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

[Display omitted] • TMOS synthesis from SiO 2 materials and sc MeOH was developed in a flow reactor. • Both circulating flow and two-cascade continuous flow reactors were designed and used. • Molecular sieves 3 Å placed outside of a heated zone were applied to remote a released water. • The highest TMOS concentration was achieved for silica gel dissolution. • Equilibrium constant K eq of the reversible reaction was determined. An original method for direct synthesis of tetramethyl orthosilicate from SiO 2 raw minerals and supercritical methanol was developed for the first time in a flow mode. The process promoted by KOH was performed at 270 °C and 100 atm using 3 Å 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% SiO 2), quartz sand (97 wt% SiO 2), expanded perlite (73 wt% SiO 2) and vermiculite (38 wt% SiO 2) were tested as SiO 2 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. [ABSTRACT FROM AUTHOR]