US2654695A - Process for preparing liquid hydrocarbon fuel from coal - Google Patents

Description

PROCESS FOR PREPARING' LIQUID HYDROCARBON FUEL FROM COAL Filed Aug. 12, 1949 Patented Oct. 6, 1953 PROCESS FOR PREPARING LIQUID HYDRO- CARBON FUEL FROM COAL William I. Gilbert and Charles W. Montgomery, Oakmont, Pa., assignors to Gulf Research &

Development Company, poration of Delaware Pittsburgh, Pa., a cor- Application August 12, 1949, Serial N0. 109,924

3 Claims.

This invention involves an improved combination of steps for preparing liquid hydrocarbon fuels from coal.

Several procedures are known for liquefying coal or for converting coal into liquid materials. For instance it has been previously proposed to liquefy coal by subjecting it to hydrocoking in the presence of hydrogen at elevated temperature and pressure. It is known that the resulting product contains a mixture of hydrocarbons, phenols and other liquid materials such as sulfurous organic substances. It is also known to subject coal to a solvent extraction with phenolic substances in the presence of hydrogen at elevated temperature and pressure and thus obtain a liquid extract from the coal. However, to date the cost of converting coal into hydrocarbons suitable as fuel has been prohibitive. Not only has the conversion process been comparatively costly but the products have required various purification procedures which further detracted from the economy of the process.

This invention has for its object to provide an improved procedure for converting coal into liquid hydrocarbons suitable as fuel. Another object is to improve the economics of the conversion of coal into liquid hydrocarbon fuel. Other objects will appear hereinafter.

These and other objects are our invention which includes liquefying a rst portion of coal by treatment with hydrogen at elevated temperature and pressure to obtain a liquid product, separating this liquid product into a hydrocarbon fraction and a phenolic fraction, extracting a second portion of coal with said phenolic fraction and subjecting a mixture of said hydrocarbon fraction, said phenolic fraction and the material extracted from the second portion of coal by said extraction treatment to a treatment with hydrogen while at elevated tempertaure and while in the presence of a metalliferous substance having the property of promoting hydrogenation.

In the following description we have set forth several of the preferred embodiments of our invention but it is to be understood that they are given by way of illustration and not in limitation thereof.

Referring to the accompanying drawing, which is a diagrammatic iiow sheet of the preferred accomplished by embodiment of our invention, powdered coal, such as powdered lignite flows from hopper I into reactor A by Way of metering device 2. Fresh hydrogen is introduced into reactor A by way of conduit 4 and recycle hydrogen by way of conduit 6. In reactor A the coal is converted in known manner at elevated temperature and pressure into a liquid product and a solid resid-ue. The residue is withdrawn intermittently from char receiver y8 and can be used as a fuel. The liquid product is removed from reactor A by Way of conduit I0 and is introduced into neutralizer B. An aqueous solution of caustic is introduced into neutralizar B through conduit I2 and the materials therein are agitated and are then stratified, the hydrocarbon upper layer being withdrawn through conduit i4. The lower layer constituting an aqueous solution of phenolic salts is Withdrawn through conduit I6 and introduced into tank C. Acid is then introduced through conduit I8 into tank C to split the phenolic salts. The contents of tank C are then stratified and the upper phenolic layer is introduced by way of conduit 20 into reactor D while the aqueous lower layer is withdrawn by way of conduit 22 and discarded or employed to make caustic' for further use in the process.

A second portion of coal such as lignite in particulate form flows from hopper 23 into reactor D by way of metering device 24 while recycle and fresh hydrogen are introduced into reactor D through conduits 21S and v23. In reactor D the coal is subjected at elevated temperature to a combined extraction and hydrogenation, resulting in liquefaction of a considerable .portion of the coal. The product, including the phenolic solvent from reactor A is withdrawn from reactor D by way of conduit 30 and is introduced into filter E where the ash and carbonaceous residue from the coal is removed by filtration. The

filtrate is withdrawn through conduit 34 and the ash is collected in 32. After heating to remove the solvent the ash or residue may be pulverized for use as fuel since this material contains only 30-50 per cent actual ash. The ltrate ows through conduit 34 and is combined with the liquid hydrocarbons owing through conduit I4 and derived from neutralizer B, i. e. the hydrocarbon from the neutralizing stage B is combined with the phenol solvent and coal extract from the D extraction stage and is introduced by way of conduit 36 into reactor F. Hydrogen in the form of fresh hydrogen is introduced into reactor F through conduit 33 while recycle hydrogen is introduced through conduit 40. This combined mixture of hydrogen flows through conduit 42 into reactor F which contains a body of pellets comprising a hydrogenating catalyst on a porous carrier. The conditions in reactor F are selected so that hydrogenation of the mixture With concomitant upgrading takes place. Conversion'of the phenols to hydrocarbons and desulfurization also takes place under conditions which result in such upgrading. The hydrogenated product is then withdrawn by way of conduit 44 and is introduced into separator G where the liquid product is separated from hydrogen. The liquid product is removed through conduit i6 and the separated hydrogen is recycled through conduit 48.

The coal utilized in reactors A and D can be of any type Such as, for instance, lignite, subbituminous, bituminous, semianthracite or anthracite. The coal in step A preferably should be of a non-caking type and the coal used in step D should contain about per cent or more volatile matter. The process is of particular value in connection with the lower grade coals such as peat and lignite. The coal may be in any state during treatment in these reactors but a particulate or finely divided form is preferred.

In step A, i. e. the hydrocoking step, the temperature utilized is usually between about 900 to 1200 F. and the pressure is usually between about 500 to 2000 p. s. i. These conditions can be lower or higher than specifically indicated herein as is well known in the prior art. It is preferred to utilize a fluidized bed of finely divided coal for this operation and to continuously introduce the powdered coal and continuously remove char from the bed. In such procedure the hydrogen proportions would be much higher. In order to maintain the fluidized bed condition with fluidized operation, the hydrogen stream would vary between about 50,000 and 100,000 c. f. s. of hydrogen per ton of coal such as lignite. Linear rates above about l5 feet per minute are required to uidize a coal bed such as a lignite bed. This stage is not greatly affected by the presence of moisture and predrying of the coal is not necessary.

This product from step A can be directly treated to separate the phenols. In the drawing it has been indicated diagrammatically that the product would be treated with caustic to separate the phenols by formation of their salts. However, it may be preferable to first distill the liquid product to concentrate the phenol fraction. For instance the product could be distilled to get a gasoline fraction, a gas-oil fraction and a bottoms fraction. The gas-oil fraction contains about to 40 per cent phenolic material and can be economically treated for their recovery.

l As indicated, the method of separating phenols is not a part of our invention and any known or satisfactory method such as direct fractionation or solvent extraction can be used. When a strong caustic such as 5 to 40 per cent sodium hydroxide is employed, agitation is required and it is desirable to utilize a temperature of about room temperature for the neutralization.

In the event that other methods for separating phenols are used, such as direct fractionation, step C may be eliminated and the phenol portion directly introduced into reactor D. Howif the phenols are separated by formation of their alkaline salts, the phenols must be reformed by treatment with acid such as 3 Vto 35 per cent sulfuric or by treatment with carbon dioxide.

The conditions in reactor D are Vthose which are known in the prior art for this operation. The coal introduced into reactor D is preferably in finely divided condition since this condition improves the Vsolvent extraction and/or hydro- Ygenation. The pressure during this stage is maintained between about 100 and 2000 p. s. i. A pressure of between about 300 and 900 p. s. i. is particularly satisfactory for lignite. The temperature is generally maintained between 700 and 850 F., although higher or lower temperatures may be used. The coal is preferably dried prior to this operation. The hydrogen is consumed in amounts of between one and three s. c. f per pound of coal. The proportion of phenolic solvent to coal on a dry weight basis is preferably between about l to l and 4 to 1 solvent :per weight unit of coa-l. The treatment is usually continued for a period of between about 15 minutes and l hour. Longer or shorter times can be used. This treatment, i. e., the solvent extraction-hydrogenation results in a conversion of about per cent of the carbonaceous material contained in the coal into liquid material. Instead of using gaseous hydrogen, a hydrogen donor, such as Itetralin may be used. See for instance Polt et al. U. S. Patent 2,147,753. While we have found it convenient to describe step D of our invention as involving a solvent extraction in the presence of hydrogen, it is to be understood that this constitutes a preferred embodiment and that solvent extraction with the phenol per se may be used.

The products from stage D are treated in order to separate the unconverted solid coal residue from the liquefied material and the admixed phenolic solvent. While any method of separation can be used this can be conveniently accomplished by filtration, as illustrated in stage E of the drawing.

The primary purpose of the hydrogen treatment in stage F is to convert the material treated therein into a higher grade product. This involves hydrogenation to convert to a hydrocarbon having a lower carbon residue. Also conversion of phenols into hydrocarbons and desulfurization takes place. This is due to the fact that hydrogenation conditions necessary to accomplish this upgrading also results in conversion of the phenols into hydrocarbons and removal of the sulfur compounds by a hydrodesulfurization action. This step is carried out in the presence of a metalliferous material having a hydrogenating action such as tungsten or molybdenum oxides or suldes or iron group metals such as nickel, cobalt and/or their oxides preferably deposited upon a porous carrier such as activated alumina, silica-alumina cracking catalysts, Alfrax etc. The temperature is preferably between about 750 and 950 F. 'Ihe pressure is preferably between about v and 1000 p. s. i. g. The hydrogen is preferably employed in amounts of between 300 and 20,000 cubic feet per barrel of material treated and the space velocity is preferably between about 0.2 and 6 volumes of liquid per hour per volume of contact for catalyst. These constitute preferred conditions of operation and higher or lower values thanthose given such as are known in the prior art, may be used. Reference is made to Horne 8a Junge U. S. patent applications Serial Nos. 699,671-2, led September 27, 1946,Vr now Patents Nos. 2,516,876-7, dated April 1, 1950, for typical hydrogenation-desulfurization procedure and conditions which may be employed in reactor F. It is to be understood, however, that any known procedure for upgrading by hydrogenation treatment at elevated temperature and Y pressure may be employed.

The separation of hydrogen from the absorbed product in separator G is accomplished in any desired manner such as release of pressure. This results in evolution of most of the absorbed hydrogen and the residual hydrogen can be then removed by distillation.

In order to have an economically satisfactory process it is necessary to utilize a low cost solvent in the solvent extraction stage. Our process satisfactorily solves this problem. The process would not be economically feasible if a highly purified solvent or an extraneous solvent were necessary. Another advantage of our invention, particularly from the economy standpoint, is that the liquid hydrocarbons produced in the hydrocoking step, i. e. the step from which the solvent is obtained, can be combined with the liquid extract from the extraction step and the hydrogenation directly applied to both of these materials at the same time, thus eliminating a separate reactor and an extra hydrogen treatment. Also by thus combining the two streams the high viscosity of the lignite extract is greatly reduced, thereby overcoming difficulty in handlng this relatively viscous material. Furthermore, because of the use of a low grade cheap phenolic solvent, it is unnecessary to recover the phenolic materials and they are directly converted in the final stage into hydrocarbons by the hydrogen treatment. Thus, in effect, at least three hydrogenations and solvent dilution of the heavy products are accomplished by this simple expedient.

What we claim:

1. The process of preparing a hydrocarbon fuel from coal which comprises in combination subjecting a rst portion of coal to destructive hydrogenation by treatment with hydrogen at a temperature between about 900 and 1200 F., at a pressure between about 500 and 2000 p. s. i., separating the liquid product thus produced into a hydrocarbon fraction and a phenolic fraction, subjecting a second portion of coal to a simultaneous solvent extraction-hydrogenation with said phenolic fraction and hydrogen while at a temperature between about 700v and 850 F., and while at a pressure between about 100 and 2000 p. s. i., and subjecting a mixture of said hydrocarbon fraction, said phenolic fraction and the material derived from the second portion of coal to a mild hydrogenation in the presence of hydrogen at a temperature between about 750 and 950 F., at a pressure between about 100 and 1000 p. s. i. in the presence of a hydrogenation catalyst whereby the phenolic fraction is substantially converted into hydrocarbons and the hydrocarbon fraction and the material derived from the second portion of coal are substantially purified.

2. The process of preparing a hydrocarbon fuel from coal which comprises in combination subjecting a rst portion of a non-caking coal to destructive hydrogenation by treatment with hydrogen While in a luidized condition at a temperature between about 900 and 1200 F., at a pressure between about 500 and 2000 p. s. i., separating the liquid product thus produced into a hydrocarbon fraction and a phenolic fraction, subjecting a second portion of coal which contains atleast ten per cent volatile matter to a simultaneous solvent extraction-hydrogenation with said phenolic fraction and hydrogen while at a temperature between about 700 and 850 F., and while at a pressure between about 100 and 2000 p. s. i., and subjecting a mixture of said hydrocarbon fraction, said phenolic fraction and the material derived from the second portion of coal to a mild hydrogenation in the presence of hydrogen at a temperature between about 750 and 950 F., at a pressure between about 100 and 1000 p. s. i. in the presence of a hydrogenation catalyst whereby the phenolic fraction is substantially converted into hydrocarbons and the hydrocarbon fraction and the material derived from the second portion of coal are substantially purified.

3. The process of preparing a hydrocarbon fuel from lignite which comprises; in combination subjecting a first portion of lignite to destructive hydrogenation by treatment with hydrogen while in fiuidized condition at between about 900 and 1200 F., at a pressure between about 500 and 2000 p. s. i., separating the liquid product thus produced into a hydrocarbon fraction and a phenolic fraction, subjecting a second portion of lignite to a simultaneous solvent extraction-hydrogenation with said phenolic fraction and hydrogen while at a temperature between about 700 and 850 F., and while at a pressure between about 100 and 2000 p. s. i., and subjecting a mixture of said hydrocarbon fraction, said phenolic fraction and the material derived from the second portion of lignite to a mild hydrogenation in the presence of hydrogen, at a temperature between about 750 and 950 F., at a pressure between about 100 and 1000 p. s. i., and in the presence of an iron group metal or metal oxide whereby the phenolic fraction is substantially converted into hydrocarbons and the hydrocarbon fraction and the material derived from the second portion of lignite are substantially purified.

WILLIAM I. GILBERT. CHARLES W. MONTGOMERY.

References Cited in the I'lle of this patent UNITED STATES PATENTS OTHER REFERENCES I-Iydrogenation of Organic Substances, Ellis,

3rd edition, D. Van Nostrand Co., New York,

1930. page 5 06, sec. 4435.

Claims (1)

1. THE PROCESS OF PREPARING A HYDROCARBON FUEL FROM COAL WHICH COMPRISES IN COMBINATION SUBJECTING A FIRST PORTION OF COAL TO DESTRUCTIVE HYDROGENATION BY TREATMENT WITH HYDROGEN AT A TEMPERATURE BETWEEN ABOUT 900* AND 1200* F., AT A PRESSURE BETWENE ABOUT 500 AND 200 P.S.I., SEPARATING THE LIQUID PRODUCT THUS PRODUCED INTO A HYDROCARBON FRACTION AND A PHENOLIC FRACTION, SUBJECTING A SECOND PORTION OF COAL TO A SIMULTANEOUS SOLVENT EXTRACTION-HYDROGENATION WITH SAID PHENOLIC FRACTION AND HYDROGEN WHILE AT A TEMPERATURE BETWEEN ABOUT 700* AND 850* F., AND WHILE AT A PRESSURE BETWEEN ABOUT 100 AND 2000 P.S.I., AND SUBJECTING A MIXTURE OF SAID HYDROCARBON FRACTION, SAID PHENOLIC FRACTION AND THE MATERIAL DERIVED FROM THE SECOND PORTION OF COAL TO A MILD HYDROGENATION IN THE PRESENCE OF HYDROGEN AT A TEMPERATURE BETWEEN ABOUT 100 750* AND 950* F., AT A PRESSURE BETWEEN ABOUT 100 AND 1000 P.S.I. IN THE PRESENCE OF A HYDROGENATION CATALYST WHEREBY THE PHENOLIC FRACTION IS SUBSTANTIALLY CONVERTED INTO HYDROCARBONS AND THE HYDROCARBON FRACTION AND THE MATERIAL DERIVED FROM THE SECOND PORTION OF COAL ARE SUBSTANTIALLY PURIFIED.

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