Evaluation of scale-up strategies for the batch synthesis of dense and hollow mesoporous silica microspheres

Despite the wide application interest in mesoporous silica micro- and nano-particles and a number of synthesis routes reported in the literature, the question of chemical engineering scale-up of the synthetic routes has rarely been addressed. The present work reports the results of an experimental and computational study of batch scale-up by a factor of 40× in the specific case of two types of dense and hollow mesoporous silica microparticles produced by the hydrolysis of tetraethoxysilane (TEOS) using a CTAB surfactant template. Volume and concentration based scale-up approaches have been investigated and systematically compared using a similarity index that included parameters related to the particle size distribution (d10, d50, d90) and pore structure (mean pore diameter, specific surface area, total pore volume, sorption hysteresis loop). The particle size distribution was found to be dependent mainly on the hydrodynamic conditions, expressed by the homogenization time, while the pore structure and the overall yield of the process were found to depend mainly on the CTAB/TEOS ratio. Overall, successful scale-up criteria in both volume and concentration based approaches have been identified.