The influence of stirring time and frequency of impeller rotation on evaluation of drops dimensions and rheological properties of the multiple emulsion

Abstract

The analysis of drops and rheological measurements of the emulsion produced were presented in the article. The influence of stirring time and rotation frequency on the drops size of the emulsion produced in the propeller of diameter D = 0.1 m and liquid height H = 0.5D equipped with four standard flat dividers was defined. The Smith turbine stirrer was used to stir the emulsion produced. The drop size was defined for three different propeller rotation frequencies, 500 rpm, 1000 rpm and 1500 rpm. The stirring time, after which the samples were collected, was accordingly 15 min and 45 min. To produce the emulsion, sunflower oil was used in the oil phase and distilled water in the water phase. There were 6 measurement series all together, and they were presented as the diameter size distribution. The mean arithmetic diameter d a , median d m and the mean Sauter diameter d 32 were determined. The rheological measurements of the produced emulsions were presented in graphics as a function τ = f(γ) and were described as Herschel-Bulkley and Bingham models presented in Table 3. Keywords Multiple emulsion • Microscopic analysis • Rheological measurements List of symbols D Diameter of the vessel (m) d Diameter of the drop (μm) d a Arithmetic mean diameter of the drop (μm) d m Median diameter of the drop (μm) d 32 Sauter mean diameter (μm) H Liquid height in the vessel (m) Greek letters τ Shear stress (Pa) γ Shear rate (s −1)

Lemieux‐Johnson oxidation with N,N‐bidentate bisPYA ruthenium complexes: insights into reaction conditions and catalyst design

“…In agreement with a reaction progress at phase boundaries, the stirring speed significantly influenced the conversion rate (Figure S42). [49] Under standard conditions, i. e., 25 mL round bottom flask as a reaction vessel and a 14×5 mm stirring bar, stirring at 500 rpm required 120 min to reach full conversion, while at 1,000 rpm and otherwise identical conditions, only 60 min were required (Table 5, entries 1, 10). Further increasing the stirring rate to 1500 rpm had no further beneficial effect and both the reaction time and the TOF max remained identical within error (entry 11).…”