A comprehensive 3D coupled mathematical model is developed to study the microwave assisted thermocatalytic decomposition of methane with activated carbon as the catalyst. A simple reaction kinetic model for methane conversion (accounting for catalyst deactivation) is developed from previously published experimental data and coupled with the governing equations for the microwaves, heat transfer, mass transfer and fluid flow physics. Temperature distribution and concentration profiles of CH4 & H-2 in the catalyst bed are presented. The temperature profiles at different input power values predict a nonuniform temperature distribution with hot -spots near the top and bottom of the catalyst. The concentration profiles predict a linear variation of CH4 and H-2 concentration along the length of the reactor and show a good agreement with experimental conversion values. The influence of volumetric hourly space velocity on methane conversion is also investigated. (C) 2016 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY license