In this study, the Schotten-Baumann reaction under continuous flow conditions is optimised over both categorical variables (choices of electrophile and solvent) and continuous variables (equivalents and flow rates). Two Bayesian optimisation algorithms qNEHVI and TSEMO are compared using a benchmark. It is demonstrated that two objectives, space-time-yield and E-factor, can be optimised simultaneously, and a set of optimal solutions can be identified.