Journal
APPLIED CATALYSIS A-GENERAL
Volume 667, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.apcata.2023.119460
Keywords
Hydrogen effects; Propylene polymerization; Ziegler-Natta catalyst; Number of active centers; Propagation rate constant
Categories
Ask authors/readers for more resources
This study investigated propylene polymerizations catalyzed by MgCl2/Di/TiCl4-AlEt3/siloxane with and without hydrogen. The time-dependent changes of catalytic activity, number of active centers, and active center distribution were determined. Three types of active centers with different stereoselectivity were identified, and their response to hydrogen was analyzed. Two hydrogen activation mechanisms were proposed to explain the different responses of the active centers.
Propylene polymerizations catalyzed by MgCl2/Di/TiCl4-AlEt3/siloxane in the absence and presence of hydrogen were studied by determining the time-dependent changes of catalytic activity, number of active centers and active center distribution. Three types of active centers with high, medium and very low stereoselectivity were differentiated by fractionating the polymer into three parts. Chain propagation rate constant of each type of active centers was estimated by linear fitting/extrapolating the time-dependent change of apparent propagation rate constant. The centers with high (Ci*), medium (Cm*) and low (Ca*) stereoselectivity responded to addition of hydrogen differently. Adding hydrogen caused marked increase of Ci*, but its propagation rate constant (kpi) was evidently reduced. In contrast, numbers of Cm* and Ca* were only slightly affected, but their propagation rate constants were evidently enhanced by hydrogen. The different hydrogen responses of Ci* with those of Cm* and Ca* were explained by two kinds of hydrogen activation mechanisms.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available