RESUMO
Manganese-containing BEA zeolites, MnxSiBEA (x = 1-4 wt%) and Mn(I.E.)AlBEA, were prepared by a two-step post-synthesis method and a conventional wet ion-exchange, respectively, and applied as catalysts in the selective catalytic reduction of NO with ammonia (NH3-SCR). The physicochemical analysis of zeolite properties by high-energy-resolution fluorescence-detected XANES (HERFD-XANES) and X-ray emission spectroscopy (XES) uncovered that the coordination, geometry and oxidation state of Mn species are strongly related to the preparation method. Additionally, the study of catalyst acidity by FTIR spectroscopy with CO and pyridine probe molecules provided important insight into the number and type of acidic centres present on the catalyst surface. The catalytic results revealed that NO conversion depended on the state and content of Mn. The zeolites obtained by the two-step post-synthesis method and with a low Mn content were very active in the medium temperature range (NO conversion â¼100%) with simultaneous high selectivity to N2 due to the presence of isolated, framework Mn(iii) and Mn(ii) species. The N2O formation was especially high in the case of catalysts containing extra-framework polynuclear Mn species and negligible in the case of Mn(I.E.)AlBEA containing predominantly isolated, extra-framework Mn(ii) species.
RESUMO
The occurrence of hepatocellular carcinoma in HBsAg-negative chronic active hepatitis is described in two patients. signs of the tumour appeared 18 years and nine years after the first clinical signs of chronic active hepatitis, although in one patients analysis of stored sera showed the serum alpha-fetoprotein levels had been rising over the previous 33 months. Female preponderance in HBsAg-negative chronic active hepatitis may partly account for the rarity of this complication, and the occurrence of hepatocellular carcinoma may also be a reflection of the better survival now being obtained in HBsAg-negative chronic hepatitis.