Effect of bone char catalyst on the pyrolysis behavior and crystal structure of cotton stalks

This study investigated the characteristics of bone char (BC) in the in situ catalytic pyrolysis of cotton stalk (CS) using a fixed-bed pyrolysis system at 600 °C. The results revealed that BC contained abundant pore structures and polar active sites, which prolonged the residence time of gases and provided numerous reaction sites for the secondary reaction of pyrolysis products. At a CS-to-BC mass ratio of 1:2 (CB-1:2), the reaction rate was accelerated. As the BC proportion increased, the crystallinity of the char decreased, while the specific surface area increased. At CB-1:2, both the crystallite size and crystallinity of BC improved. The oxygen-containing functional groups in BC, such as CO32−, PO43−, −COOH, and −OH, effectively increased the adsorption active sites. Additionally, Ca2+ in BC promoted dehydrogenation, deoxidation, fused cyclization, and decarboxylation of carboxylic acids, leading to increased production of H2, CO, and CO2. Moreover, Ca2+ facilitated the homolytic reactions of lignin, generating hydrogen free radicals. These radicals reacted with methoxy radicals formed during lignin decomposition to produce methane.