Note: Descriptions are shown in the official language in which they were submitted.
~U~ 95
- 2 -
The invention relates to a process for the preparation
of hydrocarbons by catalytic reaction of carbon monoxide
with hydrogen.
The preparation of hydrocarbons from a mixture
of carbon monoxide and hydrogen by contacting this mixture
with a catalyst at elevated temperature and pressure
is known in the literature as hydrocarbon synthesis
according to Fischer-Tropsch. Catalysts frequent]y employed
for this purpose comprise one or more metals of the
iron group together with one or more promoters to increase
the activity and/or selectivity and sometimes a carrier
material such as kieselguhr. The catalysts employed
in practice for hydrocarbon synthesis according to Fischer-
Tropsch are as a rule prepared by precipitation or by
melting. Briefly, the preparation of the catalysts by
precipitation is effected by making basic an aqueous `~
solution of a salt of a metal of the iron group to which
a salt o~ a promoter and a carrier material may be added,
if required, as a result of whlch the catalyst is formed
as a precipitate. To this precipitate a promoter and
a carrier material may be added. Examples of suitable
catalysts for the hydrocarbon synthesis prepared according
to the precipitation route, are Fe~Cu/Na/SiO2 catalysts
comprising 4.5 parts by weight of copper, 4 parts by
weight of sodiux and 20 parts by welght of silicon oxide
`''`'~ " ': ~
' . ~
~S~ 9S
per 100 parts by weight of iron, as well as Co/ThO2/~gO/
kieselguhr catalysts comprising 5 parts by weight of
thorium oxide, 8 parts by weight of magnesium oxide
` and 100-200 parts by weight of kieselguhr per 100 parts
by weight of cobalt. The preparation of the catalysts
by melting in the case of, for example, iron catalysts
is effected by fusing iron oxide with one or more promoter
oxides. Examples of suitable catalysts for hydrocarbon
synthesis prepared according to the melting route, are
Fe/Al2O3/~2O/CaO catalysts comprising 5 parts by weight
of aluminium oxide, 1 part by weight of potassium oxide
and 3 parts by weight of calcium oxide per 100 parts
by weight of iron.
Both the precipitation route and the melting route
are rather unattractive methods for the preparation
of the present catalysts, because their reproducibility
is low. Besides, the precipitation route is very time- ;
consuming, while the melting route requires much energy.
With respect to the performance of the above-mentioned
catalysts when used for hydrocarbon synthesis according
to Fischer-Tropsch the following remarks can be made.
The performance of catalysts for hydrocarbon synthesis
according to Fischer-Tropsch is ~ssessed in the light
of their activity and selectivity which have been defined
as follows. The activity of the catalyst is the number
of grammes of hydrocarbons pr-duoed per litre of catalys~
,
9~
,~
per hour. The selectivity of the catalyst is the weight
Or C3~ hydrocarbons produced, calculated as a percentage
of the total quantity of hydrocarbons produced. ~or
a catalyst for hydrocarbon synthesis according to Fischer-
Tropsch both a hi~h activity and a high selectivity
are desirable. Of these two parameters the selectivity
is considered the more important one. Apart from the
above-mentioned disadvantages of the catalysts prepared
by precipitation or melting, their catalytic performance -
is not very satisfactory either. A characteristic of ~-
the catalysts prepared by melting is that in the temperature
range of about 300-350G, considered optimal for these `~
catalysts, they exhibit a high activity, but only a
moclerate selectivity. Attempts to increase the selectivity
of the catalysts prepared by melting to the level of
the catalysts obtained by precipitation, by applying ~;
lower temperatures, as well as attempts to increase
the activity of the catalysts prepared by precipitation
to the level of the catalysts obtained by melting, ~;
by applying higher temperatures, have remained unsuccessful.
It is true that these measures can bring about an improvement
of the property in question3 but this is accompanied ~ ;
by such a deterioration of the other major property
of the catalyst that this other property has fallen
below the minimum allowable level for this property `
long before the first property has reached the desired
:.:
. ' `
`""~ ~;''
~ ~ .
~LU~9~5
high le~rel.
In view of the increasing interest in hydrocarbon
synthesis according to Fischer-Tropsch there is an urgent
need of catalysts for this purpose which possess an
activity comparable with that of catalysts obtained
by melting as well as a selectivity comparable with
that of catalysts prepared by precipitation. Further
it is desirable for preparation of these catalysts to
be effected in a way that does not have the drawbacks .
of the above-mentioned precipitation or melting route.
An extensive investigation has been carried out
by Applicant into the use for hydrocarbon synthesis
according to Fischer-Tropsch of catalysts comprising
10~75 parts by weight of one or more metals of the iron
group per 100 parts by weight of carrier, together with
one or more promoters in a quantity of 1-50% of the
metals of the iron group present on the catalyst and
which catalysts have been prepared by impregnation of
a porous carrier with one or more aqueous solutions
of salts of the metals in question of the iron group
and of the promoters in question followed by drying
and calcining of the composition. It has been found
that the selectivity of these catalysts, which can
be prepared with good reproducibility in a simple way,
is highly dependent on the quotient of the specific
average pore diameter (p~ and the specific average particle
:, :
- 6 -
diameter (d) of the catalysts. For further information
concerning p and d as well as the way :in which these
are determined, see Dutch patent application No. 7214397,
in which these catalyst data were discussed in detail.
- The investigation concerning the above-mentioned catalysts
prepared by impregnation has revealed that these catalysts ~ ~;
with a p of at most 10,000 nm and a d of at most 5 mm,
display both an excellent activity and an excellent
selectivity when used for hydrocarbon synthesis according ;~
to Fischer-Tropsch, if the quotient p/d is larger than
2.0 (p in nm and d in mm).
The present patent application therefore relates
to a process for the preparation of hydrocarbons by
catalytic reaction of carbon monoxide with hydrogen,
~15 using a catalyst prepared by impregnation having the
above-mentioned properties. ~ ~;
; Comparison of the selectivity of the present catalysts
; prepared by impregnation with that of the afore-mentioned ~-
catalysts prepared by melting~ reveals that the latter
generally display such a low selectivity that for a
hydrocarbon synthesis in which the selectivity is of
major importance - as in the present patent application - "
these catalysts are of no interest and need not be further
discussed. Comparison of the activity of the present
oatalysts prepared by impregnation with that o~ the ~:
, ~
, :
'',' ~`' '
afore-mentioned catalysts prepared by precipitation,
reveals that the former show a considerably larger increase
in activity per degree of rise of the reaction temperature
and moreover that the maximum temperature at which these
catalysts can still be employed bearing in mind the
selectivity is considerably higher. The possibility
of employing the present catalysts prepared by impregnation
at a higher temperature than those prepared by precipitation,
offers, in addition to the gain in activity, the advantage
that the waste heat of the process can be utilised more
effectively, for example for the production of steam
with a higher pressure and higher temperature than is
possible with the catalysts prepared by precipitatlon.
In the process according to the invention the starting
material has to be a mixture of hydrogen and carbon ~;
monoxide. Such a mixture can very suitably be prepared ~ ~`
; by the partial combustion of a material containing carbon
and hydrogen. Examples of such materials are lignite,
anthracite, coke, crude petroleum and fractions thereof,
as well as oils produced from tar sand and from bituminous
shale. During the partial combustion the feed, in a
finely dispersed form, is con~erted with the aid of oxygen or ~
air enriched with oxygen, if desired, into a gas mixture ~ ;
comprising inter alia, hydrogen, carbon monoxide, carbon
dioxide, nitrogen and water. In the partial combustion steam ;
;'
- 8
is preferably employed as temperature moderator. The partial
combustion is preferably carried out at a temperature between
900 and 1500C and a pressure ~etween 10 and 50 bar. In
order to be able to remove impurities such as ash, carbon- ~-
aceous material and hydrogen sulphide from the gas obtained
? in the partial combustion, which gas has a temperature of
more than 1000C, this gas must first be cooled down to
a temperature between 100 and 200C. This cooling may be
very suitably effected in a boiler in which steam is generated
by means of the waste heat. ~he cooled gas may be freed
from practically all solid matter by washing with water.
After this wash, in which the temperature of the gas has
fallen to 20-80C, the gas is further purified by removal
of hydrogen sulphide and carbon dioxide. This may be very
suitably effected by means of the ADIP process or the SULFINOL
process.
In the process according to the invention the starting
material is a mixture of hydrogen and carbon monoxide having ;~
preferably a molar ratio between 0.5 and 3. If the process ;
` 20 is carried out using an iron catalyst, special preference
is given to the use of a mixture of hydrogen and carbon
monoxide with a molar ratio between 0.5 and 1.5, and in
the case of a cobalt or nickel catalyst to the use of a
mixture of hydrogen and carbon monoxide with a molar ratio -~
between 1.2 and 2~5. If the available mixture of hydrogen ~ ;
` ''^~ :`'~
'''.`' ~. '
~9~5
. .
g
.~
and carbon monoxide does not have the requlred molar ratlo,
this .may be adjusted by adding hydrogen or carhon monoxide.
An increase of the hydrogen content of the mixture with respect
to the carbon monoxide content may also be very suitably
effected by submitting the mixture to the well-known water
gas shift reaction.
The process according to the invention is preferably
carried out at a temperature of 200-350~C, a pressure of
10-70 bar and a space velocity of 500-5000 and in particular
of 500-2500 Nl gas/litre of catalyst/hour. If the process
is carried out using an iron catalyst special preference
is given to a reaction temperature of 250-325C and a reaction
pressure of 20-50 bar and, when a cobalt or nickel catalyst
is employed, to a reaction temperature of 220-300C and a
reaction pressure of 10-35 bar.
Catalysts employed in the process according to the invention `
comprise 10-75 parts by weight of one or more metals of the
iron group, per 100 parts by weight of carrier, together ;'
with one or more promoters in a quantity of 1-50% of the ;~
quantity of metals of the iron group present on the catalyst.
With respect to metals of the iron group, preference is given
to the use of catalysts comprising 15-50 and in particular
20-40 parts by weight of one or more of these metals per
' 100 parts by weight of carrier. With respect to the promoters,
` 25 preference is given to the use of catalysts comprising one
.~
~.; ~, :,
~'~ - ':
~v~
`--- 10
or more pro~oters in a quantity of ~ 40 and in particular
10-20% o~ the metals of the iron group ~resent on the catalyst.
As promoters for the catalysts according to the inventlon
a large number of elements is eligible. As examples the following
may be mentioned: alkali metals, alkaline-earth metals,
metals of Group VIB, Ti, Zra Al, Si, As, V, Mn, Cu, Ag,
Zn, Cd, Bi, Pb, Sn, Ce, Th and U. Very suitable combinations
- of promoters for iron catalysts according to the invention
consist of an alkali metal such as K, a readily reducible
metal such as Cu or Ag and~ if desired, a metal that can
only be reduced with difficulty such as Al or Zn. An example
of a very suitable iron catalyst according to the invention
is a catalyst comprising iron, potassium and copper on silica
as the carrier. I~ in the process according to the invention
use is made of an iron catalyst comprising K as selectivity
promoter, preference is given to the use of a catalyst comprising
not more than 0.15 g of K per-g of Fe, because it has been
found that, when higher K concentrations are used, the selectivity
does not increase any fther, ~hereas,-owing to coke deposition
on the catalyst the stability decreases sharply. Very suitable
promoter combinations for cobalt catalysts according to the
invention consist of an alkaline-earth metal and Th, U or
Ce. An example of a very suitable cobalt catalyst according
. ~ . .. .
to the invention is a catalyst comprising cobalt, magnesium ;~ ~;
and thorium on silica as the carrier. Other very suitable
' ! ', ~'~,,. .`
'.'', '``~,
`''`"''~' ,';' '. ~`
'~.
cobalt catalysts according to the invention are catalysts
comprising Co/Cr, Co/Zr, Co/Zn or cO/n~g on silica as the
carrier Very suitable promoters for nickel catalysts according
~`~ to the invention are Al, Mn, Th, ~,~ and U.
In the process according to the invention catalysts
are employed which have been prepared by impregnation of
a porous carrier with one or more aqueous solutions of salts
of metals of the iron group and salts of promoters followed
by drying and calcining of the composition. The carrier
used to prepare the catalysts according to the invention
may be amorphous or crystalline. Examples of suitable carriers
are silica, alumina, zirconia, thoria, magnesia, boron oxide
as well as combinations thereof such as silica-alumina and ~`~
silica-magnesia~ Other suitable carriers are zeolites such
as mordenite, faujasite and zeolite-omegaO Zinc oxide has
also proved to be a suitable carrier for the present catalysts. ~ ;
In the preparation of the catalysts the salts can be incorporated
into the carrier in one or more steps. The material is dried
between the individual impregnation steps. Application of
a multi-step impregnation technique may be necessary for
the preparation of catalysts with a high metal content.
The salts of the metals of the iron group an~ the salts of
the promoters may be incorporated into the carrier separately `~
or together starting from one solution. An attractive manner
of incorporating the metals of the iron group and the promoters
. ,; .
,`, ' .
` ~
'~': '," '
3S
- 12 -
'; into the carrier is the dry i~pregnation technique, according
to ~ihich the carrier is contacted with an aqueous solution
of the salts concerned, which aqueous solution has a volume
substantially equal to the pore volume of the carrier. Absorption
of the aqueous solution may be facilitated by heating the
mixture gently. If this method of preparation is chosen for
the preparation of catalysts with a high metal load, it may
be necessary to carry out more than one dry impregnation
and dry the material between the individual impregnation
steps. ~;
The catalyst employed in the process according to the
; invention should have a specific average pore diamter (p)
of at most 10,000 nm and a specific average particle diameter
(d) of at most 5 mm. As regards p preference is given to
catalysts with a p of at most 1000 nm and in particular with ~;
, a p of at most 500 nm. The choice of d is determined by the
; way in which the process is carried out. A very suitable
embodiment of the process according to the invention is that ;;;~
in which the feed is passed upwards or do~nwards through
a vertically disposed reactor ccntaining a fixed or movingbed
of the catalyst parkicles concerned. The hydrocarbon synthesis ~`
may, for example, be effected by passirg the feed upwards
through a v`ertically disposed catalyst bed, the gas being " `
made to flow at such a rate as to cause expansion of the '!,`' ,`` ,,
catalyst bed. If desired, the hydrocar~on synthesis may also ~}~ `
~ I .
'' '-,~ `
3~9f~9S
be effected using a suspension of the catalyst in hydro-
carbon oil. According as the hydrocarbon synthesis is effected
using a fixed catalyst bed, an expanded catalyst bed or a
~ catalyst suspension, preference is given to the use of catalyst
', 5 particles with a d between 1 and 5 mm, 0.5 and 2.5 mm and
20 and 150 ~, respectively. ~hen the hydrocarbon synthesis
is carried out using a fixed catal~st bed, waxy hydrocarhons
will be deposited on the catalyst, as a result of which the
~ activity decreases. To get round this difficulty the catalyst
! ~0 may be was~ed periodically, for example for some hours per
1000 run hours, with a solvent for the above-mentioned heavy
hydrocarbons. A suitable solvent for this purpose is for ~ ;
example a mixture of methyl ethyl ketone and toluene. ~he
above-mentioned deactivation of the catalyst is preferably
counteracted by continuously washing the catalyst with a
fraction of the product prepared in the hydrocarbon synthesis.
For this purpose preference is given to a fraction with an
initial boiling point above 200C and a final boiling point ;
below 550C. An additional advantage of the above-mentioned -
continuous wash of the catalyst is that temperature control
; during the highly exothermic hydrocarbon synthesis reaction
is simplified. ;-
The reaction product which in the process according
to the invention leaves the reactor contains in addition
~ 25 to hydrocarbons and oxygen-containirlg hydrocarbons whose
;" molecular weight extends over a wide range, inter alia water, ~;
, . '!. ~ .
''`:` ~'':'''~. '
', " ' ' '` '
. ~.. ~.
'~ :
nitrogen, carbon dio~ide and unconverted carbon monoxide
and hydrogen. If the process according to the lnvention
is carrled out in what is known as "once-through" operation,
the C3~ fraction is separated from the reaction product as
end product. If the process according to the invention is
carried out in what is known as "recycle" operation, the
C3+ fraction is likewise separated from the reaction product
as end product, but now the rest of the reaction product
after reduction of the carbon dioxide content, if necessary,
is recycled to the reactor, applying a bleed stream to avoid
the build~up of nitrogen, inter alia.
The invention is now elucidated by means of the following
example. i~
FXAMPLE
23 catalysts (catalysts A-D and i-19) were tested for
the hy~rocarbon synthesis according to Fischer-Tropsch. The
preparation of the catalysts was carried out as follows.
~`l Catalyst A -~ -
A boiling solution of 2886 g of Fe~N03)3.9 aq and 76 g `~
of Cu(N03)2.3 aq in 10 l of water was added with stirring ~; ;
to a boiling solution of 1000 g of anhydrous Na2CO3 in 10.5 l
of water. To the mixture thus obtained were added in succession ~ `~
130 g of anhydrous Na2C03 and 14 . 4 g of clay. After filtration
~ of the mixture the filter cake was washed with hot water
`s~25 until the filtrate was free of sodium and then washed with
l~.` ~ ' ;~ " ' '
,~,.'` ' . : -` ',
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-- 15 --
10 l of an aqueous solution which contained 10 g of NHI~MO3
per litre. The filter cake was Icneaded with 240 g of soda
water glass, dried for 24 hours at 110C and ground. The
catalyst A thus prepared by precipitation comprised 3.6 parts
by weight of Cu, 4.1 parts by weight of Na and 23 parts by
weight of SiO2 per 100 parts by weight of Fe.
Catalyst B
In a similar way as described hereinbefore for catalyst A,
a catalyst B was prepared by precipitation which comprised
4.43 parts by weight of Cu, 3.95 parts by weight of Na and
20.5 parts by weight of SiO2 per 100 parts by weight of
Fe.
Catalyst C '~ ,
An aqueous solution of 225 g of Fe(N0~)3.9 aq, an aqueous '
solution of 5.9 g of Cu(NO3)2.3 aq and an aqueous solution
of 3.2 g of KNO3, were combined and the volume of the combined
solution was made up with water to 150 ml. The solution was ;~
incorporated into 125 g of SiO2 with a total pore volume ~:
of 150 ml. After some time the co~nposition was dried at 120C, ;~,
calcined for 1 hour at 500C, ground and sieved. The catalyst
C thus prepared by impregnation comprised 25 parts by weight
of Fe, 1.25 parts by weight of Cu and 1 part by weight of
K per 100 parts by weight of SiO2.
''Catàlys't's' ~' a'_d' 1'-'19 `~
,25 In a similar way as described hereinbe'fore for catalyst ; '~
: ~
. ~ ''`' ,,
9'~ 3
- 16 -
C, catalysts D and 1-19 were prepared by impregnation.
In the preparation of the catalysts containing Th, ~g,
Co, Al, Cr and/or Zn as promoters, use was made of aqueous
solutions Or nitrates of the elements concerned. In the
preparation of the catalyst which contained Zr as promoter
use was made of an aqueous solution of zirconyl chloride.
The compositions of the catalysts as well as their
specific average pore diameters and specific average particle
diameters are given in Table A. The values given in the
table for p and d were determined by means of nitrogen
adsorption/desorption, mercury penetration and sieve analysis
as described in Dutch patent application No. 7214397. ;
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Cata~y,ts A-l) and 1-19 w~re testeci for h~/drocarbon
synthesis accordin~; to Fischer-Tropsch in a 250-ml reactor
containing a fixed catalyst bed of the catalyst in question,
with a volume varying between 25 and 75 ml. Before being
~ 5 used for the hydrocarbon synthesis all the catalysts were
- first reduced for 2 hours with a mixture of hydro~en and
, nitrogen (molar ratio 3:1), at atmospheric pressure, 280C
and a superficial gas velocity of l.6 m/sec.
For the preparation of hydrocarbons a mixture of carbon
,; lO monoxide and hydrogen was passed over the catalysts at elevated
temperature and pressure. The reaction product was worked
~ up by cooling it down at the reaction pressure in two steps
:' first to 150C which caused separation of a heavy liauid `~
phase and then to 15C which caused separation of a light
15 liquid phase and a gas phase. The composition of the reaction
'-~ product was determined by means of TBP-GLC analysis.
'~~ The reaction conditions used in the experiments as
well as the results obtained are given in Table B.
With the exception of the experiments mentioned under
19 and l9A all other experiments were carried out in once-through
operation. The activities and selectivities listed relate
to the situation at run hour 500, with the exception of
those mentioned under 18, 18A, 18B, 19 and l9A.
~ The results mentioned under l9 and l9A were obtained
,~ 25 in an experiment carried out in recycle operation. In this ;;~
~;` ~.` ~, `:'
~ ~:
!: ~
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- 20 -
experiment the catalyst was continuously washed at a space
velocity of 0.6 l.l. 1.hour 1 with part of the heavy liauid
phase which had separated from it when cooling the reaction
product to 150C. The results mentioned under 19 and 19A ~
relate to the situation at run hours 150 and 700, respectively. - -
The results mentioned under 18, 18A and 18B were obtained
in an experiment in which during the experiment the catalyst
was washed for some hours per 1000 run hours with a 1~
(v/v) mixture of methyl ethyl ketone and toluene. The results ;;;
mentioned under 18, 18A and 18B relate to the situation
at run hours 400, 800 and 900, respectively. I~lashing of
,
the catalyst took place-between run hours 800 and 900~ ; ;`
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Of ~he 42 experi~ents given in Table ~ only experiments
9-42 are experiments according to the invention. In these
experiments catalysts were used which had been prepared by
lmpregnation and which satisfied the conditions: p < 10,000 nm,
d < 5 mm and p/d > 2. Experiments 1-8 are outside the scope
of the invention and have been included in the patent application
for comparison. Experiments 1-4 were carried out using catalysts
prepared by precipitation. Experiments 5-8 were carried out
using catalysts which, although prepared by impregnation,
did not satisfy the condition p/d > 2.
The experimental results presented in Table B give
rise to the following remarks~
1. Comparison of exp. 1 with exp. 2 and comparison of `~
exp. 3 with exp. 4 reveals that with the catalysts
prepared by precipitation, an increa~e in activity
~,
due to the use of a higher temperature, is accompanied
~ by a sharp decrease in selectivity. The activity and
'` selectivity observed in exp. 1 are substantially in
line with what may be expected of a good catalyst.
The activity and selectivity found are comparable with
~I those attained by Sasol in commercial application of
the process of Lurgi Chemie.
2. Comparison o~ exp. 5 with exp. ~, 113 16 and 18 and
comparison o~ exp. 7 with exp. 33 reveals that the
catalysts prepared by impregnation satisfying the condition
p/d ~ 2 have a higher activity and selectivity than ~
~ ,.
~ 3~95
:
- 25 -
catalysts prepared by impregnation which do not satisfy
this condition.
3. It is generally assumed that khe maximum temperature
and pressure at which Co-catalysts prepared by precipitation
may be used are about 215C and 15 bar, respectively.
The use of higher temperatures and/or pressures leads ~-~
to very rapid deactivation of the catalyst. The experimental
work has proved that the Co-catalysts according to
the invention may be used at considerably higher temperatures
and pressures.
4. Comparison of exp. 12, 13 and 14 with each other reveals
that the activity of the catalysts according to the
invention at first increases with increasing pressure
until a maxi~um value has been reached. Upon a further
increase in pressure a decrease in activity occurs.
5. Comparison o~ exp. 21 with 22 and comparison of exp. -
23 with 24 reveals that with the catalysts according
- ~ ~
to the invention, an increase in activity due to the ;
~` use of a higher temperature, is accompanied by only
a slight decrease in selectivity.
6. Comparison of exp. 24 with 25 reveals that with the
catalysts according to the invention, the use o~ a
lower H2/C0 ratio leads to an increase in selectivity `
and a decrease in activity.
7, Comparison of exp. 17 with 40 reveals that with the `~
Fe-catalysts according to the invention, replacement
-, ~
?~
" .
, ~ , ~
~.
. . . ~ . . .
~01~ 5
- 26 -
of Cu by Co leads to an increase in both activity and
selectivity.
8. Comparison of exp. 11, 21 and 23 with each other reveals
that with the Fe-catalysts according to the invention,
an increase in K-content leads to an increase in selectivity.
A very high K-content, however, has a detrimental effect
on the activity. The experimental work has further
shown that an increase in the K-content of the Fe-catalysts
according to the invention leads to a sharp increase
of oxygen-containing compounds in the reaction product. ;
Thus, when using an Fe-catalyst according to the invention
comprising 5 parts by weight of K per 25 parts by weight
of Fe, about 80 per cent by weight of oxygen-containing
compounds was found in the reaction product.
9. Comparison of exp. 35, 36, 37, 38, 39 and 41 with each ~; :
other reveals that in addition to the promoter combination
Th/Mg frequently used in the Co-catalysts prepared
by precipitation, each of these elements individually,
as well as the elements Cr, Zn and Zr, are likewise
very suitable for use as promoters for the Co-catalysts
according to the invention. The promoters may be ranked
as follows in order of increasing attractiveness for
this application: Zn, Th/Mg, Mg, Th, Cr and Zr.
10, Comparison of exp. 11 with 15 reveals that with the
P 25 catalysts according to the invention a reduction in
~` ~
.~
~V~ 95
- 27 -
particle size leads to an increase in activity.
11, Co~.parison of exp. 18 and 18A with 19 and l9A revea~s
that the activity of the catalysts according to the
invention is better maintained when a heavy fraction
of the reaction product is continuously passed over
the catalyst.
12. Comparison of exp. 18 with 18B reveals that a discontinuous
wash of the deactivated catalys with a solvent leads
to a complete recovery of the activity and selectivity.
Comparison of exp. 18 with 18A gives an impression
of the deactivatlon that tends to occur. Comparison
of exp. 18A with 18B gives an impression of the effect
of washing.
13" Comparison of exp. 21 with 29, 20 with 31 and 41 with
42 reveals that for the c~alysts according to the invention
not only SiO2 but also ZnO, MgO-A12O3 and Al2O3 are -
very suitable carriers.
~`~`; ;'' ''`
~ , . . ; ~ ~ , -
