Saponite catalysts with systematically varied Mg/Ni ratio: synthesis, characterization, and catalysis

Abstract

A series of saponite catalysts having systematically varied Mg and Ni ratios in the clay framework (i.e. [Mg 6–0Ni 0–6]-saponites) were synthesized using the hydrothermal synthesis method. The synthesized saponite catalysts have similar XRD patterns, indicating that all of the Mg and/or Ni elements have been incorporated as Mg and Ni ions in the octahedral positions of the clay framework, respectively. The results of the isopropanol dehydration reaction show that the saponite containing only Ni (i.e. [Mg 0Ni 6]-saponite) was very active, while the other Mg-containing saponites (i.e. [Mg 1–6Ni 5–0]-saponite) were inactive. The results of the pyridine-adsorption FTIR further show that the [Mg 0Ni 6]-saponite has Bro̵nsted and Lewis acidic sites, while the [Mg 1–6Ni 5–0]-saponites have only Lewis acidic sites. The possible interaction between Mg and Ni ions in the octahedral positions of saponite catalysts and its influence on the catalytic activity of the catalysts is discussed in this paper.