Multi-Active Site Modeling of the Multi-Zone Circulating Fluidized Bed Process for Polypropylene Production
YAO Jianghua1, CHANG Cheng1,2, GU Xueping1,2, FENG Lianfang1,2, ZHANG Cailiang1,2
1. State Key Laboratory of Chemical Engineering and Low-carbon Technology, School of Chemical and Bioengineering, Zhejiang University, Hangzhou 310058, China；
2. Zhejiang University Quzhou Research Institute, Quzhou 324000, China
Abstract： The multi-zone circulating fluidized bed (MZCR) process enables flexible control over the molecular weight distribution of polypropylene, producing homopolymers and random copolymers with molecular weight distributions ranging from extremely narrow to very broad, exhibiting excellent structural uniformity. MZCR predominantly employs Ziegler-Natta catalysts, whose multi-active site characteristics influence apparent polymerization kinetics. High-temperature gel permeation chromatography (HT-GPC) and carbon-13 nuclear magnetic resonance (13C-NMR) were employed to characterize samples from two operating conditions. This yielded the molecular weight distribution, and average copolymer composition of reactor outlet products, enabling the development of an MZCR mechanism model incorporating thermodynamics and multi-site coordination polymerization kinetics. The number of active sites and reaction kinetic parameters were determined based on condition 1 data, and the model was validated using condition 2 data. Results indicate: the maximum relative error in modeling for operating condition 1 did not exceed 6.3%; all errors in validation for operating condition 2 were below 5.0%. This study couples the multi-active-site mechanism with the PC-SAFT equation for industrial-scale simulation, providing a theoretical basis for modeling research on circulating fluidized bed processes.
. Multi-Active Site Modeling of the Multi-Zone Circulating Fluidized Bed Process for Polypropylene Production[J]. Chemical Reaction Engineering and Technology, 2026, 42(2): 97-105.
