1164
ANALYTICAL CHEMISTRY, VOL. 5 1 , NO. 8, JULY 1979
THE PROGRAM A program has been developed in BASIC on a HewlettPackard 2000F computer to allow elemental analysis data t o be predicted, or to be fitted using any of the methods described here, with excellent user convenience and ease of interactive use. T h e whole program is about 670 statements long, but all the fitting procedures described here are together only about 210 statements long, the rest being t h e calling program, which provides a default and keyword input system, displays the results, and gives help by explaining the input facilities. With a suitably crude calling program, and perhaps with restriction to using, e.g., the walking method, a very small computer could b e used. Requests for listings of t h e whole
program, or of just the working subroutines, should be addressed to t h e author.
LITERATURE CITED ( I ) W. A. Miller and C. E. Groves, "Elements of Chemistry",Part 111, 5th ed., Longmans, London, 1880, p 35. (2) C. W. Keenan, J. H. Wood, and D. C. Kleinfelter, "General College Chemistry",5th ed.,Harper InternationalEdition, Harper, New Yo&, 1976, p 145. (3) C. L. Wilkins, C. E. Klopfenstein, T. L. Isenhour, P. C. Jurs. J. S.Evans, and R. C. Williams, "Introduction to Computer Programming for Chemists-BASIC Version", Allyn and Bacon, Boston, 1974, p 164.
RECEIVED for review J u n e 19, 1978. Accepted February 22, 1979.
Determination of Asphaltenes in Fuels from Coal Hydrogenation Fred W. Steffgen, Karl T. Schroeder, and Bradley C. Bockrath" Pittsburgh Energy Technology Center, U.S. Department of Energy, 4800 Forbes Avenue, Pittsburgh, Pennsylvania 752 13
A method is described for the quantitative separation of coalderived fuels into toluene insolubles, asphaltenes (toluene soluble, pentane Insoluble), and oils (pentane soluble). The prime objective was to identify the variables in the procedure that affect the values obtained for asphaltene content. Substitutlon of toluene for benzene does not have a large effect on the values reported for either lnsolubles or asphaltenes. However, in order to obtain reproducible determinations, the precipitation of asphaltenes must be rigorously controlled. The precipitation Is carried out by adding a large excess of pentane to a slurry prepared from the toluene solubles and toluene. A significant difference was found in the values determined for asphaltenes depending upon the amount of toluene used in the slurry. I t Is recommended that the amount of toluene in the slurry be equal to or greater than 3 mL/g solubles.
Solvent analysis is a method used frequently to characterize the solid and liquid products obtained from coal liquefaction processes and the solvent refining of coal (1-5). By this method, samples are separated into fractions according to their solubilities in several solvents. For example, t h e analysis described here is reported in terms of three fractions: oils (pentane soluble), asphaltenes (toluene soluble, pentane insoluble), and toluene insolubles. By custom t h e determination of the asphaltene fraction of coal-derived products has followed the precedent established in petroleum chemistry. Thus, the definition of coal-derived asphaltenes as those materials "soluble in benzene and insoluble in hexane" has been generally accepted. However, in practice, i t has been commonly found t h a t t h e separation of liquid coal hydrogenation products is not as facile as in the case of petroleum, Several laboratories have individually developed procedures to overcome the difficulties encountered in handling these less tractable materials. This work demonstrates t h a t certain differences in procedure have a large effect upon the value reported as asphaltenes. We have examined several variables with a view toward developing a procedure t h a t employs a solvent t h a t is less toxic than benzene, yet still conforms to the sense of This
article not subject to
US.
Copyright.
t h e simple definition of asphaltenes. T h e precision of such a method was evaluated.
EXPERIMENTAL Solvent separations were conducted on samples of centrifuged liquid product obtained from the 1/2 TPD process development unit (6)at the Pittsburgh Energy Technology Center. The samples were taken from runs FB44, batch 56, and FB45, batch 57. Both products were free flowing liquids produced from Pittsburgh seam, hvAb coal from Ireland Mine, W. Va. Separations were also performed on a Solvent Refined Coal (SRC),sample number 3068, kindly provided by Southern Services, Inc., Wilsonville, Ala. The solvents were all reagent grade. Pentane was distilled just prior to use. A flow chart of the separation scheme is given in Figure 1. In a standard experiment, a 3-g sample of the product was slurried with 100 mL of benzene or toluene in a beaker. The slurry was filtered through a 33 X 80 mm one and a half thickness Soxhlet thimble. The thimble had been previously washed with solvent and dried in a vacuum oven >lo0 "C and a t pressure
