(X ? A / ~ X = )ij/nFD ~-~ = ci
(dE/dt)/nFD
+ i/nFD
(hl4j
Substitution of Equation (A413)into Equation (A12) yields Expression (12) of the main text. Expression (13) of the text is derived by transforming Equation (A3) with the condition t h a t k / C y be coilstant. The solution t o the differential equation obtained is CA
=
This on inverse transformition J.ields Equation (16) of the text. Analogous treatments can bc b' 'IVt!ll for cases involving second or higher order chemical reactions by noting that because of the displacement of the system from equilibrium is small, terms of the form kCm appearing in the Fick's law diffusion equations can be expanded in forms such as
-
kC" = k(co AC)"' = kC"" nzkC"~*-'Ac (1124)
AE =
- (dcA/bX)z-Ll x [D/(s
partial fractions should produce terms amenable to inverse transformation. Some minor simplification can be achieved by adding AEJS t o each side of Equation (A17) before starting. We have not attempted this procedure. The short-time behavior of AE can be deduced by expanding the right-hand 4 e of Equation (A17) in a Maclaurin series of s - 1 ' 2 AE,[l/s
+ k,)11/2 exp X
- l/S2Tc 4-
+ . . .I
~/S-~/*TD~'~TC
[ - T(S $- kr)liZ/Dii2] (AlSJ
Setting 2 = 0, and substituting Equation (A14) yields Expression (17). The Laplace transform of Equation (14)of the text is
(A18)
which on inverse transformation yields Equation (15) of t h e main text. The Laplace transform of Equation (14) of the text, valid when T C = T D B = Ois
+
+
and the equations thereby reduced t o linear forms. LITERATURE CITED
(1) Bereins, T., Delahay, P., J . d.m. Chem. SOC.77,6448(1955). (2) Delahay, P., ANAL. CHEW 34, 1161
(1962). (3) Ibid., p. 1267. (4) Delahay, P., A n d . Chim. Acta 27, (STK l)l/*] (A19) 90 (1962). \ T D A / ( s - T K - ~ ) ] " ' ]= AE (A16) (5) Delahay, P., J . Phys. Chem., in press. which can be simplified by the folloming ( 6 ) Delahay, P., unpublished data. or rearranging (7) Delahay, P., "New Instrumental substitution AE = A E ~ [ T C T U A ~ '(s~ TK-~)-~/* Methods in Electrochemistry," Interscience Publishers Inc., New York, p = STK f 1 (A201 TDB1/Zs-1/2] / [ s ~ c S T D A ~ 'X ~ 1945, Tf, Eq. 4-7. (s ~ ~ - 1 ) - l / 2 ( s T D B ) ~ ~ ~ 11 ( A l i ) (8) Dela ay P I Aramata, .I J. ., Phys. tCJ give C h a . , in press. (9) Delahay, P., Mohilner, D. &I., J . Direct inverse transformation of = T K A E , / ( ~ p 1 / 2 ~ ~ 1 / 2 /-~ 1) ~1'2 Am. Chon.SOC.,in press. Equation (A17), although possible in' (10) Eigen, M., Johnson, J. S., Ann. (A21) principle, would appear t o lead t'o esRev. Phys. Chem. 11, 307 (1960). ceedingly cumbersome expressions. (11) Matsuda, H., Delahay, P., J . Phys. which can be modified by factoring the Chem. 64,332 (1960). The approach would be to clear the denominator and breaking into partial (12) Matsuda, H., Delahay, P., Iileinerdenominator of terms in (s T K - ~ ) - ~ J * fractions to give man, M., J . Am. Chem. SOC.81, 63i9 by multiplying numerator and de(1957) ,- - -. ,. _nominator by a factor identical to the (13) Miller, W. L., Gordon, A. R., J . AE = ( T ~ A E , / 2 p " ~ ) [ l / ( p ' / ~A + ) f Phys. Chem. 35, 2785 (1931). denominator with the exception t h a t a A-)I (A221 (14) Reinmuth, W. H., ANAL. CHEM.,in minus sign precedes the second term. press. After clearing fractions, the denominator where (15) Reinmuth, W. H., Wilson, C. E., becomes a sixth order polynomial lbid., 34, 1159 (1962). = T K ~ / ~ / T D ~i /* in sl/zwhich in principle can be factored. RECEIVEDfor review June 25, 1062. Breaking the expression so formed into Accepted July 20, 1962. (TK/TD 4)112 (A23) ( A E ~-
saE)
(
T
+
+
+
+
+
+ -
~ (TDB/s)~/~
a=
+
7 ~ n l / 2 ~ ~ l / 2 A E , / [ ~ ~ ~ l / 2 ~ ~ ~ l / Z
+
+
+
+
+
+
+
+
+
Mass Spectrometric Method for Analysis of Petroleum Distillates in the Furnace Oil-Kerosine Boiling Range ht. E. FITZGERALD, V. A. CIRILLO, and F. J. GALBRAITH The Atlantic Refining Co., Philadelphia, Pa.
b A mass spectrometric method has been developed for a hydrocarbontype analysis of virgin and catalytically cracked furnace oils. A furnace oil sample is separated into saturate and aromatic fractions, which are then run separately on the mass spectrometer. Eleven hydrocarbon types are determined: paraffins, monoand/or noncondensed polycycloparaffins, condensed dicycloparaffins, condensed tricycloparaffins, alkylbenzenes, indans and/or Tetralins and/or cycloparaffinic benzenes, indenes and/or dihydronaphthalenes,
1276
ANALYTICAL CHEMISTRY
naphthalenes, acenaphthenes and/or diphenyls, acenaphthylenes and/or fluorenes, and tricyclic aromatics. To do separations on a routine basis, a rapid small scale elution technique was developed. Coulometric bromine numbers and infrared analyses of the saturate fractions give information of the amount and types of olefins present.
T
need for more detailed information concerning the composition of middle range petroleum distillates has become greater in recent years because IIE
of its use as a precursor of high quality and commercially valuable products. The mass spectrometer has been a valuable tool in providing iuforniation on the composition of high boiling petroleum fractions 9 ) . This paper describes a n analytical scheme using the mass spectrometer to determine the hydrocarbon types present in virgin and catalytic cracked stocks in the 400" to 650' F. boiling range. It is hard to interpret mass spectral data for high boiling pctroleuni distillates, because of the numerous types of compounds present. A reliable analysis
Table 1.
CarBon TY e so.
271 267 2123 2149 291-176 2 103-1 88 2115-186
12 100 19
Paraffins 13 14.5 15.5 100 100 100 21 23 26 0.1 0.2
- - - -
Patterns and Sensitivities for Middle Distillates
Condensed Soncondensed Cycloparaffins Condensed Dicycloparaffins Tricycloparaffins 12 13 14.5 15.5 13 14.5 15.5 13 14.5 15.5 4 4 6 6 2 1.1 1.5 1 1 2 100 100 100 160 130 150 175 170 150 -.100 1 1 26 10 20 3 100 100 100 1 0.2 5 8 100 100 100 0.2 3 4 4 5 15 15 20 0.5 1 3
-
_ .
0.4
0.4
0.4
0.4
0.5
1
1
1
1
2
2 2
0.3
5
Sens. Mole VOl.
Wt.
Type Carbon No. 271 267 2123 2149 291-176 2 103-188
148 66 87
11
0.3 0.7 0.1 1.3
192 74 97
170 70 92
Alkylbenaenes 12 13 0.3 0.4 0.7 2 0.1 0.2 1 1.5
100 .- 100 9
100 -
10
10
238
80 104
14 0.5 3 0.3 2
10 0.2
0.6 a
Type Carbon No.
4.4 0.7
4.5 1
15-34 0 0
5
20-12 3
5 1
1
10
416 165 204
439 170 209
1
220
107 122
13 1 2 2
1
,1
0.3
0.2
268 137 156
298 117 134
Indenes and/or CnHzn- IO 10 13 0.3 1.7 0.3 6.0 0.4 4.8 0.9
10 0.5 0.8 0.2
18 100
17 100
-
I -
28
5.4 1.0
15 100 25
25 7 2.5
0.6 1.5
6.2
20.3
450 242 278
450
222
258
Acenaphthenes and/or C J L - u 12 13
271 1 267 291-176 0O 31 2 103-1 88 2115-186 0 8 128 pk 1 8 2141 100 2153 27 2151 2177 Sens. Mole 330 Vol. 218 Wt. 214 0 Methyl indans. 6 Tetralins.
1 2
5 3
0 8
0 7
10
100 20
4 330 198 196
450 206 237
380 280 288
420 250 263
420 276 288
Acenaphthylenes Tricyclic and/or CJL- I O Aromatics 12 13 14 1 1 06 1 5 0 7 1 3 18 0 2 3 1 5 0 3 2 7 1 0 0 2 01 08 1 0 3 17 15 3 5 100 30 100 __ 15 100 _ .
_ .
340 199 224
of such unseparated mixtures is estremely difficult in most cases. It was convenient to make a preliminary chromatographic separation into saturate and aromatic concentrates and then to analyze each concentrate, using the mass spectrometer.
340 187 205
0.4
220 118
124
268 150 158
Naphthalenes 12 11 1.5 5.2 1.5 1.2 7.8 0.5 0.7 0.1
298 127 135
13
100 15
13 28
-,
0.1 0.6
0.9 0.1
1
1
0.1
0.1
11.4 100
23 0.7 100 -
19 5.6 100 -
6.1 4.5 0.6 450 265 304
0.1
2
Indans and/or Tetralins 11 12 0.4 0.4 0.1 0.1
0.1
0.2
b
100 9 1
a b
2115-186 128 pk 2141 2153 2151 2177 Sens. Mole Vol. Wt.
7 2
347 153 191
302 145 180
2
365 211 205
420 227
241
271 267
= =
2123
=
2149
=
291
=
2103
=
2115
=
128 = 2141 = 2153
=
2151
=
2177
=
410 307 315
372 198
200
236 211 184
360 259 254
8 7
380 248 244
18
5.6 100 10
7
380 226 224
Characteristic Mass Groupings Peaks Read Hydrocarbon Types 71,85 Parafie 67, 68, 69, 81, 82, 83, Cycloparaffins, mono- and/or 96, 97 SCP 123, 124, 137, 138, to Condensed dicycloparaffins end 149, 150, 163, 164, to Condensed tricycloparaffins end 91, 92, 105, 106, up to Alkylbenzenes 175, 176 103, 104, 117, 118, up Indans and/or Tetraline to 187, 188 115, 116, 129, 130, up Indenes and/or dihydronaphto 185,186 thalenes poly 128 pk Naphthalene 141, 142, 155, 156, to Naphthalenes end 153, 154, 167, 168, to Acenaphthenes and or other end CnH9n- 14 Acenaphthylenes and/or 151, 152, 165, 166, to end CnH2?-16 Tricyclic aromatics 177, 178, 191. 192, to end
aromatic concentrates by selective adsorption on silica gel and bauxite. Separation. APPARATUS AND TECHThe glass adsorption column is 500 NIQUE. A rapid small scale elution mm. long and 10 mm. in i.d., with a 5 0 - ~ ]reservoir . and a tapered delivery chromatograPhic Procedure was deyeloped for t h e separation of heating tip. The adsorbents, 100- t o 200-mesh oil distillate samples into saturate and silica gel and 60-mesh bauxite, are EXPERIMENTAL
VOL 34, NO. 10, SEPTEMBER 1962
1277
activated a t 160' C. for 3 hours. The solvents, n-pentane and diethyl ether, are predistilled to eliminate contamination from high boiling impurities. The adsorption column is prepared with glass wool as a support for the adsorbents. Fifteen grams of silica gel is packed into the column and topped with a 1-inch layer of bauxite. The column is prewet with 10 ml. of npentane. A 1-gram sample of oil is added with a hypodermic syringe. When all of the sample has been adsorbed, 30 to 40 ml. of n-pentane is added to the reservoir. The nonaromatic portion of the sample is collected in the first 40 ml. eluted from the column. This fraction contains paraffins, cycloparaffins, and in the case of catalytic stocks nonaromatic olefins. The remaining aromatic concentrate is eluted from the column with 75 to 100 ml. of diethyl ether. The fractions collected are quantitatively recovered from the solvents and are available for further analysis. The results of these analyses are mathematically combined according t o their weight fractions as determined by the separation procedure. The separation requires 3 man-hours, but as many as six samples can be separated simultaneously by one operator.
have similar major fragment ions and thus are grouped in the type analysis. CONDENSEDCYCLOPARAFFINS. Hydrocarbons of this type are present in petroleum in large concentrations (8). In the middle distillate range (400' to 650' F.), the condensed cycloparaffins consist mainly of the di- and tricycloparaffin types. The aromatic types corresponding to the C,H2,- 16 (acenaphthylenes, etc.) and C,Hz,-ls (tricyclic aromatics) occur in the same mass series as the condensed di-and tricycloparaffins. It is therefore necessary to separate the middle distillate samples into an aromatic-free fraction, to give an analysis which distinguishes the cycloparaffins as to the degree of condensation. When an unseparated heating oil distillate is analyzed by mass spectrometry, only the 267 can be used to give a fair estimate of both the condensed and noncondensed cycloparaffins. The major ions for the condensed cycloparaffins consist of the ring system with portions of the side chains. The condensed dicyclopagaffins are characterized by 2123. This series accounts for both the perhydroindan and Decalin types. The condensed tricycloparaffins are characterized by 2149. The pattern A separation procedure suggested by coefficients and sensitivities for the Brook and Whitman ( 2 ) had been used, condensed cycloparaffins are shown in but it was difficult to collect concenTable I. The pure compounds available trates without appreciable overlap befor these types are meager and are pretween the saturates and aromatics. The dominantly the monosubstituted type, addition of bauxite to the column whereas the types thought to be present allowed a separation with little or no are polysubstituted. Nonetheless, reasuch overlap. Both the saturate and sonable estimates of the pattern coeffiaromatic concentrates are analyzed by cients can be made. mass spectrometry for the hyrocarbon ALKYLBENZENES are characterized by types present. 291. The alkylbenzenes are the simMASS SPECTROMETRIC ANALYSIS. A plest aromatic compound type and are modified Consolidated 21 -103 analytical often found in large concentrations. mass spectrometer was used in obtaining The average carbon number of this type the spectra. The modifications have is of significance in determining the been discussed by Brown and coworkers matrix for calculating the hydrocarbon (4). The calibrations used in this types in heating oil distillates. method are based on compounds reIKDANS and/or Tetralins are charceived from the National Bureau of acterized by 2103. Narrow boiling Standards, API Project 42, commercial grade compounds, and narrow boiling point cuts of middle distillates have point cuts from heating oil distillates. shown that the indan type predominate In many cases the pattern coefficients in the distillates analyzed. and sensitivities shown are extrapolated INDEXES and/or dihydronaphthalenes values, to represent the hydrocarbon are characterized by 21 15. These types types thought to be present in petroleum. represent the CnHSn--10 aromatic types Table I shows the pattern coefficients and have been detected through low and sensitivities for the 11 hydrocarbon voltage techniques by Kearns, Martypes determined by this method. anowski, and Crable (@, in various PARAFFIKS. E71 is used to charactercrudes and petroleum products. The ize both the normal and isoparaffins patterns and sensitivities in Table I for present. Pattern coefficients among the indenes were based on methylindenes paraffins are similar. The sensitivities and a C19 indene, 2n-butyl-3n-hexylare subject to more uncertainty than indene, API Serial No. 1364. the patterns. The sensitivities for 271 NAPHTHALENEitself is calculated vary directly with nioleculur iveight and from the polyisotopic peak, 128 m/e. remain fairly constant regardless of Generally, in a full boiling heating oil branching, there is little or no naphthalene present, N O N C O N D E N S CYCLOPARAFFINS. ED but when low boiling fractions are ana267 is used to characterize both the lyzed, the concentration of naphthalene monocycloparaffins and the polynoncondensed cycloparaffins. These two types can be determined. The alkylnaph1278
ANALYTICAL CHEMISTRY
thalenes present are characterized by 2141. ACENAPHTHENESand/or other C,Hz,,-lt types are Characterized by 2153. I n Table I the Clz coefficients are based on acenaphthene and the C13 coefficients were weighted between acenaphthene and diphenyl. ACENAPHTHYLENE and/or other C,H2n-letypes are characterized by 2151. The C12coefficients in Table I are from acenaphthylene and the CI3 coefficients are based on acenaphthylene and fluorene. TRICYCLIC AROMATICS are characterized by 2177. Generally, the tricyclics are of low concentration in 400' to 650" F. distillates. Ultraviolet data show that phenanthrenes are the predominant tricyclic aromaticpresent CALCULATION PROCEDURE
The middle distillate sample is separated into a saturate and an aromatic fraction and the weight per cent of each is determined. The mass spectra of both fractions are obtained and the peaks required for the summations are read from both spectra. The peaks necessary for analysis of the saturate fraction are represented by 271, 67, 123, 149, 91, 103, and 141. The 291, 103, and 141 are included in the saturate fraction calculation as a check on the separation procedure. In case of some overlap in the separation, these aromatic types are the most likely to be present. The peaks determined for the aromatic fraction are 271, 67, 91, 103, 115, 141, 153, 151, and 177. The 271 and 67 are included for the same reason of possible overlap in the separation procedure. To set up a matrix from the data in Table I for the calculation of hydrocarbon types, i t is necessary to know the average carbon numbers of the types present. The pattern coefficients and sensitivities to be chosen depend upon carbon numbers. The alkylbenzenes and naphthalenes have predominant parent ions in the aromatic spectrum, so that their average carbon number can be calculated easily. A certain amount of prior information is necessary for determining the average carbon number of the alkylbenzenes. For instance, if the initial boiling point of the sample is 400" F., the average carbon number is determined from carbon number 10 on up, since the Cs alkylbenzenes boil a t less than 400" F. The average carbon number for the naphthalenes is calculated from carbon number 11 (m.w. 142) on up. The concentration of naphthalene itself is determined separately from the polyisotopic peak m/e 128 in the matrix calculation. Table TI shows the isotopic values and parent ion mole sensitivities necessary for calculation of the average carbon number. The mole fraction a t each
Table 11.
Parent Ion Isotope Factors and Mole Sensitivities
Carbon No. Alkylbenzenes 9 10 I1
m/e
Isotope Factor
12 13
120 134 148 162 176
I5
504 -0.i656
14
-0.0989 -0.1101 -0.1212 -0.1323 -0.1434 190 -0.1545
16 218 -0.1767 17 232 -0.1878 Naphthalenes 11 142 -0.1111 12 i5S -0.i222 13 170 -0.1333 14 184 -0.1444 15 198 -0.1556 16 212 -0.1667 17 226 -0.1778 1s 240 -0.1889 ~~
Mole Sensitivity 92 S5 63 60 57 54 .~ 51 48 45 194
is6 150 150 150 150 150 150
carbon number is first determined by dividing the monoisotopic parent peaks by the mole sensitivities. To calculate the average carbon number, the mole fraction at each carbon number is multiplied by the carbon number, the products are added, and divided by the sum of the mole fractions. The average carbon number of the paraffins and cycloparaffins has been related to the average carbon of the alkylbenzenes. Table I11 shows this relationship. The other types present (indans and/ or Tetralins, indenes and/or dihydronaphthalenes, C,,H2,-1r, - 16 and tricyclic aromatics), are generally of too low a concentration or have parent ions affected by each other, SO that their average carbon numbers are estimated by inspection of aromatic mass spectrum. From the calculated and estimated average carbon numbers of the hydrocarbon types, matrices are set up for the saturate and aromatic fractions using the calibration data shown in Table I. Examples of likely matrices are shown in Tables IV and V. If many analyses are performed for the same average carbon numbers, the matrices may be inverted for rapid calculations.
Table VI shows the comparisons between the composite analyses, based on the mass spectral results of the saturate and aromatic concentrates, and the direct mass spectral analyses of an unseparated virgin and catalytically cracked distillate. I n the direct analyses the condensed cycloparaffins cannot be determined because of the presence of the interfering aromatic types, C.H2,-le and C,H2,,-18. The matrix used in a direct analysis is the same as that used to calculate the aromatic concentrate, shown in Table V. The 267, normally used to calculate the noncondensed cycloparaffins in the saturate fraction, is essentially uncorrected for the high contributions of the condensed cycloparaffins (see Table I) and though i t is not strictly proper, the 267 in a direct analysis can provide a means for determining the total cycloparaffins, both condensed and noncondensed. The comparisons in Table VI are rather good, in that there is a fair degree of consistency between the values reported by analyzing both a separated and a nonseparated sample. A distribution of the cycloparaffins as to the degree of condensation can be determined in the composite analysis, since
Table IV.
Table
H.C.
The lack of comparative methods and standard samples makes i t difficult to evaluate analytical methods for high boiling oils. However, the internal consistency of the new method can be checked by a comparison of the results obtained from a direct mass spectral analysis of an unseparated middle range distillate. Also, ultraviolet results and parent ion analyses should agree with the results obtained by this analytical procedure.
CNo. 271 267 -. 291 2103 2115 2141 2153 2151 2177 Sens. Mol. Vol. Wt,
CP 15.5 15.5 100 6 26 100 0.4 3 2 Par.
1
12
238
81 105
V.
the interfering aromatics are absent in the saturate fraction. The ratios of mono-/di-/tricycloparaffins agree reasonably well with those reported by Mair etal. (8) of 7/3.5/1 for the CI3 to C17 fraction of petroleum. The values calculated in the aromatic concentrate are more reliable because of the absence of saturates, particularly the cycloparaffins, which would interfere. The weight per cent saturates determined by an acid treat of the virgin and cracked stocks is also shown in Table VI. The values determined by composite analyses agree better with the acid treat values than do the direct analyses. I n
Saturated Concentrate Matrix
TCPa 15.5 2 150 20
100 20 3 0.4
0.5 3
Tet. Indenes 13 13 1
100
2 15
9
100
5
25
4.50
420 227 241
237
Ind. Tet.a 13 1 2 2 0.3 15 100
Naphe." 13
2 2 4 0.5
1 0.1
100
298 450 420 380 127 206 227 226 237 241 224 135 tricycloparaffins, indans and/or Tetralins,
Ind.
AB 14
206
ABa 14 0.5 3 03 2 100 9
.Aromatic Concentrate Matrix
0.3 2 10 2 439 170 209
Paraffin and Cycloparsffin 8 9 11 12 13 15 (14.5) 16 (15.5)
Alkylbenzene 8 9 10 11 12 13 14
H.C. Type Par.0 CP' DCPS CNo. 15.5 15.5 15.5 1.5 271 100 6 267 26 100 150 2123 0.2 3 100 2149 8 291 0.4 3 5 2103 2 2141 12 0.3 Sens. Mol. 238 439 298 Vol. 81 170 1i 7 209 134 Wt. 105 a Paraffins, cycloparaffins, dicycloparaffins, naphthalenes.
Type
METHOD EVALUATION
Table 111. Carbon Number of Paraffin and Cycloparaffin Corresponding to Carbon Number of Alkylbenzene
1.7 6 6.2 20.3 100 28 6.1 4.5 0.6 372 198 200
AceAcenaphnaph Trithencs, thg'lenes cyclic Naphs. CnHBn-ll(C,HW.~~Arorn. 13 13 13 14 2 1 1 0.6 2 2 5 0.7 3 5 1 18 3 0.1 3 1.5 1 2.7 0.8 18 10 100 0.3 10 100 15 3.5 20 100 7 30 4 100 15
380 226 224
330 198 196
340 187 205
VOL 34, NO. 10, SEPTEMBER 1962
365 211 205
1279
~ ~ ~ _ _ _ _ _ _ _ _ _ _ _ _
~~
Table VI.
Analyses of Middle Distillates Virgin Stock Catalytic Stock ComComSat. Arom. posite Direct Sat. Arom. posite Direct
Hydrocarbon types PnrafFtns Cycloparaffins Mono- and/or noncondensed Condensed dicyclopar-
.
nffis
Condensed tricycloparnffins
AI ky1benzenes Indans and/or Tetralins Indeneu and/or dihydronaphthalenes Naphthalenes Acenaphthenes (C,,H2+ ,) Acenaphthylenes (CnH2,Tricyclic aromatics Weight yo ASTM distillation, B.P.,
3 4 2 6 3 2 1
1
9
7
7
6
9
2 9
12
3
7
7
8
2 7 3 2 1 100
2 6 5 1 2 100
1 19 6 4 4 50
1 20 6 4 4 100
2
1
50
-
580 644
47.4
76.8 1
4 6
5
11 20
9 19
6
Bromine No.
1.8 0.5 0.5
0.2 2.6
2.8
ANALYTICAL CHEMISTRY
-
1 21 7 4 4 100 415 540 650
410
7
24 19
5 4
77 23
both saturate fractions, virgin and catalytic stocks, the only indication oi a n overlap of aromatics is the presence of 1% naphthalenes. A check by ultraviolet nbsorption data showed that
1280
12
43 32
3 5
Determination of Olefins
Virgin stock, wt. % Cat,alytic stock, wt. % RCH=CHR' RLbCH? RzC-CHR'
12
9
Aromatic Concn., Wt. % Parent ion Matrix
Infrared 0.0
21
21
Table VII. Comparison between Parent Ion and Matrix Analyses
Table VIII.
28 (21 1
43 (33)
F. Initial Middle Final Saturates, wt. % by acid treat l.3-analyses, wt. yo Saphthalenes Tricyclic aromatics
Virgin stock Alkylbenzenes Snphthalenes Catalytic stock A1kylbenzenes Xaphthalenes
28
43
hydrocarbon types present in these middle distillates. The mass spectrometric method does not take into account the olefins t h a t may be present. However, when the sample is separated on silica gel and bauxite, any nonaromatic olefins present are eluted off the column in the npentane fraction along with the paraffins and cycloparaffins. I n the absence of aromatics infrared and bromine number analyses can be used to determine the amount and type of olefins. The infrared analyses were based on the infrared absorption as outlined by Anderson and Seyfried (I). Bromine numbers were obtained by coulometric titration as directed in ASTM D 1492-571' (Table VIII). The virgin stock shows no olefins by infrared and the catalytic stock contains olefins at the 3% level. Although the mass spectrometric method does not distinguish between cycloparafins and mono-olefins, the CnH2. compounds in the case of virgin and catalytic stocks consist primarily of cycloparaffins.
21 6
naphthalenes were absent. It appears that the calibrations, for the saturate types determined, d o not adequately take into account the pattern contributions to the 2141. This variance is likely, since the relatively high amount of paraffins present have a parent mass series, CnH2,,+2, which conflicts with that of the naphthalenes, CnH2n-12. The results of ultraviolet analyses on the aromatic concentrates are listed in Table VI. The values obtained for naphthalenes and tricyclic aromatics show reasonable agreement with the results of the mass calculations. Ultraviolet spectra also indicate that the tricyclics are of the phenanthrene type rather than the anthracene type. An internal check on the validity of the calculations is the agreement between the values for the alkylbenzenes and naphthalenes as calculated by the matrix method and the parent ion analysis used t o calculate the average carbon number. I n the parent ion calculation for average carbon number, the total mole fraction is converted to weight per cent and the results are compared to the values from the matrix calculations in Table VII. The good agreement between the values lends further credibility to the matrix analyses for the
ACKNOWLEDGMENT
The authors gratefully acknowledge the contributions of R. A. Brown for initiating this work at the Atlantic Refining Co. and of J. Colucci, V. Basil, and E. RiIcAndrews for obtaining the mass spectra. Thanks are also due to H. Morgan for infrared data, J. Moirano for ultraviolet data, and S. Blittman for hie part in the separation procedure. LITERATURE CITED 1
1 ) -4nderson, J. A., Jr., Seyfried, W. D., -4XAL. CHEM. 20, 998 (1948).
( 2 ) Brook, B. M., Whitman, B. T., J. Znst. Petrol. 44, 212 (1958). 3 ) Brown, R. A., Doherty, W,., Spontak, J., Consolidated Engineering Corp.,
Mass Spectrometer Group, Rept.
84
i 1951 'i. (4)'
Brokn, R. A,, Skahan, D. J., Cirillo,
I-.A., Melpolder, F. W., ANAL. CHEM.
31, 1531 (1959). (5) Kearns, G. L., Maranowski, N. C., Crable, G. F., Zbid., 31, 1646 (1959). ( 6 ) Lumakin. H. E.. Zbid.. 28. 1946 ' i1956): ' ' 7 j Lumpkin, H. E., Johnson, B. H., Zbid., 26, 1719 (1954).
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RECEIVED for review January 16, 1962. Accepted Jul 12, 1962. Ninth Annual Meeting, .4&M Committee E-14 on Mass Spectrometry, Chicago, Ill., June 1961.
