Fabrication & performance study of a palladium on alumina supported membrane reactor: Natural gas steam reforming,a case study

In this work, a synthetic mixture of natural gas is considered in a steam reforming process for generating hydrogen by using a membrane reactor housing a composite membrane constituted of a Pd-layer (13 μm) supported on alumina. The Pd/Al₂O₃ membrane separates part of the produced hydrogen through its selective permeation, although it shows a relatively low H₂/N₂ ideal selectivity (>200 at 0.5 bar of trans-membrane pressure and T = 425 °C).The steam reforming reaction is performed at 420 °C, by varying the gas hourly space velocity between 4400 h^?1 and 6900 h^?1 and by using two different mixtures containing some common impurities found within natural gas pipeline. Specifically, the effect of N₂ and CO₂ as impurities in the feed line is analyzed. The reaction pressure and steam-to-carbon ratio (S/C) are kept constant at 3.0 bar (abs.) and 3.5/1, respectively.The best performance of the Pd-based membrane reactor is obtained at 420 °C, 3.0 bar and 100 mL/min of sweep-gas, yielding a methane conversion of 55% and hydrogen recovery >90%.