Synthesis of Porous Emulsion-Templated Monoliths Using a Low-Energy Emulsification Batch Mixer

Emulsion-templated porous monoliths based on castor oil-in-black liquor emulsions have been prepared using a low-energy emulsification technique. Lignins from black liquor polymerize in the continuous phase of the high internal phase emulsion to obtain highly microcellular materials with interconnected open porous structures. A two-step emulsification operating mode was developed in order to increase the maximum value of the castor-oil dispersed volume fraction obtained with the one-step emulsification mode (limited to 53 % of the total emulsion volume due to the very high viscosities of the fluids). A rheological study of the black liquor and of the prepared Medium Internal Phase Emulsions, have been conducted. Depending on the emulsification operating mode used, the morphology of the porous monoliths will differ. A rather low mean droplet size (about 6 mu m) is obtained with the one-step mode, the two-step technique leads to a broader void size distribution and a further increase of added castor oil (up to 69 %) do not favor the homogeneity of the material.