Effect of Shear Rate and Soft-Templating Approach on Activated Carbon Microspheres Synthesized by Hydrothermal Carbonization

Carbon microspheres (CMSs) derived from corn starch were successfully obtained under hydrothermal carbonization (HTC). A 6-blade Pitched blade turbine (PBT) was employed to introduce the controllable shear rate and F127 as the soft template was ultized to find out their effect on the CMSs. The combination of shear rate and soft template method, introducing a controlled flow pattern based on fluid dynamics, provides an alternative to obtain CMSs with wider distribution of pore size and more mesopores, thereby enhancing their adsorption capability. The products were characterized using Scanning Electron Microscopy (SEM), Thermal Gravimetric (TG), and Brunauer-Emmett-Teller (BET) model. The results revealed that the morphology and structure of CMSs were strongly influenced by the shear rate induced by the rotated PBT during the hydrothermal reaction. At a rotating speed of 60rpm, the CMSs showed the maximum CO2 adsorption rate at 25 °C and 0.15 bar CO2, with a specific surface area of 475 m2/g and an average pore diameter of 2nm. Furthermore, the diameter of CMSs decreased with an increase of rotating speeds. The assembly of F127 resulted in products with low degree of sphericity forming a chain, which significantly increased the BJH Adsorption/Desorption average pore width (4V/A). Hence, the controllable shear rate offers an alternative approach to explore the property of CMSs.