Wanda de Oliveira

The luminescent behavior of the steamed EuY zeolite incorporated with vanadium and rare earth passivators

Abstract In the present work, the use of rare earth ions as passivating agents to prevent vanadium poisoning of Y zeolite-based cracking catalysts during typical hydrothermal operating conditions of FCC units was studied to establish the capability of each RE 3+ passivator used here (RE=La, Gd or Lu) to interact with vanadium in order to protect the zeolite from structural collapse by exploring the photoluminescent properties of the Eu 3+ ion as local probe in the zeolitic lattice environment. The Ω λ intensity parameters ( λ =2 and 4) were determined from the emission spectra which showed that Eu 3+ ion assumes a stronger covalent character in relation to V attack. In another approach, the formation of orthovanadate ion was determined by means of excitation spectra and related with the intraconfigurational transitions from the Eu 3+ ion. It was suggested that the interaction with vanadium could be associated to REVO 4 intrinsic thermodynamic values.

Preparação de compostos de alumínio a partir da bauxita: considerações sobre alguns aspectos envolvidos em um experimento didático

Aluminum metal and aluminum compounds have many applications in several branches of the industry and in our daily lives. The most important raw material for aluminum and its manufactured compounds is bauxite, a rock constituted mainly by aluminum hydroxides minerals. In this work, a didactic experiment aiming the preparation of alumina and potassium alum starting from bauxite is proposed for undergraduate students. Both compounds are of great commercial, scientific and historical interest. The experiment involves applications of important chemical principles such as acid-base and precipitation. Some chemical properties and uses of aluminum compounds are also illustrated.

Synthesis and ethylene polymerization catalysis of mono(cyclopentadienyl)lanthanide compounds with the pyrazinamide ligand

In this work the synthesis of mono(cyclopentadienyl)lanthanide compounds containing methanesulfonate anion and pyrazinamide ligand is presented. The compounds were characterized by elemental analyses, complexometric titration with EDTA, thermal analyses, and vibrational spectra in the infrared region. In a preliminary catalytic study these compounds were active in ethylene polymerization when MAO was used as cocatalyst producing low crystalline polyethylene.

Polifosfatos em detergentes em po comerciais

A didactic experiment is proposed in order to identify inorganic phosphates in home laundry detergents by ascending paper chromatography. Chemical principles related with hard water are also investigated. The role of polyphosphates in detergent formulations is discussed and the softening of hard water by sodium tripolyphosphate is illustrated. Several chemical concepts, related to the daily experience of the students, can be explored in post-lab discussions.

Synthesis, characterization and catalytic activity of some organolanthanides in ethylene polymerization

Abstract The synthesis and characterization of a new class of organolanthanide compounds containing the bromide and cyclopentadienyl anions together with a pyrazinamide ligand are presented. The compounds were characterized by elemental analyses, complexometric titration with EDTA, thermal analyses, vibrational spectra in the infrared region. The catalytic activity of these compounds in ethylene polymerization was examined.

Synthesis of rhodium (II) hydrocinnamate and some complexes with nitrogen ligands

Abstract Rhodium(II) hydrocinnamate has been prepared by the reaction of hydro-cinnamic acid with rhodium(II) acetate and has been used to prepare complexes of probable formula [Rh 2 (C 6 H 5 CH 2 CH 2 CO 2 ) 4 L 2 ] (L = imidazole, 2-methylimidazole, pyridine, di-methylamine). IR, Raman, electronic, XPE and NMR ( 1 H) spectra and magnetochemical and thermal analysis data are reported.

Synthesis and catalytic activity in ethylene polymerization of cyclopentadienylterbium dibromides with pyrazole or triphenylphosphine ligand

Abstract Organoterbium compounds TbBr2CpHPz and TbBr2CpPPh3 were obtained by reaction of pyrazole or triphenylphosphine ligands with cyclopentadienylterbium dibromide. These compounds were characterized by elemental analysis, complexometric titration with EDTA, thermal analysis, vibrational spectra in the infrared region and 1H NMR. In a preliminary catalytic study, these compounds were active in ethylene polymerization when MAO was used as cocatalyst, producing low crystalline polyethylene.

Compostos organolantanídeos contendo o ligante pirazinamida: síntese, caracterização e atividade catalítica na polimerização do etileno

In this work we report the synthesis of some organolanthanide compounds which were identified as LnCl2Cp(PzA)2, Ln = Nd, Sm, Eu and Tb, Cp = cyclopentadienyl and PzA = pirazinamide, by elemental analyses, complexometric titration with EDTA, thermal analyses and IR spectra. Thermal analysis and infrared spectra indicated that the coordination of the pyrazinamide to the lanthanide ions was made by the O atom of the carbonyl group and by one or both N atoms of the pyrazinamide ring. This class of compound showed catalytic activity of ca. 4.0 to 6.4 kgPE molLn-1 h-1 bar-1, in ethylene polymerization, using methylaluminoxane as cocatalyst. The resulting polyethylene presented low crystallinity (20%).

Synthesis and characterization of chlorovinylcyclopentadienyl lanthanides

Abstract In this work the synthesis and characterization of a novel class of organolanthanide compounds: [Ln(C 5 H 4 CHCH 2 ) 2 Cl], Ln=La, Sm, Eu, Gd, Dy, Er; [Ln(C 5 H 4 CHCH 2 )Cl 2 ], Ln=Nd, Tb and [Dy(C 5 H 4 CHCH 2 ) 3 ] are presented. Compounds were characterized by elemental analyses, complexometric titration with EDTA, argentimetric titration, thermal analyses, magnetic susceptibility and vibrational spectra in the infrared region. According to the infrared spectra, a σ-centered bonding is assumed, corresponding to a local symmetry C 5 v , for the vinylcyclopentadienyl anion.

Estudo de alguns compostos organolantanídeos: [LnCp2Cl.PPh3]

In this work we present the synthesis and characterization of some organolanthanide compounds [LnCp2Cl.PPh3], Ln = La, Nd, Eu, Yb and Lu. The catalytic activity of these compounds has been verified in cyclohexene hydrogenation. Cyclohexane was identified by 1H NMR analysis in the reaction products.