Densities and Volumetric Characteristics of Binary System of CO 2 + Decane from (303.15 to 353.15) K and Pressures up to 19 MPa Yongchen Song, Weiwei Jian, Yi Zhang,* Yong Shen, Yangchun Zhan, Jiafei Zhao, Yu Liu, and Dayong Wang Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, School of Energy and Power Engineering, Dalian University of Technology, Dalian, Liaoning, 116024, P. R. China ABSTRACT: Densities of CO 2 + decane binary mixtures were measured by using the magnetic suspension balance (MSB) at different CO 2 mole fractions, x 1 = 0.2361, 0.4698, 0.7100, 0.7725, and 0.8690 with temperatures from (303.15 to 353.15) K and pressures from (8 to 19) MPa. Excess molar volumes were calculated from the density data. The experimental results revealed that the density of CO 2 + decane mixtures increases with increasing pressure and decreases with increasing temperature. The density of mixtures increases with increasing CO 2 concentration first and then decreases at higher CO 2 concentration and higher temperature. A crossover phenomenon with compositions is observed, and the crossover pressure increases with temperature. The excess molar volumes of this mixture display more negative values with in- creasing temperature at 18 MPa and less negative values with increasing pressure at 313.15 K. Moreover, the mixture densities have been predicted with GERG- 2008 and a modi fied Benedict-Webb-Rubin-Starling (BWRS) model. The validities of the two models have been tested by predicting density data in this work and comparing with previous literature. ■ INTRODUCTION Injecting carbon dioxide into depleted oil/gas fields has been considered as one promising option for enhancing oil recovery and caused increasing attention in recent years. 1 The thermo- dynamic characterization of CO 2 + oil mixtures such as phase composition, volumetric characteristics, and densities in wide temperature and pressure ranges need to be investigated for the CO 2 displacement process. The density of CO 2 + oil solution is a key parameter for CO 2 -EOR which determines the diffusion and migration of CO 2 in the reservoir. 2 As we know, decane is one of typical components in petroleum which has similar thermal physical properties such as surface tension and viscosity with petroleum, so it can be used as a model fuel instead of petroleum in research. Researchers have investigated the densities of CO 2 + decane mixtures before. Cullick and Mathis measured the density of this binary mixtures in the range (310 to 403) K and (7 to 30) MPa with x 1 = 0.15, 0.301, 0.505, 0.649, and 0.85. 3 Bessie ̀ res et al. measured the density of this system from (308.15 to 368.15) K and (20 to 40) MPa with x 1 = 0.15, 0.30, 0.51, 0.66, 0.78, and 0.84. 4 Zú ñ iga-Moreno et al. reported densities from (313 to 363) K up to 25 MPa at x 1 = 0.0551, 0.2369, 0.4536, 0.8114, and 0.9663. 5 But this is not sufficient for evaluating the con- sistency of these data because the measurement conditions and CO 2 concentrations are different from each other. Therefore, more experimental data with high accuracy are required for the density of CO 2 + decane mixtures. The density models of CO 2 + decane mixtures have been discussed before. Zú ñiga-Moreno et al. proposed a five-parameter empirical equation to correlate the mixture densities at di fferent compositions. 5 Nishiumi ’ s equation combined with Lee-Kelser mixing rules presented by Bessie ̀ res et al. gave a good prediction for their own experimental data, but the pre- diction results for other experimental data need to be confirmed. 4 In this study, density measurements about CO 2 + decane system have been conducted in the pressure range (8 to 19) MPa and temperature range (303.15 to 353.15) K at five com- positions x 1 = 0.2361, 0.4698, 0.7100, 0.7725, and 0.8690 by a magnetic suspension balance (MSB). Comparisons of the data with two density models, a modified Benedict-Webb-Rubin- Starling (BWRS) equation of state in which the binary interaction parameter was expressed as a function of CO 2 mole fraction, and the GERG-2008 model sponsored by the Group Europe ́ en de Recherche Gaziè res are presented. ■ EXPERIMENTAL SECTION Materials. The CO 2 and N 2 are supplied by Dalian Da-te Gas Co., Ltd. with a nominal purity of 99.99 mol % and 99.999 mol %, respectively. Decane is supplied from TCI (Shanghai) Develop- ment Co., Ltd. with purity of a nominal 99.1 %. The materials above are used for density measurement without further puri- fication. The details of chemicals used in this work are stated in Table 1. Apparatus and Procedure. The magnetic suspension balance (MSB) manufactured by Rubotherm Prä zisionsmesstechnik Received: April 24, 2012 Accepted: October 23, 2012 Published: November 6, 2012 Article pubs.acs.org/jced © 2012 American Chemical Society 3399 dx.doi.org/10.1021/je300388b | J. Chem. Eng. Data 2012, 57, 3399-3407