Solvent-Free and Highly Efficient Hydrogenation of α-Pinene to Synthesize cis-Pinane by Using Ru Species Immobilized on APTS-Functionalized Cubic Phase NaNbO3

Abstract

Solvent-free selective hydrogenation of α-pinene to synthesize cis-pinane with high efficiency has always been a challenge in the catalytic research. The key to achieve this goal is the development of the highly efficient and recyclable catalysts. Cubic NaNbO3 crystals were functionalized by (γ-aminopropyl)-triethoxysilane (APTS) and decorated with Ru species by a simple solvothermal approach combined with a sol-gel method. And this compound was applied to the catalytic hydrogenation of α-pinene. The crystal phase, chemical structure and surface components of the catalysts were analyzed by X-ray diffraction, field emission transmission electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectra and thermogravimetric analysis. APTS-functionalization of the catalyst surface contributes to the highly dispersed and uniform Ru species with small particle size, leading to the outstanding conversion of α-pinene and selectivity of cis-pinane over NaNbO3/APTS/Ru catalyst. The performance of this catalyst is better than that of other similar catalysts, and is comparable to that of commercial Ru/C. The possible mechanisms of the formation of catalyst and the hydrogenation reaction were proposed and discussed. The decrease of catalytic performance after seven cycles should be ascribed to the decomposition and leaching of APTS during the hydrogenation process. The work provides an alternative strategy to design a kind of reusable catalyst with highly efficient hydrogenation performance based on the surface functionalization.