Comprehensive Analysis of Sorption Enhanced Steam Methane Reforming in a Variable Volume Membrane Reactor

The use of combined reaction-separation processes in steam methane reforming (SMR) has recently received significant attention as an enticing route to meet the challenging requirements of distributed hydrogen production for fuel cell vehicles. While many of the investigations in recent literature focus solely on either CO2 adsorption or selective H2 membrane permeation to reduce the reactor footprint and the temperature required to drive the endothermic reaction in continuous flow reactors, the CHAMP-SORB is a new variable volume, transient batch reactor technology that utilizes both strategies simultaneously. Building upon our prior study in which we experimentally demonstrated the viability of CHAMP-SORB reactor concept on bench scale, this work focuses on understanding the heat/mass transfer and reaction/separation interactions to develop guidelines for the reactor scale-up. A combined transport-kinetic model is developed, including spatial variations of SMR reaction and CO2 adsorption rates within the mixed catalyst/sorbent bed along with hydrogen removal via membrane separation. Insights gained by application of the model are used to improve the large scale reactor performance by concentrating the catalyst near the H2 permeable membrane, as compared to the baseline reactor configuration with spatially uniform catalyst/sorbent. Additionally, the modeling methodology and an approach to numerical solution of governing equations are comprehensive, including Maxwell-Stefan formalism for treating multicomponent species transport, and are generally applicable to any reactors with homogeneous and heterogeneous chemical reactions, membrane separation, and time-dependent volume change for a wide variety of chemical processes.