Promotion of the Water‐Gas‐Shift Reaction by Nickel Hydroxyl Species in Partially Reduced Nickel‐Containing Phyllosilicate Catalysts

Abstract

The role of surface hydroxyl species generated by partially reduced Ni‐containing phyllosilicate structures (Ni/SiO2P) in promoting the water‐gas‐shift (WGS) reaction and methane suppression was investigated. To analyze the effect of the surface hydroxyl species, Ni/SiO2P catalysts reduced at various temperatures were employed. All the Ni/SiO2P catalysts showed enhanced catalytic performances and methane suppression compared to the conventional Ni/SiO2 catalyst. As revealed by diffuse‐reflectance infrared Fourier transform spectroscopy (DRIFTS), methane suppression could be attributed to the inhibition of the formation of nickel subcarbonyl species, and the promotion of WGS activity was attributed to the involvement of surface hydroxyl species (Ni−OH, 3626 cm−1, and Si−OH, 3740 cm−1). The Ni/SiO2P catalyst reduced at 600 °C showed exceptionally superior performance to the other catalysts in the water‐gas‐shift reaction in terms of turnover frequency (2.79 s−1) and hydrogen formation rates (492.63 μmol H2 g−1 s−1) at 375 °C.

Sandwich‐Like Silica@Ni@Silica Multicore–Shell Catalyst for the Low‐Temperature Dry Reforming of Methane: Confinement Effect Against Carbon Formation

“…It has been reported that the crystal structure of NiPS is easily affected by the preparation and calcination environment . Previously, it was shown to be common that NiPS prepared by the same ammonia evaporation method showed different XRD patterns . In our case, from the TEM and XRD results, it can be concluded that NiO and NiPS coexist over the surface of the silica nanospheres.…”

“…As the temperature increases, the intensity of the CH 4 peak decreases and that of the gas‐phase CO peaks increases clearly, which indicates the increasing conversion. −OH peaks at =3500–3800 cm −1 are also observed, which come from the unreduced NiPS structure . Furthermore, several peaks can be seen at =1400–1650 cm −1 , which are attributed commonly to carbonate species .…”

“…After that, we used the residual ammonia in the mixture to incorporate the Ni salt directly and obtained NiPS supported on silica by ammonia evaporation. Each silica nanosphere is surrounded by a number of needle‐like branches, which are regarded as NiPS (Figure a) . We performed XRD, and the results are shown in (Figure ), however, we cannot see significant peaks for the NiPS phase.…”

Nickel‐based Catalysts for High‐temperature Water Gas Shift Reaction‐Methane Suppression

“…The methane suppression behavior for aforementioned systems is mainly due to changes in the compositions of active metals. Recently, Kawi's group has reported Ni and Ni−Cu metals supported over SiO 2 support for HT‐WGS reaction ,,. In these works the amount of methane formation is significant.…”

“…The better WGS performance for this system is mainly attributed to the formation of Ni δ− −O v −Ti 3+ interface site, which provide the necessary dual‐active‐site required for WGS reaction. Similarly, recently our group has reported Ni‐phyllosilicate based catalysts for HT‐WGS reaction ,. In this kind of catalytic systems formation of bulk Ni particles can be minimized by embedding Ni with in the matrix of SiO 2 .…”