ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

One-step synthesis of solid sulfonic acid catalyst and its application in the acetalization of glycerol: crystal structure of cis-5-hydroxy-2-phenyl-1,3-dioxane trimer

Farook Adam, Muazu Samaila Batagarawa, Kasim Mohammed Hello, and Salih S. Al-Juaid

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia

E-mail: farook@usm.my

Abstract: A one-pot method was employed to immobilize sulfonic acid onto silica obtained from rice husk ash using 3-(mercaptopropyl)trimethoxysilane to form a solid catalyst denoted as RHASO₃H. BET measurements of the catalyst showed the surface area to be 340 m² g⁻¹ with the average pore volume of 0.24 mL g⁻¹ and the pore diameter of 2.9 nm. Acidity test of cation exchange capacity and pyridine adsorption studies revealed the presence of Brønsted acid sites on the catalyst surface. The catalyst was used in the acetalization reaction of glycerol with benzaldehyde. Under optimized conditions, the reaction showed the maximum conversion of 78 % after 8 h with 67 % selectivity towards the five membered ring isomer. Variation in the glycerol concentration had a significant effect on the reactants conversion. A single crystal X-ray study of one of the products proved the existence of a unique trimer formed by hydrogen bonding by the six-membered cis-isomer. The catalyst was several times recycled without any loss of its catalytic activity.

Keywords: surface modification – sol-gel – sulfonic acid – glycerol – acetalization – cis-5-hydroxy-2-phenyl-1,3-dioxane

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-012-0203-x

Chemical Papers 66 (11) 1048–1058 (2012)