually chi-Al ₂ O ₃ ) are formed, which can not be further processed into corresponding catalyst components.

Also described are processes for the thermal decomposition of solids in which the mean residence time of the solid particles in the reaction zone is longer than that selected for shock-heating of solids (seconds range) but much shorter than the time required to produce well-crystallized oxide decomposition products needed. (DD-PS 203625, DD-PS 203038).

Therefore, hydrothermal conditions in the solid grain can not be ruled out in this principle solution as well, as a result of which well-crystallized foreign phases can form in the solid state or heal disturbances in the crystal lattice.

Accordingly, no low-crystalline or X-ray amorphous aluminas can be produced even after such a procedure. However, these are in the sense of a smooth further processing into catalyst components or '. Catalysts the target of short-term shock-heating.

The disadvantages of the known known technical solutions consist on the one hand in the inadequate ability to set defined and reproducible reaction conditions for the entire thermal degradation process and on the other hand to be able to realize the corresponding solution variants offered in the prior art in any case technically problem-free.

In the patent DD-PS 221160 examples are described, after which homogenized mixtures of solids are thermally treated by radiant heat in order to produce from the products obtained catalyst components can. A disadvantage of the case obtained by thermal radiation solid state properties mainly affects that no or only insufficient dispersion of the active components in the solid grain is achieved by this approach. Homogenization of the solid mixture before the thermal short-term treatment does not lead to a sufficient distribution of the individual components in the solid state during the shock-heating and thus also to undesirable heterogeneities in the composition of the products obtained. A particular disadvantage is that the solid state phases contained in the solid-state mixture due to relatively large particle dimensions can express only small or insufficient contacts at the phase boundaries, which can be improved only insufficiently during the thermal treatment.

Object of the invention

The aim of the invention is a process for the short-term thermal shock treatment of inorganic mixtures, which provides highly active thermal decomposition products based on alumina, in which the active components are well dispersed.

Explanation of the essence of the invention

The task is to develop a method for short-term thermal shock treatment of inorganic mixtures, which works cost-effective, material-saving and environmentally friendly.

This object is achieved by a method for short-term thermal shock treatment of inorganic solid mixtures, optionally silica or silicon dioxide-containing substances and / or metal oxides or metal compounds, preferably of those of IV. And / or Vl. and / or VIII. Subgroup of the Periodic Table of the Elements, can be solved by the invention according to the invention inorganic solid mixtures having a secondary particle size of 0.1 to 45 microns by means of a carrier gas at linear flow rates of 5 to 20 m · s ~ ¹ continuously through a tubular reactor having a LängerDurchmaßverhältnis be transported by at least 100 and subjected to a temperature shock between 623 and 973 K within 0.1 to 10 seconds.

It is particularly advantageous if the materials or material mixtures with secondary particle size between 0.1 and 5 pm at linear flow rates of 5 to 10 m · s ^-1 are used .erhitzt and pass through the reaction tube with a residence time between 0.2 and 2 s's, wherein air or oxygen and / or inert gas is used as the transport medium. The temperature shock is preferably carried out at 773 to 873 K. Vorteiihafterweise are contained in the solid mixture S1O2 or SiO ₂ -containing substances in an amount of 1 to 70 wt .-%. Furthermore, it is favorable if the starting materials used for the thermal shock treatment contain metal oxides or metal-containing compounds in an amount of 0.5 to 40% by weight, which components may be precipitated or impregnated onto the substances used before the thermal treatment. In this case, as the metal-containing compounds advantageously those of nickel, cobalt, molybdenum, tungsten or titanium are used.

For the implementation of the method according to the invention, it is important that a heated tubular reactor is used, which consists of the following components:

- The metered carrier gas supply

- the solids distribution system

- The solid dosage

- The flow tube reactor

- the heating system

- the separation system.

The reactor was constructed so that with a suitable choice of the linear flow velocity of the carrier gas from 5 to 20 m · s " ¹ both fine-grained, free-flowing and very fine, powdery substances or mixtures thereof with a particle size of 0.1 to 45 pm briefly a An advantage of the variant according to the invention is that the metering and separating device can be varied depending on the particle size of the solids used or their mixtures (use of calibrated nozzles, rotary valves, etc. for precipitated, dry, free-flowing starting materials and a fluidized-bed metering system For ensuring a continuous free passage of the solid particles (in particular of pulverulent substances or substance mixtures) through the reactor, it has proven to be very expedient to have a length: diameter ratio of the reactor tube of at least It is also of great advantage to adjust the linear flow rates mentioned in the beginning of the reactor in order to ensure, on the one hand, high turbulence of the solids-laden carrier gas stream and, on the other hand, to limit the dynamic pressure difference between the reactor inlet and outlet. The inventive solution of the problem allows the realization of a temporally and locally constant temperature field (in the temperature range up to 1 050 K), which also requires the guarantee of a uniform solid state dispersion in the heating zone and thus a continuously operating metering system.

To further minimize the temperature gradient between the reactor tube and the gas-solid mixture, the incorporation of special heat conduction and heat transfer surfaces has proved to be very advantageous. The flow direction of the gas-solid mixture can also be selected vertically in the direction of fall, with such a procedure of the reactor leads to several advantages, as in this way the occurrence of solid-state fluidized beds and thus the deposition of solid particles to certain parts of the reactor, especially during the on and Departure periods can generally be excluded.

The advantages of the solution according to the invention are to be seen in the fact that due to the continuous transport of solids through the reactor zone hydrothermal conditions in the particles of the selected grain fraction can be almost excluded, whereby the short-term thermal shock can lead to defined and reproducible degradation product.

embodiments example 1

According to the invention, a solid mixture of gibbsite (Residue on ignition of 65.7 wt .-% at 1073 K, specific surface area of 1.7 m ² · g ^"1 and a particle size fraction of 1 to 20pm) and a SiO ₂ -gei (specific surface area of 550 m ² g " ¹ ) in an amount of 20% by mass SiO ₂ (based on Al ₂ O ₃ ) for 0.5 h mechanically mixed. By means of an air stream of a linear flow velocity of 5 ms " ¹ , the solid mixture passes through the reactor within 0.2 s, passing through a temperature zone of 820 K and thereby degrading to a rho alumina or X-ray amorphous Al ₂ O ₃ -SiOa / solid ,

The thermal decomposition product obtained has a solubility of the solid in 5N NaOH of 63% by weight, has an incineration residue of 84.7% by mass and a specific surface area of 183 m ² .g.

Example 2

Dervorliegenden invention according to a pulverulent unground hydrargillite a particle size of 1 to 45 μηι, a Glückückstand of 65.8 Ma. -% at 1 073 K and a specific surface area of 1.7 m ² · g " ¹ from a supernatant TiCl ₄ solution of titanium soaked and dried at 290K for 24 h.

The hydrargillite impregnated in this way (0.5% by mass of TiO ₂ per mol of Al ₂ O ₃ ) was briefly thermally shocked according to Example 1, after which a degradation product of the following X-rayographic composition determined was obtained:

96% by mass rho alumina, 3% by mass hydrargillite and traces (<1% by mass) of titanium dioxide.

According to a corresponding chemical analysis, a content of 0.4Ma .-% TiO ₂ ZmOl Al ₂ O _{3 was} determined.

Example 3

According to the present invention, a solid mixture consisting of hydrargillite (65.7 wt.% Residue on ignition, 1.7 m ^2. Gsm. Average particle size of 25 μm) and silica gel (specific surface area of 550 m ² g ~ ¹ ) in an amount of 20% by weight of SiO ₂ and nickel carbonate (3.5% by weight of Ni per mole of Al ₂ O ₃ ) and molybdenum oxide (14% by weight of MoO ₃ per mole of Al ₂ O ₃ ) thermally activated according to Example 1, the decomposition product having the following composition:

90% by mass of rho-alumina, 10% by mass of X-ray amorphous Al ₂ O ³ -SiO ₃ and 3.2% by mass of Ni / mol Al ₂ O ₃ and 13.7% by mass of MoO ₃ / mol of Al ₂ O ₃ . ... ·. ,

The decomposition product has a residue on ignition of 97.2% by mass at 1073 K and a specific surface area of 235m ² -g- ¹ . , ''. '

Example 4

Using a solid mixture prepared according to Example 3, a hydrocarbon hydrorefining catalyst was prepared as follows:

In a kneader, 700 g of the thermally activated substance mixture were plasticized with about 3% by weight of concentrated nitric acid for 45 minutes and then shaped into extrudates with a diameter of 1.8 mm.

The resulting moldings were dried at a temperature of 400 K for 24 h and then thermally treated at a temperature of 750 K for 5 h.

The finished catalyst contained 3.2% by weight Ni / mol Al ₂ O ₃ and 13.7% by mass MoO ₃ / mol Al ₂ O ₃ with a residue on ignition of 98.2% by mass.

The catalytic test gave the following results in the desulfurization compared to a conventionally produced hydro-refining catalyst:

Test conditions - pressure in MPa = 55

Temperature in K = 593

Load in v / vh = 2

Gas / product ratio in mVm ³ = 500: 1

Raw material = vacuum distillate 623 K to 823 K ' ^i: '

Sulfur content 1.9% by mass

Test result - sulfur content in the raffinate in% by mass: 0.06

The results of testing the catalyst prepared according to Example 4 indicate that the degree of desulfurization achieved can be achieved to a corresponding extent in comparison with modern hydrorefining catalysts.

Example 5

According to the invention, a solid mixture of hydrargillite (produced in the VEB Alumini mwerk "Albert Zimmermann", Lauta) is characterized by details of the physico-chemical properties, see Table 1) and Si (VGeI (S _B et = 550 m ² · g). ¹ ) in an amount of 2 parts by mass in% SiO ₂ (based on Al ₂ O ₃ ) whose secondary particle size has been adjusted to a particle size range of from 1 to 20 μm within 30 minutes by the treatment in a tubular vibrating mill of the "Palla 35" type ,

By means of a carrier gas flow of a linear flow velocity of 5.5 m.s ^-1 , the mechanically pretreated solid mixture passes within 0.25 s of the reaction zone, where it is briefly thermally shock-treated at a temperature of 823 K. The mechanically activated in the tubular vibratory solid mixture with a particle size of 1 ^ 3 20μπι had a significantly reduced crystallinity of the starting mixture and a mean X-ray particle size of 25nm.

The short-term thermal shock treatment forms a rho-alumina which contains very small amounts of amorphous SiO ₂ -Al ₂ O ₃ (compare Figure 1, Sample 1). This product is characterized in particular by a pronounced channel shape of the pores, which are open on both sides, as shown by the curves of the adsorption-desorption isotherms of nitrogen shown in FIG. 2 (see sample 1). The specific surface area of the oxide decomposition product obtained is 230 m ² · g ^-1 .

Example 6 (comparative example, not according to the invention)

A solid mixture is used, consisting of Lauta-hydrargillite and SiO ₂ -GeI, whose grain fraction substantially coincides with those listed in Tab. 1, and the SiO ₂ content corresponds to that of Example 5. The X-ray characterization of the solid mixture used has with respect to the phase addition of hydrargillite very good crystallinity, wherein the determined X-ray graphic particle size is about 50 nm.

The resulting thermal decomposition product of the short-term thermal shock treatment (conditions analogous to Example 5) has the following properties:

The specific surface area is 266m ² · g ~ \ and the X-ray phase composition indicates a very heterogeneous product mixture, since in addition to chi- and gamma-Al 2 O ₃ there are also fractions of undecomposed hydrargillite and newly formed boehmite in the solid (see Figure 1) , Sample 2). Corresponding adsorption-desorption measurements with nitrogen show that products obtained in this way have a relatively broad spectrum of pores of different sizes and high proportions of pores of the "ink-bottle" form, which are closed on one side (cf., Sample 2, in FIG. , as can be taken from DEBOER JHP DEBOER for the classification of pores in solid bodies.

Table 1

Physical-chemical properties of the starting hydrogen carbide

parameter

analysis value

Resin (900 ° C / 4h) in wt% stoichiometry Na ₂ O content in wt% (based on Al ₂ O ₃ ) Fe ₂ O ₃ content in wt% (based on Al ₂ O ₃ )

Al ₂ O ₃ -3.00 H ₂ O

0.08 -.-.

X-ray diffractometry (phase composition)

very well crystallized hydrargillite

Electron and polarization microscopy

hexagonal panels, acicular particles, spherical agglomerates

Texture data Specific surface area in m ² · g " ¹ Porosity in% Total pore volume in cm ³ · g" ¹

Pore volume (Vp ₃ ) in the range of r _p <10 nm in cm -g ~ ¹

Vp, 10nm <r _p <90nm INCM -g V _p, r _p> 50 nm in cm ³ · g ^-1 80-90 μηη 0.01 0.07 100-250 μηη 250 μιη Particle size distribution (data in% by mass) <45μηη 45-63 pm 63-80 μιη 19.6 90-100 μιη 20.1 0.20 13.2 22.2 13.2 11.5

Claims (2)

1. A process for the short-term thermal shock treatment of inorganic solid mixtures, preferably hydrargillite or hydrargillite-containing substances which optionally contain silicon dioxide or silicon dioxide-containing substances and / or metal oxides or metal compounds, preferably those of IV. And / or Vl. and / or VIII. Subgroup of the Periodic Table of the Elements, at flow rates of 5 to 20m / s and residence times of 0.1 to 10s at temperatures of 623-973K, characterized in that inorganic solid mixtures having a secondary particle size of 0.1 ^ ε45μηη be exposed to a temperature shock. 2. The method according to claim 1, characterized in that the substances or mixtures used have Sekundärteilchengrößen between 0.1 and 5μηη.