title: Avoiding Carbothermal Reduction: Distillation of Alkoxysilanes from Biogenic, Green, and Sustainable Sources.
abstract: The direct depolymerization of SiO2 to distillable alkoxysilanes has been explored repeatedly without success for 85 years as an alternative to carbothermal reduction (1900 °C) to Si(met) , followed by treatment with ROH. We report herein the base-catalyzed depolymerization of SiO2 with diols to form distillable spirocyclic alkoxysilanes and Si(OEt)4. Thus, 2-methyl-2,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, or ethylene glycol (EGH2) react with silica sources, such as rice hull ash, in the presence of NaOH (10%) to form H2O and distillable spirocyclic alkoxysilanes [bis(2-methyl-2,4-pentanediolato) silicate, bis(2,2,4-trimethyl-1,3-pentanediolato) silicate or Si(eg)2 polymer with 5-98% conversion, as governed by surface area/crystallinity. Si(eg)2 or bis(2-methyl-2,4-pentanediolato) silicate reacted with EtOH and catalytic acid to give Si(OEt)4 in 60% yield, thus providing inexpensive routes to high-purity precipitated or fumed silica and compounds with single Si-C bonds.
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109-2136, USA. talsdad@umich.edu.|Department of Macromolecular Science and Engineering, University of Michigan, USA. talsdad@umich.edu.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Laine
authors.affiliation: Department of Chemistry, University of Michigan, USA.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Furgal
authors.affiliation: Department of Chemistry, University of Michigan, USA.
authors.forename: Phi
authors.initials: P
authors.lastname: Doan
authors.affiliation: Department of Macromolecular Science and Engineering, University of Michigan, USA.
authors.forename: David
authors.initials: D
authors.lastname: Pan
authors.affiliation: Mayaterials Inc, Ann Arbor, MI, 48108, USA.
authors.forename: Vera
authors.initials: V
authors.lastname: Popova
authors.affiliation: Department of Chemistry, Harbin Institute of Technology, Harbin, 150001, China.
authors.forename: Xingwen
authors.initials: X
authors.lastname: Zhang
keywords: depolymerization; materials science; silicon; sustainable chemistry