Heat-Sink Enhancement of Supercritical Methylcyclohexane Cracking over Lanthanum-Modified Beta Zeolite

Abstract

A series of lanthanum/beta-zeolite catalysts was prepared via hydrothermal ion exchange, and characterized by inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and ammonia temperature-programmed desorption. The lanthanum-doping effect on beta-zeolite catalysts was investigated through catalytic cracking of supercritical methylcyclohexane under the system pressure of 4.0 MPa and the mass flow rate of 1.0 g=s. For lanthanum/beta catalyst of the Cat-2 type, the gas yield of 28.3% and heat sink of 3.35 MJ · kg −1 could be achieved at the temperature of 700°C, much higher than those for the pure beta zeolite without lanthanum modification and for the thermal pyrolysis. Correspondingly, Cat-2 has a better performance on coking inhibition with the reduction of 56.2 and 29.5% at 700°C compared to beta zeolite and thermal cracking. Therefore, it was indicated that beta zeolite with the suitable lanthanum content, still maintaining its high activity and stability of the zeolite framework at high temperature due to lanthanum doping, had a great contribution to high heat sink and coking inhibition at high temperature. Nomenclature c = mass fraction of methylcyclohexane in the residues G = mass flow rate, g∕s I = current, A I 550 = intensity of the peak at 2θ 22.6 deg after calcination at 550°C for 3 h I 850 = intensity of the peak at 2θ 22.6 deg after calcination at 850°C for 30 min m 0 = initial feeding mass of methylcyclohexane, kg m 1 = mass of residues collected after a cracking reaction, kg P C = critical pressure, MPa Q m = heat sink, MJ∕kg R crystal = relative crystallinity T C = critical temperature,°C U = voltage, V W = heating power, W α MCH = conversion of methylcyclohexane, wt. % γ gas = gas yield of methylcyclohexane, % η = thermal efficiency

Catalytic Fast Pyrolysis of JP-10 and 3-Carene Using Analytical Py-GC/MS for the Production of Low Molecular Weight Hydrocarbons

“…Light alkene yields from the pyrolysis of several cyclic hydrocarbon fuels with zeolites under subcritical and supercritical conditions are listed in Table . ,,− For a very small reaction time of 50 s, light alkene yield in this study fares well with that obtained under relatively longer residence times and different reaction conditions from other studies. An ensemble of the results demonstrates that catalytic cracking of JP-10 and 3-carene using HY results in high yields of LMW hydrocarbons even at atmospheric pressure and moderate temperatures (500, 650 °C).…”

Endothermic catalytic cracking of liquid hydrocarbons for thermal management of high-speed flight vehicles

“…The vast majority of reported wall-coated catalysts were washcoated to the reactor walls thanks to a binder. Similar results to the catalysts tested in fixed-bed reactor were reported, namely that the increased acidity of ZSM-5 (due to Si/Al ratio or no ion-exchange modification) leads to a higher activity but also more coke deposition, 63–65 and that nanosized particles of ZSM-5 lead to an increased activity in comparison to conventional ZSM-5. 62 The mesoporosity of the catalytic materials has shown to ease the accessibility of the fuel to the active sites of the materials, which showed a slower deactivation rate due to the avoidance of secondary reaction.…”

“…Huang et al have developed a fast method fast to measure different fuels' endothermicity, 8 which has been adopted by other researchers in order to determine the heat sink properties. 65,74 Resistive heating is used to determine the total heat capacity of the fuels. An energy balance is applied Q sink ¼ Q in À Q env where Q in is the inlet electrical current applied through the reactor tube itself which is then converted to heat to be transferred to the fuel inside of the reactor.…”

Decomposition of Thermally Stable Fuel Using a Cerium-Modified Zeolite Catalyst and Endothermic Characteristics

“…All elements used in the modification were lanthanides, which have similar properties. Following modification with lanthanum, the activity and stability of the catalyst increased significantly. , In addition, lanthanum produces new acidic sites, which are of significant advantage to this alkylation reaction . Cerium is widely used as a structural promoter or an active component in heterogeneous catalysts because of its catalytic activity and favorable reducibility. , The use of cerium-modified HY zeolite can enhance the stability of the adsorbent structure and its acidity by interacting with BAS .…”