Thermal decomposition of sodium amide, NaNH, and sodium amide hydroxide composites, NaNH-NaOH.

Sodium amide, NaNH, has recently been shown to be a useful catalyst to decompose NH into H and N, however, sodium hydroxide is omnipresent and commercially available NaNH usually contains impurities of NaOH (<2%). The thermal decomposition of NaNH and NaNH-NaOH composites is systematically investigated and discussed. NaNH is partially dissolved in NaOH at T > 100 °C, forming a non-stoichiometric solid solution of Na(OH)(NH) (0 < x < ∼0.30), which crystallizes in an orthorhombic unit cell with the space group P222 determined by synchrotron powder X-ray diffraction. The composite xNaNH-(1 - x)NaOH (∼0.70 < x < 0.72) shows a lowered melting point, ∼160 °C, compared to 200 and 318 °C for neat NaNH and NaOH, respectively. We report that 0.36 mol of NH per mol of NaNH is released below 400 °C during heating in an argon atmosphere, initiated at its melting point, T = 200 °C, possibly due to the formation of the mixed sodium amide imide solid solution. Furthermore, NaOH reacts with NaNH at elevated temperatures and provides the release of additional NH.