Avoiding Carbothermal Reduction: Distillation of Alkoxysilanes from Biogenic, Green, and Sustainable Sources

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 Simet, 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.Ohne Umweg: Die basekatalysierte Depolymerisation von SiO2 aus unterschiedlichen Quellen führt direkt zu destillierbaren Alkoxysilanen und bietet damit eine kostengünstige Route zu hochreinem Silikat und Verbindungen mit Si‐C‐Bindungen (siehe Schema). Die Alkoxysilane wurden entweder durch Behandlung mit EtOH und einer katalytischen Menge Säure in Si(OEt)4 oder in hochreines präzipitiertes oder pyrogenes Silikat umgewandelt.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137389/1/ange201506838.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137389/2/ange201506838_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137389/3/ange201506838-sup-0001-misc_information.pd