Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto

About: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto is a based out in . It is known for research contribution in the topics: Population & Catalysis. The organization has 2143 authors who have published 3674 publications receiving 71071 citations. The organization is also known as: FFCLRP & FFCLRP-USP.

Manganese(III) porphyrins: catalytic activity and intermediate studies in homogeneous systems

Abstract: We studied how solvent, stirring method, PhIO/MnP molar ratio, presence of water and axial ligand affect the catalytic activities of Mn(TPP)Cl, Mn(MNPP)Cl, Mn(TDCPP)Cl and Mn(TFPP)Cl in the oxidation of cyclohexane by PhIO. A study of the catalytic intermediates in the reaction between Mn(TPP)Cl or Mn(TDCPP)Cl and PhIO was also carried out by UV–Vis and EPR spectroscopies. The reaction of Mn(TPP)Cl with PhIO showed the formation of a mixture of species MnIV(O)P·+ and MnV(O)P as intermediates, which were confirmed by the deconvolution of the UV–Vis spectra. Addition of imidazole as cocatalyst favoured the formation of the intermediate species MnV(O)P, evidenced by the UV–Vis band at 408 nm. The corresponding EPR spectra gave evidence that in the presence of imidazole, MnIV(O)P·+ species are formed only in very low amounts. For Mn(TDCPP)Cl the dominating intermediate species is MnIV(O)P·+. Addition of imidazole to halogen-substituted MnP systems does not result in increase of the C-ol yields because very stable bis-imidazole-MnP complexes are formed. Anchoring of such MnP on imidazole propyl gel (IPG) results in better catalytic activity because in this case, the catalyst is mono-coordinated to the support and imidazole favours the formation of the intermediate species MnV(O)P.

Generalized exponential function and discrete growth models

Abstract: Here we show that a particular one-parameter generalization of the exponential function is suitable to unify most of the popular one-species discrete population dynamic models into a simple formula. A physical interpretation is given to this new introduced parameter in the context of the continuous Richards model, which remains valid for the discrete case. From the discretization of the continuous Richards’ model (generalization of the Gompertz and Verhulst models), one obtains a generalized logistic map and we briefly study its properties. Notice, however that the physical interpretation for the introduced parameter persists valid for the discrete case. Next, we generalize the (scramble competition) θ -Ricker discrete model and analytically calculate the fixed points as well as their stabilities. In contrast to previous generalizations, from the generalized θ -Ricker model one is able to retrieve either scramble or contest models.

Photolysis of ferric ions in the presence of sulfate or chloride ions: implications for the photo-Fenton process

Abstract: The photo-Fenton process (Fe2+/Fe3+, H2O2, UV light) is one of the most efficient and advanced oxidation processes for the mineralization of the organic pollutants of industrial effluents and wastewater. The overall rate of the photo-Fenton process is controlled by the rate of the photolytic step that converts Fe3+ back to Fe2+. In this paper, the effect of sulfate or chloride ions on the net yield of Fe2+ during the photolysis of Fe3+ has been investigated in aqueous solution at pH 3.0 and 1.0 in the absence of hydrogen peroxide. A kinetic model based on the principal reactions that occur in the system fits the data for formation of Fe2+ satisfactorily. Both experimental data and model prediction show that the availability of Fe2+ produced by photolysis of Fe3+ is inhibited much more in the presence of sulfate ion than in the presence of chloride ion as a function of the irradiation time at pH 3.0.