Avoiding Carbothermal Reduction: Distillation of Alkoxysilanes from Biogenic,Green, and Sustainable Sources |
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Authors: | Richard M Laine Joseph C Furgal Phi Doan David Pan Vera Popova Xingwen Zhang |
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Institution: | 1. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA;2. Department of Macromolecular Science and Engineering, University of Michigan, USA;3. Department of Chemistry, University of Michigan, USA;4. Mayaterials Inc, Ann Arbor, MI, USA;5. Department of Chemistry, Harbin Institute of Technology, Harbin, China |
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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 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. |
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Keywords: | depolymerization materials science silicon sustainable chemistry |
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