Smart Reactors – Development of Novel Process Concepts based on the Application of Stimuli-Responsive Gels

Stimuli-responsive lyogels belong to the so-called smart materials, which undergo significant property changes when subjected to shifts in environmental conditions. Therein, the material expels or imbibes several folds of its initial volume within brief periods of time depending on the thermodynamic conditions, the structural makeup, and the dimensions of the polymer matrix. This feature allows for the chemically-inherent interpretation of conditional shifts within reactive systems via the material to perform actuation through volumetric changes. However, the application in the process engineering discipline is scarce and is limited to microfluidics and release systems of micron-sized particles. Hence, this work investigated the characteristics of gels with macroscopic dimensions and developed application scenarios of such in the context of actual reactive systems and process conditions to perform autonomous regulation of these systems. Within this explorative work, the characteristics of responsive pNiPAAm gels have been studied with regard to their equilibrium and dynamic swelling behavior, and their mechanical properties to establish a framework from which the later applications were derived. For the application, three different process concepts were developed to showcase the utility of the material response of pNiPAAm: Firstly, for a continuous polymerization process, where the heat of reaction was utilized to enable the autonomous adjustment of flow direction of the reactor outlet. Secondly, for biphasic fluid systems to regulate the mass transport between the phases facilitated by the volumetric changes of responsive lattice gel structures. And lastly, for the model esterification system, where pNiPAAm gels were applied as biocatalyst carriers to regulate the reaction conversion rate. Ultimately, these proofs-of-concept provide a first insight into the large potential these materials possess for the development of future smart reactors.