Novel oxygenated surfactants for supercritical fluids

Author(s)

Fernando Luiz Cássio Silva

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2011-12-19

Examining board members

Reinaldo Camino Bazito; Iolanda Midea Cuccovia; Alexandre Gurgel; Frank Herbert Quina; Maria Elisabete Darbello Zaniquelli

• Advisor: Reinaldo Camino Bazito

Abstract

Supercritical carbon dioxide (scCO2) is a poor solvent for polar substances in general. An interesting way to overcome this limitation and fulfill its potential as a green solvent, a possible substitute for common volatile organic solvents, is the introduction of scCO2-suitable surfactants in the system. In the present work, three series of novel oxygenated surfactants for scCO2 were synthesized. The amphiphiles contain mono and poly-hydroxylated CO2-phobic heads, most of them sugar-based, as well as three types of CO2-philic tails, two of them perfluorinated (-C7F15 and -C9F19) and one peracetylated (D-gluconic acid derivative). Their solubilities and phase behaviors in CO2 and in ternary systems (water-CO2-surfactant), as well as their activities at the CO2-water interface, were investigated. All of them dispersed water in scCO2- with water-to-surfactant ratio (W) of 10, exhibiting cloud pressures comparable to those of \"dry\" systems. Also, the surfactants reduced the CO2-water interfacial tension. The effect of both the CO2-phobic heads and the CO2-philic tails could be analyzed separately. Dynamic interfacial tension results suggest that both diffusion from bulk CO2 to subinterface and insertion and migration of molecules within the interface contribute to the time-dependent decay of the interfacial tensions. (AU)

• FAPESP's process: 06/03034-0 - Aggregation in non-conventional media: new surfactants for supercritical fluids
• Grantee: Fernando Luiz Cássio Silva
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)