Spatial, temporal and quantitative assessment of catalyst leaching in continuous flow
Spatial, temporal and quantitative assessment of catalyst leaching in continuous flow
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DOI：
10.1016/j.cattod.2017.10.013
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发表时间：
2018-06-15
期刊：
影响因子：
5.3
通讯作者：
Hii, King Kuok (Mimi)
中科院分区：
文献类型：
--
作者：
Barreiro, Elena M.;Hao, Zhimian;Hii, King Kuok (Mimi)
催化剂浸出是开发在液相中进行的商业可行工艺的主要障碍。迄今为止，还没有可靠的技术能够以定量的方式准确地确定浸出过程的程度和动态。在这项工作中，我们开发了一个串联流动反应器系统，通过比较每个反应器出口（S1, S2）对应于非均相/均相反应的优势（空间）和两种不同停留时间（时间）的转化率，使我们能够区分表面催化反应和溶液中发生的反应。随后建立了一个多尺度模型，以量化两种反应速率，并模拟交叉偶联催化剂PdEncat (TM) 30的催化剂浸出；包括：(1)催化剂尺度的多粒径模型；(2)反应器规模的分散模型。结果表明，催化剂的浸出过程不止一个，均相pd -催化剂（从固定化催化剂中浸出并在流动中溶解）在反应中占主导地位，其活性远高于非均相（固定化）pd -催化剂。此外，通过反应器尺度的分散模型，可以预测反应器内浸出钯流随轴向和反应时间的变化。
Catalyst leaching is a major impediment to the development of commercially-viable processes conducted in a liquid-phase. To date, there is no reliable technique that can accurately identify the extent and dynamics of the leaching process in a quantitative manner. In this work, a tandem flow-reactor system has been developed, which allowed us to distinguish between surface-catalyzed reactions from those occurring in solution by comparing% conversion at the exit of each reactor (S1, S2) corresponding to predominance of heterogeneous/homogeneous reactions (spatial) and two different residence times (temporal). A multiscale model is subsequently established to quantify the two types of reaction rate and simulate the catalyst leaching from a cross-coupling catalyst, PdEncat (TM) 30; including: (1) a multi-particle sizes model for catalyst scale; and (2) a dispersion model for reactor scale. The results show that catalyst leaching occurs via more than one process, and that the homogeneous Pd-catalyst (leached from the immobilized catalyst and dissolved in the flow) dominates the reaction and possesses a much higher activity than the heterogeneous (immobilized) Pd-catalyst. Additionally, the change of leached Pd stream inside reactors can be predicted along with the axial direction and the reaction time through the reactor-scale dispersion model.