Catalytic Decomposition of an Energetic Ionic Liquid Solution over Hexaaluminate Catalysts

Abstract

The objective of this study was to determine the effect of a synthesis procedure of Sr hexaaluminate on catalytic performance during the decomposition of ionic liquid monopropellants based on ammonium dinitramide (ADN) and hydroxyl ammonium nitrate (HAN). Sr hexaaluminates were prepared via both coprecipitation and a sol–gel process. The surface area of hexaaluminate synthesized via the coprecipitation method was higher than that of hexaaluminate synthesized by the sol–gel process, and calcined at the same temperature of 1200 °C or more. This is because of the sintering of α-Al2O3 on the hexaaluminate synthesized via the sol–gel process, which could not be observed on the catalysts synthesized via the coprecipitation method. The hexaaluminate synthesized via coprecipitation showed a lower decomposition onset temperature during the decomposition of ADN- and HAN-based liquid monopropellants in comparison with the catalysts synthesized via the sol–gel process, and calcined at the same temperature of 1200 °C or more. This is attributed to the differences in the Mn3+ concentration and the surface area between the two hexaaluminates. Consequently, the hexaaluminate synthesized via coprecipitation which calcined above 1200 °C showed high activity during the decomposition of energetic ionic liquid monopropellants compared with the hexaaluminate synthesized via the sol–gel process.

Synthesis of Hydroxylammonium Nitrate and Its Decomposition over Metal Oxide/Honeycomb Catalysts

“…Hence, as the quantity of nitric acid increased, the quantity of nitrogen ions in the nitric acid increased, whereas the pH of the HAN in the aqueous phase decreased. In general, synthesized HAN can generate hydroxylamine and nitric acid in a reversible reaction that proceeds according to Equation (10).…”

“…The HAN solution used in this study was composed of 80 wt% HAN and 20 wt% water. The decomposition reaction of the HAN solution was carried out in a custom-made batch-type reactor (Hanwoul Engineering, Gunpo, Korea) (Figure 17) based on earlier work [10,35,41]. The decomposition reaction of the liquid monopropellants proceeded as follows: First, 0.3 g of catalyst was loaded into a sample holder inside the reactor, after which 100 µL of the HAN solution were added using a micropipette (Sigma-Aldrich, Louis, MO, USA).…”

“…Moreover, hydrazine decomposition generates halogen compounds, which is a serious threat to human health. Proper handling and storage of this material can be both expensive and risky [2][3][4][7][8][9][10][11]. Since 2011, when hydrazine and its derivatives were added to the list of substances of very high concern (SVHC), research on eco-friendly, low-toxicity liquid propellants has drawn keen attention [1,5,9,12].…”

“…Eco-friendly, low-toxicity liquid propellants that have been topics of research as alternatives to hydrazine include hydrogen peroxide, ammonium dinitramide (ADN), and hydroxyl ammonium nitrate (HAN) [2,[8][9][10][12][13][14][15][16][17]. Among these, HAN features superior specific thrust to hydrazine, a high level of density, a low freezing point, and outstanding stability.…”

Progress in the synthesis and applications of hexaaluminate-based catalysts

“…Other catalytic applications reported for these materials include combustion of methanol over La, Mn-hexaaluminate materials, [71] decomposition of ammonium dinitramide (AND)-and hydroxyl ammonium nitrate (HAN)-based liquid monopropellants using Sr0.8La0.2MnAl11O19, [131] steam reforming of tars using BaNixAl12-xO19, [121,132,133] H2S decomposition using LaFexAl12-xO19 (LaFex, x=2, 4, 6, 8, 10 and 12) (see Figure 15), [134] partial oxidation of tetradecane (n-C14), dibenzothiophene (DBT) and 1-methylnaphthalene (1-MN) as model reaction compounds for a series of Ni-substituted lanthanum hexaaluminate catalysts, [135] La0.9NiyAl11.95-yO19-δ (y=1.0, 0.8, 0.4 and 0.2), [12] NH3 decomposition to COx-free hydrogen using Ru/Ba-hexaaluminate, [55] a Ba-hexaaluminate catalyst for the decarboxylation of biomass-derived itaconic acid to bio-based methacrylic acid, [136] and a ZrO2-modified Ni/LaAl11O18 catalyst for CO methanation. [137] More information about the catalytic performance and reaction conditions have been summarized in Table 2.…”