Active sites formation and their transformations during ethylene polymerization by the Phillips CrOx/SiO2 catalyst
Authors:
- Maciej Gierada,
- Jarosław Handzlik
Abstract
The nature of the active sites and the mechanism of ethylene polymerization over the Phillips CrOx/SiO2 catalyst are still under debate. In this work, a number of potential initiation, propagation and termination mechanisms for ethylene polymerization are investigated using density functional theory and cluster models. Cr(II), Cr(III), Cr(III)OH and Cr(V) oxide species are considered as the active site precursors. It is predicted that the oxachromacycle ring expansion mechanism is more probable than the routes involving Si(OH)Cr(II)-vinyl or Si(OH)Cr(III)-vinyl sites. We also show that the hydroxylated Cr(III)OH species, further transforming into the active Cr(III) vinyl sites, can be effective for ethylene polymerization. Additionally, we propose that defect sites in the amorphous silica framework can play a role in low-temperature transformation of the Cr(II) species into the active Cr(III) sites. A potential polymerization mechanism involving minor Cr(V) oxide species is also calculated.
- Record ID
- CUT4491d6bcf584426abf24111bd6c64084
- Publication categories
- ;
- Author
- Journal series
- Journal of Catalysis, ISSN 0021-9517, e-ISSN 1090-2694
- Issue year
- 2017
- Vol
- 352
- Pages
- 314-328
- Other elements of collation
- schem.; Bibliografia (na s.) - 327-328; Bibliografia (liczba pozycji) - 104; Oznaczenie streszczenia - Abstr.; Data udostępnienia on-line - 2017-05-30; Numeracja w czasopiśmie - Vol. 352
- Keywords in English
- phillips catalyst, chromium oxide, silica, surface, rthylene polymerization, active site, defect site, mechanism, DFT, cluster model
- DOI
- DOI:10.1016/j.jcat.2017.05.025 Opening in a new tab
- URL
- http://www.sciencedirect.com/science/article/pii/S0021951717302051 Opening in a new tab
- Language
- eng (en) English
- Score (nominal)
- 45
- Additional fields
- Indeksowana w: Web of Science, Scopus
- Uniform Resource Identifier
- https://cris.pk.edu.pl/info/article/CUT4491d6bcf584426abf24111bd6c64084/
- URN
urn:pkr-prod:CUT4491d6bcf584426abf24111bd6c64084
* presented citation count is obtained through Internet information analysis, and it is close to the number calculated by the Publish or PerishOpening in a new tab system.