![]() ![]() ![]() The addition of AlPO did not affect the morphology of the catalyst as only small lumps seemed to have been formed, but AlPO decreased the catalyst acidity considerably by specifically binding on the strong Brønsted acid sites.Ĭatalysts were studied in three operating conditions for the catalytic cracking of methylcyclohexane (MCH): at low flow rate and partial pressure of MCH for fundamental understanding of the modified catalysts, and at high flow rates and pressures (under both subcritical and supercritical conditions) to assess their catalytic behaviour in realistic conditions. The addition of alumina induced additional mesoporosity in the catalyst, was not thought to bind on specific sites of the zeolite and only partially covered strong acid sites on the zeolites. ![]() The characterization of the catalysts showed that the addition of binders did impact the textural properties and the acidity of the catalysts. ![]() Two binders, alumina and aluminophosphate (AlPO), were added in situ to three HY zeolites of varying Si:Al ratios with a zeolite:binder mass ratio of 70:30. The aim of this thesis is to study the addition of binders to zeolites to understand their impact on the catalytic behaviour and carbon deposition in the context of catalytic cracking for heat management of high-speed flight vehicles. In this context, binders are known materials used in catalysis for their properties to modify the acidity and selectivity of a catalyst, which can also lead to the decrease of coke deposition. Therefore, the development of a catalyst which can lead to a great heat sink through the formation of products of short ignition delay, and the minimised deposition of carbon on the catalyst is key to a sustainable thermal management system. During the circulation of fuel in the channels of the heat exchangers, the fuel usually reaches its supercritical state, which results in different catalytic behaviour and lower carbon deposition. The use of a catalyst can control the reaction rates and form desired products of short ignition delay, such as short chain hydrocarbons, which is essential for efficient combustion of fuel. In this regard, catalytic cracking can provide a substantial chemical heat sink for so-called endothermic fuels. In this approach, the heat sink capacity of the fuel can work as a cooling system by absorbing waste heat to undergo endothermic reactions as the fuel circulates around the combustor wall. One potential approach is to use the on-board hydrocarbon fuel to serve as both a propellant and an efficient heat sink. An index of CRSE is proposed to define contribution ratio of supercritical extraction to the activity of the HZSM-5 catalyst in the developed kinetics model, and it is found that the CRSE increases with increasing hydrocarbon feed rates and decreasing catalytic activities, and reaches maximum value when the coke formation rate equals to the coke removal rate by supercritical hydrocarbon.Ī major challenge for high-speed aircrafts is the development of an active cooling system that can efficiently reduce the heat loads experienced at the combustor walls. According to the estimated reaction rate and adsorption constant of n-dodecane on HZSM-5 at different temperature, the activation energy of 125.4 kJ/mol and adsorption heat 109.5 kJ/mol were calculated. A first-order Langmuir kinetic model with a novel decay function is developed for the supercritical catalytic cracking of hydrocarbon incorporating supercritical extraction effect on catalyst stability, which is satisfactory to describe the kinetic behaviors of catalytic cracking of supercritical n-dodecane. The results show that both the activity of the catalyst and its stabilization towards deactivation decrease with increasing pressure, and the catalyst maintains substantially higher activity when feed rate exceeds 4.00 ml/min under supercritical conditions. The catalytic cracking of n-dodecane over HZSM-5 zeolite catalyst was investigated at 400–450 ☌ under supercritical and subcritical pressures (0.1–4.0 MPa). ![]()
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