| dc.description.abstract | The European Chemical Agency is planning to ban the use of the currently most used space propellant, hydrazine, due to its high toxicity. As a response, the EU-funded GRASP research consortium nominated
high concentration hydrogen peroxide (HP) as a suitable non-toxic replacement. However, to date still
several issues impede the implementation of HP as a space propellant, which have been addressed in this research. First of all, high concentration HP is either poorly available or only at high cost. SolvGE has invented
a safe and user-friendly method to carry out purification of easily available low concentration to propellantgrade HP. Even though this purification process already has an acceptable efficiency, the waste stream
still contains HP. Since the efficiency of the concentration process itself is limited by Raoult’s law, it is only
possible to increase the overall process efficiency by recuperation of HP from the effluent flow. The company
desired that the proposed solution would not affect the current process, and would add minimal complexity
to the system. In addition, the solution should not affect neither the passive nature of the system nor the
system’s autonomy. It was found that subsequent cooling and condensation of the waste stream would be
the optimum approach to achieve this goal. In order to gain fundamental understanding of this process, a
theoretical model was set up that would predict the required condenser properties. Then, experiments were
conducted that supplied evidence to validate both the key assumptions in the model and the model itself.
Though, it was found that the model would considerably underestimate the required condenser size, which
can be attributed to both the relatively low concentration of HP in the waste stream and the relatively low
turbulence in the flow, as well as the large uncertainty in the actual flow rate. Ultimately, the research efforts
did not culminate into a detailed design solution, yet they did provide SolvGE with further understanding of
the problem and a starting point for further development.
Secondly, at this time no catalyst is available that can ignite HP - ethanol mixtures and withstand the
environment (up to 2000°C and over 20 bar) in a rocket engine for prolonged periods of time. Current research
efforts have focused on the synthesis of a HP decomposition catalyst: the hence liberated heat then serves to
ignite ethanol. Generally, when manganese oxide (MnOx) catalysts would be operated under these conditions
the active phase will rapidly deactivate. Yet, Serra Maia’s group has shown that properly supported MnOx
catalysts can be operated in decomposition for twenty-five minutes without noticeable degradation.
Though, these catalysts most likely cannot withstand the operation conditions of a HP - ethanol engine.
This research utilized drop-testing to investigate reactivity and deactivation behavior of MnOx catalysts
on different supports. Drop-testing is a common method to investigate hypergolicity, as opposed to engine
testing. It can also be employed to study decomposition behavior, for instance of HP. Even though the resemblance to decomposition chamber conditions is poor, this method allows for a fast screening of catalysts. In
addition, it mimics repeated engine starts, and can thus simulate long-term deactivation behavior. In droptesting a drop of HP is released from a set height onto the catalyst, and the subsequent reaction is monitored.
Here the reactions were monitored using high speed imaging and a fast thermal data recorder. Ceramic catalysts pellets (cercaps) were prepared by mixing 1.5 wt.% MnO2 with different metal oxides and subsequently
firing at high temperature. Of the tested support materials (i.a. silica, titania, kaolin and magnesium spinel),
only yttria-stabilized zirconia (YSZ) and γ-alumina (yAl) showed measurable acti | |
