Site items in: Content by Author Thomas F. Fuerst

Yittria-Stabilized Zirconia (YSZ) Supports for Low Temperature Ammonia Synthesis

NH3 is important as the raw material for fertilizer production and high hydrogen density (17.7 wt. %) energy carrier. Conventionally, NH3 is synthesized through the well-known Haber-Bosch process at 400-500°C and P~150 bar. Both critical reaction conditions and massive production (145 mt NH3 in 2014 globally) make it one of the most energy extensive process, consuming 1-2% of the world’s total energy expense. Here we introduce YSZ as a more active Ru catalyst support than traditionally used supports such as Al2O3. The addition of Cs promoter increased rates an order of magnitude higher by reducing the apparent activation energy from…

Dense Metallic Membrane Reactor Synthesis of Ammonia at Moderate Conditions and Low Cost

Commercial ammonia synthesis relies on the Haber–Bosch process that has remained largely unchanged for a hundred years. The equilibrium constant of this exothermic reaction quickly becomes unfavorable above 200 °C, but the catalyst requires temperatures above 400 °C to have sufficient activity. To overcome these conflicting requirements the process is conducted at extremely high pressure (100 – 200 atm) using multiple passes with inter-stage cooling to achieve sufficient conversion. A cost analysis reveals the compressors needed to reach the required pressures consist of 50% the capital cost for Haber-Bosch. Therefore, a longstanding scientific challenge has been to achieve NH3 synthesis…

Applications of hydrogen permeable membranes in ammonia synthesis and decomposition

It is well known that ammonia is being considered as a method of storing hydrogen. Although some fuel cells are being developed that can use ammonia directly as a fuel source, many fuel cell technologies still require an outside cracker to revert ammonia back into hydrogen for efficient use. In this regard, hydrogen permeable membranes, such as Pd and its alloys, have been targeted as potential membrane reactors in which the ammonia is cracked while the hydrogen is simultaneously separated. Pd and its alloys are expensive, but offer potentially perfect hydrogen purity that is highly preferable for certain fuel cells…