Ordered nanoparticles were produced using a low temperature sol-gel synthesis method carried out in a multiphase semi-batch reactor. The effects of liquid-liquid phase solubility for the HCl / 1-hexanol system and drying temperature on sol-gel properties were examined. The HCl-enriched phases of 1-hexanol were extracted as supernatant after phase separation. The resulting HCl / 1-hexanol solutions were used in the precipitation of tungsten oxide sol-gel nanomaterials via acid hydrolysis in a two-phase, semi-batch reactor system. Droplets of sodium tungstate (Na2WO4 2H2O) solution were directed through two vertically adjacent phases. Initially the droplets reacted in a mixed HCl / 1-hexanol (oil-rich) phase and finally through a HCl (aqueous-rich) phase.

Spherical sodium tungstate solution droplets were observed to transform appearance with the progression of the acid hydrolysis reaction from transparent spheres in the initial precipitating solution, followed by an opaque white droplets upon contact with the oil-rich phase, and finally bright yellow spherical droplets upon settling within the aqueous-rich HCl phase. With the removal of excess water, the spheres were observed to transform from bright yellow to a medium dark green appearance. The resulting sol-gels were characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A process model was developed to optimize the operation of the semi-batch sol-gel synthesis reactor. The effects of such parameters as droplet size, droplet speed, reactor geometry, and the composition of synthesis solutions on reactor hydrodynamics will be discussed.