Design, fabrication, and characterisation of H2-selective Pd-alloy membranes for application in pre-combustion CO2 capture cycles

In the prememCO2 project, pioneering work in the understanding of multi-component Pd-alloy membrane materials in terms of performance and stability has been performed through a multidisciplinary approach combining theoretical modelling by first principle calculations, extensive materials characterization, ternary Pd-alloy manufacturing, and H2 permeation verification efforts. Key results of the work include: - A thorough investigation of the manufacturing, characterisation, and H2 permeation properties of ternary Pd-Cu-Ag alloys with a fcc structure, focusing particularly on the H2 permeability behavior at low concentrations of the added ternary element (Ag). - Comparison of permeation results obtained through a combinatorial method based on hydrogenography (HG) for direct measurements of the intrinsic hydrogen permeability of a wide range of compositions with conventional membrane permeation (MP) experiments. Crucially, the HG technique resulted in the same permeability behaviour as function of Ag content as obtained for the MP experiments. This validated both techniques, in addition to providing a wide range of compositions; the silver concentration in Pd0.8Cu0.2-xAgx was actually varied by four orders of magnitude. - Obtained evidence of atomic-scale changes in Pd-based membranes induced by hydrogen permeation. STEM analysis shows the presence of cavities with higher density along grain boundaries or in their vicinity that could be related to the growth of the <111> columnar grains. As far as we are aware, nothing similar has been reported in membrane-related literature before, which could be explained by the fact that the bubbles first become evident in STEM analysis. These cavities do initially not contribute to unselective leakage flux, but may eventually lead to pinhole formation. The pre-memCO2 project has so far resulted in 6 journal articles in peer-reviewed journals, 16 conference contributions, 3 book chapters, and 5 popular science presentations. In addition, another 3 peer-reviewed articles are expected based on the projects results that have not been disseminated, yet. The competence and results obtained in the prememCO2 project have already exploited in other projects, most currently in the CLIMIT-demo GASSNOVA project with Hydrogen Mem-Tech AS (former Reinertsen AS), the European FCH-JU AuToRe project coordinated by General Electric (http://www.autore-fch.com/), and a newly started European EUROMET project called MetroHyVe. Further exploitation will be considered in the context of the upcoming RCN deadlines.

This project aims to research and develop improved H2 selective membrane materials for integration in pre-combustion decarbonisation process schemes, thereby targeting the priority areas in CLIMIT. Hydrogen selective membranes have frequently been studie d in membrane reactors for water-gas shift (WGS-MR) and steam reforming (SR-MR) reactions to simultaneously achieve a high CO or methane conversion and production of pure H2. A key feature of this process intensification, achieving pre-combustion decarbon isation, is that such a membrane reactor would produce both a high pressure CO2 stream, and high-purity H2 for power generation. This can greatly facilitate the economics of power generation with carbon sequestration, as recently been demonstrated by the 6th FP EU-CACHET Project . The CACHET European project evaluated and benchmarked CO2 capture technology on an aligned and consistent basis, and concluded that the WGS-MR has the highest efficiency and highest cost reduction potential of all the evaluated technologies for natural gas pre-combustion, low CO2 carbon power generation. The project projected that an integrated membrane WGS reactor increases the energy efficiency by ~6%pt and reduces the cost of CO2 capture by ~30% compared to state-of-the-art t echnology. The concept has also been proven to be an efficient technology for hydrogen production combined with CO2 capture, and is pursued by companies in the US, Japan and Europe. The partners basic knowledge in this field has been built to a high leve l through funding by the Research Council of Norway and the EU. The present project proposes extensive efforts to pursue these fundamental topics further by bridging the gap between theory and application of these material systems, thereby strengthening t he competiveness of the technology.