Plasma Conversion of C, N ₂ and H ₂ O into HCN and CO at Atmospheric Pressure and Near Ambient Temperature: Towards Oxamide Fertilisers?

HCN, the direct precursor of oxamide [H 2 N(C = O)(C = O)NH 2 )], a superior fertiliser to the urea, can be made via Haber–Bosch (HB) N 2 fixation followed by ‘Blausäure‐Methan‐Ammoniak’ (BMA) coupling of NH 3 /CH 4 . That composite route is not economically/energetically viable for oxamide fertiliser production (vs. urea). A study of an alternative route to HCN is reported herein. At 1 atm, 40°C, carbon (sustainable charcoal, graphite powder, milled carbon fibres and coal power plant fly ash) and N 2 are converted into HCN and CO by non‐thermal plasma (NTP) discharge via C 2 diradical/N 2 activation. The O‐atoms within the CO result ultimately from water. A stepwise ensemble comprising cyanogen formation (from C 2 and N 2 ), its subsequent cleavage to HCN, the water‐gas‐shift‐reaction and Boudouard reaction (CO from CO 2 /C) is proposed. No conversion of carbon is observed in the absence of NTP, but in its presence, NTP‐synergistic aluminium xerogel additives [prepared from hydrolysis of Al(O‐ sec ‐Bu) 3 in the presence of methanol soluble transition metal salts (Fe, Mg, Mo, Na, Cu, Ag)] augment the reaction selectivity/activity. For the optimal Fe II ‐xerogel concentrations of 5900–6019 ppm (ca. 0.6% HCN v/v) and 39 032–63 200 ppm (ca. 5% CO v/v) at dissipated energies within a factor of 20 of those for commercial HB‐BMA production of HCN are attained.