U.S. patent number 3,656,888 [Application Number 04/863,197] was granted by the patent office on 1972-04-18 for liquid phase oxidation process.
This patent grant is currently assigned to American Metal Climax, Inc.. Invention is credited to Henry F. Barry, Calvin J. Hallada, Robert W. McConnell.
United States Patent |
3,656,888 |
Barry , et al. |
April 18, 1972 |
LIQUID PHASE OXIDATION PROCESS
Abstract
A process for effecting an aqueous liquid phase oxidation of
molybdenum disulfide to molybdenum oxide by agitating, at elevated
temperature, a slurry of molybdenum disulfide particles in water,
under pressure, in the presence of oxygen for a period of time
sufficient to effect the conversion of at least a portion of the
molybdenum disulfide to molybdenum oxide, and thereafter extracting
the molybdenum oxide product from the reaction medium.
Inventors: |
Barry; Henry F. (Ann Arbor,
MI), Hallada; Calvin J. (Ann Arbor, MI), McConnell;
Robert W. (South Lyon, MI) |
Assignee: |
American Metal Climax, Inc.
(N/A)
|
Family
ID: |
25340519 |
Appl.
No.: |
04/863,197 |
Filed: |
October 2, 1969 |
Current U.S.
Class: |
423/57; 423/606;
423/53 |
Current CPC
Class: |
C01G
39/02 (20130101); C01P 2006/80 (20130101) |
Current International
Class: |
C01G
39/02 (20060101); C01G 39/00 (20060101); C22b
059/00 () |
Field of
Search: |
;23/15,15W,18,19,140
;75/121 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Dresher et al., "Journal of Metals," June 1956, pp. 794-800. .
Usataya, "Chemical Abstracts," Vol. 47, 1953, p. 5,313..
|
Primary Examiner: Carter; Herbert T.
Claims
What is claimed is:
1. A process for converting molybdenum disulfide to molybdenum
oxide, which comprises the steps of dispersing a particulated
molybdenum disulfide-bearing material having an average particle
size less than about 20 microns in water forming an aqueous slurry
containing up to about 40 percent by weight of said material,
heating said slurry to a temperature of at least about 80.degree.
C. and agitating said slurry while in contact with an atmosphere
containing free oxygen at an oxygen partial pressure of at least
about 215 p.s.i. for a period of time sufficient to effect the
conversion of a major portion of the molybdenum disulfide to
molybdenum oxide and sulfur oxide acid products accompanied by a
progressive reduction in the pH of said slurry, and thereafter
recovering the molybdenum oxide product from said slurry.
2. The process as defined in claim 1, wherein said particulated
molybdenum disulfide-bearing material is of an average particle
size less than about 200 mesh.
3. The process as defined in claim 1, wherein said atmosphere
comprises air.
4. The process as defined in claim 1, wherein said atmosphere
comprises substantially pure oxygen.
5. The process as defined in claim 1, wherein said slurry is heated
to a temperature ranging from about 150.degree. C. to about
250.degree. C.
6. The process as defined in claim 1, wherein said oxygen partial
pressure is at least 300 p.s.i.
7. The process as defined in claim 1, wherein said slurry contains
from about 10 percent to about 30 percent by weight of said
particulated molybdenum disulfide bearing material.
Description
BACKGROUND OF THE INVENTION
Molybdenum does not occur as a free element in nature and is
principally found in the earth's crust in the form of molybdenite
(MoS.sub.2). Molybdenite somewhat resembles graphite in appearance
but has a specific gravity of about 4.5 to about 5.0 and is in the
form of soft, hexagonal, black flaky crystals. One of the principal
sources of molybdenite exists at Climax, Colorado, in which the ore
body consists of an altered and highly silicified granite with
about half the gangue being quartz through which the molybdenite is
distributed in the form of very fine veinlets. The molybdenite
concentration in the ore as mined usually is in the order of about
0.6 percent which, through known benefication processes, provides
for a further concentration of the molybdenum disulfide constituent
to amounts generally upwards of about 80 percent by weight.
Such ore benefication processes conventionally comprise a grinding
operation by which the ore is reduced to a particle size usually
less than about 200 mesh and wherein the particles are subjected to
a flotation extraction operation using a hydrocarbon oil, such as
pine oil or petroleum oil, in combination with wetting agents to
effect a separation of the molybdenum disulfide constituent from
the gangue.
While some of the molybdenum disulfide, after further purification,
is employed directly in the compounding of lubricants, the
predominant portion is converted to the oxide form in which it is
employed as an alloying constituent in various metal alloys or is
further reduced from the oxide form to the pure metallic state for
special uses.
It has heretofore been conventional to subject such molybdenite
concentrates to a roasting operation, effecting a conversion
thereof to the oxide form. For this purpose, circular open
hearth-type furnaces such as the Herreshoff furnace, had been
employed in which the molybdenite is heated in the presence of
excess air to form molybdenum trioxide and sulfur dioxide as a
gaseous by-product.
The present invention provides for an improved oxidation process
for effecting a conversion of molybdenum disulfide to the
corresponding oxide whereby the sulfur by-product constituent can
be recovered as a sulfate and the molybdenum constituent is
recovered as the trioxide. In accordance with this improved
process, it is now economically feasible to effect a liquid phase
oxidation of molybdenum disulfide to provide molybdenum trioxide of
high purity and in commercially acceptable yields.
SUMMARY OF THE INVENTION
The benefits and advantages of the present invention are achieved
by forming an aqueous slurry consisting of finely particulated
particles containing molybdenum disulfide dispersed in water which
is heated to a temperature preferably in excess of about 80.degree.
C. under an atmosphere containing free oxygen at an oxygen partial
pressure of preferably at least about 50 p.s.i. The slurry is
subjected to agitation sufficient to maintain a substantially
uniform dispersion of the particles through the aqueous medium and
to further effect entrainment and dissolving of the free oxygen in
the aqueous medium for reaction with the surfaces of the molybdenum
disulfide particles. As the reaction progresses, sulfur oxides are
formed, which in turn form sulfuric acid that effect a progressive
reduction in the pH of the reaction medium as the reaction
continues. The reaction is continued for a period of time, normally
about one to six hours, depending on the specific
temperature-pressure-particle size conditions employed, whereafter
the molybdenum trioxide product can be separated from the acidic
aqueous medium, such as by filtration.
It is usually preferred to subject the extracted solids to a wash
with ammonium hydroxide, effecting a conversion of the molybdenum
oxide to ammonium molybdate and leaving a solid residue consisting
of unreacted molybdenum disulfide and other insoluble impurities
such as the gangue. The solid residue, if desired, can be subjected
to further liquid phase oxidation to effect conversion of the
balance of the molybdenum disulfide to molybdenum oxide. The
resultant ammonium molybdate solution can be concentrated, such as
in an evaporator, and the crystals can thereafter be subjected to
calcination, providing a relatively pure grade of molybdenum
trioxide.
Further benefits and advantages of the present invention will
become apparent upon a reading of the description of the preferred
embodiments taken in conjunction with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
The drawing comprises a diagrammatic flow sheet of the process for
effecting a liquid phase oxidation of molybdenum disulfide to
molybdenum oxide in accordance with the preferred embodiments of
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The molybdenum disulfide starting material, as previously
indicated, may comprise a concentrate as derived from flotation
extraction operations in which molybdenum disulfide is usually
present in amounts in excess of 80 percent by weight and is in the
form of finely divided particles of a size usually less than 200
mesh. Concentrates of the foregoing type derived directly from the
ore benefication process are in the form of wet oily masses which
usually contain up to about 5 percent water and up to about 7
percent of the hydrocarbon flotation oils employed in the flotation
extraction operation. Such concentrates ordinarily require no
pretreatment prior to oxidation in accordance with the practice of
the present invention, although in some situations, it has been
found advantageous to remove the predominant portion of the
flotation oils to provide for increased efficiency in the oxidation
reaction. This is particularly true when only a single-pass liquid
phase oxidation reaction is employed. The removal of the flotation
oils or a reduction in the quantity thereof can be achieved, for
example, by retorting the concentrate, effecting a volatilization
and/or thermal degradation and decomposition of the oils, providing
a resultant substantially dry concentrate usually containing less
than about 0.5 percent oil and, more usually, less than about 0.1
percent. The retorting operation is conventionally carried out at a
temperature of about 1,200.degree. F., which also effects a
corresponding reduction in the water content of the concentrate.
Alternatively, the concentrate can be subjected to solvent washing
for removing the flotation oils followed by filtration to recover
the de-oiled molybdenite.
While such molybdenite concentrates consist predominantly of
molybdenum disulfide, about 5 percent to about 10 percent silica is
also normally present. Other metals are also present in minimal
quantities such as lead, copper, zinc, iron, aluminum, calcium,
magnesium, etc. The presence of such contaminating metals, which
are present in amounts of less than 1 percent, does not detract
from the efficiency of the liquid phase oxidation process
comprising the present invention. In those instances, however,
where a substantially pure molybdenum oxide product is desired free
from such trace quantities of contaminating metals, it is
contemplated that the concentrate can be subjected to further
leaching so as to effect an extraction of one or more of such
metals with any one of a variety of techniques well known in the
art.
In any event, the concentrate as derived from the mine, or as
derived after further pretreatment, is of an average particle size
of less than about 200 mesh and can be employed directly in forming
an aqueous dispersion without further comminution. While particle
sizes of less than about 200 mesh are satisfactory for the practice
of the process of the present invention, it is generally preferred
that the concentrate have an average particle size of less than
about 20 microns, and preferably less than about 5 microns, due to
the increased surface area which further promotes the efficiency of
the oxidation reaction. Particles of such smaller size also
facilitate the formation and maintenance of a substantially uniform
aqueous dispersion and are usually preferred for this purpose.
In accordance with the present process, the molybdenum disulfide
concentrate, as shown in the drawing, is discharged from a storage
hopper 2 into a dispersion tank 4 provided with an agitator 6 for
effecting the formation of an aqueous dispersion or slurry which is
intermittently or continuously transferred by means of a pump 8
into the inlet side of an autoclave 10. Depending upon the
particular particle size of the molybdenum disulfide concentrate,
slurries which contain up to about 40 percent by weight of
molybdenum disulfide based on the total weight of the slurry can be
formed. However, at concentrations at or above about 40 percent,
the slurry becomes excessively thick, occasioning problems in its
pumping and agitating and also its inhibiting effect on the
entrapment of oxygen in the slurry to effect the liquid phase
oxidation reaction. In view of the foregoing, lower concentrations,
generally within the range of from about 10 percent to about 30
percent by weight molybdenum disulfide based on the total weight of
the slurry, are preferred. While concentrations of the molybdenum
disulfide concentrate of less than about 10 percent can also be
satisfactorily employed, such lower concentrations are generally
undesirable from an economical standpoint due to the excessive
dilution of the material and the corresponding reduction in
processing capacity occasioned by such lower concentrations. In
view of the foregoing, best results are usually obtained when the
molybdenum disulfide concentrate is employed in aqueous dispersions
containing from about 10 percent to about 30 percent by weight of
the concentrate.
In accordance with the process as diagrammatically illustrated in
the drawing, the liquid phase oxidation in the autoclave 10 can be
carried out batchwise and also, preferably, in a continuous manner
as shown. In batch operations, it is convenient to form the
dispersion directly in the autoclave, while in continuous
operation, it is preferred to form the dispersion exteriorly of the
autoclave employing a dispersion tank 4, as shown in the drawing,
from which the slurry is continuously added to the inlet side of
the autoclave and passes in a serpentine manner, as provided by the
baffles 12, to the outlet side thereof. As shown, the autoclave 10
is further provided with an agitator 14 of the mechanical mixing
type for maintaining a substantially uniform dispersion of the
particles in the aqueous medium. Alternative agitation devices can
be satisfactorily employed in lieu of the mechanical propeller-type
agitator 14, illustrated in the drawing, including, for example,
sparger-type agitators through which the free oxygen-containing gas
is admitted under pressure into the autoclave in the form of a
stream of bubbles, imparting turbulence to the aqueous medium, as
well as effecting a contact of the free oxygen with the surfaces of
the molybdenum disulfide particles. Conventionally, a combination
of mechanical and sparger-type agitators have been found
satisfactory for providing a degree of agitation sufficient to
effect the continued dispersion of the molybdenum disulfide
particles and also to effect an entrainment of minute bubbles of
free oxygen in the aqueous medium for reaction with the surfaces of
the molybdenum disulfide particles. The agitation of the slurry
also promotes a mechanical scrubbing of the particle surfaces for
removing the film of molybdenum oxide formed thereon, thereby
exposing fresh molybdenum disulfide for further reaction with free
oxygen.
The provision of free oxygen in the autoclave 10 can be
accomplished by introducing pure oxygen gas through a supply line
16 or, alternatively, can be provided by air or a mixture of the
two. Additional free oxygen is continuously or intermittently
supplied to the autoclave to replenish that consumed during the
oxidation reaction. When air is employed as the source of free
oxygen replenishment, it is preferred to provide a vent line 18 in
the upper portion of the autoclave for continuously and/or
intermittently withdrawing gas from the upper portion of the
autoclave to avoid the formation of an atmosphere which is
excessively rich in nitrogen. The autoclave, as shown in the
drawing, is operated preferably from about one-half to about
three-fourths full with slurry, providing a vapor space at the
upper end containing free oxygen which becomes dissolved and
entrained in the aqueous reaction media.
In accordance with the foregoing arrangement, the particles of
molybdenum disulfide dispersed in water under heat and pressure and
in contact with free oxygen undergo an oxidation reaction in
accordance with the equation set forth below:
MoS.sub.2 + 9/2 O.sub.2 + 2H.sub.2 O .sup.Heat .fwdarw. MoO.sub.3 +
2H.sub.2 SO.sub.4
The rate of conversion of the molybdenum disulfide to the
corresponding molybdenum oxide and sulfuric acid products increases
as the temperature of the reaction medium increases, as the
pressure of the free oxygen increases and as the particle size
decreases, exposing a greater total surface area of the molybdenum
disulfide per unit weight. Reaction temperatures at or around room
temperature (22.degree. C.) have been found to result in only a
minimal oxidation of the molybdenum disulfide resulting in
conversions of only about 1 or 2 percent of the total charge within
reasonable reaction times. At higher temperatures, and particularly
at temperatures in excess of about 80.degree. C., the reaction
takes place more quickly and, for this reason, temperatures of at
least about 100.degree. C. are usually employed. Best operation
within normal equipment limitations has been attained by employing
temperatures within a preferred range of from about 150.degree. C.
to about 250.degree. C. The uppermost temperature limitation that
can be employed is dictated by the limitations of the bursting
strength of the equipment and ultimately by the critical
temperature of water.
At oxygen pressures at or about atmospheric pressure, the oxidation
reaction has been observed to be very slow and totally impractical
from a commercial standpoint. It has been discovered that as the
partial pressure of the free oxygen is increased to above about 50
p.s.i., a marked improvement in the rate of reaction and in the
product yield takes place. Particularly satisfactory results are
attained employing oxygen partial pressures of from about 300
p.s.i. up to about 600 p.s.i. or above. While oxygen partial
pressures in excess of about 600 p.s.i. have been found to provide
for further improvements in the reaction rate, the increases in
reaction rate at these higher levels become progressively smaller
and are not significantly greater than that attained at pressures
at or about 600 p.s.i. Additionally, oxygen partial pressures in
excess of about 600 p.s.i. require that the processing equipment
employed be of substantially greater structural strength, and it is
because of the foregoing considerations that the use of such higher
pressures is not ordinarily economically justified.
In accordance with the foregoing, the liquid phase reaction medium
preferably comprises an aqueous dispersion containing from about 10
percent up to about 30 percent by weight of molybdenum disulfide
particles of an average particle size of less than about 200 mesh
which is vigorously agitated at a temperature preferably ranging
from about 150.degree. C. to about 250.degree. C. in contact with
free oxygen present at a partial pressure of from about 300 p.s.i.
to about 600 p.s.i. Under the foregoing conditions, substantially
complete reaction and conversion of the molybdenum disulfide to the
corresponding oxide takes place within about one to about six
hours.
At the completion of the reaction, the acid aqueous slurry is
withdrawn from the autoclave and is transferred, as shown in the
drawing, to a filter 20 for effecting a separation of the
molybdenum trioxide reaction product from the filtrate. The filter
cake also contains unreacted molybdenum disulfide particles and any
other solid contaminating material such as the gangue present in
the original concentrate which is predominantly in the form of
silica. The aqueous filtrate which is acidic due to the presence of
the sulfuric acid formed during the oxidation reaction also
contains some dissolved molybdenum in the form of molybdenyl
sulfate. The acidity of the filtrate conventionally ranges from a
pH of about 0 to a pH of about 2.0, depending upon the
concentration of molybdenum disulfide in the original slurry charge
and the extent to which the conversion reaction has taken
place.
The filtrate discharged from the filter 20 is preferably
transferred, as shown in the drawing, to a neutralizer 22 in which
an alkaline compound, such as caustic, is added and causes
precipitation of the dissolved molybdenum trioxide. The
precipitated molybdenum oxide can be recovered in a filter 24. The
neutralized filtrate from the filter 24 can be suitably discharged
to storage and subsequently utilized as a source of sulfate.
It is also contemplated in accordance with the practice of the
present invention that a portion of the filtrate from the filter 20
can be recycled back to the autoclave or to the tank 4 used for
preparing the slurry prior to charging the autoclave. Generally,
however, the recycling of such acidic filtrate causes the initial
slurry charge to be slightly on the acid side, resulting in an
increased acidity of the reacted slurry as withdrawn at the output
end of the autoclave. For this reason, while a recycling of a
portion of the filtrate from the filter 20 can be accomplished,
generally the quantity recycled is small. In accordance with the
preferred practice, all of the filtrate is directly transferred to
the neutralizer 22.
The filter cake derived from the filter 20 consists of a
precipitated molybdenum trioxide product in combination with
unreacted molybdenum disulfide and a small proportion of inert
contaminants, such as silica, originally introduced with the
molybdenum disulfide concentrate. An extraction of the molybdenum
trioxide product from the filter cake is conveniently achieved by
transferring the filter cake to a wash treatment 26, in which it is
subject to an aqueous ammonium hydroxide wash solution prepared in
a make-up tank 28. The aqueous ammonium hydroxide wash solution may
range in concentration from about 1 to about 12 normal (N), and
preferably, concentrations of about 10 to 12 N are used in order to
minimize water dilution of the resultant molybdate solution. The
quantity of wash solution employed is designed to provide a molar
ratio of ammonia to molybdenum of preferably at least 2.3 up to
about 3.0. The wash solution effects a dissolving of the molybdenum
oxide by converting it to ammonium molybdate. The unreacted
molybdenum disulfide and solid contaminants are thereafter removed
in a filter 30 and the filtrate containing the dissolved ammonium
molybdate can be concentrated, such as by evaporation or in a
crystalizer 32, as shown in the drawing. The solid ammonium
molybdate derived from the crystalizer can be employed as a product
in that form or, alternatively, can be transferred to a calciner 34
in which it is heated, effecting an evolution of ammonium gas which
is recycled back to the ammonium hydroxide make-up tank 28. The
resultant molybdenum trioxide product is of high purity.
The filter cake derived from the filter 30 containing unreacted
molybdenum disulfide in combination with inert contaminants is
preferably accumulated and thereafter charged to a second autoclave
36 in which an aqueous slurry is formed and a further oxidation
reaction is carried out in accordance with the reaction as
previously described in connection with the autoclave 10. The
autoclave 36 similarly is provided with appropriate agitation and
means for introducing oxygen under pressure to effect a conversion
of the residual molybdenum disulfide to the corresponding oxide
with a formation of sulfuric acid in accordance with the reaction
equation as hereinbefore set forth. The reacted slurry is
transferred from the autoclave 36 to a filter 38 in which the
precipitated molybdenum trioxide particles are removed in
combination with the contaminating inert particles along with any
residual unreacted molybdenum disulfide. The filtrate from the
filter 38 may conveniently be transferred to the neutralizer 22 at
which it is treated with caustic in a manner as previously
described. The resultant filter cake from the filter 38 similarly
is washed with an aqueous ammonium hydroxide solution, effecting a
dissolving of the molybdenum trioxide product in a treating tank
40, whereafter it is transferred to a filter 42 for removal of the
undissolved solids which comprise essential inert contaminating
materials originally present in the molybdenum disulfide
concentrate. The filtrate from the filter 42 is conveniently
transferred and is mixed with the filtrate from the filter 30 for
further concentration in the crystalizer 32 in a manner as
previously described.
In accordance with the process as hereinbefore described, a
substantially complete conversion of molybdenum disulfide to
molybdenum trioxide of relatively high purity can be achieved in a
commercially economical manner and wherein the residual solid and
liquid waste products can be harmlessly disposed of by conventional
disposal means. The efficiency of the liquid phase oxidation
process in the first autoclave is evidenced by the attainment of
yields of converted molybdenum trioxide based on the original
molybdenum content of the concentrate as charged usually in excess
of 80 percent. The efficiency of conversion can be further improved
by employing a multiple-phase reaction as exemplified by the
continuous autoclave 10 and wherein any residual unreacted
molybdenum disulfide is subsequently substantially completely
converted to the oxide form using an auxiliary autoclave 36.
In order to further illustrate the process comprising the present
invention, the following examples are provided. It will be
understood that the examples are provided for illustrative purposes
and are not intended to be limiting of the scope of the invention
as set forth in the subjoined claims.
EXAMPLE I
A regular grade molybdenum disulfide concentrate derived from an
oil flotation extracted molybdenite ore from Climax, Colo., having
an average particle size of less than 200 mesh was employed for the
liquid phase oxidation reaction. The concentrate was washed 6 times
with acetone to remove the residual oils and was thereafter dried
for several hours at a temperature of 110.degree. C. The chemical
analysis of the de-oiled concentrate revealed that it contained
52.44 percent molybdenum and 35.54 percent sulfur with a sulfur to
molybdenum mole ratio of 2.03:1.
A 1-liter capacity autoclave equipped with a magnetically driven
agitator was employed for the liquid phase oxidation reaction. A
slurry was prepared by mixing 50 grams of the molybdenum disulfide
concentrate with 450 grams of water and charging the resultant
slurry into the autoclave. The autoclave was pressurized with
oxygen and thereafter heated, during agitation, to the operating
temperature. Heating was continued to provide a substantially
constant operating temperature of about 177.degree. C. (350.degree.
F.) with a total vapor pressure of 750 p.s.i. gauge of which the
calculated oxygen partial pressure was about 615 p.s.i. Since
initiation of the reaction occurs during the heat-up period, a
replenishment of the oxygen consumed during the heat-up period as
well as during the course of the reaction at operating temperature
was achieved by connecting the upper portion of the autoclave in
communication with a cylinder containing pure oxygen set at the
selected total pressure of 750 p.s.i.g. The reaction was carried
out for a period of 6 hours under continued agitation employing a
tubular stirrer shaft adapted to pull vapor from the vapor space
above the liquid slurry down through the stirring shaft, effecting
a distribution thereof at the lower portion of the slurry, thereby
assuring intimate contact of the molybdenum disulfide particles
with free oxygen. Agitation was controlled so as to maintain a
substantially uniform slurry of the particles and to assure
adequate gas-solid contact during the course of the reaction.
At the completion of the reaction, the charge was cooled and
filtered through a Buchner funnel and the filter cake was dried for
several hours at 110.degree. C. The filtrate, at the completion of
the reaction, was at a pH of less than zero. Thirty grams of the
dry filter cake thereafter was stirred with 250 milliliters of 5 N
ammonium hydroxide for 30 minutes at room temperature, effecting a
dissolving of the molybdenum oxide and the charge was thereafter
filtered and the residue again dried at 110.degree. C. and weighed.
The yield of molybdenum oxide was calculated based on the original
filter cake recovered and the weight loss of the ammonium
hydroxide-washed filter cake which revealed a conversion of about
88.4 percent of the molybdenum disulfide to molybdenum
trioxide.
EXAMPLE II
A second test was conducted employing the same concentrate and
equipment as previously described in connection with Example I. The
same procedure utilizing the same temperature and reaction
conditions, but a total pressure of 350 p.s.i.g., was used,
providing a calculated oxygen partial pressure of 215 p.s.i. The
resultant filtrate had a pH of 0.12 and an analysis of the reaction
residue revealed a conversion of molybdenum disulfide to molybdenum
trioxide of about 81 percent based on the original charge.
EXAMPLE III
A third test was conducted employing the same concentrate and
equipment as previously described in connection with Example I. The
same procedure utilizing the same temperature and reaction
conditions were used but a total pressure of 1,500 p.s.i.g. was
employed so as to provide a calculated oxygen partial pressure of
1,365 p.s.i. The resultant filtrate obtained had a pH of less than
zero and analysis of the reaction residue revealed that 89.8
percent of the molybdenum disulfide present in the original charge
was converted to molybdenum trioxide.
EXAMPLE IV
Still another test was conducted in which the same starting
material and apparatus was employed as previously described in
connection with Example I. In this specific run, however, air
rather than pure oxygen was employed to initially pressurize the
autoclave to a total pressure of 750 p.s.i.g., providing a
calculated oxygen partial pressure of 120 p.s.i. Replenishment of
oxygen as consumed during the reaction was accomplished in the same
manner as described in Example I. At the completion of a 6-hour
reaction period, the filtrate was observed to have a pH of 0.26 and
analysis of the reaction residue revealed a conversion of
molybdenum disulfide to molybdenum trioxide of about 54.1 percent
based on the molybdenum disulfide in the original concentrate
charged.
While it will be apparent that the description of the preferred
embodiments of the process comprising the present invention will
achieve the benefits as hereinbefore set forth, it will be
understood that the invention is susceptible to modification,
variation and change without departing from the spirit of the
invention.
* * * * *