The microstructures of promoted RANEY® nickel alloys and catalysts
4 affiliations
- 1School of Chemical Engineering, Purdue University West Lafayette IN 47907 USA
- 2DuPont Wilmington DE 19803 USA
- 3School of Materials Engineering, Purdue University West Lafayette IN 47907 USA
- 4Electron Microscopy Center, Purdue University West Lafayette IN 47907 USA
Abstract
RANEY® nickel catalysts are widely used in both academia and industry to hydrogenate nitro compounds, carbonyls, alkenes, alkynes, nitriles, and vegetable oils. However, there has been a gap in knowledge concerning the microstructures of these materials, particularly when they are promoted with Fe and/or Cr. In this work, we studied the following RANEY® nickel alloys and catalysts: (i) unpromoted, (ii) multiple levels of Fe promotion, (iii) multiple levels of Cr promotion, and (iv) doubly-promoted with Fe and Cr. Microstructures and phase compositions of initial alloys were characterized using backscattered scanning electron microscopy (SEM), electron microprobe, optical microscopy, and X-ray diffraction, which showed the microstructure is composed of several phases: Al3Ni2, Al3Ni, promoter-rich phase(s) (which are absent in the unpromoted alloy), and a eutectic phase. In these alloys, the Fe and Cr promoters concentrated into promoter-rich phases, and we report the compositions of these phases. After crushing the alloys into powder and leaching in aqueous sodium hydroxide, the catalysts were washed and characterized. Nitrogen adsorption at 77 K yielded each catalyst's total surface area and pore size distribution. Carbon monoxide and hydrogen gas adsorption yielded each catalyst's metallic surface area. For some catalysts, bulk elemental composition was quantified using atomic absorption spectroscopy, and the surface compositions and oxidation states were studied using X-ray photoelectron spectroscopy (XPS). XPS results showed that Cr is oxidized to Cr(+III) during the leaching procedure to form a compound that increases the total surface area (while having negligible effect on the metallic surface area) and also leads to smaller pore diameters.
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BibTeX
@article{manz2026microstructures,
title = {{The microstructures of promoted RANEY® nickel alloys and catalysts}},
author = {Thomas A. Manz and Seqwana T. Pryor and Kevin P. Trumble and Zhufang Liu and David R. Gaskell and Dave Roberts and Carle Hager and Sourav K. Sengupta and Theodore A. Koch and W. Nicholas Delgass},
journal = {RSC Advances},
year = {2026},
month = nov,
doi = {10.1039/d6ra05868j},
url = {https://doi.org/10.1039/d6ra05868j},
note = {CC BY 3.0},
}
RIS
TY - JOUR
TI - The microstructures of promoted RANEY® nickel alloys and catalysts
AU - Thomas A. Manz
AU - Seqwana T. Pryor
AU - Kevin P. Trumble
AU - Zhufang Liu
AU - David R. Gaskell
AU - Dave Roberts
AU - Carle Hager
AU - Sourav K. Sengupta
AU - Theodore A. Koch
AU - W. Nicholas Delgass
PY - 2026
DA - 2026/11/04
JO - RSC Advances
DO - 10.1039/d6ra05868j
UR - https://doi.org/10.1039/d6ra05868j
AB - RANEY® nickel catalysts are widely used in both academia and industry to hydrogenate nitro compounds, carbonyls, alkenes, alkynes, nitriles, and vegetable oils. However, there has been a gap in knowledge concerning the microstructures of these materials, particularly when they are promoted with Fe and/or Cr. In this work, we studied the following RANEY® nickel alloys and catalysts: (i) unpromoted, (ii) multiple levels of Fe promotion, (iii) multiple levels of Cr promotion, and (iv) doubly-promoted with Fe and Cr. Microstructures and phase compositions of initial alloys were characterized using backscattered scanning electron microscopy (SEM), electron microprobe, optical microscopy, and X-ray diffraction, which showed the microstructure is composed of several phases: Al3Ni2, Al3Ni, promoter-rich phase(s) (which are absent in the unpromoted alloy), and a eutectic phase. In these alloys, the Fe and Cr promoters concentrated into promoter-rich phases, and we report the compositions of these phases. After crushing the alloys into powder and leaching in aqueous sodium hydroxide, the catalysts were washed and characterized. Nitrogen adsorption at 77 K yielded each catalyst's total surface area and pore size distribution. Carbon monoxide and hydrogen gas adsorption yielded each catalyst's metallic surface area. For some catalysts, bulk elemental composition was quantified using atomic absorption spectroscopy, and the surface compositions and oxidation states were studied using X-ray photoelectron spectroscopy (XPS). XPS results showed that Cr is oxidized to Cr(+III) during the leaching procedure to form a compound that increases the total surface area (while having negligible effect on the metallic surface area) and also leads to smaller pore diameters.
SN - 2046-2069
ER -