Evaluation of flow dynamics and liquid-solid mass transfer in solid foam packed reactors using the limiting current technique

In heterogeneous catalytic multiphase reactors, such as trickle-bed reactors, the achieved space time yield depends strongly on the individual mass transfer steps between the individual phases. Being a transfer resistance to all reactants, the liquid-solid mass transfer can be considered as the most crucial mass transfer step.
The limiting current technique (also called electrochemical method) is an established method to study liquid-solid mass transfer at any solid surface. By application of an electric potential to Nickel electrodes having a morphology representative for the solid phase of interest, the limiting electric current can be continuously measured and directly related to the liquid-solid mass transfer. Moreover, the method allows to study dynamic shear stress-related phenomena in the liquid film such as flow regime transition or dynamics of pulses.
In recent years, open-cell solid foams have gained lots of interest as catalyst support in multiphase processes. They consist of a highly tortuous continuous solid network with void fractions of approx. 90% and combine large specific surface area with low flow resistance and high thermal conductivity. Moreover, their hydrodynamic behavior in terms of flow regimes under cocurrent downflow, i.e. trickling flow at high gas and liquid flow rates, may open up new modes of operation.
In the present contribution, the limiting current technique is used to evaluate fast flow dynamics at trickling and pulsing flow and corresponding liquid-solid mass transfer in trickle-bed reactors packed with silicon-infiltrated silicon-carbide (SiSiC) foams.