A Monte Carlo Method to Quantify the Effect of Reactor Residence Time Distribution on Polyolefins Made with Heterogeneous Catalysts: Part IV—Intraparticle Transfer Resistance Effects

Abstract

An integrated Monte Carlo/polymeric multilayer model (MC/PMLM) is developed to predict the polymer particle size distribution (PSD) and microstructures of polyolefins made with heterogeneous catalysts under intraparticle mass transfer limitations. The Monte Carlo model is used to randomly sample particle sizes and residence times from the catalyst PSD and reactor residence time distribution (RTD), respectively, while the polymeric multilayer model is used to describe single‐particle growth considering intraparticle mass transfer resistances. The effect of reactor RTD, catalyst PSD, and polymerization kinetics on polymer PSD and polymer properties is systematically investigated with the MC/PMLM for the first time. The results show that intraparticle mass transfer limitations under various operating conditions may affect polymer PSD and polymer properties. In addition, due to the versatility of the Monte Carlo approach, the proposed MC/PMLM is adequate to describe complex cases, such as reactor systems with arbitrary RTD and catalyst particles having any PSD.

A conceptual multilevel approach to polyolefin reaction engineering

“…Consequently, the polymer microstructure and R p become a function of the age of the particle in the reactor (reactor residence time). [94][95][96][97] Heat and mass transfer limitations will always broaden the microstructural distributions of a polyolefin. By how much will depend on the magnitude and duration of these limitations.…”

“…A more generic approach, relying on Monte Carlo simulation, was proposed recently. [94][95][96][97] We will use this technique to illustrate the effect of RTD on the previous modelling scales. Besides being the most powerful method developed so far to describe the RTD level, it is also the easiest to comprehend.…”

“…This simulation must be repeated for a large number of catalyst particles to calculate the properties for a representative sample of the polymer particle population. In the simulations above, we only combined three levels-Catalysis, Polymerization Rate, and RTD-but other levels in Figure 2 could be considered, such as the Internal and External Transfer Phenomena [94] and the Thermodynamic Equilibrium [92] levels. This Monte Carlo approach has been used to calculate the effect of RTD on the PSD of particles made in a single or in a series of reactors, [97] on the polymer fluff packing density, [96] and on the MWD-CCD of polymers made in a series of reactors.…”

“…This Monte Carlo approach has been used to calculate the effect of RTD on the PSD of particles made in a single or in a series of reactors, [99] on the polymer fluff packing density, [98] and on the MWD-CCD of polymers made in a series of reactors. [96], [97]…”

Ethylene Polymerization Kinetics and Microstructure of Polyethylenes Made with Supported Metallocene Catalysts

“…These gradients may be spatial or temporal and broaden the microstructure of polyolefins made with homogeneous and heterogeneous metallocenes. Intraparticle mass and heat transfer resistances in supported metallocenes may also cause MWD and CCD broadening. ,− In this case, active sites located along the radius of the polymer particle are exposed to different temperatures and concentrations of monomer, comonomer, and hydrogen. Consequently, they make polymer chains with varying microstructural distributions, which, when added over all radial positions, result in broader MWDs and CCDs.…”