Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to a process of producing a
methane-containing fuel gas by a reaction of methanol and water
vapor under superatmospheric pressure on a nickel-containing
catalyst.
Town gas or a fuel gas which can be used as a sub-
stitute for natural gas can be produced by known processes,
which can be carried out with high efficiency and result in a
gas which is of excellent quality and suitable for being
supplied to existing pipe systems for distribu-ting natuxal gas
or town gasO It is also known that the capacity of napththa-
cracking plants used to produce fuel gas can be increased at times
of peak demand by an addition of methanol. In such an instance,
vaporized methanol is added to cracked gas, which contains water
vapor and is at a temperature of about 400C. The mixture is
then catalytically reacted on a catalyst which is suitable for
the shift-conversion of CO. In this way, a gas having a high
calori~ic value is produced so that the capacity of existing
cracking plants can be increased by about 25 to 30%.
The use of methanol as the only starting material in
the production of gas having a high calorific value is problematic
when the gas is to be used to meet basic demands because methanol
is expensive. On the other hand, methanol is highly suitable
for producing gas because methanol can be transported and stored
in a simple mannerO For this reason, methanol is preferred in
a supply system to meet peak demands, e.g., in winter~
In a known process, fuel gas for peak demands is
produced by a catalytic reaction of methanol and water vapor.
. In that process, methanol, water vapor, and air are supplied
at inlet temperature of about 350C and are reacted on a high-
nickel catalyst on an alumina support. Air is supplied at acontrolled rate mainly in order to produce a gas which has the
desired calorific value. ~n the other hand, the supply of air
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has the disadvantage that the produc-t gas has an excessively
high density so tha-t considerable quantities of CO2 must be
scrubbed therefrom. The supply of air has also the resul-t that
the gas leaving the cracking reactor is at an excessively high
temperature and for this reason has an undesirably high CO
content, which must be converted in a succeeding shift conversion
stage. The high reaction temperatures reached in the known
process impose a high stress on the catalyst material and cause
the same to be deteriorated wi-thin relatively short -time.
It is an object of the invention -to carry out -the
process described first hereinbefore in such a manner tha-t a
supply of air is not required and that the carbon monoxide
eontent of the produe-t gas is minimized. This is accomplished
aecording to the invention by supplying water vapor and
vaporized methanol under superatmospheric pressure on a nickel
eatalyst, the water vapor and vaporized me-thanol being supplied
at a weight ratio of about 0.5 to 1.5 and at inlet -temperature
of about 300 to 500C to a reactor and being reaeted -therein
under adiaba-tie conditions and under a pressure in the range of
about 10 to 40 bars; the niekel eatalyst eon-tains 25-50% by
weight niekel in the form of the compound Ni5MgA12Og, 5-40% by
weight high-alumina eement, and at least 5% by weight zireonium
dioxide. The produet gas leaving -the reactor at temperatures of
about 500 to 700C is subsequently eooled.
This proeess results in a produet gas whieh has
typically a earbon monoxide eontent below 5% by volume based on
dry gas. After a sufficien-t cooling of the gas and a condensation
of wa-ter vapor therefrom, -the gas can be used as town gas wi-thout
need for a further conversion of gas constituents.
For a production oE certain grades of town gas having
an upper heating value of 4000 to 5000 kcal per s-tandard m3,
the process according -to the invention is carried out in such
1~ .
~(:97~7~8
.
a manner that the product gas is withdrawn from the reactor at
temperatures of 580 to 700C and is cooled and part of the
carbon dioxide is removed from the gas to an extent which
depends on the desired density of the town gas.
When a natural gas substitute which contains more than
90% by volume of methane (on a dry basis) is desired, the hot
product gas resulting from the catalytic cracking of methanol
is cooled to 250 to 350C and is reacted in at least one methanat-
ing stage with water vapor on a nickel-containing catalyst
material, whereafter the methanated gas is scrubbed to remove
surplus carbon dioxide. The methanation is carried out under
conditions known per se.
The catalytic reaction of methanol and water vapor in
the process according to the invention is considerably improved
by the use of the above type of catalyst.
A first embodiment of such a catalyst will be described
hereinafter. This catalyst contains the compounds Ni5MgA12Og
and ZrO2 at a weight ratio of 13:1 and also contains a high-
alumina cement, which amounts to 306 of the total weight of
the catalyst. The high-alumina cement has the Eollowing
composition in percent by welght : 26.4 CaO, 71.9 A12O3 ,
0.2 Fe2O3, 0.2 MgO, 0.4 Na2O, 0.07 SiO2(and traces of K, Cr, Cu,
Mn, Ni and also Pb). The desirable catalyst of this first
embodiment is produced as follows :
Within 15 minutes, solution II is added to suspension I.
The suspension and solution have the following compositions:
Suspension I
1250 g sodium carbonate in 6 1 wa-ter containing 37.5 g ZrO2
Solution II
30 250 g Mg(NO3)2. 6H2O
1 .~`,
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1280 g Ni(N03)2. 6H20
690 g Al(N03). 9H20 in 6 1 water
The resulting precipitate consisting of Ni5Mg(OH)16.
C03.4H20 on zirconium dioxide is filtered o-ff, washed to remove
all alkali, dried at 110C for 12 hours anc~ then calcined at 400C
for four hours to produce a calcine which contains nickel oxide,
magnesia, alumina and zirconium dioxide as support components.
350 g of the calcine and 150 g high-alumina cement are mixed
in a dry state. When 60g of water have been added to the
mixture, the same is compacted to form 3x3 mm tablets, which are
then briefly watered and are subsequently caused to set completely
by being stored in a moist state at 40C in a closed system for
si~ days. The resulting tablets have an end face crushing
strength of 46~ kg/cm and a bul]~ density of 1.57 kg/l. In the
oxidic state, the catalyst has a nickel content of 28.7% by
weight. Before the catalyst is used, it is reduce~. This can
be accomplished by a treatment with hydrogen or other reducing
gases.
A second embodiment of a desirable catalyst contains
the compounds Ni5MgA1209, ZrO2 and a-A1203 at a weight ratio of
12:1:2 and also contains the high-alumina cement explained above,
in an amount of 15% of the total weight of the catalyst. The
catalyst of this second embodiment is duced as follows :
Solutions I and II are continuously combined with
suspension III at a temperature of 60C and in such a manner
tha~ the pH value of the solution does not decreas~ below 8.5.
The solutions and -the suspension have the followin~ compositions:
Solution I
~ .
1250 g sodium carbonate in 6 1 water
Solution II
255 g Mg(N03)2.6H20
1280 g Ni(No3)2.6H20
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690 g Al(NO3)3.9H2O in 6 1 water
Suspension III
-
43.2 g zirconium dioxide and 74~0 g ~- A12O3 in 3 1 water.
The resulting precipitate i~ filtered ofE and the
filter cake is washed and then dried at 110C for 12 hours and
is subsequently calcined at 400C for 4 hours.
425 g of the resulting calcine are mixed with
75 g high-alumina cement in a dry state. After an addition of
75 g water to the mixture the latter is compacted to`form
3 x 3 mm tablets. The catalyst is shortly watered and then
dried at 110C for 12 hours. After this treatmen-t, the catalyst
has an end face crushing strength of 453 kg/cm2 and a bulk
density of 1.52 kg/l. In the oxidic state, the catalyst
contains 30.3% by weight of nickel. The catalyst is reduced
beEore it is used.
Preferred embodiments of the invention will now be
described in greater detail with reference to the following
examples and the accompanying drawing which represents a flow -
diagram of a process according to the invention.
Referring first to the drawing methanol to be cracked
is supplied in conduit 1 and is forced by pump 2 into conduit 3
and conducted in the same through a plurality of heating stages
into a shaft reactor 4. The methanol is first heated in a heat
exchanger 5 and is then conducted in conduit 6 to another heat
exchanger 7 and is vaporized therein. Methanol vapor then flows
in conduit 8 to a heater 9 and thereafter in conduit 10 to the
reactor 4.
The water vapor required for the catalytic reaction in
the reactor 4 comes from the steam accumulator 12 and is added
to the methanol through conduit 11. The reactor 4 contains a
fixed bed consisting of the catal~st material. In the reactor
~, the reaction is carried out under autothermic, acliaba-tic
~LC3 777~3
conditions. Product gas leaving the reactor 4 through conduit
13 contains water vapor and owing to the exothermic reaction in
the reactor is at a temperature of 500-700C, which is higher
than the inlet temperature of the material to be reacted~
The product gas flowing in conduit 13 is first cooled
in a waste heat boiler 14, from which the product gas is
conducted in conduit 15 to the heat exchanger 7. From the latter,
the product gas is conducted in conduitl6 to a feed water preheater
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17. Further cooling stages for the product gas consist of the
heat exchanger 5, a fresh water preheater 18, and an air cooler
19. The cooled product gas in the conduit 20 may be directly
used as town gas.
When it is desired to produce certain grades of town
gas, the gas flowing in conduit 20 is fed to a known scrubber
for the removal of surplus carbon dioxide. If the gas is to be
prQcessed to produce a natural gas substitute, the product gas
is fed to a single- or multi-stage methanating plant. ~n that
case, C02 is scrubbed off before or behind the last methanating
stage.
The water vapor required for the reaction is produced
as follows: The feed water, which may consist, e.g., of condensate
recovered from the gas, is conducted in conduit 25 through the
fresh water preheater 18 and is then collected in the feed water
container 25, in which the water is degasified and from which
the water is fed through conduit 27, pump 28 and conduit 29 to
the preheater 17. From the latter, the water is fed through
conduit 30 to the steam accumulator 12. Condensate formed in the
steam accumulator 12 flows through a conduit 31 and a branch
conduit 32 to the heater 9, in which the water vapor is vaporized
by heating means, not shown. The steam flows in conduits 33 and
34 back to the accumulator 12. Another portion of the condensate
in conduit 31 is conducted in conduit 35 to the waste heat
boiler 14 and is at least partly vaporized there and fed through
conduit 36 to the return conduit 34.
Example 1
Town gas is produced in a laboratory system correspond-
ing to the flow scheme shown on the drawing. 1 kg methanol per
hour is fed in conduit 1 to pump 2 and is pressurized to the
gas-producing reaction pressure of 24 bars~ The methanol flows
in conduit 3 to the heat exchanger 5 and is preheated there to
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150C by cracked gas~ which is thus cooled. The preheated
methanol is vaporized in the heat exchanger 7. Process steam, at
a saturated-steam temperature is admixed from conduit 11 at a
rate of 1 kg/h to the methanol vapor flowing in conduit 8. The
mixture is then heated to a temperature of 460C in the fired
heater 9. At this temperature, the mixture enters the cracking
shaft reactor 4, which contains the catalyst that has been
described hereinbefore as the first embodiment of a preferred
catalyst.
The product gas which leaves the reactor 4 in conduit
13 at a rate of 1,29 standard m3 per hour and at a temperature of
630C and a pressure of 20 bars has the following composition in
% by volume on a dry basis:
C0 21.7
C0 4.4
H2 45.7
CH4 28.2
That gas also contains 1.03 standard m3 water vapor per standard
m3 of dry gas. The product gas is subsequently cooled in several
heat exchangers and is finally available in conduit 20 with the
following properties, which are typical of a town gas:
Net calorific value 4200 kcal per standard m3
Density 0.727 kg per standard m3
Relative density, based on air 0.562
The gas is delivered at a pressure of 18 bars and a
temperature of 40C~ Under these conditions, the gas is
saturated with water vapor.
Examnle 2
To produce a natural gas substitute, the product gas
which is available behind the heat exchanger 5, with its entire
water vapor content of 1.03 standard cubic meters per standard
cubic meter of dry gas, is supplied at an inlet temperature of
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260C to a wet methanating stage. The methanated gas leaving
the first methanating stage at a rate of 0.7 standard m3 per
standaxd m3 of product gas and at 480C has the following
composition in % by volume on a dry basis :
C2 24.6
C0 0.6
H2 22.1
CH4 52.7
~ That gas also contains 1.665 s-tandard m3 water vapor per standard
m3 of dry gas. The gas is cooled to 250C in a waste heat
boiler and is then fed to a second wet methanating stage, in which
a gas having the following composition in percent by volume on
a dry basis is produced at a rate of 0.82 standard m3 per standard
m3 of gas leaving the first methanating stage:
C2 25.0
C0 less than 0.1
H2 5 0
OEI~ 70.0
In both methanating stages, a known catalyst is used,
which contains 40/0 by weight nickel on a support consisting of
~rO2-A1203. The gas leaving the second methanating stage
contains 2.14 standard m3 per standard m3 of dry gas and is at
a temperature of 330C. After being cooled to 250C, this gas
flows through a further methanating stage, in which a gas having
on a dry basis the following composition in percent by volume is
produced at a rate of 0~97 standard m3 per standard m3 of gas
from the preceding stage:
C2 25.0
C0 less than 0.1
H2 1.6
CH4 73.4
In the third methanating stage, the same catalyst is used as
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in the preceding stages~ The product gas from the third methana
ting stage is scrubbed with hot potash in order to remove surplus
CO20 The scrubbed gas has the following composition in % by
volume:
97 CH4, 2 H2 and 1 C02 and constitutes a natural gas substitute~
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