Correlated X-ray Ptychography and Fluorescence Nano-Tomography on the Fragmentation Behavior of an Individual Catalyst Particle during the Early Stages of Olefin Polymerization

Abstract

A combination of X-ray ptychography and X-ray fluorescence tomography (XRF) has been used to study the fragmentation behavior of an individual Ziegler−Natta catalyst particle, ∼40 μm in diameter, in the early stages of propylene polymerization with submicron spatial resolution. The electron density signal obtained from X-ray ptychography gives the composite phases of the Ziegler−Natta catalyst particle fragments and isotactic polypropylene, while 3-D XRF visualizes multiple isolated clusters, rich in Ti, of several microns in size. The radial distribution of Ti species throughout the polymer−catalyst composite particle shows that the continuous bisection fragmentation model is the main contributor to the fragmentation pathway of the catalyst particle as a whole. Furthermore, within the largest Ti clusters the fragmentation pathway was found to occur through both the continuous bisection and layer-by-layer models. The fragmentation behavior of polyolefin catalysts was for the first time visualized in 3-D by directly imaging and correlating the distribution of the Ti species to the polymer−catalyst composite phase.

Heterogeneity in the Fragmentation of Ziegler Catalyst Particles during Ethylene Polymerization Quantified by Xray Nanotomography

“…In Figure S4 a comparison is given of the first and 362 nd PXCT projections, which are taken 22 hours of continuous scanning and therefore exposure to the X-ray beam apart. No significant beam-damage was observed in this work, whereas in our previous work we observed significant beam-damage most likely due to residual solvent molecules within the polyolefin phase [7]. It should be noted here that there is a 0.5° degree off-set between the two projections (0-180° and 180.5-360.5°).…”

“…Despite the FSC estimated 3-D spatial resolution of 217 nm for the Ti XRF data-set assessment of the state of fragmentation within each catalyst particle didn't work as done in our previous work where the system investigated was at a higher polymerization yield and therefore exhibited more pronounced and stronger catalyst support fragmentation [7]. In Figure S9 a comparison of the central slice of the Ti XRF and PXCT data-sets is given as well as a zoom-in for one randomly selected particle.…”

“…The sample loading inside a polyimide capillary was similar to that performed in our previous work and all actions were performed inside a N 2 -filled glovebox operating at <0.3 ppm H 2 O and <1 ppm O 2 unless otherwise stated [7]. Polyimide capillaries obtained from MicroLumen with an inside diameter of 120 µm and wall thickness of 10 µm were used.…”

Principles of Different X-ray Phase-Contrast Imaging: A Review

“…This achievement may permit the chemical imaging of reaction tracking areas at the nanoscale in solid materials [73]. In 2020, the fragmentation behavior of polyolefin catalysts was visualized in 3-D for the first time with this method by Bossers et al [74]. In the same year, Polo et al imaged three-dimensional fragments of the petioles of wild type and C4H lignin mutant Arabidopsis thaliana plants using synchrotron cryoptychography.…”

An ultrahigh-resolution soft x-ray microscope for quantitative analysis of chemically heterogeneous nanomaterials

“…Ptychographic microscopes are developed by researchers at most synchrotrons around the world, and they are applied to a variety of scientific problems (15)(16)(17). However, routine use is still challenging because of the high-speed diffraction data acquisition and analysis pipeline, which is needed for convenient operation.…”