Note: Descriptions are shown in the official language in which they were submitted.
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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
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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
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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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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
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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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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
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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.
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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.
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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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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
-- . . . . _ ~ -
-- 1 1 --
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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
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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
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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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