CET-vol 105


 
 
 
 
 
 
 
 
 
 
                                                                                                                                                                DOI: 10.3303/CET23105028 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper Received: 22 February 2023; Revised: 2 April 2023; Accepted: 27 April 2023 
Please cite this article as: Aziaba K., Mozina F.M., Teufner-Kabas M., Kabas F., Jordan C., Harasek M., 2023, Stability of Diethyl Carbonate in 
the Presence of Acidic and Basic Solvents, Chemical Engineering Transactions, 105, 163-168  DOI:10.3303/CET23105028 
  

 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL.  105, 2023 

A publication of 

 

The Italian Association 
of Chemical Engineering 
Online at www.cetjournal.it 

Guest Editors: David Bogle, Flavio Manenti, Piero Salatino 

Copyright © 2023, AIDIC Servizi S.r.l. 
ISBN 979-12-81206-04-5; ISSN 2283-9216 

Stability of Diethyl Carbonate in the Presence of Acidic and 

Basic Solvents 

Kouessan Aziabaa,*, Florian M. Možinaa, Magdalena Teufner-Kabasb, Florian 

Kabasb, Christian Jordana, Michael Haraseka 

a Thermal Process Engineering - Computational Fluid Dynamics, Institute of Chemical, Environmental & Bioscience 

Engineering, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria 
bkleinkraft OG, Turnergasse 27/5, 1150 Vienna, Austria 

 kouessan.aziaba@tuwien.ac.at  

Reducing carbon dioxide (CO2) emissions is an inevitable measure for fighting anthropogenic climate change. 

Carbon Capture and Utilization (CCU) technologies are gaining rising attention as an additional contributor to 

reaching the Paris Agreement goals. Giving CO2 a value as a feedstock to be refined into chemicals to be used 

in industry is a crucial aspect of making these technologies interesting for vast industrial sectors. The synthesis 

of diethyl carbonate (DEC) is recognized as a promising prospect for the successful implementation of CCU. 

DEC is considered a fully biodegradable, low-toxic solvent, which can be synthesized from CO2 and ethanol in 

the presence of a catalyst. DEC may be a non-toxic alternative to other solvents such as toluene or methyl 

isobutyl ketone (MIBK). 

The optimization of DEC synthesis is one aspect that is under investigation today. For the exploration of DEC's 

applicability, an extensive amount of data is beneficial. Many applications of solvents involve the presence of 

acids and bases. Hence, an interest in DEC in various environments is reasonable. The decomposition of DEC 

after contact with water, different acids and bases at room temperature, and the boiling point was determined 

experimentally to characterize chemical stability. Further, the influence of sodium chloride and a cerium-based 

catalyst used in DEC synthesis was investigated.  

1. Introduction 

The application of CO2-refinery processes is considered an essential contribution towards more sustainable 

strategies in the chemical industry. As a part of CO2-refinery, CCU re-introduces carbon dioxide back into 

industrial cycles and is regarded as a promising tool in fighting anthropogenic climate change. The direct 

synthesis of DEC is considered to be a promising product of such an application which uses CO2 as a feedstock. 

Another commonly positively perceived property of the reaction is the fact that the side product is water. The 

reaction of the direct synthesis of DEC is portrayed in equation 1. 

𝐶2𝐻5𝑂𝐻 + 𝐶𝑂2 ↔ 𝐶5𝐻10𝑂3 + 𝐻2𝑂 (1) 

DEC is currently used in lithium-ion batteries, organic synthesis and extraction procedures and has also been 

used in combustion engines, successfully reducing emissions.(Shukla and Srivastava, 2016) However, new 

applications for DEC must be further investigated to exploit its full potential as a green chemical. Many physical 

and chemical properties have already been described, but data about chemical stability is limited.(Huang et al., 

2015) One weakness of DEC is its susceptibility to hydrolysis under acid or alkaline conditions. An extraction 

process for phenol recovery from coal tar processing was developed. (Yang et al., 2020) applying DEC to 

recover phenols from coal tar processing wastewater from an alkaline stripping solution. However, the stripping 

process is limited to about 8 minutes due to the imminent degradation of DEC in the organic phase. Experimental 

data on DEC decomposition after exposure to different aqueous phases of various acidities were reported by 

Raiguel et al. (Raiguel et al., 2020). A "salting out"-effect was described. Dissolved inorganic salts like NaCl in 

an aqueous phase are observed to stabilize DEC. Due to the decrease in solubility, hydrolysis is slowed down. 

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The decomposition of DEC is mainly dominated by its acid- or base-catalyzed hydrolysis leading to the main 

reaction products carbon dioxide and ethanol. Other degradation mechanisms have also been observed since 

diethyl ether and chloroethane were detected as reaction products. Al-Shamary et al. (2017) investigated 

multiple dialkyl carbonates, observing an enhancement of the degradation in the presence of cationic micelles 

(Al-Shamary et al., 2017). Anionic micelles are reported to reduce hydrolysis rates. To pave the way for further 

research about applications for DEC, this work focuses on the chemical stability of DEC after being in contact 

with various acidic and basic solutions. The presence of CeO2, a catalyst, as well as the presence of NaCl shall 

also be monitored.  

2. Materials and Methods 

Different acids (HCl, H2SO4, H3PO4, formic acid, acetic acid) and bases (NaOH, KOH, Na2CO3) have been 

obtained for the investigations. DEC degradation has been calculated according to equation 2. 

𝐷𝑒𝑔𝑟𝑎𝑑𝑎𝑡𝑖𝑜𝑛 [%] =  
𝑚𝐷𝐸𝐶,0 − 𝑚𝐷𝐸𝐶

𝑚𝐷𝐸𝐶,0
∗ 100 (2) 

The experimentally determined data shall be accompanied with theoretical ethanol (EtOH) formation and mass 

loss due to CO2. The theoretical ethanol formation was calculated according to equation 3. 

𝑚𝐸𝑡𝑂𝐻,𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 =  
𝑚𝐷𝐸𝐶,0 − 𝑚𝐷𝐸𝐶

𝑀𝐷𝐸𝐶
∗ 2 ∗ 𝑀𝐸𝑡𝑂𝐻 (3) 

CeO2 which is used in the direct synthesis of DEC from CO2 as a catalyst, is neither soluble in water nor DEC. 

However, no data about its interference with DEC degradation was available (Giram et al., 2018). 3ml of DEC 

were mixed with each of these solutions with a volume ratio of 1:1. When a two-phase system developed, 

phases were separated at the end of the experiment. Afterwards, DEC and EtOH were quantified with a GC-

FID (gas chromatograph equipped with a flame ionization detector) as described in 2.2. It was assumed that 

DEC evaporation loss was negligible due to its high boiling point. For each substance, four experiments were 

carried out at ambient pressure, which differed in temperature and the presence or absence of 0,125 g of CeO2. 

The influence of sodium chloride (NaCl) dissolved in the aqueous phase on chemical stability was investigated 

with the same solutions as above, except for HCOOH which was used as a pure compound. NaCl concentration 

in the aqueous phase was 250 g/l. The resulting phases were filtered before every analysis if a catalyst was 

applied. The net weight of the mixture before and after the experiment was documented. When the catalyst was 

present, it was assumed that it accumulated only in the aqueous phase. If a separation of the product into two 

phases was observed, it was necessary to collect three samples of each product containing a sample of the 

aqueous, organic and a mixture of both phases. Emulsions were drawn into a syringe to rest for 15 minutes until 

phase separation had taken place.  

2.1 Materials 

The experiments were carried out in three-neck round bottom flasks equipped with glass plugs and 

thermometers. The thermometers were inserted through a septum into the sample in the flask. The flasks were 

placed in an aluminum bowl filled with a sand bed to enable a homogeneous heat transfer. The samples were 

stirred with a magnetic stirrer for 24 (HCOOH for 64) hours and, if necessary, heated to boiling point through a 

sand bed. To prevent losses due to evaporation, a Liebig cooler was installed. A thermometer was connected, 

and the boiling temperature was read as soon as reflux occurred and the cooler's inner surface.  

Diethyl carbonate (DEC, 99,9 %) was purchased from Carl Roth. Phosphoric acid (H3PO4, p.a., Lachema), 

fuming hydrochloric acid (HCl, 37 %, Sigma-Aldrich), potassium hydroxide (KOH, Neuber's Enkel), formic acid 

(HCOOH, >= 99 %, Merck), and acetic acid (HAc, 99,8 %, EMD Millipore) were obtained and solved in water to 

mix 0.5 M solutions of each compound. Potassium hydroxide (KOH, platelets), sodium carbonate (NaOH, 

beads), sodium chloride (NaCl, grains) and sulphuric acid (H2SO4) were obtained from the in-house laboratory 

stock and diluted in H2O to form 0.5 molar solutions as well. HCOOH and HAc were also applied as pure 

compounds additionally.  

2.2 Analytics 

Gas chromatography coupled with a flame ionization detector (GC-FID) was used to analyze the samples. GC-

FIDs are highly reliable analytic instruments for the purpose of detection and quantification of volatile organics. 

Samples were injected automatized from an autosampler (AOC 5000, Shimadzu), and 0,5 μl was set as the 

injection volume. Each sample was measured once. Dioxane was injected regularly before and between 

measurements to minimize carryover from the injector and column. Calibration curves for the quantification of 

DEC and ethanol were prepared by analyzing standards containing DEC and EtOH. 

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3. Results 

3.1 Experiments 

All chromatogram peaks have been checked manually and assigned to a substance by retention time for 

qualitative information about chemical stability. For quantitative information about chemical stability, the 

degradation of DEC was determined. The formation of EtOH as a decomposition product was considered 

unsuitable for the characterization of chemical stability because evaporation losses occurred during 

experiments. As documented in Figure 1, it can be seen that DEC may be involved in a reverse reaction with 

H2O as described in the introduction.  
 

 

Figure 1: DEC degradation of a binary DEC-Water system in dependence on added CeO2 or NaCl 

Temperature does not seem to have a significant effect on the decomposition of DEC as long as there is no 

CeO2 involved. Mentioning the catalyst CeO2, the simultaneous presence of it and elevated temperatures seem 

to boost the degradation of DEC on a comparably low scale. Even though NaCl is added to prevent 

decomposition processes, it becomes lightly visible that this effect is observed to be inverse at elevated 

temperatures. It is not clear why the decomposition of DEC is enhanced in this case. This may be connected 

with the difference in the boiling points which also vary due to the different mixtures. Therefore, more 

experiments with varied amounts of salt would be required. The presence of acidic compounds in the solution 

reveals a different dynamic which is portrayed in Figure 2. 

 

Figure 2: DEC degradation of a binary DEC-Acid (0.5 M) system in dependence of added CeO2 or NaCl with 

H2SO4, H3PO4, HCl, HCOOH and HAc used as acids 

The highest degradation is observed to occur in contact with HCl, followed H2SO4, H3PO4, HCOOH and HAc in 

a decreasing sequence. The values pKA and pKB (acid dissociation- and base dissociation constant) are 

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commonly accessed parameters to obtain an enhanced understanding of a solution's acidiy and basicity. 

Therefore, it is also consulted to observe DEC's degradation in the presence of acids and bases. Comparing 

DEC's degradation in contact with the acids mentioned earlier with the pKA – values from the literature reveals 

that the degradation at higher temperatures follows the same trend as the pKA – value (Trygg et al., 2016). The 

influence of CeO2 and NaCl does not seem to follow any trends or patterns since it appears to be quite arbitrarily 

which reagent delivers the strongest decomposition in contact with DEC. Starting with H3PO4, which mainly 

shows the highest degradation of DEC in the presence of salt, increasing the temperature seems to improve 

the activity of the catalyst and increases the DEC degradation. Interestingly, the same effect is not seen in the 

same way with any of the other tested acidic compounds. The comparably weaker organic acids HCOOH and 

HAc deliver lightly higher degradations of both – ambient temperature and on the b.p. (boiling point) if CeO2 is 

used. The application seems to avoid degradation completely. The general effect observed on the contact of 

DEC with acidic compounds is a comparably fair degradation where no presence of a catalyst is needed. The 

presence of salt, which shall incorporate an inhibitor's function as mentioned in 1.1., seems indifferent to the 

various acidic compounds. Similar to the presence of NaCl in binary DEC solutions with water it is unclear why 

no trend was observed. Therefore, further investigation with various acid concentrations and amounts of NaCl 

would be necessary. With many possible applications to be carried out in an alkaline environment the interest 

into the influence of basic compounds on DEC was present as well. Therefore, the recorded results are 

displayed in Figure 3. 

 

 

Figure 3: DEC degradation of a binary DEC-base (0.5 M) system in dependence of added CeO2 or NaCl with 

KOH, NaOH and Na2CO3 used as acids 

The decomposition of DEC already takes place at ambient temperatures. Even though the presence of CeO2 

and NaCl seems to have a moderate influence, it is not easily determined in which direction the trend of their 

effect leads. Temperature appears to be the most influential parameter for the decomposition of DEC. It can be 

stated that the exposure of DEC with all applied basic compounds leads to a complete decomposition that could 

be partially prevented with NaCl. The decomposition seems also to follow the trend following the pKB-values of 

which KOH's and NaOH's pKB-values are comparably low over the one of Na2CO3. NaCl usually dissolves in a 

fully solvated state in water. Comparably strong ions Na+ and Cl- may attract some of the water molecules, 

leaving fewer molecules behind. This results in limited availability of water to hydrolyze DEC. (Raiguel et al., 

2020) 

3.2 Ethanol losses 

The mass losses during the experiments were recorded and are displayed in Figure 4. Since the majority of the 

mass loss was associated with ethanol losses, the losses due to CO2 were neglected.  

 
 

166



 

Figure 4: calculated theoretical and measured EtOH formation after experiments with various chemicals on 

ambient and elevated temperatures 

The low boiling point of ethanol was estimated to be the reason for this. It was assumed for calculations that 

DEC loss was negligible since DEC has a higher boiling point than water and ethanol. However, this assumption 

is most likely not exact. Consequently, results are estimated to be influenced by an unknown error. 

4. Conclusions 

The experimental trial has clearly shown that decomposition of DEC can occur in various settings. At low 

temperatures degradation of DEC does not follow any obvious trends. However, the degradation mostly 

accelerated significantly at higher temperatures. The influence of catalyst was rather random and requires more 

experiments to be described in more detail. Enhanced chemical stability by adding NaCl was observed at high 

levels of DEC degradation, the influence of salt at lower degradation rates fluctuated. The expressiveness of 

the results for quantitative information about chemical stability are limited due to the rather facile setup and 

limited number of experiments. Exchanging the setup with a tightly sealed system which can also be exposed 

to elevated pressure, could have improved the expressiveness of the results but would also create the necessity 

for further possibly complex equipment such as a level sensor. Nevertheless, it was still possible to obtain 

information about DEC's behavior in acidic and basic solutions. DEC is apparently more susceptible to base-

catalyzed than acid-catalyzed hydrolysis. The strength of the acid or base increased DEC degradation at boiling 

temperature. Nonetheless, since the decomposition products of DEC are mostly considered to be CO2 and 

water, the effort which must be taken to cope with the resulting compounds is comparably low. Further, the idea 

of a reduction of the decomposition considering the limited availability of water for a reverse reaction fuels the 

idea that DEC may be a promising alternative to other electrolyte additives. 

Nomenclature

b.p. – boiling point 

FID – flame ionization detector 

GC – gas chromatograph 

pKA – acid dissociation constant 

pKB – base dissociation constant 

CeO2 – cerium oxide 

DEC – diethyl carbonate 

HAc – acetic acid 

HCl – hydrochloric acid 

HCOOH – formic acid 

H2O – water 

H2SO4 – sulfuric acid 

H3PO4 – phosphoric acid 

KOH – potassium hydroxide 

NaCl – sodium chloride 

Na2CO3 – sodium carbonate 

NaOH – sodium hydroxide 

mEtOH, theoretical – calculated mass EtOH, g 

mDEC – mass of DEC after experiment, g 

mDEC, 0 – mass of DEC fed to experiment, g 

mEtOH, theoretical – ambient temperature, K 

MEtOH – molar mass of EtOH, g/mol 

mDEC, 0 – molar mass of DEC, g/mol 

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Acknowledgments 

This research was subsidized by city of Vienna funds via the Vienna Business Agency (WAW), grant number 

2761267. Further, the authors acknowledge the funding support of K1-MET GmbH, metallurgical competence 

center. The research program of the K1-MET competence center is supported by COMET (Competence Center 

for Excellent Technologies), the Austrian program for competence centers. COMET is funded by the Federal 

Ministry for Transport, Innovation, and Technology; the Federal Ministry for Digital and Economic Affairs; the 

provinces of Upper Austria, Tyrol, and Styria; and the Styrian Business Promotion Agency (SFG). 

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	Stability of Diethyl Carbonate in the Presence of Acidic and Basic Solvents