Methane steam reforming operation and thermal stability of new porous metal supported tubular palladium composite membranes

Abstract

In 2009 cooperation between Plansee SE, Austria (PSE), Karlsruhe Institute of Technology, Germany (KIT) and the Engineering Division of Linde AG, Germany (LE) was set up with the aim to develop new tubular palladium composite membranes and a membrane reformer system for small scale on-site hydrogen production.This paper presents for the first time in detail KIT and LE laboratory results of the new membranes. They are composed of a porous metal support, a porous ceramic diffusion barrier and a dense Pd layer which was produced by physical vapor deposition (PVD) as an activation step and two additional methods: electroless plating (ELP) and electro plating (EP).Ideal H2/N2-permselectivities between 700 and almost 10,000 were measured at 600 °C and hydrogen transport kinetic parameters were determined for both membrane types. PVD/ELP-membranes reached a 15% higher H2-permeability than PVD/EP-membranes. Moreover, stability tests were carried out indicating that the membranes are resistant to temperature and feed gas changes, to thermal cycling in N2-atmosphere between room temperature and 650 °C, and to short-term high-temperature methane steam reforming (MSR) at 700 °C. Long-term operation for several hundred hours at realistic operating conditions proved that MSR can be performed without degradation of the membranes. Without optimizing membrane area versus feed load, a maximum methane conversion of 60% was achieved at a H2-recovery of 70% at 650 °C, 16 bar(a) and a S/C of 3 without the use of sweep gas.