The Quantity of Reduced Nickel in Synthetic Takovite: Effects of Preparation Conditions and Calcination Temperature*

Mark K. Titulaer1, J. Ben H. Jansen2 and John W. Geus3
1 Department of Geochemistry, Institute for Earth Sciences, University of Utrecht Budapestlaan 4, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands
2 Bowagemi B.V., Prinses Beatrixlaan 20, 3972 AN Driebergen
3 Department of Inorganic Chemistry, University of Utrecht Sorbonnelaan 16, P.O. Box 80.083, 3508 TB Utrecht, The Netherlands
* This paper is a contribution of the Debye Institute, University of Utrecht, The Netherlands.

Abstract: Takovite, Ni6Al2(OH)16CO3·5H2O, with molar Ni/Al ratios of 2.5 and 3 is prepared by precipitation at pH levels of 7 and 10, periods of reaction of 3 and 20 hr, and calcination temperatures varying between 120° and 853°C. The quantity of reduced Ni is determined as a function of the calcination temperature, and the solid phases remaining after reduction are determined with XRD. The Ni/Al ratio, pH of precipitation, and calcination temperature are important preparation conditions. A precursor of a Ni/Al ratio of 2.5 precipitated at a pH-level of 10 exhibits on reduction metallic Ni particles of about 15 nm irrespective of the drying or calcination temperature. After reduction, a considerable amount of NaAlO2 is present. Metallic Ni particles of 6 nm are present in a reduced precursor of Ni/Al ratio of 2.5 precipitated at a pH-level of 7. The size of the Ni particles present in a reduced precursor of Ni/Al ratio of 3 precipitated at a pH-level of 10 rises from 4–8 nm to 16 nm after calcination at temperatures increasing from 120° to 853°C. The last precursor contains much less sodium, and shows after reduction a disordered NiO phase containing some alumina. Especially, the takovite with the molar Ni/Al ratio of 2.5, thoroughly washed to remove Na, and calcined at T ≤ 260°C before reduction of Ni provides a promising catalyst for the production of hydrogen-carbon monoxide flows out of methane and steam.

Key Words: Calcination • Nickel particle size • Takovite • Temperature programmed reduction

Clays and Clay Minerals; June 1994 v. 42; no. 3; p. 249-258; DOI: 10.1346/CCMN.1994.0420303
© 1994, The Clay Minerals Society
Clay Minerals Society (www.clays.org)