Pd/Ag-based membrane reactors on small scale: Assessment of the feed pressure and design parameters effect on the performance

The antagonist effect of pressure on the thermodynamic equilibrium and the H2 permeation rate has been studied in a small-scale membrane reactor (MR) with no sweep gas.The influence of some design parameters as membrane surface area (Am), catalyst volume (Vcat), methane load in feed (Ls) and gas hourly space velocity (GHSV) on the MR performance has also been evaluated. In the MR, a twofold increase of the methane conversion has been obtained by enhancing the ratio Am/Vcat from 0.42 to 2.1 cm2 cm−3. A methane conversion about three-times as much as thermodynamic equilibrium limit of a traditional reactor has been obtained when the Ls/Am ratio was reduced from 11.6 to 8.4 cm3(STP) cm−2 min−1. Ultimately, a methane conversion of the 68% and a hydrogen recovery approximately of 43% have been reached for a ratio Am/Vcat = 2.1 cm2 cm−3 and Ls/Am = 8.4 cm3(STP) cm−2 min−1. Removal of hydrogen increases the tendency to carbon deposition. These effects can be reduced by operating at higher temperatures and/or pressures, but necessarily, in the presence of a reagents molar ratio higher than three.