SUMMARY
The performance of fixed-bed reactors with structured catalysts depends heavily on the gas–liquid–solid contacting pattern. For a broad range of flow conditions, the liquid phase does not cover the solid surface of the packing homogeneously; this is known as partial wetting. The wetting fraction in solid foams was obtained using a modified electrochemical measurement method with adaption of the limiting-current technique in different pre-wetting scenarios. The external wetting fraction, which is defined as fraction of the external solid-foam area covered by the liquid phase to the total external solid-foam area, is directly linked to the overall rate of reaction through the overall liquid mass transfer rate. The wetting fraction decreased with an increase in foam density, a process which was related to decreasing the strut thickness, increasing foam surface area, and consequently, decreasing the wetted area. Additionally, the results indicate that a better distribution of liquid and an increased wetting fraction occurred when a spray nozzle distributor was applied. A new wetting correlation for solid foams is proposed to estimate the wetting fraction with consideration of foam morphology and flow regime.