GB1599932A - Distributing coal-liquefaction or-gasifaction catalysts in coal - Google Patents

Description

(54) DISTRIBUTING COAL-LIQUEFACTION OR -GASIFICATION CATALYSTS IN COAL (71) We, EXXON RESEARCH AND ENGINEERING COMPANY, a Corporation duly organised and existing under the laws of the State of Delaware, United States of America, of Linden, New Jersey, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a coal liquefaction or gasification process in which cations exhibiting catalytic activity for the particular conversion process involved are effectively distributed through the coal prior to subjecting the same to the particular conversion process involved.

As is well known, coal has long been used as a fuel in many areas. For several reasons, such as handling problems, waste disposal problems and pollution problems, coal has not been a particularly desirable fuel from the ultimate consumers point of view. As a result, oil and gas have enjoyed a dominant position, from the standpoint of fuel sources, throughout the world.

As is also well known, proven petroleum and gas reserves are shrinking throughout the world and the need for alternate sources of energy is becoming more and more apparent. One such alternate source is, of course, coal since coal is an abundant fossil fuel, particularly in the United States. Before coal will be widely accepted as a fuel, however, it is believed necessary to convert the same to a form which will not suffer from the several disadvantages alluded to previously.

To this end, several processes wherein coal is either liquefied and/or gasified have been proposed heretofore. Many of these processes have employed a variety of catalytic materials that have been more or less successful in promoting the desired conversion. In order for such materials to be completely effective, however, it is important that the catalytic material be uniformly distributed throughout the coal structure. Due to the solid nature of coal, however the necessary distribution has been difficult and as a result many potential catalytically active materials cannot be effectively employed with conventional techniques.

Recently, it has been taught in Catalytic Review-Science Engineering 14(1), 131-152 (1976) that this problem can be avoided with lower ranking coals by first ion-exchanging a lower ranking coal with an alkali or an alkaline earth metal cation and, particularly, sodium or calcium. As indicated in the article, this technique was not particularly effective in higher ranking coals and the effect was not significant in bituminous coal chars. The problem still exists, then with the higher ranking coals and, indeed, the method proposed in the aforementioned article is not, apparently, the ultimate solution even with respect to lower ranking coals.The need, then, continues for a method of distributing catalytically active materials in a higher ranking coal which is destined for ultimate conversion particularly via liquefaction and/or gasification techniques. Moreover, the need exists for still further improvement with respect to catalyst distribution even within the lower ranking coals and particularly those which do not have sufficient acid, or other active sites to permit effective ion exchange.

It has now, surprisingly, been discovered that the foregoing and other disadvantages of the prior art catalyst distribution methods can be mitigated or overcome by a modification of the coal before ion exchange.

According to the present invention there is provided a method of liquefying or gasifying a coal, comprising the steps of: (A) oxidizing the coal, in finely divided coal form, at a temperature below the combustion temperature to an extent sufficient to increase the oxygen content of the coal by from 1 to 10 wt Ó based on the weight of the coal: (B) ion exchanging the thus oxidized coal with a metal cation: and (C) subjecting the exchanged coal to liquefaction or gasification conditions.

As indicated more fully hereinafter, it is important that the partial oxidation be below combustion temperature so as to prevent unnecessary loss of the coal during this pretreatment step. As is also more fully indicated hereinafter, the preferred cation used during the ion exchange step will depend upon the particular catalytic activity desired in the subsequent conversion.

The ion exchange step may, if desired, be accomplished simultaneously with the oxidation step.

In general, any coal may be used in the method of the present invention, including anthracite, bituminous, subbituminous, lignite, peat and brown coal.

However, the lowest ranking coals will generally have sufficient exchangeable sites to permit effective distribution of the catalytic material without prior treatment.

Nevertheless, even they can be improved by the treatment steps of the method of the invention. The method of the present invention is, however, especially effective with the higher ranking coals, which do not have sufficient sites to permit distribution without pretreatment, more especially with bituminous and subbituminous coals.

The coal will be employed in a finely divided state. The particular particle size, or particle size range, actually employed will depend a great deal upon the optimum size to be used in the subsequent conversion process, although the actual particle size range employed will have some effect on the rate of pretreatment and the rate of catalyst distribution. In this regard, it should be noted that the coal would, generally, when treated in accordance with this invention, be ground to a particle size of less than 1/4-inch and preferably to a particle size of less than 8 mesh NBS sieve size. With respect to particle size, it should be noted that the smaller sizes will enhance both the pretreatment reaction rate and at the same time will enhance catalyst distribution.For these reasons, then, the actual particle size employed will be as small as is practically consistent with the requirements for further processing and utilizing the coal.

In general, any cation could be distributed throughout the coal or a carbonaceous material derived from coal after the pretreatment of this invention and, surprisingly, any cation will impart some degree of catalytic activity in subsequent conversion processes. Cations that can be used in accordance with this invention, then, include those cations which are known to act as catalysts in the various coal conversion processes. Surprisingly, however, we have found that cations known to exhibit only slight or limited catalytic properties, by virtue of being physically intermixed with the coal structure, exhibit greatly improved catalytic properties when chemically combined; and thus such cations can also be used in the method of the invention.

Cations which will exhinit catalytic activity when incorporated into the coal in accordance with the present invention include the alkali metals and the alkaline earth metals of Group I-A and Il-A of the Periodic Chart of the Elements (as reprinted in the Chemical Engineers Handbook, 1973 Edition, Percy & Shulton, published by McGraw-Hill Book Company, New York). Effective cations also include the metals of Groups I-B and Il-B and the metals of Groups IV-A, IV--B, VI--B, VII--B and Group VIII.Of these, the alkali and alkaline earth metals are particularly effective when the coal is ultimately converted via a gasification reaction while the Group VIII metals, which exhibit hydrogenation promotion effects, are particularly effective when the coal is ultimately converted via a liquefaction process.

While the inventors do not wish to be bound by any particular theory, it is believed that when the oxidization step is used to impart the desired active sites, the reactions and subsequent ion exchange proceed throughout the significant internal pore surface area of the coal, which is commonly of a magnitude of several hundred square meters per gram of coal. It is also believed that peroxides are first formed and the peroxides thus formed decompose to yield acids. The acidic hydrogens can then be ion-exchanged in accordance with the present invention.

Whatever their nature, the oxidation step provides active sites which are ionexchangeable with a metal cation.

It will be appreciated that the active sites could be provided via any suitable oxidation technique. For example, with oxygen or an oxygen-containing gas such as air or a flue gas: or the use of an oxidizing agent such as an acid, a peroxide, various salts such as a permanganate or a hypochlorite. When an acid is used essentially any acid, such as nitric acid and sulfuric acid, known to be useful as an oxidizing agent can be used. When a peroxide is used essentially any peroxide including hydrogen peroxide, the various organic peroxides, the various metal peroxides and the like would be effective. When a salt such as a permanganate or hypochlorite is used essentially any such salt would be effective but it will be most convenient to use a salt containing a cation identical to that to be used in the subsequent catalyst distribution.

With respect to the foregoing, and while the inventors still do not wish to be bound by any particular theory, it is believed that coal contains a plurality of aromatic rings which are highly substituted; e.g., fused to other aromatics or hydroaromatics or attached to alkyl, ether, hydroxyl or the like, groups.

Additionally, it is believed that coal exhibits secondary structural characteristics such as hydrogen bonding interatomic ring bonds and the like, which generate the three-dimensional structure of coal. As a result, oxidation of coal can result in a broad range of free-radical or acid active sites. The formation of an active site possible from a condensed structure containing three aromatic rings, can be illustrated by the following equations:

As will be readily apparent, the free-radical sites illustrated in the second formula would readily react with essentially any cation. As will also be readily apparent, especially in light of the complex coal structure and significant pore surface area, an unlimited number of such sites are possible.Moreover, and with respect to the lower-ranking coals which contain significant oxygen concentrations, active sites different from those already contained in such coals can be imparted through controlled oxidation. The method of the present invention is, therefore, effective in the treatment of such coals and especially such which do not contain sufficient exchangeable active sites.

The oxidation step of the process of the invention will provide an increased number of reactive sites, especially in the higher ranking coals and will generally permit the inclusion of from 1 to 15 Wt ó of calcium or equivalent amounts of another desired cation or cations. In this regard, it should be noted that when monovalent cations or cations heavier than calcium are used the equivalent amount ion exchanged will represent a greater percentage by weight of the coal while with lighter or trivalent cations the weight percentage could be less. The key, then is really the number of catalytic sites per unit weight of coal and sufficient catalytic activity will be imparted when the coal contains between 5x10-4 and 8x10-3 gram atomic equivalents of catalytic-active cation per gram of coal.

With respect to the amount of catalytic-active material being incorporated into the coal, it should be noted that in those cases where the objective is to convert the coal to either a liquid or gaseous fuel, the prior oxidation, to the extent that it converts a portion of the coal to water and carbon oxides, will reduce the overall efficiency of the conversion process by reducing the quantity of coal available for subsequent conversion. The treatment does, on the other hand, improve the efficiency of the overall process by increasing catalytic activity and thereby reducing the holding time and/or temperature required in the subsequent conversion operation. The overall efficiency of the improved process or processes of this invention is, then, a balance resulting from these considerations.In this regard, however, it should be noted that the advantages resulting from effective distribution of the catalyst far outweigh the disadvantage resulting from premature conversion of the coal to CO2 and H2O so as to affect catalyst distribution.

Notwithstanding this, however, care should be exercised so as to avoid unnecessary oxidation of the coal during the pretreatment step.

In general, any method known in the prior art to be effective in controlling the rate and extent ofoxidation in a hydrocarbon can be used to affect the desired oxidation of the coal in the method of this invention. Such methods include, but are not necessarily limited to, control of oxidizing reagent concentration and the temperature of oxidation. Control of oxidizing reagent concentration can, of course, be controlled by mixing the reagent with a suitable diluent during contacting. This method would, of course, be most effective when a liquid or solid oxidizing agent is employed but could be used even when a gaseous-reducing agent is employed.In any case, and even when oxidizing-agent concentration is controlled during contacting it will, generally, be necessary to control temperature primarily to ensure that oxidation does occur within a reasonable period of time.

Effective oxidizing agent concentrations and effective oxidizing temperatures are, of course, well within the ordinary skill of the art and need not be set forth in detail herein.

Notwithstanding that effective concentrations and temperatures are within the ordinary skill of the art, it should be noted that when a gas, such as air, is employed as the oxidizing agent, essentially any temperature and pressure can be used during the oxidation and the extent of oxidation can be controlled by controlling the amount of air actually contacting the coal and the temperature at which contacting is accomplished. In this regard it should be noted that sufficient oxidation of dry coal will occur autogeneously at room temperature but at least five to seven days exposure are generally required. As a result, elevated temperatures are most effective but temperatures approaching combustion temperature should be avoided. Temperatures within the range from 18"C to 4250C are, then, considered effective.Temperatures within the range from 175"C. to 3000C. are, however, preferred since temperatures below 175"C. do not provide sufficient reaction rates while temperatures above 300"C. result in reaction rates approaching those of combustion. Due to the well-known time-temperature effect, reaction times can vary from a few minutes at the higher temperatures to several hours at the lower temperatures.

In general, any of the ion exchange techniques known to be effective for exchanging any cation for a hydrogen ion or a different cation can be be used to effect the desired catalyst distribution in the method of the present invention.

These techniques include direct contacting with a metal hydroxide in aqueous solution where the metal corresponds to the desired catalytic cation, and the various techniques wherein a metal salt is used to effect the desired ion exchange.

Again, when metal salts are used the metal portion of the salt will correspond to the cation sought to be imparted into the coal. In general, aqueous solutions of a hydroxide or a salt of a weak acid will be employed to effect the ion exchange. As is well known, the ion exchange will occur at a basic pH; i.e., a pH greater than 7.

The coal may, of course, be pretreated; i.e. prior to the ion exchange, with an -organic or inorganic acid such as formic acid or the like, to remove undesirable, naturally occurring, complexed elements. When this is done, care should be exercised to ensure that the acid employed will not impart an undesirable anion into the coal. Also, it will, generally, be necessary to wash out or neutralize the acidity of the aqueous medium prior to ion exchange. Such neutralization can, of course, be accomplished in accordance with known techniques and need not be discussed in detail herein. Notwithstanding this, however, it should be noted that ammonia can be effectively used to control the pH and that ammonia is particularly effective when an acid pretreat is used and when alkali and alkaline salts, particularly the halide salts, are used to effect the desired ion exchange. The anion can then later be removed by water washing or the like.

In the method heretofore described, the pretreatment or oxidation is accomplished prior to the ion exchange. It is, however, within the scope of this invention to effect both oxidation and ion exchange simultaneously. When this is done, oxygen will either be bubbled through the ion exchange solution during contacting with the coal, or another suitable oxidizing agent will be incorporated into the ion exchange solution. As in the previously described embodiment, the simultaneous oxidation-ion exchange will be accomplished in accordance with techniques known in the prior art.

As indicated previously, the preferred cation or cations incorporated into the coal will depend upon the subsequent conversion process employed. For example, and as indicated previously, where the subsequent conversion is to be via gasification, alkali and alkaline earth metals will preferably be employed. Metals exhibiting hydrogenation activity, on the other hand, such as the noble and nonnoble transition metals and particularly the metals of Group VIII, will, generally, be used when the coal is subsequently converted via a liquefaction reaction.

In general, any of the gasification processes known in the prior art can be improved with respect to either yield, conversion rate or both when the catalyst distribution method of this invention is employed prior to effecting the gasification reaction. In general, these gasification processes comprise a step wherein coal is reacted with a gaseous species or a mixture of gaseous species at an elevated temperature, and, generally, an elevated pressure to produce other, more desirable gases. The gaseous species generally employed as reactants include oxygen, steam, carbon oxides such as carbon dioxide, and hydrogen. Generally, temperature, pressure, and flow rate in these processes as well as the mole ratio or relative ratio of reacting gases to coal will depend on the specific process employed and the actual products desired therefrom.In this regard, it should be noted that the composition of the gaseous products from these processes can also be altered by the particular catalyst employed. For example, and as is known in the prior art, the products resulting from the gasification of coal with steam can be enriched in methane through the use of an alkali metal that promotes the conversion of carbon monoxide and hydrogen to methane.

As previously indicated, the step of distributing catalysts uniformly throughout finely divided coal offers several advantages even when the thus treated coal is to be consumed in a combustion process. First, when an oxidation catalyst such as the noble metals of Group VIII is used, the combustion will proceed more rapidly to completion and, indeed, complete combustion would be effected at a lower temperature. Second, when the imparted cation reacts with sulfur dioxide and/or sulfur trioxide at the conditions of combustion a signficant portion of the sulfur contained in the coal will be removed, in the form of metal sulfates, sulfites and sulfides, generally remaining in the ash.The net results, then, would be to reduce nitrogen oxide and particulate emission to the atmosphere as a result of lower temperature or more complete combustion and to reduce sulfur oxide and sulfur trioxide emissions to the atmosphere as a result of the reaction with a cation.

As previously indicated, the method of distributing catalysts throughout coal can be used with equal advantage in any of the liquefaction processes known in the prior art. In general, these processes include processes wherein the coal is simply subjected to pyrolysis in the absence of air or oxygen, processes of this type where the coal is heated in the presence of hydrogen and processes wherein coal is liquefied in the presence of a solvent. In those processes where the coal is pyrolyzed either in the presence of an inert gas or in the presence of hydrogen, or carbon monoxide and hydrogen, contacting can be accomplished either in a fixed bed, a fluid bed, or in a slurry. A preferred pressure for that process is from 100 to 4000 psig.Generally, pyrolysis is effected at a temperature within the range from 350"C to 800"C. In those processes where a selective solvent is used any suitable liquid-solid contacting can be employed. In those processes wherein a carrier liquid or a solvent is used liquefaction is generally accomplished at a temperature within the range from 3500C to 5000C and the ratio of coal to liquid generally ranges from 1:1 to 1:4. The carrier liquid or solvent may or may not act as a hydrogen transferring medium. In those cases where the carrier liquid and/or the solvent acids as a hydrogen donor, the carrier liquid and/or solvent will, generally, be withdrawn from the liquefaction vessel and hydrogenated so as to restore the desired hydrogen content.Such hydrogenation will, of course, be accomplished in accordance with techniques well known in the prior art. Such a process is described in U.S. Patent Number 3,617,513.

In those processes wherein liquefaction is accomplished by pyrolysis of the coal at a temperature within the range from 350"C to 8000C and in the absence of air or oxygen, it has been found that when the coal is first pretreated in accordance with the method of this invention, the alkali metals and the alkaline earth metals will catalyze the liquefaction reaction and enhance the production of the more desirable lower molecular weight liquids in comparison to the higher molecular weight tars produced by pyrolyzing untreated coals. In those processes where liquefaction is accomplished in the presence of hydrogen, it has been found that both reaction rate and liquid yields will be improved when any metal known to exhibit hydrogenation activity is incorporated into the coal by the distribution step of the process of the present invention.In liquefaction processes of this type, the non-noble transition metals and particularly the non-noble transition metals of the eighth period of the Periodic Table of the Elements have been most effective and are, therefore, preferred. Of these metals, zinc, iron, cobalt and nickel have been found to be most effective and are, therefore, most preferred.

A still further advantage of the present invention is realized in both gasification and liquefaction processes wherein the coal is rapidly heated in a gaseous medium or in a vacuum and wherein the coal particles have been previously treated such that a cation is uniformly distributed therethrough. In this regard, it should be noted that untreated coals of bituminous rank generally soften and swell to a plastic consistency when heated in this manner and often adhere to each other or to the walls of the reactor system. This sticking or adhering tendency is, however, significantly reduced or eliminated when the coal has been pretreated so as to contain a uniformly distributed cation by the method of this invention. This advantage is particularly pronounced when the cation incorporated into the coal is selected from the alkali and alkaline earth metals.

In a preferred embodiment of the present invention, a higher ranking coal; i.e..

a coal containing less oxygen in an active form than would be required to impart from 2 to 10 Wt% calcium ion, will be oxidized with air such that its oxygen content is increased by from 1 to 10% (based on wt of the coal) and such that the resulting oxidized coal will contain between 10 and 20 Wt% oxygen and sufficient active sites to impart between 1x10-3 and 5x10-3 gram atoms equivalents of a metallic cation per gram of coal, the thus oxidized coal will be ion exchanged with an alkali or alkaline earth metal cation and then subjected to gasification. In the preferred embodiment, the air oxidation of the coal will be accomplished in a fluid bed at a temperature within the range from 175 to 300"C and with an air flow rate within the range from 20 to 10,000 V/VHr.The ion exchange will be accomplished either with the hydroxide of the desired alkali or alkaline earth metal or a suitable salt thereof.

Alternately, the ion exchange could be accomplished by first contacting the oxidized coal with sodium hydroxide or other suitable sodium salt and thereafter completely exchanging the sodium ion imparted into the coal with the desired alkali or alkaline earth metal ion. The second ion exchange will also be accomplished either with the hydroxide of the desired alkali or alkaline earth metal or a suitable salt thereof. Generally, both ion exchanges will be accomplished at a temperature within the range from 18"C to 110"C and at a pH within the range from 7 to 14. In those cases where sodium or potassium is the desired cation to be distributed throughout the coal the hydroxide could be used and the second exchange will, of course, not be necessary.Sodium or potassium will be most preferred when maximum methane production from gasification by steam is desired. Calcium, on the other hand, will be most preferred when production of carbon monoxide and hydrogen by steam gasification is desired.

In the preferred embodiment, gasification of the thus treated coal will be accomplished by contacting the coal with steam at a temperature within the range 400"C to 10000C. Preferably the steam flow-rate will be within the range 0.2 to 50 W/W/Hr. It is further preferred that hydrogen is also employed, and at a flow rate of 0.2 to 50 W/W/Hr. In general, essentially any pressure could be used during this contacting, but pressures within the range from 0 to 1000 psig are most preferred.

Having thus broadly described the present invention and set forth a preferred embodiment thereof, it is believed that the same will become even more apparent by reference to the following examples. These examples are, however, intended solely for the purpose of illustration; Examples 1 to 3 relating only to the oxidation and ion exchange steps, and Example 4 relating to a gasification process in accordance with the invention.

EXAMPLE 1 In this example, two 15-gram samples of a bituminous rank coal from Illinois were oxidized with air and then ion-exchanged with sodium hydroxide so as to distribute sodium cation uniformly through the coal. Prior to oxidation, the coal was ground to a particle size range ranging from 0.15 mm to 0.59 mm. Both oxidations were accomplished at a temperature of 200--230"C and the holding time was varied to produce a product having different oxygen contents. The coal was maintained in a fluidized state during oxidation. Before oxidation, the coal contained 14 Wtoo oxygen. After oxidation, the first sample contained about 17.5 Wt o oxygen and the second sample contained above 18.0 Wt ó oxygen.Following oxidation. the oxidized coal samples were placed in an aqueous solution of sodium hydroxide and allowed to remain in this solution for several days. The ion exchange was accomplished at room temperature (Ca 18"C). The samples were then washed with pure water for several days so as to ensure complete removal of any sodium cations not actually exchanged with the coal. The ion exchanged coal samples were then analyzed to determine cation content. The results obtained are summarized in the following table which also includes the results obtained with an unoxidized coal identical to that used in this sample.

Increased Oxygen Sodium Cation Content, Wt ó Wt% 0 1.9 3.5 5.8 4.0 6.3 As will be readily apparent from the foregoing, the maximum amount of sodium cation which can be incorporated into the coal at the ion exchange conditions employed. increased with increasing oxygen content.

EXAMPLE 2 In this example. the procedure of Example 1 was repeated except that ion exchange was accomplished with potassium hydroxide rather than sodium hydroxide. Also, five samples of coal identical to that used in Example 1 were oxidized to different oxygen levels instead ofjust two. The final oxygen content and the amount of potassium ion incorporated into the coal are summarized in the table set forth below. For purposes of comparison, the amount of potassium incorporated via the same ion exchange techniques into an unoxidized coal is also included in the table.

Increased Oxygen Potassium Cation Content, Wt% Wt% 0 4.0 1.3 5.5 3.5 6.2 3.8 7.2 4.8 8.9 7.4 11.2 From the foregoing, it will again be apparent that the maximum amount of potassium incorporated into the coal at the ion exchange conditions employed increased significantly with increased oxygen content.

EXAMPLE 3 In this example, the procedure of Example 1 was repeated except that ion exchange was accomplished with calcium hydroxide rather than sodium hydroxide.

Also, eight samples of coal identical to that used in Example 1 were oxidized to different oxygen levels instead of just two. The final oxygen content and the amount of calcium ion incorporated into the coal are summarized in the table set forth below. For purposes of comparison, the amount of calcium incorporated via the same ion exchange techniques into an unoxidized coal is also included in the table.

Increased Oxygen Calcium Cation Content Wt ó Wt% 0 1.0 0.8 1.3 1.3 1.5 1.9 1.7 2.7 4.0 3.2 3.1 3.8 3.9 5.4 4.0 7.4 4.7 As again will be apparent from the foregoing the maximum amount of calcium incorporated into the coal generally increased as the oxygen content increased.

The variations indicated as oxygen content increased are, of course, within experimental error.

EXAMPLE 4 In this example, a series of coking-gasification tests were completed with ion exchange coals prepared in accordance with techniques described in Examples 1- 3. For purposes of comparision, identical runs were also made with coal samples identical to those used in Examples 1--3, which contain sodium carbonate or potassium carbonate in physical admixture therewith rather than by ion exchange.

In all runs, the coking-gasification was accomplished with steam at a flow rate of about 50 W/W/Hr at a temperature of 760"C and at atmospheric pressure. The results obtained at different cation concentrations are summarized in a table set forth below. For convenience, the results are compared on the basis of the reaction rate at 50% conversion and the rate is expressed as percent initial carbon converted per hour. For reference purposes, the method by which the ion was incorporated into the coal is also set forth in the table.

Atoms Cation/ Atoms Carbon Method of Gasification Cation In Coke Incorporation Rate Na 0.017 ion exchange 120 Na 0.021 ion exchange 250 Na 0.054 ion exchange 375 Na 0.095 ion exchange 420 K 0.048 ion exchange 430 K 0.071 ion exchange 605 Ca 0.015 ion exchange 150 Ca 0.047 ion exchange 595 Na 0.019 Physical Admixture 34 Na 0.028 Physical Admixture 94 K 0.018 Physical Admixture 119 K 0.028 Physical Admixture 214 Ca 0.018 Physical Admixture 17 None - None 10 The data clearly indicate that the gasification rate is significantly increased with increased concentration of both alkali and alkaline earth metal cations. The data also show that calcium, which is known to be relatively non-catalytic when incorporated by physical admixture, becomes quite active, catalytically, when the same is incorporated via ion exchange.This discovery is, of course, quite surprising. The data also show that when the cations are incorporated via ion exchange, even with the alkali metal cations that do impart catalytic activity when physically admixed, the catalytic activity is improved.

WHAT WE CLAIM IS: 1. A method of liquefying or gasifying a coal, comprising the steps of: (A) oxidizing the coal, in finely divided coal form, at a temperature below the combustion temperature to an extent sufficient to increase the oxygen content of the coal by from 1 to 10 wt % based on the weight of the coal; (B) ion exchanging the thus oxidized coal with a metal cation; and (C) subjecting the exchanged coal to liquefaction or gasification conditions.

2. A method according to Claim 1, wherein the ion exchange is accomplished with a metal hydroxide.

3. A method according to claim 1, wherein the ion exchange is accomplished with a metal salt.

4. A method according to any preceding claim, wherein the ion exchange is effected at a pH in the range 7 to 14.

5. A method according to any preceding claim, wherein the ion exchange step is conducted so as to incorporate from 5x 10-4 to 8x 10-3 gram atomic equivalents of cation per gram of coal.

6. A method according to any preceding claim, wherein the ion exchange is accomplished simultaneously with the oxidation step.

7. A method according to any one of claims 1 to 5, wherein the ion exchange is accomplished subsequent to the oxidation step.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (19)

**WARNING** start of CLMS field may overlap end of DESC **. As again will be apparent from the foregoing the maximum amount of calcium incorporated into the coal generally increased as the oxygen content increased. The variations indicated as oxygen content increased are, of course, within experimental error. EXAMPLE 4 In this example, a series of coking-gasification tests were completed with ion exchange coals prepared in accordance with techniques described in Examples 1- 3. For purposes of comparision, identical runs were also made with coal samples identical to those used in Examples 1--3, which contain sodium carbonate or potassium carbonate in physical admixture therewith rather than by ion exchange. In all runs, the coking-gasification was accomplished with steam at a flow rate of about 50 W/W/Hr at a temperature of 760"C and at atmospheric pressure. The results obtained at different cation concentrations are summarized in a table set forth below. For convenience, the results are compared on the basis of the reaction rate at 50% conversion and the rate is expressed as percent initial carbon converted per hour. For reference purposes, the method by which the ion was incorporated into the coal is also set forth in the table. Atoms Cation/ Atoms Carbon Method of Gasification Cation In Coke Incorporation Rate Na 0.017 ion exchange 120 Na 0.021 ion exchange 250 Na 0.054 ion exchange 375 Na 0.095 ion exchange 420 K 0.048 ion exchange 430 K 0.071 ion exchange 605 Ca 0.015 ion exchange 150 Ca 0.047 ion exchange 595 Na 0.019 Physical Admixture 34 Na 0.028 Physical Admixture 94 K 0.018 Physical Admixture 119 K 0.028 Physical Admixture 214 Ca 0.018 Physical Admixture 17 None - None 10 The data clearly indicate that the gasification rate is significantly increased with increased concentration of both alkali and alkaline earth metal cations. The data also show that calcium, which is known to be relatively non-catalytic when incorporated by physical admixture, becomes quite active, catalytically, when the same is incorporated via ion exchange.This discovery is, of course, quite surprising. The data also show that when the cations are incorporated via ion exchange, even with the alkali metal cations that do impart catalytic activity when physically admixed, the catalytic activity is improved. WHAT WE CLAIM IS:

1. A method of liquefying or gasifying a coal, comprising the steps of: (A) oxidizing the coal, in finely divided coal form, at a temperature below the combustion temperature to an extent sufficient to increase the oxygen content of the coal by from 1 to 10 wt % based on the weight of the coal; (B) ion exchanging the thus oxidized coal with a metal cation; and (C) subjecting the exchanged coal to liquefaction or gasification conditions.

2. A method according to Claim 1, wherein the ion exchange is accomplished with a metal hydroxide.

3. A method according to claim 1, wherein the ion exchange is accomplished with a metal salt.

4. A method according to any preceding claim, wherein the ion exchange is effected at a pH in the range 7 to 14.

5. A method according to any preceding claim, wherein the ion exchange step is conducted so as to incorporate from 5x 10-4 to 8x 10-3 gram atomic equivalents of cation per gram of coal.

6. A method according to any preceding claim, wherein the ion exchange is accomplished simultaneously with the oxidation step.

7. A method according to any one of claims 1 to 5, wherein the ion exchange is accomplished subsequent to the oxidation step.

8. A method according to any preceding claim, wherein step (C) comprises

gasifying the ion exchanged coal at a temperature in the range 400 to 1000 C.

9. A method according to Claim 8, wherein the gasification is accomplished in the presence of steam at a flow rate in the range 0.2 to 50 W/W/Hr.

10. A method according to Claim 8 or Claim 9, wherein the gasification is accomplished in the presence of hydrogen at a flow rate in the range 0.2 to 50 W/W/Hr.

11. A method according to any preceding claim, wherein the metal cation is selected from alkali metal ions and alkaline earth metal ions.

12. A method according to any one of claims 1 to 7, wherein the metal cation is a transition metal cation.

13. A method according to any one of claims 1 to 7 or claim 1-2, wherein step (C) comprises liquefying the ion exchanged coal at a temperature in the range 350"C to 8000C.

14. A method according to claim 13, wherein the liquefaction is accomplished in the presence of a slurrying hydrocarbon liquid in the range 1 to 4 W/W.

15. A method according to Claim 13 or Claim 14, wherein the liquefaction is accomplished in the presence of hydrogen, or carbon monoxide and hydrogen, at a pressure in the range 100 to 4000 psig.

16. A method according to any preceding claim, wherein the coal is a bituminous or subbituminous coal.

17. A method of liquefying or gasifying a coal according to claim 1 and substantially as herein described.

18. A method of gasifying a coal according to Claim 1 and substantially as hereinbefore described with reference to Example 4.

19. Coal liquefaction or gasification products whenever made by the method of any preceding claim.