Gas‐phase polymerization of butadiene. Data acquisition using minireactor technology and particle modeling

Abstract

Minireactor technology has been used for kinetic studies on polymerization kinetics, phase equilibrium, and mass transfer on a very small scale. There is a nonlinear influence of temperature and pressure on the polymerization rate. The phase equilibrium can be described by a Flory-Huggins approach, with a temperature-dependent interaction parameter. The diffusion coefficient seems to be slightly pressure dependent, and the temperature dependence can be described with an Arrhenius equation. A simple formal kinetic scheme with formation of active sites, chain propagation, chain transfer to cocatalyst, and deactivation of active sites has been applied. This kinetic scheme was implemented in two different models; they are, a particle model taking into account mass transfer and a simple chemical model with no mass transfer. In principle, both models describe the experimental results for rate and molecular weight distribution equally well, with rate constants of the same magnitude. Molecular weight distributions calculated by the chemical model are narrower. However, the chemical model gives no explanation for the experimental observed rate dependence on catalyst particle size. With increasing catalyst activity, the differences between both models become more significant and the particle model becomes more and more important.

Study of the morphology and kinetics of novel Ziegler–Natta catalysts for propylene polymerization

“…A simple chemical model was applied without considering physical processes, even though it was shown that catalyst activation was mainly a result of support fragmentation. The model presented is based on that of Bartke 33 and is valid for gas-phase polymerization of propylene with the nonsupported and silica-supported Ziegler-Natta catalysts (Cat E and Cat B). Average particle activity determined using video microscopy at 45°C and 5 bar in the absence of hydrogen or comonomer was simu- Figure 14 shows the activity, measured by video microscopy, along with the simulated activities of Cat E and Cat B versus reaction time.…”

Video Microscopy for Fast Screening of Polymerization Catalysts

“…The optical part of the video microscope system consists of a video camera (Pieper, resolution 720 6 576 pixel), a halogen lamp from Schölly Fiber Optics GmbH, light cables, and a light microscope (Carl Zeiss) with three magnifications (4,8,16). …”

“…The minireactor is equipped with a view port on its top that enables the direct observation of the growing particles. Details of the minireactor for video microscopic studies and photo analysis technique is shown by Zöllner [2,3] and Bartke [4].…”

“…Gas-phase polymerization was carried out in a minireactor originally developed by Bartke [4]. The minireactor is equipped with a view port on its top that enables the direct observation of the growing particles.…”

“…By employing the pressure drop technique [4], the instantaneous activities were measured and the averages of three runs of each catalyst are presented in Fig. 4.…”