Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, United States.
Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, United States.
J Chromatogr A. 2018 Aug 17;1563:47-61. doi: 10.1016/j.chroma.2018.05.057. Epub 2018 May 30.
Ligand-assisted displacement chromatography (LAD) has been developed for separating rare earth elements since the 1950's. Isotachic displacement trains, which are similar to those in conventional displacement chromatography, were reported previously. However, there has been no general theory delineating the conditions required to form constant-pattern displacement trains for non-ideal systems (or systems with significant mass transfer resistance). The constant-pattern state is critical for obtaining pure products with high yield and high productivity. Without theoretical guidance, all the previous studies found the constant-pattern state by experimental trial and error, which was time consuming and costly. In this study, an efficient rate model and simulations of LAD were developed and verified with experimental data for non-ideal systems. Verified simulations were used to understand the mechanisms of separations and the transition from the transient state to the constant-pattern state. The key dimensionless factors affecting the transition for binary non-ideal systems were identified. Dimensionless groups were developed to reduce the number of variables. Simulations were used to find the transition points fromthe transient state to the constant-pattern state, which indicates the minimum dimensionless column lengths in the multi-parameter space. Strategic combination of the key dimensionless groups allows the minimum dimensionless column lengths to correlate with the combined groups in a two-dimensional diagram (or a map). The correlation curve divides the multi-dimensional space into the transient region and the constant-pattern region. The correlation was further verified with five sets of experiments. It can be used to find, without process simulations or experiments, the minimum column lengths for developing constant-pattern isotachic trains for non-ideal systems, which is useful for designing efficient ligand-assisted displacement chromatography at any scale.
配体辅助置换色谱（LAD）自 20 世纪 50 年代以来就已被开发用于分离稀土元素。以前曾报道过类似于常规置换色谱的等速置换列车。然而，对于非理想体系（或存在显著传质阻力的体系），还没有一般的理论来描述形成恒型置换列车所需的条件。恒型状态对于获得高产率和高生产力的纯产物是至关重要的。没有理论指导，以前的所有研究都是通过实验试错法来找到恒型状态，这既耗时又昂贵。在这项研究中，针对非理想体系，开发了一种有效的速率模型和 LAD 模拟，并通过实验数据进行了验证。经过验证的模拟用于理解分离机制和从瞬态到恒型状态的转变。确定了影响二元非理想体系转变的关键无量纲因素。开发了无量纲组来减少变量的数量。模拟用于找到从瞬态到恒型状态的转变点，这表示在多参数空间中最小的无量纲柱长。关键无量纲组的战略组合允许最小的无量纲柱长与二维图（或地图）中的组合组相关联。该相关曲线将多维空间分为瞬态区和恒型区。用五组实验对其进行了进一步验证。它可以用于在没有过程模拟或实验的情况下找到非理想体系开发恒型等速置换列车的最小柱长，这对于在任何规模上设计高效的配体辅助置换色谱是有用的。
