Thermal stability, porosity, and catalytic activity of compound formed in a CaO-SiO2-Cu(NO3)2-H2O system

Abstract

This study examined the properties and catalytic activity of calcium silicate hydrates with copper oxide in detail. The hydrothermal method was employed to conduct the synthesis of the catalyst. The molar ratio of CaO/amorphous SiO2 = 1.5 was used. It was subsequently mixed with Cu(NO3)2 solution (c = 10 g Cu2+/dm3) to obtain the solution/solid ratio 10.0:1. A 16 h-long session of hydrothermal treatment was performed in unstirred suspensions at 175°C. Raw materials were found to react fully in the course of hydrothermal synthesis, and a mixture of copper oxide and semicrystalline calcium silicate hydrates was obtained. The results of in situ X-ray diffraction and thermal analysis showed that copper oxide was stable under all the experimental conditions, whereas calcium silicate hydrates recrystallized to calcium silicates at 800°C. During calcination, the synthetic mesoporous sample became non-porous, with a significantly high specific surface area compared to other calcium silicates. Propanol oxidation experiments showed that both synthetic and calcined samples are promising catalysts for VOC oxidation reactions. Six methods in total (FT-IR, STA, XRD, TEM, SEM, and BET) along with propanol oxidation experiments served to confirm the obtained results.