Thermochimica Acta 543 (2012) 218–225 Contents lists available at SciVerse ScienceDirect Thermochimica Acta journa l h o me page: www.elsevier.com/locate/tca Volumetric properties, viscosities, refractive indices and surface tensions for (dimethylpropanolamine (DMPA) + water) mixtures from 298.15 K to 343.15 K Kamal Narayanaswamy, Aravind V. Rayer, Salim Kadiwala, Amr Henni ∗ International Test Center for CO2 Capture, Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan S4S 0A2, Canada a r t i c l e i n f o Article history: Received 2 March 2012 Received in revised form 16 May 2012 Accepted 20 May 2012 Available online 29 May 2012 Keywords: Dimethylpropanolamine Density Viscosity Surface tension Refractive index a b s t r a c t This paper reports the experimental data for the densities and viscosities at six temperatures (298.15–343.15) K, refractive indices at nine temperatures (293.15–333.15) K, and surface tensions at seven temperatures (298.15–333.15) K for aqueous solutions of dimethylpropanolamine (DMPA). Excess properties derived from the experimental results were discussed in terms of changes in molecular inter- actions in the mixtures. The derived deviations of the properties were regressed with the Redlich–Kister equation. The derived thermodynamic properties were then compared with those of other tertiary amines available in the literature. © 2012 Elsevier B.V. All rights reserved. 1. Introduction In order to reduce the cost of CO 2 capture by chemical absorption, intensive efforts in research are under to study a multitude of different chemical solvents [1,2]. Absorbent regen- eration contributes to more than half of the operating cost in the absorption–regeneration process. Development of new CO 2 absorbents with a low heat of reaction, a fast absorption rate and a high capacity for CO 2 is needed to achieve the anticipated operating cost reduction in order to make the technology economically feasi- ble in the context of large scale greenhouse gas emission reduction. Though primary and secondary amines have a high reac- tion rate and absorption capacity, they also have a high heat of reaction. Whereas, tertiary amines have a lower heat of reac- tion, their absorption rates are somewhat limited. Considerable improvements were introduced in the technology and great sav- ings in energy were obtained by blending alkanolamines [3]. More improvements are still needed in order to reduce the cost to the desired level. A recent study screened 76 amines in terms of their rate of absorption and capacity for CO 2 . It concluded that the steric hin- drance and hydroxyl on carbons 2 or 3 from the nitrogen led to higher absorption capacities and rates [2]. Chowdry et al. [1] stud- ied CO 2 absorption rate, loading capacity and heat of reaction for 25 hindered tertiary amines. Kadiwala [4] proposed the use of two new ∗ Corresponding author. Tel.: +1 306 585 4960; fax: +1 306 585 4855. E-mail address: amr.henni@uregina.ca (A. Henni). tertiary amines based on their high reaction rates, [dimethyliso- propanolamine (DMIPA) and dimethyl propanolamine (DMPA)]. Their kinetic rate constants were much higher than those of the “standard” tertiary amine, methyldiethanolamine (MDEA). Physical properties of aqueous DMPA solution are not available in the literature, and are needed for predicting the absorp- tion rates and enhancement factors of the gases in solutions. N,N-dimethylpropanolamine ((CH 3 ) 2 N(CH 2 ) 3 OH, DMPA; CAS. No: 3179-63-3) is a tertiary amine commonly used as a cross linking catalyst in the production of polyurethanes, and as a component of insecticides, surfactants, rubber chemicals corrosion inhibitors and pigment dispersants. Information on the physical properties such as densities, viscosities, refractive indices are also required for engineering design and subsequent operations as mentioned by Astarita et al. [5]. The accuracy of measurements for the physical properties of the mixtures affects the dependability of the pro- cess design calculations in sizing the equipments. Volumetric data combined with molecular theories or models are helpful in the understanding of molecular interactions in the absorption system. Finally, solute–solvent interactions can be deduced using derived properties from the physical properties data. In this work, measurements of the densities and viscosities of aqueous DMPA were performed at (298.15, 303.15, 313.15, 323.15, 333.15 and 343.15) K. Refractive indices of aqueous DMPA were measured (293.15, 298.15, 303.15, 308.15, 313.15, 318.15, 323.15, 328.15 and 333.15) K. Surface tensions of aqueous DMPA were also measured at (298.15, 303.15, 308.15, 313.15, 318.15, 323.15, and 333.15) K. From the experimental viscosity, refractive index data, and surface tension, property deviations for the mixtures were 0040-6031/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.tca.2012.05.025