New Process for the Preparation of Monodispersed, Spherical Silica Particles

A new method is presented for preparing highly monodispersed silica particles using a two-stage semibatch/batch hydrolysis reaction of Si(OC₂H₅)₄. The slower rate of hydrolysis of the tetraethylorthosilicate (TEOS) that occurred during the semibatch process resulted in larger silica particles with a higher yield and narrower size distribution. This was in direct contrast to the batch process. In addition, the ability of four different mixed processes to produce silica particles with good packing density, narrower particle-size distribution, and higher yield were evaluated. These were batch/batch (B-B), batch/semibatch (B-S), semibatch/batch (S-B), and semibatch/semibatch (S-S) processes. The S-S system produced the largest particles with the highest yields. The size of the silica particles obtained by the S-B method decreased with increasing reaction time, while the particles obtained by the B-S process had the best particle-size distribution and packing density. In conclusion, a mixed batch/semibatch system was the best way to produce an extremely narrow particle-size distribution and a good packing density.