Preparation And Characterization Of Doped Nitrogen Molecular Sieves Supported Palladium Catalysts And Their Applications In Benzyl Alcohol Oxidation

The oxidation of alcohols, particularly benzyl alcohol to benzaldehyde, is of paramount importance in transforming functional groups in organic synthesis. The product of benzaldehyde is valuable as both intermediates and high value products for the pharmaceuticals, perfumery, dyestuffs, foods and agrochemicals industries. Traditional methods based on complex process and oxidants which are expensive and toxic were used in the reaction also cause environmental pollution. Recently, with molecular oxygen as oxidant to preparation benzaldehyde is regarded as a kind of green synthetic methods. Therefore, looking for high efficient and environment friendly catalysts becomes a focus in the study of oxidation of benzyl alcohol. Supported metals catalysts such as gold, platinum, ruthenium and palladium is commonly used as catalyst for the oxidation of benzyl alcohol. Palladium catalysts is relatively cheaper, high selectivity, varieties Palladium sources and the preparation process is relatively simple. Metal oxide, activated carbon and molecular sieve are commonly used as the carriers in the preparation of supported catalysts. Molecular sieve is a kind of porous material with special channel structure and has been widely used in the adsorption separation and catalytic reaction due to its large specific surface area and unique channel shape-selective. As a kind of new type skeleton heteroatom molecular sieve, doped nitrogen molecular sieve not only has the advantages of high specific surface area, high stability and unique porous. But also is good carrier for the load of metals due to the coordination effect between metals and -NHx functional groups on its surface.Based on the above idea, we selected HZSM-5 and SBA-15 as a typical microporous and mesoporous molecular sieves respectively and which were used as nitride precursor and studied the preparation and characterization of the two types doped nitrogen molecular sieves supported Palladium catalysts and their applications in benzyl alcohol oxidation. The research work mainly consists of two sections. The first part is the research about preparation and characterization of doped nitrogen HZSM-5 supported Palladium catalysts and its applications in benzyl alcohol oxidation. The second part is the research about preparation and characterization of doped nitrogen SBA-15 supported Palladium catalysts and its applications in benzyl alcohol oxidation. The details research content are as follows:1. The preparation and characterization of doped nitrogen HZSM-5 supported Palladium catalysts and its applications in benzyl alcohol oxidation.HZSM-5-N doped nitrogen molecular sieve was prepared in directly nitridation by different high temperature and a series of Pd/HZSM-5-N catalysts were prepared using a sol-immobilization method with PdCl2 and Pd(OAc)2 as sources of palladium. The structure and properties of the support and catalyst were characterized by EA, XRD, FT-IR, BET, ICP and SEM. Furthermore, we evaluated its catalytic performance in benzyl alcohol oxidation reaction. We investigated the effect on nitrogen content of HZSM-5-N of different nitridation temperature and determine the best nitridation temperature. Investigated the catalytic performance of different palladium source, such as PdCl2 and Pd (OAc)2 with different palladium content and optimized the best catalyst 2% Pd/HZSM-5-800N (Pd(OAc)2 as palladium source). We chose the best catalyst used in the benzyl alcohol oxidation reaction and effects of the catalyst dosage, reaction time and reaction temperature on oxidation of benzyl alcohol were investigated. At the same time, the recycling performance of catalyst were also investigated, the catalyst could be reused five times without significant loss of catalytic activity and ICP test results also suggest that without the leaching of Pd in the process of the reaction. Finally, we combined the characterization results and explored the structure and properties of doped nitrogen support as well as the factors affect the activity of catalyst.2. The preparation and characterization of doped nitrogen SBA-15 supported Palladium catalysts and its applications in benzyl alcohol oxidation.SBA-15-N doped nitrogen molecular sieve was prepared in directly nitridated by different high temperature and a series of Pd/SBA-15-N catalysts were prepared using a sol-immobilization method with PdCl2 and Pd(OAc)2 as sources of palladium. The structure and properties of the support and catalyst were characterized by EA, XRD, FT-IR, BET, ICP and TEM. The results show that the nitrogen content of molecular sieves was increased with the increase of nitridation temperature and during the nitridation the N atoms would successfully substitute for O atoms in frameworks and formed-NHx species. It is clear that the channel structure of the nitrided molecular sieves and catalysts was still remained and the skeleton structure was not collapsed. We investigated its catalytic performance in benzyl alcohol oxidation reaction, compared the catalytic activity of catalysts of different palladium source, we found the best catalyst 2% Pd/SBA-15-900N (Pd(OAc)2 as source of palladium). We chose the best catalyst used in the benzyl alcohol oxidation reaction and effects of the catalyst dosage, reaction time and reaction temperature on oxidation of benzyl alcohol were investigated. At the same time, the recycling performance of catalyst were also investigated, the catalyst could be reused five times without significant change of conversion of benzyl alcohol and selectivity of benzaldehyde and without Pd lost during the reaction and also confirmed by ICP test. These shows that the 2% Pd/SBA-15-900N catalyst with good catalytic performance and stability in the oxidation of benzyl alcohol.