Microemulsion-based nanoparticle production on a techical scale : Experimental and theoretical process evaluation

The large-scale production of tailor-made nanoparticles is becoming an important industrial process due to the increasing amount of possible applications in the last years. A variety of processes are being developed based on top-down and bottom-up approaches. While top-down processes usually yield more final product, the characteristics of the particles might be limited in the minimum achievable size. Also usually a broad particle size distribution is obtained. In this respect the bottom-up approaches have the advantage of starting at the smallest possible scale, namely that of atomic clusters. Being still in the phase of development one promising technology is a liquid-liquid reaction based microemulsion- assisted particle precipitation process. In this lecture we will present the current status of our work in this field. A technical microemulsion consisting of cyclohexane, Marlipal O13/40 and water has been investigated in its phase behavior to find suitable and stable working conditions for a precipitation reaction. The precipitation of barium sulphate and calcium carbonate have been chosen as example reactions to produce nanoparticles of well-defined size a with a narrow size distribution. The variation of process conditions like initial concentration ratios of the reactants or holding time led to significant changes in the particle properties like size and shape. Theoretical description of the process has been carried out based on population balance methods as well as on Monte-Carlo simulations. Using these model simulations for a sensitivity analysis in an enlarged process parameter space we found for example that a variation of the feeding rate will significantly influence the particle size in a controllable way. The simulations will help with the detailed process analysis, a necessary condition for a successful process control. The combination of experimental work and theoretical analysis shows the applicability of the microemulsion- assisted nanoparticle precipitation method as a useful alternative for the effective production of tailor-made nanoparticles on a technical scale