Katsumi Takahashi

The role of K2O in the selective reduction of NO with NH3 over a V2O5(WO3)/TiO2 commercial selective catalytic reduction catalyst

To elucidate the nature of the acid sites of the V2O5(WO3)/TiO2 catalyst upon K2O addition and its relation to the selective reduction of NO with NH3, measurements were made by means of infrared and Raman spectroscopy, NH3 chemisorption, and NO reduction measurements as a function of the K2O loading. The catalytic activity was found to decrease rapidly with the K2O loading, irrespective of the similar textural properties of all samples. Addition of K2O modified the vanadium species on the catalyst surface. For large additions of K2O, the potassium partially reacted with V2O5 to form KVO3. The amount of NH3 chemisorbed on the catalyst was observed to decrease with both the loading of K2O and the temperature. The adsorption of NH3 on both Bronsted and Lewis acid sites was confirmed. The strength and the number of Bronsted acid sites decrease largely with the loading of K2O in parallel with the decrease of the SCR activity, suggesting that the SCR reaction involves NH3 adsorption on the Bronsted acid sires. At low surface coverage of NH3, the isosteric heat of NH3 chemisorption was determined to be 370 kJ/mol for 0 wt.% K2O addition. With increasing K2O amount, the heat of adsorption decreased and was 150 kJ/mol for the catalyst with higher amounts of K2O addition. The results obtained imply that potassium disturbs the formation of the active ammonia intermediates, NH4+, resulting in deactivation of the catalyst

SO2 oxidation over the V2O5/TiO2 SCR catalyst

The effects of V2O5 loading of the V2O5/TiO2 SCR catalyst on SO2 oxidation activity were examined by infrared spectroscopy (DRIFT) and SO2 oxidation measurement. Vanadium oxide added to the catalyst was found to be well dispersed over the TiO2 carrier until covered with monolayer V2O5. The rate of SO2 oxidation increased almost linearly with V2O5 loading below the monolayer capacity and attained saturation with further increase. The hydroxyl groups bonded to vanadium atoms, V–OH, might be altered by SO2 oxidation. Both V=O and V–OH groups are likely involved in the adsorption and desorption of SO2 and SO3.

Surface acid property and its relation to SCR activity of phosphorus added to commercial V2O5(WO3)/TiO2 catalyst

To examine the influence of phosphorus on the commercial V2O5(WO3)/TiO2 SCR catalyst, measurements were carried out by means of infrared and Raman spectroscopy, XPS, and NO reduction measurement as a function of phosphorus loading. Phosphorus added to the catalyst was found to disperse well over the catalyst without a significant agglomeration up to 5 wt% P2O5 addition. The number of the hydroxyl groups bonded to the vanadium and titanium species decreased readily with increasing amount of phosphorus. Correspondingly, the hydroxyl groups bonded to the phosphorus species were formed. NH3 adsorbed on both hydroxyl groups bonded to vanadium and phosphorus as ammonium ions, implying that the P–OH groups formed are also responsible for the Brønsted acidity. The NO reduction activity was found to be decreased with increasing amount of phosphorus; however, the influence of phosphorus was relatively small irrespective of the large amount of phosphorus addition. The deactivation might be caused by the change in the nature of the surface hydroxyl groups as Brønsted acid sites. Phosphorus species might partially wrap the surface V=O and W=O groups, which might also contribute to the deactivation.

112 Comparative study on the hydrogen production from methanol over Cu/ZnO/Al2O3 and Pd/ZnO Catalysts

Abstract Hydrogen production from methanol through both non-oxidative and oxidative steam reforming over Cu/ZnO/Al 2 O 3 and Pd/ZnO catalysts was investigated by catalyst characterizations, and CH 3 OH reforming reactions. Over both Cu/ZnO/Al 2 O 3 and Pd/ZnO, CH 3 OH steam reforming, both non-oxidative and oxidative, was observed to proceed efficiently. For Cu/ZnO/Al 2 O 3 , hydrogen production rate and CO 2 selectivity were greatly dependent on Cu/Zn/Al metal ratio and preparation temperature. For Pd/ZnO, hydrogen production rate and CO 2 selectivity were found to be improved by an appropriate increase of Pd loading. PdZn alloy formed by pre-treatment reduction was confirmed to be stable under oxidative steam reforming conditions by X-ray analyses.

114 Catalytic steam reforming of toluene and o-dichlorobenzene

Abstract A commercial catalyst was evaluated on its catalytic performances for steam reforming of toluene + o-dichlorobenzene (o-DCB). The catalyst showed high resistance towards coke deposition. Chloride formed from destruction of o-DCB has strong poisoning effects on the catalyst for both the reforming and water-gas-shift (WGS) reactions. This poisoning effect of chloride is reversible. The catalyst also gave high destruction rate of o-DCB. Conversion of o-DCB could be higher than 99.999%