Alkaline peroxymonosulfate (PMS) has been successfully used in the laboratory for bleaching kraft pulp. Used in conjunction with oxygen, the addition of 1.0% PMS to an oxygen delignification system can increase delignification from 49% to 73% without reducing pulp strength. One promising method of achieving this is the catalytic oxidation of sodium sulfite with oxygen. Laboratory generation of PMS is readily achieved, but typically at low yields and low concentrations. Here we investigate the mixing-sensitivity of its generation under semi-batch reaction conditions using a number of laboratory mixers. Our primary focus was on the energy dissipation in the reaction zone and its effect on PMS yield and concentration. By managing the chemical contacting strategy and increasing energy dissipation in the reaction zone we were able to generate PMS at higher yields and concentrations than previously reported.