Jan Kunert

Investigation of NO adsorption and NO/O2 co-adsorption on NOx-storage-components by DRIFT-spectroscopy

NO adsorption and NO/O2 co-adsorption on CeO2 at different temperatures was studied by DRIFT-Spectroscopy. The results indicate that this oxide plays an important role in storing NOx. FTIR studies show that NO adsorption is dominated by the formation of nitrite species. Furthermore, cis- and trans hyponitrite species are detected. Co-adsorption of NO/O2 leads to the formation of nitrates. The experimental data show that the formation of nitrates is a consecutive reaction: adsorption of NO to form nitrite species (NO2−), followed by an oxidation to form nitrate species (NO3−).

Oxygen exchange at Mo/V mixed oxides: A transient and 18O isotope study under technical conditions

Abstract Mo/V mixed oxides have proven themselves to be reliable for the partial oxidation of acrolein to acrylic acid. Methacrolein which is the homologue of acrolein, reacts with clearly worse selectivity and activity on this catalyst system. By means of transient investigations (TP reduction, CP reduction, CP reaction and 18 O -SSITKA) under reaction conditions, it was possible to provide a contribution towards clarifying the oxygen exchange of the Mo/V mixed oxides during the reaction of both aldehydes to the corresponding carboxylic acids. In the case of both aldehydes, an exchange of carbonyl oxygen and solid oxygen occurs on the Mo/V mixed oxide.

Characterisation of the structure of adsorbates : An in situ DRIFTS-study of the partial oxidation of unsaturated aldehydes on Mo/V oxide catalysts

Abstract Mo/V oxides are interesting catalyst materials for the selective partial oxidation of unsaturated aldehydes (acrolein and methacrolein) to the corresponding carboxylic acids. Two catalyst systems — a mixed oxide and a heteropolyacid salt — were investigated by in situ DRIFT-spectroscopy. Using a novel DRIFTS cell, in which both the catalyst powder and the reference (KBr) were in the same reaction chamber, we are able to detect different adsorbates of (meth)acrolein and (meth)acrylic acid under reaction gases. The investigations showed that in the case of the adsorption of acrolein and methacrolein a significant difference in the structure of corresponding adsorbates could not be proved. This indicates that the reaction mechanism of the selective partial oxidation should be the same for both aldehydes. With these kind of investigations we gain access to a deeper insight into the reaction mechanism.

Mo/V-Mixed-Oxides – A New Catalyst-System for the Formation of Methacrolein by Oxidative Dehydrogenation of Isobutyraldehyde?

The applicability of Mo/V-mixed oxides for the partial oxidation of isobutyraldehyde to methacrolein is examined. The results are compared with the catalytic performance of a heteropolyacid-catalyst.