Detlef Freitag

Hydrogenated Anatase: Strong Photocatalytic Dihydrogen Evolution without the Use of a Co-Catalyst†

The high-pressure hydrogenation of commercially available anatase or anatase/rutile TiO2 powder can create a photocatalyst for H2 evolution that is highly effective and stable without the need for any additional co-catalyst. This activation effect cannot be observed for rutile; however, for anatase/rutile mixtures, a strong synergistic effect can be found (similar to results commonly observed for noble-metal-decorated TiO2). EPR and PL measurements indicated the intrinsic co-catalytic activation of anatase TiO2 to be due to specific defect centers formed during hydrogenation. These active centers can be observed specifically for high-pressure hydrogenation; other common reduction treatments do not result in this effect.

In Situ Raman spectroscopy of the decomposition of tertiary butyl peroxy pivalate under high pressure and high temperature

The decomposition of tertiary butyl peroxy pivalate (TBPPI), in n-hexane, under a pressure of 1900 bar and at a temperature of 100 °C, was studied in situ with the use of a transportable high-throughput fiber-optic Raman spectrometer. The Raman probe was conveniently coupled to an optical high-pressure cell containing the TBPPI. Time-resolved experiments with a 10 wt % solution of TBPPI in n-hexane were carried out, and information on the mechanism of decomposition and the (first-order) kinetics was obtained. It is shown that the main decomposition products of TBPPI are CO2 and t-butanol. From first-order kinetic fits, of the Raman profiles of intensity vs. time of reactants and products, the rate constant for the decomposition of TBPPI and the formation of CO2 is found to be 1.65·10−3s−1 (half-life time for TBPPI of approximately 420 s). t-Butanol formation occurs at a slower rate of approximately 1.22·10−3s−1 (characteristic time of 566 s).

Prozess zur Verkapselung von Viren zur Optimierung der Schädlingsbekämpfung im Apfelanbau

ein Organosol erzeugt, d. h. ein stabiles Kolloid in einer organischen Tragerflussigkeit. Dieser Prozess erfolgt am Beispiel von in wassriger Phase gefalltem Magnetit, der in Dichlormethan zu uberfuhren ist. Der Phasentransfer wird mit Hilfe der Dispersions-Analysenzentrifuge LUMiSizer der Firma L.U.M. GmbH untersucht. Die Resultate stellen dar, wie der Phasentransfer mit Hilfe des LUMiSizers charakterisiert werden kann und die Auswertung der Transmissionsprofile erfolgt. Als Beispiel fur die dabei involvierten Elementarprozesse werden Ergebnisse zum Adsorptionsgleichgewicht auf den Nanopartikeln gezeigt.