Effects of calcining conditions of kaolinite on pore structures of mesoporous materials prepared by the selective leaching of calcined kaolinite

Abstract

This paper describes the effects of calcining conditions of kaolinite on pore structures of the porous materials obtained from the selective leaching of calcined kaolinite using KOH solution. Mesoporous γ-Al₂O₃ was the predominant crystalline phase in the samples calcined in the temperature range between 950°C and 1050°C for 24 h. The mean specific surface area of these samples was approximately 250 m² · g⁻¹ and the mean total pore volume was approximately 0.8 ml · g⁻¹. The pore size distribution curves of these samples showed a sharp peak at around 2–3 nm pore radius. This peak was sharper for the sample calcined at 1000°C for 24 h. On the other hand, the pore sizes of the sample calcined at 1100°C for 24 h increased abruptly to 10–20 nm and this change corresponded to the formation of mullite in the sample. The pore sizes of the samples calcined at 1100°C varied with calcining time. The specific surface area and total pore volume decreased, the longer the calcining time of the samples, and this was correlated with an increase in the amount of mullite in the samples.