José Ribeiro Gregório

Ionic silica based hybrid material containing the pyridinium group used as an adsorbent for textile dye.

The present study reports the development of an ionic silica based hybrid material containing the cationic pyridinium group, which was employed for the removal of the Reactive Red 194 textile dye from aqueous solution. Three hybrid material samples were prepared with planned textural and chemical properties, varying the inorganic precursor molar percentage in the sol-gel synthesis. The obtained samples were defined as Py/Si-90, Py/Si-92 and Py/Si-94, where the number specifies the inorganic molar percentage. The hybrid samples were characterized by elemental, infrared, (13)C and (29)Si NMR, N(2) adsorption-desorption isotherms and thermogravimetric analyses. The dye-removing ability of these adsorbents was determined by the batch contact adsorption procedure. Effects such as pH value and adsorbent dosage on the adsorption capacities were studied. Four kinetic models were applied. The adsorption was best fitted to Avrami fractional-order kinetic model for the three hybrid material samples. The kinetic data were also adjusted to an intra-particle diffusion model resulting three linear regions, indicating that the adsorption kinetics follows multiple sorption rates. The equilibrium data were fitted to Langmuir, Freundlich and Liu isotherm models. The maximum adsorption capacities were 165.4, 190.3 and 195.9 mg g(-1) for Py/Si-90, Py/Si-92 and Py/Si-94, respectively. Simulated dye-house effluents were used to check the applicability of the proposed adsorbents for effluent treatment. Dye loaded adsorbents were regenerated (>98.2%) by using 0.4 mol L(-1) of NaOH solution as an eluent.

Studies on the experimental variables effects on rhodium catalyzed hydroformylation of unsaturated fatty esters and comparison of [RhH(CO)(PPh3)3] and [RhCl3.3H2O] as starting catalytic precursors

Hydroformylation experiments were performed with technical-grade methyl oleate (MO) and soybean oil (SO) using [RhH(CO)(PPh3)3] and [RhCl3.3H2O] (double bond/Rh = 745) as catalyst precursors modified or not by triphenylphosphine. [RhH(CO)(PPh3)3] shows 100% conversion and 80-91% selectivity to aldehydes in only 4h for both substrates under mild conditions (100 °C, 40 bar, CO/H2 = 2:1, ligand/Rh = 10:1). Despite the rapid isomerisation of the soybean oil, producing trans isomers and conjugated dienes, no effects were observed on its further conversion to aldehydes. The reaction of soybean oil conducted with pure [RhCl3.3H2O] produced only conjugated dienes, and when this precursor was modified with triphenylphosphine (ligand/Rh = 10:1) no reaction was observed at all. Curiously, yellow crystals corresponding to the complex [Rh(Cl)(CO)(PPh3)2] were quantitatively isolated at the end of the reaction .

Polymers oxidation with VO(acac)2 complex

Abstract The introduction of epoxy groups in the polymer backbone is one of the most promising methods of modifying polydienes. In this work the performance of the classical catalytic system VO(acac) 2 / tert -butylhydroperoxide was evaluated for the epoxidation of polydienes. The polymers investigated were a hydroxylated poly(butadiene), two polybutadienes with high and with low 1,4-content, a poly(isoprene), and a styrene–butadiene copolymer. The epoxidized polymers were characterized by IR, 1 H and 13 C NMR and GPC techniques. The vanadium system was active for the epoxidation reaction and the reactivity decreases in the order HTPB>PI>1,4-PB>1,2-PB∼SBR. The occurrence of secondary reactions to low extension could be detected by the presence of hydroxyl, carbonyl and alcohol signals in the spectra of epoxidized polymers. Incomplete mass recovery (70–90%) was observed probably due to the chain degradation or modification of the polymer polarity.

Very efficient epoxidation of 1,4-polybutadiene with the biphasic system methyltrioxorhenium (MTO)-CH2Cl2/H2O2

The biphasic system methyltrioxorhenium (MTO)-H2O2/CH2Cl2 was studied in the epoxidation of polybutadiene and the results showed that this system presents a high selectivity and the extension of epoxidation (10–50%) can be modulated by the amount of oxidant added, without significant change in the molecular weight of the polymer.

Gerenciamento dos resíduos da disciplina química inorgânica II do curso de química da Universidade Federal do Rio Grande do Sul

Beginning students in chemistry usually do not realize that wastes generated in their experimental classes constitute an environmental problem and that residues must be treated or disposed of in a suitable way. In this manuscript we describe the work that we have been doing in the inorganic chemistry course of the Federal University of Rio Grande do Sul with the objective of creating a critical consciousness in the students about the chemical wastes they generate. With this policy, students are required to take into account the nature of the residues they generate, how they can treat or segregate them, and how they can keep them in a suitable way for final destination, instead of simply throwing them away.

X-Ray crystal structure of (tetraphenylimidodiphosphinato)silver(I): an unexpected tetranuclear complex with two modes of coordination of silver

Potassium tetraphenylimidodiphosphinate reacts with silver nitrate to give, upon recrystallization from ethanol, an unexpected tetranuclear complex [Ag{N(OPPh2)2}]4·2EtOH, the structure of which is established by X-ray crystallography; preliminary results concerning its use as a catalyst for the aerobic co-oxidation of alkenes and aldehydes are described.

Hidroformilação do oleato de metila catalisada por complexos de ródio

In this work, we describe the hydroformylation of methyl oleate catalyzed by several rhodium complexes. Parameters including total pressure, phosphorous/rhodium and CO/H2 ratio, temperature and phosphorous ligands were scanned. Total conversion of the starting double bonds was achieved while maintaining excellent selectivity in aldehydes.

Synthesis, structural characterization and catalytic properties of a novel monomeric rhenium(V)methyl(oxo)bis(η2-picolinato) complex: [CH3Re(O)(pic)2]†

A methyl mono-oxo rhenium(V) complex with two picolinato chelating ligands has been synthesized and structurally characterized. When reacted with excess 10 or 30% H2O2 it forms peroxo species responsible for the catalytic activity of a highly selective two-phase medium.

A study of a new catalytic system for the metathesis of funcionalized olefins

Efetuou-se o estudo sobre um novo sistema catalítico WCI6.PMHS. Curvas de conversão, números de rotação e freqüências de rotação foram comparados àqueles para os sistemas já conhecidos na literatura. Os resultados mostram que o novo sistema tem atividades análogas nas reações de metátese do 1 0-undecenoato de meti la e 1 0-undecenonitrila que os sistemas conhecidos para esse tipo de reações, com a vantagem de utilizar como catalisador um composto menos tóxico e de menor custo que SnMe4 e Ph2SiH2.

Mesoporous organic–inorganic hybrid material containing hydrosilylated soybean oil

Vegetable oils are attractive substrates for use as renewable feedstock in polymer industry. Hydrosilylation is a way to insert silicon groups in an olefin, and if the silylated olefin has hydrolysable groups, it can be used as precursor reagent in sol–gel synthesis. In this work, for the first time, the hydrosilylation of the vegetable soybean oil is reported, and it was used as sol–gel molecular precursor, along with tetraethylorthosilicate, varying their proportions. The obtained organic–inorganic silica-based hybrid material was characterized by infrared spectroscopy, N2 adsorption–desorption isotherms, scanning electron microscopy, and thermogravimetric analysis. The hybrid contains the oil chain covalently anchored, and it presents interesting textural characteristics, such as high surface area and mesoporosity, which seem not be markedly affected by the organic amount added.Graphical Abstract