SBIR Phase I: Production of alkoxysilanes directly from biogenic silica

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The broader impact/commercial potential of this Small Business Innovation Research Phase I project is that it offers the potential for a new process technology to produce silicon using a sustainable, natural resource as the starting material. Currently, all silicon used in solar cells and computer chips, and all silicon used in the manufacture of silicon containing chemicals including silicone rubbers, oils, lubricants and fumed silica (paints, paper) etc. is produced in an energy, equipment and CO2-intensive process. Biogenic silica includes diatomaceous earth and many kinds of agricultural waste including rice hull ash, inorganic waste from bioethanol production, corn stover, and wheat chaff. The objectives of this project are to develop economical routes from these silica sources to high purity, high value silica products at significantly lower cost than currently available by using a green and sustainable technology. Key markets include electronic, optical, and photonic applications, specialty chemicals, and consumer products. The technical objectives of this Phase I project are to successfully depolymerize biogenic silicas at temperatures ¡Ü 200¡ãC to produce distillable alkoxysilanes. The primary silica source is rice hull ash (RHA), a sustainable, heavy metal free, silica rich agricultural waste. This process uses catalytic base to dissolved RHA silica in antifreeze at ¡Ö 200¡ãC followed by exchange with alcohol to produce alkoxysilanes. In contrast, traditional alkoxysilanes are made from silicon metal produced by carbothermal reduction of silica with carbon at 1900 ¡ãC in an electric arc furnace; a high energy, capital equipment and CO2 intensive process. A further advantage to this process is that the silica depleted RHA offers direct access to high purity (99.9999 %) photovoltaic grade silicon at multi-kg/day scales. If successful, the proposed project could change how high purity alkoxysilanes, precipitated silica, and fumed silica are produced as multiple RHA sources are available worldwide. The alkoxysilane products can be distilled to very high purity at very low cost compared to the same product made from Silicon metal. The initial goal is to produce tetraethoxysilane to compete against Silicon metal derived product and move thereafter to high purity precipitated silica for electronic and optical products applications.