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[Display omitted] • A geometric model based on particles with truncated octahedron shape was developed. • The model quantifies surface site concentrations for any fcc metal particle size. • Pt/Al 2 O 3 catalysts with controlled particle sizes were prepared by refilling method. • The propane dehydrogenation (PDH) was proved as a structure sensitive reaction. • Active sites in PDH correspond to the combination of corner and edge Pt atoms. A series of Pt/Al 2 O 3 catalysts with uniform Pt particle sizes ranging from 0.95 to 2.62 nm was synthesized using the refilling method to control the growing of Pt nanoparticles and evaluated in propane dehydrogenation. An effect of particle size on the initial propane activity and TOF was demonstrated, the smallest particles being the most active. A geometric model was developed to quantify the surface site concentration for any fcc metal particle size. Comparing the evolution of initial activity for propane dehydrogenation with the different surface site concentrations, it was shown that the active sites of Pt/Al 2 O 3 catalysts corresponded to the combination of corner and edge atoms. To get further, the model was confronted with numerous data extracted from literature demonstrating that it is an efficient tool to predict the structure–activity relationship of fcc metal catalysts and determine the exact nature of active sites for a wide range of reactions and metals. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Platinum-based catalysts with size ranging from 0.91 to 2.41 nm were synthesized. • Pt particle size effect on methylcyclopentane ring-opening product distribution was evaluated. • Over-production of n -hexane was observed for smaller Pt particles. • Dedicated active sites were identified for the three reaction products. • A geometric model accounting for this product distribution was developed and validated. Abstract Hydrogenolysis of methylcyclopentane was studied in the presence of supported platinum catalysts, with particle sizes between 0.9 and 2.4 nm. The distribution of ring-opening products (n -hexane, 2-methylpentane, 3-methylpentane), which are virtually the only products at 573 K, mainly depended on the platinum particle size, with no effect of the methylcyclopentane conversion. This distribution was well described by the selective or non-selective mechanisms previously proposed in the literature except for the smallest particles (d < 1.5 nm), for which a very high yield in n -hexane was observed. A simplified model was developed combining a geometric approach, for counting the fraction of accessible surface of each superficial atom whatever the Pt particle size, to the knowledge of active sites for each product formation, as determined by DFT calculation. It was demonstrated that the sites responsible for n -hexane formation are corners and some edge sites, whereas 2-methylpentane and 3-methylpentane are formed on faces and a part of the edges. [ABSTRACT FROM AUTHOR]

Cu/ZnO-based catalysts are of industrial importance for the methanol synthesis. However, the selectivity is generally moderate since methanol formation is accompanied with similar amounts of CO. The understanding of how the active site is created is a key for understanding the central role of the Cu–ZnO synergy and for the rational design of active and selective catalysts. Model Cu + ZnO mechanical mixtures with variable composition as well as core–shell structures were employed as a tool for correlating physical to catalytic properties and identify the active site. The catalyst activity was correlated to the number of contact points between Cu and ZnO particles (that generates reactive oxygen vacancies) using a mathematical model for Cu and ZnO contact quantification based on the geometry of spherical particle agglomerates, which is applicable to mechanical mixtures. The structure–activity relationships highlighted in this work opens a way to the rational design of ideal structures of catalysts. [ABSTRACT FROM AUTHOR]

Highly selective catalysts for methanol synthesis from CO 2 and H 2 are required for increasing the process efficiency that actually produces large amounts of CO. The understanding of the Cu–ZnO synergy allowed the possibility to design core–shell catalysts of the type Cu@ZnO x with enhanced selectivity for methanol. This type of core–shell structure was synthesized with variable compositions and the catalytic efficiency as well as the physicochemical properties were scrutinized in order to build structure–reactivity relationships. Zn migration is responsible for the formation of the Cu x Zn (1− x ) O y active phase. The experimental results were compared with theoretical calculations based on a geometrical model taking into account the amount of Zn migrated. A direct correlation was found between theory and experiment. Finally, a linear correlation of catalyst activity versus Zn migrated is shown for three different catalyst designs, thus confirming that a high Zn migration is needed for obtaining an efficient methanol synthesis catalyst. [ABSTRACT FROM AUTHOR]

Methanol synthesis from CO 2 over industrial catalysts suffers from a lack of selectivity, since large amounts of CO are formed as by-product. The understanding of the Cu–ZnO synergy in the creation of the active sites for methanol and CO formation is therefore a key for the development of catalysts for CO-free methanol synthesis. Cu–ZnO coprecipitate catalysts with variable compositions were employed as a tool for correlating physical to catalytic properties. Hydrogen spillover on two distinct active sites was demonstrated to be the result of Cu–ZnO contacts. The latter were quantified by using a mathematical model for sphere contact quantification in randomly packed binary mixtures. Theoretical calculations were in total agreement with experimental results. This allowed the rational design of catalysts based on core–shell structures for efficient CO-free methanol synthesis. [ABSTRACT FROM AUTHOR]