The Directly-Irradiated Annular Pressurized Receiver (DIAPR) volumetric solar absorber was adapted to operate as a methane reformer by coating the absorber pins with catalyst. A computational model is applied to assess and improve the system design. The simulation entails the solution of reactive flow and heat transfer A detailed parametric study is presented and analyzed here. An experimental system based on the present results was built and testing is currently underway.