Preparation And Catalytic Application Of Nanoporous Carbon Materials In Benzyl Alcohol Oxidation Reaction

Nanoporous carbon materials are ubiquitous and indispensable in manymodern-day scientific applications due to their unique properties, such as high surfaceareas and good electron transport ability. In the field of catalysis, because of their highthermal stability in reducing atmospheres and their ability to facilitate the prepare ofwell-dispersed metal particles on surfaces that do not exhibit acid-basic properties,nanoporous carbon materials are used to support metals for hydrogenation reaction inthe fine-chemicals industry. Besides, they can be used directly as catalysts for manyimportant catalytic processes. Their use in such diverse applications is related to theirstructure and superior physical and chemical properties.Recently, our group reported a sol-gel route to synthesis a nanoporous carbonmaterial with microporous and/or mesoporous characteristics. The mesoporousaluminum phosphate that was formed in situ during carbonation acted as the template,while citric acid and sucrose were the carbon sources. The resulting material can beused as catalyst support for highly dispersed solid base catalysts, and can also bedirectly used as the active catalyst for the aerobic oxidation of benzyl alcohol.In this thesis, several organic compounds were separately used as the substitute ofsucrose to prepare a series of nanoporous carbon materials. Different characterizationmethods were carried out to study the effect of the extra carbon sources on thestructure and surface chemistry of the NC materials. Meanwhile, we prepared a seriesof nanoporous carbon supported FeO_x catalysts by conventional wet impregnationmethod. Their catalytic performances were studied in the aerobic oxidation of benzylalcohol, and their active centers were investigated. The main experimental results andconclusions are as follows:Different organic compounds, o-dihydroxybenzene, m-dihydroxybenzene,p-dihydroxybenzene, glycol, and cyclohexylamine, were used as the extra carbon source for the preparation of a series of nanoporous carbon （NC） materials thoughdirectly carbonizing composites containing citric acid and aluminum phosphate. N2adsorption, Raman spectroscopy, FT-IR spectroscopy, Boehm titration, XPS, and TPDwere used to study the effect of the extra carbon sources on the structure and surfacechemistry of the NC material. It turns out that all of the NC materials havemicroporous and/or mesoporous characters, and possess a great quantity of functionalgroups on their surfaces. The NC material prepared using m-dihydroxybenzene hasthe largest surface area and pore volume, while the NC material prepared using glycolhas the smallest. The NC materials show different catalytic activities in the aerobicoxidation of benzyl alcohol. In this reaction, it was suggested that surface quinonegroups were the main active centers. However, it is unexpected that NC-e, whichpossesses a relatively small amount of quinone groups, showed the highest catalyticactivity. To explain this unusual result, we propose that besides surface quinonegroups, other functional groups such as acidic oxygen-containing groups ornitrogen-containing groups could also contribute to the catalytic oxidative activity.Other factors such as the structural parameters and surface polarity （originating fromoxygen or nitrogen-containing groups） of the NC materials may also be important inthe catalytic oxidation by affecting accessibility to the active centers or the transportrate of reagents.During the preparation of Fe/C catalysts, Fe（NO₃）₃was used as iron precursor, anda series of nanoporous carbon （NC-2） supported FeO_xcatalysts were prepared byconventional wet impregnation method. Different characterizations were used to studytheir structure and surface properties. It was found that their surface areas and porevolumes decreased with increasing the Fe loading, iron species were highly dispersedon the surface of NC-2as the form of small Fe₂O₃nanoparticles. Their catalyticperformances were investigated in the aerobic oxidation of benzyl alcohol. When theFe loading increased from1wt%to5wt%, the benzyl alcohol conversion increased;however, when the Fe loading reached10wt%, the benzyl alcohol conversion did notchange much, which was the result of Fe₂O₃gathering on the surface of NC-2at suchhigh loading of10wt%. Besides, the influence of calcined temperature were investigated on5wt%Fe/NC-2catalyst, it was found that the best calcined temperatureis673K. This might due to the fact that Fe（NO₃）₃did not convert to Fe₂O₃completelyat the relatively low calcined temperature. When the calcined temperature was toohigh, some Fe₂O₃transferred to Fe₃O₄, and oxygen-containing groups on the supportsurface began to decomposed, which are unfavorable to the catalytic activity.