Theoretical Study Of The CO Oxidation And Formation Of Methyl Formate From Methanol Catalyzed By Gold Clusters

gold is well known by us owing to its good plasticity, high chemical stability, and no side effects on biological system. But people never regard it as a lively participant in a chemical reaction because of his chemical stability. It has attracted our attention since Huruta's group of Japanese found gold possessing high catalytic activity on CO oxidation in 1985. the scientists all of the world began to widely study the catalytic properties of the gold, and in the recent years gold catalysis became one of the hot topics in the international academe. The nano-gold catalyzer has high catalyse activity, also possesses other advantages such as good water resistance, stability, humidity enhance and so on. compared with the traditional metal catalyst, it is more outstanding, so people give much expectations on its catalytic effects and future applications. In the Recent studies, it was found that gold had high catalytic activity in the process of CO oxidation catalysis, selective oxidation, reduction of NOx, methanol decomposition, which were attracted scientists'attention and widely studied in various countries. And the investigation on the nano-gold has extended in the fields of life, pharmaceutical, electronic, etc from material field.CO is a common poisonous gas of car exhaust and industrial production. And it caused great environmental pollution if it largely produces. people did a lot of work on this reaction, most of which are under high temperature. And the problem was well solved by nano-gold catalyst, which can oxidize CO to CO2 at lower temperatures. At present, co oxidation catalyzed by gold was studied most and had best catalytic effect. ia was found that water had important effects on the CO oxidation catalyzed by gold, and water is how to affect gold catalysis on CO oxidation? It is studied from the point of the experiment and theory research. in recent studies, it was showed that nano-gold catalysis on CO oxidation can enhanced by humidity,,catalytic activity is obviously increased along with the increase of humidity.Gold has certain catalysis on of methanol decomposition. And methanol decomposition catalysized by gold is mainly used in fuel cells. Boccuzzi etc studied detailed on methanol decomposition of gold catalysis in fuel cell, they found that gold had good effects on methanol disintegrate at 403 K, and there are formaldehyde and formate generation in the reaction. For the catalytic methanol decomposition, gold catalysts are high efficient and selective. Though the catalytic performance of gold is not good as platinum, but it's cheaper. So it has broad application prospects in the catalytic field.The synthesis of Methyl formate needs critical conditions in the industry, and has low yield, also undergos at high temperature and pressure. So people tried to selecta most appropriate catalyst of the reaction. On the basis of previous studies, Wittstock found that methanol can directly transform to methyl formate at low temperature (80℃) catalysized by nano-gold made by corrosion the alloy silver and gold at 2010, and the yield ratio is more than 97%.Based on the issues of the above two aspects of experiments, we explored the mechanism of the moisture-enhanced catalysis of CO oxidation and ethyl formate synthesis from methanol over Au clusters using density functional theory, clarified the micro-mechanism of the moisture-enhanced catalysis of CO oxidation, and gave the detailed condition of methyl formate transformed from methanol. The results logicaly explained the experimental phenomena and deepen the people's cognition to the process, provideing theoretical base for related experimental study. And it provides theoretical guidance for the reasonable design of gold catalysis.The major contents and innovative conclusions in this thesis are listed as follows.1,based on density functional theory calculations, we studied the mechanism of CO oxidation of the moisture-enhanced catalysis over Au nanoclusters in the BPW91/LANL2DZ/6-311G (d, p) level, It has been discovered that the reaction was more likely to happen with water than without water with lower energy barrier. In all case, the reactions proceed via four elementary steps:the initial interaction was between H2O and O2, producting OOH and an OH intermediates. Then these two intermediate respectively interact with CO, obtaining CO,OH and COOH intermediates. Finally, COOH interact with OH to form CO2 and H2O. and a cycle reaction was completed. It is observed that the moisture-enhanced catalysis of CO oxidation over Au nanociusters through H2O participating in the reaction.2,ased on density functional theory calculations, we studied the mechanism of methyl formate f formation from methanol over anionic gold clusters in the BPW91/LANL2DZ/6-311G(d, p)level. we found that The reactions proceed via four elementary steps:initially methanol dissociated to form a CH3O H intermediates, CH3O is an intermediate in the synthesis of methyl formate, the other one is CHO. CH3O can interact with O2 to form CH2O and OOH intermediate, and CH2O can also be obtained by CH3OH interacting with O2. Then, CH2O interact with O2 to form CHO. Finally, CH3O and CHO combined, forming a methyl formate. The energy barrier for every step of reactions is all low. The rate-controlling step is the dissociation of H on the CH3OH and it's energy barrier is 166.50kJ/mol. Through calculating, the complete reaction route was obtained, and the reaction mechanism was reasonable explained.