Catalytical ignition of deuterium – carbon monoxide – air mixtures over metallic rhodium surface at pressures of 1–2 atm

It is established that the temperature dependences of the lower limit of catalytic ignition of stoichiometric mixtures D₂ + CO + air and H₂ + CO + air over the surface of metallic rhodium at pressures above 1 atm are close to each other. The fact that the temperature dependences of the upper limit of the catalytic ignition of deuterium and hydrogen in a mixture with CO differ markedly, and these of the lower limit are very close, may be due to the different adsorption capacity of carbon monoxide poisoning the untreated surface of the noble metal hydride/deuteride on the upper limit. At the same time, at the lower limit of catalytic ignition, the surface layer of adsorbed carbon monoxide is restored with each subsequent admission of the combustible mixture, containing CO. It is shown that the primary source of ignition of a mixture of D₂ + CO + air occurs on the rhodium surface; in subsequent experiments, at a pressure above 1 atm, under the same conditions, the place of origin of the initial source changes. It has been found that the periods of delay of catalytic ignition only increase with decreasing temperature, which is associated with the adsorption of carbon monoxide poisoning the catalyst on the surface of the noble metal hydride/deuteride at the upper catalytic limit, while the state of the surface of the noble metal changes only due to the burning-out of CO layer at the first ignition. However, the surface layer of the adsorbed carbon monoxide is restored with each subsequent injection of the combustible mixture containing CO when approaching the lower catalytic limit. Analysis of the visible and infrared spectra of the catalytic ignition of D₂-CO-air mixtures allowed us to establish that the heating in the D₂ - CO–air flame is significantly higher than during the combustion of deuterium in air, and also to identify emission bands of heavy water in the combustion products.