It is proposed that the high aromatization selectivity of Pt supported in zeolite L is caused by the ability of the channels to collimate the flux of hexane molecules, leading to end-on adsorption at the Pt surface.

The copper(II) catalyzed oxidation of propylene on CuK-X zeolite was studied over the temperature range of 150 to 400°C in a flow system. Arrhenius activation energies could be obtained at less than 30%conversion from 160 to 210°C and were found to decrease with increasing copper(II) content. These results are correlated with electron spin resonance studies of the migration of copper(II) within the zeolite lattice at the reaction temperature. The change in activation energy with copper(II) content shows that a substantial part of the total activation energy is due to copper(II) migration.

We have examined the adsorption of simple alcohols and 2-propanamine on H-ZSM-5 zeolites with Si/Al2 ratios between 38 and 520. Thermogravimetric analysis (TGA) demonstrated that most of the molecules display a clearly defined adsorption state corresponding to a coverage of one molecule per Al site. Temperature programmed desorption (TPD) and transmission infrared spectroscopy results for each of the molecules in this 1:1 adsorption state are consistent with adsorption being due to the transfer of a proton from the zeolite to the adsorbed molecule. These results provide additional evidence that carefully prepared H-ZSM-5 is a Bronsted acid, with one acid site per framework Al atom, in which all of the acid sites are identical in strength.

MnOx (0.2 < × < 0.5) and AlOx (0.5 < × < 1.1) /Ni(lll) model catalysts were prepared by depositing the oxides onto clean Ni(111) surfaces under ultrahigh vacuum conditions, with the average oxide coverage varying from 0 to 1.3 monolayers (ML) for MnOx and 0 to 2.8 ML for AlOx. CO chemisorption over these catalysts at 200 K was used to titrate different adsorption sites. Thermal desorption showed the usual prominent CO desorption peak at 415 K from the clean Ni(111) surface. This 415 K peak decreases with increasing oxide coverage in an almost linear fashion, indicating a siteblocking effect by the oxide. At the same time, a new thermal desorption peak appears at 305 K from MnOx/Ni(111) and 300 K from AlOx/Ni(111), reaching maximum intensity at some intermediate oxide coverage. For MnOx/Ni(111), this coincides with the appearance of a new C-0 stretching mode at 1620 cm−1, which disappears upon heating the surface to 325 K for a few minutes, suggesting that both the 305 K thermal desorption peak and the 1620 cm−1 loss peak represent the same adsorbed CO state. This is attributed to CO adsorbed on MnOx/Ni perimeter sites. Results from Monte Carlo simulation and scanning tunneling microscopy are presented and compared with CO chemisorption data. The significance of perimeter sites in strong metal-support interaction is discussed.

The CO2 gasification rate of black liquor char (b1c) is studied in a thermogravimetric analysis set-up at temperatures between 600 to 800° C. B1c is prepared via fast pyrolysis of the dry solids in spent liquor of the kraft wood pulping process. B1c gasification by CO2 is well described by Langmuir-Hinshelwood type kinetics. The gasification rate of blc is one order of magnitude larger than a high surface area activated carbon impregnated with 12% Na2CO3. Also, the gasification rate of b1c remains high at sodium-carbon ratios where the rate of Na2CO3 impregnated chars would be strongly reduced. With SEM-EDS mapping and line scans it is shown that the unique gasification properties of b1c are caused by a very fine distribution of sodium in the carbon structure.

The influence of K, deposited on a carbon surface, on the oxidation of carbon in O2 was investigated. Reaction rate measurements, carried through in a UHV-system by use of AES, showed that potassium increases the reaction rate by up to ∼ 104 times. A theoretical model, based on the assumption that O2 dissociation is the rate limiting step, has been developed. The model shows that a charge transfer mechanism can explain the observed rate increase. Results from TPD/TPR-measurements indicate that the sticking probablility for O2 on a graphite surface with predeposited K is approximately independent on K coverage for coverages down to 0.5 × 1014 cm−2, corresponding to an effective radius of K of ∼ 7.3 Å.

While the STO catalyst characterization procedure has been applied to a variety of supported Pt catalysts, application of this technique to the characterization of supported Pd catalysts showed that there were several significant differences between the Pt and the Pd catalysts. Under STO reaction conditions each surface site on a Pt catalyst reacts only once so there is a 1:1 relationship between the product composition and the densities of the various types of active sites present. With Pd catalysts under these same conditions, alkene isomerization takes place so readily that the amount of isomerized product formed depends on the contact time of the reactant pulse with the catalyst so there is no direct relationship between the amount of isomerization and the number of isomerization sites present. On Pt there are some direct saturation sites present on which H2 is rather weakly held. Such sites are not present on Pd catalysts. The reactive surface of supported Pt catalysts remains constant on long exposure to air. With Pd catalysts exposure to air results in a decrease in saturation site densities which can be reversed by re-reduction of the surface with H2 under ambient conditions but not completely under what can be termed “reaction conditions” where the extent of surface re-reduction decreases with catalyst age.

Solid State 51V NMR spectra are sensitive to changes In the surface structure of V2O5 dispersed on Al2O3 and TiO2 supports. For V2O5 supported on alumina, wideline and magic-angle spinning experiments at 4.7 and 7.0 T reveal the presence of two vanadium species with different bonding environments. The relative proportions of these species change monotonically as a function of the vanadium concentration. In contrast, supported vanadium oxide on TiO2 substrates show a much more V2O5-like environment. Structural inferences are discussed In connection with solid state 51V NMR studies on model compounds with known crystal structures and site symmetries.

The applicability of atomic force microscopy (AFM) to both conductive and dielectric materials is the subject of this study. A representative conductor, Cu, and two dielectrics, mica and selenite, were examined. Microstructure and single lamellar steps were resolved. Surface areas on Cu and mica generated reproducible images when scanned repeatedly. There was no evidence of damage to the probe or the sample as a result of the AFM investigations. Selenite did show evidence of change after repeated scans with an AFM lever of 12 N/m spring constant exerting a 10−6N force.