In the last years, the global challenge of environmental sustainability has brought to the use of highly concentrated hydrogen peroxide as green propellant in the aerospace field. One of the most important issues for the exploitation of the hydrogen peroxide decomposition in large-scale thrusters is the generation of oxygen bubbles on the surface of the catalyst and the creation of fluid dynamics instabilities. The purpose of this thesis project was indeed to build a reproducible experiment for the analysis of kinetics and mass transfer in the catalytic decomposition of liquid H2O2 over Pt/Al2O3 pellets. That was achieved by means of several setups always with a transparent flow reactor that allowed the visual inspection of the catalytic bed, which was realized by arranging catalytic pellets in a string-like configuration. The extent of the reaction was controlled by measuring the concentration of oxygen in the outlet gas mixture through an electrochemical sensor. The main experimental campaign consisted into evaluating the impact of the interaction among chemical and physical phenomena. That was assessed by looking at the presence of maxima in the profiles of steady state conversion with respect to the inlet flow rate, varied between 0.2 and 6.0 mL/min, and to the reactant concentration, ranged among 15.0 and 30.0 %. The laboratory activity highlighted the robustness of the string-like configuration since it reduced the instabilities of the two-phase flow, favouring a systematic analysis of the industrial catalyst. Moreover, the complex interaction between kinetics and fluid dynamics was confirmed. Indeed, it caused the deviation from the expected behaviours in the profiles of conversion with respect to inlet flow rate and H2O2 concentration. In particular, bubbles stagnation over the active sites and thermal decomposition played a crucial role into determining the behaviour of the system.
In the last years, the global challenge of environmental sustainability has brought to the use of highly concentrated hydrogen peroxide as green propellant in the aerospace field. One of the most important issues for the exploitation of the hydrogen peroxide decomposition in large-scale thrusters is the generation of oxygen bubbles on the surface of the catalyst and the creation of fluid dynamics instabilities. The purpose of this thesis project was indeed to build a reproducible experiment for the analysis of kinetics and mass transfer in the catalytic decomposition of liquid H2O2 over Pt/Al2O3 pellets. That was achieved by means of several setups always with a transparent flow reactor that allowed the visual inspection of the catalytic bed, which was realized by arranging catalytic pellets in a string-like configuration. The extent of the reaction was controlled by measuring the concentration of oxygen in the outlet gas mixture through an electrochemical sensor. The main experimental campaign consisted into evaluating the impact of the interaction among chemical and physical phenomena. That was assessed by looking at the presence of maxima in the profiles of steady state conversion with respect to the inlet flow rate, varied between 0.2 and 6.0 mL/min, and to the reactant concentration, ranged among 15.0 and 30.0 %. The laboratory activity highlighted the robustness of the string-like configuration since it reduced the instabilities of the two-phase flow, favouring a systematic analysis of the industrial catalyst. Moreover, the complex interaction between kinetics and fluid dynamics was confirmed. Indeed, it caused the deviation from the expected behaviours in the profiles of conversion with respect to inlet flow rate and H2O2 concentration. In particular, bubbles stagnation over the active sites and thermal decomposition played a crucial role into determining the behaviour of the system.
Experimental study of hydrogen peroxide catalytic decomposition over Pt pellets
SCARSELLA, LORENZO LUIGI
2023/2024
Abstract
In the last years, the global challenge of environmental sustainability has brought to the use of highly concentrated hydrogen peroxide as green propellant in the aerospace field. One of the most important issues for the exploitation of the hydrogen peroxide decomposition in large-scale thrusters is the generation of oxygen bubbles on the surface of the catalyst and the creation of fluid dynamics instabilities. The purpose of this thesis project was indeed to build a reproducible experiment for the analysis of kinetics and mass transfer in the catalytic decomposition of liquid H2O2 over Pt/Al2O3 pellets. That was achieved by means of several setups always with a transparent flow reactor that allowed the visual inspection of the catalytic bed, which was realized by arranging catalytic pellets in a string-like configuration. The extent of the reaction was controlled by measuring the concentration of oxygen in the outlet gas mixture through an electrochemical sensor. The main experimental campaign consisted into evaluating the impact of the interaction among chemical and physical phenomena. That was assessed by looking at the presence of maxima in the profiles of steady state conversion with respect to the inlet flow rate, varied between 0.2 and 6.0 mL/min, and to the reactant concentration, ranged among 15.0 and 30.0 %. The laboratory activity highlighted the robustness of the string-like configuration since it reduced the instabilities of the two-phase flow, favouring a systematic analysis of the industrial catalyst. Moreover, the complex interaction between kinetics and fluid dynamics was confirmed. Indeed, it caused the deviation from the expected behaviours in the profiles of conversion with respect to inlet flow rate and H2O2 concentration. In particular, bubbles stagnation over the active sites and thermal decomposition played a crucial role into determining the behaviour of the system.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/77788