Abstract
For the first time, we report the use of zirconyl nitrate solution as a pillaring agent. Ca-montmorillonite was exchanged with zirconium species at different conditions and Zr (mmole)/clay ratios, then calcined at different temperatures to obtain stable Zr-pillared clays. These materials have been investigated by X-ray diffraction, nitrogen adsorption, and pyridine desorption. The catalytic performance towards the isomerization of n-heptane was tested in a temperature range of 250-350°C. The results show that the properties of the Zr pillared clays were affected by the aging temperature of the starting Zr solution after exchange reaction. Sample prepared at room temperature exhibited lower surface areas and smaller interlayer distance compared to that prepared at 80°C. These differences are attributed to the nature of zirconium species polymerized in the pillaring solution. The obtained pillared clays exhibited both Brönsted and Lewis acid sites, however Lewis acid sites were mainly detected at temperatures above 200°C. This Lewis acidic character influenced the n-heptane conversion, and mainly cracking products were obtained, with yield of about 10% at 300°C for some isomers.
