Wladimir Suprun

Fe- and Cu-oxides supported on γ-Al2O3 as catalysts for the selective catalytic reduction of NO with ethanol. Part I: catalyst preparation, characterization, and activity

Fe- and Cu-oxides supported on γ-alumina (γ-Al2O3; metal loading of 3 mass %) were investigated as alternative catalysts to the conventional Ag-based system in the selective catalytic reduction of NO with ethanol (EtOH-SCR). The catalysts were characterized by elemental analysis, N2 sorption, X-ray diffraction, temperature-prgrammed desorption of NH3, temperature-programmed reduction with H2, diffuse reflectance UV-VIS (DR-UV-VIS) spectroscopy, and compared with 3 mass % Ag/γ-Al2O3 as a reference catalyst. Catalytic experiments were carried out between 423 K and 773 K in the steady state and by temperature-programmed surface reaction (TPSR) experiments. For all catalysts, the highest NO conversion (900 ppm (ppm = parts of the mixture component per million parts of all mixture components) NO, 900 ppm EtOH, 0.5 vol. % H2O, 4 vol. % O2 in He) was found at 573 K. While 84 % of NO were converted over the Ag-based catalysts, only 20–60 % NO conversion was observed for the Fe- and Cu-containing catalysts. Total oxidation of ethanol as an unwanted side reaction occurs over 3 mass % Cu on γ-Al2O3 already at 573 K, whereas the highest activity of 3 mass % Fe on γ-Al2O3 for this conversion was reached at 743 K. For lower temperatures, partial oxidation of ethanol leads to organic by-products which can act as active intermediates in EtOH-SCR. TPSR experiments show that ethanol reacts over both the Fe- and the Cu-based catalysts to organic by-products, such as ethene or acetaldehyde, which affect the EtOH-SCR reaction.

Gas-phase conversion of glycerol over mixed metal oxide catalysts

A series of aluminophosphates (APO) catalysts with Ce, Cu, Cr, Fe, Mn, Mo, V, and W oxide loading at a constant ratio M: Al = 1: 10 and PO4: Al = 1: 12 were prepared and characterized by N2 physisorption, XRD and NH3-TPD. Gas-phase dehydration of glycerol to produce acrolein and acetol was investigated at 280°C in presence of water. Conversion and product distribution depended on the intrinsic acidity and the type of transition metal oxide. Best selectivity to acrolein (52–58%) was obtained for W- und Mo-APO catalysts. Cr-, Mn- and W- oxide containing catalysts enhanced the formation of phenol, acetaldehyde and COx. The catalysts containing V- and Fe-oxide promoted the formation of allyl alcohol. All catalysts showed long term stability, which can be attributed to the redox ability of the metal oxides that enhances the removal of coke deposits. The investigated catalyst a specially W-APO and Mo-APO can be recommended for further controlled trials on a pilot plant for selective conversion of water solution of glycerol to acrolein and/or acetol.

Modelling of selective NOx reduction on Ce/In-promoted sulfated zirconia catalysts

Abstract Various pseudohomogeneous models for the selective catalytic reduction of NOx by methane were developed by considering reaction schemes and kinetic mechanism. The models were applied to predict the performance of Ce/In-promoted sulfated zirconia catalysts in a wide temperature range from 300 to 700 °C in a fixed bed reactor assuming plug-flow. A nonlinear kinetic model fits the experimental data better than a simple linear model. The mass balance differential equations were solved numerically. The model parameters were estimated by the Simplex-method of Nelder–Mead with a fourth order Runge–Kutta–Merson-method. The finally chosen model is better suited for the prediction of the In-free catalysts than for the mixed oxide catalysts or the Ce-free catalysts. The model suggests that CO formed in the process plays no role in the reduction of NO by CH4. This was confirmed by experimental evidence. The investigated Ce/In zirconia system was better suited for NO reduction by CH4 than those published previously.

Comparison of a VOx-TiO2 and a VOx/SbOy-TiO2 Industrial Catalyst in the Oxidative Scission of Methyl Ethyl Ketone and 2-Butanol to Acetic Acid

The oxidative scission of methyl ethyl ketone and 2-butanol on a VOx-TiO2 and a VOx/SbOy-TiO2 catalyst was studied in the temperature range of 120 to 280°C in the presence of water vapour. The catalytic performance of the two catalysts was investigated by variation of reaction temperature and contact time, and the catalysts were characterized by BET, XRD, XPS, TPR-H2, TPD-NH3, and temperature programmed desorption of lattice oxygen (TPD-O2). The investigations indicate that the addition of Sb2O3 to VOx-TiO2 favours the selective formation of acetic acid and depresses total oxidation to COx in the catalytic oxidation of methyl ethyl ketone and 2-butanol due to changes in the redox properties of the VOx-TiO2 system. Moreover, the higher acidity of the VOx-TiO2 catalyst favours the dehydration of 2-butanol to n-butenes.

Oxidation of acetaldehyde and propionaldehyde on a V2O5-TiO2 catalyst

The partial oxidation of acetaldehyde and propionaldehyde on a TiO2 supported VOx catalyst in presence of water vapour was investigated in the temperature range from 120 to 280 °C. The selective oxidation to the appropriate carboxylic acids depended on the kind of aldehyde and the reaction temperature. An oxidative cleavage to lower carboxylic acids and COx was also found. Furthermore, the kinetic model for the process of oxidation of acetaldehyde and propionaldehyde over the V2O5-TiO2 catalyst was developed.