title: Escaping the Tyranny of Carbothermal Reduction: Fumed Silica from Sustainable, Green Sources without First Having to Make SiCl4.
abstract: Fumed silica is produced in 1000 tons per year quantities by combusting SiCl4 in H2 /O2 flames. Given that both SiCl4 and combustion byproduct HCl are corrosive, toxic and polluting, this route to fumed silica requires extensive safeguards that may be obviated if an alternate route were found. Silica, including rice hull ash (RHA) can be directly depolymerized using hindered diols to generate distillable spirocyclic alkoxysilanes or Si(OEt)4 . We report here the use of liquid-feed flame spray pyrolysis (LF-FSP) to combust the aforementioned precursors to produce fumed silica very similar to SiCl4 -derived products. The resulting powders are amorphous, necked, <50 nm average particle sizes, with specific surface areas (SSAs) of 140-230 m(2)  g(-1) . The LF-FSP approach does not require the containment constraints of the SiCl4 process and given that the RHA silica source is produced in million ton per year quantities worldwide, the reported approach represents a sustainable, green and potentially lower-cost alternative.
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109-2136, USA.
authors.forename: Eongyu
authors.initials: E
authors.lastname: Yi
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109-2136, USA.
authors.forename: Clare E
authors.initials: CE
authors.lastname: Hyde
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109-2136, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Sun
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109-2136, USA. talsdad@umich.edu.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Laine
keywords: flame spray pyrolysis; fumed silica; green chemistry; rice hull ash; spirocyclic alkoxysilanes