THE MATHEMATICAL MODELLING AND EXPERIMENTAL VERIFICATION OF PROPYLENE POLYMERIZATION IN THE LIQUID SLURRY PHASE

The slurry polymerization of propylene with solid Ziegler-Natta catalysts is an important industrial process. The polypropylene produced has a broad molecular weight distribution (MWD), for reasons that are not fully understood. Varying catalyst site activities, chain length dependent polymer termination mechanisms and catalyst particle monomer diffusion limitation have been proposed to explain the broad MWD.;Five mathematical models of particles of differing morphology were simulated for the heterogeneous catalyst particles. Intraparticle and boundary layer mass and heat transfer effects were investigated. It was determined that intraparticle mass transfer and boundary layer mass and heat transfer effects were investigated. It was determined that intraparticle mass transfer and boundary layer heat transfer are important to consider in the simulations. The models showed intraparticle diffusion limitation to monomer can be responsible for at least part of the molecular weight distribution broadening observed. A high initial boundary layer temperature rise was predicted, which could be responsible for polymer particle sticking and agglomeration observed under industrial operating conditions.;A bottle polymerization apparatus and a complex high pressure polymerization reaction system have been constructed. The high pressure reactor is interfaced with our PDP 11-55 minicomputer, which allows temperatures and reactant concentrations to be monitored and controlled.;The bottle polymerization apparatus has been used for propylene polymerization to investigate the effects of temperature, solvent type, and killing agents. A broad molecular weight distribution is observed (polydispersity Q (TURNEQ) 5-7) for runs both with and without hydrogen present. Comparing the results with the multipolymeric core model program showed assuming no monomer diffusion limitation fit the yield results best, although the molecular weights were best fit with monomer diffusion limitation present. At 30(DEGREES)C, the model predicted a Q value of 2, while a Q value of 7.03 was obtained from the experiments, indicating another mechanism must also be acting to broaden the MWD.;Diffusion limitation to monomer was postulated to be present in the catalyst particle, and we performed catalyst particle simulations and slurry polymerization experiments to investigate this phenomenon.;Experimental results from the high pressure reaction system showed polymer tacticities are higher than in the low pressure case. The molecular weights obtained were greater at the higher pressure (60 versus 250 psi), and decreased with temperature.