In recent years, the research to substitute the most widely employed propellants, such as the hydrazine family and nitrogen tetroxide, with green alternatives has received a push worldwide, not only due to a shared interest for improved environmental and workplace safety but also for the consequent economic benefits. Highly concentrated hydrogen peroxide, also known as High Test Peroxide (HTP), is considered one of the most promising candidates for near-future storable and green space propulsion, because of its low toxicity, its low environmental impact and because its decomposition produces no pollutant species. HTP can exothermically decompose into water vapor and oxygen releasing large amounts of heat. The reaction produces hot gases in a temperature range between 625 °C and 996 °C, depending on the H2O2 concentration (85-100%). The products can be directly expanded in a nozzle or injected in a combustion chamber to react with a solid or liquid fuel, allowing HTP to power either a monopropellant or a bipropellant configuration. One of the most significant technological challenges in the realization of HTP powered systems is the development of effective, reliable and durable catalytic beds. The catalyst has to fulfill several requirements, such as high stability, short response time and reproducible performance in a wide range of operating conditions, but long-term stability, high thermal and mechanical strength, as well as long lifetime and low cost are also typically required. In this thesis, the production process of catalysts based on manganese oxide (MnOx) supported on commercial alumina pellet is investigated. A production procedure based on an impregnating process with a water solution is proposed and the effects on the active phase loading of several parameters characterizing the methodology are discussed. Among others, influence of the bath temperature and stirring velocity are presented. Additionally, two other methods based on different solvents have been investigated to evaluate the influence of the change. The catalyst, which reached a loading value as high as 6.5%, has been chemically and physically characterized to obtain information on the surface chemical properties. Pellets produced using the most effective production methods have been selected and their reactivity, decomposition rate and durability have been quantified by investigating the decomposition of 87.5% HTP at lab-scale level.
Negli ultimi anni la ricerca riguardante alternative verdi ai propellenti più usati, come idrazina e tetrossido di azoto, ha subito un forte impulso. Ciò non è soltanto dovuto al crescente interesse per la protezione dell’ambiente, ma anche alla possibilità di ridurre i costi per la protezione contro la tossicità di queste sostanze. Il perossido di idrogeno ad alte concentrazioni, conosciuto anche come High Test Peroxide (HTP), è uno dei principali candidati per la propulsione green, grazie alla sua bassa tossicità e al fatto che la sua decomposizione non produce alcun gas inquinante. La decomposizione di HTP genera ossigeno, vapore d’acqua e grandi quantità di calore. Questo rende l’H2O2 estremamente versatile. Infatti, il flusso di gas caldi, che raggiunge tra i 625 °C e 996 °C a seconda della concentrazione (85-100%), può essere espanso in un ugello oppure iniettato in una camera di combustione per agire come comburente. HTP può essere usato sia in sistemi a monopropellente che a bipropellente. Una delle sfide tecnologiche più difficili nell’uso del perossido è la produzione di un catalizzatore che sia efficace e affidabile. I principali requisiti che devono essere soddisfatti sono resistenza a shock sia termici che meccanici, abilità di operare in condizioni diverse, breve tempo di risposta e lunga vita operativa ma basso costo e massa sono estremamente utili. L’obbiettivo di questa tesi è studiare il processo di produzione di catalizzatori basati su ossidi di manganese(MnOx). Una procedura basata sull’impregnaggio con una soluzione acquosa viene utilizzata come base per studiare l’effetto di vari parametri della procedura stessa, come la temperatura del bagno e la velocità di mescolamento, sul loading di fase attiva del prodotto. Inoltre sono state investigate altre due metodologie basate sull’utilizzo di un solvente differente, volte a valutare l’influenza del cambiamento. I catalizzatori, il cui massimo loading ha raggiunto il 6.5%, sono stati sottoposti ad analisi chimiche e fisiche per comprendere la composizione della loro superficie. Infine, i pellet prodotti con le procedure più efficaci sono utilizzati nella decomposizione di perossido all’85% per misurarne la reattività, il rateo di decomposizione e la resistenza all’uso e comparare i risultati.
Deposition methodologies of alumina-supported catalysts based on manganese oxides
GIUDICE, ADRIANO
2020/2021
Abstract
In recent years, the research to substitute the most widely employed propellants, such as the hydrazine family and nitrogen tetroxide, with green alternatives has received a push worldwide, not only due to a shared interest for improved environmental and workplace safety but also for the consequent economic benefits. Highly concentrated hydrogen peroxide, also known as High Test Peroxide (HTP), is considered one of the most promising candidates for near-future storable and green space propulsion, because of its low toxicity, its low environmental impact and because its decomposition produces no pollutant species. HTP can exothermically decompose into water vapor and oxygen releasing large amounts of heat. The reaction produces hot gases in a temperature range between 625 °C and 996 °C, depending on the H2O2 concentration (85-100%). The products can be directly expanded in a nozzle or injected in a combustion chamber to react with a solid or liquid fuel, allowing HTP to power either a monopropellant or a bipropellant configuration. One of the most significant technological challenges in the realization of HTP powered systems is the development of effective, reliable and durable catalytic beds. The catalyst has to fulfill several requirements, such as high stability, short response time and reproducible performance in a wide range of operating conditions, but long-term stability, high thermal and mechanical strength, as well as long lifetime and low cost are also typically required. In this thesis, the production process of catalysts based on manganese oxide (MnOx) supported on commercial alumina pellet is investigated. A production procedure based on an impregnating process with a water solution is proposed and the effects on the active phase loading of several parameters characterizing the methodology are discussed. Among others, influence of the bath temperature and stirring velocity are presented. Additionally, two other methods based on different solvents have been investigated to evaluate the influence of the change. The catalyst, which reached a loading value as high as 6.5%, has been chemically and physically characterized to obtain information on the surface chemical properties. Pellets produced using the most effective production methods have been selected and their reactivity, decomposition rate and durability have been quantified by investigating the decomposition of 87.5% HTP at lab-scale level.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/177866