ANALYTICAL CHEMISTRY
1070 agree remarkably well (Table IV). Second, analysis by the writers' two-color treatment and by converting to D D E through dehydrohalogenation also shows excellent agreement (Table V). These three independent approaches would appear to be ample evidence that D D T plus a substantial proportion of the degradation product D D E is present in human fat. Supplementing these experiments are the data on the absorption spectra before and after dehydrohalogenation of the Schechter-Haller materials isolated (8). Many additional absorption spectra data have been collected by the writers, but have not been presented for the sake of brevity. These omitted data are in all cases confirmatory. It is also believed the chromatographic experiments are highly significant (Table X). Finally, the examination of fat samples predating the advent of D D T (Table XI) showed no evidence of the presence of Schechter-Haller-positive materials. The writers believe that DDT and D D E are contaminants of human f a t of the general population.
courtesy of A. J. Miller, Department of Pathology, School of Medicine, University of Louisville, Louisville, Ky. LITERATURE CITED
(1) Clifford, P. A,, J. Assoc. (2)
(3) (4) (5) (6)
Ofic.Agr. Chemists,30, 337-49 (1947). Communicable Disease Center, Technical Development Branch, Federal Security Agency, Savannah, Ga., Chemical Memorandum 1,1952. Davidow, B., J . Assoc. Ofic.Agr. Chemists,33, 130-2 (1950). Haller, H. L., et al., J . Am. Chem. Soc., 67, 1591-602 (1945). Knudson, H. W., Meloche, 1%'.V., and Juday, C., I N D . ESG. CHEM., ANAL.ED.,12,715-18 (1940). Laug, E. P., Kunee, F. and Prickett, C. S., Arch. Ind. Hug.
ACKNOWLEDGMENT
and Occupational Med., 3,245-6 (1951). (7) Offner, R. R., and Calvary, H. O., J . Pharmacol. Erptl. Therap., 85.363-70 (1945). (8) Pearce, G. W:, Mattson, A. hl., and Hayes, W. J., Science, 116, 254-6 (1952). (9) Prickett, C. S., Kunze, F. M., and Laug, E. P., J . Sssoc. Ofic. A g r . Chemists,33,880-6 (1950). (10) Schechter, M. S., Pogorelskin, M . A, and Haller, H. L., IND. ESG.CHEM.,ANAL.ED.,19,51-3 (1947). (11) Schechter, 11.S., Soloway, S.B., Hayes, R. A., and Haller, H. , L., Ibid., 17, 704-9 (1945).
The writers wish to express their appreciation to F. -4.Gunther and R. C. Roark for supplying the o,p'-DDT used in this work. The samples of fat predating D D T were supplied through the
RECEIVEDfor review February 18, 1953. Accepted April 2 5 , 1953. Presented before the Division of Agricultural and Food Chemistry. Pesticides SOCIETY, Subdivision, at the 122nd Meeting of the AMERICANCHEMICAL Atlantic City, 37. J.
Nitrogen Compounds in Distillate Fuels LOYAL F. WARD, J R . ~R , . T. 3\IOORE, AND JOHN S. BALL Petroleum a n d Oil-Shale Experiment Station, Bureau of Mines, Laramie, Fyo. Some types of nitrogen compounds have been shown to cause instability in distillate fuels. An analytical scheme for types of nitrogen compounds in petroleum distillates has been based on a combination of methods for total nitrogen, basic nitrogen, and pyrrole nitrogen. This analysis has been made on 34 samples of distillate fuels chosen to be representative of geographical origin of the crude oil and of processing methods. With the exception of the California oils the total nitrogen content is below 0.05% for each oil. Differentiation between catalytically and thermally cracked stocks can be made on the basis of the types of nitrogen compounds present. A test for distinguishing among straight-run, catalytically cracked, and thermally cracked fuels is proposed.
T
HIRTY-four samples of distillate fuels representing production from different areas of the country and various methods of processing have been investigated for information as to types of nitrogen compounds present. -4 combination of methods for total nitrogen, basic nitrogen, and pyrrole nitrogen provides a systematic approach for obtaining this information. Results from this combination of methods show distinctive patterns for fuels obtained by different processing methods. The presence of nitrogen compounds, particularly pyrroles, has been shown (9) to affect adversely the storage characteristics of distillate fuels. This study of the types of nitrogen compounds in distillate fuels was made to provide a background for correlation with stability studies in progress on the same fuels. It also gives information on the types of nitrogen compounds present as a guide to further development of analytical methods. Comparatively little is known concerning the nitrogen compounds present in petroleum. Bailey and coworkers isolated ( I , 6) a series of pyridines and quinolines from straight-run kerosene. Sauer, Melpolder, and Brown (8) found carbazoles, indoles, pyrroles, pyridines, and quinolines in straight-run distillate fuel from Kuwait by a mass-spectrometer technique. Thompson, Symon, and Wankat (IO)have found pyrroles in virgin distillate 1 Present
addrem, Julius Hyman and Co., Denver, Colo.
fuel oils by a colorimetric method, Treibs (11)isolated porphyrins from various petroleums. Pyridines, quinolines. pyrroles, and nitriles have been identified also from shale oil (18 ) . -4nalytical methods for the determination of types of nitrogen compounds are far from satisfactory. With the exception of the California oils, the fuels studied had nitrogen contents of less than 0.05 weight % and extremely sensitive methods are needed. The most promising technique, that of Sauer, Melpolder, and Brown (8)) is time-consuming, being based on chromatography and mass spectrometry. A separation into basic and nonbasic classifications can be achieved by titration of the basic nitrogen compounds with perchloric acid (3, 6, 7), and a colorimetric method for the determination of pyrroles has been described (IO). The analysee described in this paper combine these methods to give results for basic nitrogen, nonbasic nitrogen, and pyrrole nitrogen. -4 test to distinguish between straight-run, thermally cracked, and catalytically cracked distillates is also suggested. SAMPLES
The 34 samples of distillate fuels were obtained by the Western Petroleum Refiners Association for a stability testing program being conducted a t the Petroleum Experiment Station of the Bureau of Mines, Bartlesville, Okla. These samples were selected 80 as to he representative of crude oil sources now in use in this
.
1072
ANALYTICAL CHEMISTRY
Table 11. Ratio of Basic to Total Nitrogen in Various Distillate Fuels Straight Run Western Mid-Continent
...
Eastern Mid-Continent Gulf Coast West Texas California
0.22
...
0.31 0 65 0 60
Rocky Mountain Sourry County Middle East Venezuela Mexico
Catalytically Cracked 0 39 0.25 0.23
Thermally Cracked 0.57
...
0.59
1,oo
0.09 0.02 0.43 0.22 0.28 0.67 0.32
0.67 0.58 0 49 0.62
... ... ...
0.67 0.39 ... 0.38 ... Canada 0.67 0 31 a Total nitrogen too low for ratio to be significant.
0.50 0 81
v
lower ratios, although the Middle East fuel has a high ratio. The ratio is high for all of the thermally cracked stocks. The measurement of pyrrole nitrogen is based on the development of a color with p-dimethylaminobenzaldehyde. The in tensity of the color as compared to the intensity developed by 2-methylpyrrole is used to estimate the pyrrole nitrogen content. However, rather broad absorption curves are obtained as shown for three fuels in Figure 1 and the maxima are a t different wave lengths. Table I lists these wave lengths. I t will be noted that, in general, they are higher for the straight-run fuels and lower for the catalytically cracked fuels. KOparticular trend is noticeable for the thermally cracked fuels. The maxima for pyrrole and 2-methylpyrrole are 540 and 542 mp, respectively, while that for indole is 564 mfi. The maxima may be some indication of the relative amounts of pyrrole and indole. The pyrrole nitrogen method cannot be thoroughly tested a t present because of a lack of pure compounds for standardization. The 2-methylpyrrole used as a standard would not occur in the distillate fuel boiling range. However, considering the fact that little is known concerning which compounds are present and what their properties may be, the method gives logical results. I n all cases except four, the pyrrole nitrogen is less than the nonbasic (total minus basic) nitrogen. As shown by Sauer, Melpolder, and Brown (8) there are compounds (carbazoles) present in distillate fuels that would be nonbasic but not pyrrolic to this method. For this reason, the pyrrole nitrogen would not be expected to equal the nonbasic nitrogen. As a by-product of this research, a test which appears to show differentiation among straight-run, catalytically cracked, and thermally cracked fuels was noted. I n determining pyrrole nitrogen a reference standard is prepared by shaking the oil with phosphoric and acetic acids. In the case of the straight-run fuels, virtually no color developed, but for the catalytically cracked fuels, an emerald-green color was formed. The thermally cracked fuels gave a red-brown blank. The source of this color reaction is not known, but it suggests the presence of porphyrins. For the 34 fuels of known origin used in this research, the test appeared to give accurate differentiation. ACKNOWLEDGMENT
0 525
5 50
WAVE LENGTH
575
600
Imp
Figure 1. Absorption Spectra of PyrroleEhrlich Reagent Product Extracted from Diesel Fuels
nitrogen than the catalytically cracked fuels. Two explanations are available. The catalyst may remove appreciable amounts of basic nitrogen, or there may be actual conversion of pyrrole rings to pyridine rings owing to the higher temperatures employed in thermal cracking. The ratio N B / N T (basic nitrogen/total nitrogen) has been used by Richter et al. ( 7 ) in their study of nitrogen in crude oils. This ratio was found to be remarkably constant (0.28 to 0.34) for 14 crude oils. However, deviations were found for fractions of California crudes boiling between 827' and 668" F. in which range a maximum occurs. This range is included in the distillate fuels described in this paper. The values of NBINT are shown in Table 11. Values for some fuels have been disregarded, as the low content of total nitrogen makes them unreliable. The values for the straight-run fuels are consistent with those found by Richter, in that the California oils give high results. This is also true for Venezuelan and Canadian oils. Generally the catalytically cracked oils show
The fuels on which this work was carried out mere made available by H. 11. Smith, Bureau of Mines, Bartlesville, Okla. The 2-rnethylpyrrole used for the calibration curve was obtained from R. B. Thompson, Universal Oil Products Co., Chicago, Ill. This work was made possible by funds provided by the Bureau of Ships, Department of Defense, and was done in cooperation with the University of Wyoming. LITERATURE CITED
(1) Bailey, J. R., "The Science of Petroleum," Vol. 11, p. 1047
London. Oxford Universitv Press. 1938.
(2) Ball, John S., Whisman, hl: L., and Wenger, W.J., Ind. Eng. Chem.. 4 3 , 2 5 7 7 (1951). (3) Deal, V. Z., Weiss, F. T., and White, T. T., ANAL.CHEDI.,2 4 , 919 (1952). (4)
Lake, G. R., McCutchan, P., Van Meter, R., and Neel, J. C., I b i d , 2 3 , 1634 (1951).
Lochte, H. L., I n d . Eng. Chem., 4 4 , 2 5 9 7 (1952). Moore, R. T., SlcCutchan, P., and Young, D. -4., ANAL. CHEM.,2 3 , 1639 (1951). (7) Richter, F. P., Caesar, P. D., hleisel, S. L., and Offenhauer, R. D., Ind. Eng. Chem., 4 4 , 2601 (1952). (8) Sauer, R. W., hlelpolder, F. W., and Brown, R. A , , I b i d . , 4 4 , (5) (6)
2606 (1952).
Thompson, R. B., Chenicek, J. A,, Druse, L. W., and Symon, T.. Ibid., 4 3 , 935 (1961). (10) Thompson, R. B., Symon, T.. and Wankat, C., ANAL.CHEX., (9)
2 4 , 1465 (1952). (11) Treibs, .4,, Angew. Chem., 4 9 , 682 (1936). (12) Van Meter, R., Bailey, C. W., Lloore, R. T.,
Allbright, C. S., Jacobson, I. A,, Hylton, V. hl., and Ball, J. S.,ANAL.CHEM.,
2 4 , 1758 (1952). RECEIVED for review Deoember 22, 1952. Accepted April 6. 1953. Presented before the Division of Petroleum Chemistry at the 123rd hleeting of the AMERICAN CHEMICAL SOCIETY, Los Angeles, Calif.
