Nanoglobular carbon and palladium–nanoglobular carbon catalysts for liquid-phase hydrogenation of organic compounds

Abstract

The results of studies related to the development of synthesis, determination of formation conditions and elucidation of the mechanism of palladium–carbon catalyst action are integrated and critically analyzed. The attention is focused on Pd/NGC compositions (NGC is nanoglobular carbon). Methods for NGC preparation with an emphasis on its most common form, carbon black, are considered. The following issues are addressed: mechanisms of formation of carbon nanoglobules and their aggregates, methods of varying the size of nanoglobules, functionalization of the NGC surface to make it suitable as a support for palladium nanoparticles, views on the formation mechanism of palladium clusters and nanoparticles on the carbon support surface and effect of the structure and surface chemistry of carbon nanoglobules on the state of palladium sites in Pd/NGC compositions. The published data on selective hydrogenation of organic compounds in the presence of Pd/NGC catalytic compositions are integrated and systematized. The catalytic properties of Pd/NGC are analyzed in comparison with the properties of palladium catalysts supported on other carbon materials (activated carbon, carbon nanotubes). The influence of preparation conditions of NGC-based palladium compositions on their catalytic properties in practically important hydrogenation reactions is discussed. Promising trends for further research on the development of molecular design methods, study of the genesis of Pd/NGC compositions and extension of their applications in hydrogenation processes are considered. The bibliography includes 623 references.

Activity features of catalysts for thermocatalytic hydrogenation processing of polymer waste

“…The main conclusions obtained as a result of the physicochemical studies and experimental tests of catalysts in this work are in agreement with the data mentioned in the scientific literature [2,5,[32][33][34][35][36][37][38][39][40][41].…”

The phenomenon of “dead” metal in heterogeneous catalysis: opportunities for increasing the efficiency of carbon-supported metal catalysts

“…Varieties of NGC differ significantly in such aggregate and nanoglobule sizes. 30,49 For instance, furnace NGCs consist of tens to hundreds of small nanoglobules (10–80 nm) arranged in branched aggregates, possessing a somewhat developed interglobular space teeming with “dead zones”. Supported metal NPs could be obscured from larger adsorbate or reactant molecules.…”

“…The side facets of graphite-like crystallites have been shown to bind metal species strongly. 30,32,46 Under specific conditions, metal atoms localized on these facets can infiltrate the bulk of the carbon support, becoming embedded between the graphene layers near the surface (Fig. 1c).…”

“…For instance, when H 2 [PdCl 4 ] comes into contact with the carbon support under certain conditions, it produces Pd NPs. 30,32,46…”

Role of Acetylene in the Chemical Evolution of Carbon Complexity

“…All the underlying mechanisms are currently based on the key role of PAHs in this process (Figure 19). 416 In recent work, 35 Frenklach and Mebel critically reviewed soot nucleation mechanisms. They quantitatively estimated (by performing kinetic calculations coupled with thermodynamics and DFT calculations) a number of reactions of the dimerization of PAHs.…”