Vietinghoff, Niclas vonImmken, AnneSeidensticker, Thomasde Caro, PascaleThiebaud-Roux, SophieAgar, David W.2025-02-262025-02-262023-01-16http://hdl.handle.net/2003/4351010.17877/DE290R-25343Due to the density differences between gases and liquids, the gas supply often limits the conversion of gas-liquid reactions in slug flows. This paper investigates the permeation of reacting gas into an existing gas-liquid slug flow in fluorinated ethylene propylene capillaries of up to 40 m in length, representing a significant sizing-up of tube-in-tube reactors (maximum 4 m). The amount of gas introduced can be estimated with permeation coefficients given in the literature. Moreover, existing gas bubbles serve as reservoirs for the permeating gas, maintaining the advantageous slug flow pattern.enChemical engineering & technology; 46(5)https://creativecommons.org/licenses/by/4.0/Capillary reactorsGas permeationMultiphase systemsSegmented flowsSizing-up660Article