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This work investigates the effect of the Potassium promoter and the calcination temperature on the catalytic activity in the dry reforming of methane reaction and compares the performance of the Ni, Co, Fe–Al2O3 trimetallic catalysts with the reference Ni–Al2O3. Although higher activity was achieved with the Ni–Al2O3, trimetallic catalysts resulted in a more favorable CO/H2 ratio and considerably better coke resistance. Higher calcination temperature led to the increase in coke formation which caused the sintering of the catalysts. Promoting samples with 0.5%K in order to improve the coke formation resistance, reduced the catalytic activity. [ABSTRACT FROM AUTHOR]

Zn- and Mn-doped Cerium-oxide based catalyst textured as a solid solutional as well as interfacial form was compared in CO2 hydrogenation reaction to understand the role of texture as well as dopant type. Ce0.9M0.1O2 (M = Zn, Mn) solid solution was prepared by hydrothermal method and CeO2 supported 10 mol% metal oxide (Metal = Zn, Mn) were prepared by wet impregnation method, where the catalysts were characterized by XRD, N2 adsorption/desorption isotherm, TEM, Raman spectra, HAADF-STEM and H2-TPR. During the CO2 activation reaction, CO was the major product with minor amounts of methane, ethane, methanol and ethanol. In the case of the Zn-doped CeO2 catalyst, the presence of Zn improved catalytic activity in both solid solutional and interfacial form due to the synergetic effect of Zn-Ce-based oxide. However, for MnOx/CeO2 catalysts, the CO2 consumption rate significantly decreased for 10 mol% MnOx/CeO2, Ce0.9Mn0.1O2 and Mn3O4, where the MnOx addition inhibits the reduction of CeO2. In the case of the pure CeO2, DRIFTS spectra show that formate intermediate formed by reaction between activated CO2 and OH transformed into methoxy species through formaldehyde intermediates, which leads to the formation of small amount of methanol and ethanol. [ABSTRACT FROM AUTHOR]

• Series of free-standing as well as controlled size Pt nanoparticles-loaded mesoporous metal oxides. • Pt-free NiO exhibited the highest catalytic activity and showing 100% CH 4 selectivity. • Striking catalytic properties can be ascribed to the presence of metallic Ni and the optimal dynamics of Ni/NiO x structure. In this study, a series of free-standing as well as controlled size Pt nanoparticles-loaded mesoporous metal oxides (NiO, Co 3 O 4, CeO 2 and MnO 2) with high surface area and designed pore structure were prepared by hard template method and used as catalysts for CO 2 hydrogenation together with dry reforming of CO 2 with methane. The physicochemical properties of catalysts were analysed by N 2 adsorption-desorption isotherm, XRD, TEM, and H 2 -TPR. Pt-free and Pt-loaded mesoporous NiO and Co 3 O 4 performed with high catalytic activity and selectivity for both CO 2 activation reactions. Pt-free NiO exhibited the highest catalytic activity and also showing 100% CH 4 selectivity between 473–673 K and ˜1:1 H 2 /CO 2 ratio between 673–973 K in CO 2 hydrogenation and dry reforming with methane, respectively. The enhanced catalytic properties can be due to the existence of metallic Ni as well as the optimal dynamics of Ni/NiO x structure under reaction conditions. [ABSTRACT FROM AUTHOR]

Rh is one of the most effective metals in several technologically important heterogeneous catalytic reactions, like the hydrogenation of CO2, and CO, the CO+H2O reaction, and methane and ethanol transformations. Titania and titanates are among the most frequently studied supports for Rh nanoparticles. The present study demonstrates that the nature of the support has a marked influence on the specific activity. For comparison, the catalytic activity of TiO2 P25 is also presented. It is pointed out that a certain amount of Rh can be stabilized as cation (Rh+) in ion-exchange positions (i.e., in atomic scale distribution) of the titanate framework. This ionic form does not exists on TiO2. We pay distinguished attention not only to the electronic interaction between Rh metal and the titania/titanate support, but also to the Rh-induced phase transitions of one-dimensional titanate nanowires (TiONW) and nanotubes (TiONT). Support transformation phenomena can be observed in Rh-loaded titanates. Rh decorated nanowires transform into the TiO2(B) phase, whereas their pristine counterparts recrystallize into anatase. The formation of anatase is dominant during the thermal annealing process in both acid-treated and Rh-decorated nanotubes; Rh catalysis this transformation. We demonstrate that the phase transformations and the formation of Rh nanoclusters and incorporated Rh ions affect the conversion and the selectivity of the reactions. The following initial activity order was found in the CO2 + H2, CO + H2O and C2H5OH decomposition reactions: Rh/TiO2 (Degussa P25) ≥ Rh/TiONW > Rh/TiONT. On the other hand it is remarkable that the hydrogen selectivity in ethanol decomposition was two times higher on Rh/TiONW and Rh/TiO(NT) catalysts than on Rh/TiO2 due to the presence of Rh+ cations incorporated into the framework of the titanate structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • PtNPs enhance CO 2 methanation activity in mesoporous and commercial Co 3 O 4 differently. • Partial coverage of Co-Pt alloy particles by the Co x O y layer has been postulated. • New basic centres are responsible for the higher enhancement effect of the Pt/c-Co 3 O 4. Based on our previous investigations, it turned out that the Co 3 O 4 material is a promising catalyst in the ambient pressure CO 2 methanation. This work aims at understanding the Pt-Cobalt-Oxide surface interaction and its effect on the catalytic performance. The incorporation of Pt nanoparticles into the mesoporous Co 3 O 4 (Pt/m-Co 3 O 4) and commercial Co 3 O 4 (Pt/c-Co 3 O 4) improves the catalytic activity of both catalysts by a factor of ∼ 1.4 and ∼ 1.9 respectively at 673 K. The same tendency towards the increased basicity was also observed. Morphology-induced surface basicity was previously shown to play a key role in determining the catalytic activity of free-standing supports. From HR-TEM (-EDX), EXAFS, CO 2 -TPD, and CO chemisorption measurements it was established that during the pre-treatment, Co-Pt alloy particles partially covered by the Co x O y layer are formed. It has been postulated that this structure transformation generates new basic centres, the amount of which per unit surface area is significantly larger for Pt/c-Co 3 O 4 and this in turn is responsible for the higher enhancement effect of the Pt/c-Co 3 O 4 catalyst in the CO 2 methanation. This study emphasizes the importance of the surface structure exploration for the dynamic catalytic systems in order to reach maximum activity and selectivity in the CO 2 methanation. [ABSTRACT FROM AUTHOR]