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Article
Methylation of Glycerol with Dimethyl Sulfate toProduce a New Oxygenate Additive for Diesels
Jyh-Shyong Chang, Yu-Da Lee, Lawrence Chao-Shan Chou, Tzong-Rong Ling, and Tse-Chuan ChouInd. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie201612t • Publication Date (Web): 06 Dec 2011
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1
Methylation of Glycerol with Dimethyl Sulfate to Produce a New Oxygenate
Additive for Diesels
Jyh-Shyong Changa*
, Yu-Da Leea, Lawrence Chao-Shan Chou
b, Tzong-Rong Ling
c, and
Tse-Chuan Choua,d
aDepartment of Chemical Engineering, Tatung University, 40 Chungshan North Road, 3rd
Sec., Taipei, Taiwan, ROC
bDepartment of Chemical Engineering, Case Western Reserve University, Cleveland, OH
44106, USA
cDepartment of Chemical Engineering, I-Shou University, 1, Section 1, Hsueh-Cheng
Road, Ta-Hsu Hsiang, Kaohsiung 84008,, Taiwan, ROC
dDepartment of Chemical Engineering, National Cheng Kung University,
Tainan 701,
Taiwan, ROC
* Author to whom correspondence should be addressed
Telephone number: +886-2-1822928-6266
Fax number: +886-2-5861939
E-mail: [email protected]
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Abstract
A new oxygenate additive for diesels (bio or petroleum) was manufactured using glycerol,
dimethyl sulfate (DMS), and sodium hydroxide pellets as raw materials. By feeding the
dimethyl sulfate into the batch reactor containing the sodium glycerate, a semibatch mode
operation enhanced the effective methylation of glycerol. A conventional stirred tank
reactor that can produce large quantities of oxygenate additives under a normal
atmospheric pressure operation became the main feature of the methylation process. With
a 3:2 molar ratio of DMS to glycerol, a 3:1 molar ratio of sodium hydroxide to glycerol, a
0.43:1 molar ratio of water to sodium hydroxide, and a temperature of 343 K at the
reaction time of 24 hours with the feeding time of DMS under 12 hours, the conversion of
glycerol (93.5%) and a combined yield of GDMEs and GTME of 71.2% were achieved
for a once-through operation. A product mixture of GDME (20 wt%) and GTME (80 wt%)
served as a new oxygenate additive for (bio or petroleum) diesels.
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1. Introduction
Oxygenates are used as additives for both gasoline and diesel. The gasoline
oxygenates are added to enhance the octane rating of internal combustion engines and to
reduce air pollution by ensuring a more complete fuel combustion in the engines.
Meanwhile, the use of oxygenated compounds with diesel is designed to reduce harmful
exhaust emissions, namely particulates, and sometimes NOx as well.1 The two main
families of oxygenated additives are alcohols and ethers. Alcohols are less interesting
because they have several drawbacks1,2
such as high water solubility, high Reid vapor
pressure (RVP), high volatility, high latent heat of vaporization, and a low heating value.
These drawbacks result in phase separation problems: clogging of the fuel flow, increase
of the volatile organic compound emissions, cold startup and drivability issues, and a low
heating value. By contrast, ethers, aside from retaining all the benefits of alcohols without
any separation problems, give high octane numbers, enhance gasoline combustion, and
reduce CO emissions.1
Oxygenate utilization, used to produce cleaner burning diesel fuels, has been noted
for over fifty years. Diethylene glycol dimethyl ether (DGM) and dibutyl ether (DBE) are
known as diesel cetane enhancers.1 In recent years, tert-butyl ethers of glycerol with a
high content of di-ethers produced by the etherification of glycerol with isobutylene or
tert-butyl alcohol using homogeneous or solid acid catalysts have been considered
promising as oxygenate additives for diesel fuels.3-8
The etherification of glycerol with
ethanol over solid acid catalysts can transform glycerol into monoalkyl glyceryl ethers
(MAGEs). MAGEs are interesting intermediates for the production of various chemicals,
among them dioxolane.9 With the objective of introducing new large-scale processes
based on glycerol transformation, dioxanes and dioxolanes can be interesting targets,
serving as excellent candidates to be used as co-fuels for the diesel fraction.9 The
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etherification of glycerol with methanol to produce glycerol mono-methoxy ethers
(GMMEs), di-methoxy ethers (GDMEs), and tri-methoxy ether (GTME) as a green
solvent can be found in the work of Garciá et al.10
3-methoxy-1,2-propanediol (CAS
623-39-2), 2-methoxy-1,3-propanediol (CAS 761-06-8) are the isomers of GMME; 1,3 or
2,3-dimethoxy-1-propanol (CAS 40453-77-8); 1,3-dimethoxy-2-propanol (CAS 623-69-8)
are the isomers of GDME, and 1,2,3-trimethoxypropane (20637-49-4)) is GTME.
Nevertheless, the possible oxygenate additive composed of glycerol di-methoxy ethers
and tri-methoxy ether for gasoline or diesel fuels have not been developed. GMME is a
promising cryoprotector in the low-temperature preservation of blood cells, bone marrow,
and reinoculated cell cultures.11
The production of the mixture of GDMEs and GTME as
oxygenate additive is promising,12-16
because the feedstock of methanol is much cheaper
than that of isobutylene or tert-butyl alcohol and a large amount of glycerol is being
produced during the transesterification of fatty acids into biodiesel.
The etherification reactions addressed above are generally operated under the
autogenic pressure in an autoclave. Depending on the reacting component (methanol,
ethanol, isobutylene or tert-butyl alcohol) involved in the reaction with glycerol, the
operating pressure ranges from several to around 100 atmospheric pressures. The
requirement of an autoclave to carry out these etherification reactions of glycerol will
hinder the production of a large quantity of the reacting medium, for an autoclave is
normally very expensive. Hence, the methylation of glycerol with alcohol using a suitable
methylation agent is deemed to be another synthetic route to produce the oxygenate
additive, because the methylation reaction is typically operated under normal atmospheric
pressure and thus a large quantity of the reacting medium can easily be processed in a
conventional stirred tank reactor. Procedures for preparing GMMEs were addressed in the
work of Koshchii11
involving preparations of sodium glycerate from equimolar amounts
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of anhydrous glycerol and powdered NaOH, followed by alkylation with alkyl halides to
obtain glycerol 1-monoalkyl ethers. We performed experiments to refine the conditions
for preparing the mixture of GDMEs and GTME as an oxygenate additive to gasoline or
diesel. Our goal was to find the methods and conditions that would ensure the highest
yield of the target products with the simpler possible procedure. For the route to GDMEs
and GTME, we chose the methylation of glycerol with dimethyl sulfate (DMS) in the
presence of alkali. It seemed appropriate to refine the effects of the synthesis parameters
(reaction time, reaction temperature, molar ratio of sodium hydroxide to water, and DMS
feeding time) on the yield and isomeric composition of the product.
In the following section, the main properties of the mixture of GDMEs and GTME
as a new oxygenate additive are introduced. Section 3 presents the experimental system
including glycerol methylation, product separation procedure, and product analysis.
Section 4 gives the main experimental results and discussion. Finally, the conclusions are
presented.
2. Main Properties of the Mixture of GDMEs and GTME as a New Oxygenate
Additive
The laboratory of Chinese Petroleum Company (CPC) in Taiwan analyzes the
collected product of GDMEs (20 wt%) and GTME (80 wt%) mixture. The product
properties are being used to compare with the existing diesel cetane enhancers DGM and
DBE, shown in Table 1. From the comparison, we conclude that the product mixture of
GDMEs (20 wt%) and GTME (80 wt%) can serve as a new oxygenate additive for diesels
(bio or petroleum).
3. The Experimental Section
3.1. Glycerol Methylation and Product Separation Procedure. The synthesis of
GDMEs and GTME involved the following steps: (1) mixing glycerol with NaOH and
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H2O in the molar ratio NaOH : glycerol = 3 : 1, NaOH : H2O = 2.35 : 1; (2) reflux
under reduced pressure (130 mm Hg) on an oil bath, with the bath temperature gradually
increased to 70℃ for half an hour; (3) adding DMS to the resulting sodium glycerate
(GONa) at 70℃ over a period of 5 h in the molar ratio DMS : glycerol = 3 : 2; (4)
removing Na2SO4 from the reaction mixture; (5) distilling the product mixture of CH3OH,
H2O, GDMEs and GTME from the bottoms at 180 Co /130 mm Hg; (6) extracting
GDMEs and GTME form the product mixture obtained in step 5 with chloroform in the
volume ratio CHCl3 : product mixture = 1.5 : 1 overnight; and (7) distilling the extracted
phase to remove chloroform at 90 Co /130 mm Hg to obtain the final product mixture
GDMEs and GTME. The total yield of the final product mixture was 31.8 %.
3.2. Product Analysis. A gas chromatograph, CHINA GC2000, which was provided
with a capillary column Varian CP9210 (l, 30 m; i.d., 0.32 mm; film thickness, 0.5 mm)
under the oven temperature program from 40 to 250 Co (with a heating rate of
10 Co min-1
) and at 250 Co for 3 min, analyzed the sample of the reaction products.
0.2µl of the sample was injected manually. Each data set was obtained with an accuracy
of %5.2± from an average of three independent measurements, using the internal
standard method (n-butanol, 2 wt.% in respect to the sample). Water content was
measured with the Karl Fisher Titrator, MKS-500. For quantification of the reaction
product, the GDMEs and GTME components were separated and used as the standards.
The standard 3-methoxy-1,2-propanediol (one isomer of GMMEs) was purchased from
Alfa Aesar. The way to obtain pure GDMEs and GTME components and characterization
of these two standards are summarized in the Appendix.
The glycerol conversion is defined as
Go
GGoG
)(
N
NNX
−= (1)
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and the yield of glycerol ethers is defined as
0
i
i
G
P
PN
NY = (2)
where GX is the conversion of glycerol (mol %); iPY ( iP represents GMMEs (i=1),
GDMEs (i=2), and GTME (i=3)) is the yield of different glycerol ethers (mol %); 0GN
and GN are the amounts of starting glycerol (mol) and the resulting glycerol (mol),
respectively;iPN is the total amount of glycerol ethers (mol).
4. Results and Discussions
When the methylation of glycerol with DMS synthesized the glycerol ether in the
presence of NaOH, the sodium glycerate reacted with DMS, and five glycerol ether
isomers were potentially produced including two GMMEs (3-methoxy-1,2-propanediol
and 2-methoxy-1,3-propanediol), two GDMEs (1,3-dimethoxy-2-propanol and 2,3-
dimethoxy-2-propanol), and one GTME (1,2,3-trimethoxypropane), as shown in Figure
117
. The GDMEs and GTBE were the desired products in this reaction. While, methanol
and sodium sulfate were the by-products. All the experimental data shown in the
following figures were the average of duplicative experiments.
4.1. Effects of Reaction Times. To study the influence of reaction time on the glycerol
methylation reaction, experiments using the same loading velocity of DMS were
implemented at 6, 12, 24, and 48 h. Minor variations in the conversion of glycerol are
observed in Figure 2(a); at the reaction time of 6, 12 and 24 h, the conversion of glycerol
reached 97%; but, at the reaction time of 48 h, the conversion dropped slightly to 96%.
However, the reaction time influenced the yield of glycerol ethers. In the mixture of
glycerol ethers, the yield of GMMEs obviously decreased from the reaction hour of 12 to
24 but the yield of GMMEs maintained at the hour of 48 (Figure 2(b)). The yield of
GDMEs decreased from the reaction hour of 6 to 24 and GTME manifested the opposite
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tendency with respect to the yield of GDMEs (Figure 2(a) and 2(b)). The methylation of
glycerol in this work was aimed at the combined yield of GDMEs and GTME; therefore,
the target performance of the process is conspicuously treated in the figures. Figure 2 (a)
shows the combined yield of GDMEs and GTME and Figure 2 (b) displays the yields of
GMMEs and GDMEs at the end of the reaction stage (step (3) described in Section 3.1)
and the separation stage (step (7)), respectively. The yield of GTME at the end of the
reaction increased as the reaction time increased, but the combined yield of GDMEs and
GTME at the end of the reaction reached the maximum (75.5%) at the time of 24 h and
dropped slightly at the time of 48 h. However, the maximal combined yield of GDMEs
and GTME at the end of the extraction and separation was reduced to 31.8%, because the
high solubility of GDMEs in the aqueous phase of the product mixture hindered the
recovery of GDMEs in the non-aqueous phase of the adopted solvent (chloroform) during
the extraction and distillation. These results can be explained as follows: The glycerol
methylation reaction was comprised of consecutive reversible steps: first, in the presence
of aquous NaOH, glycerol transformed into sodium glycerate. Consecutive reversible
reactions between sodium glycerate and DMS led to GMMEs, GDMEs, and GTME
(Figure 1). The transformation of GMMEs, GDMEs and GTME was enhanced with the
increase of the reaction time. However, the possible side reaction between DMS and H2O
reduced the availability of DMS (Figure 1); the maximal combined yield of GDMEs and
GTME occurred at 24 h rather than at 48 h. The presence of methanol in the product
mixture confirmed the occurrence of this side reaction. Considering the purpose of the
optimization was to obtain a high glycerol conversion and a high combined yield of
GDMEs and GTME, 24 h was thus considered as a suitable reaction time in this
experimental system.
4.2. Effects of Reaction Temperatures. To study the influence of the reaction
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temperature on the glycerol methylation reaction, experiments were conducted at 323,
343, 363, and 383 K. As shown in Figure 3(a), the conversion of glycerol increased with
the increase of temperature from 50 Co to 110 Co but showed little conversion at 323 K;
by contrast, a near complete conversion of glycerol (97%) was obtained at 343 K after 24
h. Nevertheless, the results showed that the conversion exhibited a decrease from
temperature 70 to 90 Co and also at 110 Co . As is also shown in Figure 3(b), the yield of
GMMEs increased from 50 Co to 110 Co ; that of GDMEs increased from 50 Co to
70 Co and then dropped at 90 Co and increased at 110 Co ; that of GTME increased from
50 Co to 70 Co and then fell from 70 Co to 110 Co (Figure 3(a) and 3(b)). In Figure
3(a), the combined yield of GDMEs and GTME reached the maximum (75.5%) at the end
of the reaction and at the end of the extraction and separation dropped to 31.8% at 70 Co .
In general, a comparatively higher temperature normally initiates a higher reaction rate.
Because a higher temperature could enhance the back-reactions 1, 3, an 5 shown in
Figure 1, which would lead to an decrease in the formations of GTME as shown in Figure
3(a) and 3(b). In the mean time, the reaction between DMS and H2O is an undesired side
reaction that also depends on reaction time and temperature. Higher reaction temperature
would promote this side reaction which would consume a large amount of DMS and
might influence the glycerol conversion and yield of GTME. Based on these
considerations, 70 Co was chosen as the optimizing temperature.
4.3. Effect of Molar Ratio of Water to Sodium Hydroxide. From the proposed overall
reaction network for the methylation of glycerol (Figure 1), water is a detrimental factor
to the production of the ethers due to the reversible reactions 1, 3, 5, and 7 shown in
Figure 1. However, enough initial loading of water could dissolve sodium hydroxide
pellets properly and facilitate the mixing of the dissolved sodium hydroxide with the rest
of reactants. Therefore, the effect of the H2O to NaOH molar ratio on the methylation
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reaction was studied using four different ratios in the range from 0 (anhydrous) to 2.78.
As shown in Figure 4(a), the glycerol reached a constant conversion (97 5.0± %) and the
yield of GDMEs and GTME in the glycerol ether mixture decreased with an increase in
the molar ratio from 0.43 to 2.78. With a further decrease in the molar ratio from 0.43 to
0 (anhydrous), the reaction ceases to occur, because anhydrous glycerol cannot dissolve
any sodium hydroxide pellet. The yield of GTME decreased at the end of the reaction as
the molar ratio of H2O to NaOH increased, and the combined yield of GDMEs and
GTME reached the maximum (75.5%) at the end of the reaction under the molar ratio of
0.43 (Figure 4(a) and 4(b)). However, the maximal combined yield of GDMEs and
GTME at the end of extraction and separation reduced to 31.8%, because the high
solubility of GDMEs in the aqueous phase of the product mixture reduced the recovery of
GDMEs in the non-aqueous phase of the adopted solvent (chloroform) during extraction
and distillation. Basing on these considerations, the molar ratio of H2O to NaOH (0.43)
was chosen as the optimizing initial water loading.
4.4. Effects of the Feeding Time of Dimethyl Sulfate. The feeding time of DMS is one
of the important factors influencing the reaction rate, for this highly exothermic reaction
favors a semibatch operation. Therefore, the effect of the feeding time of DMS on the
glycerol methylation reaction was investigated with various feeding time intervals of
DMS in the range from 1 to 23 h. A short feeding time means a high feed rate. As
shown in Figure 5(a), the conversion of glycerol climbed with the increasing feeding time
at the hour of 1 and 5; then it dropped and maintained at 93.5% from hour 12 to hour 23.
The highest conversion was obtained when the feeding time of DMS was hour 5. The
combined yield of GDMEs and GTME reached 75.5% at the end of reaction and dropped
to 31.8% at the end of the extraction and separation reduced under the feeding time of
DMS (5 h) as depicted in Figure 5 (a). However, a higher combined yield of GDMEs and
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GTME (34.5 %) at the end of the extraction and separation reduced under the feeding
time of DMS (12 h) can be observed. Under this feeding time of DMS (12 h), more
GTME was produced than that operated under 5 h feeding time and more GDMEs and
GTME were extracted and separated as depicted in Figure 5 (a). For the lowest feed rate
of DMS (the feeding time 23 h), the side reaction (reaction 7 depicted in Figure 1)
reduced the availability of DMS. The results of the reactions characterized by low yield
of GTME are shown in Figure 5(a). Therefore, the optimizing feeding time of DMS for
this experimental system was found to be 12 h. Figure 5(b) displays the yield variations
of GMMEs and GDMEs over the DMS feeding time. For the lowest feed rate of DMS
(the feeding time 23 h), the highest yield of GMMEs results in the low yield of GDMEs
and GTME (Figure (a)).
5. Conclusions
The methylation of glycerol with DMS in the presence of alkali under an optimizing
condition produces the product mixture of GDMEs (20 wt%) and GTME (80 wt%). This
mixture serves as a new possible oxygenate additive for diesels (bio or petroleum). The
properties of this new oxygenate additive for diesels are comparable to those of DGM and
DBE. A normal atmospheric pressure operation of the methylation of glycerol with
dimethyl sulfate is the main feature that large quantities of oxygenate additive can easily
be manufactured in a conventional stirred tank reactor.
The conversion of glycerol (93.5%) and the combined yield of GDMEs and GTME
(71.2%) were obtained using a 3:2 molar ratio of dimethyl sulfate to glycerol, a 3:1 molar
ratio of sodium hydroxide to glycerol, a 0.43:1 molar ratio of water to sodium hydroxide,
and a temperature of 343 K under the reaction time of 24 h with the feeding time of
dimethyl sulfate under 12 h. The maximal combined yield of GDMEs and GTME at the
end of the extraction and separation fell to 34.5% for a once-through operation. The
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recycle of GMMEs and GDMEs could further improve the yield of the final products.
Acknowledgments
Financial support from the National Science Council (Grant NSC
98-3114-E-036-001) is gratefully acknowledged.
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Appendix: Preparation and Identification of the Standards for GDMEs and GTME
A preparation of the standards for GDMEs and GTME involved the following
steps: (1) Mix the final product mixture obtained in Section 3.1 with CHCl3 and H2O in
the volume ratio CHCl3 : product mixture = 1 : 1 and H2O : product mixture = 2 : 1; (2)
Separate the aqueous phase and non-aqueous phase first, and then identify whether the
components of GDMEs still exist in the non-aqueous phase using GC analysis. If the
non-aqueous phase still contains GDMEs, remove the aqueous phase and go back to step
(1); (3) Distill the non-aqueous phase containing CHCl3 and GTME to obtain pure GTME
from the bottoms at 110 Co /130 mm Hg; (4) Distill the collected aqueous phase
containing H2O and GDMEs to obtain pure GDMEs from the bottoms at 100 Co /130 mm
Hg. The corresponding GC analyses of the final reaction mixture of the purified GTME
and GDMEs are presented in Figures A1-A3. The standard GMMEs was purchased from
Alfa Aesar and its GC analysis is shown in Figure A4.
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Caption of Table
Table 1. Comparison of Main Properties of the New Oxygenate Additive with the
Existing Additives
Caption of Figures
Figure 1. The proposed overall reaction network for the production of GMMEs, GDMEs
and GTME from glycerol and DMS.
Figure 2. The influence of the reaction time on (a) the conversion GX and the combined
yield of GDMEsf,Y and GTMEf,Y . Reaction conditions: reaction temperature, 343 K;
H2O/NaOH molar ratio, 0.43; feeding time of DMS, 5 hr and (b) the yields of the desired
products at the end of reaction ( GMMEsY and GDMEsY ) and at the end of extraction and
separation ( GMMEsf,Y and GDMEsf,Y ) (glycerol, 0.435 mole; DMS/glycerol molar ratio, 1.5;
NaOH/glycerol molar ratio, 3).
Figure 3. The influence of the reaction temperature on (a) the conversion GX and the
combined yield of GDMEsf,Y and GTMEf,Y . Reaction conditions: reaction time, 24 hr;
H2O/NaOH molar ratio, 0.43; feeding time of DMS, 5 hr and (b) the yields of the desired
products at the end of reaction ( GMMEsY and GDMEsY ) and at the end of extraction and
separation ( GMMEsf,Y and GDMEsf,Y ) (glycerol, 0.435 mole; DMS/glycerol molar ratio, 1.5;
NaOH/glycerol molar ratio, 3).
Figure 4. The influence of the molar ratio of H2O/NaOH on (a) the conversion GX and
the combined yield of GDMEsf,Y and GTMEf,Y . Reaction conditions: reaction time, 24 h;
reaction temperature, 343 K; feeding time of DMS, 5 hr and (b) the yields of the desired
products at the end of reaction ( GMMEsY and GDMEsY ) and at the end of extraction and
separation ( GMMEsf,Y and GDMEsf,Y ) (glycerol, 0.435 mole; DMS/glycerol molar ratio, 1.5;
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NaOH/glycerol molar ratio, 3).
Figure 5. The influence of the DMS feeding time on (a) the conversion GX and the
combined yield of GDMEsf,Y and GTMEf,Y . Reaction conditions: reaction time, 24 h; reaction
temperature, 343 K; H2O/NaOH molar ratio, 0.43 and (b) the yields of the desired
products at the end of reaction ( GMMEsY and GDMEsY ) and at the end of extraction and
separation ( GMMEsf,Y and GDMEsf,Y ) (glycerol, 0.435 mole; DMS/glycerol molar ratio, 1.5;
NaOH/glycerol molar ratio, 3).
Figure A1. Exemplary GC chromatographic analysis. 1-methanol; 2-n-butanol;
3-1,2,3-trimethoxypropane; 4-1,3-dimethoxy-2-propanol; 5-2,3-dimethoxy-1-propanol;
6-3-methoxy-1,2-propanediol; 7-2-methoxy-1,3-propanediol; 8-glycerol.
Figure A2. Exemplary GC chromatographic analysis. 1-1,2,3-trimethoxypropane.
Figure A3. Exemplary GC chromatographic analysis. 1-1,2,3-trimethoxypropane;
2-1,3-dimethoxy-2-propanol; 3-2,3-dimethoxy-1-propanol.
Figure A4. Exemplary GC chromatographic analysis. 1-1,3-dimethoxy-2-propanol;
2-2,3-dimethoxy-1-propanol; 3-3-methoxy-1,2-propanediol.
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Table 1. Comparison of Main Properties of the New Oxygenate Additive with the Existing Additives
*: The oxygenates mixtures are composed of GDMEs (20 wt%) and GTME (80 wt%)
Oxygenates of this work* Existing Oxygenates1
GDMEs GTME DGM DBE
CAS No.
Chemical formula
Chemical structure
Molecular weight, kg/kmol
Normal boiling point, K
Density, kg/m3
Heat of combustion, J/kg
Flash point, K
Lower flammability limit, %vol
Autoignition temperature, K
Cetane number
Lower heating value, kJ/g
623-69-8 40453-77-8 20637-49-4
C5H12O3 C5H12O3 C6H14O3
(CH3OCH2)2CHOH
CH3OCH2CH(OCH3)CH2OH
(CH3OCH2)2CHOCH3
120 120 134
442 453 421
968
-2.74×107
322
1.47
-
58
25.12
11-96-6
C6H14O3
(CH3OCH2CH2)2O
134
435
937
-2.52×107
343
1.2
-
112
24.5
142-96-1
C8H18O
(C4H9)2O
130.2
414
764
-3.80×107
298
1.5
467
91-100
-
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Figure 1. The proposed overall reaction network for the production of GMMEs, GDMEs and GTME from glycerol and DMS.17
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Time (h)
Time (h)
(a)
(b)
Conversion and yield
(%
)
0 6 12 24 480
10
20
30
40
50
60
YGMMEs
Yf,GMMEs
YGDMEs
Yf,GDMEs
Yield
(%
)
0 6 12 24 480
20
40
60
80
100
XG
YGDMEs+GTME
Yf,GDMEs+GTME
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Figure 2. The influence of the reaction time on (a) the conversion GX and the
combined yield of GDMEsf,Y and GTMEf,Y . Reaction conditions: reaction temperature,
343 K; H2O/NaOH molar ratio, 0.43; feeding time of DMS, 5 hr and (b) the yields of
the desired products at the end of reaction ( GMMEsY and GDMEsY ) and at the end of
extraction and separation ( GMMEsf,Y and GDMEsf,Y ) (glycerol, 0.435 mole; DMS/glycerol
molar ratio, 1.5; NaOH/glycerol molar ratio, 3).
.
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(a)
(b)
50 70 90 1100
10
20
30
40
50
YGMMEs
Yf,GMMEs
YGDMEs
Yf,GMMEs
50 70 90 1100
20
40
60
80
100
XG
YGDMEs+GTME
Yf,GDMEs+GTME
Yield
(%
)Conversion and yield
(%
)
Temperature (oC)
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Figure 3. The influence of the reaction temperature on (a) the conversion GX and
the combined yield of GDMEsf,Y and GTMEf,Y . Reaction conditions: reaction time, 24 hr;
H2O/NaOH molar ratio, 0.43; feeding time of DMS, 5 hr and (b) the yields of the
desired products at the end of reaction ( GMMEsY and GDMEsY ) and at the end of
extraction and separation ( GMMEsf,Y and GDMEsf,Y ) (glycerol, 0.435 mole;
DMS/glycerol molar ratio, 1.5; NaOH/glycerol molar ratio, 3).
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(a)
(b)
0 0.43 0.74 2.780
10
20
30
40
50
YGMMEs
Yf,GMMEs
YGDMEs
Yf,GDMEs
H2O/NaOH molar ratio (mol/mol)
0 0.43 0.74 2.780
20
40
60
80
100
XG
YGDMEs+GTME
Yf,GDMEs+GTME
Yield
(%
)Convers
ion and yield
(%
)
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Figure 4. The influence of the molar ratio of H2O/NaOH on (a) the conversion
GX and the combined yield of GDMEsf,Y and GTMEf,Y . Reaction conditions: reaction
time, 24 h; reaction temperature, 343 K; feeding time of DMS, 5 hr and (b) the
yields of the desired products at the end of reaction ( GMMEsY and GDMEsY ) and at the
end of extraction and separation ( GMMEsf,Y and GDMEsf,Y ) (glycerol, 0.435 mole;
DMS/glycerol molar ratio, 1.5; NaOH/glycerol molar ratio, 3).
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DMS feeding time (h)
1 5 12 230
20
40
60
80
100
XG
YGDMEs+GTME
Yf,GDMEs+GTME
1 5 12 230
10
20
30
40
50
YGMMEs
Yf,GMMEs
YGDMEs
Yf,GDMEs
(a)
(b)
Yield
(%
)Convers
ion and yield
(%
)
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Figure 5. The influence of the DMS feeding time on (a) the conversion GX and the
combined yield of GDMEsf,Y and GTMEf,Y . Reaction conditions: reaction time, 24 h;
reaction temperature, 343 K; H2O/NaOH molar ratio, 0.43 and (b) the yields of the
desired products at the end of reaction ( GMMEsY and GDMEsY ) and at the end of
extraction and separation ( GMMEsf,Y and GDMEsf,Y ) (glycerol, 0.435 mole; DMS/glycerol
molar ratio, 1.5; NaOH/glycerol molar ratio, 3).
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Figure A1. Exemplary GC chromatographic analysis. 1-methanol; 2-n-butanol;
3-1,2,3-trimethoxypropane; 4-1,3-dimethoxy-2-propanol;
5-2,3-dimethoxy-1-propanol; 6-3-methoxy-1,2-propanediol;
7-2-methoxy-1,3-propanediol; 8-glycerol.
Time (min)
FID
res
ponse
(m
v)
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Figure A2. Exemplary GC chromatographic analysis. 1-1,2,3-trimethoxypropane.
Time (min)
FID
resp
onse
(m
v)
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Figure A3. Exemplary GC chromatographic analysis. 1-1,2,3-trimethoxypropane;
2-1,3-dimethoxy-2-propanol; 3-2,3-dimethoxy-1-propanol.
Time (min)
FID
resp
onse
(m
v)
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Figure A4. Exemplary GC chromatographic analysis. 1-1,3-dimethoxy-2-propanol;
2-2,3-dimethoxy-1-propanol; 3-3-methoxy-1,2-propanediol.
Time (min)
FID
resp
onse
(m
v)
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