A series of Au/MnOx catalysts with the Au content ranging from 0 to 10 at%, a 19.5 wt% Pt/SnOx catalyst and a commercially available 2 wt% Pt/SnOx catalyst have been examined for activity toward low-temperature CO oxidation. A 1 atm, 10 sccm stoichiometric mixture of CO (1 vol.%) and O2 in He were reacted at 55°C over 100 mg of each catalyst for time periods as long as 20,000 min. Under these conditions a 10 at% Au/MnOx catalyst exhibits the highest activity and the lowest decay. Outgassing experiments indicate that CO2 retention is primarily responsible for the activity decay of the Pt/SnOx catalysts and that the 10 at% Au/MnOx catalyst is not significantly affected by this process.

Pt/Fe electrocatalysts (Pt/Fe) supported on Vulcan XC-72 carbon black were prepared by chemical method. The formation of Pt/Fe clusters was confirmed by transmission electron microscopy (TEM) and energy dispersive x-ray spectrometry (EDXS). The electrochemical efficiency and durability of the catalysts for direct methanol oxidation were compared with the catalyst containing Pt only (Pt) under the same reaction conditions of 1 M CH3OH in 0.1 M H2SO4 electrolyte solution. The current density for the Pt/Fe is three times of that of the Pt catalyst. Effects of various factors on the behavior of the catalysts, such as reaction time during preparation, order of the addition of the chemicals into the reaction system, methanol concentration, activation per unit Pt, scan rate for cyclic voltammograph, were examined.

A system made by combining two non-alloying metals, ruthenium and copper, using alumina as a support was studied. This bimetallic supported catalyst has been used mainly in hydrogenolysis, dehydrogenation and oxidation reactions of hydrocarbons. The samples were characterized by Electron Paramagnetic Resonance Spectrometry (EPR) and X-ray Diffraction (XRD). These two molecular techniques are ideal for studying the electronic and structural changes of the samples at different temperatures and concentrations. Catalytic reactions were performed using the catalyst in the reduced and non-reduced forms on a series of catalytic hydrogenations. A correlation between the electronic, structural and catalytic properties has been made. A correlation of catalytic process to molecular phenomena has yield a better understanding of the catalytic site.

Model Pd-Au/SiO2 catalysts were prepared via a microfabrication methodology and their catalytic activity was evaluated using the hydrogenation of 1,3-butadiene as a probe reaction. The catalytic particles of the microfabricated catalyst were Pd-Au squares, ranging in composition, each approximately 4 µm in size and separated by 4 µm on a silica/silicon support. The reaction was carried out at atmospheric pressure with a hydrogen to hydrocarbon ratio of 125. The bimetallic catalysts exhibited lower apparent activation energies than the pure Pd catalyst with a minimum occurring at ˜65 at% Pd. Corresponding to the decrease in activation energy, there is an increase in the turnover frequency over the monometallic catalyst at low temperatures, i.e. room temperature. At high temperatures (above 200°C) the pure Pd catalyst has the highest conversion (0.61) and the largest pre-exponential factor (4.71×1016 cc/g Pd/s), while the 73 at% Pd catalyst has the lowest conversion (0.45) and the smallest pre-exponential factor (5.59 × 10 6 cc/g Pd/s). The bimetallic catalysts also showed a higher selectivity towards 1-butene than the monometallic catalyst; however, at lower conversions (less than 25%) the pure Pd catalyst was more selectivity towards 1-butene. AFM was used to characterize the surface morphology of each of the samples.

The application of heterogeneous asymmetric catalysis to fine chemicals synthesis is discussed. The asymmetric synthesis of naproxen, a non-steroidal antiinflammatory drug, using a novel, heterogeneous, chiral catalyst is used as an example to illustrate the feasibility to industrial application.

Novel copolymer composite resins have been synthesized using the surface assembled hybrid technology. Monodisperse polystyrene/DVB microspheres with diameters of 5.3 and 7.5 μm and polydisperse carbonaceous and acrylic microspheres with diameters ranging from 5–30 μm have been assembled onto the surface of styrene and acrylonitrile based gel and macroreticular resins.

Carbonaceous adsorbents with holes of controlled diameter on their surfaces have been prepared using the surface assembling technique. Core-shell carbonaceous adsorbents with divergent surface chemistries have been prepared using this technique

Novel catalytic materials have been made and are envisioned using the assembling technique to form short-diffusion path reactive systems. The range of surface functional groups include: strong acid, strong base, palladium, silver, gold and reductive amine-borane.

Copper exchanged and copper-(salen) complex encapsulated in zeolite-Y were prepared. The encapsulaled complex was analysed by TGA, DRS and IR, which confirms the presence of complex in zeolite. Both copper materials were examined by EPR spectra, and the calculated spin-Hamiltonian parameter indicates the copper complex is more covalent in character than NaCu-Y.

Nearly uniform supported metal clusters are the focus of this summary, which addresses their synthesis, characterization, and catalytic properties. Supported clusters represented as Ir4 and Ir6 were prepared on MgO powder by thermal decarbonylation of [HIr4(CO)11]− and [Ir6(CO)15]2−, respectively. The most useful characterization technique for supported clusters is extended X-ray absorption fine structure spectroscopy, but the structure data are limited by the precision of the coordination numbers (about ±20%). Ir4 and Ir6 clusters on supports catalyze hydrogenation of cyclohexene and of toluene, and they are catalytically distinct from larger iridium particles, although the reactions are structure insensitive (proceeding at about the same rate per exposed metal atom) when catalyzed by metal particles larger than about 1 nm. Thus the concept of structure insensitivity does not extend to supported metal clusters, which are regarded as quasi molecular.

The transition metal sulfide clusters (MeCp)2Mo2(μ-SH)2(μ-S)2, (MeCp)2Mo2Co2(μ3-S)2(μ4-S)(CO)4 [MoCoS], and (MeCp)2Mo2 Fe2 (μ3-S)2(CO)8, (MeCp = methylcyclopentadienyl) were used to prepare γ-Al2O3-supported catalysts. For comparison, a series of supported materials was also prepared using conventional incipient wetness impregnation. Infrared spectroscopy of adsorbed species was used to characterize the sites in the clusterderived and conventionally prepared catalysts. Nitric oxide chemisorbed onto the MoCoS/A catalyst was associated initially only with Co sites and then upon gentle heating shifted to the Mo sites, indicating that Co and Mo were in close proximity. In contrast, NO adsorbed onto both Co and Mo sites in the conventionally prepared materials and desorbed independently from these two types of sites. Infrared spectra of adsorbed thiophene and pyridine were similar for the clusterderived and conventionally prepared catalysts. Thiophene reacted at 100 °C to produce both olefinic species. The most abundant products from thiophene HDS were 1-butene, cis-2-butene, and trans-2-butene. Displacement studies showed that thiophene, pyridine, and NO adsorbed to the same site. The most active sites for HDS and HDN contained both Mo and a late transition metal. The HDN product distributions suggested that Mo was selective for C=N bond cleavage while the late transition metals were more active for C=C hydrogenolysis.

Complex cobalt-carbonyl ligand based clusters of clusters are used as molecular precursors for self-supported model catalysts. These precursors consist of two metal layers: an outer of the complex Co-carbonyl ligands, and a core of metal (e.g. Co or Zn) carboxylate groups. Partial thermolysis at low temperature (LT) of these materials under hydrogen results in almost completely decarbonylated material with a mainly unchanged carboxylate metal core. Complete pyrolysis at higher temperatures (HT) in hydrogen leads to mixed metal environment. These materials were used as a heterogenous catalyst in the gas phase hydrogenation of crotonaldehyde. The maximum yield of 27 % of desired product crotyl alcohol was observed when HT-CoCo was used as the catalyst at 423 K. The catalyst activity and the crotyl alcohol selectivity remained unchanged over 2 days of operation. The bimetallic ZnCo catalysts showed lower selectivity to crotyl alcohol than the CoCo catalysts.

Our recent studies on the acidity and acid catalysis of heteropoly compounds are described, together with a brief introduction of the background. High catalytic activities were observed due to the combination of their superacidity, pseudoliquid behavior, acid-base bifunctionality and/or high surface concentration of proton. It was also shown how the acid strength and the number of acid sites as well as their tertiary structure were controlled by the constituent elements (heteroand addenda-atoms and counter cations), and how those properties were correlated with the catalytic activities

Na+ in the Preyssler heteropolytungstate anion [NaP5W30O110]14− can be exchanged for a trivalent lanthanide ion. The potential significance of this new class of lanthanide heteropolyanions relates to their applications in catalysis science. This view follows from the fact that Keggin heteropolyanions and their free acids are used as heterogeneous solid catalysts and homogeneous solution catalysts. We describe synthetic conditions that lead to the incorporation of Ce3+ and Pr3+ within the Preyssler anion, and the coprecipitation of Ce3+ and the Preyssler anion. Initial studies indicate that the latter, coprecipitated, material deserves study for bifunctional catalytic activity.

Hetreropolyoxoanions(HPAs) have received wide spread attention due to their unique oxidation-reduction properties in catalysis. Two main structural motifs groups of HPAs have been described by Keggin and Dawson. The first is composed of twelve distorted, octahedrallycoordinated metal atoms forming trimeric and tetrameric subunits connected such that a closed shell results. The second is formed by fusing two Keggin units. The most common Keggin ions(XM12O40n−,) with Td symmetry and the Dawson ions(X2M18O62n−) with D3h symmetry are the α-isomers; while the β-isomers are generated by rotating one trimer 60° along its C3 axis, thus producing the Cs, symmetry for β-Keggin ions and D34 symmetry for β-Dawson ions. Here, M is the framework metal atom, usually Mo, W, and X is the central heteroatom which can be the metal or nonmetal. From our previous studies, the instability of β-isomers caused by the “rotated” trimer can not be compensated by other coordination effects within the cluster and therefore defect states are retained between the HOMO-LUMO gap relative to the α-isomer. This enhances catalytic properties and causes thermal/photo lability. The catalytic function of a-Keggin ions are well studied; however, related research reports about Dawson ions are rare. The α-Dawson ion possesses stronger oxidizing ability and higher activities in oxidative dehydrogenation and oxygen addition reactions than the α-Keggin ions; the β-isomers have a greater tendency to be reduced than the α-isomers. Most of the characterization methods applied have not yielded the electronic or the structural requisites for the catalytic properties of the HPAs. In this work, the theoretical analysis is done through the application of crystal/tight binding theory coupled with the extended HMckel methodology. The stability trends and the redox behaviors provided by this work reliably trace the experimental data. In addition, the intrinsic instability and the redox effects in the β-isomers with respect to the α-isomers is assessed and a rationale for the observed catalytic and electronic develpoment of structrual function is also offered.

We have explored and developed laser ablation as a tool to synthesize realistic planar models of high surface area catalysts as well as novel materials, not accessible with wet chemical methods. The process is illustrated by data for dispersion and electron structure modifications following thermal treatments of alumina supported copper oxide. Planar models of different wet and dry carrier/overlayer combinations were prepared and exposed to oxidizing and reducing atmosphere at 500°C. Characterization was made by XPS/ESCA. The data reveal the importance of surface hydroxyl groups in the two initial components to control coalescence and interdiffusion. The ablation route is part of our ongoing DENOX project and comparisons are made with other materials, tested for their materials properties and catalytic behavior in HC/NO reactions.

Carbon-carbon bond cleavage catalysts produced in situ at reaction conditions from nanocrystalline hydrated iron oxides, show high activity and selectivity in model compound studies. Two highly active catalyst precursors, ferric oxyhydroxysulfate (OHS) and 6-line ferrihydrite, can be produced by a flow-through hydrothermal powder synthesis method, the Rapid Thermal Decomposition of precursors in Solution (RTDS) process. Model compound studies indicate that both catalyst precursors are active at a 400°C reaction temperature, but that there are significant differences in their catalytic characteristics. The activity of 6-line ferrihydrite is highly dependent on the particle (aggregate) size whereas the activity of the OHS is essentially independent of particle size. These differences are attributed to variations in the crystallite aggregation and particle surface characteristics of the two catalyst precursor materials. Catalytic activity is retained to lower reaction temperatures in tests using OHS than in similar tests using 6-line ferrihydrite.

NiO/ZrO2 catalyst has a selectivity for producing higher hydrocarbons, whereas NiO on classical supports gives rise to methanation of CO + H2 mixture. In this study, tetragonal and monoclinic ZrO2 gel carriers have been synthesized using sol-gel method. The interaction of nickel ions with a sol-gel derived catalyst support has been investigated using FTIR, DTA, and XPS. It is found that the nickel ions diffuses into the ZrO2 continuously over 400 to 600°C for both tetragonal and monoclinic ZrO2, and forms a thermodynamically stable Ni/ZrO2 solid solution at elevated calcination temperatures. Higher nickel surface contents are observed in tetragonal ZrO2. In addition to Ni2+, Ni3+ ions are also detected in Ni/ZrO2 system. Cation ratio of Ni2+/Ni3+ peaks at 700°C in the tetragonal ZrO2. In the monoclinic case, the ratio remains constant at different elevated temperatures. The diffusion activation energy for Ni(II,III) on both tetragonal and monoclinic in ZrO2 is 0.40 eV.

Catalysts formed by sorption of Cr(VI) on to tin(IV) oxide have been investigated by EXAFS, XPS and TEM. The latter shows that uncalcined catalysts comprise uniform, homogeneous particles of dimensions 2nm which increase to 4nm on calcination at 400°C. Calcination at higher temperatures results in an increase in particle size to 20nm × 30nm at 600°C, ca. 60nm at 800°C, and 90–100nm at 1000°C. XPS data show the evolution of chromium(III) species upon calcination and both chromium(VI) and chromium(III) species exist at all calcination temperatures. Chromium K-edge XANES also shows the presence of tetrahedral chromium(VI) species at all calcination temperatures, but the relative abundance decreases with increase in calcination temperature. Corresponding EXAFS data indicate that the uncalcined catalyst contains sorbed four-coordinated {Cr2O7} species whereas calcination produces six-coordinated {CrO6} species together with some residual tetrahedrally coordinated chromium. EXAFS data show that adsorbed {Cu(H2O)6} is the copper(II) species present prior to calcination of CuII-SnO2 catalysts.

We present a study of a Bi-Mo catalyst, obtained by solid state reaction, for the oxidation of CO. Bismuth-molybdate catalysts form several phases (β3-Bi2Mo2O9, α-Bi2Mo3O12 and γ-Bi2MoO6, among others), depending upon the Bi/Mo ratio and the preparation method [1]. The γ-Bi2MoO6 phase is the one that is stable at high temperatures, according to the phase diagram, and is the one we used as catalyst for the conversion of CO [2].

Studies of the mixed-metal interface in metal impregnated alumina have indicated the possibility of much metal-metal and metal-substrate interaction. Studies were carried out on NiCu/Al2O3 system which was evaluated to develop a better understanding of the forces that drive modification of the catalytic selectivity of Ni in the presence of Cu. Electron Paramagnetic Resonance (EPR), Powder X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD) and theoretical calculations were carried out on this bimetallic system, using Ni,Ag/Al2O3 as a reference as Ni shows negligible electron perturbation on co-adsorbance with Ag onto alumina. XRD results indicate that gross modification of the electronic fields of Ni and Cu are due to direct coupling and intercalation into the alumina matrix. As a result of this phenomena, these materials may form a good base for the development of novel ceramics based on mixed-metal interactions where the intermetallic perturbations are driven by the substrate effects.

An oxidative catalytic route for the decomposition of nerve gases was investigated using hydroxyapatite (HA, chemical composition Ca10(PO4)6(OH)2) and its partially fluorinated analog fluorhydroxyapatite (FHA, Ca10(PO4)6Fx(OH)2−x). Samples were prepared with surface areas ranging from 34 to 238 m2/g to study surface area effects; 1.2 wt. % platinum was deposited on one substrate to investigate the effect of a transition metal on activity and selectivity. Reaction studies were performed using dimethyl methylphosphonate (DMMP), a nerve gas simulant, in a stream of 80 percent nitrogen and 20 percent oxygen at 573 K and atmospheric pressure. High surface area FHA samples showed an increase in the "protection period" (period of 100% conversion) with increasing fluorine substitution; such an increase was not seen for low surface area FHA samples. In the absence of platinum, the reaction products were methanol and dimethyl ether; with platinum, CO2 was also obtained.