Effects of acid-treatment of halloysite on the characteristics and catalytic performance of palladated halloysite in lubricants hydrogenation reaction

In the following of our research on the design of halloysite-based catalysts for polyalphaolefins (PAO)s hydrogenation, herein we investigate the effect of acid-treatment of halloysite on its performance as a support for the immobilization of Pd nanoparticles. To this purpose, pristine halloysite and two acid-treated counterparts, prepared through treatment with sulfuric acid for 9 and 72 h, were palladated to furnish catalysts (Pd/Hal, Pd/ Hal-A9, Pd/Hal-A72) for the hydrogenation of PAO oil derived from 1-octene monomer. The characteristics and catalytic activity of the three catalyst samples were compared. The results showed that acid-treatment for long time significantly increases the specific surface area and induces formation of fine particles within the lumen of halloysite. However, it led to the slightly lower loading of Pd particles. Acid-treatment for short time, on the other hand, slightly increased the specific surface area and remarkably decreased Pd loading. The activity of the synthesized catalysts follows the order of Pd/Hal > Pd/Hal-A72 > Pd/Hal-A9, indicating the important role of Pd loading and accessibility of Pd nanoparticles in the catalysis of PAO hydrogenation containing structurally big molecules.