In-Depth Analysis of Key Factors Affecting the Catalysis of Oxidized Carbon Blacks for Cellulose Hydrolysis

Carbon black is treated with each of three different oxidizing agents (nitric acid, air, and ozone) to introduce oxygen-containing functional groups (OFGs) and the resulting oxidized carbon blacks are used as model catalysts for the hydrolysis of cellulose. At the same time, they are thoroughly characterized by many techniques, especially in terms of surface chemistry, including the type/number of OFGs and the site where OFGs are formed in a carbon structure. Then, by correlating the catalytic activities toward the cellulose hydrolysis with the characterization results, key factors governing the catalysis are elucidated. As a result, this study reveals that two types of acidic OFGs, carboxyl groups (including those derived from the hydrolysis of acid anhydride and lactone groups in the reaction) and phenol groups (including those from lactone groups), act as catalytic sites with almost equal activity, as long as they are present on the external surface and thereby accessible to cellulose molecules.