Porous carbon-silica composites and carbon materials from rice husk: Production technology, texture, and dispersity

Abstract

A method based on carbonization in a fluidizedbed catalytic reactor is suggested for utilization of rice husks, which are hardtorecycle waste from paddy production. The bottom ash resulting from car� bonization at 465-600°C is a carbon-silica nanocomposite (C/SiO 2 ) with a SiO 2 content of 58.7-81.8 wt % and a specific surface area of SBET = 152-232 m 2 /g. Leaching of SiO2 with hydrofluoric acid yields porous carbon materials with a specific surface area of 165-494 m 2 /g and a SiO2 content of <1%. These materials have been characterized by smallangle Xray scatte ring (SAXS), transmission electron microscopy, and Xray diffraction. Particle size data for SiO 2 in the carbon-silica nanocomposite have been obtained for the first time. As the carbonization temperature is raised from 465 to 600°C, the average particle size of silica increases from 5.5 to 8.1 nm. Development of the SAXS procedure for determining the size of silica particles in the carbon matrix would provide a promising tool for knowingly designing porous carbon materials with preset properties. The carbonization of rice husks in a fluidized catalyst bed is among the most promising methods of their conversion into C/SiO2 nanocomposites and porous carbon materials with the use of tem� plate synthesis approaches.