Aqueous phase synthesis of activated carbon supported palladium sulfides and their catalytic performance

In this work, activated carbon supported palladium sulfides with different crystalline phases were synthesized by the aqueous phase reaction of Pd/C and Na2S. Their catalytic performance was investigated through the reductive N-alkylation of aromatic amines for the synthesis of N-(1, 3-dimethylbutyl)-N'-phenyl-p-phenylenedianine (6PPD). The experimental results suggest that the formation of special crystalline phase of palladium sulfides is highly dependent on the sulfidation temperature and surrounding gas. In H2, only Pd4S can be formed in a temperature ranging from 30 to 250℃. Higher S/Pd atomic ratio palladium sulfides, such as Pd4S-Pd3S and Pd4S-Pd3S-Pd16S7-PdS, can be obtained in N2. Furthermore, different phases show different electron-deficient degrees of surface Pd, therefore, they exhibited diverse catalytic activity and stability for the synthesis of 6PPD. Pd-Pd4S/C catalyst formed in H2 at 120℃ shows the best catalytic selectivity (≥96.4%) and stability. ©, 2014, Zhejiang University. All right reserved.