Abstract: The Pd/C catalyst was prepared using impregnation method, acidizing pretreatment activated carbon as the carrier, formaldehyde as reducing agent. The catalysts was characterized and its performance on alkali lignin was examined. Finally, the oxidation resistance was explored. That showed that the content of carboxyl functional groups on the surface of activated carbon was 1.31 mmol/g after pretreatment by HNO₃ and H₂O₂. Pd/C catalyst was characterized by AAS, SEM, XRD and XPS. The AAS showed that the content of Pd was 2.9%, and the SEM photos showed that Pd was evenly and globularly distributed on the surface of the active carbon. The XRD and XPS data analysis indicated that Pd existed in the form of face-centered cubic structure, which is the main active species in the reaction. The hydroxyl groups of alkali lignin had significantly been improved after reaction. The content of hydroxy, phenolic hydroxyl and alcoholic hydroxyl increased by 158.74%, 4.21% and 255.96%, respectively. The GPC showed that the M_w of alkali lignin increased while the M_n and M_w/M_n reduced. The antioxidant properties of the lignin increased with concentration increased. It was lower than BHT at the same conditions.

Key words: alkali lignin, HNO₃-H₂O₂ modified active carbon, Pd/C catalyst, catalytic activtion