Introduction:Coke formation continues to be an important challenge for Pt-based catalysts during propane dehydrogenation (PDH) . Boron promotion drastically reduces coke formation on nickel during steam reforming and on cobalt during Fischer-Tropsch synthesis. DFT calculations and catalyst characterization indicate that reduced boron atoms selectively block step and/or subsurface sites, thus preventing nucleation and growth of deactivating carbon .In this work, boron is introduced to enhance the catalytic performance of Pt/γ-Al O catalysts during PDH. A series of catalysts with different boron loadings was prepared following various impregnation sequences. Detailed characterization and DFT calculations help identify boron's location and state (alloy/amorphous oxide). Results: XB-γ-Al O support materials (X=wt.%B) were prepared via wet impregnation of H BO onto commercial γ-Al O . Three different synthesis routes were followed: (a) Pt/XB-γ-Al O catalysts were prepared via wet impregnation of H PtCl onto XB-γ-Al O . (b) 1B/Pt-γ-Al O was prepared via wet impregnation of H BO onto Pt/γ-Al O i.e., an inverse sequential impregnation. (c) Pt-1B-γ-Al O was prepared by co-impregnation. Pt/γ-Al O was prepared as a reference. The platinum loading was fixed at 3wt.% to facilitate characterization and obtain B/Pt (mol) ratios from 1-10.Effects of boron loading and impregnation sequence were investigated during short-term (20 min) PDH tests at 600 C and a C H /H ratio of one. Unlike with nickel and cobalt, the promoting effect of boron was only observed when boron was introduced before the active metal. The Pt/1B-γ-Al O catalyst showed only a minor reduction in activity during the short-term experiment but achieved a 2.6-fold reduction in the amount of deposited carbon for an optimal loading of 1wt.% B. Long-term experiments (12 hr) confirmed the improved stability and selectivity of Pt/1B-γ-Al O , (Fig. 1a) with a 3.2-fold reduction in deposited carbon and an increase in propylene selectivity from 92 to 98%. TPO-profiles (Fig. 1b) of spent catalysts show that boron promotion eliminates and reduces the low-and high-temperature carbon oxidation peaks, respectively. Propylene decomposition experiments on pure and boron-modified γ-Al O relate the low-temperature peak to carbon formed on the support.

The ethanol steam reforming reaction, together with the adsorption and decomposition of ethanol was studied on CeO 2 and gallium-doped ceria (CeGaO x) by a combined experimental and theoretical approach using infrared spectroscopy (IR), mass spectrometry (MS) and density functional theory (DFT) calculations. At 100°C, different types of monodentate ethoxy species were identified as standing-up (SU) on Ce 4+ and lying-down (LD) on Ce 4+ and Ga 3+ , with the alkyl chain more perpendicular or parallel to the surface, respectively. It is suggested that the incorporation of Ga into the ceria lattice changes the decomposition pathway of LD species, which converts to acetate instead of ethylene, attributed to the increased lattice oxygen lability in the CeOGa interface upon doping and the propensity to form GaH surface species. Under ethanol steam reforming conditions, Ga doping of ceriabased materials has a drastic effect by improving the H 2 :CO 2 ratio, changing the product distribution and reducing coke formation.

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The ethanol surface reaction over CeO 2 nanooctahedra (NO) and nanocubes (NC), which mainly expose (111) and (100) surfaces, respectively, was studied by means of infrared spectroscopy (TPSR-IR), mass spectrometry (TPSR-MS), and density functional theory (DFT) calculations. TPSR-MS results show that the production of H 2 is 2.4 times higher on CeO 2 -NC than on CeO 2 -NO, which is rationalized starting from the different types of adsorbed ethoxy species controlled by the shape of the ceria particles. Over the CeO 2 (111) surface, monodentate type I and II ethoxy species with the alkyl chain perpendicular or parallel to the surface, respectively, were identified. Meanwhile, on the CeO 2 (100) surface, bidentate and monodentate type III ethoxy species on the checkerboard O-terminated surface and on a pyramid of the reconstructed (100) surface, respectively, are found. The more labile surface ethoxy species on each ceria nanoshape, which are the monodentate type I or III ethoxy on CeO 2 -NO and CeO 2 -NC, respectively, react on the surface to give acetate species that decompose to CO 2 and CH 4 , while H 2 is formed via the recombination of hydroxyl species. In addition, the more stable monodentate type II and bidentate ethoxy species on CeO 2 -NO and CeO 2 -NC, respectively, give an ethylenedioxy intermediate, the binding of which is facet-dependent. On the (111) facet, the less strongly bound ethylenedioxy desorbs as ethylene, whereas on the (100) facet, the more strongly bound intermediate also produces CO 2 and H 2 via formate species. Thus, on the (100) facet, an additional pathway toward H 2 formation is found. ESR activity measurements show an enhanced H 2 production on the nanocubes.

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