No abstract

No abstract

No abstract

No abstract

Redox phase unpromoted molybdenum catalysts with different Mo loadings (2.5% Mo/γ-Al 2 O 3 ; 5.0% Mo/γ-Al 2 O 3 ; 7.5% Mo/γ-Al 2 O 3 and 10.0% Mo/γ-Al 2 O 3 ) were prepared and characterized for the ammoxidation of glycerol to nitriles, such as acrylonitrile. The best catalyst (10.0% Mo/γ-Al 2 O 3 ) obtained a yield of 26% in nitriles. The increase in the molybdenum content and its oxidation states along with the amount of weak/moderate acid sites on the support surface are key points for the optimization of the catalysts.

The efficiency of niobium oxide as catalytic support of hydrodesulfurization (HDS) catalysts (CoMo and NiW) has been investigated in the HDS of a model molecule representative of sulfur compounds present in FCC gasoline (3-methylthiophene: 3MT). The NiW catalyst presented higher catalytic activity than CoMo calcined and non-calcined catalyst, however a better ratio pentane/pentene has been achieved by CoMo catalysts, which implies a lower formation of hydrogenated products. Indeed, the activity order for the catalysts evaluated is: NiW/Nb2O5 > CoMo/Nb2O5 calcined support > CoMo/Nb2O5 non-calcined support, despite the ratio pentane/pentene which has the inverse order. Furthermore, textural and chemical characterization techniques have been performed. From NH3-TPD analysis it was observed an acidity profile with a predominance of weak/strong and weak/moderate acid for CoMo and NiW catalysts, respectively. Meanwhile, the BET analysis has shown a low specific surface area for the catalysts supported by niobium oxide. Concerning the structure characteristic, the XRD analysis has suggested an amorphous phase in all catalysts analyzed.

Conhecimento dos estudantes de medicina acerca de hábitos sexuais e situações considerados de risco Medical students' knowledge about sexual habits and risk situations

Capítulo 2: Investigação sobre a condutividade e comportamento de fases de hidrocarboneto/tensoativos não iônicos/água sob a forma de micelas inversas ......... 12