Study On Catalytic Performance Of New Graphitized Nano - Carbon - Based Materials

Catalysis has been played very important role in chemistry history since been discovered. Metallic materials are undoubtedly the most vibrant catalysts due to their good performance in a series of paramount chemical reactions in modern chemical industry. However, their use on an industrial scale is restricted by limited reserves, high cost and low stability. In the drive towards green and sustainable chemistry, good stability, convenience for recycling and low toxicity are also desirable properties for various catalysts. In recent years, carbon nanomaterials have been explored and studied extensively in catalysis. Studying the performance and catalysis mechanism in some chemical reactions one of the most important and hottest topics in academic research. Graphene, which is composed of one monolayer of carbon atoms with a honeycomb structure, has attracted considerable interest among the public because of its unique electronic, optical, thermal, and mechanical properties. However, much of the research of graphene in catalysis field is still in its infancy. Some groups have reviewed the applications of grapheme based materials in catalysis, however the authors only lay emphasis on the graphene-metal/metal oxide nanocomposite catalysts. In this dissertation, we will explore the catalytic chemistry of graphene based materials, including graphene oxide, chemical reduced graphene, N-doped graphene and graphene-based carbon nitride (g-C3N4). The reactions content fine organic chemical synthesis, bulk chemical industry and chemical pollution abatement. Using our excellent characterization of catalysts, the progress of both experimental and theoretical investigations will be discussed.In the first part, we synthesis graphene oxide (GO) by the Hummer method. GO and other nano carbon materials (carbon nanotubes, etc.) are used as metal-free catalysts in liquid of aromatic selective oxidation of amine to the synthesis of imines reaction with molecular oxygen as the terminal oxidant. Experimental results show that graphene oxide is the best catalyst, which can catalysis the reaction in gentler reaction conditions to fully conversion of amine, and synthesis of imines with selectivity of 95%, using the molecular oxygen as oxidant at 100 ℃. Through control of various reaction experiment condition, we found that the reaction system can also be used in solvent-free conditions. And the results reveal the presence of an intermediary of carbo-cationic species. We also test the cross condensation reaction with a primary amine and a secondary amine and propose a plausible mechanism for aerobic oxidation of amine on GO. This method is simple, economic and environmentally benign, resulting in practical advantages for the convenient synthesis of imines and their derivatives.Furthermore, we explored the potential catalytic ability of graphene based materials for the synthesis of adipic acid, which is an important chemical for the manufacture of nylon-6,6. Most industrial processes of adipic acid production rely on a refined technology that minimizes the emission of nitrous oxide, an environmentally harmful greenhouse gas. One-step oxidative cleavage of cyclohexene to adipic acid with H2O2 has been considered to be one of the green synthetic processes with most potential up to date. But is not economical and safety to be used for adipic acid industry production. Herein we found using graphene oxide as catalyst, cyclohexene can be oxidized to adipic acid with a yield of 26.5% at an oxygen atmosphere. To our best knowledge, this is the best result for adipic acid synthesis using molecular oxygen at an initiator-free condition. We also prepared N-doped graphene by treating GO with ammonia. The N-doped graphene can catalyze the oxidation of cyclohexene to 1,2-cyclohexandione at the selectivity of 85%, indicating that the introduction of N atom into graphene sheets could modify its local electronic structures and change the catalyzing capacity.Chlorophenols are prevalent chlorinated organic contaminants in environment and cause serious threatens to human health. With the improvement of sociality environmental awareness, organic chloride liquid phase hydrodechlorination (HDC) has become increasingly urgent and desirable in recent years. HDC catalyzed by Pd catalyst using H2 as hydrogen source is considered as an economical and environmentally benign method without formation of more toxic by-products. However, the low solubility of H2 causes relative poor dechlorination efficiency. Base on the study of hydrogen transfer reaction of formic acid in our group, we explored the use of formic acid as a hydrogen source for Pd catalyzed HDC reaction. The results showed that the Pd catalyst loading of graphite carbon nitride (g-C3N4) can be achieved relatively high dechlorination efficiency at room temperature, with a conversion of nearly 100%. To the best of our knowledge, the molar ratio of formic acid cost and chlorophenols is 10:1, which is the lowest in dechlorination reaction system. Introduction of nitrogen atoms on supported metal nanoparticles have great role, which promoting the acid-base properties of the material and also increased the catalytic activity.