Determination of the Rate Constants for the NH2(X2B1) + NH2(X2B1) and NH2(X2B1) + H Recombination Reactions in N2 as a Function of Temperature and Pressure

Kinetic Study for Plasma Assisted Cracking of NH3: Approaches and Challenges

Ammonia is considered as one of the promising hydrogen carriers toward a sustainable world. Plasma assisted decomposition of NH₃ could provide cost- and energy-effective, low-temperature, on-demand (partial) cracking of NH₃ into H₂. Here, we presented a temperature-dependent plasma-chemical kinetic study to investigate the role of both electron-induced reactions and thermally induced reactions on the decomposition of NH₃. We employed a plasma-chemical kinetic model (KAUSTKin), developed a plasma-chemical reaction mechanism for the numerical analysis, and introduced a temperature-controlled dielectric barrier discharge reactor for the experimental investigation using 1 mol % NH₃ diluted in N₂. As a result, we observed the plasma significantly lowered the cracking temperature and found that the plasma-chemical mechanism should be further improved to better predict the experiment. The commonly used rates for the key NH₃ pyrolysis reaction (NH₃ + M ↔ NH₂ + H + M) significantly overpredicted the recombination rate at temperatures below 600 K. Furthermore, the other identified shortcomings in the available data are (i) thermal hydrazine chemistry, (ii) electron-scattering cross-section data of N_xH_y, (iii) electron-impact dissociation of N₂, and (iv) dissociative quenching of excited states of N₂. We believe that the present study will spark fundamental interest to address these shortcomings and contribute to technical advancements in plasma assisted NH₃ cracking technology.

Predicting third-body collision efficiencies for water and other polyatomic baths

Low-pressure-limit microcanonical (collisional activation) and thermal rate constants are predicted using a combination of automated ab initio potential energy surface construction, classical trajectories, transition state theory, and a detailed kinetic...

On the Rate Constant for NH2+HO2 and Third-Body Collision Efficiencies for NH2+H(+M) and NH2+NH2(+M)

In low-temperature flash photolysis of NH₃/O₂/N₂ mixtures, the NH₂ consumption rate and the product distribution is controlled by the reactions NH₂ + HO₂ → products (R1), NH₂ + H (+M) → NH₃ (+M) (R2), and NH₂ + NH₂ (+M) → N₂H₄ (+M) (R3). In the present work, published flash photolysis experiments by, among others, Cheskis and co-workers, are re-interpreted using recent direct measurements of NH₂ + H (+N₂) and NH₂ + NH₂ (+N₂) from Altinay and Macdonald. To facilitate analysis of the FP data, relative third-body collision efficiencies compared to N₂ for R2 and R3 were calculated for O₂ and NH₃ as well as for other selected molecules. Results were in good agreement with the limited experimental data. Based on reported NH₂ decay rates in flash photolysis of NH₃/O₂/N₂, a rate constant for NH₂ + HO₂ → NH₃ + O₂ (R1a) of k_1a = 1.5(±0.5) × 10¹⁴ cm³ mol^-1 s^-1 at 295 K was derived. This value is higher than earlier determinations based on the FP results but in good agreement with recent theoretical work. Kinetic modeling of reported N₂O yields indicates that NH₂ + HO₂ → H₂NO + O (R1c) is competing with R1a, but perturbation experiments with addition of CH₄ indicate that it is not a dominating channel. Measured HNO profiles indicate that this component is formed directly by NH₂ + HO₂ → HNO + H₂O (R1b), but theoretical work indicates that R1b is only a minor channel. Based on this analysis, we estimate k_1c = 2.5 × 10¹³ cm³ mol^-1 s^-1 and k_1b = 2.5 × 10¹² cm³ mol^-1 s^-1 at 295 K, with significant uncertainty margins.

Progress and Prospective of Nitrogen-Based Alternative Fuels

Alternative fuels are essential to enable the transition to a sustainable and environmentally friendly energy supply. Synthetic fuels derived from renewable energies can act as energy storage media, thus mitigating the effects of fossil fuels on environment and health. Their economic viability, environmental impact, and compatibility with current infrastructure and technologies are fuel and power source specific. Nitrogen-based fuels pose one possible synthetic fuel pathway. In this review, we discuss the progress and current research on utilization of nitrogen-based fuels in power applications, covering the complete fuel cycle. We cover the production, distribution, and storage of nitrogen-based fuels. We assess much of the existing literature on the reactions involved in the ammonia to nitrogen atom pathway in nitrogen-based fuel combustion. Furthermore, we discuss nitrogen-based fuel applications ranging from combustion engines to gas turbines, as well as their exploitation by suggested end-uses. Thereby, we evaluate the potential opportunities and challenges of expanding the role of nitrogen-based molecules in the energy sector, outlining their use as energy carriers in relevant fields.