Rosane Aguiar da Silva San Gil

Essential oil composition of Melissa officinalis L. in vitro produced under the influence of growth regulators

It was investigated the effects of indole-3-acetic acid (11.42 µmol L-1), benzylaminopurine (8.87 µmol L-1) on essential oil composition and on the growth of Melissa officinalis in vitro plants. In vitro plantlets developed on MS media, showed 1.4 times in the proportion of nerol and 4.1 of geraniol, when compared with ex vitro plants. Treatments with 11.42 µmol L-1 indole-3-acetic acid plus 8.87 µmol L-1 benzylaminopurine led to 1.7 and 2.2 fold in proportion of nerol and geraniol, respectively in 60-day-old whole plants. These increases might be associated with the action of growth regulators wich stimulate plant growth (shoot organogenesis and elongation) and delaying the alcohol oxidation to aldehydes.

Structure of vanadate in calcium phosphate and vanadate apatite solid solutions

Polycrystalline solid solutions of phosphate and vanadate calcium apatites were synthesized and studied by XRD, XPS, 31P and 51V NMR, FTIR and UV spectroscopies. Homogeneous distributions of vanadium within the solid and the surface were obtained. While 51V NMR spectra suggest an axial symmetry of the vanadate group, FTIR spectra indicate distortion from essentially C3v symmetry in solid solutions with low vanadium content to Cs for pure vanadate apatite, in agreement with the site symmetry group of phosphate in hydroxyapatite. Refinements of XRD pattern of vanadate apatite by Rietveld method confirm the Cs point group attribution. Three vanadium oxygen bond lengths were found around 168 pm and one close to 174 pm, suggesting that the Cs point group could be generated by a small distortion from C3v symmetry. Analysis of UV spectra confirms that distortion from Td symmetry increases with vanadium content and suggests some contraction of the vanadate ion in the apatite lattice.

Alkylation of toluene with aliphatic alcohols and 1-octene catalyzed by cation-exchange resins

The catalytic activity of macroreticular cation-exchange resin (Amberlyst-15) was evaluated for the reaction of toluene with isopropanol, 1-octanol, 2-octanol and 1-octene at 80°C, in the liquid phase. The best results were achieved with octene. The reaction yielded only monoalkylation products. The conversion of octene was 75% after 4 h of reaction. In the reaction with isopropanol the main product was propene. In the reaction with 1-octanol and 2-octanol the conversion was very low and the main products were the octyl ethers.

Zinc-modified, alumina-supported vanadium oxides as catalysts for propane oxidative dehydrogenation

Abstract Zinc-modified, γ-Al2O3 supported vanadium oxides were prepared by dry impregnation and co-precipitation methods. The solids were characterized by X-ray diffraction, UV–VIS, 51 V NMR and X-ray photoelectron spectroscopy and compared as catalysts in propane oxidative dehydrogenation (ODH). It was shown that only true co-precipitation methods lead to interaction of amorphous zinc vanadates with the surface of alumina. Selectivity spectra in propane ODH were used as a fingerprint to characterize superficial vanadates.

Biodiesel production by in situ transesterification of sunflower seeds by homogeneous and heterogeneous catalysis

The objective of this work is to show the results of the in situ transesterification of sunflower seed oil with methanol on basic homogeneous and heterogeneous catalysis for the production of biodiesel. In homogeneous catalysis, the activity of KOH and K2CO3 were evaluated using the same oil:methanol ratio of 1:90. KOH showed to be more active than K2CO3, leading to total conversion in biodiesel after 1h reaction time. In the heterogeneous catalysis the activity of K2CO3/Al2O3 was comparable to the activity of K2CO3 bulk: 53.0 and 66.6% resp. The properties of samples of biodiesel produced by homogeneous and heterogeneous catalysis were evaluated and are in accordance with the recommended fuel properties.

Characterization of a brazilian smectite by solid state NMR and X-ray diffraction techniques

X-ray diffraction (XRD), differential thermal analysis (DTA) and 27Al and 29Si solid state MAS-NMR techniques were used to monitor the fractionation steps of a brazilian smectite, previously crushed, from Campina Grande, Paraiba. The sand, silt and clay fractions were obtained by physical and chemical treatments. The XRD analysis of sand and silt fractions showed that both fractions had predominant quartz and feldspar, respectively. The XRD results of the K+ saturated and heated clay fraction confirmed that the natural clay belongs to the 2:1 clay-mineral group, whereas the analysis of the Mg2+ saturated and glycolated clay fraction confirmed the presence of a smectite group clay. The MAS-NMR results of 27Al and 29Si showed that the sand fraction contains 79% of quartz and the silt fraction contains 55% of quartz, while the clay fraction is rich in smectite with low isomorphic replacement of Si by Al, and contains 38 % of quartz.

Extração de ferro de esmectita brasileira com emprego do método ditionito-citrato-bicarbonato

A natural clay from Campina Grande region (Paraiba, Brazil), with 8.57% of Fe2O3, was used to study the most appropriate condition to carry out the iron extraction, without altering the clay structure in a significant way. Samples were treated with the Dithionite-Citrate-Bicarbonate method (DCB) for 30 and 120 minutes (pH=9.1), and also with citric acid (pH=1.8; time=15min), at 75°C. Conductivity measurements, X-ray fluorescence, X-ray diffraction, energy-dispersive spectrometry, electron-diffraction with transmission electron microscopy and textural evaluation by nitrogen adsorption were done. The treatment in a basic medium was more selective for iron removal than in acid condition. The time of 30 minutes, with 1.6 g Na2S2O4/10 g clay, was the best condition for the iron extraction.

Carbon-13 Solid State NMR Study of Polypropylene/Clay Nanocomposite

As it is known there are at least three ways to prepare a nanocomposite: solution casting, polymerization in situ and melting extrusion. In this work we have chosen to prepare the hybrids nanocomposite of polypropylene with brazilian clay (montmorillonite) using two types of blending mixers: one was a rheometer mix and the other one an extrusion process with the polypropylene/clay (PP/clay) proportion 95/5 w/w. The conditions of blending processing were: temperature 180 °C for 10 minutes. The objective of this work is to evaluate the characteristics of both types of nanocomposites obtained, employing solid state nuclear magnetic resonance (NMR). The C and Al NMR techniques were employed to obtain the nanocomposites homogeneity and dispersion of nanocomposite components. A comparison of the carbon-13 CPMAS NMR spectra of polypropylene and their nanocomposites prepared in Haake and extruder, revealed changes in the chains packing and ordination. Changes in both chemical and line width of Al NMR spectra indicates the formation of nanocomposite. To confirm these results, X-ray diffraction pattern was also registered. When the sample was prepared in the Haake only a composite was formed, but when the blend was performed in the extruder an exfoliated and dispersed nanocomposite was obtained.

Synthesis and characterization of two new niobium(V) diperoxo complexes containing 8-quinolinolate as the ligand

Abstract Two new diperoxo complexes of niobium using 8-quinolinolate (Q) as the ligand, K[NbOH(O 2 ) 2 Q]·2H 2 O ( 1 ) and K[Nb(O 2 ) 2 Q 2 ]·3H 2 O ( 2 ), have been synthesised and characterised structurally by elemental analysis, IR and NMR ( 1 H, 13 C, 93 Nb) spectroscopy. The 1 H and 13 C NMR signals of the free ligand undergo shift on complexation.

Caracterização de polimorfismo em fármacos por ressonância magnética nuclear no estado sólido

This review aims to present some features about solid state NMR and its application in the field of pharmaceutical chemistry, for the characterization of polymorphism of pharmaceutical molecules.