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 k_ij exhibits a clear temperature dependence.

四烷氧基硅烷的烷基具有不同的链长，导致溶胶-凝胶反应的反应性不同。因此，必须了解使用溶胶-凝胶反应设计化学过程的相行为。测量了 CO ₂ /原硅酸四丙酯 (TPOS) 和 CO ₂ /原硅酸四丁酯 (TBOS) 二元体系的相行为。实验是使用合成方法结合激光位移测量进行的，其中测量高压容器内活塞的运动。相界在 313–373 K 和 CO _{2 下}确定0.1–0.9 的摩尔分数。在具有不同链长的烷基的四烷氧基硅烷的相行为中没有观察到显着差异。使用 Sanchez 等人报道的原始混合规则，通过 Sanchez-Lacombe 状态方程将实验获得的两个二元系统的汽液平衡相关联。结果表明，分子相互作用参数k _ij表现出明显的温度依赖性。