Preparation Of Carbon Supported Noble Metal Catalysts And Their Liquid Phase Hydrogenation Performance

Liquid-phase hydrogenation reaction was an important reaction type in chemical engineering. The hydrogenation of C=C and C=O was very important in getting lots of green and valuable products. The hydrogenation catalysts was the key in the hydrogenation reaction, the carbon supported noble metal catalyst was an efficient and stable hydrogenation catalyst for benzene, p-methyl benzaldehyde and glucose hydrogenation reactions. Other important application included the synthesis of 1,4-cyclohexanedimethanol, esters of cyclohexane dicarboxylic, decalin,1,4-butanediol, 2,2,4,4-tetramethylcyclobutane-1,3-diol. Carbon supported nanometric noble metal catalysts were very active in the hydrogenation of C=C or C=O. So, we were going to prepare a series of monometallic and multimetallic hydrogenation catalysts through chemical reduction and bioreduction methods and applied them to different liquid phase hydrogenation reactions to synthesize valuable chemical products, this thesis mainly included the following contents:Firstly, the synthesis and utilization of bimetallic catalysts for the hydrogenation of dimethyl terephthalate and diisooctyl phthalate was described. A variety of techniques, such as low temperature N2 adsorption-desorption experiment (N2-BET), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and H2 temperature-programmed desorption (H2-TPD) were employed to characterize both the supports and the catalysts. The influence of various operation parameters, for example reaction temperature, pressure and time on the catalytic performance in hydrogenation of DMT and DOP was systematically analyzed. Under optimized conditions, the DMT conversion of 80% along with DMCD selectivity of 95% were achieved and the yield of DEHCH was 99.97%. Furthermore, efforts were also made to probe the catalysts stability. The enhanced catalytic performance of optimized Ru-Ni/CNT catalysts could be attributed to the tight immobilization of the metal particles on the carbon nanotubes and the unique properties of the nitric acid treated carbon nanotubes.Secondly, we reported a method of synthesizing alloyed platinum-nickel nanoclusters on activated carbon to enhance its hydrogenation performance of tetralin without adding solvents. The activated carbon provided a high surface area, while the highly-dispersed platinum acted as the hydrogen adsorption and dissociation site, in addition the Ni could alloy with Pt to induce more electron deficiency. Due to such favorable conditions, the bimetallic Pt-Ni/AC catalysts showed good conversion and selectivity for hydrogenation of tetralin within a very short time. Furthermore, after six consecutive cycles, no prominent fluctuations in activity and selectivity were observed. We also developed trimetallic catalysts and applied them to the hydrogenation of naphthalene. Thus, the supported nanocatalysts with excellent efficiency and prolonged lifetime for tetralin and naphthalene hydrogenation harbored great significance for future nanocatalysts design.Thirdly, Ru-based catalysts, supported on activated carbon and carbon nanotubes, were synthesized by a biogenic method via Cacumen Platycladi leaf extract and tested in the liquid phase hydrogenation of maleic anhydride. Over 2.0 wt% Ru/AC, succinic anhydride was produced with a maximum yield of 99.2% without further hydrogenation to y-butyrolactone. Well-defined spherical shapes with uniform small size of Ru nanoparticles and the residual plant biomass were responsible for the excellent catalytic activities and stabilities. The analyses of FTIR and TG confirmed that the plant extract served as both reducing and protecting agents. Reusability tests and comparison with commercial catalysts were also studied on the biosynthesized Ru-based catalysts.Fourthly, a plenty of uniform and spherical ruthenium nanoparticles were prepared by the adsorption-bioreduction method using the Cacumen Platycladi extract and supported on the activated carbon which was modified with nitric acid. The catalytic performance of as-prepared Ru/AC-HNO3 catalysts were investigated in the liquid phase hydrogenation of 2,2,4,4-tetramethylcyclobutane-1,3-dione to 2,2,4,4-tetramethylcyclobutane-1,3-diol. Different characterization techniques of BET, XRD, TEM, and FTIR were applied to understand the origin of the catalytic activity. With a comprehensive analysis of the experimental results, we can draw a conclusion that the higher dispersion of ruthenium nanoparticles and the smaller particle size give rise to the results which indicate a remarkable enhancement of the catalytic performance in comparison with the non-modified AC samples.