LITERATURE C I T E D J. E. Andrews and M. A. Littlejohn, J . Nectrochem. Soc., 122, 1273
(1975). M. Ilegems, R. Dingle, and R. A. Logan, J . Appl. fhys., 43, 3797-3800
(8) J. C. Veseley, M. Shatzkes, and P. J. Burkhardt, fhys. Rev. B. 10, 582
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11~1791
C. A. Evans, Jr., Anal. Chem., 44, (13),67A (1972). C. A. Evans, Jr., Thin Solld Films, 19, 11-19 (1973). F.‘W. Karasek, Res./Dev., 24, 40-46 (1973). M. Gettings and J. P. Coad, Surf. Sci., 53, 636-648 (1975). H. J. Hovel and J. J. Cuomo, Appl. f h y s . Lett., 20, 71-73 (1972).
RECEIVED for review August 9,1976. Accepted June 6,1977. This work was partially supported by the Office of Naval Research.
Characterization of Lignites by Pyrolysis-Gas Chromatography C. S. Glam,” T. E. Goodwln, P. Y. Glam, K. F. Rion, and S. G. Smith Department of Chemlstry, Texas A&M University, College Station, Texas 77843
A technique has been developed for the rapid characterization and “screening” of llgnite samples by pyrolysis-gas chromatography. The application of thls technique to a series of Texas lignites Is descrlbed. The production of n-parafflns and 1-olefins wlth 1-5 carbons is monltored,
Pyrolysis is probably the oldest operation to be carried out on coal (1,2)and is the foundation for many coal liquefaction (3,4) and gasification (5-7)procedures. Recent innovations in this area include vacuum pyrolysis in a mass spectrometer (8-131, laser irradiation (14, 15),“flash heating” (16,17) and the use of arc plasmas (18). While this manuscript was in preparation, Hanson, Vanderborgh, and Brookins (14) reported their applications of laser pyrolysis-gas chromatography to study the influence of coal composition on the distribution of gaseous products. Correlations between experimental results and elemental compositions were presented. RomoviEek and Kubgt (19)developed a technique for rapid pyrolysis whereby the coal sample is dropped into a bath of molten tin. The product gases were swept by an inert carrier gas into a gas chromatograph, whereby the production of selected low molecular weight hydrocarbons was monitored at several pyrolysis temperatures. Coates, Chen, and Pope (20) studied the amount and composition of gases evolved during rapid pyrolysis (1350 OC in C0.3 s) of a bituminous coal. A number of other pyrolysis-gas chromatography procedures have been reported
(21-25). Recently Gray, Cogoli, and Essenhigh (26)reviewed the literature regarding coal pyrolysis and came to the following conclusions, inter alia: (a) Rapid heating can raise coal samples to high temperatures without significant decomposition, and they can then pyrolyze at a constant temperature with a yield of volatiles that is higher than can be obtained under any other experimental conditions. (b) Pyrolysis at lower heating rates may cause part of the coal substance to cross-link during the period of temperature rise to the final, constant pyrolysis temperature. This cross-linking binds material that would otherwise be able to escape as volatiles, thus reducing the volatile yield. This manuscript describes a simple procedure for the rapid pyrolysis of lignite samples. The use of gas chromatography for determination of the C1-Cs pyrolysis products is reported. 1540
ANALYTICAL CHEMISTRY, VOL. 49, NO. 11, SEPTEMBER 1977
EXPERIMENTAL Apparatus. At our request Chemical Data Systems, Inc. (Oxford, Pa.) designed a “Controlled Atmosphere Pyrolysis System”. It consists of a “Pyroprobe” pyrolyzer with a coiled platinum wire as the heating element, an interface to a gas chromatograph, and three detectors (electron capture, thermal conductivity and flame ionization). Only the flame ionization detector was used for the analyses described herein. The gas chromatograph was fitted with a 10-ft x ‘/&I. stainless steel column packed with Poropak Q (80-100 mesh) (27).The air, hydrogen, and nitrogen (carrier gas) flow rates were 200,40, and 40 mL/min, respectively. The column was held at 60 O C for 3 min after injection, temperature-programmed at 12.5 OC/min up to 150 “C, and held at that temperature for the duration of the run. The injector, detector, interface (between pyrolyzer and GC), and final pyrolysis temperatures were 150,360,250, and 850 O C , reBpectively. A ramp speed of 1 “C/ms was used to arrive at the final pyrolysis temperature. The total pyrolysis time was 20 8. Procedure. The lignite samples were air-dried,crushed, sieved to
