The infrared spectral performance of the N x O y species observed on oxide surfaces [N2O, NO−, NO, (NO)2, N2O3, NO+, NO2 − (different nitro and nitrito anions), NO2, N2O4, N2O5, NO2, and NO3 − (bridged, bidentate, and monodentate nitrates)] is considered. The spectra of related compounds (N2, H-, and C-containing nitrogen oxo species, C─N species, NH x species) are also briefly discussed. Some guidelines for spectral identification of N x O y adspecies are proposed and the transformation of the nitrogen oxo species on catalyst surfaces are regarded.

Identification of Neutral and Charged N x O y Surface Species by IR Spectroscopy

A study is conducted to demonstrate catalytic dehydrogenation of light alkanes on metals and metal oxides. The study provides a complete overview of the materials used to catalyze this reaction, as dehydrogenation for the production of light olefins has become extremely relevant. Relevant factors, such as the specific nature of the active sites, as well as the effect of support, promoters, and reaction feed on catalyst performance and lifetime, are discussed for each catalytic Material. The study compares different catalysts in terms of the reaction mechanism and deactivation pathways and catalytic performance. The duration of the dehydrogenation step depends on the heat content of the catalyst bed, which decreases rapidly due to the endothermic nature of the reaction. Part of the heat required for the reaction is introduced to the reactors by preheating the reaction feed, additional heat being provided by adjacent reactors that are regenerating the coked catalysts.

Catalytic dehydrogenation of light alkanes on metals and metal oxides.

Focuses on the surface chemistry and spectroscopy of chromium in inorganic oxides. Characterization of the molecular structures of chromium; Mechanics of hydrogenation-dehydrogenation reactions; Mobility and reactivity on oxidic surfaces.

/pdf/surface-chemistry-and-spectroscopy-of-chromium-in-inorganic-5dnw014r22.pdf

Surface Chemistry and Spectroscopy of Chromium in Inorganic Oxides.

https://dspace.library.uu.nl/bitstream/handle/1874/21356/weckh_99_alkanedehydrogenation.pdf?sequence=1

Alkane dehydrogenation over supported chromium oxide catalysts

Chromium Oxide/Alumina Catalysts in Oxidative Dehydrogenation of Isobutane☆

Propane dehydrogenation on chromia/silica and chromia/alumina catalysts

Isobutane dehydrogenation was studied on CrOxZrO2 (ZC) catalysts (0.04 to 1.9% chromium by weight) in a flow apparatus at 673–873 K. Up to 823 K, molar selectivity to isobutene was ⩾ 95%, while the only gaseous by-products were propene, methane and traces of propane. No skeletal isomerization occurred up to 873 K. A deactivation was observed due to the formation of coke. The activity decay was considerably delayed by adding a few percent hydrogen to the reactant mixture. In all cases, catalytic activity was completely recovered by treating the catalyst with flowing oxygen at 773 K over 22 reaction regeneration cycles. The catalyst surface was conditioned mainly by the reaction atmosphere, so that sample reduction with carbon monoxide at 623 K before catalysis did not influence the activity above 773 K. The turnover frequency per total surface chromium atom was found to be independent of surface chromium concentration at all given temperatures, which indicated a mononuclear active site. A comparison with chromia/silica and chromia//gg-alumina samples of similar chromium content revealed a higher activity for the zirconia-based catalysts. The overall picture shows close similarities with that of propane dehydrogenation previously studied in our laboratory on the same catalytic system. It is concluded that the site previously proposed for propane dehydrogenation is also responsible for the activity in the dehydrogenation of isobutane; this site involves a mononuclear CrIII species with two coordinative vacancies and, most probably, an adjacent O2− ion of the support.

S. Fremiotti

Papers

Propane dehydrogenation on chromia/silica and chromia/alumina catalysts

Isobutane dehydrogenation on chromia/zirconia catalysts

Propane Dehydrogenation on Chromia/Silica and Chromia/Alumina Catalysts.