Open foam structures are very beneficial as heterogeneous catalysts for three-phase processes, because they have high efficiency and low pressure drop. A mathematical model for open foam catalyst structures was developed. It was based on the concept of axial dispersion as flow pattern, on liquid-solid mass transfer effects and intrinsic kinetics on the active sites of the catalyst. Rate equations were presented for the hydrogenation of individual sugars and binary sugar mixtures on Ru/C catalysts and they were implemented in the mass transfer and flow models of the open foam catalyst. The flow pattern in the foam structure was confirmed with step change experiments with an inert tracer. The multiphase model was applied on the hydrogenation of arabinose and galactose in a laboratory-scale open foam catalyst bed. The model was able to reproduce the main features of the experimental observations, both for individual sugars and binary sugar mixtures.