Development of a dynamic surface layer model for the prediction of deposit formation in solution polymerizations

• Applicants: Professor Dr.-Ing. Guido Grundmeier; Professor Dr.-Ing. Ulrich Nieken
• Subject Area: Chemical and Thermal Process Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563898309

Solution polymerization is often carried out in stirred tank reactors in semi-batch mode. However, to achieve constant quality and energy-efficient production, continuous production is desirable. While the transition to continuous polymerization is possible for some polymers, in other cases gel deposit formation occurs. Such deposits block the reactor after short operation time. A technically relevant example of this behaviour is the solution polymerization of N-vinylpyrrolidone (NVP) to poly(vinylpyrrolidone) (PVP). Although PVP dissolved in water can be conveyed through tubular reactors without any problems, gel formation occurs under reaction conditions after a few hours. The onset of the pressure rise varies significantly with the reaction and flow conditions, as well as with the type and pretreatment of the reactor surface. A prediction of the gel formation during scale-up is hardly possible so far. The aim of this cooperative project, which combines complementary experimental and theoretical approaches of the two research groups, is to develop a mechanistic understanding of the fouling process occurring in polymer reactors as well as to obtain a quantitative description of the fouling dynamics using CFD calculations. The new, fundamentally oriented model will only contain independently determined model parameters and thus allow a transfer to other reactor geometries and process conditions. This provides a way to design more energy-efficient, continuous processes and predict their performance. For the development of a dynamic model of the wall layer, the adhesion of the polymer at the solid/liquid interface is followed by means of various microscopic and in-situ spectroelectrochemical methods under reaction und reaction-like conditions. In order to investigate the adsorption of polymer chains at the liquid/solid interface on surfaces with different properties, technically relevant alloys and reactor surfaces will be modified with ultra-thin films of varying surface energies. This approach allows the correlation of deposit formation with chemical processes at the interface on a macromolecular level. Together with an improved description of the diffusive transport of the polymers, a quantitative description of the deposit formation as a function of the adsorption energy of the polymer segments is to be derived and validated by comparison with experiments in continuously operated reactors. Microreactors will serve as demonstrators. The methodology will be derived exemplarily for the solution polymerization of PVP but will be applicable to other solution polymerizations as well. The developed boundary layer model is validated using the 1-vinylimidazole/polyvinylimidazole system.

• DFG Programme: Research Grants