Physicochemical properties of acid/base activated kaolinite modified with oxalic acid-functionalized nickel nanoparticles

Abstract The influence of HCl and NaOH activation on kaolinite to synthesize acid and base activated kaolinite (AAK and BAK) as catalyst supports for nickel oxalate precursor synthesized via oxalic acid functionalization (OAF) was explored in the study. For comparison, another catalyst was synthesized via incorporation of nickel nitrate salt into the activated supports and the catalysts were calcined at 700 °C. The characterization results confirmed that while acid treatment reduced the crystallinity of Kaol, base treatment transformed Kaol into sodalite-zeolite according to the XRD and FESEM results. The Ni nanoparticle (NP) sizes on nickel supported on AAK (Ni/AAK-700) were nine times larger than Ni particle sizes on nickel supported on BAK (Ni/BAK-700) which itself is 1.42 times smaller than the Ni NP in oxalic acid-functionalized Ni supported on BAK (NiOL/BAK-700). The XPS Ni2p peak of Ni/BAK-700 was observed to shift towards higher binding energy signifying a higher degree of metal-support interaction with increased H2 reduction difficulty. A reversed phenomenon was observed for NiOL/BAK-700. The samples basicity followed the order Ni/BAK-700 > NiOL/BAK-700 > NiOL/BAK-800 > Ni/AAK-700, while the acidity followed the reverse. These results provide insights into modified Kaol supported Ni catalysis for various applications based on the required physicochemical properties.