Catalytic Phases Embedded in Mesostructured Matrices and their Nanocasts: Effects of Spatial Dimension and Assembling Mode on Activity

This chapter appraises the insertion of catalytic phases inside the pores of mesostructured host matrices allows simultaneous control of the catalytic phase size and assembling modes: nanoparticles ensemble, nanowires, or coating layers. These phases include transition metals, their oxides, mixed hydroxides and sulfides, zeolites, pillared clays, heteropolyacids, and other compounds. The maximization of the catalytic reaction rate (catalysts activity) requires uppermost exposure of these catalytically active atoms or atomic assembles to the reactants. The geometric modeling showed that surface areas of catalytic phases inMHMs and corresponding nanocasts are determined by their assembling mode. At the same value of CP spatial dimension it decreases in the sequence nanoparticles>nanowires> coating layer. The control of catalytic phase assembling mode in catalytic phase-mesostructured host matrix composites and their nanocasts is a viable tool for improvement of catalytic performance. The CP/MHM composites are prepared by insertion of corresponding CPs or their precursors in the mobile form of solution, vapor or melt to the pore system of an MHM at its synthesis stage or by postsynthetic treatments followed by special activation procedures. The assembling mode of a CP is usually evaluated by combining several characterization techniques including N2 adsorption-desorption (N2-AD), small and wide angle X-ray diffraction (XRD), HRTEM, and scanning electron microscopy (SEM) both united with the energy dispersive X-ray spectrometry (EDS). The available information about the directing of a catalytic phase to proper assembling modes created in mesostructured host matrices and in corresponding nanocasts and their effects on catalytic performance of catalytic phases is also analyzed in the chapter.