CA1136413A

CA1136413A - Carbonaceous material and process for producing a high btu gas from this material

Info

Publication number: CA1136413A
Application number: CA000306997A
Authority: CA
Inventors: Jack L. Blumenthal; Maksymilian Burk
Original assignee: TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1977-07-21
Filing date: 1978-07-07
Publication date: 1982-11-30
Also published as: FR2422440A1; GB2002726A; NL7807705A; IT1192620B; FR2422440B1; BR7804693A; AU527163B2; FR2421859A1; PL208541A1; IT7868711A0; FR2473350A1; YU175378A; JPH0229111B2; FR2421859B1; LU79983A1; AU3802678A; DE2831594A1; BE869185A; CH642394A5; SE7808020L

Abstract

ABSTRACT

A highly reactive carbonaceous material is disclosed which comprises at least 0.5 weight percent of a ferrous group metal component bonded to the carbon in the material.
Also disclosed are processes for manufacture of this carbonaceous material and processes for using it to manufacture methane.
The carbonaceous material may be in two forms, unpromoted carbonaceous material and hydrogen promoted carbonaceous material.
The unprompted material is formed by contacting a carbon monoxide-containing gas with a ferrous group metal carbon monoxide disproportionation initiator under conditions where the required amount of ferrous group metals diffuse into and bond at least partly to free carbon depositing on the bulk ferrous group metal initiator.
The hydrogenated promoted material is formed by contacting the unpromoted material with hydrogen. The source of the carbon monoxide may be a producer gas derived from burning coal. our material includes the free carbon as a continuous major phase and on or more ferrous group metals, metal alloys, or metal carbides associated with ant bonded to the free carbon as dispersed minor phases.

Description

~- 11364~3 NOVEL CARBONACEOI~S MATERIAL
AND PROCESS FOR PRODUCING
A HIG~ BTU GAS FROM T~IS
MATERIAL

Hydrogen reacts rapidly with the carbonaceous material to produce a methane rich gas containing at least 20~ by volume methane, thereby providing an economical method for producing a methane rich gas. The carbonaceous material may be substantially depleted of carbon without diminishing its high specific rate of reactivity with hydrogen. The carbon depleted material may be replenished with carbon by exposure to carhon monoxide. This carbon'deposition-methanation cycle may be repeated continuously, thus providing the basis for a commercial process to make methane from producer-type gas. In the course of cycling the material between carbon 15 rich and carbon lean states, the carbonaceous material undergoes ~-a transformation into a hydrogen promoted material which has a higher deposition rate and methanation rate than the unpromoted '~material used at start up. Almost all the carbon in both the unpromoted and hydrogen promoted carbonaceous material may be reacted with hydrogen without deactivating the material for carbon deposition or methanation.
.
~~ACKGROUND OF THE INVENT ION
,, Vario~s carbonaceous material are well known and have been used as pigments, sources of coke, chemical absorbers', 7~ etc. One type of carbonaceous material'forms through the di~pro-~'portionation or carbon deposition reactions of carbon monoxide in the presence of a ferrous group metal-based catalyst material.
As used herein, the word "disproportionation" means any of ,. ~., ~,i," ,~
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i~36~13 the reactions which result in the deposition of carbon from carbon monoxide, such as the following:

- 2 CO- ) C ~ C2 CO + ~2 ~ C + H2O

In many chemical processes the formation of such carbonaceous materials through the carbon monoxide disproportionation reaction is an undesirable side reaction and may even deactivate the catalyst used in such processes due to carbon deposition on the catalyst. Gènerally, the carbonaceous material so formed has had little commercial value. It has been known that carbonaceous materials will react with hydrogen to form methane, the main ingredient of natural gas. But the known carbonaceous materials have-had such a slow rate of reaction that a commercial process based on this reaction was not feasible. Society's demand for methane has, howe~er, increased and almost outstripped the supply. It has been propo3ed that methane may~be produced t from coal, and consequently, extensive research is be~ng conducted to find ways to economically convert coal into methane. For example, prior art workers have synthesized methane from carbon ,, monoxide and hydrogen. Carbon monoxide and hydrogen are produced ; by buFning coal ln a mixture of oxygen and steam. ~xygen is used rather than air because the mixture of carbon monoxide and : ::
hydrogen used for methane synthesis should not cont~ain substantial - amounts of nitrogen, because nitrogen cannot be readily separated from the synthesis gas or the methane product. One disadvantage of this process is that large and costly oxygen producing plants are used. Moreover, the carbon dioxide produced in the pre-methanation steps of the process is removed from the carbon ; ~B
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113~4i3 monoxide-hydrogen feed stream, in order to have a final pr~duct gas of high Btu content. It is relatively expensive to remove the carbon dioxide gas from the carbon monoxide-hydrogen feed stream because such removal involves a gas separation step.

THE INVENTION :-Carbonaceous Material We have dis~overed novel carbonaceous materials which are highly reactive, particularly with hydrogen, to form methane.
The carbonaceous materials may be in two forms, one being unpromoted carbonaceous material and the other being hydrogenated promoted carbonaceous material. The latter is formed by passi~g hydrogen over the unpromoted material. The carbonaceous material comprises a multiphase, intimate association of a carbon-;~ rich major phase and one or more ferrous group metai-rich minor lS phases that are dispersed in, and at least partially bonded to, the carbon. The ferrous group metal components catalyze the reactions of carb`on formation from carbon monoxide and of methane forma*ion from the hydrogenation of the carbonaceous material. To attain this catalytic activity, it appears that ~:
the ferrous group metal component should be present in an amount of at least 0.5 weight peraent based on the total weight of the material. Preferably, the ferrous qroup metal component should ;~ ~ comprise at least 1 weight percent of the total weight of the material. In the unpromoted carbonaceous material the ferrous group metal component preferably comprises between l weight percent and 3.5 weight percent, based on the total weight of the material. When the ferrous group metal is present in this amount, it has the capability to catalyze the reaction between the carbon present in the composition and hydrogen to form methane at a methanation rate of at least 0.1 mole of methane formed per hour per mole of carbon present when the carbon is contacted

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with hydrogen at a temperature of 550C, one atmosphere pressure, and a minimum hydrogen feed rate of 2 moles of hydrogen per hour per mole of carbon present. This reactivity with hydrogen is a distinguishing characteristic of our materials, and is substantially highe~- than that of other forms of carbon.
Moreover, our materials maintain their high rate of reactivity even after being substantially depleted of or enriched in carbon. Water has an effect on the reactivity of our material, and under some conditions may impede the rate at Lo which methane is formed. Consequently, at atmospheric ;..
pressure, the hydrogen should contain less than about 1 water by volume.
$he ferrous group metals appear to be transported into the partly-crystallized carbon network, and become dispersed 1~5 randomly in this network. At least some of the dispersed metal is bonded to the carbon. Some metal may occupy spaces between the planes of the carbon. Whatever the structure may be, our carbonaceous materials appear to be unique.
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;~ The unpromoted form of carbonaceous material of our ~Z invention is formed by passi~g carbon m~noxide over a ierrous group metal-based carbon monoxide disproportionation initiator.
The carbonaceous material forms on the surface of the dispro-portionation initiator when the initiator is exposed to a carbon monoxide-containing gas at a temperature of between -300C and about 700C, preferably 400C to 600C. The pressure may vary between about 1 and about 100 atmospheres, but the preferred range is from 1 to 25 atmospheres. Preferably, the carbon monoxide-containing gas includes some hydrogen.
.
Initially ferrous group metal carbides form, but as the reaction proceeds the carbonaceous material begins to accumulate on the -~ -4-,. , ~ 3 ., ~ , ' il36413 surface of the disproportionation initiator. Carbon monoxide is maintained in contact with the disproportionation initiator until substantial amounts of unpromoted carbonaceous material deposit on the-ini~iator.
The ferr~us qroup metal-based ~arbon monoxide dispropor-tionation initiators are selected fxom the group consisting of iron, cobalt and nickel, and mixtures thereof, oxides of iron, cobalt and nickel, such as cobalt oxide, nickel oxide, ferrous oxide, ferric oxide, and mixtures thereof, alloys of iron, cobalt and nickel, and mixtures of such alloy~, such as iron/
nickel alloys, and ores of iron, cobalt and nickel. We shall refer to such ferrous group metal-based carbon monoxide disproportionation initiators as the "bulk metal" in order to distinguish them from the metal dispersed in and at least partly ~15 bonded to the carbon forming the minor phase in the carbonaceous material of our invention. Only the dispersed and bonded metal forms part of our new, catalytic compositions of matter.

Examples of the ferrous metal-based initiators, and the ~20 forms those initiators taXe, are: ferric Qxide powder, hematite type iron ore composed mostly of Fe203, electrolytic iron chips, - ~ carbon steel spheres, steel wool, nickel oxide, cobalt oxide, , high purity nickel chips, high purity cobalt chips, iron-nickel alloy buttons, iron-cobalt alloy buttons, and stainless steel.
2S Various ferrous metal ores may be used to initiate the formatlon of the carbonaceous material. For example, we have used Mesabi Range iron ore with good results. The use of such ore and the llke is desirable because it is readlly available and inexpensive.
Alternatively, the bulk metal may be on a support of, for example, silica, alumina or the like without adversely affecting the formation of the carbonaceous material. One of the advantages .
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of both the unpromoted and hydrogen promoted carbonaceous material, however, is that it is not necessary to use a support to increase its surface area because the carbonaceous material has a high surface area itself. For example, the surface area of the carbonace~us material may range from 50 square meters per gram to as high as 500 square meters per gram, with the ;
normal range being from about 150 square meters per gram to about 300 square meters per gram.
For the carbonaceous material to have the desired reactivity, it appears that it must be formed in-situ. That is, simply mixing the bulk metal with carbon does not result in our carbonaceous material. Typically, the carbonaceous material grows from the surface of the bulk metal as fibers, possibly hollow flbers. Typically, the fibers have a di-ameter in the range of about 0.02 micron to about Z.0 micron and a length to diameter ratio greater than about 10. We have analyzed these fibers and found that most contain minute particles of a metal component (minor phases), such as alpha-iron, iron carbide or iron/nickel alloys. Apparently, the ferrous metal component is transported into the carbonaceous fibers. This transported ferrous metal component is no longer physically associated with the bulk ferrous metal and is an essential part of the highly reactive carbonaceous material. When we methanate our iron-based carbonaceous ; 25 materïal to convert over 95% of its free carbon to methane, mix the resulting carbon-lean material with particulate carbon, and then expose this mixture to hydrogen at the pres-sure and temperature ranges we normally use for methanation, no methane forms.

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~i36413 It should be understood that it is difficult to distinguish the active ferrous metal component in the carbon-aceous material from the bulk ferrous metal when small particles of bulk ferrous metal are used. In characterizing the carbon-aceous material of our invention, we conducted a series oftests using plates of iron, nickel, cobalt and an iron-nickel alloy as the initiator of the carbon monoxide disproportionation reaction and deposited the carbonaceous material on these ``~ plates. The carbonaceous material formed as a billowy mound of fibers on the plate, permitting the plate to be simply physically separated from the carbonaceous material. This .
allowed us to analyze the carbonaceous material separately from the bulk metal. Starting with an iron plate, the (as - separated) carbonaceous material formed in-situ contained from about 1 to about 3.5 pèrcent by weight of dispersed iron component as determined by both spectroscopic analysis and -``
. .1 ashing techniques. The balance of the material contained principally carbon with trace~amounts of hydrQgen~ The carbon was partially graphitized. Partially graphitized carbon has , ~ .
;~ been discussed in detail by R. E. Franklin in his paper published in "Acta Cryst", vol. 4, pp. 253, (1951).
In one broad aspect, the invention contemplates a process for producing a high Btu gas which comprises contactin~
a carbonaceous material made up of carbon and a ferrous group '' 25 metal component which 1s dispersed throughout the carbon and intimately associated with and at leàst partly bonded to the carbon, the carbonaceous material having a high reactivity with hydrogen to form methane, with a hydrogen containing gas, under conditions that cause the hydrogen to react with l .
~ 30 the carbonaceous materlal to form a methane-rich gas.

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113~i413 The inverltion contemplates a fiber which includes partially graphitized carbon and a nodule comprising a metal alloy con-taining as one ingredient of the metal alloy a ferrous group metal, the nodule being at least partially bonded to the car~on.
The invention also contemplates a method of increasing the reactivity of a carbonaceous material formed by disproportion-ation of carbon monoxide and having a`first level of reactivity, and it includes the steps of reacting the material with hydrogen to produce methane, thereby depleting a portion of the carbon content of the material, and reacting the carbon depleted material with carbon monoxide to replenish the carbon content through dis-proportionation of the carbon monoxide to increase the reactivity from the first level to a higher level.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a photomicrograph showing fiber detail;
Fig. 2 is a photomicrograph of the fibers in lesser detail than Fig. l;
Fig. 3 is a graph showing the methanation rate;
Fig. 4 is a schematic presentation of the inventive .: :
apparatus;
Fig. 5 is a further schematic presentation of the in-ventive apparatus, shown with Fig. 3;
Fig. 6 ls another schematic presen~atlon of the in-ventive apparatus;
, Pig. 7 is another schematic presentation of the in-ventive apparatus;
Flg. 8 is another schematic presentation of the in-ventive apparatus;
Fig. 9 is a photomicrograph of another carbonaceous material.

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11364i3 We have examined carbonaceous fibers formed on an iron plate using a scanning electron microscope. Fig-ure 2 is a micrograph showing fibers of our material as seen through a scanning electron microscope under rela- ?
tively low magnificiation. Figure l is a micrograph show-ing, in greater detail, some of the fibers under relatively high magnification using the scanning electron microscope.
The fibers shown in Figures 1 and 2 are unpromoted, i.e., not hydrogenated. In one representative sample fiber, . .
identified as A, an area of high iron concentration was ~
positively identified. Fiber ~ -areas with an electron microprobe analyzer, and the nodule B
was positively identified as containing iron. This nodule was about 3000A long and about 1000A wide. This analysis was made according to the analytical procedures~described by J. R. Ogren in ~Electron Microprobe," Chapter~6, in Systematic Materials Analysis," Volume l, Academic Press,~ -~
; Inc., New York 1975. Assuming the fiber is solid and it exhibits a density intermediate between that of amorphous and fully graphitized carbon, the detectability limit of the microprobe analysis is about l.S~ by weight iron. ~ -,, . ~ .

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~~ 31-006C
113Çi413 x-ray analysis of the samples of unpromoted car-bonaceous material ~deposited on bulk iron plates) showed iron to be present as a form of iron carbide and, pos-sibly, as alpha-iron as well. The Debye-Scherrer method was used to obtain powder diffraction patterns on a General Electric Model XRD-5 X-ray spectrometer. Using the same method to analyze hydrogenated promoted material revealed that the X-ray detectable iron in the hydrogenated material was present only as alpha-iron.
As the micrograph in Figure 1 shows, the iron - component is bonded to the carbon. We have attempted to ; break this bond and separate the iron component from the carbon by simple physical means such as sifting through sieves and pulling the iron from the carbon with magnets.
These methods, however, did not achieve separation. Since ; the iron component in the carbonaceous material cannot be separated from the carbon by simple physical means, this indicates to us that at least a part of the iron is inti- `
mately associated with the carbon and at least part of the ; 20 iron is bonded to the carbon, possibly at the atomic or molecular levels. Or, perhaps the iron is in solid solu-tion in the carbon. If this is so, the interfaces o~ the , iron-carbon solid solution and crystals of the iron compo-., nent may be active sites which cause the rapid reaction rate. Whatever bond is formed between the iron and carbon, we have found that iron by itself, activated charcoal by ` itself, commercial cementite (Pe3C), and a simple physical - ;

~ ~ -10-il36413 31-006C

mixture of iron and activated charcoal do not have the properties of the carbonaceous material of our invention.
None of these compounds or mixtures, when contacted with hydrogen at elevated temperatures, will form methane S at the rates approaching the rate attained using our car-bonaceous material. This is shown in the following Table I.

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~ 1~364i3 Methanation Carbonaceous C/Fe Rate Material Separated Atom(Moles CH4/Hr/
Starting MaterialFrom Iron Initiator RatioMole Carbon) 1. Carbon deposited from C0/H2 No 27.3* 0.10 gas stream at 550C and 1 atm onto high purity iron Eoil.
2. Carbonaceous material from Yes 176 0.]0 sample 1 separated from foil and rehydrogenated.
3. Carbonaceous material deposited Yes 220 0.28 on 1/8 inch carbon steel spheres at 500C from C0/H2 gas stream at 1 atm pressure.

4. Carbonaceous material** Yes 12.6 0.49 initially prepared by several cycles of carbon deposition and hydro-genation at 550C and pressure from 100-250 psi over 3/16 inch carbon steel spheres. Sample separated from spheres and carbon deposited from 1 atm CO/H2 BaS stream,

5. Mesabi range iron ore pre- No 7* 0.24 reduced in H2 and then used to catalyze carbon deposition from C0/H2 gas stream at .
500C and 1 atm.

6. Same as sample 5 except ex- No 7* 0.20 posed to ambienc air for 96 hrs at 25~C before hydrogenation.

7. Commercial cementite Fe3C. - 0.33 ~0 05 (no CH4 detected) .;~

8. Norit-A activated charcoal. - >1000 <0.0004

9. Char from coal gasification. - >1000 <0.0004

10. Norit-A charcoal mixed with - 4~7* <0~0004 - electrolytic iron powder 50:50 ~` wt. basis.

11. Spectoscopic graphite powder. - ~10,000 -10-7 *Includes bulk iron.
**Hydrogen promoted material.

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11364i3 31-006C

Figure 9 shows a scanning electron micrograph of another of our casbonaceous materials prepared by carbon monoxide disproportionation over a bulk metal alloy plate consisting essentially of about 50% nickel and about 50% iron. After separating the fibrous car~
bonaceous material from the alloy plate, the carbonaceous material was found to contain 98.42% C, 0.48% Fe, 0.73% Ni and 0.94% H.* The area marked by a circle in the micro-graph was analyzed with an electron microprobe and was found to contain high concentrations of both iron and ~
nickel in approximately equal amounts. X-ray analysis -; of a representative sample of the fibers indicated the presence of iron-nickel alloy. It appears likely that the nodule C shown in the circle in Figure 9 aatually 5 ` consists of an iron-nickel alloy. Whether or not the nodule C shown in Figure 9 is a true solid soIution alloy of iron and nickel, our analysis clearly shows that very small crysta11ites or nodules containing both iron and nickel were transported from the bulk metal alloy plate to the carbon fibers and became intimately associated with, and probably bonded to the ~ibers.

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~t.', ~ ~ * Unnormalized data which does not add up exactly to 100%.
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li3~413 One way of thinking about our material is that the active errous group metal component is a catalyst that is dispersed throughout a carbon matrix. This fer-rous group metal component catalyzes the reaction of the carbon in the matrix with other reactants. Carbon is depleted as the reaction proceeds, but the material may -be replenished with carbon by exposure to a carbon monoxide-containing gas. When exposed at elevated temperatures to carbon monoxide, the active component catalyzes the disproportionation of carbon monoxide.
We have discovered that even though carbon is depleted from the material by reaction with hydrogen, the material retains its high specific methanation rate. Sur-prisingly, we have been able to remove almost all the carbon from the carbonaceous material and still maintain a rela-~ .
tively high specific rate of methanation. This property of the material is illustrated by Figure 3 where the speci~ic methanation rate of the carbonaceous material is plotted .~ .
against the percent of the carbon removed by hydrogenation of the material. (The rates shown in Figure 3 were determined at 570-600C, and 1 atmosphere pressure.) The carbon rich material (i.e., the material containing about 96~
carbon) had an initial reactivity of about 0.30 moles CH4/
hr/mole of carbon. This reactivity ~radually increased to about 0.63 moles CH4/hr/'mole of carbon when about 88%
of the carbon was removed. When about 90% of the carbon was removed, or when the material contained about 25 weight percent of the iron component, its reactivity decreased - 113~413 31-006C

rapidly. If the carbon rich material had contained, initially, 95 weight percent carbon and ~ weight percent iron, the final material, after removal of about 90% carbon, would contain about 35 weight percent of iron.

The new carbonaceous material retains its important ~;
and valuable properties after many cycles of carbon enrichment/
carbon depletion. Using iron as the ferrous group metal component, we have completed 55 such cycles, and have obtained our unique, hydrogen-promoted material each time.
::. 10 1~ Our new carbonaceous materials also retain their properties after extended periods of storage, whether stored I in the carbon-enriched or in the carbon-depleted states.
However, because exposure of these materials to oxygen may - -oxidize the ferrous metal group components, and thus impair lS~ ~their catalytic aceivity, we avoid ex~posing them to air during storage. After we store our iron-based carbonaceous -: ~
~ material for 24 hours at room temperature, we observe no i ~ deterioration in its rate of methanation.
Based on the above experiments we have found that the carbonaceous material of our invention may vary in composition approximately as follows:
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~, ., ` -113~413 General ~ Preferred %
by weight by weight Partially Graphiti~ed Carbon 65-99.5% 75~99%
Dispersed FerrousGroup Metal Component 0.5-35% 1-25%
Weiyht percentages were determined after the carbonaceous material was separated from the bulk ferrous group metal.
For iron-based materials, we prefer the unpromoted carbonaceous material to contain from about 1% to about 3.5~ weight percent of ferrous metal component and from about 99 to 96.5 weight percent of carbon.

Hydrogen Promoted Material We have found that at least some of our carbonaceous materials, when subsequently hydrogenated, have an enhanced ; 15 carbon deposition rate and methanation rate. Specifically, ~ where the ferrous group metal component is iron, the hydrogen . ~, .
promoted carbonaceous material has a carbon deposition, rate exceeding 10 grams of carbon deposited per hour per gram of dispersed iron present, and a methanation rate exceeding 0-3 moles of methane formed per hour per mole of carbon present.
The carbon deposition rate was measured at 500C, one atmosphere pressure, and a feed rate of 10 moles of caxbon monoxide per hour per gram of dispersed iron using a feed gas that contains 80~ by volume carbon monoxide and 20% by volume hydrogen. ; 25 The methanation rate was measured at 550C, one atmosphere pressure, and a minimum hydrogen feed rate of 2 moleæ of j' hydrogen per hour per mole of carbon present.
Although the feed stream used to make the carbonaceous material may contain hydrogen, the hydrogen promoted material is not produced as long as conditions prevail where carbon is deposited on the bulk metal. When the carbonaceous 1~3~413 31-006C
' material formed initially is subjected to hydrogenation to produce methane, then our hydrogen promoted material begins to form. We have observed the formation of this material when about 15% by weight of the carbon was removed by hydroge-nation of the carbonaceous material initially prepared.
Moreover, the hydrogen used normally should contain not more than about l~ water by volume.
We have separated the hydrogen promoted material from the bulk metal and found that this material has the same general physical appearance as the material initially ~- prepared, but the X-ray identification indicates that, where ; the ferrous group metal component is iron, the iron is alpha-iron rather than carbidic iron. The hydrogenated material, when subjected to several cycles of carbon deposition and methanation, has an even greater reactivity than prior to such cyclic treatment. Moreover, as it undergoes such cyclic ~` treatment, its composition may vary approximately as follows:
% by weight Partially Graphitized 65-99.5 Carbon .~ .
Ferrous Metal Component .5-~5 i Hydrogen .1-3.0 ~ i The hydrogen in our new materials is strongly associated.
When we heat our iron-based carbonaceous material f in a nitrogen gas stream from a temperature of about 200C
- to a temperature of about 950C, and analyze the carrier stream for desorbed gases, principally hydrogen and carbon monoxide, we find that the quantity of hydrogen present in our carbonaceous material is more than fifty thousand times the quantity we can dissolve in alpha-iron. Moreover, more 1~3~;4i3 than two-thirds of the hydrogen released during such runs comes off at temperatures above 700C.
Again, it is emphasized that when we speak of weight percentages, we are speaking of our carbonaceous material, both hydrogenated promoted and unpromoted, after it has been separated from the bulk metal.
Examples of Carbonaceous Material The following Examples show how some of the carbonaceous materials of our invention were prepared.
10 Example 4 shows the methanation rates for several different ferrous group metal catalysts of our invention. Example 5 shows the unexpectedly good thermal stability of our catalytic materials.
Example 1 Carbon was deposited on one-eighth inch mild ` steel balls (5 grams) by decomposition of carbon monoxide at 550C from a carbon monoxide and hydrogen gas mixture in a tube furnace. The flow rate of the carbon monoxide was 100 cubic centimeters per minute and the flow rate of the hydrogen was 20 cubic centi-meters per minute. After about 4 hours, 2.7 grams of the carbonaceous material containing 3.7% by weight of iron was separated from the steel balis, and 0.27 grams of the separated carbonaceous material was also exposed to the same carbon monoxide and hydrogen gas mixture at 500C and 1 atmosphere pressure. It was found that the carbon deposition rate was 8.8 grams of carbon per hour per gram o~ dispersed iron in the carbonaceous material present. This carbonaceous material, had a methanation rate of 0.52 moles of methane formed per hour per mole of carbon. Carbon was again deposited on the hydrogenated material using the same carbon monoxide-hydroaen gas mixture and contacting the material at 500C at one atmosphere.
The carbon deposition rate was 39.4 grams of carbon per hour per gram of dispersed iron. Cycling as above between the carbon monoxide disproportionation reaction to deposit carbon and thereafter hydrogenating the resulting carbonaceous material to remove most of the carbon was continued for several cycles. The result of all the cycles is summarized in Table II
below.

113~413 TABLE II

CAR13ON DEPC)SITIO2~ T~A~lATION RAT~:
CYCLE NO.(Grams/Hr/Gram of Dis- ~Moles/Hr/Mole of persed Iron)_ Carbon) l-C~ 8 8 l-H~* 0 52 ~ 3-C 47 8 ; 3-H 1 12 ,:
* Denotes carbon deposition ** Denotes hydrogenation The hydrogen promoted material had a carbon deposition rate well in excess of lQ grams of carbon deposited per hour ; p-r gram of disperse~d iron present Aft-r this material was subjected to several cycles of~carbon d-position and methanation, ~ -~
it- methanatlon~rate increas-d substantially to in excess of ~ 1 mole of methane ~ormed per hour per mole of car~on present `~ Example 2 ~ Six hundred grams of Mqsabi Range Iron Ore ~hematite `~ 25 type iron ore containing S5 3~ Fe, 8 1~ silica, o.a~ .
alumina) ~f ~particIe size 60 to 150 mesh and bul~ density 1 91 g/cm was ~laced in a stainless steel ~ressure resis-tant verticle;tube reactor having an inner diameter Of 1 5 inches and a height of about ~ ft The ore was redueed by a hydrogen~gas stream contacting the iron ore at a space velocity of 2300 volumes of gas per volume of iron ore per hour The reduced ore was æub-i jected to a series of carbon deposition/methanation cycles Carbon deposition was perfQrmed using nitroqen~car~on ;, 30 monoxide/hydrogen gas mixtures of different compositions, i and the methanation was performed usinq pure hydrogen ? The volumes of gases entering into the reactor and exiting after cooling the reactor to room temperature were measured with flow indicators and wet test meter, and the ' composition of gases was determined by gas chromatography The conditions and results of several cycles are shown on the following Tabl- III

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~ , - 19 _ li36413 TABLE III

CARBON ~EPOSITlON

Cycle Gas Composition (X) Av.Pres- Av. Time Atomic :;~ N2 H2 CO Tempsure Res- Minutes C:Fe -. 5 C atm idence After ~: abs Time Carbu-Seconds retion :
:.~

: A46.6 8.1 45,3 4566.1 1.9 65 1.29 ~ B42.5 6.9 50.6 4403.4 1.7 75 0.88 :~ 10 C44.2 6.9 48.9 435: 3.5 1.6 90 0.80 D44.2 7.4 48.4 4164.7 1.8 110 1.12 METHANATION

Cyc~le ~Temp. : ~Preseure ~Av.: Ga8~ Time~ CH4 ~: Atomic ;.
;C* ~ ~Atm ~ Res~MInutes in Pr ~u t Gases(%) C ~ ;

~ S conds ~ Attaine- nat1on J5''~ A~540-673 6,8 4.9174 ; :53.5 0.08 B~500-700 11.6 ~9.1 ~~120~ 63.0 0.04 ZO~ :: C500-672 1~1.;6 ~ 1,0~~:: 140~ 62.0 0.01 :D500-635 13.6 ~ 15.0 ~ 165 70.0 0.15 .: ;

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~ *Reaction was highly exothermic and the temperature was held under control`' only by adjustment of hydrogen flow.
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113~413 Example 3 A 2.88 gram sample of iron-nickel alloy containing about S0 percent by weight of each of these two metals was oxidized at 982C for 10 minutes in a muffle furnace. The oxidized alloy was then carburized at 500C using a mixture of gases comprising 85 percent by volume carbon monoxide and 15 percent by volume hydrogen flowing at the rate of 200 S milliliters per minute for 9.33 hours. After separating the carbonaceous material from the bulk alloy, we found that the elemental analysis of the resulting carbonaceous material was: Carbon:98.06%; iron:0.54%; nic~el:0.53~ and hydrogen:
0.16%. The separated carbonaceous material was then subjected to a series of three methanation/carburization cycles. The conditions and results of these cycles are set forth in the following TableIV. The data in Table IV establish that both the carbon deposition rates and the methanation rates improved with cycling of the material between carbon deposition and methanation.

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113~413 TABLE IV

CYCLE t CARBON DEPOSITION RATE METHANATION RATE
(Grams/Hr/Gram Dispersed (Moles/Hr/Mole of Carbon) Iron) -: ;

l-H** 0.10 l-C* 3S~2 2-H 0.12 :~ 2-C 38.8 3-H 0.20 ~ ~
~' -3-C 45.3 * Denotes Carbon Deposition :
~ ~* Denotes Hydrogenation ,, , '~ , ' ' .~ ' ' . ~.

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: :
;

Example 4 Following the process of our invention, we prepared samples of free-carbon containing carbonaceous materials from the disproportionation of carbon monoxide over p~ates or buttons of iron, nickel, cobalt, and an iron-nickel alloy containing about 50% iron and about 50% nickel. In ea~h sample, the fibrous carbonaceous material formed was separated from the bulk metal and exposed, at 550C and 1 atmosphere pressure, to a stream of dry hydrogen flowing at a rate of about 2 moles of hydrogen per hour per mole of the carbon present. The specific rates of methane formation for each of the samples is shown in Table V below.

.

TABLE V

SPECIFIC RATE OF METHANE
CO DISPROPORTIONATIONFORMATION FOR FIBERS
INITIATOR SEPARATED FROM BULK METAL
IN MOLES/HOUR/NOLE CARBON
IRON 0.10 NICKEL 0.19 IRON/NICXEL ALLOY 0.10 ;

1~3~13 31-006C

Example 5 Ten grams of carbon steel spheres measuring one-eighth inch in diameter were placed in an alumina boat which was then suspended in the center of a ceramic reactor tube. A mixture of 100 ml/min of carbon monoxide and 20 ml/min of hydrogen was passed over the spheres at 510C and atmospheric pressure for five hours. A total of 1.94 grams of carbon was deposited. The deposited carbonaceous material was carefully separated from the carbon steel spheres, and found to contain 2.08~ iron. Of the separated material, 0.992 gram was placed in an alumina boat and returned to the reactor. A mixture of 100 ml/min of carbon monoxide and 20 ml/min of hydrogen was passed over the 0.992 gram sample at 408C for 2 hours. An esti-mated additional 0.2 grams of carbon was deposited as determined by measuring the carbon dioxide concentration of the effluent gas stream. Next, a gas stream of pure hydrogen ~110 ml/min) was passed over this modified sample at a temper-ature of 560C. Methane began to form and the hydrogenation was continued until approximately 0.2 grams of carbon were gasified, as determined by measuring the methane concentration and flow rate of the effluent gases. The average methanation rate was 0.20 moles C~ /hr/mole of carbon. The gas stream flowing over the carbo~aceous sample was then changed from hydrogen to pure nitrogen t40 cc/min) and the carbonaceous material was slowly heated to 865C. The sample was held at 865C for about one hour, and then cooled in flowing nitrogen lS to 560C. At 560C, the gas stream was again changed to pure hydrogen, flowing at a rate of 110 cc/min to effect methanation. Methanation continued until an additional 0.2 grams of car~on were gasified. The average methanation rate ~ after the high temperature thermal exposure was 0.26 moles ;~ CH /hr/gram-atom carbon. The cycle of high temperature (865C) thermal exposure to flowing nitrogen followed ~y hydrogenation at 560C was repeated. The average methanation rate was again determined and found to be 0.26 moles CH /hr/gram atom of carbon. Apparently, this short term exposure of our carbona-ceous material to high temperature does not impair its reac-tivity with hydrogen. Nor did the high temperature expo~ure ,' il3v4~3 31-006C

impair its catalytic activity in the direct conversion of carbon monoxide and hydrogen to methane. After the same thermal cycles, the remaining carbonaceous material was exposed to a mixture of 110 cc/min of hydrogen and 30 cc/min of carbon monoxide at 450C. Methane found in the effluent gas formed at an average rate of 0.24 moles/hr/mole catalyst.

, When iron oxides suah as iron ore are used at start up as the disproportionation initiator, they are first reduced by the carbon monoxide-hydrogen feed gas and then the carbona-ceous material begins to collect on the bulk iron. Consequently, the length of time the carbon monoxide containing gas contacts the bulk iron is important~ If, for example, Fe304 is used and the carbon monoxide containing gas is at 600C
and one atmosphere, initially the iron oxide is at least partially reduced to iron. This is indicated by a loss 1~3~413 31-006C

of weight of iron oxide due to the loss of oxygen. For example, after the iron oxide was contacted with pure carbon monoxide gas for 15 minutes, the sample had a weight loss of about 22~
(oxygen com~rising about 27.6% by weight of the iron catalyst) and little carbon was deposited on the bulk iron. What carbon was deposited was in the form of Fe3C. After 30 minutes of contact the sa~ple had a 15% weight loss and the carbon deposited on it was in the carbide form, primarily Fe3C.
Even after 60 minutes of contacting the iron oxide with carbon monoxide the sample still showed a weight loss of about 10~, and substantially all of the carbon deposited on the iron oxide was in the carbide form, again primarily as Fe3C. After 4 hours, however, the sample had about a 75~
weight gain and the deposited carbon was partially graphitized.
The 15 minute, 3~ minute, and 60 minute samples did not have the required methanation rate. In contrast to these samples, the fourth sample (the four hour sample) did form methane `~ ~ at at least 0.1 mole of methane per hour per mole of carbon when contacted with hydrogen at 550C, one atmosphere, and a minimum hydrogen feed rate of 2 moles of hydrogen per hour per mole of carbon present.
Process for Maki~g High Btu Gas We have also invented a process for producing a high Btu gas from coàl or other carbonaceous fuels through the vehicle of our novel carbonaceous material. In our process methane can be made without the need to use pure oxygen or to remove nitrogen, carbon dioxide or other inert gases from the feed stream. According to our process the , , - ' . ` . , :

113~413 carbon monoxide and hydrogen are extracted from the feed stream by forming our novel carbonaceous material on the bulk ferrous metal. A hydrogen-containing gas is then contacted with the carbonaceous material at a temperature, pressure, and space velocity that produces a methane containing product gas including at least 20% by volume methane. Because the carbonaceous material is so highly reactive with hydrogen, the residence time of the hydrogen in contact with the carbona-ceous material may be very short. We have found that the carbonaceous material requires little residence time with hv~rooen to produce a gas containing as high as 75% by volume or ~reater methane. For example, the residence time may vary from 1 second to 50 seconds to produce such a methane rich gas.
The preferred hydrogen residence time is from 5 seconds to 30 seconds. The desirable minimum temperature at which methanation is conducted is 350C. The preferred range is from about ~` 400 to about 700C. The pressure may range between about 1 a~d about 100 atmospheres, preferably 1-25 atmospheres.
~ In the process of our invention almost any carbon ; 20 monoxide containing gas can be used to produce a high Btu methane containing gas. Specific gases which may be used in our process are those gase~ produced by gasifying c~al using air or a mixture of air and steam to produce a low Btu producer gas of from about 7Q-150 Btu's per cubic feet. For example, coal may be burned in--situ ~i.e., without removing the coal from its natural site) to produce a gas having about 100 Btu per cubic foot. As used here, a producer gas ~ - `
1~3~413 31-006C

is one which contains carbon monoxide, hydrogen, nitrogen, and carbon dioxide. Preferably, the coal is burned in a mixture of air and steam to provide a producer gas rich in carbon noxide and hydrogen. For example, producer gases normally S will contain on a dry basis from about 15% to about 30%
carbon monoxide, from about 5% to about 30% hydrogen, from about 40~ to about 60% nitrogen, and ~rom about 2% to about 10% carbon dioxide. All of these carbon monoxide-containing gases may be converted to a methane-rich gas similar to natural gas and having a heat content of from ?
; 500 to as much as 1000 Btu per cubic feet.
In general, such producer gases will also contain water and small amounts of other gases such as methane, hydrogen sulfide, carbonyl sulfide, etc. For operation at atmospheric pressure, the water content should be reduced below about 6% by volume; the sulfur content, below about 10 parts per million. If the carbon monoxide feed gas contains hydrogen, the molar ratio of carbon monoxide to hydrogen should be greater than about 1:2, preferably greater than 1:1. The preferred molar ratio of carbon monoxide to hydrogen is between about 1:1 to about 100:1. When the feed gas contains carbon dioxide, preferably the molar ratio of carbon monoxide to carbon dioxide is high. In general the carbon monoxide to - carbon dioxide molar ratio should be 1:1 or greater, preferably greater than ~ 3:1. ~owever, carbon deposition proceeds at acceptable rates even when the ratio of carbon dioxide to carbon monoxide is as high as 3.
We have found that the initial feed gas containing carbon monoxide should not contain appreciable amounts of ., .

` 113~413 31-006C

sulfur. Specifically, the carbon monoxide feed gas should not contain more than about 20, preferably not more than 10, parts per million of sulfur calculated as hydrogen sulfide.
When required, sulfur remoYal may be accomplished by well known methods, for example, amine systems, or by contacting the feed gas with an aqueous solution of an alkali metal or alkaline earth metal carbonate such as hot potassium carbonate.
In addition to conventional methods of removing hydrogen sulfide from feed gases, we have also found that hydrogen sulfide can be removed by passing the feed gas over the carbonaceous material or a mixture of the carbonaceous material and the bulk ferrous group metal. When this is done, the ferrous metal reacts with the sulfur to form metal sulfides within - the mater al. This reaction deactivates the carbonaceous material- Therefore if this method is used ~o remove the sulfur from the feed gas, the sulfur containing carbonaceous ~ material cannot be used to produce methane.
; Since our invention is able to use gases containingnitrogen in reIatively large amounts (e.g. nitrogen may be : i~
present in amounts as great as 70% by volume or greater), it is not necessary to form the car~on monoxide aontaining gas in a nitroqen free oxygen atmosphere. That is, air may ` be used to burn coal rather than pure oxygen. What makes our I process economically attractive is that the com~ustible portion of the feed stream, principally the carbon monoxide, is ~; extracted or separated at low cost from the inert or non-combustible portion of the feed stream through the formation of the solid carbonaceous material as an intermediate. A

113~413 31-006C

methane rich gas is subsequently produced by simply contacting the carbonaceous material with hydrogen. This solid car-bonaceous material need not be immediately reacted with hydrogen, since it retains its reactivity for a considerable period of time. For example, we have stored one sample for five days and reacted the sample with hydrogen and formed methane at the same high rates as freshly prepared carbonaceous material. This enables energy to be stored until needed.
One feature of our invention is that partially depleted producer gas may be used to produce our carbonaceous material which is subsequently converted to methane. In this instance, coal is burned in air under controlled conditions to form the producer gas which is contacted with oxides of iron to reduce the oxides principally to iron, iron carbides, and iron oxides of lower oxygen content, and to provide the partially depleted producer gas. For example, the partial}y depleted producer gas may contai~l about half as much carbon monoxide and about half as much hydrogen as the producer gas initially contacting the oxides of iron.
The partially depleted producer gas is used to make the carbonaceous material by contacting it with the bulk ferrous metal group disproportionation initiator under conditions which form the carbonaceous material. Hydrogen may be produced by contacting ~he reduced oxides of iron with steam~ This hydrogen is then contacted with the carbonaceous material to produce methane.
According to one embodiment of our invention carbonaceous material (ordinarily mixed with the bulk ferrous ~ -metal) is cycled between two reaation zones, one in which the carbonaceous material is contacted with the partially depleted producer gas and one in which the material is contacted with the hydrogen rich gas to make methane. Thus, the material il3~413 31-006C

undergoes a transition between a carbon rich state and a carbon lean state. The material being fed to the zone producing methane is rich in carbon. Some of the carbon is stripped (at least 15 weight percent) from this material during the formation of methane to produce the carbon lean material which is transferred to the other zone where it is again enriched with carbon by contact with the producer gas. The carbon lean material (i.e., hydrogen promoted carbonaceous material) will, in the first cycle, contain between about S to 35 weight percent dispersed ferrousmetal, about 95 to 65 weight percent ; carbon,and about 0.1 to 3 weight percent hydrogen. The carbonaceous material may, however, remain in one zone and the gas streams flowing through such zones are alternated between producer gas and hydrogen rich gas streams.
lS Another feature of our invention is that the carbonaceous material entrained in the process fluids may be separated from these fIuids by means of a magnetic field.
The ferrous group metal component of the carbonaceous material - retains its ferromagnetic properties, thus renderinq the -<~ 20 material magnetlc.
Our prQ~ess also permits production o~ substantial : ,:
quantitles of energy from the depleted producer gas or other gas used as a source of carbon monoxide. Thus, after the - producer gas has been utilized tQ manufacture our new carbonaceousmaterial, and to make hydrogen by the steam-iron process, the depleted gases are preferably then burned in air to oxidize any remaining combustibles and the resulting gases are expanded through a gas turbine to recover their energy as electricity.
' 113~413 Detailed Description of the Preferred Processes T~e best mode which we presently contemplate for practicing our invention is shown schematically in Figure 8. -~
In Figure 8, desulphurized producer gas from source 100 is S the feed stream. This gas may include, say, 50 percent nitrogen, 25 percent carbon monoxide, 18 peraent hydrogen, 6 percent carbon dioxide and 1 percent methane, on a dry basis. Its sulphur content must be less than about 20 parts per million.
The producer gas passes via line 101 to fluidized bed carbon deposition reactor 102, which contains carbon-lean solids of a ferrous metal such as iron. Carbon deposition occurs in reactor 102 by disproportionation of the carbon .. : .
monoxide in the producer gas at a temperature of about 650C
and at a pressure iD the range 150-250 pounds per square inch. ~ -The carbonaceous mat-rLal of our invention formed in reactor 102 pas~es through line 103 to ~ethanator 104.
There, at a tempe~ature in the~range of about 525C to about 700C, the carbon in the carbonaceous material reacts with dry hydrogen entering methanator 104 through line 106 to form methan~ and hydrogen. Because methanation 1~ hlghly exothermic, ., and because lower temperatures favor the formation of methane in higher concentrations, methanation is effected in stages, with the solids and gases cooled between the stages. Depending ~ on the desired product composition, one or more i~terstage coolers -l~ 25 may be required. Here, cooling is effected with water entering ., .
methanator 10~ through line 107 and exiting as steam through line 108.
~' :

, :' .

1~3~413 31-006C

The methane/hydrogen gas mixture leaves methanator 104 in line 109, passes through cooler 110, and emerges in line 111, ready for further processing.
The partially depleted producer gas from carbon deposition reactor 102 passes therefrom through line 112 to heat exchanger 113. There, the temperature of the gas is raised from, say, 670C to about 920C, and the residual methane in the mixture converts to a mixture of water, carbon monoxide and carbon dioxide. The partially depleted producer gas leaving heat exchanger 113 has a lower ratio of carbon monoxide to carbon dioxide, and contains principally nitrogen, carbon monoxide, hydrogen, water and carbon dioxide. Though ~; lower, the C0/C02 ratio is sufficiently high to permit its use for reducing iron oxides.
The partially deple;ted producer gas leaves heat exchanger 113 and passes through line 114 to iron oxide reducer ~ 115. There, the mixture reduces ferric oxide to ferrous oxide,`~ and oxidizes carbon monoxide to carbon dioxide and hydrogen to wat-r. The reduced iron oxides pass from reducer 115 via line 116 to hydrogen producing reactor 117. Steam enters reactor 117 through llne 118 and reacts with the ferrous oxide to produce ferric oxide and hydrogen. The ferric oxide ;::
, passes to reduc~er 115 through line 119. The wet hydrogen produced passes from reactor 117 via line 120, is cooled in heat exchanger 121, and then passeæ through line 123 to condenser 122. In condenser 122, the water content of tbe hydrogen stream is reduced to less than about 1~ by weight.
Dry hydrogen emerges fxom condenser 122 in line 124, and passes to methanator 104 through line 106.

;
,.,:,~ . ' ~136413 31-006C

The partially depleted producer gas entering reducer 115 passes therefrom in line 125 as a nearly depleted gas.
However, the gas still contains useful residual energy.
That energy is preferably utilized by burning the gas in furnace 126 with air from source 127. Pressurizer 128 raises the inlet air pressure in furnace 126 to the range of about 150-250 psi. The heat produced in furnace 126 is partially consumed in heat exchanger 113 to raise the temperature of partially depleted producer gas from reactor 102. The remaining heat in the gases from furnace 126 passes from heat exchanger 113 via line 129 to turbine 130, where the gases are expanded to produce electrical power at 131. The depleted gas exits turbine 130, is cooled in heat exchanger 133, and passes to the atmosphere via line 134.
This embodiment of our process has several out-standing advantages. First, a very high percentage of the cold gas heating value of the producer gases is utilized ~ effectively in conversion to high value products, synthetic -~ natural gas and electricity. Secondly, expensive oxygen is not required in this process. Third, the heat released in the methanation ~tep and the rema~ning sensible heat in the depleted producer gas are a~ailable for use at high temperatures. This leads to high efficiencies in the ~; utiliziation and conversion of this heat to electric power, minimizing waste.
Another embodiment of our process is shown schematically ,."
,~,',5i, in Figure 4. Desulfurized producer gas,from source 1 is the ~6 feed stream. This gas, which may comprise, for example, of 50% N2, 25% CO, 18% H2, 6% CO2, and 1% CH4 on a dry basis, ~ 31-006C
~3~413 may ~e derived from conventional gasification of coal with steam and air, "in-situ" gasification of coal, etc. The raw producer gas is desulfurized to below about 10 ppm of H2S ~
Desulfurized producer gas and, for example, oxidized iron solids such as a mixture of Fe2O3, Fe3O4, and FeO are contacted in a fast fluidized bed or entrained solid lift pipe type reactor 2 at temperatures from about 550--850C and at pressures of 1-100 atm, preferably about 1-20 atm. Choice of temperature and pressure are dependent on the overall heat balance and the desired methane concentration~of the product gas. Solid-gas contact is maintained for a sufficient time to cause partial reduction by the H2 and CO in the producer gas of the iron oxides to reduced iron compounds such as FeO, Fe and Fe3C.
; 15 The ~2 and CO content of the producer gas eed is partially ; but not fully consumed in the reduction of the iron oxides.
We believe that the H2 will be more fully utilized than the CO in this step of our process.
The entrained, reduced iron solids and partially reacted producer gas are next fed to a cyclone or similar devloe 3, where the reduced iron solids are separated from the partially reacted producer gas. The separated, reduced, iron solids are fed through line 4 to the bottom of a second ~ lift pipe reactor 5 where thcy are contacted with steam from source 6 at temperatures of about 500-800C and pressures of 1-100 atm. A hydrogen rich gas is obtained from tfie reaction of the steam with the reduced iron solids. In addition to hydrogen and unreacted steam this gas will also contain some methane, carbon monoxide, and carbon dioxide.

i~3~413 31-006C

The hydrogen rich gas and entrained oxidized iron solids from the hydrogen production reactor 5 exit through line 7 and are next fed to a cyclone or similar device 8, which separates the solids from the gases. The oxidized iron solids are returned via l~ne 9 to the first lift pipe reactor 2 to complete the solid circulation loop between reactors 2 and 5.
After separation of the solids, the partially reacted producer gas, which now may contain, for example, 15~ C0, 6~ H2, 16~ C02, 1% CH4, and 62% N2 on a dry basis, is cooled in heat exchanger 10 generating process steam. This cooled gas is fed via line 11 to the bottom of the lift pipe carbon deposition reactor 12, where it contacts and entrains carbon , lean solids. The gas and solids are maintained in contact with each other for a sufficient length of time at temperatures ` of 3Q0-600C and pressures of 1-100 atm to cause carbon to deposit on the carbon lean solid-c and enrich their carbon ~, ~, .
content. Carbon deposition occurs by disproportionation of the carbon monoxide content of the partially reacted producer gas to a lesser extent by reaction of C0 and ~2 or by the reduction of C0 by other reducing agents present.
The`entrained carbon rich solids leaving the carbon deposition reactor 12 are separated from ~he now depleted produccr gas in a cyclone or similar device 13 and ~` 25 fed to the bottom of a lift pipe methanation reactor 14j where they are entrained by the hydrogen rich gas stream coming from the hydrogen production reactor 5 via heat exchange 8a and cooler 8b. The entrained carbon rich solids J U ~

113~>4i3 react with hydrogen in the first stage 15 of the methanation predominately by the direct reaction of carbon and hydrogen.
Tllis is an ex~thermic reaction and the solids and/or gases must be cooled between stages if high concentrations of methane are desired. Entrained solids and gases are cooled in an interstage cooler 16, and then further reacted in a second reactor stage 17 to produce additional methane. Depending on the desired ratio of CH4/H2 in the product gas, operating pressures in the methanation reactors may vary from about 1 ; 10 to about 100 atm, but preferably will be from about 1 to about 20 atm. Again, depending on the desired product, one or several staqes of intercooling may be employed. Operating temperatures in the initial stages of the methanation reactor may go up as high as 700-750C, but lower temperatures must be held in the final methanation stages if a high CH4~H2 ratio is desired.
The product gas and entrained carbon-lean solids Ieaving the methanation reactor 14 are primarily separated ` in cyclone 18. The carbon lean solids are then recycled via line 19 to the carbon deposition reactor 12. The raw product gas still containing some entrained dust is further cleaned in a dust separation unit 20, which may be a magnetic separation device since most of the dust will be ferromagnetic.
Sand filters, bag-house, or other type of dust cleaning operations may, however, be used. The dust free product gas is cooled in heat exchanger 21, producing process steam and further cooled and dried in cooler 22 to produce the final product gas.
The hot depleted producer gas leaving cyclone 13 is fed to a dust separator 23 which removes entrained dust not separated by the cyclone 13. The dust separator may be a .

il~413 31-006C

magnetic separatiOn device since the solids are ferromagnetic, or it may be a more conventional system such as a sand filter or bag-house. The hot, dust free, depleted producer gas, still containing some H2 and CO, is burned by the addition of excess air to yield a high temperature combustion gas product, containing N2, CO2, and H2O. This hot gas is expanded through a gas turbine 24 to produce by-product shaft work and/or electric power. Finally the spent producer gas may be further cooled to produce additional process steam.
Two of the major advantages of the process depicted in ~igure 4 are (a) that separation of undesirable N2 and C2 from CH4/H2 product gas occurs through the relatively : easy separation of solids and gases rather than the much more difficult separation of N2 from 2 as required in conventional technology, and (b) that the producer gas in this process is more fully utilized in conversion to a CH4/H2 product than in a conventional steam-iron process since the producer gas is first partially used to reduce iron oxides (steam-iron Prcess) and then more fully utilized to deposit reactant carbon.
A third way of practicing our invention is shown in Figure 5. Here, producer gas is ~nitially compressed to about 3 to 4 atmogpheres in compressor 1 and fed into a carbon deposition~ferrous metal oxide, e.g., iron oxide reduction reactor 2 where it initially contacts iron oxides and reduces these oxides and simultaneously deposits carbonaceous material on the reduced oxides. The reactor ; 2 i8 maintained at a temperature of about ~50-500C and a pressure of about 3 to 4 atmospheres. In reactor 2 about ~.

113~413 70% of the carbon monoxide and hydrogen in the producer gas reacts with the iron oxides to form reduced iron compounds and the carbonaceous material of this invention. The depleted producer gas, at a temperature of about 350-500C, is mixed with air and burned in combustion zone 3. This gas may be then passed directly to a compressor or an electric generator for expansion without passing through a waste heat boiler.
However, the gas is preferably passed through a magnetic separator to remove any entrained dust.
The carbonaceGus material, including the bulk iron, is circulated through fluidized stand pipes to a fluid bed methanation reactor 5 where it is contacted with hydrogen gas at temperatures of about 480C-535C and a pressure of about 3 to 4 atmospheres to form a methane rich gas. ~he methane rich gas is cooled in waste heat boilers 6 to produce process-ste~m. The ~carbon depleted material from methanation reactor 3 is circulated via fluidized stand-pipes to the fluid bed hydrogen generation reactor 4 and contacted with steam at about 535C-650C and a pressure of from 3 to 4 atmospheres to produce wet hydrogen. The resultinq lron oxides are recirculated back to the carbon deposition reactor 2. The wet hydrogen is cooled in cooler 7 to condense the water vapor and the dry hydrogen circulated to the methanation reactor 5.
Sulfur compounds such as H2S, COS, CS2, and SO2, if present in the producer gas, may be removed by contacting the gas with a portion of the carbonaceous material formed in carbon deposition reactor 2. Alternatively, the portion of the carbonaceous material which has been hydrogenated may be removed from the methanation reactor 5 and contacted with the producer gas to remove the sulfur compounds.
In Figure 6, there is shown another altnerative embodiment wherein the solids remain in the individual reactors, either as fixed beds or fluid beds, and the gas feed streams to the reactors are periodically switched between producer gas and steam-water. The reactors may be operated in one of the two modes,the first mode shown by the solid lines and the second mode shown by the broken lines. In the first mode, producer gas is fed into reduction reactor 6 where it contacts iron oxides. The partially depleted producer gas is then passed through a process steam boiler into reactor 2 where it contacts bulk iron to form the carbonaceous material.
Simultaneously, steam is fed into hydrogen generator reactor 4 -where it contacts reduced iron to form hydrogen gas. The hydrogen gas is then passed into methanation reactor 3 where it contacts previously formed carbonaceous material to form methane~
At selected intervals, the gas feeds to reactors 2, 3, 4, and 6 are switched. As shown by the dotted line, hydrogen which is formed in reactor 6 passes into reactor 2 causing the formation of methane from the reaction of hydrogen with the carbonaceous material. The depleted producer gas passes from reactor 4 and into reactor 3 to form the carbonaceous ~, 25 material.
In Figure 7 there is shown another embodiment of our invention in which partially depleted producer gas is used to produce a methane rich gas in a single reactor shown in cross section. In this apparatus porous walled reaction cylinders are usea, the pores of which allow passage of gas therethrough but are too small to permit passage of our solid ;
., ~ 31-006C
113~i413 carbonaceous material or the bulk iron carrying the carbonaceous material. The preferred form of bulk disproportionation initiators are iron spheres.
The iron spheres are initially located within a ; 5 hopper 1 having an outlet 2 at the bottom through which the spheres are conveyed by gravity into passage way 3 and then - -into porous walled carbon deposition reactor 4 having a cavity 5 inside. At the top of cavity 5 is gas inlet 6 for passage into cavity 5 of a partially depleted producer gas. The partially depleted producer gas passes through inside porous walls 7 and into reactor 4 where the gas contacts the iron catalyst for a sufficient length of time, and at a pressure and temperature to form our carbonaceous material on the spheres. Thereafter, the fully depleted producer gas passes through the openings or pores of outside porous wall 8.
At the bottom of reactor 4 is outlet 9 through which the spherei carrying the carbonaceous material pass into methana-tion reactor lO which is defined by outside gas porous wall ll, and inside gas poxous wall 12. Coaxially surrounding the outside porous wall 11 is impervious wall 13 which, with wall ll, defines an annular chamber 14. Hydrogen gas flows through gas inlet 16 and into cavity 15 where the hydrogen passes through the openings of inside porous wall 12 and into contact with the carbonaceous material in methanation reactor lO to form a methane rich gas. This methane rich gas then passes out of reactor 10 through the openings in outside gas porous wall ll, into cavity 14, then through gas outlet 16, into gas transfer pipe 17 which transfers it to cavity 18 located within a second methanation reactor ~13e~13 19. The cavity 18 and reactor 19 are separated by inside gas porous wall 20.
The partially carbon depleted carbonaceous solid material fro~ methanation reactor lO passes out of ~: 5 reactor lO via solids outlet 21 and is cooled with water in solids cooler 22 by passing water into cooler 22 through ~ water inlet 23 to produce steam which passes out of the :~ cooler through steam outlet 24. The cooled solids then pass into the second methanation reactor 19 where they are :
agai~ contacted with the methane-hydrogen gas passing . .~
through porous wall 20 to further react with the carbonaceous material to form methane. The enriched methane containing gas passes out of second methanation reactor 19 through outside porous wal} 24 and gas outlet 26. Carbon depleted iron-carbonaceous -olids are then transferred to solids hopper l via lift return 27 to be used again in the process.
- ~:

, ~ ' .

'h' ,.

.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for producing a high Btu gas comprising contacting a carbonaceous material comprising carbon and a ferrous group metal component which is dispersed throughout the carbon and intimately associated with and at least partly bonded to the carbon, said carbonaceous material having a high reactivity with hydrogen to form methane, with a hydrogen containing gas under conditions that cause the hydrogen to react with the carbonaceous material to form a methane-rich gas.

2. A process for producing a high Btu gas comprising contacting a carbonaceous material comprising carbon and a ferrous group metal component which is dispersed throughout the carbon and intimately associated with and at least partly bonded to the carbon, said carbonaceous material having a reactivity with hydrogen to form methane at a rate of at least 0.1 mole of methane formed per hour per mole of carbon present in the carbonaceous material when the carbonaceous material is contacted with hydrogen at a temperature of 550°C, one atmosphere pressure, and a minimum hydrogen feed rate of 2 moles per hour per mole of carbon present, with a hydrogen containing gas which is at a temperature, pressure, and space velocity to produce a methane containing product gas including at least 20% by volume methane.

3. The process of Claim 2 wherein the carbonaceous material has a reactivity with hydrogen to form methane at a rate exceeding 0.3 mole of methane formed per hour per mole of carbon present when the carbon is contacted with hydrogen at a temperature of 550 C, one atmosphere pressure, and a minimum hydrogen feed rate of 2 moles of hydrogen per mole of carbon present.

4. The process of Claim 2 wherein the carbonaceous material is formed by the disproportionation of carbon monoxide in the presence of an initiator which serves as the source of the ferrous group metal component.

5. The process of Claim 4 wherein the carbon monoxide containing gas contacts said initiator at a temperature between about 300°C and about 700°C.

6. The process of Claim 4 or Claim 5 wherein the pressure at which the carbon monoxide contacts the initiator is from about 1 to about 100 atmospheres.

7. The process of Claim 4 wherein the molar ratio of carbon monoxide to hydrogen in the carbon monoxide containing gas is greater than about 1:2.

8. The process of Claim 7 wherein the molar ratio of carbon monoxide to hydrogen is between about 1:1 and about 100:1.

9. The process of Claim 2 or Claim 3 wherein the ferrous group metal component is present in an amount of at least 0.5 weight percent.

10. The process of Claim 4 or Claim 5 wherein the ferrous group metal component is present in an amount of at least 0.5 weight percent.

11. The process of Claim 2 or Claim 3 wherein the carbonaceous material includes hydrogen.

12. The process of Claim 4 or Claim 5 wherein the carbonaceous material includes hydrogen.

13. The process of Claim 2 or Claim 3 wherein the carbonaceous material includes hydrogen and the hydrogen comprises from about 0.1 to about 3 weight percent of the carbonaceous material.

14. The process of Claim 4 or Claim 5 wherein the carbonaceous material includes hydrogen and the hydrogen comprises from about 0.1 to about 3 weight percent of the carbonaceous material.

15. The process of Claim 2 or Claim 3 wherein the hydrogen containing gas is at a temperature of from about 350°C to 800°C.

16. The process of Claim 4 or Claim 5 wherein the hydrogen containing gas is at a temperature of from about 350°C to 800°C.

17. The process of Claim 2 or Claim 3 wherein the pressure at which the carbonaceous material contacts the hydrogen containing gas is between about l atmosphere and about 100 atmospheres.

18. The process of Claim 4 or Claim 5 wherein the pressure at which the carbonaceous material contacts the hydrogen containing gas is between about l atmosphere and about 100 atmospheres.

19. The process of Claim 4 or Claim 5 wherein the carbonaceous material during disproportionation has a carbon deposition rate exceeding 10 grams of carbon per hour per gram of ferrous group metal component present when contacted with a gas consisting essentially of 80% by volume carbon monoxide and 20% by volume hydrogen, at 500°C, one atmosphere pressure, and a minimum feed rate of 10 moles of carbon monoxide per hour per gram of ferrous group metal component present.

20. The process of Claim 2 or Claim 3 wherein the hydrogen containing gas is at a temperature, pressure, and space velocity to produce a methane containing product gas including at least 75% by volume methane.

21. The process of Claim 4 or Claim 5 wherein the hydrogen containing gas is at a temperature, pressure, and space velocity to produce a methane containing product gas including at least 75% by volume methane.

22. A method of producing a high Btu gas from a low Btu producer gas including carbon monoxide, hydrogen, carbon dioxide, and nitrogen comprising:
(a) contacting the producer gas with oxides of iron to reduce the oxides and provide a partially depleted producer gas, b) contacting the reduced oxides with steam to form a hydrogen containing gas, c) contacting the partially depleted producer gas with an initiator including iron under conditions which form a carbonaceous material comprising carbon and at least 0.5 weight percent of an iron metal component which is dispersed throughout the carbon, intimately associated with, and at least partially bonded to, the carbon, said carbonaceous material being highly reactive with hydrogen, and (d) reacting the carbonaceous material with the hydrogen containing gas from step (b) to form a high Btu gas rich in methane.

23. The method according to Claim 22 wherein the steps (c) and (d) are conducted in two separate zones, with a carbon rich carbonaceous material being forwarded to the zone where step (d) is being conducted and a carbon-lean carbonaceous material is withdrawn therefrom and forwarded to the zone where step (c) is being conducted.

24. The method according to Claim 22 or Claim 23 wherein coal is burned in a mixture of air and steam to make the producer gas.

25. The method according to Claim 22 or Claim 23 wherein the producer gas contacts the initiator at a temperature between about 300°C to about 700°C.

26. The method according to Claim 22 or Claim 23 wherein the pressure at which the producer gas contacts the initiator is between about 1 atmosphere and about 100 atmospheres.

27. The method according to Claim 22 or Claim 23 wherein the molar ratio of carbon monoxide to hydrogen in the producer gas is greater than about 1:2.

28. The method according to Claim 22 or Claim 23 wherein the molar ratio of carbon monoxide to hydrogen in the producer gas is between about 1:1 to about 100:1.

29. The method according to Claim 22 or Claim 23 wherein the carbonaceous material is contacted with the hydrogen containing gas at temperatures of from about 350°C to about 800°C.

30. The method according to Claim 22 or Claim 23 wherein the pressure at which the carbonaceous material contacts the hydrogen containing gas is between about 1 and 100 atmospheres.

31. A method for producing a methane-rich gas comprising:
(a) feeding an initiator including a ferrous group metal into a first zone so that the initiator flows through said zone, (b) feeding producer gas into the first zone under conditions which form on the initiator a carbonaceous material comprising carbon and a ferrous metal component which is dispersed throughout the carbon and intimately associated with and at least partially bonded to the carbon, said carbonaceous material being highly reactive with hydrogen, (c) feeding the initiator with said carbonaceous material thereon into a second zone so that the materials flow through the second zone, (d) feeding a hydrogen containing gas into the second zone under conditions that cause the hydrogen to react with the carbonaceous material on the initiator to form a methane-rich gas, (e) collecting the methane-rich gas formed in step (d), and (f) recycling the initiator from the second zone to the first zone.

32. A method for producing a high Btu gas from a low Btu producer gas including carbon monoxide, hydrogen, carbon dioxide and nitrogen, comprising:
(a) contacting the producer gas with an initiator including a ferrous group metal to form a carbonaceous material comprising carbon and a ferrous group metal component which is dispersed throughout, intimately associated with, and at least partly bonded to the carbon, said ferrous group metal component catalyzing the reaction between the carbon present in the material and hydrogen to form methane;
(b) contacting said carbonaceous material with hydrogen to form a high Btu gas rich in methane from at least part of the carbon in the carbonaceous material;
(c) contacting the carbon-depleted carbonaceous material from step (b) with producer gas to reform said carbonaceous material; and (d) contacting said reformed carbonaceous material with hydrogen to form a high Btu gas rich in methane from at least part of the carbon in the reformed carbonaceous material.

33. The method according to Claim 32 wherein the partially depleted producer gas from step (a) is contacted with an iron oxide to reduce said oxide and to form spent producer gas, then recovering the residual energy from said spent producer gas.

34. The method according to Claim 33 wherein said residual energy is recovered by burning said spent producer gas in air.

35. The method according to Claim 34 wherein the resulting gaseous mixture is expanded through a turbine.

36. The method of Claim 33 further comprising contacting the reduced iron oxides with steam to form hydrogen, and utilizing the hydrogen so formed in steps (b), (d), or both.

37. A carbonaceous material comprising carbon and a ferrous group metal component, said ferrous group metal component being sufficiently dispersed throughout the carbon as nodules which are intimately associated with and at least partially bonded to the carbon so that the material is characterized in that the carbon present in the material will react with hydrogen to form methane at a rate exceeding 0.3 mole of methane formed per hour per mole of carbon present when the carbon is contacted with hydrogen at a temperature of 550°C, one atmosphere pressure, and a minimum hydrogen feed rate of 2 moles of hydrogen per hour per mole of carbon present.

38. The carbonaceous material of Claim 37 wherein said material is formed by disproportionation of carbon monoxide in the presence of an initiator which serves as the source of the ferrous group metal component.

39. The carbonaceous material of Claim 37 or Claim 38 wherein said material is in the form of fibers and the nodules are a part of some fibers.

40. The carbonaceous material of Claim 37 wherein the initiator is selected from the group consisting of (a) the metals iron, nickel, cobalt, or mixtures of said metals, (b) metal alloys including one of said metals, (c) the oxides of iron, nickel, cobalt, or mixtures of said oxides, (d) metal alloys including any two or all of said metals, (e) mixtures of said metal alloys or mixtures of any one or more of said metals and said metal alloys, (f) carbides of said metals, and (g) mixtures of any of the foregoing.

41. The carbonaceous material of Claim 37 wherein said material includes hydrogen.

42. The carbonaceous material of Claim 38 wherein said material includes hydrogen.

43. The carbonaceous material of Claim 41 or Claim 42 wherein the hydrogen comprises from about 0.1 to about 3 weight percent of the material.

44. The carbonaceous material of Claim 37 wherein the ferrous group metal component is present in an amount of at least 0.5 weight percent.

45. The carbonaceous material of Claim 38 wherein the ferrous group metal component is present in an amount of at least 0.5 weight percent.

46. The carbonaceous material of Claim 44 or Claim 45 wherein the carbon comprises from about 65 to about 99.5 weight percent of the material, the ferrous group metal component comprises about 0.5 to about 35 weight percent of the material, and the hydrogen comprises from about 0.1 to about 3.0 weight percent of the material.

47. The carbonaceous material of Claim 37 or Claim 38 wherein said nodules are sufficiently dispersed so that the material is further characterized in that during dis-proportionation it exhibits a carbon deposition rate exceeding 10 grams of carbon per hour per gram of ferrous group metal component present when contacted with a gas consisting

Claim 47 - cont'd ...

essentially of 80% by volume carbon monoxide and 20% by volume hydrogen, at 500°C, one atmosphere pressure, and a minimum feed rate of 10 moles of carbon monoxide per hour per gram of ferrous group metal component present.