Abstract: An HF-agent complex, such as HF-pyridine complex where the complexing agent is pyridine, is recovered and recycled from a by-product containing stream in an alkylation process using the complex by (a) selectively removing a portion of the HF from the by-product stream to produce an HF-depleted stream having a molar ratio of HF per Lewis base site of the complexing agent of 3:1 to 5:1, (b) separating the resulting HF-depleted stream into a hydrocarbon phase enriched in ASO and an acid phase depleted in ASO and containing a substantial portion of the complex, and (c) recycling the acid phase to the hydrocarbon alkylation step.