FR2473355A1 - PROCESS FOR CATALYZING CHEMICAL REACTIONS CONSISTING OF CARRYING OUT THESE REACTIONS IN THE PRESENCE OF A METAL TYPE COMPONENT OF THE IRON GROUP DISPERSED IN THE WHOLE MASS OF A CARBON MATRIX - Google Patents

Abstract

The subject of the invention is a process for catalyzing chemical reactions by carrying out these reactions in the presence of compositions comprising a component of the iron group metal type dispersed throughout the mass of a carbon matrix, said group metal component iron being: intimately associated with the carbon contained in the matrix and at least partially bound with this carbon; b present in a proportion representing at least about 0.5% by weight of the mixture of carbon and iron group metal; and c transported into the matrix by disproportionation of carbon monoxide in the presence of an initiator comprising an iron group metal.

Description

The invention relates to a carbonaceous material with high reactivity, and

it also relates to processes for the preparation of such a carbonaceous material and for its use for the purpose of

manufacture of a gas with high calorific value, containing

thane.

  Various carbonaceous materials are well known and have been used

  as pigments, coke sources, chemical absorbents, etc. linen

type of carbonaceous matter is formed as a result of dispro-

pornation (or disproportionation) or carbon deposition from carbon monoxide in the presence of a catalyst-type substance based on an iron group metal. The term "disproportionition" as used herein should be understood to mean any of the reactions accompanied by the formation of a carbon deposit from carbon monoxide, reactions such as the following:

2 CO P C + CO2

CO0 + H2 C + H 20

  During many chemical operations, the formation of such carbonaceous materials as a result of a disproportionation reaction of carbon monoxide is an undesirable side reaction and can

  even deactivate the catalyst used to carry out such operations.

  due to the formation of a carbon deposit on the cat-

  lyser. Generally, the carbonaceous material thus formed has only a low commercial value. It has been found that carbonaceous materials can react with hydrogen to form methane, the main constituent of natural gas. However, known carbonaceous materials have a reaction rate so small that they do not lend themselves to the implementation of industrial processes. However, industrial demand for methane has increased to the point of exceeding supply. It has been proposed that methane can be produced from hard coal and therefore extensive research has been carried out to find ways of economically converting hard coal into methane. For example, researchers have previously synthesized methane from carbon monoxide and hydrogen. Carbon monoxide and hydrogen are produced by burning coal in a mixture of oxygen and water vapor. We use oxygen rather than air because

  the mixture of carbon monoxide and hydrogen should be used

  read to perform methane synthesis does not contain any

considerable portions of nitrogen because nitrogen cannot be separated easily

  neither synthesis gas nor the product of metha-

  born. One drawback of this process is that it requires the use of large and expensive oxygen production plants. In

in addition, the carbon dioxide produced during elementary operations

Premethanation shutters of the process is eliminated from the feed stream to be treated which constitutes the mixture of carbon monoxide and hydrogen, in order to obtain, as final product, a gas having a high power. calorific. It is relatively expensive to remove gaseous carbon dioxide from the stream

of charge constituted by the mixture of carbon monoxide and hydro-

  gene, because such elimination involves a separation operation

gas.

In accordance with the present invention, new-

  carbonaceous materials with high reactivity, in particular with hydrogen, to form methane. carbonaceous materials in

question can be in two forms, the first being a matter

  carbonaceous not activated by a promoter, and the other being a material

  re carbonaceous activated by hydrogen. The latter is formed

by passing hydrogen over the non-activated material. The ma-

carbon content in question includes an intimate association, -nà multi-

ples phases, a main phase rich in carbon and one or more

  several phases, present in lesser proportions, rich in iron group metal and which are dispersed in carbon and are

  at least partially linked to carbon. Metallic components

  iron group tal catalyze carbon formation reactions

ne from carbon monoxide and methane formation as a result of the hydrogenation of carbonaceous material. To achieve this catalytic activity, it appears necessary that the metal type component of the iron group be present in a proportion in

  weight equal to at least 0.5% based on the total weight of the material

re carbonaceous, and this proportion is preferably equal to at least-

  1% of the total weight of said material. In carbonaceous matter-no

activated by a promoter, the proportion by weight of component of ty-

pe iron group metal is preferably between 1% and 3.5%, based on the total weight of the material. When the iron group metal is present in this proportion, it is capable of catalyzing the reaction between the carbon, present in the composition, and hydrogen to form methane at a methanation rate equal to at least 0.1 mole of methane formed per hour and per mole

  of carbon present when carbon is contacted with hy-

3 2473355

drogen at a temperature of 5500C, under a pressure of one atmosphere

  re, and at a minimum hydrogen supply rate of 2 moles of hydrogen-

born on time and per mole of carbon present. This reactivity to

gard of hydrogen is a characteristic characteristic of materials

  res according to the invention, and it is significantly higher than that

  other forms of carbon. In addition, the subjects in question

  serve their high reactivity even after being considerably depleted or enriched in carbon. Water has an effect on

  reactivity of a material of the genre in question, and in certain cases

  ditions it can delay the rate of methane formation. By

  Therefore, under atmospheric pressure, hydro-

  gene contains, by volume, less than about 1% water.

  The iron group metals appear to be transported

  tees into the partially crystallized carbon network, and they become randomly dispersed in this network. At least one

portion of the metal thus dispersed is bound to carbon. A door

tion of the metal can occupy spaces between the reticular planes of carbon. Whatever the structure, it appears that the

  carbonaceous materials in question are of a new and original type.

  The form not activated by a promoter of a carbonaceous material

  according to the invention is formed by passing carbon monoxide

ne on an initiator of disproportionation of carbon monoxide based on iron group metal. Carbonaceous matter forms on the surface of the disproportionation initiator when this initiator

is exposed to a gas containing carbon monoxide at a temperature

  ture between 3000C and about 7000C, and preferably between 4000C and 6000C. The pressure can vary between about 1 and about atmospheres, but the preferred pressure range is between 1 and 25 atmospheres. Preferably, the gas containing carbon monoxide also contains a significant proportion of hydrogen. Iron group metal carbides are initially formed, but at the

as the reaction progresses, the carbonaceous matter

begins to accumulate on the surface of the disproportional initiator

  nation. Carbon monoxide is kept in contact with the disproportionation initiator until substantial proportions of carbonaceous material not activated by a promoter

are deposited on the initiator.

The initiators of carbon monoxide disproportionation to

  iron group metal base are selected from the group consisting of

  killed by iron, cobalt and nickel, mixtures of these metals,

247.3355

  iron, cobalt and nickel oxides such as cobalt oxide, nickel oxide, ferrous oxide, ferric oxide and mixtures of

these oxides, alloys of iron, cobalt and nickel and metals

  swabs of these alloys such as iron / nickel alloys, and iron, cobalt and nickel ores. Such ini-

  carbon monoxide disproportionation initiators based on

  tal of the iron group by the expression "mass metal" in order to

distinguish from metal dispersed in carbon and at least partial-

  ment bound to the carbon forming the minor phase in the carbon material

  born according to the invention. Only dispersed and bonded metal forms a part

tie of the new catalytic compositions of matter in question.

As examples of the metal based initiators from the.

iron, and the forms that these initiators can take, we can

Mention should be made of: ferric oxide powder, iron ore of the he-

  matte mainly composed of Fe203, electro-

  lytic, carbon steel spheres, steel wool, nickel oxide,

cobalt oxide, high purity nickel chips, co-

  high purity balt, buttons or grains made of iron-nickel alloy or

  made of iron-cobalt alloy, and alloy commonly known as "stainless steel"

  x 'Various ferrous metal ores can be used for

initiate the formation of carbonaceous matter. For example, -it was used-

  successfully, with good results, an iron ore from

from a deposit called Mesabi Range. The use of such a mid-

  nerai or the like is advantageous because it is readily available and inexpensive. Alternatively, the metal

en masse can be on a support constituted, for example, by-

silica, alumina or the like without the formation of

The carbonaceous matter is adversely affected.

One of the advantages of the two types of carbonaceous material (not activated, and activated by hydrogen) lies however in the fact that it does not

  it is not necessary to use a support in order to increase the sur-

  developed face, because the carbonaceous material itself has a high developed surface. For example, the developed surface of the

  carbonaceous material can be between 50 square meters per gram-

  me and a value as high as 500 square meters per gram, the

normal interval ranging between about 150 and about 300 m2 / g.

  In order for the carbonaceous material to have the degree of reactivity

siré, it appears that it must be formed in situ. In other words, simply mixing the metal in bulk with carbon

  does not result in obtaining the carbonaceous material according to the invention.

  Typically, the growth of carbonaceous material takes place through

mass shooting of the metal surface in the form of fibers, and event-

  of hollow fiber. Typically, these fibers have a diameter of between about 0.02 microns and about 2.0 microns, with a length to diameter ratio greater than about 10. These fibers have been analyzed and found that most contain tiny particles of a metallic component (minor phases) such

  than alpha iron, iron carbide or iron / nickel alloys. Ap-

apparently the ferrous metal component is transported to

in carbon fibers. This component of the ferrous metal type trans-

worn then ceases to be physically associated with the ferrous metal in

  mass and constitutes an essential part of the carbonaceous matter

high reactivity. When we methanate the carbon material in question with an iron base until converting more than 95% of its free carbon into methane, when we mix the resulting low carbon material with carbon particles, and when we expose this mixture with hydrogen using the pressure and temperature ranges in which we normally operate

to carry out methanation, methane is not formed.

  We must not lose sight of the fact that it is difficult to distinguish

  between the component of the active ferrous metal type in the material

  good and the ferrous metal in mass when small parts are used

ferrous metal sheets in mass. When characterizing the

  carbon material in question, a series of tests is carried out

reads plates of iron, nickel, cobalt and a fernickel alloy as initiator of the disproportionation reaction of

  carbon monoxide and the carbonaceous material is deposited on these plates

  ques. The carbonaceous matter is formed by taking the appearance of monticu-

the wavy fibers on the plate, allowing the plate to be

  simply be physically separated from the carbonaceous material. This allows an analysis of the carbonaceous material separately from the mass metal. From an iron plate, the carbonaceous (separate) material formed in situ appears as containing, by weight, from approximately 1% to approximately 3.5% of component of the dispersed iron type,

  the analytical determinations being carried out both by spec-

troscopy and weighing of ashes. The rest of the material is mainly made up of carbon, accompanied by traces of hydrogen. The carbon is partially graphitized. Partially graphitized carbon has been described in detail by R. E. Franklin

  in his article published in Acta Cryst., vol. 4, p. 253 (1951).

Carbon fibers formed on an iron plate were examined using a scanning electron microscope. Fig. 2 of the attached drawings is a micrograph showing fibers of

  the material according to the invention as seen in a microsco-

eg scanning electron using relatively low magnification. Fig. 1 is a micrograph showing, in more detail, some of the fibers seen under higher magnification.

  also serving as a scanning electron microscope. The fi-

  bres as shown in fig. 1. and 2 are of the non-activated type, i.e.

say not hydrogenated. In a fiber constituting a sample

  presentative, designated in A, an area with a high concentration of iron has been positively identified. Using an electron microprobe type analyzer, a B nodule was positively identified as containing iron. This nodule is approximately 3000 A long and approximately 1000 A wide. This analysis is carried out using the procedures described by JR Ogren in "Electron Mieroprobe", chapter 6, in "Systematic Materials Analysis", volume 1, Academic Press, Inc., New York 1975. Assuming that the fiber is full and has an intermediate density between it, amorphous carbon and completely graphitized carbon, it can be calculated that the limit of

  precision with which microprobe analysis is able to detect

The presence of iron is approximately 1.5% by weight.

X-ray analysis of samples of non-activated carbonaceous material (deposited on mass iron plates) proves that iron is present in the form of iron carbide and, possibly, also

  in the form of alpha iron. We use the Debye method -

  Scherrer (on powders) to obtain powder diffraction spectra using an X-ray spectrometer General

  Electric Model XRD-5. Using the same method for ana-.

  lyse a material activated by hydrogen, it is found that the iron detectable by X-rays in the hydrogenated material is present there

  only in the form of alpha iron.

  As shown in the micrograph reproduced in fig. 1, the compound -

sant iron is linked to carbon. We tried to break this link and

to separate the iron component from carbon by simple physical means

ples such as sieving through fine metallic fabrics and

separation of iron from carbon using asbestos. We found

  However, these methods do not achieve the desired separation.

Since the iron component in carbonaceous matter cannot be separated from carbon by the use of simple physical means, this tends to prove that at least part of the iron is intimately associated with carbon and that at least one part of the iron itself

found bound to carbon, possibly on an atomic or mo-

  school. Or, perhaps, the iron is in the form of a solid solution in carbon. If this is the case, the interfaces of the solid iron-carbon solution and the crystals of the iron component can constitute active sites which are responsible for the rapid rate of reaction. Whatever the nature of the connection

  established between iron and carbon, it has been found that iron itself

  even activated carbon itself, commercial cementite (Fe3C),

  and a simple physical mixture of iron and activated charcoal does not

  the advantageous properties of the carbonaceous material according to the invention. None of these substances or any of these mixtures, when it is brought into contact with hydrogen at high temperatures, is capable of forming methane at speeds approaching that which is reached when the carbonaceous material is used according to the invention. This fact is clearly highlighted in the Table

I next.

Table I

  Raw material 1. Carbon deposited from a CO / H2 gas stream at 5500C and 1 atm. on a thin sheet of

high purity iron.

  2. Carbonaceous matter coming from a sample 1 separated from the

thin sheet and rehydrogenated.

3. Carbonaceous material deposited on 3.175 mm carbon steel spheres at 5000C from a stream of CO / H2 gas under

a pressure of 1 atmosphere.

4. Carbonaceous matter ** initial-

prepared by several cy-

Keys to carbon deposition and hydrogenation at 5500C and under a pressure of 7 to 17.5 bars on carbon steel spheres of 4,762

mm. Separate sample from

shot of the spheres and carbon

posed from a current ga-

zeux CO / H2 under 1 atm.

Separated carbonaceous material

from the ini-

titrator (iron) no yes yes yes Rate of methanation ratio C / Fe (moles of (in a- CH4 / hour / tomes) mole of carbon)

27.3 * 0.10

12.6 0.10 0.28 0.49

Table I

k Raw material 5. Iron ore from the "Mesabi Range1 'pre-reduced in H2 then

used to catalyze the

  carbon deposition from a gas mixture

C0 / H2 at 5000C and under 1 atm.

6. Identical to sample 5, except that it has

been exposed to ambient air for

for 96 hours at 250C before hydrogenation.

7. Commercial Fe3C cementite.

8. Activated carbon "Norit A".

9. Coal from

coal gasification.

  10. Activated carbon "Norit A" mixed with electrolytic iron powder according to a

weight ratio 50:50.

11. Purity graphite powder

spectroscopic.

continued) Separated carbonaceous material

from the ini-

  titrator (iron) no no Methanation Ratio 0 / Fe (moles of (in a0H4 / hour / tomes) mole of carbon)

7 * 0.24

7 * 0.33

-> 1000

-> 1000

0.20 <0.05 (CH4 not detected)

<0.0004

<0.0004

4.7 * <0.0004

> 10,000

approx. 10-7

* Contains iron in bulk.

  ** Material activated using

hydrogen as a promoter.

  Fig. 9 reproduces a micrograph obtained using a half

  scanning electron croscope on another carbon material

born according to the invention, prepared by disproportionation of carbon monoxide on a metal alloy plate in mass containing essentially about 50% of nickel and about 50% of iron. After separation of the fibrous carbon material from the alloy plate, it is found that this carbon material contains 98.42% carbon, 0.48% iron, 0.73% nickel and 0.94% hydrogen (he

  this is non-standard data, the sum of which is not exact

  100%). The area marked with a circle on the micro-

  spelling was analyzed using an electron microprobe; we have

thus found that it contains both iron and nickel in pro-

approximately equal portions. An X-ray analysis performed

  killed on a representative sample of the fibers reveals the presence of iron-nickel alloy. It also appears that the nodule visible inside the circle in FIG. 9, nodule designated by the letter C, is actually constituted by an iron-nickel alloy. Let the noxious C

visible in fig. 9 either or is not a true alloy of ty-

eg solid solution of iron and nickel, the analysis carried out clearly proves that very small crystallites or nodules containing at the

both iron and nickel are transported from the plate

of metallic alloy in mass up to carbon fibers and become intimately associated with these fibers, to which they are

probably related.

  A hypothesis regarding the nature of the carbon material

  born in question consists in admitting that the active component which is the metal of the group of iron is a catalyst which is dispersed through a carbon matrix. This component (iron group metal) catalyzes the reaction of carbon, contained in the matrix with

other reagents. The material depletes in carbon as and when

  re that the reaction is progressing, but it can be regenerated and re-energized

  chir en carbon by exposing it to a gas containing carbon monoxide

bone. When exposed to high temperatures to monoxide

of carbon, the active component catalyzes the disproportionation of mo-

carbon dioxide.

  It has been discovered that even if the material is depleted of carbon as a result of a reaction with hydrogen, it retains its high

specific methanation appearance value. We note with surprise

  that almost all of the carbon can be removed from the carbonaceous material and the latter still retain a relatively high value of the specific methanation rate. This property of the material in question is illustrated in FIG. 3 which represents the variation in the specific methanation pattern (in

  moles of CH4 / hour / mole of carbon), plotted on the ordinate, according to

tion of the percentage of carbon removed by hydrogenation of the material

  re (plotted on the abscissa). The methanation paces indicated on

  the graph in fig. 3 were determined by performing the metha-

  nation at a temperature of 570 to 6000C in a hydro-

  gene admitted at a constant flow rate of 110 cm3 / minute, the pressure being

  from 1 atm. Carbon rich material (i.e. containing approxi-

96% carbon) has an initial reactivity of around 0.30

  mole of CH4 / hour / mole of carbon. This reactivity increases

  gressively up to about 0.63 mole of CH4 / hour / mole of carbon when about 88% (by weight) of carbon has been eliminated. When '

about 90% of the carbon has been removed, or when the material con-

* holds (by weight) about 25% of iron component, its reactivity decreases rapidly. If the carbon-rich material initially contained, by weight, 95% carbon and 5% iron, the final material, after removal of approximately 90% of the carbon, would contain by weight approximately

% of iron.

  The new carbon material in question retains its important

your advantageous properties after numerous enrichment cycles

carbon / carbon depletion. Using iron

being a metallic component of the iron group, 55 cycles were thus carried out and each time we obtained the original material in question,

  activated by hydrogen serving as promoter.

The new carbonaceous materials in question also retain their properties after long periods of storage,

whether stored in the enriched carbon state or in the

carbon depleted state. However, since the exposure of

  these materials to oxygen can oxidize the metallic components

iron group, and thus harm their catalytic activity, we avoid exposing them to air during storage. After keeping such carbonaceous iron material for 24 hours

at ordinary room temperature, there is no change

  tion regarding its appearance of methanation.

Based on the experiences to which it has been referred

  sion above, it was found that the composition of the matter-carbon-

  born in question may vary approximately as follows Content% by weight Interval General preferred interval Partially graphitized carbon 65-99.5% 75-99% Metallic component (of the iron group) dispersed 0.5-35% 1-25% percentages by weight were determined after the material

  carbon was separated from the iron group metal in bulk.

  For iron-based materials, it is preferred that the carbonaceous material not activated by a promoter contains by weight between approximately 1% and approximately 3.5 eo of ferrous metallic component and between approximately 99%

and 96.5% carbon.

The material activated by hydrogen is described below.

before promoter.

It has been discovered that at least some of the carbonaceous materials in question exhibit, when they are subsequently hydrogenated, better values of the rate of formation of carbon deposition and of the rate of methanation. In particular, when

metallic component of the iron group is iron, the carbon material

born activated by hydrogen has a value of the rate of formation of a carbon deposit exceeding 10 grams of carbon deposited at

  the hour and per gram of dispersed iron present, and a value of al-

  methanation lure exceeding 0.3 mole of methane formed per hour and per mole of carbon present. The rate of formation of a carbon deposit is measured at 5000 ° C., under a pressure of one atmosphere, and at a supply rate of 10 moles of carbon monoxide per hour and per gram of iron dispersed in using a feed gas containing by volume 80% carbon monoxide and 20% hydrogen. The methanation rate is measured at 5500C, under a pressure of one atmosphere, and at a minimum hydrogen supply rate of 2 moles of hydrogen at

per hour and per mole of carbon present.

Although the charge stream used to prepare the carbonaceous material may contain hydrogen, the hydrogen-activated material is not produced as long as conditions prevail accompanied by the formation of a carbon deposit

on the mass metal. When the initial carbonaceous matter-

  ment is subjected to hydrogenation to produce methane, then the carbonaceous material in question, activated by hydrogen serving as a promoter, begins to form. The formation of

  this material when about 15% by weight of the carbon has been removed.

born by hydrogenation of the carbonaceous material initially prepared.

  In addition, the hydrogen used should not contain normal-

  not more than about 1% water, by volume.

  We separated the material, activated by hydrogen, from the mass metal and we found that this material has the same

  general physical aspect than that of matter initially prepared

However, X-ray identification proves that when the metal component of iron is iron, said iron is alpha iron rather than carbide iron. The hydrogenated material, when it is subjected to several cycles of formation of a carbon deposit and methanation, has even a higher reactivity than before such a cyclic treatment. On the other hand, when it is subjected to such a cyclic treatment, its composition can vary approximately as indicated below:

- 24? 3355

by weight Partially graphitized carbon 65 - 99.5 Component of the ferrous metal type o, 5 - 35 Hydrogen 0.1 - 3.0 Hydrogen, in the new materials in question, is found

in a strongly associated state. When heating a carbon material

born of the genus in question, based on iron, in a stream of nitrogen gas from a temperature equal to approximately 2000C up to a temperature equal to approximately 9500C, and when the carrier gas stream is analyzed to determine the desorbed gases, mainly hydrogen and carbon monoxide, it is found that the quantity of hydrogen present in the carbonaceous material according to the invention is more than fifty thousand times greater than the quantity which can be

  dissolve in alpha iron. In addition, more than two-thirds of the hy-

  drogen released during such experiments is released to

  temperatures above 7000C.

It should also be emphasized that, when percentages by weight are specified in the carbonaceous material according to the invention, it may be both the material activated by hydrogenation and the material not activated after it has been separate from

mass metal.

  When iron oxides such as iron ore are used as the raw material for the disproportionation initiator, they are first reduced by using a mixture of feed gases.

  carbon monoxide and hydrogen, after which the carbonaceous material

born begins to accumulate on iron en masse. Consequently, the duration of the contact time between the bulk iron and the gas containing carbon monoxide is important. If, for example, we use

  Fe304 and if the gas containing carbon monoxide is at a temperature

rature of 6000C and under an atmosphere pressure, initially the iron oxide is at least partially reduced to iron. this is

  indicated by weight loss of iron oxide due to loss of o-

  xygene. For example, after the iron oxide has been contacted

  with pure carbon monoxide gas for 15 minutes, the sample

  tillon shows a weight loss of around 22% (oxygen represents

te, by weight, about 27.6% of the weight of the ferrous catalyst) and there is little carbon deposited on the iron in mass. The carbon thus deposited is in the form of e 3C. After thirty minutes of

  contact, the sample shows a weight loss of 15% and the

bone deposited there is in the form of carbide, main-

even in the form of Fe C. Even after 60 minutes of 1 'contact

iron oxide with carbon monoxide, the sample still shows

  re a 10% weight loss, and practically all the carbon deposited

  dried on iron oxide is in the form of carbide, and here again

mainly in the form of Fe 3C. After four hours, all-

  times, the sample shows a weight gain of about 75%, and the

  carbon deposited is partially graphitized. The samples obtained

naked after the above time periods of 15 minutes, 30 minutes and 60

  minutes do not have the required value of the methane rate

we. Unlike these samples, the fourth sample (this-

  obtained after four hours) forms methane at a rate of at least 0.1 mole of methane per hour and per mole of carbon when it is brought into contact with hydrogen at 5500C, under a pressure of one

atmosphere, and at a hydrogen supply rate equal to 2 moles of hy-

  drogen per hour and per mole of carbon present.

The scope of the invention also encompasses a method for the pro-

  duction of a gas with high calorific value, from coal or

other carbonaceous fuels, using the new carbon material

  bonée according to the invention. When carrying out the process in question, methane can be produced without the need for oxygen or the removal of nitrogen, carbon dioxide or other inert gases from the charging gas current. During the implementation of the process according to the invention, carbon monoxide and hydrogen are extracted from the feed stream as a result of the formation of the new carbonaceous material.

question on mass ferrous metal. A gas containing hydro-

gene is then brought into contact with the carbonaceous material at a time

temperature, under a pressure and at a space speed such that it results in the production of a gaseous product containing methane, containing by volume at least 20% f of methane. On the grounds that

the reactivity of carbonaceous matter is so high with respect to hy-

drogenic, the duration of the residence time of hydrogen in contact with this carbonaceous material can be very short. It was found that the

carbonaceous matter requires only a short residence time with the hy-

  drogen to produce a gas containing a proportion by volume

  as high as 75% or more methane. For example-

Full, the duration of the residence time can vary from 1 second to 50 seconds to produce such a gas rich in methane. The duration

preferred hydrogen residence time is between 5 sec-

  30 seconds. The desired minimum temperature

mum to which methanation should be conducted is 3500C.

  This temperature is preferably between approximately 4000C and approximately 7000C. The pressure can be between about 1 and about 100 atmospheres, and preferably between 1 and 25 atmospheres. During the implementation of the method according to the invention, it is possible to

  use just about any gas containing carbon monoxide

  bone to produce a high calorific gas containing methane. Particular examples of gases which can be used during the implementation of the process in question are those which are produced by gasification of the coal using air or a mixture of air and steam in order to produce a gas of gasifier of low calorific value, between approximately 623 and approximately 1335

kilocalories per cubic meter. For example, you can burn

  hard coal in situ (i.e. without extracting it from the veins of the

  ment) in order to produce a gas with a calorific value equal to

  about 89 kcal / m3. A gasifier gas such as that used

  read here is a gas mixture containing carbon monoxide, hydrogen, nitrogen, and carbon dioxide. Preferably, we burn coal in a mixture of air and steam to

to obtain a gasifier gas rich in carbon monoxide and hy-

  drogenic. For example, gasifier gases can normally

  when calculating in the dry state, between about 15% and about 30%

  carbon monoxide, between about 5% and about 30% hydrogen

  ne, between about 40% and about 60% nitrogen, and between about 2% and about 10 e% carbon dioxide. All of these gases containing

carbon monoxide are convertible into a gas rich in methane ana-

  logue to a natural gas and having a calorific power whose value is at least 4450 kcal / m3 and can reach up to 8900 kcal / m3. In general, such gasifier gases also contain water

  and small proportions of other gases such as methane, sulfur

  re of hydrogen, carbonyl sulfide, etc. To operate under atmospheric pressure, the water vapor content should be lowered to less than about 6% by volume, while the sulfur content is less than about 10 parts per million. If the feed gas containing carbon monoxide

contains hydrogen, the molar ratio of mono-

  carbon monoxide with hydrogen is greater than about 1: 2, and either

  preferably greater than 1: 1. The preferred molar ratio of monoxy-

  from carbon to hydrogen is preferably between about 1: 1 and about 100: 1. When the feed gas contains carbon dioxide

  carbon, it is preferable that the molar ratio of carbon monoxide

  carbon dioxide bone is high. In general, the molar ratio of carbon monoxide to carbon dioxide should be

a value greater than or at least equal to 1: 1, and preferably greater than

less than 2: 1 - 3: 1. However, the formation of carbon deposits

  takes place at an acceptable pace even when the ratio of bioxy-

from carbon to carbon monoxide is as high as 3.

It has been found that the initial charge gas should

  containing carbon monoxide does not contain appreciable proportions

sulfur targets. More particularly, it is advisable that

  filler containing carbon monoxide does not contain more than

about 20, and preferably not more than 10, parts of sulfur per mil-

  lion, this sulfur being calculated as hydrogen sulfide. When it appears necessary, elimination of the sulfur is achievable by resorting to well-known methods, consisting for example of using systems based on amines, or of bringing the feed gas into contact with an aqueous solution of a carbonate. of alkali metal

or alkaline earth metal such as a hot solution of carbona-

  te of potassium. In addition to the use of conventional methods of elimination,

  nation of hydrogen sulfide from feed gas we also have

  found that it is possible to remove hydrogen sulfide by doing

being able to pass the feed gas over the carbonaceous material or over a

  lange of this carbonaceous material and the iron group metal in mas-

se. When this is done, the ferrous metal reacts with the sulfur, forming metallic sulfides inside the material. This reaction deactivates the carbonaceous material. Therefore, if this method is used to remove sulfur from the feed gas, the carbonaceous material containing sulfur becomes unusable

to produce methane.

  Since the invention makes it possible to use gases containing nitrogen in relatively large proportions (for example, nitrogen can be present therein up to proportions in volumes as high as 70%, or even more important still) , he is not

necessary to form the gas containing carbon monoxide in operation

  rant in a nitrogen-free oxygen atmosphere. In other words,

it is possible to use air, to burn coal, more

  earlier than pure oxygen. What makes the process according to the invention: 6_ economically attractive, is that the combustible portion of the charging current, mainly carbon monoxide, is extracted or

  Separated inexpensively from the inert or non-combustible portion

  ble of said charge current as a result of the formation of solid carbonaceous material as an intermediate product. A gas rich in methane

  is subsequently produced simply by putting said material

  good in contact with hydrogen. It is not necessary that -

  this solid carbonaceous material is immediately allowed to react with hydrogen, because it retains its reactivity for a time of considerable duration. For example, a sample was kept for five days and then reacted with hydrogen to form methane at the same high rates as when using a freshly prepared carbonaceous material. This allows

store energy until needed.

  A feature of the invention lies in the fact that a partially depleted gasifier gas can be used to produce the

  carbon material in question, later convertible into methane.

In this case, coal is burned in air by operating under controlled conditions in order to form the gasifier gas which is brought into contact with iron oxides in order to reduce these oxides mainly in iron, iron carbides, and iron oxides of one more

  low oxygen content, and in order to produce the gasifier gas by-

  partially impoverished. For example, partially gasifier gas

depleted can contain about half as much carbon monoxide

does and about half as much hydrogen as the gasifier gas

  initially brought into contact with iron oxides. Gaso-

  partially depleted gene is used to prepare the car-

  good by putting him in contact with the initiator of disproportionati-

  that the iron group metal constitutes in mass under conditions

to form the carbonaceous matter. Hydrogen can be produced by contacting the reduced iron oxides with water vapor. This hydrogen is then brought into contact with the

  carbonaceous material to produce methane.

  According to one embodiment of the invention, the carbon material

  born (usually mixed with ferrous metal en masse) is allowed

  to go through a cycle between two reaction zones, in the first

re of which the carbonaceous material is brought into contact with the partially depleted gasifier gas while, in the other, the material is brought into contact with the hydrogen-rich gas in order to prepare methane. Consequently, the material undergoes a transition between a carbon-rich state and a low-carbon state. The material that is brought to the methane production area is rich in carbon. A notable protion (at least 15% by weight) of the carbon is removed from this material during the methane formation in order to produce the low carbon material which is transferred to the other zone where it is again enriched in carbon by setting

contact with the gasifier gas. Low carbon material (i.e.

  ie the carbonaceous matter activated by hydrogen) may contain

during the first cycle, between about 5 and 35% by weight of dispersed ferrous metal, between about 95 and 65% by weight of carbon,

  and between about 0.1 and 3% by weight of hydrogen. The carbon material

  born can however remain in an area and the gas streams ad-

set to pass in the two zones are then switched in order to alternately deliver passage to the gasifier gas stream and to the current

hydrogen rich gas.

Another feature of the invention resides in the fact that the carbonaceous matter entrained in the fluids on which one operates can be separated from these fluids by using a magnetic field. The metallic component of the iron group contained in the carbonaceous material retains its ferromagnetic properties, in

  thus making said material magnetic.

The process according to the invention also allows the production of

substantial amounts of energy from the depleted gasifier gas

  vri or another gas used as a source of carbon monoxide.

Therefore, after the gasifier gas has been used to fa-

briquering the new carbonaceous material in question, and to produce hydrogen by implementing the steam-iron process, the depleted gases are preferably then burned in air in order to oxidize any remaining fuels, and the resulting gases are allowed to expand in a gas turbine in order to recover their energy

in the form of electricity.

The preferred embodiments are described below in detail.

res of the processes in question.

The best mode of implementation currently envisaged for a

  process according to the invention is schematically represented in fig. 8.

  In an installation such as that shown in said fig. 8, a desulfurized gasifier gas from a source 100 constitutes the charging current. This gas may contain, for example, in a state

  assumed to be dry, 50% nitrogen, 25% carbon monoxide, 18% hy-

drogen, 6% carbon dioxide and l% methane. Its content

sulfur should be less than about 20 parts per million.

  The gasifier gas is transferred via a pipe 101 to a fluidized bed reactor 102 or the formation of a carbon deposit takes place, this reactor containing solids low in carbon which are based on a ferrous metal such as of iron., The formation of a carbon deposit occurs in the reactor 102 as a result of a disproportionation of the carbon monoxide, contained in the gasifier gas, at a temperature of about 6500C and under a pressure

  between approximately 10.5 and 17.5 bars.

  0 The carbonaceous material according to the invention, formed in the reactor

102, is transferred by a pipe 103 to a metering generator

  thane 104. In this methane generator, at a temperature between

between about 5250C and about 7000C, the carbon contained in the ma-

  carbonaceous reacts with dry hydrogen allowed to enter the methane generator 104 through a line 106 to form

  a mixture of methane and hydrogen. Because the training of me-

  thane is highly exothermic and because temperatures are less

high levels favor the formation of mixtures with higher concentra-

methane, the methane is formed in several stages, by cooling the solids and the gases between the stages,

Depending on the composition of the desired product, it may be necessary to-

provide one or more coolers between stages. In the present case, the cooling is carried out by introducing water

in the methane generator 104 through a pipe 107 and enables it

  both the steam outlet through a pipe 108.

The methane / hydrogen gas mixture leaves the methane generator

  thane 104 via a pipe 109, is allowed to pass in a re-

cooler 110, and comes out of it through line 111, ready for

  subsequent processing operations.

The partially depleted gasifier gas from the reactor 102 for the formation of a carbon deposit is transferred from it by a pipe 112 to a heat exchanger 113 inside which the temperature of said gas is high, for example, from 6700C up to 'at about 9200C, and the residual methane contained in the mixture is converted into a mixture of water, carbon monoxide and carbon dioxide. the partially depleted gasifier gas which leaves the heat exchanger 113 has a lower value for the ratio of carbon monoxide to carbon dioxide, and it mainly contains nitrogen, carbon monoxide, hydrogen, water and carbon dioxide. Although the value is more

  low, the C0 / C02 ratio is high enough to allow

lisation of this gas to effect the reduction of iron oxides.

The partially depleted gasifier gas leaves the heat exchanger 113 through a line 114 which transfers it to a reducer 115 of iron oxides. Inside this reducer 115, the mixture reduces ferric oxide to ferrous oxide, and it oxidizes carbon monoxide

into carbon dioxide and hydrogen into water. Iron oxides

  lines are transferred from the reducer 115 through a line 116 to a

actor 117 producer of hydrogen. Water vapor enters reactor 117 through line 118 and reacts with ferrous oxide

  to produce ferric oxide and hydrogen. Ferric oxide

that is transferred to the reducer 115 by a pipe 119. The hydro-

wet gene produced leaves the reactor 117 via a line 120, is cooled in a heat exchanger 121, then is transferred via a line 123 to a condenser 122. In the condenser 122, the water content of the hydrogen stream is lowered up to '' less than about 1% by weight. Dry hydrogen leaves the condenser 122 through a line 124, and is transferred to the methane generator 104 through a

driving 106.

The partially depleted gasifier gas which has entered the reducer 115 exits therefrom via a pipe 125 in the form of a gas which is almost completely depleted. However, this gas still contains usable residual energy. This energy is preferably used by burning the gas in an oven 126 with air from a source 127. A compressor 128 raises the air inlet pressure in the oven 126 to a value between approximately

  and 17.5 bars. The heat produced in the oven 126 is partial

ely consumed in the heat exchanger 113 to raise the temperature of the partially depleted gasifier gas leaving the reactor 102. The heat which still remains in the gases leaving the oven 126 is transferred from the heat exchanger 113 by a line 129 to a turbine 130, where the gases are expanded in order to produce electrical energy at 131. The depleted gas leaves the turbine 130, is cooled in a heat exchanger 133, and is

  allowed to escape into the atmosphere through a pipe 134.

This embodiment of the method according to the invention has several very interesting advantages. First, a very high percentage of the calorific value, in the cold state, of the gasifier gases is actually used by conversion into

  great value; synthetic "natural" gas and electricity. In two

  xth place, the implementation of this process does not require the use of

coating oxygenation. Third, the heat released to the

  during the methanation operation and the sensible heat which

  is available in depleted gasifier gas are available for use at elevated temperatures. This leads to high yields in the use and conversion of this heat into

  electrical energy, minimizing waste.

An installation usable to implement another mode

for carrying out the process according to the invention is schematically represented

  presented fig. 4. Desulfurized gasifier gas from a sour-

this 1 constitutes the charge current brought in for treatment. This gas, which may contain, for example, 50% N2, 25% C0, 18% H2, 6% C02 and 1% CH4 (in the assumed dry state), may be the result of a conventional operation of gasification of coal with steam and air, gasification of coal "in situ", etc. The raw gasifier gas is then desulfurized to

  an H2S content of less than about 10 ppm.

  Desulfurized gasifier gas and, for example, oxidized iron solids such as a mixture of Fe203, Fe 304 and FeO are contacted in a fast fluidized bed or in a reactor of the entrained tube lift type 2 at temperatures between about 550 and 8500C - and under pressures between 1 and atm., Preferably between about 1 and 20 atm. The choice of temperature and pressure depends on the overall thermal balance and the desired methane concentration in the product gas. Contact between gas and solids is maintained for a period of time

sufficient to cause a partial reduction, by H2 and CO con-

held in the gasifier gas, iron oxides into reduced iron compounds such as FeO, Fe and Fe3C. H2 and CO contained in the feed gas feed gas are partially but not completely consumed during the reduction of iron oxides. We think that

  hydrogen will be used more completely than carbon monoxide

  do during this stage of the process in question.

Reduced entrained iron solids and gas from gas

gene that has partially reacted are then brought to a cyclone or similar device 3, where the reduced iron-based solids are separated from the gas. partially reacted gasifier. The reduced iron solids thus separated are brought by a pipe 4 to the lower part of a second reactor 5 of the lifting tube type where they are brought into contact with steam from a source 6 at temperatures between about 500 and 8000C and

at pressures from 1 to 100 atmospheres. A gas rich in hydrogen-

  ne is the result of the reaction of water vapor with reduced iron solids. In addition to hydrogen and unreacted water vapor, this gas also contains significant proportions of

methane, carbon monoxide and carbon dioxide.

The hydrogen-rich gas and the entrained oxidized iron-based solids exit the hydrogen production reactor 5 through a line 7 and are then fed to a cyclone or other similar device 8, which separates the solids from the gases. The oxidized iron-based solids are brought through a line 9 to the first reactor 2 of the

riser type to complete the circulation loop of solids

between reactors 2 and 5.

  After separation of the solids, the gasifier gas having

  partially reacted, and which can then contain, for example, 15% CO, 6% H12, 16% C02, 1% CH4 and 62% N2 (in the dry state),

is cooled in a heat exchanger 10 which generates

fear of usable water for treatments. This cooled gas is transferred by a pipe il to the lower part of a reactor

12 of the lifting tube type used for the formation of carbon deposits

ne, oh it is brought into contact with poor solids, containing carbon, which it entails. The gas and the solids are kept in contact with each other for a time of sufficient duration at temperatures between 300 and 6000C and under pressures of 1 to 100 atm. to cause the formation of a carbon deposit on the

low carbon solids and enrich them by increasing their

* carbon neur. The formation of a carbon deposit occurs through a disproportionation of the carbon monoxide contained in the partially reacted gasifier gas, to a lesser degree by reaction of CO and H2, or as a result of the reduction of CO by other agents.

reducers present.

  Solids rich in entrained carbon leaving reactor 12

  of carbon deposition are separated from the gasifier gas, de-

now depleted, in a cyclone or other similar device 13 and are brought to the lower part of a methanation reactor

14 of the riser type where they are driven by the current

  zeux rich in hydrogen coming from the reactor 5 of production of hy-

drogen through a heat exchanger 8a and a cooler

  sister 8b. Entrained carbon-rich solids react with

  the hydrogen in the first stage of methanation predominantly

22 -

nante by direct reaction of carbon and hydrogen. It's about-

  exothermic reaction, and the solids and / or gases must be cooled between stages if one wishes to obtain high concentrations of methane. The entrained solids and the gases are cooled in a cooler 16 arranged between stages, then they are admitted again

to react in a second reactor stage 17 to produce metha-

  no additional. Depending on the desired CH4 / H2 ratio in the gas produced, the operating pressures in the methanation reactors can vary from approximately 1 to approximately 100 atm., But are

  preferably between about 1 and about 20 atm. Here in-

  core, depending on the desired product, one or more steps can be used

inter-cooling systems. Operating temperatures in the initial stages of the methanation reactor can be as high as 700-7500C, but temperatures

  must be maintained in the final stages of metha-

nation if a high CH4 / H2 ratio is desired

  The gas produced and the low carbon solids entrained which

  leave the methanation reactor 14 undergo a primary separation

  mayor in a cyclone 18. Low carbon solids are then

  recycled through a line 19 which brings them back to reactor 12 of

formation of carbon deposits. The raw product gas containing still

re a significant amount of entrained dust undergoes further dust separation in a separator 20 which can be a

magnetic dust collector since most of the dust

  sieres is ferromagnetic in nature. However, other types of dust collectors can be used such as sand filters, filter bags, etc. The dust-free produced gas is cooled in a heat exchanger 21 in which water vapor usable for the treatments is generated, then it undergoes further cooling and is dried in a cooler 22

at the outlet from which the gas constituting the final product is obtained.

  The hot depleted gasifier gas leaving cyclone 13 is a-

  led to a dust separator 23 which removes dust therefrom

  driven, not separated by cyclone 13. the dust separator

  re 23 can be a magnetic device because solids are closed

romagnetic, or it can be made up of a more

classic such as a sand filter or a battery of filter bags.

Hot depleted gasifier gas, dust-free, containing

still notable proportions of H2 and CO, is burned by addi-

  tion of an excess of air to result in the production of a combustion gas

  tion at high temperature, containing N2, C02 and H20. This hot gas is

expanded in a gas turbine 24 making it possible to obtain, as a

  product, mechanical work on the tree and / or electrical energy

than. Finally, the depleted gasifier gas can be cooled again to produce new amounts of steam used

sand for treatments.

  Two of the main advantages of the method described above with reference to FIG. 4 are as follows: (a) the separation of N2 and

Unwanted CO2 from the CH4 / H2 mixture constituting the pro gas

duit occurs after a relatively easy separation of

  solids and gases rather than by the much more difficult separation

  the N2 from 02 as is necessary in conventional technology, and (b) the gasifier gas, during the implementation of

  this process is more fully used by conversion to a pro-

duit CH4 / H2 as during the implementation of a conventional process based on the steam / iron reaction because the gasifier gas is

first reliably used to reduce iron oxides (process

steam / iron), then is more completely used for deposition

  serve as carbon to serve as a reagent.

  A third way to implement the invention is

  described below with reference to fig. 5. Here, gas from gaso-

gene is initially compressed to approximately 3 to 4 atmospheres

  in a compressor 1 and is brought to a reactor 2 for re-

dustion of a ferrous metal oxide, for example iron oxide, with formation of carbon deposits, where it is initially brought into contact with iron oxides and reduces these oxides while at the same time carbonaceous matter deposits on reduced oxides. Reactor 2 is maintained at a temperature of about 350-5000C and under a pressure of about 3 to 4 atmospheres. In reactor 0 2, approximately 70% of the carbon monoxide and hydrogen contained in the gasifier gas react with the iron oxides to form reduced iron compounds and the carbonaceous material according to

  the invention. Depleted gasifier gas at a temperature of approx.

  ron 350-5000C, is mixed with air and is burned in a combustion zone 3. This gas can then be directly transferred to a compressor or to an electricity generator to undergo a

  expansion without being allowed to pass through a generator of

fear of boiler-type water using waste heat. Any-

  times, the gas is preferably allowed to pass through a separator

magnetic to separate all entrained dust.

Carbonaceous matter, including mass iron, is transferred

  by ascending fluidization tubes to a methane reactor

tion 5 in a fluid bed where it is brought into contact with a contained gas

  essentially producing hydrogen at a temperature of about 480-

  5350C and under a pressure of approximately 3 to 4 atmospheres to form a gas rich in methane. This methane-rich gas is cooled in

  boilers 6 for recovering waste heat in order to produce

  re water vapor usable for treatments. The carbon-depleted material, coming from the methanation reactor 3, is transferred by ascending fluidization tubes to a hydrogen-generating reactor 4 in a fluidized bed and is brought into contact there with steam at a temperature of about 535-650ÈC and under a

  pressure of 3 to 4 atmospheres to produce wet hydrogen.

The resulting iron oxides are brought back to the formation reactor 2

  carbon deposits. The wet hydrogen is cooled in a re-

  cooler 7 to condense water vapor, and dry hydrogen is

  transferred to the methanation reactor. 5.

Sulfur compounds such as H2S, CS2, COS and S02, if present in the gasifier gas, can be removed by

  bringing the gas into contact with a portion of the carbonaceous material

carried out in reactor 2 for the formation of carbon deposits. Alternatively, the portion of the carbonaceous material which has been hydrogenated can be removed from the methanation reactor 5 and brought into contact

  with the gasifier gas in order to remove the sulfur compounds therefrom.

  fig. 6 shows another installation which can be used to implement a process according to the invention, a process in which the solids remain in the individual reactors either in the form of fixed beds or in the form of fluidized beds, and the feed gas streams to be treated are periodically switched between gasifier gas and steam-water mixture. The reactors

may be allowed to operate in one of two modes, the

courses according to the first mode being represented in solid lines and

the routes according to the second mode being represented in inter-

broken. According to the first mode, gasifier gas is brought into a reduction reactor 6 where it is brought into contact with

  iron oxides. The partially depleted gasifier gas is then

  transferred to you, passing through a boiler serving as a steam generator, to a reactor 2 where it is brought into contact with mass iron to form the carbonaceous material. Simultaneously, steam is brought into a hydrogen generator reactor 4 where it is brought into contact with reduced iron in order to

  form hydrogen gas. This hydrogen gas is then ad-

  placed in a methanation reactor 3 o it is placed in con-

tact with carbon material, previously formed, in order to form

methane sea. At selected time intervals, the currents ga-

charge zeux brought to reactors 2, 3, 4 and 6 are switched. Com-

  shows me the broken line, hydrogen that forms

  me in reactor 6 is allowed to pass into reactor 2 where it causes the formation of methane as a result of the reaction between hydrogen and carbonaceous matter. Depleted gasifier gas is

transferred from reactor 4 to reactor 3 to form the carbonaceous material

born. Fig. 7 shows an installation making it possible to implement a method according to another embodiment of the invention according to which a partially depleted gasifier gas is used

to produce a methane-rich gas in a single reaction

schematically shown in vertical section. In this appa-

  reil, reaction cylinders with porous walls are used whose pores allow the passage of gases but are too small to allow the particles of solid carbonaceous material to pass,

  the invention or mass iron transporting this carbonaceous material.

  The initiators of mass disproportionation preferentially affect

this the shape of iron spheres.

  The iron spheres are initially located inside a hopper l having at its lower part an outlet orifice 2 through which the spheres descend under the effect of gravity

  to a passage 3 then to a reactor 4 for the formation of

carbon pdts, with porous walls, inside which is formed a cavity 5. At the upper part of the cavity 5 is arranged a

  gas inlet 6 used to admit gas into the cavity 5

partially depleted gene. This partially gasifier gas

Pauri passes through internal porous walls 7 and penetrates

  thus in reactor 4 o the gas comes into contact with the cataly-

ferrous sor for a time of sufficient duration, and under a

pressure and at a temperature to form the carbonaceous material

  born according to the invention on the spheres. Then, the completely depleted gasifier gas is allowed to pass through the openings

or pores of the outer porous wall 8.

  At the lower part of the reactor 4 is arranged an outlet opening 9 through which the spheres transporting the material pass to descend into a methanation reactor 10 which is defined by a porous outer wall 10 allowing the

  gas and by a porous inner wall 12 allowing the gases to pass.

  Coaxially surrounding the outer porous wall 1i is arranged an impermeable wall 13 which, with the wall 11, defines a chamber

annular 14. Hydrogen gas flows through a

  trée 16 '* of gas and into the cavity 15 o this hydrogen passes through the openings or pores of the porous inner wall 12 and comes into contact with the carbonaceous material in the methanation reactor 10 to form a gas rich in methane. This gas rich in

methane then leaves the reactor 10 through the openings or.

  pores established in the outer porous wall 11, thus reaches the cavity 14, then passes through the gas outlet 16 giving access to a gas transfer tube 17 which brings it up to

in a cavity 18 arranged inside a second power reactor

thanation 19. The cavity 18 and the reactor 19 are separated by a

  porous inner wall 20 allowing gases to pass through .--

  The solid carbonaceous material, partially depleted in carbon, coming from the first methanation reactor 10, leaves said reactor 10 by a solids outlet 21 and is cooled by water in a solids cooler 22 by passing water through this cooler 22 from a water inlet 23 to produce

  steam leaving the cooler through a steam outlet 24.

  The cooled solids are then allowed to enter the second methanation reactor 19 where they are again brought into contact with the gaseous mixture of methane and hydrogen passing through the porous wall 20 to further react with the carbonaceous material in order to form methane. The enriched gas containing methane leaves the second methanation reactor 19 through an external porous wall 25 and then a gas outlet 26. Carbonaceous iron-based solids depleted in carbon are then transferred to the hopper

1 to solids-by a riser return tube 27 in order to be

  calf used to implement the process.

Below are given various examples, of course not li-

mitatives, intended to illustrate the methods of implementing

  the invention with regard to the preparation of carbonaceous materials

  - Example 4 shows the methanation rates for several different catalysts based on metals from the group of

iron according to the invention. Example 5 proves the remarkable and unexpected

tense thermal stability of the catalytic substances in question.

Example 1.- Carbon is deposited on 5 grams of 3.175 mm mild steel balls by decomposition of carbon monoxide at

5500C from a gaseous mixture of carbon monoxide and hy-

drogen in a tube furnace. The flow rate of carbon monoxide is 100 cm3 per minute and the flow rate of hydrogen is 20 cm3 per minute. After approximately 4 hours, 2.7 grams of a carbonaceous material containing by weight 3.7% of iron are separated from the steel balls, and 0.27 grams of the carbonaceous material

thus separated is exposed to the same gaseous mixture of carbon monoxide

bone and hydrogen at 5000C and under a pressure of 1 atmosphere.

  It can be seen that the rate of formation of a carbon deposit is

  equal to 8.8 grams of carbon per hour and per gram of iron dis-

persed in the carbonaceous matter present. This carbonaceous material has a methanation rate equal to 0.52 mole of methane formed per hour and per mole of carbon. Carbon is again deposited on the hydrogenated material, using the same gaseous mixture of carbon monoxide and hydrogen and the material is brought into contact at 5000C and under an atmosphere. The rate of formation of a carbon deposit is equal to 39.4 grams of carbon per hour and per dO gram of dispersed iron. A cyclic succession is established as above between the disproportionation reaction of monoxide

carbon to deposit carbon, then a hydrogenation of the material

  resulting carbonaceous in order to consume most of the

  carbon, and this succession is continued for several cycles.

  The result of all the cycles is summarized in Table II below.

after.

Table II

Methanation deposit deposition rate Carbon n0 cycle (in grams per hour (in moles per hour and per gram of dispersed iron) and per mole of carbon)

1-C * 8.8

1-H ** 0.52

2-C 39.4

2-H 0.53

3-C 47.8

3-H p1.12

4-C 41.5

4-H 1.33

  * Refers to carbon deposition formation

** Refers to hydrogenation.

-28

: W 2473355 -

  The material activated by hydrogen has a form of forma-

much more than 10 grams of carbon deposited at

per hour and per gram of dispersed iron present. After this ma-

tière has been subjected to several training courses

  bone and methanation, we see that its methanation appearance

  increases until reaching a value greater than 1 mole of metha-

  only formed per hour and per mole of carbon present.

  Example 2.- Six hundred grams of an iron ore of the Mesabi Range (iron ore of the hematite type containing 55.3% of iron, 8.1% of silica, 0.8% of alumina), of which the particle size corresponds to extreme sieves with square openings measuring respectively 0.250 mm and 0.100 mm side and whose apparent density is equal to 1.91 g / cm3, are placed in a vertical pressure-resistant tubular reactor, constructed of alloy of the so-called stainless steel type, with an internal diameter of 38.1 mm and a height of around 2.45 meters. The ore is reduced by a stream of hydrogen gas brought into contact with the iron ore at a spatial speed of 2300 volumes of gas per hour and per volume of iron ore. The reduced ore is then subjected to a series of carb-one deposition / methanation formation cycles. Carbon deposition is carried out using mixtures

gaseous nitrogen / carbon monoxide / hydrogen of different compounds -

tions, and methanation is carried out using pure hydrogen.

The volumes of gases entering and leaving the reactor, after the reactor has cooled to normal room temperature, are measured using flow indicators and

  also measures the humidity level; the composition is also determined

  sition of gases by gas chromatography. The conditions and the results of several cycles are indicated in Table III below. ''

- 2473355

Table III

Formation of carbon deposits Composition of N2 46.6 42.5 44.2 44.2 H2 8.1 6.9 6.9 7.4 s CO gas, 3, 6 48.9 48.4 Temp- Pres- Duration erasure of

mo- abso- se-

yenne read day (OC) (atm.) (sec.)

456 6.1 1.9

440 3.4 1.7

435 3.5 1.6

416 4.7 1.8

Total duration (min.)

Ato- report

mique C: Fe after carburetion 1.29 0.88 0.80 1.12 Cycle temperature (OC) * A B C D

540-673

500-700

500-672

500-635

Absolute pressure (atm) 6.8 11.6 11.6 13.6 Methanation Average duration of gas residence time (seconds) 4.9 9.1 il, 0, 0 CH4% duration in gas sheets tale products (maximum (min) reached) 53.5 63.0 62.0, 0 * The reaction is highly exothermic and cannot be controlled

  temperature only by adjusting the hydrogen flow rate.

  Example 3. A 2.88 gram sample of an iron alloy

nickel containing by weight approximately 50% of each of the two metals is oxidized at 982 C for 10 minutes in a muffle furnace. The alloy thus oxidized is then fueled at 5000C using a mixture of

  gas comprising by volume 85% carbon monoxide and 15% hy-

drogbne, at a rate of 200 milliliters per minute for 9 hours and

minutes. After separation of the carbonaceous material from al-

  mass bonding, it can be seen that the composition of the carbon material

resulting result corresponds to the following elementary analysis: carbon

98.06%; iron 0.54%; nickel 0.53%, and hydrogen 0.16%. The material

The separate carbonaceous material is then subjected to a series of three methanation / carburetion cycles. The conditions and the results of these

cycles are indicated in the following Table IV. The ras data

appear in this Table IV prove that the formation paces of

  carbon deposits as well as methanation paces are improved

  improved by making this material go through successive cycles Cycle A B

10. C

D Report

atomi-

that CFe after

metha-

nation 0.08 0.04 0.01 0.15

1 .., '. -

  ... DTD: formation of carbon deposits and methanation.

Table IV

Appearance of deposit formation.

  No carbon cycle (in grams per hour -5, -and per gram of dispersed iron)

1-H **

1-C * 35.2

2-H

2-C 38.8

3-H

3-C 45.3

Methanation rate (in moles per hour and per mole of carbon) 0.10 0.12 0.20 * Refers to carbon deposition

** Refers to hydrogenation. - -

  Example 4. By implementing a method according to the invention,

  we prepare samples of carbonaceous materials, containing carbon -

free bone, by realizing the disproportionation of carbon monoxide

on plates or on buttons or grains of iron, nickel, of -

  cobalt and an alloy of iron and nickel containing approximately; 50% of -

  iron and 50% nickel. In each sample, the carbonaceous material

fibrous is separated from the mass metal and is exposed to 550 Ce -and - -

  under a pressure of one atmosphere, at a current of dry hydrogen flowing at a flow rate of about 2 moles of hydrogen per hour and- by:

mole of the carbon present. The specific training gaits' of. -

methane for each of the samples are indicated in the table = ..

V below: - -: - -.

Table V -.

Specific training pace Initiator of disproportionation of methane for fibers. o '"

carbon monoxide separated from metal. - -

  by mass .: -: - (moles / hour / mole of carbon) -: À .; Iron 0.10

Nickel - 0.19, -

Cobalt, 0.34

Iron-nickel alloy 0.10- -

Example 5.- Ten grams of steel spheres are placed in the carbo-a.

  ne, measuring 3.175 mm in diameter, in an alumina basket above -

  then hung in the center of a substantially ceramic tubular reactor

* mique. A mixture of 100 ml / minute of carbon monoxide and 20 ml / minute of hydrogen is passed over the spheres at 5100C and under

  atmospheric pressure for five hours. It is deposited there to-

tal 1.94 g of carbon. The carbonaceous matter deposited is careful-

ment separated from the carbon steel spheres, and we find that it contains 2.08% iron. 0.992 g of the material, thus separated, is placed in a nacelle which is replaced in the reactor. A mixture of 100 ml / minute of carbon monoxide and 20 ml / minute of hydrogen is passed over the 0.992 g sample to 40800 for 2 hours. An additional amount of carbon estimated at 0.2 grams of carbon, determined by measuring the concentration of carbon dioxide

  carbon in the effluent gas stream, is deposited. We do in-

  thereafter pass, over this modified sample, a gaseous stream of hydro-

  pure gene (110 ml / min) at a temperature of 5600C. Methane

  begins to form and the hydrogenation is continued until about

0.2 g of carbon has been gasified, which is determined by

monitoring the methane concentration and the flow rate of the effluent gases. The average methanation rate is equal to 0.20 mole of CH4 / hour / mole of carbon. Then replacing the gaseous stream of hydrogen allowed to pass over the carbonaceous sample with a stream of pure nitrogen (40 ml / min) and slowly heating the carbonaceous material to 8650C. It is kept there for about an hour, then cooled to 5600C in the nitrogen stream. At 5600C, the gas is again replaced by hydrogen at a rate of 110 ml / min to carry out methanation, which is continued until an additional 0.2 g of carbon has been gasified. The average methanation rate after exposure to high temperature is 0.26 mole of CH4 / hour / atom of carbon. The cycle of exposure to high temperature (8650C) to a stream of nitrogen followed by hydrogenation

  at 5600C is repeated. The average pace of me-

  thanation: it is equal to 0.26 mole of CH4 / hour / gram atom of carbon. Apparently this brief exposure of carbonaceous matter

  according to the invention at a high temperature does not decrease its reactivity

  vity towards hydrogen, nor its catalytic activity for reacting

  read the direct conversion of CO and H2 to methane. After the same

  thermal cycles, the remaining carbonaceous material is exposed to a

  lange of 110 ml / minute of hydrogen and 50 ml / minute of carbon monoxide at 4500C. It is found that methane is formed in the

  effluent gases at an average rate of 0.24 mole / hour / mole of catalyst

sister.

Claims (4)

1. Process for catalyzing chemical reactions,   characterized in that these reactions are carried out   sence of compositions comprising a component of the iron group metal type dispersed throughout the mass of a carbon matrix, said component of the iron group metal type being: (a) intimately associated with the   carbon contained in the matrix and at least partial-   ment linked with this carbon; (b) present in a proportion representing at least about 0.5% by weight of the mixture carbon and iron group metal; and (c) trans-   carried to the matrix by disproportionation of   carbon monoxide in the presence of an initiator-com- carrying an iron group metal. 2. Method according to claim 1, characterized in that the composition is obtained by the operations consisting in (a) choosing a metal substance which comprises an iron group metal ', said substance   being inactive and of low activity, such as cataly-   sor for the reaction between hydrogen and mo-   carbon dioxide; (b) put a gas containing. mono- carbon xene in contact with said substance under conditions such that carbon monoxide undergoes a disproportionation resulting in the formation of a carbonaceous material comprising carbon and a component = of the iron group metal type -transported from said substance, said component being dispersed in the whole mass of carbon and intimately associated with carbon bone, and at least partially bound to carbon; and (c)   put the carbonaceous material in contact with hydro- gene under conditions such that hydrogen reacts quickly with the carbon contained in the substance to form methane, said contacting being continued until. the carbonaceous matter is enri-   shit by compounding metal type from the iron group to occurrence of a proportion equal to said predetermined proportion. 3. Method according to claim 2, characterized in that the carbonaceous material is separated from the metallic substance before bringing it into contact with   hydrogen during the implementation of the opera- elementary tion (c).   4. Method according to claim 2 or 3, character-   risé in that one uses, as metallic substance, an alloy comprising at least two metals of the group of iron.