Titanium tetrachloride production

Details Titanium tetrachloride production Titanium tetrachloride production

2000-08-10

2002-07-23

Nguyen, Ngoc-Yen (Department: 1754)

Chemistry of inorganic compounds

Halogen or compound thereof

Binary compound containing metal

C423S076000, C423S078000, C423S079000, C423S082000

Reexamination Certificate

active

06423291

ABSTRACT:

This invention relates to the production of titanium tetrachloride, namely TiCl
4
. More particularly, the invention relates to a process for the production of TiCl
4
, which is useful in the production of titanium metal or titanium dioxide, by the chlorination of titanium values in a titanium-containing starting material.
According to the invention there is provided a process for the production of titanium tetrachloride (TiCl
4
) by the chlorination of titanium values in a titanium-containing starting material, the process including the steps of:
exposing the starting material to a chlorinating agent; and
contacting the starting material with an inert liquid, while the starting material is exposed to the chlorinating agent, the inert liquid being at a temperature of 200-350° C. and being at a pressure of 5-100 atmospheres (1 atmosphere=101.325 kN/m
2
), to cause the starting material to react with the chlorinating agent to form TiCl
4
.
Preferably the temperature is 225-300° C., eg 230-290° C. and the pressure is preferably 6-50 atmospheres, eg 10-50 atmospheres. Contacting the starting material with the inert liquid may be by immersing the starting material in the inert liquid.
The starting material may be in the particulate solid form, preferably finely divided solid form, with a particle size of less than 3000&mgr;m, preferably less than 100&mgr;m, the starting material having an average particle size of 1-3000&mgr;m, preferably 50-100&mgr;m. The process may accordingly include, as a preliminary step, size reduction of the solid starting material, for example by milling, to achieve the above maximum and average particle sizes. Immersing the particulate starting material may thus be by suspending particles thereof in the inert liquid, conveniently to form a slurry, for example a slurry in which the suspended particles form 2-50% by volume, preferably 10-30%. In other words, contacting the starting material with the inert liquid may be by immersing it as a suspension in the inert liquid to form a slurry, suspended particles of the starting material in the slurry forming 2-50% by volume of the slurry.
Suitable starting materials may include carbides of titanium, nitrides of titanium, carbonitrides of titanium, titanium monoxide (TiO), oxycarbonitrides of titanium (particularly those wherein the predominant titanium-containing crystals are in the cubic phase, such as Ti(O
x
, C
y
, N
z
) in which x+y+z=1, and mixtures of the aforegoing.
By an inert liquid is meant a liquid which reacts unacceptably neither with the starting material nor with any chlorinating agent or reductant in the reaction mixture at the reaction temperature and reaction pressure. The inert liquid may thus be a fully chlorinated liquid substrate, which is not prone to being further chlorinated, examples being SiCl
4
, VCl
4
, VOCl
3
, and in particular, TiCl
4
itself, so that the inert liquid may be selected from the group consisting of SiCl
4
, VCl
4
, VOCl
3
, TiCl
4
and mixtures thereof.
The chlorinating agent may be a suitable chlorine-containing compound, such as a chlorine-containing liquid or particularly a chlorine-containing gas. Examples of suitable chlorinating agents are HCl, CCl
4
, SCl
2
, and, in particular, molecular chlorine gas, namely Cl
2
. The chlorinating agent may thus be selected from the group consisting of HCl, CCl
4
, SCl
2
, Cl
2
and mixtures thereof. The chlorinating agent may be dispersed in the inert liquid, eg TiN, by dissolving it and/or dispersing globules or bubbles thereof in the inert liquid, conveniently under stirred and preferably turbulent conditions, to promote thorough mixing of the reaction mixture and contact between its reactive constituents, particularly between the starting material and the chlorinating agent. In other words, the chlorinating agent may be dispersed as a disperse phase in the inert liquid which forms a continuous phase, the inert liquid being agitated to promote dispersion of the chlorinating agent therein; and the agitation may be such as to produce turbulent conditions in the inert liquid to promote maintenance of homogeneous reaction mixture and rapid reaction between the starting material and the chlorinating agent.
The process may be carried out batchwise, or it may be carried out on a continuous basis.
When the process is carried out batchwise, it may be carried out in a reactor such as a temperature-controlled pressure vessel which is stirred or otherwise agitated, the pressure vessel containing a charge of inert liquid such as TiCl
4
and a charge of milled starting material having a maximum particle size of 100 &mgr;m and an average particle size of 50-100 &mgr;m, in which charge the starting material forms 10-30% by volume. The slurry may be heated to a temperature of at least 200° C., molecular chlorine liquid or gas then being admitted to the pressure vessel until an operating pressure of 10-50 atmospheres is reached. The chlorine will act strongly exothermically with titanium values in the starting material, to produce TiCl
4
. TiCl
4
in the vessel is permitted to boil at an operating temperature corresponding to the operating pressure, being vented as a constituent of a vapour from the pressure vessel to prevent the temperature and pressure in the vessel from exceeding the operating temperature and operating pressure respectively. Thus, in a particular embodiment, the process may be carried out batchwise in a pressure vessel in which the temperature and pressure are controlled and in which the inert liquid is agitated, the inert liquid being TiCl
4
, the starting material being a milled starting material having a maximum particle size of 100 &mgr;m and an average particle size of 50-100 &mgr;m and the starting material and inert liquid being present in a volume ratio of 10:90-30:70, the temperature being 225-300° C. and the pressure being 6-50 atmospheres, and the chlorinating agent being molecular chlorine (Cl
2
), TiCl
4
in the vessel being permitted to boil and being vented from the vessel, as it is produced, as a constituent of a vapour vented from the vessel, the venting being at a rate which keeps the temperature at a value of 225-300° C. and keeps the pressure at 6-50 atmospheres.
The TiCl
4
in the vented vapour can be regarded as product and can be condensed and separated from other constituents of the vented vapour, such as chlorine gas and other gases or vapours, the chlorine optionally being recovered for subsequent use in chlorinating another batch of starting material. Solid residues will remain in the pressure vessel, typically suspended in the inert liquid. The aforesaid batch reaction cycle can then be repeated, by loading a fresh charge of starting material into the vessel and chlorinating it as set forth above. Accumulated solid residues can be cleared periodically from the vessel; and the charge of inert liquid can be discarded and replaced, if and when it becomes unacceptably contaminated by dissolved or suspended impurities.
When the process is carried out continuously, a starting material such as titanium nitride, milled to a maximum particle size of 100 &mgr;m and an average particle size of 50-100 &mgr;m and mixed with an inert liquid such as TiCl
4
to form a slurry in which the solid material forms 10-30% by volume. The slurry may then be heated to a temperature of at least 200° C. as for batch operation and transferred, eg by pumping, to a suitable reactor operating at at least 200° C. such as a temperature-controlled pressure vessel which is agitated, for example an upflow slurry bubble-column reactor which may be fitted with baffles to resist back mixing and to the bottom of which liquid or gaseous molecular chlorine is introduced as chlorinating agent, eg via a sparger. As is the case with batchwise operation, the introduced chlorine reacts with titanium values, in strongly exothermic fashion, to produce TiCl
4
. Thus, in another particular embodiment, the process may be carried out continuously, milled starting material of a maximum particle size of 100 &mgr;m and avera

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