Recebido em 5/7/10; aceito em 17/9/10; publicado na web em 25/10/10 Herein, the immobilization of some Schiff base-copper(II) complexes in smectite clays is described as a strategy for the heterogenization of homogeneous catalysts. The obtained materials were characterized by spectroscopic techniques, mostly UV/Vis, EPR, XANES and luminescence spectroscopy. SWy-2 and synthetic Laponite clays were used for the immobilization of two different complexes that have previously shown catalytic activity in the dismutation of superoxide radicals, and disproportionation of hydrogen peroxide. The obtained results indicated the occurrence of an intriguing intramolecular redox process involving copper and the imine ligand at the surface of the clays. These studies are supported by computational calculations.

In this study, a novel surfactant for flowback aid application was developed based on an optimization of well-known non-ionic surfactants. The objective was to meet intrinsic surfactant properties, such as high cloud point (CP), low surface tension (ST), adequate contact angle (CA) and low critical micelle concentration (CMC). In addition to the essential physical-chemical properties, improvement in fluid recovery and emulsion compatibility were also targeted. The surfactants were optimized by tailoring the hydrophilic head through controlled introduction of ethylene oxide and propylene oxide into different hydrophobic chains. Surface tension measurements were made with a Dataphysics Instruments model OCA-15. Contact angles were measured using the sessile-drop method. The CMC concentration and cloud point were also conducted for physical chemical characterization. For the fluid recovery evaluation, flowback solutions were poured through 150g of 60/150 mesh- dry porous media contained in a 7 cm-inner-diameter, 9.5- cm-long column. Emulsion compatibility tests were also carried out using different proportions of crude oil and brine. This paper evaluates various flowback additives in hydraulic fracturing applications between linear and branched alkoxylated surfactants. High cloud point enables a wide range of temperature applications and an increase in EO content showed an increase in cloud point values, contrary to PO effect. Nevertheless, CMC measurements showed that for an optimum scenario, EO addition should not be high, because undesired increases in CMC values may occur, which will affect the final surfactant dosage needed. All flowback aids demonstrated low surface tension as expected (approximately below 32 mN/m), but each being different in terms of surface wettability (contact angle), which could not be correlated with surfactant structure. Fluid recovery and kinetics of emulsion breakage increased significantly with different alkoxylation adjustments. For the new flowback aid developed, the fluid recovery was improved when compared against standard surfactants. Additionally, significant improvement was also found during emulsion breakage evaluation in terms of superior kinetics, final breakage, and water quality. This work provided a better understanding of how EO/PO affects intrinsic surfactant properties and enabled to find a surfactant that offers several benefits in terms of fluid recovery and non-emulsification of crude oil and water.

There is an increasing demand from oil and gas industry to ensure the integrity of assets and the enviroment in the critical conditions found in presalt wells. This study evaluates new formulations of corrosion inhibitors with different types and alkoxylation degrees of nitrogen‐based inhibitors to assess corrosion behavior of carbon steel (API X65). For these studies, corrosion rates were determined through measurements of weight loss and linear polarization resistance (LPR). In the case of electrochemical measurements, experiments were carried out in a laminar flow and in a turbulent flow regime. All data were collected in the presence of CO2 and CO2/H2S mixtures. The results revealed that corrosion protection of carbon steel critically depends on the nitrogen‐based inhibitor's alkoxylation type and degree as well as the condition to which they are exposed. It was possible to notice that an ethoxylated amine whose inhibition efficiency in the presence of CO2 was about 10%, when exposed to H2S environment at the same temperature showed an efficiency of 86%. It was also observed that the inhibitor with a higher ethoxylation degree presented better efficiencies than the one with a lower degree.