Impact of the Water Removal Method on Tetraethyl Orthosilicate Direct Synthesis: Experiment and Process Assessment

Abstract

A direct synthesis pathway of tetraethyl orthosilicate from silica and ethanol was recently proposed. Although this pathway has many advantages over the conventional one producing tetraethoxysilane (TEOS) from metallurgical silicon, its potential can be further increased by the effective removal of its byproducts. This study investigates the removal of the water byproduct, which reduces the TEOS product yield and enhances the loss of raw materials. Several inorganic dehydrating agents were examined under different conditions, on the basis of which a suitable TEOS synthesis process using the selected dehydrating agent was designed and its optimal conditions were determined. The feasibility of the designed process was evaluated in comparison with our previously reported process using a molecular sieve as a water adsorbent and the conventional process. The evaluation results confirmed that the CaO process is more economically competitive and environmentally friendlier, reducing 24% production cost and 40% greenhouse gas emissions of the conventional process.

From SiO2 to Alkoxysilanes for the Synthesis of Useful Chemicals

“…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 .…”

“…In the direct synthesis of TEOS via the reaction between SiO 2 and ethanol, the removal of water using dehydrating agents strongly influences the yields and economic and environmental implications . CaO was found to be the most effective dehydrating agent among various candidates, such as MS, CaCl 2 , MgSO 4 , and Na 2 SO 4 , which produced a TEOS yield of 76%.…”

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

“…[12] Key to shifting the equilibrium reaction in Eq. ( 9) is the presence in an upper autoclave of the molecular sieves promoting the reaction between silica and ethanol by adsorbing water molecules vaporized from the reaction mixture (without dehydrating agent, the TEOS yield is only 4 %), [26] minimizing formation of hexaethoxydisiloxane (Eq. ( 10)):…”

“…Research continued, and the Japan-based team eventually reported that the use of cheap and readily available CaO as dehydrating agent further enhances the economic viability of the process. [26] Together, the biobased routes to high-purity Si, SiO 2 and Si(OR) 4 entirely by-pass the need for Si MG derived by the carbothermal reduction of quartz, establishing a circular bioeconomic route to all the primary silicon compounds employed in the chemical industry. Indeed, also chloromethane, a key raw material for the silicone industry, reacted with elemental silicon in the Rochow-Müller "direct process" to form methylchlorosilanes, can be readily synthesized from alkoxysilanes TEOS or TMOS.…”

Influence of Different Treatments on the Structure and Conversion of Silicon Species in Rice Straw to Tetraethyl Orthosilicate (TEOS)

“…For example, R. Laine et al [17] used SiO 2 as starting material to react with excess ethylene glycol under the catalysis of a strong base to produce spirosilane firstly, which was then subjected to alcohol exchange to get TEOS. Similarly, N. Fukay et al [18,19] used strong bases and a significant amount of dehydrating agent to promote the reaction of SiO 2 with ethanol to get TEOS. These studies have greatly enriched and advanced the methods for the preparation of alkoxysilanes.…”