Teresa Grzybek

X-ray photoelectron spectroscopy study of oxidized coals with different sulphur content

The aim of the study reported was to determine the effect of oxidation on the surface composition of coal as studied by X-ray photoelectron spectroscopy (XPS) method. Five coals characterized by a different degree of coalification and different amounts of sulphur were subject to oxidation with peroxyacetic acid (PAA). The process of oxidation was carried out for coal samples demineralised by the Radmacher method. Carbon, oxygen, sulphur and nitrogen peaks were registered and analysed. The effect of oxidation depended on coal rank. In case of S 2p, three or four peaks were found for the oxidized samples, corresponding to tiophene, sulphoxides (Ph 2 -SO type), sulphonic acids and in some cases, more oxidized forms of sulphur, possibly inorganic sulphates. The surface sulphur content increased upon oxidation. A possible reason could be the mobility of the S-containing species.

Selective catalytic reduction of nitric oxide by ammonia on Fe3+-promoted active carbon

Selective catalytic reduction of nitric oxide by ammonia on Fe3+-promoted active carbons was investigated. The catalysts were prepared by the impregnation of active carbon (N/m) preoxidised with concentrated nitric acid at different temperatures. The amount of oxygen-containing surface groups on the supports was determined by infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) while the distribution of active material was investigated using XPS. Catalytic activity of Fe3+-active carbon systems depended on the degree of the oxidation of the supports and pretreatment of the catalysts (drying, calcination in helium). The presence of oxygen in the reaction mixture enhanced the nitric oxide conversion. The catalysts showed a long-term stability.

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.

Pillared smectite modified with carbon and manganese as catalyst for SCR of NOx with NH3. Part II. Temperature‐programmed studies

Temperature‐programmed desorption (TPD) and surface reaction (TPSR), and additionally FTIR spectroscopy of adsorbed NO molecules were used to characterise surface sites on pillared smectites modified with carbon and manganese. Much higher adsorption of NH3 than NO was found, but acidic pre‐treatment increased NO sorption to comparable values as well as catalytic performance in SCR of NOx. In this case formation of strongly bound NO3− species was recognised, which reacted with NH3 at a temperature 200 °C higher than weaker adsorbed NO.

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.

The influence of the support structure on the iron distribution for Fe3+-active carbon catalysts

Active carbons and active carbon based Fe3+ catalysts were studied by X-ray photoelectron spectrometry (XPS). The structures of the original active carbon and of the oxidized form were compared. Both oxidized and unoxidized active carbons were impregnated with iron nitrate solutions of various concentrations. The Fe3+ distribution was discussed using XPS results and the Kerkhoff model. The influence of iron distribution on NO removal was also considered.

The influence of the addition of cobalt nickel, manganese and vanadium to active carbons on their efficiency in So2 removal from stack gases

Abstract The influence of the additions of Co 2+ , V 5+ , Ni 2+ and Mn 4+ to active carbon on the SO 2 removal from SO 2 H 2 Oair mixtures was investigated. The structure of the unreacted and reacted catalysts was determined by X-ray photoelectron spectroscopy and the argon Sorption methods. The SO 2 removal efficiency depended on the distribution of the active materials.

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.

An XPS study of the interaction of ammonia and nitric oxide with FenOy and active-carbon-supported iron oxides

The interaction of nitric oxide and ammonia with iron oxides and active-carbon-supported iron oxides was investigated using X-ray photoelectron spectroscopy. Ammonia when interacting with iron(III) oxide at 200 or 260 °C formed -NH2 groups stable in vacuum at the reaction temperature. Nitric oxide reacted neither with iron(III) at 200 °C nor with Fe-NH2 complex but did so with oxidized FeO or metallic iron. From three models of the selective catalytic reaction of NO proposed in literature, the most likely for the reaction of NO + NH3 on unsupported and active-carbon-supported Fe2O3 catalysts was chosen.

Selective catalytic reduction of nitric oxide with ammonia on Mn-promoted carbonized used silica-alumina sorbents

Deactivated (waste) silica–alumina sorbents were carbonized and used as supports. The introduction of manganese led to active and selective SCR catalysts at low temperatures. Two methods of Mn promoting were compared: wet impregnation and adsorption. They influenced the distribution of Mn and N2O production. The catalysts behaved similarly to Mn‐promoted active carbon.