Contents lists available at ScienceDirect Catalysis Today journal homepage: www.elsevier.com/locate/cattod Decomposition of endothermic fuel using washcoated HZSM-5 on metal foam Jeongin Mun a , Hoyeol Jeon a , Byunghun Jeong b , Jihoon Jung a, * a Department of Chemical Engineering, Kyonggi University, Suwon, Gyeonggi-do, 16227, South Korea b Agency for Defense Development, Jochiwongil 462, Daejeon, Yuseong, 34186, South Korea ARTICLE INFO Keywords: Endothermic fuels Washcoating NiFeCrAl metal foam Anodizing Batch reactor ABSTRACT Cooling technology exploiting the endothermic reaction of fuel has been developed to prevent structural de- formation in engines due to air friction and overheating during supersonic flight. Endothermic fuels are liquid hydrocarbon fuels that can absorb heat through endothermic reactions. The initial heat sink capacity of con- ventional pellet type catalysts for the endothermic reaction cannot be maintained, leading to more rapid de- activation due to coke formation. To maintain the heat sink performance of decomposition catalysts, HZSM-5 catalyst washcoated on metal foam(HZSM-5/metal foam) was used herein. The reactions were carried out in a batch reactor at 673 K at a pressure of 50 bar using methylcyclohexane (MCH) and n-dodecane as reactants. The total MCH conversion achieved with the pellets and HZSM-5/metal foam was same at 93 %. In the case of n- dodecane, the total conversion achieved with the HZSM-5/metal foam (91 %) was superior to that achieved with the pellets (69 %). 1. Introduction A hypersonic vehicle is defined as a vehicle that performs above Mach 5. At that speed, a vehicle can become unstable due to air friction and overheating of the engine, which may lead to structural deforma- tion and shut-down of the engine. Recently, a cooling method using endothermic fuel was developed to reduce the heat load of such ve- hicles [1–4]. The main reactions of endothermic fuel under high tem- perature and pressure conditions are catalytic cracking and dehy- drogenation [5–9]. For these reactions, the HZSM-5 catalyst exhibits a better endothermic effect than other zeolite catalysts [10]. The en- dothermic reaction produces low molecular weight products [11] as well as high molecular weight hydrocarbons that are formed by the condensation and re-synthesis of the decomposed products. The for- mation of high molecular aromatic hydrocarbons, namely coke, should be suppressed as they deactivate the catalyst by covering the catalyst surface, and increase the pressure drop by hindering fuel flow [12]. High molecular aliphatic hydrocarbons with higher molecular weight than naphthalene decrease the heat absorption by releasing synthesis heat because high molecular aliphatic hydrocarbons have a very low standard enthalpy of formation compared to other hydrocarbons. BTX (benzene, toluene, xylene), which has a lower molecular weight than naphthalene, and gas products are the advantageous products for in- creasing heat absorption due to its high standard enthalpy of formation, though the aromatic compounds act as coke precursors [13,14]. To improve the reactivity of endothermic fuel, a new catalyst with high temperature stability and reduced coke production should be devel- oped. Conventional pellet-type catalysts suffer from low conversion and slow heat and mass transfer between the catalyst and fuel [15]. The slow heat and mass transfer causes deactivation of the catalyst, in- creases the pressure drop, and decreases the heat absorption due to coke formation. Therefore, the important factor in designing catalysts is achieving fast heat and mass transfer at the catalyst/fuel interface. Coating the catalyst on a mesh type support is one way to achieve this objective [16–20]. Castaldi et al. suggested that coating the catalyst on a mesh-type support offsets the effects of the low contact area [21]. When a mesh type catalyst is used in the reactor, coke formation is reduced by suppressing the side reaction of the products due to the short retention time and the outstanding heat and mass transfer derived from using the metal foam alloy. Metal foam, which has a large surface area and low channeling effect, is utilized herein. The metal foam is coated with the catalyst by washcoat. Washcoat is widely used to coat catalysts on supports via dehydration between the catalyst and support using a silica-type binder [22]. Cohesion of the coated catalyst and metal foam is confirmed by using an ultrasonic test [23,24]. To increase the cohesion between the catalyst and the metal foam, anodizing is introduced [25–27]. The purpose of this study is to increase the conversion of https://doi.org/10.1016/j.cattod.2020.02.013 Received 8 October 2019; Received in revised form 15 January 2020; Accepted 12 February 2020 ⁎ Corresponding author. E-mail address: jhjung@kgu.ac.kr (J. Jung). Catalysis Today xxx (xxxx) xxx–xxx 0920-5861/ © 2020 Published by Elsevier B.V. Please cite this article as: Jeongin Mun, et al., Catalysis Today, https://doi.org/10.1016/j.cattod.2020.02.013