Preparation Of Carbon Supported Ruthenium Catalysts And Their Hydrogenation Performance

In this thesis, Ru-based catalysts, supported on activated carbon (AC) and carbon nanotubes (CNTs), were prepared by a simple and eco-friendly method in which Cacumen Platycladi extract was used as both reducing and protecting agents. The catalysts were characterized by a variety of techniques and successfully applied to the hydrogenation of benzene to cyclohexane and selective hydrogenation of maleic anhydride to the corresponding succinic anhydride. The main works can be summarized as follows:Firstly, a simple and eco-friendly method was provided herein for preparing Ru/CNTs and Ru/AC catalysts. Characterization results of Energy dispersive X-ray spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and X-ray diffraction (XRD) confirmed that the ruthenium nanoparticles were successfully synthesized by Cacumen Platycladi extract and homogeneously distributed over the entire supports. Characterization results of Transmission electron microscopy (TEM) showed that ruthenium nanoparticles in Ru/CNTs catalysts had a size distribution of 3.06 ± 0.67 nm and ruthenium nanoparticles in Ru/AC catalysts had that of 2.17± 0.35 nm. Thermogravimetric Analysis (TG) indicated that there was plant biomass on calcined Ru/CNTs catalysts and calcined Ru/AC catalysts. Fourier Transform infrared spectroscopy (FTIR) analysis of Cacumen Platycladi extract before and after bioreduction showed that the functional groups of C=C-H and C-O-H in the plant extract seems responsible for the reduction of Ru(III). Therefore, we speculated that the polyols, such as reducing sugars and flavonoids, played a role in the bioreduction. In addition, functional groups of-C=O, which might be the oxidation product of polyols, could play a critical role in protecting the Ru nanoparticles.Secondly, experimental results showed that bioreduction Ru/CNTs catalysts exhibited excellent performance in the hydrogenation of benzene to cyclohexane. Optimization of catalyst preparation parameters manifested that Ru loading of 2 wt%, reduction temperature of 60℃ and calcination temperature of 500℃ were optimum. Optimization of reaction conditions manifested that hydrogenation temperature of 80 ℃, reaction pressure of 4 MPa and reaction time of 0.5 h showed the best catalytic performance. Under optimal conditions, cyclohexane yield of 99.97% alone with the TOF value of 6983.09 h"1 were achieved.Afterwards, bioreduction Ru/AC catalysts were used to catalyze liquid phase hydrogenation of maleic anhydride to the corresponding succinic anhydride. Optimization of parameters manifested that Ru loading of 2 wt%, reaction temperature of 150℃, hydrogen pressure of 6 MPa, and the time length of 30 min with the choice of tetrahydrofuran as solvent were optimum. Under optimal conditions, succinic anhydride selectivity of 99.6%, almost 100% conversion of maleic anhydride and TOF value of 2084.9 h-1 were achieved.Finally, efforts were also made to probe the stability of the biosynthesized catalysts. The TEM analysis was introduced to elucidate the nature of the reused catalysts. The nanoparticles in the recycled catalysts show little change. The catalysts were carefully recollected and reused in subsequent cycles as the same conditions as the fresh catalysts. There was minor variation during the consecutive cycles which indicated remarkable stability of the bioreduction Ru catalysts. In a word, the merits of excellent durability, sound productivity and preferable reusability grant the catalysts a high hydrogenation activity and a promising future in the industrial application.