Water diffusion in polymers is relevant to a broad range of physicochemical phenomena and technological processes. Although many fields contributed to rapid progress in the fundamental knowledge of water–polymer interactions, detailed understandings come mainly from interpreting numerous experiments. These studies showed that a remarkably rich variety of diffusion forms between water and even seemingly simple polymers. In this review, focusing on the gravimetric and capacitance method, we discuss contradictions and problems existing for water diffusion in polymers in detail from perspectives of experiments and models, focusing on the analysis of error derived from widely used methods, especially for the Brasher–Kingsbury equation. We also provide a perspective on outstanding problems, challenges, and open questions, including water clusters, relaxation, and electrochemical reactions at the metal/polymer interface, as well as expanding the theoretical prospective.

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Modeling description of the riser reactor is a highly interesting issue in the development of FCC process. However, one of the challenging problems in the modeling of FCC riser reactors is that sophisticated flow-reaction models with high accuracy need long computational time, while simple flow-reaction models give rise to results with fast computation but low accuracy. This dilemma requires new type of coupled flow-reaction models. The goal of this study was to propose a novel integrated model with timeefficient computation and acceptable accuracy. The integrated model, named equivalent reactor network (ERN) model, was established based on Aspen Plus simulator with considering gas-solid hydrodynamics via built-in modules and catalytic reactions via external FORTRAN subroutines, as well as lump mixtures characterized by real components. Through comparing with pilot-scale experimental data and industrial plant data in two case studies, the developed ERN model was justified to be capable of precisely and quickly modeling FCC riser reactors. Furthermore, the proposed methodology is expected to be readily applied to studies on the dynamic simulation, optimization, and control of FCC units in future studies.

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