Phase behavior of carbon dioxide/tetrapropyl orthosilicate and tetrabutyl orthosilicate systems

• Published in: Fluid phase equilibria 2021-11, Vol.548, p.113172, Article 113172
• Main Authors: Matsukawa, Hiroaki, Otake, Katsuto
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Sanchez–Lacombe equation of state; Tetrabutyl orthosilicate; Tetrapropyl orthosilicate; Vapor–Liquid equilibrium
• ISSN: 0378-3812; 1879-0224
• DOI: 10.1016/j.fluid.2021.113172

•Phase behavior of CO2/TPOS and CO2/TBOS binary systems was measured.•The phase boundaries were determined at 313–373 K and CO2 molar fractions of 0.1–0.9.•No significant difference was observed in the phase behavior of tetraalkoxysilanes.•Molecular interaction parameter kij shows a clear temperature dependence. Alkyl groups of tetraalkoxysilane have different chain lengths, which results in different reactivity of the sol–gel reaction. Hence, it is essential to understand the phase behavior for designing chemical processes using the sol–gel reaction. The phase behavior of CO2/tetrapropyl orthosilicate (TPOS) and CO2/tetrabutyl orthosilicate (TBOS) binary systems was measured. The experiments were performed using a synthetic method combined with a laser displacement measurement wherein the movement of the piston inside the high-pressure vessel was measured. The phase boundaries were determined at 313–373 K and CO2 molar fractions of 0.1–0.9. No significant difference was observed in the phase behavior of tetraalkoxysilanes, which have alkyl groups of different chain lengths. The experimentally obtained vapor–liquid equilibria of the two binary systems were correlated by the Sanchez–Lacombe equation of state using the original mixing rule reported by Sanchez et al. The results showed that molecular interaction parameter kij exhibits a clear temperature dependence. [Display omitted]