CA1174626A - Method of solvent extraction of coal by a heavy oil - Google Patents

Abstract

"IMPROVED METHOD OF SOLVENT EXTRACTION
OF COAL BY A HEAVY OIL"

ABSTRACT

A solid carbonaceous material, such as coal, is converted to liquid products and the asphaltene content of a heavy hydrocar-bonaceous liquid is reduced in the process wherein the solid is solvent extracted by the heavy hydrocarbonaceous liquid and a hydrocarbonaceous recycle stream with a finely divided, unsupported metal catalyst and the resultant mixture of liquids is recovered as the product.

Description

117462~;

"IMPROYED METHOD OF SOLYENT EXTRACTION
OF COAL BY A HEAVY OIL"

BACKGROUND OF THE INVENTION

This lnvention relates to a process for the conversion of carbonaceous materials, such as coal, to liquid products. More particularly, this invention relates to a process for the conversion of coal to a liquid product by solvent extraction of the coal using a heavy hydrocarbonaceous liqu~d containing heptane-insoluble materi-al and a hydrocarbonaceous recycle stream, and recovery of the mixture of the solvent and liquified coal as the product of the process.
Resources of solid carbonaceous substances such as coal, lignite, oil shale, etc. represent a valuable source of raw materials for the production of liguid hydrocarbon products commonly obtained from petroleum. The relative abundance of sources of solid carbonace-ous materials with respect to those of petroleum, makes the use of 1~ these solids to supplement and replace petroleum as energy sources economically desirable.
Several processes for converting coal to valuable liquid products are known to the art. Recently, high pressure hydrogenation and solvent extraction techniques have been developed, the latter of which is related to the process of this invention. In the processes of solvent extraction known to the prior art, crushed, finely-divided . . .

11746~6 particulate coal, or other carbonaceous material, is placed in contact with a liquid solvent which dissolves a part of the solid, usually in the presence of hydrogen gas. Following the contact, the liquid solvent and the liquified part of the solid are separated from the remaining solid material by filtration, centrifuging or a similar operation. In the other processes known to the prior art, the previously solid mater-ial is separated from the solvent, typically by fractional dlstillation, and is further processed by conventional hydrocarbon processing techni-ques such as coking, cracking, hydrogenation, etc., to convert the solvent extracted material into more useful products.
A pertinent prior art reference is U. S. Patent 3,705,092 which teaches a process for the extraction of coal with heavy hydro-carbonaceous liquids while simultaneously improving the quality of the hydrocarbonaceous liquids. The present invention recognizes the fact that the prior art process is improved by recycling at leas~ a portion of the reaction zone effluent.
Another example of the typical prior art in the area of coal hydroconversion is U. S. Patent 4,077,867.
- One of the problems encountered in the solvent extraction mPthod of liquefying solid carbonaceous substances is the non-selective nature of the solvation which takes place. The process is intended to extract the most valuable, hydrogen-rich fraction of the solid. But solvents which are effective in extracting this hydrogen-rich fraction also liquify an undesirable fraction containing asphaltenes. Asphal-tenes are undistillable compounds of carbon of high molecular weight, 1~7~6Z6, and contain less than about 7% hydrogen by weight. Asphaltenes are also insoluble in normal heptane. They are present not only in the products from solvent extraction of carbonaceous materials such as coal, but also in petroleum crude oil and fractions thereof such as topped or reduced crude oils, heavy cycle stocks visbreaker liquid effluent and the bottoms from atmospheric crude towers.
The asphaltenic fractions of all these liquid hydrocarbons are of little intrinsic value and interfere with the processing of the more valuable heavy oil fractions with which they are mixed. Thus, the reduction of the asphaltene content in any processable hydro-carbon liqu~d is a deslrable improvement thereof. Further conver-sion of asphaltenes to dlstillable hydrocarbons is possible by re-cycling at least a portion of the reaction zone effluent.

OBJECTS AND EMBODIMENTS

The objective of this invention is to originate an efficient method for the conversion of solid carbonaceous materials to valuable liquid products and the simultaneous improvement of the properties of a heavy hydrocarbon liquid. More specifically, the object of this invention is an efficient method for the solvent ex-traction of valuable liquids from solid carbonaceous materials and the simultaneous conversion of a part of a heavy hydrocarbon liquid from a less desirable material to a more desirable material. The particular object of this invention is the efficient solvent extrac-tion of a valuable fraction of a solid carbonaceous material with a concurrent reduction in the asphaltenes contained:1n a heavy hydro-;~, ~ 3_ :1~7fl~62tj carbon liquid.
As hereinabove set forth, these objects are accomplished through the utilization of a heavy asphaltene-containing hydrocarbon-aceous liquid as the solvent in a process for the solvent extracting of solid carbonaceous materials. Therefore in one embodiment the present invention provides a process for producing hydrogen-enriched hydrocarbonaceous products from coal and an asphaltene containing petro-leum oil which comprises contacting said coal and asphaltene containing petroleum oil in the presence of hydrogen, and a hereinafter described liquid recycle stream containing finely divided, unsupported metal catalyst said metal being selected from the group consisting of Groups IVB, YB, YIB, VIIB and YIII of the Per;odic Table of Elements and mixtures thereof in a reaction zone at a temperature from about 12 8Ç to about 502Ç and a hydrogen pressure from about 3450 kPa gauge to about 68,950 kPa gauge to liquefy at least a portion of said coal and to reduce the asphaltene content of said oil; and solvent deashing at least a portion of the reaction zone effluent to provide said liquid recycle stream utilized in step (a) which recycle stream contains finely divided, unsupported metal catalyst.
In the preferred embodiment of my invention, comminuted coal is introduced into a solvent extraction zone where it is admixed with a petroleum crude oil and a liquid recycle stream in the presence of hydrogen gas and a finely divided, unsupported metal catalyst at a temperature and pressure which will produce a liquefaction of a portion of the coal.
The crude oil, used as the solvent in the preferred embodiment, contains sufficient heavy oils such that at least 80% of the crude boils above about 343.3C a~d 50% boils above about 538C.

1~7462i:~
In a general embodiment of the present invention, the admixed heavy hydrocarbonaceous liquid solvent, the coal, the liquid recycle stream and the finely divided, unsupported metal catalyst are subjected to sufficient temperature and pressure, in the presence of hydrogen gas, to liquefy the desired fraction of the solid. The solvent extraction and hydrocarbon conversion process may be conducted in either a batch or a continuous reaction vessel. Solvent extraction and hydrocarbon conversion conditions include a temperature of about l2.8DC to about 5lOC
and a pressure of about 3450 kPa gauge to about 68,950 kPa gauge. Hydrogen gas is present at the above-indicated pressure.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention is generally applicable to hydroconvert coal and a heavy hydrocarbonaceous liquid into more valuable hydrocarbonaceous products. The term coal is used herein to designate a normally solid carbonaceous material including all ranks of coal, such as lignite, anthracite coal, bituminous coal, semi-bituminous coal and mixtures thereof.
The heavy hydrocarbonaceous liquid solvent utilized in the - solvent extraction may be any heavy hydrocarbon substance which is liquid at the solvent extraction conditions, contains asphaltenes that are in-soluble in normal heptane, and 80% of which boils above about 343.3C
50% of which boils above about 538C. The liquid hydrocarbonaceous solvent and coal may be admixed in any weight ratio but a weight ratio from about 1 part solvent to 1 part coal up to about 5 parts solvent to 1 part coal is preferred.

11~746;~ti In the preferred embodiment of the present invention, the coal is a bituminous coal having a h;gh content of volatile material. Typi-cally, a high content of volatile material would be about 20% or higher volatiles in the moisture and ash free coal. The coal is subjected to extraction and conversion conditions in a finely-divided state. Said finely-divided state is well exemplified by coal particles which pass through about a 200 mesh or finer Tyler sieve.
The liquid hydrocarbonaceous solvent utilized in the pre~
ferred embodiment of the present invention is a heavy whole crude oil.
Typical of the préferred solvent is a Cold Lake crude oil having an API
gravity of about 10 and containing a fraction of materials insoluble in normal heptane of about 8%. The crude oil, used as the solvent in the preferred embodiment, contains sufficient heavy oils such that at least 80% of the crude boils above 343.3C and 50% boils above 538C.
In a general embodiment of the present invention, the admixed solvent, the coal and the liquid recycle stream are subjected to suffi-cient temperature and pressure, in the presence of hydrogen gas, to liquefy the desired fraction of the coal. The solvent extraction process may be conducted in either a batch or a continuous reaction vessel.
Solvent extraction conditions include a temperature of about 12.8C to about 510C and a pressure of about 3450 kPa gauge to about 68,950 kPa gauge.
Hydrogen gas is present at the above-indicated pressure.
Preferably, the admixed solvent, the coal and the liquid recycle stream are processed in a continuous reaction vessel at a flow rate which results in a liquid hourly space velocity of about 0.5 to about 10, where the liquid hourly space velocity is defined as the volumetric flow of the feed per hour divided by the volume of the re-actor. The hydrogen gas is recycled to the process from the reactor 1~7462~i effluent at a rate of about 8~8.8 to about 3555 std m3/m3 of combined solvent, coal and liquid recycle stream, and hydrogen gas is added to the reaction at a rate sufficient to maintain the above stated range of pressures.
s After the reactants have been exposed to the solvent extraction conditions for a length of time sufficient for the desired fraction of the solid to have been liquified, the reaction zone contents are with-drawn. The gas is separated from the reaction zone effluent. The slurry is solvent deashed under selected process conditions to effect a separa-tion yielding a high grade synthetic crude and a heavy liquid phase.
The heavy liquid phase contains high boiling, high molecular weight material, unconverted coal, catalyst and essentially all the mineral matter. A portion of the heavy liquid phase is recycled to the inlet of the reaction zone.
In the preferred embodiment of the present invention, the above-described, finely divided, solid bituminous coal is admixed with the above described heavy petroleum crude oil solvent at a weight ratio of two parts crude oil to one part solid coal. A portion of the subse-quently derived liquid stream is recycled to the inlet of the extraction zone at a weight ratio of one part extraction zone effluent to one part solid coal. This mixture of coal, crude oil and liquid recycle stream forms the feed to the reaction or extraction zone, wherein the solvent extraction of this preferred embodiment is maintained. The solvent extraction condltions of the preferred embodiment include a temperature Of about 454C and a hydrogen gas pressure of about 20,680 kPa gauge. The feed to the reaction zone is continuously passed through the reaction zone at a rate sufficient to maintain a liquid hourly space velocity of 1~74~26 about 0.5 based on the volume of the fresh feed. Hydrogen gas is re-cycled to the reaction zone from the reaction zone effluent at a rate of about 2666 std m31m3 of the feed to the reaction zone. The solvent extraction conditions should be maintained so as to produce a conversion of the solid coal to a liquid extract of about 70% by weight of the moisture-and-ash-free coal.
When the feed to the reaction zone has been subjected to said solvent extraction conditions, it is collected as the effluent from the reaction zone. During the period that the feed was subjected to the solvent extraction conditions, about 70% of the solid coal will have been liquefied to form valuable hydrocarbon products and a part of the crude oil solvent, which was insoluble in normal heptane, will have been converted into a material which is soluble in normal heptane.
The reaction zone effluent after removal of the normally gaseous components is separated by solvent separation to effect separa-tion of the solids from the liquid product. A portion of the solid containing liquid stream is recycled to join the fresh feed to the reaction zone inlet.
The hydrocarbons recovered from the process of the present invention constitute a synthetic crude oil which can be processed in the same manner as any common petroleum crude oil. Both the component derived from the solid and the component derived from the solvent are improved from the process of this invention in that the content of asphaltenes is reduced in both. This reduction in asphaltenes in the synthetic crude oil, particularly with respect to the component derived from the solid, renders the resulting hydrocarbon more readily process-able than is the hydrocarbon obtained in the solvent extraction processes known to the prior art.

~1~4626 A suitable liquid recycle stream may be prepared from the whole or a fraction of the extraction zone effluent. A preferred liquid recycle stream is prepared by first removing the normally gaseous components from the extraction zone effluent and then removing the desirable hydrocarbonaceous product with a relatively low molecular weight hydrocarbon solvent in a solvent separation procedure while leaving a component which is well suited for the desired liquid recycle stream and which contains essentially all of the ash, unconverted coal, asphaltenes, relatively high molecular weight hydrocarbons and a finely divided, unsupported metal catalyst.
The solvent separation procedure hereinbefore mentioned is similar to solvent deasphalting processes which are known and described in the prior art. Suitable hydrocarbon-selective solvents are l;ght hydrocarbons including ethane, propane, butane, isobutane, pentane, isopentane, neopentane, hexane, isohepane, heptane, mono-olefinic counterparts thereof, etc. The prior art has also taught that aromatic hydrocarbons may be added to enhance the solvent.
The finely divided, unsupported metal catalyst is selected from the group consist;ng of Groups IVB, VB, VIB, VIIB and VIII and mixtures thereof of the Periodic Table of Elements. The finely divided unsupported metal catalyst may be prepared in any convenient method.
The catalyst or catalyst precursor may be an oil soluble metal compound, a finely divided metal or oil insoluble metal compound which is merely suspended in the hydrocarbon oil.
The finely divided, unsupported metal catalyst is generally present in an amount from about 10 wppm to about 4 weight percent cal-culated as the elemental metal, based on the weight of coal in the mixture.

Suitable metal compounds convertible to active catalyst under process conditions include inorganic metal compounds such as oxides, hydrated oxides, sulfides, thiosalts, heteropoly acids, isopolyacids, halides, oxyhalides; metal salts of organic acids, metal salts of organic amines; inorganic and organic metal complexes, organometallic compounds.
Yarious methods can be used to form the finely divided catalyst but a preferred method of forming the finely divided catalyst from the metal compound is to heat the mixture of metal compound, coal and petro-leum oil to a temperature ranging from about ~l5.6e~ to a~out 426.7~ and at a pressure rangin~ from about 3447 to about 34470 kPa ga~e in the presen~e of a hydrogen-containing gas. Preferably, the hydrogen-containin~ gas also comprises hydrogen sulfide. The hydrogen sulfide may comprise from about 1 to about 90 mole percent and preferably from about 1 to 30 mole percent of the hydrogen containing gas mixture.
The conversion of the metal compound into a finely divided metal catalyst according to the above-described method may be performed in a separate catalyst preparation step or process, or, in situ, in the hydroconversion or reaction zone.
The following example is given to illustrate the process of the present invention and the effectiveness thereof for producting hydrogen-enriched hydrocarbonaceous products from coal and asphaltene containing petroleum oil. It is not intended that the present invention be unduly limited by the example presented.
In this example, the experiments were conducted batch-wise in a rocker autoclave with a capacity of 1800 cc. This example demonstrates the results achieved by the conversion of coal and petroleum oil in the presence of a finely divided unsupported metal catalyst.
A 100 gram sample of finely divided Illinois No. 6 coal having the characteristics presented in Table I was charged to the autoclave ~ ~L 7~I6 Z t;

together with 200 grams of Boscan topped crude oil having the characteristics presented in Table II and 22.1 grams of molybdenum hexacarbonyl. The autoclave was then pressured with a 10/90 hydrogen sulfide-hydrogen mixture to about 7583 kPa gauge and then pressured with pure hydrogen to about lO34l kPa gauge. The charged autoclave was then heated to a temperature of about 390C. and maintained at a pressure of about 17,235 kPa gauge for one hour. The cooled contents of the autoclave were recovered with a toluene r1nse. After the toluene was flashed, the product was solvent separated with 1sopentane at four volumes of isopentane for each volume of autoclave product. The 1sopentane soluble fraction was recovered and the isopentane was removed by flashing. The solvent free lsopentane soluble product weighed 185.8 grams. The lsopentane insoluble fraction which weighed 56.3 grams and contained the finely divided unsupported metal catalyst was re-cycled wlth 100 grams of coal and 200.7 grams of Boscan topped crude o1l to the autoclave. The hereinabove described heating and pressuring of the autoclave was repeated in an ldentical fashion. Here again the cooled contents of the autoclave were recovered with a toluene r1nse. After the toluene was flashed, the product was solvent se-parated with lsopentane at four volumes of lsopentane for each volume of autoclave product. The isopentane soluble fraction was recovered and the isopentane was removed by flash1ng. The solvent free isopen-tane soluble product weighed 98.4 grams. The isopentane insoluble fraction which weighed 118.4 grams and contained the finely dlvided unsupported metal catalyst was recycled wlth 100 grams of coal and 198.1 grams of Boscan topped crude oil to the autoclave.
The correspond1ng heating, pressuring and subsequent separating as hereinabove described was again repeated in an identical fashion. The solvent free isopentane soluble product weighed 189.7 grams and the isopentane insoluble fraction weighed 178.7 grams. The most recent t ~7462t~

isopentane insoluble fraction weighing 178.7 grams was charged to the autoclave with 100 grams of coal and 188.1 grams of eoscan reduced crude oil. The hereinabove described autoclave process was again performed to yield an isopentane soluble product weighing 164.1 grams and an isopentane ~nsoluble product weighing 186.7 grams. The resulting isopentane insoluble product was solvent extracted with toluene to yield 130.7 grams of toluene soluble material which is useful for heavy fuel oil and 51.1 grams of toluene insoluble material which contained unconverted coal,mineral matter and catalyst.
The four autoclave runs are summarized in Table III and the toluene extraction of the isopentane insolubles is summarized in Table IV.

TABLE I
ANALYSIS OF ILLINOIS NO. 6 COAL
Carbon, wt. % 70.05 Hydrogen, wt. % 5.88 Oxygen, wt. % 9.01 Sulfur, wt. % 2.68 Nitrogen, wt. % 1.20 Ash, wt. % 9.02 Moisture (Water), wt. % 2.15 ~74626 TABLE Il ANALYSIS OF BOSCAN CRUDE OIL

Gravity, API at 15.5C. 5.5 Distillation, IBP, F. 769 10 % 804 30 % 977 % OVER t~OLUME) 30.5 Carbon, wt. % 82.8 Hydrogen, wt. % 10.6 Nitrogen, wt. % 0.8 Sulfur, wt b 19 04 Vanadium, ppm 1500 Nickel, ppm 130 7~626 TABLE III

SUMMARY OF BATCH RECYCLE AUTOCLAVE RUNS

Run No. 1 2 3 4 Charge Coal, 9 100 100 100 100 Topped Boscan Oil, 9 200 200.7 198.1 188.1 Mo(C0~6 9 22.1 56.3 117.3 177.9 Product Recovery Toluene Free, 9 261.1 221.5 381.1 422.0 Isopentane Soluble, 9185.8 98.4 189.7 164.1 Carbon, wt. % 86.22 84.03 Hydrogen, wt. % 11.44 10.78 Oxygen, wt. % 0.17 0.10 Sulfur, wt. % 2.77 3.17 N1trogen, wt. % 0.43 0.56 Nickel, ppm 2.7 1.8 Vanadium, ppm <1 18 Heptane Insoluble, wt. X ~ 0.01 0.3 Isopentane Insoluble, 9 56.3 118.4 178.7 186.7 li7~62~

TABLE IV

TOLUENE EXTRACTION OF THE ISOPENTANE INSOLUBLES

Charge, 9 186.7 Toluene Soluble Toluene Insoluble Recovered Weight, g130.7 51.1 Carbon, wt. % 84.74 31.60 Hydrogen, wt. % 7.66 3.04 Oxygen wt % 2 736 14.1 Nitrogen, wt. % 1.43 --Molybdenum, wt. % 6.70 Vanadium, wt. % 1.73 Nickel, wt. % 0.15 Iron, wt. X 6.8 From the foregoing description and example, it is apparent that the process of the present invention provides a superior method for producing hydrogen-enriched hydrocarbonaceous products from coal and asphaltene containing petroleum oil.

Claims (7)

CLAIMS:

1. A process for the production of hydrogen-enriched hydrocarbonaceous products from hydrocarbonaceous materials which comprises:
(a) commingling coal and a crude petroleum oil containing asphaltenes and heavy oils in an amount such that at least 80% of the crude boils above 343.3°C;
(b) subjecting the resultant mixture to conversion together with a hereinafter described liquid recycle stream containing finely divided, unsupported metal catalyst in which the metal is selected from the group consisting of the elements from Groups IV, VB, VIB, VIIB and YIII of the Periodic Table of Elements and mixtures thereof in a reaction zone at a temperature from about 12.8°C to about 510°C and a hydrogen pressure from about 3,450 kPa gauge to about 68,950 kPa gauge to liquefy at least a portion of said coal and to reduce the asphaltene content of said oil;
(c) separating gas from the resultant reaction zone effluent;
(d) then solvent deashing at least a portion of the reaction zone effluent with a relatively low molecular weight hydrocarbon solvent to separate therefrom a heavy liquid phase containing substantially all of the ash, unconverted coal, asphaltenes, relatively high molecular weight hydrocarbons and finely divided, unsupported metal catalyst; and, (e) supplying at least a portion of said heavy liquid phase to the reaction for use as said liquid recycle stream in the aforesaid step (b).

2. The process of claim 1 wherein said asphaltene containing petroleum oil has a 50% boiling point greater than about 538°C.

3. The process of claim 1 wherein said finely divided un-supported metal catalyst comprises molybdenum.

4. The process of claim 1 wherein said finely divided unsupported metal catalyst comprises vanadium.

5. The process of claim 1 wherein the weight ratio of asphaltene containing petroleum oil to coal is from about 1:1 to about 5:1.

6. The process of claim 1 wherein the liquid flow rate in said reaction zone results in a liquid hourly space velocity of about 0.5 to about 10.

7. The process of claim 1 wherein the hydrogen circulation rate in said reaction zone is from about 888.8 to about 3555 std m3/m3 based on the reaction zone charge.