Alumina-supported cobalt-molybdenum catalyst for slurry phase Fischer–Tropsch synthesis

An evaluative investigation of the Fischer–Tropsch performance of two catalysts (20%Co/Al₂O₃ and 10%Co:10%Mo/Al₂O₃) has been carried out in a slurry reactor at 2 MPa and 220–260 °C. The addition of Mo to the Co-catalyst significantly increased the acid-site strength suggesting strong electron withdrawing character in the Co-Mo catalyst. Analysis of steady-state rate data however, indicates that the FT reaction proceeds via a similar mechanism on both catalysts (carbide mechanism with hydrogenation of surface precursors as the rate-determining step). Although chain growth, , on both catalysts were comparable (  0.6), stronger CH₂ adsorption on the Co-Mo catalyst and lower surface concentration of hydrogen adatoms as a result of increased acid-site strength was responsible for the lower individual hydrocarbons production rate compared to the Co catalyst. The activation energy, E, for Co (96.6 kJ mol⁻¹), is also smaller than the estimate for the Co-Mo catalyst (112 kJ mol⁻¹). Transient hydrocarbon rate profiles on each catalyst are indicative of first-order processes, however the associated surface time constants are higher for alkanes than alkenes on individual catalysts. Even so, for each homologous class, surface time constants for paraffins are greater for Co-Mo than Co, indicative that the adsorption of CH₂ species on the Co-Mo surface is stronger than on the monometallic Co catalyst.     

Surface plasmons and vibrations of self-assembled silver nanocolumns

Optical and vibrational properties of novel self-assembled silver nanocolumns are studied experimentally and theoretically. The split of the surface plasmon resonance into transverse and longitudinal modes verifies the one-dimensional character of the nanocolumns. In this work, we have identified the acoustic vibration modes of the nanocolumns using Raman scattering, as spheroid-like modes (l = 2, m = +/-2) involving vibrations of the nanocolumns along their minor axes and the existence of surface plasmon-vibration coupling mechanisms.     

Effects of novelty and familiarity on illness-induced aversions to food and place cues in coyotes (Canis latrans).

Two experiments investigated the effects of novelty and familiarity on illness-induced aversions to taste and place cues in 10 coyotes. Ss were made ill on familiar food laced with Li?CO? in a novel place and then received preference tests. In Exp I, Ss avoided the previously poisoned familiar food in the novel treatment place but readily ate the same familiar food in a familiar safe place. Exp II replicated the results of Exp I, and it was found that Ss would eat a different familiar food in the novel treatment place. A model for averting animals from places where they are not wanted is presented. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)