(560h) From Elementary Steps of Multistep Catalytic Polymer Upcycling Mechanisms to Derived Population Balance Models

Traditional population balance models (PBEs) for polymerization and depolymerization are phenomenological – they model cleavage rates as single steps with no link to the underlying catalyst adsorption isotherms or rate constants of the catalytic steps. In this talk, we present new systematic tools to transform multistep reaction mechanisms and rate constants into PBEs while retaining the connection to the original rate constants. The procedure uses pseudo-steady-state approximations (PSSA), continuum molecular weight approximations, and new kinetic local density approximations (KLDA) and kinetic generalized gradient approximations (kGGA). In contrast to phenomenological PBEs, the new approach yields PBEs with coefficients that are derived functions of the underlying rate constants and adsorption constants. The new derived PBE models will help to (i) interpret experimental data, (ii) provide rate parameters to test predictions from ab initio mechanistic studies, and (iii) incorporate (and test) predictions from simulations and theoretical models of polymer adsorption on surfaces and in pores. We show examples from work on tandem polymer upcycling catalysts.