Solvent-Free Hydrogenation of α-Pinene to cis-Pinane by Using Ru/TiO2 Nanocomposite with Strong Acid Sites

Abstract Ru/TiO 2 nanocomposite was prepared via loading the active ruthenium species on anatase TiO 2 by a simple hydrothermal approach combined with a sol–gel method. The optimal catalyst with 5.0% of Ru species showed excellent catalytic performance in the solvent-free selective hydrogenation of α-pinene with the conversion of α-pinene and selectivity to cis -pinane of 100.0 and 97.1%, respectively. It has been verified that the superior performance depends on the large amounts of acidic sites induced by HF acid and the SMSI effect between the reducible TiO 2 support and Ru species on its surface. The partial loss of its activity after five hydrogenation cycles should be due to the agglomeration of the catalyst particles and the carbon deposition on the surface. The possible hydrogenation mechanism was also discussed. This work provides an effective approach to develop a highly efficient and recyclable catalyst for the solvent-free selective hydrogenation of α-pinene.