Vapor-liquid equilibria for the CO2 + trimethoxymethylsilane and CO2 + triethoxymethylsilane systems under high-pressure conditions

New binary isotherms are crucial for designing chemical separation processes within supercritical carbon dioxide (CO₂) + trialkoxysilane systems. Vapor-liquid equilibria (VLE) were investigated for two-component systems, trimethoxymethylsilane + CO₂ and triethoxymethylsilane + CO₂, at five temperatures (313.2, 333.2, 353.2, 373.2, and 393.2 K) and pressures up to 14.07 MPa using a synthetic high-pressure phase equilibria apparatus. The pressure-temperature (P-T) plot indicates that the critical mixture curve lies between the critical points of CO₂ and the trialkoxysilane compounds. The solubility of trimethoxymethylsilane and triethoxymethylsilane in CO₂ increased with increasing temperature at constant pressure, following a type-I phase behavior characteristic. The experimentally observed VLE values of the CO₂ + trialkoxysilane systems were correlated using the Peng-Robinson equation of state with binary parameters (k_ij and η_ij) in the conventional mixing rule. The model accuracy was validated by calculating the average relative deviation percentage for the pressure of the binary systems, resulting in values of 4.98% for the trimethoxymethylsilane + CO₂ system and 3.64% for the triethoxymethylsilane + CO₂ system. The estimated variables fell within reasonable limits and showed no significant differences between the predicted and observed VLE data for both systems.