One-pot synthesis of TMOS from SiO2-enriched minerals and supercritical MeOH in a flow reactor

An original method for direct synthesis of tetramethyl orthosilicate from SiO2 raw minerals and supercritical methanol was developed for the first time in a flow mode. The process promoted by KOH was performed at 270 degrees C and 100 atm using 3 angstrom zeolite molecular sieves to shift the reversible reaction toward TMOS formation by removing released water. The equilibrium constant K-eq of the reaction was determined as 0.839E-08. Silica gel (100 wt% SiO2), quartz sand (97 wt% SiO2), expanded perlite (73 wt% SiO2) and vermiculite (38 wt% SiO2) were tested as SiO2 minerals. The highest equilibrium concentration of TMOS equal to 20.4 g/L was achieved for silica gel that can be increased using larger amount of water adsorbent.

Automated summary

A new method for direct synthesis of tetramethyl orthosilicate from SiO2 raw minerals and supercritical methanol was developed, with experimental conditions and equilibrium constant determined. Different SiO2 minerals were tested, with silica gel showing the highest equilibrium concentration of TMOS that can be increased using more water adsorbent.