PRODUCTION OF TITANIUM CHLORIDES

Abstract: Titanium dichloride and or titanium trichloride is produced directly from a titaniferous ore such as ilmenite by means of a selective chlorination reaction. A mixture of particles of the ore and particles of carbon is contacted at a temperature greater than 1500°C with a quantity of chlorine less than that required in theory for the production of titanium tetrachloride, for example, from 0.75 to 1.75 moles of chlorine per mole of titanium dioxide. Provided a sufficient quantity of carbon is used the iron content of the ore may be converted into the metallic form and recovered as such. The titanium chlorides produced may be further chlorinated to titanium tetrachloride.

Description: PRODUCTION OF TITANIUM CHLORIDES This invention relates to the production of titanium compounds and, in particular, to the production of titanium chlorides. There is described in US Patent No. 2 589 466 a process for the direct proauction of titanium tetrachloride from an iron-containing titaniferous ore by the selective chlorination of the iron content of the ore without allowing any iron present in the ore to be chlorinated. The process involves separately pre-heating ilmenite and chlorine tc a temperature between 0 0 1250 and 1450 C and maintaining them at such a temperature while bringing them together for reaction. British Patent No. 1 431 480 makes reference to US Patent 2 589 466 reports that attempts to repeat the process of the US patent had failed and suggests that this is consistent with the findings reported in the following papers: Suomen Kemistilehti, 29A, pages 220-225 (1956) Chemical Abstracts (1957) 4801(f) Transactions of the Metallurgical Society of AIME, 218, pages 219-225 (April 1960). British Patent o. 1 431 480 proposes an alternative prccess for the chlorination of the titanium constituent of a titaniferous material at a temperature of from 95O0C to 14000C in the presence of a carbonaceous material and a chlorinating agent comprising iron chloride. Titanium trichioride may be produced from titanium tetrachloride. Titanium dichloride may also be produced from titanium tetrachloride or, alternatively, from titanium trichloride. The present invention provides a process whereby the titanium di- and/or trichlorides, hereafter referred to collectively as lower titanium chloride, may be produced directly from a titaniferous ore. In its broadest aspect the present invention provides a process for the production of titanium lower chloride characterised forming a mixture of particles of a titaniferous ore and particles of carbon the mixture 0 having a temperature greater than 1500 C and contacting with the particles chlorine in a quantity less than that required in theory for the conversion of the titanium values in the ore to titanium tetrachloride. Preferably the mixture of particles in the form of a gaseous dispersion is contacted with the chlorine. According to a preferred aspect of the present invention the ore is an iron-containing titaniferous ore, for example ilmenite r or rutile, or a synthetic rutile and the particles are cause to react with chlorine according to one or both of the equations FeO.TiO2 + 3C + C12 = 3CO + Fe + TiC12 FeO.TiO2 + 3C + liy12 = 3CO + Fe + TiC13 and the resulting titanium lower chloride is separated from the metallic iron produced. Preferably a hot gaseous dispersion is heated according to this invention to at least 15500C, However, to avoid loss of reaction selectively to the desired products and the production of minor quantities of iron chlorides and/or titanium tetrachloride it is particularly preferred to maintain the temperature at at least l6000C. The energy input required for the reaction of the ore particles with chlorine according to the invention is higher for higher reaction temperatures quite apart from the tendency to increased heat losses from the apparatus at higher temperatures. This effect becomes very marked at temperatures above 20000C. For example, in an electrically powered reaction furnace the power input required for the reaction FeO.TiO2 + 3C + l¸C12 = 3CO + Fe + TiC13 may increase by up to about 500 kilowatt/hours per Mg of TiO2 in the ore for a reaction temperature of 22000C in comparison with a reaction temperature of 17000C. Preferably, therefore, the gaseous dispersion is heated 0 according to the invention to not more than 2000 C and, particularly preferably to not more than 19000C. The restriction of the chlorine supply to the reaction is an important parameter in the operation of this invention. An excess of chlorine leads to the formation of iron chloride and/or titanium tetrachloride whereas a deficiency leads to the incomplete reaction of the titanium values in the ore. Under the conditions above described an excellent degree of selectivity can be obtained where from 1 to 1i moles of chlorine are used per mole of titanium dioxide in the ore, titanium chloride or titanium trichloride predominating in the product depending on the actual quantity used within the above-stated range. A certain degree of process inefficiency may be acceptable in practice and, because of this, the invention is not rigidly limited to the use of a quantity of chlorine within the above-stated range. Preferably the quantity of chlorine used is not more than 0.25 moles and particularly preferably not more than 0.1 moles outside the preferred range of 1 to 1 moles per mole of titanium dioxide. Where a predominace of titanium chloride is desIred in the product less than 1.25 moles of chlorine, and where a predominance of titanium trichioride is desired in the product more than 1.25 moles of chlorine, are preferably used per mole of titanium dioxide. Because of the effect of the chlorine/titanium dioxide ratio on the selectivity of the reaction it is desirable to avoid variations in the ratio in the course of the process. It is noted that the present invention would not be possible to operate in a fluidised bed, could the desired temperature be generated in such a bed, because of the inevitable excess of chlorine at its point of entry into the bed. Titaniferous ores tend to sinter in a fluidised bed at any temperature above about 11000C. Carbon should preferably be used in excess of the quantity required to react with the oxygen released from the titanium values and the iron values, if any, in the ore. The carbon may be in the form of coke. The particles of ore and of carbon used in the practice of this invention are preferably not more than 500 microns and 3500 microns and particularly preferably are not more than 350 microns and 3000 microns in diameter respectively. It is an advantageous feature of the present invention that it allows the use of iron-containing titaniferous ores, such as ilmenite ore, without substantial contamination of the titanium chloride product with iron chlorides. Under the conditions utilised in the practice of this invention the iron values in the ore are not substantially chlorinated. It is a further advantageous feature of this invention that the iron values in an iron-containing titaniferous ore are reduced in the course of the process to metallic iron which, under the preferred temperature employed, may be in the liquid form. The liquid iron may simply be collected in a reservoir, tapped continuously or intermIttently, and cast directly into ingots if desired. The present invention may be carried out in any of a variety of electrical discharge furnaces capable of imparting temperatures in excess of 15000C to a particulate solid feed. Alternatively, the process may be conducted in an electrical induction furnace which has the advantage of not being subject to interference with a discharge by particles being treated, or products of that treatment, for example iron in liquid form, some of which may be electrically conductive. Suitably the process is conducted by allowing a mixture of particles of ore and carbon to fall through a reaction chamber in the presence of chlorine. The titanium lower chloride produced according to this invention may be further chlorinated, in the gas phase and preferably without recovery from the gaseous stream remaining after the removal of the metallic iron, to produce titanium tetrachloride. Such a use of the lower chloride product of the invention is particularly advantageous since it offers a particularly efficient method of producing titanium tetrachloride from an iron-containing titaniferous ore without the formation of iron chlorides. The further chlorination of the lower chloride is exothermic and is readily accomplished merely by mixing the gaseous stream, containing the lower chlorides, with the requisite extra quantity of chlorine. The further chlorination may be conducted at any temperature at which the lower chlorides and the titanium tetrachloride are stable and is preferably conducted at a temperature below 22000C and, particularly preferably, not above 20000C. Preferably the further chlorination is conducted at a temperature above 1000 C. Titanium tetrachloride formed may be recovered readily from the other gases present,and from any particles of carbon and ore which may not have reacted and which may have been carried through in the stream of gases, by known recovery techniques. Titanium trichloride produced according to this invention may, alternatively, be used in the manufacture of titanium metal by disproportionation at an elevated temperature to the metal and titanium tetrachloride, or as a catalyst in polymer production. Titanium dichloride produced according to this Invention may alternatively be used as a catalyst in polymer production. The present invention may give rise to the formation of phosgene. Normal precautions applicable to gases containing phosgene should therefore be applied. An Example of the operation of this invention will now be described. A coreless induction furnace Raydyne Model C95 was used. (Raydyne is a Trade Mark.) The heating chamber was of electrically conducting graphite because the charge is initially non-conductinc. This chamber was sealed at each end with a graphite screw plug and thermally insulated with ceramic wool. The chamber was 18 cms long 8 cm in external diameter and 4 cms internal diameter and arranged in a horizontal mode. There was facility to pass gas thrcugh the chamber and over the charge into a condenser for product collection. An induction coil fitted around the thermally insulated graphite chamber. Heat losses were minimised by surrounding the whole system in an asbestos box. The furnace had an output of 6 kw. 90 g of ilmenite ore (54% wt TiO2 and less than 500 micron mesh particle size) and 25 g of -SBSS mesh petroleum coke were placed in the heatinc chamber and power applied to the induction coil. When a temperature of 19500C was attained on the end of the chamber as measured by an optical pyrometer the power was switched off and a iridium/408 iridium-rhodium thermocouple lead down the gas feed facility indicated a temperature 0 f 1600 C inside the chamber. The thermocouple was v moved, the power was switched back on and chlorine gas passed over the reactants at the rate of 3 1/2 litres per minute for 5 mins. The power was switched off and the chamber purged with argon. A temperature of 1610C was measured in the chamber at the end of the run. Purple crystals mainly comprising TiC13 were condensed from the off gases. This lower chloride product weighed 31,8 g. When the furnace was cooled there was a small unreacted residue mainly of coke and some beads of solid iron weighing 13.6 grams and which analysed about 92% wt of metallic iron.

Claims: 1. A process for the production of titanium lower chloride characterised by forming a mixture of particles of a titaniferous ore and particles of carbon the mixture having a temperature greater than 15000C and contacting the particles with chlorine in a quantity less than required in theory for the conversion of the titanium values in the ore to titanium tetrachlcride. 2. A process as claimed in claim 1 wherein a mixture of particles of ore and carbon in the form of a gaseous dispersion is contacted with the chlorine. 3. A process as claimed in claim 1 or 2. wherein the ore is an iron-containing titanifercus ore, 4. A process as claimed in claim 2 or 3. wherein the gaseous dispersion of particles of titaniferous ore and of particles of carbon has a temperature of from 1550 C tc 20000 5. A process as claimed in any preceding claim wherein the quantity of chlorine is from 0.75 moles to 1.75 moles per mole of titanium dioxide in the ore. 6. A process as claimed in any preceding claim wherein the particles of ore are not more than 500 microns in diameter and the particles of carbon are not more than 3500 microns in diameter. 7. A process as claimed in any preceding claim wherein-the carbon is in excess of the quantity of oxygen released from the ore. 8. A process as claimed in any preceding claim conducted in an electrical discharge furnace. 9. A process as claimed in any one of claims 1 to 7 conducted in an electrical induction furnace. 10. A process as claimed in any preceding claim wherein the titaniferous ore is an iron-containing ore and the iron content thereof is recovered as the metal. 11. A process as claimed in any preceding claim wherein the titanium lower chloride produce is further chlorinated to titanium tetrachloride. 12. A process as claimed in claim 11 conducted by contacting the titanium lower chloride in the gas phase with a further quantity of chlorine. 13. A process as claimed in claim 11 or 12 wherein the titanium lower chloride is chlorinated at a temperature of from IOQOOC to 20000C. 14. Titanium lower chloride whenever produced by a process as claimed in any one of claims 1 to 10 15. Titanium tetrachloride whenever produced by a process as claimed in any one of claims 11 tc 13.

Inventors: ROBINSON, MICHAEL
Applicants: LAPORTE INDUSTRIES LIMITED
Application year: 1979
Main classification: C01G23
IPC codes: C01G23, C22B34