Bottom-Up Synthesis of Multi-Grained Ziegler–Natta Catalyst Based on MgO/MgCl2/TiCl4 Core–Shell Catalyst

Morphology control plays a major role in the design of solid catalysts. Since the heterogeneous Ziegler–Natta catalyst (ZNC) is based on the in situ synthesis of MgCl2 support in a top-down manner, the individual control of the exterior and the interior structure of the catalyst macro-particles is challenging. In this study, we successfully prepared a ZNC with a multi-grain interior structure by the spray-drying of MgO nanoparticles, inspired by the fact that the MgO/MgCl2/TiCl4 core–shell catalyst can maintain the morphology of the raw MgO nanoparticles. This catalyst is the first example of the bottom-up preparation of MgCl2-supported ZNC. Here, we report its basic preparation method, characterization results, and performance in the homo-polymerization of ethylene and propylene, and copolymerization with 1-hexene.

Modeling of Ethylene Polymerization with Ziegler-Natta Catalyst in a Bubbling Fluidized Bed Reactor

In the present study, a new dynamic fluidized bed reactor (FBR) model is developed to account for the effect of bubble growth in the bed height on the dynamic behaviour of the reactor and the molecular properties of the polymer product. The model takes into account the existence of solid catalyst in both phases and consequently, the occurrence of polymerization reaction in both bubble and emulsion phases. A dynamic two-phase model is employed for predicting the key hydrodynamic parameters of the bed. A comprehensive kinetic model for ethylene polymerization in the presence of multiple-site Ziegler-Natta catalyst is considered to describe the number and molecular weight averages and molecular weight distribution of polymer in the FBR. The hydrodynamic model and the kinetic model have been coupled and solved simultaneously to simulate the performance of the fluidized bed reactor. The study incorporates the effects of the most important reactor parameters such as superficial gas velocity, mean particle size, inlet gas temperature, bubble size, recycle stream and chain transfer agent on the steady-state behaviour of the FBR. The proposed dynamic model is capable of predicting both the performance of the reactor and the polymer physiochemical properties.