High-pressure conversion of ammonia additivated with dimethyl ether in a flow reactor

The oxidation of ammonia (NH3) mixed with dimethyl ether (DME) was investigated from experimental and modeling points of view using a quartz flow reactor with argon as bath gas from 350 K to 1225 K, for two different DME/NH3 ratios (0.05 and 0.3), three oxygen excess ratios (lambda = 0.7, 1 and 3) and various pressures (1, 10, 20 and 40 bar). The effect of pressure, oxygen stoichiometry, temperature, and DME/NH3 ratio has been analyzed on DME, NH3, NO, NO2, N2O, N2, O2, H2, HCN, CH4, CO, and CO2 concentrations. The present study indicates that oxygen availability, DME/NH3 ratio, and pressure are important variables that shift NH3 and DME conversion to lower temperatures as their values increase. Under certain conditions, the pressure effect can avoid NO and HCN production, which would represent a benefit for pressure applications. The main products of ammonia/dimethyl ether oxidation are N2, N2O, CO, and CO2, and under certain conditions, NO, H2, CH4, and HCN are also produced. NO2 is always detected below 5 ppm for all the conditions considered. The N2O formation is favored by increasing the O2 stoichiometry, pressure, and/or DME/NH3 ratio. The experimental results are interpreted and discussed in terms of an updated detailed chemical kinetic mechanism, which captures, with a general good agreement, the main trends of NH3 and DME conversion under the considered conditions. Despite this, some calculated species present discrepancies with the experimental results. The main challenge is the consideration of the C-N interactions that can be present in the combustion of DME/NH3 mixtures.