4,372,755 Production of a fuel gas with a stabilized metal carbide catalyst

Patent Number/Link:

United States Patent [19]

Tolman et at

[11]

[45]

4,372,755

Feb. 8, 1983

[54] PRODUCfION OF A FUEL GAS WITH A

STABILIZED METAL CARBIDE CATALYST

[75] Inventors: Radon Tolman, Evergreen; Frank M.

Stephens, Jr., Lakewood, both of

Colo.

[73] Assignee: Enrecon, Inc., Golden, Colo.

[21] Appl. No.: 202,319

[22] Filed: Oct. 30, 1980

Related U.S. Application Data

[63] Continuation-in-part of Ser. No. 928,506, Jul. 27, 1978,

abandoned.

4,II8,204 10/1978 Eakman et al. 48/197 R

4,134,907 111979 Stephens 48/197 R

4,184,852 111980 Russ 48/197 R

OTHER PUBLICATIONS

Burton et aI., Levy, Properties of Carbides, Nitrides,

Borides, Advanced Materials in Catalysis, pp. 101-127,

1977.

EPRI, "Thermodynamically Stable Forms of Elements

in the Hygas Gasifier".

Bulletin of Alloy Phase Diagrams, vol. 2, No.1, 1981, p.

25.

Kirk-Othmer, Encyclopedia of Chern. Tech., vol. 18,

2nd Ed., 1969, pp. 125-128.

27 Claims, 2 Drawing Figures

Primary Examiner-Peter F. Kratz

Attorney, Agent, or Firm--:Sheridan, Ross & McIntosh

A fuel gas containing methane is produced from a carbonaceous

material in a single reaction zone by reacting

the carbonaceous material in the presence of a stabilized

metal carbide catalyst and water vapor and/or carbon

dioxide at a temperature of from about 500· C. to about

900· C. The water vapor and/or carbon dioxide is maintained

in an amount of from about 10 to about 30 percent

by volume.

[51] Int. Cl.3 C10J 3/54

[52] U.S. Cl 48/197 R; 48/202;

48/209; 48/210

[58] Field of Search 48/197 R, 202, 206,

48/209, 210; 252/373; 585/733

[56] References Cited

U.S. PATENT DOCUMENTS

1,495,776 5/1924 Burdick 48/210

2,113.774 4/1938 Schmalfeldt 48/202

2,527,130 8/1950 Hemminger.

2,589,925 5/1952 Cain et al. .

2,694,623 1111954 Welty et al. 48/197 R

3,031,287 4/1962 Benson et al. 48/197

3,847,567 1111974 Kalina et al. 48/202

[57] ABSTRACf

HEAT

RECOVERY

BOILER

REHEATER

REACTOR

CARBONACEOUS

FEED

(7) CO + 3Hz --CH4 +HzO· ( co ~I )

(6) CO+HzO......Hz+COz

HEAT

>--

""C a("D

:::1

-\0

CIl ::r

.(.D...

o......

c..en

'"w

-J

'"-J

(n xM+2CO-MxC+COz

(2) xM+C-+MxC

CATALYST 1l (c(]~l)

(3) MxC+Hz-+CH4+xM

( co<l )

( ca ~I )

HzO, CO, Hz

(CH4 , COz)

INLET

GAS

PRODUCT

GASf

( H2 , CO)

HZO, CO2 , CH4

(co<l)

CH4 rH2

(8) ex H

CARBONACEOUS

MATERIAL

Fig- J

(5) C+Hz0--'CO+ Hz

(4) C+COz-+ 2CO

c..en

I ~/I

10c PRODUCT n:GAS

12~

"""'l

"Tj

(I) r::r

......

(1)

=:s

!'""'t'"

C/)

i:l'"

(I)

.(.I.)..

N---,6"L..

120~

13.) ~WATER

HEAT Pr8 9

RECOVERY GAS

BOILER CLEANER

r--

REHEATER

1./3

V 22

1/'19

REACTOR

20",--

CARBONACEOUS

FEED

'"W

'"-J

L-r14

SEPARATOR

AIR

(17

REFORMER I*J

2/ - ~ ~ COMB~STOR

ASH

Fig_ 2

PRIOR ART STATEMENT

4,372,755

BACKGROUND ART

PRODUCTION OF A FUEL GAS WITH A

STABILIZED METAL CARBIDE CATALYST The use of iron carbides as catalysts in gasification

processes has also been taught. Stephens in U.S. Pat.

5 No.4, 134,907 teaches a means for enhancing the fuel

value of a gas by heating it to a temperature of

600·-1200· F. (315·-650· C.) at a pressure of 1-10 atmospheres

to promote the production of carbon from carbon

monoxide and hydrogen in the presence of iron.

10 The iron and carbon react to form Fe3C which in turn

reacts with hydrogen to form methane and reform iron.

Russ in U.S. Pat. No. 4,184,852 teaches the use of

metal carbide complexes to form methane; however, his

process consumes the metal carbide complexes in the

15 methane reactor. Moreover, he forms binary or ternary

metal carbides at a temperature of about 2200· F. and a

low pressure of about 2 atmospheres and then forms the

The prior art discloses numerous methods of obtain- methane in another reactor maintained at a maximum

ing hydrocarbon gases from carbonaceous materials, temperature of 350· F.

such as those proposed in U.S. Pat. No. 3,775,072, 20 Benson, et al in U.S. Pat. No. 3,031,287 form a carbuwherein

the organic material is reacted under pressure rized iron in a reduction stage of their process which is

with steam; U.S. Pat. No. 2,759,677 which provides for then utilized in an oxidation or,methanation stage to aid

use of steam generated in the process for reaction with in the production of a gas mixture comprised of hydrowaste

materials; U.S. Pat. No. 3,776,150 which uses a gen, carbon monoxide and methane. Benson, et aI, prefluidized

bed for methanation reactions; U.S. Pat. No. 25 fer the methanation to be conducted at a temperature of

3,817,724 wherein oxygen-free recycle gases are intro- 1000·-1200· F.

duced into the combustion zone; and U.S. Pat. No. U.S. Pat. No. 2,527,130 to Hemminger discloses the

3,817,725 wherein methanated gases are recycled to a addition of small amounts of silicon to iron type catacombustion

zone for purposes of transferring sensible lysts used in the production of liquid hydrocarbons in

heat and increasing methane content in the product. 30 order to reduce the tendency of the catalyst to carbon-

Many hydrogenation, gasification and methanation ize. The temperature of the Hemminger process for the

processes utilize metals as catalysts. For example, U.S. production of synthetic liquids is about 650· F., and it is

Pat. Nos. 3,759,677 and 3,817,725 disclose alkali carbon- conducted in a manner to avoid the formation ofmethates

as preferred gasification catalysts. U.S. Pat. No. ane and to enhance the formation of butane and higher

3,817,725 further uses Group VIII metals, such as 35 hydrocarbons.

nickel, either as oxides or sulfides, as catalysts in a met- U.S. Pat. No. 2,589,925 teaches a hydrocarbon synhanation

zone having a temperature of 500·-1000· F. thesis process conducted at a temperature of 550·-750·

Catalysts consisting of single metals, including oxides, F. which utilizes an iron catalyst preconditioned with

sulfides or carbonates or mixtures of these, selected carbon monoxide to form mainly Fe2C in order to prefrom

Groups IB, VIB and VIII, in addition to an alkali- 40 .vent non-carbiqecarbon formation on the catalyst. This

type promoter from Group lA, IIA and VII rare earths, reference further discloses maintaining a sufficiently high hydrogen partial pressure in order to impair the

are used in a two stage gasification and methanation formation of non-carbide carbon: on the catalyst.

process of U.S. Pat. No.' 3,904,386. U.S. Pat. No. The prior art teaches the use of Group VIII metals,

3,594,305 teaches the use of a two component catalyst 45 including iron carbides, an methanation catalysts or

system for the hydrogasification of coal at a tempera- reactants at temperatures that are generally less than

ture of 750·-800· F., wherein the first catalyst is se- 1200· F. (650· C.) in order to produce methane in re1alected

from Group VIII and is preferably an alloy such tively high amounts. Generally, as temperature inas

cobalt/molybdenum, nickel/tungsten or nickel/- creases, the production of methane decreases. Moremolybdenum

and the second catalyst is a noble metal. 50 ovei', many of the methanation catalysts of the prior art

U.S. Pat. No. 3,505,204 obtains hydrocarbons from will act as methane reforming catalysts at temperatures

carbonaceous materials in a single reactor having aofgrtea er than about 1300· F. (705· C.), e.g., U.S. Pat.

temperature of 800·-1200· F. by using a twocomponent No. 3,847,567, and/or will lose catalytic activity, e.g.,

catalyst comprising an alkali metal or alkaline earth due to oxidation, at temperatures ofabout 1200· F. (650·

metal in conjunction with a Group VIII metal. U.S. Pat. 55 C.) and higher. The prior art does not combine in one

No. 3,847,567 utilizes a Group VIII or an alkali metal as reactor the gasification of a carbonaceous material with

a methane reduction catalyst in a gas reformer of a coal the methanation of the gas produced by the gasification

hydrogasification process. U.S. Pat. No. 2,629,728 dis- of the carbonaceous material, because the temperatures

closes the use of an iron nitrite catalyst to hydrogenate for gasification are not generally conducive to methanacarbon

oxides. Additionally, iron and iron oxide are 60 tion. In order to obtain adequate rates of gasification of

taught as catalysts in a methanation zone having a tem- carbonaceous material, a minimum temperature of

perature of 800·_1200· F. for the production of gaseous about 500· C., with over 800· C. being preferred, is

fuels by synthesis in U.S. Pat. No. 2,543,759. U.S. Pat. usually used. Moreover, many of the prior art catalysts

No. 1,495,776 teaches a catalytic process for converting are active site catalysts, e.g., nickel, cobalt, vanadium

carbonaceous material into gases. Lime is the preferred 65 and molybdenum, which are prone to sulfur poisoning.

catalyst; however, other reagents such as calcium, alu- The stabilized metal carbide catalysts of the present

mina, magnesia, silica, iron, nickel or copper and mix- invention maintain their catalytic activity at temperatures

thereof may be used. tures exceeding 650· C. and, therefore, can be used in a

CROSS REFERENCE TO RELATED

APPLICAnONS

This application is a continuation-in-part application

of Ser. No. 928,506, filed July 27, 1978 now abandoned.

TECHNICAL FIELD

The present invention relates to a process for producing

a fuel gas by reacting in a single reaction zone a

carbonaceous material with water vapor in the presence

of a stabilized metal carbide catalyst.

4,372,755

This combination provides most of the heat required to

gasify the organic feed material and increases. overall

thermal efficiency of the process. Overall thermal efficiency

can be further increased by using the sensible

heat in the off-gas to produce steam by direct contact

with water being fed into the system and by further

heating this steam and an inlet gas stream to a temperature

above the temperature of the gasification/methanation

reaction zone.

The gasification/methanation reaction zone is composed

of a reactor bed containing a catalytic bed material

of the stabilized metal carbide particles, sized to

prevent the agglomeration and caking of the organic

feed. A fluidized bed is preferred as it provides isothermal

operation, high surface area for catalysis and permits

control of particle residence time.

Hydrogen for hydrogasification of the carbonaceous

feed material can be produced by heating a recycle gas

stream, using the sensible heat in the reactor off-gas and

hot gases from char combustion, to a temperature over

800° C., thereby shifting the composition of the recycled

gas to higher levels of hydrogen and carbon monoxide

by reforming the methane with water vapor. The

sensible heat in the recycled gas also helps provide the

heat required to raise the carbonaceous feed material to

gasification temperature. Thus, the ratio of hydrogen,

carbon monoxide, methane, water vapor and carbon

dioxide must be properly maintained within the gasification/

methanation reactor to maintain the catalytic

activity of the stabilized metal catalyst and to maintain

a desirable production level of methane.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the primary

reactions involved in a combined gasification/methanation

process utilizing a stabilized metal carbide catalyst.

FIG. 2 is a flow diagram for a process which combines

gasification of a carbonaceous material and methanation

of its gas in the presence of a stabilized metal

carbide catalyst.

equilibrium of the Boudouard reaction toward the production

of carbon monoxide. Therefore, carbon deposition

and carbide formation can be controlled by the

addition of water vapor and/or carbon dioxide to the

fluidized bed reactor. Thus, water vapor and/or carbon

dioxide is continuously added to the fluid bed in an

amount of from about 10 to about 30 volume percent of

the gas contained in the reaction zone. The steam carbon

and Boudouard reactions are endothermic, and

they can influence the carbon deposition and carbide

formation as a function of temperature. Moreover, since

the presence of either two much water vapor and/or

carbon dioxide can cause excessive oxidation of the

stabilized metal catalyst resulting in a loss of its methanation

activity, the resistance to oxidation of the stabilized

metal carbide catalyst is also controlled by temperature

and/or the amount of water vapor or carbon dioxide

present.

The methanation reaction and the side reactions pro-

20 ducing carbon dioxide are highly exothermic, whereas

the reactions producing carbon monoxide and hydrogen

from the organic feed materials and steam are endothermic.

Combining these reactions in a single system

provides a very nearly thermoneutral overall reaction

approaching the following:

DISCLOSURE OF THE INVENTION

The present invention provides a process for production

of a fuel gas from organic materials, such as coal

and solid municipal waste. The produced fuel gas con- 25

tains greater than 8 mole percent methane, and greater

than 30 mole percent under preferred conditions, in

addition to carbon monoxide, carbon dioxide and hydrogen.

The carbonaceous material is reacted in a

chemically active fluid bed in the presence of hydrogen, 30

carbon monoxide, steam and a stabilized metal carbide

catalyst. The stabilized metal carbide may be added to

the reactor directly or it may be formed in the reactor

by the deposition of carbon on the stabilized metal to

form surface carbides. The stabilized metal carbide 35

catalyst remains catalytically active at gasification temperatures

which exceed about 6500 C. (12000 F.),

thereby allowing the gasification and methanation processes

to be conducted in a single reaction zone.

The term "stabilized" as used herein in reference to a 40

metal carbide catalyst refers to the ability of the catalyst

to maintain its catalytic activity, including its physical

integrity, under gasification conditions and it primarily

refers to an oxidation resistant metal carbide catalyst.

The term is not intended to imply total chemical stabil- 45

ity or inertness, because the stabilized metal carbide

catalyst must have the ability to act as a bulk chemical

catalyst, actively partaking in the formation of methane.

The stabilized metal carbide catalyst must be sufficiently

chemically active to enable it to accept carbon, 50

e.g., to enable the stabilized metal to be carbided, and

sufficiently chemically active to transfer carbon to hydrogen

to form methane. In accepting carbon from

carbon monoxide, the stabilized metal also accepts oxygen

which is subsequently transferred to carbon monox- 55

ide resulting in the formation of carbon dioxide. Thus,

the stabilized metal catalyst is continuously carbided

and decarbided.

The deposition of carbon on the stabilized metal carbide

and/or the stabilized metal within the reactor is 60

dependent upon the interaction of the contact of the

stabilized metal catalyst with the carbonaceous feed

material, the Boudouard reaction (C02+~2CO) and

the steam carbon reaction (C+H20+ZCO+H2). Carbon

monoxide, e.g., produced by the steam carbon reac- 65

tion, reacts readily with steam to produce carbon dioxide

via the water gas shift reaction (CO+ H20+ZC02+

H2)' The carbon dioxide aids in maintaining the

combined gasification and methanation reactor for the

production of a synthetic gas having a relatively high

methane content from carbonaceous material. Although

generally the temperatures required for gasification will

reduce methane production, the gasification of the car- 5

bonaceous material, e.g., coal, will cause the formation

of some methane by the volatilization of higher hydrocarbons

than methane. These volatilized higher hydrocarbons

react with hydrogen to form methane. Moreover,

the stabilized metal carbide catalysts are active 10

methanation catalysts at much lower carbon levels than

those of conventional metal carbides such as cementite,

Fe3C, and they are not poisoned by the presence of

gaseous sulfur compounds.

Additionally, the process of the present invention can 15

utilize untreated water and/or effluents, unsuitable for

use in a boiler, to generate steam by means of heat from

product gas being cleaned by the water. Process char

can be used to heat the steam and recycle gases to create

a heat-efficient, thermoneutral reaction.

4,372,755

5 6

With respect to a particular stabilized metal catalyst,

PREFERRED MODE FOR CARRYING OUT THE the particular alloy component should be comprised of

INVENTION metals which exhibit a relative difference in free energy

The process of the present invention entails the use of of formation of the carbides of each metal such that one

a stabilized metal carbide as a catalyst in the production 5 metal forms a sufficiently stronger carbide to act as a

of fuel gas by synthesis. Depending upon the carbona- stabilizing component thereby enhancing the chemical

ceous feedstock, a wide variety of fuel gases can be activity of the other metal carbide. It is preferred that

produced including a medium Btu (British thermal unit) there be a difference in free energy of formation befuel

gas having a Btu value of greater than about 300 tween at least two of the metal components of the alloy

Btu per cubic foot for gas turbine fuel, synthetic natural 10 of at least about 5,000 British thermal units per pound

gas and synthesis gas for methanol or gasoline produc- atom of carbon. Additionally, the effects of combining

tion. The process can be operated at a thermal effi- two or more metals to form the alloy or stabilized metal

ciency of greater than 80 percent while producing a fuel component of the catalyst results in the alloy having a

gas which can have a Btu value of over 400 Btu per lower capability for carburization and oxidation than

cubic foot offuel gas. The carbonaceous material can be 15 each of the metals separately, Moreover, the alloy apany

of a number of carbon containing materials which pears to exhibit metastable oxidation states thereby

are combustible, for example, peat and lignite, sub- allowing for its absorption and desorption of both carbI"

tummous, bI u'tm'mous and anthracI'te coaIs and soII'd bidEe andloxfygen. b'I' d I b'd . I 'I d

mUnI"ClpaI and'mdustrl'alwaset. , xam'1'p.es 0 sta 'dI Ize meta car Ihe ca'ta ysts mcbu'd e

Although the exact mechanism of action of the stabi- 20 Iron Sl lCld~ carbl ~, manganese c romlUm car ! e,

II,zed metaI carbI'de cataIyst'IS not known, I't I's thoUght ferrochromlUm carbIde and m.an. ganese cobalt .carbIde.

, , . '" One group of preferred stabIlIzed metal carbIde catathat'

the stabIlIzed metal ca,rbIde c.atalyst IS actmd"g pn- Iysts I"S Iron S'I1I'CI'de carbI'de cataIysts contam,.mg from

manly as a, bulk cat"alyst whIch acts as an mterm. e late m about 4 t0 about 50 wel'ght percent 0 f Sl'I'ICI'de or Sl'II'con

.th'e chem..Ical reactlOn(s)'behmg catalydzefd hand IS p're(sen)t 25 and from about 0.5 t b t 3 0 'ht t f car 0 a ou . welg percen 0 -

mItS on~l~al concentratI~n at teen 0 t e reactIOn. s , bon by weight of the catalyst. With respect to iron

The stab~lIze~ metal carbIde ,catalyst may also be ~ctmg silicide carbides, it is preferred that the catalyst contain

as an ,actIve Slt~ catalyst, whIch does not partake .m the less than about 32 weight percent of silicon, because

chemIcal reactlOn(s) bemg, cataly~ed but wh.erem the within this range the catalyst is magnetic allowing for

surface of the catalyst pro":l?es a sIte for re~ctlOn of the 30 its more convenient separation from elutriated char and

reactants, Beca~se th~ stabIlI~ed .metal,carbl?e, cat,alysts ash for subsequent reuse. Moreover, as long as the iron

of the present mventlOn mamtam theIr a~tlvlty m the silicide carbide catalyst contains a sufficient amount of

pr~sen~e of s~lfur, they are not susce~tIble, to sulfur silicon to maintain its stability, then generally the more

pOISOnIng and It appears th~t th~~ ac~ pnman~y. as buI,k iron present in· the catalyst, the greater its catalytic

~ataly~ts, Therefo!e: for slmplIclt~, m descnbmg t~IS 35 activity. It is more preferred that an iron silicide carbide

mventlOn, ,the actIvlt~ of t,he stabIlIzed metal carbIde catalyst contain from about 10 to about 20 percent by

catalyst ",:Ill be descnbed m terms of a bulk catalyst, weight of silicon. At silicon levels less than about 4

alt~ough, It ~ust ,be remembered that they may also be percent, the catalyst looses its stability at temperatures

actmg as a~t,lve sIte catalys~s, , , greater than about 6500 C. At silicon levels greater than

The stabIlIzed metal carbIde catalyst IS compnsed of 40 about 50 percent, the silicon impedes the surface carbutwo

components, carbon and an alloy of at least two rization of the iron silicide preventing the formation of

different metals, each of which is capable of forming a the iron silicide carbide catalyst. If an iron silicide carmetal

carbide. More specifically, the catalyst is defined bide catalyst has a carbon level less than about 0.5 peras

a composition of these components which has a free cent by weight, the catalyst is not sufficiently active.

energy of formation of from about - 30,000 to about 45 Since the maximum carbide content of an iron silicide is

10,000 British thermal units per pound atom of carbon about 3 percent, any carbon present on the catalyst

at a temperature offrom about 500° to about 900° C. and which is above about 3 percent will be in the form of

a pressure from about 100 to about 8,300 kilopasca1s elemental carbon, not as a surface carbide. Silvery pig

(about 15 to about 1200 p.s.i.a.) and preferably a temper- iron, which generally contains from about 0.5 to about

ature from about 750° C. to about 900° C. and prefera- 50 1.5 percent carbon, from about 12 to about 20 percent

bly a pressure from about 1,000 to about 4,000 kilopas- silicon and from about 82 to about 84 percent iron by

ca1s (about 150 to about 600 p.s.i,a.). weight, is an example ofa preferred iron silicide carbide

Each of the metals which comprise the alloy compo- catalyst.

nent must have the ability to form a metal carbide at the The catalyst is employed in a fluidized bed reactor

process conditions ofthe gasification/methanation reac-.55 which has a single reaction zone for the production of

tion zone. Examples of suitable metals include, iron, fuel gas. The stabilized metal carbide catalyst employed

silicon, manganese, cobalt, chromium, nickel, alumi- in the reaction zone is sufficiently physically stable and

num, vanadium, tungsten, molybdenum, calcium, bo- dense to remain in the bed during the gasification of

ron, sodium and magnesium. It is preferred that one or many tons of feed material, requiring only makeup as a

both metals be selected from the group consisting of 60 result of elutriation and sulfidation. The amount of catasilicon

and those metals which form intermediate car- Iyst required in a particular system is dependent upon

bides (carbides which are intermediate in character the temperature of the fluidized bed, time of contact

between ionic and interstitial carbides), I.e., iron, cobalt, with the carbonaceous material and the reactivity of the

chromium, manganese and nickel. The intermediate carbonaceous material. There should be a sufficient

carbides tend to be more chemically active than intersti- 65 amount of the stabilized metal carbide catalyst in the

tial carbides and tend to exhibit a greater physical stabil- reaction zone to prevent caking and agglomeration of

ity and chemical stability, e,g., with respect to oxida- the carbonaceous materials and provide adequate surtion,

than ionic carbides. face area for catalysis. Therefore, it is preferred that the

4,372,755

catalyst be present in a greater amountthan the amount

of fresh, unreacted (as opposed to char) carbonaceous

material. For example, a suitable mixture in the reactor

may comprise about four parts by weight of the stabilized

metal carbide catalyst to about one part by weight 5

of fresh carbonaceous material.

The particle size of the catalyst is such as to prevent

caking and agglomeration of materials in the fluidized

bed. Generally, the particle size of the catalyst should

be compatible with the space velocity required for its 10

fluidization in the reaction zone.

The catalyst may be added directly to the reactor or

it may be formed in the reactor. It can be formed in the

reactor by the addition of the metal alloy component to

the reactor and the deposition of carbon in amounts 15

which are sufficient to form a stabilized metal carbide

having a free energy of formation of from about

- 30,000 to about 10,000 British thermal units per

pound atom of carbon at the gasification/methanation

conditions of the process. The carbon should be in a 20

reactive form, for example, carbon produced from a

gaseous reaction.

The gasification of a carbonaceous material and/or

the methanation of a gas inyolves a number of dynamic

and interrelated chemical reactions. Heretofore, the 25

prior art has separated gasification and methanation

reactions in order to utilize different conditions to affect

the separate chemical reactions involved in gasifying a

carbonaceous material and those reactions involved in

forming methane. Although the process of the present 30

invention can be used to gasify carbonaceous material

or to increase the methane value of a gas containing

hydrogen and carbon monoxide, the essence of the

invention lies in balancing the equilibriums and/or kinetics

ofthe chemical reactions to allow for the gasifica- 35

tion and methanation of a carbonaceous material to

occur within the same reactor while maintaining the

catalytic activity of a stabilized metal carbide catalyst.

The primary reactions involved in a combined reaction

zone are those relating to the gasification of carbon, the 40

water gas shift reaction, the carbiding and decarbiding

of the catalyst acting as a bulk catalyst, the oxidation

and reduction of the catalyst acting as a buik catalyst,

and the formation of methane. A schematic representation

of these reactions is presented in FIG. 1. Since the 45

optimization of some of the reactions is detrimental to

others in the reaction zone, it is necessary to control the

kinetics and equilibriums of the chemical'reactions involved

in order to maximize methane production while

still obtaining adequate gasification of the carbonaceous 50

material. The control is a function of the ratio of gases

present, temperature, pressure and catalyst used. The

kinetics and equilibriums of the chemical reactions are

preferably controlled primarily by temperature and the

addition of water vapor and/or carbon dioxide. The 55

chemical interactions can be explained with reference

to FIG. 1. (The numbers used to depict the reactions are

for reference purposes only and are not indicative ofthe

order of occurrence. Additionally, "M", as used in the

figure, refers to the metal alloy component of the cata- 60

lyst).

In FIG. 1, an inlet gas comprising primarily water,

hydrogen and carbon monoxide with lesser amounts of

methane and carbon dioxide is injected into a reaction

zone containing a source of carbon, e.g., a carbonaceous 65

material, and a stabilized metal carbide catalyst, MxC.

The carbon activity (ca) of the gases contained within

the reaction zone will vary from a value less than one to

approximately one depending upon the location in the

reaction zone. The carbon activity of a gas is an equilibrium

value which denotes the ability of the gas to form

elemental carbon. A value of one represents equilibrium,

at a value greater than one the gas will tend to

form elemental carbon and at a value of less than one

the gas will tend to consume elemental carbon. The

inlet gas will have a carbon activity of less than one

enabling its water and carbon dioxide components to

readily react with the carbon from the carbonaceous

material, including char, causing the gasification of the

carbon by the formation of carbon monoxide and hydrogen,

reactions (4) and (5). Since the stabilized metal

carbide catalyst is not readily oxidized at reaction conditions,

the inlet gas will preferentially oxidize the carbonaceous

material as long as the concentrations' of

water and/or carbon dioxide are not excessive, e.g.,

greater than about 30 volume percent of the gas in the

reaction zone. The presence of hydrogen in the inlet gas

and from reaction (5) allows for the decarburization of

the stabilized metal carbide catalyst, reaction (3),

thereby forming the desired methane. The stabilized

metal alloy is carbided in accordance with reactions (1)

and (2). To a lesser extent, methane is also formed by

the reaction of carbon or a source of carbon, e.g., carbon

monoxide, with hydrogen, reaction (7). The production

of any significant quantity of methane from

reaction (7) occurs to the extent that the stabilized metal

carbide catalyst is acting as an active site catalyst. The

carbon monoxide reacts with water vapor to form hydrogen

and carbon dioxide, reaction (6). The heat given

off in the formation of carbon dioxide and methane

provides most of the heat necessary for gasifying the

carbonaceous material.

The presence of water, in the form of steam, aids the

gasification of elemental carbon. Since the kinetics of

the reactor are controlled, mainly by temperature, any

inlet gas, e.g., recycle gas or feed gas, added to the

process will be at least the temperature of the gasifier,

about 500· to about 900· C., and preferably of a sufficient

temperature to maintain the reactor at the preferred

temperature for a particular process. At these

temperatures, a portion .of the carbonaceous material

readily volatilizes in the form of higher hydrocarbons

which react w,ith hydrogen to form methane, reaction

(8). The product gas comprising carbon dioxide, methane

and water is continuously removed from the process.

Thus, FIG. 1 represents the favored primary reactions

of the process. However, since all of the reactions

portrayed are reversible, their equilibriums are shifted

toward the forward reactions by the addition of carbonaceous

material, water vapor, hydrogen and carbon

monoxide. Carbon dioxide can be used in place of or in

conjunction with water vapor. Water vapor is preferred

to carbon dioxide because it is more easily produced

within the process, for example, through a recycle gas

stream, and it supplies a source of hydrogen. The source

of water vapor is not critical and it can be from the

carbonaceous material and/or the inlet gas, e.g., a recycle

gas or feed gas. Although the addition of water

vapor (or carbon dioxide) to the reactor is not narrowly

critical, it cannot be so great to cause excessive or rapid

oxidation ofthe stabilized metal carbide catalyst. Therefore,

water vapor and/or carbon dioxide is maintained

in the reactor in an amount from about 10 to about 30

volume percent of the gas used in the reactor. At water

vapor and/or carbon dioxide levels ofless than about 10

4,372,755

9 10

volume percent excess carbon deposition will occur The pressure of the process can vary over a wide

which can cause plugging of the off-gas system. Water range offrom about 100 kilopascals (15 p.s.i.a.) to about

vapor and/or carbon dioxide levels greater than about 8,300 kilopascals. However, a pressure of 1,000 kilopas-

30 volume percent will tend to cause excessive oxida- cals (150 p.s.i.a.) to about 4,000 kilopascals (600 p.s.i.a.)

tion of the catalyst. However, within this recited range, 5 is preferred.

generally as the temperature of the reactor is increased, The stabilized metal carbide catalyst is useful in any

the more water vapor and carbon dioxide which can be process for synthesizing hydrocarbon gases from carbopresent.

naceous sources. It is especially useful in those pro-

The additional source of hydrogen and carbon mon- cesses wherein heat is taken from the produced gas and

oxide supplied to the reactor may be a recycle gas 10 is used to heat water to produce steam and to reheat a

stream from a portion of the product gas. In such an portion of the produced gas which is recycled in the

application, it is preferred that the recycled product gas process and wherein the char produced in the process is

be reformed, by the addition of heat, water and a re- combusted and the heat produced therefrom is used to

forming catalyst, to higher levels of carbon monoxide further heat the recycle gas in order to reform the methand

hydrogen which is recycled into the reaction zone. 15 ane contained therein to carbon monoxide and hydro-

The reforming catalyst is a steam hydrocarbon reform- gen. Preferred processes utilize fluidized bed reactors.

ing catalyst and any such catalyst active at these condi- A general process ofthis type is shown in FIG. 2. In the

tions may be used. Examples of such catalysts include process of FIG. 2, carbonaceous feed material is intro-

Group VIII metals, for example, nickel, nickel oxide duced into reactor 1 wherein it is reacted in a single

and chromium oxide. The gasification of the carbona- 20 reaction zone consisting of a fluidized bed comprised of

ceous material results in the formation of char which unreacted carbonaceous feed material and a catalytic

can be removed and combusted in a separate combus- bed material comprised of a stabilized metal carbide and

tor. The heat from the combustor can be used in the a process recycle gas stream 3 which is reheated by the

reformation of the product gas which can then be recy- combustor gases prior to entry into reactor 1. The offcled

to the reactor. 25 gas produced in reactor 1 is then conducted to separator

Temperature and pressure are also used to favorably 4 wherein the particulate matter is removed. The particbalance

the equilibriums and the kinetics of the reac- ulate free off-gas is then conducted to reheater 5

tions. The temperature must be sufficient to cause the wherein the temperature of the off-gas is reduced from

gasification of the carbonaceous material but not so a temperature from about 500° C._900° C. to a temperahigh

so as to substantially reduce methane equilibrium. 30 ture of about 400° C.-750° C. by indirectly heating

Therefore, the temperature is a function of the reactiv- recycle gas stream 6 having a temperature from about

ity of the particular carbonaceous feed material and the 90° C.-325° C. to a temperature of about 400° C.-825°

desired methane content of the produced fuel gas. Thus, C. The reactor off-gas is then conducted from reheater

the temperature of the reactor will be from about 500° 5 to a heat recovery boiler 7 where it is further cooled

C. to about 900° C. The more reactive the carbonaceous 35 to a temperature of about 200° C.-550° C. by the indimaterial

is, generally, the lower the temperature of the rect heating ofwater vapor stream 8.

process and the more methane the fuel gas will contain. The reactor off-gas then passes from heat recovery

Hence, the process temperature required for peat will boiler 7 to gas Cleaner 9 wherein any tar or water conbe

lower than that required for a lignite coal which is tained with the gas are separated from the product gas

lower than that required for bituminous coal which is 40 10. The tar and water are removed from gas cleaner 9

lower than that required for anthracite coal. For exam- via conduit 11. The tars and water 11 are cooled in heat

pIe, if the carbonaceous feed is a peat, the temperature exchanger 12 from a temperature of from about 200°

of the process could be about 500° C., its gasification C.-550° C. to a temperature of about 100°-300° C. by

temperature, whereas, the temperature of the process the indirect heating of water stream 13. The cooled tar

for a bituminous coal would be from about 760° C. to 45 and water stream 14 undergoes separation in separator

about 870° c., its gasification temperature. Peat, there- 15. The water from separator 15, which is directed

fore, has a greater potential for producing greater through heat exchanger 12a where its temperature is

amounts of methane compared to a bituminous coal. A further reduced to about 70°-90° C. by indirect heating

preferred temperature of a particular process is the with water stream 16, can be recycled to gas cleaner 9

threshold temperature at which the carbide form of the 50 for reuse.

stabilized metal carbide catalyst is more stable than its The non-water materials from separator 15, e.g., tars,

oxidized form. Threshold temperature is defined as the and the particulate matter 19 from separator 4 are added

temperature range at which the carbide activity of the to combustor 2 wherein they are combusted in the prescatalyst,

i.e., the activity of the carbide form of the ence of air (or another source ofoxygen) 17 at a tempercatalyst

relative to the oxidized form ofthe catalyst, just 55 ature of from about 950° C. to about 1650° C. The comexceeds

a value of one. The carbide activity of the cata- bustor gases 22 and ash 21 are removed from the comlyst

is an equilibrium value, wherein a value of one bustor.

represents equilibrium and a value greater than one The water for reactor 1 is supplied through recycle

represents a greater tendency of the catalyst to be in a gas stream 3. Water 16 is introduced into the process

carbided form as opposed to an oxidized form. Within 60 and is subsequently heated in exchangers 12 and 120 and

the process conditions heretofore described, e.g., tem- then introduced into heat recovery boiler 7 as water

perature, pressure, and amount of water vapor, the stream 8. The water stream 8 is further heated in heat

threshold temperature of a particular process is primar- recovery boiler 7 to a temperature of from about 200° to

ily dependent upon the particular stabilized metal car- about 350° C. after which it is combined as saturated

bide catalyst. For example, when silvery pig iron is the 65 steam with recyCle gas stream 6 and introduced into

stabilized metal carbide catalyst, the threshold tempera- reheater 5 where they are heated to a temperature of

ture will be from about 775° C. (1425° F.) to about 845° about 400°-825° C. The combined recycle gas stream 3

C. (1550° F.). is introduced into reformer 18 where it is reformed to

"Composition of the catalyst at the beginning of the test, about 3% of carbon was

present at the end of the test (a portion of the 3% carbon may have been in elemental

form).

Gas-catalyst

Catalyst % CH4in Contact Time, Rate %

Composition OfT-gas min. ClLVmin.

24 Fe 68 Cr 6.2C 24 7.4 3.24

% Gas-catalyst Rate %

Catalyst Composition Steam CH4in Contact Time ClLV

wt,% Vol,% OfT-gas min. min.

76.6 Mn 21.2 Cr 4.4C 0.99 40 6.04 6.62

67.5 Mn 22.2 Co 2.6C 0.74 33 3.8 8.81

Si02 (sand) 10.0 10 10.1 0.99

"Fe304 FeSi03 0.74 15 26.5 0.54

·Obtained from an excess oxidation of an iron silicide carbide catalyst.

EXAMPLE 2

A gas comprising 3 parts hydrogen and 1 part carbon

monoxide was used to fluidize a 2 inch continuous fluid

bed reactor containing the gas and different catalysts.

Steam was also present in the gas in the amount indicated

in Table 2. Because a carbonaceous material was

not being gasified, it was not necessary that water vapor

and/or carbon dioxide be present in the reactor in an

amount of from about 10 to about 30 volume percent.

The bed was maintained at a pressure of 100 psig (690

kilopascals) and a temperature of 700° C. The composition

of the catalyst used in each run is given in Table 2

as is the volume percent of methane in the produced

off-gas, the actual contact time between the gas and

catalyst and the rate of methanation.

TABLE 2

TABLE I-continued

4,372,755

higher levels of carbon monoxide and hydrogen. It is

preferred that the recycle gas stream be reformed by

increasing its temperature to about 850° C.-lloo° C. at

a pressure offrom about 1,725-2,750kilopascals in the

presence of a steam hydrocarbon reforming catalyst. 5

The reformation of the recycled gas stream with water

vapor need not be performed in the combustor 2. However,

the combustor supplies a ready source of heat.

Reformed recycle gas stream 20 is introduced into reac- 10

tor 1 to provide carbon monoxide, hydrogen and water

to reactor 1.

Since a process for the combined gasification and

methanation of a carbonaceous feed material in the

presence of a metal stabilized carbide catalyst is prefera- 15

bly conducted in a manner which is heat efficient, there

are a wide variety of changes which could be made in

the flow diagram of FIG. 2. For example, a portion of

the recycled product gas stream might be used to preheat

the carbonaceous feed material prior to its injec- 20

tion into reactor 1. The water added to the system, i.e.,

water 16, could be heated e~ternally from the process or

converted to steam by direct contact of the water

stream 16 with a portion of the hot reactor off-gas or

product gas. Since air being added to a combustor is 25

generally preheated, air 17 might be preheated externally

from the process or by heat produced in the process,

e.g., heat of the stack gases. Depending upon the

nature of the carbonaceous feed material, product gas 30

10 may be subjected to an acid removal step. If an acid

removal step is included, it would be preferable that the

recycled gas stream 6 be taken from the acid cleaned

product gas.

EXAMPLE 1 35

A gas representative of one produced by a carbonaceous

material and having a composition of 6.3 percent

carbon dioxide, 33.4 percent carbon monoxide, 4.8 percent

methane and 55.5 percent hydrogen was used to 40

fluidize a 2 inch continuous fluid bed reactor containing

the gas and different catalysts. (All percentages of gases

given in the examples are volume percent). Steam was

also present in the gas in an amount of about 0.3 volume

percent or less by volume of fluidizing gas to control 45

the deposition of carbon. Because a carbonaceous material

was not being gasified, it was not necessary that

water vapor and/or carbon dioxide be present in the

reactor in an amount of from about 10 to about 30 vol- 50

ume percent. The bed was maintained at a pressure of

100 psig (690 kilopascals) and a temperature of 700° C.

The composition of the catalyst used in each run is

given in Table 1 as is the volume percent of methane in

the produced off-gas, the actual contact time between 55

the gas and catalyst and the rate of methanation. The

volume percent of methane is based on the equilibrium

gas composition normalized to 100 percent by volume

on a dry basis.

TABLE 1

EXAMPLE 3

A gas comprising 32.2 percent hydrogen, 3.5 percent

carbon monoxide, 10.3 percent carbon dioxide and 54.0

percent methane was used to fluidize a two inch continuous

fluid bed reactor containing the gas and iron carbide

as cementite, Fe3C. Steam was also present in the

gas in an amount of about 10 volume percent or less by

volume of the fluidizing gas. The fluidized bed was

maintained at a pressure of 100 psig (690 kilopascals)

and a temperature of 700° C. After the reactor reached

stabilized conditions, the off-gas comprised 7.5 percent

nitrogen (nitrogen was used to initially purge the reactor),

46.0 percent hydrogen, 33.5 percent methane, 6.9

percent carbon monoxide and 0.8 percent carbon dioxide.

A Mossbauer analysis ofthe composition ofthe iron

carbide was taken prior to initiating the reactor (Starter

Bed) and after the completion of the reactor run (Final

Bed) and the compositions are given below in Table 3.

Catalyst

Composition

% CH4in

OfT-gas

Gas-catalyst

Contact Time,

min.

Rate %

ClLVmin.

Compound

Fe3C

Fe304

Fe203

FeO

TABLE 3

Starter

Bed (wt %)

72.1

3.5

10.5

Final

Bed (wt %)

91.8

2.1

ooo

46.8 Fe 46.0 Si 2.OC

"46.8 Fe 46.0 Si 2.OC

69.1 Fe 27.0 Si 2.9C

"82.3 Fe 15.1 Si O..,C

89.3 Fe 6.1 Si 1.6C

18.1

12.0

15.4

6.0

4.6

1.73

2.92

2.27

5.27

7.61

EXAMPLE 4

A gas comprising 34.8 percent hydrogen, 19.2 percent

carbon monoxide, 32.0 percent carbon dioxide and

ing a free energy of formation of from - 30,000 to

10,000 British thermal units per pound atom of carbon

at the reaction conditions, said metal alloy comprising

at least two metals selected from the group consisting of

5 iron, silicon, manganese, cobalt, chromium, nickel, aluminum,

vanadium, tungsten, molybdenum, calcium,

boron, sodium and magnesium wherein one of said two

metals forms a sufficiently stronger carbide to act as a

stabilizing component thereby enhancing the chemical

IO activity of the other metal carbide and a gas of which

from about 10 to about 30 volume percent is selected

from the group consisting of water vapor, carbon dioxide

and mixtures thereof at a temperature and pressure

sufficient to cause the gasification of the carbonaceous

15 material and cause the formation of a sufficient amount

of methane to produce a fuel gas wherein the temperature

is from about 500· C. to about 900· C. and the

pressure is from about 100 kilopascals to about 8300

20 kilopascals.

2. The process of claim 1 wherein the relative difference

of at least two of the metals in their free energy of

formation of their respective carbides is at least 5,000

British thermal units per pound atom of carbon.

3. The process of claim 1 wherein the temperature of

the reaction zone is within the threshold temperature

range of the stabilized metal carbide catalyst.

4. The process of claim 1 wherein the stabilized metal

carbide catalyst is selected from the group consisting of

iron silicide carbide, manganese chromium carbide,

ferrochromium carbide and manganese cobalt carbide.

5. The process of claim 4 wherein the stabilized metal

carbide catalyst is an iron silicide carbide.

6. The process of claim 5 wherein the stabilized metal

carbide catalyst comprises from about 4 to about 50

weight percent silicon, from about 0.5 to about 3 weight

percent carbon and the remainder of the catalyst comprises

primarily iron.

7. The process of claim 6 wherein the stabilized metal

carbide catalyst comprises from about 10 to about 20

weight percent silicon, from about 0.5 to about 3 weight

percent carbon and from about 77 to about 90.5 weight

percent iron.

8. A process for the production of a fuel gas from a

solid carbonaceous material comprising:

(a) reacting the solid carbonaceous material in a single

fluidized reactor in the presence of a stabilized

metal carbide catalyst comprising carbon and a

metal alloy and having a free energy of formation

offrom - 30,000 to 10,000 British thermal units per

pound atom of carbon at the reaction conditions,

said metal alloy comprising at least two metals

selected from the group consisting of silicon, manganese,

cobalt, chromium, nickel, aluminum, vanadium,

tungsten, molybdenum, calcium, boron, sodium

and magnesium, wherein one of said two

metals forms a sufficiently stronger carbide to act

as a stabilizing component thereby enhancing the

chemical activity of the other metal carbide and

wherein said metal alloy has a lower capacity for

carburization and oxidation than each of the individual

metals of the alloy and a fluidizing gas

wherein from about 10 to about 30 volume percent

of the fluidizing gas is selected from the group

consisting of water vapor, carbon dioxide and mixtures

thereof at a temperature of from about 500·

C. to about 900· C. and a pressure of from about

4,372,755

42.4

26.1

25.5

Final

Bed (wI %)

91.8

2.1

ooo

Slarter

Bed (WI %)

TABLE 4

EXAMPLE 5

Fe3C

Fe304

Fez03

FeO

Compound

Fuel gases were produced from Illinois No.6 coal, a

bituminous coal containing about 3.45 percent by

weight sulfur, by fluidizing the coal with a gas comprising

about 7-7.5 percent carbon dioxide, about 34.8 per- 30

cent carbon monoxide, about 4.2 percent methane and

about 53.9 percent hydrogen and gasifying the coal,

constituting about 5 weight percent of the fluidizing

gas, at a temperature of about 700· C. and a pressure of

about 100 p.s.i.g. in the presence of an iron silicide car- 35

bon catalyst. Steam was maintained in the reactor in an

amount of from about 6 to about 10 percent by volume

of the fluidizing gas. In sample 1, the iron silicide carbon

catalyst was produced in the reaction vessel by the

carbiding of an iron silicide comprising about 50 weight 40

percent iron and about 50 weight percent silicon. In

sample 2, the iron silicide carbide catalyst comprised, at

the beginning of the reaction process, about 82 weight

percent iron, about 16 weight percent silicon and about

0.6 weight percent carbon. The actual contact time 45

between the gas and catalyst in sample 1 was about 6

minutes and the equilibrium composition of the fuel gas

produced was about 1.1 percent nitrogen, about 55.5

percent hydrogen, about 21.5 percent methane, about

15 percent carbon monoxide and about 7.4 percent car- 50

bon dioxide. The rate of methanation in sample 1 was

about 3.62 percent methane per minute.

The actual contact time between the gas and the

catalyst of sample 2 was about 7.44 minutes and the

equilibrium gas composition of the fuel gas produced 55

was about 1.5 percent nitrogen, about 31 percent hydrogen,

about 44 percent methane, about 17.5 percent carbon

monoxide and about 5.5 percent carbon dioxide.

The rate of methanation for sample 2 was about 5.94

percent methane per minute. 60

What is claimed is:

1. A process for the production of a fuel gas from a

solid carbonaceous material comprising reacting in a

single reaction zone the solid carbonaceous material in

the presence of a stabilized metal carbide catalyst capa- 65

ble of substantially maintaining its physical integrity and

chemical activity under gasification conditions, said

catalyst comprising carbon and a metal alloy and hav-

14.0 percent methane was used to fluidize a two inch

continuous fluid bed reactor containing the gas and iron

carbide as cementite, Fe3C. Steam was also present in

the gas in an amount of about 20 volume percent of the

fluidizing gas. Additionally, carbon dioxide was added

intermittently throughout the reaction in order to maintain

the volume percent of water and carbon dioxide at

a level of about 35 percent by volume of the fluidizing

gas. The bed was maintained at a pressure of 100 psig

(690 kilopascals) and a temperature of 700· C. The reactor

off-gas obtained a maximum of 33.9 percent methane

and then the methane content decreased, apparently as

a result of the decomposition of the catalyst which is

shown by the Mossbauer analyses of the composition of

the iron carbide in Table 4.

4,372,755

15. A process for the production of a fuel gas from a

solid carbonaceous material comprising reacting in a

single reaction zone the solid carbonaceous material in

the presence of a stabilized metal carbide catalyst comprising

a carbon and a metal alloy and having a free

energy of formation of from -30,000 to 10,000 British

thermal units per pound atom of carbon at the reaction

conditions, said metal alloy comprising at least two

metals selected from the group consisting of iron, sili-

10 con, manganese, cobalt, chromium, nickel, aluminum,

vanadium, tungsten, molybdenum, calcium, boron, sodium

and magnesium, wherein one of said two metals

forms a sufficiently stronger carbide to act as a stabilizing

component thereby enhancing the chemical activity

15 of the other metal carbide, said catalyst having characteristics

of a bulk chemical catalyst and capable of substantially

maintaining its physical integrity and chemical

activity under gasification conditions and a gas mixture

comprising hydrogen, carbon monoxide and from

about 10 to about 30 volume percent of gas selected

from the group consisting of water vapor, carbon dioxide

and mixtures thereof at a temperature and pressure

sufficient to cause the gasification of the carbonaceous

material and cause the formation of a sufficient amount

of methane to produce a fuel gas having a Btu value

greater than about 300 Btu per cubic foot of fuel gas,

wherein a portion of the hydrogen and carbon monoxide

is obtained by recycling a portion of the methane

and the recycled gas is reformed to hydrogen and carbon

monoxide by the addition of heat and water

wherein the temperature is from about 500· C. to about

900· C. and the pressure is from about 100 kilopascals to

about 8300 kilopascals.

16. The process of claim 14 wherein the stabilized

metal carbide catalyst is selected from the group consisting

of iron silicide carbide, manganese, chromium

carbide, ferrochromium carbide and manganese cobalt

carbide.

17. The process of claim 16 wherein the stabilized

metal carbide catalyst is an iron silicide carbide comprising

from about 4 to about 50 weight percent silicon,

from about 0.5 to about 3 weight percent carbon and the

remainder of the catalyst comprises primarily iron and

wherein the temperature of the process is the threshold

temperature range of the stabilized metal carbide catalyst.

18. The process ofclaim 17 wherein the Btu value of

the fuel gas produced is greater than 400.

19. A process for the production of a fuel gas from a

solid carbonaceous material comprising:

(a) reacting the solid carbonaceous material in a single

reactor in the presence of a stabilized metal

carbide catalyst capable of maintaining its physical

integrity and chemical activity under gasification

conditions, said catalyst comprising carbon and a

metal alloy and having a free energy of formation

of from - 30,000 to 10,000 British thermal units per

pound atom of carbon at the reaction conditions,

said metal alloy comprising at least two metals

selected from the group consisting of iron, silicon,

manganese, cobalt, chromium, nickel, aluminum,

vanadium, tungsten, molybdenum, calcium, boron,

sodium and magnesium, wherein one of said two

metals forms a sufficiently stronger carbide to act

as a stabilizing component thereby enhancing the

chemical activity of the other metal carbide, and a

gas mixture comprising hydrogen, carbon monoxide

and from about 10 to about 30 volume percent

100 kilopascals to about 8,300 kilopascals to produce

a fuel gas containing methane;

(b) removing char produced in step (a) to a combustor

and combusting it;

step (a) for recycle back to the reactor;

(d) removing a portion of the heat contained in the

fuel gas produced in step (a) to heat water to produce

water vapor and to heat a portion of the recycle

gas;

(e) using the heat produced from the combustion of

the char to further heat the water vapor and to

further heat the recycle gas; and

(t) introducing the water vapor and the heated recycle

gas into the reactor.

9. The process of claim 8 wherein the water vapor

and recycle gas stream are combined and then heated

with the heat produced from the combustion of the

char.

10. The process of claim 8 wherein the temperature of 20

the reactor is the threshold temperature range of the

stabilized metal carbide catalyst.

11. The process of claim 10 wherein the stabilized

metal carbide catalyst comprises (rom about 10 to about

20 weight percent silicon, from about 0.5 to about 3 25

weight percent carbon and from about 77 to about 90.5

weight percent iron, and wherein the threshold temperature

of this stabilized metal carbide catalyst is from

about 775· C. to about 845" C.

12. The process of claim 10 wherein the stabilized 30

metal carbide catalyst is selected from the group consisting

of iron silicide carbide, manganese chromium

carbide, ferrochromium carbide and manganese cobalt

carbide.

13. The process of claim 10 wherein the stabilized 35

metal carbide catalyst is an iron silicide carbide comprising

from about 4 to about 50 weight percent silicon,

from about 0.5 to about 3 weight percent carbon and the

remainder of the catalyst comprises primarily iron.

14. A process fot the production of a fuel gas from a 40

solid carbonaceous material comprising reacting in a

single reaction zone the solid carbonaceous material in

the presence of a stabilized metal carbide catalyst having

a free energy of formation of from - 30,000 to

10,000 British thermal units per pound atom of carbon 45

at the reaction conditions, said metal alloy comprising

at least two metals selectedfrom the group consisting of

iron, silicon, manganese, cobalt, chromium, nickel, aluminum,

vanadium, tungsten, molybdenum, calcium,

boron, sodium and magnesium, wherein one of said two 50

metals forms a sufficiently stronger carbide to act as a

stabilizing component thereby enhancing the chemical

activity of the other metal carbide, said catalyst having

characteristics of a bulk chemical catalyst and capable

of substantially maintaining its physical integrity and 55

chemical activity under gasification conditions, and a

gas of which from about 10 to about 30 volume percent

is selected from the group consisting of water vapor,

carbon dioxide and mixtures thereof under reaction

conditions to cause the formation of carbon monoxide, 60

carbon dioxide, hydrogen and methane wherein the

heat produced by the formation of carbon dioxide and

methane is directly used to supply heat needed for the

formation of hydrogen and carbon monoxide and

wherein a sufficient amount of methane is formed to 65

produce fuel gas wherein the temperature is from about

500· C. to about 900· C. and the pressure is from about

100 kilopascals to about 8300 kilopascals.

4,372,755

of a gas selected from the group consisting of water

vapor, carbon dioxide and mixtures thereof at a

temperature of from about 500· C. to about 900· C.

and a pressure of from about 100 kilopascals to

about 8,300 kilopascals to produce a fuel gas con- 5

taining methane; .

(b) removing char produced in step (a) to a combustor

and combusting it;

step (a) for recycle back to the reactor;

(d) removing a portion of the heat contained in the

fuel gas produced in step (a) to heat a water stream

and to heat a portion of the recycle gas;

(e) combining the heated water stream and the heated

recycle gas; 15

(f) using the heat produced from the combustion of

the char to further heat the combined water and

recycle gas stream to form water vapor and to

reform a portion of the methane contained in the

recycle gas to increase its level of hydrogen and 20

carbon monoxide; and

(g) introducing the combined stream of step (f) into

the reactor.

20. A process for the production of a fuel gas from a

solid carbonaceous material comprising reacting in a 25

single reaction zone the solid carbonaceous material in

the presence of a stabilized metal carbide catalyst comprising

carbon and a metal alloy and having a free energy

of formation of from - 30,000 to 10,000 British

thermal units per pound atom of carbon at the reaction 30

conditions, said metal alloy comprising at least two

metals selected from the group consisting of iron, silicon,

manganese, cobalt, chromium, nickel, aluminum,

vanadium, tungsten, molybdenum, calcium, ·boron, sodium

and magnesium, wherein one of said two metals 35

.forms a sufficiently stronger carbide to act as a stabilizing

component thereby enhancing the chemical activity

of the other metal carbide, said catalyst having characteristics

of a bulk chemical catalyst and capable of substantially

maintaining its physical integrity and chemi- 40

cal activity under gasification conditions and a gas mixture

comprising hydrogen, carbon monoxide and from

about 10 to about 30 volume percent of a gas selected

from the group consisting of water vapor, carbon dioxide

and mixtures thereof at a temperature of from about 45

500· C. to about 900· C. and a pressure of from about

10<? kilopascals to about 8,300 kilopascals under conditions

which maintain the ratio of the reactant gases and

product gases in order to cause the gasification of the

carbonaceous material and the formation of a sufficient 50

amount of methane to produce a fuel gas having a Btu

value of from about 400 to about 450 Btu per cubic foot

of fuel gas while maintaining the activity of the stabilized

metal carbide catalyst.

21. The process of claim 19 or claim 20 wherein the 55

temperature of the reactor is the threshold temperature

range of the stabilized metal carbide catalyst.

22. The process of claim 21 wherein the stabilized

metal carbide catalyst is selected from the group consisting

of iron silicide carbide, manganese, chromium 60

carbide, ferrochromium carbide and manganese cobalt

carbide.

23. The process of claim 22 wherein the stabilized

metal carbide catalyst is an iron silicide carbide catalyst

comprising from about 4 to about 50 weight percent 65

silicon, from about 0.5 to about 3 weight percent carbon

and the remainder of the catalyst comprises primarily

iron.

24. A process for the production of a fuel gas from a

solid carbonaceous material comprising:

(a) reacting the solid carbonaceous material in a single

reactor in. the presence of a stabilized metal

carbide catalyst capable of maintaining its physical

integrity and chemical activity· under gasification

conditions, with a gas comprising hydrogen and,

carbon monoxide and from about 10 to about 30

volume percent of the gas is selected from the

group consisting of water vapor, carbon dioxide

and mixtures thereof at a temperature of from

about 500· C. to about 900· C. and a pressure of

from about 100 kilopascals to about 8,300 kilopascals,

wherein the stabilized metal carbide catalyst

comprises carbon and a metal alloy and has a free

energy of formation of from - 30,000 to 10,000

British thermal units per pound atom of carbon at

the reactor conditions, said metal alloy comprising

at least two metals selected from the group consisting

of iron, silicon, manganese, cobalt, chromium,

nickel, aluminum, vanadium, tungsten, molybdenum,

calcium, boron, sodium and magnesium

wherein one of said two metals forms a sufficiently

stronger carbide to act as a stabilizing component

thereby enhancing the chemical activity of the

other metal carbide, and wherein the reactant gases

and product gases are maintained at ratios which

allow for the gasification of the carbonaceous material

and the formation of a sufficient amount of

methane to produce a fuel gas having a Btu value

of at least about 400 Btu per cubic foot of fuel gas;

(b) removing char produced in step (a) to a combustor

and combusting it;

step (a) for recycle back to the reactor;

(d) removing a portion of the heat contained in the

fuel gas produced in step (a)to heat a water stream

and to heat a portion of the recycle gas;

(e) reforming the recycle gas stream of step (c) to

obtain higher levels of hydrogen and carbon monoxide;

(f) using the heat produced from the combustion of

the char to further heat the water vapor and to

further heat the recycle gas to aid in reforming the

methane contained in the recycle gas to hydrogen

and carbon monoxide; and

(g) introducing the water vapor and the reformed

recycle gas into the reactor.

25. The process of claim 24 wherein the temperature

of the reactor is the threshold temperature range of the

stabilized metal carbide catalyst and the stabilized metal

carbide catalyst is selected from the group consisting of

iron silicide carbide, manganese chromium carbide,

ferrochromium carbide and manganese cobalt carbide.

26. A process for the production of a fuel gas from a

solid carbonaceous material comprising reacting in a

single fluidized reaction zone the solid carbonaceous

material in the presence of a stabilized metal carbide

catalyst comprising carbon and a metal alloy and having

a free energy of formation of from -30,000 to

10,000 British thermal units per pound atom of carbon

at the reaction conditions, said metal alloy comprising

at least two metals selected from the group consisting of

iron, silicon, manganese, cobalt, chromium, nickel, aluminum,

vanadium, tungsten, molybdenum, calcium,

boron, sodium and magnesium, wherein one of said two

metals forms a sufficiently stronger carbide thereby

enhancing the chemical activity of the other metal car4,372,755

bide and a lower capacity for carburization and oxidation

than each of the individual metals of the alloy and

a fluidizing gas wherein from about 10 to about 30 volume

percent of the fluidizing gas is selected from the

group consisting of water vapor, carbon dioxide and 5

mixtures thereof at a temperature and pressure sufficient

to carbide the stabilized metal alloy, to cause the gasification

of the carbonaceous material and cause the formation

of a sufficient amount of methane to produce a

fuel gas having a Btu value greater than about 300 Btu 10

per cubic foot of fuel gas wherein the temperature is

from about 500· C. to about 900· C. and the pressure is

from about 100 kilopascals to about 8300 kilopascals.

27. A process for the production of a fuel gas from a

solid carbonaceous material comprising:

(a) reacting the solid carbonaceous material in a single

reactor in the presence of a stabilized metal

carbide catalyst comprising at least two metals

selected from the group consisting of iron, silicon,

manganese, cobalt, chromium, nickel, aluminum, 20

vanadium, tungsten, molybdenum, calcium, boron,

sodium and magnesium, wherein one of said two

metals forms a sufficiently stronger carbide to act

as a stabilizing agent thereby enhancing the chemical

activity of the other metal carbide and having a 25

lower capacity for carburization and oxidation

than each of the individual metals of the alloy and

a gas wherein from about 10 to about 30 volume

percent of the gas is selected from the group consisting

of water vapor, carbon dioxide and mixtures

thereof at a temperature of from about 500· C. to

about 900· C. and a pressure of from about 100

kilopascals to about 8,300 kilopascals to cause the

carbiding of the stabilized metal alloy, to cause the

gasification of the carbonaceous material and the

formation of a sufficient amount of methane in

order to obtain a fuel gas having a fuel value of at

least 300 Btu per cubic foot of fuel gas, said metal

carbide catalyst being formed at said conditions by

the carbidizing of said metal alloy;

(b) removing char produced in step (a) to a combustor

and combusting it;

to a combustor and combusting it;

(d) removing a portion of the heat contained in the

gas produced in step (a) to heat water to produce

water vapor and to heat a portion of the recycle

gas;

(e) using the heat produced from the combustion of

the char to further heat the water vapor and to

further heat the recycle gas; and

(f) introducing the water vapor and the reformed

recycle gas into the reactor.

* * * * *