CA1116374A - Process for the production of titanium disulphide - Google Patents

Abstract

A B S T R A C T

Titanium disulphide having a stoichiometry very near to the theoretical value may be produced by reacting titanium tetrachloride and hydrogen sulphide in the vapour phase under controlled temperature conditions, the product particles being entrained in a gas stream and thereby removed from the reaction zone. The partial pressure of the reactants is preferably also controlled. Product particles substantially consisting of particles having diameters in the range 1 to 50 microns may be produced. The product may be used as a cathode material in batteries.

Description

~P77 ` ~L1637~

This invention relates to the production of titanium compounds, particularly to the production of .itanium disulphide, Titanium disulphide has been proposed as, or for use in, lubricants. For such an application the precise stoichiometry of the titanium disulphide was not considered -to he of importance. It has now been suggested that titanium disulphide may be used as a cathode material in certain ty?es of hatteries and that for this end use it is important that the stoichiometr~ of such titanium disulphide be at or near the theoretical value.
~` United States Patent No. 3980761 describes a method ror the preparation of titanium disulphide which method comprises heating metallic titanium to a reaction temperature between ahout 400 C and 1000C, contactiny the heated titanium ith less tllan stoichiometric amounts of elemental sul~hur and then annealiny the titanium-rich non-stoichiometric titanium - disulphicle so produced at a temperature between about 400C and 600 C in an atmosphere haviny a sulphllr partial .~ 20 pressure suhstantially equal to the equilibrium sulphur partial pressure over titanium disulphide at the annealing temperature to for~ substantially stoichiometric titanium clisulphide. As s~ecifically described in the afQresaid United States Patent the reaction hetween the heated titanium

2~ and the elemental sulphur was allowed to proceed for one week -~id the annealiny stage of the process was then conducted f3r a further time of one week. Ti~anium disulphide so produced could be represented by the formula TiyS2 where y . . , - , .: . . , . ~ ...
, . ~ , , , , . , . ~ . , 37~

has a value from about 1.00 to 1.02.
The present invention relates to a new or improved process for producing titani-ml disulphide.
The present invention provides a process for the production of tita-nium disulphide which comprises reacting titanium tetrachloride and hydrogen ~: sulphide in an e~cess over the stoichiometric quantity for reaction with the : titanium tetrachloride in a dry oxygen free reactant gas mixture in a reaction zone, the titanium tetrachloride and the hydrogen sulphide being separately preheated to temperatures within at most 100C of each other and such that upon mixing the reactants, if no reaction were to take place, the temperature of the reactant gas mixture would be in the range of from 460C to 570C, :~ passing the reactant gas mixture through the reacti.on zone as a gas stream having a velocity sufficient to entrain particles of titanium disulphide as formed in the course of the reaction and subjecting the reactant gas stream to an inward positive heat gradient in the reaction zone by heat exchange with a material having a temperature not more than 100C above the said temperature in the range of from 460C to 570C, removing the gas stream containing the still entrained particles of titanium disulphide from the reaction zone and recovering the titanium disulphide particles.
The term "mixed gas temperature" is used herein to mean the tempera-~:~ ture which the reaction mixture would reach within the reaction zone if no reaction were to take place upon mixing and if the reaction stream were not subjected to the heat gradient. The mixed gas temperature is calculable from the volumes and temperatures of the constituents of the reactant gas stream, bearing in mind the possibility of heat losses during the transport of pre-heated constituents of the reactant gas stream to the : - 3 -'' 6~

~P77 .
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reaction zone.
When we reEer to a dry oxygen-free reactan-t gas mixture we mean -that normal precautions should be employed to remove ' water vapour and oxygen from the constituents of the gas Inixture so that the residual levels of these suhstances are as low as reasonably practicable. If water vapour is present in the reactant gas mixture it could react with the titanium tetrachloride resulting in the formation of small particles of titanium oxychloride. If oxygen is present in the reactant gas stream it could react with the titanium tetra-chloride to form small particles oE titanium dioxide.
T7tanium oxychloride or titanium dioxide so formed are undesirable impurities in the titanium disulphide product.
, Preferably the quantity of hydrogen present in the reactantgas stream is also as low as possible since its presenca could affect the stoichiometry or the titanium disulphide ,~ ~ product by a reduction mechanism.
The close control of temperatures is extremely important for the efficient operation of the present process. The mixed yas temperature is preferably not more than 560 C and, particularly preferably, not more than 540C. The mixed gas temperature is preferahly at least 470 C and, particularly preferabi~, at least 475C. Particularly suitahly the mixed gas temper~ture is from 475C to 510C.
Differences between the temperatures of the constituents -,- the reac-tant gas mixture are preferably minimised or avoided.
~-efçrably any difference between the temperatures of the constituents of the reactant gas mixture is less than 100 C

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~P77 ii3~

par-ticularly preferably less than 50 C.
~Iydro~en sulphide gas tends to decompose at lower -temperatures than rllicJht be expected from -the published literature. The decomposition of hydrogen sulphide gas during the operatiDn of the present process could result ln a relatively high content of sulphur in the titanium disulphide product. Since sulphur is an undesirable impurity it would be necessary to conduct a further process step to remove the sulphur, for example,by solvent extraction. The hydrogen sulphide should preferably, there-fore,not be preheated to a temperature above 600aC and further should preferably not be preheated using heat exchange surfaces having a tem~erature a~ove 650 C.
The positive inward heat gradient utilised in the present proces~ -tends to counteract any tendency for the temperature of the reactant gas mixture to drop ~ue to~the endothermicity of the reaction between titanium tetrachloride and hydrogen sulphide. Such a heat gradient may be achieved by heat exchange with a wall surrounding the reaction zone and maintained at or above the mixed gas temperature by external heating means. For example the wall may be equipped with electrical heating means and externally lagged to reduce heat loss. Preferably, and to ensure so far as possible that the temperature of the reactant gas stream dses not fall below 460 C the po~tive gradient is provided ~y heat exchange with a material having a temperature of at l~ast 490C, for example, by heat exch~nge with a reactor wall, P-eferably the said material has a temperature less than , I . , . , . ~ ; . , ., . ~, , . ~

i374 100C and particularly preferably less than 50C above -the mixed gas temperature employed.
Preferably the preheat temperature of each constituent of the reactant gas mixture and the temperature of the material used to achieve the positive temperature gradient ` are all in the range 460C to 570C.
Preferably the reactant gas mixture contains an inert diluent gas.
For the efficient operation of the present process it ;~ 10 is important to select the initial partial pressures of the constituents of the reactant gas mixture. Preferably the initial partial pressures of the titanium tetrachloride and the hydrogen sulphide are from 0.01 to 0.2-5 and from 0.05 to 0.60 atmospheres respectively. Particularly preferably the initial partial pressures of the titan1um tetrachloride and the hydrogen sulphide are from 0.02 to 0.20 and from 0.10 -to 0.50 atmospheres respectively, for example, from 0.03 to 0.12 and from 0.10 to 0.35 atmospheres respectively.
; ~ In one very efficient embodiment of the present process the titanium tetrachloride has an initial partial pressure of ~; from 0.05 to 0.12 atmospheres and the;hydroyen sulphide has an initial partial pressure of from 0.20 to 0.35 atmospheres.
The inert diluent gas may, for example, be argon, helium or nitroyen. Preferably the inert diluent gas is divided - between the titanium tetrachloride and the hydrogen sulphide and mixed with these gases before they are introduced into the reactant gas mixture.
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37gl Preferably, for the eEficient opera-tion of the present process, the hydrocJen sulphide is present in an excess or at least 25% and not more than 100% and,par-ticularly preferably,from 25~ to 75O in excess of the stoichiometric ~uantity for the formation of titanium disulphide.
Preferably~the present process is operated in a tube or tunnel reactor. Particularly suitable materials of construction for the reactor are silica or other similar re:Eractory materials. The reactor may be positioned vertically or horizonta]ly. It is a hasic requirement of the present process that the particles of titanium disulphide be formed in a gaseous medium. If the reactor is positioned vertically and the reactant stream flows downwardly the particles as ~formed will be in free~fall and a high minimum velocity in the reactant gas stream will not be necessary.
In such a case it is preferred that the reactant gas stream has a velocity yiving a ~eynolds Num~er of from 100 to 400.
On the other hand,if the reactant is pasitioned horizontally, a velocity hiyh enough to entrain the p~rticIes of titanium disulphide will be necessary. It is desirable to avoid,so far as possible,localised zones within the reaction zone in which hydrogen sulphide is not in excess over titani~
te-trachloride. L'referably,thererore,the reactants are in turbulence at their point of entry into the reactor and, ~or example, titanium tetrachloride may be passed into a turbulant ~--,dy of hydrogen sulphide. Pre-ferably the titanium '_~tL achloride and hydrogen sulphide are passed into a reactor in the form of streams having Reynolds Numbers of at least

3~

3000. Preferably the dimensions of the reac-tor are such that the reactant stream has a Reynolds Number below 2000.
Preferably the reactants have a residence time of from 2 to 20 seconds, for example from 3 to lO seconds, in the reaction zone.
The titanium disulphide particles are suitably separated from entraining gases by passing the gas stream to a collection box the box being maintained at a temperature above the dew point of volatile chlorides, e.y. TiCl4, present therein and preferably also maintained at a temperature not above 250C, Prererably the collection box is maintained at a temperature of from 130 C to 200C.
The titanium disulphide particles are then allowed to cool under dry oxygen-free gas such as nitrogen. The desired temperature control may be attained by the use of an unla~ged or partially layged pipe through which the entrained product is transported to the collection box from - the reaction zone. The product is preferably stored~
under an ;nert gas such as nitragen. Titanlum~disuIphide can be pyrophoric and the usual safety precautions should be us~d to prevent ignition.
The invention will now be illustrated by means of the following Examples. Examples 3 and 7 are according to the invention. Exam~les, l, 2, 4 and 6 are comparative Examples.
The reactor used was a vertically positioned silica ~_be 4 inches in diameter and 34 inches in len~th in the ^a;e of Examples l to 3 and 7 and ll~2 inches in diameter and l~ inches in lenyth in the case of Examples 4 to 6.

~P77 3~4 In -the 4" reactor 2n inlet pipe for TiC14 0.118 inches in diameter protruded axially 5 inches into the reactor from the upper end and H2S inlet pipe 0~118 inches in diameter was fixed tangentially into the reactor wall 31~ inches below the upper end of the reactor. The TiC14 and H2S inlet pipes were connected to preheaters and suitably lagged to reduce heat losses. The TiC14 was vapourised in a boiler before being passed to the preheater. The reactor was provided with external electrically operated heating means over the portion extending from 2 to 30 inches from the top of the reactor and was suitably lagged. Means to measure the temperature within the TiC14 and H2S inlet pipes and at the internal surface of the reactor wall were provided.
In the 1'~ inch reactor an inlet pipè for TiC14 0.118 inches in diameter protruded axially 3 inches into the reactor from the upper end. The H2S inlet was a 1 inch diameter pipe externally co-axial with the TiC14 pipe so that in use the~TiC14~ discharged into an atmosphere of S. A similar arranyement of co-axial tubes passing through a preheater was used to prehea-t the reactants.

The reactor was provided with external electrical heating means over the upper 14 inches of its length and was la~gecl.
Means for temperature measurement as in the 4 inch reactor ~ere provided.
2~ Both reactors opened into a collection box maintained at a temperature a~ove 136C in which particles of product ~7ere allo~ed to clisentrain.

:
~ , ~77 In carrying out Examples 1 to 6 preheated streams of TiC14 and H2S dilu-ted with argon were passed into -the reactor already heated to the desired temperature, reaction occuring while the resulting reactant stream was passing through the reactor. The resulting particles of titanium disulphide were collected and subjected variously to particle size analysis, x-ray diffraction analysis for structure and thermogravimetric and chemical analysis to - determine stoichiometry and the quantities of impurities.
lo Example 7 was carried out in a similar manner except that the diluent gas`was nitrogen. The TiC14 used was commercially pure, as used for the manufacture of titanium dioxide pigment by the chloride process~ The H2S used was commercially pure t>99% wt H2S) and, additionally, had been dried by passing it through a molecular sieve. The argon and nitrogen used were passed over solid manganous oxide in the cold and were then passed through a molecular sieve to remove moisture.
The process conditions and the results Qf t he examination of the products are shown in the following Table~

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~)~77 379~

TABLE
PART A

Example No.
_ _ ~1 TiC14 l/min 0.94 1 1.18 0.94 Diluent gas l/min10 10 10 Preheat C gas temp. 450 490 545-585 . _ __ . , -H2S l/min 3 3 3 ~iluent gas l/min10 10 10 Preheat C gas temp.450 .410 540-565 , .___ Reac-tant stream Mixed gas temp. C450 447 558 ~S/TiCl~ noles 3.125 2.5 3~075 TiC14 ) partial pressure 0.04 0.05 O.Q4 H2S ) (atmospheres) 0.125 0.12 0.125 , _ __ _ Reactor ~all tempO C 450 00 550-560 :` _ _ ,,~_ ~ :., _ .
. TiS2 product yield % 3 ~49 61 x in TiXS2 _ l, 1.0 1.02 . . Partic]e size ranye- ~ _ ' 1-2 1-20 .: Averaye- ~ _ ~ _ &
. X-ray diffraction analysic l .~ titaniu~-sulphide Di/-tri-¦ - di-Impurities S~ 3.8 1.6 . ~ _ ~ _ I _ 0.7 'J
-- . . . . _ ~ -., .

~77 37~}

TABLE
PART B
_ 7 ~ . ._._ _ ~ . ._. __ __ Example Mo. 4 5 6 7 ._ ._ _ _ _ _ _ _ ~_ TiCl~ l/min 0.490.45 0 n 96 2.2 Diluent gas l/min 2.8 3 3 7 Preheat C gas temp. S75 640 685 60-470 ~ ._ . _ _.
E~2S l/min 1.5 ¦ 0.6 2.0 6 Diluent gas l/min 0 0 0 7 Preheat C gas temp.575 6~0 685 70-500 =,__ ____............... _ _ ... .__ .
Reactant_stream Mixed gas temp. C 575 640 685 77 H2S/TiC14 moles 3 1 0.73 1~125 TiC14 ) partial pressure~ 0.1 0.15 0.16 0.09 ~-12S ) (atmospheres) 0.31 0.11 0.34 0.27 ~ ~ __ _ _ ._. .. _ .- __ Reactor wall temp. C 635 700 750 80-500 ..._ ..,.. ___. __._ _ . _ ~ _ TiS2 ~roduct yield ~ _ _ _ 84 x in TiX~2 1.06 1.1 1.2 1.00 Particle size range-~ ~.05-Q4 <1 <1 1-25 Average-~ 0.25 _ _ 15 ~X-ray dif-fraction analysis ¦titanium-sulphide _ _ _ di-Impuri-ties S% 6.5 4.1 8.5 0.54 Cl~ 0.4 0.9 1.1 0.8 0~77 37~

Example 1 - hardly any reaction occurred due to the low temperatures o -the titanium tetrachloride and hydrogen sulphide and the lo~ reac-tor wall temperature.
Example 2 - the product had exact stoichio~try but the yeild was reduced due to the lo~r temperature of the hydrogen sulphide and an insufficiently high mixed gas temperature.
Example 3 - the yield was good and the impurity levels in the product were low but the product has departed somewhat from exact stoichiometry due to the higher temperature used.
Examples - due to the increasing temperature there is an

4 - 6 unacceptable departure from stoichiometry and an unacceptably high level of sulphur ln the product.
Example 7 - the product has exact stoichiometry and a low sulphur and chlorine impurity level and was obtained in excellent yield.
Noté the change in the partial pressures of titanium tetrachloride and hydrogen sulphide in Examples 4-7 in comparison with Examples 1-3.
The particle size of the product of Examples 3 and 7 is particularly advantageous. It is a feature of this invention that the product does not have either the extremely small particle size characteristic of a prior vapour phase process (majority<2 microns diameter) or ~P77 ~i374 ,, ' ~, the very large particle size characteristic of prior fluid bed processes but has an intermediate size in the range 1 to 50 microns. It is a preferred feature of the invention that the product substantially consis-ts of particles having diameters in the range 1 to 25 microns and, particularly preferably, having an average particle size in the range 6 to 16 microns. The above described particle sizes are associated with particulær product utility.
~: ~ The subiect matter of this application is related to our Canadian copending application Serial No 296 369 filed February 7, 1978.

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Claims (19)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the production of titanium disulphide which comprises reacting titanium tetrachloride and hydrogen sulphide in an excess over the stoichiometric quantity for reaction with the titanium tetrachloride in a dry oxygen free reactant gas mixture in a reaction zone, the titanium tetrachloride and the hydrogen sulphide being separately preheated to temperatures within at most 100°C of each other and such that upon mixing the reactants, if no reaction were to take place, the temperature of the reactant gas mixture would be in the range of from 460°C to 570°C, passing the reactant gas mixture through the reaction zone as a gas stream having a velocity sufficient to entrain particles of titanium disulphide as formed in the course of the reaction and subjecting the reactant gas stream to an inward positive heat gradient in the reaction zone by heat exchange with a material having a temperature not more than 100°C above the said temperature in the range of from 460°C to 570°C, removing the gas stream containing the still entrained particles of titanium disulphide from the reaction zone and recovering the titanium disulphide particles.

2. A process as claimed in claim 1 wherein the mixed gas temperature is at least 470°C.

3. A process as claimed in claim 2 wherein the mixed gas temperature is not more than 540°C.

4. A process as claimed in claim 3 wherein the mixed gas temperature is from 475°C to 510°C.

5. A process as claimed in claim 3 wherein any difference between the preheat temperatures of the constituents of the reactant gas mixture is less than 50°C.

6. A process as claimed in claim 1 wherein the hydrogen sulphide is not preheated to a temperature of above 600°C and is not preheated using heat exchange surfaces having a temperature above 650°C.

7. A process as claimed in claim 1 wherein the heat gradient is provided by heat exchange with a material having a temperature of at least 490°C.

8. A process as claimed in claim 7 wherein the heat source has a temperature less than 50°C above the mixed gas temperature.

9. A process as claimed in claim 1 wherein the reactant gas mixture contains an inert diluent gas.

10. A process as claimed in claim 9 wherein the initial partial pressure of titanium tetrachloride in the reactant gas mixture is from 0.01 to 0.25.

11. A process as claimed in claim 9 wherein the initial partial pressure of the hydrogen sulphide in the reactant gas mixture is from 0.05 to 0.60.

12. A process as claimed in claim 11 wherein the initial partial pressures of titanium tetrachloride and hydrogen sulphide in the reactant gas mixture are respectively from 0.02 to 0.20 and from 0.10 to 0.50.

13. A process as claimed in claim 12 wherein the said initial partial pressures are from 0.03 to 0.12 and from 0.10 to 0.35 respectively.

14. A process as claimed in claim 13 wherein the said initial partial pressures æ e from 0.05 to 0012 and from 0.20 to 0.35 respectively.

15. A process as claimed in claim 1 wherein the hydrogen sulphide is initially in the reactant gas mixture in an excess of from 25% to 75% over the quantity required in theory to react with the titanium tetrachloride.

16. A process as claimed in claim 1 wherein the separately preheated titanium tetrachloride and hydrogen sulphide each mixed with inert diluent gas are passed into a reactor in the form of streams having Reynolds Numbers at their points of entry into the reactor of at least 3000 and the reactant gas stream formed in the reactor has a Reynolds Number below 2000.

17. A process as claimed in claim 1 wherein the residence time of the reactant gas in the reaction zone is from 2 seconds to 20 seconds.

18. A process as claimed in claim 1 wherein the titanium disulphide particles are separated from the entraining gases by passing the gas stream into a collection box maintained at a temperature above the dew point of titanium tetrachloride in the stream but not above 250°C.

19. A process as claimed in claim 18 wherein the collection box is maintained at a temperature of from 130°C to 200°C.