Production of cis-Na2N2O2 and NaNO3 by Ball Milling Na2O and N2O in Alkali Metal Halide Salts

Progress and challenges in nitrous oxide decomposition and valorization

Nitrous oxide (N2O) decomposition is increasingly acknowledged as a viable strategy for mitigating greenhouse gas emissions and addressing ozone depletion, aligning significantly with the UN's sustainable development goals (SDGs) and carbon neutrality objectives. To enhance efficiency in treatment and explore potential valorization, recent developments have introduced novel N2O reduction catalysts and pathways. Despite these advancements, a comprehensive and comparative review is absent. In this review, we undertake a thorough evaluation of N2O treatment technologies from a holistic perspective. First, we summarize and update the recent progress in thermal decomposition, direct catalytic decomposition (deN2O), and selective catalytic reduction of N2O. The scope extends to the catalytic activity of emerging catalysts, including nanostructured materials and single-atom catalysts. Furthermore, we present a detailed account of the mechanisms and applications of room-temperature techniques characterized by low energy consumption and sustainable merits, including photocatalytic and electrocatalytic N2O reduction. This article also underscores the extensive and effective utilization of N2O resources in chemical synthesis scenarios, providing potential avenues for future resource reuse. This review provides an accessible theoretical foundation and a panoramic vision for practical N2O emission controls.

Mechanistic Pathways for N2O Elimination from trans-R3Sn-O-N═N-O-SnR3 and for Reversible Binding of CO2 to R3Sn-O-SnR3 (R = Ph, Cy)

The rate and mechanism of the elimination of N₂O from trans-R₃Sn-O-N═N-O-SnR₃ (R = Ph (1^Ph) and R = Cy (1^Cy)) to form R₃Sn-O-SnR₃ (R = Ph (2^Ph) and R = Cy (2^Cy)) have been studied using both NMR and IR techniques to monitor the reactions in the temperature range of 39-79 °C in C₆D₆. Activation parameters for this reaction are ΔH^⧧ = 15.8 ± 2.0 kcal·mol^-1 and ΔS^⧧ = -28.5 ± 5 cal·mol^-1·K^-1 for 1^Ph and ΔH^⧧ = 22.7 ± 2.5 kcal·mol^-1 and ΔS^⧧ = -12.4 ± 6 cal·mol^-1·K^-1 for 1^Cy. Addition of O₂, CO₂, N₂O, or PPh₃ to sealed tube NMR experiments did not alter in a detectable way the rate or product distribution of the reactions. Computational DFT studies of elimination of hyponitrite from trans-Me₃Sn-O-N═N-O-SnMe₃ (1^Me) yield a mechanism involving initial migration of the R₃Sn group from O to N passing through a marginally stable intermediate product and subsequent N₂O elimination. Reactions of 1^Ph with protic acids HX are rapid and lead to formation of R₃SnX and trans-H₂N₂O₂. Reaction of 1^Ph with the metal radical •Cr(CO)₃C₅Me₅ at low concentrations results in rapid evolution of N₂O. At higher •Cr(CO)₃C₅Me₅ concentrations, evolution of CO₂ rather than N₂O is observed. Addition of 1 atm or less CO₂ to benzene or toluene solutions of 2^Ph and 2^Cy resulted in very rapid reaction to form the corresponding carbonates R₃Sn-O-C(═O)-O-SnR₃ (R = Ph (3^Ph) and R = Cy (3^Cy)) at room temperature. Evacuation results in fast loss of bound CO₂ and regeneration of 2^Ph and 2^Cy. Variable temperature data for formation of 3^Cy yield ΔH^o = -8.7 ± 0.6 kcal·mol^-1, ΔS^o = -17.1 ± 2.0 cal·mol^-1·K^-1, and ΔG^o_298K = -3.6 ± 1.2 kcal·mol^-1. DFT studies were performed and provide additional insight into the energetics and mechanisms for the reactions.