Nonlinear Dynamics in Chemical Reaction Engineering: In Celebration of Moshe Sheintuch's 70th Birthday

Abstract

This special issue of the Israel Journal of Chemistry is dedicated to Moshe Sheintuch, one of the pioneers in the field of nonlinear dynamics of chemical reactors. Moshe, who turned 70 in July of 2017, is Professor Emeritus at the Chemical Engineering Department at the Technion – Israel Institute of Technology, where he has worked since 1977. A central theme in his versatile research, which spans more than three decades, is the analysis of increasingly complex dynamic regimes in chemical reactors. Moshe's career started with the analysis of chemical oscillations in heterogeneous catalysis. This was the “golden age” of nonlinear dynamics in chemistry, when most of the nonlinear effects predicted by mathematicians were being systematically confirmed in experiments with homogeneous reacting systems, including chemical oscillations in solutions and gas phase combustion. Moshe's research was devoted to examining these phenomena and their possible practical applications in real chemical reactors. Moshe's work on nonlinear chemical dynamics investigated the effects on interphase transport, which plays a critical role in heterogeneous catalysis and electrochemistry. He showed how these effects can both destroy the patterns that exist in homogeneous reactors and create new spatiotemporal regimes. Most notably, he discovered the emergence of symmetry broken states, such as standing fronts and antiphase oscillations, in chemical systems under global control and predicted, over three decades ago, their plausible role in biological systems (1–3). The full significance of these patterns has been understood only recently, in the context of the analysis of symmetry breaking in cell biology. Indeed, many of the processes involved in directed cell migration and asymmetrical localization of intracellular proteins can be successfully interpreted using the theory developed by Sheintuch and his colleagues (4, 5). Another set of important results is related to the analysis of propagating reaction fronts and pulses. Moshe's experiments revealed the existence of such patterns in a packed bed catalytic reactor, a workhorse of chemical industry (6–8). In addition to explaining how such patterns arise through the interplay of interphase transport and chemistry, he proposed several strategies for harnessing these patterns in novel reactor configurations (9–14). These are just two key examples from the list of Moshe's contributions to nonlinear analysis of chemical reactors. The field of nonlinear chemical dynamics is in excellent shape and continues to offer exciting problems to the new generation of scientists and engineers. This collection of articles is a snapshot of the current research. The topics range from the mathematics of chemical reaction networks (paper by Craciun), to propagating chemical waves (papers by Pribyl and colleagues, and Yochelis), and studies of nonlinear dynamics on networks (paper by Kiss). A new research direction use nonlinear dynamics in the design of new materials (papers by Steinbock and Kuksenok). Another class of interesting problems comes from the efforts to systematically engineer nonlinear regimes starting from individual reactions; see the reviews by Taylor, Epstein, and Semenov. Finally, even though the practical uses of nonlinear dynamics in chemical industry are still rare, there has been a recent resurgence of interest in periodic operation chemical reactors. The reviews by Simakov et al and Morgenstein and Petkovska present theoretical progress in this area. Given the fact that biology provides numerous of examples of successful uses of nonlinear patterns (see the review of traveling waves during embryonic cell cycles by Di Talia), the efforts to emulate this success in chemical industry are worth pursuing. Studies of nonlinear dynamics in chemistry have gone a long way since Moshe started his research career. We argue that some of the most exciting developments are still to come, enabled by the recent advances in monitoring multivariable chemical dynamics in chemical reactors and living systems. Furthermore, we are yet to establish truly predictive models, which can be used to design and control nonlinear dynamics of chemical systems to the extent accomplished in electrical engineering and optics. How does one start to construct and validate such models? This question often arises in conversations with Moshe. He recommends starting with the simplest possible model, analyzing it completely, and adding realistic details as needed. This approach served him well throughout his distinguished career and continues to be an excellent example for his students and colleagues. However, the recent revolution in information technology and big data may disrupt long held conventions (see the review by Kevrekidis). We wish both Moshe and the entire field of nonlinear chemical dynamics many more healthy and productive years.