Elsevier

Fluid Phase Equilibria

Volume 358, 25 November 2013, Pages 105-107
Fluid Phase Equilibria

Solubility of CO2 in glycerol at high pressures

https://doi.org/10.1016/j.fluid.2013.07.051Get rights and content

Abstract

The solubility of CO2 in liquid glycerol was measured at the temperatures of 353.2 K, 393.2 K and 423.2 K, and pressures up to 32 MPa. The static synthetic method was used in a variable-volume view cell. The solubility of CO2 in glycerol was enhanced by pressure increase and by temperature decrease. When compared with reported values for alcohols with the same chain length, the solubility increased in the following order: glycerol < 1,2-propylene glycol < 1-propanol < 2-propanol.

Introduction

The recent expansion of biodiesel production industry has led to glycerol overproduction. This fact has originated numerous scientific studies regarding glycerol utilization as a chemical platform towards development of new chemicals. Among different possibilities, glycerol carbonate represents one of the most attractive. Glycerol carbonate is a valuable chemical included in the category of so-called “green solvents” due to its low toxicity, good biodegradability and high boiling point. Beyond environmental benign solvent, it has further been investigated as fuel additive, monomer, chemical intermediate and drug carrier [1], [2], [3].

Traditional synthetic routes comprise reacting glycerol with fossil fuel derived carbonyl sources, such as phosgene, dialkyl carbonate and urea [2], [3].

A few authors have tried a direct synthetic strategy by combining glycerol and CO2. Aresta and co-workers were the first to successfully undertake this reaction [4], [5]. Experiments were performed at 180 °C and 5 MPa with formation of some glycerol carbonate. The authors explained the low yields with catalyst deactivation. But the role played by the unfavourable thermodynamics of the reaction [2] and the solubility of carbon dioxide in glycerol must also be limiting factors.

George et al. [6] reported increased reaction yields by adding methanol to the reaction mixture, in order to enhance the solubility of CO2 in the liquid phase, although their results could not be reproduced by Dibenedetto et al. [5]. The recent study of Podilla et al. [7] has shown the importance of taking into consideration phase equilibria in the interpretation of the kinetics and yields of the reaction.

The phase behaviour for ternary mixtures of CO2 + glycerol + short chain alcohols, namely methanol, has been recently published [8], [9], [10]. But published results are very scarce for the binary system (CO2 + glycerol). There are two sets of experimental data for the solubility of glycerol in CO2, obtained by Eissler et al. [11] and Sovova et al. [12], but none for the solubility of CO2 in liquid glycerol, with the exception of Francis [13], who reported one experiment at 298.15 K and 6.5 MPa. Results on a wide range of temperatures and pressure are needed to allow a better interpretation of the phase equilibrium effects on the kinetics of glycerol carbonate synthesis.

In this paper solubility measurements for CO2 in glycerol were performed at the temperatures of 353.15, 393.15 and 423.15 K, and pressures up to 32 MPa.

Section snippets

Materials

The characteristic of chemicals used in this work are presented in Table 1. 99.998 mol% carbon dioxide CAS [124-38-9] were supplied by Air Liquide, Glycerol (≥99.0%) was supplied by Sigma–Aldrich.

Experimental procedure

Solubility measurements were performed using a high pressure apparatus built by New Ways of Analytics GmbH, Germany. It is described in detail elsewhere [7]. Briefly, the apparatus is composed by an equilibrium cell made of a stainless steel cylinder with an internal diameter of 3.6 cm. The cell is

Results and discussion

Table 2 gives the experimental results of the solubility of carbon dioxide in glycerol, in mole fraction of CO2, at three temperatures, 353.15 K, 393.15 K and 423.15 K, and pressures between 4 MPa and 32 MPa. These results were obtained through repeated measurements with a calculated standard deviation of 0.65 MPa, and are further illustrated in Fig. 1. As expected, the solubility of CO2 in glycerol was enhanced by pressure increase and by temperature decrease. To the best of our knowledge, no

Conclusions

Experimental results obtained in this work show that the solubility of CO2 in glycerol is low, over the pressure and temperature range investigated. CO2 is much less soluble in glycerol than in other alcohols with the same chain length. Solubilities expressed in mass fraction are of the same order of magnitude as those observed in water.

Acknowledgements

This work was supported by Fundação para a Ciência e a Tecnologia – FCT (Portugal) through PEst-C/EQB/LA0006/2011 and research project PTDC/EQU-EQU/104552/2008. A.V.M. Nunes and G.V.S.M. Carrera are thankful to FCT for the post-doctoral fellowships SFRH/BPD/74994/2010 and SFRH/BPD/72095/2010 respectively.

References (18)

  • M. Aresta et al.

    Journal of Molecular Catalysis A: Chemical

    (2006)
  • A. Dibenedetto et al.

    Tetrahedron

    (2011)
  • J. George et al.

    Journal of Molecular Catalysis A: Chemical

    (2009)
  • G.V.S.M. Carrera et al.

    Fluid Phase Equilibria

    (2011)
  • O.A.S. Araujo et al.

    Journal of Supercritical Fluids

    (2012)
  • L.F. Pinto et al.

    Journal of Supercritical Fluids

    (2011)
  • H. Sovova et al.

    Fluid Phase Equilibria

    (1997)
  • O. Elizalde-Solis et al.

    Fluid Phase Equilibria

    (2007)
  • A.C. Galvao et al.

    Fluid Phase Equilibria

    (2010)
There are more references available in the full text version of this article.

Cited by (25)

  • Solubility of CO<inf>2</inf> in methanol, ethanol, 1,2-propanediol and glycerol from 283.15 K to 373.15 K and up to 6.0 MPa

    2019, Journal of Chemical Thermodynamics
    Citation Excerpt :

    The Henry’s law constants obtained by Ostonen et al. are very similar to our results. Some other papers studied the solubility of CO2 in glycerol but for higher pressures [36–38], where the Henry’s law is not applicable. All the Henry’s law constants for the four solvents are reported in Table 8 and plotted in Fig. 11.

View all citing articles on Scopus
View full text