Study On Emulsion Phase Inversion Mechanisms And Ammoximation Of Cyclohexanone

Surfactants (Span80and Tween80) and colloidal particles (TS-1) were used asemulsifiers to prepare emulsions and phase inversions in the systems wereinvestigated. Moreover, Ammoximation of cyclohexanone in Pickering emulsionstabilized by TS-1particles employing cyclohexanone and ammonium hydroxide wasstudied.Appearance of paraffin oil/water emulsions prepared via the catastrophic phaseinversion method employing mixed emulsifiers (Span80and Tween80) wasinvestigated. U-shape dependence of phase inversion locus and droplet size on HLBwas presented with minimum phase inversion point, best emulsion stability andsmallest droplet size at HLB of9.7. The different absorbed infrared radiations ofhydroxyl groups between the two normal morphologies indicated phase inversion. Itcan be concluded that IR spectroscopy is a potential effective tool to monitor phaseinversion of emulsions and explain the morphologies changes.Tween80was used as surfactant to create Tween80-stabilized emulsions, andthe consequences of the competitive adsorption at the emulsion interfacial layer wereexamined. The mechanism of the emulsion inversion is that the continuous stirringcauses the formation of an intermediate W/O/W multiple emulsion, which results inthe final inversion.Lipophilic surfactants were used in the oil/water system to form W/O emulsions,and addition of hydrophilic surfactants to the emulsions was used to prepare O/W/Omultiple emulsion. The mechanism of the emulsion inversion is that micelle transportcauses the formation of O/W/O multiple emulsion. With hydrophilic surfactantsconcentrations increased, multiple emulsion droplets enlarged and coalesced witheach other, leading to the final inversion.The effect of Span80on emulsions containing cyclohexanone and waterstabilized by TS-1particles was investigated. Surprisingly, a novel double phaseinversion was triggered by simply changing the Span80concentration. In this process,different emulsifiers occupied the composition of the interfacial layer, and theemulsion type was correspondingly controlled. When low concentration Span80wasadded, TS-1particles synergisted with Span80to stable the emulsions, and the type was W/O as TS-1particles were in domination. At moderate Span80concentrations,the emulsions were stabilized mainly by Span80, and O/W emulsions were obtained.For high Span80concentration, Span80replaced TS-1particles from thecyclohexanone-water interface and dominated the interfacial layer of emulsion droplet,thus W/O emulsions were formed again.Ammoxiamtion of cyclohexanone in Pickering emulsion containingcyclohexanone and ammonium hydroxide stabilized by TS-1particles wasinvestigated. The success of surface modification of TS-1particles by silylation wasconfirmed by high-angle XRD, IR and UV-vis spectroscopy. Catalysis test showedthat catalytic activity of modified TS-1particles significantly improved and selectivityof cyclohexanone oxime significantly enhanced. Moreover, selectivity ofcyclohexanone oxime with HMDSO/TS-1was parabolic.