Synthesis, Characterization And Catalytic Activity Of Transition Metal Complexes Of Ascorbic Acid Encapsulated In Fly Ash Based Zeolite

Abstract

A new route for the utilization of fly ash has been formulated. X-type zeolite has been synthesized from fly ash by alkali fusion followed by hydrothermal treatment. Ascorbic acid was used as a ligand for the synthesis of metal complexes of copper, nickel and vanadium encapsulated in the super cages of fly ash based zeolite (FAZ) by flexible ligand method and characterized by FTIR, XRD, Atomic Absorption Spectrometry (AAS), Ultra Violet–Visible spectroscopy and Thermo gravimetric analysis (TGA). The additional peaks corresponding to that of the complex have been observed which confirms the loading of the metal complexes in the zeolite cavities. The shifting of C=C-O stretching frequency found at 682 cm -1 in ascorbic acid to 601 cm -1 confirms the co-ordination of the ligand resulting in the formation of the metal complex. The thermo grams show deflation in three regions corresponding to the loss of the intra-zeolite water, metal complexes and the structural –OH group respectively. The catalytic activity of these complexes towards the liquid phase hydroxylation of phenol with hydrogen peroxide has been established. The extent of the reaction as a function of time has been investigated. Vanadium-ascorbate complex had the highest conversion of 78%. The product was identified as hydroquinol by GC-MS. This study reports a highly attractive catalytic method for the preparation of hydroquinol from phenol using aqueous hydrogen peroxide as the oxidising agent which is industrially significant.