Nonaqueous, Differential Titration Applied to a Classification of Basic and Very Weak Basic Nitrogen Compounds in Petroleum B. E. Buell Union Research Center, Union Oil Co. OfCalifornia, Brea, Calif.
A scheme based primarily on pK, range is presented for classifying basic and very weak basic nitrogen compounds in petroleum. Differential titrations with perchloric acid in acetonitrile and acetic anhydride solvents are used to establish the pK, range. Examples of pure compound titrations a r e presented and discussed, the results a r e given for the titrations of crude oil, crude oil fractions, and cracked samples such as gasoline and cycle oil. Titration in acetonitrile is also applied to the determination of alkylamine additives in gasoline. I N CONTRAST TO THE NONAQUEOUS
TITRATION
OF
ACIDS,
considerable work has been done on titration procedures for nitrogen bases in petroleum samples. For the determination of total basic nitrogen, perchloric acid titration in acetic acid is routinely used ( I ) . Using the same system with benzene added for better solubility of samples, Richter et al. ( 2 ) studied the distribution of nitrogen according to boiling range and basicity; basic nitrogen was defined as all compounds titrating in this system (pK, > 2). Deal et a[. (3) reviewed the basic nitrogen compounds found in oils and differentiated stronger bases by comparing titrations with hydrochloric acid and perchloric acid. Nicksic and Judd ( 4 ) used selective acetylation and titration in acetic acid and acetic anhydride [the latter solvent was originally shown by Wimer (5) t o titrate weak bases such as amides]. With this scheme they classified petroleum bases as: (1) primary and secondary aliphatic amines, (2) primary and secondary aromatic amines, (3) tertiary amines, and (4) very weak bases. Titration in acetic anhydride before and after reduction with lithium aluminum hydride has been employed in studies of crude oil by Bezinger et al. (6) and Okuno et al. (7). This was intended t o classify further the very weak bases (amides, etc.). Bezinger found that essentially all of the nonbasic nitrogen in Russian crudes titrated as very weak bases, while Okuno found a smaller amount of very weak bases in American crudes. Okuno also subdivided very weak bases into three classes based o n titration after reduction. Doelman and Vlugter (8), during catalytic hydrogenation studies, used some of these techniques for the titration of six types of nitrogen compounds; in addition t o the techniques already presented, these authors also utilized the reaction of primary amines with salicyclic aldehyde. Critchfield (9) and Siggia (1) R. T. Moore, Philip McCutchan, and D. A. Young, ANAL.
CHEM.,23, 1639 (1951). (2) F. P. Richter, P. D. Caesar, S. L. Meisel, and R. D. Offenhauer, Ind. O r g . Chem., 44, 601 (1952). (3) V. 2. Deal, F. T. Weiss, and T. T. White, ANAL.CHEM.,25, 426 (1953). (4) S. W. Nicksic and S. H. Judd, Ibid., 32, 998 (1960). (5) D. C. Wimer, Ibid., 30, 77 (1958). (6) N. N. Bezinger, et al., Petroleum Chem. (English trans.), 1, No. 1, 13, 485 (1961). (7) I. Okuno, D. R. Latham, and W. E. Haines, ANAL.CHEM., 37, 54 (1965). (8) J. Doelman and J. C. Vlugter, Sixth World Petroleum Congress, Sec. 111, Paper 12-PD-7 (1963). (9) F. E. Critchfield, “Organic Functional Group Analysis,” Macmillan, New York, 1963.
756
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ANALYTICAL CHEMISTRY
(10) give a more complete review of amine determinations as well as titration procedures. Titrations in the petroleum industry have not utilized the differentiating solvent acetonitrile used by Fritz (11). This report presents a classification of petroleum bases arranged according to strengths found upon titration in acetonitrile, The classification is extended by titration in acetic anhydride to include very weak bases and primary plus secondary amines. These titrations, combined with a detaiied knowledge of boiling points and dissociation constants of the compounds present in petroleum, can provide much information rapidly and simply. The current study is mainly concerned with these titrations used in conjunction with a longrange project concerning the identification and separation of heterocyclic compounds from heavy crude oil fractions (12, 13). An application for determining natural bases and alkylamine additives in gasoline is also presented. EXPERIMENTAL
Reagents. All reagents conform t o ACS reagent grade specifications unless stated otherwise. Standard perchloric acid solutions, 0.05 and O.O25N, were prepared in purified dioxane as described by Wimer (5). Acetonitrile, practical grade, was redistilled before use and stored in brown glass bottles under nitrogen. Apparatus. Beckman Zeromatic p H meter and Beckman combination electrode NO. 39142 with methanolic-KC1 electrolyte. Procedure. The method is the same as that given by Fritz and Wimer (5, I I ) , except that smaller quantities are used. Dissolve a sample to contain about 0.01 meq of total bases in benzene and adjust the solutions to contain about 30 rnl of 1 to 2 benzene-acetonitrile or 1 to 2 benzene-acetic anhydride. A titrant strength of no lower than 0.05N is preferred for these titrations, because of higher blanks in acetic anhydride. Use acetonitrile for determination of basic nitrogen and for differentiation of bases with a pK. greater than 2. For determining very weak bases such as amides, and for further differentiation of basic nitrogen, use acetic anhydride. For very weak base values, subtract the basic nitrogen from the value obtained for the titration in acetic anhydride. For determining parts per million concentrations of alkylamine additives in gasoline, add 100 ml of sample, 75 ml of benzene, and 200 ml of acetonitrile to a 500-ml titration beaker. Titrate with 0.025N perchloric acid. To correlate half-neutralization potentials (HNP), set the millivolt scale to 50 =t 10 for the H N P of pyridine in acetic anhydride and 400 for acetonitrile. Acetamide may be used as a secondary reference compound for every weak bases. (10) S . Siggia, “Quantitative Organic Analysis via Functional Groups,’’ 3rd ed., Wiley, New York, 1963. 25,407(1953). (11) J. S. Fritz, ANAL.CHEM., (12) L. R. Snyder and B. E. Buell, Proc. Am. Petrol. imt.,42 (VIII), 95 (1962). (13) L. R. Snyder and B. E. Buell, Anal. Chim. Acta, 33,285(1965).
Titration i n Acetonitrile
r
Class 1 Alkylamines (Also t i t r a t e as Class 4 compounds i n a c e t i c anhydride,
Alkylpyrid i n e s
Not found i n crudes
Amides (No t i t r a t i o n i n a c e t o n i t r i l e )
Anilines Limited i n Petroleum
Quinolines and Phenanthridines ( o v e r l a p with Class 2 compounds)
Figure 1. Flowsheet for classification of bases by nonaqueous titration RESUL’I‘S AND DISCUSSION
Pure Compound Titrations. All compounds titrating in acetic acid or acetonitrile are here called “basic nitrogen” and those titrating in acetic anhydride, but not acetonitrile, “very weak bases.” Titration in acetonitrile and acetic anhydride can differentiate bases and very weak bases in the pK, range 11 t o - 2 . From these titra’ions a system may be devised which arranges compounds in:o four main classes according t o pK,, as shown in Table I and Figure 1. Titration in acetonitrile is possible down to a pK, of about 2 and places a compound in class 1, 2, or 3. Titration in acetic anhydride, but not acetonitrile, places a compolind in class 4. These classes are designed t o aid in identifying compound types in petroleum. Snyder and Buell (14) have tabulated pK, data for petroleum. Class 2 contains the ‘.ow boiling alkyl-substituted pyridines known to be present in light petroleum fractions. Pyridine (14) L. R. Snyder and El. E. Buell, J . Chem. Eng. Data, 11, 545
(1966).
itself and higher boiling, more hindered alkylpyridines maoverlap into class 3, which contains the anilines and quinoy lines. The pK, range for most of the alkylpyridines is 5.8 t o 7.3, while the quinolines and anilines range mainly from 3.8 to 5.2. Albert (19, Albert and Serjeant (16), and Katritzky (17) give data on dissociation constants. Because primary and secondary amines, such as aniline, acetylate and titrate as very weak bases (amides) in acetic anhydride, further division of class 3 into subgroups 3A and 3B is possible, as shown in Table I. Because anilines are the only class 3 compounds which acetylate and are likely to be present in petroleum, class 3B is specific for them. As class 1 compounds, which also acetylate, were not found in petroleum, this complication is absent. An exception in (15) A. Albert, “Heterocyclic Chemistry,’’ Athlove Press, London, 1959. (16) A. Albert and E. P. Serjeant, “Ionization Constants of Acids and Bases,” Wiley, New York, 1962. (17) A. R. Katritzky, ed., “Physical Methods in Heterocyclic Chemistry,’’ Vol. 1, Academic Press, New York, 1963.
Table 1. Compound Classes Defined by pK, Hange Which May Be Differentiated by Perchloric Acid Titration in Acetonitrile and/or Acetic Anhydride HNP range Class p K, range Acetonitrile Acetic anhydride Class examples I .>8 U-p to 150 303-5500 Alkyl amines and aromatic amines 2 8 to 5 . 7 150-350 Up to 50b Alkyl-substituted pyridines and misc. compounds 3A 5 . 7 to 2 356600 50-300b Quinolines, hindered pyridines, phenanthridines, etc. 3B .5.7 to 2 350-600 300-550a Anilines and certain acridines which acetylate and titrate as amides in acetic anhydride 4 2 to -2 303-550 Amides and a few misc. compounds; sulfoxides and oxygen bases such as 4-pyrone may titrate also Acetylate and titrate as amides in acetic anhydride and also titrate in acetonitriie. Not differentiated as :lasses 2 and 3 in acetic anhydride. 0
VOL. 39, NO. 7 . JUNE 1967
757
r
/
r
/
mv700[ 600
-
500
400mv 300 -
4001
200 -
I
I
I
I
I
1
0.2 0.4 ml TITRANT
Figure 3. Titration curve for a mixture of phenazine and benzamide in acetic anhydride
100-
0.2
0.4 0.6 m l TITRANT
0.8
Figure 2. Titration curve for a mixture of ethylamine, nicotine, and pyridine in acetonitrile
Other unusual results are connected with acetylation reactions. The compounds 2,6-dimethylaniline and diethylamine give strong breaks for part of their stoichiometric titration value and a second weak break equivalent to their amides (acetylation products). With 0.06N perchloric acid titrant, the ratios of weak to strong breaks are 2.8 to 7.4, respectively. With less concentrated perchloric acid the ratio appears to decrease, suggesting that acid catalysis of the acetylation is reduced. These results indicate that caution should be used in predicting pK, from titrations of unknowns, as well as in using the Nicksic and Judd ( 4 ) selective acetylation procedure. Their claims that primary and secondary aliphatic amines constitute up to 25% of certain fractions, and primary and secondary aromatic amines constitute u p to 90% of other fractions, seems out of line by comparison with other results (3, 19, 20) and the present study. Only part of these may be accounted for by the additives they included in “some cases.” Their report of no very weak bases in one crude oil is unexpected, in view of those found in the current study and other studies of both Russian and American crudes (6, 7, 13, 2123). Also there appears t o be an error in their Table I1 for the crude distillate boiling from 405” t o 612” C. They show 0.75 meq per liter total bases for the titration in acetic anhydride but only 0.05 meq per liter each for tertiary amines and very weak bases. Obviously the figure for very weak bases is in error, as primary and secondary amines are claimed to amount to 0.70 meq per liter and would titrate as very weak bases in acetic anhydride. Sample Titrations. The present titration techniques were developed primarily for determining compound classes in various crude oil fractions before and after separation by ion exchange and elution adsorption chromatography (12). Table I11 shows values obtained for fractions of a Wilmington, Calif., crude oil. Data for the gasoline fraction are not included, because it contains less than 0.01 % nitrogen. Analyses for total nitrogen obtained by the Kjeldahl method are included. The first three fractions were obtained from a distillation of the original crude and the last two from molecular distillation of the residuum. The basic nitrogen values were obtained by titration in acetonitrile. In each case only one break was obtained.
class 3B is acridine, whose pK, of 5.6 appears far too weak. I n acetonitrile it titrates like a compound with a pK, of less than 4, and in acetic anhydride it appears to acetylate and titrate like a weak amide. I t is also possible that certain alkylacridines may acetylate, depending on the location of the alkyl groups. Generally, dissociation constants given in the literature (pK, in water) correlate well with titrations in acetonitrile. A much smaller pK, difference is required in acetonitrile for resolution of mixtures, especially in the pK, range 7 t o 5. An example of four titration breaks for a mixture of ethylamine, nicotine, and pyridine is shown in Figure 2. Additional mixtures (including the latter) which are resolved in acetonitrile are listed in Table 11. Some examples of mixtures not resolved are also given. The pK, difference required for resolution appears to vary from 0.7 to a little over 2, depending on the type of compound and pK, involved. Further differentiation of certain compounds in class 3A is possible. A titration in acetic anhydride places a compound in class 4, provided it does not titrate in acetonitrile. If it does, such a compound belongs in class 1 or 3B; the exact classification is easily established, as they are resolved by titration in acetonitrile. I n acetic anhydride, further differentiation of class 4 compounds is possible. Mixtures of benzotriazole (pK, = 1.6) or phenazine (pK, = 1.3) with pyridine and benzamide (pK,= 0.8) give three breaks. These data, showing phenazine to be weaker than pyridine, are contrary to the data of Okuno et al. (3,who quote phenazines and even pyrazines (pK, = 0.7) as being “strongly basic nitrogen.” Figure 3 shows two breaks for the titration of a mixture of phenazine and benzamide. Contrary t o titrations in acetonitrile, pK, (in water) does not appear to correlate well for titrations of some compounds in acetic anhydride. The amides, 2-quinolone (2-hydroxyquinoline) and N-methyl-2-quinolone (pK, = - 0.7), are anomalous, appearing almost as strong as phenazine. Nitrogen compounds, usually considered to be nonbasic, also partially titrate in this system, according to Okuno (7) to the extent of 30z for pyrroles and 65 to 80% for indoles and tetrahydrocarbazoles. Snyder and Buell (14) give a further discussion and a tabulation of extrapolated pK, data for acetic anhydride obtained by the calibration technique of Streuli (18).
(19) H. L. Lochte and E. R. Littmann, “The Petroleum Acids and Bases,” Chemical Publishing Co., New York, 1955. (20) A. C. Nixon and R. E. Thorpe, J . Chem. Eng. Data, 7 , 429 (1 962). (21) E. C. Copelin, ANAL.CHEM., 36,2274 (1964). (22) D. M. Jewel and G. K. Hartung, J . Chem. Eng. Data,9,29?
( i 8 , C. A , Streuli, ANAL.CHEM., 30,997(1958).
11964). (23) L, R Snyder and B. E. Buell, .4~a:,.CHEM., 36,767 (1964).
758 *
ANALYTICAL CHEMISTRY
Table 11. Titration of Mixtures in Acetonitrile Resolved Not resolved P K ~ APKo Compounds PKa 9.4 10.7 Benzylamine 7.3 3.4 Collidine 7.3 7.3 2.1 Pyridine 5.2 5.2 7,8-Benzoquinoline 4.3 5.9 Acridine 5.6a 4.7 1.2 7,8-Benzoquinoline 4.3 3.1 1.6
Compounds Ethylamine Collidine Collidine Pyridine Nicotine, KI 3,4-Benzacridir.z Nicotine, KQ Pyridine Acridine Ethylamine Nicotine, K1 Pyridine Nicotine, K2 a
ApK, 2.1
0.9 1.3
5.2
5.6* 10.7 5.9 5.2 3.1
0.4 4.8
0.7 2.1
Acridine titrates much weaker than its pK, indicates.
Titration of the light gas oil (LGO) indicates the presence of class 2 compound$;. This suggests that only alkyl-substituted pyridines are present, although some overlap of stronger class 3 compc'unds is possible. F o r further verification of this point, 7,8-benzquinoline was mixed with the L G O ; the titration g,ave two breaks with quantitative recovery of the LGO from the first break. Pyridine mixed with 7,8-benzquinoline gave only one break. Additional 200" t o 316" C, LGO cuts from various crudes were titrated in acetonitrile. The results are shown in Table IV (sample 1 is the hilmington LGO). All titrations show only one break similar to the Wilmington LGO. Class 1 compounds were absent. In Table 111, the very weak base values (class 4) were obtained by subtracting basic nitrogen from the total titration values in acetic anhydride. All of the titrations in acetic anhydride gave two breaks, the first of which is equivalent to those obtained in acetonitrile for fractions u p through the heavy gas oil (HGO). This indicates that no class 3B compounds are present. 'The first breaks for the last two heavy samples appear t o give slightly low results compared t o acetonitrile. Additional titrations made during a n 8-hour period with identical ;.itrant indicated that they were about 6 % low in each case. To determine how much of this might be experimental error, replicate titrations in acetic anhydride over a period of 3 days were made for the H G O as shown in Table V. A typical titration curve is shown in Figure 4. F o r the first break, 0.101 mec, per gram was obtained and for the combined breaks, 0.276 meq per gram. In each case the average deviation from the mean was 3 . 6 z ; . Titrations at this time in acetonitrilc and acetic acid gave 0.100 and 0.097 meq per gram, respe'2tively. This indicates that class 3B compounds in the heavy samples, if present, occur in only very small amounts (on the order of 3 to 6x of the basic nitrogen or 0.01 to 8.02 meq per gram). For further vsrikcaiior precision for the titrations and distillations, material IJalances were ca1cu:ated. The weigh; of the recovered distillation fractions totaled 9 9 . 6 z RE the amount charged. The I,CiO, HGO, and residuum constituted 25.7, 30.2, and 32.9 wl:ight %, respectiveii. Rased OP titration vaiues for the original crude, calculated recoveries tor very weak bases and total basic nitrogeii were each 103x. For the molecular dist Ilation, calcuiated recoveries (based o n !>'
Table 111. Nitrogen in Wilmington Crude Oil Fractions
Fraction Original crude Light gas oil Heavy gas oil Residuum Molecular distillate Molecular distillation bottoms
Concentration found, meq/g Very Boiling Basic weak Total range, " C nitrogena basesb nitrogene 0.12 0.22 0.42 2&370 0.022 0.012 0.039 37c.540 0.10 0.18 0.32 0.27 0.50 0.99 540 540-650 0.21 0.40 0.72
+
650
+
0.37
0.59
1.34
Titration in acetonitrile. Titration in acetic anhydride. Kjeldahl method.
Table IV. Titration of Light Gas Oils in Acetonitrile Sample Meq/g HNP Miocene (California) (Wilmington LGO) 0,022 325 Miocene (California) 0.027 310 Miocene (California) 0.020 310 Oligocene (California) 0,029 310 Devonian (Canada) 0. oO29 330
Table V. Replicate Titrations of Basic Nitrogen and Total Bases in Heavy Gas Oil Using Acetic Anhydride Solvent Basic nitrogen, meq/g -_ Basic nitrogen, 1st break Total bases, 2nd break 0.111 0 270 0.099 0 219 0.108 0 252 0.095 0.261 0 . 100 0 217 0.101 0 281 0.096 0 286 0.098 0 296 0.100 0 28i 0,100 0 287 ... 0 265 Av. 0.101 0 276
VOL. 39, NO. 7 , JUNE 1967
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700,
I
:v
ml T I T R A N T
Figure 4. Titration curve for a heavy gas oil in acetic anhydride
200
1
the residuum) were 96% of the weak bases and 100% of the total basic nitrogen. N o significant amounts of primary and secondary amines were found in the straight-run crude oil fractions. Because Nixon and Thorpe (20) found anilines in a lower boiling cracked stock, additional cracked samples were examined for these compounds. Table VI shows the results for light and medium catalytically cracked gasolines and for several fractions of fluid catalytically cracked (FCC) gas oils. The gasolines and the first gas oil cut verify the data of Nixon and Thorpe, showing class 3B compounds (anilines). Titration in acetonitrile gave two breaks, with the first equivalent to class 2 compounds (alkylpyridines). A typical gasoline titration in acetonitrile is shown in Figure 5 . Titration in acetic anhydride also gave two breaks, the first break including classes 2 and 3A and the second including classes 3B and 4. Included in Table VI are results for class 3B compounds obtained by difference. For the lower boiling samples, the first break in acetic anhydride is equivalent to only slightly more than the class 2 compounds. By difference, 90% or more of the class 3 compounds are class 3B (most likely anilines). Only small amounts of class 3A and 4 compounds are present, and class 1 compounds are absent. Correlation with boiling points can provide further information-for example, only pyridines, anilines, weak bases, and no quinolines should be present in the 199" to 213" fraction. Class 2 and 3 compounds likely to be present in petroleum, beginning with the lowest boiling, are pyridines (1 15' and up), anilines (184" and up), quinolines (238" and up), acridines (346" and up), and so on. For the remaining samples boiling above 260°, only one break equivalent t o class 3 compounds is obtained in aceto-
Sample boiling range, " C
I
I
1
I
0.2
0.4 m l TITRANT
Figure 5. Titration curve for a gasoline in acetonitrile nitrile. The corresponding first breaks in acetic anhydride amount to about 90% of the class 3 compounds; therefore, class 3B compounds amount to only about 10%. Class 4 compounds are present in high concentrations and represent most of the unaccounted for nonbasic nitrogen previously reported for some of these fractions (13, Table v). Determination of Alkylamine Additives. Titration of finished gasolines in acetonitrile with and without alkylamine additives show three and two breaks, respectively. A titration curve for a finished gasoline with an aliphatic primary amine of high molecular weight added is shown in Figure 6. Recovery of the added amine was 103%. Because of the excellent resolution shown by the three breaks and the good recovery, the titration was tested further for application to quantitative determination of small amounts of alkylamine additives. Figure 7 shows titration curves for an alkylamine alone and added to 75 ml of gasoline at a concentration of about 20 ppm. The sensitivity of the determination is limited by the size of sample and titrant strength. Optimum results were obtained using 0.025N titrant. With this titrant strength, maximum sample size is limited to about 100 ml because of progressive lowering of the end point slope. For determining concentrations on the order of 20 ppm of additive, precision and accuracy are limited by the sensitivity of the method, which is about i1 to 2 ppm. In addition to routine determinations, differential titrations may be utilized for studying stability of alkylamine additives
Table VI. Titration of Catalytically Cracked Samples Nitrogen found, ppm Titration in acetic anhydride Titration in acetonitrile Classes 2 + 3A Classes 4 3B Class 3B Class 2 Class 3 (1st break) (2nd break) (by difference)
+
Gasolines Light Medium
8.3 70
>4a 150
8.5 85
7.8 175
>3.8 135
FCC gas oils 199-21 3 260-330 274-288
310-370 440-454 0
320 None None None None
Interference, poor end point.
760
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ANALYTICAL CHEMISTRY
320 360
340 330
540 290 420
480
230 370
530 450 770 410
370
300 30 60 60 50
-
f
700 NATURAL CLASS 3 BASES IN THE
600 -
GASOLINE
500 -
i
700-
600500-
400NATURAL CLASS 2 BASES IN THE
mv 300 -
GASOLINE
/
200c
r
mv
400-
300 -
/
200 rnl TITRANT
Figure 6. Titration curve in acetonitrile for an alkylamine added to gasoline in gasoline. Certain instabilities have been noted when dilute solutions of addi tive in stoppered volumetric flasks were left on the laboratory bench for short periods of time. These solutions were prepared in a finished gasoline treated with cation exchange resin to remove all basic nitrogen, and in benzene. The benzene solutions appeared to be stable for short periods, with a tendency for some loss of the alkylamine. After 2 weeks, only about 1 7 x of the original additive remained in the gasoline solution and two breaks were observed for the titration. Froin the second break, it could be shown that about 6 0 x of the original amine was converted to basic nitrogen equivalent in strength to bases with a pK, of about 5 . 5 . The nature of the compounds formed wdS not investigated. They are assumed to be products of light-catalyzed reactions with peroxides or other compounds present in gasoline which d o not contain basic nitrogen groups. CONCLUSIONS
A scheme for classifying petroleum bases (including very weak compounds) is based on titrations with perchloric acid using acetonitrile (11) 2nd acetic anhydride (5). The excellent differentiating solvent, acetonitrile, has not been utilized previously in the petrc'leum industry for such an application. The classes are based on pK, ranges down to 2 using acetonitrile and from 2 to about - 2 using acetic anhydride. A study of pure compound titrations is presented and the scheme
107% RECOVERY OF THE ADDED A L K Y L A M I N E
100-
-
0.2
0.4 m l TITRANT
Figure 7. Titration curves in acetonitrile for an alkylamine alone and added to gasoline is applied to various crude oil and cracked oil fractions. A determination of alkylamine additives in gasoline is also presented. The following observations were deduced from sample titrations. Alkylamines (class 1) were not detected in any samples. Anilines (class 3B) were found only in cracked stocks and were concentrated in the fractions boiling below 260" C. Very weak bases such as amides (class 4) were concentrated in the heavier fractions for both cracked stocks and crude oil distillates. The latter fractions contained only alkyl pyridines (class 2), quinoline and benzoquinoline derivatives (class 3A), and very weak bases. The class 2 compounds were found only in fractions boiling below 370". They appeared to be the only type of bases in light gas oil fractions from various crude oils. Finished gasolines gave three titration breaks, caused, respectively, by alkyl amine additives (class l), alkyl pyridines (class 2), and class 3 compounds (probably anilines).
RECFJVED for review October 11, 1966. Accepted March 20, 1967. Division of Petroleum Chemistry, 152nd Meeting, ACS, New York, N.Y., September 1966.
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