Development of high-temperature stable Pd based composite membrane for membrane reformer

Development of high-temperature stable Pd based composite membrane for membrane reformer

Long-term thermal stability is one of the essential issues in the membrane industries, especially membrane reformer. Some literatures reported that Pd based membranes prepared by electroless plating (ELP) on various PSS substrates were highly stable at high-temperature and most of them showed the stability at 723-773 K or for < 1 day at 873-923. Most ELP studies have used EDTA salt because it increases the stability of the bath and assists in controlling the plating process at different temperatures. However, the EDTA salt causes low purity in the palladium layer due to the incorporation of the EDTA complex within the metal deposit and the contamination of carbon. Recently, the University of British Columbia (UBC) developed an EDTA-free ELP method, which was performed at room temperature. The room temperature ELP method has several advantages, including very high selectivity, stability, favorable energy efficiency and simplicity. In spite of several advantages of EDTA-free ELP method, there is a drawback to overcome. When using planar substrates in EDTA-free ELP method, the plating solution diffuses into the bottom of the substrate, and palladium is plated on the surface of the metal grain that composes the substrate because of low stability of plating solution. Occasionally, the palladium growth on the surface of the metal grain connects the membrane layer with the metal substrate and causes an intermetallic diffusion between the two components during high temperature processing. Moreover, the palladium plating on the surface of the metal grain of the substrate causes palladium ion waste in the plating solution. This study was performed to avoid palladium deposition in the pores of a planar metal support during electroless palladium plating using an EDTA-free bath. The bottom of the ceramic-modified planar porous stainless steel (PSS) was shielded by palmitic acid prior to palladium plating. Following palladium plating, the palmitic acid