Synthesis and application of 2,3-Dihydroxybutanedioic Acid Esters as efficient additives in Methanol-Gasoline

Article abstract of DOI:10.14233/ajchem.2013.14780

In this paper, 2,3-dihydroxybutanedioic acid esters (tartaric esters) were synthesized and used as phase stabilizer and saturation vapour pressure depressor of methanol-gasoline. The results show that the stabilities of the methanol-gasoline depend on the

Full text of DOI:10.14233/ajchem.2013.14780

Asian Journal of Chemistry; Vol. 25, No. 15 (2013), 8451-8454
http://dx.doi.org/10.14233/ajchem.2013.14780
Synthesis and Application of 2,3-Dihydroxybutanedioic
Acid Esters as Efficient Additives in Methanol-Gasoline
1
2,*
XIAOYAN JIANG and YING TANG
1College of Energy Engineering, Yulin University, Yulin 719000, Shaanxi Province, P.R. China
2College of Chemistry and Chemical Engineering, Xi'an Shiyou University, Xi'an 710065, Shaanxi Province, China
*Corresponding author: Tel: +86 29 88382693; E-mail: tangying78@xsyu.edu.cn
(Received: 5 November 2012;
Accepted: 24 August 2013)
AJC-13971
In this paper, 2,3-dihydroxybutanedioic acid esters (tartaric esters) were synthesized and used as phase stabilizer and saturation vapour
pressure depressor of methanol-gasoline. The results show that the stabilities of the methanol-gasoline depend on the length of the tartaric
esters’ alkoxy group. Several tartaric esters were found to be effective in various gasoline-methanol blends and the tartaric esters display
high capacity to depress the saturation vapour pressure of methanol-gasoline. According to the results, it can be concluded that the tartaric
esters have the great potential to be bifunctional gasoline-methanol additives.
Key Words: Methanol-gasoline, Tartaric esters, Phase stability, Evaporation.
and screened in the methanol-gasoline as a bifunctional
additive.
INTRODUCTION
Facing on the rising huge consumption of oil, develop-
ment of clean and alternative fuels increasingly draws world-
wide attentions1. In a large number of alternative fuels, methanol
displays fine combustion properties similar to gasoline and
has advantages such as high octane number, low emissions,
antiknock, rich resource, mature technology, etc., so it can be
used as alternative fuel for gasoline2. In recent years, extensive
research of the low percentage methanol-gasoline has been
carried out and it has been applied in Shanxi, Sichuan,
Zhejiang, Inner Mongolia, Shaanxi, Xinjiang and other places
of China gradually 3. However, there are several problems
needing to resolve in methanol-gasoline research, in which
the phase stability is the most important one. One of the
popular solutions is to add phase stabilizer to reduce alcohol-
oil interfacial tension4,5, such as ethers, ketones, esters, fatty
alcohols, aliphatic hydrocarbons, fatty acids, non-ionic surfac-
tants, acetal/ketones, biodiesels and amidines6-11. Secondly, the
low boil point of methanol leads to high possibility of vapour
EXPERIMENTAL
All the solvents wereAR grade and purchased from Xi’an
ChemicalAgent Co and the 93# gasoline is commercially avail-
able. The phase stabilizing and pressure reducing were tested
on DFY-cryostat instrument (Xi’anYuhui Instrument Co. Ltd.)
and DSL-080 vapour pressure detector (Dalian the Ceon Elec-
tronic Equipment Co. Ltd.).
Synthesis of tartaric esters
Method A: Tartaric acid (23 g), methanol (18 mL) and
p-toluenesulfonic acid (TsOH) (0.6g) was added to the flask.
After 10 h of refluxing, the reaction mixture was cooled to
room temperature. Methanol and methyl tartaric were distillated,
respectively. The synthesis of ethyl tartaric and propyl tartaric
is same to method above25.
Method B: Tartaric acid (0.15 mol), n-butanol (0.45 mol),
cyclohexane (30 mL), p-toluenesulfonic acid (0.5 g) were
refluxed for 5 h and the produced water was separated by a
water separator.After cooled to room temperature, cyclohexane,
n-butanol and n-butyl tartaric were separated by vacuum disti-
llation. The synthesis of amyl tartaric ester, hexyl tartaric ester,
hepyl tartaric, octyl tartaric ester and decyl tartaric ester is
lock by raising the vapour pressure of methanol-gasoline12-14
.
The current solution for vapour lock is to add pressure reducers,
such as aliphatic ketones, fatty acids, fatty aldehydes, fatty
ethers, acetals/ketals, etc.15-24. At present, few researches have
carried out to develop bifunctional additives with the abilities
of both phase stability and vapour pressure depressing for
methanol-gasoline. In this work, a series of 2,3-dihydroxy-
butanedioic acid esters (tartaric esters) was synthesized
same to method above26,27
.
Phase stability test: The fuel blends were prepared by
blending 15, 30, 50 and 65 vol. % of methanol with base gasoline

8452 Jiang et al.
Asian J. Chem.
and the fuel blends were assigned as M15, M30, M50 and
M65. The phase stabilizing tests were carried out according
to Chinese National standards of GB 8017-87, GB/T 23799-
2009, DB61/T 352-2004 and DB51/T 448-2004. First the test
tube full of methanol-gasoline with different ratios was placed
in a cryostat and then the temperature was adjusted from 40-
25 ºC. At each degree, the tube was taken out and was shaken
for two to three seconds and the phase separation temperature
propyl tartaric
hexyl tartaric
decyl tartaric
butyl tartaric
hepyl tartaric
amyl tartaric
octyl tartaric
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
was determined as the solution becomes cloudy28-30
.
Vapour pressure test: The effect of tartaric esters on
vapour pressure of methanol-gasoline was investigated accor-
ding to Chinese standards of GB 8017-87. The methanol-gaso-
line was poured into the vapour pressure detector and put into
the water bath of 37.8 ºC. The methanol-gasoline was intensive
mixed by taking the detector from the water bath every 5 min
and reversing violently. The operation was repeated until the
pressure becomes steady.
2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0
Dosage of tartaric acid esters/% (V)
Fig. 1. Effect of the tartaric ester dosage on the phase stability of M15.
(The dosages of methyl tartaric and ethyl tartaric are beyond 11.1
% at 40 ºC)
propyl tartaric
hexyl tartaric
decyl tartaric
butyl tartaric
hepyl tartaric
amyl tartaric
octyl tartaric
RESULTS AND DISCUSSION
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
Synthesis of tartaric esters: The reaction of tartaric acid
and alcohols are shown in Scheme-I and both the reaction
conditions and the yield are summarized in Table-1. In this
reaction, diester (a) is the main product and the monoester (b)
is the undesired byproduct. To reduce the byproduct, high
quantities of alcohol was used. For the synthesis of the first
three esters, the alcohols were employed with higher ratio over
1:30. For the rest esters, the tartaric acid and alcohol ratio is as
high as 1:5. The yields were obtained in the range from 60.2
to 77.6 % as shown in Table-1.
0.0
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0
Dosage of tartaric acid esters/% (V)
Fig. 2. Effect of the tartaric ester dosage on the phase stability of M30.
(The dosages of methyl tartaric and ethyl tartaric are beyond 11.1
% at 40 ºC)
O
O
O
HO
HO
HO
HO
HO
HO
TsOH
OH
OH
OR
OR
OH
OR
+
+
ROH
propyl tartaric
hexyl tartaric
decyl tartaric
butyl tartaric
hepyl tartaric
amyl tartaric
octyl tartaric
O
O
(a)
O
(b)
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
Scheme-I: Reaction of tartaric acid and alcohol
TABLE-1
RESULTS OF THE SYNTHESIS OF TARTARIC ESTERS
Esters
Tartaric acid:alcohol
Method
Yield (%)
Methyl tartaric
Ethyl tartaric
Propyl tartaric
Butyl tartaric
Amyl tartaric
Hexyl tartaric
Hepyl tartaric
Octyl tartaric
Decyl tartaric
1:30
1:30
1:30
1:5
A
A
A
B
B
B
B
B
B
70.9
71.1
76.5
77.6
64.5
60.2
72.1
71.5
72.2
0.0
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.011.0 12.013.014.015.0
Dosage of tartaric acid esters/% (V)
1:5
1:5
1:5
Fig. 3. Effect of the tartaric ester dosage on the phase stability of M50.
(The dosages of methyl tartaric and ethyl tartaric are beyond 11.1
% at 40 ºC)
1:5
1:5
Effect of tartaric ester on the phase stability of metha-
nol-gasoline: The phase stabilities of tartaric esters for the
methanol-gasoline blends of M15, M30, M50 and M65 at diffe-
rent temperatures from -25 ºC to 40 ºC were investigated and
summarized in Figs. 1-4. The experimental data indicate that
the length of carbon chain of tartaric ester effects on the phase
stability of methanol-gasoline significantly. For the esters with
very short, such as methyl tartaric, ethyl tartaric, the phase
stability to methanol-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 lipo-
philic property of short-carbon-chained tartaric ester, leading
them not to dissolve in gasoline. With the increase of the carbon
chain of tartaric esters, lipophilic property of the ester is markedly
enhanced and the dissolution in gasoline is intensified, resulting
in higher solubilization in the various blends. According to
the results, it can be found that long-carbon-chained tartaric
esters are with the effective phase stability to methanol-gaso-
line. The phase separation temperatures of the four methanol-

Vol. 25, No. 15 (2013)
Synthesis and Application of 2,3-Dihydroxybutanedioic Acid Esters 8453
methyl tartaric
butyl tartaric
hepyl tartaric
ethyl tartaric
amyl tartaric
octyl tartaric
propyl tartaric
hexyl tartaric
decyl tartaric
methyl tartaric
butyl tartaric
hepyl tartaric
ethyl tartaric
amyl tartaric
octyl tartaric
propyl tartaric
hexyl tartaric
decyl tartaric
60.0
55.0
50.0
45.0
40.0
35.0
30.0
25.0
20.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
-5.0
-10.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
Dosage of tartaric acid esters/% (V)
Fig. 4. Effect of the tartaric ester dosage on the phase stability of M65
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Dosage of tartaric esters (%)
50
Fig. 6. Effect of tartaric esters on the evaporation of methanol-gasoline
M15 system
M15
M50
M30
M65
45
40
35
30
25
20
15
10
5
ester, propyl tartaric ester, butyl tartaric ester, amyl tartaric
ester, hexyl tartaric ester and decyl tartaric ester can depress
the saturation vapour pressure lower than that of gasoline,
among which decyl tartaric 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 tartaric esters on the surface of methanol-gaso-
line, which prevent the formation of an azeotrope with low
boiling point.
0
Conclusion
-5
Tartaric 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 tartaric esters effects on the phase stability
of methanol-gasoline significantly. The phase stability of
tartaric esters with long length is more potent than that with
short length.All of the synthesized esters are potent to depress
the saturation vapour pressure of methanol-gasoline. With the
dosage of 0.1 %, all tartaric esters can depress the saturation
vapour pressure lower than that of gasoline and decyl tartaric
ester is the most effective one.
0
1
2
3
4
5
6
7
8
9
10
Carbon atom number of alkoxy groups
Fig. 5. Relationship of the alkoxy groups and the phase separation
temperature
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, the phase separation temperature comes to the lowest
as the carbon atom number of alkoxy group comes to 6. For
M30, the carbon atom number of alkoxy group comes to 7.
For M50, the carbon atom number of alkoxy group comes
to 8. For M65, the lowest phase separation temperature was
obtained as the carbon atom number of alkoxy group comes
to 8.
ACKNOWLEDGEMENTS
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 tartaric 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 tartaric 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 %, methyl tartaric ester, ethyl tartaric
REFERENCES
1. W. Liang, J. Chin. Foreign Energy, 11, 95 (2006).
2. X.L. He, Y. H. Zhan and S.S. Li, China Petrochemical Press: Fuel of
Internal Ombustion Engine, Beijing, pp. 11/352-11/392 (1999).
3. J.J.Yang and H.B. Huang, J. Internal Combustion Engine Power Equip.,
4, 40 (2007).
4. W.H. Fu, J. Learned J. Petroleum, 2, 69 (1986).
5. P. He, Research and Application of the Additive of Methanol Gasoline,
Liao Ning Normal University, pp. 9-10 (2010).
6. Y.B. Qiao, J. Contemp. Petroleum Petrochem., 11, 7 (2003).
7. G.Z. Cao and S.Y. Tan, Research on Application of Methanol Gasoline,
Chong Qing University, pp. 1-2 (2008).
8. Y.Z. Wang, Physical and Chemical Properties of the Vehicle of Methanol
Gasoline, Chang’an University, pp. 28-31 (2006).

8454 Jiang et al.
Asian J. Chem.
9. S.X. Song and Z.F. Wang, Chinese Patent 1332227 (2002).
10. M.Q. Zhang, Chinese Patent 1400290 (2003).
11. S.S. Xiang, Chinese Patent 1364856 (2002).
20. G. Zhao, Chinese Patent 101033418 (2007).
21. C.R. Zhang, Chinese Patent 101705122 (2010).
22. S.S. Xiang, Chinese Patent 1364856 (2002).
23. B. Li, Chinese Patent 101787311 (2010).
12. M.Q. Wang and Y.B. Hu, J. Guang Zhou Chem., 39, 87 (2010).
13. T.T. Luo and L. Yang, J. Times J. Chem., 19, 1 (2005).
14. H.J. Guo, J. Polym. Mater. Sci. Eng., 18, 171 (2002).
15. H.R. He and R. Zhang, Chinese Patent 1429893 (2003).
16. J.P. Hu, Chinese Patent 86104230 (1987).
24. H.Y. Shang and Y.P. Lin, Chinese Patent 102031104 (2011).
25. D.L. Chen, Q. Li and W. Chu, J. Nat. Gas Chem., 25, 5 (2000).
26. W.R. Zhu, J.G. Li andY. Chen, J.Yulin Teachers College, 24, 46 (2003).
27. J. Zhang, C.C.Yang andY. Tang, J. Speciality Petrochem., 28, 66 (2011).
28. X.J. Yang and J. Zhu, J. Chem. Eng., 8 (1995).
17. L. Chen and S. Yang, Chinese Patent 1410520 (2003).
18. Q.F. Chen and J.Y. Wang, Chinese Patent 1821359 (2006).
19. B. Jiang, Chinese Patent 1743432 (2006).
29. Q. Xi, C.G. Li and F.L. Xu, Times J. Chem., 21, 10 (2007).
30. B. Yuan and X.M. Dou, J. Spectrosc. Spectral Anal., 24, 1320 (2004).