Because of the high dimensionality and the high degree of coupling the simulation of multicomponent mixture processes requires a suitable technique for model size reduction to facilitate the numerical solution if the mixture comprises a large number of components. Established techniques of pseudo-component lumping group (lump) the chemical species by introducing pseudo-components and formulate reaction kinetics for these fictitious components. The introduced error associated with this procedure can neither be estimated nor controlled. A continuous compositional representation of the mixture introduces more flexibility in the model size reduction. Using a Galerkin discretization scheme in combination with a wavelet-based error control and adaptation strategy a model size reduction technique is introduced which allows the specification of a desired accuracy. A simple example representing the thermal cracking of a hydrocarbon mixture modeled by means of the breakage equation is used to illustrate the new method.