Production of MCM-41 nanoparticles with control of particle size and structural properties: optimizing operationalconditions during scale-up.

Abstract

The synthesis of MCM-41mesoporous silica nanoparticles (MSNs) of controlled sizes and porous structure has been performed at laboratory and pilot plant scales. Firstly, the effects of the main operating conditions (TEOS addition rate, nanoparticle maturation time, temperature, and CTAB concentration) on the synthesis at laboratory scale (1 L round-bottom flask) were studied via a Taguchi experimental design. Subsequently, a profound one-by-one study of the effects of temperature and CTAB to TEOS molar ratio allowed to set these variables in 60 ºC and 8, avoiding particle enlargement and deformation of the internal structure. The final runs were performed at pilot plant scale (5 L cylindrical thermostated reactor) to analyze stirring speed, type of impeller, TEOS addition rate and nanoparticle maturation time effects, confirming results at laboratory scale. Despite slight variations on the morphology of the nanoparticles, this methodology provided MSNs with adequate sizes and porosities for biomedical applications regardless of the reactor/scale. The process showed to be robust and reproducible using mild synthesis conditions (2 mLmin-1 TEOS addition rate, 400 rpm stirred by a Rushton turbine, 60 minutes maturation time, 60 ºC, 2 gL-1 CTAB, molar ratio TEOS/CTAB=8), providing prismatic short mesoporous 100-200 nm nanorods with non-connected 3 nm parallel mesopores.