The trials of KCl conversion with sulfuric acid into sulfate salt were performed in a membrane reactor. The conversion process proceeded on the feed side of the membrane distillation system. HCl-the gaseous product of the conversion was continuously separated by means of the membrane, whereas non-volatile KHSO4 and H2SO4 were completely retained in the feed solution. The model solutions containing HCl and H2SO4 or KCl and H2SO4 were applied as the feed. The influence of the feed composition on the HCl molar flux and volumetric flux through the membrane was studied. Potassium bisulfate was precipitated from the reaction liquor after cooling of the reaction mixture. Potassium sulfate was obtained as a result of desalting from KHSO4 solution using methanol. The results of the current studies were promising and showed a potential of applying a combination of reactor with membrane distillation in production of potassium sulfate. (C) 2007 Elsevier B.V. All rights reserved.