Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 It was early recognized that some mineral and trace
2 inorganic constituents naturally present in some coal could
3 exert favorable catalytic influences in gasii~ation reac-
4 tions vis-a-vis thermal reactions, and a variety of catalytic ~-
materials have been added to coal to alter the natural chem-
6 istry inherent in various of the prior art coal gasification
7 processes. There is a prousion of information covering cat-
8 alytic coal gasificatlon processes; both domestic and foreign,
9 this including both patents and literature. Illustrative -~
thereof is a recent paper by James L. Johnson; Catal. Rev.
11 Sci. Eng., 14(1) pp. 131-152 (1976), which includes a survey
12 of the catalytic gasification art. Therein various materials
13 have been characteriæed as generally useful catalysts for the
14 gasification o~ coal, or carbonaceous solids, the survey nam -;;
ing various metals, metal oxides, metal halides, ~ransition
16 metals, and iron carbonyls. Group I and Group II metal com-
17 pounds as a class, notably potassium carbonate, sodium carbon~
18 ate, potassium chloride, sodium chloride, and calcium oxide
19 are given special recognition, it being suggested that few
catalysts are as effective in promoting gasification rates as
21 alkali metals, and that none are more activeO In the article,
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1 the catalytic properties of sodium and calcium are specifi-
2 cally discussed. Each of these cations, respectively, have
3 been ion-exchanged into lignite, exchange being possible,
4 and attributed to the presence of the carboxy functional
groups known to be present in lignite, and other low rank
6 coal structures. Gasification rates with steam-hydrogen mix-
7 tures were increased when sodium or calcium were added to the
8 lignite via the exchange mechanism. However, attempts to add
9 sodium or calcium to bituminous coals via ion-exchange were
unsuccessful due, as suggested in the article, to the lack of
11 exchange sites on high rank coals.
12 In a catalytic coal gasification process, i.e., one
13 whose object is to protuce high-BTU gas, steam, and particu-
14 late coal are fed to a gasifier at elevated temperature and
pressure and converted to a synthesis gas, or gaseous mixture
16 of high methane content, which contains significant amounts
17 of carbon monoxide and hydrogen which must also be catalyti-
18 cally converted in situ or ex situ within the gasifier to
19 methane. Prac~ical objectives require increased thermal
efficiencies, with simultaneous reduction of reactor size and
21 temperature, as well as simplification and reduction of the
22 steps involved in the operation. It has been recognized, and
23 is evident that these and other objectives might be obtainable
24 by improved catalytic materials added to the mass of feed
coal. Though much of the prior art disclosures relate to dis-
26 closures of physical admix~ures o a catalyst and a coal, it
27 has been recognized that a thorough dispersion of the catalyst
28 throughout the coal better promotes gasiication rates, and
29 activity than a physical mixture. In the pas~, however,
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1 whereas i~ has not proven particularly difficult to effec-
2 tively, uniformly, disperse catalytic materials throughout
3 low rank coal structures, this has not been true of high rank
4 coals, notably subbituminous and bituminous coals. This is
because l~w rank coals have active sites which makes feasible
6 the exchange oE cations onto these sites. Wi~h high rank
7 coals, however, the coal particle is devoid of such sites.
8 It has been reported by Batelle Memorial Ins~i~ute9
9 subsequPnt to this invention, that "Batelle-treated coal" has
been prepared from a high rank coal, i.e., Pittsburgh No. 8
11 coal in Batelle Memorial Institute's Hydrothermal Coal pro-
12 cess by treating in aqueous sodium hydroxide/calcium oxide
13 (CaQ) solution (0.13:1 CaO to coal) at 2S0C (480F), up to
14 3% of the CaO being chemisorbed on the coal. It is disclosed
that at 850~C (1560F) and 500 psig 65% of the trea~ed coal
16 can be converted by steam in three minu~eæ compared with 90
17 minutes for untreated coal. S. P. Chauhan (Batelle Memorial
18 Institute, Columbus Lab), K. Woodcock (E.R.D.A.) et al 173rd
19 ACS National Meeting (New Orleans 3/20-25/77) ACS Div. Fuel
Chem. Prepr. 22 ~1:38-52 (1977).
21 There is, and remains a need for providing better
22 catalytic coal gasification processes, or catalysts for use
23 in catalytic coal gasification processes which are capable of
24 producing high-BTU fuel gases from various coals, particularly
high rank coals for commercial usages at improved economies,
26 or efficiencies.
27 It is, accordingly, ~he primary objec~ive of ~he
28 present invention to supply this need.
29 A par~icular object is to provide a process for the
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treatment of coals, notably high rank coals, or coals which
have insufficient active sites to permit ion-exchange, to
render such coals amenable to gasification at increased rate,
particularly for use in the production of high-BTU fuel gases.
A further object is to provide, as compositions or
articles of manufacture, a pretreated particulate coal feed
which has been rendered amenable to gasification by treating to
form therein relatively inexpensive species of Group I-A or
Group II-A metals, or admixtures thereof, in high concentra-
tions.
These objects and others are achieved in accordance
with the present invention embodying a novel process, and the
articles o~ manufacture, or compositions, formed thereby,
wherein a Group II-A metal (Periodic Table of the Elements,
Sargent-Welch Scientific Company, Copyright 1968), or compound
thereof, can be ion-exchanged onto coal, preferably a high
rank coal, by contacting and soaking the coal in an alkali
solution comprising a Group I-A metal compound or an admixture
of Group I-A metal compounds, preferably a hot solution of
such compounds sufficient to incorporate said metal compound,
or cation portion thereo~, inta said coal to form ion-exchange
sites, and ion-exchanging a Group rI-A metal onto the active
sites thus created. The composition can be pyrolyzed, and
gasi~ied, to form a high-BTU, intermed~ate-BTU or synthesis
fuel gas. Enhanced gasification rates are achieved by gasi-
fication of the so-treated coal, or composition which contains
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both the Group II-A and Group I-A metals, as contrasted
with a composition otherwise similar except that it contains
an equal molar quantity of either a Group II-A metal or Group
I-A metal, rather than both metals. Moreover, the Group
I-A or Group II-A metals can act as a sulfur absorbent during
the gasification or pyrolysis.
It is essential to incorporate a Group II-A metal,
or metals, onto a coal via ion-exchange. This is convenient-
ly accomplished with low rank coals, or coals which have
adequate ion-exchange sites, by contacting and soaking the
coal, suitably in particulate form, in a dispersion, or solution
of a Group ~I-A metal compound, preferably an aqueous hydroxide
solution containing sufficient of the Group II-A metal com-
pound to exchange all the aYailable sites and impart
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1 from about 0.1 to about 10 atomic percent, preferably from
2 about 1 to about 8 atomic percent, of the Group II-A metal on-
3 to the coal, based on the carbon present in the char after i~
4 is pyrolyzed and devolatilized. Suitably, the treatment is
conducted at temperatures ranging from about 20F. to about
6 230F., preferably from about 40F. to about 90F., suitably
7 for periods ranging at least about 1 hour, preerably from
8 about 1 hour to about 72 hours, more prefexably ~rom about 24
9 hours to about 48 hours, when the temperature o~ the solution
is maintained within the expressed preferred ranges. The
11 period of contact, or soak, is not critical, and lesser soak
12 periods can be employed as coal particle size is decreased.
13 High rank coals, though lacking in natural ion-ex-
14 change capacity (compared to low rank coals), to permit sub-
stantial direct ion-exchange of a Group II-A metal onto the
16 coal, can also be treated to form Group II-A metal ion-ex-
17 changeable sites, or sites on which Group II-A metal cations
18 can be exchanged. In one embodiment, a high rank coal i9
19 treated with a solution of a Group I-A metal compound to form
the necessary sites necessary for exchange therewith of Group
21 II-A cations. Suitably, in accordance therewith, a particulate
22 coal containing less oxygen in an ac~ive form than would be
23 required to impart from about 2 to about 10 wt. percent cal-
24 cium ion is contacted and soaked in an alkali solution com-
prising a Group I-A metal compound, or compounds3 preferably
26 an aqueous alkali hydroxide of from about 0.25 to about 5
27 normality, more preferably from about 0.5 to about 2 normality,
28 at conditions sufficient to form active sites on~o which can
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1 be exchan~ d between about 5 x 10 4 to about 8 x 10 3 gram
2 atom equivale~ts of a Group I-A metal, preferably from about
3 1 x 10 3 to about 5 x 10 3 gram atom equivalents o a Group I-
4 A ~etal. Suitably, the treatment is conducted at temperatures
ranging from about 20F. to about 250F., preferably from
6 about 40F. to about 90F., suitably for periods ranging at
7 least about 0.1 hour, preferably from about 0.25 hour to about
8 12 hours~ more preferably from about 0.25 hour to about 2 hours,
~ when the temperature of the solution is maintained within the
expressed preferred ranges. The period of contact, or soak,
11 is variable and lesser soak periods can be employed as tem?er-
12 atures are increased and as particle size is decreased. The
13 coal can be treated in a single step using a solution within
14 which both the Group I-A and Group II-A metal compounds are
dispersed, or dissolved, or in multiple steps wherein the
16 coal is first contacted with a solution of Group I-A metal com
17 pound, or compounds, thence with a solutinn which contains
18 the Group II-A metal compound, or compounds. ThP coal within
19 which ion-exchange sites (i.e. Group II-A cation exchangeable
sites) have been created is then, in one embodiment, separated
21 from the alkali solution of the Group I-A metal compound, or
22 compounds, and then contacted and soaked with a solution,
23 dispersion or slurry, preferably an aqueous solution of from
24 about 0.25 to about 5 normality, preferably from aDout 0.5 to
about 2 normality, of a Group II-A metal compound, or compounds,
26 sufficient to exchange at least a portion of the Group I metal
27 cations with Group II metal cations. Solution temperatures
28 ranging from about 20F. to about 200F., preferably from
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1 about 40F. to about 90F., have been found satisfactory for
2 ion-exchange and replacement of Group I-A metal cations by
3 Group II-A metal cations. The period of treatment is not
4 critical, but generally requires at least about 1 hour, suit~
ably from about 0.25 hour to about 48 hours, and preferably
6 from about 1 hour to about 8 hours for adequate exchange at
7 the preferred conditions. Faster exchange rates can be
8 achieved by increasing the temperature of the solution and
9 decreasing the particle size.
In forming the novel compositions, or articles of
11 manufacture, of this invention, suitably from about 1 percent
12 to about 10 percent, preferably from about 3.5 percent to about
13 7 percent, of the Group I-A metal, or metals, calculated as
14 metallic metal based on the weight of the coal (MAF), is in
corporated onto the coal, and from about 1 percent to about
16 10 percent, preferably from about 3 percent to about 5 per-
17 cent of the Group I-A metal cation, calculated as metallic
18 metal based on the weight of the coal (~F~, is then replaced
19 with a Group II-A metal, or metals, via ion-exchange. Suit-
ably therefore, the coal is one which contains, after treat-
21 ments with the solution, or solutions, a sum-total of from
22 about 1 percent to about 10 percent, preferably from about 3.5
23 percent to about 7 percent, of Group I A and Group II-A metals,
24 calculated as metallic metal based on the total weight of the
coal (MAF). From about 0.; percent to about 4 percent, pre-
26 ferably from about 0.5 percent to about 2 percent, of the
27 total metal is thus characterized as a Group I-A metal, or
28 metals, and from about 0.5 percent to about 6 percent9 prefer-
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1 ably from about 3 percent to about 5 percent, as a ~roup II-A
2 metal, or metals.
3 Alternatively, a high rank coal, notably a sub-
4 bituminous or bituminous coal, can be contacted with an al-
kali solution of an admixture of compounts of Group I-A and
6 Group II-A metals~ preferably a hot solution of such compounds,
7 inclusive of a soluble alkali metal salt and an alkaline earth
8 me~al hydroxide, each of which interacts one with the other to
9 form an alka ~ metal hydroxide, and an insoluble alkaline
earth metal salt precipitate. The coal is treated in a single
11 step by contact with the solution within which both the Group
12 I-A and II-A metal compounds are dispersed, or dissolved.
13 Where the coal does not contain adequate ion-exchange sites,
14 these are formed by reaction between the alkali metal hydrox-
ide generated by the reac~ion, and the coal, and in turn all
16 or a portion of the alkali metal catiOns are exchanged or re-
17 placed by excess alkaline earth metal cations which are pres-
18 ent in the alkali metal hydroxide that is formed. ~referably,
19 the treatment is continued until substantially all of the
alkali metal cations have been replaced by the alkaline earth
21 metal cations, and then the solution is evaporated while in
22 contact with the coal to redeposit and physically disperse
23 the alkali metal upon the coal.
24 The presence of the alkali metal hydroxide formed
by the interchange permits the formation wi~hin the coal of
26 reactive sites, or ion-exchange sites on which the alkaline
27 earth metals can be exchanged, but the sites are created from
28 an alkali metal hycroxide formed in situ from an interaction
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1 between an inexpensive alkali metal salt and an inexpensive
2 alkaline earth metal hydroxide. For example, it is known
3 that active sites are formed on coal by direct contact and
4 treatment with a sodium hydroxide solution, but sodium hydrox-
ide is rather expensive. Sodium carbonate, however, is rather
- 6 inexpensive as is lime, and hence sodium carbonate, ~a2co3~
7 can be dissolved in water and hydrated lime, Ca(OH)2, added
8 thereto, such that sodium hydroxide is formed in situ from
9 the alkali metal carbonate as a source of sodium ions and
the alkaline earth metal hydroxide as a source of hydroxyl
11 ions. CaCo3 precipitates out. In such solution the sodium
12 hydroxide reacts with the coal to form ion-exchange sites,
13 and as these sites are formed, alkaline earth metal cations
14 from excess dissolved Ca(OH)2 are exchanged thereupon as con-
tact of the coal with such solution is continued.
16 Sufficient of the alkaline earth metal cations are
17 contained within the solution for subs~antial exchange and
18 replacement of the alkali metal ~rom the coal at ambient con-
19 ditions by soaking the coal in the solution for a period rang-
ing at least about 0.25 hour, suitably from about 1 hour to
21 about 100 hours, preferably from about 24 hours to about 96
22 hours. The contact period, however, can be decreased by re-
23 duction of the temperature. Thus, lime is not very soluble, ~-
24 especially in basic solution and an insoluble calcium carbon-
ate precipitate is formed such ~hat relatively few calcium
26 ions are present in the solution. However, sufficient of the
27 calcium cations are maintained in solution for reasonably
28 rapid exchange of calcium onto the active sites to produce
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acceptable gasification rates, and methanation activity, by
elevating the temperature of the solution.
In one embodiment, a particulate coal containing less
oxygen in an active form than would be required to impart from
about 1 to about 10 wt. percent calcium ion, particularly a
bituminous coal, is contacted, heated or boiled and soaked in
an alkali solution comprising an admixture of compounds, in-
clusive o a soluble alkali metal salt and an alkaline earth
metal hydroxide in excess of that amount required to react to
form an alkali metal hydroxide and an insoluble alkaline earth
metal salt precipitate. The solution formed, preferably with
water as a solvent, is characterized as an aqueous alkali
hydroxide of from about 0.1 to about 10 molarity, preferably
from about 0.5 to about 2 molarity, and this solution is main-
tained in contact with said coal at conditions suf~icient to
form active sites onto which can be exchanged between about
5 x 10 4 to about 8 x 10 3 gram atom equivalents o~ a Group
I-A or Group II-A metal, or both, per gram of coal, preferably
from about 1 x 10 3 to about 5 x 10 3 gram atom equivalents of
a Group I-A or Group II-A metal, or both per gram of coal.
Suitably/ the treatment is ~onducted at temperatures ranging
from about 20F. to about 250F., preferably from about 180F.
to about 220F., suitably for periods ranging from about O o l
to about 48 hours, preferably from about 0.25 hour to abou~
6 hours, more preferably from about 0.25 hour to about 1 hour,
when the temperature of the solution is maintained within the
expressed preferred ranges.
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The process of this invention is generally applic-
able for the inclusion of Group I~A and Group II-A metals in
virtually any rank of coal~ including lignite, brown coal,
peat, and the like, subbituminous coals such as Wyodak and
the like, and bituminous coals such as Illinois No. 6,
Pittsburgh No. 8 and the like. The process, however, has ;.
special utility in the treatment of the high rank coals,
notably the subbituminous and bituminous coals which have in-
sufficient natural sites to permit high per se dispersion of
the Group I-A and Group II-A metals into the structure.
Suitable Group II-A metals, or alkaline earth metals,
suitable for the practice of this invention are exemplified
by magnesium, calcium, strontium and barium, the effectiveness
of which for gasification purposes increases directly with in-
creasing atomic weight except for calcium which is a highly
preferred species of Group II metal based on i~s cost effect-
iveness, and exceptional reactivity. The alkaline earth
metals are suitably employed in solution as salts, preferably
as weak acids, and hydroxides illustrative of which are magnes-
ium carbonate, calcium hydroxide, strontium oxalate, barium
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1 acetate and the like. Suitable Group I-A metals, or alkali
2 metals, are exemplified by lithium, sodium, potassium,rubid-
3 ium and cesium, the effectiveness of the metals as gasifica-
4 tion catalysts increasing in direct proportion to their in-
creased atomic weight, though sodium and potassium are pre-
6 ferred metals based on cost-effectiveness. These are suitably
7 employed as salts or hydroxides, e.g., sodium carbonate, po-
8 tassium hydroxide, potassium nitrate, cesium acetate and the
9 like.
Group I-A metals, or alkali metals, suitable for
11 the practice of this invention are exemplified by lithium,
12 sodium, potassium, rubidium and cesium, the effectiveness of
13 the metals as gasification catalysts increasing in direct pro-
14 portion to their increased atomic weight, though sodium and
lS potassium are preferred metals based on cost-effectiveness.
16 These are suitably employed as salts or hydroxides, e.g.,
17 sodium carbonate, potassium hydroxide, potassium nitrate,
18 cesium nitrate and ~he like. In the embodiment of this inven-
L9 tion which re~uires the treatment of the coal with an admix-
ture of Group I-A and Group II-A compounds~ virtually a~y al-
21 kaline earth metal hydroxide or alkaline earth metal compound
22 which will decompose and form a hydroxide in situ, can be
23 employed in the practice of this invention. Exemplary of
24 such compounds are hydroxides formed from magnesium, calcium, -
strontium and barium, with calcium being preferred. The al-
26 kali metal salt is constituted of any of lithium, rubidium,
27 cesium, but particularly sodium or potassium, in combination
28 with an anion which provides a soluble salt, and forms an in-
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1 soluble molecular species with the specific alkaline earth
2 metal of the alkaline earth metal hydroxide employed in the
3 admixture added to the solvent. ExPmplary of alkali metal
4 salts suitable for use in the practice of this invention are
S sodium bicarbona~e and sodium carbonate which form an insol-
6 uble salt on reaction in solution with bariu~9 strontium or
7 calcium; sodium oxalate, potassium oxalate which form an in-
8 soluble salt on reaction with barium, strontium or calcium;
9 sodium chromate or cesium chromate which form an insoluble
precipitate on reaction in solution with barium or strontium;
11 sodium fluoride which forms an insoluble precipitate with
12 strontium; and the like.
13 In the past, low rank coals have been successfully
14 treated via ion-exchange with alkali or alkaline earth metal
cations, including, e.g., sodium or calcium, because of
16 natural exchange sites. The exchange of alkali or alkaline
17 earth metal cations, particularly the latter, onto bituminous
18 coals, however, has been ineffective because of the nature
19 of bituminous coals which are lacking in natural exchange sites.
In accordance with the present process, nonetheless, ion-ex-
21 change sites are created in the coal by oxidation of the coal
22 or treatmen~ with a strong alkaLi solution of Group I-A metal
23 compounds or the solution which is generated by reaction be-
24 tween the admixture of the soluble alkali metal salt and al-
kaline earth metal hydroxide, this making feasible the addi-
26 tion, or incorporation of considerably greater amounts of al-
27 kaline earth metal cations into the coal than heretofore be-
28 lieved possible. Whereas substantially complete exchange of
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1 alkaline earth metal into the created ion-exchange sites is
2 possible, the presence of both alkali and alkaline earth metal
3 cations in the coal is highly preferable for it has been found
4 that gasification rates are considerably higher for a coal
which contains both types of metal vis-a-vis a coal similarly
6 treated, and otherwise similar except that it contains either
7 an alkali metal or alkaline earth metal to the substantial ex-
8 clusion of the other. After complete exchange and replacement
9 of substantially all of the Group I-A metal by a Group II-A
metal, in any event, the Group I-A metal can be physically
11 dispersed upon the structure to provide a highly reactive feed
L2 for use in gasification reactions.
13 Gasification processes as generally known in the
14 art can be improved with respect to yield or conversion rate,
or both,.when the process of this invention is employed in
16 the formation of the novel carbonaceous feed compositions.
17 The compositions are reacted with a gaseous species or a mix-
18 ture of gaseous species at elevated temperatures, and general- ;
19 ly elevated pressures to produce and optimize the composition
~0 of the fuel gases. The gaseous species generally employed as
21 reactants include oxygen, stea~, hydrogen, and carbon oxides
22 such as carbon dioxide. Generally, temperature, pressure,
23 flow rate, mole ratios and relative mole ratios depend on the
24 specific process employed and the actual products desired
therefrom. In any event, the composi~ion of the gaseous pro-
26 ducts are altered by the particular catalyst employed. For ~-
27 example, the products resulting from the gasification of coal
28 with steam is enriched in methanP by judicious selection of the
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optimum alkali and alkaline earth metal, and concentration
thereof within the feed composition, to promote the conversion
of carbon monoxide and hydrogen to methane. Generally sodium
or potassium in relatively high concentration are most pre-
ferred when maximum methane production from gasification by
steam is desired, and calcium in high concentration is most
preferred when production o~ carbon monoxide and hydrogen by
steam gasification is desired. Gasification is generally ac-
complished by contacting the treated coal with steam at a
temperature within the range from about 750 F. to about 1850F.
at a steam flow rate within the range from about 0.2 to a~out
100 W/W~Hr. Pressure is not critical, but generally ranges
from about 0 to about 1000 psig~
These and other features of the present invention
will be better understood by reference to the following demon-
strations which involve treatment of coals with Group II-A
and Group I-A metals, and runs conducted by gas.ification of
the coal with and without bene~it of treatment with the al-
kaline earth and alkali metal compounds and salts, particular-
ly with re~erence to comparative data showing gasification o~coal pretreated with both alkali and alkaline earth metal com-
pounds and salts in accordance with this invention, All units
are in terms of weight unless otherwise specified.
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EXAMPLE 1
A lS g. portion of -16 ~20 mesh (NBS~ Illinois hi~h
volatile C bituminous coal was boiled for 3.5 hours in an aq-
ueous 1 normal NaOH solution. The specimen was then soaked in
several hundred ml of distilled water for several hours. The
specimen was then soaked for several days in about 5 g~ of
Ca(OH)2 and fresh distilled water. Excess, unutilized Ca(OH)2
was elutriated from the coal specimen.
Analysis o~ treated coal specimen indicated 5.1
weight percent calcium on the impregnated coal specimen. In
contrast, soaking coal not pretreated with NaOH in Ca(OH)2 re-
sulted in an uptake of only 1~9 weight percent calcium~
(Boiling a sample of the coal in Ca(OH)2 solution with excess
powdered Ca(OH)2 did not enhance the calcium uptake).
The steam gasification rate at comparable conditions
was 1.8 times higher for the NaOH/Ca(OH~2 treated composition
than for tAe Ca(OH~2 composition.
The followin~ example contrasts the difference in
uptake of a Gr~up II-A metal ~rom a specimen of coal pre-
treated with an a~ueous solution o~ a Group I-A metal vis-a
; vis uptake of a Group II A metal by an untreated, but other-
wise similar c~al specimen.
EXAMpLE 2
~ 5 g. sample o~ the s~me c~al specimen as used in
Example 1 was soaked for 64 hours in 2 normal aqueous NaOH at
ambient temper~ture (appxoximately 76 F~, The specimen was
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cleared of NaOH and soaked for 55 hours in wat4r containing
several grams of Ca(OH)z powder. Excess, unutilized Ca(OH)2
powder was elutriated from the specimen. The sample was found
tocontai~ after treatment, 4.5 weight percent calcium.
In contrast, a similar coal specimen soaked in
Ca(OH)2 only witho~t an NaOH pretreatment took up 2.1 weight
percent calcium. Additional tests have established that NaOH
treatments as short as 2 hours at room temperature allow sub-
sequent calcium uptake of greater than 4 weight percent.
In accordance with the following data a bituminous
coal is treated simultaneously with the Group I-A and II-A
metal.
EXAMPLE 3
A 5 g. specimen of the Illinois coal of Example~l
and 2 was soaked in 52 ml of 1 normal aqueous NaOH containing
0.13 g. powdered Ca(OH)2 ~equivalent to 1.4 weight percent cal-
cium on coal) for 89 hours at room temperature. Excess NaOH and
Ca(OH)2 were removed with distilled water. The treated sample
contained 2.6 weight percent sodium and 1.0 weight percent
calcium.
When gasified under conditions identical to those in
Example 1, the steam gasification rate was 4.5 times that ob-
tained for the sample exchanged only with Ca(OH)2 and 2.5
times the rate obtained on the specimen that was boiled in
NaOH and then exchanged with calcium.
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EXAMPLE 4
In a series of runs, portions of Illinois No. 6 ;~
coal, a bituminous coal, were treated with aqueous solutions,
or slurries of admixtures of sodium carbonate and/or lime, at
solution boiling temperature, then soaked at ambient tempera-
ture for varying time periods. It was observed that sodium
hydroxide was formed and calcium carbonate was precipitated.
The sodium hydroxide wa5 found to attack the coal to form sodi-
um ion-exchanged sites, while excess calcium hydroxide dis-
solved such that calcium ions were exchanged for the sodium
ions. Since the hydroxyl ion was f~und to suppress the solu-
b~lity of the calcium hydroxide somewhat, a soak time was
necessary to achieve adequate calcium ion exchange for the sodi-
um. All of the sodium left in solution was distributed by dry-
ing and pyrolysis to form tAe active sodium promoted calcium
catalyst.
For comparatiye purpo$es, portions of the coal were
also physically admixed with various weight port~ons of potas-
sium car~onate, a catalyst of known high commercial potential
for use in the treatment and gasification of coal. Also, a
portion o the coal ~as treated with a physical admixture of
sodium car~onate, and a similar portion of the coal was soaked
In a lime slurr~. These several treated coal specimens were
tAen dried and gasified at 1300 F., ambient pr~ssure, by in-
~ection`o~ steam t~ proYide an ~erage steam:carbon ratio of
7.5 ~Hr.
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The weight percent of the potassium carbonate, and
the weight percent of the sodium carbonate or calcium oxide,
or both, in texms of weight percent on coal; the boil or soak
periods, and the gasification rates achieved are identi~ied
in the table.
TABLE I
Comparison of Na/Ca Catalyst with K2CO3 On Illinois Coal
Wt. % on Coal Time, Hr.
~ -- Gasification
Catalyst 2 3 2 3 CaO Boil Soak Rate-~/Hr.(l)
.
K2CO3 10 ~ - -- 72
K2C03 15 -- __ __ __ 100
Na2CO3~CatOH)2 __ 5 8 0.5 0 47
Na2CO3/Ca~OH)2 -- 5 8 0.5 72 89
Na2CO3/Ca(OH)2 -- 5 8 1 0 47
Na2CO3/Ca(OH)2 -- 5 8 l l 61
Na2CO3/Ca(OH)2 -- 5 8 l 7 64
Na~co3/ca(oH)2 ~~ 5 8 l 24 75
Na2co3/ca(oH)2 8 l 96 81
2 3 ~~ 5 ~- _ 21
Ca(OH)2 -- ~~ 2 9(2)__ 24 41
-
(l) Weighted average rate from 0-90% carbon conversion at 1300F.
Weighked average steam/carbon is 7.5 W/W/Hr. Based on carbon
actually present~
(2~ Actually ion-exchanged on the coal.
20 -
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s~
These data clearly show, in particular, the pro-
motional effect of sodium on calcium. A comparison of the
Na/Ca combination with potassium carbonate, the ~tandard
catalyst, shows an activity equal to 13% potassium carbonate.
The data illustrates that soak times of 72 to 96 hours are
generally necessary for maximum activity to be developed at
ambient conditions.
It is apparent that various modifications can be made
without departing the spirit and scope of the invention. For
example, these alkali-promoted alkaline earth catalysts will
also prove effective in the treating of coal derived carbon-
aceous products such as liquefaction bottoms, and with other
gasification agents such as hydrogen and carbon dioxide.
- 21 -
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