Limit conversion of a palladium membrane reactor using counter-current sweep gas on methane steam reforming

Membrane reactors (MRs), where the removal of some products takes place simultaneously with the reaction, can improve and control the reaction. Sweep gas is generally employed to gain permeation-driving force. There are two typical possibilities in the sweep gas flow direction: cocurrent and counter-current configuration against the reaction-side flow. These two are expected to be different in performance. The co-current MR is known to have an upper limit in conversion, which can be found using an equilibrium condition on reaction and hydrogen permeation at the end of the reactor [1]. In the counter-current, the reaction side meets pure sweep gas through the membrane at the end of the reactor. Therefore, if the reactor length is long enough, hydrogen pressure in the reaction side might also be zero at the end and the complete conversion seems to be realized regardless of temperature or sweep rate. But there is no report supporting this speculation. This might be attributed only to the reactor length assumed, because simulations were usually done for a given reactor length. In this study, therefore, the performance of MRs was studied using mathematical modeling to identify the limit conversion. Methane steam reforming is selected as a model reaction because it is an important process to produce hydrogen for fuel cells.