Continuous synthesis of TiO₂ fine particles and increase of particle size using a two-stage slug flow tubular reactor

A novel continuous process has been developed, which consists of a two-stage slug flow tubular reactor (SFTR) to increase the size of titanium dioxide fine particles. In a single-stage process, particle growth stops at a certain conversion level with unreacted titanium ethoxide remaining. In this process, however, water is added to the particle suspension containing unreacted titanium ethoxide to allow the particle growth to proceed again. The particles prepared using the two-stage SFTR process have a larger mean particle size and smaller geometric standard deviation (GSD) than those from the single-stage process. The two-stage process also provides a higher conversion to particles than the single-stage process does. A smaller amount of water fed into the first stage and a larger amount of water fed into the second stage results in a larger mean particle size, higher conversion to particles, and smaller GSD. The width of the particle size distribution of the two-stage process is almost the same as that of the single-stage process. The calculated results using a mathematical model are in agreement with the experimental data.