Dry reforming of methane in membrane reactors using Pd and Pd–Ag composite membranes on a NaA zeolite modified porous stainless steel support

This paper reports the results obtained with different composite membranes used on a membrane reactor for the production of high purity hydrogen. The dry reforming of methane was carried out over a Rh/La2O3 catalyst. Two types of composite membranes were synthesized, Pd and a Pd–Ag alloy. The metal films were deposited by electroless plating on modified porous stainless steel. The support surface was previously modified with a NaA zeolite by dip coating and hydrothermal synthesis. The composition and crystalline structures of the alloy films were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The membrane reactor was designed and built to use either the Pd or the Pd–Ag composite membrane whose crystalline structure and typical morphology were not affected after different reaction conditions. The Pd membrane showed the best behavior in the membrane reactor with the highest methane conversion, H2/CH4 selectivity and permeation flux. After operation of the membranes at 450–500 °C on stream for up to 570 h no modification of the permeation parameters was observed.