ANALYTICAL CHEMISTRY
350 sults appeared to be especially significant in the magnesium determinations. The important data obtained are listed in Table 111. I t is apparent from the data in Table I11 that a marked change in the tip of the upper electrode generally affects the accuracy of a series of determinations on a specific sample. It would then appear advisable to keep the upper electrodes a t the same shape for successive runs. Since i t is not feasible to machine after each sparking, the writers recommend that the upper electrodes be machined originally to have flat tips rather than 120” points. The data from Table I indicate that in general magnesium and calcium can be determined with the following precision, stated in terms c>f the per cent standard deviation of a single measurement: For magnesium: 5.70% in the range of 0.100 to 1.00 p.p.m.; 9.96% in the range of 1.00 to 10.0 p.p.m.; 1.8070 in the range of 3.00 to 20.0 p.p.m. For calcium: 5.56Y0 in the range of 0,100 to 1.00 p.p.m.; 3.7670in the rangeof 0.500 to3.00 p.p.m,; 10.6% in the range of 3.00 to 30.0 p.p.m.; 5.08% in the range of 10.0 to 30.0 p.p.m. Of course, a greater number of determinations for a given sample lessens the standard deviation. In this case, in which four determinations were made, the values of the standard deviation of the mean are half of the values given above. Whereas the sensitivity and reliability of the silver disk electrode method in the range of 0.100 to 1.00 p.p.m. are somewhat superior to those of the Beckman flame photometer a i t h photomultiplier attachment and oxyacetylene flame, the flame photometric method is capable of yielding a t least equivalent reliability in the higher ranges of concentration of the elements described. ACKNOWLEDGMENT
The work described was supported in part by the Research
Committee of the Graduate School from funds supplied by the Wisconsin Alumni Research Foundation, LITERATURE CITED
Addicks, L., “Silver in Industry,” p. 173, Sew York, Reinhold Publishing Corp., 1940. Blank, 0. V., and Sventitsky, N. S.,Compt. rend. acad. sci. U.R.S.S., 44, 58 (1944). Boyle, A. J., Whitehead, T., Bird, E., Batchelor, T. If.,Iseri. L. T., Jacobson, S.D., and Meyers, G. E., J . Lab. Clin. M e d . , 34, 625 (1949). Churchill, J. R., IND.ENG.CHEX.,AXAL.ED., 16, 653 (1944). Churchill, J. R., “Modern Instrumental Analysis,” ed. by D. F. Bolta, p. 1, Ann Arbor, hIich., Edwards Bros., 1949. Dixon, W.J., and Massey, F. J., ”Introduction to Statistical Analysis,” p. 119, New York, McGraw-Hill Book Co., 1951. Fred, SI.,Kachtrieb, ?;. H., and Tompkins, F. S., J . O p t . SOC. Amer., 37, 279 (1947). Gambrill, C. AI., Gassman, A. G., and O’Neill, W. R., XSAL. CHEW,23, 1365 (1951). Latimer, W. >I., and Ilildebrmd, J. H., “Reference Book of Inorganic Chemistry,” p. 112, Kew York, RIacmillan Co.. 1940. Lohuis, D., hleloche, V. W., and Juday, C., Trans. Wiscoriain A c n d . Sci., 31, 285 (1938). Moorc, C. E., “A Multiplet Table of Astrophysical Interest,” Parts I and 11, Princeton, X.J . , Observatory, 1945. Rloore, C. E., Katl. Bur. Standards, Circ. 488 (1950, 1952). Nachtrieb, N. H., “Principles and Practice of Spectrochemical Analysis,” p. 264, Ken- York, LlcGraw-Hill Book Co., 1950. Pagliassotti, J. P., and Porsche, F. W., ANAL. CHEM.,23, 198 (1951). Ibid.,p. 1820. Ihid.,24, 1403 (1952). Pierucci, l I . , and Barbanti-Silva, L., .Vuovo cimcnto, 17, 275 (1940). Youden, W.J., “Statistical Methods for Chemists,” pp. 18, 84, Xew York, John Wiley & Sons, 1951. RECEIVED for review .4ugust 21, 1953. Accepted October 26, 1963.
Functional Group Analysis Characterization of Coal Hydrogenation Products R. A. GLENN and ELIZABETH D. OLLEMAN’ Coal Research Laboratory, Carnegie Institute
of Technology, Pittsburgh 13, Pa.
P
REVIOUS studies in this series on the chemical nature of products from the hydrogenolysis of coal have described the resolution of the distillate oils by means of chromatography on alumina (10, 14)and/or silica gel ( 1 ) and by means of multistage molecular distillation ( 2 ) . The resultant fractions were investigated by means of such properties as molecular weight, elemental composition, spectral analysis, and in a few instances by acid and alkali solubility and by hydroxyl content as indicated by acetylation. This paper reports the progress made on the determination of the classes of oxygen and nitrogen compounds present in coal hydrogenation oils. The classes of compounds other than hydrocarbons that may be found in coal hydrogenation oils include primary, secondary, and tertiary alcohols; primary, secondary, and tertiary amines; and phenols ( 2 , 5-7, f4). Functional group analysis in combination with ultimate analysis and molecular weight constitute the basis of an analytical procedure for the quantitative, estimation of these compounds. The coal hydrogenation oil used in this study was accumulated from the hydrogenolysis of seventeen 200-gram batches of Pittsburgh Seam coal R-ith ddkins catalyst a t 375’ C. for 12 1
Present address, Verona Research Center, Koppers Co , Inc , Verona, Pa.
hours (4) using the procedure already described (6). The ultimate composition, average molecular weight, and average molecular formula are given in Table I for the neutral oil resulting from the alternate extraction of the distillate oil with acid and with both aqueous and alcoholic alkali (4). ANALYTICAL PROCEDURES
The various analytical procedures used for the determination of the different functional groups and classes of compounds, either individually and/or collectively, are, in general, applications of semimicrotechniques described in the literature, but which have been refined for application to coal hydrogenation products.
Sodium aminoethoxide titration (8) in anhydrous ethylenediamine determines quantitatively carboxylic acids and monohydric phenols, either hindered or unhindered, without interference from nitrogen compounds. The dihydric and the unhindered monohydric phenols are assumed to have been removed completely by the repeated extraction with both aqueous and alcoholic alkali. Carboxylic acids are not found in coal hydrogenation oils, so the observed value represents the hindered phenols present. Perchloric acid titration (9) in glacial acetic acid determines all basic nitrogen compounds-Le. all primary, secondary, and tertiary amines except those cydlic secondary amines of the
V O L U M E 26, NO. 2, F E B R U A R Y 1 9 5 4
35 1
A procedure has been developed for estimating the amount of several classes of compounds present in a neutral oil from the hydrogenolysis of a Pittsburgh Seam coal. In addition to ultimate analysis and molecular weight determination, the procedure employs functional group analysiswhich is based on a combination of five different methods of determining either individually and/or collectively the various kinds of functional groups present in coal hydrogenation products. Quantitative data on the presence of pyrrole-type nitrogen compounds, both N-substituted and N-unsubstituted; ether-type and alcoholtype oxygen compounds; and primary, secondary, and tertiary amine nitrogen compounds have all been obtained for the first time.
pyrrole type. A few highly substituted pyrroles are titrated by this technique (11, IS), but they are assumed to he a negligible portion of the pyrroles present in coal hydrogenation oils. Therefore, the observed value represents the combined amounts of primary, secondary, and tertiary amines present which, presumably because of their high molecular weight, were not removed by the repeated acid extraction. Analytical acetylation ( 3 ) with acetic anhydride-pyridine reagent acetylates primary and secondary alcohols, primary and secondary amines (except pyrroles), and unhindered phenols. Since the latter are assumed to have been removed by the alkali
Table I.
Analytical Data on Coal Hydrogenation Neutral Oil
Ultimate composition, %
c,__K
88 13 9 58 " .l-
0.99 1.32 235
0 (by . _diff.). Average molecular weight" Average molecular formula, atoms per mole C
'
0
17.3 22.3 0.17 0.19
H N 0 Determined ebullioscopically in benzene.
Table 11. Distribution of Components of Coal Hydrogenation Neutral Oil (Analytical Scheme and Calculations) Component0 Total nitrogen
Designation A
Total oxygen l 0 Z o alcoholsb Hindered phenols l 0 Z 0 amines Py r r o1e8 l 0 Z 0 alcohols Hindered phenol l 0 Z o aminesd Pyrroles l 0 Z o amines I02O alcohols 1°20 amines
B
loZ03O aminea Hindered phenols
G H
l o Z 0 alcohols
I J
Ethers l o Amines
Amines 3O Amines Pyrroles' (unsubstituted) Pyrroles (substituted) 2 O
C
Quantities Present Meq./GrAm 0.71
Determined by Ultimate analysis Ultimate analysis Grignard reagent temperature)
0.83 (room
0.5OC
D
Grignard reagent (90" C.)
0.57b
E
Analytical acetylation
0.26b
F
Analytical acetylation selective hydrolysis Perchloric acid titration Sodium aminoethoxide titration E - F = 0.26 - 0.19 B - ( I H) = 0.83 (0.07 0.17) D - C = 0.57 - 0 . 6 0 F - K = 0.19 - 0.07 G F = 0.31 0.19
K L &I
++
-
n-
C
0
A
-
+
-
- (I + H + F) = 0.50 - (0.07 + 0.17 4- 0.19) - (G + N) = 0.71 -
(0.31
+ 0.07)
O.l!4b 0.31b 0.17b 0.07 0.59 0.07 0.12 0.12 0.07 0.33
Tertiary alcohols assumed t o be absent, and unhindered phenols assumed t o be extiacted. b Symbols 1 , 2O, and 3O denote primary, secondary, and tertiary, respectively. 0 Average of two or more determinations. d Two moles of methane instead of one are liberated from 1' amines at the elevated temperature. e Includea tert-alcohols if present. 0
extractions, the observed value represents the sum of the primafy and secondary alcohols and the primary and secondary amines. Analytical acetylation followed by selective hydrolysis determines only acetylatable nitrogen compounds-i. e., primary and secondary amines except pyrroles. The 0-acetyl groups formed during an analytical acetylation may be selectively hydrolyzed in aqueous alkali-acetone mixtures a t 0" C. in 1 hour; the N-acetyl groups are not hydrolyzed under such conditions (15). The increase in the amount of standard acid required to back-titrate the alkali added for the selective hydrolysis, in comparison to a blank, is a measure of the acetylatable amino groups present. Therefore, the observed value represents the sum of only the primary and secondary amines, and the value for total basic nitrogen compounds corrected for those which are acetylated represents the tertiary amines present. Furthermore, the value for acetylatable hydrogen found by analytical acetylation when corrected for the amount of acetylatable nitrogen represents the amount of primary and secondary alcohols. -___
Table 111. Molar Composition of Coal Hydrogenation Neutral Oil Class of Compounds Nitrogen compounds Amines, primary secondary (by diff.) tertiary Pyrroles, N-unsubstituted AT-substituted (by diff.) Total nitrogen compounds Oxygen compounds Phenols hindered Alcohol;, primary and secondary Ethers (by diff.) Total oxygen compounds Nitrogen-oxygen compounds Hydrocarbons (by diff.) Grand total
Observed, Millimoles/Gram 0.07 0.12 0.12 0.07 __ 0.33 0.71 0.17 0.07
Calculated, Weight 3' % Basis 4 Basis B 1.6 2.8 2.8 1.6 7.9 1 ~. 6.7
-
8.. . 3
4.0 1.6
0.59 0.83
13.9 19.5
. .
...
9.7 9.1
63.8
72.9
2.71 4.25
1oo.o1oo.o
Grignard reagent a t elevated temperatures liberates 1 mole of methane from each mole of primary, secondary and tertiary alcohols, secondary amines including pyrroles and phenols both hindered and unhindered, and 2 moles of methane from primary amines (19). At room temperature, only 1 mole of methane is liberated from primary amines (16). Thus, N-unsubstituted pyrroles are determined by this procedure in addition to all those compounds, except tertiary amines, which are determined by the other techniques. RESULTS AND DISCUSSION
The values obtained in the analysis of the coal hydrogenation neutral oil by each of the five techniques are listed in Table I1 together with the derived data on the amounts of each class of compound present. The composition of the entire neutral oil is given in Table I11 as calculated from ultimate composition and average molecular weight, in addition to the data on functional group analysis in Table 11. The composition is expressed in column 1 as milliper gram of oil, assuming that the weight and equivalent weight of each compound are the same-Le., t h a t no molecule contains more than one functional group.
ANALYTICAL CHEMISTRY
352 The amount (0.71 millimole per gram) of nitrogen compounds as calculated from ultimate analysis exceeds the amount (0.38 millimole per gram) as determined by functional group analysis. The difference (0.33 millimole per gram) is taken as the amount of pyrroles or condensed pyrroles present which are N-substitilted and consequently do not contain an active hydrogen. The quantity (0.83 millimole per gram) of oxygen compounds obtained by ultimate analysis exceeds that found (0.24 millimole per gram) by functional group analysis and the difference (0.59 millimole per gram) is taken to be ethers. The observed average molecular weight of 235 for the neutral oil (Table I) corresponds to 4.25 millimoles per gram, and that portion unaccounted for as nitrogen- and oxygen-containing compounds is taken as the amount of hydrocarbons present. In columns 2 and 3, Table 111, the composition of the neutral oil is calculated on a weight percentage basis; first (column 2), on the assumption that there is not more than one functional group in any given molecule (compare column l), and second (column 3), on the assumption that one third of the nonhydrocarbon compounds contain both oxygen and nitrogen in one form or other (2). Additional data on the further resolution of the neutral oil are needed to determine which, if either, of these two assumptions is correct. Heretofore, ultimate analysis has shown only that repeated acid and alkali extraction failed to remove all the oxygen and nitrogen compounds. The data from functional group analysis show that almost half the nitrogen compounds remaining after acid and alkali extraction are basic and that almost three fourths of the oxygen compounds are ethers and that about one fifth the oxygen compounds are acidic. Although additional examination of these procedures is necessary to demonstrate their general applicability to the problem, the information obtained from their application to only one oil sample has contributed to the understanding of the chemical nature of coal hydrogenation oils. Quantitative data on the presence of pyrrole-type nitrogen compounds, both N-substituted and N-unsubstituted; ether-type and alcohol-type oxygen compounds; and primary, secondary, and tertiary amine nitrogen compounds have all been obtained for the first time. By means of functional group analysis in combination with ultimate composition and molecular weight, the quantitative
estimation of the various types of oxygen and nitrogen compounds in coal hydrogenation neutral oils now appears feasible and promises to be of considerable value in following the resolution of these complex mixtures and in studying the effects of process variables on the hydrogenation process. ACKNOWLEDGMENT
The authors wish to thank Max Katz for making the eodium aminoethoxide titrations, Joy S. Wolfarth for making the perchloric acid titrations, C. W. DeWalt, Jr., for making the analytical acetylations, and E. W. D. Huffman, Denver, Colo., for average of duplicate analysis in Table I. LITERATURE CITED
(1) Basu, A. N., and Glenn, R. A,, Fuel, 27, 96-9 (1948). (2) Ibid., 29,134-7 (1950). (3) DeWalt, C. W., Jr., and Glenn, R. A., ANAL.CHEM.,24, 178+ 96 (1952). (4) DeWalt, C. W., Jr., and Glenn, R. A., Division of Gas and Fuel Chemistry, 116th Meeting, AMERICAN CHEMICALSOCIETY, Atlantic City, S . J., 1949. (5) Glenn, R. A., Basu, A. N.. Wolfarth, J. S., and Katz, M., Fuel, 29,149-59 (1950). (6) Hirst, L. L., Eisner, A , , Field, .J. H., Cooper, H. M.,Abernethy, R. F., and Storch, H. H., U. 5‘. Bur. Mines, Tech. Pappr 646 (1942). (7) Kaplan, E. H., Storch, H. I
