Study of the Crystal Structure of CaO/SiO₂, MgO/SiO₂, and CaO–MgO/SiO₂ Catalysts

Andreas Venans Nahak (Department of Chemistry Education, Faculty of Teacher Training and Education, Universitas Nusa Cendana)
Kasimir Sarifudin (Department of Chemistry Education, Faculty of Teacher Training and Education, Universitas Nusa Cendana)
Lolita A. M Parera (Department of Chemistry Education, Faculty of Teacher Training and Education, Universitas Nusa Cendana)

Jurna Beta Kimia
Vol 6 No 1 (2026): Volume 6 Issue 1, May 2026

This study aims to analyze the crystal structure characteristics and phase composition of the CaO/SiO2, MgO/SiO2, and CaO-MgO/SiO2 catalysts, and to synthesize SiO2 from Ende Flores Natural Zeolite using the hydrothermal and sol-gel methods. CaO was synthesized from Kupang NTT hard water lime deposits, refluxed with HCl, and titrated with Na2CO3, then calcined at 1000 ºC to obtain CaO. MgO was synthesized from MgCO3 calcined at 800 °C. The synthesis of each type of catalyst, CaO/SiO2, MgO/SiO2, and CaO-MgO/SiO2, was carried out using the impregnation method. The XRD characterization results show that, in SiO2, the tridymite phase with a triclinic crystal structure is formed. CaO forms the Lime phase with a cubic crystal structure, while the MgO catalyst shows the Periclase phase and also has a cubic crystal structure. The CaO/SiO2 catalyst forms a single phase, namely Larnite (Ca2SiO4), with a monoclinic crystal structure. The MgO/SiO2 catalyst formed three phases, namely the dominant Periclase phase (MgO) with a cubic crystal structure, the Olivine phase (Mg2SiO4) with an orthorhombic crystal structure, and the Tridymite phase (SiO2) with a cubic crystal structure. The CaO-MgO/SiO2 catalyst forms two phases, namely the dominant phase Olivine (Mg2SiO4) with an orthorhombic crystal structure and the Portlandite phase (CaH2O2) with a trigonal crystal structure.