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.

RRKM and ab initio investigation of the NH (X) oxidation by dioxygen

We performed a detailed study of the NH + O(2) potential energy surface by means of a number of multireference (CASSCF, MC-QDPT2, MR-AQCC, MR-CISD(18;13)+Q with 6-311+G(d,p), and aug-cc-pVTZ basis sets) and composite (G3B3, G3MP2B3, CBS-QB3, W1U) methods. Parent nitroso oxide, HNOO, was found to be the key intermediate of this process. In its ground state, (1)A', HNOO exists in two conformations, where the cis form is 8.1-10.9 kJ x mol(-1) more stable than the trans-nitroso oxide. The mechanism of nitrene oxidation by dioxygen may be represented as a set of various transformations of vibrationally excited HNOO, namely, decomposition into NO and OH radical pair, O-O dissociation reaction, and a number of thermal deactivation processes. We localized all stationary points of these transformations on both the singlet and the triplet reaction PES. The energies of reactants, products, and transition states were calculated at the RI-MR-CISD(18;13)+Q/aug-cc-pVTZ level of theory; the vibrational analysis of these species was done by means of CASSCF(18;13)/6-311+G(d,p). Apparent rate constants of the NH + O(2) reaction were calculated using RRKM theory. The total rate constant k(total) corresponds well to available experimental data. The temperature dependence of k(total) is rather nontrivial and consists of three quasi-linear intervals. At low temperatures (up to room temperature) the slope of log(k(total)) vs 1/T is negative due to prevailing stabilization of HNOO. The rate-determining channel of the "NH + O(2)" reaction in the medium-temperature interval (up to approximately 1000 K) was found to be formation of the NO + OH radical pair via H transfer to the terminal oxygen atom. This reaction is accelerated by a factor of 4.2 (214 K) and 1.2 (2500 K) due to tunnel effect. The distinctive feature of the NH + O(2) high-temperature chemistry is the increase of the effective activation energy due to prevailing dissociation of the HNOO peroxide bond.