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[Display omitted] • Non-precious intermetallic compound catalysts for propane dehydrogenation. • Scaling relations are established using formation energies over terraces and steps. • Descriptor-based microkinetic analysis is carried out to obtain volcano curves. • Fe 3 Ga 1 is a good catalyst candidate with improved catalytic performance. By using a descriptor-based microkinetic analysis combined with results from density functional theory calculations over eight transition-metal (including Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) terrace and stepped surfaces, intermetallic compounds have been screened to search for inexpensive and environmentally friendly propane dehydrogenation (PDH) catalysts with enhanced catalytic performance. Based on the scaling relations, the formation energies of ethyl on terrace and methylidyne on stepped surfaces are identified as two descriptors to represent the energetics of other reaction intermediates and transition sates. The derived PDH activity and propylene selectivity volcano curves not only provide a rational interpretation of the previously experimentally reported catalyst candidates, but also predict several unexpected binary combinations by screening 1482 A 3 B 1 and 741 A 1 B 1 intermetallic compounds. The non-precious Fe 3 Ga 1 is then synthesized and evaluated. Its improved propylene selectivity and catalytic stability with respect to those of the Pt catalyst validates the theoretical predictions experimentally. [ABSTRACT FROM AUTHOR]

[Display omitted] • Atomically dispersed Pt-rTiO 2 catalyst shows good catalytic performance for PDH. • Single and dual Pt atoms can be tightly held by vacancies created on reduced TiO 2. • Dual-Pt-atom structure is the active ensemble for the C H bond activation. Tailoring atomically dispersed catalysts by various methods has been the subject of intense current research in heterogeneous catalysis. In this work, the structural stability and propane dehydrogenation performance of Pt-TiO 2 catalysts with single, dual, and triple Pt atoms doped on the reduced TiO 2 surface have been examined. Experimental results indicate the atomically dispersed Pt is thermally very stable and shows exceptionally high activity (TOF propane = 4.93 s−1) and selectivity (∼98.5 %) for the dehydrogenation reaction. The recently developed machine-learning-based SSW-NN method is then employed to explore the global potential energy surface of the atomically dispersed Pt atom-doped TiO 2 , which suggests that the single and dual Pt atoms can be tightly held by the vacancies created on the reduced transition-metal oxide, as confirmed by DFT + U calculated energetics. After that, advanced characterization techniques are used in conjunction with microkinetic analysis to establish the quantitative structure–activity relationships. It is found that the dual-Pt-atom structure with two Pt atoms embedded in adjacent Ti and O vacancies is the only active ensemble that dramatically promotes the C H bond activation and hydrogen recombination, as compared to single Pt atoms accommodated by either Ti or O vacancies. These results provide new and direct evidence in support of the idea that specific function can be imparted to specific active sites by tuning their coordination environments, which makes it possible to tailor the catalytic properties of metal oxides to a particular reaction such as propane dehydrogenation. [ABSTRACT FROM AUTHOR]

Abstract: Dehydrogenation of propane (DHP) was studied over a series of xCr–SBA-15 and xCr–Al2O3 catalysts, prepared by incipient wetness impregnation, to gain a better understanding of the nature and distribution of Cr species and their catalytic function. To this end, the catalysts were characterized by N2-physisorption, X-ray diffraction (XRD), UV-Raman spectroscopy, scanning transmission electron microscopy–energy dispersive X-ray spectroscopy (STEM–EDXS) and X-ray absorption spectroscopy (XANES and EXAFS). All these characterization techniques indicate that, at ⩽1 wt% Cr, SBA-15 contains exclusively uniform distribution of chromium as isolated Cr(VI) species in tetrahedral () coordination, whilst on γ-Al2O3 a fraction of oligomers (including dimers) is present along with isolated species. At ⩾5 wt% Cr, SBA-15 is dominated by crystalline α-Cr2O3 particles, besides a fraction of isolated Cr(VI) species in coordination. Remarkably, γ-Al2O3 contains mainly oligomers with different degrees of nuclearity and a fraction of isolated species but no Cr2O3 particles. Among xCr–SBA-15 catalysts, those containing exclusively isolated Cr species (i.e., ⩽1 wt% Cr) exhibit higher activity and selectivity with respect to per mole of Cr than the catalyst dominated by crystalline α-Cr2O3 particles (⩾5 wt% Cr). The intrinsic activity of these isolated Cr species is higher than those observed on γ-Al2O3 (⩽1 wt% Cr). Interestingly, among xCr–Al2O3, the catalysts dominated by oligomeric species show the highest activity, indicating the important role of the species in the reaction. In situ XAS studies evidence that active Cr sites are apparently generated on-site during the reaction and that Cr is typically in (III) oxidation state. Based on ex situ and in situ characterization results and catalytic data, it appears that the activity of the Cr species is different in xCr–SBA-15 and xCr–Al2O3. For xCr–SBA-15, isolated Cr(III) sites with coordination number greater than four are more active, selective and stable than Cr sites on the surface of crystalline Cr2O3. In contrast, for xCr–Al2O3, oligomeric Cr species are more active and selective than the isolated Cr sites. [Copyright &y& Elsevier]