Fluid Phase Equilibria 358 (2013) 105–107 Contents lists available at ScienceDirect Fluid Phase Equilibria j ourna l ho me page: www.elsevier.com/locate/fluid Solubility of CO 2 in glycerol at high pressures Ana V.M. Nunes, Gonc ¸ alo V.S.M. Carrera, Vesna Najdanovic-Visak, Manuel Nunes da Ponte ∗ REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal a r t i c l e i n f o Article history: Received 29 December 2012 Received in revised form 25 July 2013 Accepted 26 July 2013 Available online 7 August 2013 Keywords: Phase-equilibrium High pressure CO2 Glycerol a b s t r a c t The solubility of CO 2 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 CO 2 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. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The recent expansion of biodiesel production industry has led to glycerol overproduction. This fact has originated numerous sci- entific studies regarding glycerol utilization as a chemical platform towards development of new chemicals. Among different possi- bilities, glycerol carbonate represents one of the most attractive. Glycerol carbonate is a valuable chemical included in the cate- gory 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 [1–3]. Traditional synthetic routes comprise reacting glycerol with fossil fuel derived carbonyl sources, such as phosgene, dialkyl car- bonate and urea [2,3]. A few authors have tried a direct synthetic strategy by com- bining glycerol and CO 2 . 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 deac- tivation. 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 solubil- ity of CO 2 in the liquid phase, although their results could not be reproduced by Dibenedetto et al. [5]. The recent study of Podilla ∗ Corresponding author. Tel.: +351 2129 48353; fax: +351 212948550. E-mail addresses: mnponte@fct.unl.pt, mnp@dq.fct.unl.pt (M. Nunes da Ponte). 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 CO 2 + glycerol + short chain alcohols, namely methanol, has been recently published [8–10]. But published results are very scarce for the binary system (CO 2 + glycerol). There are two sets of experimental data for the solubility of glycerol in CO 2 , obtained by Eissler et al. [11] and Sovova et al. [12], but none for the solubility of CO 2 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 CO 2 in glycerol were performed at the temperatures of 353.15, 393.15 and 423.15 K, and pressures up to 32 MPa. 2. Experimental 2.1. Materials The characteristic of chemicals used in this work are pre- sented 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. 2.2. Experimental procedure Solubility measurements were performed using a high pressure apparatus built by New Ways of Analytics GmbH, Germany. It is 0378-3812/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fluid.2013.07.051