A novel liquid collector assembly has been developed for a reactor used in the sweetening of sour hydrocarbons (e.g. sour gasoline). This refinery process normally involves contacting a reaction liquid, comprising both aqueous (caustic solution) and organic (hydrocarbon) phases, with a fixed bed of oxidation catalyst. The collector assembly design, comprising a piping manifold and a plurality of dependent, vertically aligned, and perforated conduits, allows for improved separation of the reaction products into essentially pure treated hydrocarbon and spent alkaline reagent streams. If sodium hydroxide is used as caustic solution, for example, the treated hydrocarbon product will normally contain less than 1 ppm by weight of sodium.