|Publication number||US3143489 A|
|Publication date||Aug 4, 1964|
|Filing date||Nov 24, 1961|
|Priority date||Nov 24, 1961|
|Publication number||US 3143489 A, US 3143489A, US-A-3143489, US3143489 A, US3143489A|
|Original Assignee||Consolidation Coal Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Referenced by (19), Classifications (12)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Aug. 4, 1964 E. GoRlN PROCESS FOR MAKING LIQUID FUELS FROM COAL Filed NOV. 24, 1961 Immun United States Patent C) 3,143,489 PRCESS FR MAKING LIQUID FUELS FROM CGAL Everett Gerin, Pittsburgh, Pa., assigner to Consolidation Coal Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Nov. 24, 1961, Ser. No. 154,451 9 Claims. (Cl. 208-8) This invention relates lto a process for making liquid fuels from coal. More particularly, this invention relates to a process for making gasoline from coal at a cost which is equal to or less than the cost per gallon of similar gasoline made from petroleum (based on present coal and petroleum prices).
For many years investigators have been trying to develop commercially feasible processes for the production of hydrogen-enriched liquid fuels such as gasoline from materials other than petroleum. Inasmuch as coal is the most abundant natural energy supply (on a B.t.u. basis) in the United States, much of the research eort in this country to find a synthetic liquid fuel has been devoted to coal. Obviously, the importance of an economic process for producing gasoline from coal is immeasurable in terms of the national welfare and defense.
Coal is an ash-containing and hydrogen-deficient hydrocarbonaceous solid. By ash I mean metallic contaminants and the compounds of silica that are present in coal and coal-derived materials. In addition to containing ash, coal contains relatively large amounts of oxygen, sulfur, and nitrogen compounds which are undesirable in hydrogen-enriched liquid fuels such as gasoline. The most serious disadvantage of coal, however, particularly with regard to the production of liquid fuels therefrom, is the low hydrogen content of coal. For example, the hydrogen to carbon ratio (weight ratio) of a representative Pittsburgh seam bituminous coal is about 0.06 to 0.07, while the hydrogen to carbon ratio (weight ratio) of premium gasoline is about 0.14 to 0.18. It follows, therefore, that in any process for the production of liquid fuels from coal, it is necessary to raise the hydrogen to carbon ratio of the coal either by the direct addition of hydrogen or by the rejection of carbon or both.
Historically, only three processes to produce liquid fuels such as gasoline from coal have been tested commercially or semi-commercially to date. The oldest process is the hydrogenation process, that is, the Bergius Process. In the Bergius Process substantially all of the coal is liquefied (via hydrogenation) in the presence of a diluent hydrocarbon oil, hydrogen, and catalyst, under pressures up to 10,000 p.s.i.g. or higher. The eiuent hydrogenation product is subsequently treated with additional hydrogen to yield liquid fuels. A second process is the well-known Fischer-Tropsch Process wherein substantially all of the coal is gasied (via reaction with steam and oxygen). The raw synthesis gas is subsequently catalytically treated to yield liquid fuels. The third process is the Pott-Broche Process wherein substantially all of the coal is liquefied (via solvent extraction). I'he resulting coal extract is subsequently catalytically hydrogenated to yield liquid fuels. In spite of extensive research and development programs, however, none of the above processes are economically attractive for the production of liquid fuels from coal in the United States today.
If any one reason can be attributed for the failure to develop a commercially feasible coal-to-gasoline process in the United States, it is the erroneous belief that substantially all of the coal substance should be immediately converted (via either gasication or liquefaction) to an intermediate product such as coal extract, raw synthesis gas, etc. which is then upgraded to the desired liquid fuel.
Patented Aug. d, ifl
For example, in the Pott-Broche Process as close to 100 weight percent of the coal as possible is converted to coal extract. It was believed the resulting coal extract would be more amenable to subsequent catalytic hydrogenation than the original coal. Unfortunately, when substantially all of the coal is converted to extract, the resulting extract is as diflicult to hydrogenate as the coal. Moreover, the expense of extracting substantially all of the coal is economically prohibitive, as fully discussed in my copending application, Serial No. 61,518, filed October l0, 1960, now Patent No. 3,018,242 which is assigned to the assignee of the kpresent application.
I have found that liquid fuels such as gasoline can be economically obtained from coal if the coal is subjected to a partial conversion process. By this I mean a process wherein the coal and the intermediate coal-derived products are sequentially and incrementally upgraded in a series of process steps, each of which is designed to partially upgrade the particular feed material. It is surprising, in view of the number of process steps that are used in my partial conversion process, that the gasoline produced therefrom is less expensive than the gasoline produced via the aforementioned complete conversion processes, i.e., the Bergius, Fischer-Tropsch, and Pott- Broche Processes.
Accordingly, it is the primary object of this invention to provide an economic process for the production of synthetic liquid fuels from coal such that the resulting fuels can be marketed on a competitive basis with similar fuels produced from petroleum.
A further and more specific object of this invention is to provide an economic, commercially feasible process for the production of liquid fuels such as gasoline from coal by a series of sequential process steps, in each of which hydrogen is added or carbon is rejected, as the case may be, under the most etiicient conditions for obtaining a product which is most amenable to treatment in the succeeding process step. l
In accordance with my invention, a process is provided for the conversion of coal to synthetic liquid fuels which comprises a series of sequential, partial conversion steps, each of which is designed to effect most efficiently the incremental addition of hydrogen or the progressive rejection of carbon, as the case may be. In its broadest embodiment the process comprises:
(l) Coal extraction;
(2) Separation of extract from undissolved coal residue;
(3) A primary catalytic hydrocracking zone;
(4) Catalytic hydroiining; and
(5 A secondary catalytic hydrocracking zone.
In the foregoing listed steps, progressive, incremental addition of hydrogen is effected in the following generalized fashion. In the coal extraction step a small amount of hydrogen is added to the extraction zone either by the use of a hydrogen-transfer solvent or by the introduction of hydrogen gas or both. The purpose of this additional hydrogen is to permit the solvent extraction of up to weight percent of the MAF (MAF means moisture-free and ash-free) coal. It is obviously desirable (for economic reasons) to recover a major portion of the coal as coal extract. However, coal as such has limited solubility in those solvents which it is practical to use in this process, unless hydrogen is added to partially upgrade the coal. While larger addition of hydrogen will permit greater depths of extraction, I have found that as the depth of extraction exceeds 80 weight percent, the hydrogen addition required to exceed such depths becomes economically prohibitive, as further explained ereinafter.
The products of extraction are separated in the second step to yield extract and undissolved coal residue. Most of the ash in the feed coal, that is, 99 weight percent or more, is recovered with the residue. The extract is a solid at room temperature and contains very little (in general, less than about weight percent) material boiling below 400 C. The remainder of the extract is substantially non-distillable without decomposition.
Itis highly desirable that the extract be free of ash before it or its upgraded products are introduced into the hydrogenation zones, particularly the latter two hydrogenation zones. The presence of such ash constituents, even in amounts as small as hundredths of one percent, seriously affects the activity and selectivity of the catalysts in the three hydrogenation zones. Deashing can be effected in the separation zone, in a distinctly separate deashing zone, in the primary hydrocracking zone, or in all three of these zones, as will be more fully discussed later. For the moment, it is sufficient to point out that the ash that is left in the coal extract following separation from the residue is quite different in composition from that of the gross ash in the coal feedstock.
The function of the primary catalytic hydrocracking zone is to convert at least a portion of and preferably the major portion of the non-distillable coal extract to an ash-free, distillable hydrocarbonaceous liquid boiling below about 500 C. Generally the major portion of the distillable hydrocarbonaceous liquid boils in the range of 200 to 400 C. This partial upgrading treatment is carried out under relatively mild catalytic hydrogenation conditions which are particularly chosen so as to minimize gas and coke formation. These conditions, however, are not suiciently severe to yield a distillable product which is free of nitrogen, oxygen, and sulfur (i.e., N-O-S) compounds, or to yield a distillable product, the major'portion of which boils below about 200 C., that is, in the gasoline boiling range.
The function of the catalytic hydroiining zone is to remove substantially all of the N-O-S contaminants from the ash-free, distillable hydrocarbnaceous liquid fed thereto. lf desired, all of the distillable hydrocarbonaceous liquid obtained from the primary hydrocracking zone may be introduced into the hydroning zone; preferably, however, only the fraction boiling below about 400 C. is introduced therein. It is important to note that the hydroning treatment is designed primarily to remove N-OS contaminants from the feed material and is not designed to effect any major lowering of the boiling range of the feed material. For example, the major portion of the N.OS-free eluent hydroner products still boils above about 200 C., and generally in the range of 200 to 400 C.
The function of the secondary catalytic hydrocracking zone is to lower the boiling range of at least the higher boiling fraction of the euent hydroner products. This final, partial upgrading treatment is carried out under hydrogenation conditions and in the presence of an eficient cracking catalyst especially suite for such purpose. The selection of the optimum cracking catalyst in the secondary catalytic hydrocracking zone is permitted because of the previous removal of ash contaminants and N-OS contaminants and because of the previous conversion of the original non-distillable extract to substantially non-coking, distillable hydrocarbonaceous liquid. In general, the liquid fuel product from the secondary hydrocracking zone boils below 200 C., that is in the gasoline boiling range.
The foregoing has, of necessity, omitted many of the subsidiary features of my process. These will be discussed in the description of the preferred embodiment. The integration of these major and subsidiary features into the preferred embodiment of my coal-to-gasoline process makes it possible to produce for sale, at competitive prices, premuim grade gasoline having a leaded blending octane number in accordance with the research method (F1l-3 cc. TEL) of at least 100.
The use of the terms primary and secondary is 4 merely for convenience of reference and does not mean that the secondary hydrocracking Zone is subordinate to the primary hydrocracking ione.
For a better and more complete understanding of my invention, its objects and advantages, reference should be had to the following description and to the accompanying drawing which is a diagrammatic illustration of the preferred embodiment of the present invention.
PREFERRED EMBODIMENT The following, with reference to the drawing, is a description of the preferred embodiment of the present invention. The preferred embodiment comprises:
1) A solvent extraction zone 10 wherein the coal is extracted;
(2) A separation zone 20 wherein the extract is separately recovered from the residue;
(3) A carbonization zone 26 wherein the residue is carbonized to produce a liquid distillate and a solid hydrocarbonaceous solid product, referred to as char;
(4) A deashing zone 40 wherein at least a portion of the residual ash remaining in the extract subsequent to separation from the residue is removed;
(5) Three primary catalytic hydrocracking Zones 50 wherein the extract is converted to distillable hydrocarbonaceous liquid;
(6) A colring zone 68 wherein a portion of the uncon- Verted extract from the primary hydrocracking zones is coked to produce coke and a liquid distillate;
(7) A hydrofining zone 74 wherein N-O-S compounds are removed from distillable hydrocarbonaceous liquid; and
(8) A secondary catalytic hydrocrackinng zone 84 wherein high boiling N-O-S-free effluent hydrotiner products are converted to gasoline.
FEED COAL Any coal may be used in the process of my invention, non-limiting examples of which are lignite, bituminous coal, and sub-bituminous coal. Preferably, the coal fed to my process is one having a volatile matter content of at least 20 weight percent, for example, a high volatile bituminous coal such as Pittsburgh Seam coal. A typical composition of a Pittsburgh Seam coal suitable for use in the process of my invention is shown in Table I.
l MF means moisture-free.
The feed coal is preferably ground to a finely divided state, for example, minus 14 mesh Tyler Standard screen, and is freed of substantially all extraneous water before introduction into the process.
SOLVENT EXTRACTION ZONE Coal is introduced into a solvent extraction zone 10 via a conduit 12. Fresh hydrocarbonaceous solvent and recycle solvent are introduced into the extraction zone 10, via conduits 14 and 16, respectively. The coal and the solvent react therein to yield ythe desired coal extract.
The solvent extraction process may be any of the processes commonly used by those skilled in the art, e.g., com
tinuous, batch, countercurrent, or staged extraction, at a temperature in the range of 300 to 500 C., a pressure in the range of l to 6500 p.s.i.g., a residence time in the range of 1 to 120 minutes, a solvent to coal ratio of 0.5/ 1 to 4/1, and, if desired, in the presence of a catalyst and/or up to 50 standard cubic feet of hydrogen per pound of MAF coal.
Suitable solvents for the coal in the extraction step are polycyclic, aromatic hydrocarbons which are liquid under the temperature and pressure of extraction. Preferably, at least a portion of the aromatics are partially or completely hydrogenated. Mixtures of the above hydrocarbons are generally used and are derived from intermediate or final steps of the process of this invention, for exarnple, from the primary hydrocracking zone products or from the hydroiining zone products. Those hydrocarbons or mixtures thereof boiling between 260 and 425 C. are preferred. Examples of suitable solvents are tetrahydronaphthalene, decalin, biphenyl, methylnaphthalene, and dimethylnaphthalene. ther types of coal solvent such as oxygenated aromatic compounds may be added to the abovementioned types for special reasons, for example, to improve the solvent characteristics, but the resulting mixture should be predominantly of the types mentioned. Examples of additive oxygenated solvents are the phenolic compounds such as phenol, cresols, and xylenols.
A particularly preferred solvent is a portion of the product obtained from the primary catalytic hydrocracking zone. This solvent normally comprises a 325 to 425 fraction blended with some lower boiling material.
The coal and the solvent are maintained in intimate contact within the extraction Zone until the solvent has extracted, i.e., converted or dissolved, up to 80 Weight percent of the MAF feed coal. As previously mentioned, in order to attain the above depths of extraction, hydrogen must be added to the coal during extraction. I prefer to add the hydrogen by the use of a hydrogen-transfer solvent of the types described above.
I have found that at least 50 weight percent of the MAF coal must be extracted in order to attain economic extract yields. I have further found that if more than 80 weight percent of the MAF coal is extracted, the cost associated with the non-selective transfer of hydrogen that takes place at those depths becomes prohibitive, as further discussed in my copending application, Serial No. 61,518, supra. Thus, the amount of hydrogen which is added to the coal during extraction is only that amount which is necessary to accomplish the desired coal extraction, i.e., to dissolve up to 80 Weight percent and preferably to dissolve between 50 and 80 weight percent of the MAF coal.
Following extraction, the mixture of solvent, extract, and residue is conducted rapidly, so as to avoid cooling of the mixture, through a conduit 18 to a separation zone 20. Preferably, the separation zone 20 is a filtration Zone; however, if desired, a centrifuge, sedimentation zone, hydroclone and the like may be used. T he primary function of the separation zone 20 is to separate the undissolved coal residue from the coal extract. The secondary function of this separation zone is to separate a portion of the benzene-insoluble rich coal extract from the whole extract produced.
The feed coal contains about 13 weight percent ash. When the extraction products are separated, for example, by filtration, more than 99 weight percent of the total ash will remain with the residue. The remaining one percent, however, is of such a finely divided nature, or in fact soluble in the extract, that it can not be removed by filtration and thus passes with the extract (ltrate). As fully discussed in my copending application, Serial No. 81,177, tiled January 6,1961, now abandoned, which is assigned to the assignee of this application, I have found that the major portion of this so-called ltrable ash is associated with the benzene-insoluble rich extract material. Thus, while, if desired, all of the extract produced during extraction may be separately recovered from the residue in the separation zone and thereafter hydrogeneated, I prefer to remove a portion of the benzeneinsoluble rich extract from the Whole extract feed and thereby recover a benzene-soluble rich extract containing less than about 0.5 weight percent ash. This remaining ash in the benzene-soluble rich extract may be separated therefrom as hereinafter discussed. Furthermore, as discussed in my copending application, Serial No. 61,517, filed October 10, 1960, now Patent No. 3,018,241, which is assigned to the assignee of the present application, removing a benzene-insoluble rich extract fraction from the whole extract enhances the subsequent hydrogenation of the remaining benzene-soluble rich extract (coke yield and gas yield are lower). To accomplish this secondary function, i.e., separating a benzene-insoluble rich extract fraction from the Whole extract feed, I preferably maintain the temperature in the separation zone 20 below the temperature in the solvent extraction Zone 10. Thus, the benzene-insoluble rich fraction is precipitated onto the residue and recovered therewith, as further discussed in my copending application, Serial No. 61,517, supra.
The liquid extraction (filtrate), comprising recovered extract and solvent, are withdrawn from the separtion zone 20 via a conduit 22. The solid extraction products, comprising undissolved coal residue, ash, and precipitated extract, if any, are withdrawn via a conduit 24.
The extract produced during solvent extraction is sometimes hereinafter referred to as as extract yield. The recovered extract, which is the extract present in the liquid products (filtrate) recovered from the separation zone, is equal to the extract yield only if no extract is precipitated during the separation of the residue and the extract.
A typical coal extract, produced from a Pittsburgh Seam bituminous coal via solvent extraction with tetrahydronaphthalene solvent at 380 C., 600 p.s.i.g. and a soivent to coal ratio of 2/ 1, gives the following yields and analysis as shown in Table Il.
Table II [Analysis of recovered coal extract* separated from undissolved coal residue via filtration at 205 C.]
Yields: Wt. percent MAF coal Conversion 76.5 Extract Yield 68.3 Extract precipitate (during ltration) 8.3 Recovered extract 60.0
Ultimate Analysis (solvent free basis):
The recovered coal extract contained about 0.15 weight percent ash. f
CARBONIZATION ZONE The solid extraction products, after drying (not shown) to recover any occluded extraction solvent therefrom (the recovered solvent being recycled to the extraction zone 10) are instroduced via the conduit 24- into a conventional type low temperature carbonization zone 26.
The carbonization zone 26 is maintained at a temperature in the range of 4.25 to 760 C. Preferably, the Zone 26 is a fluidized low temperature carbonization Zone; however, if desired, other conventional devolatilization zones may be used e.g., a rotary kiln. Hydrocarbonaceous solids, i.e., char, are withdrawn from the zone 26 via a conduit 28, while a liquid distillate is withdrawn via a conduit 30. Preferably, the liquid distil- The liquid distillate usually contains some entrained Y vsolids from the low temperature carbonization zone. These solids are concentrated in the bottomsV fraction and are removed along with the coal residue in the separation zone 20. Y
DEASHING ZONE Returning to the recovered extract (the extract obtained from separation zone 20 via the conduit 22), the extract, prior to hydrogenation in the primary catalytic hydrocracking zone, is preferably treated in a deashing Zone 40 to remove any remaining ash contained therein. The presence of as little as 0.20 weight percent ash in the extract is sufficient to materially affect the activity and selectivity of hydrogenation catalyst, particularly aluminabased catalyst such as used in the primary catalytic hydrocracking zone. I have found that the particular ash constituents present in coal extract react with aluminabased catalyst under the elevated temperature and pressure conditions of hydrogenation to cause the surface of the catalyst particle to sinter. A relatively impervious lrn is formed at the catalyst surface which prevents contact of the extract with the interval catalytically active surface and pore area of the catalyst. The ash that remains in the extract may be removed, at least in part by chemical treatment, for example, with acids.
The following Table III is a comparison of the ash components present in the gross feed coal and the ash components present in a recovered extract (similar to the extract analyzed in Table Il) *Silicon is included although it is actually a non-metallic. element. TThe ignition loss is due to subsequent conversion of metal compounds gleasre stable at the ashing temperature of 11U0 F. to the corresponding The deashed extract is withdrawn from the deashing zone 40 via a conduit 42 and preferably introduced into a ash still 44 wherein at least a portion of the extraction solvent is separately recovered. The extraction solvent is recycled to the extraction zone via the conduit 16. Because hydrogen-transfer efliciency of recycle solvent is not as high as that of fresh solvent, it is undesirable to recycle to the extraction zone 10 all of the solvent recovered via the flash still 44. Thus, a portion of the recycle solvent stream is conducted via conduit 46 into the hydroning zone, as hereinafter discussed. The topped extract is withdrawn from the ash still 44 via a conduit 48.
PRIMARY HYDRGCRACKING ZONE Extract, which has preferably beenV deashed in the zone 40, is introduced via the conduit 48 into the first of a series of staged, dense bed, liquid phase uidized catalytic hydrocracking zones 50. For convenience purposes, three primary hydrocracking zones are shown; however, if desired, any number may be used. The operation and conditions of the liquid phase fluidized catalytic hydrocracking zone are fully described in my copending application, Serial No. 31,455, filed May 24, 1960, which is assigned to the assignee of the present application.
The extract, which as previously mentioned is substantially non-distillable without decomposition, is reacted with hydrogen in the presence of the uidized catalyst in the primary hydrocracking zones 50 under the following conditions:
Reactor temperature 410 to 475 C. Reactor pressure (total pressure) 2500 to 6000 p.s.i.g. Hydrogen feed rate 2000 to 42,000
s.c.f./bbl. feed. Liquid hourly space velocity (individual stage) 0.5 to 3.0 volume/ volume/hour.
Vaporous products, which are ash-free, are withdrawn from the zones 50 via the conduits 52 and conveyed via a common conduit 54 to a condenser (not shown) wherein non-condensable gases are separately recovered. The condensed Vaporous product, i.e., the ash-free, distillable hydrocarbonaceous liquid product, is then introduced into a fractionation zone 56, wherein it is fractionated to yield:
(l) A fraction boiling below 260 C. (withdrawn via a conduit 5S) which is subsequently catalytic-ally hydrolined;
(2) A fraction boiling between 260 and 325 C. (withdrawn via a conduit 60), the major portion of which is subsequently catalytically hydroned; and
(3) A fraction boiling above 325 C. (withdrawn via the conduit 14) which is introduced Vinto the extraction zone 10 as fresh solvent.
Preferably, a portion of the 260 to 325 C. fraction is conveyed via a conduit 62 and introduced into the extraction zone 1t) along with the +325 C. fraction, which usually boils below about 500 C. In some instances it may be desirable to further fractionate the +325 C. fraction such that only the 325 to 425 C. fraction is used as extraction solvent while the +425 C. bottoms are recycled to the primary hydrocracking zones 50 or to a coking zone as hereinafter discussed. Gbviously, many other variations in the above fractionation of the distillable hydrocarbonaceous liquid may be practiced by those skilled in the art. For example, all of the distillable liquid product may be hydrofined, in which case fresh extraction solvent would be recovered from the hydroner products.
To fully appreciate the present invention, it is important to understand that the non-distillable extract fed to the primary hydrocracking zones is only subjected to suicient hydrocracking therein to yield a distillable liquid product suitable for subsequent hydrofining. The distillable hydrocarbonaceous liquid product is not completely free of N-OS compounds, nor does a significant portion thereof boil in the gasoline boiling range, i.e., boil below about 200 C. Generally, the major portion of the distillable hydrocarbonaceous liquid boils in the range of 200 to 400 C.
Returning to the primary hydrocracking zones, the nonvaporized extract is withdrawn from each of the zones 50 (via a conduit 64) and then introduced into the following zones in succession. If desired, however, rather than introduce all of the unconverted extract into the next primary hydrocracking zone, a portion may be recycled to aid in maintaining the hydrocracking catalyst in a lluidized bed. The non-vaporized extract from the Il last primary hydrocracking zone is preferably recycled to the same zone. In order to prevent any ash build-up in the last primary hydrocracking zone, a portion of the recycle liquid may be conducted into the separation zone 29 wherein the ash will be removed with the residue.
Preferably, substantially all of the recovered extract is converted to the distillable hydrocarbonaceous liquid; however, if desired, a portion of the recycled unconverted extract may be coked, eg., in a delayed coker to yield a liquid distillate and coke. As shown in the drawing, a portion of the recycled unconverted extract is conveyed via a conduit 66 into any conventional type coking zone 68. Liquid distillate is recovered from the coking zone 68 via a conduit 70 and conveniently fractionated with the liquid distillate of carbonization in the fractionation zone 32. Coke is withdrawn from the coking zone 68 via a conduit 72.
In some instances it may be desirable to maintain the primary hydrccracking zones at different pressures and temperatures, for example, increasing the temperature and possibly the pressure in each succeeding stage. The catalyst may also be the same or different in each of the zones.
Instead of maintaining the catalyst in the form of a uidized bed in the zones 50, the catalyst may be maintained in the form of a fixed or gravitating bed. The catalyst may also be dispersed Nithin the extract in the form of a slurry and thence introduced into a slurry phase primary hydrocracking zone such that the catalyst is introduced into, maintained therein, and withdrawn therefrom, in the form of slurry or a suspensoid.
Numerous catalysts have been suggested for use in the hydrocracking of coal extract. In the patent literature alone, for example, can be found many combinations of a suliide or oxide of a metal belonging to Groups to 8 of the Periodic Chart. However, for the rst time, l have shown that coal extract can be hydrogenated in the presence of an active, supported, regenerable catalyst, specifically a catalyst comprising a mixture of a group 6B oxide or sulfide with a group 8 metal. The main reasons for my success in contrast to the failures of others are that I particularly limit the depth to which the coal is extracted in the solvent extraction zone 10, and l selectively remove, in one or more steps, the ash contained in the coal extract. The use of such a supported catalyst to hydrogenate the extract in the primary hydrocracking zone makes possible the conversion of the extract to the distillable hydrocarbonaceous liquid product at much milder conditions of temperature and pressure than were heretofore possible. Thus, not only is there a considerable economic savings in using milder conditions in the prrimary hydrocracking zone, but because the active catalyst is used, the selectivity of conversion of the vextract is enhanced, i.e., less coke and gas are produced per unit of conversion.
Preferably, the catalyst used in the primary hydrocracking zone is a catalytic composite of alumina, `an oxide of molybdenum, and at least one oxide from the group of cobalt and nickel. The catalytic base, which is preferably substantially all alumina, may, if desired, contain a small amount of additive components such as silica, which tends to make the catalyst more resistant to high temperatures. Prior to using the catalyst in the primary hydrocracking zone, the catalyst is usually sulded.
The alumina base is preferably a high surface area material, i.e., greater than 150 square meters per gram, which has a high porosity, i.e., a pore volume greater than 0.3 cubic centhneter per gram, and is prepared in catalytically active form from alumina gel. The alumina base also should preferably be one of the low temperature crystallographic forms commonly characterized as gamma, kappa, or theta. The gamma form is preferred from the point of view of thermal stability against conl@ version to the relatively inactive high temperature form, namely, alpha.
A particularly preferred catalyst is one comprising:
Wt. percent of catalyst Broad I Preferred Molybdenum oxide 3.50 to 20.00 5. 55 Nickel oxide Total nickel oxide 4. 64
plus cobalt oxide, Cobalt oxide 2.00 to 8.00. 0.11 Alumina Remainder 89.70
HYDROFINING ZONE Broad Preferred Temperature 340 to 470 C 380 to 430 C. Pressrre (total pres- 500 to 4500 p.s. 1000 to 3000 p.s.i.g.
sure Hydrogen ratio 1000 to 10,000 s.c.f./ 1500 to 3000 sci/bbl.
bbl. feed. feed. Liquid hourlyr space 0.2 to 2.0 volume] 0.5 to 1.5 volume/ velocity. volume/hour. volume/hour.
Theeliiuent hydroiiner products, recovered from the zone 74 via a conduit 76, are substantially free of nitrogen, oxygen, and sulfur compounds. The eflluent products are fractionated in a fractionation zone 7S into a gasoline fraction boiling below about 193 C. (recovered via a conduit 30) and a secondary hydrocracker zone feedstock boiling above about 193 C. (recovered via a conduit 82.). lf desired, to increase the octane of the gasoline fraction, the portion of the fraction boiling between about and 193 C. may be catalytically reformed in any of the reforming zones known to those skilled in the art (not shown on flowsheet).
The hydroning catalyst may be disposed in a fixed stationary bed, or various moving bed or fluidiz'ed bed techniques may be used. Generally the fixed bed technique, which is illustrated on the drawing, is most satisfactory. Suitable catalysts may comprise any of the oxides or suldes lof the transitional metals, and especially an oxide or sulfide of a group 8 metal (preferably iron, cobalt, or nickel) mixed with an oxide or sulde of a group 6B metal (preferably molybdenum or tungsten). Such catalysts may be used in undiluted form, but normally are supported on an adsorbent carrier such as alumina, silica, zirconia, titania, and naturally occurring porous supports, i.e., activated high alumina ores such as bauxite or clays such as bentonite, etc. Preferably, the carrier should display relatively little cracking activity, and hence highly acidic carriers are generally to be avoided. The preferred carrier is activated alumina such as previously described with reference to the primary hydrocracking Zone 50.
SECONDARY EYDROCRACKING ZONE At least the higher boiling portion of the eflluent hydroner products are introduced via the conduit 82 into a secondary catalytic hydrocracking zone 84. The hydrofiner products are reacted therein in the presence of a catalyst with hydrogen under the following conditions to produce additional gasoline boiling below about 193 C. (recovered via a conduit 86).
a, 14 a, es e As in the case of the gasoline recovered from the hydroiining zone 74, the 90 to 193 C. gasoline fraction may be catalytically reformed to increase the octane rating thereof.
Since the nitrogen, sulfur, and oxygen compounds present in the distillable hydrocarbonaceous liquid recovered from primary hydrocracking zone 50 are removed in the hydroning zone 74, the hydrocracker feedstock is preferably reacted with hydrogen in the secondary hydrocracking zone 84 in the presence of an active cracking catalyst which also exhibits some hydrogenation activity. Suitable catalysts include a mixture of a transition group metal such as cobalt and an oxide of a Group 6B metal such as molybdenum on an acid support such as silica-alumina. Platinum acidic oxide catalysts, for example, those which include between about 0.05 and 2.0 weight percent of the catalyst of at least one metal of the platinum and palladium series deposited upon a synthetic support, are frequently used. Transition group metals in the form of oxides or suldes, particularly nickel and/ or cobalt, may be used without other metals. The synthetic support, i.e., the carrier, can also contain halogens and other materials which are known in the art as promoters for cracking catalysts. The synthetic support can also contain small amounts of alkali metals added for the purpose of controlling the cracking activity of the carrier. Non-limiting examples of the synthetically-produced carriers include silica-alumina, silica-zirconia, silica-alumina-zirconia, silica-aluminathoria, alumina-boria, silica-magnesia, slica-alurninamagnesia, silica-alumina-uorine and the like. A preferred support is a synthetic composite of silica and alumina.
The various gasoline fractions obtained from the above process steps may be blended in any known manner. Preferably, the gasoline fractions are blended to produce a premium gasoline having an octane number of at least 100 (Reseach Method-i-S cc. TEL).
' The following is an illustration, by way of example, of the preferred embodiment of my invention.
SOLVENT EXTRACTION ZONE Temperature C 380 Pressure p.s.i.g. 70 Solvent/coal (wt. ratio) 1.0 Residence time minutes 30 The extraction products, comprising a mixture of solvent, extract, and undissolved coal residue, are filtered at 250 C. whereby a mixture of extract and solvent (filtrate) are separately recovered from the residue.
COAL EXT RACTION YIELDS Wt. percent MA1:` coal Coal conversion 70.1 Extract yield 66.3 Gas produced during extraction l 3.8 Extract recovered via ltration 61.3
if Gas includes Cl-Cs hydrocarbons, B2S, CO2. CO and NH3.
An analysis of the extraction products is shown in the following Table IV.
Table IV [Analysis of extraction products] Feed coal, Recovered Residue* MAF wt. extract MAF wt. percent MAF wt. percent percent *Includes occluded extract.
CARBONIZATION ZONE The residence is subsequently carbonized in a fluidized low temperature carbonization zone under the following conditlons and giving the following yields:
Temperature C 510 Residence time minutes 20 Yields, MAF wt. percent Gas-l-C., 2.8 Liquor 2.8 Light Oil 0.6 Tar 1 1.1 Chai 82.7
PRIMARY HYDROCRACKING ZONE The recovered extract and the +325 C. tar from carbonization are reacted with hydrogen under the followlng conditions and giving the following yields:
A more detailed analysis of the C5/325 C. fraction is as follows:
Distillate analysis (J5/200 O. 20D/325 C. (J5/325 C.
Wt. percent of total distillate 8. 0 92. 0 100. 0
Ultimate analysis, wt. percent:
14. 2 1l. 5 11.9 6 88. l 87. 7 0. 2 0. 2 1 0. l 0. 1 1 0. l 0. l
The primary hydrocracking product, although not suitable for direct use as gasoline, may be used as diesel fuel, fuel oil, and coker feed to make electrode carbon.
13 HYDRoF-INING ZONE Distillate hydrocarbonaceous liquid boiling below about 325 C., which is obtained from the primary hydrocracking zone, is hydroned in admixture with a 260 to 325 C.
fraction (recovered from carbonization of the residue) under the following conditions and giving the following yields:
Temperature 399 C. Pressure 1500 p.s.i.g. Space velocity (WHSV) 0.80 volume/ volume/hour. Catalyst CGU-M003 on A1203 base. Hydrogen consumption, scf/bbl. 988.
Yields: Weight percen C, 1.2 C2 0.7 C3 1.0 C., 0.3
C5 0.1 Cs/93" C. 2.0 93 C./l93 C. 32.5 +193 C. 62 2 The following Table Vl is a further breakdown of the hydroner feed and eiuent product.
Table VI Stream Feed Cri/93 C. S33/193 C. |l93 C.
API gravity 25 65 45 25 Specific gravity 0. 90 0.72 0. 80 0. 90 Molecular weight 185 95 110 200 Ultimate analysis,
H 11. 2 14. 5 13.0 12.0 ss. 2 sa. 5 s?. 0 as. 0 (\5 p.p.1n 10 p.p.rn.) 2 :2:21: (Z-p-Sn-.S f-65.53115 The portion of the hydroiiner products not suitable for direct use as gasoline may be used as gas oil, jet fuel and the like.
SECONDARY HYDROCRACKING ZONE The +193" C. fraction from hydroining is hydrocracked in a xed bed hydrocracking zone under the following conditions and giving the following yields:
Temperature 399 C. Pressure 1800 p.s.i.g. Space velocity (WHSV) 0.96 volume/volume/hour. Catalyst Ni-silica alumina. Hydrogen consumption 21100 s.f.c./ bbl.
Yields: Weight percent C1 0.2 C2 0.3
C3 3.9 C4 9.6 C5 10.3 C6/93 C. 44.9
A more detailed secondary hydrocracker product breakdown is shown in the following Table VII.
Table VII Cl93 C. 93/193 C.
API gravity 65 45 Spacic gravity 0.72 0. S0 Molecular weight- 95 110 Ultimate analysis, wt. percent:
Hydrogen 15. 2 13.0 Carbon 84.8 87. 0
The 93 to 193 C. fraction from the secondary hydrocracldng zone and the hydroiining zone are catalytically reformed under the following conditions and giving the following yields:
Table VIII [Reformer product properties] C6/210 C. reformate API gravity 33.00
Specific gravity `0.85
Molecular weight Ultimate analysis, wt. percent:
The following fractions from hydroining, secondary hydrocracking, and reforming are blended as shown in the following Table IX to give a premium gasoline having a leaded blended octane by the research method (F-l-I-3 cc. TEL) of at least 100.
Table IX Blending F-l-l-Scc. RVP TEL Ca 189.0 120.0 Ci 59. 0 103. 0 C5. 16. 0 8S. 7 Cta/93 C. (Hydroiiner product) 6.0 97.0 Cri/93" C. (Hydrocracker product) 6.0 97.0 Cri/210 C. (Reforming product). 2. 9 104. 1
According to the provisions of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A process for the production of liquid fuel from coal which comprises (a) subjecting the coal to solvent extraction to convert up to 80 weight percent of the MAF coal,
(b) recovering from the extraction products of step (a) a coal extract substantially all of which is nondistillable below 400 C.,
(c) treating said coal extract from step (b) in a primary catalytic hydrocracking Zone with sufficient hydrogen to convert at least the major portion thereof to a distillable hydrocarbonaceous liquid, the major portion of which boils in the range of 200 to 400 C.,
(d) recovering said distillable hydrocarbonaceous liquid from step (c) in a substantially ash-free state,
(e) catalytically hydroining at least the major portion of said distillable hydrocarbonaceous liquid from step (d) to yield eifluent hydroiiner products substantially free of nitrogen, oxygen, and sulfur compounds, but at least the major portion of which boils in the range of 200 to 400 C., and
(f) thereafter treating at least a portion of the hydrofner products boiling between 200 and 400 C. in a secondary catalytic hydrocracking zone with suicient hydrogen to yield a liquid fuel which boils below 200 C.
2. The process of claim 1 wherein the extract from step (b) is treated in the primary catalytic hydrocracking zone at a temperature between 410 and 475 C. and at a pressure between 2500 and 6000 p.s.i.g.
3. The process of claim 2 wherein the distillable hydrocarbonaceous liquid from step (d) is catalytically hydrofmed -at a temperature between 340 and 470 C. and at a pressure between 500 and 4500 p.s.i.g.
4. The process of claim 3 wherein the higher boiling portion of said hydroner products is treated in the secondary catalytic hydrocracking zone at a temperature between 340 and 500 C. and at a pressure between 500 and 4500 p.s.i.g.
5. The process of claim 4 wherein at least a portion of the distillable hydrocarbonaceous liquid recovered from the primary catalytic hydrocracking Zone is used as solvent for the solvent extraction of the coal in step (a).
6. The process of claim 5 wherein the extract is deashed prior to treatment in the primary catalytic hydrocracking zone.
7. The process of claim 6 wherein the remainder of the unconverted coal extract is recovered from th'e'primary catalytic hydrocracking zone and thereafter coked to yield ,45
a liquid distillate and coke.
16 8. The process of claim 7 wherein a lower boiling portion of the eluent hydroner products and a higher boiling portion of the liquid fuel products recovered from the secondary catalytic hydrocracking zone are reformed to yield a liquid fuel having a higher octane number.
9. A proces for the production of liquid fuels from coal which process comprises,
(a) subjecting the coal to solvent extraction to convert up to weight percent of the MAF coal,
(b) separately recovering from the products of step (a) a coal extract, which contains N-O-C contaminants and substantially all of which is nondistillable below 400 C., and undissolved coal residue,
(c) subjecting the undissolved coal residue to carbonization at low temperature to yield a liquid distillate,
(d) separately recovering from the liquid distillate produced in step (c) low, middle, and high boiling fractions,
(e) subjecting coal extract from step (b) and high boiling fraction from step (d) to catalytic hydrogenation in a rst hydrogenation zone to yield a distillable product the major portion of which boils in the range of 200 to 400 C. and still contains N-O-S contaminants,
(f) subjecting product obtained from step (e) which boils in the range of 200 to 400 C. and middle boiling fraction from step (d) to catalytic hydrogenation in a second hydrogenation zone to yield a product which is free of N-O-S contaminants but the major portion of which still boils in the range of 200 to 400 C., and
(g) thereafter subjecting product obtained from step (f) to catalytic hydrogenation in a third hydrogenation zone to yield a product the major portion of which boils below 200 C.
References Cited in the file of this patent UNITED STATES PATENTS 1,864,855 Pier et al lune 28, 1932 2,215,206 Biggs et al. Sept. 17, 1940 2,499,255 Parker Feb. 28, 1950 2,654,695 Gilbert et al. Oct. 6, 1953 FOREIGN PATENTS 756,542 Germany Nov. 9, 1953
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|U.S. Classification||208/413, 208/430, 208/415, 208/434|
|International Classification||C10G1/00, C10G47/00|
|Cooperative Classification||C10G47/00, C10G1/002, C10G1/006|
|European Classification||C10G1/00B, C10G47/00, C10G1/00D|