Catalytic Micro-Membrane Reactor (MMR) Development for Hydrogen Purification

Catalytic Micro-Membrane Reactor (MMR) Development for Hydrogen Purification

Shuai Tan, Dongmei Li

Department of Chemical and Petroleum Engineering

University of Wyoming

Coal and nature gas resources will continually play a dominant role in our energy consumption for the next 20+ years [1]. Meanwhile, advanced conversion technologies are being developed to enable the use of traditional fossil fuels in a clean manner. Recently, Hydrogen separation/ purification technologies have been expanded to nearly eliminate carbon emission, which has been one of the major challenges. Among these technologies, hydrogen separation membranes have been widely used in industry, thanks to their inherent cost-effective and environmentally friendly nature. However, most membranes used today are susceptible to contaminants commonly found in coal-derived syngas, such as sulfur, ammonia, mercury, and trace metals. Therefore, it is highly desirable to further optimize membrane performance and increase their resistance to common contaminants.

The current project presents a novel approach to develop composite, catalytic micro membrane reactors (MMR) applying recent finding in sulfur tolerant catalysts, such as Lanthanide oxysulfides (Eu2O2S), and a cutting edge thin film deposition technique. It has been reported that Lanthanide oxysulfides can be used as catalysts for the high-temperature water-gas shift reaction, and remain highly active and stable in wide range of sulfur content (0-700ppm H2S) of gas mixture [2]. However, synthesizing nanoparticles of lanthanide oxysulfides has been very complicated until recently [3]. Taking advantage of the recently developed facile nanocatalyst synthesis and their stellar performance in wide range of sulfur content, MMRs are being developed starting with a ceramic substrate, subsequently impregnating the substrate with the catalyst nanoparticles. A Palladium (Pd) thin layer will then be deposited onto the catalyst impregnated ceramic support via atomic layer deposition (ALD) to minimize the thickness, thus resulting in maximized hydrogen permeability.

To test the feasibility of the MMR fabrication approach, X-ray diffraction (XRD) and scanning electron microscope (SEM) have been utilized to characterize the MMR. Our XRD data have confirmed the crystalline phase matching of the lanthanide oxysulfides nanoparticles synthesized in our group, while SEM pictures have shown good adhesion between the nanocatalysts and several substrates, including the ¦Á-alumina (Al₂O₃) tubes, alumina hollow fiber and ZrO2. Process parameters of the impregnation procedure are currently being further optimized to improve nanoparticle distribution on the surface and across the pores of various substrates. System testing with natural or syngas will be performed, following the successful fabrication of MMR.

Key Words: lanthanide oxysulfides, palladium, MMR, hydrogen purification

Bibliography

1.      Chu, S. and A. Majumdar, Opportunities and challenges for a sustainable energy future. Nature, 2012. 488(7411): p. 294-303.

2.      Valsamakis, I. and M. Flytzani-Stephanopoulos, Sulfur-tolerant lanthanide oxysulfide catalysts for the high-temperature water-gas shift reaction. "Applied Catalysis B, Environmental", 2011. 106(1-2): p. 255-263.

3.         Zhao, F., et al., Monodisperse Lanthanide Oxysulfide Nanocrystals. Journal of the American Chemical Society, 2006. 128(36): p. 11758-11759.