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The in situ microwave cavity perturbation technique was used to study the complex permittivity and conductivity of polycrystalline α-V2O5 in a tubular reactor under reactive high-temperature conditions with a TM110 cavity resonating at 9.2 GHz. The sample was investigated at 400 °C in flowing air and air/n-butane mixtures while simultaneously measuring the total oxidation products CO and CO2 by gas chromatography. The V2O5 powder was identified as an n-type semiconductor and the dynamic microwave conductivity correlated well with the near-infrared (NIR) absorption assigned to V3d1 band gap states. Correlations between catalytic performance, real and imaginary parts of the permittivity, and NIR absorption allowed the differentiation between bulk and surface contributions to the charge transport in reactive atmospheres. The stability of the crystalline bulk phase was proven by in situ powder X-ray diffractometry for all applied testing conditions.

Lanthana–zirconia supported chromium oxide and magnesium chromium mixed oxide catalysts were studied in the dehydrocyclization of n-octane and characterized by temperature-programmed desorption of NH3, temperature-programmed reduction, XPS and DRIFTS. The Mg-free catalyst shows the highest activity, but suffers from rapid deactivation due to coke formation. The addition of Mg decreases the initial activity of the supported chromium oxide and retards its deactivation. The characterization results reveal that the deactivation retarding effect of Mg species not only consists in the deletion of strong acid sites but also in the decoration and/or dilution of Cr3+ oxide cluster, supposedly due to the formation of Mg–Cr surface compounds and, thus, in preventing the formation of coke.

The paper concentrates on the study of Mo–V–Te–Nb oxide mixtures by electron microscopy combined with catalytic investigation of these materials in the partial oxidation of propane. Surface texturing of catalyst particles composed of two phases referred to in the literature as M1 and M2 is revealed by high-resolution transmission electron microscopy of high performing catalysts. The chemical composition of the catalyst surface is modified by treatment in water to obtain a significant increment in yield of acrylic acid. A chemical realization of the site isolation concept recurring on a supramolecular arrangement of catalyst and reactant rather than on atomic site isolation is suggested. A complex Mo–V–Te–Nb–O x precursor phase carries nanoparticles made from a network of oxoclusters active as catalyst for the conversion of propane to acrylic acid. The designed synthesis of the multi-element oxide bulk and of the surface structure with a different composition than the precursor phase improved the performance by a factor of 4.

The NO storage properties of MnO x /support materials (5–50 wt% MnO x loading) was experimentally investigated in the presence of O2 and H2O between 50 and 700 °C applying a non-isothermal temperature-programmed method. In dependence on MnO x loading and NO supply, the materials show an intermediate decrease of NO storage capacity between 200 and 300 °C. This effect is caused by decomposition of surface nitrites with release of NO into the gas phase as proved by in situ DRIFT measurement. The interpretation is corroborated by modelling of the underlying adsorption/desorption reaction steps, considering the different thermal stability of nitrite/nitrate surface species.

Sulfated zirconia (SZ) has been used as a heterogeneous catalyst in the synthesis of aromatic ketones. A number of carboxylic anhydrides and acid chlorides proved to be appropriate acylating agents in the reaction with anisole and chlorobenzene. The rate of anisole acylation was found to be dependent on the type of acylating agent used. Thus, acetic anhydride and benzoic anhydride reacted faster on SZ with anisole than benzoyl chloride. Successful SZ-catalyzed acylations of chlorobenzene were limited to acceptor substituted benzoyl chlorides as acylating agents. Acetic anhydride and benzoic anhydride did not react with chlorobenzene in the presence of SZ.

The acidic properties of HNaY zeolites with different degrees of exchange have been studied by means of two complementary techniques of temperature-programmed desorption (TPD) of ammonia, namely, FTIR-TPD and conventional TPD. In HNaY zeolites with low exchange levels only a single type of OH group is observed. The analysis of the spectra in the region of NH bending modes during NH3-FTIR-TPD on zeolites with higher proton content (40% or higher) shows that ammonia is bound in two different adsorption states. This assessment is further confirmed by evaluation of the OH stretching region. Furthermore, desorption energy distribution functions for the different types of OH groups have been calculated using a numerical regularization method.

The benzoylation of anisole with benzoic anhydride over sulfated zirconia has been investigated, especially with regard to catalyst deactivation and regeneration. Calcined sulfated zirconia and spent catalysts have been characterized by BET analysis, C-H elemental analysis, DRIFTS, NH3-TPD, 13C-NMR and UV-Vis spectroscopy. In batch-mode experiments, a moderate deactivation attributed to the deposition of carbonaceous surface species has been observed. The surface deposits consist of benzoate species and strongly adsorbed molecules of anisole. A color change of the solid, observed immediately after the introduction of the catalyst into the reaction mixture, has been attributed to the protonation of the reaction products 2- and/or 4-methoxybenzophenone. The surface species formed may cover or modify surface acid sites and, in this way, reduce the accessibility of active centers. Removing the deposited and adsorbed species by calcination in air restores the initial activity of sulfated zirconia.

The adsorption of ethylene on Rh/SiO2 and Rh-VOx/SiO2 has been studied by transmission FTIR spectroscopy. For C2H4 chemisorption at 298 K on Rh/SiO2 molecularly adsorbed C2H4 and ethylidyne species are identified. It has been found that ethylidyne can be hydrogenated toward surface ethyl species in a reversible reaction at room temperature. On Rh-VOx/SiO2 the fragmentation of C2H4 into methylene species has been observed during C2H4 adsorption at 298 K.

Molybdenum promoted Rh/SiO2 catalysts have been prepared by using the heteronuclear cluster (C5H5)3RhMo2(CO)5 as well as metal salt precursors. The promoting effect of molybdenum has been studied for the hydroformylation of ethene and propene and the hydrogenation of acetaldehyde. It has been found that molybdenum, especially on the cluster-derived catalyst, increases both the hydrogenation and the hydroformylation rate of the olefins. No specific influence on the CO insertion reaction could be obtained. As an explanation, the promotion of the initial step to form intermediate surface alkyl groups has been proposed as the rate determining step for ethene hydroformylation. The promotion of the alcohol formation by bimetallic centers having Rh and Mo in close vicinity has been supported by the results of the hydrogenation of acetaldehyde.