Vol. 25, No. 15 (2013)
Preparation and Application of Hydroxyacetic Acid Esters as Methanol-Gasoline Additives 8449
70
gasoline are ineffective, even as the dosage over 10 %, methanol
and gasoline homogenized blends can not obtained in M15,
M30, M50 and M65 at 40 ºC. The reason may be due to the
strong hydrophilic property but weak lipophilic property of
short-carbon-chained glycolic ester, leading them not to
dissolve in gasoline. With the increase of the carbon chain of
glycolic esters, lipophilic property of the ester is markedly
enhanced and the dissolution in gasoline is intensified, resulting
in higher solubilization in the various blends. With too long
carbon chain, decyl glycolic is hardly soluble in methanol,
resulting to the poor phase stability even under high temperature.
According to the results, it can be found that only glycolic
esters with moderate carbon atoms are with the effective phase
stability to methanol-gasoline. The esters with alkoxy groups
of 5-8 carbon atoms are more effective than others. The phase
separation temperatures of the four methanol-gasoline blends
with the ester dosage of 10 % was estimated and shown in
Fig. 5. It can be found that the phase separation temperature
declines along with the length of the alkoxy group. For M15,
M30 and M50 and the phase separation temperature comes to
the lowest as the carbon atom number of alkoxy group comes
to 8, while it rises sharply as the carbon atom number lengthens
to 10. For M65, the lowest phase separation temperature was
obtained as the carbon atom number of alkoxy group comes
to 6.
methyl glycolic
butyl glycolic
hepyl glycolic
ethyl glycolic
amyl glycolic
octyl glycolic
propyl glycolic
hexyl glycolic
decyl glycolic
65
60
55
50
45
40
35
30
25
20
15
10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Dosage of glycolic esters (%)
Fig. 6. Effect of glycolic esters on the evaporation of methanol-gasoline
M15 system
pressure lower than that of gasoline, among which decyl
glycolic ester is the most effective one. Further increase of the
dosage depresses the saturation vapour pressure ineffectively.
The main reason is contribute to the distribution of glycolic
esters on the surface of methanol-gasoline, which prevent the
formation of an azeotrope with low boiling point.
Conclusion
Glycolic esters were synthesized and screened for their
performances of phase stabilizing in M15, M30, M50 and M65
and pressure reducing in M15. The results show that the length
of alkoxy group of glycolic esters effects on the phase stability
of methanol-gasoline significantly. Methyl glycolic ester, ethyl
glycolic ester and decyl glycolic ester, are ineffective on the
phase stability of methanol-gasoline, even as the dosage over
10 %, while hexyl glycolic ester and decyl glycolic ester are
the most effective for M15, M30, M50 and M65, respectively.
All of the synthesized esters are potent to depress the saturation
vapour pressure of methanol-gasoline. With the dosage of
0.1 %, ethyl glycolic ester, propyl glycolic ester, butyl glycolic
ester, amyl glycolic ester, hexyl glycolic ester and decyl glycolic
ester can depress the saturation vapour pressure lower than that
of gasoline and decyl glycolic ester is the most effective one.
M15
M50
M30
M65
50
45
40
35
30
25
20
15
10
5
0
-5
0
1
2
3
4
5
6
7
8
9
10
Carbon atom number of alkoxy groups
ACKNOWLEDGEMENTS
Fig. 5. Relationship of the alkoxy groups and the phase separation
temperature
This work was financially supported by the grants from
Scientific Research Program Funded by Shaanxi Provincial
Education Department (11JK0898, 2013JK0646) and National
Science Foundation of China (No. 21306149).
Effect of glycolic ester on the evaporation of methanol-
gasoline: The saturation vapour pressure will rise over that of
gasoline as it blends with low percentage methanol such as
M15 and M30, which will lead to vapour block as it used
under relative high temperature. Some chemicals with lower
saturation vapour pressure can be added to depress the high
pressure of gasoline. In this work, the effect of glycolic ester
on the saturation vapour pressure of M15 methanol-gasoline
was investigated referred to GB 8017-87 “petroleum products
the vapour pressure determination method (Reid Method)”
and the results are shown in Fig. 6. The original saturation
vapour pressure of M15 is 63.5 kPa, which is 5.7 kPa higher
than that of gasoline. As little amount of esters were added in,
the saturation vapour pressure was depressed obviously. With
the esters’dosage of 0.1 %, ethyl glycolic ester, propyl glycolic
ester, butyl glycolic ester, amyl glycolic ester, hexyl glycolic
ester and decyl glycolic ester can depress the saturation vapour
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