Conversion of Rice Husks to Chemical Compounds

Abstract

Rice husk (RH) was collected from a rice mill in central Sudan and was used as a dual source for silica and cellulose. Amorphous silica was extracted from rice husk ash (RHA) through chemical treatment with nitric acid(3M) and combustion. It was then used to extract amorphous silica through dissolution in aqueous alkali solutionNaOH (1M) and subsequent gelation in acidic medium following the sol-gel process. Pure cellulose was obtained from RH after complete removal of lignin and hemicellulose by treatment with strong alkaline solutionNaOH(1M) and bleaching with sodium hypochlorite solution. Silica sulfonic acid (ASO3H) was produced by impregnating the Chlorosulfonic acid with RHA amorphous silica, Silica Aluminate (AS) was produced by mixing equal amounts of sodium aluminate and sodium silicate. The extracted silica and cellulose as well as the produced ASO3H, AS solid acid were characterized with FT-IR, XRD, XRF and SEM-EDX. A 5% of 5-HMF was produced by a catalytic hydrolysis of extracted cellulose over ASO3H for 8hrs at 110°C in the presence of DMF as a solvent. Also 63% furfural was produced by a catalytic hydrolysis of xylose over (AS) for 5hrs at 110°C in the presence of water as a solvent. The process is very simple and appears to be economically attractive utilizing biomass usually regarded as wasteful material.