Rasmus Fehrmann

Several supported liquid-phase (SLP) catalysts with immobilized Rh-biphephos complexes on monolithic supports were prepared and applied for continuous gas-phase hydroformylation (HyFo) of 1-butene. The support comprised macroporous monolithic silicon carbide (SiC) with deposited silica nanoparticles (NPs) in order to provide mesopores with enhanced capillary forces to retain the liquid-phase. Variable parameters were examined for the monolithic SiC supports, including size and loading of deposited silica NPs and intermediate calcination between silica deposition steps to obtain the most efficient support configuration for the SLP system. The SLP catalysts with larger deposited silica NPs gave higher catalytic activity (i.e. 1-butene conversion and turnover frequency) compared to the supports with smaller sized silica NPs. However, the selectivity towards the preferred linear aldehyde was higher in the SLP catalysts with supports containing less silica with small silica NPs. Importantly, the prepared SLP catalyst systems showed long-term stability in HyFo with negligible formation of high boiling aldol condensation products.

Preparation of Mn/TiO₂, Mn-Fe/TiO₂, and Mn-Fe-Ce/TiO₂ by the deposition-precipitation (DP) method can afford very active catalysts for low-temperature NH₃-SCR (selective catalytic reduction of NO with NH₃). The effect of precursor choice (nitrate vs. acetate) of Mn, Fe, and Ce on the physiochemical properties including thermal stability and the resulting SCR activity were investigated. The resulting materials were characterized by N₂-Physisorption, XRD (Powder X-ray diffraction), XPS (X-ray photoelectron spectroscopy), H₂-TPR (temperature-programmed reduction with hydrogen), and the oxidation of NO to NO₂ measured at 300 °C. Among all the prepared catalysts 5Mn_Ace/Ti, 25Mn_0.75AceFe_0.25Nit/Ti, and 25Mn_0.75AceFe_0.20NitCe_0.05Ace/Ti showed superior SCR activity at low temperature. The superior activity of the latter two materials is likely attributable to the presence of amorphous active metal oxide phases (manganese-, iron- and cerium-oxide) and the ease of the reduction of metal oxides on TiO₂. Enhanced ability to convert NO to NO₂, which can promote fast-SCR like pathways, could be another reason. Cerium was found to stabilize amorphous manganese oxide phases when exposed to high temperatures.

Cu-, Fe-, and Mn-zeolite (SSZ-13, ZSM-5, and BEA) catalysts have been prepared by incipient wetness impregnation and characterized by N₂ physisorption, H₂-TPR, NH₃-TPD, and XPS methods. Both metal and zeolite support influence the deNO_x activity and hydrothermal stability. Cu-zeolites and Mn-zeolites showed medium temperature activity, and Fe zeolites showed high temperature activity. Among all the catalysts, Cu-SSZ-13 and Fe-BEA are the most promising hydrothermally resistant catalysts. Fresh and hydrothermally treated catalysts were further examined to investigate the acidic and redox properties and the zeolite surface composition. Increased total acidity after metal impregnation and loss of acidity due to hydrothermal treatment were observed in all the catalysts. Hydrothermal treatment resulted in migration of metal or in strong metal support interations, whereby changes in reduction patterns are observed.

Firing of biomass can lead to rapid deactivation of the vanadia-based NH₃-SCR catalyst, which reduces NO_x to harmless N₂. The deactivation is mostly due to the high potassium content in biomasses, which results in submicron aerosols containing mostly KCl and K₂SO₄. The main mode of deactivation is neutralization of the catalyst’s acid sites. Four ways of dealing with high potassium contents were identified: (1) potassium removal by adsorption, (2) tail-end placement of the SCR unit, (3) coating SCR monoliths with a protective layer, and (4) intrinsically potassium tolerant catalysts. Addition of alumino silicates, often in the form of coal fly ash, is an industrially proven method of removing K aerosols from flue gases. Tail-end placement of the SCR unit was also reported to result in acceptable catalyst stability; however, flue-gas reheating after the flue gas desulfurization is, at present, unavoidable due to the lack of sulfur and water tolerant low temperature catalysts. Coating the shaped catalysts with thin layers of, e.g., MgO or sepiolite reduces the K uptake by hindering the diffusion of K⁺ into the catalyst pore system. Intrinsically potassium tolerant catalysts typically contain a high number of acid sites. This can be achieved by, e.g., using zeolites as support, replacing WO₃ with heteropoly acids, and by preparing highly loaded, high surface area, very active V₂O₅/TiO₂ catalyst using a special sol-gel method.

Supported ionic liquid phase (SILP) technology was applied for the first time to the Pd‐catalyzed continuous, gas‐phase methoxycarbonylation of ethylene to selectively produce methyl propanoate (MP) in high yields. The influence of catalyst and reaction parameters such as, for example, ionic liquid loading, metal concentration, and ligand loadings was studied, and in particular the SILP catalyst activity and stability was found to be strongly dependent on the ligand to metal ratio.

A new strategy for capturing nitrogen oxide, NO, from the gas phase is presented. Dilute NO gas is removed from the gas phase by ionic liquids under ambient conditions. The nitrate anion of the ionic liquid catalyzes the oxidation of NO to nitric acid by atmospheric oxygen in the presence of water. The nitric acid is absorbed in the ionic liquid up to approximately one mole HNO₃ per mole of the ionic liquid due to the formation of hydrogen bonds. The nitric acid can be desorbed by heating, thereby regenerating the ionic liquid with excellent reproducibility. Here, time‐resolved in‐situ spectroscopic investigations of the reaction and products are presented. The procedure reveals a new vision for removing the pollutant NO by absorption into a non‐volatile liquid and converting it into a useful bulk chemical, that is, HNO₃.

Mechanistic investigations including in situ infrared spectroscopy and Hammett investigations of the oxidative dehydrogenation of amine compounds using RuO₂/Al₂O₃ catalysts.

The epoxidation of propene is performed in homogeneous phase using various molecular catalysts and H₂O₂ or tert-butyl hydroperoxide as oxidants. A comparison between some molybdenum catalysts and methyltrioxorhenium (MTO) shows that the well known Re catalyst is the best among the examined catalysts.