Note: Descriptions are shown in the official language in which they were submitted.
12496'~35
FIEL~ OF THE INVENTION
This invention relates to a Fischer-Tropsch
process for producing high amounts of C2 to C20
olefins, particularly those in the C2-C4 range, using
as a catalyst, an unsupported iron-cobalt sinyle phase
spinel, in which the atomic ratio of Fe:Co is 7:1 or
above.
DISCLOSURES IN THE ART
Fischer-Tropsch processes have long been
known to produce gaseous and liquid hydrocarbons con-
taining olefins. Because of the importance of these
olefins, particularly as feedstocks for the chemical
industry, modifications of the Fischer-Tropsch process
are constantly being pursued toward the goals of maxi-
mizing olefin selectivity with the particular objective
of maintaining high catalyst activity and stability
under the reaction conditions. The main thrust of the
efforts in this area has been in the area of catalyst
formulation.
Coprecipitated iron-based catalysts, inslud-
ing those containing cobalt, are known for producing
olefins. ~igh levels of cobalt in an iron-cobalt alloy
are known to produce enhanced selectivity to olefinic
products, as described in Stud. Surf. Sci. Catal. 7,
Pt/A, pp. 432 (1981).
Other disclosures in the art directed to
coprecipitated iron-cobalt catalysts and/or alloys
include: U.S. Patent 2,850,515, U.S. Patent 2,686,195,
U.S. Patent 2,662,090, and U.S. Patent 2,735,862; AICHE
~Z4~96(~5
1981 Summer Nat'l Meeting Preprint No. 408, "The
Synthesis of Light Hydrocarbons from CO and H2 Mixtures
over Selected Metal Catalysts" ACS 173rd Symposium,
Fuel Division, New Orleans, March 1977; J. Catalysis
1981, No. 72(1), pp. 37-50; Adv. Chem. Ser. 19~1, 194,
573-88; Physics Reports (Section C of Physics Letters)
12 No. 5 (1974) pp. 335--374;
J. Catalysis 72, 95-110 (19~1); Gmelins
Handbuch der Anorganische Chemie 8, Auflage (1959), pp.
59; Hydrocarbon Processing, l~lay 1983, pp. 88-96; and
Chem. Ing. Tech. 49 (1977) No. 6, pp. 463-468.
There is further disclosed a m~thod for
producing high surface area metal oxides in the French
article, "C. R. Acad. Sc. Parisn, p. 268 (28 May 1969)
by P. Courte and B. Delmon. The article describes a
process for producing high surface area metal oxides by
evaporating to dryness aqueous solutions of the cor-
responding glycolic acid, lactic acid, malic or tar-
taric acid metal salts. One oxide that was prepared by
their described method was CoFe2O4.
However, the above references do not des-
cribe or suggest the use of single phase iron-cobalt
spinels having an Fe:Co atomic ratio of 7:1 or above or
suggest their applicability in conductin~ or carrying
out Fischer-Tropsch processes for synthesizing
olefins.
What is particularly desired in fixed bed
Fischer-Tropsch processes are new catalysts for selec-
tively producing high levels of olefins and low levels
o methane under the desirable combined conditions of
high catalyst activity and stability.
12~36~5
SU~MARY OF THE INVENTION
It has been found that an unsupported
iron-cobalt single pnase spinel which is isostructural
with Fe304 as determined by X-ray diffractometry and
possesses an initial BET surface area of about 0.1 m2/g
and greater and an iron:cobalt atomic ratio of 7:1 or
greater provide desirable catalyst properties in
Fischer-Tropsch processes. It has also been found that
if a product predominating in C2-C~ olefins is desired,
a smaller spinel surface area, such as for example, in
the range of about 0.1 to 5 m2/g, would be preferred
while if a product predominating in C2-C20 olefins is
desired, a spinel surface area of greater than 5 m2/g
would be preferred.
Spinels can be conveniently prepared in a
high temperature solid state sintering reaction in a
temperature range of about 600 to 1100C between
stoichiometric amounts of mixtures of the componen~
metal oxides and/ or metals, in an inert or vacuum
atmosphere. The spinels prepared in this manner can
then be treated, if desired, with promoter agents, such
as Group Ih or IIA metal salts, and particularly
potassium carbonate. The resulting combined iron and
cobalt/potassium atomic ratio is desirably in the range
of about 2n:1 to 200:1. The promoted catalyst is then
reduced in a hydrogen containing gas and carbided
before use in the Fischer-Tropsch process.
In accordance with the above-described
procedure, there is provided a hydrocarbon synthesis
catalyst composition comprising an unsupported iron-
cobalt single phase spinel, said spinel having the
initial empirical formula:
12~96US
-- 4 --
Fex Coy 4
wherein x and y are integer or decimal values, other
than zero~ with the proviso that the sum of x + y is 3
and the ratio of x/y is 7:1 or above, said spinel exhi-
biting a powder X-ray diffraction pattern substantially
isostructural with Fe304 and said spinel having an
initial 8ET surface area of up to about 5 m2/g. If
desired, the spinel can contain a promoter agent, such
as Group IA or IIA rnetal salts.
Preferred embodiments of the co~position
include the substantially reduced and carbided form of
the spinel, which is an active Fisher-Tropsch catalyst
in processes for producing low molecular weight
olefins.
. .
Furthermore, the process for pro-ducing the
subject spinel portion of the composition comprises, as
mentioned above, the step of heating a mixture of
cobalt and iron, as their oxides, free rnetalsj or
mixtures thereof, to produce the empirical composition:
FexCoyO4, where x and y are integers or decimal values,
other than zero, and where the sum of x+y is 3, and the
ratio of x/y is about 7:1, or above, for a time
sufficient to produce said single phase spinel being
isostructural with Fe304, and having a surface area of
up to about 5 m2/q.
There is further provided in accordance with
the present invention, a process for synthesizing a
hydrocarbon mixture containing C2-Cs olefins comprising
the step of contacting a catalyst composition,
comprised of an unsupported iron cobalt spinel,
optionally promoted with Group IA or IIA metal salts,
said spinel initially exhibiting a single spinel phase,
. "
~2~ JS
being isostructural with Fe3O4, as determined by X-ray
diffractometry, and possessing an initial BET nitrogen
surface area of up to about 5 m2/g, and an iron-cobalt
atomic ratio of 7:1 or above, with a mixture of CO and
hydrogen under process conditions of pressure, space
velocity and elevated temperature for a time sufficient
to produce said C2-C6 olefins.
Generally, it is preferred that the spinels
have a surface area greater than S m~/g and, it has
been found that such high surface area, iron-cobalt
catalysts can be prepared by the process of adding an
alpha-hydroxy aliphatic carboxylic acid, e.g., glycolic
acid, to an aqueous solution containing dissolved iron
and cobalt salts and subsequently evaporating the
solution to dryness to yield an amorphous mixed metal
oxide, which on calcining at elevated temperature,
exhibits a spinel crystal structure and possesses a
high surface area.
These preferred unsupported high surface
area Fe-Co spinels prepared in this manner, possess
surface areas (BET) in the range of about 100-200 m2/g
(square meters per gram), which are significantly
higher than corresponding Fe-Co spinels prepared by a
process such as previously described.
After the optional addition of promoter
agents, by surface deposition or impregnation, such as
a Group IA or IIA metal salt, particularly an alkali
carbonate, the high surface area spinels are then
subjected to high temperature, e.g., 3no-400Oc, H2
reduction to obtain a fully reduced alloy, followed by
treatment with H2/CO at 300-400C to convert the alloy
to a fully carburized state.
12~96~5
The resulting high surface are a reduced and
carburized catalysts, provide unusually high activity,
selectivity and activity maintenance in the direct
conversion of CO/H2 to alpha-olefins under reactor
conditions. These catalysts are especially useful in
low pressure slurry reactor systems where alpha-olefin
residence times in the reaction zone can be minimized,
and the physical properties of the catalysit bed are
conducive to use of finely divided powdered catalyst.
In accordance with this last described
procedure, there is provided a composition of matter
comprising an unsupported, iron-cobalt spinel,
optionally promoted with Group IA or IIA metal salts,
said spinel exhibiting a single phase powder X-ray
diffraction pattern substantially isostructural with
Fe304, and possessing a BET surface area yreater than 5
m2/g and an iron-cobalt atomic ratio of about ? to 1 or
above.
Further provided is a composition of matter
comprising an iron-cobalt metallic alloy, being
isostructural with metallic alpha-iron, as determined
by X-ray diffractometry, and possessing a BET surface
area greater than 5 m2/g, said alloy being produced by
contacting the above-described Fe:Co spinel with a
reducing atmosphere.
Also provided is a composition of matter
comprising a reduced and carbided iron-cobalt alloy,
said composition being substantially isostructural with
Chi-FesC2 (Hagg carbide), as determined by X-ray
diffractometry, and possessing a BET surface area of
about 0.1 m2/g or greater, said composition produced by
contacting the above-described iron-cobalt alloy Witil
i24~36~S
-- 7 --
a carbiding atmosphere. ~ related composition is also
provided being isostructural with Fe3C (cementite) and
having a sE~ surface greater than 5 m2/g.
The process or producing the iron-cobalt
spinel composition described above comprises the steps
of: (a) evaporating a liquid solution comprising a
mixture of iron and cobalt salts of at least one
alpha-hydroxy aliphatic carboxylic acid, wherein the
molar ratio of total moles of said acid to total moles
of said iron and cohalt, taken as the free metals, is
about 1:1 or above, and wherein the atomic ratio of
iron:cobalt, taken as the free metals in said mixture
is greater than 2 to 1; yielding an amorphous residue;
and (b) calcining said residue at elevated temperature
for a time sufficient to yield an iron-cobalt spinel,
exhibiting a single spinel phase, isostructural with
Fe304, as determined by powder X-ray diffractometry.
The above-described iron-cobalt alloy
composition of matter may be prepared by a process
comprising contacting the above-described iron-cobalt
spinel, with a reducing atmosphere under conditions of
elevated temperature, pressure, space velocity for a
time suficient to substantially reduce the metal
oxides of the spinel.
The above-described reduced and carbided
spinel may be prepared by a process comprising the step
of contacting the above-described iron-cobalt metal
alloy, with a carbiding atmosphere under conditions of
elevated temperature, pressure, space velocity, for a
time sufficient to substantially carbide said alloy.
i:24~6~}5
-- 8 --
There i5 further provided by the present
invention a process for synthesizing a hydrocarbon
mixture containing C2-C20 olefins comprising the step
of contacting a catalyst composition, co~prised of an
unsupported iron cobalt spinel, said spinel initially
exhibiting a sin~le spinel phase being isostructural
with Fe304, as determined by X-ray diffractometry, and
possessing an initial BET surface area greater than 5
m2/~ and an Fe:Co atomic ratio of 7:1 or above, said
contactin~ conducted with a mixture of CO and hydrogen
under conditions of pressure, space velocity and
elevated temperature for a time sufficient to produce
said C2-C20 olefins.
DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
The subject iron-cobalt spinels useEul in
the subject process are as already noted compositions
of matter which are isostructural with Fe304, as
determined by x-ray diffractometry using copper K alpha
radiation and exhibit a single spinel phase. By the
term "spinel" is meant a crystal structure whose
~eneral stoichiometry corresponds to AB204, where A and
B can be the same or different cations. Included within
this definition is the commonly found spinel MgA1204. A
and B can have the following cationic cllarge combina-
tions: A=+2, B=+3, A=+4, B=+2, or A=+5, B=+l. Spinels
are arranged of an approximately cubic close-packed
arrangement of oxygen atoms with l/8th of the available
tetrahedral interstices and 1/2 of the octahedral
interstices filled, and can exhibit hundreds of
different phases. Further description of the spinel
structure can be found in "Structural Inorganic
Chemistry" by A. F. Wells, Third Edition, Oxford Press,
and the article "Crystal Chemistry and Some Magnetic
Properties of Mixed Metal Oxides ~ith the Spinel
~24~ 5
Structure" by G. Blasse, Phillips Research Review
Supplement, Volume 3, pp 1-30 (1964). By the term
"isostructural" is meant crystallizing in the same
general structure type in that the arrangement of the
atoms remains very similar with only minor changes in
unit cell constants, bond energies and angles. sy the
term "single phase spinel", as used herein, is meant
one structural and compositional formula, corresponding
to a single spinel material into which all of the metal
components are incorporated, and exhibiting one charac-
teristic X-ray diffraction pattern.
The subject iron-cobalt spinel possesses a
BET surface area of about 0.1 m2/g and greater,
preferably greater than 5 m2/g, as determined by the
well-known nitrogen gas BET surface area measurement
technique as described in the reference JACS ~0, p. 309
(1938) by S. Brunauer, P. H. Emmett, and E. Teller.
Generally, the spinel prepared by the above-described
sintering of component oxides has a surface area of
about 0.1 to 1 m2/g. This range of surface area
generally corresponds to a particle size range of about
1 to 10 microns. The spinel prepared by the above-
described procedure of evaporating a liquid solution of
a mixture of iron and cobalt salts of at least one
alpha-hydroxy aliphatic carboxylic acid and calcining
the residue at elevated temperatures has a surface area
of greater than 5 m2/g and generally in the range of
about 50-300 m2/g. This high surface area generally
corresponds to a particle size range of about O.nl to
0.002 microns.
The iron to cobalt atomic ratio of the
metals in the spinel is about 7:1 or above and is
preferably in the range of about 7:1 to 35:1 and
particularly preferred in the range of 19 to 20:1.
'`3~ 5
-- 10 --
The spinel can be represented by the for-
mula: FexCoyO4, wherein x and y are decimal or integer
values, other than zero, and wherein the sum of x plus
y is 3, and the ratio of x to y is 7:1 or above and
preferably being about 7:1 to 35:1. Particularly pre-
ferred is where the iron to cobalt atomic ratio is
about 19 to 20:1.
Representative examples of the various
spinels corresponding to the formula are
Fe2.85coo.l5o4~Fe2~625coo.37so4~ Fe2 97Coo 03o4 and
Fe2.2sCoo.75o4
Physical properties in general of these
subject spinels are similar to those of magnetite,
Fe34, and include: melting point of above 1400C, and
color of brownish to blackish.
The iron-cobalt spinels are used in unsup-
ported form in H2/CO hydrocarbon synthesis.
A promoter agent can also be used in the
composition and can be used to particularly promote
olefin formation in the process. Representative
examples of classes of suitable promoter a~ents include
alkali metal and alkline earth metal salts including
carbonates, bicarbonates, organic acid salts, i.e.,
acetates, inorganic acid salts, i.e. nitrates, halides,
sulfates, and hydroxide salts of Group IA and IIA
metals including lithium, sodium, potassium, cesium,
rubidium, barium, strontium, magnesium, and the like.
Preferably, the promoter agent is deposited or im-
pregnated substantially on the surface of said spinel
composition.
12L'~3 6~S
-- 11 --
Representative examples of specific promoter
agents are potassium carbonate, potassium sulfate,
potassium bicarbonate, cesium chloride, rubidium
nitrate, lithium acetate, potassium hydroxide, and the
like. Preferred are the Group IA compounds and a par-
ticularly preferred promoter agent is potassium carbon-
ate. The promoter, if used, is generally present in
about a 0.1 to 10 gram-atom % as the metal ion of the
total combined metal gram-atoms present. A preferred
level of promoter agent is in the range of 1 to 2 gram-
atom % of the total combined metal gram-atoms present.
In the empirical formulas used herein, the amount of
the promoter agent, e.g., potassium, is expressed in
terms of gram atom percent based on the total gram-
atoms of metals used. Thus, "1 gram-atom of potassium"
signifies the presence of 1 gram-atom of potassium per
100 total gram atoms of combined gram atoms of Fe and
Co. Thus, the symbol "1~ K" as used herein indicates 1
gram-atom percent potassium based on each 100 gram
atoms of the total combined gram atoms of iron and
cobalt present.
A particularly preferred spinel composition
of the subject invention is Fe2.85Coo.l504/1%K
(potassium taken as the carbonate).
The catalyst spinel in the subject process
may also be used in conjunction and admixture with a
diluent material; one which aids in heat transfer and
removal from the catalyst bed. Suitable materials
include powdered quartz, silicon carbide, powdered
borosilicate glass, SiO2, porous silica, kieselguhr,
zeolites, talc, clays, Group II to VII metal oxides and
rare earth oxides including TiO2, SiO2, A1203, MgO,
La203, CeO2, Cr203, MnO2j and the like. Preferred is
po~dered quartz.
lZ4~36(~S
- 12 -
The diluent, if used, is generally used in a
1:4 to 9:1 diluent/spinel catalyst composition weight
ratio. Preferred is a 1:1 weight ratio.
The utility of these spinels is their
ability upon subsequent reduction and carbiding to form
active catalysts in a Fisher-Tropsch process for makin~
C2-C20 olefins from CO/hydrogen.
The reduced and carbided forms of the above-
described spinel are also subjects of this invention.
As hereinabove described, a low surface area
spinel, i.e., up to about 5 m2/g, can be prepared by a
solid state high temperature reaction between (1) the
component oxides, i.e. Fe3O4 and Co3O4, or (2) a
mixture of iron metal, cobalt oxide and iron oxide,
i.e. Fe metal, Co304 and Fe203, or (3) a mixture of
cobalt metal, iron oxides and cobalt oxide, i.e. Co,
Fe304, Fe203 and Co304 or (4) a mixture of iron and
cobalt metals, iron oxide and cobalt oxide, i.e. Fe,
Co, Fe203 and Co304, in the correct stoichiometric
metals and oxygen ra~io to result in the empirical
formula for the composition as given above. Preferred
is indicated reaction (1) between iron oxide and cobalt
oxide. The reaction is conducted at temperatures in
the range of about ~00 to 1100C and preferably from
about 800 to 900C, in an inert gas, oxygen-free
atmosphere, or vacuum environment. Examples of useful
inert gases are helium, nitrogen, argon, and the like.
The solid state high temperature reaction "sintering"
should be performed on thoroughly mixed samples of the
metal oxides and/or metal and metal oxide mixtures. A
method of forming the mixture is by intimate grinding
and shaking. The sintering reaction should be conducted
1249~05
- 13 -
until a powder X-ray diffraction pattern indicates a
single spinel phase is formed, being isostructural with
Fe304, which generally requires about an 8 to 24 hour
period and preferably about a 12 to 18 hour period.
Generally, at the end of each reaction period the
material is thoroughly ground and mixed and then
resubjected to the high temperature conditions for an
additional 1 to 5 cycles or until powder x-ray dif-
fraction reveals the presence of a single spinel phase.
.
As hereinabove described, the preferred high
surface area i.e. greater than about 5 m2/g, spinel
composition can be made by a process in which an
aqueous solution of cobalt and iron salts of an
alpha-hydroxy aliphatic carboxylic acid, is evaporated
to dryness, leavinq an amorphous residue, which is then
heated at elevated temperature to substantially form
the spinel, in a single spinel phase, being isostruc-
tural with Fe3o4 and possessing a surface area greater
than 5 m2/g, preferable above 50 m2/g. The heating is
conducted such that no significant loss in surface area
of the final spinel is incurred.
The key to the synthesis of the subject
spinels is in the use of an organic, ~aturated,
aliphatic, alpha-hydroxy carboxylic acid to form a
complex salt, which is soluble in the aforementioned
aqueous medium, at a pH on the acidic side, i.e., pH of
5-7. The solubility of the iron and cobalt organic
salts of the alpha-hydroxy carboxylic acid prevent
crystallization from occurring, resulting in a
crystalline product being obtained from the solution,
which would possess a relatively low surface area.
1243~ 5
- 14 -
The subject method utilizes an alpha-
khydroxy aliphatic carboxylic acid which acts as a
solubilizing agent for the iron and cobalt salts in the
aqueous solution. ~ny saturated aliphatic alpha-
hydroxy carboxylic acid, containing at least one
alpha-hydroxy grouping, can be used to form the soluble
iron and cobalt salts in the subject invention process
in mildly basic aqueous solution, is deemed to be
incll~ded within the scope of this invention.
Representative examples of such acids which can be
mono-hydroxy or di-hydroxy or mono-carboxylic or
di-carboxylic are glycolic, malic, glyceric, mandelic,
tartaric, lactic acids and mixtures thereof. A
preferred carboxylic acid used in the process is
glycolic acid.
The amount of acid used is at least the
stoichiometric amount, i.e., 1 to 1 molar ratio for
each metal present and preferably in about a 5~10%
molar excess of the stoichiometric amount. Higher
ratios can be used, if it is economical to do so.
Lower amounts can also be used but would result in
incomplete iron and cobalt acid salt formation.
The first step in the process comprises
forming an aqueous solution by dissolving iron salts
and cobalt salts, in a water-soluble salt form such as
their nitrates, sulfates, chlorides, acetates, and the
like, in water.
The concentration of the salts in the
aqueous liquid is not critical to the extent that the
salts are present in less than a saturated solution to
avoid precipitation. For example, an 80-90~ saturated
9~S)5
- 15 -
solution, of combined dissolved metal molarities for
avoiding precipitation in the process, can ~e
effectively used.
The temperature of the aqueous solution is
not critical and may be above room temperature to aid
in the solubilizing process. However, room temperature
is adequate and is the temperature generally used in
the process. The pressure also is not critical in the
process and atmospheric pressure is generally used.
The aqueous solution can also contain a
small amount of organic solvent such as ethanolr
acetone, and the like for aiding in the solubilizing of
the iron and cobalt salts of the alpha-hydroxy
carboxylic acid.
Following the dissolving of the iron and
cobalt salts, the alpha-hydroxy carboxylic acid is
added, together with a sufficient quantity of base,
usually being ammonium hydroxide, sodium hydroxide,
potassium hydroxide, and the like, preferably ammonium
hydroxide, to solubilizing the resulting acid salts.
The amount of base added is sufficient to keep the pH
in the range of about 5 to 7Ø
It should be noted that the exact sequence
of steps need not be adhered to as described above,
with the proviso that the resulting aqueous solution
contain dissolved iron and cobalt salts in
stoichiometric amounts as iron and cobalt salts of
alpha-hydroxy carboxylic acid in solution. If there
are any insoluble materials present after addition of
the base and organic acid, they should be filtered
prior to the evaporation step.
i2~ V5
- 16 -
At this point, the resulting solution is
evaporated, as for example, by air drying, or under
reduced pressure, at elevated temperature, as practiced
in a rotary evaporator, or in a vacuum drying oven.
The resulting material from the evaporation
step is an amorphous residue, generally being a powder.
This residue is heated at elevated temperature at 100
to 600C for about 1 to 24 hours in generally air to
result in a substantially single spinel phase which is
isostructural with Fe2O4, as determined by X-ray
diffractometry, as previously described herein.
Preferred temperature range is 100-400C, and
particularly preferred is about 350C for single phase
spinel formation.
The details of the preparation of the high
surface area spinel as well as reduced iron-cobalt
alloys formed from the spinel by reduction and
carbiding procedures are fully set out in U.S. Patent
4,518,707 and are not included in the present
invention.
Prior to the hydrocarbon synthesis run, the
iron-cobalt spinel is reduced in a reducing atmosphere
at elevated temperature, generally in a temperature
range of about 2nO to 500C and preferably 300 to
450C. The reduction can be carried out with various
reducing gases including hydrogen, C0, and mixtures
thereof, and the like. Preferably, hydrogen gas,
either by itself or in an inert carrier medium such as
helium, neon, argon, or nitrogen, is preferably used.
The pressure of the reducing gas in this procedure may
be in the range of 1.5 to 1000 psig and preferably in
the range of 15 to 150 psig. The reducing gas feed rate
may be in the range of 1-10,000 V/V/hr and preferably
12'~6(~5
- 17 -
in the range of 10-1000 V/V/hr. The reduction is
carried out until the resulting Fe-Co alloy is sub-
stantially reduced and exhibits a powder X-ray diffrac-
tion pattern isostructural with alpha iron. This re-
duction usually requires about 2-20 hours.
In the reduction treatment of the low
surface area spinel, the resulting reduced spinel
generally has a BET surface area of up to 3 m2/g and is
useful in forming a carbided iron-cohalt catalyst
useful in the subjec~ Fischer-Tropsch process Eor
making C2 to C~ olefins as described herein.
In the reduction of the high surface area
spinel the resulting reduced spinel has a sET surface
area of greater than 5 m2/g, preferably in the range of
about 5-10 m2/g and particularly preferred in the range
of about 6-8 m2/g. These are useful in forming a
carbided iron-cobalt catalyst useful in the embodiment
of the subject Fischer-Tropsch process for making
C2-C20 olefins.
The iron-cobalt alloy can be prepared ex
s _ in a tube reactor or in situ in a Fischer-Tropsch
slurry process. The in situ preparation is conducted
in the slurry apparatus when the above-described spinel
is reduced while suspended in the slurry liquid, in a
reducing atmosphere being preferably a hydrogen
atmosphere at elevated temperature being about 240C,
or above, preferably at 240-300C, at a space velocity,
pressure, and hydrogen concentration sufficient to
cause substantial reduction of the spinel to the alloy.
Substantial reduction is complete when the X-ray
diffraction pattern shows a pattern substantially
isostructural with alpha-iron.
12~36~5
- 18 -
The iron-cobalt catalyst which is believed
to be the primary active catalyst in the process can be
produced by carbiding the reduced iron-cobalt spinel,
described hereinabove, generally having an X-ray dif-
fraction pattern isostructural with chi FesC2 (Hagg
carbide), by heating at elevated temperature in a suit-
able carbiding atmosphere, containing C0, H2/C0, and
mixtures thereof. The spinel can also be réduced and
carbided, concurrently, by contact with a C0/H2
atmosphere under the hydrocarbon synthesis conditions
described below.
Carbiding atmospheres which can be used
include C0/hydrogen, aliphatic hydrocarbons, acetylene,
aromatic hydrocarbons, and the like. A preferred
carbiding atmosphere is~C0/hydrogen. When using a
C0/hydrogen carbiding atmosphere, mixtures of
C0/hydrogen can be used in a 10:1 to 1:10 molar volurne
ratio. A preferred ratio used for carbiding purposes
is 1:1 molar ratio.
The carbiding step is generally conducted at
a temperature of 300 to 450C and preEerably 350 to
400C. The pressure is generally about 0.30 psig, and
a space velocity of about 200-1000 V/V/hr are chosen in
order to completely carbide the reduced iron-cobalt
spinel which can be subjected to X-ray diffractometry
to determine when the material becomes isomorphous with
Chi-Fe5c2- At carbiding temperatures above about
450C, the resulting Hagg type carbide,
Fes-(s/3)yco(s/3)yc2~ becomes unstable and can re-
arrange crystallographically to the corresponding
cementite type structure, Fe3_yCoyC. Also, in the ex
situ carbiding step, a significant amount of carbon is
~2~96~5
-- 19 --
also formed on the surface of the catalyst which tends
to increase the surface area of the reduced, carbided
catalyst.
A preferred method of carbiding the alloy is
in situ in the slurry liquid to be used in a slurry
Fischer-Tropsch process. A particularly preferred
method is where the spinel is treated with a mixture of
C0/hydrogen and reduced and carbided in situ in one
step prior to hydrocarbon synthesis. The pressure is
generally about 1 atmosphere, and a space velocity of
about 20-20,000 V/V/hr is chosen in order to completely
carbide the starting iron-cobalt oxide which can be
determined by X-ray diffractometry when the material
becomes isostructural with Haag carbide, Fe5C2. The
Haag-type Fe-Co carbides produced in this process are
of the general formula: Fes_(s/3)yC(s/3)yC2~ and also
include surface carbon produced during the`carbiding
process. Carbiding temperatures above 500C and
preferably 500-700C, lead to formation of a mixed
Fe-Co carbide of the general formula Fe3_yCoyC, which
is generally formed under ex situ procedures which
allow the use of higher temperatures than possible in
the in situ slurry procesC.
The above-described reduced spinel and
carbided spinel, when prepared ex situ are generally
pyrophoric and inconvenient to handle. In that case,
the material is generally passivated by contact with 1
volume oxygen in 100 volumes of helium for a sufficient
time to reduce or eliminate the pyrophoric nature.
Generally, the oxygen used in the passivating process
is used in an inert gas stream carrier such as helium
for a sufficient time to cause passivation. Generally,
this is conducted at room temperature and atmospheric
~Z~ 5
- 20 -
pressure and space velocity which are convenient and
easy to control and to result in an efficient process
needed for complete passivation.
The Fischer-Tropsch process utilizing the
catalysts described herein may be operated as a fixed
bed process or as a slurry-type process wherein the
catalyst is suspended in a liquid hydrocarbon and the
C0/hydrogen mixture forced through the catalyst slurry
allowing good contact between the C0/hydrogen and the
catalyst to initiate and maintain the hydrocarbon
synthesis process.
Advantages of a slurry process over that of
a fixed bed process are that there is better control of
the exothermic heat produced in the Fischer-Tropsch
process during the reaction and that better control
over catalyst activity maintenance by allowing con-
tinuous recycle, recovery, and rejuvenation procedures
to be implemented. The slurry process can be operated
in a batch or in a continuous cycle, and in the
continuous cycle, the entire slurry can be circulated
in the system allowing for better control of the
primary products residence time in the reaction zone.
The slurry liquid used in the process is a
liquid at the reaction temperature, must be chemically
inert under the reaction conditions and must be a
relatively good solvent for C0/hydrogen and possess
good slurrying and dispersing properties for the finely
divided catalyst. Re~resentative classes of organic
liquids which can be utilized are high boiling par-
affins, aromatic hydrocarbons, ethers, amines, or
mixtures thereof. The high boiling paraffins include
C10-C50 linear or branched paraffinic hydrocarbons; the
aromatic hydrocarbons include C7-C20 single ring and
~24~36~5
- 21 - ~
multi- and fused ring aromatic hydrocarbons; the ethers
include aromatic ethers and substituted aromatic ethers
where the ether oxygen is sterically hindered from
being hydrogenated; the amines include long chain
amines which can be primary, secondary, and ter-
tiaryamines wherein primary amines preferably contain
at least a C12 alkyl group in length, secondary amines
preferably contain at least two alkyl groups being Cg
or greater in length, and tertiary amines preferably
contain at least three alkyl groups being C6 or higher
in length. The slurry liquid can contain N and 0 in
the molecular structure but not S, P, As or Sb, since
these are poisons in the slurry process. ~epresent-
ative examples of specific liquid slurry solvents
useful are dodecane, tetradecane, hexadecane, octa-
decane, cosane, tetracosane, octacosane, triacontane,
dotriacontane, hexatriacontane, tetracontane, tetra-
tetracontane, toluene, o-, m-, and p-xylene, mesi-
tylene, Cl-C13 mono- and multi-alkyl substituted
benzenes, dodecylbenzene, naphthalene, anthracene,
biphenyl, diphenylether, dodecylamine, dinonylamine,
trioctylamine, and the like. A preferred liquid
hydrocarbon slurry solvent is octacosane.
The amount of catalyst used in the liquid
hydrocarbon slurry solvent is generally about 10 to 60
g. of dry catalyst per 500 g. slurry liquid. Preferably
about 30 to 50 g. dry catalyst per 500 q. slurry liquid
slurry is utilized, being in about a respective 5:1 to
10:1 weight ratio.
The slurry system, comprised of the slurry
liquid and finally divided catalyst, is generally
stirred to promote good dispersion during the pre-
treatment process to avoid catalyst settling and to
eliminate mass transport limitations between the gas
12~36~5
- 22 -
and liquid phases. In a typical laboratory unit the
rate of stirring is generally carried out in the range
of about ~00 to 1200 rpm and preferably lO00 to 1200
rpm.
Prior to the CO/hydrogen hydrocarbon
synthesis run, the reduced and carbided iron-cobalt
catalyst is generally conditioned in the slurry by
purging with nitrogen to remove reactive oxygen-
containing qases and then the temperature is increased
while stirrin~ to the reaction temperature range. Then
~he system is generally subjected to a hydrogen
-treatment for a sufficient time to insure complete
removal of any surface metal oxide present which would
interfere in hydrocarbon synthesis. The pressure and
space velocity during the inert gas-hydrogen con-
ditioning step are not critical and can be utilized in
the range which is actually used during actual hydro-
carbon synthesis.
Following the hydrogen reduction step, the
CO/hydrogen feedstream is introduced into the slurry
catalyst chamber and the pressure, space velocity,
temperature and hydrogen/CO molar ratio is then
adjusted, as desired, for hydrocarbon synthesis
conditions.
In the slurry process, the hydrogen and CO
are used in a molar ratio in the gaseous feedstream in
about a lO:l to l:10 molar ratio, preferably 3:1 to
0.5:1, and particularly preferred l:l to 2:1 molar
ratiO.
The temperature in the slurry process is
generally in the ranqe of about 200 to 300C,
preferably beiny 230 to 270C, and particularly
36U5
- 23 -
preferred of about 240-260C. Higher temperature
ranges can also be used but tend to lead to lighter
products and more methane, lower temperature ranges can
also be used but tend to lead to lower activity and wax
formation.
The pressure useful in the slurry process is
generally conducted in the range of about 50 to 400
psig and preferably about 70 to 225 psig. Higher
pressures can also be used but tend to lead to waxy
materials particularly in combination with lower
temperature.
The space velocity, expressed as standard
hourly space velocity (SHSV), used in the slurry
process is generally about 100 to 4,000 volumes of
gaseous feedstream/per volume of dry catalyst in the
slurry/per hour and $s preferably in the range of about
400 to 1,200 V/V/hr, and particularly preferred of
800-1,200 V/V/hr. Higher space velocities can also be
used but tend to lead to lower % C0 conversions, and
lower space velocities can also be used but tend to
lead to more paraffinic products.
Generally, after the pretreatment the
CO/hydrogen feedstream is introduced to initiate and
maintain hydrocarbon synthesis. By the use of the
above-described catalysts in the system, the activity
maintenance is very good and on a laboratory scale,
e.g., 500 cc of slurry containing 50 g. of catalyst
described herein, 30 days of continuous run have been
observed without significant decline in percent C0
conversion activity while maintaining good olefin
synthesis activity.
12496~35
- 24 -
The percent CO conversion obtainable in the
subject process, while providing substantial quantities
of olefins, ranges from about 30 to 80 percent or
higher.
"Total hydrocarbons'l produced in the process
is related to the selectivity of percent C0 conversion
to hydrocarbons being hydrocarbons from Cl to about C40
inclusive and is generally about 0 to 75 percent of the
total C0 converted, the remainder being converted to
CO2 .
In that embodiment of the subject process
utilizing a low surface area catalyst, the percent
C2-C6 hydrocarbons of the total hydrocarbons produced
including methane and above is about 10 to 30 wt.%. The
percent of C2-C~ olefins produced, of the C2-C6 total
hydrocarbons produced is about 80 to 90 wt.%. The
olefins produced in the process are substantially `alpha
olefins. In the embodiment utilizing a high surface
area catalyst, i.e., greater than 5 m2/g, the percent
of C2-C20 hydrocarbons of the total hydrocarbons
produced is about 60 to 90 wt.~. The percent of C2-C20
olefins produced, of the C2-C20 total hydrocarbons
produced is about 60 to 70 wt.%. Again, the olefins
produced are substantially alpha olefins.
The selectivity t~ methane based on the
amount of CO conversion is about 1 to 10 weight percent
of total hydrocarbons produced. Preferably about 5
percent, and lower, methane is produced in the process.
Preferably, the reaction process variables
are adjusted to minimize C02 production, minimize
methane production, maximize percent CO conversion, and
~2496~S
- 25 -
maximize percent C2-C20 and particularly C2-C4 olefin
selectivity, while achieving activity maintenance in
the catalyst system-.
Generally, this format can be derived in a
preferred mode of operating the process wnere the
slurry liquid used is hexadecane, the catalyst used is
re~uced, carbided Fe2 gsCoo.lsO4/1 ~ K as K2Co3, the
catalyst liquid weight ratio is 40/500, the system is
stirred at 600-1200 rpm, and the pretreatment procedure
is conducted in situ in a single step using 9:1 H2/N2,
at 220C, atmospheric pressure, 1200 V/V/hr space
velocity for a period of up to 5 hours, and the olefins
synthesis process conducted at a hydrogen:CO molar
ratio of 1:1, a temperature of about 2~5C, a pressure
of about 7-150 psig, and space velocity 1000-1200
V/V/hr. By carrying out the above process in the
stated variable ranges efficient activity maintenance
and production of C2-C20 and particularly C2-C6 olefins
can be acl~ieved.
The effluent gases in the process exiting
from the reactor may be recycled, if desired, to the
reactor for further CO hydrocarbon synthesis.
As hereinbefore mentioned, the subject
process may be carried out as a fixed bed process
utilizing the claimed catalysts described herein.
Prior to the CO/hydrogen hydrocarbon syn-
thesis fixed bed run, the iron-cobalt spinel is gener-
ally conditioned in the apparatus by purging with ni-
trogen to remove reactive gases and then the tempera-
ture is increased to the reaction temperature range.
Then the system is generally subjected to the above-
described hydrogen treatment for a sufficient time to
i2~9~S~5
- 26 -
insure complete reduction of metal oxides. However, the
pressure, space velocity, and temperature during this
reduction step are not critical and can be utilized in
the range which is actually used during actual hydro-
carbon synthesis.
Following the reduction step, the CO/hydro-
gen feedstream is introduced into the fixed bed
apparatus catalyst chamber and the pressure, space
velocity, temperature, and hydrogen/CO molar ratio aee
then adjusted as desired, for hydrocarbon synthesis
conditions. Optionally, the reduction/carbiding can be
carried out concurrently by contact with the CO/H2
mixture at elevated temperature.
In the fixed bed process, the hydrogen and
CO are used in a molar ratio in the gaseous feedstream
of about a 10:1 to 1:10, preferably about a 3:1 to
0.5:1 molar H2/CO ratio and more preferably 1:1 to 2:1
molar ratio. Higher and lower molar ratios may also be
used.
The temperature in the fixed bed process is
generally in the region of about 200 to 300C and
preferably being 250 to 280C. Higher temperatures,
such as in the range 300-350C, tend to promote higher
~ CO conversion, lighter products, more methane and
more CO2, formed from the water-gas shift reaction.
The pressure useful in the fixed bed process
is generally conducted in the range of about 50 to 1000
psig and preferably about 100 to 300 psig. Higher and
lower pressures can also be used.
i2~ S
- 27 -
The space velocity, used in the fixed bed
process is expressed as "standard" hourly- space
velocity (SHSV) and is generally about 200 to 4000
volumes of gaseous feedstream/per volume of dry
catalyst (excluding diluent)/per hour and is preferably
in the range of about 400 to 1200 V/V/hr. Higher and
lower space velocities can also be used where higher
space velocities tend to lead to increased olefin
contents but decreased % CO conversion.
The percent CO conversion obtainable in the
subject fixed bed process while providin~ substantial
quantities of C2-C6 olefins, ranges from about 20 to
98% and preferably above about 30%. Higher and lower
ratio percentages of CO conversion may also be
utilized.
"Total hydrocarbons" produced in the fixed
bed process is related to the selectivity of percent Co
conversion to hydrocarbons, being hydrocarbons from Cl
to about C40 and above inclusive, and is generally
about 0 to 50 percent, and higher, of the total CO
converted and the remainder being substantially
converted to CO2.
The percent total C2-C6 hydrocarbons of the
total hydrocarbons produced in the fixed bed process,
including olefins and paraffins is generally about 20
to 80 wt. ~ and preferably about 50 to 80 wt. ~. The
percent of C2-C6 olefins produced of the C2-C6 total
hydrocarbons produced is generally about 50 to 9~ wt. ~
and preferably about 70 to 90 wt. ~ of the C2-C6 total
hydrocarbons. The olefins produced in the process are
substantially alpha olefins.
- ~2496~S
- 28 -
The seleetivity to methane in the fixed bed
proeess based on the amount of CO eonversion is about 2
to 12 weight percent of total hydrocarbons produced.
Preferably about 10 percent and lower methane is
produced in the process.
As diseussed above, the pereent selectivity
to CO2 formation in the proeess is in the range of
about 10 to 50 pereent of C0 eonverted, and generally
about 30 to 50 pereent.
The reaction process variables in the fixed
bed process are preferably adjusted to minimize CO2
production/ minimize methane production, maximize
percent CO conversion, and maximize percent C2-C6
olefin seleetivity, while achieving activity main-
tenance in the eatalyst system.
The eatalyst in the process may beeome con-
taminated with high molecular weight hydrocarbons on
exposure to carbon monoxide hydrogenation reaction
conditions. As a result of this catalyst aetivity may
be diminished. In the event that this is observed it
may be possible to reeover nearly full catalyst
activity by exposing the catalyst to a solvent wash
and/or hydrogen treatment at elevated temperatures. We
have found that this proeedure ean in some cases
restore the catalyst with its initial performanee
characteristics.
Generally, this format can be achieved in a
preferred mode of operating the fixed bed process where
the formula of the catalyst used is Fe2 85Co0 15O4/1%
K. The pretreatment procedure is conducted at 500C in
a 9:1 H2/N2 stream @ 580 v/v/hr. under 100 psig for 5-7
hours, and the hydrocarbon synthesis run is conducted
:~2~6~5
- 29 -
at the CO/hydrogen molar ratio is 1:1 to 2:1, the tem-
perature is conducted in the range 230-270C, at a
pressure of 150-300 psig, and space velocity 1000-1800
v/v/hr (SHSV). By carrying out the above process in the
stated variable ranges efficient activity maintenance
and production of C2-C6 olefins can be achieved.
The effluent gases in the process exiting
from the reactor may be recycled if desired to the
reactor for further CO/hydrocarbon synthesis.
Methods for collecting the products in the
process are known in the art and include distillation,
fractional distillation, and the like. Methods for
analyzing the product liquid hydrocarbons and gaseous
streams are also known in the art and generally include
gas chromatography, liquid chromatography, high
pressure liquid chromatography and the like.
Apparatus useful in the subject process can
include any conventional fixed bed type reactor, being
horizontal or vertical, moving bed, fluid bed, and the
like or any conventional slurr~"-type reactor for
carrying out the slurry-phase type of operation. The
slurry-type reactors can be horizontal or vertical,
stationary or cyclical. Other apparatus not speci-
fically described herein will be obvious to one skilled
in the art from a reading of this disclosure.
The following examples are illustration of
the best mode of carrying out the claimed invention as
contemplated by us and should not be construed as being
limitations on the scope and spirit of the instant
invention.
~Z4~6~5
- 30 -
EXAMPLE 1
Solid solutions with the generic empirical
formula: Fe3_yCoyO4/1%K (1 gram-atom percent potassium
as the carbonate) were prepared by the following pro-
cedure. Mixtures of Fe2O3, Fe metal and Co3O4 in the
following molar ratios, (4/3 - 4y/9) Fe2O3 + 1/3
(l-y/3) Fe + y/3 Co3O4,where the value of y indepen-
dently was: 0, 0.03; 0.150; 0.375; and 0.750, corres-
ponding respectively to the following weights in grams
of Fe2O3, Fe metal, and Co3O4; 21.080, 1.8~00, 0.00;
22,750, 1.9891, 0.2594; 21.797, 1.9054, 1.2974;
20.0163, 1.7502, 3.2338; 11.381, 0.9590, 4.2904. The
materials (reagent quality or better from Alfa
Chemicals Co.) were well mixed, placed into a quartz
tube, evacuated to 10-3 torr, sealed in the tube under
vacuum and then heated to 800C for 24 hours. The
resulting solids were isoiated after cooling and break-
ing the tube open, ground to a powder, and resubjected
to the same high temperature sintering procedure, at
800 to 1000C for an additional 24 hours. Powder X-ray
diffraction analysis was then conducted to ensure that
the sintered material was isostructural with pure stan-
dard sample of Fe3O4. The catalyst powder was then
pelletized and sintered in a sealed tube as described
above under vacuum at 1000C for several hours. The
sintered pellets were then crushed, seived and the
resulting pellets impregnated with aqueous potassium
carbonate to achieve the desired potassium loading,
being about 1 gram-atom percent potassium, and dried.
The BET (nitrogen) surface areas measured were in the
range from about 0.25 to 0.30 m2/g. The results are
listed below in Table I.
` 1249~'5
- 31 -
TABLE 1
Compositio~ Fe3_ Co 04/1% K
Y Y
y BET (m2/g)
Control 0.00 0. G7
A 0.0275 0.30
B 0.150 0.29
C 0.375 0.25
D 0.750 0.28
The powder x-ray diffraction spectrum of
each of the obtained Fe-Co spinels showed that they
were a single phase and isostructural with Fe3O4. They
differed from one another in slight shifts of the 2
theta reflection values without altering the overall
profile,
EXAMPLE 2
Catalyst 8, Fe2.gsCo.lsO4/1% K, where y =
0.15, was prepared by the procedure described in
Example 1. X-ray diffraction analysis showed this
material to be isostructural with Fe3O4, although there
was a slight change in the unit cell constant where the
unit cell constant is about 0.01 to 0.02 ~ smaller than
that of Fe3O4. The sintered material was found to have
a low surface area, less than 5 m~/g. This material
was crushed and sieved to 20-80 mesh before use in this
example under F-T (Fischer-Tropsch) fixed bed reaction
conditions. The reactor was charged with 8.8 cc of
catalyst with a thermocouple placed at the center of
the bed. The catalyst compositions of 20-80 mesh par-
ticle size, were pretreated with hydrogen gas in nitro-
gen (90% hydrogen/nitro~en) at 500C, 100 sccm (680
v/v/hr.) of hydrogen gas at 100 psig for 5 to 7 hours
~24!~6~5
- 32 -
in a fixed bed tubular vertical reactor constructed of
316 stainless steel, and being 0.51" internal diameter
and lS" long. The runs were conducted using a 1:1
H2/CO mixture, at 570 v/v/hr., 300 psig, at the indica-
ted temperatures, which are furnace temperatures in
this and the remaining examples unless otherwise indi-
cated as bed temperatures. In many of the cases, the
bed temperature was 10-30C higher than the indicated
furnace temperature, due to primarily to the limited
heat removal capabilities of the reactor system and the
highly exothermic nature of the reaction. The overall
collected products which were collected after catalyst
pretreatment, and one hour on stream with C0/H2, were
analyzed by gas chromatography.
Representative results obtained with
catalyst composition B, Fe2 gsCoo lsO4/1%K, relative to
the control (see Table I) are presented below in Table
II
- 1249~i~S
-- 33 --
TABLE II
CatalystFe3O4/1%KaFe2.85C0.154/1%K
Temp C 305 270
C0 Conversion 79 98
CO to CO2 36 42
% CO to HCC 43 56
Wt. % Selectivity
CH4 8.5 9.1
C2H6 2.1 4.3
C2H4 6.5 9.8
C3Hg 1.4 1.9
C3H6 10.6 20.3
C4Hlo 1.7 tr.
C4Hg 9.5 9 3
C5~ 59.7 45.2
acOntrol -
bComposition B.
CHydrocarbons.
As is seen from the data, Catalyst B,
derived from the cobalt-containing spinel, exhibited
greater activity at lower temperatures and higher C2-C4
olefin selectivity than the all iron control catalyst.
It should be noted that unless stated dif-
ferently herein, the catalysts used in each of the
following examples were in powder form of 20-80 mesh,
used as is, or diluted with crushed quartz powder,
totalling a catalyst volume of about 8-8.8 cc.
12496~$
- 34 -
Further, the apparatus used was the same as
described in this Example 2 and the pretreatment
procedure was substantially the same as described in
Example 2.
Values for selectivity weight percentages of
product hydrocarbons are reported on a CO2-free basis
unless otherwise stated.
EXAMPLE 3
Four (4) cc. of Catalyst B, described above
in Example 2, was mixed with 20-80 mesh solid quartz
powder (crushed quartz tubes) in 4.0 cc quantity, and
the mixture was placed into the reactor described.in
Example 1, and pretreated by contacting with a 9:1
H2/N2 feedstream at 500C, 750 v/v/hr., 100 psig, for
5.5 hours.
The mixed diluted catalyst was then con-
tacted with 1:1 H2/CO at 270C, 300 psig, at 2000
v/v/hr. for 12 hours on stream. The product distribu-
tion was analyzed by gas chromatography, and the
results are given below in Table III.
~2496~5
TABLE III
Catalystl:l Catalyst B/quartz powder
% Conversion 62
C0 to C02 24
% C0 to H.C. 38
Wt. ~ Selectivity
CH4 9.2
C2-Cs 7-9
C2=-C5= 48.2
C6+ 34.7
As is seen from the data, the catalyst
derived from the iron-cobalt spinel provides good
activity and high C2-Cs olefin selectivity with hi~h
H2/C0 feed rates.
EXAMPLE 4
Catalyst B, in a 1:1 admixture with crushed
~uartz, as described in Example 3, wa run under a dif-
ferent set of F-T synthesis conditions as described
below.
Following substantially the same pretreat-
ment, described in Example 3, about 8 cc of the cata-
lyst in the same described apparatus as above was con-
tacted with l:l H2/C0, at a bed temperature of 250 to
270C, a standard hourly space velocity (SHSV) of lO00
v/v/hr. at 300 psig, for 12 hours. The products were
collected and the product distribution data were ana-
lyzed by gas chromatography. Results are given below in
Table IV.
- ~2a~96~5
- 36 ~
TAsLE IV
% CO conversion 98
% CO to C02
% CO to HC 55
Wt. % Selectivity CH4. 7.2
C2=/C2o . 2.6
C2/Cl . 2.1
% C2-C6 50.8
~ Olefins (of C2-C6 total) 86
C7+ 42
As is seen from the data, the Fe-Co Catalyst
B generates a C2-C6 fraction which is olefin rich even
at high conversion conditions.
EXAMPEE 5
Catalyst B and the control, prepared by the
procedure described in Example l, were pretreated by
the procedure described in Example 3 in the apparatus
described in Example 2.
Each catalys~ in 8 cc volume, after pre-
treatment, was contacted with 1:1 H2/CO at 300 psig
pressure, 1000 v/v/hr. (SHSV) for 12 hour run times at
the temperatures listed below in Table V, in same
apparatus described in Example 2. Product samples were
collected and analyzed after 12 hours onstream with
CO/H2
i2~ 5
37 -
TABLE V
Catalyst B Control Control
% Co Conversion 98 67 87
% CO to CO2 40 31 37
% CO to HC 58 36 50
Temp. C 270 305 340
C2:C1 2.2 1.2 0.7
% C2-c6 62 41 53
~ Olefin (of C2-C6 total) 89 88 70
Weight % Selectivity
Cl 774 5.8l9.0
C2 4.4 1.3 7.8
c2= 11.6 5.4 5.7
C3 1.5 1.0 2.6
C3 20.0 9.415.9
C4 tr. 1.4 2.0
C4= 11.3 8.8 8.6
Cs 0.3 l~0 1.1
C5 7.4 7.0 4.0
C6 0.8 0.3 2.6
c6= 4.6 5.0 3.0
C7+ 30.7 53.627.?
As is seen from the data, the catalyst
derived from the cobalt containing spinel provided
greater activity, i.e. 98% CO conversion, than the
all-iron oxide control catalysts even though they were
operated at 35C and 70C higher temperatures. The
Fe-Co catalyst generated more C2-C6 olefins than either
of the control catalysts and substantially less methane
than the control catalyst at high conversion (about
87%) conditions.
12~ 5
- 38 -
EXAMPLE 6
Catalyst Preparation
Following the general procedure described in
Example 1 the following catalysts were prepared having
the empirical formula: Fe3_yCoyO4/1%K: where y = 0.03,
0.15, 0.375 and 0.75, respectively. The surface areas
of the obtained materials were in the range of 0.1 to
0.5 m2g.
The above-prepared catalysts were pretreated
by the procedure described in Example 2 and in the
apparatus described in Example 4, and subjected to
hydrocarbon synthesis under the following reaction
conditions:
Temperature = 295 + 10C
Pressure = 300 psig
Space Velocity = 1000 v/v/hr.
H2/CO ratio = 1:1
Run Time = 12 hours
Catalyst = 8 cc volume, 20-80 mesh size
Analysis of products were performed after 12
hours of run time. Results are shown in Table VI
below.
lZ4~ I5
39
TABLE VI
Performance of Fe3_~ oyO4/1%K
y = 0.03 0.15 0.375 0.80
% Co Conversion 97 98 97 98
To CO2 27 40 41 42
To HC's 70 58 56 56
Wt. % Selectivity
CH4 8.3 7.4 18.0 13.2
C2=-C6 46.5 53.1 41.4 53.0
C2-C6 6.9 7.2 13.3 10.6
C7+ 38.3 32.3 27.3 23.2
The results show the importance of main-
taining the Fe:Co atomic ratio within the preferred
range i.e. y = 0.03 to y = 0.40 at the specific con-
ditions in this Example, excessive levels of CH4 are
generated at high cobalt levels, i.e., y = 0.375 where
Fe:Co = 7:1.
.
EXAMPLE 7
This example shows the performance of Cata-
lyst C~ Fe2.625C0,3754 in hydrocarbon synthesis atdifferent temperatures.
The catalyst was pretreated according to the
procedure described in Example 2 and in the same des-
cribed apparatus. The hydrocarbon synthesis runs were
conducted at the indicated temperatures ~sing 8 cc.
volume of catalyst being undiluted with quartz and
20-80 mesh particle size at 1:1 H2/CO, 1000 v/v/hr.
(SHSV), 300 psig for 1-12 hours onstream.
i2496~5
.,
- 40
TABLE VII
Performance of Fe2.625Co 375O4/l~K
Furnace
Temp C 225 240 260 270 280 290
Bed Temp C230 248 304 325 331 340
% CO Conversion30 31 97 98 98 98
To C2 4 7 40 33 41 41
To HC's 26 24 57 55 57 57
Wt. % Selectivity - CO2-free basis
CH48.1 8.2 19.1 16.7 18.319.1
C2=-C542.3 55.3 37.1 31.9 37.824.8
C2-C514.4 22.0 17.7 10.6 13.214.8
C6+35.2 34.5 26.1 40.8 30.741.3
As seen fro.n the data, the change in CH4
selectivity as a function of temperature-conversion
indicates that catalysts which contain relatively high
levels of cobalt, i.e. an iron/cobalt atomic ratio of
7.0, while useful should be operated at lower temper-
ature-conversion conditions to achieve low CH4 produc-
tivity. As further seen in the data, good C2-C6 olefin
selectivity is achieved over the entire operating
range. The system provided optimal performance in runs
where the bed temperature was lower than 304C.
EXAMPLE 8
This example shows the improved performance
of Catalyst C, Fe2.62sCoo.37sO4~ at low (150 psig)
pressure relative to (300 psig) high pressure condi-
tions. The catalyst was prepared by the procedure
12'~ 6~S
- 41 -
outlined in Example 1, and subjected to the pretreat-
ment and operating procedures substantially as des-
cribed in Examples 2 and 4, respectively.
The results in Table VIII below show that
even at relatively high cobalt levels, i.e. Fe:Co of
7.0, good olefin selectivity and high conversion can be
achieved at lower pressures, i.e. 150 psig.
TABLE VIII
Performance of Fe2.62sCo.375o4/l%K
at 150 and 300 psig
Pressure (psig) 150 300
% CO Conversion 92 97
To CO2 38 41
~ To HC 54 56
Wt. % Selectivity (CO2-free basis)
CH4 7.2 17.9
C2 -C5 53.4 38.1
c2-Cs 4-5 12.7
C6+ 34.9 31.3
EXAMPLE 9
This example shows the effect of H2
treatment at 350C to reduce CH4 selectivity of an
"aged catalyst", in this case Catalyst B, which had
been onstream for 72 hours. It is believed that the
treatment with H2 at 350C for 5 hrs. at 100 psig, 750
SHSV, removes a carbonaceous surface layer which
develops on the catalyst during extended operating
periods. The procedures described in Examples 1, 3 and
3 were used to respectively prepare, pretreat, and
operate this catalyst under the hydrocarbon synthesis
l'Z4!~5
42
conditions of 270C, 0.66:1 H2/CO, 2000 v/v/hr. (SHSV),
300 psig, 50% catalyst dilution with quartz powder in
8 cc total volume, catalyst particle size of 20-80
mesh.
TABLE IX
H2 Treatment ~mproves Time Dependent
PerformanCe of Fe2.85C.154/1%K
Hours on stream 72a g6b
% CO Conversion 48 62
% CO to CO2 23 28
% CO to HC 25 34
Wt. % Selectivity (CO2-free basis)
CH4 12.0 7.9
C2=-Cs= 43.3 46.3
C2-C5 7.1 ` 6.6
C6+ 37.6 40.1
aPrior to hydrogen rejuvenation.
bAfter 72 hours onstream, H2 treatment described above,
then additional 24 hours onstream with CO/H2.
EXAMPLE 10
This example demonstrates the performance of
Catalyst B, Fe2.gsCoo.lso4~ at various temperatures
under hydrocarbon synthesis conditions. The catalyst
was 50% diluted with quartz powder as described in the
previous Example. The respective procedures outlined in
Examples 1 and 3 were used to prepare, pretreat and
operate this catalyst under the hydrocarbon synthesis
conditions listed below in Table X.
- 43
TABLE X
Fe2.85co.lso4/l%K Performance
Run 1 2 3
Temp C 230 250 270
Pressure
(psig) 300 300 300
H2/CO 1.0 1.0 1.0
SHSV 1800 1800 1800
% CO Conv.36.4 97.5 98.4
HR on Stream 2 4 6
% CO to CO214 44.0 43.0
% CO to HC22.4 53.5 55.4
Wt. % Selectivity (CO2-free basis)
C2 37 9 45.0 43.8
CH4 1.3 (2.1)2.6 (4.7) 3.2 (5.7)
c2= 2.0 (3.22)3.0 (5.5) 3.4 (6.0)
c2o 0.4 (0.6)0.8 (1.5) 0.8 (1.4)
c3= 4.1 (6.6)5.4 (9.8) 6.3 (11.2)
C3 0.8 (1.3)0.6 (1.1) 0.6 (1.1)
c4= 1.7 (2.7)3.4 (6.2) 4.0 (7.1)
C4 0.1 (0.2)0.5 (0.9) 0.5 (0.9)
c5= 1.4 (2.3)2.6 (4.7) 3.5 (6.2)
C5O 0.3 (0.5)0.5 (0-9) 0.9 (1.6~
c6= 1.2 (1.9)1.9 (3.5) 2.2 (3.9)
c6o 0.4 (0.6)0.3 (0.5) 0-3 (0-5)
c7+ 48.4 (78.0)33.4 (60.7) 30.5 (54.4)
EXAMPLE 11
This example demcnstrates the performance of
Catalyst B, Fe2.gsCoo.lso4 at various temperatures in
the form of undiluted catalyst. The catalyst was pre-
pared by the procedure described in Example 1 and
pretreated and operated as respectively described in
Examples 2 and 4. The process conditions for each run
124~9G~5
- 44 _
are listed below in Table XI. In contrast to Run 4
shown below, bed dilution as employed in Example 10
allows the system to operate under more isothermal
conditions thereby minimizing the extent of carbon and
carbonaceous deposit formation.
TABLE XI
Fe2.85C.1504/1%K Performance
~ndiluted sed
Run 1 2 3 4
SHSV: 1000 1000 570 570
Temp. 235 270 235 270
H2:CO 1.0 1.0 1.0 1.0
Press 300 300 300 300
Time on
stream hr. 8 10 16 18
% CO Conv. 29.4 98.0 49.1 98.0*
CO to CO2 8.0 42.0 22.0 40.0
~ CO to HC 21.4 56.0 27.1 58.0
Wt. ~ Select. (CO2-free basis)
C2 26.2 42.5 43.5 ~40.2
CH4 1.9 3.0 1.7 3.7
(2.6) (5.2) (2.0) (6.2)
C2= 4.3 4.5 2.5 4.0
(5.8) (7.8) (4.4) (6.7)
C2 1.4 1.7 0.9 1.7
(1.9) (2.9) (1.6) (2.8)
C3= 6.4 7.8 6.6 8.3
(8.7) (13.4) (11.6) (13.8)
C3 0.6 0.6 0.7 0.8
(0.8) (1.0) (1.2) (1-3)
C4= 1.4 4.4 2.5 3.8
(1.9) (7.6) (4.4) (6.3)
C4 tr. 0.2 0.4 3.5
(tr.) (0.3) (0.7) (0.8)
Cs= 0.9 2.8 1.7 2.7
(1.2) (4.8) (2.9) (4.5)
Cs tr. 0.1 0.4 0.35
(tr.) (0.2) (0.7) (0.8)
C6+ 56.9 32.4 39.1 34.2
(76.8) (55.9) (68.6) (57.0)
*Note: Bed plugging with wax and carbonaceous deposits
limited continuous operating periods to < 40-50
hrs.
124!~if~5
EXAMPLE 12
Preparation of Fe~ ~Con l~~ Spinel
198.04 grams of ferric nitrate in 144 ec of
water and 7.5 grams of cobalt nitrate in 8 cc of water
were mixed together. To this solution was added a
solution of 41.6 grams of 85% glycolic acid containing
45 cc of ammonium hydroxide such that the resulting p~
of the ammonium glycolate solution was about 6.5. The
ammonium glycolate solution constituted 0.51 moles of
glycolic acid such that about a one to one molar ratio
of total metals including iron and cobalt to glycolic
acid resulted. The ammonium glycolate solution was
added to the aqueous solution containing iron and co-
balt salts and the contents stirred. The resulting
solution was allowed to evaporate by air drying. Upon
drying at room temperature the resulting solid was
shown by X-ray diffraction to be an amorphous material
because of lack of sharp discrete reflections. The
solid was heated in air at 350C for 2 hours. An X-ray
diffraction pattern of the resulting material showed it
to be a single phase cobalt-iron spinel isomorphous
with Fe3O4. The X-ray diffraction peaks were broadened
relative to a compositionally equivalent material
obtained by a high temperature procedure. This indi-
cated that the resulting obtained material was of very
small particle size. The surface area of the resulting
material was about 200 square meters per gram. Carbon
analysis of the material indicated approximately 0.15~
. .
124~6~5
., .
46 -
carbon percent. The result,ng material was impreg-
nated with one gram atomic percent of potassium using
an aqueous 501 ution of potassium carbonate and drying
of the resulting impregnated sample at 125C. The
resulting solid had an empirical formula of
Fe2.85Coo.lso4/l% R
Preparation of Alloy
The above obtained oxide was reduced at 400C
in a stream of 15 volume percent hydrogen/85~ helium at
200 v/v/hr (S~SV) for 4 hours. One percent of oxygen
in helium was introduced at room temperature for one
hour to passivate the material. The X-ray of the re-
sulting material was isostructural with alpha iron. ~he
resulting BET nitrogen surface area was 8 m2/9.
Preparation of Carbide
Thé above reduced material was treated at
400C in a stream of 15 volume percent hydrogen/80~
helium/5% CO at 200 v/v/hr. for four hours. Following
this the sample was cooled to room temperature and 10~
oxygen in helium was introduced for one hour to passi-
vate the material. Tbe X-ray diffraction pattern of
the resulting material was isostructural with Fe5C2.
The BET nitrogen surface area of the material was
about 118 m2/g. Analysis showed that about 60-70
weight percent of the material was carbon and thus the
material was a composite of Fe4.75Co0 25C2/1
gram-atom % K and surface carbon.
EXAMPLE 13
Into a slurry reactor, being a 300 cc Parr
CSTR (continuous stirred tank reactor) was charged: 50
g of octacosane and 5.0 of the high surface area
spinel, described above in Example 12. The system was
lZ~ (}S
- -- 47 --
purged with nitrogen and then H2 while the t~mperature
was increased from room temperature to 220C, wher- the
system was maintained under these conditions in a hy-
drogen atmosphere with st~rring for a one-hr period at
600 rpm. The system was then placed under C0 hydro-
genation reaction conditions by adjusting the reaction
temperature to 270C, the H2/C0 volume ratio to 1:1,
the space velocity to 1200 ~ gaseous feedstream/V dry
catalyst/hr, the pressure to 70 psig, and the slurry
stirrer speed to 600 rpm in the octacosane solvent. The
effluent gas from the reactor was monitored by an
~P-5840A Refinery Gas Analyzer to determine percent C0
conversion and the nature of the hydrocarbon products.
The results are listed below in Table XII under the
high surfa~e area spinels as "oxide".
Further runs were made based on the spinel
which was (1) reduced ex situ, and (2) reduced/carbided
ex situ, prior to being charged into the slurry liguid.
The results are listed below in the Table as ~reduced~
and ~reduced/carburized~, respectively, together with
the specific pretreatment conditions. The control, and
the low surface area spinel also run under substan-
tially the same conditions, are listed below.
The listed comparative sample, Fe203, was
obtained from Alpha Chemicals and had a BET surface
area of less than 10 m2/g.
The listed comparative sample Fe2.gsCoO.ls
04/1~ K was made by sintering an intimate mixture of
Fe203, Fe metal and Co304, in the appropriate molar
ratio, at 800-1,000C for 24 hours in an evacuated
sealed tube. The solid was collected, crushed, pellet-
ized and then the sintering procedure repeated. The
1i~4.~ 5
48
obtained solid was crushed and then impregnated with
aqueous potassium carbonate and then dried at 125C for
several hours in a drying oven. The surface area of
the obtained solid was about 0.3 m2/9.
TABLE XI I
Slurried F-T Catalysts with 1:1 H~:CO
%CO %olef in
Catalysts Conv. %C0~%~1~ %C7-C~ C2-C~
Fe23 <4.0 - _ _ _
Fe2,85C.15o4/ <4.0
1% R
Spinels (lOO+m2/g)
Fe~ ~ Con~l~oa
Oxide 78 48 3.1 7.3 92
Reduceda 55 62 2.210.9 88
Reduced/Carburizedb 79 48 4.5, 16.0 92
Conditions: 270C, 1:1 H2:C0, 1200 v/v/cat/hr. 70 psig,
600 rpm, octacosane solvent.
a H2 at 350C for 12 hours and 400C for 24 hours.
b H2/C0 at 350C for 12 hours and 400C for 24 hours.
As is seen in this example, catalysts prepared
from the high surface area spinel gave higher activity
and C2~C4 olefin selectivity than conventional iron
oxide catalysts.
i2~ 5
- 49
EXAMPLE 14
The catalysts, apparatus, catalyst pretreat-
ment and general CO hydrogenation procedures of Example
13 wereused and repeated except that modified C0 hydro-
genations conditions were used at 250C and 2:1 H2:CO
as listed in Table XIII.
TZ~LE XI I I
Slurried F-T Catalysts with 2:1 H~:CO
%Olef~
Catalysts ~nv. %~ %~ %C~-C~ C~-C4
Fe2~ <5.0 20+ 15+ 14.0 60.0
*Fe2.85C.154/ <4-0* NA NA NA NA
1%K
Spinels (lOO+m2/g)
Fe~ps con 1~0~
Oxide 31 62 4.1 18.2 go
Reduoeda 54 63 2.4 11.1 89
Reduced/Carburizedb 64 50 3.6 14.0 83
Conditions: ~0C, 2:1 H2:CO, 1200 vh/cat/hr. 70 psig,
600 rpm, octacosane solvent.
*Note: less than ~ conversion observed even at 270C.
aH2 at 350C for 12 hours and 400C for 24 hours.
bH~CO at 350C for 12 hours and 400C for 24 hours.
hXAMPLF. 1 5
Utilizing the catalysts, apparatus, catalyst
pretreatment and general C0/hydrogenation procedures
described in Example 13f the following runs were made
utilizing the specific process conditions listed in
Table XIV below:
12'~9tj~5
TABLE XIV
Comparative study of
Fe-Co Catalysts from High
and Low Surface S~inel Precursors
Fe2.85C.154/1% K
Spinel Initial
Surface Area 100l m2/g <10 m2/g
% CO Conversion 45 44
% C0 to C2
~ CO to HC - -
Wt~ Selectivity
C~4 1.9 2.0
C2-C4 8.3 8.4
c5+ 32.3 23.6
C2 57.0 66.0
Olein in C2-C4 90 90
onditions: 250C, 1200 v/g CAT/hr, 1:1 ~2:CO, 70
psig, 600 RPM, octacosane solvent. Cata-
lysts subjected to ex situ H2 treatment at
300+C followed by ex situ H2/CO treat-
ment 350+C to affect complete reduction-
carburization followed by oxygen passiva-
tion.
The results in Table XIV indicate that cata-
lysts prepared from low and high surface area Fe-Co
spinels provide comparable performance when they are
both fully prereduced and carburized ex situ. The cata-
lyst derived from the low surface area precursor gener-
ated more CO2 and less Cs+ hydrocarbon than the
catalyst generated from the high surface area precur-
sor, under the sta~ed reaction conditions.
12~fi~t5
~ 51 -
EXAMPLE 16
Vtilizing the catalysts, apparatus, pretreat_
ment and general Co hydrogenation procedures described
in Examplel3, the following runs were made under the
specific process conditions listed below in Table xv:
TABLE XV
Comparative Study o' Carb~rized
Catalysts from High Surface Area
Soinel Precursors
.
Precursor A(a) B(b) Fe~O~/1% X(~)
% C0 Conversion 64 42 65
% C0 ~o C02 36 24 39
% CO to HC 28 18 26
Wt.% Selectivity
CH4 3.6 4.1 5.1
C2- 4.2 2.8 2.6
c2o 0.6 l.l 1.6
c3~ 5.1 6.0 6.7
C3 0.6 0.7 0.8
c4~ 2.7 3.1 3.6
C4 0.4 0.6 0.8
c5+ 26.6 25.6 18.8
C2 56 56 60
Olefin in 88 83 80
C2-C4
~ _ .
(a) Fe2 ~sCoo l504/1% K @ lO0+ m2/g.
(b) same as A but less than l m2/g.
(c) surface area - lO0 + m2/g.
onditions: 250C, 1200 V~G CAT/hr, 2:1 H2:C0, 70 psig,
600 RPM, octacosane, ex situ treated in ~2 at
300+C and then H2/CO at 350C+.
12~9~ 15
- 52 -
As seen, catalysts gcnerated from Fe-Co and
Fe spinel precursors which are ully reduced and car-
bid-d ex situ, exhibited comparable actlvity under C0
hydrog-nation conditions ~owev~r, the F--Co based
syst-~ generated less unwanted C~4 and C02 and a C2-C4
fraction which is richer in alpha-olefins wh-n co~pared
to the Fe only analog
Comparison o Fe-Co catalysts from high and
low surface area spinel precursors~ Runs A and B, indi-
cates that the high surSace pr-cursor generated higher
yields of alpba-oleflns and low-r methane than the low
surf~c- area precursor when both c~talysts are pre-
r-duced/carbid-d ex situ Similar results w~re noted
in previous Example 15
EXAMPLE 17
Utilizing the spinel catalysts, apparatus,
and general C0 hydrogenation conditions described in
Example 13, the following runs were carried out utiliz-
ing the specific in situ pretreatment and hydrocarbon
synthesis proccss conditions listed below in Table XVI:
12~6~35
53
TABLE XVI
Comparative Study of High Surface
Area Oxide Catalysts
Catalys~ -Fe2.85 Co l5O4/l% K Fe~O4~1~ X
Surface Area100+ m2/q 100+ m2/g
% CO Conversion 60 8
% CO to C2 36 5.2
% CO to ~C 24 2.8
Wt~ Selectivity
C~4 1.8 4.0
C2-C4 8.0 15
C5+ 30.2 11
C2 60.0 65
~ Olefin in C2-C4 88 80
onditions: 250C, 1200 ~/G CA~/hr, 2:1 H2:CO, 70
psig, 600 R*M octacosane. Catalyst charged
to reactor as oxide, treated in situ with
H2 at 100 psig at 200C for 1 hr before
use.
As is seen, catalysts derived from high sur-
face area spinels, with and without added cobalt,
exhibited substantially different activities when em-
ployed and pretreated in situ directly under slurry
reactor conditions. ~he Fe-Co catalyst is ca. 5-fold
more active than the Fe only catalyst. The Fe-Co cata-
lyst also generated less CH4 and CO2 than the Fe only
catalyst and generates a C2-C4 fraction which is richer
in alpha-olefins.
124g6;~5
- 54 -
EXAMPL~ 18
Utilizing the catalysts, apparatus, pretreat-
ment and general CO hydrogenation procedures, describ-
ed in Example 13, the following runs were made using the
specific conditio~s listed below in TablexvIIincluding
comparative runs made at H2/CO ratios of 1.0 and 2.0
TABLE XVII
Performance of Fe and Fe-Co
Alloy Catalxst~
Precursor Fe~O4/1%K(a) Fe~ ~Co ~O4/1~ R(b)
% C0 Con. 44 28 55 54
H2/C0 1.0 2.0 1.0 2.0
% C0 to C2 26 15 34 34
% CO to HC 18 13 21 ~0
Wt. % Sel.
CH4 1.8 1.0 2.2 2.4
C2-C4 11.1 5.0 10.9 11.1
c5+ 28.1 41.0 24.8 23.5
C2 59 53 62 63
% olefin in 93 94 88 91
C2-C4
Condi~ions: 270C, 1:1 H2:C0, 1200 v/v Cat/hr., 70
psig, 600 rpm. Catalyst prereduced
ex situ in H2 at 350C for 12 hours and
400C for 24 hours.
(a) Initial spinel surface area - about 100 m22/g.
(b) Initial spinel surface area - about 100 m /g.
12496~S
-- 55 --
EXAMPLE 1 9
.
Utilizing the pretreatment and general C0
hydrogenation procedures described in Example 13, the
following runs were made utilizing the specific cata-
lyst and C0 hydrogenation conditions described below.
The spinel described in Example 13,
Fe2~gsCoO.1504/1% K, was reduced and carbided ex 5itU
similar to the procedure described in Example 13. A
hydrogen/C0/helium feedstream in 1:1:7 molar ratio at
350C and about 300 v/v/hr. for 24 hours was used.
Powder x-ray diffraction analysis revealed the result-
`ing material was isostructural with Hagg Carbide,
FesC2. The elemental analysis of the material showed it
to contain: Fe and Co in about a 19:1 atomic ratio and
about 60-70 weight percent carbon. The surface area of
the material was determined to be about 180-200 m2/9.
The catalyst (40 cc. catalyst volume) was run
under two different pressures in C0 hydrogenation under
the conditions listed below in Table XVIII.
The apparatus used was a 1 liter stirred tank
reactor (316 S.S.) equipped with a Magnedrive~M head
and an internal gas recycle.
` ~2~6~S
- 56
Table XVIII
Fe4_~ O 2~C2/1_ R
% CO Conve~sion 24 53
~ CO to C2 11 23
S C0 to HC 13 30
Pressure (psig) 75 150
Wt.~ Selectivity
C~4 4.9 4.7
C2'-C20' 59.3 53.2
Cl-Clo Alcohols 7.8 11.5
C20-C20O 26.2 20.6
C21+ trace 10.6
Conditions: 240C, 1:1 ~2/CO, 1,000 v/v/hr. 1,200 RPM,
100-150 hr. on stream.
i2~96~5
EXAMPLE 20
Reduction of Spinel
The above obtained Spinel B of Example
I was reduced at 400C in a stream of 15 volume
percent hydrogen/85~ helium for 4 hours. One
percent of oxygen in helium was introduced at room
temperature for one hour to passivate the material.
The X-ray of the resulting material was
isostructural with alpha iron.
Preparation of Carbide
_
The above reduced Spinel B was treated
at 400C in a stream of 15 volume percent
hydrogen/80~ helium/5~ CO at 200 v/v/hr. for four
hours. Following this the sample was cooled to room
temperature and 1.0~ oxygen in helium was intro-
duced for one hour to passivate the material. The
X-ray diffraction pattern of the resulting material
was isostructural with chi-FesC2. The measured BET
nitrogen surface area of the material, including
the carbide Fe(s)-(s/3)yco(s/3)yc2 and de~os'ted
carbon, was 17~ m2g.
124~ 5
- 5~ -
EXAMPLE 21
A slurry reactor, being a 300 cc Parr CSTR
(continuous stirred tank reactor) was charged with 50 g
of octaeosane and 5.0 g. of the resulting reduced, car-
bided, Spinel B, described above. The system was
purged with nitrogen and then ~2 while the temperature
was increased from room temperature to 220C, where the
system was maintained under these conditions with
stirring for a one-hr period at 6D0 rpm to insure
reduction. The system was then placed under CO hydro-
genation reaction conditions by adjusting the reaction
temperature to 270C, the H2/C0 volume ratio to 1:1,
the space velocity to 1200 V gaseous feedstream/V dry
catalyst/hr, the pressure to 70 psig, and the slurry
stirrer speed to 600 rpm in the octacosane solvent. The
effluent gas from the reactor was monitored by an
HP-5840A Refinery Gas Analyzer to determine percent CO
conversion and the nature of the hydrocarbon products.
The selectivity weight percentages of product hydro-
carbons exclude CO2 as a product.
A second run was conducted using a reduced,
carbided spinel of the same empirical formula,
Fe2.8scoo.lso4/l%~ and reduced and carbided by the
same above-described procedure, but having an initial
spinel ~ET surface area of above 100 m2/g as prepared
in accordance with the procedure of Exam~le 12.
12496~)5
- 59 -
The results ~re l~sted below in Table XIX.
T~BLE XIX
Comparative Study of Fe-Co Catalysts from
High and Low Surface Spinel PrecursorS
F'2.85C.154~1~ K
SpinelPrecursor
~Surface Area)100+ m2/g B
CO Conversion 4S 44
C0 to C2 26 29
~ C0 to ~C 19 15
Wt~ Selectivity
C~4 4.4 5.9
C2-C4 19.3 25
C5+ 76.3 69.1
% Olefin in C2-C4 90 90
londitions: 250C, 1200 v/g CAT~hr, 1:1 H2:C0, 70
psig, 600 RPM, octacosane solvent. ~ata-
lysts sub3ected to ex situ H2 treatment ae
300+C followed by ex situ H2/C0 treatment
3~0+C to affect complete reduction-car-
burization.
The results in Ta~le XIX indicate that
catalysts prepared from low and h~gh surface area Fe-Co
spinels provide comparable performance when they are
fully x situ prereduced and carburized.
12~96~5
As is seen, the catalyst derived from the
low surface area precursor generated more C02, less Cs~
hydrocarbons, but more C2-C4 olefins than the catalyst
generated from the high surface area precursor, under
the stated reaction conditions.
EX~IPLE 22
Utilizing the catalysts, app~ratus, pre-
treatment and general Co hydrogenation conditions
described in Exa~ple 21,the following runs were carried
out utilizing the specific process conditions listed
below in Table XX. The conversion for Catalyst B
under the stated conditions was too low for accurate
determination of products (NA - not available).
12~.q6~S
- 61
TABLE XX
Comparative Study of ~igh Surface
_ Are~ Oxide Catalysts
C~talyst Fe2.85C.15o4/l~ X e3O4/1~ R B
Surfaee Area 100l m2/q 100l ~2/g 0.29 m2/g
-
~ CO Conversion 60.0 8.0 4.0
Wt.~ Selectivity
c~4 1.8 4.0 NA
C2-C4 8.0 15 N~
c5+ 30.2 11 NA
C2 60.0 65 NA
% Ole~in in C2-C4 8-8 80 NA
onditions: 250C, 1200 V/G CAT~hr, 2:1 H2:CO, 70
psig, 600 RP~ octacosane. Catalyst
charged to reactor as oxide, treated in
situ with H2 at 100 psig at 200C for 1 hr
before use.
As is seen, the catalysts derived from low
surface.area spinels, wi$h added cobalt, gave low
activity when employed directly under the conditions
described. By contrast, catalysts derived from the
high surface area ~e-Co spinels exhib ted high activity
when employed under the above conditions. ~owever, the
enhanced activity effect is not due to the high surface
area alone, but primarily to the presence of cobalt,
since the high surface area cobalt-free catalyst also
exhibited low activity.
