DE2158956A1 - Prepn of violet titanium trichloride - by plasma chemical conversion of titanium tetrachloride - Google Patents

Abstract

The violet modification of TiC, suitable for use as a polymerisation catalyst, esp. for propylene, is made by plasmachemical conversion of TiC., using low voltage/high current arc across metal electrodes, esp. of Mg, Al, Cd, Ti or Fe. around bottom flask is coated internally with TiCl4 and the arc struck. The electrodes are adjustable, esp. the cathode, to compensate for metal loss during separation. After about 1 hr. the arc is stopped and the flask contents are heated to distil off unconverted TiCl4. The process has a relatively low energy comsumption.

Description

Process for the preparation of titanium trichloride The present invention relates to a process for the production of titanium trichloride in its purple modification.

It is known to produce titanium trichloride by reducing titanium tetrachloride by using chemically reducing agents such as hydrogen organometallic compounds or metals, such as aluminum in particular, implemented will. Implementation with metal, e.g. B. aluminum, is usually very sluggish, so that a reaction acceleration through temperature increase or addition catalytically acting substances is required. The reaction with organometallic compounds z. B.

with aluminum triethyl, is usually quick, but it forms the so-called brown modification of titanium trichloride.

Only when tempering at elevated temperature does this become the for the Polymerization of e.g. B. Propylene obtained desired purple form type.

Even with the action of so-called silent electrical resp.

of glow discharges was already a reduction of titanium tetrachloride observed for the brown form of titanium trichloride. However, this is also sufficient do not run out of energy to produce the violet form of titanium trichloride directly.

It has now been found that the violet modification by plasma chemical Implementation of titanium tetrachloride in a low voltage / high current arc using can be obtained from metal electrodes. This creates the purple modification immediately, while at the same time the material of the cathode in stoichiometric Amount is consumed. Numerous metals are suitable as electrode material. Particularly Magnesium, aluminum, cadmium, titanium or iron have proven to be favorable.

It has been found that the conversion is generally Faraday Law in analogy to the known electrochemical reactions such as electrolysis corresponds, as can be seen in Table 1.

Table 1 Electrode g / amp.h amp.h / mole Mg 8.17 24.8 Zn 7.47 29.9 Cd 7.25 34.0 1 Faraday = 26.8 Amp.h / Mol The electrical voltage drop of the inside the liquid burning arc is relatively low with about 20 volts, so that the electrical energy required for this plasma-chemical conversion at high temperatures of some 10,000K is also relatively minimal, as Table 2 shows.

Table 2 Electrode kWh / kg Mg 2.45 Zn 2.68 Cd 2.76 As electrodes the respective metals are used in the form of compact rods with diameters usually from a few millimeters to a few centimeters. During operation as a direct current arc, the cathode material is evenly consumed, which is compensated by constant replenishment of the electrodes during prolonged operation. Operation is also possible with AC voltage, but the course of the Turnover under DC voltage is less disturbed by interruption. The ignition of the Arc is done by touching each other and immediately pulling the Electrodes immersed deep in the liquid.

The implementation can be carried out batchwise or continuously. Appropriately, it is submitted up to a conversion of about 10 wt Titanium tetrachloride led or at continuous operation With this composition the reactor contents are continuously discharged and fresh Titanium tetrachloride added again.

The difficult to move to pulpy suspension discharged is through Working up the unreacted titanium tetrachloride by distillation, the Titanium trichloride formed remains as a loose and finely divided violet powder.

However, if zinc electrodes are used, it will eventually form a rock-hard mass, which only after it has been crushed again (e.g. by grinding) is suitable for use as a polymerization catalyst.

Example One according to FIG. 1 with a reflux condenser 1 and two aluminum electrodes 2 equipped glass round-bottom flasks 5 of 1 liter content is under gassing with Nitrogen charged with 750 cm) of titanium tetrachloride. Both electrodes 2 are means Screw spindles 4 adjustable to compensate for the burn-off, in particular on the cathode side, a large adjustment range of the screw spindle 4 by remote control is provided via a flexible shaft 5.

According to the circuit diagram of Fig. 2, wherein L is a triple throttle for Limitation of the current flow, T a transformer and G a rectifier, a DC voltage of 1100 volts is applied to the electrodes. A 10 ohm resistor in the feed and a capacity of 300 micro-farads connected in parallel to the sheet serve to dampen the bow operation.

Immediately after the arc is ignited, shoot from the arc plasma Radiant streaks of initially brown-colored titanium trichloride emerge. Already After about a minute, the original water-clear contents of the flask have turned dark purple colored.

With an arc current of about 9 amps and an arc voltage of about 25 to 50 volts the titanium tetrachloride soon begins to boil, with the addition of evaporated liquid also purple Titanium trichloride fumes climb into the cooler 1.

After an hour, after turning off the arc, it becomes mushy Double violet suspension obtained from which, after distilling off the unreacted Titanium tetrachloride obtained 85 grams of a loose and finely divided violet powder will.

89.0% by weight of titanium trichloride were found in this powder.

Claims (2)

Claims 1. Process for the production of titanium trichloride by reducing Titanium tetrachloride, characterized in that titanium tetrachloride of the plasma chemical Implementation of a low voltage / high current arc using metal electrodes is exposed. 2. The method according to claim 1, characterized in that the metal electrodes consist of magnesium, aluminum, cadmium, titanium or iron. Blank page