Vliv bází na průběh reakcí přenosu vodíku katalyzovaných heterogenními Lewisovými kyselinami

Veselá, Klára

Heterogeneous Lewis acid zeolites catalyzed Meerwein-Ponndorf-Verley (MPV) reduction (transfer hydrogenation), where ketones and aldehydes are reduced to the corresponding alcohols. The hydrogen is taken from a secondary alcohol. These Lewis acid zeolite catalysts have a great advantage over homogenous catalysts as they are well separable from the reaction mixture and recyclable. Lewis acid zeolites are materials that contain incorporated tin or zirconium species, which act as Lewis acid sites. MPV reduction of citronellal provides citronellol as a product. However, the reaction of citronellal with 2- propanol also proceeds via a parallel reaction pathway providing isopulegol as the major product. Addition of pyridine (an organic base) to the reaction mixture switches the selectivity of the reaction, i.e., citronellol becomes the main product of the cited citronellal reaction with 2-propanol. It was investigated whether this phenomenon would also be observed for reactions with the addition of different bases. To answer these questions, Sn-BEA and Zr-BEA were prepared by hydrothermal synthesis. Impreg-Zr-BEA and impreg-Sn-BEA were prepared by postsynthesis metal incorporation. In addition, highly porous 2D Self-pillared pentasil zeolites containing tin and zirconium were hydrothermally synthesized....

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