(539f) Synthesis of Mesoporous Carbons: Oxidative Modification and Hydrothermal Carbonization for Efficient Chemical Activation

Preparation of mesoporous carbons and activated carbons in general has always been a resource intensive process. Generally, chemical activation is carried out by simple mixing and drying of the activating agent with the raw material, which might lead to ineffective utilization of the former. Improvised chemical activation using hydrothermal treatment and incorporation of oxygen functional groups can lead to more effective chemical utilization and therefore render the process less resource-intensive. In this work, the effect of oxygen functional groups present in the hydrothermally treated precursor on porosity and mesoporosity was investigated. The amount of oxygen containing functional group was varied by appropriate changes to the processing and activating conditions.  Coconut shell precursors were subjected to hydrothermal treatment in the presence of hydrogen peroxide as the oxidizing agent at various temperatures. The hydrothermal pre-treatment was followed by chemical activation with ZnCl₂ accompanied by pyrolysis.  The samples were characterized by surface area methods, titrations and microscopy. Hydrothermal treatment in the presence of H₂O₂ results in significant improvement in the mesoporosity of the final product compared to conventionally processed samples. Samples pretreated with H₂O₂ at 200⁰C resulted in highest mesoporosity and this was consistent with the observation of the highest amount of oxygen functional groups in precursor. By the use of H₂O₂ and hydrothermal treatment there is an increase in mesoporous area by 144% and BET surface area by 35%. The hydrothermal pretreatment and surface oxygen functional groups in the precursor, coupled with the use of H₂O₂ as the oxidizing agent, together contribute to improved chemical activation, thereby increasing mesoporosity.