Carmen Luisa Barbosa Guedes

Photochemical weathering study of Brazilian petroleum by EPR spectroscopy

Abstract The EPR spectrum of the petroleum of the Campos Basin, Rio de Janeiro, Brazil shows signals characteristic of free radical, vanadyl (VO 2+ ) and iron III ion (Fe 3+ ). The value of g =2.0045±0.0001 corresponds to free radical species with a peak-to-peak line width Δ H =4.64±0.03 G. The g spectroscopic factor suggests the presence of free radicals in aromatic systems containing carbon, nitrogen and oxygen. Δ g o (chemical shift)=21.6±0.1 determined for the VO 2+ species characterizes porphyrin and non-porphyrin (with sulfur) complexes in asphaltenes of the crude oil. The species observed with g =2.16±0.01 corresponds to Fe 3+ in Fe 2 O 3 , and therefore is not part of the molecular structure of the oil under study. The photochemical weathering of Brazilian oil as a film over seawater was monitored by EPR. After 100 h of solar irradiation the line width of the radical decreased by 10.6%, indicating rearrangement among radicals. The Δ g o value for VO 2+ in the irradiated oil decreased to 19.5±0.1, characterizing degradation of porphyrin systems. Solar irradiation promotes the partial destruction of the asphaltenic fraction of the oil.

Genotoxic evaluation of an industrial effluent from an oil refinery using plant and animal bioassays

Polycyclic aromatic hydrocarbons (PAHs) are genotoxic chemicals commonly found in effluents from oil refineries. Bioassays using plants and cells cultures can be employed for assessing environmental safety and potential genotoxicity. In this study, the genotoxic potential of an oil refinery effluent was analyzed by means of micronucleus (MN) testing of Alium cepa, which revealed no effect after 24 h of treatment. On the other hand, primary lesions in the DNA of rat (Rattus norvegicus) hepatoma cells (HTC) were observed through comet assaying after only 2 h of exposure. On considering the capacity to detect DNA damage of a different nature and of these cells to metabolize xenobiotics, we suggest the association of the two bioassays with these cell types, plant (Allium cepa) and mammal (HTC) cells, for more accurately assessing genotoxicity in environmental samples.

Aplicação do delineamento simplex-centroide no estudo da cinética da oxidação de biodiesel B100 em mistura com antioxidantes sintéticos

Antioxidants are an alternative to prevent or slow the degradation of the biofuel. In this study, it was evaluated the oxidative stability of B100 biodiesel from soybean oil in the presence of three commercial synthetic antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), pure or blended, from the experimental design of simplex-centroid mixture. The reaction order and rate constant were also calculated for all tests. The treatment containing pure TBHQ proved to be the most effective, proven by design, the optimum mix obtained and the rate constant. Binary and ternary mixtures containing TBHQ also showed appreciable antioxidant effect.

Avaliação de biocombustível derivado do bio-óleo obtido por pirólise rápida de biomassa lignocelulósica como aditivo para gasolina

A biofuel was prepared from acid aqueous fraction (pH = 2) of bio-oil produced by fast pyrolysis (Bioware Technology) of lignocellulosic biomass (sugar cane residue) and tested in blends (2, 5, 10 e 20% v/v) with gasoline type C (common) marketed in Brazil. The specification tests made in the Refinery President Getulio Vargas (PETROBRAS) showed increasing in the octane number (MON) and antiknock index (AKI) with reduction in the residue generation during the combustion. The physicochemical characteristics of the biofuel were similar that combustible alcohol allowing its use as gasoline additive.

Multifrequency (X-band to W-band) CW EPR of the organic free radical in petroleum asphaltene

Petroleum of Arabian and Colombian origin was studied by electron paramagnetic resonance (EPR) spectroscopy at X- (9 GHz), Q- (34 GHz) and W-bands (94 GHz). The experiments were performed at room temperature (about 300 K) and at 77 K (W-band only). The asymmetry in the lines corresponding to free radicals was observed more intensely in the W-band spectra. The values of the line width ΔH in the spectra increased linearly with the microwave frequency utilized in the EPR experiments. A mathematical simulation of the free radical signal for the EPR spectra in three bands with a set of parameters corresponding to a single species was attempted, but this was not exactly coincident with the experimental signals, suggesting that the hyperfine interaction of the unpaired electron with its neighborhood corresponds to more than one species of radical in the molecular structure of the petroleum asphaltene.

ESR and calculations on electronic structure of phenalenyl and phenalenyl derivative radicals

Calculations on electronic structure of the perinaphthenyl radical and phenalenyl derivative radicals responsible for the composition of the ESR spectrum of marine diesel under heating were performed to obtain support for the experimental ESR results. The parameters calculated were the hyperfine coupling constants (A), which were then used for comparison with the experimental data. The energy‐minimized structures were obtained using the density functional theory method. In all cases, the symmetry system was taken into account in theoretical calculations. The differences between experimental and theoretical values were below 7% for nearest hydrogens in molecules, named hyperfine coupling constant A (first neighbors) and 18% for farthest hydrogens atoms named hyperfine coupling constants A′ (second neighbors), for all structures analyzed. Copyright

Morphological and Structural Analysis of Magnetic Support Produced from Magnetite (Fe3O4) Nanoparticles and Recycled Polyamide

In recent years, the number of systems that involves the use of magnetic nanoparticles has exponentially increased. Magnetic nanoparticles have been a viable alternative as catalyst support. Its high surface area results in high catalyst loading capacity, high dispersion, outstanding and convenient catalyst recycling. Hybrid nanoparticles consisting of polymers and magnetic nanoparticles are based on a polymeric layer either coating the surface of magnetic nanoparticles or the magnetic nanoparticles are embedded on a polymer network [1].

Crude Oil by EPR

Electron paramagnetic resonance (EPR) or Electron spin resonance (ESR) is a high resolution spectroscopy that consists in energy absorption of microwave, for electron spin, in the presence of a magnetic field (Ikeya, 1993). As the name itself suggests, EPR is applied in samples containing some paramagnetic species or used as an investigative method, to verify the presence of some paramagnetic species. Paramagnetism is characteristic of species with a total magnetic moment different from zero.