ERE Autumn Seminar Series-Ed Ma
Yi (Ed) Hua Ma | Worcester Polytechnic Institute
Professor, Chemical Engineering
Composite Pd-based Hydrogen Separation Membranes – From Laboratory to Field Tests
Developing technologies which can economically produce hydrogen with CO2 at high pressures suitable for sequestration is of great importance to the hydrogen production and to protecting our environment. Pd-based membrane separators and reactors can satisfy both requirements and are especially suited for process intensification by combining reaction, product concentration and separation in a single unit operation, providing high energy efficiency and low capital costs. Therefore, composite Pd-based membranes are highly suitable for hydrogen separation and production in membrane reactors due to their high stability at elevated temperatures and infinite theoretical selectivity of dense Pd and Pd alloys towards H2. We have devoted considerable effort to develop hydrogen separator and WGS (water gas shift) catalytic membrane reactor for IGCC (Integrated gasification combined cycle) and steam reforming applications and have been studying the characteristics and stability of composite Pd based membranes not only in the laboratory but also in actual coal derived syngas atmospheres at the US Department of Energy sponsored National Carbon Capture Center (NCCC) in Wilsonville, Alabama. This presentation will provide an over view of the basis of composite Pd and Pd/alloy membranes for hydrogen separations with a special emphasis on the method of electroless plating for the membrane preparation. In addition, the fundamental studies carried out in our laboratory on membrane synthesis, characterization and long-term membrane stability of Pd and Pd/alloy membranes supported on porous stainless steel (PSS) will be presented. The fundamental concept we developed for improving the long-term thermal stability of composite Pd and Pd/alloy PSS membranes by the controlled in-situ oxidation of the PSS substrate to create an intermetallic diffusion barrier layer in conjunction with pore grading technique will be described. The field tests include the study of the H2 flux, permeance and purity of Pd and Pd/Au alloy membranes at 450°C, 12.6 bar and an average H2 feed concentration of 35%. More importantly, the high H2 purity in excess of 99.89% achieved for over 200 h in the syngas at 12.6 bar and 450°C obtained from the field tests at NCCC using syngas from an actual coal gasifier represents significant advancement and breakthrough results, never reported before in the pertinent literature for the application of composite Pd membranes for H2 production from coal gas. The presentation will conclude with a brief discussion on the perspective of the commercialization of the technology.