Reaction kinetics of peracetic acid from acetic acid and hydrogen peroxide in a helical capillary microreactor was investigated and modelled via regression of the measured conversion rate of hydrogen peroxide. It was found that the activity of the proton in the sulphuric acid solution played a significant role in the synthesis as a catalyst. The activities of the proton were calculated with the ELECNRTL equation and used to obtain a kinetic model with the apparent activation energy of peracetic acid synthesis and hydrolysis of 53.63 and 54.45 kJ/mol, respectively. A new continuous process for industrial manufacture of peracetic acid solution (30 wt. %) was proposed, where the reacted solution from the microreactor is distilled to separate unreacted reactants and sulfuric acid which are recycled as feed. The feasibility of the new process was validated by economic assessment.