Note: Descriptions are shown in the official language in which they were submitted.
1049049
The invention relates to a process for the preparation
of hydrocarbons.
The process of the invention comprises the following
steps:
1) preparation of a hydrogen- and carbon monoxide-containing
gas by partial combustion of a carbonaceous material;
2) conversion of carbon monoxide with steam into carbon
dioxide and hydrogen in the gas obtained in step (1),
3) separation of part of the carbon dioxide from the gas
obtained in step (2),
4) reaction of the remaining gaseous carbon dioxide with
hydrogen to form hydrocarbons, and
; 5) separation and drying of the resultant hydrocarbons.
The partial combustion according to step (1) of the
process according to the invention can be carried out in any
desired manner. A survey of the known processes for preparing
hydrogen- and carbon noxide-containing gases by partial com-
bustion of coal or oil is given in "Ullmanns Enzyklopadie der
technischen Chemie". Vol. 10 (1958), pp. 360-458. Several
processes for the partial combustion of carbonaceous material
are used on a commercial scale. If the qtarting material is
liquid, preference is given to the "Shell Gasification Process"
for step (1) of the process according to the invention. In the
r case of solid starting material it is advantageous to use the
"Koppers-Totzek Process".
Any carbonaceous material can be used as feed for the
process according to the invention. By carbonaceous material is
meant any fuel consisting substantially of chemically bound or
unbound
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1049049
carbon. This material may contain oxygen, sulphur, nitrogen,
metals, hydrogen and/or ash. A starting material of this type
comprises, for example, lignite, bituminous coal, sub-bituminous
coal, anthracite, coke, mineral oil or a fraction thereof, oil
derived from tar sand and oil derived from bituminous shale.
If the feed is solid, it is preferably first rendered
into powder form before being converted by partial combustion,
in order that the partial combustion will proceed more rapidly
and more completely. The particle size of this powder is
preferably so chosen that 70% of the solid feed can pass a
200-mesh sieve.
In the partial combustion according to step (1) of the
process according to the invention the carbonaceous feed is
converted with oxygen into a gas mixture containing mainly
hydrogen and carbon monoxide. The purity of the oxygen is
preferably at least 90% by volume, nitrogen, carbon dioxide
and argon being allowed as impurities. Steam can be supplied
as temperature moderator. A quantity of 5-150% by volume of
steam, based on the oxygen, is suitably added to the oxygen
or to the reaction mixture.
The oxygen is preferably preheated before it is supplied
to the carbonaceous fuel. This preheating is suitably performed
i by indirect heat exchange, for example with the hot product
' gas obtained in step (1) of the present process. By preheating,
1049049
the oxygen is preferably brought to a temperature in the range
from 200 to 500C.
After the preheating, the hot oxygen is advantageously
mixed with the carbonaceous ruel and the oxygen/fuel mixture
is introduced, preferably as a jet, into a reactor. This reactor
preferably consists of an empty steel vessel the interior Or
which is lined with heat-resistant material. A preferred
reactor is described in the U.K. patent¦specifications 780,120,
832,385, 850,409 and 967,885.
The partial combustion is preferably carried out at a
temperature in the range from 900 to 1800C, which temperature
results from the reaction between the carbonaceous fuel with
oxygen and steam.
In a preferred embodiment the mixture of fuel and oxygen
is introduced into the reactor at a high velocity. A suitable ~ -
' linear velocity is in the range from 10 to 200 m/sec. The
pressure maintained in the reactor may vary within wide limits
and is advantageously maintained within the range from 1 to
200 bar abs.
In order to convert into gas as much as possible of the
fuel introduced into the reactor, the fuel particles or droplets
must be present in the reactor for a certain residence time.
It has been found that a residence time in the range from 0.1
to 12 seconds is sufficient to achieve this object.
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1049049
After the carbonaceous starting material has been converted
into gas, this reaction product, which consists mainly of H2,
C0, C02 and H20, is discharged from the reactor.
This gas has a hieh temperature, generally a temperature
over 1100C, and may contain impurities such as ash, solid
carbonaceous material and hydrogen sulphide.
To permit the removal of any impurities the gas is preferably
first cooled in a boiler in which steam is generated by means
of the waste heat.
The solid matter content of the crude gas leaving the boiler
is kept low by choosing the conditions in the reactor appropriately.
A reduction of the solid matter content may nevertheless be
desirable, for example if the gas must be desulphurized and also
for the next step of the present process in which carbon monoxide
is converted with steam into carbon dioxide and hydrogen.
For this purpose the gas is preferably passed through a
scrubber in which it is washed with water. An apparatus of this
t type is described in the U.K. patent specification 826,209. Such
a washing treatment yields a gas which contains substantially
no solid matter and which has a temperature in the range from
20 to 80C. The gas freed of solid matter has a composition which
usually varies within the following limits.
,
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1049049
Table I
Vol.%
H2 20-60
CO 70-40
C2 0-20
H20 0-20
CH4 0-20
H2S 0-3
N2 0-5 ~ :~
A 0-5 --
The gas can be further purified by removing H2S and, ir ~:
desired, part of the C02. This purification can be carried out
in a known manner.
H2S and C02 are preferably removed from the gas by the
ADIP process or the SULFINOL process, which are described in
the U.K. patent specifications 1,444,963, 1,131,989, 965,358,
957,260 and 972,140.
The gas freed of solid matter and H2S has a composition
which varies within the following limits:
Table II
`.` . Vo~
. H2 20-60
CO 70-40
C2 0-20
.. ~ H20 0-20
CH4 0-20
H2S 0-0.01
A 0-5
'`',
."`.
^'.
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1049049
It is passed to step (2) of the process according to the
invent lon .
In this step a large part of the carbon monoxide present
is converted by reaction with steam into carbon dioxide and
hydrogen according to the reaction
CO + H20 ~ co2 H2
This step may be performed in any desired manner. It is generally
preferred to carry out this conversion in two or three steps in
the presence of a catalyst. The first step(s) is (are) suitably
performed at a temperature in the range from 250 to 450C. The
last step is advantageously performed at a temperature in the
range from 200 to 400C. For the relatively low-temperature step
; a copper-zinc catalyst is preferably used. For the relatively
high-temperature step(s) an iron-chromium catalyst can suitably
be used. The pressure may vary within wide limits. The reaction
is preferably carried out at a pressure between 10 and 100 bar.
The quantity of steam present in the gas mixture which is
subjected to this reaction is preferably 1-20 mol per mol of C0.
After passing the second or third step of the present process
the dry gas mixture has the following composition:
Table III
Vol.%
H2 30-70
` C0 0.2 3
C2 25-50
CH4 0-15
N2 ~4
A 0-4
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1049049
This gas mixture is generally not of suitable composition
fcr use in the production of hydrocarbons by hydrogenation of
the carbon dioxide and carbon monoxide present. Part of the
carbon dioxide must therefore be remove~ fr~m the gas mixture.
This may be performed in any desired manner, such as washing
with a physical or chemical solvent for carbon dioxide, or by
selective adsorption of the carbon dioxide to solid materials
suitable for this purpose. Such processes are described in
"Ullm~nns Enzyklopadie der technischen Chemie", Vol. 9 (1958),
pp. 756-766.
To remove part of the carbon dioxide, the gas mixture is
preferably entirely or partly cooled to a temperature in the range
from -10 to -80C and at a pressure between 1 and 200 bar abs.
In certain combinations of sufficiently low temperature and
sufficiently high pressure, part of the C02 liquefies so that
it can be separated in a simple manner. It is therefore indeed
preferable to select the combination of temperature and pressure
in such a way that liquid C02 is formed. It is also possible,
however, to render part of the C02 directly into the solid state
and subsequently separate it, although this latter treatment is
more difficult than the separation of liquid C02.
The conditions are preferably so selected that 50-80% of
the C02 can be separated.
After the separation of part of the C02 the gas mixture has
~ 25 the following composition:
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Table IV
Vol.%
H2 60-78
C0 0.2-3
C2 20-25
CH4 0-15
N2 0-5
A 0-5
This gas mixture is used for the production of hydrocarbons
according to the reactions:
) 2 + 3nH2 J CnH2n + 2nH2
(b) nC02 + (3n+1)H2 ~ CnH2n+2 2
(c) nC0 + 2nH2 ~'~~ CnH2n + nH2
(d) nC0 + (2n+1)H2 ~~~~ CnH2n+2 + nH2'
This step can be carried out in any desired manner.
A survey of the known methods is given in "Ullmanns Enzyklopadie
der technischen Chemie" (1957), Vol. 9, pp. 739 and 740.
The gas mixture is preferably passed over a catalyst at a
temperature in the range from 150 to 380C and a pressure in the
range from 2 to 100 atm.g. The catalyst used preferably contains
iron, cobalt, nickel or ruthenium on a carrier.
After the formation of the hydrocarbons the reaction product
has the following composition:
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~049049
Table V
Weight %
H20 60-70
C2 5-10
Hydrocarbons 20-26
N2 0-26
A 0-7
H2 0-2
CO 0-1
The reaction product is subsequently cooled, as a result
of which most of the hydrocarbons and water becomes liql~id and is
separated from the still gaseous mixture of light hvdrocarbons
with at most 4 carbon atoms and C02, N2, A and non-converted H2
and C0. After separation and drying of the liquid product pure
hydrocarbons are obtained.
The invention will now be further elucidated with reference
to the following Example.
EXAMPLE
The starting material used was coal of the following com-
position:
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Weight %
C 73.7
H 5.1
0 8.8
S 0 9
N 1.6
ash 9.9
This coal contained 33.8% by weight of volatile components and
also 2.6% by weight of water.
The coal was gasified by partial combustion by means of
0.841 kg of 2 and 0.234 kg of steam per kg of anhydrous and
ashless coal. The temperature used was 1100C and the pressure
40 bar abs.
After cooling to 40C and removal of solid matter, the
resultant gas had the following composition:
Vol.%
H20 0.18
H2 33 95
C0 62.08
. C2 1.19
CH4 1.33
H2S 0.30
', N2 0~75
A 0.22
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This gas was purified by means Or the Sulfinol Process, in
which the gas was washed at 40C and 39 bar with a mixture Or
sulfolane, di-isopropanolamine and water.
The composition of the purified gas was as follows:
Vol.%
H20 0.18
H2 34.46
C0 63.o3
~H4 1.35
N2 0.76
A 0.22
The purified gas was subjected to the water gas shift
reaction, in which carbon monoxide is converted with steam into
carbon dioxide and hydrogen in three steps.
All the steps were carried out at a pressure of 38 bar. In
the first two steps an iron-chromium catalyst was used. The
~0 temperature was 300-400C.
In the last step a copper-zinc catalyst was used at a
temperature of 250C.
After drying, the product gas of the water gas shift reaction
had the following composition:
,
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. :. . . -
., ~ ' ' ' ' :~ :
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1049049
Vo 1 . %
H2 59.66
C0 0.50
C2 38.40
CH4 0.83
N2 0.47
A 0.14
This gas was subsequently cooled at a pressure of 30 bar to
a temperature Or -50C, as a result of which about half of the
C2 present condensed. This liquid C02 was separated after which
the dry residual gas had the following composition:
Vol.%
H2 73.21
C0 0.61
2 24.41
CH4 1.02
N2 0.58
A 0.17
This gas was heated to 265C and it was passed at this
temperature and a pressure of 50 atm.g. over an iron-containing
catalyst, forming hydrocarbons by hydrogenation of the carbon
dioxide and carbon monoxide present. After condensation, separation
of gaseous components and water, and drying pure hydrocarbons were
obtained.
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1049049
By means of the process described hereinbefore a quantity of
390 kg of hydrocarbons was produced from 1000 kg of anhydrous and
ashless coal.
