This paper describes experiments and related modelling on a new method for separating aqueous phase slugs from the surrounding organic matrix phase in segmented two phase flow in a plastic microcapillary film (MCF). Kerosene or paraffin oil was metered through a plastic capillary of 630 microns diameter and aqueous phase slugs were generated within the capillary by the continuous sidestream injection of water. It was found that the resulting aqueous phase slugs formed in the MCF could be subsequently easily separated from the organic phase by piercing the downstream sidewall of the plastic capillary with a hydrophilic metal hypodermic needle to draw off an aqueous sidestream. Optical scrutiny of the phase separation process indicated that two distinct disengagement mechanisms are involved, in which the metal needle tip either remains submerged in the aqueous phase or becomes periodically exposed to the organic phase at certain stages of the segregation process. The separation efficiency, i.e. the degree of residual phase cross-contamination, was determined as a function of both the sidestream needle angle and the depth of needle penetration into the capillary for a given flow rate and phase ratio. It was established that the separation efficiency was very sensitive to the downstream pressure balance between the organic mainstream flow in the plastic capillary and the aqueous sidestream flow through the needle. A mathematical model for the pressure balance conditions was developed by making certain simplifying assumptions and taking the Laplace interfacial pressure into account. The model predictions agreed surprisingly well with the experimental findings, thus providing circumstantial evidence for the validity of the insights into the phase separation mechanism.

In this work, the external liquid−solid mass transfer properties of horizontal gas−liquid (G−L) and liquid−liquid (L−L) "slurry Taylor" flow are investigated. The catalytic particles (d P = 40−200 μm) are transported in a cylindrical capillary (d T = 1.6−1.65 mm) in the form of a suspension in the aqueous liquid phase and kept in motion due to the recirculation patterns present in the liquid slugs. Ion exchange particles are used to follow the neutralization of dilute sodium hydroxide solutions in order to estimate the mass transfer coefficients. The influence of two phase velocity, particle size, slug length, and inert physical properties was investigated. No influence of slug length on the liquid−solid mass transfer coefficient was detected, and the particle size appears likewise to have no effect for particles larger than 50 μm. The mass transfer coefficient depends mainly on overall flow velocity and an adequate circulation of solid particles in the liquid phase. For toluene−water L−L Taylor flow, particles agglomerate in the rear end of the droplet, and for the operating conditions (u TP = 1− 6.5 cm s −1 ) applied in this study the Sherwood number was always found to be smaller than 2. For hexanol−water flow (u TP = 1−2.5 cm s −1 ) on the contrary, particles are well suspended in the lower part of the droplet, and higher Sherwood numbers could be found (2.5−8.75). The maximal possible flow rate to obtain stable Taylor flow conditions is, however, limited to quite low values in L−L Taylor flow. In G−L Taylor flow it is possible to work at higher two phase velocities (up to 28 cm s −1 ) under stable flow conditions and with homogeneously dispersed particles over the entire slug height. Sherwood numbers up to 15 were obtained under such conditions.

For merging two facets of process intensification, namely, slug flow in microcapillaries and ionic liquid extraction, the fluid mechanic stability of organic-ionic liquid slug flow is mapped for [EMIM] [Alkyl-SO 4 ] and [Alkyl-MIM] [Ntf2] in 0.5-1.0 mm ID plastic capillaries. The choice of the ionic liquid solvent is restricted by physical properties. The internal circulation within ionic liquid slugs is found to be slower by a factor of 2-10 compared to aqueous slugs, but is accelerated by optimizing velocity, temperature, and wall material. Extraction of acetic acid from n-heptane with EMIM ethyl sulfate is proposed as a system to verify the contribution of internal circulation to mass transfer. In the long run, this research affirms the fluid dynamic feasibility of microcapillary slug-flow extraction with ionic liquids.

Pfropfenströmungs‐Kapillarreaktoren bieten einen Ansatz zur zweiphasigen Suspensionskatalyse die eine einfachere Katalysatorrückgewinnung und Reduzierung der Partikelgröße ermöglicht, sofern eine ausreichende Stofftransportleistung durch die Zirkulationsströmung gewährleistet wird. Experimentelle Messungen und ein dynamisches Modell zeigen, dass der Flüssig/Fest‐Stofftransport zunächst eine Limitierung darstellt und durch eine inhomogene Suspendierung gehemmt wird. Die Reduzierung der Katalysatorgröße hebt diese Limitierung jedoch auf, so dass die zweiphasige Suspensionskatalyse vielversprechend erscheint.

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