Nitrogen Compounds in Domestic Heating Oil Distillates R. W. SAUER, F. W. MELPOLDER, AND R. A. BROWN The Atlantic Refining Co., Philadelphia, Pa. Interest in nitrogen compounds in petroleum centers chiefly around their detrimental effect on the storage stability of petroleum products, their poisoning effect on catalysts, and on the philosophy that a knowledge of these compounds may lead to some understanding relative to the origin and mechanism of formation of petroleum. Nitrogen compounds previously isolated have been basic and therefore extractable with acids. The presence, however, of nonbasic nitrogen compounds of the pyrrole type has been indicated. This paper presents a study of
+
+'
A
REVIEW of the knowledge of nitrogen compounds in petroleum has been presented by Lochte (4). T o date the compounds isolated and identified have been basic and therefore extractable from hydrocarbons by dilute acids. The presence, however, of nonbasic nitrogen compounds also has been known (6),and the purpose of this study was to extend the knowledge of nitrogen compounds in petroleum to those which are not extractable by acids. The work of Thompson and coworkers (6) has indicated the presence of pyrrole-type compounds in distillate fuels, and a recent paper ( 7 ) presents a spectrophotometric method for determining pyrrole nitrogen. l h e s e workers had also demonstrated that the addition of pyrroles and indoles to fuel oil caused a considerable decrease in storage stability. Further interest in nitrogen compounds centers around their poisoning effect on catalysts and on the philosophy that studies of this kind may in the long run lead to some understanding of the origin and mechanism of formation of petroleum. EXPERIMENTAL
Analytical Methods. The principal instrumental method was baaed on the use of a Consolidated mass spectrometer, Model 21-102, as modified in this laboratory with a high temperature inlet system ($3). Using this heated introduction system it was possible to obtain spectra of compounds with boiling points as high as 430' C. Since the ASTM distillation end point of heating oil is approximately 335 O C., the mass spectrometer appeared to be well suited for the analysis of nonhydrocarbon compounds. For calibration purposes mass spectra were obtained of 19 nitrogen compourids: AT-n-Butylpyrrole N-Bena ylpyrrole Indole 3-Methylindole 1,3-Dimethylindole Carbazole Pyrrole
Piperidine 3,5-Dimethylpyraaole Pyridina 2,4-Dimethylpyridine Quino!ine Isoquinoline 2,6-Dimethylquinoline
Decahydroquinoline Acridine 2,2'-Dip,yridyl Benaotriaaole 1-Methyl-2-pyridone
the nitrogen compounds in a catalytically cracked and a virgin heating oil distillate, with emphasis on the nonbasic compounds. Carbazoles, indoles, pyrroles, quinolines, and pyridines were determined a t concentrations of the order of 0.001 to 0.1%. Carbazoles and indoles showed a higher degree of alkyl substitution in the virgin distillate than in the catalytically cracked distillate; derivatives substituted with three carbon atoms were most abundant in the virgin oil and those with two carbon atoms in the catalytically cracked stock. 4
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spectra. Thus, as indicated in Table I, quinoline peaks a t masses 128, 129, 142, 143, 156, and 157 are not masked by other compounds. Similarly, ions a t 130, 131, 144, 145, 158, and 159 hdicate the presence of indoles, and peaks at 166. 167, 180, 181,194, and 195 are attributed t o carbazoles. Qualitative identifkation
Table I. Mass Spectra of Some Nitrogenous Compounds of the Type Found in Heating Oil Distillate m(e Ratio6 81 105 106 107 108 109 120 121 122 123 128 129 130 131 134 135 136
137
2,4-Dimet,hylpyridine
Ar-n-Butylpyrrole,
%
%
...
100 0.21 0.72 0.23 2.18 0.22 0.21
... ...
3.95 35 0
.
.
I
3.9 37.6 100 7.9
...
... I . .
...
... ...
..
1
... . . I
...
l,3-Dimethvlindoie,
70
...
i:i7
0.04 0.01 0.03
0.01
0.18 0.14 0.34
... ... ...
0.01 0.02 3.55 3.89 3.96 0.60 0.05
145
148 ... ... 149 ... ... 150 ... ... 151 ... 156 157 158 159 162 ... ... 163 ... ... 164 ... ... 165 ... ... 166 ... ... 167 ... ... Sensitivity (div./jL) 32 50 Sensitivity of n-butane at m / ~ = 43 42.1 42.1 a n / e = mass-to-charge ratio.
... ... ... ... ...
The complete spectra appear as Kos. 616-32, 638-39 in the Catalog of Mass Spectral Data published by API Project 44. Typical compound spectra are presented in Table I. I n most cases, the compounds were Eastman Grade chemicals. It was possible to resolve most of the mass ions according to compound type because of the absence of overlap among the 2606 INDUSTRIIAL AND E N G I N E E R I N G CHEMISTRY
...
Carbasole, %
0.12
0.10
0.02 0.01
... ... ... ...
%
0.16
0.17
...
2,6-Dimethylquinoline,
0.05
0.03 0 2.36 8.77 100 (1.9
... .. .. ..
... ... ... ... ...
...
...
... ... ... ...
0.07 0.05
0.01 0.02 0.02 0.02 0.03 4.02 2.34 2.37 0.95 0.01 0.02 0.01 0.02 8.80 1.59 0.13
0.01 < o , 01 0.01
0.02 0.09 32.6
100
12.8 1.08
...
.. ... ... ... ...
0.11
0.04 0.15
0.11
0.14 0.38 0.14
0.06 0 07 0.05 0.11 0.12
0.74 0.11
0.07 0.04
0.09 0.02 0.07 0.09 0.21 0.03 0.06
0.02 0.05 0.07 0.21 2.02 2.46 14.2 100
62
52
44
39.4
38.3
35.9
Vol. 44, No. 11
PETROLEUM-COMPOSITION Secondary Chromatographic Fractions
ACETATE
/-csddt'm CnLOROFORM
1
4 C Solution
Diluted with Solvent Str Isohexane (Id ond
Diluted wlth Black Tar Benzane In
4 8 Solid
I
1
* -(iiLn
Sodium Hvdroxide in Woter
i
Total Carbazoles, Yo Fraction No.& 3A1 3-42 3B 3C 5A 6 58 79 25 7 89 93 Ultraviolet 74 79 34 8 97 96 Mass spectrometer a Fractions 3B, 3'2, 5A, and 6 were calculated allowing for the interference of other compound types determined by the mass spectrometer.
3A(l)
ne I
Solid
l
1 3 A ( 2 ) Cryrtolline Solid
LSdutian
-
Rid-
TETRACHLORIDE
1
I
ISOHEXANE 2A Secondary Chromatographic Froctloni 0.02% Nitrogen Not studied
6s
300 r
260
PRIMARY CHROMATOGRAPHIC FRACTIONS
Figure 1. Fractionation of the Concentrate of Nonhydrocarbon Constituents of Catalytically Cracked Distillate
of pyridines is more difficult as their major peaks a t 107, 121, 135, and 149 may occur because of cresols. Sizable peaks at 106, 120, 134, and 148, however, can only be accounted for as pyridines. Interference caused by cresols was minimized by extraction of samples with caustic prior to analysis. Analyses were obtained using five simultaneous equations to solve for total carbazoles, indoles, pyrroles, pyridines, and quinolines. The scheme used is similar to the compound-type analysis applied to naphthas (1). Peaks which had been identified qualitatively were combined and used as one peak. I n this way, five mixture peaks and appropriate calibration sufficed for the determination of five components. Pattern and sensitivity coefficients used in the calculations are given in Table 11. Results based on these calibrations are shown in Table I11 for a known mixture. The mass spectrum of a typical unknown sample (fraction 5B) is given in Table IV. I n order to obtain an independent check on the accuracy of mass spectrometer analyses, a cursory study was made of the applicability of other instruments to the analytical problem. It was found that the presence of carbazoles was characterized by a
Table 11.
Z 66a 2116; Z166 Z 78d
strong ultraviolet absorption band in the region 291 to 294 mH. RIolar absorptivities were determined for carbazole, E = 21,000, and for the low molecular weight carbazoles separated as a solid from the catalytically cracked distillate (fraction 3A1), E = 16,200. Individual fractions were then analyzed for total carbazoles using a molar absorptivity of 16,000 and a molecular weight based on the mass spectra. Results obtained were as follows:
h t \
220h y 180
Legend:
--.- CARBAZOLE -FRACTION 3A-(I) c (GRAMS PER L I T E R P ( C M - ~ )
'7
f,
I4O1
01 230
1
I
I
I
240
250
260
270
I
2.80
X
I
,
I
I
I
I
290
300
310
320
330
340
(my)
Figure 2. Ultraviolet Absorption Spectra Solvent, ethyl alcohol
Chromatography. Two heating oil distillates fromTthe-refinery, one catalytically cracked of mixed crude source and t h e other straight-run Kuwait, were fractionated by chromatography using activated alumina (Aluminum Ore Co., Grade F-1, 48-100 mesh).
Matrix for Calculation of Nitrogen Compound Types i n Heating Oil Distillate Pyrroles,
Indolea,
%
%
100 0.06
0.6 100 0.02 1.9
Carbazoles, Pyridines, Quinolines,
%
%
%
9.6 17 1.3 0 0 100 0 3.8 3 2 100 2128e 0.4 8 0.9 0 ZF (div./p) 100 85 53 80 a Includes ions at m / e + 66. 6 7 . 80. 81. 94. 95. etc Includes ions a t m / e + 116 117 ~130' I 3 i -144-145 etc. Includes ions at m / e + 166' 167' 180' 181' 194' 195' etc. d Includes ions at m / e + 78 b9 d2 93' 106' lo? etc.' a Includes ions at m / e + 128, lis, i42,' 143,' 156,' 157, etc.
1.2 15 0.1 3.3 100 80 :hromatographlc Fractions
Figure 3.
Table 111. Mass Spectrometer Analysis of a Known Mixture Containing Cyclic Nitrogen Compounds Wt. % Compound Carbazoles (carbazole) Indoles (2,3-dimethylindole) Pyrroles (N-n-butylpyrrole) Pyridines (2,4-dimethylpyridine) Quinolines (2,6-dimethylquinoline) Total
November 1952
Known 18.1 9.7 9.9 53 3 9.0
1oo.o
Mass spectrometer 21 10 - 9 53 7 100.0
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Fractionation of Virgin Kuwait Distillate
Nineteen gallons of catalytically cracked distillate, boiling between 190" and 335' C., were percolated through an aluuahmnaa column 137 X 15.2 cm. diameter. The column was then eIutedl with 10 gallons of light naphtha, (88" API), followed by desorption with 10 gallons of 50% methanol in light naphtha. Three gallons of colored methanol solution was collected, and the solvent was stripped to one-half volume at atmospheric pressure, the remaining solvent being stripped isothermally under vacuum a t room temperature. The residue, 197 grams, contained 2.0%
INDUSTRIAL AND ENGINEERING CHEMISTRY
2607
nitrogen as determined by modified Kjeldahl analysis and was further fractionated in an alumina column 45 X 8 cm. diameter. The chromatogram was developed to give six fractions, using successively isohexane, carbon tetrachloride, benzene, chloroform, ethyl acetate, and methanol. Fraction 1, representing 67% of the total desorbed material, analyzed 4.3y0sulfur and
