- Email: [email protected]
Gas-chromatographic analysis of isomeric octenes
GAS-CHROMATOGRAPHIC ANALYSIS OF ISOMERIC OCTENES* ~¢[. S. VIGDERGAUZ and M. I. AFANAS'EV Scientific Research Institute for Synthetic Alcohols and Organic Products, Novokuibyshev Branch (Received 16 October 1962)
IN SPITE of the enormous success of gas chromatography in the analysis of various hydrocarbon systems, literature data on the retention volumes of olefins are practically limited to components with up to 6-7 carbon atoms. The retention characteristics of aliphatic octenes given in the literature relate only to 2,4,4-trimethylpent-l-eae, 2,4,4,-trimethylpent-2-ene, oct-l-ene, and the oct-2-enes [1-3]. Thus, in order to analyse mixtures of isomeric octenes chromatographically, a preliminary calibration with standard components must first be carried out, and these are by no means always available to the investigator. The object of the present work was to analyse some products of the dimerization of the butylenes. The work was carried out on a M K I I B chromatograph of the firm of Griffin with air as the carrier gas. To separate the fractions of olefins boiling between 100 and 116.5 °, we used co|umns filled with Inzensk brick (particle dimensions 0.25-0.5 ram) with 20% by weight of di-(fl-cyanoethyl) sulphide or 15% by weight of liquid paraffin. The first of the stationary liquid phases was prepared in the laboratory. Figure 1 gives a chromatogram of the octene fraction obtained on a column ~5.3 m long and 6.35 mm in diameter with 20% by weight of di-(fl-cyanoethyl) sulphide at 70°; Figure 2 gives a ehromatogram of the same fraction on a column ~2.6 m long with liquid paraffin at 100 °. Since the liquid paraffin is a non-polar liquid, separating substances according to their boiling points, it is obvious from the chromatograms that in the analysis of the octenes on di-(eyanoethyl) sulphide the order of elution is also determined by dispersion forces of interaction. In order to identify the components present in the mixture, narrow fractions were obtained in a rectifying column with an efficiency of the order of 25 theoretical plates and these were subjected to further investigations. Analysis of the fractions boiling between 100 and 104 ° by infra-red spectrometry showed t h a t peak 2, which is the main one here, corresponds to an ~-olefin with a branched structure. The refractive index of the 100-101 ° fraction, n ~ was 1.4080, and t h a t for the 103-104 ° fraction was 1.4105. I t * Neftekhimiya 3, :No. 3, 425-429, 1963. 178
Gas-chromatographic analysis of isomeric octenes
179
f o l l o w s f r o m l i t e r a t u r e d a t a o n t h e p h y s i c o c h e m i c a l p r o p e r t i e s o f t h e o c t e n e s [4] t h a t t w o o c t e n e s b o i l b e t w e e n 100 a n d 1 0 3 . 5 ° - - 2 , 4 , 4 - t r i m e t h y l p e n t - l - e n e w i t h b . p . 101.36 ° a n d n ~ 1.4086, a n d 5 , 5 - d i m e t h y l h e x - l - e n e w i t h b . p . 103.1 ° a n d n ~ 1.4043. I t is o b v i o u s t h a t p e a k 2 c o r r e s p o n d s t o 2 , 4 , 4 - t r i m e t h y l p e n t - l - e n e . A c c o r d i n g t o a s p e c t r o s c o p i c a n a l y s i s o f t h e f r a c t i o n s b o i l i n g b e t w e e n 112 a n d 113 ° a n d b e t w e e n 113 a n d 114 °, t h e m a i n p e a k 4 c o r r e s p o n d s t o a fl-olefin 41 12
ImY
5
4
4mV IV S
r
andsec ~ ~
Fm.
andsec ~, ~ , ~ , ~
1.
F i e . 2.
'~
~- ~
~,
FIG. 3.
FIG. 1. Chromatogram of the 100-116-5 ° oetene fraction. Feed of carrier gas (air) to the column inlet 2-1 1./hr. Pressure at the inlet to the column 725 m m Hg and at the outlet 26 m m Hg. E x p l a n a t i o n applying to each of Figs. 1-3: / - - n o t identified; 2--2,4,4-trimethylpent-l-ene; 3--2,4-dimethylhex-3-ene; 4 - - 3 4,4-trimethylpent-2-ene; 5--2,3,4-trimethylpent-2-ene; 6 - - o c t - l - e n e ; 7 - - n o t identified. Fro. 2. Chromatogram of the 100-116"5 ° octene fraction. Feed of air to the inlet 2.5 1./hr. Pressure at the inlet to the column 725 m m Hg, at the outlet 505 m m Hg. FIG. 3. Chromatograms of narrow octene fractions. A - - 1 1 4 - 1 1 5 ° fraction. B - - 1 1 5 - 1 1 6 ° fraction. Conditions of analysis (as for Fig. 1)
~V
180
M. S. VIGDERGAUZ a n d M. I. AFA)rAS'EV
with a branched structure. The refractive indices of these fractions were 1-4210 and 1.4211. According to literature data, the fl-olefins boiling between 112 and 114 ° have refractive indices of about 1.41 except for 3,4,4-trimethylpent-2-ene with b.p. about 112.3 ° and n~ 1.4235. Spectroscopic analysis of the fractions boiling between 114 and 115 ° and between 115 and 116 ° (the chromatograms of these fractions are given in Fig. 3) showed the predominance of branched fl-olefins. The refractive indices of the fractions were 1.4228 and 1.4232. Since the octenes boiling at temperatures of about 115-116 ° have refractive indices of about 1.41 with the exception of 2,3,4-trimethylpent-2-ene (b.p. 116.26 °, n~ 1.4274), it is obvious that this is present in the product under investigation. The slight lowering of the value of n~ in the fraction is apparently due to impurities. In order to identify the other peaks, a curve was constructed of the relationship between the residence times of the octenes given and their boiling points. The residence time, t~ corresponds to the difference between the time of issue of the maximum of the peak of the substance being analysed tR and the time of issue t o of the peak of a non-sorbed gas, in our case the methane-hydrogen fraction. For the values of t~, see Table 1 ; the graph, plotted on a semilogarithmic scale, is given in Fig. 4. T A B L E 1. R E D U C E D
RETENTION
TIMES OF THE COMPONENTS (tR)
ON A COLUMN CONTAINING LIQUID PARAFFI~
I N SEC. T I M E O F
I S S U A N C E (t0) O F T H E P E A K O F A N O N - S O R B E D GAS -- 4 9 SEC.
P e a k No.
r tR
1 2 3 4 5 6
239 282 346 385 444 509
The points corresponding to the three components identified above lie on a straight line, and this is an additional confirmation of the correctness of the identifications made. Peak 1, having t~----239 sec. corresponds (on the graph) to a component with b.p. 95.8 °. However, since the octenes begin to boil only at a temperature of about 100 °, this component does not belong to this group of substances and it was not identified. For peak 3, t~=346 sec. characterizes a component with b.p. 107"6 °. This figure corresponds to the b.p. of 2,4-dimethylhex-3-ene. Peak 6 (t~----509 sec.) corresponds to a component with b.p. 121.3 °, which agrees with the b.p. of oct-l-ene. The presence of the latter was also confirmed b y introducing a standard sample into the mixture undergoing analysis.
(~as-ehromatographic analysis of isomeric oetenes
i8|
The heavier compounds present in the form of impurities had boiling points above 125 ° and did not belong to the octene group.
5
10q
. . . . .
95
100
i i . . . . . . . . . . . . . . . . . . . . 105 110 it5 t20 B.p
8
ltO 2 t25
FIG. 4. Relationship between the reduced residence times t~ and the boiling points of the oetenes. Column containing liquid paraffin. (Conditions of analysis as for Fig. 2)
Quantitative determination of the composition was carried out by the method of internal normalization of the area of the peaks without the application of correction factors. The results of the calculation are given in Table 2. TABLE 2. COMPOSITION OF THE 1 0 0 - 1 1 6 . 5 ° FRACTION OF TIlE PRODUCTS OF THE DIMERIZATION OF BUTYLENES Alnount,
Component
P e a k No.
Not identified 2,4,4-Trimethylpent- 1-ene 2,4-Dimethylhex- 3-ene 3,4,4-Trimethylpent-2 -ene 2, 3,4 -Trimethylpent-2-ene Oct- 1-erie Not identified
% by weight 1.3 32 "3 9.45 36"5 18.0 0.45 2.0
The oetenes in fractions of the products of an organoaluminium synthesis were also identified, the relevant chromatogram being given in Fig. 5. A curve was constructed of the relationship between the relative retention volumes of the octenes on a column containing di-(eyanoethyl) sulphide and the boiling points. The relative retention volumes Vre1 were calculated from the formula: ! . . . . .
Vrel-
p tR
tR(st>
where the magnitude t'R (~o relates to n-hexa~ae.
182
M. S. VIGDERGAUZ a n d M. I . AFANAS'EV
nV
FIG. 5. Chromatogram of a fraction of the products of anorganoaluminium synthesis. (Conditions of analysis as for Fig. 1) The values o f Vre1 given in Table 3 show t h a t on the di-(eyanoethyl)sulphide c o l u m n a linear relationship between Vrel and the boiling point again exists, as shown in Fig. 6. T A B L E 3. R E T E N T I O N CHARACTERISTIC OF THE O C T E N E S O N A C O L U M N CONTAINING
Peak No.
DI-~-CYANOETHYL SULPHIDE. to = 1 10 sec., t~(st)= 68 sec. t
Component
2,4,4-Trimethylpent- 1-ene 2,4 -Dimethylhex- 3-one 3,4,4-Trimcthylpent -2-one 2,3,4-Trimethylpent-2-ene Oct- 1-ene
t R , sec. 219 262 292 333 380
Vre1 3"23
3"85 4"30 4"91
5"60
P e a k n has a r e t e n t i o n v o l u m e VreI of 5"9, which, f r o m the graph, corresponds to a c o m p o n e n t with b.p. 123"2 °. Substances with boiling points v e r y close to this (122.9 a n d 123.0 °) are cis- a n d tranz-oct-3-enes, which are e v i d e n t l y present in the m i x t u r e concerned.
Gas-chromatographic analysis of isomeric octenes
183
4
3 2
100 102 I 0 4
106
108 110
II2
114
116
I201"22124
10o
B.p FIG. 6. Relationship between the relative retention volumes Vrel and the boiling points of the octenes. Column containing di-fl-cyanoethyl sulphide• (Conditions of analysis as for Fig. 1} T h e heavier c o m p o n e n t s h a d b.p.s a b o v e 125 ° a n d did not belong to the group o f s u b s t a n c e s u n d e r consideration. T h e a u t h o r s express their t h a n k s to V. A. T e r e n t ' e v f o r carrying out the spectroscopic analyses. SUMMARY
1. A n u m b e r o f isomeric octenes have been identified in complex mixtures. T h e i r r e t e n t i o n characteristics on columns w i t h polar a n d non-polar phases h a v e been d e t e r m i n e d . 2. The isomeric octenes are d i s t r i b u t e d on a c o l u m n containing di-(flc y a n o e t h y l ) sulphide in strict a c c o r d a n c e with their boiling points. Translated by B. J. HAZZAR~) REFERENCES
1. E. BAYER, Khromatographiya gazov. (Translation of Gas-Chromatography•) Foreign Literature Publishing House, Moscow, 1959 2. B. I. ANVAYEY, A. A. ZHU~HOVITSKII and N. M. TURKEL'TAUB, Sb. Gazovaya khromatographiya. (In symposium: Gas Chromatography.) Gos INTI, p. 44, Moscow, 1962 3. P. W. WEST, B. SEN, B. R. SANT, K. L. MALLIK and J. G. SEN GUPTA, J. Chromatog. 6, 220, 1961
4. R. D. OBOLENTSEV, Fizicheskiye konstanty uglevodorodov zhidkikh topliv i masel. (Physical Constants of the Hydrocarbons of Liquid Fuels and Oils.) Gostoptekhizdat, Moscow, 1953
IN SPITE of the enormous success of gas chromatography in the analysis of various hydrocarbon systems, literature data on the retention volumes of olefins are practically limited to components with up to 6-7 carbon atoms. The retention characteristics of aliphatic octenes given in the literature relate only to 2,4,4-trimethylpent-l-eae, 2,4,4,-trimethylpent-2-ene, oct-l-ene, and the oct-2-enes [1-3]. Thus, in order to analyse mixtures of isomeric octenes chromatographically, a preliminary calibration with standard components must first be carried out, and these are by no means always available to the investigator. The object of the present work was to analyse some products of the dimerization of the butylenes. The work was carried out on a M K I I B chromatograph of the firm of Griffin with air as the carrier gas. To separate the fractions of olefins boiling between 100 and 116.5 °, we used co|umns filled with Inzensk brick (particle dimensions 0.25-0.5 ram) with 20% by weight of di-(fl-cyanoethyl) sulphide or 15% by weight of liquid paraffin. The first of the stationary liquid phases was prepared in the laboratory. Figure 1 gives a chromatogram of the octene fraction obtained on a column ~5.3 m long and 6.35 mm in diameter with 20% by weight of di-(fl-cyanoethyl) sulphide at 70°; Figure 2 gives a ehromatogram of the same fraction on a column ~2.6 m long with liquid paraffin at 100 °. Since the liquid paraffin is a non-polar liquid, separating substances according to their boiling points, it is obvious from the chromatograms that in the analysis of the octenes on di-(eyanoethyl) sulphide the order of elution is also determined by dispersion forces of interaction. In order to identify the components present in the mixture, narrow fractions were obtained in a rectifying column with an efficiency of the order of 25 theoretical plates and these were subjected to further investigations. Analysis of the fractions boiling between 100 and 104 ° by infra-red spectrometry showed t h a t peak 2, which is the main one here, corresponds to an ~-olefin with a branched structure. The refractive index of the 100-101 ° fraction, n ~ was 1.4080, and t h a t for the 103-104 ° fraction was 1.4105. I t * Neftekhimiya 3, :No. 3, 425-429, 1963. 178
Gas-chromatographic analysis of isomeric octenes
179
f o l l o w s f r o m l i t e r a t u r e d a t a o n t h e p h y s i c o c h e m i c a l p r o p e r t i e s o f t h e o c t e n e s [4] t h a t t w o o c t e n e s b o i l b e t w e e n 100 a n d 1 0 3 . 5 ° - - 2 , 4 , 4 - t r i m e t h y l p e n t - l - e n e w i t h b . p . 101.36 ° a n d n ~ 1.4086, a n d 5 , 5 - d i m e t h y l h e x - l - e n e w i t h b . p . 103.1 ° a n d n ~ 1.4043. I t is o b v i o u s t h a t p e a k 2 c o r r e s p o n d s t o 2 , 4 , 4 - t r i m e t h y l p e n t - l - e n e . A c c o r d i n g t o a s p e c t r o s c o p i c a n a l y s i s o f t h e f r a c t i o n s b o i l i n g b e t w e e n 112 a n d 113 ° a n d b e t w e e n 113 a n d 114 °, t h e m a i n p e a k 4 c o r r e s p o n d s t o a fl-olefin 41 12
ImY
5
4
4mV IV S
r
andsec ~ ~
Fm.
andsec ~, ~ , ~ , ~
1.
F i e . 2.
'~
~- ~
~,
FIG. 3.
FIG. 1. Chromatogram of the 100-116-5 ° oetene fraction. Feed of carrier gas (air) to the column inlet 2-1 1./hr. Pressure at the inlet to the column 725 m m Hg and at the outlet 26 m m Hg. E x p l a n a t i o n applying to each of Figs. 1-3: / - - n o t identified; 2--2,4,4-trimethylpent-l-ene; 3--2,4-dimethylhex-3-ene; 4 - - 3 4,4-trimethylpent-2-ene; 5--2,3,4-trimethylpent-2-ene; 6 - - o c t - l - e n e ; 7 - - n o t identified. Fro. 2. Chromatogram of the 100-116"5 ° octene fraction. Feed of air to the inlet 2.5 1./hr. Pressure at the inlet to the column 725 m m Hg, at the outlet 505 m m Hg. FIG. 3. Chromatograms of narrow octene fractions. A - - 1 1 4 - 1 1 5 ° fraction. B - - 1 1 5 - 1 1 6 ° fraction. Conditions of analysis (as for Fig. 1)
~V
180
M. S. VIGDERGAUZ a n d M. I. AFA)rAS'EV
with a branched structure. The refractive indices of these fractions were 1-4210 and 1.4211. According to literature data, the fl-olefins boiling between 112 and 114 ° have refractive indices of about 1.41 except for 3,4,4-trimethylpent-2-ene with b.p. about 112.3 ° and n~ 1.4235. Spectroscopic analysis of the fractions boiling between 114 and 115 ° and between 115 and 116 ° (the chromatograms of these fractions are given in Fig. 3) showed the predominance of branched fl-olefins. The refractive indices of the fractions were 1.4228 and 1.4232. Since the octenes boiling at temperatures of about 115-116 ° have refractive indices of about 1.41 with the exception of 2,3,4-trimethylpent-2-ene (b.p. 116.26 °, n~ 1.4274), it is obvious that this is present in the product under investigation. The slight lowering of the value of n~ in the fraction is apparently due to impurities. In order to identify the other peaks, a curve was constructed of the relationship between the residence times of the octenes given and their boiling points. The residence time, t~ corresponds to the difference between the time of issue of the maximum of the peak of the substance being analysed tR and the time of issue t o of the peak of a non-sorbed gas, in our case the methane-hydrogen fraction. For the values of t~, see Table 1 ; the graph, plotted on a semilogarithmic scale, is given in Fig. 4. T A B L E 1. R E D U C E D
RETENTION
TIMES OF THE COMPONENTS (tR)
ON A COLUMN CONTAINING LIQUID PARAFFI~
I N SEC. T I M E O F
I S S U A N C E (t0) O F T H E P E A K O F A N O N - S O R B E D GAS -- 4 9 SEC.
P e a k No.
r tR
1 2 3 4 5 6
239 282 346 385 444 509
The points corresponding to the three components identified above lie on a straight line, and this is an additional confirmation of the correctness of the identifications made. Peak 1, having t~----239 sec. corresponds (on the graph) to a component with b.p. 95.8 °. However, since the octenes begin to boil only at a temperature of about 100 °, this component does not belong to this group of substances and it was not identified. For peak 3, t~=346 sec. characterizes a component with b.p. 107"6 °. This figure corresponds to the b.p. of 2,4-dimethylhex-3-ene. Peak 6 (t~----509 sec.) corresponds to a component with b.p. 121.3 °, which agrees with the b.p. of oct-l-ene. The presence of the latter was also confirmed b y introducing a standard sample into the mixture undergoing analysis.
(~as-ehromatographic analysis of isomeric oetenes
i8|
The heavier compounds present in the form of impurities had boiling points above 125 ° and did not belong to the octene group.
5
10q
. . . . .
95
100
i i . . . . . . . . . . . . . . . . . . . . 105 110 it5 t20 B.p
8
ltO 2 t25
FIG. 4. Relationship between the reduced residence times t~ and the boiling points of the oetenes. Column containing liquid paraffin. (Conditions of analysis as for Fig. 2)
Quantitative determination of the composition was carried out by the method of internal normalization of the area of the peaks without the application of correction factors. The results of the calculation are given in Table 2. TABLE 2. COMPOSITION OF THE 1 0 0 - 1 1 6 . 5 ° FRACTION OF TIlE PRODUCTS OF THE DIMERIZATION OF BUTYLENES Alnount,
Component
P e a k No.
Not identified 2,4,4-Trimethylpent- 1-ene 2,4-Dimethylhex- 3-ene 3,4,4-Trimethylpent-2 -ene 2, 3,4 -Trimethylpent-2-ene Oct- 1-erie Not identified
% by weight 1.3 32 "3 9.45 36"5 18.0 0.45 2.0
The oetenes in fractions of the products of an organoaluminium synthesis were also identified, the relevant chromatogram being given in Fig. 5. A curve was constructed of the relationship between the relative retention volumes of the octenes on a column containing di-(eyanoethyl) sulphide and the boiling points. The relative retention volumes Vre1 were calculated from the formula: ! . . . . .
Vrel-
p tR
tR(st>
where the magnitude t'R (~o relates to n-hexa~ae.
182
M. S. VIGDERGAUZ a n d M. I . AFANAS'EV
nV
FIG. 5. Chromatogram of a fraction of the products of anorganoaluminium synthesis. (Conditions of analysis as for Fig. 1) The values o f Vre1 given in Table 3 show t h a t on the di-(eyanoethyl)sulphide c o l u m n a linear relationship between Vrel and the boiling point again exists, as shown in Fig. 6. T A B L E 3. R E T E N T I O N CHARACTERISTIC OF THE O C T E N E S O N A C O L U M N CONTAINING
Peak No.
DI-~-CYANOETHYL SULPHIDE. to = 1 10 sec., t~(st)= 68 sec. t
Component
2,4,4-Trimethylpent- 1-ene 2,4 -Dimethylhex- 3-one 3,4,4-Trimcthylpent -2-one 2,3,4-Trimethylpent-2-ene Oct- 1-ene
t R , sec. 219 262 292 333 380
Vre1 3"23
3"85 4"30 4"91
5"60
P e a k n has a r e t e n t i o n v o l u m e VreI of 5"9, which, f r o m the graph, corresponds to a c o m p o n e n t with b.p. 123"2 °. Substances with boiling points v e r y close to this (122.9 a n d 123.0 °) are cis- a n d tranz-oct-3-enes, which are e v i d e n t l y present in the m i x t u r e concerned.
Gas-chromatographic analysis of isomeric octenes
183
4
3 2
100 102 I 0 4
106
108 110
II2
114
116
I201"22124
10o
B.p FIG. 6. Relationship between the relative retention volumes Vrel and the boiling points of the octenes. Column containing di-fl-cyanoethyl sulphide• (Conditions of analysis as for Fig. 1} T h e heavier c o m p o n e n t s h a d b.p.s a b o v e 125 ° a n d did not belong to the group o f s u b s t a n c e s u n d e r consideration. T h e a u t h o r s express their t h a n k s to V. A. T e r e n t ' e v f o r carrying out the spectroscopic analyses. SUMMARY
1. A n u m b e r o f isomeric octenes have been identified in complex mixtures. T h e i r r e t e n t i o n characteristics on columns w i t h polar a n d non-polar phases h a v e been d e t e r m i n e d . 2. The isomeric octenes are d i s t r i b u t e d on a c o l u m n containing di-(flc y a n o e t h y l ) sulphide in strict a c c o r d a n c e with their boiling points. Translated by B. J. HAZZAR~) REFERENCES
1. E. BAYER, Khromatographiya gazov. (Translation of Gas-Chromatography•) Foreign Literature Publishing House, Moscow, 1959 2. B. I. ANVAYEY, A. A. ZHU~HOVITSKII and N. M. TURKEL'TAUB, Sb. Gazovaya khromatographiya. (In symposium: Gas Chromatography.) Gos INTI, p. 44, Moscow, 1962 3. P. W. WEST, B. SEN, B. R. SANT, K. L. MALLIK and J. G. SEN GUPTA, J. Chromatog. 6, 220, 1961
4. R. D. OBOLENTSEV, Fizicheskiye konstanty uglevodorodov zhidkikh topliv i masel. (Physical Constants of the Hydrocarbons of Liquid Fuels and Oils.) Gostoptekhizdat, Moscow, 1953