Abstract:Crude oil asphaltenes contain a wide series of chemical species, which includes the most polar compounds and interfacially active agents from the petroleum. Asphaltenes have been considered to be implicated in foam and emulsion formation during the petroleum recovery and production process. In this work, the interfacial activity of organic solutions containing asphaltene and n-alcohols was investigated. Asphaltene extraction from a 28 • API crude oil produced 2.5 wt % of n-pentane precipitated asphaltene (C5I). Dynamic surface and interfacial tensions of asphaltene solutions were assessed by the pendant drop method. Asphaltene films were evaluated at the air-water interface using a Langmuir trough. Results were expressed by means of the interfacial tension time-dependence. Interfacial tension measurements showed alcohols reduce the toluene/water interfacial tension of asphaltene solutions. The interfacial tension was reduced from 23 mN/m to 15.5 mN/m for a 2 g/L solution of asphaltene plus n-butanol. Higher asphaltene concentrations did not affect the toluene/air surface tension. The effects of n-alcohols on the asphaltene surface activity was dependent on the asphaltene aggregation state. n-Alcohols modify the asphaltene film elasticity and the film phase behavior.

In this work, nanocellulose particles were obtained from eucalyptus bers by high-pressure homogenization (CNF) and by high-intensity ultrasound (SCNF). The nanocellulose was applied as a solid emulsi er for soybean oil in water (O/W) emulsions. The adding of 0.25 -1 wt.% of both CNF and SCNF produced stable O/W emulsions without conventional surfactants. SCNF emulsions showed the highest stability and displayed the narrowest size distribution. Zeta potential values (-40 to -70 mV) indicated an electrical barrier to the droplet coalescence. The rheological behavior of O/W emulsions stabilized with CNF and SCNF was described by the Herschel-Buckley model. O/W emulsions produced with nanocellulose particles behave as shear thinning uid, and their behavior index ranged from 0.33 to 0.68. Both CNF and SCNF emulsions displayed maximum yield stress at a particle concentration of 0.5wt.% and 0.75wt.%, respectively. Besides, the prepared O/W emulsions using 0.5 to 1.00 wt.% CNF or SCNF did not showed phase separation until 30 days of rest. The data point out to the feasibility of using nanocellulose as a natural emulsi er, which can replace conventional surfactants. Novelty StatementThe wastes biomass from the agriculture and forest activities, are renewable materials currently recognized as a valuable source of energy and chemical products. Cellulose is the main component of lignocellulosic biomass, and it has been converted into value-added materials. Recently, cellulose nanoparticles have been produced to be used as an emulsion stabilizer, replacing conventional surfactants. Nanocellulose particles were successfully generated by means of high-energy ultrasound, an intensive energy process, displaying useful properties to stabilize oil-in-water (O/W) emulsions. Surface properties of cellulose nanoparticles were determined. The equivalent hydrophilic-lipophilic balance for nanoparticles was assessed by comparison with conventional fossil-derived surfactant. The Pickering soya oil-in-water emulsions were very stable, showing their usability as emulsion stabilizers. O/W emulsions display a shear-thinning behaviour.

RESUMO-Asfaltenos compreendem os compostos mais polares e interfacialmente ativos do petróleo e tem sido apontado como o principal responsável por problemas relacionados a deposição de sólidos. No presente estudo, a tensão interfacial de sistemas contendo asfaltenos e álcoois intermediários foi investigada, usando um tensiômetro óptico. Asfaltenos foram extraídos de um óleo leve da reserva petrolífera nacional e dissolvidos em tolueno. Os resultados mostram uma continua redução da tensão interfacial com o tempo, que permite inferir a cinética de adsorção de moléculas à interface. A presença de álcoois acentua a redução da tensão interfacial da solução, até uma concentração limite, permitindo inferir a presença de álcoois na interface.

In this work, nanocellulose particles were obtained from eucalyptus fibers by high-pressure homogenization (CNF) and by high-intensity ultrasound (SCNF). The nanocellulose was applied as a solid emulsifier for soybean oil in water (O/W) emulsions. The adding of 0.25 - 1 wt.% of both CNF and SCNF produced stable O/W emulsions without conventional surfactants. SCNF emulsions showed the highest stability and displayed the narrowest size distribution. Zeta potential values (-40 to -70 mV) indicated an electrical barrier to the droplet coalescence. The rheological behavior of O/W emulsions stabilized with CNF and SCNF was described by the Herschel-Buckley model. O/W emulsions produced with nanocellulose particles behave as shear thinning fluid, and their behavior index ranged from 0.33 to 0.68. Both CNF and SCNF emulsions displayed maximum yield stress at a particle concentration of 0.5wt.% and 0.75wt.%, respectively. Besides, the prepared O/W emulsions using 0.5 to 1.00 wt.% CNF or SCNF did not showed phase separation until 30 days of rest. The data point out to the feasibility of using nanocellulose as a natural emulsifier, which can replace conventional surfactants.