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In this work three mathematical models for methane steam reforming in membrane reactors were developed. The first one is a steady state, non isothermal, non isobaric and one dimensional model derived from material and energy balances and validated using experimental data from the literature. It is referred as full model. The influence of two different intrinsic kinetics available, as well as, the influence of five important parameters on methane conversion (X CH 4 ) and hydrogen recovery (Y H 2 ) were parametrically evaluated through simulations. The second model, referred as meta-model, was obtained though the response surface technique. This metamodel was included into a constrained optimization problem solved using NPSOL. The third model, referred as a simplified model, takes into account only mass balances from the full model. Using this model, a gradient based method (DIRCOL) was used to perform the optimization of the sum of methane conversion and hydrogen recovery. High methane conversions and hydrogen recoveries were reached through these methodologies. List of symbolsa Constant in Ergun's equation [-] A 0 Pre-exponential factor of the permeability [ mol m 2 s Pa 0.5 ] L.C. Silva, in memoriam. The author passed away in November 2009. 442 L.C. Silva et al. A 1 Heat transfer area between the reaction chamber and the external reactor temperature [m 2 ] A 2 Heat transfer area between the reaction chamber and the permeate side [m 2 ] A m Permeation area of membrane [m 2 ] b Constant in Ergun's equation [-] Cv p Specific heat at constant volume of the permeate side mixture [ J mol K ] Cv r Specific heat at constant volume of the reaction side mixture [ J mol K ] d p Equivalent diameter of catalyst particle [m] E Activation energy [ J mol ] f Friction factor [-] f H 2p Dimensionless flow rate of hydrogen in the permeate side [-] f i Dimensionless flow rate of i component in the reaction side [-] FCH40 = F 0 CH 4 Methane feed flow rate [ mol s ] F H 2p Hydrogen flow rate in the permeate [ mol s ] F i Molar flow rate of component i in the reaction side [ mol s ] FI Molar flow rate of inert or sweep gas [ mol s ] H H 2 Hydrogen enthalpy [ J mol ] J H 2 Hydrogen permeation flux [ mol m 2 s ] L Reactor length [m] M Steam to methane feed flow ratio H 2 O e CH 4 [-] PR0 Inlet reactor pressure [Pa] P R Reactor pressure [Pa] P r Dimensionless reaction pressure [-] P p Permeate pressure [Pa] p H 2 Hydrogen partial pressure in the reaction side [Pa] p H 2p Hydrogen partial pressure in the permeate side [Pa] Q 1 Heat exchanged between the reaction side and external environment [ J s ] Q 2 Heat exchanged between the reaction side and the permeate side [ J s ] r j Rate of the reaction j [ kmol kg cat h ] R Universal gas constant [ J mol K ] Re Reynolds' number [-] T m Membrane temperature [K] T p Dimensionless permeate temperature [-] T r Dimensionless temperature of the reaction side [-] T R Temperature of the reaction side [K] T w External temperature [K] u s Gaseous velocity of the reaction chamber [ m s ] U 1 Overall heat...