Catalytic Decomposition of an Energetic Ionic Liquid Solution over Hexaaluminate Catalysts

Sunghoon Hong,Sujeong Heo,Wooram Kim,Young Jo,Jong-Ki Jeon,Young-Kwon Park

doi:10.3390/catal9010080

Sunghoon Hong, Sujeong Heo + Show 4 more

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https://doi.org/10.3390/catal9010080

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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.

Highlights

Ionic liquid monopropellants, referred to as energetic ionic liquid solutions, are used for propulsion in aerospace applications
The N2 -adsorption isotherms of the Sr hexaaluminate catalysts synthesized via the sol–gel process which calcined at a temperature of 1000 ◦ C or lower (Figure 1) showed a type IV(a) isotherm in the International Union of Pure and Applied Chemistry (IUPAC) classification [19]; they exhibited the H3 type of hysteresis loop, stemming from the pore network, which consists of macropores that are not entirely filled with pore condensate [19]
In the case of the Sr hexaaluminate catalysts synthesized via the coprecipitation method which calcined at a temperature of 1000 ◦ C or lower, the characteristics of the N2 -physisorption isotherm did not differ much from those of the

Summary

Introduction

Ionic liquid monopropellants, referred to as energetic ionic liquid solutions, are used for propulsion in aerospace applications. Hydrazine is commonly used in the aerospace industry, replacing this conventional monopropellant with an eco-friendly monopropellant is crucial because of the high toxicity and high processing costs of hydrazine [1,2,3]. Liquid monopropellants containing ammonium dinitramide (ADN, NH4 N(NO2 )2 ) or hydroxyl ammonium nitrate (HAN, NH3 OHNO3 ) are considered the most attractive alternatives [4]. ADN-based liquid monopropellants consisting of an ADN aqueous solution, methanol, and ammonia were commercialized [5]. An HAN-based liquid monopropellant was used in aqueous solutions [6,7]

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