3D printed catalytic stirrers with permeable blades made of porous carbon

This work introduces a new type of catalytic stirrer made entirely of porous carbon. These stirrers are made by printing 3D structures directly from whey pastes that were subsequently carbonised to produce impellers with meshed surfaces made of porous carbon with up to a 3% N content. The characteristics of the carbon pieces include a high porosity of approximately 70%, mainly in the macropore range, although there is also some development of mesoporosity and microporosity obtained by a simple washing process with HCl (SBET = 400 m2/g). The blades are strong (mechanical strength of 165 Pa) and able to sustain high stirring speeds (2000 rpm) immersed in highly viscous fluids without damage. The blade design of the stirrer is optimised to provide effective mixing, and to facilitate fluid circulation through the blades, as demonstrated experimentally and by CFD simulation. All these characteristics are expected to enhance the contact between the catalyst and the reactants and/or favour the deposition of selected catalysts on their surfaces.