EAGER: Nitrogen-Selective Membrane for Carbon Capture with Simultaneous Ammonia Synthesis

Stanford University, Stanford CA

Investigators

Abstract

ABSTRACT #1249494 Wilcox, Jennifer Technical Impacts This award represents a continuation of the first attempts to synthesize and test membranes that selectively separate N2 from gas mixtures by Professor Jennifer Wilcox at Stanford University. This novel, crosscutting technology will have numerous applications at the industrial scale, including CO2 capture from flue gas, natural gas purification, air separation, and ammonia synthesis. In the proposed work, metallic membranes made from alloys of ruthenium and earth-abundant Group V metals, such as vanadium and niobium, are proposed for catalytic selective N2 separation. The effort includes both theoretical modeling with electronic structure theory calculations and experimental testing using a high-temperature benchscale membrane reactor. Including both theory and experiment will allow for the design of a metallic membrane material with optimal selectivity and permeability for a given application. The strength of the modeling component to this work is that many alloys can be screened with only the most promising candidates synthesized and tested. The computations by Wilcox predict the alloys with Ru will allow for an increase in transport through the membrane. An EAGER award was made last year to carry out this potentially exciting experimentation. A bench-scale high-temperature membrane reactor was designed and built to investigate N2 permeabilities and selectivities of membrane foils comprised of Nb and V metals and their varying-composition alloys with Ru. The PI has been able to measure N2 flux and permeance using 40 m-thick membrane foils of pure V and Nb supplied by a vendor (Goodfellow). However, there have been significant challenges associated with material synthesis of the VRu and NbRu alloys, despite the thermodynamic stability of the bcc phase up to 40 at. % Ru in each of these alloys. Two different vendors, i.e.,the Materials Preparation Center at Ames Laboratory and Goodfellow, were asked to synthesize RuV and RuNb alloys at varying compositions. Despite their efforts, neither was able to fabricate alloys of varying compositions into micron-thick foils due to the brittleness of the alloys. This prevented the evaluations at the heart of the Project from being made. An alternative vendor and fabrication methodology has been found. The PI will be working with Dr. Kent Coulter of Southwest Research Institute to sputter deposit alloys of V/Nb with Ru on porous Hastelloy X supports. This EAGER proposal allows for the fabrications to be conducted and the preliminary data to be taken to allow completion of the proof of concept. Broader Impacts Broader impacts of the results of the proposed work are many. Carbon dioxide abatement from point sources such as coal-fired power plants through the design of cost-effective membrane technology will result in a decrease of CO2 emitted into the atmosphere. In addition to carboncapture, this technology may provide a route to carry out the ammonia synthesis process at atmospheric pressures, adding huge savings to the agricultural industry. Nearly half of the hydrogen produced globally is used for ammonia synthesis, which is primarily used for agriculture, a demand that is directly proportional to world population increase. Fertilizers are one of the most important factors in securing sufficient global food production. Through the application of selective-N2 membrane technology, ammonia could be produced at a lower energy cost than the traditional high-pressure Haber-Bosch process and the ammonia can be used directly to advance the agriculture industry.