Topic: Chemical Separation

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Ammonia Absorbents with High Stability and High Capacity for Fast Cycling

By , , , , and on November 14, 2019
Ammonia absorption is an alternative separation to condensation in ammonia production. Metal chloride salts selectively incorporate ammonia into their crystal lattices with remarkably high capacity. Regeneration and stability of these salts are further improved by dispersing them onto a porous silica support. Here, we discuss the optimal preparation methods of supported metal halides, as well as optimal conditions for uptake and release of ammonia. The metal halide salt particle size, support particle size, support composition and preparation methods are optimized for material stability, speed of uptake and release, and maximum ammonia capacity. An automated system was used to rapidly screen…

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300°C Proton-Exchange Membrane for Low-Pressure Electrolytic Ammonia Synthesis

By on November 12, 2019
The two North Dakota universities and Proton OnSite are developing a 300°C-capable polymer–inorganic composite (PIC) proton exchange membrane for low-pressure (15-psi) ammonia synthesis. The PIC membrane comprises an inorganic proton conductor strategically composited within a high-temperature polymer to enable a proton conductivity of 10-2 siemens/centimeter at 300°C. Integrated with appropriate low-cost anode and cathode catalysts in a membrane–electrode assembly, the gas-impermeable PIC membrane is projected to enable ammonia production at a total energy input of about 6400 kilowatt-hours/ton (kWh/ton), versus about 8500 kWh/ton for state-of-the-art Haber Bosch-based ammonia production. The PIC membrane will also have application in high-temperature water electrolysis…

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Optimizing Absorptive Separation for Intensification of Ammonia Production

By , and on November 12, 2019
High pressure requirements of Haber-Bosch process imposes substantial operating (e.g., compression) and capital (compressor cost, advanced costly alloys, thick reactor casing, etc.) expenses in the ammonia production. Cost considerations force ammonia producers to take advantage of the economy of scale to drive down the manufacture cost, while small and energy-efficient processes that can be powered with off-grid renewable energy are required for ammonia-mediated hydrogen economy. Small-scale reaction-absorption process is proposed to be a viable technology to reduce the operating pressure requirements of Haber-Bosch process.1–4 Here, we present an overview of our efforts to further intensify ammonia production via reaction-absorption process.…

Paper

Electrochemical Synthesis of Ammonia Using Metal Nitride Catalsyts

By , , , and on October 31, 2018
With the development of the Haber process and the subsequent work done by Bosch, ammonia production become an industrially and economically viable way to fix nitrogen. This helped increase the global population and estimates put it at about 40% of the global population’s food comes from ammonia made by the Haber-Bosch process[1]. However, the Haber-Bosch process is an energy intensive process requiring high pressure (15-30 MPa) and relatively high temperature (430 °C – 480 °C) and is highly centralized with only about 13 companies and about 29 plants[2,3]. Renewable energy resources offer a possible alternative way to fix nitrogen at…

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Ammonia Absorption and Desorption in Ammines

By , , , and on October 31, 2018
While adsorption onto solids is a common separation process, absorption into solids is much less often used. The reason is that absorption is usually assumed ineffective because it includes very slow solute diffusion into the solid. An exception may be the separation of ammonia from nitrogen and hydrogen using ammines, especially at temperatures close to those used in ammonia synthesis. There, ammonia can be selectively absorbed by calcium chloride; nitrogen and hydrogen are not absorbed. The kinetics of ammonia release seem to be diffusion controlled. The kinetics of absorption are consistent with a first order reaction and diffusion in series,…

Paper

Functionalized Ordered Mesoporous Silica Composites As Potential Ammonia Storage Materials

By , and on October 31, 2018
Ammonia may provide an alternative energy supplier for its strong capability as hydrogen carrier. However, it is a problem that how to storage this kind of chemical at relatively high temperature, for example 300°C in fuel cell. In this work, a composite material based on metal halides and ordered mesoporous silica framework is developed and used to target ammonia at relatively high temperature. The silica framework is fabricated via evaporation induced self-assembly method and has tunable mesoporous structure with addition of hexadecyl trimethyl ammonium bromide (CTAB). Several metal salts at various concentrations are added to the mesoporous framework via wetness…
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