Enhancement of hydrothermal carbonization of chitin by combined pretreatment of mechanical activation and FeCl3

In this work, a combined mechanical activation and FeCl3 (MA + FeCl3) method was applied to pretreat chitin to enhance the degree of hydrothermal carbonization. MA + FeCl3 pretreatment significantly disrupt the crystalline region of chitin and Fe3+ entered into the molecular chain, resulting in the destruction of the stable structure of chitin. The chemical and structural properties of hydrochars were characterized by EA, SEM, FTIR, XRD, XPS, 13C solid state NMR, and N2 adsorption-desorption analyses. The results showed that the H/C and O/C atomic ratios of HC-MAFCT/230 (the hydrochar derived from MA + FeCl3 pretreated chitin with hydrothermal reaction temperature of 230 °C) were 0.96 and 0.34, respectively. Van Krevelen diagram indicated that the hydrothermal carbonization of chitin underwent a series of reactions such as dehydration, decarboxylation, and aromatization. HC-MAFCT/230 had abundant oxygen- and nitrogen-containing functional groups. HC-MAFCT/230 exhibited a porous structure, with the specific surface area of 128 m2 g−1, which was a promising carbon material.