Hydroisomerisation of C6-C7 n-alkanes over Pt loaded zirconium containing Al-MCM-41 molecular sieves

Mesoporous Al-MCM-41 and zirconium containing Al-MCM-41 (Si/Zr ratio 200, 100 and 50) molecular sieves were hydrothermally synthesised. The low angle XRD patterns confirm the mesoporous nature of the materials. The higher d-spacing values of Zr-Al-MCM-41 molecular sieves than that of Al-MCM-41 indicate the incorporation of Zr in Al-MCM-41 framework. Further, the SEM picture of Zr-Al-MCM-41 indicates the formation of aggregates without regular shape and size. Also, the nitrogen adsorption studies reflect the mesoporous nature of the materials. The DRS spectrum confirm the presence of Zr in tetrahedral coordination in the framework. The n-hexane and n-heptane hydroisomerisation reactions were carried out over 0.3 wt% Pt loaded Al-MCM-41 and Zr-Al-MCM-41 molecular sieves. Zirconium containing catalysts always show higher activity in both reactions than Al-MCM-41 due to strong Bronsted acid sites strengthened by appropriately positioned Lewis acid sites. Further, the activity of the catalysts increased with increasing Zr content. Also, the Zr containing materials show higher selectivity towards the high octane multibranched isomers in both n-hexane and n-heptane hydriosomerisation than that of M-MCM-41. (C) 2004 Elsevier Inc. All rights reserved.