Preparation and Characterization of Amorphous Silica and Metal Modified Silica Catalyst from Rice Husk

Abstract

Rice husk ash, an agricultural waste material obtained from rice mills. It is a low density material that causes disposal problems but is rich in amorphous chemically reactive silica (>90% ash). Alkaline extraction of Pyrolysed rice husk ash followed by acid precipitation led to the production of amorphous silica having high surface area and very less mineral contaminants. In the present work, pyrolysis of controlled burning conditions and later leaching alkali is used to produce amorphous silica. After pretreatment of rice husk with different acids were Pyrolysed at different temperatures in a furnace and then leached with alkali NaOH. The obtained sodium silicate was titrated with HCl to produce silica. Metal modified silica was also prepared by incorporating the metals chromium and copper into silica matrix. This leads to the production of metal modified silica catalyst. Both the catalysts were sent for characterization of BET, SEM, EDX and XRD analysis. The amorphous nature of silica was confirmed by XRD analysis. The average surface area and total pore volume were obtained by using N2 adsorption-desorption calculations by BET analysis. High surface areas were obtained. The amorphous nature and percentage of silica were determined from SEM and EDX analysis. Oxidation of styrene was performed by using metal modified catalyst at different pH. The products formed were analysed by GC-MS. A better conversation was found at lower pH.