The phase behaviors of carbon dioxide (CO2)/trimethoxy(methyl)silane (MTMS) and CO2/Methylsilicate 51 (MS-51: methylsilicate tetramer) binary systems were determined. The experiments were performed using a synthetic method by observing the bubble point. The phase boundaries were determined at temperatures of 313.2 K-393.2 K and CO2 molar fractions of 0.2-0.9. The experimentally obtained bubble, points of the CO2/MTMS binary system were correlated using the Peng-Robinson equation of state (PR EoS), and the molecular interaction parameters k(ij) and l(ij) were determined. The results of the CO2/ MS-51 binary system were correlated using the PR EoS and the Sanchez-Lacombe equation of state (SL EoS). In the SL EoS, two types of mixing rules, originally proposed by Sanchez et al. which uses k(ij) as a fitting parameter and modified by McHugh et al. which uses two fitting parameters k(ij) and l(ij), were used. For this system, the experimental results were correlated better using the SL EoS than using the PR EoS, and the latter mixing rule was more suitable than the former. (C) 2017 Elsevier B.V. All rights reserved.