GB2086414A - Hydrotreating of Carbonaceous Materials - Google Patents

Abstract

Coal, peat or wood is converted to liquid and gaseous hydrocarbons by reaction with an alkali metal sulfide, polysulfide and/or hydrosulfide, in the presence of water, steam and/or hydrogen sulfide at 50-450 DEG C.

Description

SPECIFICATION Hydrotreating of Carbonaceous Materials This invention relates to a process for hydrotreating carbonaceous materials and particularly to a process for the conversion of such materials to gaseous hydrocarbons, volatile distillates or mixtures thereof.

The application discloses further, highly beneficial developments of a process first disclosed in my United States Patent Application Serial No. 063,824 filed August 6, 1979; United States Patent Application Serial No. 114,207 filed January 22nod,1980; United States Patent Application Serial No.

140,604 filed April 15th, 1980 and UK Patent Application No. 8024908 (Serial No. 2,055,892). The specifications of the first two of the above-mentioned United States Patent Applications are open to public inspection in the file of published UK Patent Application No. 8024908. A copy of the specification of Serial No. 140,604 accompanies the present specification and is marked Appendix A.

In my first filed U.S. Patent Application, I disclosed a method for preparing an alkali metal reagent and a reaction based on this reagent with oxygen, nitrogen and sulfur in coal.

In U.S. Patent Application Serial No. 114,207, 1 disclose the utilization of the method disclosed in the first filed application on coals of various rank and peat and the use of water or steam in the process which may be practiced batchwise or continuously. U.S. Patent Application Serial No. 114,207 contains also a disclosure for varying the conditions so as to obtain a product mix by use of different temperatures, reagents, rank of coal as well as reaction stages. Further, in U.S. Patent Application Serial No. 114,207, I disclose addition of sulfur to stabilize a reagent as a less hydrolyzed polysulfide.

In U.S. Patent Application Serial No. 140,604, (on which the present application is in part, based) I disclose a number of methods for preparing reagents, the stabilization of these reagents by employing hydrogen sulfide in hydrotreating carbonaceous materials and stagewise reactions. I have now found that besides stabilization of the reagent, for coals and peat, the addition of hydrogen sulfide surprisingly provides heretofore unknown, further benefits based on the difference in the chemistry of coals or peat as distinguished from the carbonaceous materials disclosed in that application. Parts of the subjectmatter of U.S. Patent Application Serial No. 140,604 are described and claimed in my copending UK Patent Application No. and filed today.

This invention incorporates further developments in the inventions disclosed in the above applications and relates to conversion of coal and other carbonaceous materials to various useful component parts thereof, either, principally gaseous component parts or various proportions of gaseous and liquid component parts, including substantially liquid products with appropriate recovery of reagent and hydrogen sulfide being provided as part of the conversion process.This invention further describes conversion of these gaseous components into other distillates; more particularly, this invention relates to the conversion of coal and other carbonaceous materials to desired conversion products thereof such as hydrocarbons in liquid or gaseous form by reacting coal in one or more stages with a particular reagent therefor, which may be the same or different for each of the stages, but in each stage, the reagent is in the presence of water or steam, and hydrogen sulfide. The process is conducted at a iow to moderate temperature and between atmospheric pressure and pressure less than 5 psig.

Still further, this invention relates to conversion of coal and other carbonaceous materials to various preselected component cuts thereof, either principally gaseous component parts, gaseous and liquid components or principally liquid components by means of specific reagents, whereby coal or peat, in the presence of this reagent, water, steam, and hydrogen sulfide, and optionally sulfur, is converted into useful breakdown materials of coal or peat. These breakdown materials are either principally gaseous hydrocarbons obtained in a single stage reaction or principally liquid hydrocarbons obtained in a single stage, or the gaseous and light liquid products ("light" means low boiling point liquid), from a single stage. These products may be further reacted in one or more additional stages in presence of different reagents, steam and hydrogen sulfide to obtain liquid distillates.Ultimately, at the high temperatures, coal in the presence of the reagent, hydrogen sulfide, and steam, causes production of some hydrogen.

Background of the Invention It has become increasingly evident that liquid and gaseous hydrocarbon sources such as petroleum and natural gas are being depleted at such rapid rate than an intensive effort is needed to meet anticipated future needs for obtaining substitute energy, feedstock, or chemical starting materials. One of the most readily available sources of hydrocarbon materials is coal. Heretofore, there has been no ready means, without extensive capital investment on economically justifiable basis, to produce hydrocarbons from coal.Although various processes are known for conversion of coal at high temperatures, such as high temperature i.e. above 6000 C, high pressure e.g. above 25 atmospheres coal gasification, there has been no readily available lower-temperature, low-pressure process which would readily convert coal into its component hydrocarbons.

It has now been found that when coal or other carbonaceous materials is treated with a particular reagent, it can be converted in the presence of this reagent and in the presence of water and/or steam and hydrogen sulfide to various hydrocarbon fractions either principally gaseous hydrocarbon fractions of one to five carbon atoms (C to C5), e.g., methane, ethane, ethene, etc., or principally liquid distillates or in a ratio which is for practical purposes between these limits. Hydrogen is also co-produced.

Thus according to the present invention, there is provided a process for conversion of coal or peat to gaseous hydrocarbons or volatile distillates or mixtures of these by reacting coal or peat and, as a reagent, a hydrosulfide, a sulfide or a polysulfide of an alkali metal or mixtures thereof characterized by the fact that a conversion reaction is carried out in presence of water or hydrogen sulfide and optionally sulfur at a temperature between 500C and up to 4500C in one or more stages wherein the temperatures in each stage may be the same or different and the reagent may be the same or different based on sulfur content of the reagent and recovering volatile liquid distillates and hydrocarbon gases.

At higher temperatures, more or principally gaseous hydrocarbons will be produced; moreover when using a different reagent in another reactor the gaseous hydrocarbons in the presence of steam and hydrogen sulfide may be further reacted to obtain different hydrocarbons such as liquid or gaseous hydrocarbons. It has also been discovered that by changing the reagent and using apparently anhydrous and eutectic mixtures of sulfides as further explained herein the above conditions may be reversed.

Further, it has been surprisingly found that hydrogen sulfide addition is considerably more beneficial than sulfur addition disclosed in my prior application because hydrogen sulfide stabilizes the reagent more effectively, and helps in conversion of the thiosulfate or the tetrathionate (and 2e) such that 2 thiosulfate ions are formed. ("2e" denotes two electrons).

There is some breakdown of KHS to K2S in the presence of water. This breakdown is partial.

Hence, in hydrogenating coal, both KHS and K2S should be present in the reaction. When sulfur is added, a less hydrolyzed, and therefore, a more water-stable polysulfide e.g. potassium pentasulfide is also provided. Hydrogen sulfide not only improves the stabilization, but decreases the amount of reagent needed.

It has further been found that when mixtures of alkali sulfides are reacted these may be added in liquid state to coal to facilitate the reaction, e.g., such as mixtures of polysulfides or hydrates thereof.

When the K2S and various polysulfide species thereof, react with coal, these preferentially attack the oxygen, sulfur and nitrogen present in coal in a bound form to withdraw or abstract these components of coal. As derivative hydrocarbon components are forming in the presence of reagent steam or water, and hydrogen sulfide, the bond scission of the various coal constituent parts and abstraction of oxygen, nitrogen and sulfur, allow the introduction of hydrogen from water or hydrogen sulfide and thus the formation of hydroaromatic, aromatic and shorter chain aliphatic compounds. The severity of attack can be tailored from where the product is essentially gas to where the product is essentially liquid, based on the reagent(s) employed and the operating conditions.

In order to illustrate further the present invention, a drawing is presented wherein: Figure 1 illustrates, schematically, hydrogen sulfide recovery from a gaseous value recovery train.

In the process, once the desired operating temperature is reached and hydrogen sulfide or steam and hydrogen sulfide is being introduced into the system, an inert gas such as nitrogen or helium, first used to purge the system of oxygen, may no longer be needed. Hydrogen sulfide may be introduced through the steam line.

In Figure 1, a schematic illustration of a hydrogen sulfide gas recovery is provided. A reactor 22, typically at 3500C to 3900C has been charged with coal, a reagent in liquid form, water, in the form of steam, and hydrogen sulfide gas. A cooling jacket 24, surrounding the condenser 26 facilitates the cooling of the reaction gases. The initial and heavier products are recovered from condenser bottoms 27. The gaseous products are sent on to vessel 30 in which water and alkanol (typically methane or ethane) are held. Vessel 30 receives water or alkanol from the reactor when alkanol solubilized reagent is used. The mixture of water and alcohol in vessel 30 is kept below the boiling point of the mixture and thus the lighter gases pass through such as the C1 to C5 including hydrogen sulfide.

In vessel 31 the contents are cooled to about -350C at which temperature liquid C4 and C5 are removed. While most of C4 and C5 fractions are removed in vessel 31, some still are carried over to vessel 32 where these are removed at -300C with the C3 fraction in ethanol or methanol. A fritted glass disk 33 removes any residual mist of these components. At this state substantially only H2S and Ct and C2 fractions are present in the gas stream which is then introduced into vessel containing KOH and alcohol, typically ethanol or methanol in water solution. Hydrogen sulfide therein reconstitutes the reagent, which is recovered as a precipitate, while the light fraction gases predominantly C, and C2 pass. About 97% and more of H2S is recovered as a reagent component and may be reused. No H2S is vented to air. The alcohol-water fraction from vessel 30 is used to replenish the alcohol dragged out from vessel 35. However, this mixture must be cooled in heat exchanger 36.

As mentioned before, hydrogen sulfide may be introduced in the reactor as a separate stream or with steam. When it is introduced with steam it is at a point, i.e., at about 1 350C and above, but at 170--1900C when steam is used typically hydrogen sulfide is introduced with steam. Steam is not introduced into the reaction vessel until a methanol-water mixture used for introducing the reagent has been expelled because the water-methanol mixture will hold the temperature at a specific temperature range during this distillation. Hydrogen sulfide is present from the beginning of the reaction.

After the introduction of the steam or the steam and continuing hydrogen sulfide introduction, various lignites, and sub-bituminous coals, based on the inherent makeup of these, display different distillation points in the production of sizable amounts of gaseous hydrocarbon.

The gas production increases substantially when 3600C is reached and when the final temperature is between 3800C and 4500C a very rapid gas production is encountered with some hydrogen being produced. At a temperature of 360 to 3800C carbonyl sulfide is also produced. In subbituminous coal e.g. 4.7% by weight of the total hydrocarbon gas may be carbonyl sulfide. When hydrogen sulfide is used carbonyl sulfide production appears to be suppressed, all other conditions being equal.

Without being bound to any particular theory, the reactions, via the water and hydrogen sulfide molecules, provides hydrogen to react with coal at the point where coal is being deoxygenated, desulfurized or denitrogenated. Hence, for practice of this invention, it is necessary that oxygen be present in coal but the benefit is also gained when sulfur and nitrogen is present in coal in a form such as an organic sulfur or organic nitrogen species. Moreover, higher rank coal, such as bituminous coal, may not as readily be converted to gaseous hydrocarbons although, as explained below, it still may be done when the reaction scheme is appropriately modified.

The present invention is further concerned preferably with lignite and sub-bituminous coal gasification, but all coals may be gasified or liquid products obtained therefrom; even wood in chip form may be gasified. Moreover, wood (cellulose, lignite, sugars, etc.) can be converted into gaseous or liquid products.

An anthracite coal of 92% carbon content when it is partially oxidized, can be readily converted into liquid and gaseous reaction products.

If potassium in coal ash is converted to hydrosulfide, no loss of potassium hydrosulfide is experienced; and the reagent balance for the reaction, on batch or continuous basis, is very favorable.

Moreover, with hydrogen sulfide stabilization of the reagent, the amount of reagent used may be decreased and excess sulfur and potassium from coal utilized, e.g., for reagent or hydrogen sulfide production.

In general, it is emphasized that sufficient amounts of sulfur hydrogen sulfide, hydrosulfide or polysulfide should be present to take up the sulfur expelled from the reagent or to take up oxygen or sulfur in coal during deoxygenation thereby preventing the expelled sulfur from dehydrogenating the coal at a temperature above 1 750C. Also, the integrity of the various reagent species must be preserved above 325"C since a temperature increase above this level will cause a slow dehydrogenation of coal by alkali metal hydroxide melt.As sulfur causes the formation of polysulfides and the alkali polysulfide is less hydrolyzed with increasing sulfur content thereof, the decomposition by steam (or other water) of the hydrolysis product, i.e., the hydrosulfide is thereby prevented: however, hydrogen sulfide addition accomplishes best the stabilization as further explained herein.

The hydrogen sulfide generated in the addition of the elemental sulfur to the alkanoic solution of alkali metal hydrosulfide and the reaction of the sulfur displaced by oxygen during the conversion of coal to hydrocarbon forms is used to form additional alkali metal hydrosulfide from the alkali metal hydroxide recycled in the process; but hydrogen sulfide is also introduced into the reactor(s) to stabilize the reagent and therefore may be in excess of the amount needed in the reaction.

Some of the potassium hydrosulfide is decomposed, following hydrolysis, into potassium hydroxide and hydrogen sulfide. This potassium hydroxide provides a medium at temperatures of 3600C and higher whereby the calcium carbonate of the limestone (in the ash content of coal) reacts with the potassium sulfate (from the reagent residue) to form calcium sulfate and a mixture of potassium hydroxide and potassium carbonate. The potassium content of the coal ash is also extracted in the hydroxide form.

As shown above, steam is employed at a temperature at which the reaction is sought to be conducted, i.e., depending on the type of coal and the decomposition levels of coal as well as the desired product. Water contained in coal is also a source of water and/or steam.

As the amount of sulfur content of the reagent is increased, i.e., from sulfur in coal, from the added elemental sulfur or from the hydrogen sulfide, the reaction temperature is lowered. For example, a reaction temperature of 3800C is lowered to 3500C, when, as an illustration, the sulfur balance is representative of a theoretical compound K2S3 produced and maintained during reaction conditions. A corollary of this phenomenon is that larger molecules are produced, for example, pentane, i.e., isopentane and pentane.

Further, rank of coal affects the distillate makeup, the higher the rank of coal, the higher the proportion of liquid distillates under equivalent conditions, e.g., when using the theoretical K2S3 compound at the same temperature conditions.

Of course, when the temperature is varied, the product composition changes. Moreover, as illustrated above, when the amount of sulfur in the reagent is changed, the product composition is also changed.

Thus, based on the above, one can vary temperature, sulfur content of reagent, employment of mixtures of reagents, e.g. liquid or dissolved forms thereof, rank of coal, and use a recycle of alcohol absorbed distillates to obtain the desired product cut.

The above described variations are within the following prescription: temperature up to 4250C to 4500C but distillation starts at 400 to 500 C; sulfur content in reagent (e.g., for potassium) K2S but the sulfur content may go up to K2S5; sulfur or hydrogen sulfide addition; mixtures of these reagents; liquid or solid state of reagents; contacting of a product stream with another composition of reagents, including hydrogen sulfide; and rank of coal (desirably in the lignite to bituminous coal range). When applied to anthracite, the results are less advantageous although a distillate may be obtained at +380"C and using a reagent such as K2S4. Partial oxidation of the high rank coal also helps.

Moreover, the amount of recycle may also be varied. Thus, up to about 2800C, the product composition can be forced towards a composition which is a liquid distillate of a boiling point below about 1 800C. At a reaction temperature up to about 31 00C paraffin distillates are formed when employing the above-described alcohol recycle to the reaction vessel. As before, and in this recycle condition, water, i.e., steam at a temperature of about 1350C (and above) and hydrogen sulfide must be present in order for the reaction to occur advantageously.

When starting the process at about ambient conditions (and raising the temperature), elemental sulfur or preferably hydrogen sulfide is added to coal or to the reagent to obtain the selected sulfur content for the reagent. At these conditions H2S formed in the system during the reaction of the sulfur and the reagent is removed from the gas stream and wash system to reconstitute the reagent as shown in Figure 1. As the temperature is being brought up, when steam is not used, any hydrogenation of coal that occurs is from the water content in coal or the reagent. At about 1 350C, steam may be added if light distillates are desired. Typically, steam is added, however, at about the temperature when a hydrate of the reagent starts reforming or reconstitutes itself to a lower hydrate thereof.For potassium based reagent, steam addition temperature is selected at about 1 700C.

In summary, as oxygen is removed as well as nitrogen and organic sulfur, water or, to a lesser extent, hydrogen sulfide (continually produced by contact between water and the reagents) yield hydrogen to the coal at the point where coal has been deoxygenated, desulfurized, or denitrogenated; nitrogen comes off principally as ammonia; the sulfur comes off to form an alkali (e.g. potassium) polysulfide and at lower temperatures forms a mercaptan with the alkanol solvent. Mercaptans are absorbed in alcohol and in the KOH-alcohol solution. This overall reaction proceeds through reduction of the hydrogen sulfide gas to sulfur and water, with subsequent reaction of the sulfur with the KOH to form the potassium thiosulfate and the potassium sulfide.The potassium sulfide can then acquire additional sulfur from hydrogen sulfide to form potassium polysulfide and are the reagents used in the reaction.

The hydrocarbon compositions i.e., gaseous fractions, obtained at different temperature levels, may be further treated such as in another reactor with other reagent composition, that is, one higher in sulfur content and at a lower temperature from that in the first stage where the reaction temperature is 3400C to 3900C, e.g., in the next stage the temperature may be 2800C to 3400C with increasing sulfur content in the reagent; in the third stage, the temperature may be 2250C to 2800C or 1 800C to 2250 C. As the dehydrogenation reaction is in competition with hydrogenation reaction, with increasing sulfur content in reagent and the presence of sulfur, this causes dehydrogenation of the product stream that is initially gaseous.This stream can then be treated to obtain the desired product composition, i.e., API Number, for a preselected product. In other words the initial gaseous products are reformed into products as dictated by the demand.

As mentioned before, the above process has been improved by the addition of hydrogen sulfide to the reagent during the coal or coal product hydrogenation stage. i.e., the alkali metal sulfides, mixtures of sulfides such as in their hydrated form etc. The hydrogen sulfide addition, apparently, keeps the selected reagent in a stable state so that a reaction once initiated with that particular reagent or reagent mixture will produce, with few variations, from the same source material, when keeping all other conditions constant, substantially the same products or mixtures of products.Consequently, proper stagewise arrangement of reagents, their compositions for each of the stages, temperature conditions and water addition will be further improved by the hydrogen sulfide addition to the above described process so that a greater range of products, selected product mixture and a more precise degree of hydrogenation (including dehydrogenation of a product stream(s), when desired), are now possible.

The appropriate alkali metal sulfides, mixtures of the sulfides, and mixtures of the foregoing sulfide(s) hydrates with hydrogen sulfide present give the desired reagent stability, and the selected product. When the reagent is thus properly maintained in the "active" reagent state by the addition of hydrogen sulfide, the benefits are: reduced amount of reagent, better yields, and better product control.

The reasons for the hydrogen sulfide addition follow from the illustrated reactions.

1. 4KOH+4H2Se4KHS+4H20 When coal derived sulfur is present then 2. 4S+6KoHoK2S2O3+2K2s+3H2o in turn 3. K2S203+3H2S4K2S5+3H20 the decomposition of K2S2 is as follows: 4. 4K2S2+8H2Oo4KOH+4KHS+4S+4H2O Hence, if H2 S is present, KOH is converted to KHS and if any KOH forms the thiosulfate, then the thiosulfate is converted to K2S5.

Further reactions are as follows: 5. K2S5oK2S4+S (above 3000C) 6. K2S4oK2S3+S (above 460"C) 7. KHS+K2S+3H2O3KOH+2H2S 8. K2S+H2OoKOH+KHS 9. KHS+H20oH2S+KOH 10. KHS+KOHoK2S xH2O (x can be, e.g., 2, 5, etc., depending on temperature).

Hence, enough H2S should be present to keep the reactions, by mass action, in a state, where the reagent is stable, i.e., sulfur is taken up either when freed from coal or from the reagent, and hydrogen sulfide keeps the reagent from hydrolyzing. Moreover, the thiosulfate generated by the oxygen present in coal is regenerated during the reaction to the desired K2S5 sulfate. Thus, the reagent is kept in the desired hydrolysis level by H2S.

Of the various reagents, the following are preferred because of stability and sulfur acquisition ability, KHS, NaHS, K2S, K2S2, K2S3; and of these1 the order of preference is as follows: K2S2, K2S and then K2S3. The other sulfides display instability at their melting points, e.g., Na2S2 at 445 OC, Na2S4 at 2750C; or give off sulfur at 760 mm, e.g., K2S5 at 3000C yields K2S4+S; K2S4 at 4600C yields K2S3+S; and K2S3 yields K2S2+S at 7800C.

Melting points of the alkali sulfides illustrated above are as follows: for K2S at 948 OC; K2S2 at 4700C;K2S3 at2790C (solidification point); K2S4 at 1450C; K2S5 at 2060C; K2S5 at 1900C.Melting points for mixtures of the sulfides (pure or eutectic mixtures) are as follows: for K2S-K2S2 it is 3500C; for K2S2-K2S3 it is 225 or; for K2S3-K2S4 it is about 1 1 OOC; for K2S4-K255 it is 1 C. Based on the various illustrations above, appropriate temperature conditions are selected as dictated by decomposition and/or melting point characteristics so as to allow the use of a solid reagent, or a stable liquid reagent such as for coating the coal. Of course, the various hydrates of the alkali sulfides have various melting and/or decomposition points which, of course, also holds true for the eutectic mixtures.

These temperature points may be readily established thermographically as it is well known to thsoe skilled in the art.

The coal conversion process proceeds without a reagent instability, i.e., alkali sulfide hydrate instability, because hydrogenation of coal is preferential to reagent decomposition and addition of hydrogen sulfide aids in the stabilization of the reagent. Moreover, while the reaction with coal will proceed with adequate amount of reagent present, the addition of hydrogen sulfide also decreases the amount of the reagent necessary because the reagent is in a more stable form, hence, the process is also improved on that basis. The use of hydrogen sulfide doubles at least the product recovery, all other conditions being the same.

In general, the hydrogen sulfide addition will be on a space time velocity basis and will be typically in a range from 40 to 1 20 ml/min/gal (about 10 ml/min/liter to 30 ml/min/liter) of reactor space with about 20 ml/min/liter being typical. Expressed on another basis, one half gram mole, and less of H2S is added for 1000 ml of water removed by the hydrogenation reaction. In describing the various sulfides and their decomposition temperatures including the reactiqns, my U.S. Patent 4,210,526 issued July 1, 1980 is relevant.

At peak operating temperature herein, e.g., 4500C, K2S5 will yield sulfur, (which is a useful phenomenon as has been explained herein in connection with dehydrogenation of further process streams). Inasmuch as the decomposition temperatures are lowered at lower pressures, the coal conversion at atmospheric pressure is entirely feasible, although some benefit is gained by operating at elevated pressures, e.g. above 5 atm., the added cost and other expenditures make this merely a less desired method of operating the coal conversion process. Hence, for practical purposes the variation of the pressure conditions can be from about 1/2 atmosphere to about 5 atmospheres, but the ambient atmospheric pressure is preferred.

Although the reaction mass of coal and reagent may be appropriately stirred, it is best to precoat coal with a reagent in the absence of oxygen, as oxygen has a tendency to destroy the reagent.

For this reason, it has also been found useful to employ a liquid or a dissolved reagent. Liquid, yet stable reagents may be employed for coating coal at or above the appropriate melting point of the selected reagent or the liquid eutectic mixture of these.

For example, a mixture of K2S3-K2S4 may be used above 1 00C in a liquid state to coat coal. As solvent for the above reagent, glycerol has been found to be very useful. Any solvent which will dissolve the sulfides and will not affect their activity may be employed. About 88 grams of KHS is solubilized to make a total of 200 ml glycerol solution. When the mixture is heated up to 1 750C (glycerol will decompose above 1 900C), H20 is driven off from the dissolved KHS mixture and the mixture will then contain K2S . xH2O. Oxygen is excluded also from this reaction mixture. This mixture can then be readily used for coating coal and thus serve as a reagent.

Inasmuch as the severity of the attack on sulfur, nitrogen and oxygen on coal is a function of the reactant composition and the amount thereof, the following points may be mentioned. Gaseous conversion of coal is accomplished when degradation, of coal, i.e., reagent attack thereon is most severe. Less severe degradation produces lighter distillates. At 1 750C,sulfur starts to dehydrogenate coal and therefor presence of sulfur is not desired for coal conversion. Therefore, a stable reagent is employed at those conditions. However, for reformation, i.e., dehydrogenation and reaction of dehydrogenated species with each other, that reaction is important as it allows preselected obtention of liquids of different boiling points (or preselected API number). Of course, coal derived gases are an ideal feedstock for reforming hydrocarbons.As mentioned above, the rank of coal also affects the reactions. For poorer coal, to achieve least degradation high sulfur content reagents are used. For more complete gasification, the amount of sulfur in the reagent is decreased, e.g., K2S is used, whereas K2S5 is used for less severe attack. This is especially true for peat when it was reacted with K2S5, it gave essentially naphthalene.

The above illustration of the process as well as the invention herein is described by reference to the examples which are not intended as a limitation of the invention, but rather as an illustration of an embodiment thereof.

Example 1 A reaction vessel of, 1 gallon capacity, is equipped with a steam line, a heating-cooling means, a thermocouple, stirrer, and an exit conduit for the reaction gases. Hydrogen sulfide is added with steam and it may also be added separately. The products are recovered in a condenser appropriately cooled while the gases are collected as previously illustrated in the Figures herein.

To 800 grams of Kentucky #g coal held under a helium gas blanket, in the described vessel, was added a liquid mixture of K2S3 and K2S. 5H2O. The added amount of the reagent mixture was 2 moles, i.e., one mole of each. One mole was K2S3 obtained from a mixture of K2S and K2S5 in a water solution adjusted to an empirical formula K2S3. Further, 4 grams of KOH was added, which serves to drive off NH3 at process conditions. The mixture was stirred so as to coat the coal particles with the reagent.

After this, steam was added together with H2S at 80 ml/min at a temperature of 500C. The reaction was exothermic and was not allowed to rise about 4500C but kept as much as possible at about 350 C to 3900C. Steam was added at 1 350C at a rate equivalent to hydrocarbon withdrawal or at 130% thereof, the recovered product was a clear amber red solution, which, when treated under same conditions with 19 gr of KHS, up to 2400 C, completely distilled to a water clear hydrocarbon liquid distillate (almost water clear hydrocarbon) and of a water like viscosity. A total of 324 ml of distillate was recovered including 12 liters (N.T.P.) of gas during the first reaction stage. The product analyzed as follows: Boiling Point Range 1 8O0F initial boiling point and 10%--4600F ioo4790F 30--4860F 40--4920F 500--5000F 60%--5080F 700/6--5220F 80%--5380F 900--5620F 95%--5920F 98.6%--6320F (1.4% Residue-heavy liquid) Example 2 In order to illustrate the efficacy of H2S addition, 110 grams of bituminous coal (on a dry ashless basis), was reacted with solid NaHS (technical grade), or KHS (in water solution), in a reaction vessel as previously described, with addition of H2S at 80 ml/min and 200 ml helium. Steam was added at a temperature above 1 370C at a rate from equal to 130% of hydrocarbon condensate removal. Addition of KOH, suppresses ammonia reactions within reactor and expels ammonia.The reaction becomes exothermic at 3900C. 252 liters of gas and 70 ml of liquid hydrocarbon condensate was obtained before the reaction run off exothermically above 39O0C.

When runs were made on lignite with and without HzS addition, the yields were more than doubled for the run with H2S addition. Another reagent was as illustrated in Example 1. The reaction also became exothermic above 3900 C.

About 3 moles of H2S per mole of K25203 formed is necessary. Further, about 48 grams of coal based oxygen is used up when one mole of K2S2o3 is formed.

About 42% of wood is oxygen and about 2% of anthracite is oxygen. Between these limits H2S is added based on the above reaction as a maximum, as there are other competing reactions. The above is a rough indication of the amount of H2S needed but in practice lesser amounts are used, e.g. due to the principal side reaction of diatomic hydrogen uniting with oxygen to form water.

When KHS and/or NaHS are used these produce copious amounts of gas, and the reaction becomes exothermic above 3900C. K2S2. 5H2O plus K2S (empirical, based on equal molar quantities of K2S. SH2O and K2S3) produces little gas and considerable amounts of liquid condensate, from the same source material, but the reaction is exothermic from inception, i.e. about 500C and the reaction seems to maintain itself at 390 C with little heat input. K2S2 (derived from a melt of K2S. 5H2O plus sulfur) mixed with an equal quantity of K2S (derived from hot KOH aqueous solution plus sulfur in a ratio of 6KOH+4S) as a reagent, produces liquid distillate and gas.The reaction becomes exothermic at 2400C when used on the same source material. In all three instances the source material was -200 mesh Kentucky No. 9 bituminous coal and the reaction condition were otherwise identical, i.e. steam, H2S, and helium were used as previously illustrated. The foregoing shows the possibilities of obtaining gas, gas and distillates, and substantially distillates, and moreover, shows the highly advantageous nature of the exothermic reactions. During these exothermic reactions, negligible amounts of CO and CO2 were formed. In the gas streams, after scrubbing, hydrogen sulfide was nondetectable. Apparently, no COS was formed.

The above is further illustrated by the following example.

Example 3 The following reagent was employed on Kentucky :29 coal: (1) K2S. 5H20+S- theoretically: K2S2 (K2S+K2S5) (2) Two layer (4S)x(0.83) (aqueous) +6KOH- of each (1) and (2) above, one half mole of each was used when making up the reagent.

The coal analysis is as follows: Tablet Untreated Kentucky 9 Coal: % As Recd % Dry Ultimate ofAsh Moisture 2.58 SiO2 54. 15% Ash 8.52 8.75 Awl203 24.79% Volatile 35.36 36.90 Fe2O3 13.72% Fixed Carbon 53.54 54.95 TiO2 1.69% Sulfur 2.62 2.69 CaO 0.72% Btu/lb 12952 13295 MgO 0.85% Btu/lb minus ash fraction 14569 Na2O 0.35% Carbon 71.60 73.50 K20 2.44% Hydrogen 4.87 5.00 Li2O 135 PPM Nitrogen 1.59 1.63 P205 0.38% Oxygen 8.22 8.43 SO4 0.77% Chlorides 0.22 0.23 Table II Product Recovered After Reaction:: Degrees API @600F 16.9 Specific Gravity @600F 0.9530 Sulfur% 0.17 BTU per pound 18145 BTU Per gallon 144089 Carbon 88.62 Hydrogen 10.19 Sulfur 0.17 Nitrogen 0.19 Oxygen 0.83 Table III Distillation Results of Product Shown in TABLE II: Initial Boiling Point 3420F 5% Recovery 440"F 10% Recovery 4860F 20% Recovery 4920F 30% Recovery 5100F 40% Recovery 5280F 50% Recovery 5380F 60% Recovery 5440F 70% Recovery 5780F 80% Recovery 6100F 90% Recovery 6700F 95% Recovery 7100F End Point 7100F % Recovered 96.0 % Residue 3.7 % Loss 0.3 Table IV Analysis of 0-50% Distillate Product:: Degrees API 0ì60 F 20.9 Specific Gravity @600F 0.9287 Sulfur% 0.15 BTU per pound 18691 BTU per gallon 144519 Carbon 87.17 Hydrogen 10.08 Sulfur 0.15 Nitrogen 0.18 Oxygen 2.42 Table V Analysis of 50% to End Point Distillate: Degrees API @600F 16.4 Specific Gravity @6O0F 0.9568 Sulfur % 0.14 BTU per pound 18550 BTU Per gallon 147788 Carbon 90.45% Hydrogen 8.47% Sulfur 0.14% Nitrogen 0.31% Oxygen 0.63% The above Example 3 illustrates typical upgrading of coal and conversion of same to liquid products.

It has been demonstrated above, that a readily available source of a great variety of hydrocarbons may be realized from coal by a very flexible process carried out at low temperature, low pressure and, under certain conditions, exothermically.

Claims (29)

Claims

1. A process for conversion of coal or peat to gaseous hydrocarbons or volatile distillates or mixtures of these by reacting coal or peat and, as a reagent, a hydrosulfide, a sulfide or a polysulfide of an alkali metal or mixtures thereof characterized by the fact that a conversion reaction is carried out in presence of water or hydrogen sulfide and optionally sulfur at a temperature between 50 OC and up to 4500C in one or more stages wherein the temperature in each stage may be the same or different and the reagent may be the same or different based on sulfur content of the reagent and recovering volatile liquid distillates and hydrocarbon gases.

2. A process for conversion of coal, peat, or wood to gaseous hydrocarbons or volatile distillates, mixtures of these by reacting coal, peat or wood and as a reagent, an alkanolic solution of an alkali metal hydrosulfide, a sulfide a polysulfide or mixtures thereof, characterized by the fact that a conversion reaction is carried out at a temperature of 500C and above, in the presence of water as water of hydration, water, or steam, with hydrogen sulfide being present, continuing said reaction in one or more stages at a temperature up to 4500C with the temperature being the same or different in each stage and the reagent being the same or different based on the sulfur content of the reagent, and further conducting said reaction at exothermic conditions, at least in the first stage and recovering volatile liquid distillates and hydrocarbon gases.

3. A process as claimed in claim 2, wherein elemental sulfur is added to an alkanolic solution of said alkali metal hydrosulfide.

4. A process as claimed in claim 1 or claim 2, wherein said alkali metal hydrosulfide is potassium hydrosulfide.

5. A process as claimed in claim 1 or claim 2, wherein said alkali metal sulfide is sodium hydrosulfide.

6. A process as claimed in claim 1 or claim 2, wherein said alkali metal hydrosulfide is a mixture of rubidium, potassium, and sodium hydrosulfides and sulfides.

7. A process according to any preceding claim, wherein hydrogen sulfide is recovered.

8. A process according to any preceding claim, wherein the coal is lignite coal.

9. A process according to any one of claims 1 to 7, wherein the coal is sub-lignite.

1 0. A process according to any one of claims 1 to 7, wherein the coal is anthracite coal, partially oxidized anthracite coal, bituminous or sub-bituminous coal.

11. A process according to any one of claims 1 to 7, wherein peat is reacted.

12. A process as claimed in any one of claims 1 to 3, wherein the alkali metal is potassium.

1 3. A process according to any preceding claim, wherein part of the distillate is treated in another stage with a reagent with higher sulfur content in the presence of hydrogen sulfide.

14. A process according to any preceding claim, wherein the reaction is conducted at a temperature between 1 350C and 4500C.

1 5. A process as defined in claim 14, wherein the reaction is conducted at a temperature between 1 700C and 3800C.

1 6. A continuous process for conversion of coal, peat, or wood to gaseous hydrocarbons and volatile distillates characterized by the fact that the coal, peat or wood is introduced continuously into a reaction zone, coated with a reagent, said zone being maintained above 500C and up to 4500C, said coal, peat or wood being treated to expel atmospheric oxygen, wherein as a reagent, are used a hydrosulfide, a sulfide or polysulfide of an alkali metal, or mixed alkali metals and mixtures of hydrosulfides, sulfides and polysulfides thereof so as to coat said coal, peat or wood; introducing hydrogen sulfide, water or steam, in at least one reaction zone at a temperature between 1 6O0C and up to 4500 C;; reacting continuously in at least one zone at a predetermined temperature and a predetermined reagent composition, said coal, peat or wood or decomposition products thereof with 1) a predetermined reagent as based on the sulfur content of said reagent, its hydrate form, or melting points of same, or 2) mixtures of said reagents, in the presence of said introduced water, steam or hydrogen sulfide; recovering volatile and/or gaseous products from said reaction zone; recovering hydrogen sulfide from said reaction zone; recovering coal, peat or wood ash from said reaction zone; recovering unreacted reagent in said coal, peat or wood ash and alkali metal values as alkali metal hydroxides;; reacting said alkali metal hydroxides with at least part of hydrogen sulfide given off during said reaction and reconstituting said reagent, and recovering hydrogen sulfide for supplying the same to the reaction; introducing a sufficient amount of said reconstituted reagent in said reaction zone so as to continue said reaction of coal, peat or wood or decomposition products thereof with said reagent.

1 7. A process as claimed in Claim 16, wherein a first reaction zone is maintained at a set, predetermined temperature for production of gaseous hydrocarbons.

1 8. A process as claimed in claim 16, wherein the reaction zone is maintained at a temperature suitable for recovery of a predetermined liquid hydrocarbon cut.

19. A process as claimed in any one of claims 16 to 18, wherein the gaseous hydrocarbon is treated in a second reaction zone with a different reagent to produce liquid distillates.

20. A process as claimed in any one of claims 1 6 to 19, wherein lignite coal is the coal being reacted.

21. A process as claimed in any one of claims 16 to 19, wherein anthracite coal or oxidized anthracite coal is reacted with said reagent.

22. A process as claimed in any one of claims 1 6 to 21, wherein potassium sulfide, potassium polysulfide, a potassium hydrosulfide or hydrates thereof, or a mixture of same is used as a reagent.

23. A process as claimed in any one of claims 1 6 to 22, wherein said reaction is exothermic in a first reaction zone.

24. A process as claimed in any one of claims 1 6 to 23, wherein the temperature in said reaction zone is in stages between 1 700C to 4500C.

25. A process as claimed in any one of claims 16 to 24, wherein said hydrocarbon product, in liquid or gaseous form, is treated in separate stages with said alkali reagent with increasing sulfur content of said reagent at discrete, decreasing temperature ranges below 4000C but at a temperature above 1000C.

26. A process as claimed in claim 25, wherein the gaseous hydrocarbon is scrubbed in an alkali metal hydroxide solution thereby removing hydrogen sulfide from said gaseous hydrocarbon as a reaction product with said alkali metal and further recovering said reagent for recycle of same.

27. A process as claimed in any one of claims 16 to 21, wherein as said reagent there is used a theoretical composition K2S3, on basis of material balance.

28. A process according to any one of claims 1,2 and 1 6 and substantially as hereinbefore described.

29. Gaseous hydrocarbons or volatile distillates whenever produced by a process according to any preceding claim.