Catalyst for converting synthesis gas to liquid motor fuels

The addition of an inert metal component, such as gold, silver or copper, to a Fischer-Tropsch catalyst comprising cobalt enables said catalyst to convert synthesis gas to liquid motor fuels at about 240.degree.-370.degree. C. with advantageously reduced selectivity of said cobalt for methane in said conversion. The catalyst composition can advantageously include a support component, such as a molecular sieve, co-catalyst/support component or a combination of such support components.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to the conversion of synthesis gas to hydrocarbons. 
More particularly, it relates to the conversion of such synthesis gas to 
C.sub.5.sup.+ hydrocarbons suitable for use as liquid motor fuels. 
2. Description of the Prior Art 
It is well known in the art that synthesis gas, i.e., hydrogen and carbon 
monoxide, can be converted to hydrocarbons in the presence of a variety of 
transition metal catalysts. Thus, certain Group VIII metals, particularly 
iron, cobalt, ruthenium and nickel, are known to catalyze the conversion 
of CO and hydrogen, also referred to as syngas, to hydrocarbons. Such 
metals are commonly called Fischer-Tropsch catalysts. While the use of 
nickel preferentially produces methane upon conversion of syngas, the use 
of iron, cobalt and ruthenium tends to produce hydrocarbon mixtures 
consisting of hydrocarbons having a larger carbon number than methane, as 
determined by a number of analytical means including mass spectrographic 
analysis of individual components and the boiling point curve method. At 
higher reaction temperatures, all Fischer-Tropsch catalysts tend to 
produce gaseous hydrocarbons, and it is readily feasible to select 
processing conditions to produce methane as the principal product. At 
lower temperatures, and usually at higher pressures, however, iron, cobalt 
and ruthenium produce hydrocarbon mixtures consisting of larger 
hydrocarbons. These products usually contain very long straight-chain 
hydrocarbon molecules that tend to precipitate as wax. Such wax material, 
boiling well beyond the boiling range of motor fuels, typically 
constitutes a significant fraction of the product produced in such 
catalytic conversion operations. Fischer-Tropsch catalysts have not been 
advantageously employed in the production of liquid hydrocarbon motor 
fuels, therefore, instead commonly producing either principally gaseous 
hydrocarbons, on the one hand, or hydrocarbons containing an unacceptably 
large amount of wax on the other. In addition, the gasoline boiling 
hydrocarbon fraction that has been produced has an unacceptably low octane 
number. 
In light of such circumstances, efforts have been made to improve the 
performance of Fischer-Tropsch catalysts for use in various desired syngas 
conversions. For example, the Breck et al. patent, U.S. Pat. No. 
3,013,990, discloses the use of zeolitic molecular sieves containing a 
Fischer-Tropsch catalyst as improved catalyst compositions. Thus, Type A, 
X and Y molecular sieves loaded with iron or cobalt are shown to be 
suitable Fischer-Tropsch hydrocarbon synthesis catalysts, as for the 
production of methanol from syngas. Also with respect to the conversion of 
syngas, Fraenkel et al., U.S. Pat. No. 4,294,725, teach that zeolites A 
and Y loaded with cobalt, incorporated by ion exchange and reduced in-situ 
with cadmium, serve as useful catalysts of the Fischer-Tropsch type. Those 
skilled in the art will appreciate that such catalyst materials tend to be 
relatively expensive and, in any event, do not produce hydrocarbon 
products advantageous for use as liquid motor fuels. 
Efforts have also been made to improve Fischer-Tropsch catalyst performance 
by preparing intimate mixtures of Fischer-Tropsch metals, such as iron, 
with an acidic crystalline aluminosilicate, such as ZSM-5. The Chang et 
al. patents, U.S. Pat. Nos. 4,086,262, and 4,096,163, disclose such 
catalyst compositions employed in the conversion of synthesis gas to 
hydrocarbon mixture useful in the manufacture of heating fuels, gasoline, 
aromatic hydrocarbons and chemical intermediates. When it is desired to 
convert syngas specifically to hydrocarbons boiling in the jet fuel+diesel 
oil boiling range, however, such an approach is not suitable, experiencing 
an effective limitation at C.sub.10 carbon number as was the case using 
ZSM-5 in methanol conversion, as disclosed in the Owen et al. patent, U.S. 
Pat. No. 3,969,426. 
While iron is the currently preferred Fischer-Tropsch catalyst component 
for use in syngas conversion operations, cobalt had originally been 
preferred because of its various desirable properties. Thus, cobalt has a 
higher level of catalytic activity in syngas conversion operations as well 
as a better selectivity to total motor fuels than is obtained using iron. 
One very objectional characteristic of cobalt, however, is the excessive 
amount of undesired methane that is produced when it is employed in syngas 
conversion operations, the level of methane production being considerably 
out-of-line with the level of other hydrocarbons produced and 
significantly diminishing the overall performance of said syngas 
conversion operations using cobalt as the Fischer-Tropsch catalyst. 
It is nevertheless desirable in the art to develop improvements with 
respect to the use of cobalt as a Fischer-Tropsch catalyst for syngas 
conversion. More particularly, it is desirable to overcome the 
objectionable charactristics of cobalt by lowering its selectivity to 
methane during syngas conversion operations. 
In prior art development work relating to various Fischer-Tropsch catalysts 
other than cobalt, the addition of copper and silver have been found to 
have varying effects on the selectivity of methane production. Thus, G. 
Bond and B. Turnham report in the Journal of Catalysis 1976, vol. 45, p. 
128-136, that the addition of 50 mole % copper to a ruthenium catalyst 
causes the catalyst to lose significant activity and to become more 
selective for methanation and less selective for heavier hydrocarbon 
production, although one catalyst with only 3 mole % copper was found to 
follow the trend of the higher percentage copper catalysts, but to a 
lesser degree. On the other hand, D. Elliott and J. Lundsford report, in 
said Journal of Catalysis, 1979, vol. 57, p. 11-26, the observation of a 
decrease in methane selectivity upon addition of copper to a ruthenium-y 
zeolite composition, with this result attributed to a lower hydrogenolysis 
activity for the ruthenium-copper catalyst. Furthermore, J. Amelse, L. 
Schevarty and J. Butt report, again in said Journal of Catalysis, 1981, 
vol. 72, p. 95-110, that the use of an iron-copper Fischer-Tropsch 
catalyst containing about 25% copper based on the amount of iron therein 
produces more methane and less olefins than a corresponding iron catalyst 
without copper added thereto. The effects observed in such prior art work 
appear to have been dependent upon the nature of the particular 
Fischer-Tropsch metal component employed and upon the processing 
conditions employed. 
It should be noted that such prior art activities relating to iron and 
ruthenium Fischer-Tropsch catalysts were carried out under processing 
conditions of high methane yield, but with varying, unpredictable results. 
Earlier prior art work using cobalt as the Fischer-Tropsch catalyst, 
however, was carried out under processing conditions of low methane 
selectivity, and no effect was seen with respect to said methane 
selectivity. Thus, the use of copper and silver in cobalt catalysts, as to 
reduce the reduction temperature of the cobalt, constitutes old work 
discussed in "The Fischer-Tropsch and Related Synthesis" by H. Storch, N. 
Golumbic and R. Anderson, John Wiley & Sons, N.Y. In addition, Fischer is 
known to have studied 9:1 and 1:1 cobalt:copper catalysts at atmospheric 
pressure and temperatures of about 190.degree.-220.degree. C. At these 
conditions, such catalysts gave quite saturated products and oxygenates. 
The copper was added to lower the reduction temperature of the cobalt 
because of equipment restrictions. No decrease in methane selectivity was 
observed in these experiments carried out for other purposes under 
conditions of low methane selectivity. Prior art experiments at I. G. 
Farben using a 1% silver in cobalt catalyst composition are also known to 
have been made, presumably at low temperature and with no noted reduction 
in methane yield although easier reduction and longer catalyst life were 
noted under th processing conditions employed. Once again, no advantageous 
reduction in the methane selectivity of the cobalt was either sought or 
observed, notably because the conditions employed for the purposes of such 
prior art work were such that the hydrogenolysis reaction likely leading 
to the production of methane as a secondary product were not employed. 
Despite the variety of prior art activity referred to above, the 
disadvantageous characteristics of cobalt performance remain, precluding 
the use of cobalt as a Fischer-Tropsch catalyst, despite its outstanding 
activity and motor fuel selectivity when employed for syngas conversion. 
The desire also remains in the art, therefore, for the development of 
improvements enabling cobalt to be used for syngas conversion with lower 
selectivity for methane and a corresponding increase in selectivity for 
desired liquid hydrocarbon fuels. 
It is an object of the invention, therefore, to provide an improved process 
and Fischer-Tropsch catalyst composition for the conversion of syngas to 
liquid motor fuels. 
It is another object of the invention to provide a process and 
Fischer-Tropsch catalyst composition for lowering the selectivity of 
cobalt for methane. 
With these and other objects in mind, the invention is hereinafter 
described in detail, the novel features thereof being particularly pointed 
out in the appended claims. 
SUMMARY OF THE INVENTION 
The methane selectivity of cobalt in syngas conversion operations is 
advantageously reduced by the addition to the cobalt of an inert metal 
component comprising gold, silver or copper. The conversion operations in 
which such reduction in methane selectivity is obtained are carried out at 
a reaction temperature of about 240.degree.-370.degree. C. The catalyst 
composition of the invention, employed under such operating conditions and 
supported by a molecular sieve co-catalyst/support components in 
particular embodiments, thus increases the selectivity of the cobalt to 
desired liquid hydrocarbon fuels. 
DETAILED DESCRIPTION OF THE INVENTION 
The objects of the invention are accomplished by the deactivation of 
methane production, which appears to constitute a secondary, 
hydrogenolysis reaction, by the addition of an inert metal component to 
the cobalt Fischer-Tropsch catalyst employed for syngas conversion to 
liquid motor fuels. The inert metal component, i.e. gold, silver or 
copper, accomplishes this desirable result without accompanying 
deactivation of the Fischer-Tropsch reactor itself. Such desirable 
lowering of the selectivity of cobalt for methane is effective at reaction 
temperatures of from about 240.degree. C. to about 370.degree. C. as 
further described below. 
The synthesis gas, or syngas, treated in accordance with the practice of 
the invention generally comprises a mixture of hydrogen and carbon 
monoxide, usually together with smaller amounts of carbon dioxide, 
methane, nitrogen or other components as is well known in the art. Syngas 
is commonly produced by steam reforming of hydrocarbons or by the partial 
oxidation of coal and petroleum deposits, or by similar gasification of 
other carbonaceous fuels such as peat, wood and cellulosic waste 
materials. The hydrogen/carbon oxide volume ratio of such syngas is 
desirably in the range of from about 0.2/1 to about 6.0/1 prior to 
conversion to liquid motor fuels as herein disclosed and claimed. This 
ratio can be adjusted, if desired, by reaction of carbon monoxide with 
steam in the well-known water-gas shift reaction. If required, sulfur 
impurities can be removed from the syngas mixture by conventional means 
known in the art. It should also be noted that the syngas as described 
herein includes art-recognized equivalents, such as mixtures of carbon 
monoxide and steam, or of carbon dioxide and hydrogen, that can provide 
synthesis gas mixture by in-situ reaction under the operating conditions 
employed. 
For the reasons indicated above, the invention is directed and specifically 
limited to the use of cobalt as the Fischer-Tropsch metal component of the 
syngas conversion catalyst composition herein disclosed and claimed. As a 
second component thereof, gold is advantageously employed to achieve the 
desired lowering of the methane selectivity of said cobalt. Copper and 
silver are other metals that can be employed, in place of gold, as the 
second component. Gold, silver and copper, or mixtures thereof, are herein 
referred to as the inert metal component conveniently mixed with the 
cobalt to form the Fischer-Tropsch catalyst composition of the invention. 
Any convenient means may be employed to obtain the desired admixture of 
cobalt and said inert metal component. Thus, the inert metal component can 
be coprecipitated or otherwise intimately interdispersed with said cobalt, 
conveniently in the form of cobalt oxide, before or after the activation 
of said cobalt. It is generally preferred, however, to impregnate the 
cobalt metal component with a solution of a suitable salt of the inert 
metal component employed. Thus, the cobalt metal may conveniently be 
impregnated with a solution of auric acid (HAuCl.sub.4), followed by the 
drying of the thus impregnated cobalt. Those skilled in the art will 
appreciate that various other salt solutions can be employed in other 
embodiments of the invention to achieve the desired admixing of cobalt 
with the inert metal component. For purposes of the invention, the inert 
metal component is employed in an amount within the range of from about 
0.1 to about 50, preferably from about 0.5 to about 5, mole % based on the 
total amount of cobalt and said inert metal component present in the 
Fischer-Tropsch catalyst composition. 
In the practice of the invention the desired lowering of the selectivity of 
cobalt for methane is effectively achieved in syngas conversion operations 
carried out, as indicated above, at a reaction temperature of from about 
240.degree. C. to about 370.degree. C. It will be appreciated that the 
invention is applicable to processing conditions such that the cobalt 
catalyst, not modified as herein provided, would produce excess amounts of 
methane when employed for syngas conversion. At reaction temperatures 
below about 240.degree. C., excess methane is not produced in any event, 
and the practice of the invention is not needed although the results 
obtainable at such lower temperature conditions are otherwise not suitable 
for the production of liquid motor fuels. At reaction temperature above 
about 370.degree. C., on the other hand, the cobalt catalyst produces 
large amounts of methane in any event so that the addition of an inert 
metal component will not result in a significant and meaningful lowering 
of the selectivity of the catalyst for methane. The catalytic conversion 
reaction can be carried out, in the practice of the invention, at any 
desired pressure level, as at pressures of from about 0 to about 1,000 
psig, typically at from about 0 to about 350 psig. 
Prior to syngas conversion, the cobalt catalyst of the invention is reduced 
or activated by techniques employing hydrogen where or with other treating 
materials as known in the art. For example, the catalyst may be activated 
by first carbiding with a low H.sub.2 /CO ratio gas, or with CO alone, at 
a temperature in the range of about 250.degree.-320.degree. C. and a 
pressure of from 0 psig to the synthesis gas pressure. The catalyst is 
then further treated with hydrogen under similar temperature and pressure 
conditions. Further information regarding the preparation and activation 
of Fischer-Tropsch catalysts is provided in the published art, as in 
CATAL.REV.-SCI.ENG.,21(2), 225-274 (1980), "The Fischer-Tropsch Synthesis 
in the Liquid Phase", by Herbert Kolbel and Miles Ralek, particularly pp. 
242-247 thereof. 
It will also be appreciated by those skilled in the art that the cobalt 
catalyst of the invention may also have a suitable promoter component 
incorporated therein. Potassium, sodium and thorium are examples of known 
promoters, with thorium being a preferred promoter for purposes of the 
syngas conversion operations of the invention. Thorium promotion can 
readily be accomplished by impregnating said cobalt catalyst or a 
metal-loaded, molecular sieve co-catalyst/support component with a thorium 
nitrate solution prior to drying and calcining. For example, a catalyst 
composition of the invention having cobalt precipitated on UHP-Y zeolite 
as hereafter described can be prepared by first precipitating the cobalt 
on the zeolite by the addition of aqueous ammonia to a boiling slurry of 
cobalt nitrate and said UHP-Y zeolite. After washing and drying the 
cobalt-loaded molecular sieve, said molecular sieve can be impregnated 
with a thorium nitrate solution, dried, pressed into pellets if desired, 
and air-calcined at 250.degree. C. In another representative example, a 
physical mixture of cobalt and zeolite, promoted with thorium, is 
conveniently prepared from a solution of 0.05 g/ml of cobalt nitrate 
solution. Cobalt powder comprising CoO.times.H.sub.2 O is first 
precipitated by the addition of a stoichiometric amount of aqueous sodium 
carbonate. The resulting powder is collected, washed with hot distilled 
water, e.g. at about 95.degree. C., and dried at 110.degree. C. overnight. 
The cobalt powder is then impregnated with thorium nitrate solution and 
dried. Such thorium-promoted catalysts will typically contain about 15 wt. 
% ThO.sub.2 although it will be appreciated that the concentration of 
thorium or other promoter employed will vary depending upon the promoter 
employed in any particular embodiment. In the latter example above, the 
thorium-promoted, precipitated cobalt powder can be ground slightly, mixed 
with an equal weight of UHP-Y zeolite, pressed into pellets, and air 
calcined at 250.degree. C. for two hours to produce a metal and 
co-catalyst support composition comprising a physical mixture of said 
cobalt and UHP-Y zeolite containing about 20% cobalt by weight. 
Potassium-promoted catalysts will in general have a potassium 
concentration of from about 0.1 to about 5 wt. percent of K.sub.2 O, with 
sodium-promoted catalysts having a similar concentration range and 
thorium-promoted catalysts having such a concentration extended up to 
about 15%. 
The Fischer-Tropsch catalyst composition of the invention, as indicated 
above, advantageously includes a support component for said cobalt and 
said inert metal component. In preferred embodiments, said support 
component comprises a molecular sieve co-catalyst/support component rather 
than an inert support component such as .alpha.-alumina. The presence of 
such a co-catalyst material facilitates the desired conversion of syngas 
to liquid motor fuels. In particularly preferred embodiments of the 
invention, the co-catalyst/support component comprises steam-stabilized, 
hydrophobic zeolite Y catalyst, sometimes referred to as ultrahydrophobic 
type zeolites, or simply as UHP-Y zeolites. The cobalt and the inert metal 
component may be positioned mainly within the large pores between the 
crystallites formed during the extrusion of the catalyst. It has also been 
found possible to place the cobalt and the metal component substantially 
within the crystallites of said UHP-Y zeolite or of aluminum extracted or 
acid extracted, UHP-Y zeolite as referred to below. The Y zeolites used in 
this invention are prepared by the steaming of the low-sodium forms of 
zeolite Y substantially as described in Belgian Pat. No. 874,373, issued 
Feb. 22, 1979. Such zeolites are organophilic zeolitic aluminosilicate 
compositions having a SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio equal to or 
greater than 4.5, and an essential X-ray powder diffraction pattern of 
zeolite Y. Furthermore, the zeolites have a crystallographic unit cell 
dimension, a.sub.o, of less than 24.45 Angstroms, a sorptive capacity for 
water vapor at 25.degree. C. and a p/p.sub.o value of 0.10 of less than 
10.0 weight percent. In preferred compositions, said unit cell dimension 
of the catalyst is from 24.20 to 24.35 Angstroms. In addition, the water 
adsorption capacity at 25.degree. C. and a p/p.sub.o value of 0.10 is 
desirably less than 6.0 or even 4.0 weight percent. More particularly, the 
SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio for certain embodiments is from 
4.5 to 20.0. In a desirable embodiment in which the UHP-Y zeolite is acid 
extracted as discussed below, the SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio 
may be extended up to about 100 or more, as the alumina content of the 
zeolite is generally reduced to less than about 3 weight % or even to 
about 1 weight % or less in practical commercial applications. 
For the determination of the sorptive capacity of the hydrophobic zeolite Y 
compositions for any particular adsorbate, e.g. water, the test zeolite 
sample is activated by perheating at 425.degree. C. for 16 hours at a 
pressure of 5 micrometers of mercury in a conventional McBain apparatus. 
The temperature of the sample is thereafter adjusted to the desired value 
and contacted with the vapor of the test adsorbate at the desired 
pressure. 
The hydrophobic zeolites suitable for purposes of the invention, as 
described above, have also been found especially suited for use as 
adsorbents in applications where it is desired to preferentially adsorb 
organic constituents from solutions or mixtures thereof with water. In the 
formation of synthesis gas by the distillation of coal for example, it is 
desirable, for environmental and economic reasons, to recover the 
relatively small portion of phenol present in the condensate fraction of 
principally water that is produced therein. For this purpose, the 
condensate can be contacted at ambient temperature with said hydrophobic 
zeolite that will selectively absorb the phenol from said condensate. Such 
zeolites have also been found highly suitable for use as base materials 
foor catalyst compositions having important commercial applications, e.g. 
in midbarrel hydrocracking catalyst compositions. The UHP-Y zeolites 
described in particular detail in the Belgian patent referred to above 
have been found active for the conversion of methanol to hydrocarbons 
ranging from methane to those boiling in the jet fuel and diesel oil 
boiling range up to about C.sub.22 material.

The invention is hereinafter described with reference to specific 
comparative tests that are presented to illustrate the invention and the 
advantages thereof. These illustrative comparative tests should not be 
construed, however, as limiting the scope of the invention as set forth in 
the appended claims. 
EXAMPLE I 
This example is presented as a comparative reference and is based on the 
conversion of syngas using a thorium-promoted cobalt catalyst supported on 
a UHP-Y co-catalyst/support component without the admixture of an inert 
metal component with said cobalt as in the practice of the invention 
illustrated in Example II below. For purposes of this Example I, the 
cobalt metal component was prepared by precipitiation upon the addition of 
a 10% excess of sodium carbonate solution to a stirred, room temperature 
aqueous solution of 400 g. of cobalt nitrate, Co(NO.sub.3).sub.2.6H.sub.2 
O, in 1600 ml of water. The cobalt precipitate was washed with hot 
distilled water and dried at 110.degree. C. overnight. It was then 
impregnated with thorium nitrate solution to provide a 15 wt. % thorium 
concentration, based on the weight of cobalt, on the precipitate, which 
was then dried at 110.degree. C. 
This thorium-promoted cobalt metal component was formed as 1/8" silica 
bonded extrudate containing 15% Co/ThO.sub.2, 70% UHP-Y zeolite and 15% by 
wt. silica binder. The resulting extrudate was dried at 110.degree. C. and 
calcined in air at 250.degree. C. for two hours. 
80 cc. of this catalyst was loaded into an internal recirculation reactor, 
in which it was heated, for cobalt activation, with hydrogen, at 300 psig, 
from room temperature up to 350.degree. C., where it was held for 24 hours 
before cooling to 270.degree. C. for treatment with 1:1 syngas. The syngas 
was fed to the reactor at a rate of about 300 GHSV, i.e., gas hourly space 
velocity, or volume of gas (at 0.degree. C., 1 atm)/volume catalyst/hour. 
The conversion reaction was carried out at a pressure of about 300 psig 
and at a temperature of about 270.degree. C. The results obtained in terms 
of the conversion of syngas, the primary product selectivity between 
hydrocarbons and CO.sub.2, the hydrocarbon selectivity to the desirable 
C+.sub.5 range and other pertinent product characterizations are as set 
forth below; including Table I, under the various operating conditions 
recited in the Table. 
TABLE I 
______________________________________ 
Run 1 2 3 4 5 
______________________________________ 
Hours on Stream 
19.5 115.5 139.5 163.5 187.5 
Temperature, .degree.C. 
272 269 269 270 269 
Feed, cc/min. 
400 400 400 400 400 
Conversion, wt. % 
on CO 62.86 44.21 39.12 40.43 38.31 
on H.sub.2 89.40 72.07 66.43 67.26 65.97 
on (CO + H.sub.2) 
75.66 58.36 52.78 53.81 52.12 
Product Selectivity, wt. % 
CH.sub.4 14.67 19.66 23.12 22.63 24.15 
C.sub.2 -C.sub.4 
13.23 12.86 15.47 13.70 14.59 
C.sub.5 -420.degree. F. 
50.41 42.22 38.71 41.04 39.90 
420-700.degree. F. 
19.19 20.35 16.74 16.65 15.78 
700.degree. F. End Point 
2.51 4.91 5.95 5.98 5.58 
C.sub.5 End Point 
72.10 67.48 61.41 63.67 61.26 
Iso/Normal mole ratio 
C.sub.4 0.2857 0.1226 0.1778 
0.1370 
0.1327 
C.sub.5 0.5572 0.2546 0.2698 
0.2540 
0.2473 
C.sub.6 0.9660 0.4117 0.4181 
0.4006 
0.3892 
Paraffin/Olefin ratio 
C.sub.3 0.6912 1.4156 1.1943 
1.2831 
1.2776 
C.sub.4 0.4206 0.7010 0.7044 
0.6503 
0.6289 
C.sub.5 0.5004 0.7141 0.6954 
0.6438 
0.6146 
______________________________________ 
Those skilled in the art will appreciated that the gasoline end point is 
about 420.degree. F., while the diesel oil end point is about 700.degree. 
F. It will also be appreciated that the 420.degree.-700.degree. F. 
hydrocarbon material comprises molecules with more carbon atoms than 
C.sub.10 hydrocarbons up to about C.sub.22 material. Hydrocarbon material 
in the C.sub.22 -C.sub.28 range generally comprises heavy distillate 
material, with material above C-.sub.28 generally comprising wax. 
It will be seen that the cobalt catalyst shows an initial deactivation that 
tends to continue with time on stream. The level of methane production, 
which is relatively high initially, likewise increases with time on 
stream. While the selectivity to liquid hydrocarbons is relatively high, 
it will be appreciated that it could be higher in the event that the 
methane selectivity were reduced. The quality of the condensed product 
obtained was found not to be entirely satisfactory, since it contained 
some solid along with liquid hydrocarbons. The total condensed product 
obtained was distilled and fractioned into gasoline (initial boiling 
point-420.degree. F.), jet fuel (300.degree.-550.degree. F.) and diesel 
oil (300.degree.-700.degree. F.) fractions. Upon FIA, i.e. Florescence 
Indicator Absorption, analysis, the gasoline fraction was found to contain 
36.4% olefins, and the jet fraction was found to contain 31.6% olefins but 
to have a pour point, i.e. the lowest temperature at which the liquid 
flows, of 0.degree. F. The diesel fraction had a pour point of 50.degree. 
F. 
EXAMPLE II 
In this comparative example illustrating the practice of the invention, the 
catalyst composition was prepared as in Example I above except that the 
thorium-promoted cobalt component was impregnated with sufficient 
chloroauric acid solution, prior to formulation into the extrudate, to 
obtain approximately 2% gold deposited on the cobalt oxide. The metal 
component was dried and then formulated into an extrudate as in said 
Example I. The catalyst loading, pretreatment and testing for syngas 
conversion were also essentially as set forth in Example I. The results 
obtained are set forth in Table II below. 
TABLE II 
______________________________________ 
Run 1 2 3 4 5 
______________________________________ 
Hours on Stream 
70.9 118.9 143.4 168.8 214.5 
Temperature, .degree.C. 
270 269 269 268 269 
Feed, cc/min. 
400 400 400 400 400 
Conversion, wt. % 
on CO 38.68 35.34 34.85 34.69 36.25 
on H.sub.2 77.62 73.11 72.54 71.71 71.93 
on (CO + H.sub.2) 
58.27 53.90 53.35 53.00 54.04 
Product Selectivity, wt. % 
CH.sub.4 14.14 17.70 18.58 18.17 17.78 
C.sub.2 -C.sub.4 
12.80 13.85 13.95 14.97 13.08 
C.sub.5 -420.degree. F. 
46.86 42.37 40.23 40.29 38.95 
420.degree. F.-700.degree. F. 
21.70 21.59 21.62 18.64 23.96 
700.degree. F.- 
4.49 4.50 5.63 7.92 6.23 
end point 
C.sub.5 - 73.06 68.45 67.47 66.86 69.14 
end point 
Iso/normal mole ratio 
C.sub.4 0.1913 0.1272 0.1092 
0.1471 
0.1122 
C.sub.5 0.3226 0.2085 0.1966 
0.1678 
0.1561 
C.sub.6 1.2078 1.0447 0.9495 
1.0217 
1.0011 
Paraffin/Olefin ratio 
C.sub.3 0.6638 0.6912 0.6770 
0.6824 
0.7207 
C.sub.4 0.4198 0.4097 0.4061 
0.4937 
0.4593 
C.sub.5 0.6082 0.6016 0.5933 
0.4282 
0.5622 
______________________________________ 
It will be seen from the results of Example II as compared with those of 
Example I, the activity of the reference catalyst and of the catalyst of 
the invention are comparable at similar run times on stream. However, the 
selectivity to methane of the catalyst of the invention is and remains 
lower than that of the corresponding reference catalyst without gold added 
thereto. The desirably lower methane selectivity of the catalyst of the 
invention leads, in turn, to better selectivity for both gasoline and 
diesel oil, the desired products of the syngas conversion operation. 
The admixing of the inert metal component, i.e. gold in the subject 
example, is also found to lower the paraffin/olefin ratio of the C.sub.3, 
C.sub.4 and C.sub.5 hydrocarbons produced. The liquid fractions obtained, 
i.e. gasoline, jet and diesel oil fractions, are also more olefinic than 
in Example I. This is especially desirable in catalyst compositions 
containing a molecular sieve material, since the molecular sieve can act 
upon olefins much easier than it can act upon paraffins, leading to the 
production of more desirable liquid motor fuel materials. The gasoline 
fraction in Example II was found to contain 46% olefins, while the jet 
fraction contained 45% olefins. The pour point of the jet material is 
-5.degree. F., and the diesel oil has a pour point of 50.degree. F. While 
this combination is barely improved from the results of Example I, the 
condensed liquid product of Example II advantageously contains no solid 
material therein. 
Those skilled in the art will appreciate that various changes and 
modifications can be made in the details of the invention without 
departing from the scope of the invention as set forth in the appended 
claims. Thus, as noted above, the desired deactivation of methane 
production, by the addition of gold, silver or copper as an inert metal 
component to a cobalt metal component can be facilitated by the use of a 
modified UHP-Y co-catalyst/support component or by the use of other such 
desirable support components. For example, he UHP-Y zeolite referred to 
above can be employed in aluminum-extracted form. Furthermore, the cobalt 
and inert metal particles can advantageously be positioned substantially 
within the crystallites of the UHP-Y zeolite or of aluminum-extracted 
UHP-Y zeolite and not merely within the large pores between the 
crystallites formed during extrusion of the catalyst, thus enhancing 
catalyst stability. For such uses with UHP-Y, and in general when a 
co-catalyst support component is used, the cobalt metal component will be 
employed in an amount within the range of from about 1% to about 25% by 
weight based on the overall weight of the catalyst composition, with 
cobalt concentrations of from about 5% to about 15% being generally 
preferred in most applications. When a co-catalyst/support component is 
not employed, from about 1% to about 100% cobalt by weight is useful, 
based on the total weight of cobalt, inert metal and possibly other 
additives with about 5% to about 50% cobalt being preferred. 
For purposes of achieving the aluminum-extracted form of said UHP-Y 
zeolite, the zeolite is conveniently acid washed or extracted essentially 
by the process as described in the Eberly patent, U.S. Pat. No. 3,591,488, 
to remove a large portion of the alumina from its pores prior to treatment 
to incorporate the metal component therein. By employing a suitable 
cobalt-containing liquid, such as cobalt carbonyl or a solution of cobalt 
nitrate or other cobalt salt, the metal can be positioned within the 
crystals, the adsorbed therein to form a co-catalyst/support composition 
highly advantageous for purposes of the invention. In an illustrative 
example, UHP-Y molecular sieve zeolite was refluxed in a 13% slurry of 
said sieve in 3.75M hydrochloric acid for three hours. The slurry was then 
cooled, and the supernatent was decanted therefrom. The remaining slurry 
was diluted in half, filtered and washed chloride-free with 0.001M nitric 
acid. The slurry was then washed with distilled water, dried at 
110.degree. C. for 16 hours and then at 250.degree. C. for 16 hours and at 
500.degree. C. for an additional two hours and bottled at 400.degree. C. 
The thus-treated material comprises acid-extracted substantially 
alumina-free, or aluminum extracted, UHP-Y zeolite. 
In preparing the catalyst composition of the invention in embodiments 
including a co-catalyst/support component, the cobalt metal component, 
promoted and admixed with said inert metal component, can be physically 
mixed with the co-catalyst/support component, as in the examples above, or 
can be precipitated on or pore filled in said co-catalyst/support 
component. For purposes of positioning the cobalt within the crystals of 
UHP-Y zeolite or the aluminum-extracted form thereof, a suitable cobalt 
solution can be loaded into the zeolite by impregnation followed by 
heating or treatment with base. Addition of the inert metal and/or of 
thorium or other promoter can be accomplished either during cobalt 
impregnation or separately thereafter. 
Another advantageous co-catalyst/support component for purposes of the 
invention is a crystalline, microporous SAPO silicoaluminophosphate, 
non-zeolite molecular sieve catalyst. Such catalyst materials, known as 
SAPOs and available at Union Carbide Corporation, are described in U.S. 
Pat. No. 4,440,871, issued Apr. 3, 1984. Individual members of the SAPO 
class are designated as SAPO-5, SAPO-11, SAPO-17, SAPO-20, SAPO-31, 
SAPO-34 and the like as disclosed in said patent application. SAPO-11 and 
SAPO-31 are generally preferred for purposes of the invention, although it 
will be appreciated that other SAPOs, or combinations thereof alone or 
with other molecular sieves, may also be employed. It is, for example, 
within the scope of the invention to employ a steam-stablized, hydrophobic 
zeolite Y, i.e. UHP-Y, as an additional co-catalyst/support component in 
addition to said SAPO material. In particular embodiments, the cobalt and 
said inert metal component admixed therewith are positioned inside said 
zeolite Y component, as inside the crystallites of said UHP-Y, or of the 
aluminum-extracted form thereof, with the thus-loaded UHP-Y 
co-catalyst/support component being used together with said SAPO or other 
suitable co-catalyst/support component. It will be understood that such 
specific embodiments are intended to achieve the desired reduction in 
methane selectivity by the use, under the syngas conversion conditions 
disclosed and claimed herein, of catalyst compositions that also have 
desirable stability and catalytic activity favorable to the production of 
the desired liquid motor fuels. In such specific embodiments and more 
generally, the invention utilizes a modification of cobalt not previously 
appreciated, in the context of syngas conversion and of excess methane 
selectivity therein, to achieve a significant advance in the production of 
motor fuels from such syngas. The invention thus enables the methane 
formation reaction to be deactivated to an appreciable extent, thereby 
overcoming the principal disadvantage of the otherwise preferred use of 
cobalt for syngas conversion. The invention thus represents an important 
advance in the continuing desire and need for improvements in the ability 
of the art to provide the liquid motor fuel requirements of industrial 
societies.