Modeling For Ethylene-propylene Polymerization Processes Towards Sequence Microstructures

This paper builds a model based on the mechanism of ethylene-propylene polymerization towards the chain structure. Polyolefin is one of the most important materials, and the chain structure, including molecular weight(MW), molecular weight distribution(MWD), copolymer composition distribution(CCD) and sequence distribution (SD) decide the properties of the ethylene-propylene copolymers.In industrial production, the quality of product and fine controlling of products require more sophisticated test method than decting the melt index (MI) and density, because these two properties can not describe the essential characteristics, and have bad performance of real-time.Thus, building a model based on the polymerization process mechanism towards the polymer chain structure is needed. The model can describe the polymerization process, predict the quality of polymer products, as well as meet the requirement of online estimating and advanced controlling of polymer production process.1) Builds a universal model towards the chain structure, especially the sequence microstructure based on the mechanism of ethylene-propylene copolymerization. The model has two modules including molecular weight distribution model and sequence structure model, so it can calculate the molecular weight distribution and the sequence structure of ethylene-propylene copolymerization at the same time. Achieve the high efficiency operation of model on gPROMS.2) The model can be used in a switching atmosphere olefin polymerization process based on the Zigler-Natta catalyst. Use the kinetics from the literature into the model, and calculate the molecular weight distribution and sequence structure of polypropylene copolymer. The result shows the MWD and sequence distribution of the two kinds of active centers (random and block), which are verified by the13C-NMR test. The effect of the polymerization time, the monomer concentration, the reaction temperature and the switching frequency on the sequence structure is revealed.3) The model is also applied to simulate the EPR production process, which uses the non-bridged Metallocene catalysts(Bis (2,4,6-tri-Me-Ind) ZrCl2/MMAO). The kinetics are fitted through the cumulative molecular weight distribution model, when applied the parameters into the model, we can obtain the sequence structures of EPR. The sequence structure is verified by the13C-NMR, which proves the model can achieve the calculation of the chain structures.