A Monte Carlo Method to Quantify the Effect of Reactor Residence Time Distribution on Polyolefins Made with Heterogeneous Catalysts: Part III—Particle Composition Distribution Effects

Abstract

Polymer reactor blends, such as bimodal polyethylene or high‐impact polypropylene, are usually produced in multistep processes using two or more reactors in series. Since the polymer particles are subject to reactor residence time distributions (RTD) during the polymerizations, the fractions of the polymer populations made in each reactor will vary from particle to particle. It is shown in the previous publications in this series that reactor RTD has a marked effect on the particle size distribution and on the packing density of polyolefin particles. In this article, the versatile Monte Carlo model is extended to demonstrate how reactor RTD affects particle composition and molecular weight distributions of polyolefin reactor blends made in multistep processes. Increasing the number of reactors in series favors the homogeneity of the product. Moreover, the average fraction of the different polymer populations in the particles depends strongly on the mean reactor residence time and polymerization kinetics.

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.…”

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

“…In the previous publications in this series, we used a Monte Carlo model to investigate the effect of reactor RTD on different polyolefin properties such as polymer PSD, [23] packing density, [24] and particle composition distribution of reactor blends. [25] In the present article, we extended the use of our Monte Carlo methodology to predict polymer PSD and MWD in a solid catalyzed polymerization process in the presence of intraparticle transfer resistances, by coupling our Monte Carlo method with a single particle model PMLM. This is the very first time such an integrated model has been used to tackle this complex problem.…”

“…[23] We showed that the proposed Monte Carlo model was extremely versatile, being able to predict polymer PSD in reactor systems with any arbitrary RTD for catalyst particles having any PSD shape. Subsequent articles discussed how to use a similar Monte Carlo approach to predict polyolefin particle packing density, [24] and particle composition distribution [25] as a function of reactor RTD.…”

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.…”