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

Abstract

This paper reports results obtained with different composite membranes usedon a membrane reactor for the production of high purity hydrogen. The dry reformingof methane was carried out over a Rh/La2O3 catalyst. Two types ofcomposite membranes were synthesized, Pd and a Pd-Ag alloy. The metal filmswere deposited by electroless plating on modified porous stainless steel. The supportsurface was previously modified with a NaA zeolite by dipcoating and hydrothermal synthesis. The composition and crystallinestructures of the alloy films were characterized by scanning electronmicroscopy (SEM), energy-dispersive X-ray analysis (EDS), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy (XPS). The membrane reactor wasdesigned and built to use either the Pd or the Pd-Ag composite membrane whosecrystalline structure and typical morphology were not affected afterdifferent reaction conditions. The Pd membrane showed the best behavior inthe membrane reactor with the highest methane conversion, H2/CH4 selectivityand permeation flux. After operation of the membranes at 450º-500ºC onstream for up to 570 h no modification of the permeation parameters wasobserved.