08/15/2023
By Danielle Fretwell

The Francis College of Engineering, Department of Mechanical and Industrial Engineering, invites you to attend a doctoral dissertation proposal defense by Visal Veng on "Catalytic Membrane Dielectric-Barrier Discharge Reactor for Ammonia Synthesis."

Student: Visal Veng
Date: Monday, Aug. 28
Time: 2 to 4 p.m.
Location: Southwick Hall 240

Advisor: Juan Pablo Trelles, Department of Mechanical and Industrial Engineering, UMass Lowell

Committee:

  • Fanglin Che, Assistant Professor, Department of Chemical Engineering, UMass Lowell
  • Fuqiang Liu, Associate Professor, Department of Mechanical and Industrial Engineering, UMass Lowell
  • John Hunter Mack, Department of Mechanical and Industrial Engineering, UMass Lowell

Abstract:

Ammonia synthesis via non-thermal plasma presents advantages over the currently-dominant Haber-Bosch process, particularly for small-scale and distributed operations powered by intermittent electricity from renewable energy sources. This doctoral dissertation research focuses on the design, characterization, and assessment of a catalytic membrane Dielectric-Barrier Discharge (mDBD) reactor for ammonia synthesis from nitrogen and hydrogen. The research first addressed the design and evaluation of the mDBD reactor without catalyst. The reactor used a porous alumina membrane as dielectric barrier and as distributor of H2. This arrangement enabled greater residence time for N2 decomposition together with greater H2 availability in the reaction zone, as assessed by a computational thermal-fluid model. We evaluated the reactor's operation with membranes of 0.1, 1.0, and 2.0 µm pore size and porosities between 25% and 51%, and also in conventional DBD mode using a non-porous dielectric. The experimental characterization of the reactor encompassed electrical, optical, and spectroscopic diagnostics, as well as Fourier-Transform Infrared Spectroscopy (FTIR) to analyze gas products, as function of driving voltage. The results showed that both, ammonia production and power consumption, vary inversely with membrane pore size. The highest energy yield of 0.25 g-NH3/kWh was obtained with the 1.0 µm pore membrane, whereas the maximum yield under conventional DBD operation was three-times lower. Our findings demonstrate that the use of a membrane dielectric can enhance the performance of DBD-based ammonia synthesis. Our ongoing and future investigations will focus on the integration of catalysts within the mDBD reactor to enhance its performance. The integration will be based on filling the membrane-ground electrode gap with catalyst powder embedded in glass wool. Three different metal catalysts are evaluated: nickel (Ni), cobalt (Co), and bi-metallic nickel-cobalt (Ni-Co), all loaded at 5% by weight on alumina powder (surface area ~ 200 m2/g). The performance of the catalytic mDBD reactor under different operating conditions and catalysts during the synthesis of ammonia will be studied. Preliminary assessment of the catalytic mDBD reactor revealed that the Ni-Co bi-metallic catalyst leads to the greatest energy yield of 1.4 g-NH3/kWh, compared to a maximum of 1.2 and 1.3 g-NH3/kWh for Ni and Co, respectively, and 1.0 g-NH3/kWh for the alumina powder support only. This research will lead to the design, characterization, and assessment of a novel type of nonthermal plasma reactor aimed at modular ammonia synthesis operations.