This isn't exactly "coal-to-oil", but it's closely related to that subject in that we are finding many ways to replace dwindling petroleum with abundant coal.
Have a look at the enclosed patent.
Herewith some excerpts, comment following. We know it's loooong, but it's worth the read:
" US Patent 5888469 - Method of making a carbon foam material and resultant product
Inventors: Alfred Stiller, Peter Stansberry, John Zondlo
Assignee: West Virginia University
BACKGROUND
1. Field of the Invention
The present invention relates to a method of making an improved carbon foam material and particularly a graphitized carbon foam material having superior compressive strength and electrical conductivity.
2. Description of the Prior Art
It has been known for many decades that coal can be beneficiated for application in a wide variety of environments. For example, it has been known that coal may be employed as a fuel in electric utility plants and, in respect of such usages, beneficiating of the coal will reduce the ash content and the amount of sulfur and nitrogen species contained in the gaseous exhaust products.
It has also been known to convert coal into coke for use in various process metallurgy environments.
It has also been known to create carbon foam materials from feedstocks other than coal, which can be glassy or vitreous in nature, and are brittle and not very strong. These products which lack compressive strength tend to be very brittle and are not graphitizable.
It has been suggested to convert petroleum-derived mesophase pitch into a carbon foam product by employing a blowing/foaming agent to create bubbles in the material, followed by graphitization of the resultant carbonized foams above 2300° C. It is noted that one of the conclusions stated in this article is that the mechanical properties of the graphitic cellular structure were quite low when compared to model predictions.
It has been known to suggest the use of graphitic ligaments in an oriented structure in modeling related to structural materials.
It has been known to make carbon fibers by a spinning process at elevated temperatures using precursor materials which may be polyacrylonitrile or mesophase pitch. This mesophase pitch is said to be achieved through conversion of coal-tar or petroleum pitch feedstock into the mesophase state through thermal treatment. This thermal treatment is followed by extrusion in a melt spinning process to form a fiber. The oriented fiber is then thermoset and carbonized. To make a usable product from the resulting fibers, they must be woven into a network, impregnated, coked and graphitized. This involves a multi-step, costly process.
There remains, therefore, a very substantial need for an improved method of making carbon foam product which has enhanced compressive strength and is graphitizable and the resultant products.
SUMMARY OF THE INVENTION
The present invention has met the above-described needs. In one preferred method of the present invention, a coke precursor is provided by de-ashing and hydrogenating bituminous coal. The hydrogenated coal is then dissolved in a suitable solvent which facilitates de-ashing of the coal and separation of the asphaltenes from the oil constituent.
In a preferred practice of the invention, a blend of hydrogenated and unhydrogenated solvent separated asphaltenes may be employed in order to adjust the degree of anisotropy present in the carbon foam. Also, it is preferred that the voids in the foam may be generally of equal size. The size of the individual bubbles or voids may be adjusted by altering the amount of volatile material contained in the asphaltenes or varying the pressure under which coking is effected.
In a preferred practice of the invention, after coking, the foamed material is subjected to calcining at a temperature substantially higher than the coking temperature to remove residual volatile material. The preferred temperature is about 975° C. to 1025° C. and the time is that which is adequate to achieve a uniform body temperature for the material.
The method produces a graphitized carbon foam product having a compressive strength in excess of about 600 lb/in2.
It is an object of the present invention to provide a method of producing coal-derived carbon foam which may be graphitized.
It is a further object of the present invention to provide such a method and the resulting product which may be produced by hydrogenating bituminous coal followed by separation of asphaltenes, and coking the same.
It is a further object of the present invention to provide a method and resultant product which permits control of the degree of anisotropy of the carbon foam.
It is a further object of the present invention to provide such a method wherein solvent partitioning of the unhydrogenated coal or hydrogenated coal is employed to select the proper fraction for making the desired foam or removing inorganic species from the coal.
It is a further object of the present invention to provide such a method which permits control over the size of the voids in the carbon foam and the density of the same.
It is a further object of the invention to provide a method of producing such a product which is capable of being graphitized and has much higher compressive strength than previously known carbon foams.
It is a further object of the present invention to provide such a method which produces a controllable, low-density carbon foam product having either isotropic or anisotropic graphite structure which may have open-cell or close-cell configurations.
It is a further object of the present invention to provide a method of producing such a product which is lightweight and possesses a controllable degree of electrical and thermal conductivity.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a preferred practice of the present invention, bituminous coal is provided in size of about -60 to -200 mesh and, preferably, about -60 to -80 mesh. In the embodiment, as shown in FIG. 1, wherein anisotropic carbon foam will be produced, the coal is first hydrogenated in step 2. This may be accomplished at a temperature of about 325° C. to 450° C. at a hydrogen over-pressure of about 500 to 2,500 psig hydrogen cold for a reaction time of about 15 minutes to 1.5 hours. Tetralin may be employed as a proton-donating agent. After the reactor has cooled, the contents are removed and the tetralin separated by distillation. The resulting hydrogenated coal may be exhaustively extracted with Tetrahydrofuran (THF) with the residue being filtered to remove inorganic matter. It has been found that under these hydrogenating conditions, more than one-half of the coal mass will be rendered soluble in THF. The hydrogenated coal is subjected to preliminary beneficiation as by de-ashing, which may be accomplished in the manner disclosed in Stiller et al., U.S. Pat. No. 4,272,356. The THF portion will contain all of the asphaltenes, or coal-derived pitch precursors, and oils. The THF, after extraction is complete, may be evaporated for recycling and the recovered coal-derived pitch precursor separated by employing a suitable solvent, such as toluene. The toluene-soluble fraction will be referred to generally as "oils" and the remainder referred to as the asphaltene fraction or coal-derived pitch precursor fraction which is dried.
In a preferred practice of the invention, after coking, the foamed material is subjected to calcining at a temperature substantially higher than the coking temperature to remove residual volatile material. The preferred temperature is about 975° C. to 1025° C. and the time is that which is adequate to achieve a uniform body temperature for the material.
The method produces a graphitized carbon foam product having a compressive strength in excess of about 600 lb/in2.
It is an object of the present invention to provide a method of producing coal-derived carbon foam which may be graphitized.
It is a further object of the present invention to provide such a method and the resulting product which may be produced by hydrogenating bituminous coal followed by separation of asphaltenes, and coking the same.
It is a further object of the present invention to provide a method and resultant product which permits control of the degree of anisotropy of the carbon foam.
It is a further object of the present invention to provide such a method wherein solvent partitioning of the unhydrogenated coal or hydrogenated coal is employed to select the proper fraction for making the desired foam or removing inorganic species from the coal.
It is a further object of the present invention to provide such a method which permits control over the size of the voids in the carbon foam and the density of the same.
It is a further object of the invention to provide a method of producing such a product which is capable of being graphitized and has much higher compressive strength than previously known carbon foams.
It is a further object of the present invention to provide such a method which produces a controllable, low-density carbon foam product having either isotropic or anisotropic graphite structure which may have open-cell or close-cell configurations.
It is a further object of the present invention to provide a method of producing such a product which is lightweight and possesses a controllable degree of electrical and thermal conductivity.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a preferred practice of the present invention, bituminous coal is provided in size of about -60 to -200 mesh and, preferably, about -60 to -80 mesh. In the embodiment, as shown in FIG. 1, wherein anisotropic carbon foam will be produced, the coal is first hydrogenated in step 2. This may be accomplished at a temperature of about 325° C. to 450° C. at a hydrogen over-pressure of about 500 to 2,500 psig hydrogen cold for a reaction time of about 15 minutes to 1.5 hours. Tetralin may be employed as a proton-donating agent. After the reactor has cooled, the contents are removed and the tetralin separated by distillation. The resulting hydrogenated coal may be exhaustively extracted with Tetrahydrofuran (THF) with the residue being filtered to remove inorganic matter. It has been found that under these hydrogenating conditions, more than one-half of the coal mass will be rendered soluble in THF. The hydrogenated coal is subjected to preliminary beneficiation as by de-ashing, which may be accomplished in the manner disclosed in Stiller et al., U.S. Pat. No. 4,272,356. The THF portion will contain all of the asphaltenes, or coal-derived pitch precursors, and oils. The THF, after extraction is complete, may be evaporated for recycling and the recovered coal-derived pitch precursor separated by employing a suitable solvent, such as toluene. The toluene-soluble fraction will be referred to generally as "oils" and the remainder referred to as the asphaltene fraction or coal-derived pitch precursor fraction which is dried.
The next step in creating carbon foam is to coke the asphaltenes.
In a preferred practice of the invention, after coking, the foamed material is subjected to calcining at a temperature substantially higher than the coking temperature to remove residual volatile material. The preferred temperature is about 975° C. to 1025° C. and the time is that which is adequate to achieve a uniform body temperature for the material.
This foaming operation, when conducted in the coking oven in this manner, serves to partially devolatilize the asphaltenes with the evolution of the volatile matter serving to provide bubbles or voids and thereby create the carbon foam product.
If desired, the carbon foam may be used in this form for many uses, such as structural materials, light-weight automotive composites, impact and energy-absorbing structures and heat insulators, for example.
In the embodiment ... hydrogenation involves large coal molecules being broken apart thermally with the resultant fragments being capped by hydrogen. This results in formation of smaller aromatic molecules.
With respect to the bubble or void dimension in the foam, the bubbles will generally be of equal dimension to each other. The bubble dimension may be varied by altering the volatile content of the asphaltenes obtained through the extraction process.
It has been found that the graphitized foam product produced in this manner has a very high compressive strength and generally will be greater than about 600 lb/in2. The compressive strength is related to bubble size with smaller bubble size increasing compressive strength.
Among the advantageous properties of the present carbon foam are that it is lightweight and can be either a thermal insulator, which is electrically conductive, or an efficient conductor of heat and electricity. The foam can be molded into any desired shape by coking within appropriately shaped molds. The foam may also find use in building and structural members, such as a substitute for wood and steel beams. Numerous, advantageous automotive uses, such as in pistons, vehicle frames, impact absorbers for doors, and connecting rods exist. Further, in view of the strength and lightweight nature of the product, aerospace and airplane uses, such as in wings, brakes, as well assatellite and space station structures involve advantage end uses.
While it will be appreciated by those skilled in the art that numerous uses may be made of a material having the blend of desired properties of those of the present invention, among additional uses would be as a catalyst support for high temperature catalysts, in biological materials, such as bone and prosthetic items, as well as in environmental waste remediation as by heavy metal removal, electrostatic precipitators and in nuclear waste containers wherein undesired leaching or degradation of the carbon material would be resisted.
It will be appreciated that the present invention has provided a method of creating a unique, high-compressive strength, coal-derived carbon foam material, which ... possesses a great number of desirable properties. All of this is accomplished by starting with bituminous coal ... ."
In the embodiment ... hydrogenation involves large coal molecules being broken apart thermally with the resultant fragments being capped by hydrogen. This results in formation of smaller aromatic molecules.
With respect to the bubble or void dimension in the foam, the bubbles will generally be of equal dimension to each other. The bubble dimension may be varied by altering the volatile content of the asphaltenes obtained through the extraction process.
It has been found that the graphitized foam product produced in this manner has a very high compressive strength and generally will be greater than about 600 lb/in2. The compressive strength is related to bubble size with smaller bubble size increasing compressive strength.
Among the advantageous properties of the present carbon foam are that it is lightweight and can be either a thermal insulator, which is electrically conductive, or an efficient conductor of heat and electricity. The foam can be molded into any desired shape by coking within appropriately shaped molds. The foam may also find use in building and structural members, such as a substitute for wood and steel beams. Numerous, advantageous automotive uses, such as in pistons, vehicle frames, impact absorbers for doors, and connecting rods exist. Further, in view of the strength and lightweight nature of the product, aerospace and airplane uses, such as in wings, brakes, as well assatellite and space station structures involve advantage end uses.
While it will be appreciated by those skilled in the art that numerous uses may be made of a material having the blend of desired properties of those of the present invention, among additional uses would be as a catalyst support for high temperature catalysts, in biological materials, such as bone and prosthetic items, as well as in environmental waste remediation as by heavy metal removal, electrostatic precipitators and in nuclear waste containers wherein undesired leaching or degradation of the carbon material would be resisted.
It will be appreciated that the present invention has provided a method of creating a unique, high-compressive strength, coal-derived carbon foam material, which ... possesses a great number of desirable properties. All of this is accomplished by starting with bituminous coal ... ."
Mike, the foam they described herein is similar in many respects to foams derived from petrochemicals, and it has many of the same uses.
And, allow us to repeat one important passage:
"The present invention has met the above-described needs. In one preferred method of the present invention, a coke precursor is provided by de-ashing and hydrogenating bituminous coal. The hydrogenated coal is then dissolved in a suitable solvent which facilitates de-ashing of the coal and separation of the asphaltenes from the oil constituent."
_______________
They hydrogenate the coal, Mike, and then dissolve it in a solvent before they use it as a substitute for petrochemical plastics. Those are the same steps that need performed so that coal can be converted into liquid fuel substitutes for petroleum.
The solvent they specify in the body of the text is tetralin, which again appears to be the most effective coal liquefaction agent yet identified.
We are learning how to fill all of our petroleum needs, including those for plastic foam raw materials, ... with coal.