Numerical methods of particle technology are used to model the formation of catalyst precursors with the purpose to control disperse properties. A multicomponent and multiphase population balance model is applied to the precipitation of catalyst precursors in a T-mixer. Copper precursors are chosen to be investigated in detail as a basis for catalysts with a broad range of applications such as in methanol synthesis, water-gas shift and hydrogenation reactions. The simulations results could be validated by ex situ measurements such as the pH of the suspension, the solid dry weight of the precipitate, and the yield. Simulations show that dissociation reactions of copper and carbonate species in water control significantly the formation of Georgeite. Consumption of the copper component by solid formation can be controlled in a range of 20-100% by the adjustment of the pH of the copper nitrate reactant solution. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 2104-2116, 2015