Catalytic CO Hydrogenation: Mechanism and Kinetics from Chemical Transients at Low and Atmospheric Pressures

The hydrogenation of CO over Co model catalysts was studied using relaxation-type methods operating in situ either at atmospheric pressures or under surface science conditions. Emphasis was laid on providing information on the surface composition and on how it changes with time under catalytic reaction conditions. Using pressure forcing in chemical transient kinetics (CTK), the build-up of the steady-state was studied at 503 K and atmospheric pressure to demonstrate that the active catalyst surface is not metallic but covered with carbon, oxygen and hydrogen in excess of a monolayer equivalent. Both buildup and backward transients suggest CO to act as the "monomer" which probably inserts into an O-H bond to form the primary surface complex necessary for hydrocarbon and oxygenate formation. Repetitive electric field pulses (pulsed field desorption mass spectrometry, PFDMS) at low pressures have allowed the CO dissociation kinetics on a nano-sized Co 3D crystal ("tip") to be monitored in the millisecond time range. No evidence for the occurrence of the Boudouard reaction was obtained in either PFDMS or CTK. Adsorbed CH x (x = 1-3) species were detected in small amounts demonstrating that CO dissociation is fast compared to carbon hydrogenation. Adsorbed Co-subcarbonyl species, Co(CO)x were also detected by PFDMS and possibly mediate the necessary surface mobility during the initial restructuring of the catalyst. Surface carbon seems to inhibit Co-subcarbonyl formation. © Springer Science+Business Media, LLC 2008.SCOPUS: cp.jinfo:eu-repo/semantics/publishe

Organizational factors influencing scholarly performance: A multivariate study of biomedical research groups

Bibliometric studies often measure and compare scholarly performance, but they rarely investigate why universities, departments, and research groups do have different performance. In this paper we try to explain differences in scholarly performance of research groups in terms of organizational variables. In order to do this, we extensively review the relevant literature, and develop a model using two theoretical approaches. A multivariate analysis shows which of the independent variables do play a role in the various scholarly performance dimensions. The study shows what organizational strategies may help in optimizing performance in various dimensions. Implications are discussed