Alkyl polyglycosides (APGs) of different hydrocarbon chain lengths were prepared using an indirect method involving the condensation of fatty alcohol with dextrose. The chemical structures of the prepared compounds were confirmed using different spectroscopic techniques, primarily Fourier transform infrared spectroscopy, nuclear magnetic resonance and mass spectroscopy. The surface properties of the solutions containing different concentrations of the prepared APGs were determined at different temperatures. The results of the spectroscopic analysis demonstrate that these materials were prepared through the correct techniques, producing pure materials. The results of the critical micelle concentration (CMC) determination demonstrate that the surface properties of these compounds depend mainly on the nature of their hydrophobic component.

A series of cationic surfactants was prepared using economical raw materials. The chemical structures of the prepared compounds were confirmed using elemental analysis, FTIR and 1 H-NMR spectra, and melting point determination. The synthesized surfactants were evaluated as oil-field protective additives. In this regard, several surface properties of the synthesized surfactants were studied including surface tension, critical micelle concentration, effectiveness, efficiency, maximum surface excess and minimum surface area. The results obtained from the surface activity measurements were correlated to their chemical structures. The emulsification power measurements for solutions of these surfactants showed their low emulsifying tendency towards paraffin and crude oil. The synthesized surfactants also exhibited high biocidal activity towards gram-positive and gram-negative bacteria and fungi. This activity was increased by increasing the hydrophobic chain length. The corrosion inhibition measurement of these surfactants for mild steel alloys in acidic media using a weight loss technique showed good protection of mild steel alloys against acidic environments. These properties qualify the synthesized compounds as economical oil-field protective additives.

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In this study, the bacterium Bacillus licheniformis has been isolated from oil reservoir; the ability of this bacterium to produce a biosurfactant was detected. Surface properties of the produced biosurfactant were confirmed by determining the emulsification power as well as surface and interfacial tension. The crude biosurfactant has been extracted from supernatant culture growth, and the yield of crude biosurfactant was about 1 g/l. Also, chemical structure of the produced biosurfactant was confirmed using FTIR analysis. Results revealed that, the emulsification power has been increased up to 96% and the surface tension decreased from 72 of distilled water to 36 mN/m after 72 h of incubation. The potential application of this bacterial species in microbial-enhanced oil recovery (MEOR) was investigated. The percent of oil recovery was 16.6% upon application in a sand pack column designed to stimulate an oil recovery. It also showed antimicrobial activity against the growth of different strains of SRB (sulfate reducing bacteria). Results revealed that a complete inhibition of SRB growth using 1.0% crude biosurfactant is achieved after 3 h. ª 2015 Production and hosting by Elsevier B.V. on behalf of Egyptian Petroleum Research Institute. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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