Helmut Papp

Screening of catalysts in the oxidative dehydrogenation of ethylbenzene with carbon dioxide

The influence of the type and concentration of transition and alkali metal oxides, type of the catalyst support as well as pretreatment method on catalytic activity and stability of catalysts in the dehydrogenation of ethylbenzene in the presence of carbon dioxide was determined. Active carbon-supported iron oxide promoted by alkali metal oxide was found to show the highest performance in the reaction. An increase in the catalyst mass was observed during time-on-stream. Additionally the specific surface area of the catalyst decreased. Temperature programmed oxidation showed the presence of carbon deposits which could only be gasified above 700°C.

Oxidative dehydrogenation of ethylbenzene with carbon dioxide on alkali‐promoted Fe/active carbon catalysts

The catalytic behavior of iron supported on activated carbon was investigated in the oxidative dehydrogenation of ethylbenzene. CO2 was applied as oxidant. High ethylbenzene conversion (>70%) and selectivity towards styrene (>90%) were observed at 550 °C. Apart from styrene, benzene, toluene, carbon monoxide and water were formed as products.

CO2 reforming and partial oxidation of methane

CO2 reforming and partial oxidation of CH4 were investigated on different supported noble metal and Ni catalysts. A detailed thermodynamic analysis was performed for both reactions. The observed reaction behaviour can be predicted by thermodynamics. Product selectivity is catalyst independent, the role of the catalyst is to bring the reactants to approach equilibrium. The partial oxidation is a two-stage process, total oxidation of CH4 is followed by CO2 and H2O reforming of the remaining CH4. A staged addition of O2 to the reactor is tested and recommended. TPSR show that the catalyst surface for CO2 reforming was highly covered with carbonaceous species of four different types; two were identified as reactive intermediates.

Characterization and activity of novel copper-containing catalysts for selective catalytic reduction of NO with NH3

Abstract Cu/Mg/Al mixed oxides (CuO = 4.0–12.5 wt%), obtained by calcination of hydrotalcite-type (HT) anionic clays, were investigated in the selective catalytic reduction (SCR) of NO by NH3, either in the absence or presence of oxygen, and their behaviours were compared with that of a CuO-supported catalyst (CuO = 10.0 wt%), prepared by incipient wetness impregnation of a Mg/Al mixed oxide also obtained by calcination of an HT precursor. XRD analysis, UV-visible-NIR diffuse reflectance spectra and temperature-programmed reduction analyses showed the formation, in the mixed oxide catalysts obtained from HT precursors, mainly of octahedrally coordinated Cu2+ ions, more strongly stabilized than Cu-containing species in the supported catalyst, although the latter showed a lower percentage of reduction. The presence of well dispersed Cu2+ ions improved the catalytic performances, although similar behaviours were observed for all catalysts in the absence of oxygen. On the contrary, when the mixture with excess oxygen was fed, very interesting catalytic performances were obtained for the catalyst richest in copper (CuO = 12.5 wt%). This catalyst exhibited a behaviour comparable to that of a commercial V2O5–WO3TiO2 catalyst, without any deactivation phenomena after four consecutive cycles and following 8 h of time-on-stream at 653 K. Decreasing the copper content or increasing the calcination time and temperature led to considerably poorer performances and catalytic behaviours similar to that of the CuO-supported catalyst, due to the side-reaction of NH3 combustion on the free Mg/Al mixed oxide surface.

Supported manganese catalysts for the selective catalytic reduction of nitrogen oxides with ammonia Part II. Catalytic experiments

Manganese-promoted active carbons have been studied as catalysts for selective catalytic reduction with ammonia. Activity, selectivity and stability depend on the preparation procedure, the choice of the precursors and the chemistry of the starting support. The highest activity in the low-temperature region was shown by samples prepared from manganese nitrate. An even (near monolayer) distribution of manganese species led to nitrogen as the sole product, and bigger manganese oxide crystallites resulted, additionally, in N2O as a by-product. Manganese addition did not influence the stability of active carbons except those prepared from potassium permanganate where increased gasification due to the presence of potassium was observed at higher temperatures. Side reactions: ammonia oxidation and direct decomposition of nitric oxide are also discussed.

Metal doped sulfated ZrO2 as catalyst for the selective catalytic reduction (SCR) of NO with propane

Abstract The selective catalytic reduction of nitric oxide with propane was studied using metal oxide (Pt, Mn, Fe, Ni, Cu, Ga) loaded sulfated zirconia as catalysts under lean conditions at reaction temperatures between 300 and 600°C. Pure and sulfated zirconia showed only a low activity for selective catalytic reduction (SCR) with propane. After loading sulfated zirconia with Cu and especially Ga oxide, a high catalytic activity with NO conversion of 80% in the case of the Ga loading was achieved. The selectivities towards the main product of the SCR product N2 were very promising. The catalytic activity only slightly decreased upon introduction of SO2 into the reaction mixture.

Manganese supported catalysts for selective catalytic reduction of nitrogen oxides with ammonia Part 1 Characterization

The preparation of active carbons promoted with manganese was studied with low temperature argon sorption techniques temperature-programmed desorption and X-ray photoelectron spectroscopy. As supports, unoxidized and oxidatively pretreated carbons were used. The introduction of active material was accomplished by an adsorption method using solutions of KMnO4, KMnO4+H2SO4 or Mn(NO3)2. The oxidation state of the active phase and its distribution depended on the precursor and the amount/type of oxygen surface functionalities of their support. KMnO4 solutions led to the precipitation of Mn2O3/MnO2 crystallites, mostly on the outer surface of active carbon particles. Mn(NO3)2 solutions, when introduced onto unpretreated support, resulted in Mn3O4/MnO2 as large aggregates. When H2SO4 was added to KMnO4 solution, small clusters with a broad distribution of sizes were deposited. A monolayer coverage of manganese species could only be obtained when active carbon was pretreated in an oxidizing environment strong enough to produce a considerable amount of carboxylic functionalities. Additionally, the preparation procedures influenced the textural properties.

Synthesis of highly ordered boron-containing B–MCM-41 and pure silica MCM-41

Abstract This study deals with the hydrothermal synthesis of highly ordered MCM-41 and B–MCM-41. Four techniques for the generation of MCM-41 were compared: thermal treatment in polypropylene vessels, in static autoclaves, in a stirred autoclave in ovens, and in microwave reactors heated with microwave radiation. The formation process of MCM-41 and the condensation of the framework were monitored by X-ray diffraction. The high periodicity of the materials was detected with X-ray powder diffraction and transmission electron microscopy. Highly ordered samples showing reflections up to sixth order in the selected area electron diffraction were produced.

Pillared smectite modified with carbon and manganese as catalyst for SCR of NOx with NH3. Part I. General characterization and catalyst screening

Carbon- and manganese-modified zirconia-pillared smectites were prepared, characterized (XRD, BET and pore analysis, XPS) and tested in selective catalytic reduction of NOx with NH3. Both untreated and acidic pretreated smectites were used. The acid pretreatment increased NO conversion and influenced the extent of carbon introduction into the porous system. The carbon deposit improved selectivity of the catalytic reduction to N2.

Investigation of the surface of vanadyl pyrophosphate catalysts

The surface composition of (VO) 2 P 2 O 7 catalysts was investigated by x-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS). The P/V ratio on the surface of (VO) 2 P 2 O 7 catalysts from aqueously prepared precursors lies between 1.3 and 1.4, based on XPS calibrations with different VPO glasses as standard materials. With ISS we obtained a higher P/V ratio of (VO) 2 P 2 O 7 catalysts in the outermost layer of ∼ 2-3. The addition of caesium (Cs + ) caused a further increase in the P/V ratio of the surface of (VO) 2 P 2 O 7 with increasing Cs + concentration. Ion scattering spectroscopy indicated that Cs + was mainly confined to the uppermost layers, and at high doping concentrations a total surface coverage with Cs + was achieved. The influence of water vapour on the surface composition of the catalysts was also investigated. A migration and a loss of phosphorus was found after and during water vapour treatment using XPS, ISS and thermogravimetric measurements. The surface of (VO) 2 P 2 O 7 is assumed to be a dynamic system influenced by the partial pressure of water vapour in the gas phase. The rate of bulk oxidation of (VO) 2 P 2 O 7 was dependent on the water vapour content in the gas phase.