Direct Transformation of Silica from Natural Resources to Form Tetramethoxysilane

Abstract

A simple and practical method for direct synthesis of tetramethoxysilane (TMOS) from silica (SiO2) and methanol was achieved using a base catalyst and acetal as a dehydrant under carbon dioxide (CO2). The production of TMOS was strongly influenced by the kind of the acetal used, with 2,2-dimethoxypropane identified as the most effective dehydrant. We observed that the acetal used enabled the production of a high yield of dimethyl carbonate (DMC), which promoted the TMOS production. DMC is an intermediate product from the reaction of CO2 and methanol, which supported the SiO2 depolymerization process. When the reaction is conducted with 2,2-dimethoxypropane at 260 °C for 24 h, TMOS can be produced in up to 59% yield. For practical applications, the TMOS synthesis has been developed on a 250 mL and 1 L-scale reaction with constant yield (>50%) from various silica resources.

From SiO2 to Alkoxysilanes for the Synthesis of Useful Chemicals

“…Another acetal, 1,1-dimethoxycylohexane, afforded a lower TMOS yield of 36% (entry 4). 19 These results indicated that both CO 2 and the acetals were important for optimizing the TMOS yield. As a dehydrating agent, the acetal was responsible for DMC (dimethyl carbonate) formation and accelerated TMOS production ( Figure 7 ).…”

“…The use of excess acetal (25 mmol) significantly increased the TMOS yield to 83% (entry 3). Another acetal, 1,1-dimethoxycylohexane, afforded a lower TMOS yield of 36% (entry 4) . These results indicated that both CO 2 and the acetals were important for optimizing the TMOS yield.…”

“…Recently, our group has developed a direct synthesis of TROS from SiO 2 and alcohols. − This method appears promising because of its nontoxicity and the use of abundant alcohols. However, SiO 2 is thermodynamically stable, and the H 2 O byproduct easily reacts with the TROS product to form oligomeric or polymeric SiO 2 .…”

Spirocyclic alkoxysilane synthesized from rice straw ash for preparation of eco-friendly hydrophobic silicone coatings

“…At the same time, silicon-based materials play an important role in the field of high technology. The silicon chemical industry is a high consumer of energy (Putro et al 2020) and high generator of pollution (Furgal and Lenora 2019). Thus, it is important to find green and environmentally friendly routes for the synthesis of silicon-based materials.…”

Biobased Silicon and Biobased Silica: Two Production Routes Whose Time has Come**

“…For example, it is now possible to depolymerize silica using catalytic base in the presence of alcohols especially diols such as ethylene glycol or hexylene glycol to afford in the later case distillable alkoxysilanes (e. g. spirosiloxanes, SP) in one-pot at low temperature. [12][13][14] Currently obtained by reacting SiCl 4 with alcohols, tetraalkoxysilanes such as tetraethoxysilane (TEOS) and tetramethoxysilane (TMOS) are key precursors to silicabased sol-gel materials. Their direct synthesis at lower cost from biobased silica or replacement with SP would open-up sol-gel applications that remained elusive (e. g. aerogels) due to the high cost of said precursors.…”