Plasma Conversion of C, N2 and H2O into HCN and CO at Atmospheric Pressure and Near Ambient Temperature: Towards Oxamide Fertilisers?

HCN, the direct precursor of oxamide [H2N(C = O)(C = O)NH2)], a superior fertiliser to the urea, can be made via Haber-Bosch (HB) N2 fixation followed by `Blaus & auml;ure-Methan-Ammoniak' (BMA) coupling of NH3/CH4. 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 degrees C, carbon (sustainable charcoal, graphite powder, milled carbon fibres and coal power plant fly ash) and N2 are converted into HCN and CO by non-thermal plasma (NTP) discharge via C2 diradical/N2 activation. The O-atoms within the CO result ultimately from water. A stepwise ensemble comprising cyanogen formation (from C2 and N2), its subsequent cleavage to HCN, the water-gas-shift-reaction and Boudouard reaction (CO from CO2/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 FeII-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.