Phase-transfer catalysis and ultrasonic waves II: saponification of vegetable oil

Abstract

Saponification of oils which is a commercially important heterogeneous reaction, can be speeded up by the application of ultrasound in the presence of phase-transfer catalyst (PTC). This paper focuses on the ability of ultrasound to cause efficient mixing of this liquid-liquid heterogeneous reaction. Castor oil was taken as a model oil and the kinetic of the reaction was followed by the extent of saponification. The hydrolysis of castor oil was carried out with different PTC such as cetyl trimethyl ammonium bromide (CTAB), benzyl triethyl ammonium chloride (BTAC) and tetrabutyl ammonium bromide (TBAB) in aqueous alkaline solution. As hydroxyl anion moves very slowly from aqueous to oil phase, the presence of a PTC is of prime importance. For this purpose, cationic surfactants are selected. The sonication of biphasic system were performed by 20 kHz (simple horn and cup horn) and 900 kHz. It was found that CTAB was better than the two others and this could be related to the molecular structure of the PTCs. The effect of temperature was also studied on the saponification process. By increasing the temperature, the yield was also increased and this could be explained by intermolecular forces, interfacial tension and mass transfer. Saponification of three different vegetable oils shows that the almond oil is saponified easier than the two others and this could be related to their properties such as surface tension, viscosity and density.

Ultrasonically treated liquid interfaces for progress in cleaning and separation processes

“…In acid-catalyzed reactions ultrasound increases the reaction rate and shifts the equilibrium yielding higher product yields in shorter reaction times. 97 This is due to the accumulation of these catalysts at the interface acting as surface active compounds with ionic properties. 87 Overall, the Please do not adjust margins Please do not adjust margins reaction rate of ultrasonic transesterification increases with longer chain-length of alcohol, as the miscibility between oil and alcohol increases, but the separation of formed esters becomes difficult.…”

Simultaneous removal of copper and lead ions from a binary solution by sono-sorption process

“…For the sorption in a batch system, Schueller and Yang [21] found that ultrasound act like a mixer, improving the mass transfer coefficients through cavitation and acoustic streaming. It is well understood that ultrasonic wave have a greater efficiency for interface mixing than control agitation [27,28]. This behavior could be the reason for the enhancement of the sorption kinetic process [22].…”

Ultrasound facilitates and improves removal of Cd(II) from aqueous solution by the discarded tire rubber

“…Ultrasonic waves strongly affect mass transfer between two phases. It is well understood that ultrasonic waves have a greater efficiency for interface mixing than conventional agitation [12,13]. This behavior could be the reason for the enhancement of the sorption kinetic process [14][15][16][17]19].…”