Afonso Avelino Dantas Neto

New microemulsion systems using diesel and vegetable oils

Abstract The need to rationalize the use of the conventional existing fuels, associated to the impositions of severe legislation for controlling the level of emissions, has been demanding the development of optional fuels and the increase in the efficiency of the current engines. This study presents new microemulsion systems containing diesel and different percentages of vegetable oils (soy, palm and ricin), that can be used as alternative fuels. The main parameters that influence the microemulsion area, such as, nature of surfactant (T) and cosurfactant (C), C/T ratio and composition of the oil phase, have been studied. The results showed that it was possible to obtain new microemulsion systems with different oil phase composition (mixtures of diesel and vegetable oils), whose properties indicate the possibility to apply them as alternative fuels.

Microemulsion systems applied to breakdown petroleum emulsions

Abstract Microemulsion systems obtained using commercial surfactants with demulsifier and emulsion prevention properties have been employed to break down Brazilian crude water-in-oil (W/O) emulsions. These crude oils were supplied by the Brazilian oil company—PETROBRAS—and were characterized by the different Balance sheet of Sediment and Water (BSW) values of 48%, 36%, and 32%. The microemulsion systems formed in this study were composed of an aqueous phase (HCl 5.2% solution); an oil phase (toluene); a cosurfactant/surfactant (C/S) phase (isopropyl alcohol (C)/surfactants (S) with a ratio C/S of 9.0). The microemulsion efficiency to break down oil emulsions was evaluated by a direct contact method between the microemulsions and crude (W/O) emulsions. The Scheffe net statistical planning for mixtures was used to relate the component mass fractions to the relative breakdown of petroleum emulsions. The best composition of the microemulsion system for the complete breakdown of oil emulsions with high BSW values had the lowest C/S phase percentage.

Development of a new propolis microemulsion system for topical applications

Microemulsion systems (MES) offer advantages as drug delivery systems, among them favour drug absorption, being in most case more efficient than other methods in delivering of drug. In this work a new MES was obtained in order to be applied as a pressurized aerosol formulation containing bee propolis ethanolic extract (PEE). For that, pseudoternary phase diagrams were used to characterize the microemulsions boundaries and also to define the Winsor IV microemulsion region of the PEE-MES system containing Tween 80 as surfactant and the cosurfactant ethyl alcohol in small percentage. The obtained results indicated that the best MES was composed by Tween 80 and ethyl alcohol with C/S (cosurfactant/surfactant) ratio equal to 1.0, since it provided a large boundaries in the obtained O/W microemulsion region. This PEE-MES formulation, in which bee propolis consisting as oil phase, is herein designed for topical uses (PEE-MES spraying) in order to treat mouth and throat inflammatory infections. Considering the very large uses of bee propolis in conventional vehicles, MES type of delivery system has to be compatible with achieving the highest drug aim loadings, determined substantially by the specific MES application (drug solubilization in water systems) improving in this case, propolis farmacological aplications. Additionally, PEE-MES antibacterial effect was evidenced and the microemulsion system PEE-MES was also used as newest chemical approach for extraction of bee propolis material from resinous hive.

Recent Advances on the Use of Surfactant Systems as Inhibitors of Corrosion on Metallic Surfaces

In this chapter, we seek to provide a general overview on the use of surfactant systems, particularly micelle solutions and microemulsions, as corrosion inhibitors on metallic surfaces. In addition to important industrial applications of surfactants, particularly in the petroleum industry, surfactant molecules have been studied and employed as successful corrosion inhibitors due to their ability to adsorb onto surfaces, forming an interfacial film and protecting them from corrosive agents. Several parameters affect the mechanism of corrosion inhibition, such as the type of surfactant, temperature, and composition of the chemical systems used. Different adsorption phenomena are established that determine the ultimate ability of the inhibiting system to impair the development of a corrosion environment. Theoretical aspects of surfactant aggregation are considered to discuss the general features of corrosion inhibition, as in salt- and acid-induced corrosion phenomena. The chemical nature of the surfactant molecule and how it is synthesized or produced are also important aspects that may be accounted for in the formulation of novel systems. Particular emphasis is given to the use of natural, renewable raw material, like vegetable oils such as cashew-nut shell liquid and castor oil, to synthesize surfactants that are precursors of corrosion inhibitors, at lower costs, as part of worldwide concerns regarding the search for environmentally friendly options for science and technology. Aggregation parameters such as surface excess, surface area, and variation of free energy of micellization, together with potentiokinetic and small-angle X-ray scattering measurements, are useful to describe the adsorption mechanism of surfactant molecules on solid–liquid interfaces, explaining the distinct behavior of specific systems on metallic surfaces. Our experimental work involves the use of some anionic and cationic surfactants with special chemical moieties that render them potentially good corrosion inhibitors, like amine and epoxy groups. Some recent advances on their use are also presented and discussed; they are part of a major series of both fundamental and practical research activities that have been undertaken in order to diversify the use of surfactant systems in the industry, particularly as inhibitors of corrosion of metallic surfaces.

The Use of Microemusion Systems in Oil Industry

Microemulsions are thermodynamically stable, isotropic, and macroscopically homogeneous dispersions of two immiscible fluids, generally oil and water, stabilized with surfactant molecules, either alone or mixed with a cosurfactant, as shown in Figure 1 (Robb, 1981). Cosurfactant is a nonionic molecule (e.g. a short-chain of alcohols or amine) that has the function of stabilizing a microemulsified system by decreasing the repulsion forces between the hydrophilic parts of the surfactant.