Co/Al2O3 catalysts were synthesized by dry impregnation and controlled adsorption. The effect of catalyst preparation methods on their performance in methane dry reforming was studied.

The surface species formed by glycerol on γ-Al2O3, TiO2 anatase, ZrO2, MgO, and CeO2 both in the presence and in the absence of bulk water are investigated with infrared spectroscopy. The acid–base properties of the metal oxides are characterized by pyridine and CO2 adsorption/temperature-programmed desorption. The metal oxides studied provide a distribution of strengths of Lewis acid sites as well as strengths and types of basic sites which afford insight into the role of these various sites in polyol/metal oxide surface interactions. Even in the presence of bulk water, glycerol forms a bridging alkoxy bond through a primary alcohol group to two coordinatively unsaturated metal atoms and participates in a Lewis acid/base interaction between the oxygen atom of the other primary alcohol and a coordinatively unsaturated metal atom that is also involved in the alkoxy bond. These interactions only occur with metal oxides which contain strong Lewis acid sites. A quantitative correlation between the C–O stretching frequencies of the chemisorbed groups and the electronegativity of the metal atoms is established. Glycerol experiences an additional surface interaction via a hydrogen-bonding interaction between its secondary alcohol group and a relatively weak basic surface oxygen atom. Stronger base sites are blocked by adsorbed water or CO2. In the absence of strong Lewis acid sites, in the case of MgO, hydrogen-bonding interactions between glycerol and surface hydroxyls are the dominant means of interaction.

a b s t r a c tNickel catalysts prepared by a variety of different methods are commonly used for reforming reactions such as methane dry reforming. Two preparation methods, controlled adsorption and dry impregnation, are implemented to explore the effect of preparation method on the formation of active sites on alumina supported nickel catalysts. By varying only the preparation method, comparison of catalysts that differ primarily in metal-support interactions, strong metal-support interaction (controlled adsorption) and weak metal-support interactions (dry impregnation), are obtained. For controlled adsorption, optimal synthesis conditions are identified using point of zero charge measurements, pH-precipitation experiments, and adsorption isotherms. Using these conditions, a catalyst with a higher dispersion and strong metal-support interactions is prepared. Physicochemical characterization by N 2 physisorption, H 2 chemisorption, temperature programmed reduction (TPR), transmission electron microscopy (TEM), and environmental TEM (ETEM) shows that the types of nickel sites formed strongly depend on the synthesis method. Methane dry reforming reactivity studies show stable catalytic performance for at least 9 h and provide additional insight into the types of active centers present. After reductive pretreatment, the nickel catalyst prepared by dry impregnation is found to primarily have nickel present as a surface NiAl 2 O 4 . In contrast, the active centers for the nickel catalyst prepared by controlled adsorption consist of nickel particles that are encapsulated by a nickel aluminate layer with 1-2 nm in thickness. Combustion analysis and XPS of spent catalysts reveal different amounts and nature of carbonaceous deposits as a function of the synthesis method.

Carbide-derived carbons with embedded Fe nanoparticles are synthesized by partial chlorination of iron carbide at 600 o C. Interestingly, the residual Fe studied by X-ray absorption near edge spectroscopy, scanning electron microscopy, and transmission electron microscopy show the extraction process does not follow a layer-by-layer extraction process, as proposed in the literature for the chlorination of other carbides. Instead, a large percentage of iron carbide converts to iron (II) and iron (III) chloride nanoparticles, which remain trapped within the resulting nanoporous carbon framework. Further reductive treatment can be used to produce dispersed Fe nanoparticles with an average particle diameter approaching 10nm.