TY - JOUR
T1 - Revisiting the identity of δ-MgCl2: Part II. Morphology and exposed surfaces studied by vibrational spectroscopies and DFT calculation
AU - Piovano, Alessandro
AU - D'AMORE, MADDALENA
AU - Wada, Toru
AU - Cleto Bruzzese, Paolo
AU - Takasao, Gentoku
AU - Thakur, Ashutosh
AU - Chammingkwan, Patchanee
AU - Terano, Minoru
AU - Civalleri, Bartolomeo
AU - Bordiga, Silvia
AU - Taniike, Toshiaki
AU - Groppo, Elena
PY - 2020
Y1 - 2020
N2 - The activation of MgCl2 is an essential step for preparing performant Ziegler-Natta (ZN) catalysts for olefin polymerization, either by mechanical grinding of pristine MgCl2 or by chemical conversion of a precursor. Depending on the adopted activation process, different nanostructures are obtained in terms of disorder and morphology, which in turn influence the overall catalytic performance. In this work, we focused on the morphology of d-MgCl2 nanoparticles (i.e. the relative extension of the exposed surfaces), by investigating with vibrational spectroscopies a series of mechanically and chemically activated MgCl2 samples, and by building up a comprehensive set of model structures (both ordered and disordered) and relative surfaces in order to highlight nanosizing effects and achieve an accurate description of MgCl2 particles at an atomistic level. We found that both mechanical and chemical activation promote the expression of MgCl2 surfaces exposing strongly acidic Mg2+ sites, which are those mostly involved in the catalysis, together with an increase of inter-surfaces edges, which have been recently considered as the main responsible for the ZN catalysts stereo-selectivity.
AB - The activation of MgCl2 is an essential step for preparing performant Ziegler-Natta (ZN) catalysts for olefin polymerization, either by mechanical grinding of pristine MgCl2 or by chemical conversion of a precursor. Depending on the adopted activation process, different nanostructures are obtained in terms of disorder and morphology, which in turn influence the overall catalytic performance. In this work, we focused on the morphology of d-MgCl2 nanoparticles (i.e. the relative extension of the exposed surfaces), by investigating with vibrational spectroscopies a series of mechanically and chemically activated MgCl2 samples, and by building up a comprehensive set of model structures (both ordered and disordered) and relative surfaces in order to highlight nanosizing effects and achieve an accurate description of MgCl2 particles at an atomistic level. We found that both mechanical and chemical activation promote the expression of MgCl2 surfaces exposing strongly acidic Mg2+ sites, which are those mostly involved in the catalysis, together with an increase of inter-surfaces edges, which have been recently considered as the main responsible for the ZN catalysts stereo-selectivity.
KW - Ziegler-Natta catalysts
Nanocrystal
Morphology
FT-IR spectroscopy
DFT-D calculation
KW - Ziegler-Natta catalysts
Nanocrystal
Morphology
FT-IR spectroscopy
DFT-D calculation
UR - https://iris.uniupo.it/handle/11579/200242
U2 - 10.1016/j.jcat.2020.04.017
DO - 10.1016/j.jcat.2020.04.017
M3 - Article
SN - 0021-9517
VL - 387
SP - 1
EP - 11
JO - Journal of Catalysis
JF - Journal of Catalysis
ER -