Hydrogen peroxide gas generator with dual catalytic beds for nonpreheating startup

I NTERESTS in rocket-grade hydrogen peroxide have been renewed in recent years as a new demand for a nontoxic alternative to rocket propellants arises. The use of high-concentrated hydrogen peroxide as a propellant in propulsion dates back to the 1940s. After the SecondWorldWar, it was used as amonopropellant and as an oxidizer in a bipropellant system for thrusters. Hydrogen peroxide was eventually replaced by higher-performing propellants such as hydrazine and N2O4. In the middle of the 1990s, there was renewed interest in hydrogen peroxide due to low toxicity, clean products, and enhanced versatility [1,2]. The performance of the catalyst is crucial in the design of the propulsion devices that use the decomposition of hydrogen peroxide. Silver has been the most widely used catalyst despite many shortcomings, including low melting point, nonuniform flow path, high-pressure loss, and need of preheating [2]. In addition, silver cannot withstand the high decomposition temperatures of hydrogen peroxide at concentration levels higher than 92% [3]. Alternative catalysts including manganese oxides [3– 6] and perovskites [7] have been tested with varying degree of effectiveness. Perovskite material such as La0:8Sr0:2CoO3 (hereafter referred to as LSC) had superior characteristics at elevated temperature but displayed very slow reactivity at room temperature [8]. On the other hand, permanganate-based catalysts displayed very high reactivity at room temperature but were not stable at elevated temperature [9]. In the gas generator proposed in the present study (Fig. 1), hydrogen peroxide goes through two distinct reaction phases: catalytic and thermal decomposition [10]. In the inlet region, the liquid-phase hydrogen peroxide decomposes mainly by catalytic decomposition upon contact with the catalyst surface. In this region, unreacted hydrogen peroxide vaporizes by the heat of the decomposition process. The vapor content of the partially decomposed hydrogen peroxide increases along the axial direction of the reactor bed. Down the reactor bed, the unreacted hydrogen peroxide in vapor state decomposes by further catalytic reaction. Good startup performance and catalytic reactivity are required in the inlet region, and high catalytic reactivity and thermal stability at high temperature are required in the outlet region. The LSC catalyst has good thermal stability and high reactivity at high temperature, but is hard to start up at room temperature [8]. To use the LSC catalyst for the high-temperature region, various catalysts for a vaporizer catalyst bed were selected and evaluated using a constant volume reactor and gas generator. Finally, the gas generator with a dual catalytic bedwas tested and evaluated.