(34a) Influence of Silica Nanoparticles on Transport and Interfacial Phenomena in Liquid/Liquid Systems

The hydroformylation of organic reactants through the Ruhrchemie/Rhône-Poulenc process is one of the most important homogenous catalytic reactions in chemical industry. The catalyst is designed to be soluble in water to provide a good separation from the likewise organic products, leading to a liquid/liquid system. In these systems, the reaction is controlled by the interface through interfacial and transport phenomena. The process fails for long chained olefins â?? vegetable oils and fats from renewable resources â?? due to their strong insolubility in water. Nanoparticles can be used as emulsifiers to create Pickering emulsions and increase the reaction speed. The particles adsorb at the interface and affect the transport processes and thus the reaction yield and selectivity.

In this study the influence of nanoparticles on mass transfer and drop size distributions is investigated and the occurring interfacial phenomena are characterized.

As material system water and the reactant 1-Dodecen with added silica nanoparticles is used. For simplicity reasons no catalyst is considered. The mass transfer is measured in a droplet swarm by using a model reaction in a stirred reactor. The occurring drop size distribution is detected with an endoscope camera. The properties of the interface are characterized by pendant drop and spinning drop tensiometry.

With increasing particle mass fraction, the system shows rising interfacial tensions until a constant value is reached. Nonetheless, decreasing drop sizes were found, suggesting a better mass transfer due to larger interfacial area. Contrary to these observations, the mass transfer is reduced. The results lead to the assumption of an increasing particle coverage at the interface that hinders coalescence and forms an additional transport resistance. To get a better understanding of the occurring effects, the influence of the surface rheology and coverage has to be quantified. Therefore, the dilatational viscosity was measured using the oscillation drop method. A hardening of the drop interface could be determined.