X-ray physico-chemical imaging during activation of cobalt-based Fischer–Tropsch synthesis catalysts

Abstract

The imaging of catalysts and other functional materials under reaction conditions has advanced significantly in recent years. The combination of the computed tomography (CT) approach with methods such as X-ray diffraction (XRD), X-ray fluorescence (XRF) and X-ray absorption near-edge spectroscopy (XANES) now enables local chemical and physical state information to be extracted from within the interiors of intact materials which are, by accident or design, inhomogeneous. In this work, we follow the phase evolution during the initial reduction step(s) to form Co metal, for Co-containing particles employed as Fischer–Tropsch synthesis (FTS) catalysts; firstly, working at small length scales (approx. micrometre spatial resolution), a combination of sample size and density allows for transmission of comparatively low energy signals enabling the recording of ‘multimodal’ tomography, i.e. simultaneous XRF–CT, XANES–CT and XRD–CT. Subsequently, we show high-energy XRD–CT can be employed to reveal extent of reduction and uniformity of crystallite size on millimetre-sized TiO2 trilobes. In both studies, the CoO phase is seen to persist or else evolve under particular operating conditions and we speculate as to why this is observed.This article is part of a discussion meeting issue ‘Providing sustainable catalytic solutions for a rapidly changing world’.

5D operando tomographic diffraction imaging of a catalyst bed

“…4 are a purely temporal phenomenon (Supplementary Figures 13 – 15 and accompanying text). The retardation in the full reduction of the Ni–O and Ni–Al–O species could be due to the formation/presence of water produced from the formation of metallic Ni closer to the reactor inlet 19 , 23 .

Fig.

…”

Preparation of isolated Co3O4and fcc-Co crystallites in the nanometre range employing exfoliated graphite as novel support material

“…7b), which is in line with literature. 83,[85][86][87][88] Reduction of the 4.9 nm Co 3 O 4 nanoparticles in sample Co_4.9/EG was conducted at 350 C with a 5 h holding time. The rst reduction step to CoO was observed at 245 C (Fig.…”

Exploring cycling induced crystallographic change in NMC with X-ray diffraction computed tomography

“…Over the last decade, the potential of XRD-CT as a characterization tool has been realized, especially for functional materials, such as heterogeneous catalysts and fuel cells. [40][41][42][43][44] The technique has also been used to characterize different aspects of battery materials. [45][46][47][48][49][50] Jensen et al have used the technique to single out individual elements of a commercial Li-ion coin cell and nickel metal hydride AAA battery.…”