Modelling the catalyst fragmentation patternin relation to molecular properties and particleoverheating in olefn polymerization

Atwo-dimensional single particle fnite element model was used to examine the effects of particle fragmental pattern on the average molecular weights, polymerization rate and particle overheating in heterogeneousZiegler-Natta olefn polymerization. A two-site catalyst kinetic mechanism was employed together with a dynamictwo-dimensional molecular species in diffusion-reaction equation. The initial catalyst active sites distributionwas assumed to be uniform, while the monomer diffusion coeffcient was considered to be different inside thefragments and cracks. In other words, the cracks were distinguished from fragments with higher monomer diffusioncoeffcient. To model the particle temperature a lumped heat transfer model was used. The fragmentation patternwas considered to remain unchanged during the polymerization. A Galerkin fnite element method was used tosolve the resulting two-dimensional (2-D) moving boundary value, diffusion-reaction problem. A two-dimensionalpolymeric flow model (PFM) was implemented on the fnite element meshes. The simulation results showed thatthe fragmentation pattern had effects on the molecular properties, reaction rate and the particle temperature at earlystages of polymerization. Polyolefns J (2014) 1:77-91

Keywords:

particle overheating , fnite element method , modelling , particle growth , polyolefn