Requimte/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
J Chromatogr A. 2012 Oct 19;1260:132-42. doi: 10.1016/j.chroma.2012.08.076. Epub 2012 Aug 30.
We present a new class of multicolumn chromatographic processes that change the classical way of handling the product outlets of simulated moving-bed (SMB) chromatography to avoid the use of flow controllers or an extra pump-the objective is to have just two- or three-way valves at a column outlet-while maintaining the analogy with the SMB in terms of displaced volumes of fluid per switch interval. In this class of processes the flow through a zone (or column) is always in one of the three states: (i) frozen, (ii) completely directed to the next zone (or column), or (iii) entirely diverted to a product line. We use the term relayed stream to refer to this particular type of manipulation of the outflow from a column. For this class of processes we derive a SMB analog-the R-SMB process-and demonstrate, under the framework of the equilibrium theory, that this process has the same separation region as the classical SMB for linear adsorption systems. In addition, the results from the equilibrium theory show that the R-SMB process consists of two distinct cycles that differ only in their intermediate sub-step: one cycle for selectivities α smaller than (3+√5)/2 and another cycle for larger values of α; in the former case no product stream is collected during the intermediate sub-step, whereas in the latter case both product streams are collected. We also examine the R-SMB process under conditions of finite column efficiency and compare its performance against those of the classical open- and closed-loop SMBs. Our simulation results show that the R-SMB process requires less desorbent and is more productive than the standard SMB processes under conditions of finite column efficiency and that the comparison increasingly favors the R-SMB as the column efficiency decreases.
我们提出了一类新的多柱色谱过程，改变了模拟移动床（SMB）色谱中处理产品出口的经典方法，避免使用流量控制器或额外的泵——目标是在柱出口处仅使用两个或三个三通阀——同时保持与 SMB 在每个开关间隔内流体置换体积方面的类比。在这类过程中，一个区域（或柱）中的流动始终处于以下三种状态之一：（i）冻结，（ii）完全导向下一个区域（或柱），或（iii）完全分流到产品线上。我们使用术语“接力流”来指代这种对柱流出物的特殊操作类型。对于这类过程，我们推导出了 SMB 的类比——R-SMB 过程，并在平衡理论的框架下证明，对于线性吸附系统，该过程与经典 SMB 具有相同的分离区域。此外，平衡理论的结果表明，R-SMB 过程由两个不同的循环组成，它们仅在中间子步骤上有所不同：一个循环用于选择性 α 小于（3+√5）/2，另一个循环用于选择性 α 较大；在前一种情况下，中间子步骤期间不收集产品流，而在后一种情况下，两个产品流都被收集。我们还在有限柱效率条件下研究了 R-SMB 过程，并将其性能与经典开环和闭环 SMB 进行了比较。我们的模拟结果表明，在有限柱效率条件下，与标准 SMB 过程相比，R-SMB 过程需要较少的洗脱剂，并且更具生产力，并且随着柱效率的降低，这种比较越来越有利于 R-SMB。
