Interface Control And Functional Assembly Of Copper-based Composite Catalysts

The development of non-noble metal catalysts with high performance and multi-functions is a hot research topic in the field of catalysis in the new energy era. And how to use simple and effective synthesis method to control the catalytic active sites, improve their dispersion and stability and reduce their agglomeration, loss and inactivation in severe reaction conditions, is the key to obtain advanced catalytic materials. In this thesis, copper-based compounds, which are inexpensive and readily available, were uesd as the main active substance to build the catalytic activity interface. Different functional groups/structures were designed to realize the interface control and the obtained catalysts were applied in different catalytic reaction systems in order to achieve the enhanced catalytic activity and functional improvement.Research in this paper includes three kinds of copper-based catalysts with different structure and compositions and their applications in different catalytic reactions, the main conclusions are sumerized as follows:(1) A novel core-shell SPS-Cu(II)@Cu3(BTC)2catalyst composed of a sulfonated-polystyrene (SPS) core, an active Cu(II) interface and a microporous Cu3(BTC)2shell was synthesized via a facile step-by-step assembly method for catalyzing aerobic oxidation of alcohols by molecular oxygen under base-free conditions. The free Cu2+ions and-SO3H groups on the SPS-Cu(II) interface promoted the disproportionation of the co-catalyst2,2,6,6-tetramethyl-piperidyl-l-oxy (TEMPO) and finally enhanced the catalytic activity. The porous Cu3(BTC)2shell outside of the SPS-Cu(II) core protected the active component from metal leaching as well as provided porous channels for mass transfer, resulting in high stability and recyclability in the catalysis procedure.(2) A novel Fe3O4-CuO@meso-SiO2catalyst consisting of a Fe3O4-CuO nanohybrid core and a tunable mesoporous silica shell with perpendicularly aligned pore channels was synthesized. The obtained catalyst exhibited excellent activity and good stability in the catalytic epoxidation of olefin. The Fe3O4microspheres not only offered fast and effective recycling properties for the catalyst but also acted as electron donors to CuO, leading to a higher electron density on the CuO surface and a subsequently enhanced catalytic performance. The mesoporous silica shell provided strong protection against the aggregation and leaking of the active CuO nanoparticles and also offered appropriate channels for an efficient mass transfer of the catalytic reaction.(3) A novel ultrasonic post-grafting method has been developed to synthesize highly-loaded and well-dispersed CuO nanoclusters inside the channels of mesoporous silica (SBA-15) to prepare the CuO@SBA-15nanocomposite. To enhance the loading capacity of the mesoporous silica support, the external and internal surfaces of SBA-15were modified with-CH3groups and-NH2groups, respectively. The-CH3groups on the external surface can restrain the growth of Cu particles outside of the channels of SBA-15and the-NH2groups on the internal surface of the channels can increase the ability to anchor copper ions.The acoustic cavitation generated by the ultrasonic treatment creates extreme local pressures, temperatures and cooling rates at the collapse sites which can provide a driving force for higher loading and better dispersion of the CuO nanoparticles into the mesopores of the SBA-15support. The CuO@SBA-15composite exhibited good catalytic activity and selectivity for the direct hydroxylation of benzene to phenol. Higher catalytic activity was observed when the Cu content increased. The optimal catalytic results was gained from the sample of CuO@SBA-15with13.4wt.%Cu content. With the same Cu content, the increase of the CuO dispersion led to a higher catalytic activity.