In Situ S K-Edge X-ray Absorption Spectroscopy for Understanding and Developing SO_x Storage Catalysts

Abstract

In situ S K-edge XANES experiments were carried out on second-generation SO(x)() trapping materials under oxidizing and reducing conditions. The experiments clearly show that the strong release of SO(2) under rich conditions at plug flow conditions is caused by the facilitated reduction of sulfite species on Pt. In the absence of Pt the sulfite species were stable under reducing conditions, while maintaining a similar total SO(2) uptake capacity. Thus, SO(x)() trapping materials without a noble metal are a clearly better option. The enhancing effect on the SO(x)() storage process of water present in the gas mixture is attributed to the formation of a higher sulfate fraction in the samples. The application of the in situ S K-edge XANES technique clearly reveals new information and insights on the behavior of the sulfur in the trapping process compared to that from the ex situ measurements and is therefore essential for designing new SO(x)() trapping materials.

Redox dynamics of sulphur with Ni/GDC anode during SOFC operation at mid- and low-range temperatures: An operando S K-edge XANES study

“…But, up to now, spectroscopic measurements with X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), or, Raman microspectroscopy either obtain information from SOFC anode surface in the presence of H 2 S, H 2 , and, possibly even heat, or ex-situ and under postmortem conditions [14,15,22,33]. The molecular structure of sulphur compounds has been studied with sulphur K-shell edge Xray absorption spectroscopy in various fields of application, particularly in relation to fossil fuels, such as sulphur in coal [34], sulphur in residual oil fly ash [35] and heterogeneous catalysis [36]. High temperature oxidation and reduction studies [34] and catalysis studies [36] have also been made recently with in-situ or operando sulphur XAS, for example.…”

“…The molecular structure of sulphur compounds has been studied with sulphur K-shell edge Xray absorption spectroscopy in various fields of application, particularly in relation to fossil fuels, such as sulphur in coal [34], sulphur in residual oil fly ash [35] and heterogeneous catalysis [36]. High temperature oxidation and reduction studies [34] and catalysis studies [36] have also been made recently with in-situ or operando sulphur XAS, for example. Sulphur as the ligand ion is also of interest in connection with metal ions [37] and could in future studies open up new opportunities for the understanding and quantification of electronic transport processes in SOFC anodes, where newly formed NieS compounds are subject to exchange interactions, in analogy to 3d metal oxides at SOFC cathodes, for example [38,39].…”

On the trapping of SOx on CaO–Al2O3-based novel high capacity sorbents

“…The XAFS experiments at the S K-edge were performed at the XAS beamline at Angstro¨mquelle Karlsruhe (ANKA). The samples were pressed into self supporting wafers and placed in the reaction chamber described by Dathe et al 21 All samples were measured in the fluorescence mode. The storage ring was operated at 2.5 GeV with an electron current between 100 and 200 mA.…”

X-ray spectroscopy for chemistry in the 2-4 keV energy regime at the XMaS beamline: ionic liquids, Rh and Pd catalysts in gas and liquid environments, and Cl contamination in γ-Al2O3

“…Developing methods (see, for instance, Tamenori, 2010Tamenori, , 2013Tamenori et al, 2011) or sample environment suitable for the study of any given process at these energies is therefore subject to considerably more constraints (both in terms of design and materials) than is the case at high energies. However, several examples exist for the study of gas-solid chemistry and catalysis (see, for example, van der Eerden et al., 2000;Hayter et al, 2002;Dathe et al, 2005;Nurk et al, 2013;Bolin et al, 2013;Kö nig et al, 2014) and studies using a liquid media (Brown et al, 2012;Fulton et al, 2012;Pin et al, 2013).…”

“…Developing methods (see, for instance, Tamenori, 2010Tamenori, , 2013Tamenori et al, 2011) or sample environment suitable for the study of any given process at these energies is therefore subject to considerably more constraints (both in terms of design and materials) than is the case at high energies. However, several examples exist for the study of gas-solid chemistry and catalysis (see, for example, van der Eerden et al., 2000;Hayter et al, 2002;Dathe et al, 2005;Nurk et al, 2013;Bolin et al, 2013;Kö nig et al, 2014) and studies using a liquid media (Brown et al, 2012;Fulton et al, 2012;Pin et al, 2013).The XMaS beamline at the ESRF was originally conceived as an instrument to study X-ray magnetic scattering (Paul et al, 1995;Brown et al, 2001) and is situated on the soft end of an ESRF dipole magnet (critical energy = 9.8 keV). At this time there was much interest in the scattering community for actinide magnetism (see, for example, Isaacs et al, 1989) and for resonant diffraction at the U M 5 absorption edge ($ 3.55 keV).…”