DE2329045A1 - METHOD FOR CLEANING UP TITANIUM TRACHLORIDE - Google Patents

Description

23290A5

Bayer Aktiengesellschaft

Central area of patents, trademarks and licenses

Gr / IK 509 Leverkusen, Bayerwerk

Process for cleaning titanium tetrachloride

The invention relates to a process for the continuous or batchwise purification of titanium tetrachloride from added vanadium compounds and other impurities by heating the TiCl ₂ in the presence of special cyclic aliphatic or aromatic compounds.

The so-called combustion process is also used today to produce white titanium dioxide pigments or optical oxides. In the process, TiCl ₁₁ and oxygen are converted directly to titanium oxide pigments at an elevated temperature. The TiCl ^ required for this is obtained by chlorinating titanium-containing materials such as ilmenite, leucoxene or rutile in the presence of carbon, but is contaminated by a large number of other chlorides (so-called ROh-TiCl _1. ). The chlorides of iron, aluminum and silicon, as well as the chlorides and oxychlorides of vanadium, are mainly present in TiCl _{2 ^.}

For the production of TiOg pigments with a pure white Hue, the removal of these impurities is absolutely necessary. As a cleaning method for titanium tetrachloride offers the distillation takes place. TiCl .. boils under normal

Le A 15 O65 - 1 -

409881/0570

23290A5

pressure at 136 C and can therefore be separated from most impurities such as iron, aluminum, silicon by distillation. In this way, a product can be obtained which is called "technical titanium tetra chloride" in the following. In this technical TiCl ₁ ^ vanadium is normally as VOCl ₃ (bp - 127 ⁰ C) or _VCl4 (kp - 154 ⁰ C) before; Both compounds are very difficult to separate from titanium tetrachloride due to their similar boiling points by distillation.

In order to simplify the laborious distillation, a number of proposals have already been made, almost all of them are based on the fact that vanadium is converted into a low oxidation state and then the TiCl ^ by distillation to separate. For example, cleaning methods with HpS (German Offenlegungsschrift 1 923 479), with animal and vegetable oils, fats, waxes, resins and soaps, with liquid or vapor or gaseous hydrocarbons, oils, fats, alcohols, ketones, organic acids, amines (Swiss Patent 365 393, 262 267, German Auslegeschriften 1 289 836, 1 275 524, 1 237 08I, Deutsche Patent 867 544, French Patent Specifications

1 466 478, 1 460 362) and with metals and metal salts (Belgian patent 539 078, German Offenlegungsschrift 1,922,420, German Auslegeschrift 1,271,693 and U.S. Patents 2,915,364, 2,871,094, 2,754,255,

2 56O 424, 2 555 361, 2 530 735) known. What effort is necessarily operated, can be seen from the German Offenlegungsschrift 2,135,250. To TiCl ^ with To clean a vanadium content of 50 ppm is under Addition of Benzolsulphonsäuredichloramid and metallic copper boiled under reflux and TiCl ^ distilled off, the then still contains 1 to 5 ppm vanadium.

Le A 15 O65 - 2 -

409881/0570

Additives that are easily cleaned from the skin are particularly beneficial TICK can be separated, either because they have a different boiling point or because they are in the form of solids can be removed together with the reduced vanadium compounds.

A particularly elegant, albeit uneconomical, process is the addition of titanium subhalides such as TiCl. When TiCl is added, after several hours of boiling at the boiling point, purified, colorless TiCl ₂ can be distilled off (US Pat. No. 2,178,685). The long reduction time required for vanadium oxychloride can be shortened to a few minutes according to a previously unpublished proposal by using TiCl, 0.33 AlCl, but the use of this process on an industrial scale is accompanied by the high price of the co-crystallized TiCl, 0.33 AlCl.

A process has now been found for purifying crude or technical titanium tetrachloride by treating with organic compounds with subsequent distilling off of purified titanium tetrachloride, which is characterized in that the titanium tetrachloride in the temperature range from 25 to 136 ⁰ C with a cyclic aliphatic or aromatic compound the series anthracene, furfural, cyclohexanol and / or xylene is treated individually or in any combination.

The organic compounds referred to react at temperatures from 25 to 136 ⁰ C, preferably at temperatures of about 60 to 100 ⁰ C, rapidly Vanadinchloriden or -oxychloriden and therefore also allow a continuous cleaning of the titanium tetrachloride. Although technical TiCIh is preferably cleaned according to the invention, further contaminants can also

Le A 15 O65 - 3 -

409881/0570

cleaning agents in addition to the vanadium chlorides contained in TiCl ^ be. Iron and aluminum chlorides «SiCl ^, ZrCl ^ or others Chlorides do not interfere. The presence of elemental chlorine leads to a corresponding higher consumption of the Reduction component, but offers the advantage that a further cleaning step, namely dechlorination, is saved can be. The compounds to be used according to the invention are so inexpensive that there is a somewhat higher demand as a result of Cl «is easy to carry and affects economy of the method according to the invention does not have a negative effect.

Today titanium tetrachloride in its water-clear form is a sought-after starting product for a multitude of areas of application. Particular emphasis is placed on a water-clear, light-stable TiCl ^. Up to now, a special cleaning stage was required to produce a light-stable titanium tetrachloride necessary. After adding the compounds according to the invention, for. B. of anthracene, can in a continuous Process based on that used in the chlorination of TiClj. resulting crude product is a water-clear, light-stable TiCIk can be obtained without additional purification steps.

The purification process according to the invention can be carried out continuously or in batches by adding a corresponding compound to the TlCl ^ and, after heating with subsequent distillation, a vanadium-free TiClb is formed. When the process is carried out continuously, crude TiClh, as is obtained after the separation of a large part of solid impurities (e.g. PeCl), and one of the cyclic aliphatic or aromatic compounds according to the invention, possibly suspended or dissolved in crude TiCl ^, are introduced into a distillation flask. During the subsequent distillation of the pure TiCl ^, the remaining solids accumulate, the reduced vanadium compounds

Le A 15 O65 - 4 -

409881/0570

bonds and the secondary products of the effective according to the invention cyclic aliphatic or aromatic compounds in the still and can at a solids content from 10 to 40 wt .- #, based on the contents of the distillation flask, continuously or partially discharged and evaporated. In the process, TiCl ^ distilling off can up to about 50 Jtf are added to the purified distillate, the rest can be mixed again with the crude TiCl ^ and the Solid can be obtained as a residue. This residue contains the vanadium in enriched form and can therefore used to make vanadium compounds. There is another major advantage of the process in a wide dosage range of the compounds used according to the invention as cleaning agents.

The amounts required for cleaning are about 0.1 to 5 mol, based on vanadium or 0.1 to 10% by weight , based on crude TiCl ^, depending on the vanadium content, preferably 0.2 to 1.5 wt -.% is used. When adding a sufficient amount occurs at temperatures above 25 ° C, preferably at 60 to 100 ⁰ C instantaneously reducing the VOCl, and it is a colorless or pale-colored distillate having a vanadium content of less than 10 ppm, usually less than 1 ppm obtained. The method according to the invention is to be explained in more detail in the following examples:

Le A 15 065 - 5 -

409881/0570

Example It *

A round-bottom flask equipped with a stirrer, column (30 cm) and distillation attachment is placed in a vessel with crude TiCl ^ with a vanadium content of 680 ppm and 1% anthracene, based on TiClj ₁₄ , is added. The suspension is heated to boiling and 80 % of the submitted TiCl ^ are distilled off directly. While the heating is still in progress, the reaction begins with the separation of a black precipitate. The distillate is pale yellow in color and contains less than 1 ppm vanadium. A second distillation leads to a water-clear TiClj. The residue can be easily discharged and shows no tendency towards caking on the flask wall.

Example 2:

The procedure is analogous to Example 1, only instead of anthracene with 1 wt .- # xylene, based on crude TiCl ^. That the resulting distillate shows an orange color. After a subsequent further distillation, a TiCl ^ in is obtained the desired pure form, which is suitable for the production of particularly white TiOp pigments.

Example 3:

In accordance with the foregoing Examples 1 and 2, a 680 ppm containing crude TiCl ^ without Fes is tstof fanteile with 10 g of furfural / kg TiCl ^ and heated to 136 ⁰ C. During the heating process, the VOCl begins to be reduced, the TiCIh turning dark and a solid, dark residue then being formed. The yellow distillate is subjected to a further distillation and then shows less than 9 ppm vanadium with a water-clear appearance.

Le A 15 O65 - 6 -

409881/0570

Example 4:

2 kg of a crude TiCl ^ obtained by chlorination of rutile are placed in a distillation flask and mixed with 20 g of cyclohexanol. After heating to the boiling point, a pale yellowish distillate containing 2 ppm vanadium can be drawn off directly. After a second distillation, a colorless TiCl ^ is formed, which is used for the Production of pigments or technical oxides of high purity is suitable.

Example 5t

Crude TiClh is placed in a round bottom flask equipped with a stirrer, dropping funnel and distillation attachment and heated to 60.degree. At temperatures above 60 ° C., 10 g anthracene / kg TiClj are added and the suspension is heated to the boil. At the beginning of the distillation, further vanadium-containing crude TiCl ^ with 700 ppm vanadium is introduced at the same time. The corresponding amount of anthracene (3 g anthracene / g vanadium) is added to the raw TiCl ^. The contaminated crude TiCl ^ is added to the extent that the vanadium-free distillate is withdrawn. Despite the unfavorable residence time spectrum, TiCl ^ can be obtained practically free of vanadium with a slightly yellowish color. A second distillation produces a water-clear titanium tetrachloride that can be used directly to generate TlO ₂ . The rapid reduction of the VOCl by anthracene enables the TICK to be continuously cleaned by adding crude TiCl ^ and anthracene to a reaction vessel, with purified TiCl ^ being distilled off.

Le A 15 065 - 7 -

409881/0570

Claims (2)

Patent claims: - -Κι) Process for purifying crude or technical titanium tetrachloride by treating with organic compounds with subsequent distilling off of purified titanium tetrachloride, characterized in that the titanium tetrachloride in the temperature range from 25 to 136 ⁰ C with a cyclic aliphatic or aromatic compound from the series anthracene, Furfural, cyclohexanol and / or xylene is treated individually or in any combination. 2) Method according to claim 1, characterized in that 0.1 to 10 wt -.% Of cyclic aliphatic or aromatic compound, preferably 0.2 - 1.5 weight -, related to the crude titanium tetrachloride used.%. J>) Process according to one of claims 1 and 2, characterized in that 0.1 to 5 mol of the cyclic aliphatic or aromatic compound, based on vanadium, are used. h) Use of anthracene, furfural, cyclohexanol and / or xylene individually or in combination for the purification of raw or technical titanium tetrachloride. Le A 15 Ο65 - 8 - 409881/0570