Thermal decomposition of sodium amide, NaNH 2 , and sodium amide hydroxide composites, NaNH 2 -NaOH.

Sodium amide, NaNH2 , has recently been shown to be a useful catalyst to decompose NH3 into H2 and N2 , however, sodium hydroxide is omnipresent and commercially available NaNH2 usually contains impurities of NaOH (<2%). The thermal decomposition of NaNH2 and NaNH2 -NaOH composites is systematically investigated and discussed. NaNH2 is partially dissolved in NaOH at T > 100 °C, forming a non-stoichiometric solid solution of Na(OH)1-x (NH2 )x (0 < x < ∼0.30), which crystallizes in an orthorhombic unit cell with the space group P21 21 21 determined by synchrotron powder X-ray diffraction. The composite xNaNH2 -(1 - x)NaOH (∼0.70 < x < 0.72) shows a lowered melting point, ∼160 °C, compared to 200 and 318 °C for neat NaNH2 and NaOH, respectively. We report that 0.36 mol of NH3 per mol of NaNH2 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 NaNH2 at elevated temperatures and provides the release of additional NH3 .