Surface mediated isotope exchange reactions between water and gaseous deuterium

Kinetics and reactive stripping modelling of hydrogen isotopic exchange of deuterated waters

“…Most of the studies in literature presented kinetic models that consider reaction 1 only. Associated side reactions and intermediate isotopologues were however demonstrated in our previous works [10, 11 and 24] and were validated by a recent study by Roland et al [26]. Kawakami et al [27] and Sagert and Pouteau [28] studied the kinetics of the gas-phase exchange reaction (reaction 1) with the deuterium isotopologue over the supported platinum catalysts and proposed a reaction mechanism based on the Langmuir−Hinshelwood approach.…”

“…Herein, the kinetics of reaction (1) were investigated by observing the evolution of the six molecular species of hydrogen gas (H2, HD and D2) and water vapour (H2OV, D2OV and HDOV) involved in the overall catalytic process. Although a total of six reactions between the water vapour isotopes and hydrogen have been reported by Roland et al [26], only three reactions were, in fact, independent as confirmed by Roland et al [26]. Two of these reactions were determined to be under kinetic control.…”

“…Strong pore diffusion was observed, leading to internal effectiveness factors ranging from 13 to 20 %, while the external mass transfer resistance was negligible at the operated conditions. Roland et al [26] reported rate coefficients for the isotope exchange reactions between deuterium gas and water vapour taking place at the surface of a stainless steel vessel. Time transients of D2OV and HDOV, produced via isotope exchange reactions in the mixture of D2, H2, and D2OV, H2OV, HD and HDOV, were measured.…”

“…D2 compound was completely consumed while HD was partly consumed by H2OV into HDOV. Therefore, the model of Roland et al [26] is still valid but reduced to three reactions (i.e. reactions [4][5][6] where reactions 4 and 6 were assumed to be under kinetic control and reaction 5 under a quasi-equilibrium state [26].…”

“…Therefore, the model of Roland et al [26] is still valid but reduced to three reactions (i.e. reactions [4][5][6] where reactions 4 and 6 were assumed to be under kinetic control and reaction 5 under a quasi-equilibrium state [26]. H2 + D2OV <mml:math><mml:mo>&DoubleLeftRightArrow;</mml:mo></mml:math>D2 + H2OV (4) H2 + D2 <mml:math><mml:mo>&DoubleLeftRightArrow;</mml:mo></mml:math>2HD (5) HD+ H2OV <mml:math><mml:mo>&DoubleLeftRightArrow;</mml:mo></mml:math>H2 + HDOV (6) The sum of these reactions (the reverse reaction of Eq.…”