Anker Degn Jensen

Low-Temperature NH3–SCR of NO on Mesoporous Mn0.6Fe0.4/TiO2 Prepared by a Hydrothermal Method

Mesoporous 30xa0wt% Mn0.6Fe0.4/TiO2 has been prepared by a novel hydrothermal method using a structure directing agent and characterized by N2 adsorption, SEM, XRD, EDX, H2-TPR and the catalytic activity for the selective catalytic reduction (SCR) of NO by ammonia was measured under power plant flue gas conditions. Compared to 30xa0wt% Mn0.6Fe0.4/TiO2 prepared by impregnation, the average pore size was significantly increased. The method of preparation has only a small effect on the catalytic activity at temperatures between 125 and 300xa0°C. The hydrothermal preparation method leads to a somewhat higher (NH4)2SO4 tolerance at 150xa0°C compared to the impregnation preparation method. Regeneration of the (NH4)2SO4 loaded samples by heating to 400xa0°C was not possible whereas water washing yielded better regeneration. The catalysts are significantly more active than a commercial VWT SCR catalyst at temperatures up to 200xa0°C, but do not match the activity of the latter at the higher temperatures typically encountered at the high dust position in power plants.Graphical Abstract

Ceria Prepared by Flame Spray Pyrolysis as an Efficient Catalyst for Oxidation of Diesel Soot

Ceria has been prepared by flame spray pyrolysis and tested for activity in catalytic soot oxidation. In tight contact with soot the oxidation activity (measured in terms of the temperature of maximal oxidation rate, Tmax) of the flame made ceria is among the highest reported for CeO2. This can to a significant degree be ascribed to the large surface area achieved with the flame spray pyrolysis method. The importance of the inherent soot reactivity for the catalytic oxidation was studied using various soot samples, and the reactivity of the soot was found to have a significant impact, as the Tmax-value for oxidation in tight contact with a catalyst scaled linearly with the Tmax-value in non-catalytic soot oxidation. The Tmax-value in non-catalytic soot oxidation was in turn observed to scale linearly with the H/C ratio of the carbonaceous materials.Graphical Abstract

Trends in the Hydrodeoxygenation Activity and Selectivity of Transition Metal Surfaces

This paper reports the use of a combination of density functional theory and microkinetic modelling to establish trends in the hydrodeoxygenation rates and selectivites of transition metal surfaces. Biomass and biomass-derived chemicals often contain large fractions of oxygenates. Removal of the oxygen through hydrotreating represents one strategy for producing commodity chemicals from these renewable materials. Using the model developed in this paper, we predict ethylene glycol hydrodeoxygenation selectivities for transition metals that are consistent with those reported in the literature. Furthermore, the insights discussed in this paper present a framework for designing catalytic materials for facilitating these conversions efficiently.Graphical Abstract

High pressure CO hydrogenation over bimetallic Pt-Co catalysts

The potential of bimetallic Pt–Co catalysts for production of higher alcohols in high pressure CO hydrogenation has been assessed. Two catalysts (Pt3Co/SiO2 and PtCo/SiO2) were tested, and the existing literature on CO hydrogenation over Pt–Co catalysts was reviewed. It is found that the catalysts produce mainly methanol in the Pt-rich composition range and mainly hydrocarbons (and to a modest extent higher alcohols) in the Co-rich composition range. The transition between the two types of behavior occurs in a narrow composition range around a molar Pt:Co ratio of 1:1.Graphical Abstractxa0

Hydrothermally Stable Fe–W–Ti SCR Catalysts Prepared by Deposition–Precipitation

Fe/TiO2 based catalysts were prepared by incipient wetness impregnation and deposition–precipitation (DP). The catalysts were characterized by activity measurements, N2 physisorption, X-ray powder diffraction, electron paramagnetic resonance spectroscopy, energy dispersive X-ray spectroscopy, H2-temperature programmed reduction and NH3-temperature programmed desorption. The 3xa0wt% Fe–10xa0wt% WO3/TiO2 (3Fe–10WTi-DP) catalyst prepared by DP using ammonium carbamate as a precipitating agent was found to be the most active and hydrothermally stable with 11xa0vol% H2O in air at 650xa0°C for 3xa0h. The hydrothermal stability of the catalyst can be attributed to the retained crystal structure, and mild change in acidic and redox properties of the catalyst. Furthermore, hydrothermal stability of the 3Fe–10WTi-DP catalyst is competitive with that of 3Fe–ZSM-5 and much better than 3V2O5–10WO3–TiO2 catalysts.Graphical AbstractRelative SCR activity of catalysts at 450xa0°C.

Deactivation behavior of an iron-molybdate catalyst during selective oxidation of methanol to formaldehyde

An iron molybdate/molybdenum oxide catalyst (Mo/Fe = 2) was synthesized by a hydrothermal method and the catalysts performance and compositional changes were followed during selective oxidation of methanol to formaldehyde for up to 600 h. The activity was continuously measured for a series of experiments performed in a laboratory fixed-bed reactor with 10, 100, 250 and 600 h on stream under reaction conditions (5% MeOH, 10% O2 in N2, Temp. = 384–416 °C, W/F = 1.2 gcat h molMeOH−1). The structural and compositional changes of the catalyst were investigated by a number of techniques including: XRD, Raman spectroscopy, XPS, SEM-EDS and STEM-EDS. Methanol forms volatile species with molybdenum at reaction conditions, leading to depletion of Mo from the catalyst. Excess MoO3 was shown to volatilize and leave the catalyst during the first 10 h on stream, leading to an initial loss in activity of 50%. From 10 to 600 h on stream leaching of molybdenum from the remaining iron molybdate phase (Fe2(MoO4)3, Mo/Fe = 1.5) leads to iron rich phases (FeMoO4 and Fe2O3, Me/Fe < 1.5) and simultaneously an increase in activity to approximately 1.5 times the initial activity. Even at high degrees of molybdenum loss (Mo/Fe = 0.49) the formaldehyde selectivity remained above 92%, and the combined CO/CO2 selectivity was below 4%. This is likely due to a surface layer of MoOx on the catalyst at all times due to segregation and a surface in equilibrium with the gaseous molybdenum compounds. After 600 h on stream formation of β-MoO3 was observed, indicating that this molybdenum oxide phase is stable to some extent under reaction conditions.