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Investigations on Romashkino asphaltic bitumen.2. Study of maltenes fractions using inverse gas-liquid chromatography
Investigations on Romashkino asphaltic bitumen. 2. Study of maltenes fractions using inverse gas-liquid chromatography Mieczyslaw
Boduszyhski
and Teresa Szkuta-Pochopieti
Polska Akademia Nauk, Zaklad Petro- i Karbochemii, ul. l-go Maja 62, 44- 100 Gliwice, Poland (Received 23 July 1976)
Inverse gas-liquid functionality study’.
chromatography
of the various maltenes
The effectiveness
has been ascertained. action coefficient interact behaviour
strongly
(IG LC) has been used to investigate the them ical fractions
of the separation
Results of analysis by IGLC
(I,) values of the fractions. with
obtained
of maltenes
many
in I,, values with
test compounds. the chemical
and identified
indicated
Acidic
significant
Inverse gas-liquid chromatography (IGLC), a technique for studying asphalts, was developed by Davis, Petersen and Haines’. In IGLC, asphalt or an asphalt fraction is used as the liquid stationary phase in a GLC column and is characterized by measuring the retention behaviour of selected volatile test compounds possessing different functional groups. The retention characteristic is a measure of functional group interactions between the test compounds and the asphalt or asphalt fraction and is thus related to the chemical composition of the material studied. The successful application of ICLC to indicate differences in the chemical composition of asphalts as well as to study oxidation characteristics of asphalts has already been demonstrated2-B. In the work reported here, the IGLC technique is used to differentiate maltenes fractions previously separated’ from Romashkino asphaltic bitumen. The various fractions of maltenes obtained in the previous study have different chemical compositions as indicated by elemental and densimetric analyses and should therefore exhibit differences in molecular association forces which, consequently, may influence the IGLC data. EXPERIMENTAL
Samples The Romashkino asphaltic bitumen, IOO-penetration straight-reduced, used in this study was separated into asphaltenes and maltenes using pentane treatment. The maltenes were further separated into acidic, basic and ncutral fractions using ion-exchange chromatography. The neutral fraction was then separated into group components using adsorption chromatography through alumina. The separation procedure and properties of the fractions have been described previously’. The asphaltenes obtained as above will bc dealt with separately’. Samples used in this investigation consisted of maltenes with and without ion-exchange resin treatment, polararomatics (PA-I) fractions separated from the above-
of the fractions
chromatography variation
and basic fractions
Based on these studies,
composition
in the previous
by ion-exchange
in inter-
were shown to
interpretation has been
of the
given.
mentioned materials by adsorption chromatography, and sub-fractions of maltenes which comprised two acidic fractions, three basic fractions and three group components of the neutral fraction, i.e. saturates (S), naphthenee aromatics (N-A) and polar-aromatics (PA-l). All samples are given the same symbols as in the previous study.
Reagerl ts The test compounds used for the ICLC determinations were of reagent grade. The test-compound phenol was used as a 50% solution in toluene. Fluoropak 80 (45-60 mesh, 0.33-0.25 mm was used as an inert support.
Procedure ICLC data were obtained using a dual-column gas chromatograph model ICSO-5. A procedure, similar to that used by Davis, Petersen and Haines’, has been described previously’. The IGLC column was prepared using 200 cm by 4 mm stainless steel tubing packed with one part of sample on 24 parts by weight of Fluoropak 80 and conditioned for a minimum of 6 h using nitrogen carrier gas and an instrument operating temperature of 130°C. After conditioning, 0.1 ~1 quantities of the test compounds were injected individually and retention times were determined.
Calculation of‘ the interactiorz coef;ficient (I,,) The interaction coefficient (f,) is a term devised for expressing ICLC data2. It is obtained by first determining on the asphalt or its fraction the corrected retention volumes (I$) for a series of straight-chain paraffins covering the molecular-weight range of the test compounds. The logarithms of the Vg values for the paraffins arc then plot ted as a function of their molecular weight. The I,, for a given test compound on the asphalt (or asphalt fraction) column is then defined as 100 times the
FUEL,
1977,
Vol 56, April
149
Investigations on Romashkino asphaltic bitumen (2): M. Boduszyriski and T. Szkuta-Pochopieti IGLC Table I resin treatment
analysis of maltenes with and without
interaction
ion-exchange
coefficient
UpI -
No.
Test compound
Original maltenes (MI
1 2 3 4 5 6 7 8 9 10 11 12
Propionic acid Acetic acid m-Cresol Phenol P-Methylthiophene Formamide Pyridine Toluene Butanol Tetrahydrofuran Heptaldehyde Butyl acetate
36 36 89 83 17 68 33 22 20 21 19 -7
Acid-free maltenes (M-AF)
Acid- and base-free maltenes (M-ABF)
26 26 83 77 17 57 29 21 16 16 20 -6
22 24 69 61 17 61 32 22 17 19 18 -8
difference between the logarithm of the Vg of the test compound and the logarithm of the Vg of a hypothetical paraffin (obtained from the above plot). The hypothetical paraffin is one having the same molecular weight as the test compound. The experimental value of 6 obtained has a reproducibility of+l.
for maltenes with and without ion-exchange resins treatment. should be evident to a greater extent in the case of the PA-l fractions separated from appropriate maltenes fractions. ICLC results presented in Table 2 gave good support to this. Interaction coefficients for all the test compounds arc larger now as the samples are richer in nonhydrocarbon components, but trends in variations of Ip values remained similar to those of the appropriate maltenes fractions, except for the three test compounds No. 5, No. 11 and No. 12 which exhibit the same retention behaviour as the test compounds No. 6 to No. 10. Significant reduction in $ values for all the test compounds and the fraction PA-l obtained from acid-free maltenes indicates that the acidic components removed from maltenes probably contain reasonably high contents of functional groupings which interact with all the test compounds used in this study. For the PA-I fraction free from both acidic and basic components the retention behaviour of the test compounds varies. The test compounds No. 1 to No. 4 (see Table 2) exhibit subsequent decrease in $, values after removal of basic components from the sample while all the other test compounds exhibit increases in Ip values. This is not surprising, as the test compounds propionic acid, m-cresol and phenol are acidic in nature and would be expected to interact strongly with basic components removed from maltenes.
Analysis of maltenes subfractions by IGLC RESULTS AND DISCUSSION
IGLC results on maltenes with and without ionexchange resin treatment The IGLC data on the original maltenes and those which had prior anion- and cation-exchange resin treatment are shown in Table 1. The more polar test compounds showed the larger I’~ values and generally more variation from sample to sample. Examples of this response are m-cresol, phenol. both propianic and acetic acids, and formamide. A good relation is evident between Q values and the composition of maltenes before and after removal of acidic components. The interaction coefficients for the acid-free maltenes and for most of the test compounds decreased in comparison with the fp values for the original maltenes, except for 2-methylthiophene, the Ip of which remained unaffected, and heptaldehyde and butyl acetate the fp values of which slightly increased. The removal of basic components from the acid-free maltenes resulted in a subsequent decrease of II, values for m-cresol, phenol and both propionic and acetic acids. The other test compounds gave larger Ip values with the exception of 2-methylthiophene which again gave the unchanged I& and heptaldehyde and butyl acetate, the tp values of which now decreased. The deviations from uniform changes in I,, between the fractions might be expected because many different types of polar groups exist in these complex mixtures. Results of the previous studies showed that acidic and basic components removed from maltenes have mainly concentrated in a group-type component of maltcnes designated as the polar-aromatics fraction (PA- 1) which accounted for 28.2 wt % of original maltenes. It has also been demonstrated’ that fraction PA-l exhibited the strongest intcractions (largest lp values) among all the group-type components of the Romashkino asphaltic bitumen. Thus, it may be expected that the above-discussed trends in I,, values
150
FUEL,
1977, Vol 56, April
Interaction coefficients of the maltenes subfractions are given in Table 3. Significant differences are seen among the fractions, thus indicating differences in their chemical composition. Neurral fractions. The analysis indicates that the fraction designated saturates(S) was least affected by polar groups present in the test compounds. This was expected because the fraction S consists of paraffins and naphthenes (2.6 naphthene rings/mol) and contains no nitrogen or oxygen. The sulphur content in this fraction is less than 0.1 wt %. The Ip of 54 for formamide was the largest among all the test compounds used on this fraction. It should be noted here that all the other maltenes subfractions showed the largest fp values for the m-cresol test compound. The Ip values obtained on the fraction designated naphthene-aromatics (N-A) showed an increase in comparison with the respective IP values for the previous fraction Tab/e 2 maltenes
IGLC analysis of polar-aromatics fractions, separated before and after ion exchange resin treatment Interaction Polar-aromatics
coefficient (PA-1
Test compound
Original maltenes
Acid-free maltenes
1 2 3 4 5 6 7 8 9 10 11 12
Propionic acid Acetic acid m-Ores01 Phenol 2-Methylthiophene Formamide Pyridine Toluene Butanol Tetrahydrofuran Heptaldehyde Butyl acetate
64 60 134 125 22 89 42 25 26 21 29 0
58 52 132 123 18 82 37 z: 19 25 -2
UpI
1separated
No.
from
from: Acid- and base-free maltenes 46 43 117 109 20 83 42 24 24 22 28 -1
M. Boduszyriski and T. Szkuta-Pochopiefi: Table 3
Elemental
and IGLC analyses of maltenes
subfractions Neutral
Elemental
analysis (wt %I
Carbon Hydrogen Sulphur Nitrogen Total No.
Test compound
1 2 3 4
Propionic acid Acetic acid m-Cresol Phenol
5 6 7 8 9 10 11 12 l
2-Methylthiophene Formamide Pyridine Toluene Butanol Tetrahydrofuran Heptaldehyde Butyl acetate Very strong interaction.
Investigations on Romashkino asphaltic bitumen (2)
s
N-A
86.1 13.8 0.1 0.0 100.0
85.2 11.4 3.1 0.0 99.7
fractions
Acidic
PA-1
M-Al
84.1 10.1 2.8 0.7 97.7
M-A2
83.2 8.8 3.3 1.4 96.7 Interaction
fractions
Basic fractions M-61
79.3 8.5 2.8 1.6 92.2 coefficient
80.7 10.1 5.3 0.8 96.9
25 25 79 69
46 43 117 109
48 44 112 104
56 52 119 109
43 40 108 101
13 54 25 19 15 17 11 -13
17 62 34 23 18 20 23 -7
20 83 42 24 24 22 28 -1
20 81 40 21 21 19 31 3
21 102 46 21 24 22 30 13
20 78 38 25 24 23 26 -4
retained
in a column
M-B3
81.3 106 4.4 1 .o 97.3
78.0 9.2 2.8 2.3 92.3
(/,I
25 24 49 41
Test compound
M-B2
90 86
. .
l
l
l
l
19 103 37 24 34 25 24 -2
19 117 37 24 26 20 30 -1
more than 2 h.
except for propionic and acetic acids, the values for which remained practically unchanged. The larger interaction coefficients for this fraction are due to its naphthene -aromatic nature (3.1 naphthene and 1.7 aromatic rings/mol). The hetero-atom content of this fraction accounts for 3.1 wt % sulphur, but no nitrogen and oxygen are present. The highly aromatic character (3.4 aromatic rings/mol) as well as the presence of nitrogen compounds (0.7 wt % N) in fraction PA- 1 resulted in fairly large increases in the values for all the test compounds. Greater increases in the $ values for acidic test compounds suggest the presence of polar groups in the fraction PA- 1 which interact more strongly with these test compounds. Acidic fractions. Both acidic fractions (M-Al and M-A2) showed strong interactions with most of the test compounds. The fraction M-A2 which was held more tightly by the anionexchange resin would be expected to contain a higher content of more-polar interacting groups. This is also evident from the data in Table 3. The test compounds show a fairly regular increase in Ip from the M-A I sample to the M-A2 sample. With m-cresol, which showed the largest values for both fractions, there was a net increase in lp of 7 from M-Al to M-A2, while formamide showed a net increase in lp of 2 1. That certain test compounds are selective in indicating differences in functional groups within fractions is also illustrated by comparing the retention behaviour of butyl acetate on both acidic fractions. With butyl acetate test compound there were negative $ values for all the maltenes subfractions except for the acidic fractions M-AI and M-A2, on which positive values were obtained (3 and 13 respectively). Basic fractions, As in the case of acidic fractions, the basic fractions which were more tightly held by the cationexchange resin (fraction M-B 1 to fraction M-B3) would be expected to contain a higher content of more polar interacting groups. This can be seen from data in Table 3. The acidic test compounds generally showed larger interaction coefficients for all three basic fractions. With both propionic and acetic acids there were more than doubled $ values for fraction M-B2 compared with the respective values
for fraction M-B 1. The values for both acids on fraction M-B3 could not even be measured because of very strong interactions between these compounds and the sample; the test compounds were retained in the column for more than 2 h. A similar response, but even more pronounced, is evident with m-cresol and phenol test compounds. Again. retention of these test compounds on the column exceeded 2 h. The retention behaviour of the basic test compound pyridine on all three basic fractions indicates very weak interactions and the $, was slightly decreased with increased basic strength of the fractions. The less-polar test compounds showed luwcr fp values and less variation from sample to sample but no generalization can be made. Certain deviations from uniform changes in 1, indicate the usefulness of IGLC in detecting differences in the functionality of the fractions.
CONCLUSIONS 1. With the aid of IGLC the effectiveness of the separation by ion-exchange chromatography to obtain the most reactive (polar) components of maltenes is ascertained. 2. IGLC data indicate that the separation of maltenes by ion-exchange chromatography is taking place according to the increasing acidic or basic strength of the fractions recovered. 3. Acidic and basic fractions are shown to interact strongly with many test compounds, the basic fractions exhibiting the strongest interactions among the fractions tested. 4. A correlation between the nitrogen content of the fraction and interaction coefficients of more-polar test compounds as typified by m-cresol, phenol, formamide, propionic and acetic acids is evident. The higher nitrogen containing fractions generally showed the larger fp values. 5. The usefulness of the IGLC technique in predicting the chemical functionality of asphaltic bitumen components is evident.
FUEL,
1977,
Vol
56,
April
151
Investigations
on Romashkino
asphaltic
bitumen
(2): M. Boduszyriski
ACKNOWLEDGEMENT The authors are grateful to Professor W. Kisielow, Director of the Department of Petroleum and Coal Chemistry of the Polish Academy of Sciences, Gliwice, for his keen interest in carrying out these studies and permission to publish this work.
3 4
5 6 1
REFERENCES
8
I 2
9
152
Boduszyriski, M., Chadha, B. R. and Pineles, H. Fuel 1977, 56, 145 Davis. T. C.. Petersen, J. C. and Haines, W. E. Anal.vt. Chem.
FUEL,
1977, Vol 56, April
and T. Szkuta-Pochopieri 1966,38,2,241 Davis, T. C. and Petersen, J. C. Analyr Chem. 1966,38, 13, 1938 Davis, T. C. and Petersen, J. C. Proc. Assoc. Asphalt Paving Tcchrrol. 1967, 36, 1 Davis,T. C. and Petersen, J. C. Analyf. Chem. 1967,39, 14, 1853 Barbour, F. A., Dorrence, S. M. and Petersen, J. C. Analyr. Chem. 1970,42,6,668 Barbour, F. A., Barbour, R. V. and Petersen, J. C.J. appl. Chem. Biorechnol. 1974,24,645 Boduszyhski, M. and Szkuta-Pochopied, T. Nafta Krakbw), 1976, 32,9 Boduszyriski, M., Chadha, B. R., Pineles, H. and Szkuta-Pochopie6, T. (submitted to Fuel), Part 3
Boduszyhski
and Teresa Szkuta-Pochopieti
Polska Akademia Nauk, Zaklad Petro- i Karbochemii, ul. l-go Maja 62, 44- 100 Gliwice, Poland (Received 23 July 1976)
Inverse gas-liquid functionality study’.
chromatography
of the various maltenes
The effectiveness
has been ascertained. action coefficient interact behaviour
strongly
(IG LC) has been used to investigate the them ical fractions
of the separation
Results of analysis by IGLC
(I,) values of the fractions. with
obtained
of maltenes
many
in I,, values with
test compounds. the chemical
and identified
indicated
Acidic
significant
Inverse gas-liquid chromatography (IGLC), a technique for studying asphalts, was developed by Davis, Petersen and Haines’. In IGLC, asphalt or an asphalt fraction is used as the liquid stationary phase in a GLC column and is characterized by measuring the retention behaviour of selected volatile test compounds possessing different functional groups. The retention characteristic is a measure of functional group interactions between the test compounds and the asphalt or asphalt fraction and is thus related to the chemical composition of the material studied. The successful application of ICLC to indicate differences in the chemical composition of asphalts as well as to study oxidation characteristics of asphalts has already been demonstrated2-B. In the work reported here, the IGLC technique is used to differentiate maltenes fractions previously separated’ from Romashkino asphaltic bitumen. The various fractions of maltenes obtained in the previous study have different chemical compositions as indicated by elemental and densimetric analyses and should therefore exhibit differences in molecular association forces which, consequently, may influence the IGLC data. EXPERIMENTAL
Samples The Romashkino asphaltic bitumen, IOO-penetration straight-reduced, used in this study was separated into asphaltenes and maltenes using pentane treatment. The maltenes were further separated into acidic, basic and ncutral fractions using ion-exchange chromatography. The neutral fraction was then separated into group components using adsorption chromatography through alumina. The separation procedure and properties of the fractions have been described previously’. The asphaltenes obtained as above will bc dealt with separately’. Samples used in this investigation consisted of maltenes with and without ion-exchange resin treatment, polararomatics (PA-I) fractions separated from the above-
of the fractions
chromatography variation
and basic fractions
Based on these studies,
composition
in the previous
by ion-exchange
in inter-
were shown to
interpretation has been
of the
given.
mentioned materials by adsorption chromatography, and sub-fractions of maltenes which comprised two acidic fractions, three basic fractions and three group components of the neutral fraction, i.e. saturates (S), naphthenee aromatics (N-A) and polar-aromatics (PA-l). All samples are given the same symbols as in the previous study.
Reagerl ts The test compounds used for the ICLC determinations were of reagent grade. The test-compound phenol was used as a 50% solution in toluene. Fluoropak 80 (45-60 mesh, 0.33-0.25 mm was used as an inert support.
Procedure ICLC data were obtained using a dual-column gas chromatograph model ICSO-5. A procedure, similar to that used by Davis, Petersen and Haines’, has been described previously’. The IGLC column was prepared using 200 cm by 4 mm stainless steel tubing packed with one part of sample on 24 parts by weight of Fluoropak 80 and conditioned for a minimum of 6 h using nitrogen carrier gas and an instrument operating temperature of 130°C. After conditioning, 0.1 ~1 quantities of the test compounds were injected individually and retention times were determined.
Calculation of‘ the interactiorz coef;ficient (I,,) The interaction coefficient (f,) is a term devised for expressing ICLC data2. It is obtained by first determining on the asphalt or its fraction the corrected retention volumes (I$) for a series of straight-chain paraffins covering the molecular-weight range of the test compounds. The logarithms of the Vg values for the paraffins arc then plot ted as a function of their molecular weight. The I,, for a given test compound on the asphalt (or asphalt fraction) column is then defined as 100 times the
FUEL,
1977,
Vol 56, April
149
Investigations on Romashkino asphaltic bitumen (2): M. Boduszyriski and T. Szkuta-Pochopieti IGLC Table I resin treatment
analysis of maltenes with and without
interaction
ion-exchange
coefficient
UpI -
No.
Test compound
Original maltenes (MI
1 2 3 4 5 6 7 8 9 10 11 12
Propionic acid Acetic acid m-Cresol Phenol P-Methylthiophene Formamide Pyridine Toluene Butanol Tetrahydrofuran Heptaldehyde Butyl acetate
36 36 89 83 17 68 33 22 20 21 19 -7
Acid-free maltenes (M-AF)
Acid- and base-free maltenes (M-ABF)
26 26 83 77 17 57 29 21 16 16 20 -6
22 24 69 61 17 61 32 22 17 19 18 -8
difference between the logarithm of the Vg of the test compound and the logarithm of the Vg of a hypothetical paraffin (obtained from the above plot). The hypothetical paraffin is one having the same molecular weight as the test compound. The experimental value of 6 obtained has a reproducibility of+l.
for maltenes with and without ion-exchange resins treatment. should be evident to a greater extent in the case of the PA-l fractions separated from appropriate maltenes fractions. ICLC results presented in Table 2 gave good support to this. Interaction coefficients for all the test compounds arc larger now as the samples are richer in nonhydrocarbon components, but trends in variations of Ip values remained similar to those of the appropriate maltenes fractions, except for the three test compounds No. 5, No. 11 and No. 12 which exhibit the same retention behaviour as the test compounds No. 6 to No. 10. Significant reduction in $ values for all the test compounds and the fraction PA-l obtained from acid-free maltenes indicates that the acidic components removed from maltenes probably contain reasonably high contents of functional groupings which interact with all the test compounds used in this study. For the PA-I fraction free from both acidic and basic components the retention behaviour of the test compounds varies. The test compounds No. 1 to No. 4 (see Table 2) exhibit subsequent decrease in $, values after removal of basic components from the sample while all the other test compounds exhibit increases in Ip values. This is not surprising, as the test compounds propionic acid, m-cresol and phenol are acidic in nature and would be expected to interact strongly with basic components removed from maltenes.
Analysis of maltenes subfractions by IGLC RESULTS AND DISCUSSION
IGLC results on maltenes with and without ionexchange resin treatment The IGLC data on the original maltenes and those which had prior anion- and cation-exchange resin treatment are shown in Table 1. The more polar test compounds showed the larger I’~ values and generally more variation from sample to sample. Examples of this response are m-cresol, phenol. both propianic and acetic acids, and formamide. A good relation is evident between Q values and the composition of maltenes before and after removal of acidic components. The interaction coefficients for the acid-free maltenes and for most of the test compounds decreased in comparison with the fp values for the original maltenes, except for 2-methylthiophene, the Ip of which remained unaffected, and heptaldehyde and butyl acetate the fp values of which slightly increased. The removal of basic components from the acid-free maltenes resulted in a subsequent decrease of II, values for m-cresol, phenol and both propionic and acetic acids. The other test compounds gave larger Ip values with the exception of 2-methylthiophene which again gave the unchanged I& and heptaldehyde and butyl acetate, the tp values of which now decreased. The deviations from uniform changes in I,, between the fractions might be expected because many different types of polar groups exist in these complex mixtures. Results of the previous studies showed that acidic and basic components removed from maltenes have mainly concentrated in a group-type component of maltcnes designated as the polar-aromatics fraction (PA- 1) which accounted for 28.2 wt % of original maltenes. It has also been demonstrated’ that fraction PA-l exhibited the strongest intcractions (largest lp values) among all the group-type components of the Romashkino asphaltic bitumen. Thus, it may be expected that the above-discussed trends in I,, values
150
FUEL,
1977, Vol 56, April
Interaction coefficients of the maltenes subfractions are given in Table 3. Significant differences are seen among the fractions, thus indicating differences in their chemical composition. Neurral fractions. The analysis indicates that the fraction designated saturates(S) was least affected by polar groups present in the test compounds. This was expected because the fraction S consists of paraffins and naphthenes (2.6 naphthene rings/mol) and contains no nitrogen or oxygen. The sulphur content in this fraction is less than 0.1 wt %. The Ip of 54 for formamide was the largest among all the test compounds used on this fraction. It should be noted here that all the other maltenes subfractions showed the largest fp values for the m-cresol test compound. The Ip values obtained on the fraction designated naphthene-aromatics (N-A) showed an increase in comparison with the respective IP values for the previous fraction Tab/e 2 maltenes
IGLC analysis of polar-aromatics fractions, separated before and after ion exchange resin treatment Interaction Polar-aromatics
coefficient (PA-1
Test compound
Original maltenes
Acid-free maltenes
1 2 3 4 5 6 7 8 9 10 11 12
Propionic acid Acetic acid m-Ores01 Phenol 2-Methylthiophene Formamide Pyridine Toluene Butanol Tetrahydrofuran Heptaldehyde Butyl acetate
64 60 134 125 22 89 42 25 26 21 29 0
58 52 132 123 18 82 37 z: 19 25 -2
UpI
1separated
No.
from
from: Acid- and base-free maltenes 46 43 117 109 20 83 42 24 24 22 28 -1
M. Boduszyriski and T. Szkuta-Pochopiefi: Table 3
Elemental
and IGLC analyses of maltenes
subfractions Neutral
Elemental
analysis (wt %I
Carbon Hydrogen Sulphur Nitrogen Total No.
Test compound
1 2 3 4
Propionic acid Acetic acid m-Cresol Phenol
5 6 7 8 9 10 11 12 l
2-Methylthiophene Formamide Pyridine Toluene Butanol Tetrahydrofuran Heptaldehyde Butyl acetate Very strong interaction.
Investigations on Romashkino asphaltic bitumen (2)
s
N-A
86.1 13.8 0.1 0.0 100.0
85.2 11.4 3.1 0.0 99.7
fractions
Acidic
PA-1
M-Al
84.1 10.1 2.8 0.7 97.7
M-A2
83.2 8.8 3.3 1.4 96.7 Interaction
fractions
Basic fractions M-61
79.3 8.5 2.8 1.6 92.2 coefficient
80.7 10.1 5.3 0.8 96.9
25 25 79 69
46 43 117 109
48 44 112 104
56 52 119 109
43 40 108 101
13 54 25 19 15 17 11 -13
17 62 34 23 18 20 23 -7
20 83 42 24 24 22 28 -1
20 81 40 21 21 19 31 3
21 102 46 21 24 22 30 13
20 78 38 25 24 23 26 -4
retained
in a column
M-B3
81.3 106 4.4 1 .o 97.3
78.0 9.2 2.8 2.3 92.3
(/,I
25 24 49 41
Test compound
M-B2
90 86
. .
l
l
l
l
19 103 37 24 34 25 24 -2
19 117 37 24 26 20 30 -1
more than 2 h.
except for propionic and acetic acids, the values for which remained practically unchanged. The larger interaction coefficients for this fraction are due to its naphthene -aromatic nature (3.1 naphthene and 1.7 aromatic rings/mol). The hetero-atom content of this fraction accounts for 3.1 wt % sulphur, but no nitrogen and oxygen are present. The highly aromatic character (3.4 aromatic rings/mol) as well as the presence of nitrogen compounds (0.7 wt % N) in fraction PA- 1 resulted in fairly large increases in the values for all the test compounds. Greater increases in the $ values for acidic test compounds suggest the presence of polar groups in the fraction PA- 1 which interact more strongly with these test compounds. Acidic fractions. Both acidic fractions (M-Al and M-A2) showed strong interactions with most of the test compounds. The fraction M-A2 which was held more tightly by the anionexchange resin would be expected to contain a higher content of more-polar interacting groups. This is also evident from the data in Table 3. The test compounds show a fairly regular increase in Ip from the M-A I sample to the M-A2 sample. With m-cresol, which showed the largest values for both fractions, there was a net increase in lp of 7 from M-Al to M-A2, while formamide showed a net increase in lp of 2 1. That certain test compounds are selective in indicating differences in functional groups within fractions is also illustrated by comparing the retention behaviour of butyl acetate on both acidic fractions. With butyl acetate test compound there were negative $ values for all the maltenes subfractions except for the acidic fractions M-AI and M-A2, on which positive values were obtained (3 and 13 respectively). Basic fractions, As in the case of acidic fractions, the basic fractions which were more tightly held by the cationexchange resin (fraction M-B 1 to fraction M-B3) would be expected to contain a higher content of more polar interacting groups. This can be seen from data in Table 3. The acidic test compounds generally showed larger interaction coefficients for all three basic fractions. With both propionic and acetic acids there were more than doubled $ values for fraction M-B2 compared with the respective values
for fraction M-B 1. The values for both acids on fraction M-B3 could not even be measured because of very strong interactions between these compounds and the sample; the test compounds were retained in the column for more than 2 h. A similar response, but even more pronounced, is evident with m-cresol and phenol test compounds. Again. retention of these test compounds on the column exceeded 2 h. The retention behaviour of the basic test compound pyridine on all three basic fractions indicates very weak interactions and the $, was slightly decreased with increased basic strength of the fractions. The less-polar test compounds showed luwcr fp values and less variation from sample to sample but no generalization can be made. Certain deviations from uniform changes in 1, indicate the usefulness of IGLC in detecting differences in the functionality of the fractions.
CONCLUSIONS 1. With the aid of IGLC the effectiveness of the separation by ion-exchange chromatography to obtain the most reactive (polar) components of maltenes is ascertained. 2. IGLC data indicate that the separation of maltenes by ion-exchange chromatography is taking place according to the increasing acidic or basic strength of the fractions recovered. 3. Acidic and basic fractions are shown to interact strongly with many test compounds, the basic fractions exhibiting the strongest interactions among the fractions tested. 4. A correlation between the nitrogen content of the fraction and interaction coefficients of more-polar test compounds as typified by m-cresol, phenol, formamide, propionic and acetic acids is evident. The higher nitrogen containing fractions generally showed the larger fp values. 5. The usefulness of the IGLC technique in predicting the chemical functionality of asphaltic bitumen components is evident.
FUEL,
1977,
Vol
56,
April
151
Investigations
on Romashkino
asphaltic
bitumen
(2): M. Boduszyriski
ACKNOWLEDGEMENT The authors are grateful to Professor W. Kisielow, Director of the Department of Petroleum and Coal Chemistry of the Polish Academy of Sciences, Gliwice, for his keen interest in carrying out these studies and permission to publish this work.
3 4
5 6 1
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